Abstract
Interferon induces an activity which strongly inhibits the growth of is-1, an interferon-response mutant of mengovirus. This activity is not expressed in protected cells infected with either is+ (the wild-type parent) or vaccinia virus, or in cells infected with is-1 in the presence of actinomycin D. A failure of is-1 to shut off host RNA and/or protein synthesis could explain these observations. The present paper, however, shows that is-1 and is+ are equally effective in suppressing host syntheses, and suggests that is+ actively inhibits the interferon-mediated activity directed against is-1.