A role for proteolysis during chemical induction of endogenous xenotropic Type C virus from Kirsten sarcoma virustransformed mouse cells was examined. Two distinct classes of protease inhibitors, the trypsin inhibitor, α-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.


This work was supported by Contract N01-CO-75380 with the National Cancer Institute, NIH, Bethesda, Md. 20205.

This content is only available via PDF.