The roles of DNA polymerases alpha, beta, and gamma in DNA repair synthesis induced in hamster and human cells by different DNA damaging agents.

Abstract

The involvement of DNA polymerases alpha, beta, and gamma in DNA repair synthesis was investigated in subcellular preparations of cultured hamster and human cells. A variety of DNA damaging agents, including bleomycin, neocarzinostatin, UV irradiation, and alkylating agents, were utilized to induce DNA repair. The sensitivity of repair synthesis, as well as replicative synthesis and purified DNA polymerase beta activity, to inhibition by the DNA polymerase inhibitors dideoxythymidine triphosphate, aphidicolin, cytosine arabinoside triphosphate, and N-ethylmaleimide was determined. No evidence was obtained for a major role of polymerase gamma in any type of repair synthesis. In both hamster and human cells, the sensitivity of bleomycin- and neocarzinostatin-induced repair synthesis to ddTTP inhibition was essentially identical with that observed for purified polymerase beta, indicating these repair processes proceeded through a mechanism utilizing polymerase beta. Repair synthesis induced by UV irradiation and alkylating agents was not sensitive to ddTTP, indicating repair of these lesions occurred through a pathway primarily utilizing a different DNA polymerase; presumably polymerase alpha. However, replicative synthesis was much more sensitive to polymerase alpha inhibitors than was repair synthesis induced by UV irradiation or alkylating agents. Neither the amount of DNA damage nor the amount of induced repair synthesis influenced the degree to which the different DNA polymerases were involved in repair synthesis. The possibility that "patch size" or the actual type of DNA damage determines the extent to which different polymerases participate in DNA repair synthesis is discussed.