The dynamic structure of nuclear chromatin and its regulation in the formation of repair complex is essential in DNA damage response and repair. Using single molecule localization microscopy STORM this work discovered that the nuclear chromatin organization was relaxed from 200 to 400 nm thick irregular frame and remodeled to dispersed sub-100 nm structure in HeLa cells after X-ray irradiation. The DSB repair factors (γ-H2AX, MDC1, 53BP1) showed distribution as microscale-colocalized and nanoscale interlaced substructure in the DSB repair complex. The dual-color nanoscopic imaging of γ-H2AX and chromatin at the DSB sites suggest that DNA damage response and repair cascade are chromatin structure-dependent and also partly dependent on the distance to the DSB sites. The sub-100 nm structure of fibers and nanoclusters of the relaxed nuclear chromatin and the DSB repair factors highly resembled the cross-section view of chromatin organization. These data demonstrated the polymorphic and dynamic behavior of the chromatin organization in vivo, and provided nanoscale insight into the interplay between chromatin remodeling and DNA damage response and DNA repair.

核染色质的动态结构及其在修复复合物形成中的调控对于DNA损伤反应和修复至关重要。使用单分子定位显微镜STORM，这项工作发现X射线照射后，核染色质组织从200到400 nm厚的不规则框架松弛，并重塑为HeLa细胞中分散的100 nm以下结构。DSB修复因子（γ-H2AX，MDC1、53BP1）在DSB修复复合物中显示为微尺度共定位和纳米级交错的子结构。γ-H2AX和染色质在DSB位点的双色纳米成像表明，DNA损伤反应和修复级联是染色质结构依赖性的，并且还部分取决于到DSB位点的距离。松弛核染色质的纤维和纳米簇的亚100 nm结构以及DSB修复因子高度类似于染色质组织的横截面图。这些数据证明了染色质组织在体内的多态性和动态行为，并提供了对染色质重塑与DNA损伤反应和DNA修复之间相互作用的纳米级见解。