Effects of protease inhibitors on chemical induction of type C virus.

A role for proteolysis during chemical induction of endogenous xenotropic Type C virus from Kirsten sarcoma virus-transformed mouse cells was examined. Two distinct classes of protease inhibitors, the trypsin inhibitor, alpha-N-tosyl-L-lysine chloromethyl ketone, and two naturally occurring oligopeptide inhibitors, antipain and leupeptin, were found to inhibit induction of virus by cycloheximide and histidinol. Virus activation by 5-iododeoxyuridine was inhibited to a lesser degree. During the time cells were exposed to these compounds, there was little inhibition of [3H]uridine incorporation into total cellular RNA or polyadenylic acid cytoplasmic messenger RNA, suggesting that inhibition of proteolysis, and not RNA transcription, was responsible for blocking virus induction.