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NIH grant 1R56AI189822-01A1: Functional dissection of a novel E2 complex critical for the HPV16 life cycle
Institute: {'code': 'AI', 'abbreviation': 'NIAID', 'name': 'National Institute of Allergy and Infectious Diseases', 'admin_org_id': '12500003', 'admin_funding_url': ''}. PI: Iain Morgan. Award: $768308.
Start: 2026-09-24T00:00:00.
ABSTRACT
While immunization will reduce the HPV disease burden on future generations, novel HPV targeted therapeutics
remain a priority due to world-wide availability issues and the majority of the current population being
unprotected. Enhancing viral-host interaction understanding will identify therapeutic targets and this proposal will
focus on an E2-host complex.
HPV16 is the most prevalent cancer related HPV and during the viral life cycle the E2 protein regulates replication
in association with the viral E1 helicase, regulates viral and host gene transcription, and segregates the viral
genome into daughter nuclei following mitosis. In this latter function, E2 binds to specific DNA sequences on the
viral genome using a carboxyl-terminal DNA binding domain, while the amino-terminal domain interacts with host
chromatin. E2 acts as a “bridge” allowing the viral genome to “hitchhike” onto host mitotic chromatin so that viral
genomes reside in daughter nuclei following mitosis. We demonstrated that E2 interaction with TOPBP1 (a host
protein involved in DNA metabolism) is required for E2 segregation function and that during mitosis activates the
DNA damage response (DDR). These observations were extended into HPV16 life cycles and we have
demonstrated that E2 is responsible for DDR activation during the viral life cycle in differentiating epithelium. E2-
TOPBP1 creates an “ATM up ATR down” phenotype which promotes viral replication via homologous replication
(HR), and promotes proliferation of the infected cell by blocking ATR replication stress signaling and cell cycle
arrest. We have also demonstrated that E2 activates the DDR via displacement of CIP2A from TOPBP1 during
differentiation (and mitosis); CIP2A then inhibits PP2A which promotes ATM phosphorylation triggering the DDR.
While the viral oncogenes can cause DNA damage, they cannot activate the DDR; we have discovered the
mechanism for activation of a major signaling pathway required for the viral life cycle. ATM activation
creates vulnerability of E2 positive cells to ATM inhibitors. Also, disruption of the TOPBP1-CIP2A complex by
E2 creates synthetic lethality with inhibition of HR; RAD51 inhibitors kill E2 expressing cells.
Aim 1 will extend our understanding of the E2-TOPBP1 centered complex (ETCC). Our preliminary proteomic
screening has identified additional ETCC members and their role in the viral life cycle will be determined. We
also demonstrate here that E2 disrupts DNA repair pathways in keratinocytes and this will be further
characterized, as well as the roles of E6 and E7 in regulating these pathways. Using Cut&Run (an alternative to
ChIP-seq) we have demonstrated that E2 interaction with host chromatin changes during differentiation. We will
investigate the overlap in chromatin binding between E2 and ETCC host factors, and whether E2 regulates host
factor chromatin interaction during differentiation. Finally, we will determine whether HPV18 and 31 E2 behaves
similarly to HPV16 to expand the significance of our results. Aim 2 will develop the synthetic lethality generated
by E2 to ATM or RAD51 inhibition into in vivo models in order to generate pre-clinical data.document fetched 2026-10-04 02:44