Rhabdovirus
| Rhabdoviridae | |
|---|---|
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|
| vesicular stomatitis Indiana virus (VSIV), the prototypical rhabdovirus | |
| Virus classification | |
| Group: | Group V ((−)ssRNA) |
| Order: | Mononegavirales |
| Family: | Rhabdoviridae |
| Genera | |
The Rhabdoviridae are a family of viruses in the order Mononegavirales. Vertebrates (including mammals and humans), invertebrates, and plants serve as natural hosts. Currently, 74 species are placed in this family, within 11 genera. Diseases associated with viruses of this family include rabies fatal encephalitis caused by rabies virus, and vesicular diseases and encephalitis flu-like symptoms in humans caused by vesiculoviruses. The name is derived from the Greek rhabdos, meaning rod, referring to the shape of the viral particles.
Rhabdovirions are enveloped, with bullet-shaped and bacilliform geometries. These virions are about 75 nm wide and 180 nm long. Rhabdoviruses have helical nucleocapsids and their genomes are linear, around 11–15 kb in length. Rhabdoviruses carry their genetic material in the form of negative-sense single-stranded RNA. They typically carry genes for five proteins: large protein (L), glycoprotein (G), nucleoprotein (N), phosphoprotein (P), and matrix protein (M). Rhabdoviruses that infect vertebrates (especially mammals and fishes), plants, and insects are usually bullet-shaped., However, in contrast to paramyxoviruses, rhabdoviruses do not have hemagglutinating and neuraminidase activities.
Table legend: "*" denotes type species.
In addition to the above, there are a large number of rhabdo-like viruses (~130) that have not yet been officially classified by the ICTV.
Transcriptase of rhabdovirus is composed of 1 L and 3 P proteins. Transcriptase components always presents in the virion; so rhabdoviruses can start transcription right after the entry with no need to produce anything.
Transcriptase starts to move from 3' end to 5' end on the genome, and the movement terminates randomly at the end of protein sequences. For example, if a transcription finishes at the end of M sequence; leader RNA and N, P and M mRNAs are formed separately from each other.
Also mRNAs accumulate according to the order of protein sequences on the genome, and this solves the logistics problem in the cell. For example, N protein is needed too much for the virus, because it coats outside of the replicated genomes completely. Because of having the N protein sequence at the beginning of the genome (3' end) after the leader RNA sequence, mRNAs for N protein can always be produced and accumulate in high amounts with every termination of transcription. After the transcription processes, all of the mRNAs are capped at the 5' end and polyadenylated at the 3' end by L protein.
This transcription mechanism provides to produce mRNAs according to the need of the viruses.
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