BET

Class

small molecule

Notes

original target text: BET Inhibitor

BET proteins (bromodomain and extraterminal domain family, comprising BRD2, BRD3, BRD4, and the testis-restricted BRDT) are epigenetic 'reader' proteins. They recognize acetylated lysine residues on histone tails, the chemical marks that flag chromatin as transcriptionally active, and use this recognition to dock onto DNA-packaging proteins. Once bound, BET proteins recruit the machinery that drives RNA polymerase II to transcribe genes, including several oncogenes and inflammatory response genes. Because BET occupancy at these loci can sustain unusually high expression of growth- and survival-promoting genes, cancer cells and inflammatory processes often become dependent on this reading mechanism. BET inhibitors are small molecules that occupy the same acetyl-lysine binding pocket the BET proteins normally use, competitively displacing them from chromatin and reducing transcription of the genes they support. This mechanism is broadly relevant across hematologic and solid tumors where oncogene transcription is a driving vulnerability, and it is also being explored in inflammatory and fibrotic conditions where BET-dependent gene programs contribute to disease. Because BET proteins regulate transcription genome-wide rather than acting on a single gene, their inhibition has wide-reaching, dose-dependent effects on both diseased and normal tissue, a consideration central to how these agents are developed.