Control or KO ATAD3B HeLa cells were treated with 4 mM 3-NPA for 2 h. Cells were washed with fresh medium and incubated for another 1 h. Cells were then fixed and immunostained with DAPI and anti-8-oxo-dG antibodies and were analyzed by confocal microscopy. Scale bar, 10 µm. Quantification of the relative 8-oxo-dG fluorescence intensity in cells described in (D). Data are presented as mean ± SD (n = 3 independent experiments, 20 cells per experiment), statistical significance was assessed by two-tailed student's t-test , N.S., not significant, **p < 0.01. 