Proliferation-dependent regulation of base excision repair in normal and SV-40 transformed human cells

The effect of SV-40 viral transformation of human cells on the proliferation-dependent regulation of base excision repair was examined. Normal human diploid WI-38 fibroblasts and SV-40 transformed WI-38 cells were used to examine whether the process of transformation perturbed the regulation of base excision repair. The regulation of excision repair enzymes in each cell type was examined by quantitating: the specific activities of the base excision repair enzymes uracil DNA glycosylase and hypoxanthine DNA glycosylase as a function of cell growth; and immunological analysis of the uracil DNA glycosylase using monoclonal antibodies to human uracil DNA glycosylase. In each cell type, both DNA glycosylase activities were increased as a function of cell proliferation; the extent of enhancement being greater in the transformed cells. As defined by ELISA and immunoblot analysis, the induced uracil DNA glycosylases in both cell types share the same determinants. Although other repair processes are altered upon SV-40 transformation, these results suggest that the proliferation-dependent regulation of these base excision repair enzymes is retained in SV-40 transformed human cells.