DNA polymerase activities induced by polyoma virus infection of 3T3 mouse fibroblasts

Resting mouse 3T3 fibroblasts were stimulated to synthesize DNA either by infection with polyoma virus or by injection of fresh serum. Changes in the levels of DNA polymerase (alpha-, beta-, and gamma-enzymes) were measured in the cytoplasm and the cell nucleus. Both types of stimulation gave very similar increases for all three enzyme activities. In the cell nucleus, both alpha- and gamma-polymerases increased almost tenfold, whereas the beta-enzyme only was stimulated twofold. In the cytoplasm alpha- and gamma-polymerases increased two- to four-fold. Only insignificant amounts of the beta-enzyme were found in the cytoplasm.