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DNA Polymerase Theta and its Potential Role in Cancer

Investigator: Jamie Towle-Weicksel, Rhode Island College

Mentor: Sarah Delaney, Brown University

Scientific Theme: Cancer

Abstract: DNA is randomly damaged on a daily basis by many factors including environmental exposure and random replicative errors.  This damaged DNA can lead to genomic instability and eventually cancer. The cell copes with this damage through DNA repair pathways and this proposed study focuses on one key member, DNA polymerase Theta (Pol θ) or POLQ.  DNA polymerases synthesize new DNA by “reading” the original DNA template.  Poorly functioning DNA polymerases have been shown to contribute to genetic instability by incorporating the wrong nucleic acid across from the original DNA template.  Pol θ performs low fidelity repair for certain types of DNA damage.  Interestingly, POLQ expression has been shown to be upregulated in several types of cancer and is associated with poor survival rates.  There are limited research studies exploring aberrant Pol θ mutants and their link to cancer.  We have identified several POLQ mutations from patient-derived melanomas and aim to study how their polymerization mechanisms differ from wild-type and how they may be a driver of cancer.  Our preliminary studies suggest Pol θ variants experience different polymerase activity compared to wild-type Pol θ and we will continue to define the polymerase activity of these mutants.  In addition, we will generate a fluorescence resonance energy transfer (FRET) system to track conformational changes that occur during nucleotide incorporation.  This will provide a method in which to observe the pathway for nucleotide incorporation.  By setting up such a system, we can compare movements of wild-type Pol θ compared to the cancer-associated variants to provide evidence for different kinetic pathways.   We hypothesize that variant Pol θ will exhibit a preference for incorporation of the incorrect nucleotide leading to mutagenesis of the DNA and experience different conformational changes during nucleotide incorporation compared to wild-type.  This research is significant in that we aim to demonstrate a mechanism of carcinogenesis as well as identify a potential biomarker of melanoma.

Human Health Relevance: DNA polymerases are necessary for maintaining DNA fildelity as increased mutagenesis has been associated with cancer.  Pol θ may play an important role in overall genomic stability due to its DNA repair capabilities. By identifying and characterizing cancer-associated variants of Pol θ that have reduced DNA repair abilities, our studies will provide fundamental insight as to the mechanism of mutagenesis and cancer.

 

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