Conventional epifluorescence images were taken using an Olympus IX71 microscope with a 40×/0.6-NA objective and a digital EMCCD camera (Cascade 512B; Photometrics), and confocal imaging was done on a Leica TCS SP8 system with a 63×/1.4-NA oil-immersion objective. Fixed samples were either immersed in PBS for epifluorescence or mounted with antifade (Prolong Gold, P10144; Thermo Fisher Scientific) for confocal microscopy at room temperature. All fluorochromes (secondary antibodies) are listed in Immunostaining. Higher-NA lenses give higher-resolution images and should increase foci counts. Only Fig. S2 (B and D) in this study and images in Irianto et al. (2017) (link); Fig. 3 Ci) were taken using the 40×/0.6 NA objective, and control cells consistently show ∼10 γH2AX foci. Other images of γH2AX here and in Irianto et al. (2017) (link) (Fig. 1, C and D) were all taken with a 63×/1.4 NA objective, and control cells consistently show ∼15 γH2AX foci. Raw images were used directly for image quantification, and ImageJ was the only software used for analysis.