Abstract

Jens-Uwe Sommer1,2,3, Holger Merlitz1 and Helmut Schießel2,3   1Leibniz Institute of Polymer Research Dresden, Germany2Institute for Theoretical Physics, TU Dresden, Germany3Cluster of Excellence “Physics of Life” TU Dresden, Germany     Liquid-liquid phase separation of proteins is increasingly recognized as a fundamental concept to understand biological functions. Biomolecular condensates are formed at specific places in the cell, but what controls their size and life-time, and by which mechanisms different condensates interact or exchange material (and possibly information) with each other as well as with the environment is still largely unexplored. We introduce polymer-assisted condensation (PAC) which can explain the formation of localized and size-controlled condensates using concepts from polymer physics and phase separation theory. Our work, consisting of mean-field theory and simulations, highlights the role of meta-stable states of multi-component solutions near the miscibility gap which can be switched into condensed states triggered by a weak attractive interaction with a polymer. A significant change in interaction strength between proteins and polymer leaves the properties of the polymer-assisted condensate nearly invariant, and fluctuations in the concentration of the proteins outside the condensate are buffered which makes polymer-assisted condensates to be robust against variation of environmental factors. As an example we consider the case of hetero-chromatin. Here, the features of PAC provide a rational basis to explain preservation of epigenetic information during the cell cycle.   J.-U. Sommer, H. Merlitz, H. Schießel Polymer-Assisted Condensation: A Mechanism for Hetero-Chromatin Formation and Epigenetic Memory Macromolecules 55, 4841 (2022)