This study investigates the regulation of human papillomavirus type 16 (HPV-16) DNA replication, focusing on the viral E2 protein and its interaction with cellular factors. Using mutational analysis of conserved regions in the E2 protein's N-terminal domain, researchers identified multiple functional domains with separable activities. Several E2 mutants could be isolated that retained some but not all E2 functions, demonstrating that transcriptional activation and DNA replication activities can be separated. Notably, mutant M11 retained wild-type E1-binding and near wild-type transcriptional activity while being defective in DNA replication, indicating E2 has roles beyond simply localizing E1 to the replication origin. The study also examined how cellular hormones and growth factors regulate viral replication. Glucocorticoid hormone (dexamethasone) significantly stimulated HPV-16 DNA replication by at least 33%, while epidermal growth factor (EGF) modestly inhibited replication by approximately 20%. These findings suggest that the relative levels of E2 protein, glucocorticoid hormones, and EGF within infected epithelial tissue may substantially influence the outcome of HPV infection and progression to cervical disease.

Key findings

• E2 protein contains multiple separable functional domains for E1 binding, transcriptional activation, and DNA replication, with some mutations disrupting replication while preserving other functions
• Glucocorticoid hormone (dexamethasone) stimulates HPV-16 DNA replication by at least 33%, while EGF inhibits replication by approximately 20%
• E2 has roles in DNA replication beyond simply targeting E1 to the origin, as demonstrated by mutant M11 which retains E1-binding ability but is replication-defective
• Multiple conserved regions in E2's N-terminal domain are essential for efficient viral DNA replication, including amino acids 23-26, 33, 47, 73, 156-159, and 186