Xipapillomavirus (taxid:333921)



Non-enveloped. Small, icosahedral, about 52-55 nm in size. A single molecule of circular dsDNA is contained within the T=7 icosahedral capsid, which is composed of 72 pentamers.



Circular dsDNA, about 7 kb in size, associated with cellular histones. A characteristic E6 ORF is absent.
On rare non-specific recombination, the viral genome can be integrated in host chromosome. This inactivates the integrated virus but can gives the host cell a replicative advantage sometimes leading to malignant tumours.


Only one strand of the genome is transcribed and yield two classes of proteins expressed by alternative splicing: a) Early Proteins: non-structural regulatory proteins (E1-E7).
b) Late Proteins: the structural proteins L1 and L2.



Replication is divided in two distinct steps that are linked to the differentiation state of the host epithelial cell:

a) The plasmid replication takes place in the basal squamous epithelial cells. It corresponds to viral DNA replication in synchrony with the host cell chromosome in order to ensures an average of one viral genome per basal cell.

  1. Attachment of the viral proteins to host receptors mediates endocytosis into vesicles in the basal squamous epithelial cell.
  2. Transport to the nucleus and uncoating of the viral DNA.
  3. Early-region transcription and translation of the early proteins.
  4. Steady-state viral DNA nuclear replication. Requires the origin of DNA replication in cis and the viral E1 and E2 proteins in trans.

b) The vegetative replication, which occurs in differentiated keratinocytes. In these cells, which no longer undergo cellular DNA synthesis, there is a burst of viral DNA synthesis with active production of virions.

  1. Vegetative viral DNA synthesis.
  2. Transcription of the late region.
  3. Capsid proteins L1 and L2 synthesis.
  4. Nuclear capsid assembly and release of viruses.

Matching UniProtKB/Swiss-Prot entries

(all links/actions below point to uniprot.org website)

22 entries grouped by strain

7 entries

Bovine papillomavirus type 3 reference strain

VL2_BPV3 Minor capsid protein L2
VE2_BPV3 Regulatory protein E2
VE1_BPV3 Replication protein E1 (EC (ATP-dependent helicase E1)
VE7_BPV3 Protein E7
VE8E2_BPV3 Protein E8^E2C
VL1_BPV3 Major capsid protein L1
VE8_BPV3 Uncharacterized protein E8

11 entries

Bos taurus papillomavirus 4 (Bovine papillomavirus 4)

VL2_BPV4 Minor capsid protein L2
VE1_BPV4 Replication protein E1 (EC (ATP-dependent helicase E1)
VE2_BPV4 Regulatory protein E2
VE7_BPV4 Protein E7
VL1_BPV4 Major capsid protein L1
VL3_BPV4 Probable protein L3
VE3_BPV4 Probable protein E3
VE4_BPV4 Probable protein E4
VE5A_BPV4 Probable protein E5A
VE5B_BPV4 Probable protein E5B
VE8_BPV4 Uncharacterized protein E8

4 entries

Bos taurus papillomavirus 6 (Bovine papillomavirus 6)

VE2_BPV6 Regulatory protein E2
VE1_BPV6 Replication protein E1 (EC (ATP-dependent helicase E1)
VE7_BPV6 Protein E7
VE8_BPV6 Uncharacterized protein E8