In Diverse Conditions Intrinsic Chromatin Condensates Have Liquid-like Material Properties

Bryan A. Gibson, Claudia Blaukopf, Tracy Lou, Lynda K. Doolittle, Ilya J. Finkelstein, Geeta J. Narlikar, Daniel W. Gerlich, Michael K. Rosen , BioRxiv (2021).

Abstract

Eukaryotic nuclear DNA is wrapped around histone proteins to form nucleosomes, which further assemble to package and regulate the genome. Understanding of the physical mechanisms that contribute to higher order chromatin organization is limited. Previously, we reported the intrinsic capacity of chromatin to undergo phase separation and form dynamic liquid-like condensates, which can be regulated by cellular factors. Recent work from Hansen, Hendzel, and colleagues suggested these intrinsic chromatin condensates are solid in all but a specific set of conditions. Here we show that intrinsic chromatin condensates are fluid in diverse solutions, without need for specific buffering components. Exploring experimental differences in sample preparation and imaging between these two studies, we suggest what may have led Hansen, Hendzel, and colleagues to mischaracterize the innate properties of chromatin condensates. We also describe how liquid-like in vitro behaviors can translate to the locally dynamic but globally constrained movement of chromatin in cells.