Coronavirus mRNA synthesis involves fusion of non-contiguous sequences.

Abstract

Positive‐stranded genomic RNA of coronavirus MHV and its six subgenomic mRNAs are synthesized in the cytoplasm of the host cell. The mRNAs are composed of leader and body sequences which are non‐contiguous on the genome and are fused together in the cytoplasm by a mechanism which appears to involve an unusual and specific ‘polymerase jumping’ event.

Coding Sequence of Coronavirus MHV-JHM mRNA 4

“…This is identical to the sequence found in the intergenic region of MHV, between genes 6 and 7 (Spaan et al, 1983), and differs by one base from the sequence upstream of gene 6 (AAUCCAAAC; M. A. Skinner, unpublished).…”

“…These RNA species form a nested set, each RNA having 3' sequences in common with all smaller RNAs. At the 5' end, each mRNA bears a common leader of about 70 bases derived from the 5' end of the genome (Lai et al, 1983;Spaan et al, 1983;Skinner & Siddell, 1983;Armstrong et al, 1984a). Translation studies in vitro and in oocytes have shown that the primary translation products that give rise to the three virion structural proteins, peplomer (150K), membrane (26K) and nucleocapsid (50K), are produced from mRNAs 3, 6 and 7, respectively (Rottier et al, 1981 ;Siddell et al, 1981 ;Leibowitz et al, 1982).…”

“…that portion not found in the next smallest mRNA. Sequencing of mRNA 7 (Skinner & Siddell, 1983) and of mRNA 6 (Armstrong et al, 1984b;M. A. Skinner, unpublished) has indeed shown that most of the available unique sequence is used as coding sequence, except for a long 3' non-coding sequence at the end of mRNA 7.…”

“…A primer (3'-ATTAGATTTGA-5', Pharmacia P-L Biochemicals), complementary to a sequence just upstream of the initiating codon for the nucleocapsid protein (Skinner & SiddeU, 1983) was used to synthesize cDNA from poly(A)-containing RNA isolated from Sac(-) cells infected with MHV-JHM as previously described (Skinner & Siddell, 1983). Methods used for the synthesis and cloning of double-stranded cDNA as well as for the characterization and chain-terminator sequencing of the cloned cDNA have been described previously (Skinner & SiddeU, 1983).…”

Sequence analysis of the 3′ end of the feline coronavirus FIPV 79-1146 genome: Comparison with the genome of porcine coronavirus TGEV reveals large insertions

“…Furthermore, these results suggest that the body of RNA 6 has a length of 1212 nucleotides, provided that there are no additional insertions. Assuming an RNA leader sequence of 60-70 nucleotides (Spaan et al, 1983;Lai eta/., 1984;Brown eta/., 1984) and a poly(A) tail of about 100 nucleotides we arrive at a predicted length of approximately 1400 nucleotides. Previously, RNA 6 was estimated to be 1600 nucleotides (de Groot et aL, 1987a).…”