Fig. 5: PRC1 condensates lead to chromatin compaction.

a Schematic of compaction experiment. After inducing condensate formation, chromatin compaction is examined and tested to determine whether compaction remains after deactivation. b CBX2-Corelet cell with H2B-miRFP670 before (t = 0) and after activation (30 min). Scale bar is 5 µm. c The normalized variance in the CBX2 signal increases rapidly as condensates form and decreases rapidly upon deactivation, as condensates dissolve. Data are presented as mean +/− SD, n = 10 cells. d The normalized variance in the H2B-miRFP670 signal increases gradually over time, and the high variance remains after deactivation, indicating sustained compaction. Error band represents mean +/− SD. e Integral of the CBX2 variance, showing that compaction sums over the prior history of CBX2 phase separation. Error band represents mean +/− SD. f Result of molecular dynamics simulation: chromatin bead density over time. Vertical line indicates time point at which proteins no longer bind chromatin. Error band represents mean +/− SD. g Snapshot images from molecular dynamics simulation. The chromatin chain in blue, with H3K27me3 patches in yellow, proteins in brown, and H2AK119Ub chromatin beads in red. h Long durations of prior PRC1 phase separation can lead to strong sustained chromatin compaction, even in the absence of sustained PRC1 phase separation.