BRD4 Bromodomain 1 Inhibitor Screening Using a Homogeneous Proximity Assay

Epigenetics refers to a dynamic set of processes that regulate transcription of the genome, some involving chemical modification of histone proteins. Histones associate with DNA to form nucleosomes, which bundle to form chromatin and chromosomes. Histones contain a flexible N-terminus tail, which protrudes from the nucleosome and is the site for epigenetic modifications. Modifications to amino acid residues in the histone tail include the addition and removal of functional groups, such as methyl and acetyl groups by specific enzymes. Other proteins affect epigenitic changes by reading whether the histone tail has been modified. A bromodomain protein is one such protein that recognizes and binds to the acetylated lysine residues in the histone tail. Inhibition of this protein: protein binding event is of major interest in some forms of cancer. This application highlights an HTS screening assay useful for studying the inhibition of bromodomain/histone binding. Continued interest in histone modifying proteins as druggable targets makes these types of assays an important focus area given the increased performance of the Synergy™ Neo HTS instrument. The assay is an extremely rapid and easy to perform biochemical assay with little optimization required aside from some initial instrumentation optimization. This assay was easily scaled to a 384-well format required for screening of small compound libraries.