Induction of an error-prone mode of DNA repair in UV-irradiated monkey kidney cells.

The survival of UV-irradiated simian virus 40 (SV40) on UV-irradiated monkey kidney CV-1P cells at 33 degrees was increased over survival on unirradiated cells. During this process - called induced-virus reactivation - the progeny virus yielded by UV-irradiated cells had a much higher mutation frequency than did the progeny from unirradiated cells. Mutation rates were quantified by using phenotypic reversion towards wild-type growth of an early (tsA 58) or a late (tsB 201) temperature-sensitive SV40 mutant. Analysis of SV40 revertant genomes indicated that no detectable deletions of additions were responsible for the reversion process. These results suggest that enzymes from UV-irradiated cells are able to replicate UV-irradiated DNA by an error-prone mode of DNA repair. Induced virus reactivation and error-prone replication are probably one of the expressions of SOS functions in mammalian cells.