Chrysoviridae (taxid:249310)

VIRION

Non-enveloped capsid with T=1 icosahedral symmetry and composed of 60 protein subunit monomers. However, each subunit is thought to contain two genetically duplicated domains, and these 120 putative domains might therefore adopt a pseudo-T=2 structure. The capsid is about 35-40 nm in diameter. The four genomic segments are encapsidated separately.

GENOME

Segmented linear dsRNA genome about 12.5 kb: 4 segments encoding for 4 proteins.

GENE EXPRESSION

Each genomic segment encodes for a single protein. Translation is initiated on a unique internal ribosome entry site (IRES) element situated at the 5'-UTR.

ENZYMES

• RNA-directed RNA polymerase [RdRp]
• No capping activity [IRES]

REPLICATION

CYTOPLASMIC

1. Virus penetrates into the cytoplasm.
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 virion 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 by cytoplasmic exchange, sporogenesis or Hyphal anastomosis.