Non-enveloped, round, T=1 icosahedral symmetry, about 20 nm in diameter. The capsid consists of 12 pentagonal trumpet-shaped pentamers.


Monopartite, circular, ssDNA genome of about 1.8 to 3.8 kb.
The genome is replicated through double-stranded intermediates. The replication (Rep) protein initiates rolling circle replication.


One or two mRNAs encode for the Rep, capsid, and possibly others proteins. Some mRNA can undergo alternative splicing.



  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

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

27 entries grouped by strain (browse by keywords)

2 entries

Canary circovirus (CaCV) reference strain

REP_CACV Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase Rep) ...
CAPSD_CACV Probable capsid protein

2 entries

Human associated cyclovirus 1 (isolate Homo sapiens/Pakistan/PK5510/2007) (HuCyV-1) (Cyclovirus PK5510) reference strain

CAPSD_HCYV5 Capsid protein
REP_HCYV5 Replication-associated protein (Rep) (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase ...

2 entries

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

REP_PCV1C Replication-associated protein (Rep) (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase ...
CAPSD_PCV1C Capsid protein

7 entries

Beak and feather disease virus (BFDV)

REP_BFDV Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase Rep) ...
CAPSD_BFDV Capsid protein
ORF6_BFDV Uncharacterized protein ORF6
ORF4_BFDV Uncharacterized protein ORF4
ORF5_BFDV Uncharacterized protein ORF5
ORF7_BFDV Uncharacterized protein ORF7
ORF3_BFDV Uncharacterized protein ORF3

5 entries

Pigeon circovirus (PiCV) (Columbid circovirus)

REP_PICV Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase Rep) ...
CAPSD_PICV Probable capsid protein
ORFC2_PICV Uncharacterized protein ORFC2
ORFC3_PICV Uncharacterized protein ORFC3
ORFC4_PICV Uncharacterized protein ORFC4

5 entries

Porcine circovirus 2 (PCV2)

REP_PCV2 Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase Rep) ...
CAPSD_PCV2 Capsid protein
ORF3_PCV2 Protein ORF3
ORF4_PCV2 Anti-apoptotic ORF4 protein
NS0_PCV2 Protein NS0

4 entries

Goose circovirus (GoCV)

REP_GOCV Replication-associated protein (EC 2.7.7.-) (EC 3.1.21.-) (EC (ATP-dependent helicase Rep) ...
CAPSD_GOCV Probable capsid protein
ORFC2_GOCV Uncharacterized protein ORFC2
ORFV2_GOCV Uncharacterized protein ORFV2