Molecular biology

VIRION

Non-enveloped, rod shaped about 85-390 nm in length and 20 nm in diameter. The right-handed helix with a pitch of 2.6 nm has an axial repeat of four turns, involving 49 capsid subunits. Each capsid protein covers four nucleotides on the genomic RNA.

GENOME

Segmented, linear, ssRNA(+) genome. The four to five segments are 1.3 to 6.7 kb in size. The genomic RNA are capped, and polyadenylated.

GENE EXPRESSION

Genomic RNAs serve as messenger RNA. Subgenomic RNAs are synthesized during replication for segments 2 and 3. A ribosomal readthrough on segment 2 produces the 75k protein.

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 the two proteins necessary for RNA synthesis (replication and transcription).
4. A negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
5. The antigenome is used as template to synthesize new genomic RNA and subgenomic RNAs.
6. Each segments are encapsidated
7. New virions are released by cell lysis.