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Heterochromatin

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https://www.readbyqxmd.com/read/28648780/the-histone-acetyltransferase-mst2-protects-active-chromatin-from-epigenetic-silencing-by-acetylating-the-ubiquitin-ligase-brl1
#1
Valentin Flury, Paula Raluca Georgescu, Vytautas Iesmantavicius, Yukiko Shimada, Tahsin Kuzdere, Sigurd Braun, Marc Bühler
Faithful propagation of functionally distinct chromatin states is crucial for maintaining cellular identity, and its breakdown can lead to diseases such as cancer. Whereas mechanisms that sustain repressed states have been intensely studied, regulatory circuits that protect active chromatin from inactivating signals are not well understood. Here we report a positive feedback loop that preserves the transcription-competent state of RNA polymerase II-transcribed genes. We found that Pdp3 recruits the histone acetyltransferase Mst2 to H3K36me3-marked chromatin...
June 14, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28642500/genome-wide-mapping-of-dnase-i-hypersensitive-sites-reveals-chromatin-accessibility-changes-in-arabidopsis-euchromatin-and-heterochromatin-regions-under-extended-darkness
#2
Yue Liu, Wenli Zhang, Kang Zhang, Qi You, Hengyu Yan, Yuannian Jiao, Jiming Jiang, Wenying Xu, Zhen Su
Light, as the energy source in photosynthesis, is essential for plant growth and development. Extended darkness causes dramatic gene expression changes. In this study, we applied DNase-seq (DNase I hypersensitive site sequencing) to study changes of chromatin accessibility in euchromatic and heterochromatic regions under extended darkness in Arabidopsis. We generated 27 Gb DNase-seq and 67.6 Gb RNA-seq data to investigate chromatin accessibility changes and global gene expression under extended darkness and control condition in Arabidopsis...
June 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28638402/dna-methylation-nuclear-organization-and-cancer
#3
REVIEW
Bhavani P Madakashira, Kirsten C Sadler
The dramatic re-organization of the cancer cell nucleus creates telltale morphological features critical for pathological staging of tumors. In addition, the changes to the mutational and epigenetic landscape in cancer cells alter the structure and stability of the genome and directly contribute to malignancy. DNA methylation is one of the best studied epigenetic changes in cancer, as nearly every type of cancer studied shows a loss of DNA methylation spread across most of the genome. This global hypomethylation is accompanied by hypermethylation at distinct loci, and much of the work on DNA methylation in cancer has focused on how local changes contribute to gene expression...
2017: Frontiers in Genetics
https://www.readbyqxmd.com/read/28638390/characterization-genomic-organization-abundance-and-chromosomal-distribution-of-ty1-copia-retrotransposons-in-erianthus-arundinaceus
#4
Yongji Huang, Ling Luo, Xuguang Hu, Fan Yu, Yongqing Yang, Zuhu Deng, Jiayun Wu, Rukai Chen, Muqing Zhang
Erianthus arundinaceus is an important wild species of the genus Saccharum with many valuable traits. However, the composition and structure of its genome are largely unknown, which have hindered its utilization in sugarcane breeding and evolutionary research. Retrotransposons constitute an appreciable fraction of plant genomes and may have played a significant role in the evolution and sequence organization of genomes. In the current study, we investigate the phylogenetic diversity and genomic abundance of Ty1-copia retrotransposons for the first time and inspect their chromosomal distribution patterns in E...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28636937/the-conserved-rna-binding-cyclophilin-rct1-regulates-small-rna-biogenesis-and-splicing-independent-of-heterochromatin-assembly
#5
An-Yun Chang, Stephane E Castel, Evan Ernst, Hyun Soo Kim, Robert A Martienssen
RNAi factors and their catalytic activities are essential for heterochromatin assembly in S. pombe. This has led to the idea that siRNAs can promote H3K9 methylation by recruiting the cryptic loci regulator complex (CLRC), also known as recombination in K complex (RIKC), to the nucleation site. The conserved RNA-binding protein Rct1 (AtCyp59/SIG-7) interacts with splicing factors and RNA polymerase II. Here we show that Rct1 promotes processing of pericentromeric transcripts into siRNAs via the RNA recognition motif...
June 20, 2017: Cell Reports
https://www.readbyqxmd.com/read/28636604/liquid-droplet-formation-by-hp1%C3%AE-suggests-a-role-for-phase-separation-in-heterochromatin
#6
Adam G Larson, Daniel Elnatan, Madeline M Keenen, Michael J Trnka, Jonathan B Johnston, Alma L Burlingame, David A Agard, Sy Redding, Geeta J Narlikar
Gene silencing by heterochromatin is proposed to occur in part as a result of the ability of heterochromatin protein 1 (HP1) proteins to spread across large regions of the genome, compact the underlying chromatin and recruit diverse ligands. Here we identify a new property of the human HP1α protein: the ability to form phase-separated droplets. While unmodified HP1α is soluble, either phosphorylation of its N-terminal extension or DNA binding promotes the formation of phase-separated droplets. Phosphorylation-driven phase separation can be promoted or reversed by specific HP1α ligands...
June 21, 2017: Nature
https://www.readbyqxmd.com/read/28636597/phase-separation-drives-heterochromatin-domain-formation
#7
Amy R Strom, Alexander V Emelyanov, Mustafa Mir, Dmitry V Fyodorov, Xavier Darzacq, Gary H Karpen
Constitutive heterochromatin is an important component of eukaryotic genomes that has essential roles in nuclear architecture, DNA repair and genome stability, and silencing of transposon and gene expression. Heterochromatin is highly enriched for repetitive sequences, and is defined epigenetically by methylation of histone H3 at lysine 9 and recruitment of its binding partner heterochromatin protein 1 (HP1). A prevalent view of heterochromatic silencing is that these and associated factors lead to chromatin compaction, resulting in steric exclusion of regulatory proteins such as RNA polymerase from the underlying DNA...
June 21, 2017: Nature
https://www.readbyqxmd.com/read/28633925/the-discovery-of-plasma-cells-an-historical-note
#8
REVIEW
Domenico Ribatti
The name plasma cell was introduced by the anatomist Heinrich H. von Hartz-Waldeyer in 1875. Plasma cells derive from small B lymphocytes after their activation. A fully mature plasma cell lacks surface immunoglobulin expression. Its form is round or oval, with characteristic basophilic cytoplasm and an eccentric nucleus that contains coarse heterochromatin. Antigen activation of mature B cells leads initially to germinal center development, the transient generation of plasmablasts that secrete antibody while still dividing, and short-lived extrafollicular plasma cells that secrete antigen-specific germ line-encoded antibodies...
June 17, 2017: Immunology Letters
https://www.readbyqxmd.com/read/28630280/ki-67-contributes-to-normal-cell-cycle-progression-and-inactive-x-heterochromatin-in-p21-checkpoint-proficient-human-cells
#9
Xiaoming Sun, Aizhan Bizhanova, Timothy D Matheson, Jun Yu, Julie L Zhu, Paul D Kaufman
Ki-67 protein is widely used as a tumor proliferation marker. However, whether Ki-67 affects cell cycle progression has been controversial. Here, we demonstrate that depletion of Ki-67 in human hTERT-RPE1, WI-38, IMR90, hTERT-BJ cell lines and primary fibroblast cells slowed entry into S phase and coordinately downregulated genes related to DNA replication. Some gene expression changes were partially relieved in Ki-67-depleted hTERT-RPE1 cells by co-depletion of the Rb checkpoint protein, but more thorough suppression of the transcriptional and cell cycle defects was observed upon depletion of cell cycle inhibitor p21...
June 19, 2017: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/28628380/low-frequency-noise-effects-on-the-rat-parotid-gland-a-transmission-electron-microscopy-study
#10
Pedro Oliveira, Goncalo Martins Pereira, Margarida Seara Simões, Emanuel Monteiro, António Pedro Alves de Matos, Artur Águas, José Martins Dos Santos
INTRODUCTION: Low-frequency noise (LFN) is a ubiquitous physical stressor known to cause degenerative cellular changes and organ alterations with functional repercussions both in humans and animals. MATERIALS AND METHODS: After acceptance of the study protocol by a local ethics committee, 20 Wistar rats were randomly divided into two equal groups. One group was kept in silence and the other continuously exposed to LFN during 13 weeks. The rats had unlimited access to water and were fed standard rat chow...
June 19, 2017: Ultrastructural Pathology
https://www.readbyqxmd.com/read/28623274/reduction-in-chromosome-mobility-accompanies-nuclear-organization-during-early-embryogenesis-in-caenorhabditis-elegans
#11
Ritsuko Arai, Takeshi Sugawara, Yuko Sato, Yohei Minakuchi, Atsushi Toyoda, Kentaro Nabeshima, Hiroshi Kimura, Akatsuki Kimura
In differentiated cells, chromosomes are packed inside the cell nucleus in an organised fashion. In contrast, little is known about how chromosomes are packed in undifferentiated cells and how nuclear organization changes during development. To assess changes in nuclear organization during the earliest stages of development, we quantified the mobility of a pair of homologous chromosomal loci in the interphase nuclei of Caenorhabditis elegans embryos. The distribution of distances between homologous loci was consistent with a random distribution up to the 8-cell stage but not at later stages...
June 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28623258/chromatin-organization-regulates-viral-egress-dynamics
#12
Vesa Aho, Markko Myllys, Visa Ruokolainen, Satu Hakanen, Elina Mäntylä, Jori Virtanen, Veijo Hukkanen, Thomas Kühn, Jussi Timonen, Keijo Mattila, Carolyn A Larabell, Maija Vihinen-Ranta
Various types of DNA viruses are known to elicit the formation of a large nuclear viral replication compartment and marginalization of the cell chromatin. We used three-dimensional soft x-ray tomography, confocal and electron microscopy, combined with numerical modelling of capsid diffusion to analyse the molecular organization of chromatin in herpes simplex virus 1 infection and its effect on the transport of progeny viral capsids to the nuclear envelope. Our data showed that the formation of the viral replication compartment at late infection resulted in the enrichment of heterochromatin in the nuclear periphery accompanied by the compaction of chromatin...
June 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28621425/epigenetic-mechanism-of-fmr1-inactivation-in-fragile-x-syndrome
#13
Merav Hecht, Amalia Tabib, Tamar Kahan, Shari Orlanski, Michal Gropp, Yuval Tabach, Ofra Yanuka, Nissim Benvenisty, Ilana Keshet, Howard Cedar
Fragile X syndrome is the most frequent cause of inherited intellectual disability. The primary molecular defect in this disease is the expansion of a CGG repeat in the 5' region of the fragile X mental retardation1 (FMR1) gene, leading to de novo methylation of the promoter and inactivation of this otherwise normal gene, but little is known about how these epigenetic changes occur during development. In order to gain insight into the nature of this process, we have used cell fusion technology to recapitulate the events that occur during early embryogenesis...
2017: International Journal of Developmental Biology
https://www.readbyqxmd.com/read/28615290/a-post-translational-modification-switch-controls-coactivator-function-of-histone-methyltransferases-g9a-and-glp
#14
Coralie Poulard, Danielle Bittencourt, Dai-Ying Wu, Yixin Hu, Daniel S Gerke, Michael R Stallcup
Like many transcription regulators, histone methyltransferases G9a and G9a-like protein (GLP) can act gene-specifically as coregulators, but mechanisms controlling this specificity are mostly unknown. We show that adjacent post-translational methylation and phosphorylation regulate binding of G9a and GLP to heterochromatin protein 1 gamma (HP1γ), formation of a ternary complex with the glucocorticoid receptor (GR) on chromatin, and function of G9a and GLP as coactivators for a subset of GR target genes. HP1γ is recruited by G9a and GLP to GR binding sites associated with genes that require G9a, GLP, and HP1γ for glucocorticoid-stimulated transcription...
June 14, 2017: EMBO Reports
https://www.readbyqxmd.com/read/28614747/rna-mediated-regulation-of-heterochromatin
#15
REVIEW
Whitney L Johnson, Aaron F Straight
The formation of condensed, transcriptionally repressed heterochromatin is essential for controlling gene expression throughout development, silencing parasitic DNA elements, and for genome stability and inheritance. Cells employ diverse mechanisms for controlling heterochromatin states through proteins that modify DNA and histones. An emerging theme is that chromatin-associated RNAs play important roles in regulating heterochromatin proteins by controlling their initial recruitment to chromatin, their stable association with chromatin, their spread along chromatin, or their enzymatic activity...
June 11, 2017: Current Opinion in Cell Biology
https://www.readbyqxmd.com/read/28609254/chromosomal-diversity-of-three-species-of-hypostomus-lac%C3%A3-p%C3%A3-de-1803-siluriformes-loricariidae-from-the-paran%C3%A3-river-basin-brazil-a-species-complex-in-hypostomus-ancistroides-reinforced-by-a-zz-zw-sex-chromosome-system
#16
Marcia Cristina de Souza Lara Kamei, Lucas Baumgärtner, Suzana Paiva, Cláudio Henrique Zawadzki, Isabel Cristina Martins-Santos, Ana Luiza de Brito Portela-Castro
Hypostomus shows wide morphological patterns, corroborated by great chromosomal diversity that has suggested the existence of new species, especially from small tributaries. Cytogenetic analysis has contributed to estimate a cryptic diversity providing important data for taxonomic and evolutionary studies. Cytogenetic techniques were carried out on species from a small tributary of Ivaí River, Keller River (upper Paraná River basin): Hypostomus aff. ancistroides, Hypostomus topavae, and Hypostomus aff. hermanni that presented 2n = 68, 80, and 72 chromosomes, respectively...
June 13, 2017: Zebrafish
https://www.readbyqxmd.com/read/28606110/a-c9orf72-bac-mouse-model-recapitulates-key-epigenetic-perturbations-of-als-ftd
#17
Rustam Esanov, Gabriela Toro Cabrera, Nadja S Andrade, Tania F Gendron, Robert H Brown, Michael Benatar, Claes Wahlestedt, Christian Mueller, Zane Zeier
BACKGROUND: Amyotrophic Lateral Sclerosis (ALS) is a fatal and progressive neurodegenerative disorder with identified genetic causes representing a significant minority of all cases. A GGGGCC hexanucleotide repeat expansion (HRE) mutation within the C9ORF72 gene has recently been identified as the most frequent known cause of ALS. The expansion leads to partial heterochromatinization of the locus, yet mutant RNAs and dipeptide repeat proteins (DPRs) are still produced in sufficient quantities to confer neurotoxicity...
June 12, 2017: Molecular Neurodegeneration
https://www.readbyqxmd.com/read/28605523/retrotransposons-are-specified-as-dna-replication-origins-in-the-gene-poor-regions-of-arabidopsis-heterochromatin
#18
Zaida Vergara, Joana Sequeira-Mendes, Jordi Morata, Ramón Peiró, Elizabeth Hénaff, Celina Costas, Josep M Casacuberta, Crisanto Gutierrez
Genomic stability depends on faithful genome replication. This is achieved by the concerted activity of thousands of DNA replication origins (ORIs) scattered throughout the genome. The DNA and chromatin features determining ORI specification are not presently known. We have generated a high-resolution genome-wide map of 3230 ORIs in cultured Arabidopsis thaliana cells. Here, we focused on defining the features associated with ORIs in heterochromatin. In pericentromeric gene-poor domains ORIs associate almost exclusively with the retrotransposon class of transposable elements (TEs), in particular of the Gypsy family...
June 10, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28604675/identification-of-the-elementary-structural-units-of-the-dna-damage-response
#19
Francesco Natale, Alexander Rapp, Wei Yu, Andreas Maiser, Hartmann Harz, Annina Scholl, Stephan Grulich, Tobias Anton, David Hörl, Wei Chen, Marco Durante, Gisela Taucher-Scholz, Heinrich Leonhardt, M Cristina Cardoso
Histone H2AX phosphorylation is an early signalling event triggered by DNA double-strand breaks (DSBs). To elucidate the elementary units of phospho-H2AX-labelled chromatin, we integrate super-resolution microscopy of phospho-H2AX during DNA repair in human cells with genome-wide sequencing analyses. Here we identify phospho-H2AX chromatin domains in the nanometre range with median length of ∼75 kb. Correlation analysis with over 60 genomic features shows a time-dependent euchromatin-to-heterochromatin repair trend...
June 12, 2017: Nature Communications
https://www.readbyqxmd.com/read/28600551/epe1-contributes-to-activation-of-ampk-by-promoting-phosphorylation-of-ampk-alpha-subunit-ssp2
#20
Yongyi Chen, Xiaoyue Hu, Chao Guo, Yao Yu, Hong Lu
AMP-activated protein kinase (AMPK) is a pivotal cellular energy sensor. It is activated by stresses that cause depletion of energy and initiates adaptive responses by regulating metabolism balance. AMPK forms αβγ heterotrimer. In fission yeast, activation of AMPK mainly depends on the phosphorylation of AMPKα subunit Ssp2 at Thr(189) by upstream kinase Ssp1. However, not much is known about the regulation of this process. In this study, we identified Epe1 as a novel positive regulator of AMPK. Epe1, a jmjC-domain-containing protein, is best-known as a negative regulator of heterochromatin spreading...
June 9, 2017: Scientific Reports
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