Replication of tobacco mosaic virus: VI. Replicative intermediate and TMV-RNA-related RNAs associated with polyribosomes

Polyribosomes prepared from both the membrane (bound polyribosomes) and cytoplasmic (free polyribosomes) fractions of tobacco mosaic virus (TMV)-infected tobacco leaves were found to contain small RNAs of several sizes which, by molecular hybridization with denatured double-stranded TMV-RNA, were shown to consist of portions of the TMV-RNA genome. In addition, full-length (30 S) TMV-RNA was found on the free but not the bound polyribosomes. These RNAs were associated with all sizes of polyribosomes as analyzed on sucrose gradients, with the larger species of RNA predominating the regions containing the larger polyribosomes. A heterogeneous population of replicative intermediate molecules was associated with the bound, but not the free polyribosomes. Here, too, the molecules were distributed throughout the polyribosome gradient. The possible functions of the ribosome-associated RNAs as messenger RNAs for viral-coded proteins are discussed.