Abstract
Seven virus-specific, polyadenylated RNA species have been identified in mouse cells infected with the murine coronaviruses MHV-A59 (A59V) or MHV-JHM (JHMV). MHV-infected 17CL·1 cells were labeled with [(32)P]orthophosphate in the presence of actinomycin D and the cytoplasmic RNA was extracted and analyzed by agarose gel electrophoresis. These RNA species range in size from 6.3 × 10(5) to 6.1 × 10(6) daltons. The A59V and JHMV-specific RNAs have identical molecular weights and comigrate in agarose gels. The largest intracellular RNA species is identical to RNA isolated from purified virions, as determined by agarose gel electrophoresis and oligonucleotide fingerprint studies of ribonuclease T(1) digests. Oligonucleotide fingerprints of the six subgenomic RNAS show that the sequences they contain are present in virion RNA, confirming their virus-specific nature. The fingerprinting studies also demonstrate that the six subgenomic RNA species make up a nested set. The sequences present in each RNA species are also present in all larger RNA species. These larger RNAs also contain additional sequences consistent with their greater size. The subgenomic RNAs fulfull many of the criteria for mRNAs. Possible mechanisms for generating these RNAs are discussed.