Non-enveloped capsid with a T=7d icosahedral symmetry, about 50 nm in diameter.


Circular dsDNA about 5 kb in size, associated with cellular histones in a chromatin-like complex. Encodes for 5-9 proteins.
On rare non-specific recombination, the viral genome can be integrated in host chromosome. This inactivates the integrated virus but can give the host cell a replicative advantage sometimes leading to malignant tumours.


Transcription is nuclear, in two phases; early (replication), late (virion assembly/exit). 5-9 proteins are expressed from the two pre-MRNA by alternative splicing. All genes are transcribed by host RNA pol II.



  1. Attachement of the viral proteins to host receptors triggers lipid-mediated endocytosis of the virus into the host cell.
  2. Virion transits through endoplasmic reticulum where host protein disulfide isomerases rearrange its capsid structure
  3. Export of misfolded virion to the cytoplasm possibly through host ERAD pathway
  4. Loss of VP1 in the low-calcium conditions of the cytosol
  5. Import of genomic DNA into host nucleus.
  6. Transcription of early genes (LT and sT genes)
  7. Replication of the DNA genome in the nucleus.
  8. Transcription of late genes encoding for structural proteins (VP1, VP2 and VP3).
  9. Assembly of new virions in nuclear viral factories.
  10. Virions are released by lysis of the cell.

Host-virus interaction

Cell-cycle modulation

The large T antigen binds to host key cell cycle regulators retinoblastoma protein RB1/pRb and TP53 and induces the disassembly of host E2F1 transcription factors from RB1, thus promoting transcriptional activation of E2F1-regulated S-phase genes.

Matching UniProtKB/Swiss-Prot entries

79 entries grouped by protein (browse by keywords)

All proteins are shown (view only 50 complete proteome entries)

Agnoprotein (Agno)

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AGNO_POVBOBovine polyomavirus (BPyV) reference strain

Bovine agnoprotein (Agno)

AGNO_POVJCJC polyomavirus (JCPyV) (JCV) reference strain
AGNO_SV40Simian virus 40 (SV40) reference strain


AGNO_POVBKBK polyomavirus (BKPyV)
AGNO_POVBABK polyomavirus (strain AS) (BKPyV)
AGNO_POVS1Simian virus 12 (strain wt100) (SV-12) (Baboon polyomavirus 1)
AGNO_POVSMSquirrel monkey polyomavirus

Squirrel monkey agnoprotein (Agno)

Avian agnoprotein 1a (Agno-1a)

AGNO1_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain

Avian agnoprotein 2b (Agno-2b)

AGNO2_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain

Large T antigen (LT) (LT-AG) (EC 3.6.4.-)

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LT_POVBOBovine polyomavirus (BPyV) reference strain
LT_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain
LT_POVHAHamster polyomavirus (HaPyV) reference strain
LT_POVJCJC polyomavirus (JCPyV) (JCV) reference strain
LT_POVMAMurine polyomavirus (strain A2) (MPyV) reference strain
LT_SV40Simian virus 40 (SV40) reference strain
LT_POVLYB-lymphotropic polyomavirus (LPV)
LT_POVBKBK polyomavirus (BKPyV)
LT_POVBABK polyomavirus (strain AS) (BKPyV)
LT_POVKIKI polyomavirus (isolate Stockholm 350) (KIPyV)
LT_POVM3Murine polyomavirus (strain 3) (MPyV)
LT_POVMCMurine polyomavirus (strain Crawford small-plaque) (MPyV)
LT_POVMKMurine polyomavirus (strain Kilham) (MPyV) (Murine pneumotropic virus)
LT_POVS1Simian virus 12 (strain wt100) (SV-12) (Baboon polyomavirus 1)
LT_POVSMSquirrel monkey polyomavirus
LT_POVWUWU polyomavirus (WUPyV)

Middle T antigen (MT) (MT-AG)

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MT_POVHAHamster polyomavirus (HaPyV) reference strain
MT_POVMAMurine polyomavirus (strain A2) (MPyV) reference strain
MT_POVM3Murine polyomavirus (strain 3) (MPyV)
MT_POVMCMurine polyomavirus (strain Crawford small-plaque) (MPyV)

SV40 early leader protein (SELP)

SELP_SV40Simian virus 40 (SV40) reference strain

Small t antigen (ST) (ST-AG)

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ST_POVBOBovine polyomavirus (BPyV) reference strain
ST_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain
ST_POVHAHamster polyomavirus (HaPyV) reference strain
ST_POVJCJC polyomavirus (JCPyV) (JCV) reference strain
ST_POVMAMurine polyomavirus (strain A2) (MPyV) reference strain
ST_SV40Simian virus 40 (SV40) reference strain
ST_POVLYB-lymphotropic polyomavirus (LPV)
ST_POVBKBK polyomavirus (BKPyV)
ST_POVBABK polyomavirus (strain AS) (BKPyV)
ST_POVKIKI polyomavirus (isolate Stockholm 350) (KIPyV)
ST_POVM3Murine polyomavirus (strain 3) (MPyV)
ST_POVMCMurine polyomavirus (strain Crawford small-plaque) (MPyV)
ST_POVMKMurine polyomavirus (strain Kilham) (MPyV) (Murine pneumotropic virus)
ST_POVS1Simian virus 12 (strain wt100) (SV-12) (Baboon polyomavirus 1)
ST_POVSMSquirrel monkey polyomavirus
ST_POVWUWU polyomavirus (WUPyV)

Major capsid protein VP1 (Major structural protein VP1)

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VP1_POVBOBovine polyomavirus (BPyV) reference strain
VP1_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain
VP1_POVJCJC polyomavirus (JCPyV) (JCV) reference strain
VP1_POVMAMurine polyomavirus (strain A2) (MPyV) reference strain
VP1_SV40Simian virus 40 (SV40) reference strain
VP1_POVLYB-lymphotropic polyomavirus (LPV)
VP1_POVBKBK polyomavirus (BKPyV)
VP1_POVBABK polyomavirus (strain AS) (BKPyV)
VP1_POVHAHamster polyomavirus (HaPyV)
VP1_POVKIKI polyomavirus (isolate Stockholm 350) (KIPyV)
VP1_POVM3Murine polyomavirus (strain 3) (MPyV)
VP1_POVMCMurine polyomavirus (strain Crawford small-plaque) (MPyV)
VP1_POVMKMurine polyomavirus (strain Kilham) (MPyV) (Murine pneumotropic virus)
VP1_POVMPMurine polyomavirus (strain P16 small-plaque) (MPyV)

Capsid protein VP1

VP1_POVS1Simian virus 12 (strain wt100) (SV-12) (Baboon polyomavirus 1)
VP1_POVSMSquirrel monkey polyomavirus
VP1_POVWUWU polyomavirus (WUPyV)

Minor capsid protein VP2 (Minor structural protein VP2)

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VP2_POVBOBovine polyomavirus (BPyV) reference strain
VP2_BFPYVBudgerigar fledgling disease virus (BFPyV) reference strain
VP2_POVHAHamster polyomavirus (HaPyV) reference strain
VP2_POVJCJC polyomavirus (JCPyV) (JCV) reference strain
VP2_POVMAMurine polyomavirus (strain A2) (MPyV) reference strain
VP2_SV40Simian virus 40 (SV40) reference strain
VP2_POVLYB-lymphotropic polyomavirus (LPV)
VP2_POVBKBK polyomavirus (BKPyV)
VP2_POVBABK polyomavirus (strain AS) (BKPyV)
VP2_POVKIKI polyomavirus (isolate Stockholm 350) (KIPyV)
VP2_POVM3Murine polyomavirus (strain 3) (MPyV)
VP2_POVMCMurine polyomavirus (strain Crawford small-plaque) (MPyV)
VP2_POVMKMurine polyomavirus (strain Kilham) (MPyV) (Murine pneumotropic virus)
VP2_POVS1Simian virus 12 (strain wt100) (SV-12) (Baboon polyomavirus 1)
VP2_POVSMSquirrel monkey polyomavirus
VP2_POVWUWU polyomavirus (WUPyV)