RESUMEN
The development of malignant tumors is caused by a complex combination of genetic mutations and epigenetic alterations, the latter of which are induced by either external environmental factors or signaling disruption following genetic mutations. Some types of cancer demonstrate a significant increase in epigenetic enzymes, and targeting these epigenetic alterations represents a compelling strategy to reverse cell transcriptome to the normal state, improving chemotherapy response. Curaxin CBL0137 is a new potent anticancer drug that has been shown to activate epigenetically silenced genes. However, its detailed effects on the enzymes of the epigenetic system of transcription regulation have not been studied. Here, we report that CBL0137 inhibits the expression of DNA methyltransferase DNMT3a in HeLa TI cells, both at the level of mRNA and protein, and it decreases the level of integral DNA methylation in Ca Ski cells. For the first time, it is shown that CBL0137 decreases the level of BET family proteins, BRD2, BRD3, and BRD4, the key participants in transcription elongation, followed by the corresponding gene expression enhancement. Furthermore, we demonstrate that CBL0137 does not affect the mechanisms of histone acetylation and methylation. The ability of CBL0137 to suppress DNMT3A and BET family proteins should be taken into consideration when combined chemotherapy is applied. Our data demonstrate the potential of CBL0137 to be used in the therapy of tumors with corresponding aberrant epigenetic profiles.
Asunto(s)
Desmetilación del ADN , Proteínas Nucleares , Humanos , Proteínas Nucleares/genética , Factores de Transcripción/genética , Metilasas de Modificación del ADN , Epigénesis Genética , Proteínas de Ciclo CelularRESUMEN
The bromodomain and extra-terminal (BET) family proteins, which are involved in chromatin function, have been shown to be promising drug targets in several pathological conditions, including cancer and inflammation. There is considerable interest in the development of BET inhibitors with novel scaffolds to modulate the epigenesis of such diseases. Here, high-resolution crystal structures of the purine class of FDA-approved drugs (theophylline, doxophylline and acyclovir) and non-FDA-approved compounds (3-methyl-7-propylxanthine and theobromine) complexed with hBRD2 bromodomains BD1 and BD2 are reported. Remarkably, a new binding site is exhibited by stacking the compounds against the WPF shelf of BD1 and BD2. This serendipitous binding, in addition to the known acetyl-lysine binding site, sufficiently anchors the ligands in the solvent-exposed region. In addition, slight variations in the lipophilicity of these molecules significantly affected the in vitro binding affinity and selectivity towards BD1 compared with BD2. This idiosyncratic binding provides a new structural framework to link these sites for the development of next-generation inhibitors of the BET family.
Asunto(s)
Neoplasias , Factores de Transcripción , Humanos , Factores de Transcripción/metabolismo , Dominios Proteicos , Sitios de Unión , Purinas/farmacología , Proteínas de Ciclo Celular/químicaRESUMEN
Bromodomain and extra-terminal domain (BET) family proteins play important roles in regulating the expression of multiple proto-oncogenes by recognizing acetylation of histones and non-histone proteins including transcription factors, which subsequently promote tumor cell proliferation, survival, metastasis and immune escape. Therefore, BET family proteins are considered attractive therapeutic targets in various cancers. Currently, blocking of the BET proteins is a widely used therapeutic strategy for MYCN amplified high-risk neuroblastoma. Here, we summarized and reviewed the recent research progresses for the critical function of BET proteins, as an epigenetic reader, on tumorigenesis and the therapeutic potential of the BET/BRD4 inhibitors on MYCN amplified neuroblastoma. We also discussed the combined therapeutic strategies for BET inhibitor-resistant neuroblastoma.
RESUMEN
Chemical modifications of histone tails influence genome accessibility and the transcriptional state of eukaryotic cells. Lysine acetylation is one of the most common modifications and acetyllysine-binding bromodomains (BDs) provide a means for acetyllysine marks to be translated into meaningful cellular responses. Here, we have investigated the mechanism underlying the reported association between the Bromodomain and Extra Terminal (BET) family of BD proteins and the essential histone variant H2A.Z. We use NMR spectroscopy to demonstrate a physical interaction between the N-terminal tail of H2A.Z and the BDs of BRD2, BRD3, and BRD4, and show that the interaction is dependent on lysine acetylation in H2A.Z. The BDs preferentially engage a diacetylated H2A.Z-K4acK7ac motif that is reminiscent of sequences found in other biologically important BET BD target proteins, including histones and transcription factors. A H2A.Z-K7acK11ac motif can also bind BET BDs-with a preference for the second BD of each protein. Chemical shift perturbation mapping of the interactions, together with an X-ray crystal structure of BRD2-BD1 bound to H2A.Z-K4acK7ac, shows that H2A.Z binds the canonical AcK binding pocket of the BDs. This mechanism mirrors the conserved binding mode that is unique to the BET BDs, in which two acetylation marks are read simultaneously by a single BD. Our findings provide structural corroboration of biochemical and cell biological data that link H2A.Z and BET-family proteins, suggesting that the function of H2A.Z is enacted through interactions with these chromatin readers.
Asunto(s)
Proteínas de Ciclo Celular/química , Histonas/química , Factores de Transcripción/química , Acetilación , Cristalografía por Rayos X , Humanos , Unión Proteica , Dominios Proteicos , Relación Estructura-ActividadRESUMEN
While many contraception options are available for women, birth control methods for men are limited to condoms and vasectomy. Past research into male contraceptives has focused on hormonal options but the associated side effects have thus far precluded this method from reaching the market. Non-hormonal male contraceptives and vas occlusion have also been explored, but to date no method has progressed past clinical testing. Recent interest in epigenetic research has unveiled a new potential non-hormonal male contraceptive target: the testis-specific bromodomain BRDT. Potent inhibitors for bromodomain-containing proteins are described in the literature, but a BRDT-specific compound has yet to be designed, prepared and tested. The high similarity between bromodomain proteins of the BET family makes development of selective and specific inhibitors both difficult and necessary. Selective inhibition of BRDT by a small molecule is an exciting new target in the search for a new non-hormonal male contraceptive.
Asunto(s)
Anticoncepción/métodos , Anticonceptivos Masculinos/química , Proteínas Nucleares/antagonistas & inhibidores , Compuestos Orgánicos/química , Proteínas/antagonistas & inhibidores , Anticonceptivos Masculinos/farmacología , Diseño de Fármacos , Humanos , Masculino , Modelos Moleculares , Conformación Molecular , Compuestos Orgánicos/metabolismo , Compuestos Orgánicos/farmacología , Unión Proteica , Relación Estructura-ActividadRESUMEN
Members of the bromodomain and extra-terminal domain (BET) family of proteins (bromodomain-containing (BRD) 2, 3, 4, and T) are widely expressed and highly conserved regulators of gene expression in eukaryotes. These proteins have been intimately linked to human disease, and more than a dozen clinical trials are currently underway to test BET-protein inhibitors as modulators of cancer. However, although it is clear that these proteins use their bromodomains to bind both histones and transcription factors bearing acetylated lysine residues, the molecular mechanisms by which BET family proteins regulate gene expression are not well defined. In particular, the functions of the other domains such as the ET domain have been less extensively studied. Here, we examine the properties of the ET domain of BRD3 as a protein/protein interaction module. Using a combination of pulldown and biophysical assays, we demonstrate that BRD3 binds to a range of chromatin-remodeling complexes, including the NuRD, BAF, and INO80 complexes, via a short linear "KIKL" motif in one of the complex subunits. NMR-based structural analysis revealed that, surprisingly, this mode of interaction is shared by the AF9 and ENL transcriptional coregulators that contain an acetyl-lysine-binding YEATS domain and regulate transcriptional elongation. This observation establishes a functional commonality between these two families of cancer-related transcriptional regulators. In summary, our data provide insight into the mechanisms by which BET family proteins might link chromatin acetylation to transcriptional outcomes and uncover an unexpected functional similarity between BET and YEATS family proteins.
Asunto(s)
Ensamble y Desensamble de Cromatina , Péptidos/química , Proteínas de Unión al ARN/metabolismo , Transactivadores/metabolismo , ATPasas Asociadas con Actividades Celulares Diversas , Acetilación , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Fenómenos Biofísicos , ADN Helicasas/metabolismo , Proteínas de Unión al ADN/metabolismo , Regulación de la Expresión Génica/fisiología , Redes Reguladoras de Genes , Células HEK293 , Humanos , Complejo Desacetilasa y Remodelación del Nucleosoma Mi-2/metabolismo , Proteínas Nucleares/metabolismo , Unión Proteica , Dominios Proteicos , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/fisiología , Homología de Secuencia de Aminoácido , Transactivadores/química , Factores de TranscripciónRESUMEN
Histone deacetylase (HDAC) inhibitors have demonstrated clinical benefits in subtypes of hematological malignancies. However, the efficacy of HDAC inhibitors in solid tumors remains uncertain. This study takes breast cancer as a model to understand mechanisms accounting for limited response of HDAC inhibitors in solid tumors and to seek combination solutions. We discover that feedback activation of leukemia inhibitory factor receptor (LIFR) signaling in breast cancer limits the response to HDAC inhibition. Mechanistically, HDAC inhibition increases histone acetylation at the LIFR gene promoter, which recruits bromodomain protein BRD4, upregulates LIFR expression, and activates JAK1-STAT3 signaling. Importantly, JAK1 or BRD4 inhibition sensitizes breast cancer to HDAC inhibitors, implicating combination inhibition of HDAC with JAK1 or BRD4 as potential therapies for breast cancer.