VIRION
Non enveloped virion, about 40 nm in diameter with a T=4 icosahedral symmetry (240 copies of two proteins derived from the capsid precursor cleavage).
GENOME
Bipartite, linear ssRNA(+) genome of about 5.3 kb and 2.5 kb. The 5' terminus is capped, and the 3' terminus is not polyadenylated but terminates with a pseudoknot structure.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. Genomic RNAs are translated into a capsid protein and a polyprotein which is cleaved presumably by a viral protease into replication proteins. The capsid protein is expressed by leaky scanning of the mRNA2.
ENZYMES
- RNA-dependent RNA polymerase [RNA polymerase]
- Alpha type capping
- RNA TPase ?
- N7 MTase [RNA polymerase]
- GTase ?
- 2'O MTase ?
- Asparagine proteases (Peptidase N2) [Capsid]
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- Genomic RNA is translated to produce replication proteins.
- Replication takes place in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Expression of the subgenomic RNA encoding the capsid protein.
- Assembly of new virus particles.
- Virion maturation by the viral protease.