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bioRxiv · 10.1101/2025.05.09.653121

Roles of histone chaperone Nap1 and histone acetylation in regulating phase-separation of chromatin arrays

Gao, J.·Li, H.·Tan, S.·Zhou, R.·Lee, T.-H.
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Abstract

Chromatin condensation is dynamically regulated throughout the cell cycle and plays key roles in modulating gene accessibility at the highest physical level in a cell. The DNA-histone dynamics in short- and long-range inter-nucleosomal interactions are central to the regulation mechanisms of chromatin condensation which remain under active investigation. We employed 12-mer nucleosome arrays to investigate the roles of histone chaperone Nap1, and histone H3 and H4 N-terminal tails and their acetylation in regulating the formation and the properties of phase-separated chromatin condensates. These arrays form liquid-like condensate droplets under a physiological salt condition of 150 mM NaCl. According to our results from bright-field microscopy, fluorescence recovery after photobleaching, optical super-resolution imaging, and microrheology with optical tweezers, histone H4 tail lysine residues are the main drivers of liquid-liquid phase separation of chromatin arrays. We also found that the condensed liquid-like droplets contain both a mobile fraction and a relatively immobile structural scaffold and that histone chaperone Nap1 and histone H3 tail acetylation facilitate DNA-histone dynamics within the structural scaffold to lower the overall viscosity of the droplets. These results suggest that histone chaperone and histone H3/H4 tails play critical roles in regulating chromatin condensation and gene accessibility in condensed chromatin.

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Gao, J., Li, H., Tan, S., Zhou, R., Lee, T.-H.. 2025-05-14. Roles of histone chaperone Nap1 and histone acetylation in regulating phase-separation of chromatin arrays. https://doi.org/10.1101/2025.05.09.653121

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