Sequence 1135(siRNA-5 , siRNA5)
|Sequence siRNA-5 , siRNA5|
|Target||SMARCA4 (Homo sapiens )|
|Description|| SWI/SNF related, matrix associated, actin dependent regulator of chromatin, subfamily a, member 4
Ensembl: ENSG00000127616 UniGene: Hs.327527 EntrezGene: 6597 Ensembl Chr19: 10932606 - 11033953 Strand: 1 GO terms: 0000122 0000166 0000792 0001832 0001835 0003676 0003677 0003682 0003700 0003713 0004386 0005515 0005524 0005634 0005654 0006346 0006350 0006357 0007403 0008134 0016787 0030900 0030902
|Sequence||siRNA sense (19b) GGAGGATGACAGTGAAGGC / siRNA antisense (19b) GCCTTCACTGTCATCCTCC|
|Name||siRNA-5 , siRNA5|
Protein profile of tax-associated complexes.Wu K, Bottazzi ME, de la Fuente C, Deng L, Gitlin SD, Maddukuri A, Dadgar S, Li H, Vertes A, Pumfery A, Kashanchi F.J Biol Chem. 2004 Jan 2;279(1) :495-508. Epub 2003 Oct 6. Intrathecal Injections in Children With Spinal Muscular Atrophy: Nusinersen Clinical Trial Experience. Hache M, Swoboda KJ, Sethna N, Farrow-Gillespie A, Khandji A, Xia S, Bishop KM. J Child Neurol. 2016 Jun;31(7):899-906. PubMed:26823478
Description. The SMARCA4 gene encodes a catalytic subunit of SWI/SNF complexes, which function as regulators of gene expression by remodeling chromatin to alter nucleosome conformation, making it more accessible to transcriptional activation (summary by Jelinic et al., 2014). Gene Function. Using chromatography, Khavari et al. (1993) demonstrated that, like SWI2 in yeast, BRG1 is part of a protein complex in human cells. A chimeric SWI2 protein containing the BRG1 DNA-dependent ATPase motif restored normal mitotic growth and capacity for transcriptional activation to yeast swi2 mutant cells. Point mutation of a conserved ATP binding site residue in BRG1 generated a transcriptional dominant-negative in human cells. Khavari et al. (1993) suggested that the dominant-negative effect is due to formation of nonfunctional activator complexes at specific promoter sites.
Using a combination of affinity- and conventional chromatographic techniques, Bochar et al. (2000) isolated a predominant form of a multiprotein BRCA1 (113705)-containing complex from human cells displaying chromatin-remodeling activity. Mass spectrometric sequencing of components of this complex indicated that BRCA1 is associated with a SWI/SNF-related complex, and the authors showed that BRCA1 can directly interact with the BRG1 subunit of the SWI/SNF complex. Moreover, p53 (TP53; 191170)-mediated stimulation of transcription by BRCA1 was completely abrogated by either a dominant-negative mutant of BRG1 (Khavari et al., 1993) or the cancer-causing deletion of exon 11 of BRCA1 (Xu et al., 1999). These findings revealed a direct function for BRCA1 in transcriptional control through modulation of chromatin structure.
Otsuki et al. (2001) used yeast 2-hybrid analysis and immunofluorescence to identify an interaction between the Fanconi anemia protein, FANCA (607139) and BRG1. The authors suggested that FANCA may recruit the SWI/SNF complex to target genes, thereby enabling coupled nuclear functions such as transcription and DNA repair.
Huang et al. (2002) determined that BRG1 interacts with STAT2 (600556) and mediates the expression of 2 interferon-alpha (INFA; see 147660)-induced genes, IFITM1 (604456) and IFI27 (600009). Expression of these genes was impaired in human adrenocortical carcinoma and cervical carcinoma cell lines lacking expression of BRG1 protein. Expression of IFITM1 and IFI27 was restored in the adrenocortical carcinoma cells following transfection with wildtype BRG1, but not with an ATPase-defective BRG1 mutant and not with 2 BRG1 deletion mutants that were defective in STAT2 binding. The expression of 4 other INFA-induced target genes was independent of BRG1 expression.
Kadam and Emerson (2003) showed that BRG1 and BRM associate with different promoters during cellular proliferation and differentiation, and in response to specific signaling pathways by preferential interaction with certain classes of transcription factors. BRG1 binds to zinc finger proteins through a unique N-terminal domain that is not present in BRM. BRM interacts with 2 ankyrin repeat proteins that are critical components of Notch signal transduction. The authors concluded that BRG1 and BRM complexes may direct distinct cellular processes by recruitment to specific promoters through protein-protein interactions that are unique to each ATPase. Animal Model.Bultman et al. (2000) generated Brg1-null mice by gene targeting. Brg1 -/- mice died during the periimplantation stage. Furthermore, blastocyst outgrowth studies indicated that neither the inner cell mass nor trophectoderm survived. Experiments with other cell types, however, demonstrated that Brg1 is not a general cell survival factor. Brg1 +/- mice were predisposed to exencephaly (5 of 36) and tumors (3 of 20 displayed large subcutaneous tumors localized to the neck or inguinal regions). These results provided evidence that biochemically similar chromatin-remodeling complexes have dramatically different functions during mammalian development.
Chi et al. (2002) generated transgenic mice expressing dominant-negative mutants of Baf57 lacking the N terminus, including the HMG and proline-rich domains, or bearing a point mutation, lys112 to ile (K112I), that disrupted DNA binding. T-cell-specific expression of these mutants gave rise to complexes specifically deficient in HMG-mediated functions. Flow cytometric analysis demonstrated a compromise in CD4 (186940) silencing, indicated by premature CD4 expression at double-negative stage 3 (DN3) and the absence of a DN4 stage, and impaired CD8 (see 186910) expression. Heterozygous Brg deletions indicated that CD8 expression was inhibited at the immature single-positive and double-positive stages independently of CD4 derepression. Mutational and flow cytometric analyses showed that CD4 silencer mutations and the Baf57 dominant-negative transgene each partially derepressed CD4 on DN3 cells. Immunoprecipitation analysis confirmed that Baf57 and Brg interacted with the CD4 silencer, but not with the CD8 enhancers III or IV. Chi et al. (2002) noted that the alterations in CD4 and CD8 expression during thymic development were not associated with changes in CD4/CD8 coreceptor expression in mature T cells, which were relatively normal. The authors concluded that BRG is a major regulator of CD8 expression. They suggested that chromatin remodeling is dependent on the DNA-bending activity unique to the HMG domain and that other DNA/chromatin-binding domains exist in BAF complexes.
Using Cre/loxP methodologies, Gebuhr et al. (2003) ablated Brg1 function in mouse T lymphocytes. These mice had gross thymic abnormalities and CD4 derepression at the double-negative stage with no transition to the double-positive stage. Brg1 deficiency did not lead to increased cancer incidence, but there was an increase in death associated with rectal prolapse and endogenous Helicobacter infection. Gebuhr et al. (2003) concluded that chromatin-remodeling complexes are important at different stages in development of the T-cell lineage and the immune response.
Zygotic genome activation (ZGA) is a nuclear reprogramming event that transforms the genome from transcriptional quiescence at fertilization to transcriptional activity shortly thereafter. In order to study the role of Brg1 in ZGA in mice, Bultman et al. (2006) conditionally deleted the Brg1 gene in oocytes. In conditionally mutant females, Brg1-depleted oocytes were meiotically competent and capable of being fertilized, but embryos conceived from depleted eggs exhibited a ZGA defect. Development was arrested at the 2- to 4-cell stage, and transcriptional activity was reduced for about 30% of genes expressed at this stage. Genes involved in transcription, RNA processing, and cell cycle regulation were particularly affected. Examination of covalent histone modification in maternally depleted embryos implicated maternal Brg1 in establishing chromatin structure and transcriptional competence at the 2-cell stage.