Stimulation of the nuclear uracil DNA glycosylase in proliferating human fibroblasts.

The cell cycle stimulation of individual species of the uracil DNA glycosylase was examined in WI-38 normal diploid fibroblasts. The nuclear uracil DNA glycosylase was induced as WI-38 cells traversed the cell cycle. In contrast, the specific activity of the mitochondrial glycosylase remained constant during cell proliferation. The two enzyme activities can be further distinguished by their elution patterns on DNA-cellulose, by differential cation sensitivity, and by kinetic differences. The singular stimulation of the nuclear glycosylase in the cell cycle is a further suggestion that normal human cells actively regulate excision repair pathways.