title: Association of a murine 53,000-dalton phosphoprotein with simian virus 40 large-T antigen in transformed cells.
abstract: Serum raised against a mouse 53,000-dalton (53K) phosphoprotein precipitates both the 53K immunogen and simian virus 40 large-T from lysates of simian virus 40-transformed 3T3 cells. This serum, designated F5, does not recognize antigenic determinants on native or denatured large-T and precipitates large-T because the 53K phosphoprotein forms a stable complex with large-T. This complex sediments at 23S on sucrose density gradients, corresponding to a molecular weight of 600K to 1,000K, and appears to contain only 53K and large-T as major components. It is held together by noncovalent bonds and is located in the cell nucleus. All the 53K immunoprecipitated from cell lysates by F5 is present in the high-molecular-weight complex, but large-T can be separated into a complexed and a free form on sucrose density gradients. The complexed form of large-T is more readily phosphorylated than the free form. We have been unable to detect an association of large-T with comparable host cell proteins during productive infections with simian virus 40.
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D055598:Chemical Phenomena; D011232:Chemical Precipitation; D002621:Chemistry; D051379:Mice; D008970:Molecular Weight; D010750:Phosphoproteins / Q000032:analysis; D013539:Simian virus 40 / Q000276:immunology*
chemical_list: D000956:Antigens, Viral; D010750:Phosphoproteins