Chromatin Mechanics and the Biological Implication*

The nucleus of the cell is a dense repository of information. But the DNA of the genome is more than just a string of letters – it forms “chromatin” a protein-nucleic-acid fiber with complex organization. Increasingly, the spatial organization of the genome has come into focus based on a suite of new technologies. The emerging picture spans scales from nucleosomes to loop domains to phase-separated regions. In parallel, the mechanics of chromatin has been probed by passive and active rheology, with its own emerging picture of chromatin as a viscoelastic and heterogeneous material. How are these two pictures related? To address this question, we developed a mechanistic model of chromatin using coarse-grained molecular dynamics simulations. The model captures chromatin’s central viscoelastic nature and its observed heterogeneity, and has revealed long-range cross-links as critical to reproduce experimental observations. Our results further elucidate the role of mechanics in fundamental biological processes taking place in the cell nucleus.