Evidence that the Rous sarcoma virus transforming gene product phosphorylates phosphatidylinositol and diacylglycerol.

The ability of purified Rous sarcoma virus transforming gene product, pp60v-src, to phosphorylate phosphatidylinositol and diacylglycerol was investigated. Phosphatidylinositol was phosphorylated to form both mono- and diphosphorylated derivatives. 1,2-Diacylglycerol was phosphorylated to form phosphatidic acid. These activities showed the same thermolability and the same sensitivity to inhibitors as shown by the casein kinase activity of pp60v-src. In addition, when serum-starved chicken embryo fibroblasts transformed by a virus mutant temperature-sensitive for transformation were shifted from the nonpermissive to permissive temperature, an increase of 50-100% in the labeling of phosphatidylinositol 4-phosphate, phosphatidylinositol 4,5-bisphosphate, and phosphatidic acid was observed, as compared to uninfected cells.