Mutational specificities of environmental carcinogens in the lacI gene of Escherichia coli. VI: Analysis of methylene chloride-induced mutational distribution in Uvr+ and UvrB- strains.
To better understand the mechanisms of mutagenesis by the carcinogen, methylene chloride (DCM), we have determined the nature and distribution of forward mutations induced by DCM in the N-terminal region of the lacI gene of Escherichia coli. A total of 116 lacI-d mutations (50 from Uvr+, 66 from UvrB- strain) were characterized by DNA sequencing. Both similarities and differences were observed. Although in both strains base substitutions predominated (74-88%) the distribution among the classes differed. In the case of the Uvr+ strain, DCM substantially increased the frequency of G:C-->C:G transversion and duplication events. Direct repeats were not observed at the endpoints of the duplications, however, all endpoints were in an A:T-rich region. In contrast, in the UvrB- strain, DCM induced A:T-->G:C, A:T-->C:G, G:C-->C:G events as well as deletions. The mutational spectra presented here represent a first step in the elucidation of the mechanism(s) of DCM-induced mutation.
Department of Biology, University of Victoria, BC, Canada.
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Zielenska
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Ahmed
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Pienkowska
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Anderson
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Glickman
D001482:Base Composition; D001483:Base Sequence; D002273:Carcinogens / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D004785:Environmental Pollutants / Q000633:toxicity; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D016368:Frameshift Mutation; D005798:Genes, Bacterial / Q000187:drug effects*; D008752:Methylene Chloride / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009153:Mutagens / Q000494:pharmacology*; D017354:Point Mutation; D014466:Ultraviolet Rays
D002273:Carcinogens; D004269:DNA, Bacterial; D004785:Environmental Pollutants; D009153:Mutagens; D008752:Methylene Chloride