The same normal cell protein is phosphorylated after transformation by avian sarcoma viruses with unrelated transforming genes

The phosphorylation of a normal cellular protein of molecular weight 34,000 (34K) is enhanced in Rous sarcoma virus-transformed chicken embryo fibroblasts apparently as a direct consequence of the phosphotransferase activity of the Rous sarcoma virus-transforming protein pp60(src). We have prepared anti-34K serum by using 34K purified from normal fibroblasts to confirm that the transformation-specific phosphorylation described previously occurs on a normal cellular protein and to further characterize the nature of the protein. In this communication, we also show that the phosphorylation of 34K is also increased in cells transformed by either Fujinami or PRCII sarcoma virus, two recently characterized avian sarcoma viruses whose transforming proteins, although distinct from pp60(src), are also associated with phosphotransferase activity. Moreover, comparative fingerprinting of tryptic phosphopeptides shows that the major site of phosphorylation of 34K is the same in all three cases.