title: Dysregulated human Tyrosyl-DNA phosphodiesterase I acts as cellular toxin.
abstract: 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.
authors.affiliation: Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.
authors.forename: Selma M
authors.initials: SM
authors.lastname: Cuya
authors.affiliation: Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.|Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN 38105-3678, USA.
authors.forename: Evan Q
authors.initials: EQ
authors.lastname: Comeaux
authors.affiliation: Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.|Department of Medicine, Division of Clinical Immunology & Rheumatology, University of Alabama at Birmingham, Birmingham, AL 35294-0001, USA.
authors.forename: Keith
authors.initials: K
authors.lastname: Wanzeck
authors.affiliation: Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.
authors.forename: Karina J
authors.initials: KJ
authors.lastname: Yoon
authors.affiliation: Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL 35294-0019, USA.
authors.forename: Robert C A M
authors.initials: RC
authors.lastname: van Waardenburg
mesh_terms: D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D010727:Phosphoric Diester Hydrolases / Q000502:physiology*; D019772:Topotecan / Q000494:pharmacology
chemical_list: D019772:Topotecan; D004247:DNA; D010727:Phosphoric Diester Hydrolases; C122147:tyrosyl-DNA phosphodiesterase; D004264:DNA Topoisomerases, Type I
keywords: DNA repair; DNA topoisomerases; DNA-adducts; TDP1; biochemistry