Table 1: Major functions of HPV proteins.

HPV proteinsFunctionsReference

E1Involved in productive HPV replication.[9]
E2Regulates transcription from different HPV promoters.[13]
E3Recently identified gene located in early gene region and found only in a few papillomavirus types (HPV1, 11, 16, 31, 33); its function has not been identified.[24]
E4Represent up to 30% of total wart protein produce by HPV-1a and might serve as scaffold, transport, or structural protein.[14]
E5Inactivates with cellular host proteins (MHC I, Bap31); these interactions are important for the biological activity of the protein in cell transformation and evasion of the immune response.
Play a role in regulation of transduction pathways through up-regulation of phosphatidylinositol-3′-kinase.
[16, 17, 19]
E6Inactivates the tumor suppressor protein p53, involved in the control of cell proliferation and cell response to genotoxic stress and in DNA damage.[20]
E7Interacts with the pRb tumor suppressor protein. These interactions influence the gene expression involved in progression to S-phase of the cell cycle, such as cyclin A, cyclin D, and cyclin E genes.[20, 22]
E8Recently identified gene located in early gene region and found only in a few papillomavirus types (HPV 1, 11, 16, 31, 33). A fusion protein, E8E2C, functions as a negative regulator for HPV DNA replication playing a role in the control of viral copy number as well as in the stable maintenance of HPV episomes.[24]
L1
L2
Major capsid protein.
Minor capsid protein.
[26]