Uncoupling RNA virus replication from transcription via the polymerase: functional and evolutionary insights.
Many eukaryotic positive-strand RNA viruses transcribe subgenomic (sg) mRNAs that are virus-derived messages that template the translation of a subset of viral proteins. Currently, the premature termination (PT) mechanism of sg mRNA transcription, a process thought to operate in a variety of viruses, is best understood in tombusviruses. The viral RNA elements involved in regulating this mechanism have been well characterized in several systems; however, no corresponding protein factors have been identified yet. Here we show that tombusvirus genome replication can be effectively uncoupled from sg mRNA transcription in vivo by C-terminal modifications in its RNA-dependent RNA polymerase (RdRp). Systematic analysis of the PT transcriptional pathway using viral genomes harboring mutant RdRps revealed that the C-terminus functions primarily at an early step in this mechanism by mediating both efficient and accurate production of minus-strand templates for sg mRNA transcription. Our results also suggest a simple evolutionary scheme by which the virus could gain or enhance its transcriptional activity, and define global folding of the viral RNA genome as a previously unappreciated determinant of RdRp evolution.
Wu
Baodong
B
Department of Biology, York University, Toronto, Ontario, Canada.
White
K Andrew
KA
D001483:Base Sequence; D018553:Cucumis sativus / Q000166:cytology / Q000378:metabolism; D004252:DNA Mutational Analysis; D019143:Evolution, Molecular; D016679:Genome, Viral; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011523:Protoplasts / Q000502:physiology; D012328:RNA Viruses / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017864:Tombusvirus / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014779:Virus Replication
D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase