Involvement of DNA polymerases in the repair of DNA damage by benzo[a]pyrene in cultured Chinese hamster cells.

Mechanisms for induction of single-strand scissions in DNA by S9-activated benzo[a]pyrene (B[a]P) and their repair in cultured Chinese hamster V79 cells were investigated with inhibitors of DNA-repair synthesis using alkaline sucrose gradient sedimentation analysis. The marked induction of single-strand scissions in DNA was observed following 3 h treatment of V79 cells with 5 micrograms/ml of B[a]P. These DNA lesions were repaired to the control level within 4 h after removal of B[a]P. The simultaneous addition of inhibitors of DNA-repair synthesis. 1-beta-D-arabinofuranosylcytosine (araC) plus hydroxyurea with B[a]P did not increase the formation of DNA single-strand scissions. When these inhibitors were added after removal of B[a]P, however, they significantly blocked the rejoining of DNA-strand scissions. On the other hand, when aphidicolin, a specific inhibitor of DNA polymerase alpha, was used instead of araC, a partial inhibition of the rejoining was observed, and further addition of 2',3'-dideoxythymidine, an inhibitor of DNA polymerase beta, augmented the inhibitory effect. These results indicate that B[a]P-induced single-strand scissions of DNA in V79 cells could be repaired mostly by excision repair which involved DNA polymerase alpha and a non-alpha polymerase, presumably polymerase beta.