Triatovirus

VIRION

Non enveloped, T=pseudo3 icosahedral capsid, about 30 nm in diameter.

GENOME

Monopartite, linear ssRNA(+) genome of 9 kb, with a VPg bound at the 5'-terminus and a 3'-polyA tract. Contains two non-overlapping open reading frames, ORF1 and ORF2, which respectively encode the nonstructural and structural proteins.

GENE EXPRESSION

The virion RNA is infectious and serves as both genome and mRNA. The genome ORF1 and ORF2 encode two polyproteins, the first of which contains the non-structural proteins involved in replication, while the second, contains three (or more) capsid proteins. Each ORF is preceded by one internal ribosome entry site (IRES) located at the 5' end and in the middle of the mRNA.

REPLICATION

  1. Virus penetrates into the cell.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
  3. Synthesis and proteolytic cleavage of the replicase polyprotein RNA1.
  4. Replication occurs in viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
  5. The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
  6. Expression of the RNA2 polyprotein (structural proteins).
  7. virus release (or cell-cell spread of viral RNAs?).