The productive phase of the HPV life cycle is restricted to the uppermost layer of the epithelium, in cells that have normally exited the cell cycle. The E7 protein maintains differentiating cells active in the cell cycle, allowing for productive replication and virion production. Cell cycle deregulation by E7 results in genomic instability that contributes to cancer development. Our long-term goal is to identify mechanisms that regulate the productive phase of the viral life cycle, which is important to understanding how HPV causes cancer. This proposal focuses on determining how HPV commandeers the ATM DNA damage-signaling pathway to facilitate productive replication. We will identify the mechanisms by which HPV activates ATM and determine how HPV utilizes ATM activity to drive viral replication. We hypothesize that HPV highjacks DNA signaling pathways through E7, leading to ATM activation that drives productive replication through homologous recombination repair.
Specific Aims to test this are: (1) To determine how HPV causes DNA damage by determining the contribution of E2F and STAT5 transcription factors to E7-induced ATM signaling. (2) To determine if ATM activity alters viral assembly of chromatin to facilitate DNA repair factor recruitment, as well as the contribution of the histone variant H2AX to viral replication. (3) To determine how DNA double strand break (DSB) repair pathways are regulated in HPV infected cells by using chromosomally integrated reporters for distinct repair pathways. We will also determine the contribution of the ATM target Nbs1, and the homologous recombination repair factors Rad51 and Brca1, to viral replication. Since ATM is essential to the maintenance of genomic stability and the prevention of cancer, it is important to understand how HPV manipulates this pathway to ensure completion of the viral life cycle. These studies will provide insight not only into viral life cycle, but also the potential mechanisms by which HPV induces genomic instability.
A subset of HPV types are the causative agents of cervical cancer, and are also associated several other human cancers. Our studies focus on the interaction between HPV and the DNA damage kinase ATM, a major regulator of genomic stability. Understanding how HPV activates and utilizes ATM signaling for viral replication has the potential to identify targets that could be important clinically for the treatment of HPV- associated diseases.