Differential interaction of temperature-sensitive simian virus 40 T antigens with tumor suppressors pRb and p53.

Previous studies have shown that simian virus 40 large T antigen transforms cells by binding and inactivating suppressors of cell cycle progression and tumor formation. Here, we characterize the interactions of five temperature-sensitive T antigens with the tumor suppressor proteins pRb and p53. All five mutant T antigens bind pRb at the nonpermissive temperature with efficiencies similar to that of wild-type T antigen. A single transformation-competent mutant, with a substitution of amino acid 186, binds p53 at the nonpermissive temperature. Four transformation-defective mutants, with a substitution at T antigen position 357, 422, 427, or 438, are temperature sensitive for the binding and inactivation of p53. Our findings provide a basis for understanding the behavior of cells transformed by temperature-sensitive T antigens.