Studies into the Mechanism of MHV Transcription
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Coronaviruses are enveloped, plus-polarity RNA viruses which replicate by a unique mode of RNA transcription.1, 2, 3 Previous studies in our laboratory have indicated that RNA recombination occurs at very high frequency during mixed infection with two heterologous strains of MHV4, 5. These data, coupled with the presence of discrete larger leader-containing RNAs which range from 47 to 1000 nucleotides in length in MHV-infected cells,6 suggest that discrete RNA intermediates are synthesized during transcription which may dissociate and reassort between viral RNA templates to generate recombinant viruses by a copy-choice mechanism4. Therefore, the larger leader-containing RNAs in MHV-infected cells may represent functional intermediates of RNA transcription and recombination. In this paper, we have analyzed the origin, structure, and probable mechanism of synthesis of these RNAs. These data provide evidence that MHV RNA transcription pauses at sites corresponding to hairpin loops in the RNA template or product strands and that these RNA intermediates may dissociate and reassociate with the RNA template intermittently during the course of transcription.
KeywordsSmall RNAs Hairpin Loop Mouse Hepatitis Virus Hairpin Loop Structure Murine Coronavirus
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