FACT mediates cohesin function on chromatin

Cohesin is a key regulator of genome architecture with roles in sister chromatid cohesion 1,2 and the organisation of higher-order structures during interphase 3 and mitosis 4,5 . The recruitment and mobility of cohesin complexes on DNA is restricted by nucleosomes 6-8 . Here we show that cohesin role in chromosome organisation requires the histone chaperone FACT. Depletion of FACT in metaphase cells affects cohesin stability on chromatin reducing its accumulation at pericentric regions and binding on chromosome arms. Using Hi-C, we show that cohesin-dependent TAD (Topological Associated Domains)-like structures in G 1 and metaphase chromosomes are disrupted in the absence of FACT. Surprisingly, sister chromatid cohesion is intact in FACT-depleted cells, although chromosome segregation failure is observed. Our results uncover a role for FACT in genome organisation by facilitating cohesin-dependent compartmentalization of chromosomes into loop domains.