Molecular biology
VIRION
Enveloped, spherical, icosahedral, 65-70nm in diameter, capsid made of 240 monomers. The envelope contains 80 trimer spikes, each spike = 3 x E1/E2 heterodimers.
GENOME
Monopartite, linear, single-stranded, positive-sense RNA genome of 11-12 kb. The genome is capped and polyadenylated.
GENE EXPRESSION
The virion RNA is infectious and serves as both genome and viral messenger RNA. The whole genome is translated in a non-structural polyprotein which is processed by host and viral proteases. Structural polyprotein is expressed through a subgenomic mRNA
REPLICATION
CYTOPLASMIC
- Virus attaches to host receptors though E glycoprotein and is endocytosed into vesicles in the host cell.
- Fusion of virus membrane with the vesicle membrane occurs; RNA genome is released into the cytoplasm.
- The positive-sense genomic ssRNA is translated into a polyprotein, which is cleaved into non structural proteins.
- Replication takes place at the surface of endoplasmic reticulum. A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
- New genomic RNA as well as subgenomic RNA are synthesized using the negative-sense RNA as a template. Subgenomic RNA is translated in structurals proteins.
- Virus assembly occurs at the endoplasmic reticulum. The virion buds at the endoplasmic reticulum, is transported to the Golgi apparatus, and then bud from the cell membrane.