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Current Biology : CB Oct 1999Recent studies have shown that two nucleosome-remodeling complexes, NURF and CHRAC, open chromatin for transcription and replication by using their common catalytic... (Review)
Review
Recent studies have shown that two nucleosome-remodeling complexes, NURF and CHRAC, open chromatin for transcription and replication by using their common catalytic subunit, the nucleosomal ATPase ISWI, to increase the mobility of nucleosomes relative to DNA sequence.
Topics: Adenosine Triphosphatases; Animals; Chromatin; Chromosomal Proteins, Non-Histone; DNA-Binding Proteins; Drosophila Proteins; Histones; Insect Proteins; Models, Molecular; Molecular Chaperones; Nuclear Proteins; Nucleosomes; Pyrophosphatases; Retinoblastoma-Binding Protein 4; Transcription Factors; Transcription, Genetic
PubMed: 10530996
DOI: 10.1016/s0960-9822(99)80473-4 -
The EMBO Journal Jun 2000The ISWI ATPase of Drosophila is a molecular engine that can drive a range of nucleosome remodelling reactions in vitro. ISWI is important for cell viability,...
The ISWI ATPase of Drosophila is a molecular engine that can drive a range of nucleosome remodelling reactions in vitro. ISWI is important for cell viability, developmental gene expression and chromosome structure. It interacts with other proteins to form several distinct nucleosome remodelling machines. The chromatin accessibility complex (CHRAC) is a biochemical entity containing ISWI in association with several other proteins. Here we report on the identification of the two smallest CHRAC subunits, CHRAC-14 and CHRAC-16. They contain histone fold domains most closely related to those found in sequence-specific transcription factors NF-YB and NF-YC, respectively. CHRAC-14 and CHRAC-16 interact directly with each other as well as with ISWI, and are associated with functionally active CHRAC. The developmental expression profiles of both subunits suggest specialized roles in chromatin remodelling reactions in the early embryo for both histone fold subunits.
Topics: Adenosine Triphosphatases; Amino Acid Sequence; Animals; CCAAT-Binding Factor; Chromatin; DNA-Binding Proteins; Drosophila; Drosophila Proteins; Gene Expression Regulation; Histones; Molecular Sequence Data; Nucleoproteins; Nucleosomes; Protein Binding; Protein Conformation; Protein Structure, Secondary; Sequence Homology, Amino Acid; Transcription Factors
PubMed: 10856248
DOI: 10.1093/emboj/19.12.3049 -
Developmental Biology Mar 2016The Chromatin Accessibility Complex (CHRAC) consists of the ATPase ISWI, the large ACF1 subunit and a pair of small histone-like proteins, CHRAC-14/16. CHRAC is a...
The Chromatin Accessibility Complex (CHRAC) consists of the ATPase ISWI, the large ACF1 subunit and a pair of small histone-like proteins, CHRAC-14/16. CHRAC is a prototypical nucleosome sliding factor that mobilizes nucleosomes to improve the regularity and integrity of the chromatin fiber. This may facilitate the formation of repressive chromatin. Expression of the signature subunit ACF1 is restricted during embryonic development, but remains high in primordial germ cells. Therefore, we explored roles for ACF1 during Drosophila oogenesis. ACF1 is expressed in somatic and germline cells, with notable enrichment in germline stem cells and oocytes. The asymmetrical localization of ACF1 to these cells depends on the transport of the Acf1 mRNA by the Bicaudal-D/Egalitarian complex. Loss of ACF1 function in the novel Acf1(7) allele leads to defective egg chambers and their elimination through apoptosis. In addition, we find a variety of unusual 16-cell cyst packaging phenotypes in the previously known Acf1(1) allele, with a striking prevalence of egg chambers with two functional oocytes at opposite poles. Surprisingly, we found that the Acf1(1) deletion--despite disruption of the Acf1 reading frame--expresses low levels of a PHD-bromodomain module from the C-terminus of ACF1 that becomes enriched in oocytes. Expression of this module from the Acf1 genomic locus leads to packaging defects in the absence of functional ACF1, suggesting competitive interactions with unknown target molecules. Remarkably, a two-fold overexpression of CHRAC (ACF1 and CHRAC-16) leads to increased apoptosis and packaging defects. Evidently, finely tuned CHRAC levels are required for proper oogenesis.
Topics: Alleles; Animals; Apoptosis; Chromatin Assembly and Disassembly; Drosophila Proteins; Drosophila melanogaster; Female; Gene Expression Regulation, Developmental; In Situ Hybridization; Male; Nucleosomes; Oocytes; Oogenesis; Ovary; Phenotype; Protein Structure, Tertiary; RNA, Small Interfering; Stem Cells; Transcription Factors
PubMed: 26851213
DOI: 10.1016/j.ydbio.2016.01.039 -
Cell Jun 1999The chromatin accessibility complex (CHRAC) belongs to the class of nucleosome remodeling factors that increase the accessibility of nucleosomal DNA in an ATP-dependent...
The chromatin accessibility complex (CHRAC) belongs to the class of nucleosome remodeling factors that increase the accessibility of nucleosomal DNA in an ATP-dependent manner. We found that CHRAC induces movements of intact histone octamers to neighboring DNA segments without facilitating their displacement to competing DNA or histone chaperones in trans. CHRAC-induced energy-dependent nucleosome sliding may, in principle, explain nucleosome remodeling, nucleosome positioning, and nucleosome spacing reactions known to be catalyzed by CHRAC. The catalytic core of CHRAC, the ATPase ISWI, also mobilized nucleosomes at the expense of energy. However, the directionality of the CHRAC- and ISWI-induced nucleosome movements differed drastically, indicating that the geometry of the native complex modulates the activity of its catalytic core.
Topics: Adenosine Triphosphatases; Animals; Chromatin; DNA; Drosophila; Histones; Nucleosomes; Polyglutamic Acid; Transcription Factors
PubMed: 10399913
DOI: 10.1016/s0092-8674(00)80797-7 -
Molecular Cell Jan 2004The histone fold is a structural motif with which two related proteins interact and is found in complexes involved in wrapping DNA, the nucleosome, and transcriptional...
The histone fold is a structural motif with which two related proteins interact and is found in complexes involved in wrapping DNA, the nucleosome, and transcriptional regulation, as in NC2. We reveal a novel function for histone-fold proteins: facilitation of nucleosome remodeling. ACF1-ISWI complex (ATP-dependent chromatin assembly and remodeling factor [ACF]) associates with histone-fold proteins (CHRAC-15 and CHRAC-17 in the human chromatin accessibility complex [CHRAC]) whose functional relevance has been unclear. We show that these histone-fold proteins facilitate ATP-dependent nucleosome sliding by ACF. Direct interaction of the CHRAC-15/17 complex with the ACF1 subunit is essential for this process. CHRAC-17 interacts with another histone-fold protein, p12, in DNA polymerase epsilon, but CHRAC-15 is essential for interaction with ACF and enhancement of nucleosome sliding. Surprisingly, CHRAC-15/17, p12/CHRAC-17, and NC2 complexes facilitate ACF-mediated chromatin assembly by a mechanism different from nucleosome sliding enhancement, suggesting a general activity of H2A/H2B type histone-fold complexes in chromatin assembly.
Topics: Amino Acid Sequence; Animals; Chromatin; DNA; DNA Polymerase II; DNA Polymerase III; DNA-Binding Proteins; Dose-Response Relationship, Drug; Drosophila; Glutathione Transferase; Histones; Humans; Molecular Sequence Data; Nucleoproteins; Nucleosomes; Protein Binding; Protein Folding; Protein Structure, Tertiary; Recombinant Fusion Proteins; Sequence Homology, Amino Acid; Time Factors
PubMed: 14759371
DOI: 10.1016/s1097-2765(03)00523-9 -
The Journal of Biological Chemistry Apr 2009The histone fold is a structural element that facilitates heterodimerization, and histone fold heterodimers play crucial roles in gene regulation. Here, we investigated...
The histone fold is a structural element that facilitates heterodimerization, and histone fold heterodimers play crucial roles in gene regulation. Here, we investigated the nuclear import of two human histone fold pairs, which belong to the H2A/H2B family: CHRAC-15/CHRAC-17 and p12/CHRAC-17. Our results from in vitro nuclear import assays with permeabilized cells and in vivo cotransfection experiments reveal that importin 13 facilitates nuclear import of both histone fold heterodimers. Using glutathione S-transferase pulldown experiments, we provide evidence that heterodimers are required for efficient binding of importin 13 because the monomers alone do not significantly interact. Mutational analysis shows that stepwise substitution of basic amino acid residues conserved among the histone fold subunits leads to a progressive loss of importin 13 binding and nuclear accumulation of CHRAC-15/CHRAC-17 and p12/CHRAC-17. The distribution of basic amino acid residues among the histone fold subunits essential for nuclear uptake suggests that heterodimerization of the histone fold motif-containing proteins forms an importin 13-specific binding platform.
Topics: Active Transport, Cell Nucleus; Amino Acid Motifs; Chromatin; Cytoplasm; DNA Mutational Analysis; Dimerization; Glutathione Transferase; HeLa Cells; Histones; Humans; Karyopherins; Models, Biological; Mutagenesis, Site-Directed; Protein Folding; Recombinant Proteins
PubMed: 19218565
DOI: 10.1074/jbc.M806820200 -
Molecular and Cellular Neurosciences Mar 2018The mammalian ISWI (Imitation Switch) genes SMARCA1 and SMARCA5 encode the ATP-dependent chromatin remodeling proteins SNF2L and SNF2H. The ISWI proteins interact with... (Review)
Review
The mammalian ISWI (Imitation Switch) genes SMARCA1 and SMARCA5 encode the ATP-dependent chromatin remodeling proteins SNF2L and SNF2H. The ISWI proteins interact with BAZ (bromodomain adjacent to PHD zinc finger) domain containing proteins to generate eight distinct remodeling complexes. ISWI complex-mediated nucleosome positioning within genes and gene regulatory elements is proving important for the transition from a committed progenitor state to a differentiated cell state. Genetic studies have implicated the involvement of many ATP-dependent chromatin remodeling proteins in neurodevelopmental disorders (NDDs), including SMARCA1. Here we review the characterization of mice inactivated for ISWI and their interacting proteins, as it pertains to brain development and disease. A better understanding of chromatin dynamics during neural development is a prerequisite to understanding disease pathologies and the development of therapeutics for these complex disorders.
Topics: Adenosine Triphosphatases; Animals; Brain; Cell Nucleus; Chromatin; Chromatin Assembly and Disassembly; Humans; Neurodevelopmental Disorders; Transcription Factors
PubMed: 29249292
DOI: 10.1016/j.mcn.2017.10.008 -
PLoS Genetics Nov 2013ATP-dependent chromatin remodelers control DNA access for transcription, recombination, and other processes. Acf1 (also known as BAZ1A in mammals) is a defining subunit...
ATP-dependent chromatin remodelers control DNA access for transcription, recombination, and other processes. Acf1 (also known as BAZ1A in mammals) is a defining subunit of the conserved ISWI-family chromatin remodelers ACF and CHRAC, first purified over 15 years ago from Drosophila melanogaster embryos. Much is known about biochemical properties of ACF and CHRAC, which move nucleosomes in vitro and in vivo to establish ordered chromatin arrays. Genetic studies in yeast, flies and cultured human cells clearly implicate these complexes in transcriptional repression via control of chromatin structures. RNAi experiments in transformed mammalian cells in culture also implicate ACF and CHRAC in DNA damage checkpoints and double-strand break repair. However, their essential in vivo roles in mammals are unknown. Here, we show that Baz1a-knockout mice are viable and able to repair developmentally programmed DNA double-strand breaks in the immune system and germ line, I-SceI endonuclease-induced breaks in primary fibroblasts via homologous recombination, and DNA damage from mitomycin C exposure in vivo. However, Baz1a deficiency causes male-specific sterility in accord with its high expression in male germ cells, where it displays dynamic, stage-specific patterns of chromosomal localization. Sterility is caused by pronounced defects in sperm development, most likely a consequence of massively perturbed gene expression in spermatocytes and round spermatids in the absence of BAZ1A: the normal spermiogenic transcription program is largely intact but more than 900 other genes are mis-regulated, primarily reflecting inappropriate up-regulation. We propose that large-scale changes in chromatin composition that occur during spermatogenesis create a window of vulnerability to promiscuous transcription changes, with an essential function of ACF and/or CHRAC chromatin remodeling activities being to safeguard against these alterations.
Topics: Adenosine Triphosphate; Animals; Chromatin; Chromatin Assembly and Disassembly; DNA Breaks, Double-Stranded; DNA Repair; Drosophila; Fibroblasts; Gene Expression Regulation, Developmental; Humans; Infertility, Male; Male; Mice; Mice, Knockout; Nucleosomes; Primary Cell Culture; Spermatogenesis; Transcription Factors
PubMed: 24244200
DOI: 10.1371/journal.pgen.1003945 -
The EMBO Journal Jul 2001The chromatin accessibility complex (CHRAC) was originally defined biochemically as an ATP-dependent 'nucleosome remodelling' activity. Central to its activity is the...
The chromatin accessibility complex (CHRAC) was originally defined biochemically as an ATP-dependent 'nucleosome remodelling' activity. Central to its activity is the ATPase ISWI, which catalyses the transfer of histone octamers between DNA segments in cis. In addition to ISWI, four other potential subunits were observed consistently in active CHRAC fractions. We have now identified the p175 subunit of CHRAC as Acf1, a protein known to associate with ISWI in the ACF complex. Interaction of Acf1 with ISWI enhances the efficiency of nucleosome sliding by an order of magnitude. Remarkably, it also modulates the nucleosome remodelling activity of ISWI qualitatively by altering the directionality of nucleosome movements and the histone 'tail' requirements of the reaction. The Acf1-ISWI heteromer tightly interacts with the two recently identified small histone fold proteins CHRAC-14 and CHRAC-16. Whether topoisomerase II is an integral subunit has been controversial. Refined analyses now suggest that topoisomerase II should not be considered a stable subunit of CHRAC. Accordingly, CHRAC can be molecularly defined as a complex consisting of ISWI, Acf1, CHRAC-14 and CHRAC-16.
Topics: Adenosine Triphosphatases; Amino Acid Sequence; Animals; Base Sequence; Blotting, Western; DNA Primers; DNA Topoisomerases, Type II; Drosophila; Drosophila Proteins; Histones; Nucleosomes; Precipitin Tests; Recombinant Proteins; Transcription Factors
PubMed: 11447119
DOI: 10.1093/emboj/20.14.3781 -
Genes & Development Jan 2004Chromatin assembly is required for the duplication of chromosomes. ACF (ATP-utilizing chromatin assembly and remodeling factor) catalyzes the ATP-dependent assembly of...
Chromatin assembly is required for the duplication of chromosomes. ACF (ATP-utilizing chromatin assembly and remodeling factor) catalyzes the ATP-dependent assembly of periodic nucleosome arrays in vitro, and consists of Acf1 and the ISWI ATPase. Acf1 and ISWI are also subunits of CHRAC (chromatin accessibility complex), whose biochemical activities are similar to those of ACF. Here we investigate the in vivo function of the Acf1 subunit of ACF/CHRAC in Drosophila. Although most Acf1 null animals die during the larval-pupal transition, Acf1 is not absolutely required for viability. The loss of Acf1 results in a decrease in the periodicity of nucleosome arrays as well as a shorter nucleosomal repeat length in bulk chromatin in embryos. Biochemical experiments with Acf1-deficient embryo extracts further indicate that ACF/CHRAC is a major chromatin assembly factor in Drosophila. The phenotypes of flies lacking Acf1 suggest that ACF/CHRAC promotes the formation of repressive chromatin. The acf1 gene is involved in the establishment and/or maintenance of transcriptional silencing in pericentric heterochromatin and in the chromatin-dependent repression by Polycomb group genes. Moreover, cells in animals lacking Acf1 exhibit an acceleration of progression through S phase, which is consistent with a decrease in chromatin-mediated repression of DNA replication. In addition, acf1 genetically interacts with nap1, which encodes the NAP-1 nucleosome assembly protein. These findings collectively indicate that ACF/CHRAC functions in the assembly of periodic nucleosome arrays that contribute to the repression of genetic activity in the eukaryotic nucleus.
Topics: Adenosine Triphosphatases; Animals; Cell Cycle Proteins; Chromatin; Chromatin Assembly and Disassembly; Drosophila; Drosophila Proteins; Histones; Larva; Nuclear Proteins; Nucleosome Assembly Protein 1; Polycomb Repressive Complex 1; Proteins; S Phase; Transcription Factors
PubMed: 14752009
DOI: 10.1101/gad.1139604