Bromodomain and extraterminal protein (BET protein)

Bromodomain and extraterminal proteins (BET proteins) are a family of epigenetic regulators that function as "readers" of acetylated lysine residues on histones and other nuclear proteins. The canonical members include BRD2, BRD3, BRD4, and the testis-specific BRDT. Structurally, they contain two conserved N-terminal bromodomains that bind acetylated lysines, an extraterminal domain involved in recruiting components of the transcriptional machinery, and sometimes a C-terminal domain important for further regulatory interactions. BET proteins play central roles in regulating gene expression by facilitating the assembly or activation of RNA polymerase II complexes at key genomic loci—especially at super-enhancers controlling cell identity genes. They influence diverse cellular processes including cell cycle progression, proliferation, differentiation, inflammation responses, chromatin architecture maintenance through interactions with factors like CTCF—and are implicated across a wide range of diseases such as cancer (by modulating oncogenes like MYC), inflammatory disorders, cardiovascular conditions like heart failure/hypertrophy, neurodegeneration/multiple sclerosis models as well as viral infections. Pharmacological inhibition—most notably by small molecules such as JQ1—blocks their ability to recognize acetylated lysines on chromatin. This disrupts pathological gene expression programs driven by aberrant enhancer activity or oncogenic signaling pathways. While several drugs targeting these proteins have entered clinical trials for cancer and inflammatory diseases due to their promising preclinical efficacy profiles—including tumor regression—the broad physiological functions also present challenges regarding selectivity/toxicity. Overall BET proteins represent validated therapeutic targets whose biology continues to be actively explored both for direct drug development efforts and deeper understanding into epigenetic control mechanisms underlying health/disease states.

Other names

BET family proteinBromodomain and extra-terminal domain proteinBRD2/BRD3/BRD4/BRDT (family members)

– Competitive inhibition of bromodomain-acetyl lysine interaction on histones and non-histone proteins, displacing BET proteins from chromatin to suppress transcription of target genes – Induction of proteasomal degradation via PROTACs for some newer agents – Disruption of recruitment of transcriptional machinery such as P‑TEFb complex