Human FACT subunits coordinate to catalyze both disassembly and reassembly of nucleosomes

作者：Micah J. McCauley, Michael A Morse, Nicole A. Becker, Qi Hu, Maria Victoria Botuyan, Emily Navarrete, Ran Huo, Uma M. Muthurajan, Ioulia F. Rouzina, Karolin Luger, Georges Mer, Louis James Maher, Mark C. Williams · 发表于：Cell Reports · 年份：2022 · DOI：10.1016/j.celrep.2022.111858 · 被引用次数：25 · 研究领域：RNA modifications and cancer、RNA and protein synthesis mechanisms、Genomics and Chromatin Dynamics

The histone chaperone FACT (facilitates chromatin transcription) enhances transcription in eukaryotic cells, targeting DNA-protein interactions. FACT, a heterodimer in humans, comprises SPT16 and SSRP1 subunits. We measure nucleosome stability and dynamics in the presence of FACT and critical component domains. Optical tweezers quantify FACT/subdomain binding to nucleosomes, displacing the outer wrap of DNA, disrupting direct DNA-histone (core site) interactions, altering the energy landscape of unwrapping, and increasing the kinetics of DNA-histone disruption. Atomic force microscopy reveals nucleosome remodeling, while single-molecule fluorescence quantifies kinetics of histone loss for disrupted nucleosomes, a process accelerated by FACT. Furthermore, two isolated domains exhibit contradictory functions; while the SSRP1 HMGB domain displaces DNA, SPT16 MD/CTD stabilizes DNA-H2A/H2B dimer interactions. However, only intact FACT tethers disrupted DNA to the histones and supports rapid nucleosome reformation over several cycles of force disruption/release. These results demonstrate that key FACT domains combine to catalyze both nucleosome disassembly and reassembly.