Molecular biology
VIRION
Non-enveloped, icosahedral with T=3 symmetry, about 38-40 nm in diameter. The capsid is composed of 180 VP1 proteins. Small empty virions are about 23nm in diameter, and would be of icosahedral T=1 symmetry, composed of 60 VP1 proteins.
GENOME
Monopartite, linear, single-stranded, positive-sense RNA genome of 7.3 to 8.3 kb. At 5’-terminus a virus protein (VPg)is covalently linked to genome, whereas 3’-terminus is polyadenylated.
GENE EXPRESSION
The virion RNA is infectious and serves as both genome and viral messenger RNA. ORF1 encodes for the non-structural polyprotein. Cleavage of ORF1 polyprotein by the virus-encoded 3C-like cysteine proteinase yields the mature nonstructural proteins. Subgenomic RNA encodes for ORF2 capsid protein and ORF3 minor structural protein. ORF2 encodes a capsid precursor protein that is proteolytically processed by the viral proteinase to yield the mature capsid protein.
REPLICATION
CYTOPLASMIC
- Virus attaches to host receptors and is endocytosed into vesicles in 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 mature non-structural proteins involved in RNA transcription.
- Negative-sense complementary ssRNAs are synthesized using the genomic RNAs as a templates.
- New genomic RNA is synthesized using the negative-sense RNA as a template, as well as subgenomic RNA encoding for structural proteins.
- Assembly and release of new virions.