Loss of an apurinic/apyrimidinic site endonuclease increases the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine to Escherichia coli.

Abstract

xthA-Escherichia coli, which are missing a major cellular apurinic/apyrimidinic (AP) endonuclease, are 5-to 10-fold more sensitive than xthA+ bacteria to mutagenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) under conditions that induce the "adaptive response." The xthA--dependent mutations are also dependent on SOS mutagenic processing and consist of both transversion and transition base substitutions. When MNNG-adapted xthA-bacteria are challenged with a high dose of MNNG, more xthA-dependent SOS-dependent mutations are induced, and transversions are enhanced relative to transitions. The mutations induced by challenge are eliminated in xthA-alkA-bacteria, which are also deficient for 3-methyladenine glycosylase II activity. These data are consistent with the hypothesis that AP sites, at least some of which are produced by glycosylase activity, are mutagenic intermediates following cellular DNA alkylation.Apurinic and apyrimidinic (AP) sites cause errors in DNA replication in vitro and are mutagenic when present in transforming DNA (1, 2). In addition to being a probable cause of spontaneous mutations (3, 4), AP sites have been implicated as a common mutagenic lesion created by a number of DNA-damaging agents (reviewed in ref.

Ionizing radiation-induced mutagenesis

“…AP sites AP sites in DNA arise spontaneously through depurination (Lindahl & Nyberg, 1972 Kunkel, 1984;Miller & Low, 1984;Gentil et al, 1984;Loeb, 1985;Granger-Schnarr, 1986;Cunningham et al, 1986;Loeb & Preston, 1986;Foster & Davis, 1987). Analysis of DNA synthesis on templates containing AP sites has shown that dAMP residues are preferentially introduced opposite these lesions (Boiteux & Laval, 1982;Strauss et al, 1982;Schaaper et al, 1983;Kunkel, 1984).…”

“…Church and Gilbert (1984) can be used in mutation studies. An alternative would be to amplify the region of interest (Saiki et al, 1985 (Lindahl, 1982;Cunningham et al, 1986;Smith, 1987;Foster & Davis, 1987;Yatagai et al, 1987). Some of the DNA-repair systems involved in the correction of alkylation damage and complex lesions are present in very small amounts intracellularly, but are inducible in E. coli (Witkin, 1976;Lindahl, 1982;Walker, 1984).…”

An analysis of the mutagenicity of 1,2-dibromoethane to Escherichia coli: Influence of DNA repair activities and metabolic pathways

“…True revertants of hisG428 were first identified by the transfer of the His + phenotype upon mating and then were sequenced (Foster and Davis, 1987). Suppressor tRNAs of hisG428 were identified by their ability to suppress known ochre mutations in the lacI gene, as has been described (Foster and Eisenstadt, 1985).…”

“…All E. coli strains used in this study are derivatives of PF260 (= F − ara Δ (gpt-lac-pro) thiA Δhis5 supD60; Foster and Davis, 1987). Construction of DNA repair-deficient derivatives was as previously described for uvrB5 (Foster et al, 1983), ΔxthA and umuC122::Tn5 (Foster and Davis, 1987).…”

“…The targets for mutagenesis were the hisG46 and hisG428 loci from the Ames Salmonella typhimurium tester strains, carried on F′ episomes (Foster and Davis, 1987). hisG46 is a CCC codon that can be reverted by any base change at the first base and by GC to AT transitions and GC to TA transversions at the second base of the codon (Miller and Barnes, 1986).…”