Aparavirus (taxid:1213379)

VIRION

Non enveloped, pseudo T=3 icosahedral capsid, about 30 nm in diameter.

GENOME

Monopartite, linear ssRNA(+) genome of 8.0-10.2 kb 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 encodes the non-structural proteins helicase, 3C-protease and RNA-dependent RNA polymerase, while the second encodes four capsid proteins. Each ORF is preceded by an internal ribosome entry site (IRES) located at the 5' end and at the intergenic region (IGR) between the two ORFs. Tha IGR IRES allows translation of ORF2 at a non-AUG codon.

ENZYMES

• RNA-dependent RNA polymerase [RdRp Q9DSN9]
• VPG-type capping [VPg Q9DSN9]
• NTPase-helicase [NTPase Q9DSN9]
• Polyprotein major protease (Peptidase C3) [Protease-Pol Q9DSN9]

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.