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Effects of histone hyperacetylation on the preimplantation development of male and female bovine embryos

Oliveira, Clara S.; Saraiva, Naiara Z.; de Souza, Marcela M.; Tetzner, Tatiane A. D.; de Lima, Marina R.; Garcia, Joaquim Mansano
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica Formato: 1041-1048
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Trichostatin A (TSA) induces histone hyperacetylation by inhibiting histone deacetylases and consequently increasing gene expression. The hypothesis was that TSA supplementation during the in vitro culture (IVC) of bovine embryos would increase the blastocyst rate, particularly in low-quality and female embryos. Oocytes were fertilised separately with X and Y spermatozoa and, 70 h after IVF, the IVC medium was supplemented with 5 nM and 15 nM TSA for 48 or 144 h. Incubation of female embryos with 5 nM and 15 nM TSA resulted in similar increases in acetylated histone H3K9 levels. However, to see comparable effects on acetylated histone H3K9 levels in male embryos, the culture medium needed to be supplemented with 15 nM TSA (as opposed to 5 nM TSA for female embryos). Treatment of male and female embryos with 5 nM TSA for 48 h or female embryos with 5 nM for 144 h had no effect on blastocyst rates, although 15 nM TSA compromised embryonic development. The terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay revealed increased apoptosis in female embryos treated with 5 nM TSA for 144 h, as well as in male and female embryos treated with 15 nM TSA for 48 h...

Supplementation with the histone deacetylase inhibitor trichostatin A during in vitro culture of bovine embryos

Oliveira, Clara Slade; Saraiva, Naiara Zoccal; De Souza, Marcela Maria; De Almeida Drummond Tetzner, Tatiane; De Lima, Marina Ragagnin; Garcia, Joaquim Mansano
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 59-63
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Summary Trichostatin A (TSA) is a histone deacetylase inhibitor that induces histone hyperacetylation and increases gene expression levels. The aim of the present study was to establish a suitable condition for the use of TSA in in vitro cultures of bovine embryos, and to determine whether TSA would increase blastocyst rates by improvement of chromatin remodelling during embryonic genome activation and by increasing the expression of crucial genes during early development. To test this hypothesis, 8-cell embryos were exposed to four concentrations of TSA for different periods of time to establish adequate protocols. In a second experiment, three experimental groups were selected for the evaluation of embryo quality based on the following parameters: apoptosis, total cell number and blastocyst hatching. TSA promoted embryonic arrest and degeneration at concentrations of 15, 25 and 50 nM. All treated groups presented lower blastocyst rates. Exposure of embryos to 5 nM for 144 h and to 15 nM for 48 h decreased blastocyst hatching. However, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay (TUNEL) assay revealed similar apoptosis rates and total cell numbers in all groups studied. Although, in the present study...

Ornithine Decarboxylase Antizyme Induces Hypomethylation of Genome DNA and Histone H3 Lysine 9 Dimethylation (H3K9me2) in Human Oral Cancer Cell Line

Matsuo, Kou; Hu, Guo-fu; Sasaki, Akira; Tsuji, Takanori; Yamamoto, Daisuke; Shima, Kaori; Nishioka, Takashi; Chen, Chang-Yan
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
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Background: Methylation of CpG islands of genome DNA and lysine residues of histone H3 and H4 tails regulates gene transcription. Inhibition of polyamine synthesis by ornithine decarboxylase antizyme-1 (OAZ) in human oral cancer cell line resulted in accumulation of decarboxylated S-adenosylmethionine (dcSAM), which acts as a competitive inhibitor of methylation reactions. We anticipated that accumulation of dcSAM impaired methylation reactions and resulted in hypomethylation of genome DNA and histone tails. Methodology/Principal Findings: Global methylation state of genome DNA and lysine residues of histone H3 and H4 tails were assayed by Methylation by Isoschizomers (MIAMI) method and western blotting, respectively, in the presence or absence of OAZ expression. Ectopic expression of OAZ mediated hypomethylation of CpG islands of genome DNA and histone H3 lysine 9 dimethylation (H3K9me2). Protein level of DNA methyltransferase 3B (DNMT3B) and histone H3K9me specific methyltransferase G9a were down-regulated in OAZ transfectant. Conclusions/Significance: OAZ induced hypomethylation of CpG islands of global genome DNA and H3K9me2 by down-regulating DNMT3B and G9a protein level. Hypomethylation of CpG islands of genome DNA and histone H3K9me2 is a potent mechanism of induction of the genes related to tumor suppression and DNA double strand break repair.

Dynamic regulation of histone lysine methylation via the ubiquitin-proteasome system.

Lim, Hui Jun
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
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Lysine methylation is an important post-translational modification found on histones that is added and removed by histone lysine methyltransferases and demethylases, respectively. Lysine methylation occurs in a specific and well-regulated manner, and plays key roles in regulating important biological processes such as transcription, DNA damage and cell cycle. Regulation of the protein abundance of these methylation enzymes particularly by the ubiquitin-proteasome system has emerged as a key mechanism by which the histone methylation status of the cell can be regulated, allowing cells to respond rapidly to specific developmental and environmental cues. In my thesis, I focus on two histone lysine demethylases, KDM4A and PHF8, both of which appear to be regulated by E3 ligases; this regulation impacts their function in the cell. Chapter 2 shows that KDM4A is targeted for proteasomal degradation by the SCFFBXO22, and mis-regulation of KDM4A results in changes in global histone 3 lysine 9 and 36 (H3K9 and H3K36) methylation levels and impacts the transcription of a KDM4A target gene, ASCL2. Chapter 3 shows how PHF8 is targeted for proteasomal degradation by the APCCDC20 via a novel, previously unreported LxPKxLF motif on PHF8. I also found that similar to other APCCDC20 substrates like Cyclin B...

Characterization of genome-wide H3K27ac profiles reveals a distinct PM2.5-associated histone modification signature

Liu, Cong; Xu, Junhui; Chen, Yahong; Guo, Xinbiao; Zheng, Yinan; Wang, Qianfei; Chen, Yiyong; Ni, Yang; Zhu, Yidan; Joyce, Brian Thomas; Baccarelli, Andrea; Deng, Furong; Zhang, Wei; Hou, Lifang
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
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Background: Current studies of environmental health suggest a link between air pollution components, such as particulate matter (PM), and various diseases. However, the specific genes and regulatory mechanisms implicated in PM-induced diseases remain largely unknown. Epigenetic systems such as covalent modification of histones in chromatin may mediate environmental factors in gene regulation. Investigating the relationships between PM exposure and histone modification status may help understand the mechanisms underlying environment-associated health conditions. Methods: In this study, we obtained genome-wide profiles of H3K27ac (histone 3 lysine 27 acetylation), known to be an active gene regulatory histone modification marker, in blood samples collected from four Chinese individuals exposed to high or low PM2.5 (particles with diameters up to 2.5 μm). Results: The genome-wide chromatin immunoprecipitation sequencing (ChIP-Seq) data indicated a comprehensive differential H3K27ac landscape across the individual genomes, which was associated with high PM2.5. Moreover, a substantial number of these PM2.5-associated differential H3K27ac markers were in genes involved in immune cell activation, potentially linking these epigenetic changes with air pollution-induced immune and inflammatory responses. Conclusions: Our study provides the first genome-wide characterization of H3K27ac profiles in individuals subjected to different exposure levels of PM2.5. Future systematic investigations of the relationships between air pollutants and histone modifications in large population samples are warranted to elucidate the contributions of histone modifications to environment-associated diseases. Electronic supplementary material The online version of this article (doi:10.1186/s12940-015-0052-5) contains supplementary material...

Core histone tail domain mediated inter-nucleosome interactions in higher order chromatin structures

Kan, Pu-Yeh ; Hayes, Jeffrey J.
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:x, 118 leaves
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Thesis (Ph. D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Pathology, 2008. ; The core histone tail domains play a central role in chromatin structure and epigenetic processes controlling gene expression. Although little is known regarding the molecular details of tail interactions, it is likely that they participate in both short-range and long-range interactions between nucleosomes. Previously, we demonstrated that the H3 tail domain participates in internucleosome interactions during MgCl2-dependent condensation of model nucleosome arrays. However, these studies did not distinguish whether these internucleosome interactions represented short-range intra-array or longer-range interarray interactions. To better understand the complex interactions of the histone tail domains during chromatin condensation, we developed a new site-directed cross-linking method to identify and quantify interarray interactions mediated by histone tail domains. Interarray cross-linking was undetectable under salt conditions that induced only local folding, but was detected concomitant with salt-dependent interarray oligomerization at higher MgCl2 concentrations. Interestingly, lysine-to-glutamine mutations in the H3 tail domain modeling posttranslational acetylation as well as bona fide lysine acetylation in the H4 tail domain resulted in modest (H3) or no (H4) reduction in interarray cross-linking. In contrast...

The Role of NPAT in S-Phase-Dependent Histone Gene Transcription and DNA Double-Strand Break Repair

DeRan, Michael ; Zhao, Jiyong
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado
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Thesis (Ph.D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Molecular Biology, 2010.; In eukaryotic cells, DNA is packaged into chromatin by the histone proteins. The bulk of histone synthesis occurs in S-phase in order to package the nascent DNA. Thus, the core histones, H2A, H2B, H3, and H4 and the linker histone H1 are termed the replication-dependent histones. The expression of the replication-dependent histones is coordinately controlled and tightly coupled to DNA replication in S-phase. It is clear that coordination and coupling are critical. Perturbations to coordination result in chromosome loss and uncoupling of histone gene expression from DNA replication lead to developmental arrest. The mechanisms through which coordination is achieved are poorly understood. It has been shown previously that the cyclin E/Cdk2 substrate NPAT plays an essential role in activating transcription of all of the replication-dependent histone genes at the G1-S transition. Here we show that NPAT regulates the transcription of the replication-dependent histone genes through a novel amino acid motif that is functionally conserved in E2F and E1A proteins. Through this motif, NPAT interacts with members of the Tip60 histone acetyltransferase complex. Two members of this complex...

Molecular Determinants of Linker Histone Binding to Nucleosomes

Caterino, Tamara ; Hayes, Jeff
Fonte: Universidade de Rochester Publicador: Universidade de Rochester
Tipo: Tese de Doutorado
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Thesis (Ph.D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Biochemistry & Biophysics, 2010.; Linker histones are multi-functional proteins that are involved in a myriad of processes ranging from the stabilization of folding and condensation of chromatin to playing a direct role in regulating gene expression. Previous evidence indicates that linker histones bind to the exterior of nucleosomes and stabilize the wrapping of DNA around the histone octamer. Specific binding is provided by the conserved globular domain via structure-specific interactions at the nucleosome dyad, while the majority of chromatin functions are provided by the C-terminal domain (CTD), which typically encompasses approximately half of the mass of the linker histone and includes a large excess of positively charged amino acid residues. However, little is known regarding the structure and interactions of the CTD. While the primary sequence of the CTD has diverged among H1 isoforms, the amino acid compositions are surprisingly similar. The CTD does not adopt a stable fold in solution and has been proposed to function in chromatin as an unstructured polycation which indiscriminately screens the negatively charged phosphate backbone of linker DNA in condensed chromatin through electrostatic mechanisms. However...

Caractérisation de la fonction des complexes histone déacétylases Rpd3S et Set3C

Drouin, Simon
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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La chromatine est essentielle au maintien de l’intégrité du génome, mais, ironiquement, constitue l’obstacle principal à la transcription des gènes. Plusieurs mécanismes ont été développés par la cellule pour pallier ce problème, dont l’acétylation des histones composant les nucléosomes. Cette acétylation, catalysée par des histones acétyl transférases (HATs), permet de réduire la force de l’interaction entre les nucléosomes et l’ADN, ce qui permet à la machinerie transcriptionnelle de faire son travail. Toutefois, on ne peut laisser la chromatine dans cet état permissif sans conséquence néfaste. Les histone déacétylases (HDACs) catalysent le clivage du groupement acétyle pour permettre à la chromatine de retrouver une conformation compacte. Cette thèse se penche sur la caractérisation de la fonction et du mécanisme de recrutement des complexes HDACs Rpd3S et Set3C. Le complexe Rpd3S est recruté aux régions transcrites par une interaction avec le domaine C-terminal hyperphosphorylé de Rpb1, une sous-unité de l’ARN polymérase II. Toutefois, le facteur d’élongation DSIF joue un rôle dans la régulation de cette association en limitant le recrutement de Rpd3S aux régions transcrites. L’activité HDAC de Rpd3S...

Histone H2B-R95A mutant identifies the pheromone pathway that signals cell cycle arrest during rapamycin response

Ayachi, Sami
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
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La rapamycine est un immunosuppresseur utilisé pour traiter plusieurs types de maladies dont le cancer du rein. Son fonctionnement par l’inhibition de la voie de Tor mène à des changements dans des processus physiologiques, incluant le cycle cellulaire. Chez Saccharomyces cerevisiae, la rapamycine conduit à une altération rapide et globale de l’expression génique, déclenchant un remodelage de la chromatine. Nous proposons que les modifications des histones peuvent jouer un rôle crucial dans le remodelage de la chromatine en réponse à la rapamycine. Notre objectif principal est d’identifier d’une banque de mutants d’histone les variantes qui vont échouer à répondre à la rapamycine dans une tentative de réaliser une caractérisation des modifications d’histone critiques pour la réponse à cette drogue. Ainsi, nous avons réalisé un criblage d’une banque de mutants d’histone et identifié plusieurs mutants d‘histone dont la résistance à la rapamycine a été altérée. Nous avons caractérisé une de ces variantes d’histone, à savoir H2B, qui porte une substitution de l’alanine en arginine en position 95 (H2B-R95A) et démontré que ce mutant est extrêmement résistant à la rapamycine, et non à d’autres drogues. Des immunoprécipitations ont démontré que H2B-R95A est défectueux pour former un complexe avec Spt16...

Role of CREB-binding protein on histone acetylation and cocaine-associated behaviors

MHILLAJ, EMANUELA
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
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Evidence shows that cocaine exposure triggers altered gene expression within the nucleus accumbens, contributing to the development and persistence of drug addiction. Chromatin modification is emerging as a major molecular mechanism involved in the regulation of gene expression critical for long lasting forms of synaptic plasticity, memory processes, and drug-induced neural and behavioral change. Cocaine induces specific chromatin modifications, such as histone acetylation, that modulate histone-DNA interactions and the recruitment of transcriptional regulatory complexes, leading to changes in transcription that may underlie aspects of cocaine addiction. Although changes in histone acetylation in response to cocaine have been documented, relatively little is known about the specific histone acetylation enzymes involved in cocaine-induced plasticity. The enzymes that regulate levels of histone acetylation are histone acetyltransferases (HATs) and histone deacetylases (HDACs), which generally promote or silence gene expression, respectively. Studies have demonstrated that HDACs may negatively regulate cocaine-induced behaviors, but very little is known about the role of specific HATs in long-lasting drug induced plasticity. The histone acetyltransferase CREB-binding protein (CBP) mediates transcriptional activation by recruiting basal transcription machinery and acetylating histones. CBP is a critically important chromatin modifying enzyme involved in regulating gene expression required for long-term plasticity and memory. However...

Centromere-specific acetylation of histone H4 in barley detected through three-dimensional microscopy

Wako, Toshiyuki; Houben, Andreas; Furushima-Shimogawara, Rieko; Belyaev, Nikolai D.; Fukui, Kiichi
Fonte: Kluwer Publicador: Kluwer
Tipo: Artigo de Revista Científica
Publicado em //2003 Português
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Histone acetylation affects chromatin conformation and transcriptional activity. However, the structural role of histone acetylation at specific chromosomal regions, such as the centromere, is poorly understood. In this study, histone H4 acetylation and its localization in barley interphase nuclei are revealed by three-dimensional microscopy. The centromeres form a ring-like allocation near the nuclear membrane in barley. Immunofluorescence studies on non-fixed, interphase nuclei treatment revealed ring-like distribution of the highly acetylated histone H4, located near the nuclear membrane at one pole of the nucleus. This fluorescent structure was similar to the centromere cluster and referred to as hyperacetylated region (HAR). The distribution pattern of the acetylated histone H4 was similar to each of the K5, K8, K12 and K16 lysine residues, although H4 acetylated at K5, K8 and K12 residues was found in almost all nuclei, whereas H4 acetylated at K16 was weakly observed in only half of the nuclei. Each HAR consists of two strongly acetylated cores and a halo-like, less acetylated surrounding area. Fluorescence signals from centromere-specific repetitive sequences of barley, detected through three-dimensional fluorescence in situ hybridization (3D-FISH)...

Identification of the linker histone H1 as a protein kinase Cε-binding protein in vascular smooth muscle; Identification of the linker histone H1 as a protein kinase Cepsilon-binding protein in vascular smooth muscle

Zhao, M.; Sutherland, C.; Wilson, D.; Deng, J.; MacDonald, J.; Walsh, M.
Fonte: Natl Research Council Canada Publicador: Natl Research Council Canada
Tipo: Artigo de Revista Científica
Publicado em //2004 Português
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A variety of anchoring proteins target specific protein kinase C (PKC) isoenzymes to particular subcellular locations or multimeric signaling complexes, thereby achieving a high degree of substrate specificity by localizing the kinase in proximity to specific substrates. PKCε is widely expressed in smooth muscle tissues, but little is known about its targeting and substrate specificity. We have used a Far-Western (overlay) approach to identify PKCε-binding proteins in vascular smooth muscle of the rat aorta. Proteins of ~32 and 34 kDa in the Triton-insoluble fraction were found to bind PKCε in a phospholipid/diacylglycerol-dependent manner. Although of similar molecular weight to RACK-1, a known PKCε-binding protein, these proteins were separated from RACK-1 by SDS-PAGE and differential NaCl extraction and were not recognized by an antibody to RACK-1. The PKCε-binding proteins were further purified from the Tritoninsoluble fraction and identified by de novo sequencing of selected tryptic peptides by tandem mass spectrometry as variants of the linker histone H1. Their identity was confirmed by Western blotting with anti-histone H1 and the demonstration that purified histone H1 binds PKCε in the presence of phospholipid and diacylglycerol but absence of Ca2+. The interaction of PKCε with histone H1 was specific since no interaction was observed with histones H2A...

Histone H3 and its Centromeric Variant Cse4 Co-Occupy the Centromeric DNA in Saccharomyces cerevisiae; Histon H3 und seine zentromere Variante Cse4 co-okkupieren die zentromere DNS in Saccharomyces cerevisiae

Lochmann, Berit
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
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For cell division, the replicated genetic information of a cell needs to be accurately segregated to the emerging daughter cells. This is achieved by packaging the DNA into sister chromatids, which are separated by the poleward pulling force of microtubules. Microtubules are attached to the centromeres of the sister chromatids by a multi-protein complex called the kinetochore. The assembly of the kinetochore at the centromere is directed by specialized centromeric chromatin. Conventional chromatin contains nucleosomes, which are comprised of two copies each of the histones H3, H4, H2A, and H2B. This protein octamer organizes 147 bp of DNA by wrapping it in 1.7 turns. In contrast to canonical nucleosomes it is believed that centromeric nucleosomes are devoid of histone H3 and contain in its place the variant CENP-A. CENP-A is an essential protein necessary for kinetochore formation and homologues have been identified in all eukaryotes studied so far. Whereas higher eukaryotes have long arrays (kilo- to megabases of DNA) of centromeric chromatin with CENP-A containing nucleosomes, the budding yeast centromeric DNA is approximately 125 bp with only a single Cse4 (budding yeast homologue of CENP-A) containing nucleosome that is sufficient to recruit and assemble the kinetochore. This so-called point centromere is thought to represent the smallest unit of larger centromeres. However...

Cell-cycle-dependent translation of histone mRNAs is the key control point for regulation of histone biosynthesis in Leishmania infantum

Soto, Manuel; Iborra, Salvador; Quijada, Luis; Folgueira Fernández, Cristina; Alonso, Carlos; Requena, José María
Fonte: Biochemical Society Publicador: Biochemical Society
Tipo: Artículo Formato: 245881 bytes; application/pdf
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The cell-cycle-dependent expression of the four core histones (H2A, H2B, H3 and H4) has been studied in the protozoan parasite Leishmania infantum. For that purpose, the cell cycle was arrested by incubation of promastigotes with the DNA synthesis inhibitor hydroxyurea, which induced an accumulation of cells stalled in G1 phase. Hydroxyurea release resulted in a semi-synchronous entry into the cell cycle, as determined by flow cytometry. The steady-state levels of histone mRNAs in the G1, S and G2/M phases were found to be constant along the cell cycle. However, the levels of histone synthesis increased when parasites enter the S phase, in agreement with previous results showing that histone synthesis in Leishmania is tightly coupled with DNA replication. In addition, we analysed the distribution of histone mRNAs on polyribosomes at different stages of the cell cycle by separation of cytoplasmic RNAs in sucrose gradients. Remarkably, a drastic change in the polysome profiles of histone mRNAs was observed during the progression from G1 to S phase. Thus, in the S phase, histone mRNAs are present in ribosome-bound fractions, but in the G1 phase, the histone transcripts are exclusively found in the ribosome-free fractions. These results support a regulatory model in which the cell-cycle-regulated synthesis of histones in Leishmania is controlled through a reversible interaction between translational repressors and histone mRNAs; This work was supported by Grant BMC2002-04107-C02-01 from Ministerio de Ciencia y Tecnología of Spain. Also...

Linker histone post-translational modifications and effects of phosphorylation on secondary structure and chromatin aggregation

Lopez Ramos, Rita
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2014 Português
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Les histones linker juguen un paper important en l'organització i manteniment de la cromatina en estructures d'ordre superior i en la regulació transcripcional. La histona H1 en vertebrats té una estructura característica en tres dominis: un domini N-terminal curt i flexible; un domini globular central; i un domini C-terminal llarg. Els dominis N- i C-terminals (CTD) són molt bàsics i es troben desestructurats en solució aquosa. La distribució de càrrega és bastant uniforme al llarg de tot el CTD. La interacció amb el DNA indueix un plegament total i estable del CTD en condicions fisiològiques, fet que permet classificar aquest domini en el grup de les proteïnes intrínsecament desordenades, on el plegament i la unió al lligand estan acoblades. La fosforilació post-traduccional del CTD de la H1 té efectes en l'estructura secundària de la proteïna i en la condensació del DNA. L'estructura secundària de la H10 sencera es va analitzar per espectroscòpia d'infrarroig. La H10, igual que el CTD aïllat, també es plegà degut a la interacció amb el DNA i l'estructura secundària també va ser modulada per fosforilació. El canvi estructural induït per la fosforilació va consistir en un increment de la quantitat d'estructura β...

Cathepsin L stabilizes the histone modification landscape on the y chromosome and pericentromeric heterochromatin

Bulynko, Yaroslava; Hsing, Lianne; Mason, Robert; Tremethick, David; Grigoriev, Sergei A
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
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Posttranslational histone modifications and histone variants form a unique epigenetic landscape on mammalian chromosomes where the principal epigenetic heterochromatin markers, trimethylated histone H3(K9) and the histone H2A.Z, are inversely localized in relation to each other. Trimethylated H3(K9) marks pericentromeric constitutive heterochromatin and the male Y chromosome, while H2A.Z is dramatically reduced at these chromosomal locations. Inactivation of a lysosomal and nuclear protease, cathepsin L, causes a global redistribution of epigenetic markers. In cathepsin L knockout cells, the levels of trimethylated H3(K9) decrease dramatically, concomitant with its relocation away from heterochromatin, and H2A.Z becomes enriched at pericentromeric heterochromatin and the Y chromosome. This change is also associated with global relocation of heterochromatin protein HP1 and histone H3 methyltransferase Suv39h1 away from constitutive heterochromatin; however, it does not affect DNA methylation or chromosome segregation, phenotypes commonly associated with impaired histone H3(K9) methylation. Therefore, the key constitutive heterochromatin determinants can dynamically redistribute depending on physiological context but still maintain the essential function(s) of chromosomes. Thus...

Nucleosomes containing the histone variant H2A.Bbd organize only 118 base pairs of DNA

Bao, Y; Konesky, Kasey; Park, Young Ju; Rosu, Simona; Dyer, Pamela; Rangasamy, Danny; Tremethick, David; Laybourn, Paul; Luger, Karolin
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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H2A.Bbd is an unusual histone variant whose sequence is only 48% conserved compared to major H2A. The major sequence differences are in the docking domain that tethers the H2A-H2B dimer to the (H3-H4)2 tetramer; in addition, the C-terminal tail is absent

A New Fluorescence Resonance Energy Transfer Approach Demonstrates That the Histone Variant H2AZ Stabilizes the Histone octamer within the Nucleosome

Park, Young Ju; Dyer, Pamela; Tremethick, David; Luger, Karolin
Fonte: American Society for Biochemistry and Molecular Biology Inc Publicador: American Society for Biochemistry and Molecular Biology Inc
Tipo: Artigo de Revista Científica
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Nucleosomes are highly dynamic macromolecular complexes that are assembled and disassembled in a modular fashion. One important way in which this dynamic process can be modulated is by the replacement of major histones with their variants, thereby affecting nucleosome structure and function. Here we use fluorescence resonance energy transfer between fluorophores attached to various defined locations within the nucleosome to dissect and compare the structural transitions of a H2A.Z containing and a canonical nucleosome in response to increasing ionic strength. We show that the peripheral regions of the DNA dissociate from the surface of the histone octamer at relatively low ionic strength, under conditions where the dimer-tetramer interaction remains unaffected. At around 550 mM NaCl, the (H2A-H2B) dimer dissociates from the (H3-H4)2 tetramer-DNA complex. Significantly, this latter transition is stabilized in nucleosomes that have been reconstituted with the essential histone variant H2A.Z. Our studies firmly establish fluorescence resonance energy transfer as a valid method to study nucleosome stability, and shed new light on the biological function of H2A.Z.

Histone Dynamics on the Interleukin-2 Gene in Response to T-Cell Activation

Chen, Xin; Wang, Jun; Woltring, Donna; Gerondakis, Steve; Shannon, M Frances
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Português
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Several models have been proposed for the mechanism of chromatin remodelling across the promoters of inducible genes in mammalian cells. The most commonly held model is one of cooccupation where histone proteins are modified by acetylation or phosphorylation and nucleosomes are remodelled, allowing the assembly of transcription factor complexes. Using chromatin immunoprecipitation, we observed an apparent decrease of histone acetylation and phosphorylation signals at the proximal promoter region of the inducible interleukin-2 and granulocyte-macrophage colony-stimulating factor genes in response to T-cell activation. We showed that this apparent decrease was due to a loss of histone H3 and H4 proteins corresponding to a decrease in nucleosome occupation of the promoter. This histone loss is reversible; it is dependent on the continual presence of appropriate activating signals and transcription factors and is not dependent on the acetylation status of the histone proteins. These data show for the first time that histone proteins are lost from a mammalian promoter upon activation of transcription and support a model of activation-dependent disassembly and reassembly of nucleosomes.