Figure 5: Substrate binding is enhanced by activation.
From: Structural basis of oncogenic histone H3K27M inhibition of human polycomb repressive complex 2
(a) Schematic representation of the principal interactions between the H3K27M peptide and the EZH2 SET domain. The peptide is outlined in green, interactions involving the peptide main chain are shown above the peptide, and with peptide side chains are shown beneath the peptide. For clarity the interactions with the methionine side chain are omitted. SET-I residues are shown in blue and other SET domain residues in green. (b) Fluorescence anisotropy displacement titrations in which unlabelled peptides (H3K27M (green circles), H3K27 (red circles) and R26AK27M (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) and H3K27me3 (40 μM). H3K27me3 was used as the activating peptide rather than Jarid116me3. Although both peptides clearly exhibited essentially the same enhancement of binding, at higher substrate peptide concentrations readings in the presence of Jarid116Kme3 were less stable and Kd values were less reliable. A full description of the binding experiment is provided in the ‘Methods’ section and in Supplementary Fig. 4. (c) Dissociation constants for substrate peptides in the presence of repressive peptide.
