Togaviridae (taxid:11018)
VIRION
Enveloped, spherical, icosahedral, 65-70nm in diameter, capsid with a T=4 icosahedral symmetry made of 240 monomers. The envelope contains 80 trimer spikes, each spike = 3 x E1/E2 heterodimers.
GENOME
Monopartite, linear, ssRNA(+) genome of 9.7-11.8 kb. The genome is capped and polyadenylated.
GENE EXPRESSION
The virion RNA is infectious and serves as both genome and viral messenger RNA. The whole genome is translated into a non-structural polyprotein which is processed by host and viral proteases. Structural polyprotein is expressed through a subgenomic mRNA.
In alphaviruses, RdRp is expressed by suppression of termination at the end of 10% of nsP polyproteins. Moreover a ribosomal frameshifting in the 6K region induces the translation of the TF protein in alphaviruses.
ENZYMES
- Alpha-type capping
- N7MTase + GTase: [nsp1]
- RNA-dependent RNA polymerase [nsp4]
- Helicase [nsp2]
- Polyprotein major protease (Peptidase C9) [nsp2]
- Capsid protease (Peptidase S3) [capsid]
- ADP-Ribosylhydrolase [nsp3]
REPLICATION
CYTOPLASMIC
- Attachement of the viral E glycoprotein to host receptors mediates clathrin-mediated endocytosis of virus into the host cell.
- Fusion of virus membrane with host endosomal membrane. RNA genome is released into the cytoplasm.
- The positive-sense genomic ssRNA is translated into a polyprotein, which is cleaved into non-structural proteins necessary for RNA synthesis (replication and transcription).
- Replication takes place in cytoplasmic viral factories at the surface of endosomes. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Expression of the subgenomic RNA (sgRNA) gives rise to the structural proteins.
- Capsid assembly occurs in cytoplasm.
- The capsid is envelopped by budding at the plasma membrane where the virion exits the cell.
Host-virus interaction
Autophagy modulation
Chikungunya probably activates an autophagic process which promotes viral replication
.
Host gene expression shutoff by virus
Togaviruses mediate host translation shutoff.
Alphaviruses induce strong PKR activation leading to
leading to the almost complete phosphorylation of eIF2alpha and host translation arrest
.
Alphaviruses perform host transcription shutoff by inhibiting host RNA polymerase II. Host RNA-pol II catalytic subunit is targeted for degradation as early as 4-6h p.i.
.
Kurkela S, Manni T, Vaheri A, Vapalahti O.
Emerg Infect Dis. 2004 May;10(5):889-94.
Matching UniProtKB/Swiss-Prot entries
(all links/actions below point to uniprot.org website)60 entries grouped by strain
Chikungunya virus (strain S27-African prototype) (CHIKV) reference strain
3 entries
Semliki forest virus (SFV) reference strain
2 entries
Sindbis virus (SINV) reference strain
3 entries
Semliki forest virus (SFV)
1 entry
Alphavirus salmon subtype 1 (SAV1) (Salmon pancreas disease virus subtype 1)
2 entries
Alphavirus salmon subtype 2 (SAV2) (Sleeping disease virus)
2 entries
Aura virus (AURAV)
2 entries
Barmah forest virus (BFV)
2 entries
Chikungunya virus (strain 37997) (CHIKV)
2 entries
Eastern equine encephalitis virus (strain Florida 91-469) (EEEV) (Eastern equine encephalomyelitis virus)
2 entries
Eastern equine encephalitis virus (strain PE-0.0155) (EEEV) (Eastern equine encephalomyelitis virus)
2 entries
Eastern equine encephalitis virus (strain PE-3.0815) (EEEV) (Eastern equine encephalomyelitis virus)
2 entries
Getah virus (GETV)
2 entries
Mayaro virus (strain Brazil) (MAYV)
2 entries
O'nyong-nyong virus (strain Gulu) (ONNV)
2 entries
O'nyong-nyong virus (strain Igbo Ora) (ONNV) (Igbo Ora virus)
2 entries
O'nyong-nyong virus (strain SG650) (ONNV)
2 entries
Ross river virus (strain NB5092) (RRV)
2 entries
Sagiyama virus (SAGV)
2 entries
Sindbis virus subtype Ockelbo (strain Edsbyn 82-5) (OCKV) (Ockelbo virus)
2 entries
Venezuelan equine encephalitis virus (strain 3880) (VEEV)
2 entries
Venezuelan equine encephalitis virus (strain Mena II) (VEEV)
2 entries
Venezuelan equine encephalitis virus (strain P676) (VEEV)
2 entries
Venezuelan equine encephalitis virus (strain Trinidad donkey) (VEEV)
2 entries
Western equine encephalitis virus (WEEV)
2 entries
Alphavirus salmon subtype 3 (SAV3) (Norwegian salmonid alphavirus)
1 entry
Chikungunya virus (strain Nagpur) (CHIKV)
1 entry
Eastern equine encephalitis virus (EEEV) (Eastern equine encephalomyelitis virus)
1 entry
Eastern equine encephalitis virus (strain va33[ten broeck]) (EEEV) (Eastern equine encephalomyelitis virus)
1 entry
Middelburg virus
1 entry
Ross river virus (strain T48) (RRV)
1 entry
Venezuelan equine encephalitis virus (VEEV)
1 entry
Venezuelan equine encephalitis virus (strain Everglades Fe3-7c) (VEEV)
1 entry
Venezuelan equine encephalitis virus (strain TC-83) (VEEV)
1 entry
Chikungunya virus (strain S27-African prototype) taxid:371094
| Protein | ModelArchive |
| Structural polyprotein (p130) | ma-jd-viral-30956 |
Eilat virus taxid:1231903
| Protein | ModelArchive |
| Structural polyprotein (p130) | ma-jd-viral-30954 |
Middelburg virus taxid:11023
| Protein | ModelArchive |
| Structural polyprotein (p130) | ma-jd-viral-30953 |
Sagiyama virus taxid:59303
| Protein | ModelArchive |
| Structural polyprotein (p130) | ma-jd-viral-30952 |
Sindbis virus taxid:11034
| Protein | ModelArchive |
| Frameshifted structural polyprotein (p130) | ma-jd-viral-35113 |
Tai Forest alphavirus taxid:1930825
| Protein | ModelArchive |
| Structural polyprotein (p130) | ma-jd-viral-30951 |