VIRION
Non-enveloped, flexuous, filamentous, about 720 nm long and 12-13 nm in diameter.
GENOME
Linear ssRNA(+) genome of 6.8 kb in size. The 5' is capped and 3' terminus is polyadenylated. Encodes 2 ORFs.
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 by readthrough of a 'leaky' stop codon between the helicase and RdRp regions. The capsid (coat) protein is transcribed presumably as a monocistronic subgenomic mRNA (sgRNA).
ENZYMES
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 promoter is used to transcribe the sgRNA. Traduction of this sgRNA yields the capsid protein.
- Assembly of new virus particles.