title: Induction of transversion mutations in Escherichia coli by N-methyl-N'-nitro-N-nitrosoguanidine is SOS dependent.
abstract: Escherichia coli alkA mutants, which are deficient for an inducible DNA glycosylase, 3-methyladenine-DNA glycosylase II, are sensitive to mutagenesis by low doses of the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). As many as 90% of the alkA-dependent mutations induced by MNNG are also umuC+ dependent and thus are due to DNA lesions that are substrates for the mutagenic functions of the SOS response. A great number of these mutations are base substitutions at A . T sites, particularly A . T transversions. We discuss which DNA lesions may be responsible for these mutations. Our results show that the induction of 3-methyladenine-DNA glycosylase II, which occurs as part of the adaptive response to alkylating agents such as MNNG, significantly reduces the mutagenicity as well as the lethality of alkylation damage.
mesh_terms: D000478:Alkylation; D045647:DNA Glycosylases; D004260:DNA Repair; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D006639:Histidine / Q000235:genetics; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D008780:Methyltransferases / Q000502:physiology; D009154:Mutation / Q000187:drug effects*; D009699:N-Glycosyl Hydrolases / Q000502:physiology*; D019853:O(6)-Methylguanine-DNA Methyltransferase; D014364:Tryptophan / Q000235:genetics
chemical_list: D008769:Methylnitronitrosoguanidine; D006639:Histidine; D014364:Tryptophan; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C076131:DNA-3-methyladenine glycosidase II