A bump-and-hole approach to engineer controlled selectivity of BET bromodomain chemical probes

Abstract

Small molecules are useful tools for probing the biological function and therapeutic potential of individual proteins, but achieving selectivity is challenging when the target protein shares structural domains with other proteins. The Bromo and Extra-Terminal (BET) proteins have attracted interest because of their roles in transcriptional regulation, epigenetics, and cancer. The BET bromodomains (protein interaction modules that bind acetyl-lysine) have been targeted by potent small-molecule inhibitors, but these inhibitors lack selectivity for individual family members. We developed an ethyl derivative of an existing small-molecule inhibitor, I-BET/JQ1, and showed that it binds leucine/alanine mutant bromodomains with nanomolar affinity and achieves up to 540-fold selectivity relative to wild-type bromodomains. Cell culture studies showed that blockade of the first bromodomain alone is sufficient to displace a specific BET protein, Brd4, from chromatin. Expansion of this approach could help identify the individual roles of single BET proteins in human physiology and disease.

Heat stress: A risk factor for skin carcinogenesis

“…Cell cycle arrest is imposed on cells with DNA damage to provide time for correction of any DNA defects (Andersen, 2015;Baud et al, 2014). The cell cycle arrest mechanism in mammalian cells is primarily controlled by the p53 protein, a product of the TP53 gene (Geranton and Tochiki, 2015;Kastan et al, 1991).…”

JQ1 affects BRD2-dependent and independent transcription regulation without disrupting H4-hyperacetylated chromatin states

“…The BET family shares a C-terminal extra-terminal domain and two tandem bromodomains, BD1 and BD2, that primarily bind to multi-acetylated histone H4 tail at K5, K8, K12, and K16 in vitro , but not to the monoacetylated histone H3/H4 peptides, including that of acetylated H3 K27 (H3K27ac) [9,10,12,13]. Since acetylation of histone H4 in the nucleus is proposed to occur at K16 first, then at K12, K8, and K5 [14], the simultaneous acetylation of K5 and K8 indicates a typical state of histone H4 hyperacetylation [14].…”

“…Since acetylation of histone H4 in the nucleus is proposed to occur at K16 first, then at K12, K8, and K5 [14], the simultaneous acetylation of K5 and K8 indicates a typical state of histone H4 hyperacetylation [14]. Indeed, BET proteins preferentially bind to the K5/K8-diacetylated H4 tail peptides mimicking hyperacetylated H4 in vitro [12,13]. Additionally, H4 K5 acetylation (H4K5ac) facilitated by histone acetyltransferase p300 (EP300) and disruptor of telomere silencing 1-like (DOT1L) might facilitate the binding of BRD4 to the chromatin [15].…”

Bromodomains in Protozoan Parasites: Evolution, Function, and Opportunities for Drug Development

“…Several classes of bromodomain inhibitors that bind within the hydrophobic pocket, resulting in the exclusion of acetyl-lysine, have been reported. Many of the bromodomain inhibitors act as acetylated lysine analogues, forming hydrogen bonds in the hydrophobic pocket in a manner similar to the binding of the acetylated lysine (25)(26)(27).…”