Importance of the aromatic cage and basic surface of the PWWP domain in binding affinity and specificity. (a) Titration of non-modified (H3K36) or modified nucleosomes (H3K36Cme3) with 0, 0.5, 1, 2 and 3 molar equivalents of the indicated GST-PWWP protein added and analyzed by staining EMSA gels with ethidium bromide. Free nucleosome particles (NCP) or complexes with either one (+1) or two (+2) PWWPs, and the relevant PWWP mutation are indicated. (b) FRAP-recovery curves for GFP-PSIP1, indicated mutants or controls H2B-GFP or NLS-GFP. An average of 10 cells is presented. (c) Density plots are shown for the ratios PSIP1 (or mutant)/control for all genes (black), genes enriched for H3K36me3 (red) and genes not enriched for H3K36me3 (blue).