Molecular biology
VIRION
Enveloped, spherical, about 50 nm in diameter. Mature virions contain two virus-encoded membrane proteins (E1 and E2) in addition to the capsid protein.
GENOME
Monopartite, linear, ssRNA(+) genome of about 10 kb. The genome 3’ terminus is not polyadenylated but forms a loop structure. There is an IRES at the 5’ end.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and the viral messenger RNA. The whole genome is translated in a polyprotein, which is processed co- and post-translationally by host and viral proteases.
REPLICATION
- Virus attaches to host receptors through E1/E2 glycoproteins 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 all structural and 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 is synthesized using the negative-sense RNA as a template.
- 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.