Dysregulated human Tyrosyl-DNA phosphodiesterase I acts as cellular toxin
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Selma M. Cuya1, Evan Q. Comeaux1,2, Keith Wanzeck1,3, Karina J. Yoon1, Robert C.A.M. van Waardenburg1
1Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA
2Department of Pathology, St. Jude Children’s Research Hospital, Memphis, TN 38105-3678, USA
3Department of Medicine, Division of Clinical Immunology & Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294-0001, USA
Robert C.A.M. van Waardenburg, email: [email protected]
Keywords: TDP1, DNA-adducts, biochemistry, DNA topoisomerases, DNA repair
Received: July 16, 2016 Accepted: November 09, 2016 Published: November 23, 2016
Tyrosyl-DNA phosphodiesterase I (TDP1) hydrolyzes the drug-stabilized 3’phospho-tyrosyl bond formed between DNA topoisomerase I (TOPO1) and DNA. TDP1-mediated hydrolysis uses a nucleophilic histidine (Hisnuc) and a general acid/base histidine (Hisgab). A Tdp1Hisgab to Arg mutant identified in patients with the autosomal recessive neurodegenerative disease SCAN1 causes stabilization of the TDP1-DNA intermediate. Based on our previously reported Hisgab-substitutions inducing yeast toxicity (Gajewski et al. J. Mol. Biol. 415, 741-758, 2012), we propose that converting TDP1 into a cellular poison by stabilizing the covalent enzyme-DNA intermediate is a novel therapeutic strategy for cancer treatment. Here, we analyzed the toxic effects of two TDP1 catalytic mutants in HEK293 cells. Expression of human Tdp1HisnucAla and Tdp1HisgabAsn mutants results in stabilization of the covalent TDP1-DNA intermediate and induces cytotoxicity. Moreover, these mutants display reduced in vitro catalytic activity compared to wild type. Co-treatment of Tdp1mutant with topotecan shows more than additive cytotoxicity. Overall, these results support the hypothesis that stabilization of the TDP1-DNA covalent intermediate is a potential anti-cancer therapeutic strategy.
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