UV-reactivation, virus production and mutagenesis of SV40 in VU-irradiated monkey kidney cells.

The survival of UV-irradiated simian virus 40 (SV40) is higher in VU-irradiated than in non-irradiated monolayers of BSC-1 monkey cells. A similar reactivation is found when cells are infected with SV40-DNA, suggesting that reactivation acts on viral DNA. The enhanced reactivation of VU-irradiated SV40 and SV40-DNA is optimal when infection is delayed for 2--3 days after irradiation of the cells. UV-pretreated cells infected with SV40-DNA produce more virus than infected control cells; the time curve of this process is similar to that found for enhanced virus reactivation and suggests that facilitated virus production in UV-irradiated cells and enhanced virus reactivation might be manifestations of the same process. If the non-irradiated SV40 thermosensitive mutant BC245 is propagated in UV-irradiated BSC-1 cells the rate of back mutation to phenotypically wild-type is increased compared with that of the control. This suggests that an inducible error-prone system is functional in these cells. When the UV-irradiated tsBC245 is propagated in non-irradiated cells the reversion frequency is greatly enhanced, which suggest that either the introduction of UV-irradiated SV40-DNA is sufficient to induce an error-generating system, or that a constitutive error-prone mechanism is operative on this DNA.