Chromatin compartmentalization regulates the response to DNA damage

DNA Double Strand Breaks (DSBs) repair is essential to safeguard genome integrity but little is known about the contribution of chromosome folding into these processes. Here we unveiled basic principles of chromosome dynamics occurring post-DSB both locally and at a genome wide scale in mammalian cells. We report that topologically associating domains (TAD) that experience a DSB undergo acute ATM-dependent but DNAPK- independent changes. Within these damaged TADs, DSB-induced loop extrusion ensures local transcriptional regulation in response to DSBs. Damaged TADs further coalesce in an ATM-dependent manner, forming a new “D” compartment, where upregulated genes of the DNA damage response (DDR) physically localize suggesting a function of DSB clustering in activating the DNA damage Response. However, these alterations of chromosome folding induced by DSB also come at the expense of an increased translocations rate. Our work highlights the critical impact of chromosome conformation in the maintenance of genome integrity.