Molecular biology
VIRION
Non-enveloped, round, icosahedral, 30 nm in diameter. The capsid is composed of 180 proteins.
GENOME
Segmented, bipartite linear ssRNA(+) genome composed of RNA1=3.1 kb and RNA2=1.4 kb. Each genome segment 5’ end is capped. The 3’end has no poly (A) tract.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. RNA1 encodes directly the RNA-dependent RNA polymerase (protein A), and RNA2, the capsid protein. A subgenomic RNA (sgRNA3), 3’ colinear to RNA1 is also produced and encode proteins B1 and B2.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the host cell.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA-1 is translated to produce the RdRpol protein.
- 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, as well as sub-genomic RNA-3.
- Translation of RNA-2 produce capsid protein alpha.
- Formation of new virus particles in the cytoplasm around genomic RNA1 and RNA2.
- Assembled capsid protein alpha is cleaved into capsid protein beta and gamma.
- Release of infectious particles (lysis?)