title: Relationship between cellular RecA protein concentration and untargeted mutagenesis in Escherichia coli.
abstract: We measured the production of untargeted mutations in the cI and cII genes of untreated lambda phage undergoing a lytic cycle in UV-irradiated bacterial hosts. As previously shown, treatment with 4 micrograms/ml of rifampicin during post-irradiation incubation inhibited amplification of the RecA protein in these cells. In addition, we observed a decreased mutation rate compared to the untreated, irradiated bacteria. Treatment with 4 micrograms/ml or 8 micrograms/ml rifampicin did not prevent the UV induction of the umuDC operon, as judged by assay of beta-galactosidase activity in a umuC-lacZ fusion strain. In contrast, the UV-induction of beta-galactosidase in the sulA-lacZ fusion strain was decreased by 4 micrograms/ml rifampicin. The inhibition of untargeted mutagenesis by this drug treatment was also observed in a strain constitutive for SOS functions (lexA (Def)) as well as in a RecA-overproducing plasmid strain, suggesting the requirement of other factor(s) in wild-type recA+ cells. An htpR165-carrying strain, that blocks induction of heat-shock proteins, exhibited normal UV-promoted mutagenesis. A correlation was observed between the cellular concentration of RecA protein, increased spontaneously by a temperature shift in a lexA(Ts) strain, and the extent of UV-promoted untargeted mutagenesis. These results suggest a mechanistic role of RecA protein in this process.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D010582:Bacteriophage lambda / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial / Q000528:radiation effects; D005814:Genes, Viral / Q000528:radiation effects; D006360:Heat-Shock Proteins / Q000502:physiology; D009154:Mutation; D011938:Rec A Recombinases / Q000032:analysis / Q000502:physiology*; D012293:Rifampin / Q000494:pharmacology; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D014466:Ultraviolet Rays; D014764:Viral Proteins / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D014764:Viral Proteins; D011938:Rec A Recombinases; D012293:Rifampin