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.

Neuroprotection and repair of 3′-blocking DNA ends by glaikit (gkt) encoding Drosophila tyrosyl-DNA phosphodiesterase 1 (TDP1)

“…The nervous system coordinates the defenses of the whole body to endogenous and exogenous insults by modulating the activities of neuroendocrine pathways and the autonomic nervous system (53). Hydrolysis of the 3′-terminal glycolate-DNA phosphodiester by TDP1 repairs oxidative damage (2,4,5,15,21). Restoration of the lifespan of TDP1 mutant females by expression of TDP1 with nrv2-Gal4 in the central nervous system suggests that resistance to oxidative stress in the nervous system is a prerequisite for normal lifespan.…”

“…aging | neuroscience | DNA repair | topoisomerase | fly D NA repair is indispensable to maintaining genomic integrity against the various endogenous and exogenous agents and enzymes that react with DNA, including reactive oxygen species (1-3), base-damaging agents (4,5), and chain-terminating nucleosides (6), which yield nonligatable DNA ends. In addition, topoisomerase I (Top1) (7-9) is capable of generating strand breaks with protein-blocked 3′ ends.…”

Synthesis and biological evaluation of novel tyrosyl-DNA phosphodiesterase 1 inhibitors with a benzopentathiepine moiety

“…13,14 Furthermore, camptothecin and etoposide cause less DNA damages in cells with heightened TDP1 expression. [15][16][17][18] In addition, TDP1 activity suppression makes tumor cells hypersensitive to the anticancer agent temozolomide (purine methylation), 19 methyl methanesulfonate (AP-sites generation), bleomycin (single/double strand breaks with 3 0 -phosphoglycolates), H 2 O 2 and ionizing radiation (breaks and other lesion types). 20 For all of these DNA damaging agents it can be assumed that TDP1 is involved in DNA repair.…”

Topoisomerase-mediated chromosomal break repair: an emerging player in many games

“…Similarly, in vitro studies demonstrated trapping of TOP1 by nicks or DNA secondary structures 28 . More recent in vivo work has shown that ionizing radiation and chemotherapies such as alkylating agents can also generate PDBs, at least a subset of which are repaired by activities that liberate TOP1 from DNA termini [29][30][31] .…”