Mutation frequency decline in MMS-treated Escherichia coli K–12 mutS strains

• Published in: Mutagenesis 1998-03, Vol.13 (2), p.127-132
• Main Authors: Grzesiuk, Elzbieta, Janion, Celina
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases; Bacterial Proteins - biosynthesis; Bacterial Proteins - drug effects; Bacterial Proteins - genetics; Biological and medical sciences; Chemical mutagenesis; DNA Repair - drug effects; DNA-Binding Proteins; DNA-Directed DNA Polymerase; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli Proteins; Medical sciences; Methyl Methanesulfonate - toxicity; Mutagenesis - drug effects; Mutagens; Mutation - drug effects; MutS DNA Mismatch-Binding Protein; Toxicology
• ISSN: 0267-8357; 1464-3804
• DOI: 10.1093/mutage/13.2.127

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 Ml (mutS) and in EC2416 (mutS Δ 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 Ml (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.