Removal of T4 endonuclease V-sensitive sites from SV40 DNA after exposure to ultraviolet light.

The induction and removal of sites sensitive to T4 endonuclease V from ultraviolet-irradiated Simian Virus 40 (SV40) Form I (supercoiled) DNA during a lytic infection of monkey CV-1 cells was investigated by agarose tube gel electrophoresis. Endonuclease-sensitive sites were induced at a rate of 0.049 sites/SV40 genome per J/m2, or 1.4 sites/1 . 10(8) daltons of DNA per J/m2. This value is similar to the yield of endonuclease-sensitive sites and pyrimidine dimers in uninfected host CV-1 cell DNA. Removal of endonuclease-sensitive sites was dose dependent and non-linear for at least 24 h after irradiation. These results suggest that SV40 DNA is subject to the excision repair mechanisms of the host cell, and that the excision of pyrimidine dimers may be one of the biochemical events underlying host cell reactivation.