Nairoviridae (taxid:1980415)

VIRION

Enveloped, spherical. Diameter from 80 to 120nm.

GENOME

Segmented Negative-stranded RNA linear genome, L segment is between 6.8 and 12 kb, M segment between 3.2 and 4.9 kb and S segment between 1 and 3 kb.
Encodes for four to six proteins.

GENE EXPRESSION

The viral RNA dependent RNA polymerase (L) binds to a promoter on each encapsidated segment, and transcribes the mRNA. Transcription is terminated by a strong hairpin sequence at the end of each gene. These are capped by L protein during synthesis using cap snatching .

ENZYMES

• RNA-dependent RNA polymerase [L]
• Polynega-type cap snatching [L]
• Ubiquitinyl hydrolase (Peptidase C87) [L]

REPLICATION

CYTOPLASMIC

1. Virus attaches to host receptors though Gn-Gc glycoprotein dimer, and is endocytosed into vesicles in the host cell.
2. Fusion of virus membrane with the vesicle membrane; ribonucleocapsid segments are released in the cytoplasm.
3. Transcription, viral mRNAs are capped in the cytoplasm.
4. Replication presumably starts when enough nucleoprotein is present to encapsidate neo-synthetized antigenomes and genomes.
5. The ribonucleocapsids buds at Golgi apparatus, releasing the virion by exocytosis.

Host-virus interaction

Inhibition of host innate immunity

The nairovirus L protein contains an ovarian tumor domain-containing deubiquitinase that targets activated RIG-I to control innate immune signaling.