title: Phosphorylation of middle T by pp60c-src: a switch for binding of phosphatidylinositol 3-kinase and optimal tumorigenesis.
abstract: Substitution of phenylalanine for tyrosine 315 of the polyoma virus middle T (mT) protein lowers the incidence and limits the spectrum of tumors induced following inoculation of the virus into newborn mice. This substitution removes the major site of phosphorylation by pp60c-src without altering the ability of mT to associate with or to activate pp60c-src. The mutant mT fails to show binding of a phosphatidylinositol 3-kinase (Ptdlns 3-kinase) activity that is normally present in wild-type mT complexes. Furthermore, an anti-peptide antiserum that specifically recognizes mT lacking phosphate at tyrosine 315 precipitates binary (mT-pp60c-src) but not ternary (mT-pp60c-src-Ptdlns 3-kinase) complexes from wild-type infected cell extracts. Reprecipitation with either anti-pp60c-src or anti-mT serum brings down ternary complexes containing mT phosphorylated on tyrosine 315. Phosphorylation of mT by pp60c-src in vivo is therefore a critical event for binding of Ptdlns 3-kinase and for expression of the full tumorigenic potential of the virus.
authors.affiliation: Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: D A
authors.initials: DA
authors.lastname: Talmage
authors.forename: R
authors.initials: R
authors.lastname: Freund
authors.forename: A T
authors.initials: AT
authors.lastname: Young
authors.forename: J
authors.initials: J
authors.lastname: Dahl
authors.forename: C J
authors.initials: CJ
authors.lastname: Dawe
authors.forename: T L
authors.initials: TL
authors.lastname: Benjamin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism*; D001665:Binding Sites; D002471:Cell Transformation, Neoplastic / Q000378:metabolism; D002472:Cell Transformation, Viral; D004789:Enzyme Activation / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D014412:Tumor Virus Infections / Q000201:enzymology / Q000209:etiology / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000952:Antigens, Polyomavirus Transforming; D014638:Vanadates; D014443:Tyrosine; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D015688:Oncogene Protein pp60(v-src)