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Heterochromatin

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https://www.readbyqxmd.com/read/29467217/hp1%C3%AE-targets-the-chromosomal-passenger-complex-for-activation-at-heterochromatin-before-mitotic-entry
#1
Jan G Ruppert, Kumiko Samejima, Melpomeni Platani, Oscar Molina, Hiroshi Kimura, A Arockia Jeyaprakash, Shinya Ohta, William C Earnshaw
The chromosomal passenger complex (CPC) is directed to centromeres during mitosis via binding to H3T3ph and Sgo1. Whether and how heterochromatin protein 1α (HP1α) influences CPC localisation and function during mitotic entry is less clear. Here, we alter HP1α dynamics by fusing it to a CENP-B DNA-binding domain. Tethered HP1 strongly recruits the CPC, destabilising kinetochore-microtubule interactions and activating the spindle assembly checkpoint. During mitotic exit, the tethered HP1 traps active CPC at centromeres...
February 21, 2018: EMBO Journal
https://www.readbyqxmd.com/read/29466322/environmental-temperature-controls-accumulation-of-transacting-sirnas-involved-in-heterochromatin-formation
#2
Marcello Pirritano, Ulrike Götz, Sivarajan Karunanithi, Karl Nordström, Marcel H Schulz, Martin Simon
Genes or alleles can interact by small RNAs in a homology dependent manner meaning that short interfering (siRNAs) can act in trans at the chromatin level producing stable and heritable silencing phenotypes. Because of the puzzling data on endogenous paramutations, their impact contributing to adaptive evolution in a Lamarckian manner remains unknown. An increasing number of studies characterizes the underlying siRNA accumulation pathways using transgene experiments. Also in the ciliate Paramecium tetraurelia , we induce trans silencing on the chromatin level by injection of truncated transgenes...
February 21, 2018: Genes
https://www.readbyqxmd.com/read/29464754/development-of-the-duct-system-during-exocrine-pancreas-differentiation-in-the-grass-snake-natrix-natrix-lepidosauria-serpentes
#3
Magdalena Kowalska, Weronika Rupik
We analyzed the development of the pancreatic ducts in grass snake Natrix natrix L. embryos with special focus on the three-dimensional (3D)-structure of the duct network, ultrastructural differentiation of ducts with attention to cell types and lumen formation. Our results indicated that the system of ducts in the embryonic pancreas of the grass snake can be divided into extralobular, intralobular, and intercalated ducts, similarly as in other vertebrate species. However, the pattern of branching was different from that in other vertebrates, which was related to the specific topography of the snake's internal organs...
February 21, 2018: Journal of Morphology
https://www.readbyqxmd.com/read/29464330/the-interplay-of-histone-h2b-ubiquitination-with-budding-and-fission-yeast-heterochromatin
#4
REVIEW
Alexis Zukowski, Aaron M Johnson
Mono-ubiquitinated histone H2B (H2B-Ub) is important for chromatin regulation of transcription, chromatin assembly, and also influences heterochromatin. In this review, we discuss the effects of H2B-Ub from nucleosome to higher-order chromatin structure. We then assess what is currently known of the role of H2B-Ub in heterochromatic silencing in budding and fission yeasts (S. cerevisiae and S. pombe), which have distinct silencing mechanisms. In budding yeast, the SIR complex initiates heterochromatin assembly with the aid of a H2B-Ub deubiquitinase, Ubp10...
February 20, 2018: Current Genetics
https://www.readbyqxmd.com/read/29463699/massive-crossover-elevation-via-combination-of-hei10-and-recq4a-recq4b-during-arabidopsis-meiosis
#5
Heïdi Serra, Christophe Lambing, Catherine H Griffin, Stephanie D Topp, Divyashree C Nageswaran, Charles J Underwood, Piotr A Ziolkowski, Mathilde Séguéla-Arnaud, Joiselle B Fernandes, Raphaël Mercier, Ian R Henderson
During meiosis, homologous chromosomes undergo reciprocal crossovers, which generate genetic diversity and underpin classical crop improvement. Meiotic recombination initiates from DNA double-strand breaks (DSBs), which are processed into single-stranded DNA that can invade a homologous chromosome. The resulting joint molecules can ultimately be resolved as crossovers. In Arabidopsis , competing pathways balance the repair of ∼100-200 meiotic DSBs into ∼10 crossovers per meiosis, with the excess DSBs repaired as noncrossovers...
February 20, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29462803/chromosome-painting-in-tyrant-flycatchers-confirms-a-set-of-inversions-shared-by-oscines-and-suboscines-aves-passeriformes
#6
Benilson S Rodrigues, Rafael Kretschmer, Ricardo J Gunski, Analia D V Garnero, Patricia C M O'Brien, Malcolm Ferguson-Smith, Edivaldo H C de Oliveira
Tyrannidae is the largest family of Passeriformes in the Neotropical region. However, despite an interesting chromosomal diversity, there are only few cytogenetic studies of this family, and most of these are based on conventional cytogenetics. Hence, we analyzed here the chromosomal diversity and karyotypical evolution of this group by chromosome painting in 3 different species - Pitangus sulphuratus, Serpophaga subcristata, and Satrapa icterophrys - and make comparisons with previous data. In addition to chromosome painting with Gallus gallus (GGA) and Leucopternis albicollis (LAL) probes, karyotypes were analyzed by conventional staining, C-banding, and FISH with 18S rDNA and telomeric probes...
February 21, 2018: Cytogenetic and Genome Research
https://www.readbyqxmd.com/read/29462646/cbx3-promotes-tumor-proliferation-by-regulating-g1-s-phase-via-p21-downregulation-and-associates-with-poor-prognosis-in-tongue-squamous-cell-carcinoma
#7
HuaYong Zhang, WeiChao Chen, XiaoYan Fu, Xuan Su, AnKui Yang
Chromobox protein homolog 3 (CBX3), a core component of the heterochromatin proteins 1, is recently proved to be involved in human cancerogenesis and associated with the prognosis of patient. However, the role of CBX3 in Tongue squamous cell carcinoma (TSCC) remains unclear. In the present study we found that CBX3 was upregulated in TSCC tissues when compared to adjacent non-tumor tissues, and multivariable analysis showed that high CBX3 expression was associated with clinical stage and cervical node metastasis, which was an independent prognostic indicator of TSCC...
February 17, 2018: Gene
https://www.readbyqxmd.com/read/29458329/mouse-chromocenters-dna-content-sequencing-and-in-silico-analysis
#8
Dmitrii I Ostromyshenskii, Ekaterina N Chernyaeva, Inna S Kuznetsova, Olga I Podgornaya
BACKGROUND: Chromocenters are defined as a punctate condensed blocks of chromatin in the interphase cell nuclei of certain cell types with unknown biological significance. In recent years a progress in revealing of chromocenters protein content has been made although the details of DNA content within constitutive heterochromatin still remain unclear. It is known that these regions are enriched in tandem repeats (TR) and transposable elements. Quick improvement of genome sequencing does not help to assemble the heterochromatic regions due to lack of appropriate bioinformatics techniques...
February 20, 2018: BMC Genomics
https://www.readbyqxmd.com/read/29456084/rescue-of-fragile-x-syndrome-neurons-by-dna-methylation-editing-of-the-fmr1-gene
#9
X Shawn Liu, Hao Wu, Marine Krzisch, Xuebing Wu, John Graef, Julien Muffat, Denes Hnisz, Charles H Li, Bingbing Yuan, Chuanyun Xu, Yun Li, Dan Vershkov, Angela Cacace, Richard A Young, Rudolf Jaenisch
Fragile X syndrome (FXS), the most common genetic form of intellectual disability in males, is caused by silencing of the FMR1 gene associated with hypermethylation of the CGG expansion mutation in the 5' UTR of FMR1 in FXS patients. Here, we applied recently developed DNA methylation editing tools to reverse this hypermethylation event. Targeted demethylation of the CGG expansion by dCas9-Tet1/single guide RNA (sgRNA) switched the heterochromatin status of the upstream FMR1 promoter to an active chromatin state, restoring a persistent expression of FMR1 in FXS iPSCs...
February 8, 2018: Cell
https://www.readbyqxmd.com/read/29444174/chromosome-evolution-in-cophomantini-amphibia-anura-hylinae
#10
Juan M Ferro, Dario E Cardozo, Pablo Suárez, Juan M Boeris, Ailin Blasco-Zúñiga, Gastón Barbero, Anderson Gomes, Thiago Gazoni, William Costa, Cleusa Y Nagamachi, Miryan Rivera, Patricia P Parise-Maltempi, John E Wiley, Julio C Pieczarka, Celio F B Haddad, Julián Faivovich, Diego Baldo
The hylid tribe Cophomantini is a diverse clade of Neotropical treefrogs composed of the genera Aplastodiscus, Boana, Bokermannohyla, Hyloscirtus, and Myersiohyla. The phylogenetic relationships of Cophomantini have been comprehensively reviewed in the literature, providing a suitable framework for the study of chromosome evolution. Employing different banding techniques, we studied the chromosomes of 25 species of Boana and 3 of Hyloscirtus; thus providing, for the first time, data for Hyloscirtus and for 15 species of Boana...
2018: PloS One
https://www.readbyqxmd.com/read/29443341/super-resolution-localization-microscopy-of-radiation-induced-histone-h2ax-phosphorylation-in-relation-to-h3k9-trimethylation-in-hela-cells
#11
Michael Hausmann, Emma Wagner, Jin-Ho Lee, Gerrit Schrock, Wladimir Schaufler, Matthias Krufczik, Franziska Papenfuß, Matthias Port, Felix Bestvater, Harry Scherthan
Ionizing radiation (IR)-induced damage confers functional and conformational changes to nuclear chromatin associated with DNA single and double strand breaks. This leads to the activation of complex DNA repair machineries that aim to preserve the integrity of the DNA molecule. Since hetero- and euchromatin are differentially accessible to DNA repair pathways, local chromatin re-arrangements and structural changes are among the consequences of an activated DNA damage response. Using super-resolution localization microscopy (SRLM), we investigated the X-ray-induced repositioning of γ-H2AX and histone H3K9me3 heterochromatin marks in the nuclei of HeLa cells...
February 14, 2018: Nanoscale
https://www.readbyqxmd.com/read/29440488/pivotal-roles-of-pcna-loading-and-unloading-in-heterochromatin-function
#12
Ryan Janke, Grant A King, Martin Kupiec, Jasper Rine
In Saccharomyces cerevisiae , heterochromatin structures required for transcriptional silencing of the HML and HMR loci are duplicated in coordination with passing DNA replication forks. Despite major reorganization of chromatin structure, the heterochromatic, transcriptionally silent states of HML and HMR are successfully maintained throughout S-phase. Mutations of specific components of the replisome diminish the capacity to maintain silencing of HML and HMR through replication. Similarly, mutations in histone chaperones involved in replication-coupled nucleosome assembly reduce gene silencing...
February 13, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29437926/ccctc-binding-factor-acts-as-a-heterochromatin-barrier-on-herpes-simplex-viral-latent-chromatin-and-contributes-to-poised-latent-infection
#13
Jennifer S Lee, Priya Raja, Dongli Pan, Jean M Pesola, Donald M Coen, David M Knipe
Herpes simplex virus 1 (HSV-1) establishes latent infection in neurons via a variety of epigenetic mechanisms that silence its genome. The cellular CCCTC-binding factor (CTCF) functions as a mediator of transcriptional control and chromatin organization and has binding sites in the HSV-1 genome. We constructed an HSV-1 deletion mutant that lacked a pair of CTCF-binding sites ( CTRL2 ) within the latency-associated transcript ( LAT ) coding sequences and found that loss of these CTCF-binding sites did not alter lytic replication or levels of establishment of latent infection, but their deletion reduced the ability of the virus to reactivate from latent infection...
February 6, 2018: MBio
https://www.readbyqxmd.com/read/29432976/epigenomic-and-genomic-landscape-of-drosophila-melanogaster-heterochromatic-genes
#14
Parna Saha, Divya Tej Sowpati, Rakesh K Mishra
Heterochromatin is associated with transcriptional repression. In contrast, several genes in the pericentromeric regions of Drosophila melanogaster are dependent on this heterochromatic environment for their expression. Here we present a comprehensive analysis of the epigenetic landscape of heterochromatic genes across all the developmental stages of Drosophila using the available histone modification and expression data from modENCODE. We find that heterochromatic genes exhibit combinations of active and inactive histone marks that correspond to their level of expression during development...
February 9, 2018: Genomics
https://www.readbyqxmd.com/read/29432187/global-changes-of-h3k27me3-domains-and-polycomb-group-protein-distribution-in-the-absence-of-recruiters-spps-or-pho
#15
J Lesley Brown, Ming-An Sun, Judith A Kassis
Polycomb group (PcG) proteins maintain the silenced state of key developmental genes in animals, but how these proteins are recruited to specific regions of the genome is still poorly understood. In Drosophila , PcG proteins are recruited to Polycomb response elements (PREs) that include combinations of sites for sequence specific DNA binding "PcG recruiters," including Pho, Cg, and Spps. To understand their roles in PcG recruitment, we compared Pho-, Cg-, and Spps-binding sites against H3K27me3 and key PcG proteins by ChIP-seq in wild-type and mutant third instar larvae...
February 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29429989/nucleolus-as-an-emerging-hub-in-maintenance-of-genome-stability-and-cancer-pathogenesis
#16
REVIEW
Mikael S Lindström, Deana Jurada, Sladana Bursac, Ines Orsolic, Jiri Bartek, Sinisa Volarevic
The nucleolus is the major site for synthesis of ribosomes, complex molecular machines that are responsible for protein synthesis. A wealth of research over the past 20 years has clearly indicated that both quantitative and qualitative alterations in ribosome biogenesis can drive the malignant phenotype via dysregulation of protein synthesis. However, numerous recent proteomic, genomic, and functional studies have implicated the nucleolus in the regulation of processes that are unrelated to ribosome biogenesis, including DNA-damage response, maintenance of genome stability and its spatial organization, epigenetic regulation, cell-cycle control, stress responses, senescence, global gene expression, as well as assembly or maturation of various ribonucleoprotein particles...
February 12, 2018: Oncogene
https://www.readbyqxmd.com/read/29424472/characterization-of-a-satellite-dna-in-the-genera%C3%A2-lacerta%C3%A2-and-timon-reptilia-lacertidae-and-its-role-in-the-differentiation-of-the-w-chromosome
#17
Massimo Giovannotti, Paola Nisi Cerioni, Verónica Rojo, Ettore Olmo, Tahar Slimani, Andrea Splendiani, Vincenzo Caputo Barucchi
In this study, IMO-TaqI satDNA, previously isolated in several species of Lacertidae, was isolated and characterized from four species of the genus Lacerta and three of the genus Timon. The aim was to gain further insights into the evolutionary dynamics of this satDNA, its occurrence among lacertids and to understand if it plays any role in sex chromosome evolution in these seven species. The results here obtained highlighted the presence of this repetitive element in the genome of all the species investigated, thus indicating that IMO-TaqI satDNA is evolutionary conserved among a wide variety of lacertids...
February 9, 2018: Journal of Experimental Zoology. Part B, Molecular and Developmental Evolution
https://www.readbyqxmd.com/read/29424342/yth-rna-binding-protein-prevents-deleterious-expression-of-meiotic-proteins-by-tethering-their-mrnas-to-nuclear-foci
#18
Yuichi Shichino, Yoko Otsubo, Yoshitaka Kimori, Masayuki Yamamoto, Akira Yamashita
Accurate and extensive regulation of meiotic gene expression is crucial to distinguish germ cells from somatic cells. In the fission yeast Schizosaccharomyces pombe, a YTH family RNA-binding protein, Mmi1, directs the nuclear exosome-mediated elimination of meiotic transcripts during vegetative proliferation. Mmi1 also induces the formation of facultative heterochromatin at a subset of its target genes. Here, we show that Mmi1 prevents the mistimed expression of meiotic proteins by tethering their mRNAs to the nuclear foci...
February 9, 2018: ELife
https://www.readbyqxmd.com/read/29417178/cellular-and-molecular-mechanisms-of-hiv-1-integration-targeting
#19
REVIEW
Alan N Engelman, Parmit K Singh
Integration is central to HIV-1 replication and helps mold the reservoir of cells that persists in AIDS patients. HIV-1 interacts with specific cellular factors to target integration to interior regions of transcriptionally active genes within gene-dense regions of chromatin. The viral capsid interacts with several proteins that are additionally implicated in virus nuclear import, including cleavage and polyadenylation specificity factor 6, to suppress integration into heterochromatin. The viral integrase protein interacts with transcriptional co-activator lens epithelium-derived growth factor p75 to principally position integration within gene bodies...
February 7, 2018: Cellular and Molecular Life Sciences: CMLS
https://www.readbyqxmd.com/read/29415520/consequences-of-lamin-b1-and-lamin-b-receptor-downregulation-in-senescence
#20
REVIEW
Emilie Lukášová, Aleš Kovařík, Stanislav Kozubek
Anchoring of heterochromatin to the nuclear envelope appears to be an important process ensuring the spatial organization of the chromatin structure and genome function in eukaryotic nuclei. Proteins of the inner nuclear membrane (INM) mediating these interactions are able to recognize lamina-associated heterochromatin domains (termed LAD) and simultaneously bind either lamin A/C or lamin B1. One of these proteins is the lamin B receptor (LBR) that binds lamin B1 and tethers heterochromatin to the INM in embryonic and undifferentiated cells...
February 6, 2018: Cells
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