Mutation Research/DNA Repair最新文献

{"title":"Evolution of the two-step model for UV-mutagenesis","authors":"Roger Woodgate","doi":"10.1016/S0921-8777(00)00076-8","DOIUrl":"10.1016/S0921-8777(00)00076-8","url":null,"abstract":"<div><p><span>It is quite remarkable how our understanding of translesion DNA synthesis (TLS) has changed so dramatically in the past 2 years. Until very recently, little was known about the molecular mechanisms of TLS in higher eukaryotes and what we did know, was largely based upon </span><em>Escherichia coli</em> and <span><em>Saccharomyces</em><em> cerevisiae</em></span> model systems. The paradigm, proposed by Bryn Bridges and I [Mutat. Res. 150 (1985) 133] in 1985, was that error-prone TLS occurred in two steps; namely a misinsertion event opposite a lesion, followed by extension of the mispair so as to facilitate complete bypass of the lesion. The initial concept was that at least for <em>E. coli</em><span>, the misinsertion event was performed by the cell’s main replicase, DNA polymerase III holoenzyme<span>, and that elongation was achieved through the actions of specialized polymerase accessory proteins, such as UmuD and UmuC. Some 15 years later, we now know that this view is likely to be incorrect in that both misinsertion </span></span><em>and</em> bypass are performed by the Umu proteins (now called pol V). As pol V is normally a distributive enzyme, pol III may only be required to “fix” the misincorporation as a mutation by completing chromosome duplication. However, while the role of the <em>E. coli</em> proteins involved in TLS have changed, the initial concept of misincorporation followed by extension/bypass remains valid. Indeed, recent evidence suggests that it can equally be applied to TLS in eukaryotic cells where there are many more DNA polymerases to choose from. The aim of this review is, therefore, to provide a historical perspective to the “two-step” model for UV-mutagenesis, how it has recently evolved, and in particular, to highlight the seminal contributions made to it by Bryn Bridges.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"485 1","pages":"Pages 83-92"},"PeriodicalIF":0.0,"publicationDate":"2001-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00076-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"56179619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The “Dutch DNA Repair Group”, in retrospect","authors":"Dirk Bootsma","doi":"10.1016/S0921-8777(00)00080-X","DOIUrl":"10.1016/S0921-8777(00)00080-X","url":null,"abstract":"<div><p><span><span>The “Dutch DNA Repair Group” was established about 35 years ago. In this brief historical review some of the crucial decisions are described that have contributed to the relative success of the research of this group. The emphasis of the work of this group has been for many years on the genetic analysis of nucleotide excision repair (NER) and genetic diseases based on defects in this repair process: </span>xeroderma pigmentosum (XP), </span>Cockayne syndrome and trichothiodystrophy.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"485 1","pages":"Pages 37-41"},"PeriodicalIF":0.0,"publicationDate":"2001-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00080-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"56179661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Induced mutagenic effects in the nucleotide excision repair deficient Drosophila mutant mus201D1, expressing a truncated XPG protein","authors":"Fabienne M.G.R. Calléja ,&nbsp;Madeleine J.M. Nivard ,&nbsp;Jan C.J. Eeken","doi":"10.1016/S0921-8777(00)00055-0","DOIUrl":"10.1016/S0921-8777(00)00055-0","url":null,"abstract":"<div><p><span><span>Defects in nucleotide excision repair (NER) as defined by the UV sensitivity of </span>xeroderma pigmentosum (XP), </span>Cockayne syndrome<span> (CS) and trichothiodystrophy (TTD) patients has lead to the identification of most of the genes involved: XPA through XPG, CSA and CSB. Whereas XP patients often show an increased risk for skin cancer after exposure to sunlight, this is not the case for patients with CS and TTD. Several CS patients have been shown to carry a defect in the XPG gene. The XPG, a structure specific endonuclease makes the incision 3′ of damage and is also involved in the subsequent 5′incision during the NER process. In addition, XPG plays a role in the removal of oxidative DNA damage.</span></p><p>The <em>Drosophila</em> XPG gene was isolated and based on the molecular defect of a spontaneous (insertion) and an EMS induced mutant, it was shown that a mutated XPG is responsible for the <em>Drosophila</em> mutagen-sensitive mutants <em>mus201</em>. One of these mutants, <em>mus201^D1</em> has been used extensively in studies of the effects and mechanisms of many chemical mutagens as well as X-rays. The results of these studies are discussed in the light of the finding that mus201p is the <em>Drosophila</em> homologue of XPG.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 279-288"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00055-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21929090","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"tert-Butoxyl radicals generate mainly 7,8-dihydro-8-oxoguanine in DNA","authors":"Hanns-Christian Mahler ,&nbsp;Ina Schulz ,&nbsp;Waldemar Adam ,&nbsp;Günther N Grimm ,&nbsp;Chantu R Saha-Möller ,&nbsp;Bernd Epe","doi":"10.1016/S0921-8777(00)00057-4","DOIUrl":"10.1016/S0921-8777(00)00057-4","url":null,"abstract":"<div><p><span>Like hydroxyl radicals, alkoxyl radicals have been implicated in the generation of cellular oxidative DNA damage under physiological conditions; however, their genotoxic potential has not yet been established. We have analyzed the DNA damage induced by a photochemical source of </span><em>tert-</em>butoxyl radicals, the water soluble peroxy ester [4-(<em>tert</em>-butyldioxycarbonyl)benzyl]triethylammonium chloride (BCBT), using various repair endonucleases as probes. The irradiation (UV³⁶⁰) of BCBT in the presence of bacteriophage PM2 DNA was found to generate a DNA damage profile that consisted mostly of base modifications sensitive to the repair endonuclease Fpg protein. Approximately 90% of the modifications were identified as 7,8-dihydro-8-oxoguanine (8-oxoGua) residues by HPLC/ECD analysis. Oxidative pyrimidine modifications (sensitive to endonuclease III), sites of base loss (AP sites) and single-strand breaks were only minor modifications. Experiments with various scavengers and quenchers indicated that the DNA damage by BCBT+UV³⁶⁰ was caused by <em>tert-</em><span>butoxyl radicals as the ultimate reactive species. The mutagenicity associated with the induced damage was analyzed in the </span><span><em>gpt</em></span> gene of plasmid pSV2<em>gpt</em>, which was exposed to BCBT+UV³⁶⁰ and subsequently transfected into <em>Escherichia coli</em><span><span>. The results were in agreement with the specific generation of 8-oxoGua. Nearly all point mutations (20 out of 21) were found to be GC→TA </span>transversions known to be characteristic for 8-oxoGua. In conclusion, alkoxyl radicals generated from BCBT+UV</span>³⁶⁰<span><span> induce 8-oxoGua in DNA with a higher selectivity than any other </span>reactive oxygen species analyzed so far.</span></p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 289-299"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00057-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21929091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of RAD52 homologs in the fission yeast Schizosaccharomyces pombe","authors":"Michael van den Bosch ,&nbsp;Kees Vreeken ,&nbsp;José B.M Zonneveld ,&nbsp;Jourica A Brandsma ,&nbsp;Marcel Lombaerts ,&nbsp;Johanne M Murray ,&nbsp;Paul H.M Lohman ,&nbsp;Albert Pastink","doi":"10.1016/S0921-8777(00)00060-4","DOIUrl":"10.1016/S0921-8777(00)00060-4","url":null,"abstract":"<div><p>The <span><em>RAD52</em></span> gene of <em>Saccharomyces</em> <em>cerevisiae</em><span> is essential for repair of DNA double-strand breaks (DSBs) by homologous recombination. Inactivation of this gene confers hypersensitivity to DSB-inducing agents and defects in most forms of recombination. The </span><em>rad22</em>⁺ gene in <em>Schizosaccharomyces</em> <em>pombe</em> (here referred to as <em>rad22A</em>⁺) has been characterized as a homolog of <em>RAD52</em><span> in fission yeast. Here, we report the identification of a second </span><em>RAD52</em> homolog in <em>Schizosaccharomyces</em> <em>pombe</em>, called <em>rad22B</em>⁺<span><span>. The amino acid sequences of Rad22A and Rad22B show significant conservation (38% identity). </span>Deletion mutants of respectively, </span><em>rad22A</em> and <em>rad22B</em>, show different phenotypes with respect to sensitivity to X-rays and the ability to perform homologous recombination as measured by the integration of plasmid DNA. Inactivation of <em>rad22A</em>⁺ leads to a severe sensitivity to X-rays and a strong decrease in recombination (13-fold), while the <em>rad22B</em><span> mutation does not result in a decrease in homologous recombination or a change in radiation sensitivity. In a </span><em>rad22A</em>–<em>rad22B</em> double mutant the radiation sensitivity is further enhanced in comparison with the <em>rad22A</em> single mutant. Overexpression of the <em>rad22B</em>⁺ gene results in partial suppression of the DNA repair defects of the <em>rad22A</em><span> mutant strain. Meiotic recombination<span> and spore viability are only slightly affected in either single mutant, but outgrowth of viable spores is almost 31-fold reduced in the </span></span><em>rad22A</em>–<em>rad22B</em> double mutant. The results obtained imply a crucial role for <em>rad22A</em>⁺ in repair and recombination in vegetative cells just like <em>RAD52</em> in <em>S.</em> <em>cerevisiae</em>. The <em>rad22B</em>⁺ gene presumably has an auxiliary role in the repair of DSBs. The drastic reduced spore viability in the double mutant suggests that meiosis in <em>S. pombe</em> is dependent on the presence of either <em>rad22A</em>⁺ or <em>rad22B</em>⁺.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 311-323"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00060-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21928416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Endonuclease V of Escherichia coli prevents mutations from nitrosative deamination during nitrate/nitrite respiration","authors":"Bernard Weiss","doi":"10.1016/S0921-8777(00)00062-8","DOIUrl":"10.1016/S0921-8777(00)00062-8","url":null,"abstract":"<div><p>Endonuclease V (Endo V) of <em>Escherichia coli</em><span><span><span> participates in the excision repair of hypoxanthine and </span>xanthine (deaminated </span>adenine<span><span> and guanine) in DNA. It thereby reduces the mutagenic effects of </span>nitrous acid<span> by attacking lesions caused by nitrosative deamination. Nitrosating agents may be produced endogenously when </span></span></span><em>E. coli</em> is grown in oxygen-poor cultures, during which nitrate and nitrite replace oxygen as preferred electron acceptors. In this study, the protective effect of Endo V was observed under such conditions. During micro-aerobic growth, an <em>nfi</em> (Endo V) mutation enhanced the frequency of nitrate- and nitrite-induced A:T→G:C and G:C→A:T transition mutations, which are consistent with a defect in the removal of DNA hypoxanthine and xanthine, respectively. Similar effects were observed in saturated, aerobic cultures but not in well-aerated, logarithmically growing ones. A <em>narG</em><span> (nitrate reductase) mutation blocked the mutagenesis of the </span><em>nfi</em> mutant by nitrate but not by nitrite. These results differed from those of previous studies in which cell suspensions generated an exogenous nitrosating agent from nitrite, but not from nitrate, in a reaction that was <em>narG</em>-dependent. Nitrate/nitrite metabolism is also known to generate endogenous alkylating agents through <em>N</em>-nitrosation. However, an <em>nfi</em> mutation did not appreciably enhance mutagenesis by <em>N</em>-methyl-<em>N</em>-nitrosourea, suggesting that the mutator effect of <em>nfi</em><span> is not due to a defect in alkylation repair. The overall results indicate that Endo V functions during normal growth by helping to repair nitrosatively deaminated bases in DNA, which are by-products of anaerobic nitrate/nitrite respiration.</span></p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 301-309"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00062-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21928415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The XRCC1 399 glutamine allele is a risk factor for adenocarcinoma of the lung","authors":"Kevin K Divine ,&nbsp;Frank D Gilliland ,&nbsp;Richard E Crowell ,&nbsp;Christine A Stidley ,&nbsp;Therese J Bocklage ,&nbsp;Dennis L Cook ,&nbsp;Steven A Belinsky","doi":"10.1016/S0921-8777(00)00059-8","DOIUrl":"10.1016/S0921-8777(00)00059-8","url":null,"abstract":"<div><p><span><span><span>Defects in the repair and maintenance of DNA increase risk for cancer. X-ray cross-complementing group 1 protein (XRCC1) is involved with the repair of DNA single-strand breaks. A nucleotide substitution of </span>guanine to </span>adenine leading to a non-conservative amino acid change was identified in the </span><em>XRCC1</em><span> gene at codon 399 (Arg/Gln). This change is associated with higher levels of aflatoxin B</span>₁<span><span>-adducts and glycophorin A </span>somatic mutations. A case-control study was conducted to test the hypothesis that the 399Gln allele is positively associated with risk for adenocarcinoma of the lung. </span><em>XRCC1</em> genotypes were assessed at codon 399 in 172 cases of lung adenocarcinoma and 143 cancer-free controls. Two ethnic populations were represented, non-Hispanic White and Hispanic. The distribution of <em>XRCC1</em> genotypes differed between cases and controls. Among cases, 47.7% were Arg/Arg, 35.5% were Arg/Gln, and 16.9% were Gln/Gln. Among controls, <em>XRCC1</em> allele frequencies were 45.5% for Arg/Arg, 44.8% for Arg/Gln, and 9.8% for Gln/Gln. Logistic regression analysis was used to assess the association between lung adenocarcinoma and the G/G genotype relative to the A/A or A/G genotypes. In non-Hispanic White participants, the lung cancer risk associated with the G/G genotype increased significantly after adjustment for age (OR=2.81; 95% CI, 1.2–7.9; <em>P</em>=0.03) and increased further after adjustment for smoking (OR=3.25; 95% CI, 1.2–10.7; <em>P</em><span>=0.03). Among all groups, a significant association was found between the G/G homozygote and lung cancer (OR=2.45; 95% CI, 1.1–5.8; </span><em>P</em>=0.03) after adjustment for age, ethnicity, and smoking. This study links a functional polymorphism in the critical repair gene <em>XRCC1</em> to risk for adenocarcinoma of the lung.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 273-278"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00059-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21929089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fanconi anemia lymphocytes: effect of dl-α-tocopherol (Vitamin E) on chromatid breaks and on G2 repair efficiency","authors":"Juana Pincheira ,&nbsp;Mireya Bravo ,&nbsp;Manuel J Santos ,&nbsp;Consuelo de la Torre ,&nbsp;Jorge F López-Sáez","doi":"10.1016/S0921-8777(00)00058-6","DOIUrl":"https://doi.org/10.1016/S0921-8777(00)00058-6","url":null,"abstract":"<div><p>The high frequency of chromosomal breaks in Fanconi anemia (FA) lymphocytes has been related to the increased oxidative damage shown by these cells.</p><p>The effect of 100<!--> <!-->μM <span>dl</span>-α-tocopherol (Vitamin E) on the level of chromosomal damage in mitosis was studied in lymphocytes from five FA patients and from age matched controls, both under basal conditions and when G₂ repair was prevented by 2.5<!--> <!-->mM caffeine (G₂ unrepaired damage). In addition, the effect of this antioxidant on G₂ duration and the efficiency of G₂ repair was also evaluated in the sample.</p><p>α-Tocopherol (AT) decreased the frequency of chromosomal damage (under basal and inhibited G₂ repair conditions) and the duration of G₂<span> in FA cells. This antioxidant protective effect, expressed as the decrease in chromatid breaks, was greater in FA cells (50.8%) than in controls (25%).</span></p><p>The efficiency of the G₂ repair process (G₂R rate) defined as the ratio between the percentage of chromatid breaks repaired in G₂<span> and the duration of this cell cycle phase was lesser in FA cells (10.6) than in controls (22.6). AT treatment slightly increased this G</span>₂R rate, both in FA cells and controls.</p><p>These results suggest that an increased oxidative damage and a lower G₂ repair rate may be simultaneously involved in the high frequency of chromatid damage detected in FA cells.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 265-271"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00058-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72070964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The instability within: problems in current analyses of microsatellite instability","authors":"Yoshihiko Maehara ,&nbsp;Shinya Oda ,&nbsp;Keizo Sugimachi","doi":"10.1016/S0921-8777(00)00061-6","DOIUrl":"10.1016/S0921-8777(00)00061-6","url":null,"abstract":"<div><p><span><span>Microsatellite<span><span> instability is regarded as one of the phenotypes of defective DNA mismatch repair and, consequently, as a marker of high risk for cancer. Despite numerous studies, the reported rates for positive microsatellite instability differ widely in each human malignancy. These discrepancies may relate to problems in the methods used. To establish a methodology for an accurate microsatellite instability analysis, technical requirements for a precise assay and biological conditions required for positive microsatellite instability were discussed. First, to describe microsatellite changes in detail, a </span>sensitive detection system with linear detection characteristics and </span></span>electrophoresis<span><span> with standardised migration and minimised migration errors are considered to be necessary. Therefore, systems using fluorescent labelling and laser scanning are recommended. For reproducible </span>polymerase chain reactions<span>, it is essential to control the terminal deoxynucleotidyl transferase activity in </span></span></span><em>Taq</em> polymerase. Second, as a biological condition for positive microsatellite instability, feasible selection and combination of microsatellite markers, mutations in specific DNA mismatch repair genes and existence of monoclonal populations enriched sufficiently in a sample are essential. Finally, one possible diagnostic criterion for positive microsatellite instability is proposed, that is the existence of one of the patterns shown in the panel (see <span>Fig. 6</span>) at one or more loci in a set of more than five microsatellite markers.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 249-263"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00061-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21929087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sequence variation in the human uracil-DNA glycosylase (UNG) gene","authors":"Kirsti Kvaløy ,&nbsp;Hilde Nilsen,&nbsp;Kristin S Steinsbekk,&nbsp;Aina Nedal,&nbsp;Bruno Monterotti,&nbsp;Mansour Akbari,&nbsp;Hans E Krokan","doi":"10.1016/S0921-8777(00)00063-X","DOIUrl":"10.1016/S0921-8777(00)00063-X","url":null,"abstract":"<div><p><span>Spontaneous deamination<span> of cytosine results in a premutagenic G:U mismatch that may result in a GC→AT transition during replication. The human </span></span><span><em>UNG</em></span><span><span><span>-gene encodes the major uracil-DNA glycosylase (UDG or UNG) which releases uracil from DNA, thus, initiating base excision repair to restore the correct </span>DNA sequence. Bacterial and yeast mutants lacking the homologous UDG exhibit elevated spontaneous </span>mutation frequencies. Hence, mutations in the human </span><em>UNG</em> gene could presumably result in a mutator phenotype. We screened all seven exons including exon–intron boundaries, both promoters, and one intron of the <em>UNG</em> gene and identified considerable sequence variation in cell lines derived from normal fibroblasts and tumour tissue. None of the sequence variants was accompanied by significantly reduced UDG activity. In the <em>UNG</em> gene from 62 sources, we identified 12 different variant alleles, with allele frequencies ranging from 0.01 to 0.23. We identified one variant allele per 3.8<!--> <!-->kb in non-coding regions, but none in the coding region of the gene. In promoter B we identified four different variants. A substitution within an AP2 element was observed in tumour cell lines only and had an allele frequency of 0.10. Introduction of this substitution into chimaeric promoter–luciferase constructs affected transcription from the promoter. UDG-activity varied little in fibroblasts, but widely between tumour cell lines. This variation did not however correlate with the presence of any of the variant alleles. In conclusion, mutations affecting the function of human <em>UNG</em> gene are seemingly infrequent in human tumour cell lines.</p></div>","PeriodicalId":100935,"journal":{"name":"Mutation Research/DNA Repair","volume":"461 4","pages":"Pages 325-338"},"PeriodicalIF":0.0,"publicationDate":"2001-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0921-8777(00)00063-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"21928417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}