Circovirus

VIRION

Non-enveloped, round, T=1 icosahedral symmetry, about 17 nm in diameter. The capsid consists of 12 pentagonal trumpet-shaped pentomers.

GENOME

Monopartite, circular, ssDNA genome of about 1800 to 2000bp.
The genome is replicated through double-stranded intermediates. The replication (Rep) protein initiates and terminates rolling circle replication, the host DNA polymerase being used for DNA replication itself. There is a potential stem-loop structure in the intergenic region that includes a conserved nonanucleotide sequence (AGTATTAC) where ssDNA synthesis is initiated.

GENE EXPRESSION

The encapsidated viral DNA and the complementary DNA of the replicative intermediate encode two mRNAs for the Rep and capsid proteins.
Rep mRNA can undergo alternative splicing in some strains to produce Rep’ protein.

REPLICATION

NUCLEAR

  1. Virus penetrates into the host cell probably by clathrin- and caveolae-independent endocytosis.
  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 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 the capsid proteins and form virions released from the cell by budding.

Host-virus interaction

Autophagy modulation

Cap protein of PCV2 induces activation of host autophagy in order to enhance its own replication .

Apoptosis modulation

PCV2 ORF3-encoded protein induces apoptosis by activating caspase-8 and caspase-3 pathways . This protein may be a candidate for PML bodies inhibition which is essential for nuclear virus replication in mammals.

Matching UniProtKB/Swiss-Prot entries

24 entries grouped by strain (browse by keywords)

All proteins are shown (view only 23 complete proteome entries)

2 entries

Porcine circovirus 1 (isolate China) (PCV1) reference strain

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CAPSD_PCV1CCapsid protein
REP_PCV1CReplication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...

7 entries

Beak and feather disease virus (BFDV)

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CAPSD_BFDVCapsid protein
ORF3_BFDVUncharacterized protein ORF3
ORF4_BFDVUncharacterized protein ORF4
ORF5_BFDVUncharacterized protein ORF5
ORF6_BFDVUncharacterized protein ORF6
ORF7_BFDVUncharacterized protein ORF7
REP_BFDVReplication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...

5 entries

Pigeon circovirus (PiCV) (Columbid circovirus)

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CAPSD_PICVProbable capsid protein
ORFC2_PICVUncharacterized protein ORFC2
ORFC3_PICVUncharacterized protein ORFC3
ORFC4_PICVUncharacterized protein ORFC4
REP_PICVReplication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...

4 entries

Goose circovirus (GoCV)

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CAPSD_GOCVProbable capsid protein
ORFC2_GOCVUncharacterized protein ORFC2
ORFV2_GOCVUncharacterized protein ORFV2
REP_GOCVReplication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...

4 entries

Porcine circovirus 2 (PCV2)

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CAPSD_PCV2Capsid protein
NS0_PCV2Protein NS0
ORF3_PCV2Protein ORF3
REP_PCV2Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...

2 entries

Canary circovirus (CaCV)

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CAPSD_CACVProbable capsid protein
REP_CACVReplication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC 3.6.1.3) ...