Biochemical characterization of DNA repair enzyme inhibitors, molecules with possible applications to improving cancer treatment
Polynucleotide kinase-phosphatase (PNKP), inhibitors, cancer treatment
Polynucleotide kinase-phosphatase (PNKP) is a critical DNA repair enzyme responsible for processing DNA damage caused by radiation. A loss of function in this enzyme results in increased cell susceptibility to radiation-induced DNA damage and subsequent cell death. As radiation therapy is commonly used in cancer treatment, targeted inhibition of PNKP has been proposed to increase the effectiveness of radiation therapy at lower doses. We characterized two previously identified PNKP inhibitors, Candesartan and S4, by their effects on the kinase activity, kinase substrate binding, and phosphatase substrate binding of Caenorhabditis elegans and mouse PNKP. The binding assays were conducted using electromobility shift assays (EMSA), while in vitro kinase assays were performed to assess kinase activity. Both inhibitors had an effect on both domains of PNKP, but were more effective at displacing the phosphatase substrate than the kinase substrate. Comparisons of kinase activity inhibition by new and older samples of inhibitors showed that both Candesartan and S4 degrade over a span of 3-4 months and lose their effectiveness. These inhibitors show promise for applications in cancer treatment, but further research is needed.
Presented May 25-26, 2020 online at the Undergraduate Research in Science Conference of Alberta (URSCA) hosted by the University of Lethbridge, Lethbridge, Alberta.
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