title: The expression and properties of polyoma virus middle-T antigen in simian cells.
abstract: SV40 late replacement vectors containing the polyoma middle-T coding sequences have been constructed. Mixed hybrid virus stocks have been obtained through complementation with a defective SV40 helper genome (dl 1055) following DNA transfection into CV-1 cells. Middle-T antigen is expressed in the infected simian cells at about 5-10 fold higher levels than in polyoma virus-infected mouse cells and has the pp60c-src-associated tyrosine-specific protein kinase activity in vitro. However, the 'specific activity' of the kinase in extracts of the infected CV-1 cells is lower than that observed in polyoma infected 3T6 cell extracts. The half-life of middle-T antigen in the CV-1 cells is about 4 h but the in vitro kinase activity associated with middle-T has a half-life of at least 8 h and hence appears to be stabilized. The in vivo phosphorylated species of middle-T has been shown by sucrose gradient analyses to be largely distinct from the middle-T with associated protein kinase activity in vitro.
mesh_terms: D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D004262:DNA Restriction Enzymes; D004279:DNA, Viral / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005822:Genetic Vectors; D006207:Half-Life; D000882:Haplorhini; D009693:Nucleic Acid Hybridization; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000276:immunology; D010766:Phosphorylation; D010957:Plasmids; D011120:Polyomavirus / Q000201:enzymology / Q000235:genetics / Q000276:immunology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013539:Simian virus 40 / Q000235:genetics
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D009856:Oncogene Proteins, Viral; D011505:Protein-Tyrosine Kinases; D004262:DNA Restriction Enzymes