Identification of DNA polymerases involved in DNA excision repair in diploid human fibroblasts.

We have used inhibitors to identify the DNA polymerases which are involved in DNA excision repair induced in confluent diploid human fibroblasts by several DNA damaging agents: UV radiation, N-acetoxy-2-acetylaminofluorene, N-methyl-N-nitrosourea, and bleomycin. We find that DNA repair synthesis involves both DNA polymerase alpha and a non-alpha DNA polymerase, probably polymerase beta. The fraction of repair synthesis mediated by each of the two polymerases is dependent on which DNA-damaging agent is administered and on the dose of damaging agent. Low doses of DNA damage induce DNA repair synthesis which is mediated to a great extent by a non-alpha DNA polymerase, and with an increasing dose of damage there is increasing participation of DNA polymerase alpha in repair synthesis. At high doses of damage, the fraction of repair synthesis mediated by DNA polymerase alpha reaches a maximal level which is dependent on the damaging agent; the maximal level of polymerase alpha involvement is about 80% for UV radiation and N-acetoxy-2-acetylaminofluorene, about 70% for N-methyl-N-nitrosourea, and about 40% for bleomycin.