title: TDP1 deficiency sensitizes human cells to base damage via distinct topoisomerase I and PARP mechanisms with potential applications for cancer therapy.
abstract: Base damage and topoisomerase I (Top1)-linked DNA breaks are abundant forms of endogenous DNA breakage, contributing to hereditary ataxia and underlying the cytotoxicity of a wide range of anti-cancer agents. Despite their frequency, the overlapping mechanisms that repair these forms of DNA breakage are largely unknown. Here, we report that depletion of Tyrosyl DNA phosphodiesterase 1 (TDP1) sensitizes human cells to alkylation damage and the additional depletion of apurinic/apyrimidinic endonuclease I (APE1) confers hypersensitivity above that observed for TDP1 or APE1 depletion alone. Quantification of DNA breaks and clonogenic survival assays confirm a role for TDP1 in response to base damage, independently of APE1. The hypersensitivity to alkylation damage is partly restored by depletion of Top1, illustrating that alkylating agents can trigger cytotoxic Top1-breaks. Although inhibition of PARP activity does not sensitize TDP1-deficient cells to Top1 poisons, it confers increased sensitivity to alkylation damage, highlighting partially overlapping roles for PARP and TDP1 in response to genotoxic challenge. Finally, we demonstrate that cancer cells in which TDP1 is inherently deficient are hypersensitive to alkylation damage and that TDP1 depletion sensitizes glioblastoma-resistant cancer cells to the alkylating agent temozolomide.
authors: Kreb's Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK, Genome Damage and Stability Center, University of Sussex, Falmer, Brighton, BN1 9RQ, UK and Center of Genomics, Helmy Institute, Zewail City of Science and technology, Giza, Egypt.
authors: Meryem
authors: M
authors: Alagoz
authors: Owen S
authors: OS
authors: Wells
authors: Sherif F
authors: SF
authors: El-Khamisy
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity; D002460:Cell Line; D045744:Cell Line, Tumor; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000037:antagonists & inhibitors; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy; D010727:Phosphoric Diester Hydrolases / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000477:Alkylating Agents; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases; D010727:Phosphoric Diester Hydrolases; C498508:TDP1 protein, human; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D004264:DNA Topoisomerases, Type I; C528909:TOP1 protein, human