Polymerase theta, genome instability, and cancer

PROJECT SUMMARY: OVERALL DNA Polymerase theta (Pol θ) in mammalian cells confers resistance to chemotherapeutic drugs like topoisomerase inhibitors and crosslinking agents. It is excessively engaged in cells deficient in a wide variety of other DNA damage response (DDR) genes, including those associated with hereditary breast cancer (BRCA1/2). Thus, while Pol θ inhibition or deficiency is generally tolerated in normal cells, it is lethal in BRCA-deficient cancers (synthetic lethality). Accordingly, inhibitors of Pol θ have been employed in clinical trials as therapy for patients with BRCA-deficient breast or ovarian cancer. We propose here to clarify the mechanism of Pol θ mediated repair and identify cellular contexts most likely to emphasize cancer-specific vulnerability to Pol θ inhibitors Our multidisciplinary program is founded on an interest in molecular mechanism, and address how molecular structure dictates its function using in vitro models. In the context of cellular repair we will address how it functions in its conventional role in repair of chromosomal double strand breaks caused by exogenous agents, like ionizing radiation. We will compare this mechanism to Pol θ function in repair of damage caused by different types of cancer relevant-replication stress, including replication stress caused by endogenous elements (at risk sequences, transcription-replication conflicts) and chemotherapeutic drugs. . Accordingly, our project unites 5 researchers in 4 projects with complementary expertise: Sylvie Doublié (structural biology), Gaorav Gupta (cancer cell biology), Dale Ramsden (molecular biology), Eli Rothenberg (biophysics), and Richard Wood (biochemistry). We seek to exploit the apparent synergy of our team to achieve the following overall aims: Aim 1. We will determine molecular requirements for Pol θ -dependent repair Aim 2. We will identify cancer-relevant contexts that engage Pol θ Aim 3. We will develop new strategies for targeting Pol θ -dependent repair in cancer