Figure 2: Inhibition of PRC2 by H3K27M.
From: Structural basis of oncogenic histone H3K27M inhibition of human polycomb repressive complex 2
(a) Stick representation of the EZH2 ‘lysine’ pocket (blue) with the Fourier Map covering the histone H3K27M side chain (green). An unbiased Fourier Map (Fo-Fc omit map contoured at 2σ) covering the H3K27M peptide (green stick representation) is included. The peptide occupies the canonical substrate binding cleft of EZH2 and there is good density for the methionine side chain. (b) Equivalent view of the lysine binding channel in GLP/EHMT1–H3K9me1 (ref. 13) and (c) Dim5–H3K9 complexes26 (lower panel). (d) Fluorescence anisotropy displacement titrations in which unlabelled peptides (H3K27M (green circles), H3K27 (red circles) and H3R26AK27M (blue circles)) were added to a mixture of FAM-H3K27M (0.4 μM) and PRC2 (4.3 μM) in the presence of SAM (320 μM). A full description of the binding experiment is provided in the ‘Methods’ section and in Supplementary Fig. 4 (e) Dissociation constants for peptide binding to PRC2. (f) Sequence flanking the methylated lysine (red) of repressive chromatin marks indicating the invariant arginine residue (green). (g) Surface representation of the substrate binding site in the EZH2 SET domain indicating the Arg(−1) binding pocket and showing the unbiased Fourier Map (Fo-Fc omit map contoured at 2σ). (h) Equivalent views of repressive histone substrate binding in the structures of SET domains of PRC2, Dim-5, GLP/EHMT1 and PRSET7 highlighting the presence of related Arg (−1) interactions.
