2',3'-Dideoxythymidine 5'-triphosphate inhibition of DNA replication and ultraviolet-induced DNA repair synthesis in human cells: evidence for involvement of DNA polymerase .delta.

Abstract

It is well established that DNA replication and ultraviolet-induced DNA repair synthesis in mammalian cells are aphidicolin-sensitive and thus are mediated by one or both of the aphidicolin-sensitive DNA polymerases, .alpha. and/or .delta.. Recently, it has been shown that DNA polymerase .delta. is much more sensitive to inhibition by the nucleotide analogue 2'',3''-dideoxythymidine 5''-triphosphate (ddTTP) than DNA polymerase .alpha. but is less sensitive than DNA polymerase .beta. [Wahl, A. F., Crute, J. J., Sabatino, R. D., Bodner, J. B., Marraccino, R. L., Harwell, L. W., Lord, E., M., and Bambara, R. A. (1986) Biochemistry 25, 7821-7827]. We find that DNA replication and ultraviolet-induced DNA repair synthesis in permeable human fibroblasts are also more sensitive to inhibition by ddTTP than polymerase .alpha. and less sensitive than polymerase .beta.. The Ki for ddTTP of replication is about 40 .mu.M and that of repair synthesis is about 25 .mu.M. These are both much less than the Ki of polymerase .alpha. (which is greater than 200 .mu.M) but greater than the Ki of polymerase .beta. (which is less than 2 .mu.M). These data suggest that DNA polymerase .delta. participates in DNA replication and ultraviolet-induced DNA repair synthesis in human cells.