Molecular biology

VIRION

Non-enveloped, 28-30 nm in diameter, with icosahedral pseudo T=3 symmetry. The capsid is composed of 60 CPS (whih one jelly rolls domain) and 60 CPL proteins (with two jell rolls domains). Genomic RNAs are encapsidated separately into two different types of particle of similar size.

GENOME

Segmented, bipartite linear ssRNA(+) genome composed of RNA-1=6-8 kb and RNA-2=4-7 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 the 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 RNA2 encodes 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.