The formation of virus polyribosomes in L cells infected with vaccinia virus.

The fate of early virus messenger RNA in the cytoplasm of vaccinia-infected L cells has been studied during the first hour after infection. The RNA is made in the virus core structure from which it is rapidly released. It accumulates in the polyribsome fraction, where at least 75% is bound to ribosomes through an EDTA-sensitive link. Three distinct structures have been identified as possible intermediates in virus polyribosome formation. The first is a ribonucleoprotein complex (RNP) in which virus RNA is associated with cellular proteins. A complex having apparently similar properties, is formed when virus RNA is added to a cytoplasmic extract in vitro. The other two structures may consist of an RNP moiety associated with the small ribosomal subunit, or with a single ribosome. At least part of the RNA isolated as RNP appears to be a precursor of the virus messenger found in polyribosomes.