(A) Co-crystal structure of 6 with BRD4 D1. Three structured waters are indicated in red sphere. The imidazole ring forms a conserved hydrogen bond with Asn140. The distance between N, N-dimethyl amino group and Asp144 is indicated. (B) Backbone overlay of BRD4 D1 bound to H4 K5ac,K8ac (PDB: 3UVW, wheat) and BRD4 D1 bound to 1 (PDB:6MH1) or 6 (PBD:6WGX, grey). The Lys141 side chain was removed for clarity. (C) Possible water network bridging 6 to D144. Three waters are indicated in red sphere and B-factor are labeled in yellow, for which higher B-factors indicate less stable waters.