2h60 | pdb_00002h60
Solution Structure of Human Brg1 Bromodomain
Structural highlights
Disease[SMCA4_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] Function[SMCA4_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] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedHuman brahma-related gene 1 (Brg1) is a core protein in human SWI/SNF chromatin-remodeling complex which regulates gene expression. Brg1 contains a bromodomain that has been shown to anchor the entire complex to promoter nucleosomes by interacting with histones that are acetylated at specific lysine residues. The Brg1 bromodomain belongs to an important subclass of the bromodomain family for which no structural information is known. Here we report the solution structure of the Brg1 bromodomain determined by NMR. The Brg1 bromodomain conserves the left-handed, four-helix bundle topology found in other bromodomain structures. However, the alphaZ helix of Brg1 bromodomain is about 4 residues shorter relative to previously published bromodomain structures. Using NMR perturbation studies, we demonstrate the Brg1 bromodomain binds acetyllysine in the context of histone tails, with no comparable affinity for unacetylated peptides. The estimated dissociation constants (KD) for acetylated histone peptides H4-AcK8 and H4-AcK12 are 4.0 and 3.6 mM, respectively. In this study the dominant substrate was H3-AcK14 (KD approximately 1.2 mM). Mutagenesis analysis reveals several residues important for the binding specificity. Using molecular dynamics simulations, we present a model of the Brg1 bromodomain in complex with H3-AcK14 and discuss the potential interactions which provide the selectivity of the Brg1 bromodomain for histone H3-AcK14. Solution structure of human Brg1 bromodomain and its specific binding to acetylated histone tails.,Shen W, Xu C, Huang W, Zhang J, Carlson JE, Tu X, Wu J, Shi Y Biochemistry. 2007 Feb 27;46(8):2100-10. Epub 2007 Feb 3. PMID:17274598[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. 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