KAT5 and Friedreich ataxia: We show that a) 53BP1 foci over-accumulate in the nuclei of FANCcore complex-deficient and FANCD2-deficient cells following MMC treatment; b) 53BP1 accumulation is due to the local maintenance of the chromatin in a hypoacetylated state as a consequence of the failure of TIP60 accumulation at damaged chromatin; and c) siRNA-mediated depletion of 53BP1 as well as exposure to deacetylase inhibitors significantly restores MMC resistance in FA cells by favoring the HR process.