Strains of Escherichia coli possessing the pcbA1 mutation, a functional DNA polymerase I, and a temperature-sensitive mutation in DNA polymerase III can survive at the restrictive temperature (43°C) for DNA polymerase III. The mutation rate of the bacterial genome of such strains after exposure to either UV light or ethyl melthanesulfonate was measured by its rifampicin resistance or amino acid requirements. In addition, Weigle mutagenesis of preirradiated λ phage was also measured. In all cases, no increase in mutagenesis was noted at the restrictive temperature for DNA polymerase III. Introduction of a cloned DNA polymerase III gene returned the mutation rate of the bacterial genome as well as the Weigle mutagenesis to normal at 43°C. Using a recA-lacZ fusion, the SOS response after UV irradiation was measured and found to be normal at the restrictive and permissive temperature for DNA polymerase III, as was induction of λ prophage. Recombination was also normal at either temperature. Our studies demonstrate that a functional DNA polymerse III is strictly required for mutagenesis at a step other than SOS induction.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 1 1987|
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