Molecular biology

VIRION

Non enveloped virion, about 40 nm in diameter with an icosahedral T=4 symmetry (240 protein subunits).

GENOME

Linear ssRNA(+) genome of 6.5 kb. The 5’ terminus is capped, and the 3’ terminus is not polyadenylated but terminates with a distinctive tRNA-like structure. Subgenomic RNA is encapsidated in some species.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. Genomic RNA is translated into a polyprotein which is cleaved presumably by a viral protease into replication proteins. Replication produces a subgenomic RNA which encodes for capsid protein.

REPLICATION

CYTOPLASMIC

1. Virus penetrates into the host cell.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. Genomic RNA is translated to produce replication proteins.
4. An antigenomic complementary ssRNA is synthesized using the genomic RNA as a template.
5. Using antigenomic RNA as a template, new genomic RNAs are synthesized as well as subgenomic RNAs encoding for capsid protein.
6. Assembly of new virus particles.