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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have identified a novel Escherichia coli RNA polymerase (RNAP)-associated protein, an ATPase named RapA. Almost all of this 110-kDa protein in the cell copurifies with RNAP holoenzyme as a 1:1 complex. Purified to homogeneity, RapA also forms a stable complex with RNAP, as if it were a subunit of RNAP. The ATPase activity of RapA is stimulated by binding to RNAP, and thus, RapA and RNAP interact physically as well as functionally. Interestingly, RapA is a homolog of the SWI/SNF family of eukaryotic proteins whose members are involved in transcription activation, nucleosome remodeling, and DNA repair.
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PMID:RapA, a novel RNA polymerase-associated protein, is a bacterial homolog of SWI2/SNF2. 950 9

The yeast SWI/SNF chromatin remodeling complex is comprised of 11 tightly associated polypeptides (SWI1, SWI2, SWI3, SNF5, SNF6, SNF11, SWP82, SWP73, SWP59, SWP61, and SWP29). We have used matrix-assisted laser desorption ionization time-of-flight mass spectrometry to identify the genes that encode the SWP59 and SWP61 subunits. Surprisingly, we find that SWP59 and SWP61 are encoded by the ARP9 and ARP7 genes, respectively, which encode members of the actin-related protein (ARP) family. Sequence analyses have shown that ARP9 and ARP7 are 24-26% identical (48-51% similar) to yeast actin and that they are likely to maintain the overall actin fold. Deletion of either the ARP9 or ARP7 gene causes typical swi/snf phenotypes, including growth defects on media containing galactose, glycerol, or sucrose as sole carbon sources. ARP9 and ARP7 are also required for expression of an HO-lacZ fusion gene and for full transcriptional enhancement by the GAL4 activator. The identification of two ARP family members as crucial subunits of the SWI/SNF complex suggests that the complex may contain a total of three different ATPase subunits; furthermore, the similarity of ARP7 and ARP9 to the HSP and HSC family of ATPases suggests the possibility that chromatin remodeling by SWI/SNF may involve chaperone-like activities.
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PMID:Subunits of the yeast SWI/SNF complex are members of the actin-related protein (ARP) family. 972 66

The trithorax group gene brahma (brm) encodes an activator of Drosophila homeotic genes that functions as the ATPase subunit of a large protein complex. To determine if BRM physically interacts with other trithorax group proteins, we purified the BRM complex from Drosophila embryos and analyzed its subunit composition. The BRM complex contains at least seven major polypeptides. Surprisingly, the majority of the subunits of the BRM complex are not encoded by trithorax group genes. Furthermore, a screen for enhancers of a dominant-negative brm mutation identified only one trithorax group gene, moira (mor), that appears to be essential for brm function in vivo. Four of the subunits of the BRM complex are related to subunits of the yeast chromatin remodeling complexes SWI/SNF and RSC. The BRM complex is even more highly related to the human BRG1 and hBRM complexes, but lacks the subunit heterogeneity characteristic of these complexes. We present biochemical evidence for the existence of two additional complexes containing trithorax group proteins: a 2 MDa ASH1 complex and a 500 kDa ASH2 complex. These findings suggest that BRM plays a role in chromatin remodeling that is distinct from the function of most other trithorax group proteins.
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PMID:The Drosophila trithorax group proteins BRM, ASH1 and ASH2 are subunits of distinct protein complexes. 973 57

Lymphocyte activation is accompanied by visible changes in chromatin structure. We find that antigen receptor signaling induces the rapid association of the BAF complex with chromatin. PIP2, which is regulated by activation stimuli, is sufficient in vitro to target the BAF complex to chromatin, but it has no effect on related chromatin remodeling complexes containing SNF2L or hISWI. Purification and peptide sequencing of the subunits of the complex revealed beta-actin as well as a novel actin-related protein, BAF53. beta-actin and BAF53 are required for maximal ATPase activity of BRG1 and are also required with BRG1 for association of the complex with chromatin/matrix. This work indicates that membrane signals control the activity of the mammalian SWI/SNF or BAF complex and demonstrates a direct interface between signaling and chromatin regulation.
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PMID:Rapid and phosphoinositol-dependent binding of the SWI/SNF-like BAF complex to chromatin after T lymphocyte receptor signaling. 984 65

SWI/SNF and RSC are large, distinct multi-subunit complexes that use the energy of ATP hydrolysis to disrupt nucleosome structure, facilitating the binding of transcription factors or restriction enzymes to nucleosomes [Cote, J., Quinn, J., Workman, J. L., and Peterson, C. L. (1994) Science 265, 53-60 (1); Lorch, Y., Cairns, B. R., Zhang, M., and Kornberg, R. D. (1998) Cell 94, 29-34 (2)]. Here we have used a quantitative assay to measure the activities of these ATP-dependent chromatin remodeling complexes using nucleosomal arrays reconstituted with hypoacetylated, hyperacetylated, or partially trypsinized histones. This assay is based on measuring the kinetics of restriction enzyme digestion of a site located within the central nucleosome of a positioned 11-mer array [Logie, C., and Peterson, C. L. (1997) EMBO J. 16, 6772-6782 (3)]. We find that the DNA-stimulated ATPase activities of SWI/SNF and RSC are not altered by the absence of the histone N-termini. Furthermore, ATP-dependent nucleosome remodeling is also equivalent on all three substrate arrays under reaction conditions where the concentrations of nucleosomal array and either SWI/SNF or RSC are equivalent. However, SWI/SNF and RSC cannot catalytically remodel multiple nucleosomal arrays in the absence of the histone termini, and this catalytic activity of SWI/SNF is decreased by histone hyperacetylation. These results indicate that the histone termini are important for SWI/SNF and RSC function; and, furthermore, our data defines a step in the remodeling cycle where the core histone termini exert their influence. This step appears to be after remodeling, but prior to intermolecular transfer of the remodelers to new arrays.
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PMID:The core histone N-terminal domains are required for multiple rounds of catalytic chromatin remodeling by the SWI/SNF and RSC complexes. 1002 46

Protein complexes of the SWI/SNF family remodel nucleosome structure in an ATP-dependent manner. Each complex contains between 8 and 15 subunits, several of which are highly conserved between yeast, Drosophila, and humans. We have reconstituted an ATP-dependent chromatin remodeling complex using a subset of conserved subunits. Unexpectedly, both BRG1 and hBRM, the ATPase subunits of human SWI/SNF complexes, are capable of remodeling mono-nucleosomes and nucleosomal arrays as purified proteins. The addition of INI1, BAF155, and BAF170 to BRG1 increases remodeling activity to a level comparable to that of the whole hSWI/SNF complex. These data define the functional core of the hSWI/SNF complex.
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PMID:Reconstitution of a core chromatin remodeling complex from SWI/SNF subunits. 1007 7

Yeast and mammalian SWI-SNF complexes regulate transcription through active modification of chromatin structure. Human SW-13 adenocarcinoma cells lack BRG1 protein, a component of SWI-SNF that has a DNA-dependent ATPase activity essential for SWI-SNF function. Expression of BRG1 in SW-13 cells potentiated transcriptional activation by the glucocorticoid receptor, which is known to require SWI-SNF function. BRG1 also specifically repressed transcription from a transfected c-fos promoter and correspondingly blocked transcriptional activation of the endogenous c-fos gene. Mutation of lysine residue 798 in the DNA-dependent ATPase domain of BRG1 significantly reduced its ability to repress c-fos transcription. Repression by BRG1 required the cyclic AMP response element of the c-fos promoter but not nearby binding sites for Sp1, YY1, or TFII-I. Using human C33A cervical carcinoma cells, which lack BRG1 and also express a nonfunctional Rb protein, transcriptional repression by BRG1 was weak unless wild-type Rb was also supplied. Interestingly, Rb-dependent repression by BRG1 was found to take place through a pathway that is independent of transcription factor E2F.
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PMID:Human SWI-SNF component BRG1 represses transcription of the c-fos gene. 1008 38

Chromatin organization plays a key role in the regulation of gene expression. The evolutionarily conserved SWI/SNF complex is one of several multiprotein complexes that activate transcription by remodelling chromatin in an ATP-dependent manner. SWI2/SNF2 is an ATPase whose homologues, BRG1 and hBRM, mediate cell-cycle arrest; the SNF5 homologue, INI1/hSNF5, appears to be a tumour suppressor. A search for INI1-interacting proteins using the two-hybrid system led to the isolation of c-MYC, a transactivator. The c-MYC-INI1 interaction was observed both in vitro and in vivo. The c-MYC basic helix-loop-helix (bHLH) and leucine zipper (Zip) domains and the INI1 repeat 1 (Rpt1) region were required for this interaction. c-MYC-mediated transactivation was inhibited by a deletion fragment of INI1 and the ATPase mutant of BRG1/hSNF2 in a dominant-negative manner contingent upon the presence of the c-MYC bHLH-Zip domain. Our results suggest that the SWI/SNF complex is necessary for c-MYC-mediated transactivation and that the c-MYC-INI1 interaction helps recruit the complex.
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PMID:c-MYC interacts with INI1/hSNF5 and requires the SWI/SNF complex for transactivation function. 1031 72

Repressive chromatin must be remodeled to allow for transcriptional activation of genes in eukaryotic cells. Factors that alter chromatin structure to permit access of transcriptional activators, RNA polymerase II and the polymerase-associated general transcription factors to nucleosomal promoter sequences are as highly conserved as the basic mechanism of transcription. One group of promoter restructuring factors that perturbs chromatin in an ATP-dependent manner includes NURF, CHRAC, ACF, the SWI/SNF complex, and SWI/SNF-related proteins. Each member of this group contains a subunit homologous to the DNA-dependent ATPase; however, their individual mechanisms of action are unique. The small amount of SWI/SNF complex (100-200 copies/cell), its affiliation with a select number of inducible genes, and its interaction with the glucocorticoid and estrogen receptors, suggests the SWI/SNF complex might be preferentially targeted to active promoters. The SWI/SNF-related family of RUSH proteins which includes RUSH-1alpha and beta, hHLTF, HIP116, Zbu1, P113, and the transcription factor RUSH-1alpha isolog has been implicated as a highly conserved DNA binding site-specific ATPase.
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PMID:After chromatin is SWItched-on can it be RUSHed? 1041 19

Chromatin structure is inextricably linked to transcription regulation and differentiation. It consists of a multicomponent system, and impairments in such complex arrays may elicit dramatic biological effects and diseases. We present an overview of human genes involved in chromatin remodeling, which consist of the histone acetyltransferase/deacetylase system and the SWI/SNF-like complexes containing DNA-dependent ATPase activity. Special attention is given to the functional and physical interactions in which these components are involved, notably as transcriptional coactivators and/or corepressors of a large variety of genes. Linking seemingly distinct pathways allows integration of individual components into complex genetic and molecular processes and assessment of the underlying molecular bases of diseases. This was performed using GENATLAS (http://www.infobiogen.fr/), a gene database which compiles the information relevant to the mapping efforts from the published literature.
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PMID:Human genes involved in chromatin remodeling in transcription initiation, and associated diseases: An overview using the GENATLAS database. 1044 37


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