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.
Alagoz M, Wells OS, El-Khamisy SF (2013). TDP1 deficiency sensitizes human cells to base damage via distinct TOP1 and PARP mechanisms with applications for cancer therapy. Nucleic Acids Res 1; 42(5): 3089-103.
Professor of Molecular Medicine, Director of Research and Innovation and co-founder of the Healthy Life Span Institute, University of Sheffield, United Kingdom
Sherif El-Khamisy is a Wellcome Trust Investigator and co-founder of the Healthy Lifespan Institute at the University of Sheffield. El-Khamisy lab studies how cells maintain genomic integrity and their impact on health. The lab uses interdisciplinary approach fusing genetics, chemistry and biology with clinical expertise. We use mouse and zebrafish models to stay ageing and multimorbidity at the molecular and organismal level. We link our molecular understanding to public health challenges through interactions with social scientists.