Super-resolved heterochromatin structure during DNA damage response revealed by CRISPR imaging.

Abstract

Heterochromatin plays an important role in gene expression regulation and accurate chromosome segregation. Heterochromatin undergoes a DNA damage repair process distinct from that of euchromatin, involving large-scale rearrangement coupled to nuclear membrane and motor proteins. Revealing the nanoscale structure and dynamics of heterochromatin during its repair is essential for understanding the detailed mechanism of the wholeness DNA repair process, and the role of the distinct compaction and reorganization of heterochromatin. Here, we observed the novel structure and dynamics of heterochromatin in super resolution using CRISPR labeling techniques. Dense labeling of a pericentromeric region with CRISPR prevented cell cycle progression and induced DNA damage response accompanied by domain expansion and fiber-like extension beyond its chromosome territory. This structural change correlates with the DNA damage repair proteins. Due to persistent binding of an array of CRISPR complexes, the cell failed to repair the perceived damage, resulting in senescence-like phenotype. Use of advanced CRISPR labeling techniques allowed super-resolution imaging of the chromatin domain under repair in live cells. Our work highlights the DNA damage response in heterochromatin induced by molecular blockades and the resulting structural changes, providing a platform to study DNA repair process with high spatiotemporal resolution.