RESUMO
Covalent modification of histones is a fundamental mechanism of regulated gene expression in eukaryotes, and interpretation of histone modifications is an essential feature of epigenetic control. Bromodomains are specialized binding modules that interact with acetylated histones, linking chromatin recognition to gene transcription. Because of their ability to function in a domain-specific fashion, selective disruption of bromodomain:acetylated histone interactions with chemical probes serves as a powerful means for understanding biological processes regulated by these chromatin adaptors. Here we describe the discovery and characterization of potent and selective small molecule inhibitors for the bromodomains of CREBBP/EP300 that engage their target in cellular assays. We use these tools to demonstrate a critical role for CREBBP/EP300 bromodomains in regulatory T cell biology. Because regulatory T cell recruitment to tumors is a major mechanism of immune evasion by cancer cells, our data highlight the importance of CREBBP/EP300 bromodomain inhibition as a novel, small molecule-based approach for cancer immunotherapy.
Assuntos
Proteína de Ligação a CREB/antagonistas & inibidores , Proteína p300 Associada a E1A/antagonistas & inibidores , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologia , Linfócitos T Reguladores/efeitos dos fármacos , Acetilação/efeitos dos fármacos , Proteína de Ligação a CREB/química , Proteína de Ligação a CREB/metabolismo , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular , Células Cultivadas , Proteína p300 Associada a E1A/química , Proteína p300 Associada a E1A/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Histonas/metabolismo , Humanos , Simulação de Acoplamento Molecular , Estrutura Terciária de Proteína/efeitos dos fármacos , Linfócitos T Reguladores/citologia , Linfócitos T Reguladores/metabolismo , Transcriptoma/efeitos dos fármacosRESUMO
Bromodomains are epigenetic readers that are recruited to acetyllysine residues in histone tails. Recent studies have identified non-acetyl acyllysine modifications, raising the possibility that these might be read by bromodomains. Profiling the nearly complete human bromodomain family revealed that while most human bromodomains bind only the shorter acetyl and propionyl marks, the bromodomains of BRD9, CECR2, and the second bromodomain of TAF1 also recognize the longer butyryl mark. In addition, the TAF1 second bromodomain is capable of binding crotonyl marks. None of the human bromodomains tested binds succinyl marks. We characterized structurally and biochemically the binding to different acyl groups, identifying bromodomain residues and structural attributes that contribute to specificity. These studies demonstrate a surprising degree of plasticity in some human bromodomains but no single factor controlling specificity across the family. The identification of candidate butyryl- and crotonyllysine readers supports the idea that these marks could have specific physiological functions.