Notes on Genus: Nairovirus

enveloped spheres

Type member: Dugbe virus

Contents

• Members of this Genus
• General Description
• Morphology
• Electron Micrograph
• Genome
• Genus Genomic Organization
• Genome Map
• Type Member Genomic Organization
• All Known Sequences
• Curated Sequences

General Description

This is one of the four animal virus genera in the family Bunyaviridae. The L segment (about 12 kb) is much larger than those of any of the other genera in the family. The name is derived from Nairobi sheep disease virus, the first member of the genus to be recognised.

Morphology

Virions pleomorphic in shape and size, spheroidal and enveloped, 80-110 nm in diameter. 3 filamentous nucleocapsids per envelope, each 200-3000 nm long (depending on arrangement) and 2-2.5 nm in diameter. Symmetry helical.

Virions composed of 1-2 % nucleic acid, over 50 % protein and 20-30 % lipid.

Genome

Linear, tripartite negative sense ssRNA: L (c.12000 nt), M (c.4800 nt) and S (c.1700 nt).

Genus Genomic Organization

Translation of the RNAs produces a polymerase (RNA-L), a protein precursor which is cleaved into two glycoproteins and possibly other products (RNA-M), and the coat protein (RNA-S).

Type Member Genomic Organization

All the RNAs are translated from the complementary strand:

1. RNA-L is predicted to produce a single protein (L) of 459.4 kDa (RNA polymerase)
2. RNA-M produces a protein precursor of 173.3 kDa, from which other proteins are generated:
   • Glycoprotein G1 (73 kDa)
   • Glycoprotein G2 (35 kDa)
3. RNA-S produces the N (nucleocapsid, or coat protein) protein of 49.4 kDa