Characterization of pp85, a target of oncogenes and growth factor receptors.
An 85,000-molecular-weight polypeptide (85K polypeptide) has previously been identified as a common substrate for tyrosine phosphorylation upon polyomavirus middle T transformation or upon platelet-derived growth factor stimulation of 3T3 cells. In each case, pp85 has an associated phosphatidylinositol kinase activity. The tissue distribution of pp85 was determined by middle T blotting experiments; the highest levels were found in brain, lung, and spleen tissues. High-resolution examination of 85K by isoelectric focusing demonstrated that there are at least 10 different forms. These were resolved into two families, 85K and 86K; the ratio of the two families changed in different cells. Similar forms were found for pp85 associated with pp60v-src. Individual species within each family differed by phosphorylation. Analysis of pp85 and pp86 by immunoprecipitation with anti-phosphotyrosine antibody showed increasing phosphorylation in response to middle T or pp60v-src transformation. The association of middle T with pp85 and pp60c-src was examined in pulse-chase experiments. Association of middle T with pp60c-src was slow and was accompanied by progressive modification of middle T. pp85 formed a dissociable complex with middle T within 2.5 min.
Cohen
B
B
Department of Biochemistry, Tufts University Health Sciences Campus, Boston, Massachusetts 02111.
Liu
Y X
YX
Druker
B
B
Roberts
T M
TM
Schaffhausen
B S
BS
D019870:1-Phosphatidylinositol 4-Kinase; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics* / Q000302:isolation & purification; D001358:Avian Sarcoma Viruses / Q000235:genetics; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D006133:Growth Substances / Q000378:metabolism; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051379:Mice; D008970:Molecular Weight; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D009928:Organ Specificity; D010449:Peptide Mapping; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism; D014422:Turkeys
D000952:Antigens, Polyomavirus Transforming; D006133:Growth Substances; D007527:Isoenzymes; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase; D015688:Oncogene Protein pp60(v-src)