Altered sites of tyrosine phosphorylation in pp60c-src associated with polyomavirus middle tumor antigen.
We characterized the tyrosine phosphorylation sites of free pp60c-src and of pp60c-src associated with the polyomavirus middle tumor antigen (mT) in transformed avian and rodent cells. The sites of tyrosine phosphorylation in the two populations of pp60c-src were different, both in vitro and in vivo. Free pp60c-src was phosphorylated in vitro at a single site, tyrosine 416. pp60c-src associated with mT was phosphorylated in vitro on tyrosine 416 and on one or more additional tyrosine residues located in the amino-terminal region of the molecule. Free pp60c-src in polyomavirus mT-transformed cells was phosphorylated in vivo on tyrosine 527. In contrast, pp60c-src associated with mT was phosphorylated in vivo on tyrosine 416 and not detectably on tyrosine 527. Thus, the in vivo phosphorylation sites of pp60c-src associated with mT in transformed cells are identical to those of pp60v-src, the Rous sarcoma virus transforming protein. The results suggest that altered phosphorylation of pp60c-src associated with mT may play a role in the enhancement of the pp60c-src protein kinase activity and in cell transformation by polyomavirus.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D002642:Chick Embryo; D009052:Leukemia Virus, Murine / Q000235:genetics*; D051379:Mice; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D010449:Peptide Mapping; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src); D014357:Trypsin; D014443:Tyrosine
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D009856:Oncogene Proteins, Viral; D011518:Proto-Oncogene Proteins; D014443:Tyrosine; D016392:Proto-Oncogene Proteins pp60(c-src); D014357:Trypsin