A Clonogenic survival assays were carried out in wild‐type (WT), USP45 knockout (KO) or USP45 KO cells re‐expressing wild‐type USP45 (RESWT) or catalytically inactive USP45 [Cys199Ala] (RESCA). The cells were treated with the indicated doses of mitomycin C (MMC) 16 h. Medium was changed and number of colonies quantified after 10 days. Each data point is the average of 3 experiments undertaken with 6 replicates ± SD. 