Fig. S1.

MS402, a BD1-selective BET bromodomain inhibitor. (A) Binding affinity of MS402 to BrDs that represent different subgroups of the human BrD family, as determined in a fluorescence anisotropy assay. See experimental details in SI Materials and Methods. (B) Characterization of MS402 binding to representative human BrDs, as assessed by measuring protein thermal stability with and without the presence of the chemical ligand. The results are depicted in the phylogenetic tree of the human BrD family with dots that are color-coded for high affinity (red), modest affinity (blue), or low or no binding (gray). PCAF is also known as histone acetyltransferase KAT2B. (C) Sequence alignment of BET-BD1 and BD2 using the UniProt database and the PROMALS3D server. The conserved Asn and the gatekeeper residue in αC are highlighted with green and blue background, respectively. The WPF shelf residues are highlighted in yellow and the key residue Gln85 is colored in red for BRD4-BD1 and its counterpart Lys in BRD4-BD2 is in blue. (D) (Left) A detailed view of the polar interactions engaged by MS402 with binding site residues of BRD4-BD1. Hydrogen bonds are shown by dashed lines. (Right) Superimposition of MS402 bound to BRD4-BD1 (5E87, colored in white) with BRD4-BD2 (2YEM, colored in cyan).