Tumor antigen activity in viral DNA-protein complexes from cells productively infected with papovaviruses

A polypeptide with a molecular weight in the range from 70,000 to 90,000 daltons, previously identified in DNA-protein complex isolated from polyoma virus- and SV40-infected cells, was isolated after deoxyribonuclease treatment of the complex followed by extensive dialysis and hydroxylapatite chromatography. The nonstructural protein was specifically retained by columns of protein A-Sepharose CL-4B onto which antibodies directed against SV40 T-antigen had been bound. T-antigen was unable to react with SV40-transformed cells in an immunofluorescence test. Finally the same antiserum reacted positively with the partially purified protein in the radioimmunoassay. These data are interpreted as indicating that, in productively infected cells, some of the nascent papovavirus DNA is complexed with T-antigen and viral structural polypeptides.