Abstract
Microinjection of purified protein kinase C (PKC) into Swiss 3T3 fibroblasts pretreated with the phorbol ester phorbol-12,13-dibutyrate restores the mitogenic response of the cells to phorbol-12,13-dibutyrate (G. Pasti, J.C. Lacal, B.S. Warren, S.A. Aaronson, and P.M. Blumberg, Nature [London] 324:375-377, 1986). Our present studies demonstrate that the mitogenic activity of the H-ras oncogene in H-ras p21-microinjected quiescent cells is markedly reduced under conditions in which PKC is downregulated by chronic phorbol ester treatment. The ability to reconstitute the mitogenic response upon microinjection of both H-ras p21 and PKC implies involvement of functional PKC in the mitogenic activity of the H-ras oncogene product.