VIRION
Enveloped, spherical. Diameter from 80 to 120nm.
GENOME
Segmented Negative-stranded RNA linear genome, L segment is about 6.7kb, M segment about 3.3kb and S segment about 0.8kb.
Encodes for 3 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 using cap snatching ., but are not polyadenylated. Enzymes: RNA dependent RNA polymerase, endonuclease (cap-snatching)
ENZYMES
REPLICATION
CYTOPLASMIC
- Virus attaches to host receptors though G glycoprotein, 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.
- Replication presumably starts when enough nucleoprotein is present to encapsidate neo-synthetized antigenomes and genomes.
- The ribonucleocapsids buds at Golgi apparatus, releasing the virion by exocytosis.