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Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis    [4 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0027-5107
     Published by Elsevier Homepage  [2556 journals]   [SJR: 0.324]   [H-I: 11]
  • Interplay between base excision repair activity and toxicity of
           3-methyladenine DNA glycosylases in an  E. coli complementation
    • Abstract: Publication date: Available online 4 April 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Christopher J. Troll , Suraj Adhikary , Marie Cueff , Ileena Mitra , Brandt F. Eichman , Manel Camps
      DNA glycosylases carry out the first step of base excision repair by removing damaged bases from DNA. The N3-methyladenine (3MeA) DNA glycosylases specialize in alkylation repair and are either constitutively expressed or induced by exposure to alkylating agents. To study the functional and evolutionary significance of constitutive versus inducible expression, we expressed two closely related yeast 3MeA DNA glycosylases—inducible S. cerevisiae MAG and constitutive S. pombe Mag1—in a glycosylase-deficient E. coli strain. In both cases, constitutive expression conferred resistance to alkylating agent exposure. However, in the absence of exogenous alkylation, high levels of expression of both glycosylases were deleterious. We attribute this toxicity to excessive glycosylase activity, since suppressing spMag1 expression correlated with improved growth in liquid culture, and spMag1 mutants exhibiting decreased glycosylase activity showed improved growth and viability. Selection of a random spMag1 mutant library for increased survival in the presence of exogenous alkylation resulted in the selection of hypomorphic mutants, providing evidence for the presence of a genetic barrier to the evolution of enhanced glycosylase activity when constitutively expressed. We also show that low levels of 3MeA glycosylase expression improve fitness in our glycosylase-deficient host, implying that 3MeA glycosylase activity is likely necessary for repair of endogenous lesions. These findings suggest that 3MeA glycosylase activity is evolutionarily conserved for repair of endogenously produced alkyl lesions, and that inducible expression represents a common strategy to rectify deleterious effects of excessive 3MeA activity in the absence of exogenous alkylation challenge.

      PubDate: 2014-04-05T13:11:06Z
    • Abstract: Publication date: April 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Volume 762

      PubDate: 2014-04-05T13:11:06Z
  • Apoptosis inducing lead compounds isolated from marine organisms of
           potential relevance in Cancer Treatment
    • Abstract: Publication date: Available online 28 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Rima Beesoo , Vidushi Neergheen-Bhujun , Ranjeet Bhagooli , Theeshan Bahorun
      Apoptosis is a critical defense mechanism against the formation and progression of cancer and exhibits distinct morphological and biochemical traits. Targeting apoptotic pathways becomes an intriguing strategy for the development of chemotherapeutic agents particularly if the process is selective to cancer cells. Marine natural products have become important sources in the discovery of antitumor drugs, especially when recent technological and methodological advances have increased the scope of investigations of marine organisms. A high number of individual compounds from diverse organisms have induced apoptosis in several tumor cell lines via a number of mechanisms. Here, we review the effects of selected marine natural products and their synthetic derivatives on apoptosis signaling pathways in association with their pharmacological properties. Providing an outlook into the future, we also examine the factors that contribute to new discoveries and the difficulties associated with translating marine-derived compounds into clinical trials.

      PubDate: 2014-03-31T08:32:14Z
  • Damaging and protective bystander cross-talk between human lung cancer and
           normal cells after proton microbeam irradiation
    • Abstract: Publication date: Available online 28 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Sejal Desai , Alisa Kobayashi , Teruaki Konishi , Masakazu Oikawa , Badri N. Pandey
      Most of the studies of radiation-induced bystander effects (RIBE) have been focused on understanding the radiobiological changes observed in bystander cells in response to the signals from irradiated cells in a normal cell population with implications to radiation risk assessment. However, reports on RIBE with relevance to cancer radiotherapy especially investigating the bidirectional and criss-cross bystander communications between cancer and normal cells are limited. Hence, in present study employing co-culture approach, we have investigated the bystander cross-talk between lung cancer (A549) and normal (WI38) cells after proton-microbeam irradiation using γ-H2AX foci fluorescence as a measure of DNA double-strand breaks (DSBs). We observed that in A549–A549 co-cultures, irradiated A549 cells exert damaging effects in bystander A549 cells, which were found to be mediated through gap junctional intercellular communication (GJIC). However, in A549–WI38 co-cultures irradiated A549 did not affect bystander WI38 cells. Rather, bystander WI38 cells induced inverse protective signalling (rescue effect) in irradiated A549 cells, which was independent of GJIC. On the other hand, in response to irradiated WI38 cells neither of the bystander cells (A549 or WI38) showed significant increase in γ-H2AX foci. The observed bystander signalling between tumour and normal cells may have potential implications in therapeutic outcome of cancer radiotherapy.
      Graphical abstract image

      PubDate: 2014-03-31T08:32:14Z
  • Nonhomologous DNA end joining and chromosome aberrations in human
           embryonic lung fibroblasts treated with environmental pollutants
    • Abstract: Publication date: Available online 30 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Pavel Rossner , Andrea Rossnerova , Olena Beskid , Nana Tabashidze , Helena Libalova , Katerina Uhlirova , Jan Topinka , Radim J. Sram
      In order to evaluate the ability of a representative polycyclic aromatic hydrocarbon (PAH) and PAH-containing complex mixtures to induce double strand DNA breaks (DSBs) and repair of damaged DNA in human embryonic lung fibroblasts (HEL12469 cells), we investigated the effect of benzo[a]pyrene (B[a]P) and extractable organic matter (EOM) from ambient air particles <2.5μm (PM2.5) on nonhomologous DNA end joining (NHEJ) and induction of stable chromosome aberrations (CAs). PM2.5 was collected in winter and summer 2011 in two Czech cities differing in levels and sources of air pollutants. The cells were treated for 24h with the following concentrations of tested chemicals: B[a]P: 1μM, 10μM, 25μM; EOMs: 1μg/ml, 10μg/ml, 25μg/ml. We tested several endpoints representing key steps leading from DSBs to the formation of CAs including histone H2AX phosphorylation, levels of proteins Ku70, Ku80 and XRCC4 participating in NHEJ, in vitro ligation activity of nuclear extracts of the HEL12469 cells and the frequency of stable CAs assessed by whole chromosome painting of chromosomes 1, 2, 4, 5, 7 and 17 using fluorescence in situ hybridization. Our results show that 25μM of B[a]P and most of the tested doses of EOMs induced DSBs as indicated by H2AX phosphorylation. DNA damage was accompanied by induction of XRCC4 expression and an increased frequency of CAs. Translocations most frequently affected chromosome 7. We observed only a weak induction of Ku70/80 expression as well as ligation activity of nuclear extracts. In summary, our data suggest the induction of DSBs and NHEJ after treatment of human embryonic lung fibroblasts with B[a]P and complex mixtures containing PAHs.

      PubDate: 2014-03-31T08:32:14Z
  • Hydrogen sulfide (H2S)/cystathionine γ-lyase (CSE) pathway
           contributes to the proliferation of hepatoma cells
    • Abstract: Publication date: Available online 20 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Yan Pan , Shuang Ye , Dexiao Yuan , Jianghong Zhang , Yang Bai , Chunlin Shao
      Hydrogen sulfide (H2S)/cystathionine γ-lyase (CSE) pathway has been demonstrated to play vital roles in physiology and pathophysiology. However, its role in tumor cell proliferation remains largely unclear. Here we found that CSE over-expressed in hepatoma HepG2 and PLC/PRF/5 cells. Inhibition of endogenous H2S/CSE pathway drastically decreased the proliferation of HepG2 and PLC/PRF/5 cells, and it also enhanced ROS production and mitochondrial disruption, pronounced DNA damage and increased apoptosis. Moreover, this increase of apoptosis was associated with the activation of p53 and p21 accompanied by a decreased ratio of Bcl-2/Bax and up-regulation of phosphorylated c-Jun N-terminal kinase (JNK) and caspase-3 activity. In addition, the negative regulation of cell proliferation by inhibition of H2S/CSE system correlated with the blockage of cell mitogenic and survival signal transduction of epidermal growth factor receptor (EGFR) via down-regulating the extracellular-signal-regulated kinase 1/2 (ERK1/2) activation. These results demonstrate that H2S/CSE and its downstream pathway contribute to the proliferation of hepatoma cells, and inhibition of this pathway strongly suppress the excessive growth of hepatoma cells by stimulating mitochondrial apoptosis and suppressing cell growth signal transduction.

      PubDate: 2014-03-21T23:21:09Z
  • A ΔdinB mutation that sensitizes Escherichia coli to the lethal
           effects of UV and X-radiation
    • Abstract: Publication date: Available online 20 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Mei-Chong W. Lee , Magdalena Franco , Doris M. Vargas , Deborah A. Hudman , Steven J. White , Robert G. Fowler , Neil J. Sargentini
      The DinB (PolIV) protein of Escherichia coli participates in several cellular functions. We investigated a dinB mutation, Δ(dinB-yafN)883(::kan) [referred to as ΔdinB883], which strongly sensitized E. coli cells to both UV- and X-radiation killing. Earlier reports indicated dinB mutations had no obvious effect on UV radiation sensitivity which we confirmed by showing that normal UV radiation sensitivity is conferred by the ΔdinB749 allele. Compared to a wild-type strain, the ΔdinB883 mutant was most sensitive (160-fold) in early to mid-logarithmic growth phase and much less sensitive (twofold) in late log or stationary phases, thus showing a growth phase-dependence for UV radiation sensitivity. This sensitizing effect of ΔdinB883 is assumed to be completely dependent upon the presence of UmuDC protein; since the ΔdinB883 mutation did not sensitize the ΔumuDC strain to UV radiation killing throughout log phase and early stationary phase growth. The DNA damage checkpoint activity of UmuDC was clearly affected by ΔdinB883 as shown by testing a umuC104 ΔdinB883 double-mutant. The sensitivities of the ΔumuDC strain and the ΔdinB883 ΔumuDC double-mutant strain were significantly greater than for the ΔdinB883 strain, suggesting that the ΔdinB883 allele only partially suppresses UmuDC activity. The ΔdinB883 mutation partially sensitized (fivefold) uvrA and uvrB strains to UV radiation, but did not sensitize a ΔrecA strain. A comparison of the DNA sequences of the ΔdinB883 allele with the sequences of the Δ(dinB-yafN)882(::kan) and ΔdinB749 alleles, which do not sensitize cells to UV radiation, revealed ΔdinB883 is likely a “gain-of-function” mutation. The ΔdinB883 allele encodes the first 54 amino acids of wild-type DinB followed by 29 predicted residues resulting from the continuation of the dinB reading frame into an adjacent insertion fragment. The resulting polypeptide is proposed to interfere directly or indirectly with UmuDC function(s) involved in protecting cells against the lethal effects of radiation.

      PubDate: 2014-03-21T23:21:09Z
  • Reciprocal bystander effect between α-irradiated macrophage and
           hepatocyte is mediated by cAMP through a membrane signaling pathway
    • Abstract: Publication date: Available online 20 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Mingyuan He , Chen Dong , Yuexia Xie , Jitao Li , Dexiao Yuan , Yang Bai , Chunlin Shao
      Irradiated cells can induce biological effects on vicinal non-irradiated bystander cells, meanwhile the bystander cells may rescue the irradiated cells through a feedback signal stress. To elucidate the nature of this reciprocal effect, we examined the interaction between α-irradiated human macrophage cells U937 and its bystander HL-7702 hepatocyte cells using a cell co-culture system. Results showed that after 6h of cell co-culture, mitochondria depolarization corresponding to apoptosis was significantly induced in the HL-7702 cells, but the formation of micronuclei in the irradiated U937 cells was markedly decreased compared to that without cell co-culture treatment. This reciprocal effect was not observed when the cell membrane signaling pathway was blocked by filipin that inhibited cAMP transmission from bystander cells to irradiated cells. After treatment of cells with exogenous cAMP, forskolin (an activator of cAMP) or KH-7 (an inhibitor of cAMP), respectively, it was confirmed that cAMP communication from bystander cells to targeted cells could mitigate radiation damage in U739 cells, and this cAMP insufficiency in the bystander cells contributed to the enhancement of bystander apoptosis. Moreover, the bystander apoptosis in HL-7702 cells was aggravated by cAMP inhibition but it could not be evoked when p53 of HL-7702 cells was knocked down no matter of forskolin and KH-7 treatment. In conclusion, this study disclosed that cAMP could be released from bystander HL-7702 cells and compensated to α-irradiated U937 cells through a membrane signaling pathway and this cAMP communication played a profound role in regulating the reciprocal bystander effects.

      PubDate: 2014-03-21T23:21:09Z
  • Bipyridine (2,2′-dipyridyl) potentiates Escherichia coli lethality
           induced by nitrogen mustard mechlorethamine
    • Abstract: Publication date: Available online 13 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): T.A.M. De Alencar , T.C. Wilmart-Gonçalves , L.S. Vidal , R.S. Fortunato , A.C. Leitão , C. Lage
      Alkylating agents are used in anti-tumor chemotherapy because they bind covalently to DNA and generate adducts that may lead to cell death. Bifunctional (HN2) and monofunctional (HN1) nitrogen are two such agents, and HN2 was the first drug successfully employed in anti-leukemia chemotherapy. Currently, HN2 is used either alone or combined with other drugs to treat Hodgkin's disease. It is well known that several crosslinking agents require metabolic activation via reactive oxygen species (ROS) to exert their lethal effects. The objective of this work was therefore to determine whether the abovementioned mustards would also require metabolic activation to exert lethal action against Escherichia coli. For this purpose, we measured survival following exposure to HN2 in E. coli strains that were deficient in nucleotide excision repair (uvrA NER mutant), base excision repair (xthA nfo nth fpg BER mutant) or superoxide dismutase (sodAB mutant) activity. We also performed the same experiments in cells pretreated with an iron chelator (2,2’-dipyridyl, DIP). The NER and BER mutants were only sensitive to HN2 treatment (survival rates similar to those of the wild-type were achieved with 5-fold lower HN2 doses). However, wild-type and sodAB strains were not sensitive to treatment with HN2. In all tested strains, survival dropped by 2.5-fold following pretreatment with DIP compared to treatment with HN2 alone. Furthermore, DIP treatment increased ROS generation in both wild type and sodAB-deficient strains. Based on these data and on the survival of the SOD-deficient strain, we suggest that the increased production of ROS caused by Fe2+ chelation may potentiate the lethal effects of HN2 but not HN1. This potentiation may arise as a consequence of enhancement in the number of or modification of the type of lesions formed. No sensitization was observed for the non-crosslinkable HN2 analog, HN1.

      PubDate: 2014-03-16T20:15:18Z
  • Reduced repair capacity of a DNA clustered damage site comprised of
           8-oxo-7,8-dihydro-2′-deoxyguanosine and 2-deoxyribonolactone results
           in an increased mutagenic potential of these lesions
    • Abstract: Publication date: Available online 11 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Siobhan Cunniffe , Peter O’Neill , Marc M. Greenberg , Martine E. Lomax
      A signature of ionizing radiation is the induction of DNA clustered damaged sites. Non-double strand break (DSB) clustered damage has been shown to compromise the base excision repair pathway, extending the lifetimes of the lesions within the cluster, compared to isolated lesions. This increases the likelihood the lesions persist to replication and thus increasing the mutagenic potential of the lesions within the cluster. Lesions formed by ionizing radiation include 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo) and 2-deoxyribonolactone (dL). dL poses an additional challenge to the cell as it is not repaired by the short-patch base excision repair pathway. Here we show recalcitrant dL repair is reflected in mutations observed when DNA containing it and a proximal 8-oxodGuo is replicated in Escherichia coli. 8-oxodGuo in close proximity to dL on the opposing DNA strand results in an enhanced frequency of mutation of the lesions within the cluster and a 20 base sequence flanking the clustered damage site in an E. coli based plasmid assay. In vitro repair of a dL lesion is reduced when compared to the repair of an abasic (AP) site and a tetrahydrofuran (THF), and this is due mainly to a reduction in the activity of polymerase β, leading to retarded FEN1 and ligase 1 activities. This study has given insights in to the biological effects of clusters containing dL.

      PubDate: 2014-03-16T20:15:18Z
  • Rad51C: A novel suppressor gene modulates the risk of head and neck cancer
    • Abstract: Publication date: Available online 12 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Peter Gresner , Jolanta Gromadzinska , Ewa Twardowska , Konrad Rydzynski , Wojciech Wasowicz
      We conducted a case–control study to investigate the possible association between the head and neck cancer (HNC) and genetic variability of Rad51C tumor suppressor gene. Eight polymorphic sites spanning over non-coding regions of Rad51C promoter, exon 1 and intron 1 were genotyped in 81 HNC cases and 156 healthy controls using the real-time PCR technique. One investigated site turned out to be not polymorphic, while among the remaining seven sites a significant HNC risk-increasing effect was found for rs16943176 (c.-118G>A), rs12946397 (c.-26C>T) and rs17222691 (c.145+947C>T) on both allelic (OR=1.8; p <0.05) and genotypic (OR=2.0; p <0.05) level. Furthermore, our data seem to provide marginal evidence, that this effect might possibly be confined to women only (OR=2.8; p =0.05 for allelic and OR=3.7; p =0.05 for genotypic comparisons). These SNPs were found to co-segregate together forming two distinct, HNC risk-modulating haplotypes. The genetic variability of Rad51C might thus be of relevance with respect to HNC risk.

      PubDate: 2014-03-16T20:15:18Z
    • Abstract: Publication date: March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Volume 761

      PubDate: 2014-03-11T12:51:43Z
  • Nucleotide excision repair gene polymorphisms, meat intake and colon
           cancer risk
    • Abstract: Publication date: Available online 6 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Susan E. Steck , Lesley M. Butler , Temitope Keku , Samuel Antwi , Joseph Galanko , Robert S. Sandler , Jennifer J. Hu
      Purpose Much of the DNA damage from colon cancer-related carcinogens, including heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH) from red meat cooked at high temperature, are repaired by the nucleotide excision repair (NER) pathway. Thus, we examined whether NER non-synonymous single nucleotide polymorphisms (nsSNPs) modified the association between red meat intake and colon cancer risk. Methods The study consists of 244 African-American and 311 white colon cancer cases and population-based controls (331 African Americans and 544 whites) recruited from 33 counties in North Carolina from 1996 to 2000. Information collected by food frequency questionnaire on meat intake and preparation methods were used to estimate HCA and benzo(a)pyrene (BaP, a PAH) intake. We tested 7 nsSNPs in 5 NER genes: XPC A499V and K939Q, XPD D312N and K751Q, XPF R415Q, XPG D1104H, and RAD23B A249V. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression. Results Among African Americans, we observed a statistically significant positive association between colon cancer risk and XPC 499 AV + VV genotype (OR=1.7, 95% CI: 1.1, 2.7, AA as referent), and an inverse association with XPC 939 QQ (OR=0.3, 95%CI: 0.2, 0.8, KK as referent). These associations were not observed among whites. For both races combined, there was interaction between the XPC 939 genotype, well-done red meat intake and colon cancer risk (OR=1.5, 95% CI=1.0, 2.2 for high well-done red meat and KK genotype as compared to low well-done red meat and KK genotype, p interaction =0.05). Conclusions Our data suggest that NER nsSNPs are associated with colon cancer risk and may modify the association between well-done red meat intake and colon cancer risk.

      PubDate: 2014-03-11T12:51:43Z
           ESSENTIAL OIL)
    • Abstract: Publication date: Available online 10 March 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): André Luiz Ventura Sávio , Glenda Nicioli da Silva , Elaine Aparecida de Camargo , Daisy Maria Fávero Salvadori
      Allyl isothiocyanate (AITC) is present in plants of the cruciferous family and is abundant in mustard seed. Due to its high bioavailability in urine after ingestion, AITC has been considered a promising antineoplastic agent against bladder cancer. Because TP53 mutations are the most common alterations in bladder cancer cells and are frequently detected in in situ carcinomas, in this study, we investigated whether the AITC effects in bladder cancer cells are dependent on the TP53 status. Two bladder transitional carcinoma cell lines were used: RT4, with wild-type TP53; and T24, mutated TP53 gene. AITC was tested at concentrations of 0.005, 0.0625, 0.0725, 0.0825, 0.0925, 0.125 and 0.25μM in cytotoxicity, cell and clonogenic survival assays, comet and micronucleus assays and for its effects on cell cycle and apoptosis by flow cytometry and on TP53 gene expression. The data showed increased primary DNA damage in both cell lines; however, lower concentrations of AITC were able to induce genotoxicity in the mutant cells for the TP53 gene. Furthermore, the results demonstrated increased apoptosis and necrosis rates in the wild-type cells, but not in mutated TP53 cells, and cell cycle arrest in the G2 phase for mutated cells after AITC treatment. No significant differences were detected in TP53 gene expression in the two cell lines. In conclusion, AITC caused cell cycle arrest, increased apoptosis rates and varying genotoxicity dependent on the TP53 status. However, we cannot rule out the possibility that those differences could reflect other intrinsic genetic alterations in the examined cell lines, which may also carry mutations in genes other than TP53. Therefore, further studies using other molecular targets need to be performed to better understand the mechanisms by which AITC may exert its antineoplastic properties against tumor cells.

      PubDate: 2014-03-11T12:51:43Z
  • A novel mutation in the thyroglobulin gene that causes goiter and dwarfism
           in Wistar Hannover GALAS rats
    • Abstract: Publication date: Available online 28 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Akira Sato , Kuniya Abe , Misako Yuzuriha , Sakiko Fujii , Naofumi Takahashi , Hitoshi Hojo , Shoji Teramoto , Hiroaki Aoyama
      Outbred stocks of rats have been used extensively in biomedical, pharmaceutical and/or toxicological studies as a model of genetically heterogeneous human populations. One of such stocks is the Wistar Hannover GALAS rat. However, the colony of Wistar Hannover GALAS rat has been suspected of keeping a problematic mutation that manifests two distinct spontaneous abnormalities, goiter and dwarfism, which often confuses study results. We have successfully identified the responsible mutation, a guanine to thymine transversion at the acceptor site (3′ end) of intron 6 in the thyroglobulin (Tg) gene (Tg c.749−1G>T ), that induces a complete missing of exon 7 from the whole Tg transcript by mating experiments and subsequent molecular analyses. The following observations confirmed that Tg c.749−1G>T /Tg c.749−1G>T homozygotes manifested both dwarfism and goiter, while Tg c.749−1G>T /+ heterozygotes had only a goiter with normal appearance, suggesting that the mutant phenotypes inherit as an autosomal semi-dominant trait. The mutant phenotypes, goiter and dwarfism, mimicked those caused by typical endocrine disrupters attacking the thyroid. Hence a simple and reliable diagnostic methodology has been developed for genomic DNA-based genotyping of animals. The diagnostic methodology reported here would allow users of Wistar Hannover GALAS rats to evaluate their study results precisely by carefully interpreting the data obtained from Tg c.749−1G>T /+ heterozygotes having externally undetectable thyroidal lesions.

      PubDate: 2014-03-01T07:39:18Z
  • Chromosome loss caused by DNA fragmentation induced in main nuclei and
           micronuclei of human lymphoblastoid cells treated with colcemid
    • Abstract: Publication date: Available online 27 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Mika Yamamoto , Akihiro Wakata , Yoshinobu Aoki , Yoichi Miyamae , Seiji Kodama
      Aneuploidy, a change in the number of chromosomes, plays an essential role in tumorigenesis. Our previous study demonstrated that a loss of a whole chromosome is induced in human lymphocytes by colcemid, a well-known aneugen. Here, to clarify the mechanism for colcemid-induced chromosome loss, we investigated the relationship between chromosome loss and DNA fragmentation in human lymphoblastoid cells treated with colcemid (an aneugen) compared with methyl methanesulfonate (MMS; a clastogen). We analyzed the number of fluorescence in situ hybridization (FISH) signals targeted for a whole chromosome 2 in cytokinesis-blocked binucleated TK6 cells and WTK-1 cells treated with colcemid and MMS, and concurrently detected DNA fragmentation by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Results revealed that DNA fragmentation occurred in 60% of all binucleated TK6 cells harboring colcemid-induced chromosome loss (30% of micronuclei and 30% of main nuclei). DNA fragmentation was observed in colcemid-induced micronuclei containing a whole chromosome but not in MMS-induced micronuclei containing chromosome fragments. In contrast, colcemid-induced nondisjunction had no effect on induction of DNA fragmentation, suggesting that DNA fragmentation was triggered by micronuclei containing a whole chromosome but not by micronuclei containing chromosome fragments or nondisjunction. In addition, the frequency of binucleated cells harboring chromosome loss with DNA fragmentation in micronuclei or main nuclei was higher in wild-type p53 TK6 cells than in mutated-p53 WTK-1 cells treated with colcemid. Taken together, these present and previous results suggest that colcemid-induced chromosome loss is caused by DNA fragmentation, which is triggered by a micronucleus with a whole chromosome and controlled by the p53-dependent pathway.

      PubDate: 2014-03-01T07:39:18Z
  • The Impact of Homologous Recombination Repair Deficiency on Depleted
           Uranium Clastogenicity in Chinese Hamster Ovary Cells: XRCC3 Protects
    • Abstract: Publication date: Available online 19 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Amie L. Holmes , Kellie Joyce , Hong Xie , Carolyne Falank , John M. Hinz , John Pierce Wise Sr.
      Depleted uranium (DU) is extensively used in both industry and military applications. The potential for civilian and military personnel exposure to DU is rising, but there are limited data on the potential health hazards of DU exposure. Previous laboratory research indicates DU is a potential carcinogen, but epidemiological studies remain inconclusive. DU is genotoxic, inducing DNA double strand breaks, chromosome damage and mutations, but the mechanisms of genotoxicity or repair pathways involved in protecting cells against DU-induced damage remain unknown. The purpose of this study was to investigate the effects of homologous recombination repair deficiency on DU-induced genotoxicity using RAD51D and XRCC3-deficient Chinese hamster ovary (CHO) cell lines. Cells deficient in XRCC3 (irs1SF) also exhibited similar cytotoxicity after DU exposure compared to wild-type (AA8) and XRCC3-complemented (1SFwt8) cells, but DU induced more break-type and fusion-type lesions in XRCC3-deficient cells compared to wild-type and XRCC3-complemented cells. Surprisingly, loss of RAD51D did not affect DU-induced cytotoxicity or genotoxicity. DU induced selective X-chromosome fragmentation irrespective of RAD51D status, but loss of XRCC3 nearly eliminated fragmentation observed after DU exposure in wild-type and XRCC3-complemented cells. Thus, XRCC3, but not RAD51D, protects cells from DU-induced breaks and fusions and also plays a role in DU-induced chromosome fragmentation.

      PubDate: 2014-02-19T20:56:56Z
  • Illegitimate V(D)J recombination-mediated deletions in Notch1 and Bcl11b
           are not sufficient for extensive clonal expansion and show minimal age or
           sex bias in frequency or junctional processing
    • Abstract: Publication date: Available online 14 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Devin P. Champagne , Penny E. Shockett
      Illegitimate V(D)J recombination at oncogenes and tumor suppressor genes is implicated in formation of several T cell malignancies. Notch1 and Bcl11b, genes involved in developing T cell specification, selection, proliferation, and survival, were previously shown to contain hotspots for deletional illegitimate V(D)J recombination associated with radiation-induced thymic lymphoma. >Interestingly, these deletions were also observed in wild-type animals. In this study, we conducted frequency, clonality, and junctional processing analyses of Notch1 and Bcl11b deletions during mouse development and compared results to published analyses of authentic V(D)J rearrangements at the T cell receptor beta (TCRβ) locus and illegitimate V(D)J deletions observed at the human, nonimmune HPRT1 locus not involved in T cell malignancies. We detect deletions in Notch1 and Bcl11b in thymic and splenic T cell populations, consistent with cells bearing deletions in the circulating lymphocyte pool. Deletions in thymus can occur in utero, increase in frequency between fetal and postnatal stages, are detected at all ages examined between fetal and 7 months, exhibit only limited clonality (contrasting with previous results in radiation-sensitive mouse strains), and consistent with previous reports are more frequent in Bcl11b, partially explained by relatively high Recombination Signal Information Content (RIC) scores. Deletion junctions in Bcl11b exhibit greater germline nucleotide loss, while in Notch1 palindromic (P) nucleotides are more abundant, although average P nucleotide length is similar for both genes and consistent with results at the TCRβ locus. Non-templated (N) nucleotide insertions appear to increase between fetal and postnatal stages for Notch1, consistent with normal terminal deoxynucleotidyl transferase (TdT) activity; however, neonatal Bcl11b junctions contain elevated levels of N insertions. Finally, contrasting with results at the HPRT1 locus, we find no obvious age or gender bias in junctional processing, and inverted repeats at recessed coding ends (Pr nucleotides) correspond mostly to single-base additions consistent with normal TdT activity.

      PubDate: 2014-02-14T12:03:13Z
  • Mesenchymal Stem Cells and Cancer: Friends or Enemies'
    • Abstract: Publication date: Available online 7 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): In-Sun Hong , Hwa-Yong Lee , Kyung-Sun Kang
      There is increasing evidence that mesenchymal stem cells (MSCs) have the ability to migrate and engraft into tumor sites and exert stimulatory effects on cancer cell growth, invasion and even metastasis through direct and/or indirect interaction with tumor cells. However, these pro-tumorigenic effects of MSCs are still being discovered and may even involve opposing effects. MSCs can be friends or enemies of cancer cells: they may stimulate tumor development by regulating immune surveillance, growth, and angiogenesis. On the other hand, they may inhibit tumor growth by inhibiting survival signaling such as Wnt and Akt pathway. MSCs have also been proposed as an attractive candidate for the delivery of anti-tumor agents, owing to their ability to home into tumor sites and to secrete cytokines. Detailed information about the mutual interactions between tumor cells and MSCs will undoubtedly lead to safer and more effective clinical therapy for tumors. In this article, we summarize a number of findings to provide current information on the potential roles of MSCs in tumor development; we then discuss the therapeutic potential of engineered MSCs to reveal any meaningful clinical applications.
      Graphical abstract image

      PubDate: 2014-02-10T05:08:51Z
  • Investigating the Mechanisms of Ribonucleotide Excision Repair in
           Escherichia coli
    • Abstract: Publication date: Available online 1 February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Alexandra Vaisman , John P. McDonald , Stephan Noll , Donald Huston , Gregory Loeb , Myron F. Goodman , Roger Woodgate
      Low fidelity Escherichia coli DNA polymerase V (pol V/UmuD2C) is best characterized for its ability to perform translesion synthesis (TLS). However, in recA730 lexA(Def) strains, the enzyme is expressed under optimal conditions allowing it to compete with the cell's replicase for access to undamaged chromosomal DNA and leads to a substantial increase in spontaneous mutagenesis. We have recently shown that a Y11A substitution in the “steric gate” residue of UmuC reduces both base and sugar selectivity of pol V, but instead of generating an increased number of spontaneous mutations, strains expressing umuC_Y11A are poorly mutable in vivo. This phenotype is attributed to efficient RNase HII-initiated repair of the misincorporated ribonucleotides that concomitantly removes adjacent misincorporated deoxyribonucleotides. We have utilized the ability of the pol V steric gate mutant to promote incorporation of large numbers of errant ribonucleotides into the E.coli genome to investigate the fundamental mechanisms underlying ribonucleotide excision repair (RER). Here, we demonstrate that RER is normally facilitated by DNA polymerase I (pol I) via classical “nick translation”. In vitro, pol I displaces 1–3 nucleotides of the RNA/DNA hybrid and through its 5→3 (exo/endo) nuclease activity releases ribo- and deoxyribonucleotides from DNA. In vivo, umuC_Y11A-dependent mutagenesis changes significantly in polymerase-deficient, or proofreading-deficient polA strains, indicating a pivotal role for pol I in ribonucleotide excision repair (RER). However, there is also considerable redundancy in the RER pathway in E. coli. Pol I's strand displacement and FLAP- exo/endonuclease activities can be facilitated by alternate enzymes, while the DNA polymerization step can be assumed by high-fidelity pol III. We conclude that RNase HII and pol I normally act to minimize the genomic instability that is generated through errant ribonucleotide incorporation, but that the “nick-translation” activities encoded by the single pol I polypeptide can be undertaken by a variety of back-up enzymes.

      PubDate: 2014-02-05T03:25:12Z
    • Abstract: Publication date: February 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Volume 760

      PubDate: 2014-01-31T22:21:27Z
  • Does bacterial infection cause genome instability and cancer in the host
    • Abstract: Publication date: Available online 25 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Olga Kovalchuk , Paul Walz , Igor Kovalchuk
      Research of the past several decades suggests that bacterial infection can lead to genome instability of the host cell often resulting in cancer development. However, there is still a substantial lack of knowledge regarding possible mechanisms involved in the development of genomic instability. Several questions remain unanswered, namely: Why has the causative relationship between the bacterial infection and cancer been established only for a small number of cancers' What is the mechanism responsible for the induction of genome instability and cancer' Is the infection process required to cause genome instability and cancer' In this review, we present a hypothesis that the bacterial infection, exposure to heat-killed bacteria or even some bacterial determinants may trigger genome instability of exposed and distal cells, and thus may cause cancer. We will discuss the mechanisms of host responses to the bacterial infection and present the possible pathways leading to genome instability and cancer through exposure to bacteria.

      PubDate: 2014-01-27T12:20:35Z
  • Frequent POLE1 p.S297F mutation in Chinese patients with ovarian
           endometrioid carcinoma
    • Abstract: Publication date: Available online 25 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Yang Zou , Fa-Ying Liu , Huai Liu , Feng Wang , Wei Li , Mei-Zhen Huang , Yan Huang , Xiao-Qun Yuan , Xiao-Yun Xu , Ou-Ping Huang , Ming He
      The catalytic subunit of DNA polymerase epsilon (POLE1) functions primarily in nuclear DNA replication and repair. Recently, POLE1 mutations were detected frequently in colorectal and endometrial carcinomas while with lower frequency in several other types of cancer, and the p.P286R and p.V411L mutations were the potential mutation hotspots in human cancers. Nevertheless, the mutation frequency of POLE1 in ovarian cancer still remains largely unknown. Here, we screened a total of 251 Chinese samples with distinct subtypes of ovarian carcinoma for the presence of POLE1 hotspot mutations by direct sequencing. A heterozygous somatic POLE1 mutation, p.S297F (c.890C>T), but not p.P286R and p.V411L hotspot mutations observed in other cancer types, was identified in 3 out of 37 (8.1%) patients with ovarian endometrioid carcinoma, this mutation was evolutionarily highly conserved from Homo sapiens to Schizosaccharomyces. Of note, the POLE1 mutation coexisted with mutation in the ovarian cancer-associated PPP2R1A (Protein phosphatase 2, regulatory subunit A, α) gene in a 46-year-old patient, who was also diagnosed with ectopic endometriosis in the benign ovary. In addition, a 45-year-old POLE1-mutated ovarian endometrioid carcinoma patient was also diagnosed with uterine leiomyoma while the remaining 52-year-old POLE1-mutated patient showed no additional distinctive clinical manifestation. In contrast to high frequency of POLE1 mutations in ovarian endometrioid carcinoma, no POLE1 mutations were identified in patients with other subtypes of ovarian carcinoma. Our results showed for the first time that the POLE1 p.S297F mutation, but not p.P286R and p.V411L hotspot mutations observed in other cancer types, was frequent in Chinese ovarian endometrioid carcinoma, but absent in other subtypes of ovarian carcinoma. These results implicated that POLE1 p.S297F mutation might be actively involved in the pathogenesis of ovarian endometrioid carcinoma, but might be not actively involved in other subtypes of ovarian carcinoma.

      PubDate: 2014-01-27T12:20:35Z
  • A common variant in pre-miR-146 is associated with coronary artery disease
           risk and its mature miRNA expression
    • Abstract: Publication date: Available online 19 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Xing-dong Xiong , Miook Cho , Xiu-ping Cai , Jie Cheng , Xia Jing , Jin-ming Cen , Xinguang Liu , Xi-li Yang , Yousin Suh
      MiRNAs are small non-coding RNAs that play an important role in numerous physiological processes. Common single nucleotide polymorphisms (SNPs) in pre-miRNAs may change their property through altering miRNAs expression and/or maturation, resulting in diverse functional consequences. To date, the role of genetic variants in pre-miRNAs on coronary artery disease (CAD) risk remain poorly understood. Here we aimed to evaluate the influence of three common SNPs in pre-miRNAs (miR-146a rs2910164 G>C, miR-196a2 rs11614913 C>T, miR-499 rs3746444 T>C) on individual susceptibility to CAD in a Chinese population of 295 CAD patients and 283 controls. Genotyping was performed using polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) method. In a logistic regression analysis, we detected an association of rs2910164 in pre-miR-146a with the CAD risk; compared with the GG homozygotes, the GC heterozygotes [odds ratio (OR)=1.89, 95% confidence interval (CI)=1.06-3.36, P =0.029] and the CC homozygotes (OR=1.83, 95% CI=1.01-3.32, P =0.046) genotype were statistically significantly associated with the increased risk for CADs. As we used further genotype association models, we found a similar trend of the association in recessive model (OR=1.86, 95% CI=1.09-3.19, P =0.023). We also found that the genotypes of miR-146a rs2910164 were associated with its mature miRNA expression by analyzing 23 PBMC samples from CAD patients. Individuals carrying rs11614913 GC or CC genotypes showed 3.2-fold higher expression compared to GG genotype carriers (P <0.05). We observed no association of the other two SNPs in miR-196a2 (rs11614913) and miR-499 (rs3746444) with the CAD incidence. Our data provide the first evidence that the miR-146a rs2910164 polymorphism is associated with increased risk of CAD in Chinese Han population, which may be through influencing the expression levels of the miRNA.

      PubDate: 2014-01-23T04:31:39Z
  • Trianthema portulacastrum Linn. exerts chemoprevention of
           7,12-dimethylbenz(a)anthracene-induced mammary tumorigenesis in rats
    • Abstract: Publication date: Available online 19 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Anupam Bishayee , Animesh Mandal
      Due to limited treatment options for advanced-stage metastatic breast cancer, a high priority should be given to develop non-toxic chemopreventive drugs. The value of various natural and dietary agents to reduce the risk of developing breast cancer is well established. Trianthema portulacastrum Linn. (Aizoaceae), a dietary and medicinal plant, has been found to exert antihepatotoxic and antihepatocarcinogenic properties in rodents. This study was initiated to investigate mechanism-based chemopreventive potential of an ethanolic extract of T. portulacastrum (TPE) against 7,12-dimethylbenz(a)anthracene (DMBA)-initiated rat mammary gland carcinogenesis, an experimental tumor model that closely resembles human breast cancer. Rats had access to a basal diet supplemented with TPE to yield three dietary doses of the extract i.e., 50, 100 and 200mg/kg body weight. Following two weeks of TPE treatment, mammary tumorigenesis was initiated by oral administration of DMBA (50mg/kg body weight). At the end of the study (16 weeks after DMBA exposure), TPE exhibited a striking reduction of DMBA-induced mammary tumor incidence, total tumor burden and average tumor weight and reversed intratumor histopathological alterations. TPE dose-dependently suppressed proliferating cell nuclear antigen and cyclin D1 expression, induced apoptosis, upregulated proapoptotic protein Bax, downregulated antiapoptotic protein Bcl-2 and diminished the expression of nuclear and cytosolic β-catenin in mammary tumors. Our results clearly provide the first experimental evidence that TPE exerts chemopreventive effect in the classical DMBA model of breast cancer by suppressing abnormal cell proliferation and inducing apoptosis mediated through alteration of Bax/Bcl-2 ratio. Mechanistically, TPE is capable of diminishing activated canonical Wnt/β-catenin signaling to exhibit antiproliferative, proapoptotic and oncostatic effect during an early-stage breast cancer. These results may encourage further studies to explore full potential of T. portulacastrum phytoconstituents as breast cancer chemopreventive agents.

      PubDate: 2014-01-23T04:31:39Z
  • p53-Dependent Suppression of Genome Instability in Germ Cells
    • Abstract: Publication date: Available online 7 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Shinji Otozai , Tomoko Ishikawa-Fujiwara , Shoji Oda , Yasuhiro Kamei , Haruko Ryo , Ayuko Sato , Taisei Nomura , Hiroshi Mitani , Tohru Tsujimura , Hidenori Inohara , Takeshi Todo
      Radiation increases mutation frequencies at tandem repeat loci. Germline mutations in γ-ray-irradiated medaka fish (Oryzias latipes) were studied, focusing on the microsatellite loci. Mismatch-repair genes suppress microsatellite mutation by directly removing altered sequences at the nucleotide level, whereas the p53 gene suppresses genetic alterations by eliminating damaged cells. The contribution of these two defense mechanisms to radiation-induced microsatellite instability was addressed. The spontaneous mutation frequency was significantly higher in msh2 -/− males than in wild-type fish, whereas there was no difference in the frequency of radiation-induced mutations between msh2 -/− and wild-type fish. By contrast, irradiated p53 -/− fish exhibited markedly increased mutation frequencies, whereas their spontaneous mutation frequency was the same as that of wild-type fish. In the spermatogonia of the testis, radiation induced a high level of apoptosis both in wild-type and msh2 -/− fish, but negligible levels in p53 -/− fish. The results demonstrate that the msh2 and p53 genes protect genome integrity against spontaneous and radiation-induced mutation by two different pathways: direct removal of mismatches and elimination of damaged cells.

      PubDate: 2014-01-11T07:17:32Z
  • The Radiomimetic Compound Streptonigrin Induces Persistent Telomere
           Dysfunction in Mammalian Cradiomimetic compound streptonigrin induces
           persistent telomere dysfunction in mammalian cells
    • Abstract: Publication date: Available online 6 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Natalia S. Paviolo , Daniel C. Castrogiovanni , Alejandro D. Bolzán
      We analyzed the chromosomal aberrations involving telomeres in the progeny of mammalian cells exposed to the radiomimetic compound streptonigrin (SN) in order to determine if this antineoplastic drug induces long-term telomere instability. To this end, rat cells (ADIPO-P2 cell line, derived from adipose cells from Sprague-–Dawley rat) were treated with a single concentration of SN (100ng/ml), and chromosomal aberrations were analyzed 18h and 10 and 15 days after treatment by using PNA-FISH with a pan-telomeric probe [Cy3-(CCCTAA)3] to detect (TTAGGG)n repeats. Cytogenetic analysis revealed a higher frequency of telomere dysfunction-related aberrations (additional telomeric FISH signals, extra-chromosomal telomeric FISH signals, and telomere FISH signal loss and duplications) in SN-exposed cultures vs. untreated cultures at every time points analyzed. The yield of SN-induced aberrations remained very similar at 18h, 10 days as well as 15 days after treatment. Thus, our data demonstrate that SN induces persistent telomere dysfunction in mammalian cells. Moreover, we found that the level of telomerase activity in SN-treated cells was significantly lower (up to 77%) than that of untreated control cells at each time points analyzed. This fact suggests that telomerase could be involved in SN-induced telomere dysfunction.

      PubDate: 2014-01-11T07:17:32Z
    • Abstract: Publication date: January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Volume 759

      PubDate: 2014-01-07T07:18:53Z
  • The strategies to control prostate cancer by chemoprevention approaches
    • Abstract: Publication date: Available online 2 January 2014
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Harold Ting , Gagan Deep , Chapla Agarwal , Rajesh Agarwal
      Prostate cancer (PCA) is the most commonly diagnosed cancer in men in the United States with growing worldwide incidence. Despite intensive investment in improving early detection, PCA often escapes timely detection and mortality remains high; this malignancy being the second highest cancer-associated mortality in American men. Collectively, health care costs of PCA results in an immense financial burden that is only expected to grow. Additionally, even in cases of successful treatment, PCA is associated with long-term and pervasive effects on patients. A proactive alternative to treating PCA is to prevent its occurrence and progression prior to symptomatic malignancy. This may serve to address the issue of burgeoning healthcare costs and increasing number of sufferers. One potential regimen in service of this alternative is PCA chemoprevention. Here, chemical compounds with cancer preventive efficacy are identified on the basis of their potential in a host of categories: their historical medicinal use, correlation with reduced risk in population studies, non-toxicity, their unique chemical properties, or their role in biological systems. PCA chemopreventive agents are drawn from multiple broad classes of chemicals, themselves further subdivided based on source or potential effect, with most derived from natural products. Many such compounds have shown efficacy, varying from inhibiting deregulated PCA cell signaling, proliferation, epithelial to mesenchymal transition (EMT), invasion, metastasis, tumor growth and angiogenesis and inducing apoptosis. Overall, these chemopreventive agents show great promise in PCA pre-clinical models, though additional work remains to be done in effectively translating these findings into clinical use.

      PubDate: 2014-01-07T07:18:53Z
  • Induction of genomic instability, oxidative processes, and mitochondrial
           activity by 50Hz magnetic fields in human SH-SY5Y neuroblastoma cells
    • Abstract: Publication date: Available online 26 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Jukka Luukkonen , Anu Liimatainen , Jukka Juutilainen , Jonne Naarala
      Epidemiological studies have suggested that exposure to 50Hz magnetic fields (MF) increases the risk of childhood leukemia, but there is no mechanistic explanation for carcinogenic effects. In two previous studies we have observed that a 24-h pre-exposure to MF alters cellular responses to menadione-induced DNA damage. The aim of this study was to investigate the cellular changes that must occur already during the first 24h of exposure to MF, and to explore whether the MF-induced changes in DNA damage response can lead to genomic instability in the progeny of the exposed cells. In order to answer these questions, human SH-SY5Y neuroblastoma cells were exposed to a 50-Hz, 100-μT MF for 24h, followed by 3-h exposure to menadione. The main finding was that MF exposure was associated with increased level of micronuclei, used as an indicator of induced genomic instability, at 8 and 15 days after the exposures. Other delayed effects in MF-exposed cells included increased mitochondrial activity at 8 days, and increased reactive oxygen species (ROS) production and lipid peroxidation at 15 days after the exposures. Oxidative processes (ROS production, reduced glutathione level, and mitochondrial superoxide level) were affected by MF immediately after the exposure. In conclusion, the present results suggest that MF exposure disturbs oxidative balance immediately after the exposure, which might explain our previous findings on MF altered cellular responses to menadione-induced DNA damage. Persistently elevated levels of micronuclei were found in the progeny of MF-exposed cells, indicating induction of genomic instability.

      PubDate: 2013-12-30T07:15:52Z
  • Mutagenesis of mitochondrial DNA in Fuchs endothelial corneal dystrophy
    • Abstract: Publication date: Available online 26 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): P. Czarny , A. Seda , M. Wielgorski , E. Binczyk , B. Markiewicz , E. Kasprzak , M.P. Jiménez-García , I. Grabska-Liberek , E. Pawlowska , J. Blasiak , J. Szaflik , J.P. Szaflik
      Fuchs endothelial corneal dystrophy (FECD) is an age-related, slowly progressive disease, which may lead to loss of vision resulting from apoptosis of corneal endothelial (CE) cells, dysfunction of Descemet membrane (DM) and corneal edema. A growing body of evidence suggests that oxidative stress may play a major role in the pathogenesis of FECD and that mitochondria of CE cells are its main target. Mitochondrial DNA (mtDNA) is particularly prone to oxidative stress and changes in mtDNA were reported in FECD patients. In the present work we studied mtDNA damage and repair, mtDNA copy number, and the 4977 common deletion in mtDNA in DM cells and peripheral blood lymphocytes (PBLs) isolated from FECD patients. PBLs from 35 FECD patients and 32 controls were challenged for 10min with hydrogen peroxide at 20μ and then left in a fresh medium for 3h, resulting in a decrease in mtDNA copy number in both groups. Damage to mtDNA was not fully repaired after 3h and the extent of remaining lesions was significantly higher in the patients than the controls. We observed a higher copy number and an increased extent of mtDNA damage as well as a higher ratio of the common 4977bp deletion in DM cells of FECD patients than controls. Our results confirm that mutagenesis of mtDNA may be involved in FECD pathogenesis and disturbance in mtDNA sensitivity to damaging agent as well as changes in mtDNA damage repair along with alternations in mtDNA copy number may underline this involvement.
      Graphical abstract image

      PubDate: 2013-12-30T07:15:52Z
  • High incidence of multiple antibiotic resistant cells in cultures of in
           enterohemorrhagic Escherichia coli O157:H7
    • Abstract: Publication date: Available online 17 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Benjamin R. Carone , Tao Xu , Kenan C. Murphy , Martin G. Marinus
      The spontaneous incidence of chloramphenicol (Cam) resistant mutant bacteria is at least ten-fold higher in cultures of enterohemorrhagic E. coli O157:H7 strain EDL933 than in E. coli K-12. It is at least 100-fold higher in the dam (DNA adenine methyltransferase) derivative of EDL933, compared to the dam strain of E. coli K-12, thereby preventing the use of Cam resistance as a marker in gene replacement technology. Genome sequencing of Cam-resistant isolates of EDL933 and its dam derivatives showed that the marR (multiple antibiotic resistance) gene was mutated in every case but not in the Cam-sensitive parental strains. As expected from mutation in the marR gene, the Cam-resistant bacteria were also found to be resistant to tetracycline and nalidixic acid. The marR gene in strain EDL933 is annotated as a shorter open reading frame than that in E. coli K-12 but the longer marR+ open reading frame was more efficient at complementing the marR antibiotic-resistance phenotype of strain EDL933. Beta-lactamase-tolerant derivatives were present at frequencies 10-100 times greater in cultures of marR derivatives of strain EDL933 than the parent strain. Spontaneous mutation frequency to rifampicin, spectinomycin and streptomycin resistance was the same in E. coli O157:H7 and E. coli K-12 strains.

      PubDate: 2013-12-22T07:14:54Z
  • Investigations on potential co-mutagenic effects of formaldehyde
    • Abstract: Publication date: Available online 17 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Günter Speit , Regina Linsenmeyer , Giang Duong , Julia Bausinger
      The genotoxicity and mutagenicity of formaldehyde (FA) has been well-characterized during the last years. Besides its known direct DNA-damaging and mutagenic activity in sufficiently exposed cells, FA at low concentrations might also enhance the mutagenic and carcinogenic effects of other environmental mutagens by interfering with the repair of DNA lesions induced by these mutagens. To further assess potential co-mutagenic effects of FA, we exposed A549 human lung cells to FA in combination with various mutagens and measured the induction and removal of DNA damage by the comet assay and the production of chromosomal mutations by the cytokinesis-block micronucleus assay (CBMN assay). The mutagens tested were ionizing radiation (IR), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), N-nitroso-N-methylurea (methyl nitrosourea; MNU) and methyl methanesulfonate (MMS). FA (10 to 75μM) did not enhance the genotoxic and mutagenic activity of these mutagens under the test conditions applied. FA alone and in combination with MNU or MMS did not affect the expression (mRNA level) of the gene of the O6-methylguanine-DNA methyltransferase (MGMT) in A549 cells. The results of these experiments do not support the assumption that low FA concentrations might interfere with the repair of DNA damage induced by other mutagens.

      PubDate: 2013-12-18T04:30:27Z
  • Low concentration of exogenous carbon monoxide protects mammalian cells
           against proliferation induced by radiation-induced bystander effect
    • Abstract: Publication date: Available online 12 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Liping Tong , K.N. Yu , Lingzhi Bao , Wenqing Wu , Hongzhi Wang , Wei Han
      Radiation-induced bystander effect (RIBE) has been proposed to have tight relationship with the irradiation-caused secondary cancers beyond the irradiation-treated area after radiotherapy. Our previous studies demonstrated a protective effect of low concentration carbon monoxide (CO) on the genotoxicity of RIBE after α-particle irradiation. In the present work, a significant inhibitory effect of low-dose exogenous CO, generated by tricarbonyldichlororuthenium (II) dimer [CO-releasing molecule (CORM-2)], on both RIBE-induced proliferation and chromosome aberration was observed. Further studies on the mechanism revealed that the transforming growth factor β1/nitric oxide (NO) signaling pathway, which mediated RIBE signaling transduction, could be modulated by CO involved in the protective effects. Considering the potential of exogenous CO in clinical applications and its protective effect on RIBE, the present work aims to provide a foundation for potential application of CO in radiotherapy.

      PubDate: 2013-12-14T08:54:12Z
  • Corrective Effects of Acerola (Malpighia emarginata DC.) Juice Intake on
           Biochemical and Genotoxical Parameters in Mice Fed on a High-Fat Diet
    • Abstract: Publication date: Available online 1 December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Daniela Dimer Leffa , Juliana da Silva , Francine Daumann , Ana Luiza Formentin Dajori , Luiza Martins Longaretti , Adriani Paganini Damiani , Fabio de Lira , Fernanda Campos , Alexandre de Barros Falcão Ferraz , Dione Silva Côrrea , Vanessa Moraes de Andrade
      Acerola contains high levels of vitamin C and rutin and shows the corresponding antioxidant properties. Oxidative stress on the other hand is an important factor in the development of obesity. In this study, we investigated the biochemical and antigenotoxic effects of acerola juice in different stages of maturity (unripe, ripe and industrial) and its main pharmacologically active components vitamin C and rutin, when given as food supplements to obese mice. Initial HPLC analyses confirmed that all types of acerola juice contained high levels of vitamin C and rutin. DPPH tests quantified the antioxidant properties of these juices and revealed higher antioxidant potentials compared to pure vitamin C and rutin. In an animal test series, groups of male mice were fed on a standard (STA) or a cafeteria (CAF) diet for 13 weeks. The latter consisted of a variety of supermarket products, rich in sugar and fat. This CAF diet increased the feed efficiency, but also induced glucose intolerance and DNA damage, which was established by Comet assays and Micronucleus tests. Subsequently, CAF mice were given additional diet supplements (acerola juice, vitamin C or rutin) for one month and the effects on bone marrow, peripheral blood, liver, kidney, and brain were examined. The results indicated that food supplementation with ripe or industrial acerola juice led to a partial reversal of the diet-induced DNA damage in the blood, kidney, liver and bone marrow. For unripe acerola juice food supplementation, beneficial effects were observed in blood, kidney and bone marrow. Food supplementation with vitamin C led to decreased DNA damage in kidney and liver, whereas rutin supplementation led to decreased DNA damage in all tissue samples observed. These results suggest that acerola juice helps to reduce oxidative stress and may decrease genotoxicity under obesogenic conditions.

      PubDate: 2013-12-02T06:35:04Z
  • Hsa-miR-196a2 polymorphism increases the risk of acute lymphoblastic
           leukemia in Chinese children
    • Abstract: Publication date: Available online 28 November 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Na Tong , Bin Xu , Danni Shi , Mulong Du , Xin Li , Xiaojing Sheng , Meilin Wang , Haiyan Chu , Yongjun Fang , Jie Li , Dongmei Wu , Zhengdong Zhang
      Acute lymphoblastic leukemia (ALL) is a major cause of mortality and morbidity in childhood, and the causes of ALL are not completely understood. microRNAs (miRNAs) regulate various biological processes including organ development, cell growth regulation, cell differentiation, apoptosis, and tumorigenesis. We performed a case-control study with 570 childhood ALL cases and 673 cancer-free controls to investigate the association between hsa-miR-196a2 rs11614913 T>C polymorphism and ALL risk. The bioinformatics was used to estimate the potential target of hsa-miR-196a2. In the present study, the hsa-miR-196a2 variant TC heterozygote, and CC/TC genotypes were found to be associated with a significantly increased childhood ALL risk, compared with the TT wild-type homozygote (adjusted OR=1.50, 95% CI=1.15-1.95 for TC and OR=1.40, 95%CI=1.09-1.79 for CC/TC). Further, the difference was pronounced in younger (≤ 6) subjects or parental non-drinker. The significance of the increased risk is more obvious than the higher treatment branch. Additionally, we found that the rs11614913 TC genotype can increase B-phenotype ALL risk (OR=1.37, 95% CI=1.07-1.76). Finally, combination of three bioinformatics approaches revealed that HOXC8 may be the target gene of hsa-miR-196a2. Taken together, our finding suggested that hsa-miR-196a2 rs11614913 T>C may increase the risk of childhood ALL. Large studies with the function of hsa-miR-196a2 are needed in the further study.

      PubDate: 2013-12-02T06:35:04Z
  • Editorial Board
    • Abstract: Publication date: November–December 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, Volumes 751–752

      PubDate: 2013-11-28T03:05:23Z
  • Effect of dNTP pool alterations on fidelity of leading and lagging strand
           DNA replication in E. coli
    • Abstract: Publication date: Available online 22 November 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Damian Gawel , Iwona J. Fijalkowska , Piotr Jonczyk , Roel M. Schaaper
      The fidelity with which organisms replicate their chromosomal DNA is of considerable interest. Detailed studies in the bacterium Escherichia coli have indicated that the fidelity of leading- and lagging-strand DNA replication is not the same, based on experiments in which the orientation of certain mutational targets on the chromosome was inverted relative to the movement of the replication fork: different mutation rates for several base-pair substitutions were observed depending on this orientation. While these experiments are indicative of differential replication fidelity in the two strands, a conclusion whether leading or lagging strand is the more accurate depends on knowledge of the primary mispairing error responsible for the base substitutions in question. A broad analysis of in vitro base-pairing preferences of DNA polymerases led us to propose that lagging-strand is the more accurate strand. In the present work, we present more direct in vivo evidence in support of this proposal. We determine the orientation dependence of mutant frequencies in ndk and dcd strains, which carry defined dNTP pool alterations. As these pool alterations lead to predictable effects on the array of possible mispairing errors, they mark the strands in which the observed errors occur. The combined results support the proposed higher accuracy of lagging-strand replication in E. coli.

      PubDate: 2013-11-24T04:31:09Z
  • Dietary flavonoids bind to mono-ubiquitinated annexin A1 in nuclei, and
           inhibit chemical induced mutagenesis
    • Abstract: Publication date: Available online 21 November 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Fusao Hirata , Takasuke Harada , George B. Corcoran , Aiko Hirata
      In order to investigate mechanisms of anti-mutagenic action by dietary flavonoids, we investigated if they inhibit mutation of the thymidine kinase (tk) gene in L5178Ytk(+/-) lymphoma cells. Silibinin, quercetin and genistein suppressed mutation of the tk gene induced in L5178Ytk(+/-) lymphoma cells by methyl methansulfonate (MMS) and As3+. Flavone and flavonol were less effective. To establish that mutation of the tk gene in L5178Ytk(+/-) lymphoma cells by MMS and As3+ is mediated through mono-ubiquitinated annexin A1, L5178Ytk(+/-) lymphoma cells were treated with annexin A1 anti-sense oligonucleotide. The treatment reduced mRNA as well as protein levels of annexin A1, and suppressed mutation of the tk gene. Nuclear extracts from L5178Ytk(+/-) lymphoma cells catalyzed translesion DNA synthesis with an oligonucleotide template containing 8-oxo-guanosine in an annexin A1 dependent manner. This translesion DNA synthesis was inhibited by the anti-mutagenic flavonoids, silibinin, quercetin and genistein, in a concentration dependent manner, but only slightly by flavone and flavonol. Because these observations implicate involvement of annexin A1 in mutagenesis, we examined if flavonoids suppress nuclear annexin A1 helicase activity. Silibinin, quercetin and genistein inhibited ssDNA binding, DNA chain annealing and DNA unwinding activities of purified nuclear mono-ubiquitinated annexin A1. Flavone and flavonol were ineffective. The apparent direct binding of anti-mutagenic flavonoids to the annexin A1 molecule was supported by fluorescence quenching. Taken together, these findings illustrate that nuclear annexin A1 may be a novel and productive target protein of prevention for DNA damage induced gene mutation, ultimately conferring cancer chemoprevention.

      PubDate: 2013-11-24T04:31:09Z
  • Excision Repair Cross-Complementation group 1 (ERCC1) C118T SNP does not
           affect cellular response to oxaliplatin
    • Abstract: Publication date: Available online 9 November 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Lieke H. van Huis-Tanja , Dina M. Kweekel , Xiaobo Lu , Kees Franken , Miriam Koopman , Hans Gelderblom , Ninja F. Antonini , Cornelis J.A. Punt , Henk-Jan Guchelaar , Tahar van der Straaten
      Aims ERCC1 is involved in the repair of oxaliplatin-induced DNA damage. Studies for the association of the C118T SNP with clinical response to treatment with platinum drugs have rendered inconsistent results. We investigated the ERCC1 C118T SNP with respect to overall and progression-free survival in patients with advanced colorectal cancer (ACC) treated with oxaliplatin and in vitro DNA repair capacity after oxaliplatin exposure. In addition we discuss discrepancies from other studies concerning ERCC1 C118T. Materials and methods Progression-free survival was determined in 145 ACC patients treated with oxaliplatin-based chemotherapy in a phase 3 trial. For the in vitro studies regarding ERCC1 functionality, we transfected an ERCC1 negative cell line with 118C or 118T ERCC1. Cellular sensitivity and DNA repair capacity after exposure to oxaliplatin were examined by Sulphorodamine B growth inhibition assay, COMET assay and Rad51 foci staining. Results We found no association between ERCC1 C118T and progression-free or overall survival. In addition, transfection of either 118C or 118T restores DNA-repair capacity of UV20 cells to the same level and chemosensitivity to oxaliplatin was similar in ERCC1 118C and 118T transfected cells. Conclusion This study shows that the ERCC1 C118T variants are not associated with survival in ACC patients treated with oxaliplatin or the in vitro sensitivity and DNA-repair capacity in 118C and 118T transfected cell lines. Therefore, ERCC1 C118T genotyping seems of no value in individualizing oxaliplatin based chemotherapy in ACC.

      PubDate: 2013-11-12T03:05:19Z
  • Comparison of the biological effects of MMS and Me-lex, a minor groove
           methylating agent: Clarifying the role of N3-methyladenine
    • Abstract: Publication date: Available online 7 November 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Paola Monti , Giorgia Foggetti , Paola Menichini , Alberto Inga , Barry Gold , Gilberto Fronza
      N3-methyladenine (3-mA), generated by the reaction of methylating agents with DNA, is considered a highly toxic but weakly mutagenic lesion. However, due to its intrinsic instability, some of the biological effects of the adduct can result from the formation of the corresponding depurination product [an apurinic (AP)-site]. Previously, we exploited Me-lex, i.e. {1-methyl-4-[1-methyl-4-(3-methoxysulfonylpropanamido)pyrrole-2-carboxamido]-pyrrole-2 carboxamido}propane, a minor groove equilibrium binder with selectivity for A/T rich sequences that efficiently reacts with DNA to afford 3-mA as the dominant product, to probe the biology of this lesion. Using human p53 cDNA as a target in a yeast system, a weak increase in mutagenicity was observed in the absence of Mag1 (3-methyladenine-DNA glycosylase 1, mag1), the enzyme devoted to remove 3-mA from DNA. Moreover, a significant increase in mutagenicity occurred in the absence of the enzymes involved in the repair of AP-sites (AP endonucleases 1 and 2, apn1apn2). Since methyl methanesulfonate (MMS) has been extensively used to explore the biological effects of 3-mA, even though it produces 3-mA in low relative yield, we compared the toxicity and mutagenicity induced by MMS and Me-lex in yeast. A mutagenesis reporter plasmid was damaged in vitro by MMS and then transformed into wild-type and Translesion Synthesis (TLS) Polζ (REV3) and Polη (RAD30) deficient strains. Furthermore, a mag1rad30 double mutant strain was constructed and transformed with the DNA plasmid damaged in vitro by Me-lex. The results confirm the important role of Polζ in the mutagenic bypass of MMS and Me-lex induced lesions, with Polη contributing only towards the bypass of Me-lex induced lesions, mainly in an error-free way. Previous and present results point towards the involvement of AP-sites, derived from the depurination of 3-mA, in the observed toxicity and mutagenicity.

      PubDate: 2013-11-08T04:31:01Z
  • Corrigendum to “Significance of DNA polymerase I in in vivo
           processing of clustered DNA damage” [Mut. Res.: Fundam. Mol. Mech.
           Mutagen. 749 (2013) 9–15]
    • Abstract: Publication date: Available online 30 October 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Naoya Shikazono , Ken Akamatsu , Momoko Takahashi , Miho Noguchi , Ayumi Urushibara , Peter O’Neill , Akinari Yokoya

      PubDate: 2013-11-04T04:32:43Z
  • Base excision DNA repair defect in thioredoxin-1 (Trx1),-deficient cells
    • Abstract: Publication date: Available online 26 October 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Hye Lim Kim , Preeyaporn Koedrith , Sang Min Lee , Yeo Jin Kim , Young Rok Seo
      Thioredoxin-1 (Trx1) is an antioxidant enzyme with a protective role in the removal of oxidative stress. We investigated the mechanism by which the redox modulator Trx1 affects base excision repair (BER) activity to understand the protective role of Trx1. We constructed a Trx1 knockdown system to demonstrate the specific mechanism of Trx1. DNA damage in terms of relative intensity of the DNA tail and γ-H2AX foci was markedly higher in the Trx1 shRNA cells compared with that in the wild type cells, leading to increased cellular susceptibility to a sublethal dose of BER-inducible toxicant, nitrosomethylurea (NMU). In addition, we observed a modulatory role of Trx1 in the BER pathway via the p53 downstream gene, growth arrest, and DNA-damage-inducible protein 45 α (Gadd45a). The protein level and function of p53, a Trx1 downstream gene, coincidently decreased in the Trx1 shRNA cells. Furthermore, Trx1 shRNA cells showed decreased Gadd45a expression and interaction of Gadd45a with apurynic/apyrimidinic endonuclease 1 (APE1) as well as APE1 activity. In conclusion, Trx1 might cooperate in the control of APE1 function by modulating the p53-mediated BER via the protein-protein interaction between Gadd45a and APE1, providing insight into the novel role of redox factor Trx1 in modulation of BER.

      PubDate: 2013-10-27T04:34:28Z
  • Analysis of mutant frequencies and mutation spectra in hMTH1 knockdown TK6
           cells exposed to UV radiation
    • Abstract: Publication date: Available online 19 October 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Asal Fotouhi , Winta Woldai Hagos , Marina Ilic , Andrzej Wojcik , Mats Harms-Ringdahl , Frank de Gruijl , Leon Mullenders , Jacob G. Jansen , Siamak Haghdoost
      Ultraviolet radiation is a highly mutagenic agent that damages the DNA by the formation of mutagenic photoproducts at dipyrimidine sites and by oxidative DNA lesions via reactive oxygen species (ROS). ROS can also give rise to mutations via oxidation of dNTPs in the nucleotide pool, e.g. 8-oxo-dGTP and 2-OH-dATP and subsequent incorporation during DNA replication. Here we show that expression of human MutT homolog 1 (hMTH1) which sanitizes the nucleotide pool by dephosphorylating oxidized dNTPs, protects against mutagenesis induced by long wave UVA light and by UVB light but not by short wave UVC light. Mutational spectra analyses of UVA-induced mutations at the endogenous Thymidine kinase gene in human lymphoblastoid cells revealed that hMTH1 mainly protects cells from transitions at GC and AT base pairs.

      PubDate: 2013-10-19T21:16:00Z
  • Repair kinetics of acrolein–and
           (E)-4-hydroxy-2-nonenal–derived DNA adducts in human colon cell
    • Abstract: Publication date: Available online 7 October 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Sujata Choudhury , Marcin Dyba , Jishen Pan , Rabindra Roy , Fung-Lung Chung
      ω-3 and ω-6 Polyunsaturated fatty acids (PUFAs) play a role in the pathogenesis of colon cancer. Upon oxidation, PUFAs generate α,β-unsaturated aldehydes or enals, such as acrolein (Acr) and (E)-4-hydroxy-2-nonenal (HNE), which can form cyclic adducts of deoxyguanosine (Acr-dG and HNE-dG, respectively) in DNA. Both Acr-dG and HNE-dG adducts have been detected in human and animal tissues and are potentially mutagenic and carcinogenic. In vivo levels of Acr-dG in DNA are at least two orders of magnitude higher than those of HNE-dG. In addition to the facile reaction with Acr, the higher levels of Acr-dG than HNE-dG in vivo may be due to a lower rate of repair. Previous studies have shown that HNE-dG adducts are repaired by the NER pathway (Choudhury et al., Biochemistry 43 (2004) 7514-7521). We hypothesize that Acr-dG adducts are repaired at a slower rate than HNE-dG and that HNE-dG in DNA may influence the repair of Acr-dG. In this study, using a DNA repair synthesis assay and a LC-MS/MS method, we showed that Acr-dG in a plasmid DNA is repaired by NER proteins, but it is repaired at a much slower rate than HNE-dG in human colon cell extracts, and the slow repair of Acr-dG is likely due to poor recognition/excision of the lesions in DNA. Furthermore, using a plasmid DNA containing both adducts we found the repair of Acr-dG is significantly inhibited by HNE-dG, however, the repair of HNE-dG is not much affected by Acr-dG. This study demonstrates that the NER repair efficiencies of the two major structurally-related in vivo cyclic DNA adducts from lipid oxidation vary greatly. More importantly, the repair of Acr-dG can be significantly retarded by the presence of HNE-dG in DNA. Therefore, this study provides a mechanistic explanation for the higher levels of Acr-dG than HNE-dG observed in tissue DNA.

      PubDate: 2013-10-12T06:16:42Z
  • Mutation effects of C2+ ion irradiation on the greasy Nitzschia sp.
    • Abstract: Publication date: Available online 21 September 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Y.N. Yang , C.L. Liu , Y.K. Wang , J.M. Xue
      Screening and nurturing algae with high productivity, high lipid content and strong stress resistance are very important in algae industry. In order to increase the lipid content, the Nitzschia sp. was irradiated with a 3MeV C2+ beam. The sample pretreatment method was optimized to obtain the best mutagenic condition and the survival ratio curve. The positive mutants with a significant improvement in lipid content were screened and their C2+ mutagenic effects were analyzed by comparing the greasiness and growth characteristics with the wild type algae. Results showed that when the Nitzschia sp. was cultivated in nutritious medium containing 10% glycerol solution, and dried on the filter for 5min after centrifugation, the realization of the microalgae heavy ion mutagenesis could be done. The survival ratio curve caused by C2+ irradiation was proved to be “saddle-shaped”. A positive mutant was screened among 20 survivals after irradiation, the average lipid content of the mutation increased by 9.8% than the wild type after 4 generations. But the growth rate of the screened mutation didn’t change after the heavy ion implantation compared to the wild type algae.

      PubDate: 2013-09-27T02:04:06Z
  • The circling mutant Pcdh15roda is a new mouse model for hearing loss
    • Abstract: Publication date: Available online 14 September 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Adriana Amorim Torres , Agnieszka K. Rzadzinska , Andrea Frozino Ribeiro , Daniel Almeida da Silva e Silva , Jean-Louis Guénet , Sílvia Maria Gomes Massironi , Ana Lúcia Brunialti Godard
      Mouse mutagenesis is a key tool for studying gene function and several mutant alleles have been described and constitute mouse models for human hereditary diseases. Genetic hearing loss represents over 50% of all hearing loss cases in children and, due to the heterogeneity of the disorder, there is still a demand for the isolation and characterization of new genes and alleles. Here we report phenotypic and molecular characterization of a new mouse model for hereditary hearing loss. The mutant rodador, isolated by Massironi and colleagues in 2006, presents an autosomal recessive disorder characterized by deafness and balance dysfunction associated with abnormal stereocilia in the inner ear. The mutation was mapped to mouse chromosome 10, and characterization of the gene Pcdh15 revealed an AT-to-GC transition in intron 23 of mutant animals. The alteration led to the switch of a dinucleotide ApA for ApG, creating a novel intronic acceptor splice site, which leads to incorporation of eight intronic bases into the processed mRNA and alteration of the downstream reading frame. In silico analysis indicated that the mutated protein is truncated and lacks two cadherin domains, and the transmembrane and cytoplasmic domains. Real Time PCR analyses revealed a significantly reduced Pcdh15 mRNA level in the brain of mutant mice, which might be due to the mechanism of non-sense mediated decay. In man, mutations in the orthologue PCDH15 cause non-syndromic deafness and Usher Syndrome Type 1F, a genetic disorder characterized by hearing loss and retinitis pigmentosa. Rodador mouse constitutes a new model for studying deafness in these conditions and may help in the comprehension of the pathogeneses of the disease, as well as of the mechanisms involved in the morphogenesis and function of inner ear stereocilia. This is a new ENU-induced allele and the first isolated in a BALB/c background.

      PubDate: 2013-09-17T02:08:49Z
  • Apparent mtDNA sequence heterogeneity in single human blood CD34+ cells is
           markedly affected by storage and transport
    • Abstract: Publication date: Available online 14 September 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Yong-Gang Yao , Sachiko Kajigaya , Leigh Samsel , J. Philip McCoy Jr. , Giuseppe Torelli , Neal S. Young
      Single CD34+ cells from adult human peripheral blood show mtDNA sequence heterogeneity. In this study, we compared mtDNA sequence variation in single CD34+ cells from peripheral blood (PB) mononuclear cells (MNCs) from the same donors but under different conditions of storage and transport: group I, MNCs from heparinized PB that inadvertently required six days to be transported to the testing laboratory; group II, MNCs which were isolated from PB within a day of phlebotomy and frozen prior to transportation and storage. We observed more cell death for MNCs of group I than group II. Concordantly, group I CD34+ cells had a very low potential for hematopoietic colony formation in vitro compared with group II cells. CD34+ cells of group II showed an unexpectedly higher level of mtDNA sequence heterogeneity than was present group I cells. These observations suggest that reduced mtDNA sequence heterogeneity in single CD34+ cells of group I was likely due to elimination of cells harboring mutations. CD34+ cells that survive stress ex vivo may be more enriched in quiescent primitive hematopoietic stem cells, with fewer mtDNA mutations than committed progenitors. Technically, attention is required for conditions of preparation of human blood samples for single cell mtDNA analysis.

      PubDate: 2013-09-17T02:08:49Z
  • Transplacental clastogenic and epigenetic effects of gold nanoparticles in
    • Abstract: Publication date: Available online 1 September 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Roumen Balansky , Mariagrazia Longobardi , Gancho Ganchev , Marietta Iltcheva , Nikolay Nedyalkov , Petar Atanasov , Reneta Toshkova , Silvio De Flora , Alberto Izzotti
      The broad application of nanotechnology in medicine, biology, and pharmacology is leading to a dramatic increase of the risk of direct contact of nanoproducts, among which gold nanoparticles (AuNP), with the human organism. The present study aimed at evaluating in vivo the genotoxicity of AuNPs with average size of 40nm and 100nm. A single intraperitoneal treatment of adult male and female Swiss mice (strain H) with AuNPs, at a dose of 3.3mg/kg body weight, had no effect on the frequency of micronucleated polychromatic erythrocytes (MN PCEs) in bone marrow. Conversely, the transplacental treatment with AuNP-100nm, but not with AuNP-40nm, applied intraperitoneally at a dose of 3.3mg/kg to pregnant mice on days 10, 12, 14, and 17 of gestation, resulted in a significant increase in the frequency of MN PCEs in both liver and peripheral blood of mouse fetuses. In parallel, the same treatment with AuNP-100nm, but not with AuNP-40nm, produced significant changes in microRNA expression. In particular, out of 1,281 mouse microRNAs analyzed, 28 were dys-regulated more than two-fold and to a statistically significant extent in fetus lung, and 5 were up-regulated in fetal liver. Let-7a and miR-183 were significantly up-regulated in both organs. The data presented herein demonstrate for the first time the transplacental size-dependent clastogenic and epigenetic effects of AuNPs in mouse fetus, thus highlighting new aspects concerning the putative genotoxicity of AuNPs during a vulnerable period of life.

      PubDate: 2013-09-05T03:39:05Z
  • Inter-individual variation in nucleotide excision repair pathway is
           modulated by non-synonymous polymorphisms in ERCC4 and MBD4 genes
    • Abstract: Publication date: Available online 1 September 2013
      Source:Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
      Author(s): Alessandra Allione , Simonetta Guarrera , Alessia Russo , Fulvio Ricceri , Rituraj Purohit , Andrea Pagnani , Fabio Rosa , Silvia Polidoro , Floriana Voglino , Giuseppe Matullo
      Inter-individual differences in DNA repair capacity (DRC) may lead to genome instability and, consequently, modulate individual cancer risk. Among the different DNA repair pathways, nucleotide excision repair (NER) is one of the most versatile, as it can eliminate a wide range of helix-distorting DNA lesions caused by ultraviolet light irradiation and chemical mutagens. We performed a genotype-phenotype correlation study in 122 healthy subjects in order to assess if any associations exist between phenotypic profiles of NER and DNA repair gene single nucleotide polymorphisms (SNPs). Individuals were genotyped for 768 SNPs with a custom Illumina Golden Gate Assay, and peripheral blood mononuclear cells (PBMCs) of the same subjects were tested for a NER comet assay to measure DRC after challenging cells by benzo(a)pyrene diolepoxide (BPDE). We observed a large inter-individual variability of NER capacity, with women showing a statistically significant lower DRC (mean±SD: 6.68±4.76; p=0.004) than men (mean±SD: 8.89±5.20). Moreover, DRC was significantly lower in individuals carrying a variant allele for the ERCC4 rs1800124 non synonymous SNP (nsSNP) (p=0.006) and significantly higher in subjects with the variant allele of MBD4 rs2005618 SNP (p=0.008), in linkage disequilibrium (R2 =0.908) with rs10342 nsSNP. Traditional in silico docking approaches on protein-DNA and protein-protein interaction showed that Gly875 variant in ERCC4 (rs1800124) decreases the DNA-protein interaction and that Ser273 and Thr273 variants in MBD4 (rs10342) indicate complete loss of protein-DNA interactions. Our results showed that NER inter-individual capacity can be modulated by cross-talk activity involving nsSNPs in ERCC4 and MBD4 genes, and they suggested to better investigate SNP effect on cancer risk and response to chemo- and radiotherapies.

      PubDate: 2013-09-05T03:39:05Z
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