Discontinuous and non-discontinuous subgenomic RNA transcription in a nidovirus.
Arteri-, corona-, toro- and roniviruses are evolutionarily related positive-strand RNA viruses, united in the order Nidovirales. The best studied nidoviruses, the corona- and arteriviruses, employ a unique transcription mechanism, which involves discontinuous RNA synthesis, a process resembling similarity-assisted copy-choice RNA recombination. During infection, multiple subgenomic (sg) mRNAs are transcribed from a mirror set of sg negative-strand RNA templates. The sg mRNAs all possess a short 5' common leader sequence, derived from the 5' end of the genomic RNA. The joining of the non-contiguous 'leader' and 'body' sequences presumably occurs during minus-strand synthesis. To study whether toroviruses use a similar transcription mechanism, we characterized the 5' termini of the genome and the four sg mRNAs of Berne virus (BEV). We show that BEV mRNAs 3-5 lack a leader sequence. Surprisingly, however, RNA 2 does contain a leader, identical to the 5'-terminal 18 residues of the genome. Apparently, BEV combines discontinuous and non-discontinuous RNA synthesis to produce its sg mRNAs. Our findings have important implications for the understanding of the mechanism and evolution of nidovirus transcription.
van Vliet
A L W
AL
Institute of Virology, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands.
Smits
S L
SL
Rottier
P J M
PJ
de Groot
R J
RJ
D001483:Base Sequence; D008969:Molecular Sequence Data; D012315:RNA Caps; D012326:RNA Splicing; D012333:RNA, Messenger; D017003:Torovirus / Q000235:genetics*; D014158:Transcription, Genetic
D012315:RNA Caps; D012333:RNA, Messenger