Fig. 4: PP promotes the wetting of genomic DNA by nuclear speckle condensates.

a Diagram showing NE-supplemented SON IDR2 condensates are expected to compartmentalize splicing factors and exhibit less spherical morphology. b, c Representative images of droplet formation with HeLa NE-supplemented SON IDR2 with increasing concentration of PP (b) and quantification of sphericity (n = 12 quantifications from 12 image frames for NE and 42 quantifications from 42 image frames for without NE from three separate droplet formation assays for each treatment) (c left) and area-normalized perimeter changes (c right) in the time span of 20 min (n = 3 quantifications from three separate droplet formation assays for each treatment). d–g Diagram of droplet formation assay where SON IDR2 is expected to compartmentalize splicing factors, including GFP::SRSF2 into the nuclear speckle-like condensates. GFP::SRSF2 is expected to exhibit a broader spatial distribution than the SON IDR2 core (d). Representative images (e) and box and whiskers plot (box and whiskers represents 25^th to 75^th, and minimum to maximum, respectively, with center line representing the median) of the quantification of sphericity (n = 30 quantifications from 30 image frames per channel, across three separate droplet formation assays for each treatment) (f) and spatial distribution of mCherry::SON IDR2 and GFP::SRSF2 (n = 15 ~ 41 nuclear speckles quantified across three separate droplet formation assays for DMSO and 0.1 µM PP) (g). h, i Mouse genomic DNA was further added to the solution. Representative images (h) and quantification (n = 60 nuclear speckles quantified across three separate droplet formation assays for each treatment) (i) of spatial distribution of mCherry::SON IDR2, GFP::SRSF2 and DNA. j Diagram showing how PP reduces the surface tension of nuclear speckle condensate to promote wetting of genomic DNA. All data mean ± S.E.M. Statistical tests used: mixed-effects analysis for (g). Ordinary one-way ANOVA for (c, f). Two-way RM ANOVA for i. The corresponding quantified data points (for c, f, g, and i), each annotated to indicate their respective independent experiments, are provided in the source data file.