Biological activities and molecular targets of the human papillomavirus E7 oncoprotein.

The human papillomavirus (HPV) E7 protein is one of only two viral proteins that remain expressed in HPV-associated human cancers. HPV E7 proteins share structural and functional similarities with oncoproteins encoded by other small DNA tumor viruses such as adenovirus E1A and SV40 large tumor antigen. The HPV E7 protein plays an important role in the viral life cycle by subverting the tight link between cellular differentiation and proliferation in normal epithelium, thus allowing the virus to replicate in differentiating epithelial cells that would have normally withdrawn from the cell division cycle. The transforming activities of E7 largely reflect this important function.