The polymerase subunit of a dsRNA virus plays a central role in the regulation of viral RNA metabolism.
Bacteriophage &phi;6 has a three-segmented double-stranded (ds) RNA genome, which resides inside a polymerase complex particle throughout the entire life cycle of the virus. The polymerase subunit P2, a minor constituent of the polymerase complex, has previously been reported to replicate both &phi;6-specific and heterologous single-stranded (ss) RNAs, giving rise to dsRNA products. In this study, we show that the enzyme is also able to use dsRNA templates to perform semi-conservative RNA transcription in vitro without the assistance of other proteins. The polymerase synthesizes predominantly plus-sense copies of &phi;6 dsRNA, medium and small segments being more efficient templates than the large one. This distribution of the test-tube reaction products faithfully mimics viral transcription in vivo. Experiments with chimeric ssRNAs and dsRNAs show that short terminal nucleotide sequences can account for the difference in efficiency of RNA synthesis. Taken together, these results suggest a model explaining important aspects of viral RNA metabolism regulation in terms of enzymatic properties of the polymerase subunit.
Makeyev
E V
EV
Institute of Biotechnology and Department of Biosciences, PO Box 56, Viikinkaari 5, FIN-00014, University of Helsinki, Finland.
Bamford
D H
DH
D017126:Bacteriophage phi 6 / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D021122:Protein Subunits; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D021122:Protein Subunits; D012330:RNA, Double-Stranded; D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases