Chromatin mobility is increased at sites of DNA double-strand breaks

DNA double-strand breaks (DSBs) can efficiently kill cancer cells, but they can also produce unwanted chromosome rearrangements when DNA ends from different DSBs are erroneously joined. Movement of DSB-containing chromatin domains might facilitate these DSB interactions and promote the formation of chromosome rearrangements. Therefore, we analyzed the mobility of chromatin domains containing DSBs, marked by the fluorescently tagged DSB marker 53BP1, in living mammalian cells and compared it with the mobility of undamaged chromatin on a time-scale relevant for DSB repair. We found that chromatin domains containing DSBs are substantially more mobile than intact chromatin, and are capable of roaming a more than twofold larger area of the cell nucleus. Moreover, this increased DSB mobility, but not the mobility of undamaged chromatin, can be reduced by agents that affect higher-order chromatin organization.