Fig. 3: Hetero-oligomerization contributes to condensate formation.

a Domain architecture of BMI1^WT (top). Images show BMI1^WT-mCh-sspB in HEK293 cells with NLS-Ferritin-Corelet before (t = 0) and after blue light activation (3 min). Scale bar is 5 µm. b Phase-diagram of BMI1^WT. Filled red circles are phase-separated cells, red pluses are non-phase-separated cells. c Domain architecture of BMI1^ΔIDR (top). Images show BMI1^ΔIDR-mCh-sspB in HEK293 cells with NLS-Ferritin-Corelet before (t = 0) and after blue light activation (3 min). Scale bar is 5 µm. d Phase-diagram of BMI1^ΔIDR. Filled grey circles are phase-separated cells, grey pluses are non-phase-separated cells. e Relative change in recruitment of PRC1-GFP fusions for BMI1^WT (n = 3/7/9/6 for BMI1/CBX2/PHC1/RNF2) and BMI1^ΔIDR (n = 3/3/3/3 for BMI1/CBX2/PHC1/RNF2). Self-interactions are decreased for BMI1^ΔIDR (as indicated by negative ΔPCC), but recruitment of CBX2-GFP is slightly increased (positive ΔPCC). Recruitment of PHC1 and RNF2 shows little change (ΔPCC close to zero). Data represented as difference +/− standard error of the difference. f Domain architecture of BMI1^ΔOD (top). Images show BMI1^ΔOD-mCh-sspB in HEK293 cells with NLS-Ferritin-Corelet before (t = 0) and after blue light activation (3 min). Scale bar is 5 µm. g Phase-diagram of BMI1^ΔOD, showing that BMI1^ΔOD does not phase-separate in this regime. h Domain architecture of PHC1^WT (top). Images show PHC1^WT-mCh-sspB in HEK293 cells with NLS-Ferritin-Corelet before (t = 0) and after blue light activation (3 min). Scale bar is 5 µm. i Phase diagram of PHC1^WT. Filled blue circles are phase-separated cells and blue pluses are non-phase separated cells. j Domain architecture of PHC1^ΔOD (top). Images show PHC1^ΔOD-mCh-sspB in HEK293 cells with NLS-Ferritin-Corelet before (t = 0) and after blue light activation (3 min). Scale bar 5 µm. k Phase diagram for PHC1^ΔOD, showing that PHC1^ΔOD does not phase-separate in this regime. l Relative change in recruitment to PRC1-mCh-sspB fusions for PHC1^WT (n = 9/4/6/5 for BMI1/CBX2/PHC1/RNF2) and PHC1^ΔOD (n = 3/3/4/5 for BMI1/CBX2/PHC1/RNF2). Recruitment of all subunits is decreased for PHC1^ΔOD (negative ΔPCC). Neither PHC1^WT nor PHC1^ΔOD recruits CBX2 (ΔPCC near zero). Data represented as difference +/− standard error of the difference.