title: A membrane-associated, carbohydrate-modified form of the v-abl protein that cannot be phosphorylated in vivo or in vitro.
abstract: Abelson murine leukemia virus encodes a transforming protein which contains tyrosine kinase activity and is phosphorylated in vivo and in vitro. We found that P160 and P160-derived virus strains expressed an additional, altered v-abl protein which could not be phosphorylated. The altered v-abl protein (L-v-abl) differed from the phosphorylated form (K-v-abl) in that it was glycosylated and localized exclusively to the membrane fraction. Tunicamycin inhibition of N-linked carbohydrate addition did not restore phosphorylation. It did, however, reveal that L-v-abl had additional sequences relative to K-v-abl. The coding sequences required for this region and for the expression of L-v-abl were identified by replacing sequences in the P120 virus genome, which did not express L-v-abl, with sequences from the P160 virus genome. The necessary sequences were localized to the Moloney murine leukemia virus-derived gag gene. Comparison between the in vitro altered P120 and wild-type P120 virus strains indicated that expression of L-v-abl did not increase the efficiency of lymphoid transformation. Although the biological role of L-v-abl is not clear, our analyses have revealed that a specific amino terminal gag sequence can prevent v-abl from acting as a kinase substrate and can alter the cellular localization and modification of v-abl. These properties distinguish L-v-abl from previously reported v-abl proteins.
mesh_terms: D000011:Abelson murine leukemia virus / Q000235:genetics*; D000818:Animals; D000956:Antigens, Viral / Q000235:genetics*; D001483:Base Sequence; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D015683:Gene Products, gag; D005796:Genes; D005814:Genes, Viral; D006023:Glycoproteins / Q000235:genetics*; D009052:Leukemia Virus, Murine / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D010957:Plasmids; D011494:Protein Kinases / Q000235:genetics; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases; D014415:Tunicamycin / Q000494:pharmacology; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D000956:Antigens, Viral; D015683:Gene Products, gag; D006023:Glycoproteins; D014764:Viral Proteins; D014415:Tunicamycin; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases