Role of the dinB gene product in spontaneous mutation in Escherichia coli with an impaired replicative polymerase.
We isolated several new mutator mutations of the Escherichia coli replicative polymerase dnaE subunit alpha and used them and a previously reported dnaE mutation to study spontaneous frameshift and base substitution mutations. Two of these dnaE strains produce many more mutants when grown on rich (Luria-Bertani) than on minimal medium. A differential effect of the medium was not observed when these dnaE mutations were combined with a mismatch repair mutation. The selection scheme for the dnaE mutations required that they be able to complement a temperature-sensitive strain. However, the ability to complement is not related to the mutator effect for at least one of the mutants. Comparison of the mutation rates for frameshift and base substitution mutations in mutS and dnaE mutS strains suggests that the mismatch repair proteins respond differently to the two types of change. Deletion of dinB from both chromosome and plasmid resulted in a four- to fivefold decrease in the rate of frameshift and base substitution mutations in a dnaE mutS double mutant background. This reduction indicates that most mistakes in replication occur as a result of the action of the auxiliary rather than the replicative polymerase in this dnaE mutant. Deletion of dinB from strains carrying a wild-type dnaE had a measurable effect, suggesting that a fraction of spontaneous mutations occur as a result of dinB polymerase action even in cells with a normal replicative polymerase.
Strauss
B S
BS
Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA. bs19@midway.uchicago.edu
Roberts
R
R
Francis
L
L
Pouryazdanparast
P
P
D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D020137:Base Pair Mismatch; D004258:DNA Polymerase III / Q000235:genetics* / Q000378:metabolism; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D016368:Frameshift Mutation; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D008969:Molecular Sequence Data; D051719:MutS DNA Mismatch-Binding Protein; D016297:Mutagenesis, Site-Directed; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; C074904:DNA polymerase III, alpha subunit; D004258:DNA Polymerase III; D019951:DNA Polymerase beta; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli