Coronavirus transcription: a perspective.
At the VIth International Symposium on Corona and Related Viruses held in Quebec, Canada in 1994 we presented a new model for coronavirus transcription to explain how subgenome-length minus strands, which are used as templates for the synthesis of subgenomic mRNAs, might arise by a process involving discontinuous RNA synthesis. The old model explaining subgenomic mRNA synthesis, which was called leader-primed transcription, was based on erroneous evidence that only genome-length negative strands were present in replicative intermediates. To explain the discovery of subgenome-length minus strands, a related model, called the replicon model, was proposed: The subgenomic mRNAs would be produced initially by leader-primed transcription and then replicated into minus-strand templates that would in turn be transcribed into subgenomic mRNAs. We review the experimental evidence that led us to formulate a third model proposing that the discontinuous event in coronavirus RNA synthesis occurs during minus strand synthesis. With our model the genome is copied both continuously to produce minus-strand templates for genome RNA synthesis and discontinuously to produce minus-strand templates for subgenomic mRNA synthesis, and the subgenomic mRNAs do not function as templates for minus strand synthesis, only the genome does.
Sawicki
S G
SG
Department of Microbiology, Medical College of Ohio, Toledo, OH 43614, USA. ssawicki@mco.edu
Sawicki
D L
DL
D000818:Animals; D016679:Genome, Viral; D051379:Mice; D006517:Murine hepatitis virus / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D014158:Transcription, Genetic