Molecular biology

VIRION

Non-enveloped, isometric, icosahedral, about 30 nm in diameter.

GENOME

Linear, C-rich, ssRNA(+) genome of 6-7 kb. There is no VPg at the 5’-terminus. Some members (but not the type member) have a polyA tail at the 3’-terminus.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. The genomic RNA encodes a large replication polyprotein which is cleaved. The capsid proteins are probably translated from a 3’-coterminal subgenomic RNA.

REPLICATION

1. Virus penetrates into the host cell.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. The viral RNA is translated to produce the proteins necessary for RNA synthesis (replication and transcription).
4. A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
5. New genomic RNA is synthesized using the negative-sense RNA as a template.
6. The RdRp recognizes internal subgenomic promoters on the negative-sense RNA to transcribe the 3’co-terminal subgenomic RNA that will generate the capsid proteins.
7. Formation of new virus particles.