Coronavirus subgenomic minus-strand RNAs and the potential for mRNA replicons.

Abstract

The genome of the porcine tanmisible gastroenteritis coronavirus is a plus-stand, polyadenylylated, infectious RNA molecule of "'20 kilobases. During virus replication, seven subgenomic mRNAs are generated by what is thought to be a leader-primng mensm to form a 3'-coterminal nested set. By using radiolabeled, strand-specifc, synthetic oligodeoxynucleotide probes in RNA blot hybridization analyses, we have found a minus-strand counterpart for the genome and for each subgenomic mRNA species in the cytoplasm of infected cells. Subgenomic minus strands were found to be components of double-stranded replicative forms and in numbers that surpass full-length antigenome. We propose that subgenomic mRNA replication, in addition to leaderprimed transcription, is a significant mechanism of mRNA synthesis and that it functions to amplify mRNAs.

Evaluation of the role of heterogeneous nuclear ribonucleoprotein A1 as a host factor in murine coronavirus discontinuous transcription and genome replication

“…In vivo, it is questionable whether hnRNP A1 would have access to the negative-strand IGS, because intracellular negative-strand MHV RNA is entirely duplexed with its positive-strand counterpart (37), which is at least 10-fold more abundant (8). Additionally, elegant work with an infectious clone of the arterivirus equine arteritis virus has shown that if the IGS consensus sequence, in this case the five nucleotides 5Ј-UCAAC-3Ј, was completely changed at a given IGS to 5Ј-AGUUG-3Ј, then synthesis of the corresponding sgRNA was abolished.…”

“…1B). However, the exact nature of the discontinuous leader-body fusion step, whether it occurs during positive-strand or negative-strand RNA synthesis, and the significance of the negative-strand counterparts of the sgRNAs are all matters of controversy (8)(9)(10).…”

Sequences of 3' end of genome and of 5' end of open reading frame 1a of lactate dehydrogenase-elevating virus and common junction motifs between 5' leader and bodies of seven subgenomic mRNAs

“…However, the rules that determine the joining of the 5' leader to the bodies of the subgenomic mRNAs are not fully understood (Lai, 1990;Makino et al, 1991 ;Jeong & Makino, 1992;La Monica et al, 1992). Furthermore, the discoveries of subgenomic negative strands in coronavirus-infected cells (Hoffmann et al, 1990;Sawicki & Sawicki, 1990;Sethna et al, 1989) and of subgenomic mRNAs in purified virions (Sethna et al, 1989) suggest that the formation of the subgenomic mRNAs may be more complex than initially postulated and may involve the independent replication of the subgenomic mRNAs .…”

Toroviruses: replication, evolution and comparison with other members of the coronavirus-like superfamily

“…This implies that coronavirus subgenomic RNAs may function as replicons (Sawicki & Sawicki, 1990;Sethna et al, 1989), although the possibility of negativestranded, subgenomic dead-end products (Jeong & Makino, 1992) remains to be excluded.…”