ABSTRACT: Skin exposed to UV light is one of the major contributing factors for developing melanoma. It is hypothesized that cancer begins at the DNA level through genomic instability as UV light distorts the DNA bases and disrupts DNA replication and transcription. This damage can result in an increase in mutations, disruption of normal cell function, and uncontrolled cell growth. The cell has a way of coping with this damage through DNA repair pathways including translesion repair and nucleotide excision repair. These repair pathways utilize specialized enzymes that recognize the damage, remove the distorted bases, and DNA Polymerase replaces it with the correct nucleotide that complements the opposing strand ensuring genomic integrity. In a clinical setting, we have identified mutations in DNA Polymerase, POLQ (Pol θ) in melanoma patients with sun-exposed tumors. Although POLQ is not typically associated with the UV- damage repair pathway, our preliminary data suggest that these variants experience decreased polymerase activity and might contribute to mutagenesis and melanoma. This project, in collaboration with Sarah Delaney at Brown University, seeks to uncover the connection between POLQ and repair of UV damaged DNA potentially uncovering a new biological role for Pol θ. To accomplish this, we propose a series of biochemical and cellular experiments that look at the ability of WT Pol θ and the cancer- associated variants to  bypass and extend  UV-damaged DNA (aim 1) as well as structural studies to explore the differences in nucleotide selection between WT and variant Pol θ (aim 2). The results from our efforts seek to provide evidence for the mechanism of cancer due to a defective DNA repair enzyme with Pol θ as a potential drug target for treatment of melanoma.

RELEVANCE: UV-light is one of the major contributing factors for developing cancer.  Although the cell has ways of coping with this damage through DNA repair pathways, dysfunctional repair enzymes have been implicated in cancer.  This proposal seeks to uncover how cancer-associated variants of the DNA repair enzyme, Pol θ, repair UV-damaged DNA.