Molecular biology
VIRION
Non-enveloped, spherical, about 32-34 nm in diameter. The RNA genome is enclosed within a capsid that is composed of 60 capsid proteins, assembled into a T=1 icosahedral particle.
GENOME
Monopartite, linear, single-stranded, positive-sense RNA genome of 7.2 kb. The 5’ end is capped and the 3’ terminus is polyadenylated. Their is no VPg at the 5’-terminus of the genome. The genome consists of three partially overlapping ORFs.
GENE EXPRESSION
The virion RNA is infectious and serves as both the genome and viral messenger RNA. ORF 1 encodes the nonstructural proteins, it is not clear wether this polyprotein is cleaved or not; ORF 2 encodes the capsid protein; ORF 3 encodes a small immunogenic protein. ORF2 and ORF3 are encoded by a bicistronic subgenomic RNA.
REPLICATION
- Virus attaches to host receptors and is internalized.
- Uncoating, and release of the viral genomic RNA into the cytoplasm.
- The viral RNA is translated into a processed ORF1 polyprotein to yield the mature non-structural proteins involved in RNA transcription.
- Negative-sense complementary ssRNAs are synthesized using the genomic RNAs as a templates.
- New genomic RNAs are synthesized using the negative-sense RNAs as templates.
- Expression of two other messenger RNAs, a 3.7 kb subgenomic one and a 2.0 kb coterminal one.
- Virus release.