Inhibition of Rous sarcoma virus by α-amanitin: Possible role of cell DNA-dependent RNA polymerase form II

Abstract

The effect of α-amanitin, an inhibitor of the cell nuclear form II DNA-dependent RNA polymerase, on Rous sarcoma virus (RSV) synthesis in RSV-transformed cells was examined. Utilizing incorporation of [ 3H]uridine into virions as a sensitive measure of RSV synthesis and of inhibition of synthesis by α-amanitin, inhibition of virus production could be detected within 2 hr after addition of the toxin to the cells. Analysis of the appearance of newly labeled [ 3H]RNA onto polyribosomes showed early partial inhibition by the toxin at a rate similar to the rate of inhibition of RSV synthesis. Little if any inhibition of ribosomal RNA (rRNA), the product of the nucleolar form I DNA-dependent RNA polymerase, is detectable until several hours after the initial inhibition of RSV is observed. These data indicate that RSV requires the form II polymerase, or an enzyme with a similar sensitivity to α-amanitin, for replication.