2025/02/11 by Alberto Marín-González, Adam T Rybczynski, Namrata M. Nilavar +8 · 2 voices
Biochemistry, Genetics and Molecular Biology · #Genomics and Chromatin Dynamics #RNA and protein synthesis mechanisms #Bacterial Genetics and Biotechnology
paper · pdf · doi:10.1101/2025.02.10.637451
openalex publication_date 2025/02/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/22
ABSTRACT Cohesin folds genomes into chromatin loops, whose roles are under debate. We report that double strand breaks (DSB) induce de novo formation of chromatin loops, with the break positioned at the loop base. These loops form only in S/G2 phases and occur during repair via homologous recombination (HR), concomitant with DNA end resection and RAD51 assembly. RAD51 showed two-tiered accumulation around DSBs, with a broad (~Mb) domain arising from the homology search. This domain is regulated by cohesin unloader, is constrained by TAD boundaries, and it overlaps with chromatin regions reeled through the break-anchored loop, suggesting that loop extrusion regulates the homology search. Indeed, depletion of NIPBL results in reduced HR, and this effect is more pronounced when the HR donor is far (~100 kb) from the break. Our data indicates that loop-extruding cohesin promotes the mammalian homology search by facilitating break-chromatin interactions within the damaged TAD. One-Sentence Summary High spatiotemporal resolution analysis of double strand beak repair in 3D genome revealed the role of cohesin-driven loop extrusion in the homology search.