Notes on Genus: Lentivirus
Type member: Human immunodeficiency virus 1
This is one of the genera in the family Retroviridae
. Members are distinguished from those of the other genera by the presence of more than 4 ORFs, a genome of not more than 10 kb, and a distinctive bar or cone-shaped core to the virions, which assemble at the cell membrane.
Virions are spherical and enveloped, 80-100 nm in diameter, with suface projections of glycoprotein.
A dimer of linear, positive sense, ssRNA molecules, each 8-10 kb long and with a 3'-polyA tail.
Genus Genomic Organization
In addition to the standard 4 genes of the family (gag, pro, pol and env), a number of additional regulatory genes are encoded, most of them initiated upstream of the env gene. Frameshifting is used to generate the pro and the pol from the same mRNA as the gag. The other genes are translated from a series of spliced mRNAs.
Type Member Genomic Organization
The major genes are
- gag: structural polyprotein of 55.9 kDa
- pro: protease of 10.8 kDa
- pol: polyprotein (96.6 kDa) containing the reverse transcriptase (RT, 51.3 kDa) and integrase (IN, 32.2 kDa)
- vif: 22.5 kDa
- vpr: 9.3 kDa
- tat: 9.8 kDa
- vpu: 9.2 kDa
- env: envelope proteins (97.2 kDa) consisting of surface protein (SU, 53.9 kDa) and transmembrane protein (TM, 39.6 kDa)
- nef: 13.7 kDa