A Representative immunofluorescence microscopy images of endogenous wild‐type (WT) and USP45 knockout (KO) U2OS cells treated with no drug, BrdU (10 μM, 24 h), psoralen or angelicin (25 μM, 3 h). Cells were fixed 10 min after laser micro‐irradiation and stained for localisation of endogenous USP45, phosphorylated γ‐H2AX and DAPI. The right‐hand panel shows magnification of one micro‐irradiated cell. Similar results were obtained in at least three independent experiments. Scale bar, 10 μm. 