Abelson murine leukemia virus: characterization of a polyprotein containing phosphorylated component(s) encoded by newly acquired sequences.

A previously described 120,000 dalton polyprotein, P120, encoded by the Abelson strain of murine leukemia virus (AbLV) is compared to translational products representing the entire Moloney murine leukemia virus (MuLV) genome. Each of three [35S]-methionine tryptic present in Moloney-MuLV Pr65gag are also represented in Pr180gag-pol. Of these, one peptide corresponding to Moloney-MuLV p12, but neither of two p30 specific peptides are present in AbLV P120. None of the twelve remaining methionine containing peptides present in AbLV P120 appear to correspond to those of either Moloney-MuLV Pr82env. AbLV P120 and a 110,000 dalton polyprotein encoded by a second transforming isolate of mouse origin, designated AK-T8, are both shown to be highly phosphorylated. Sites of phosphorylation included known phosphorylated structural (p12) components, as well as components encoded by acquired cellular sequences. Immunoprecipitates of AbLV P120 obtained from either cells or pseudotype virions are shown to contain protein kinase activity which recognizes AbLv P120 as substrate. This activity may represent an intrinsic property of the polyprotein itself or represent a cellular enzyme associated with AbLV P120 in the form of an enzyme-substrate complex.