# Organization of fast and slow chromatin revealed by single-nucleosome dynamics

## TL;DR

This study reveals that chromatin in living human cells is organized into dynamic domains of fast and slow nucleosomes, characterized by their movement patterns and interactions, influenced by histone modifications and chromatin tethering.

## Contribution

It introduces a novel statistical analysis of single-nucleosome dynamics, identifying bi-modal movement patterns and dynamic domains in chromatin organization.

## Key findings

- Nucleosomes exhibit bi-modal mean squared displacement distribution.
- Dynamic domains of fast and slow nucleosomes are identified.
- Histone modifications and chromatin tethering influence nucleosome dynamics.

## Abstract

Understanding chromatin organization and dynamics is important since they crucially affect DNA functions. In this study, we investigate chromatin dynamics by statistically analyzing single-nucleosome movement in living human cells. Bi-modal nature of the mean squared displacement distribution of nucleosomes allows for a natural categorization of the nucleosomes as fast and slow. Analyses of the nucleosome-nucleosome correlation functions within these categories along with the density of vibrational modes show that the nucleosomes form dynamically correlated fluid regions, i.e., dynamic domains of fast and slow nucleosomes. Perturbed nucleosome dynamics by global histone acetylation or cohesin inactivation indicate that nucleosome-nucleosome interactions along with tethering of chromatin chains organize nucleosomes into fast and slow dynamic domains. A simple polymer model is introduced, which shows the consistency of this dynamic domain picture. Statistical analyses of single-nucleosome movement provide rich information on how chromatin is dynamically organized in a fluid manner in living cells.