Stoichiometry of Cellular and Viral Components in the Polyomavirus Middle-T Antigen-Tyrosine Kinase Complex

Abstract

Our results indicate that only one type of tyrosine kinase is present within each middle-T antigen—tyrosine kinase complex, suggesting that middle-T antigen forms separate complexes with different tyrosine kinases. Furthermore, we determined that there is only one molecule of middle-T antigen within any one of these complexes. We interpret this to mean that in any given cell, polyomavirus transformation involves, at least in part, the simultaneous deregulation of a number of separate pathways controlling cellular proliferation. Finally, we also demonstrate that the separate middle-T:pp60^c-src and middle-T:pp59^c-fyn complexes are each able to interact with the same cellular p81/85-kDa phosphoprotein, a possible component of the phosphatidylinositol kinase.