Yeast viral RNA polymerase is a transcriptase

ScV-L is a simple double-stranded RNA virus of yeast, consisting of a 4.8 kilobase pair double-stranded RNA (L) encapsidated in isometric particles composed mainly of one polypeptide (ScV-Pl) of 88,000 daltons. L encodes ScV-Pl. There is a capsid-associated RNA polymerase that synthesizes in vitro predominantly single-stranded RNA. We show that this polymerase activity is a transcriptase, at the least one product of which is the mRNA for ScV-Pl. The transcript, like its template, is uncapped.