VIRION
Non-enveloped, flexuous, filamentous,640 nm long and 12 nm in diameter.
GENOME
Linear ssRNA(+) genome of 6.5-7.5 kb in size. The 3' terminus is polyadenylated. Encodes at least 3 proteins.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. RNA-dependent RNA polymerase (RdRp) is translated directly from the genomic RNA. ORF2 protein is translated by subgenomic RNA. Capsid (CP) protein may be produced by cleavage of ORF1, but expression by a subgenomic RNA is more probable.
ENZYMES
- RNA-dependent RNA polymerase [Polyprotein]
- Alpha-type capping [Polyprotein]
- Polyprotein major protease (Peptidase C23) [Polyprotein]
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated as a monocistronic mRNA to produce the RdRp (encoded by the 5'-proximal ORF).
- Replication occurs in viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Internal subgenomic promoters are used to transcribe the sgRNAs. Traduction of these sgRNAs yields the capsid and movement proteins.
- Assembly of new virus particles.
- Movement protein allows cell-to-cell movement.