Monomer molecular weight of T antigen from simian virus 40-infected and transformed cells.

Abstract

T [tumor] antigens from SV 40 transformed and lytically infected cells were isolated by immunoprecipitation and their MW estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. T-antigen from SV40-transformed mouse and hamster cells had an apparent MW of 94,000 but that from several lines SV40-infected monkey cells was 84,000. In a wheat germ cell-free system, mRNA from either transformed or productively infected cells was translated into a 94,000 species. Experiments with the protease inhibitors L-1-(tosylamide-2-phenyl)ethylchloromethyl ketone HCl and N-.alpha.-p-tosyl-L-lysylchloromethyl ketone HCl suggested that the 84,000 species of T-antigen found in infected cells was derived from the larger species by proteolytic cleavage. The cleavage pathway probably involved a 2 step reaction with an 89,000 intermediate. The biological significance of the 2 molecular weight forms of T-antigen is unknown but the possibility that they have different physiological activities is discussed.