Yeast killer virus transcription initiation in vitro.

Killer virions isolated from infected Saccharomyces cerevisiae cells contain an RNA polymerase activity which catalyzes the transcription in vitro of positive polarity RNAs from the L-A and M double-stranded RNA genomic segments of the virus. The RNA polymerase can initiate transcription in vitro with gamma-thio-GTP, whose thiophosphate group is found on the 5' terminus of transcripts. Transcripts produced in vitro by the virion-associated RNA polymerase in the presence of 7mGpppG are significantly more active as translational templates than are transcripts produced in its absence. However, unlike Escherichia coli RNA polymerase transcripts from viral cDNA made in the presence of 7mGpppG, transcripts produced by viral RNA polymerase in the presence of 7mGpppG fail to bind to antibody against 7mG.