Control of DNA double-strand break repair by the KDM8 histone demethylase

KDM8 is a histone demethylase initially characterized for its activity on H3K36me2, although its function is now more widely recognized as a hydroxylase. Through a high-throughput screening on histone demethylases, we identified KDM8 as a regulator of the γH2AX response following ionizing radiation. Experiments using specific reporter substrates revealed that KDM8 depletion increases homologous recombination (HR), while its overexpression reduces HR. This shift is counterbalanced by a concomitant decrease in non-homologous end joining (NHEJ), an effect partly independent of its demethylase activity and unrelated to cell cycle alterations. Despite this imbalance, cellular sensitivity to DNA-damaging agents - such as ionizing radiation, mitomycin C, and camptothecin - remains unchanged. FRET experiments in living cells demonstrated an interaction between KDM8 and Rad51 after DNA damage induced by camptothecin. These findings identify KDM8 as a key player in DSB repair, specifically influencing HR.