Interferon inhibition of DNA synthesis in Swiss 3T3 cells: dissociation from protein kinase C activation.
We have examined the role of protein kinase C in the anti-proliferative effects of interferon in Swiss 3T3 cells. Treatment of these cells with interferon did not stimulate the phosphorylation of an acidic Mr 80,000 cellular protein which serves as a substrate for protein kinase C. In addition, interferon did not inhibit the binding of 125I-epidermal growth factor to specific receptors or induce the expression of the proto-oncogene, c-fos in Swiss 3T3 cells. Thus, interferon does not activate protein kinase C. Moreover, interferon can still inhibit DNA synthesis in protein kinase C down-regulated 3T3 cells, indicating that the presence of this phosphotransferase is not essential for the anti-proliferative effects of interferon.