Inhibition of influenza virus replication by -amanitin: mode of action.

The replication of influenza virus in chick embryo fibroblast cells is inhibited by alpha-amanitin added during the first 2 hr of infection at concentrations similar to those required to inhibit cellular DNA-dependent RNA polymerase form II in vivo. Of two periods of increased RNA synthesis observed in cells infected with influenza virus, only the first, occurring from 0 to 2 hr after infection, is sensitive to alpha-amanitin. During this early period, there is a stimulation of the activity of DNA-dependent RNA polymerase II of nuclei isolated from infected cells. The data suggest that DNA transcription mediated by polymerase II is essential for influenza virus replication.