Molecular biology
VIRION
Non-enveloped, isometric, icosahedral, about 30 nm in diameter.
GENOME
Monopartite, linear, C-rich, ssRNA(+) genome of 6-7.5 kb. The 3’-terminus may have a tRNA-like structure or a polyA tract, depending upon the virus.
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 protein is translated from a 3’-coterminal subgenomic RNA. There are additional ORFs in some genera.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated to produce the protein necessary for RNA synthesis (replication and transcription).
- A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
- New genomic RNA is synthesized using the negative-sense RNA as a template.
- The RdRp recognizes internal subgenomic promoters on the negative-sense RNA to transcribe the 3’co-terminal subgenomic RNA that will generate the capsid protein.
- Formation of new virus particles.