Molecular biology

VIRION

Non-enveloped, icosahedral, about 30 nm in diameter, with icosahedral pseudo T=3 symmetry. Genome segments are encapsidated separately into two different types of particle similar in size.

GENOME

Segmented, bipartite linear ssRNA(+) genome composed of RNA.1=7.8 kb and RNA-2=5.4 kb. Each genomic segment has a VPg linked to its 5’ end and a 3’ poly(A) tract.

GENE EXPRESSION

The virion RNA is infectious and serves as both genome and mRNA.
RNA-1 and RNA-2 are translated into two polyproteins, which are then processed into functional proteins. RNA-1 encodes proteins necessary for replication, while RNA-2 encodes one or two capsid proteins and product(s) involved in cell-to-cell movement.

REPLICATION

CYTOPLASMIC

1. Virus penetrates into the cell.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. Expression of the RNA-1 polyprotein products that promote the replication of genomic RNAs in the cytoplasm.
4. Negative-sense complementary ssRNAs are synthesized using the genomic RNAs as a templates.
5. New genomic RNAs are synthesized using the negative-sense RNAs as templates.
6. Formation of new virus particles.