Fast inducible repair of microinjected UV-irradiated SV40 DNA in monkey kidney cells

In monkey kidney cells (TC-7), microinjected with UV-irradiated (103-362 J/m2) SV40 DNA, the expression of viral antigens decreases in a UV-dose-dependent manner and the viral genes are not repaired constitutively. When the viral DNA is microinjected 4 h after UV-irradiation (40 J/m2) of host cells, the expression of viral antigens is restored in all cells. The time course of restoration of viral gene expression function shows that in UV-irradiated cells the repair is induced rapidly and fully within 2 h and the induced state is maintained for 24 h. Intact viral DNA molecules, microinjected during the period of induction of cellular UV repair, are expressed less efficiently than UV-irradiated viral genomes.