Gyrovirus

VIRION

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Non-enveloped, round, T=1 icosahedral symmetry, about 25 nm in diameter. The capsid consists of 12 pentagonal trumpet-shaped pentamers.

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GENOME

Monopartite, circular, ssDNA genome of about 2300 bp.
The genome is replicated through double-stranded intermediates. A replication Rep-like protein would initiates rolling circle replication.

GENE EXPRESSION

One mRNA is transcribed by cellular RNA polymerase II and encodes for three proteins: VP1, VP2 and VP3 probably through leaky scanning mechanism.

REPLICATION

NUCLEAR

  1. Virus penetrates into the host cell.
  2. Uncoating, the viral ssDNA genome penetrates into the nucleus.
  3. Viral ssDNA is converted into dsDNA with the participation of cellular factors. dsDNA transcription gives rise to viral mRNAs.
  4. Viral mRNAs are translated to produce viral proteins.
  5. Replication may be mediated by a Rep protein, and would occur by rolling circle replication producing ssDNA genomes.
  6. These newly synthesized ssDNA can either
    a) be converted to dsDNA and serve as a template for transcription/replication
    b) be encapsidated by capsid protein and form virions released by cell lysis.

Host-virus interaction

Apoptosis modulation

Chicken anemia virus VP3 protein induces apoptosis observed in CAV infection. Virus-induced apoptosis accounts for the severe depletion of cortical thymocytes and erythroblastoid cells in the bone marrow .