Mutual Antagonism Between PRC1 Condensates and SWI/SNF in Chromatin Regulation

Opposing activities of conserved chromatin regulatory complexes, such as the Polycomb Repressive Complex 1 (PRC1) and the activating chromatin remodeler SWI/SNF play critical roles in regulating gene expression. However, the mechanisms by which these complexes compete to regulate chromatin states remain poorly understood. Here, we demonstrate that the condensate-forming properties of PRC1 play an important role in excluding SWI/SNF from chromatin. Consistently, PRC1 compositions with a higher propensity for condensate formation are more effective in preventing SWI/SNF binding. Conversely, SWI/SNF-bound chromatin significantly reduces PRC1 binding and subsequent condensate formation. Notably, SWI/SNF can suppress PRC1 condensate formation in an ATP-hydrolysis independent manner, suggesting a mechanism driven by competitive binding and steric hindrance rather than active remodeling. Our findings reveal a mutual antagonism between PRC1 condensates and SWI/SNF chromatin remodeling, highlighting the importance of PRC1 composition and condensate formation in regulating gene repression.