Molecular biology
VIRION
Enveloped, spherical, about 50 nm in diameter. The surface proteins are arranged in an icosahedral-like symmetry. Mature virions contain two virus-encoded membrane proteins (M and E), while immature virions contain a membrane protein precursor.
Source: Zhang et al(Pubmed)
GENOME
Monopartite, linear, ssRNA(+) genome of of 10-11 kb. The genome 3’ terminus is not polyadenylated but forms a loop structure. The 5’ end has a methylated nucleotide cap (allows for translation) or a genome-linked protein (VPg).
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 E glycoprotein and is endocytosed into vesicles in the host cell.
- Fusion of virus membrane with the vesicle membrane; 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.