VIRION
Non enveloped, icosahedral virion with a double capsid structure (except for cypoviruses and dinovernaviruses which have only the equivalent of the inner capsid). The outer capsid has a T=13 icosahedral symmetry, the inner capsid a T=2* icosahedral symmetry.
GENOME
Segmented linear dsRNA genome. Contains 10 to 12 segments coding for 10 to 14 proteins. Segments size range from 0.2 to 3.0 kb. Genome total size range from 18.2 to 30.5 kb.
GENE EXPRESSION
The dsRNA genome is never completely uncoated to prevent activation of antiviral state by the cell in response to dsRNA. Viral polymerase synthesizes mRNA from each of the dsRNA segments. These mRNAs are translocated to the cell cytoplasm where they are translated.
Further proteins are produced by leaky scanning and protein processing.
ENZYMES
REPLICATION
CYTOPLASMIC
- Attachement to host receptors probably mediates endocytosis of virus into host cell.
- Particles are partially uncoated in endolysosomes, but not entirely, and penetrate in the cytoplasm.
- Early transcription of the dsRNA genome by viral polymerase occurs inside this sub-viral particle (naked core), so that dsRNA is never exposed to the cytoplasm.
- Transcription from each of the dsRNA segments produces mRNA templates for translation.
- Viral proteins and genomic RNAs aggregates in cytoplasmic viral factories.
- (+)RNAs are encapsidated in a sub-viral particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
- The capsid is assembled on the sub-viral particle.
- Mature virions are released presumably following cell death and associated breakdown of host plasma membrane.
