Papillomavirus a double-stranded, DNA virus, with a circular, monopartite genome. Its genome is approximately 8 kbp in length and has early and late kinetic classes.
The genome encodes eight early proteins (E1 through E8), which carry out a variety of replicative and regulatory functions. E1 and E2 are involved in DNA replication. E2 downregulates E6 and E7, which are involved in the oncogenic potential of the virus. E4 binds to epithelial cytoskeleton, but its function is not well established. E5, E6, and E7 serve as oncoproteins. E5 binds to growth factor receptors. E6 binds to p53, a tumor suppressor, and targets it for degradation. E7 binds to Rb-1, another tumor suppressor. The functions of E3 and E8 are unknown.
L1 and L2 are the capsid proteins that are encoded in the late region in the genome.
Papillomavirus replicates in the nucleus of the host cell and uses the host's polymerase. It does not encode its own polymerase. The virally encoded early proteins mentioned above act to facilitate replication.
The genome is divided into early and late regions based on the timing of gene expression. It has ten open reading frames that are encoded on a single strand of DNA. Transcriptional control is affected by the state of differentiation of the squamous epithelium. A variety of transcripts are produced by differential splicing. The genome contains long regulatory regions (LCR) that contain an enhancer element and control the replication and transcription of early genes.