Alternaviridae (taxid:2973077)

VIRION

Non enveloped, icosahedral virion composed of a single capsid protein (CP), about 33 nm in diameter. The capsid has a T=2* icosahedral symmetry.

GENOME

Linear dsRNA genome consisting of 3 to 4 segments of about 8.4 to 10.7 kbp.

GENE EXPRESSION

The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response to dsRNA. The viral polymerase synthesizes a mRNA, which is translocated to the cell cytoplasm where it is translated. Genomic and messenger RNAs are probably capped

ENZYMES

• RNA-dependent RNA polymerase [L]
• Unknown capping?
  • Methyltransferase [M1]

REPLICATION

CYTOPLASMIC

1. Virus either remains intracellular (totivirus) or attachement to host receptors mediates endocytosis of virus into host cell (Giardiavirus).
2. 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.
3. (+)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.
4. Mature virions are transmitted to new cell during cell division, sporogenesis, or cell fusion.