Molecular biology

VIRION

Quasi-spherical, 25-35 nm in diameter.

GENOME

Segmented, tripartite linear ssRNA(+) genome composed of RNA1, RNA2, RNA3. Each genomic segment has a 5’cap.

GENE EXPRESSION

Genomic RNA serves as messenger RNAs. RNA1 and RNA2 encode respectively proteins 1a and 2a, both involved in genome replication and internal transcription of sgRNA4 from the minus-strand copy of RNA3.

REPLICATION

CYTOPLASMIC

1. Virus attaches to host receptors.
2. Uncoating, and release of the viral genomic RNA into the cytoplasm.
3. Expression of protein 1a and 2a that promote the replication of genomic RNAs.
4. Replication of viral RNA: a negative-sense complementary ssRNA is synthesized using the genomic RNA as a template.
5. New genomic RNAs are synthesized using the negative-sense RNAs as templates.Subgenomic RNA4 is transcribed from RNA3 antigenome.
6. Subgenomic RNA4 is translated producing capsid proteins.
7. Assembly of new virions.
8. Virions are released by lysis of the cell.