Designing BET(ter) Inhibitors to Guide Therapy for Cancer and Inflammatory Diseases

bet proteins brd nanoluc

Transcriptional activation of genes within the nucleus of eukaryotic cells occurs by a variety of mechanisms. Typically, these mechanisms rely on the interaction of regulatory proteins (transcriptional activators or repressors) with specific DNA sequences that control gene expression. Upon DNA binding, regulatory proteins also interact with other proteins that are part of the RNA polymerase II transcriptional complex.

One type of transcriptional activation relies on inducing a conformational change in chromatin, the DNA-protein complex that makes up each chromosome within a cell. In a broad sense, “extended” or loosely wound chromatin is more accessible to transcription factors and can signify an actively transcribed gene. In contrast, “condensed” chromatin hinders access to transcription factors and is characteristic of a transcriptionally inactive state. Acetylation of lysine residues in histones—the primary constituents of the chromatin backbone—results in opening up the chromatin and consequent gene activation. Disruption of histone acetylation pathways is implicated in many types of cancer (1).

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Detecting Inhibition of Protein Interactions in vivo

Protein Interactions with NanoBRETIn a paper published in the September issue of ACS Medicinal Chemistry Letters, researchers from GlaxoSmithKline in the UK and Germany report on the discovery, binding mode and structure:activity relationship of a new, potent BRPF1 (bromodomain and PHD finger containing protein family) inhibitor. This paper came to our attention as it is one of the first publications to apply Promega NanoBRET technology in an vivo assay that reversibly measures the interaction of protein partners. The technology enabled the identification of a novel inhibitor compound that disrupts the chromatin binding of this relatively unstudied class of bromodomain proteins.

What exactly are bromodomains and why do they matter?
Bromodomains are regions (~100 amino acids) within chromatin regulator proteins that recognize and “read” acetylated lysine residues on histones. These acetylated lysines act as docking stations for regulatory protein complexes via binding of the bromodomain region. Because of their role in chromatin binding and gene regulation, bromodomains have attracted interest as potential targets for anti-cancer treatments. Although some bromodomain-containing proteins (e.g., those in the bromodomain and extraterminal domain (BET) subfamily) are well characterized and have been identified as potential therapeutic targets, others are less well understood. Continue reading “Detecting Inhibition of Protein Interactions in vivo”