Totiviridae

VIRION

Non enveloped, icosahedral virion composed of a single capsid protein (CP), about 40 nm in diameter. The capsid has a T=2 icosahedral symmetry.


Virion structure at ViperDB

GENOME

Linear dsRNA genome of 4.6-6.7 kb. Contains 2 overlapping ORFs gag and pol, respectively encoding CP and RdRp. Some totiviruses contain a third small 5’-proximal potential ORF.

GENE EXPRESSION

The dsRNA genome is never completely uncoated, to prevent activation of antiviral state by the cell in response to dsRNA. The viral polymerase synthesizes a mRNA, which is translocated to the cell cytoplasm where it is translated.
Translation is initiated on a unique internal ribosome entry site (IRES) element situated at the 5’-UTR.
In most totiviruses, the plus-strand viral transcript is flanked by a 5’untranslated region (5’-UTR) and a 3’-UTR and directs the translation of a major CP (Gag) and a minor fusion protein CP-RdRP (Gag-Pol) via a -1 ribosomal frameshift.
In other totiviruses (e.g. Hv190SV), RDRP is detected only as a separate, non-fused polypeptide and may be expressed through a termination-reinitiation mechanism.

REPLICATION

CYTOPLASMIC

  1. Virus either remains intracellular (totivirus) or attachement to host receptors mediates endocytosis of virus into host cell (Giardiavirus).
  2. Transcription of the dsRNA genome by viral polymerase occurs inside the virion, so that dsRNA is never exposed to the cytoplasm. This plus-strand transcript is used as template for translation.
  3. (+)RNAs are encapsidated in a sub-viral particle, in which they are transcribed to give RNA (-) molecules with which they become base-paired to produce dsRNA genomes.
  4. Mature virions are transmitted to new cell during cell division, sporogenesis, cell fusion (totivirus) or are released from the host cell (Giardiavirus).

Matching UniProtKB/Swiss-Prot entries

13 entries grouped by strain (browse by keywords)

All proteins are shown (view only 9 complete proteome entries)

3 entries

Leishmania RNA virus 1 - 1 (isolate Leishmania guyanensis) (LRV-1-1) reference strain

Select_all Deselect_all  
CAPSD_LRVLGMajor capsid protein (Major coat protein)
ORF1_LRVLGPutative ORF1 protein
RDRP_LRVLGProbable RNA-directed RNA polymerase (EC 2.7.7.48)

2 entries

Giardia lamblia virus (isolate Wang) (GLV) reference strain

Select_all Deselect_all  
CAPSD_GLVWBMajor capsid protein (Gag protein) (Major coat protein)
RDRP_GLVWBProbable RNA-directed RNA polymerase (EC 2.7.7.48) (Gag-Pol protein)

2 entries

Helminthosporium victoriae virus-190S (Hv190SV) reference strain

Select_all Deselect_all  
CAPSD_HV19SMajor capsid protein (Major coat protein)
RDRP_HV19SProbable RNA-directed RNA polymerase (EC 2.7.7.48)

2 entries

Saccharomyces cerevisiae virus L-A (ScV-L-A) (ScVL1) reference strain

Select_all Deselect_all  
GAG_SCVLAMajor capsid protein (Gag protein) (Major coat protein)
RDRP_SCVLAProbable RNA-directed RNA polymerase (EC 2.7.7.48) (Gag-Pol protein)

2 entries

Saccharomyces cerevisiae virus L-BC (ScV-L-BC) (ScVLa)

Select_all Deselect_all  
GAG_SCVLBMajor capsid protein (Gag protein) (Major coat protein)
RDRP_SCVLBProbable RNA-directed RNA polymerase (EC 2.7.7.48) (Gag-Pol protein)

1 entry

Ustilago maydis P4 virus (UmV4) (UmV-P4)


KP4T_UMV4KP4 killer toxin (Fungal toxin KP4) (Killer protein 4)

1 entry

Ustilago maydis P6 virus (UmV6) (UmV-P6)


KP6T_UMV6KP6 killer toxin (Killer protein 6)