VIRION
Non-enveloped, capsid of about 35 nm in diameter, with T=3 icosahedral symmetry. The capsid is composed of 180 capsid proteins. T=1 particles composed of 60 capsid proteins, about in diameter 15nm are also observed. Genomic or subgenomic RNA are encapsidated in different particles.
GENOME
Monopartite, linear ssRNA(+) genome of 7.3 to 8.3 kb. The 5'-terminus is linked to a VPg protein and the 3'-terminus has a poly(A) tract.
GENE EXPRESSION
The virion RNA is infectious and serves as both genome and viral messenger RNA. Cleavage of ORF1 polyprotein by the virus-encoded 3C-like cysteine proteinase yields the non-structural proteins and the capsid protein. ORF2 encodes a small structural protein VP2 which is expressed through RNA termination-reinitiation.
ENZYMES
- RNA-dependent RNA polymerase [RdRp P27410]
- VPG-type capping [VPg Q288N7]
- NTPase-helicase [NTPase P27410]
- Polyprotein major protease (Peptidase C24) [3CLpro P27410]
REPLICATION
CYTOPLASMIC
- Attachement to host receptors mediates endocytosis of the virus into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- VPg is removed from the viral RNA, which is then translated into a processed ORF1 polyprotein to yield the replication proteins.
- 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.
- Subgenomic RNA translation gives rise to the capsid protein and VP2.
- Assembly of new virus particles and release by cell lysis.
