Fig. 1: DNA drives condensation of Klf4 at concentrations below the saturation concentration for liquid–liquid phase separation.

a, Sodium dodecyl sulphate gel showing recombinantly expressed and purified MBP-Klf4-GFP. b, Test of the affinity of Klf4-GFP to short dsDNA oligonucleotides using EMSA (Extended Data Fig. 1 and Supplementary Tables 1 and 2). Green, N = 3: oligonucleotide containing Class B sequence; blue, N ≥ 3: oligonucleotide containing Class A sequence; grey, N = 3: oligonucleotide without reported Klf4 consensus sequence. Large circles, mean values; error bars, standard deviation; dots, individual experiments. c,d, Bulk-phase separation assay of Klf4-GFP reveals droplet formation above a saturation concentration of ~1.0 µM (Extended Data Fig. 2a). Confocal microscopy images of Klf4-GFP FRAP (Extended Data Fig. 2b) and droplet fusion. The droplets retain their liquid nature for about 40 min (Extended Data Fig. 6b,c). e, Addition of λ-DNA to 500 nM Klf4-GFP triggers foci formation. f, Schematic of the optical tweezers assay: a single λ-DNA molecule (black) is held between two optically trapped (orange cones) beads via biotin–streptavidin interactions (red and orange) at tension of ~8 pN (Extended Data Fig. 3f,g). The exposure of DNA to a solution of Klf4-GFP (light green) triggers foci formation (dark green). g, Top, representative kymograph revealing Klf4-GFP foci formation and dynamics. White horizontal bar, foci displacement on DNA (Extended Data Fig. 5f–h). Bottom, confocal image 200 s after exposure of DNA to Klf4-GFP. h, Average number of Klf4-GFP molecules per focus saturates over time. Black line, mean; grey shading, standard error of the mean at 95% confidence (20 foci from 13 experiments). i, Foci fusion observed in the indicated region in the kymograph (white box in g) (Extended Data Fig. 5a–c and Supplementary Video 1).