Molecular biology

VIRION

Non-enveloped, icosahedral with T=3 symmetry, about 35 nm in diameter. 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, 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. th

GENE EXPRESSION

The virion RNA is infectious and serves as both genome and viral messenger RNA. ORF1 encodes a polyprotein cleaved into non-structural proteins and capsid protein. ORF2 encodes for a small structural protein (VP10) Cleavage of ORF1 polyprotein by the virus-encoded 3C-like cysteine proteinase yields the mature nonstructural proteins.

REPLICATION

1. Virus attaches to host receptors and is internalized.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. 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.
4. Negative-sense complementary ssRNAs are synthesized using the genomic RNAs as a templates.
5. New genomic RNA is synthesized using the negative-sense RNA as a template, as well as subgenomic RNA encoding for ORF2 protein.
6. Assembly and release of new virions.