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Soya Shinkai, Tadasu Nozaki, Kazuhiro Maeshima, Yuichi Togashi
The mammalian genome is organized into submegabase-sized chromatin domains (CDs) including topologically associating domains, which have been identified using chromosome conformation capture-based methods. Single-nucleosome imaging in living mammalian cells has revealed subdiffusively dynamic nucleosome movement. It is unclear how single nucleosomes within CDs fluctuate and how the CD structure reflects the nucleosome movement. Here, we present a polymer model wherein CDs are characterized by fractal dimensions and the nucleosome fibers fluctuate in a viscoelastic medium with memory...
October 2016: PLoS Computational Biology
Emilie Lukasova, Aleš Kovařík, Alena Bačíková, Martin Falk, Stanislav Kozubek
The cellular transition to senescence is associated with extensive chromatin reorganization and gene expression changes. Recent studies appeared implying an association of lamin B1 (LB1) reduction with chromatin rearrangement in human fibroblasts promoted to senescence, while the mechanisms and structural features of these relations were not yet clarified. In this work we examined the functions of LB1 and lamin B receptor (LBR) in human cancer cells. We found that both LB1 and LBR tend to deplete during cancer cells transfer to senescence by γ-irradiation...
October 19, 2016: Biochemical Journal
Vanessa Bellini Bardella, Sebastián Pita, André Luis Laforga Vanzela, Cleber Galvão, Francisco Panzera
The subfamily Triatominae (Hemiptera, Reduviidae) includes 150 species of blood-sucking insects, vectors of Chagas disease or American trypanosomiasis. Karyotypic information reveals a striking stability in the number of autosomes. However, this group shows substantial variability in genome size, the amount and distribution of C-heterochromatin, and the chromosome positions of 45S rDNA clusters. Here, we analysed the karyotypes of 41 species from six different genera with C-fluorescence banding in order to evaluate the base-pair richness of heterochromatic regions...
October 2016: Memórias do Instituto Oswaldo Cruz
Clara Lopes Novo, Peter J Rugg-Gunn
Pluripotent cells are characterized by a globally open and accessible chromatin organization that is thought to contribute to cellular plasticity and developmental decision-making. We recently identified the pluripotency factor Nanog as a key regulator of this form of chromatin architecture in mouse embryonic stem cells. In particular, we demonstrated that the transcription factors Nanog and Sall1 co-dependently mediate the epigenetic state of pericentromeric heterochromatin to reinforce a more open and accessible organization in pluripotent cells...
October 19, 2016: Nucleus
Olga I Podgornaya, Irina N Vasilyeva, Vladimir G Bespalov
Only limited sequencing data of the normal extracellular DNA (ecDNA) are currently available. The uptake of the ecDNA by cultured cells and its integration into the host chromatin have been demonstrated. A number of membrane-bearing vesicles in plasma and serum have been shown to carry nucleic acids. The presence of Tandem Repeat (TR) in both apoptotic DNA of HUVEC culture medium and membrane-associated DNA is shown. The existence and successful application of CREST serum also show the presence of fragments of the centromeric heterochromatin together with their TR and specific proteins in blood...
2016: Advances in Experimental Medicine and Biology
Yinyin Li, Yi Shen, Philipp Hohensinner, Jihang Ju, Zhenke Wen, Stuart B Goodman, Hui Zhang, Jörg J Goronzy, Cornelia M Weyand
Immune aging manifests with a combination of failing adaptive immunity and insufficiently restrained inflammation. In patients with rheumatoid arthritis (RA), T cell aging occurs prematurely, but the mechanisms involved and their contribution to tissue-destructive inflammation remain unclear. We found that RA CD4(+) T cells showed signs of aging during their primary immune responses and differentiated into tissue-invasive, proinflammatory effector cells. RA T cells had low expression of the double-strand-break repair nuclease MRE11A, leading to telomeric damage, juxtacentromeric heterochromatin unraveling, and senescence marker upregulation...
October 10, 2016: Immunity
B Roche, B Arcangioli, R A Martienssen
Quiescent cells play a predominant role in most organisms. Here, we identify RNA interference (RNAi) as a major requirement for quiescence (G0) in Schizosaccharomyces pombe RNAi mutants lose viability at G0-entry and are unable to maintain long-term quiescence. We obtained dcr1Δ G0 suppressors, which mapped to genes involved in chromosome segregation, RNA polymerase-associated factors, and heterochromatin formation. We propose a model in which RNAi promotes RNA polymerase release in cycling and quiescent cells: (i) RNA pol II release mediates heterochromatin formation at centromeres allowing proper chromosome segregation during mitotic growth and G0-entry, and (ii) RNA pol I release prevents heterochromatin formation at rDNA during quiescence maintenance...
October 13, 2016: Science
Daisuke Muramatsu, Hiroshi Kimura, Kaoru Kotoshiba, Makoto Tachibana, Yoichi Shinkai
Pericentric regions form epigenetically organized, silent heterochromatin structures that accumulate histone H3 lysine 9 tri-methylation (H3K9me3) and heterochromatin protein 1 (HP1), a methylated H3K9-binding protein. At pericentric regions, Suv39h is the major enzyme that generates H3K9me3. Suv39h also interacts directly with HP1. However, the importance of HP1 interaction for Suv39h-mediated H3K9me3 formation at the pericentromere is not well characterized. To address this question, we introduced HP1 binding-defective, N-terminally truncated mouse Suv39h1 (ΔN) into Suv39h-deficient cells...
October 12, 2016: Cell Structure and Function
Richard T Timms, Iva A Tchasovnikarova, Robin Antrobus, Gordon Dougan, Paul J Lehner
The histone methyltransferase SETDB1 plays a central role in repressive chromatin processes, but the functional requirement for its binding partner ATF7IP has remained enigmatic. Here, we show that ATF7IP is essential for SETDB1 stability: nuclear SETDB1 protein is degraded by the proteasome upon ablation of ATF7IP. As a result, ATF7IP is critical for repression that requires H3K9 trimethylation by SETDB1, including transgene silencing by the HUSH complex. Furthermore, we show that loss of ATF7IP phenocopies loss of SETDB1 in genome-wide assays...
October 11, 2016: Cell Reports
Xiujun Zhang, Yinbo Qu, Yuqi Qin
BACKGROUND: Heterochromatin protein 1 (HP1, homologue HepA in Penicillium oxalicum) binding is associated with a highly compact chromatin state accompanied by gene silencing or repression. HP1 loss leads to the derepression of gene expression. We investigated HepA roles in regulating cellulolytic enzyme gene expression, as an increasingly number of studies have suggested that cellulolytic enzyme gene expression is not only regulated by transcription factors, but is also affected by the chromatin status...
2016: Biotechnology for Biofuels
Thai V Hoang, Caroline Kizilyaprak, Danièle Spehner, Bruno M Humbel, Patrick Schultz
Focused Ion Beam milling combined with Scanning Electron Microscopy is a powerful tool to determine the 3-D organization of whole cells and tissue at an isotropic resolution of 3-5nm. This opens the possibility to quantify several cellular parameters and to provide detailed phenotypic information in normal or disease states. Here we describe Biocomputing methods to extract in an automated way characteristic features of mouse rod photoreceptor nuclei such as the shape and the volume of the nucleus; the proportion of heterochromatin; the number, density and distribution of nuclear pore complexes (NPC)...
October 8, 2016: Journal of Structural Biology
Silvina Laura Lompardía, Mariángeles Díaz, Daniela Laura Papademetrio, Matías Pibuel, Élida Álvarez, Silvia Elvira Hajos
Chronic myeloid leukemia (CML) is a myeloproliferative syndrome characterized by the presence of the Philadelphia chromosome which encodes a constitutively activated tyrosine kinase (BCR-ABL). The first line treatment for CML consists on BCR-ABL inhibitors such as Imatinib. Nevertheless, such treatment may lead to the selection of resistant cells. Therefore, it is of great value to find molecules that enhance the anti-proliferative effect of first-line drugs. Hyaluronan is the main glycosaminglican of the extracellular matrix which is involved in tumor progression and multidrug resistance...
October 8, 2016: Investigational New Drugs
R C R Noronha, L M R Barros, R E F Araújo, D F Marques, C Y Nagamachi, C Martins, J C Pieczarka
BACKGROUND: Cytogenetic studies were conducted in the Brazilian Amazon turtles, Podocnemis expansa Schweigger, 1912 (PEX) and Podocnemis unifilis Troschel, 1848 (PUN) to understand their karyoevolution. Their chromosomal complements were compared using banding techniques (C, G-, Ag-NOR and Chromomycin A3) and fluorescence in situ hybridization (FISH), and efforts were made to establish evolutionary chromosomal relationships within the Podocnemidae family. RESULTS: Our results revealed that both species have a chromosome complement of 2n = 28...
2016: Molecular Cytogenetics
K-E Lee, E-J Lee, H-S Park
Recent advances in computational epigenetics have provided new opportunities to evaluate n-gram probabilistic language models. In this paper, we describe a systematic genome-wide approach for predicting functional roles in inactive chromatin regions by using a sequence-based Markovian chromatin map of the human genome. We demonstrate that Markov chains of sequences can be used as a precursor to predict functional roles in heterochromatin regions and provide an example comparing two publicly available chromatin annotations of large-scale epigenomics projects: ENCODE project consortium and Roadmap Epigenomics consortium...
August 30, 2016: Genetics and Molecular Research: GMR
J Stephen Dumler, Sara H Sinclair, Valeria Pappas-Brown, Amol C Shetty
Anaplasma phagocytophilum, an obligate intracellular prokaryote, infects neutrophils, and alters cardinal functions via reprogrammed transcription. Large contiguous regions of neutrophil chromosomes are differentially expressed during infection. Secreted A. phagocytophilum effector AnkA transits into the neutrophil or granulocyte nucleus to complex with DNA in heterochromatin across all chromosomes. AnkA binds to gene promoters to dampen cis-transcription and also has features of matrix attachment region (MAR)-binding proteins that regulate three-dimensional chromatin architecture and coordinate transcriptional programs encoded in topologically-associated chromatin domains...
2016: Frontiers in Cellular and Infection Microbiology
Keshi Chen, Qi Long, Tao Wang, Danyun Zhao, Yanshuang Zhou, Juntao Qi, Yi Wu, Shengbiao Li, Chunlan Chen, Xiaoming Zeng, Jianguo Yang, Zisong Zhou, Weiwen Qin, Xiyin Liu, Yuxing Li, Yingying Li, Xiaofen Huang, Dajiang Qin, Jiekai Chen, Guangjin Pan, Hans R Schöler, Guoliang Xu, Xingguo Liu, Duanqing Pei
Reprogramming of somatic cells to induced pluripotent stem cells rewrites the code of cell fate at the chromatin level. Yet, little is known about this process physically. Here, we describe a fluorescence recovery after photobleaching method to assess the dynamics of heterochromatin/euchromatin and show significant heterochromatin loosening at the initial stage of reprogramming. We identify growth arrest and DNA damage-inducible protein a (Gadd45a) as a chromatin relaxer in mouse embryonic fibroblasts, which also enhances somatic cell reprogramming efficiency...
October 4, 2016: EMBO Reports
Peter G Vos, M João Paulo, Roeland E Voorrips, Richard G F Visser, Herman J van Eck, Fred A van Eeuwijk
The number of SNPs required for QTL discovery is justified by the distance at which linkage disequilibrium has decayed. Simulations and real potato SNP data showed how to estimate and interpret LD decay. The magnitude of linkage disequilibrium (LD) and its decay with genetic distance determine the resolution of association mapping, and are useful for assessing the desired numbers of SNPs on arrays. To study LD and LD decay in tetraploid potato, we simulated autotetraploid genotypes and used it to explore the dependence on: (1) the number of haplotypes in the population (the amount of genetic variation) and (2) the percentage of haplotype specific SNPs (hs-SNPs)...
October 3, 2016: TAG. Theoretical and Applied Genetics. Theoretische und Angewandte Genetik
Ke Zhang
An important aspect of RNAi-mediated heterochromatin assembly is the production of short interfering RNAs (siRNAs) in cis at the heterochromatic target. These populations of small RNAs (20-30 nt) can be detected via northern blot analysis with radiolabeled RNA probes corresponding to the siRNAs. Most heterochromatin-associated siRNAs originate from both strands of the pericentromeric dg and dh repeats. Thus, production of RNA probes by in vitro transcription utilizes a DNA template with sequences corresponding to either dg or dh repeats...
October 3, 2016: Cold Spring Harbor Protocols
Hugh P Cam, Simon Whitehall
Reporter gene silencing assays provide a facile method for assessing the function of heterochromatin in Schizosaccharomyces pombe They use strains containing auxotrophic markers (commonly ura4(+) or ade6(+)) located within a heterochromatic region. Transcriptional silencing of these reporters can be assessed by plating serial dilutions of cells onto minimal agar. In addition, silencing of ura4(+) renders cells resistant to 5-fluoroorotic acid (5-FOA) and ade6(+) silencing results in red colony color on adenine-limiting agar...
October 3, 2016: Cold Spring Harbor Protocols
Adriana Gonzalez-Sandoval, Susan M Gasser
In eukaryotic organisms, gene regulation occurs in the context of chromatin. In the interphase nucleus, euchromatin and heterochromatin occupy distinct space during cell differentiation, with heterochromatin becoming enriched at the nuclear and nucleolar peripheries. This organization is thought to fine-tune gene expression. To elucidate the mechanisms that govern this level of genome organization, screens were carried out in C. elegans which monitored the loss of heterochromatin sequestration at the nuclear periphery...
2016: Worm
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