FACT maintains nucleosomes around promoters and opposes to the spreading of chromatin factors, thereby playing a major role in chromatin architecture

Amounting evidence suggests nucleosome organization is key for higher levels of chromatin packaging. However, studying it in higher eukaryotes is challenging due to the difficulty to manipulate nucleosomes in vivo and reconstitute their large higher-order chromatin domains in vitro. Facilitates chromatin transcription (FACT) is a H2A/B histone chaperone that displaces and re-assembles histones, being important for processes such as transcription. Recent studies report a minor role of FACT in chromatin architecture. Here, we studied chromatin organization upon rapid FACT degradation employing a multidimensional 3C technique with base-pair resolution (MCC-u) and genomic approaches. FACT loss leads to nucleosome depletion around active promoters, nano-scale domain collapse and emergence of larger nucleosome-free regions with increased protein binding. At a larger scale, we detect increased interactions between promoters across topologically associated domains. Thus, we demonstrate FACT plays a major role in chromatin organization and gain insights into the role of nucleosomes in genome architecture.