title: Mutation frequency decline in MMS-treated Escherichia coli K-12 mutS strains.
abstract: It has been shown that the decline in mutant frequency (MFD) (argE3(ochre)-->Arg+) which occurs in MMS-treated and then transiently starved AB1157 Escherichia coli K-12 cells concerns revertants which arose by supL suppressor formation in a process which is umuDC dependent. Here we have examined whether MMS-induced Arg+ revertants are susceptible to decline when bacteria are deficient in mismatch repair. We show that there is an absence of MFD in MMS-treated M1 (mutS) and in EC2416 (mutS delta umuDC) cells defective in mismatch repair which is associated with a change in the spectrum of MMS-induced mutations formed. In contrast to AB1157, transformation of M1 (mutS) bacteria with plasmids harbouring various combinations of umuD(D')C genes does not enhance the level of MMS-induced mutations but may influence the proportion of supL mutations. These supL mutations show MFD. Repair processes under MFD conditions were confirmed by analysis of plasmid DNA isolated from MMS-treated bacteria at different stages of their starvation and digestion with Fpg protein.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warszawa, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Grzesiuk
authors.forename: C
authors.initials: C
authors.lastname: Janion
mesh_terms: D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000187:drug effects* / Q000235:genetics; D004260:DNA Repair / Q000187:drug effects*; D004268:DNA-Binding Proteins; D004259:DNA-Directed DNA Polymerase; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D008741:Methyl Methanesulfonate / Q000633:toxicity*; D051719:MutS DNA Mismatch-Binding Protein; D016296:Mutagenesis / Q000187:drug effects; D009153:Mutagens; D009154:Mutation / Q000187:drug effects*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009153:Mutagens; C078202:UmuC protein, E coli; D008741:Methyl Methanesulfonate; D004259:DNA-Directed DNA Polymerase; C055218:UmuD protein, E coli; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli