Abstract
Three different inhibitors of RNA synthesis, actinomycin, alpha- amanitin and camptothecin, and five different inhibitors of protein synthesis were able to superinduce interferon production in human diploid fibroblasts treated with poly(rI).poly(rC). Camptothecin was shown to be a reversible inhibitor of virus induced interferon formation. It also substantially reduced the interferon yield from human diploid fibroblasts which had been superinduced with actinomycin D and cycloheximide. This suggests that the previously reported failure of camptothecin to inhibit interferon production in human diploid cells after induction with poly(rI).poly(rC) is the result of two mutually opposing effects: a marked inhibition of interferon messenger RNA synthesis, but a stimulation of the activity of the interferon messenger RNA that is formed.