Presence of leader sequences in the mRNA of mouse hepatitis virus

Abstract

To determine the structure and the mechanism of synthesis of mouse hepatitis virus mRNA, the map positions of the large RNase T1-resistant oligonucleotides of the seven mouse hepatitis virus strain A59 intracellular mRNA species were studied. We found that all but one of the oligonucleotides were mapped at the positions within each mRNA consistent with the nested-set, stairlike structure of mouse hepatitis virus mRNA (Lai et al., J. Virol. 39:823-834). However, one oligonucleotide, 10, was mapped near the 5' ends of every mRNA and virion genomic RNA. In other words, oligonucleotide 10 and, therefore, the sequences around the 5' ends of the mRNAs are not colinear with the genomic sequences. Because this oligonucleotide is present only once in the genomic RNA, this result indicates that oligonucleotide 10 is not transcribed from multiple sites on the genomic template, but rather represents a leader RNA sequence which is joined to the body sequences of the different mRNAs during mRNA transcription. This provides the most direct evidence thus far for the presence of leader sequences in the mRNAs of mouse hepatitis virus, which is a cytoplasmic virus. Several possible mechanisms of RNA synthesis are discussed.

Coronavirus cis-Acting RNA Elements

“…Following transfer of the nascent minus strand from its downstream position on the template (at the TRS-B) to the TRS-L close to the 5 0 end of the genome, negative-strand RNA synthesis is resumed and completed by copying the 5 0 leader sequence. The resulting set of 3 0 antileadercontaining sg minus-strand RNAs is subsequently used as templates for the production of the characteristic nested set of 5 0 leader-containing mRNAs in coronavirus-infected cells (Lai et al, 1983;Sawicki and Sawicki, 1995;Sawicki et al, 2001;Sethna et al, 1989;Spaan et al, 1983). Sg minus-strand RNAs contain a U-stretch at their 5 0 end, providing a possible template for 3 0 polyadenylation of sg mRNAs Wu et al, 2013).…”

Analysis of genomic and intracellular viral RNAs of small plaque mutants of mouse hepatitis virus, JHM strain

“…These experiments also identify for the first time oligonucleotide 8 as being derived from sequences which are encompassed within the leader of MHV-JHM. Also in each subgenomic RNA of MHV-JHM (with the exception of RNAZ) oligonucleotides can be identified which are not found in genomic RNA and it can be assumed that these "unique" oligonucleotides have arisen from the combination of sequences during the, synthesis of mRNAs involving the joining of leader and body transcripts (Lai et aL, 1983b;Spaan et aL, 1933). It is interesting to note that at least for some of the subgenomic RNAs (e.g., RNA7 and RNAG) these "unique" oligonucleotide are apparently very similar in their electrophoretic behavior, suggesting that the sequences combined during RNA synthesis may be very similar.…”

RNA structure analysis of alphacoronavirus terminal genome regions

“…Guided by basepairing interactions between the negative-strand complement of a TRS-B and the TRS located downstream of the 5 leader on the viral genome ("leader TRS", TRS-L), the nascent minus strand may be transferred from its downstream position on the template (at the TRS-B) to the TRS-L, where negative-strand RNA synthesis is then resumed and completed by copying the 5 leader sequence. The set of 3 antileader-containing sg minus-strand RNAs is subsequently used as templates for the production of the characteristic nested set of 5 capped, 5 leader-containing and 3 -polyadenylated sg mRNAs in coronavirus-infected cells (Lai et al, 1983;Sawicki et al, 2001;Sawicki and Sawicki, 1995;Sethna et al, 1989;Spaan et al, 1983). Sg minus-strand RNAs contain a U-stretch at their 5 end, thus providing a template for 3 polyadenylation of sg mRNAs Wu et al, 2013).…”