scholarly journals Octamer Transfer and Creation of Stably Remodeled Nucleosomes by Human SWI-SNF and Its Isolated ATPases

2000 ◽  
Vol 20 (17) ◽  
pp. 6380-6389 ◽  
Author(s):  
Michael L. Phelan ◽  
Gavin R. Schnitzler ◽  
Robert E. Kingston
Keyword(s):  
Chromatin Remodeling ◽  
Dependent Manner ◽  
Chromatin Remodeling Complexes ◽  
Atpase Subunits ◽  
Histone Octamers

ABSTRACT Chromatin remodeling complexes help regulate the structure of chromatin to facilitate transcription. The multisubunit human (h) SWI-SNF complex has been shown to remodel mono- and polynucleosome templates in an ATP-dependent manner. The isolated hSWI-SNF ATPase subunits BRG1 and hBRM also have these activities. The intact complex has been shown to produce a stable remodeled dimer of mononucleosomes as a product. Here we show that the hSWI-SNF ATPases alone can also produce this product. In addition, we show that hSWI-SNF and its ATPases have the ability to transfer histone octamers from donor nucleosomes to acceptor DNA. These two reactions are characterized and compared. Our results are consistent with both products of SWI-SNF action being formed as alternative outcomes of a single remodeling mechanism. The ability of the isolated ATPase subunits to catalyze these reactions suggests that these subunits play a key role in determining the mechanistic capabilities of the SWI-SNF family of remodeling complexes.

scholarly journals MyoD Targets Chromatin Remodeling Complexes to the Myogenin Locus Prior to Forming a Stable DNA-Bound Complex

2005 ◽  
Vol 25 (10) ◽  
pp. 3997-4009 ◽  
Author(s):  
Ivana L. de la Serna ◽  
Yasuyuki Ohkawa ◽  
Charlotte A. Berkes ◽  
Donald A. Bergstrom ◽  
Caroline S. Dacwag ◽  
...  
Keyword(s):  
Chromatin Remodeling ◽  
Dominant Negative ◽  
Regulatory Proteins ◽  
Specific Gene ◽  
Dependent Manner ◽  
Independent Manner ◽  
Chromatin Remodeling Complexes ◽  
Direct Binding ◽  
Induced Genes ◽  
Step Mechanism

ABSTRACT The activation of muscle-specific gene expression requires the coordinated action of muscle regulatory proteins and chromatin-remodeling enzymes. Microarray analysis performed in the presence or absence of a dominant-negative BRG1 ATPase demonstrated that approximately one-third of MyoD-induced genes were highly dependent on SWI/SNF enzymes. To understand the mechanism of activation, we performed chromatin immunoprecipitations analyzing the myogenin promoter. We found that H4 hyperacetylation preceded Brg1 binding in a MyoD-dependent manner but that MyoD binding occurred subsequent to H4 modification and Brg1 interaction. In the absence of functional SWI/SNF enzymes, muscle regulatory proteins did not bind to the myogenin promoter, thereby providing evidence for SWI/SNF-dependent activator binding. We observed that the homeodomain factor Pbx1, which cooperates with MyoD to stimulate myogenin expression, is constitutively bound to the myogenin promoter in a SWI/SNF-independent manner, suggesting a two-step mechanism in which MyoD initially interacts indirectly with the myogenin promoter and attracts chromatin-remodeling enzymes, which then facilitate direct binding by MyoD and other regulatory proteins.

scholarly journals Neuronal Activity-Induced BRG1 Phosphorylation Regulates Enhancer Activation

2020 ◽  
Author(s):  
Bongwoo Kim ◽  
Yi Luo ◽  
Xiaoming Zhan ◽  
Zilai Zhang ◽  
Xuanming Shi ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Chromatin Remodeling ◽  
Neuronal Activity ◽  
Phosphorylation Site ◽  
Serine Phosphorylation ◽  
Dependent Manner ◽  
Enhancer Rna ◽  
Induce Activity ◽  
Chromatin Remodeling Complexes ◽  
Activity Dependent

SUMMARYNeuronal activity-induced enhancers drive the gene induction in response to stimulation. Here, we demonstrate that BRG1, the core subunit of SWI/SNF-like BAF ATP-dependent chromatin remodeling complexes, regulates neuronal activity-induced enhancers. Upon stimulation, BRG1 is recruited to enhancers in an H3K27Ac-dependent manner. BRG1 regulates enhancer basal activities and inducibility by affecting cohesin binding, enhancer-promoter looping, RNA polymerase II recruitment, and enhancer RNA expression. Furthermore, we identified a serine phosphorylation site in BRG1 that is induced by neuronal activities and is sensitive to CaMKII inhibition. BRG1 phosphorylation affects its interaction with several transcription co-factors, possibly modulating BRG1 mediated transcription outcomes. Using mice with knock-in mutations, we showed that non-phosphorylatable BRG1 fails to efficiently induce activity-dependent genes, whereas phosphomimic BRG1 increases the enhancer activities and inducibility. These mutant mice displayed anxiety-like phenotypes and altered responses to stress. Therefore, our data reveal a mechanism connecting neuronal signaling to enhancer activities through BRG1 phosphorylation.

scholarly journals Chromatin Remodeling Complexes Interact Dynamically with a Glucocorticoid Receptor–regulated Promoter

2008 ◽  
Vol 19 (8) ◽  
pp. 3308-3322 ◽  
Author(s):  
Thomas A. Johnson ◽  
Cem Elbi ◽  
Bhavin S. Parekh ◽  
Gordon L. Hager ◽  
Sam John
Keyword(s):  
Rna Polymerase Ii ◽  
Chromatin Remodeling ◽  
Transcriptional Activation ◽  
Tandem Repeats ◽  
Inducible Promoter ◽  
Kinetic Properties ◽  
Dependent Manner ◽  
Chromatin Remodeling Complexes ◽  
Mmtv Promoter

Brahma (BRM) and Brahma-related gene 1 (BRG1) are the ATP-dependent catalytic subunits of the SWI/SNF family of chromatin-remodeling complexes. These complexes are involved in essential processes such as cell cycle, growth, differentiation, and cancer. Using imaging approaches in a cell line that harbors tandem repeats of stably integrated copies of the steroid responsive MMTV-LTR (mouse mammary tumor virus–long terminal repeat), we show that BRG1 and BRM are recruited to the MMTV promoter in a hormone-dependent manner. The recruitment of BRG1 and BRM resulted in chromatin remodeling and decondensation of the MMTV repeat as demonstrated by an increase in the restriction enzyme accessibility and in the size of DNA fluorescence in situ hybridization (FISH) signals. This chromatin remodeling event was concomitant with an increased occupancy of RNA polymerase II and transcriptional activation at the MMTV promoter. The expression of ATPase-deficient forms of BRG1 (BRG1-K-R) or BRM (BRM-K-R) inhibited the remodeling of local and higher order MMTV chromatin structure and resulted in the attenuation of transcription. In vivo photobleaching experiments provided direct evidence that BRG1, BRG1-K-R, and BRM chromatin-remodeling complexes have distinct kinetic properties on the MMTV array, and they dynamically associate with and dissociate from MMTV chromatin in a manner dependent on hormone and a functional ATPase domain. Our data provide a kinetic and mechanistic basis for the BRG1 and BRM chromatin-remodeling complexes in regulating gene expression at a steroid hormone inducible promoter.

Abstract 17084: Nuclear Smooth Muscle α-actin Participates in Chromatin Remodeling at Smooth Muscle Contractile Gene Promoters

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Callie Kwartler ◽  
Shuangtao Ma ◽  
Caroline Kernell ◽  
Xue-yan Duan ◽  
Charis Wang ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Cardiac Muscle ◽  
Chromatin Remodeling ◽  
Muscle Cells ◽  
Cytoskeletal Proteins ◽  
Nuclear Localization Sequence ◽  
Serum Starvation ◽  
Cell Fractionation ◽  
Gene Promoters ◽  
Chromatin Remodeling Complexes

Actin genes encode for cytoskeletal proteins that polymerize to function in cellular motility, adhesion, and contraction. In mammalian cells, ubiquitously expressed β-actin also moves into the nucleus and associates with chromatin remodeling complexes, however a nuclear function of muscle-specific α-actins has not been previously assessed. We hypothesized that smooth muscle α-actin (SMA) plays a role in chromatin remodeling during the differentiation of smooth muscle cells (SMCs) to enable cell fate specification of SMCs. In explanted SMCs from human and mouse ascending aortas, cell fractionation and 2D gel electrophoresis identify both SMA and β-actin in the nuclear lysates. Nuclear SMA but not β-actin accumulates with SMC differentiation driven by serum starvation and transforming growth factor-β1 treatment. SMA accumulates into the nucleus early in the differentiation of SMCs from neural crest progenitor cells, prior to cytosolic accumulation. Immunoprecipitation studies show that SMA binds specifically to the INO80 and the SWI/SNF chromatin remodeling complexes, and this binding increases with SMC differentiation. Chromatin immunoprecipitation reveals that SMA is bound to the promoters of SMC-specific genes, including Acta2 , Cnn1, and Myh11 and that SMA is enriched over β-actin at these promoters with SMC differentiation. Finally, overexpression of SMA tagged with a nuclear localization sequence (NLS) in multiple cell types increases expression of SMC markers, whereas NLS-tagged β-actin localizes to the nucleus to the same extent but does not increase SMC marker expression in any cell type. Finally, we assessed whether skeletal muscle α-actin (SKA) and cardiac muscle α-actin (CMA) may play a similar role in skeletal and cardiac muscle cells. Both SKA and CMA translocate into the nucleus. CMA accumulates into the nucleus early in the differentiation of cardiomyocytes from pluripotent stem cells. Immunoprecipitation reveals that SKA binds to the SWI/SNF complex in differentiated C2C12 myotube cell cultures. These data support that nuclear SMA enriches with and participates in SMC differentiation, and suggest a potential nuclear role for other muscle specific α-actins in developing muscle cells.

scholarly journals Combinatorial depletion analysis to assemble the network architecture of the SAGA and ADA chromatin remodeling complexes

2011 ◽  
Vol 7 (1) ◽  
pp. 503 ◽  
Author(s):  
Kenneth K Lee ◽  
Mihaela E Sardiu ◽  
Selene K Swanson ◽  
Joshua M Gilmore ◽  
Michael Torok ◽  
...  
Keyword(s):  
Chromatin Remodeling ◽  
Network Architecture ◽  
Chromatin Remodeling Complexes

scholarly journals Identification and Functional Characterization of Protest SWI/SNF and ISWI Complexes

2021 ◽  
Author(s):  
Alejandro Saettone Chipana
Keyword(s):  
Chromatin Remodeling ◽  
Tetrahymena Thermophila ◽  
Affinity Purification ◽  
Functional Characterization ◽  
Peptide Array ◽  
Interacting Proteins ◽  
Silent Chromatin ◽  
Lysine Residues ◽  
Chromatin Remodeling Complexes

The thesis aims to identify and initiate functional characterization of the SWI/SNF and ISWI complexes in Tetrahymena thermophila. Through affinity purification of the conserved subunit Snf5 followed by mass spectrometry (AP-MS), I identified the first SWI/SNF complex in protists. One of the subunits I found is a small bromodomain containing protein named Ibd1. Through AP-MS of Ibd1 I found Ibd1 is versatile and interacts with several additional chromatin remodeling complexes. Bromodomains are known to have affinity for acetylated lysine residues within proteins such as histones. A peptide array experiment suggests that Ibd1 also has affinity for acetylated chromatin. Indirect immunofluorescence (IF) of Ibd1 hints at a role in transcription. My analysis of Tetrahymena Iswi1 shows expression during meiosis, vegetative growth and starvation. IF data shows its localization is consistent with Iswi1 function in mitosis/meiosis or maintenance of silent chromatin. AP-MS of ISW1 discovered several interacting proteins of unknown function.

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