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 9.7 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 structural 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.