Figure 1.

Human papillomavirus (HPV) genome map. The HPV genome encodes 8 major proteins. E6 and E7 are the viral oncoproteins of HPV that function to disrupt cell cycle control mechanisms in the host cell, driving cell proliferation and viral replication. The other “early” genes, E1, E2, E4, and E5, encode proteins that have roles in viral replication. E2 is also involved in controlling viral oncogene expression. One function is to serve as a transcriptional repressor of E6 and E7, coordinating the viral life cycle with keratinocyte differentiation. After viral genome amplification in the suprabasal cells, E6 and E7 expression is attenuated and viral capsid production begins. The 2 “late” genes, L1 and L2, encode for structural proteins that constitute the viral capsid necessary for packaging and transmission of the newly replicated virus (Munger et al. 2004).