Victorivirus

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.

GENOME

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.

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, nonfused polypeptide and may be expressed through a termination-reinitiation mechanism.

REPLICATION

CYTOPLASMIC

  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. (+)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 by cytoplasmic exchange, sporogenesis or hyphal anastomosis.

Matching UniProtKB/Swiss-Prot entries

2 entries grouped by strain (browse by keywords)

2 entries

Helminthosporium victoriae virus-190S (Hv190SV) reference strain

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CAPSD_HV19S Major capsid protein (Major coat protein)
RDRP_HV19S Probable RNA-directed RNA polymerase (EC 2.7.7.48)