Fig. 1. Mini-Ph forms phase-separated condensates with chromatin.

a Schematic of Polyhomeotic–proximal and Mini-Ph, which spans aa 1389–1577 and includes the 3 conserved domains and an unstructured linker. The gray line indicates predicted disordered sequence (using PONDR-VSL2)⁹². Note that 91.9% of the sequence is predicted to be disordered (disregarding segments less than 30 amino acids), with only the SAM predicted to be ordered. b Schematic depicting the oligomeric state of Mini-Ph, which forms limited polymers of 4–6 units (6 are shown)⁵. c Structure of nine units of the Ph SAM polymer demonstrating its helical architecture. The N terminus, from which the linker extends, is shown in cyan. PDB 1D 1KW4. d, e Neither chromatin (d) nor Mini-Ph (e) form condensates in buffer. f Mini-Ph forms phase-separated condensates with chromatin. This observation was repeated with three different preparations of Mini-Ph and more than ten different chromatin preparations. g Time lapse of droplet fusion of Mini-Ph-chromatin condensates, visualized with Alexa-647-labeled Mini-Ph. h 3D reconstruction of confocal stack of images demonstrating that Mini-Ph-chromatin condensates form a fused layer on the bottom of the imaging plate. Scale is in microns. i Representative images from a matrix of Mini-Ph and chromatin showing the relationship between protein and chromatin concentration and condensate formation. [Nucleosomes] assume 8 fmol of nucleosomes per 1 ng of DNA. Images are representative of two independent experiments. j Graph depicting the conditions where one phase and two phases were scored in two experiments like the one shown in (i). See also Supplementary Figs. 1–3 and Supplementary Movies 1–3.