Video 1
Specific subnuclear regions were photoactivated, and DSBs were introduced in H2AX -/- MEFs by UV laser microirradiation. H2AX -/- MEFs expressing H2B-PAGFP and incubated with Hoechst dye were exposed to UV laser irradiation as described in Fig. S2. The pre-UV (arrow denotes zoomed circular region shown in the inset) and post-UV images are shown in the left panel, and corresponding differential interference contrast images are shown in the right panel. Images were collected every 20 s over a 10-min time period and were not corrected for cell migration or changes in rotation.