Progress in the discovery of small-molecule inhibitors of bromodomain--histone interactions

Bromodomains are structurally conserved protein modules present in a large number of chromatin-associated proteins and in many nuclear histone acetyltransferases. The bromodomain functions as an acetyl-lysine binding domain and has been shown to be pivotal in regulating protein-protein interactions in chromatin-mediated cellular gene transcription, cell proliferation, and viral transcriptional activation. Structural analyses of these modules in complex with acetyl-lysine peptide ligands provide insights into the molecular basis for recognition and ligand selectivity within this epigenetic reader family. However, there are significant challenges in configuring assays to identify inhibitors of these proteins. This review focuses on the progress made in developing methods to identify peptidic and small-molecule ligands using biophysical label-free and biochemical approaches. The advantage of each technique and the results reported are summarized, highlighting the potential applicably to other reader domains and the caveats in translation from simple in vitro systems to a biological context.