VIRION
Enveloped, spherical, about 50 nm in diameter. The surface proteins are arranged in an icosahedral-like symmetry.
Source: Zhang et al
GENOME
Monopartite, linear, ssRNA(+) genome of about 9.7-12 kb. The genome 3’ terminus is not polyadenylated but forms a loop structure. The 5’ end has a methylated nucleotide cap (to allow 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 into a polyprotein, which is processed co- and post-translationally by host and viral proteases.
REPLICATION
CYTOPLASMIC
- Attachement of the viral envelope protein E to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis.
- Fusion of virus membrane with host endosomal 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 (to yield the replication proteins).
- Replication takes place at the surface of endoplasmic reticulum in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Virus assembly occurs at the endoplasmic reticulum and seems to be facilitated by the viral ionic channel p7. The virion buds via the host ESCRT complexes at the endoplasmic reticulum, is transported to the Golgi apparatus, and then exits the cell via the secretory pathway.