Totivirus (taxid:11007)



Non enveloped, icosahedral virion composed of a 60 asymmetric dimers of the single capsid protein (CP), about 40 nm in diameter. The capsid has a T=2* icosahedral symmetry.



Linear dsRNA genome of 4.6-6.7 kb. Contains 2 overlapping ORFs gag and pol, respectively encoding CP and RdRp.
Some isolates contain additional satellite dsRNAs which encode "killer" proteins and are encapsidated separately.


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, nonfused polypeptide and may be expressed through a termination-reinitiation mechanism.
Cap-snatching in totivirus L-A furnishes its transcript with a cap structure derived from host mRNAs .




  1. Virus remains intracellular.
  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. The 5' termini of the transcripts are diphosphorylated.
  4. (+)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.
  5. Mature virions are transmitted to new cell by cytoplasmic exchange, sporogenesis or hyphal anastomosis.

Matching UniProtKB/Swiss-Prot entries

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6 entries grouped by strain

2 entries

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

GAG_SCVLA Major capsid protein (Gag protein) (Major coat protein)
RDRP_SCVLA Probable RNA-directed RNA polymerase (EC (Gag-Pol protein)

2 entries

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

RDRP_SCVLB Probable RNA-directed RNA polymerase (EC (Gag-Pol protein)
GAG_SCVLB Major capsid protein (Gag protein) (Major coat protein)

1 entry

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

KP4T_UMV4 KP4 killer toxin (Fungal toxin KP4) (Killer protein 4)

1 entry

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

KP6T_UMV6 KP6 killer toxin (Killer protein 6) [Cleaved into: KP6 killer toxin subunit alpha (VP10); KP6 killer ...