The transforming proteins of PRCII virus and Rous sarcoma virus form a complex with the same two cellular phosphoproteins

Abstract

P105 and P110, the presumptive transforming proteins of PRCII avian sarcoma virus, were found to be present in transformed chicken cells in 2 forms: as monomers and as part of a complex which contains both a 50,000-dalton [50 kD] and a 90 kD cellular phosphoprotein. The 90 kD cellular protein was found to be identical to 1 of the proteins in chicken cells whose synthesis is induced by stress. The 50-kD protein was found to contain phosphotyrosine when isolated from the complex and therefore may be a substrate for the tyrosine protein kinase activity which is associated with P105 and P110. These same 2 cellular phosphoproteins have previously been shown to be present in a complex with pp60src, the tyrosine protein kinase which is the transforming protein of Rous sarcoma virus. Not all avian sarcoma virus transforming proteins with associated tyrosine protein kinase activities form a complex efficiently with these cellular proteins. Little if any of P90, the putative transforming protein of Yamaguchi 73 virus, was found in a complex with the 50 kD and 90 kD cellular phosphoproteins.