Molecular biology
VIRION
Non enveloped, icosahedral, non-turreted virion with a triple capsid structure, about 60-70 nm in diameter. The intermediate capsid has an icosahedral T=13 symmetry, the inner capsid an icosahedral symmetry T=2.
GENOME
Segmented dsRNA linear genome. Contains 12 segments encoding 12 proteins. Segments size range from 862 to 3747 bp, genome total size is about 21 kb (BAV).
GENE EXPRESSION
The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response of dsRNA. The viral polymerase synthesizes a capped mRNA from each dsRNA segment. This capped mRNA is translocated to the cell cytoplasm where it is translated.
REPLICATION
CYTOPLASMIC
- Virus penetrates into the cytoplasm.
- Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
- (+)RNAs are encapsidated in virion particle, inside which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
- Mature virions are released presumably following cell death and associated breakdown of host plasma membrane.