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Crystal Structure of SMARCA4 bromodomain in complex with MPDCrystal Structure of SMARCA4 bromodomain in complex with MPD
Structural highlights
DiseaseSMCA4_HUMAN Defects in SMARCA4 are the cause of rhabdoid tumor predisposition syndrome type 2 (RTPS2) [MIM:613325. RTPS2 is a familial cancer syndrome predisposing to renal or extrarenal malignant rhabdoid tumors and to a variety of tumors of the central nervous system, including choroid plexus carcinoma, medulloblastoma, and central primitive neuroectodermal tumors. Rhabdoid tumors are the most aggressive and lethal malignancies occurring in early childhood.[1] Defects in SMARCA4 are the cause of mental retardation autosomal dominant type 16 (MRD16) [MIM:614609. A disease characterized by multiple congenital anomalies and mental retardation. Mental retardation is defined by significantly below average general intellectual functioning associated with impairments in adaptative behavior and manifested during the developmental period. MRD16 patients manifest developmental delay, absent or hypoplastic fifth fingernails or toenails, thick eyebrows and long eyelashes, hirsutism. Additional findings include hypotonia, microcephaly, seizures, a Dandy-Walker malformation, and vision and hearing problems.[2] FunctionSMCA4_HUMAN Transcriptional coactivator cooperating with nuclear hormone receptors to potentiate transcriptional activation. Component of the CREST-BRG1 complex, a multiprotein complex that regulates promoter activation by orchestrating a calcium-dependent release of a repressor complex and a recruitment of an activator complex. In resting neurons, transcription of the c-FOS promoter is inhibited by BRG1-dependent recruitment of a phospho-RB1-HDAC repressor complex. Upon calcium influx, RB1 is dephosphorylated by calcineurin, which leads to release of the repressor complex. At the same time, there is increased recruitment of CREBBP to the promoter by a CREST-dependent mechanism, which leads to transcriptional activation. The CREST-BRG1 complex also binds to the NR2B promoter, and activity-dependent induction of NR2B expression involves a release of HDAC1 and recruitment of CREBBP. Belongs to the neural progenitors-specific chromatin remodeling complex (npBAF complex) and the neuron-specific chromatin remodeling complex (nBAF complex). During neural development a switch from a stem/progenitor to a post-mitotic chromatin remodeling mechanism occurs as neurons exit the cell cycle and become committed to their adult state. The transition from proliferating neural stem/progenitor cells to post-mitotic neurons requires a switch in subunit composition of the npBAF and nBAF complexes. As neural progenitors exit mitosis and differentiate into neurons, npBAF complexes which contain ACTL6A/BAF53A and PHF10/BAF45A, are exchanged for homologous alternative ACTL6B/BAF53B and DPF1/BAF45B or DPF3/BAF45C subunits in neuron-specific complexes (nBAF). The npBAF complex is essential for the self-renewal/proliferative capacity of the multipotent neural stem cells. The nBAF complex along with CREST plays a role regulating the activity of genes essential for dendrite growth. SMARCA4/BAF190A may promote neural stem cell self-renewal/proliferation by enhancing Notch-dependent proliferative signals, while concurrently making the neural stem cell insensitive to SHH-dependent differentiating cues (By similarity). Also involved in vitamin D-coupled transcription regulation via its association with the WINAC complex, a chromatin-remodeling complex recruited by vitamin D receptor (VDR), which is required for the ligand-bound VDR-mediated transrepression of the CYP27B1 gene. Acts as a corepressor of ZEB1 to regulate E-cadherin transcription and is required for induction of epithelial-mesenchymal transition (EMT) by ZEB1.[3] [4] [5] Publication Abstract from PubMedBromodomains are protein modules that bind to acetylated lysine side chains in histones and other proteins. The bromodomain adjacent to zinc finger domain protein 2B (BAZ2B) has been reported to be poorly druggable. Here, we screened an in-house library of 350 fragments by automatic docking to the BAZ2B bromodomain. The top 12 fragments according to the predicted binding energy were selected for experiments of soaking into apo crystals of BAZ2B which yielded the structure of the complex for four of them, which is a hit rate of 33%. Additional crystal structures were solved for BAZ2B and two scaffolds identified by analogy. For three topologically similar fragments, the crystal structures reveal binding modes with different penetration, i.e., with zero, one, and two water molecules, respectively, located between the fragment and the side chain of a conserved tyrosine (Tyr1901) in the bottom of the acetyl lysine pocket of BAZ2B. Furthermore, a remarkable stereoselectivity of the acetyl lysine pocket emerges from the crystal structures of the bromodomains of BAZ2B and SMARCA4 in complex with the chiral diol MPD (2-methyl-2,4-pentanediol). High-Throughput Fragment Docking into the BAZ2B Bromodomain: Efficient in Silico Screening for X-Ray Crystallography.,Lolli G, Caflisch A ACS Chem Biol. 2016 Mar 18;11(3):800-7. doi: 10.1021/acschembio.5b00914. PMID:26942307[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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