VIRION
Non-enveloped, spherical, about 30-32 nm in diameter, pseudo T=3 icosahedral capsid surrounding the naked RNA genome. The capsid consists of a densely-packed icosahedral arrangement of 60 protomers, each consisting of 3 polypeptides.
GENOME
Monopartite, linear ssRNA(+) genome of 8.8-9.5 kb, polyadenylated, lacking a cap structure, has two major open reading frames (ORFs) that code for two polyproteins. ORF-1 codes for the replicases and ORF-2 codes for the 3 structural proteins. The two ORFs are flanked by a 5'-UTR and a 3'-UTR.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA.
ENZYMES
- RNA-dependent RNA polymerase [RdRp Q2HWK3]
- VPG-type capping [VPg Q2HWK3]
- NTPase-helicase [NTPase Q2HWK3]
- Polyprotein major protease (Peptidase C3) [Protease Q2HWK3]
REPLICATION
CYTOPLASMIC
- Attachement of the virus to host receptors mediates virus internalization.
- The viral RNA is translated into a processed polyprotein.
- Replication occurs in viral factories made of membrane vesicles derived from the ER. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- New genomic RNA is believed to be packaged into preassembled procapsids.
- Virions accumulate in the host cytoplasm forming a crystalline array.
- Cell lysis and virus release.