Figure 5.

Putative models for HPV E2 DNA binding and activation of the low-risk and high-risk replication origins. The E2 protein in low-risk HPV binds to its specific sequence and creates a loop formation to initiate DNA replication. The E2 protein in high-risk HPV binds the sequence with weaker affinity, thus decreasing the loop formation and inactive origin, which leads to no replication of viral DNA.