Molecular biology
VIRION
Enveloped, spherical. Diameter from 80 to 120nm.
GENOME
Segmented Negative-stranded RNA linear genome, L segment is about 6.9kb, M segment about 4.5kb and S segment about 1kb.
Encodes for six proteins.
GENE EXPRESSION
Transcription starts by viral RNA dependent RNA polymerase (L) binding to a promoter on each encapsidated segment, and is terminated by a strong hairpin sequence at the end of each gene. mRNAs are capped by L protein during synthesis, but are not polyadenylated.
S segment encodes for NSs protein by leaky scanning. M segment encodes for a polyprotein which is cleaved by host protease into Gn, NSm and Gc proteins.
REPLICATION
CYTOPLASMIC
- Virus attaches to host receptors though Gn-Gc glycoprotein dimer and is endocytosed into vesicles in the host cell.
- Fusion of virus membrane with the vesicle membrane; ribonucleocapsid segments are released in the cytoplasm.
- Transcription, viral mRNAs are capped in the cytoplasm.
- Viral genome is replicated and encapsidated in cytoplasmic viral factories.
- The ribonucleocapsids migrate under the Golgi membrane and buds, releasing the virion.