Sequiviridae

Molecular biology

VIRION

Non-enveloped, isometric, icosahedral, about 30 nm in diameter.

GENOME

Linear ssRNA(+) genome of 9-12 kb. The 5’ terminus has a genome-linked protein (VPg). A poly (A) tract is present at the 3’-end of the Waikavirus genus, but not in the Sequivirus genus.

GENE EXPRESSION

The virion RNA is infectious and serves as both the genome and viral messenger RNA. The genome single (or major) ORF is translated into a polyprotein which is subsequently processed by virus-encoded proteases into functional products. There may be also be two small ORFs near the 3’-end in the Waikavirus genus.

REPLICATION

CYTOPLASMIC

1. Virus penetrates into the host cell.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. The viral RNA is translated to produce a polyprotein which is processed by viral proteases.
4. A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
5. New genomic RNA is synthesized using the negative-sense RNA as a template.
6. Formation of new virus particles.