Bromodomain and extra-terminal domain (BET) family (BET)

The Bromodomain and extra-terminal domain (BET) family consists of four conserved mammalian proteins—BRD2, BRD3, BRD4, and the testis-specific BRDT—that serve as vital "readers" of the epigenetic code. These proteins possess two tandem N-terminal bromodomains that specifically recognize and bind acetylated lysine residues on histone tails and various transcription factors. By acting as molecular scaffolds, BET proteins recruit essential transcriptional machinery, including the positive transcription elongation factor b (P-TEFb) and the Mediator complex, to active promoters and super-enhancers. This recruitment facilitates the transcription of genes central to cell growth, cell cycle progression, and the inflammatory response. In diseases like cancer, BET proteins are often dysregulated or involved in chromosomal translocations (e.g., NUT midline carcinoma), leading to the aberrant over-expression of oncogenes such as MYC and BCL2. Consequently, small-molecule BET inhibitors have emerged as a significant therapeutic class designed to displace these proteins from chromatin, thereby suppressing oncogenic transcriptional programs. Clinical development of these agents continues to evolve, focusing on overcoming dose-limiting toxicities such as thrombocytopenia and identifying predictive biomarkers for patient stratification.

Other names

BET familyBET proteinsBromodomain-containing protein familyBromodomain and extra-terminal motif proteinsEpigenetic readers

BET inhibitors act as competitive acetyl-lysine mimetics that bind to the bromodomain pockets (BD1 and BD2) of BET proteins, thereby preventing their interaction with acetylated histones and transcription factors; this results in the displacement of the BET complex from chromatin and the subsequent downregulation of super-enhancer-driven oncogenes and pro-inflammatory genes [12, 14, 16, 18].