Transcriptional regulation by human papillomaviruses.

Human papillomaviruses are the causative agent of cancers in stratified epithelial surfaces. They replicate in the upper parts of the epithelium, where cells would normally be dying to produce a cornified layer. Therefore, they need to inhibit or delay differentiation and stimulate cell cycle progression to create an environment conducive for replication of the viral genome. The alterations both in differentiation and in the cell cycle are achieved by the viral proteins E6 and E7, which modulate cellular transcription mainly through their effects on p53 and the retinoblastoma family.