Involvement of DNA polymerase III in UV-induced mutagenesis of bacteriophage lambda.

It has been proposed that the mutation fixation processes stimulated by SOS induction result from an induced infidelity of DNA replication (Radman 1974). The aim of this study was to determine if mutator mutations in the E. coli DNA polymerase III might affect UV-induced mutagenesis. Using a phage lambda mutation assay which can discriminate between targeted and untargeted mutations, we show that the polC74 mutator mutation (Sevastopoulos and Glaser 1977) primarily affects untargeted mutagenesis, which occurs in a recA1 genetic background and is amplified in the recA+ genetic background. The polC74 mutation also increases the UV-induced mutagenesis of the bacterial chromosome. These results suggest that DNA polymerase III is involved in the process of UV-induced mutagenesis in E. coli.