Circadian PERIOD proteins regulate TC-DSB repair through anchoring to the nuclear envelope

Repair of DNA double-strand breaks (DSBs) produced in transcriptionally active chromatin occurs through a poorly characterized pathway called transcription-coupled DSB repair (TC-DSBR). Here, using a screening approach scoring multiple outputs in human cells, we identified proteins from the PERIOD complex, ensuring circadian oscillations, as previously unknown TC-DSBR players. We show that PER2 is recruited at TC-DSBs and contributes to their targeting to the nuclear envelope (NE), where SUN1 and the nuclear pore complex (NPC) act as docking sites. TC-DSB anchoring at the NE fosters RAD51 assembly and prevents DSB clustering and translocations. In agreement, the circadian clock regulates TC-DSB targeting to the NE, RAD51 assembly, and DSB clustering. Our study shows a direct link between the circadian rhythm and the response to DSBs in transcribed genes, opening strategies for chrono-chemotherapies based on topoisomerase poisons that induce DSBs in active loci.