Iflavirus

VIRION

Non enveloped, icosahedral with a T=pseudo3 symmetry, about 30 nm in diameter.

GENOME

Monopartite, linear ssRNA(+) genome of 8.8-9.7 kb in size, with a VPg bound at the 5’-terminus and a 3’-polyA tract. The long UTR at the 5’ end contains an internal ribosome entry site.

GENE EXPRESSION

The viral RNA is infectious and serves as both the genome and viral messenger RNA. The IRES allows direct translation of the polyprotein. The polyprotein is initially processed by the viral protease(s) into various precursor and mature proteins to yield the structural proteins, replicase, VPg, and a number of proteins that modify the host cell, ultimately leading to cell lysis.
Ribosomal skipping may also be used to express 2A protein from the infectious flacherie virus polyprotein.

REPLICATION

CYTOPLASMIC

  1. Attachement to host receptors.
  2. Uncoating, and release of the viral genomic RNA into the cytoplasm possibly through the formation of a pore in the host cell membrane.
  3. Synthesis and proteolytic cleavage of the polyprotein.
  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. Genomic RNA neo-synthesized is believed to be packaged into preassembled procapsids.
  7. Cell lysis and virus release.