Cleavage of Rous sarcoma viral polypeptide precursor into internal structural proteins in vitro involves viral protein p15.

The polypeptide precursor pr76 to the internal viral group specific (gs) antigen proteins of Rous sarcoma virus, synthesized in a cell-free system of ascites cells, has been processed in vitro into the viral proteins by purified viral protein p15 as well as by disrupted Rous sarcoma virus. Disrupted Rauscher murine leukemia virus does not stimulate the cleavage process in vitro. Autocatalytic cleavage of the polypeptide precursor pr76 or Rous sarcoma virus, which contains the peptide sequence of p15, is not observed.