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Abstract
Nuclear lamins are components of the peripheral lamina that define the mechanical properties of nuclei and tether heterochromatin to the periphery. A-type lamins localize also to the nuclear interior, but the regulation and specific functions of this nucleoplasmic lamin pool are poorly understood. In this Commentary, we summarize known pathways that are potentially involved in the localization and dynamic behavior of intranuclear lamins, including their post-translational modifications and interactions with nucleoplasmic proteins, such as lamina-associated polypeptide 2α (LAP2α; encoded by TMPO). In addition, new data suggest that lamins in the nuclear interior have an important role in chromatin regulation and gene expression through dynamic binding to both hetero- and euchromatic genomic regions and promoter subdomains, thereby affecting epigenetic pathways and chromatin accessibility. Nucleoplasmic lamins also have a role in spatial chromatin organization and may be involved in mechanosignaling. In view of this newly emerging concept, we propose that the previously reported cellular phenotypes in lamin-linked diseases are, at least in part, rooted in an impaired regulation and/or function of the nucleoplasmic lamin A/C pool.
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Affiliation(s)
- Nana Naetar
- Center of Medical Biochemistry, Max F. Perutz Laboratories (MFPL), Medical University of Vienna, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 9, Vienna A-1030, Austria
| | - Simona Ferraioli
- Center of Medical Biochemistry, Max F. Perutz Laboratories (MFPL), Medical University of Vienna, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 9, Vienna A-1030, Austria
| | - Roland Foisner
- Center of Medical Biochemistry, Max F. Perutz Laboratories (MFPL), Medical University of Vienna, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 9, Vienna A-1030, Austria
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202
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Fenelon KD, Hopyan S. Structural components of nuclear integrity with gene regulatory potential. Curr Opin Cell Biol 2017. [PMID: 28641117 DOI: 10.1016/j.ceb.2017.06.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The nucleus is a mechanosensitive and load-bearing structure. Structural components of the nucleus interact to maintain nuclear integrity and have become subjects of exciting research that is relevant to cell and developmental biology. Here we outline the boundaries of what is known about key architectural elements within the nucleus and highlight their potential structural and transcriptional regulatory functions.
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Affiliation(s)
- Kelli D Fenelon
- Program in Developmental and Stem Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, M5S 1A8, Canada
| | - Sevan Hopyan
- Program in Developmental and Stem Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Molecular Genetics, University of Toronto, M5S 1A8, Canada; Division of Orthopaedic Surgery, Hospital for Sick Children and University of Toronto, M5G 1X8, Canada.
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203
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Athirasala A, Hirsch N, Buxboim A. Nuclear mechanotransduction: sensing the force from within. Curr Opin Cell Biol 2017. [PMID: 28641092 DOI: 10.1016/j.ceb.2017.04.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cell nucleus is a hallmark of eukaryotic evolution, where gene expression is regulated and the genome is replicated and repaired. Yet, in addition to complex molecular processes, the nucleus has also evolved to serve physical tasks that utilize its optical and mechanical properties. Nuclear mechanotransduction of externally applied forces and extracellular stiffness is facilitated by the physical connectivity of the extracellular environment, the cytoskeleton and the nucleoskeletal matrix of lamins and chromatin. Nuclear mechanosensor elements convert applied tension into biochemical cues that activate downstream signal transduction pathways. Mechanoregulatory networks stabilize a contractile cell state with feedback to matrix, cell adhesions and cytoskeletal elements. Recent advances have thus provided mechanistic insights into how forces are sensed from within, that is, in the nucleus where cell-fate decision-making is performed.
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Affiliation(s)
- Avathamsa Athirasala
- Alexander Grass Center for Bioengineering, School of Computer Science and Engineering, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Nivi Hirsch
- Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Amnon Buxboim
- Alexander Grass Center for Bioengineering, School of Computer Science and Engineering, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel; Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
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204
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Abstract
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. However, the emerging picture is that the changes to DNA methylation in cancer cells has little direct effect on gene expression but instead impacts the organization of the genome in the nucleus. Several recent studies that take a broad view of the cancer epigenome find that the most profound changes to the cancer methylome are spread across large segments of the genome, and that the focal changes are reflective of a whole reorganization of epigenome. Hallmarks of nuclear reorganization in cancer are found in the long regions of chromatin marked by histone methylation (LOCKs) and nuclear lamina interactions (LADs). In this review, we focus on a novel perspective that DNA methylation changes in cancer impact the global structure of heterochromatin, LADs and LOCKs, and how these global changes, in turn, contribute to gene expression changes and genomic stability.
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Affiliation(s)
| | - Kirsten C Sadler
- Program in Biology, New York University Abu Dhabi,Abu Dhabi, United Arab Emirates
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205
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Douet J, Corujo D, Malinverni R, Renauld J, Sansoni V, Posavec Marjanović M, Cantariño N, Valero V, Mongelard F, Bouvet P, Imhof A, Thiry M, Buschbeck M. MacroH2A histone variants maintain nuclear organization and heterochromatin architecture. J Cell Sci 2017; 130:1570-1582. [PMID: 28283545 DOI: 10.1242/jcs.199216] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 03/07/2017] [Indexed: 12/15/2022] Open
Abstract
Genetic loss-of-function studies on development, cancer and somatic cell reprogramming have suggested that the group of macroH2A histone variants might function through stabilizing the differentiated state by a yet unknown mechanism. Here, we present results demonstrating that macroH2A variants have a major function in maintaining nuclear organization and heterochromatin architecture. Specifically, we find that a substantial amount of macroH2A is associated with heterochromatic repeat sequences. We further identify macroH2A on sites of interstitial heterochromatin decorated by histone H3 trimethylated on K9 (H3K9me3). Loss of macroH2A leads to major defects in nuclear organization, including reduced nuclear circularity, disruption of nucleoli and a global loss of dense heterochromatin. Domains formed by DNA repeat sequences are disorganized, expanded and fragmented, and mildly re-expressed when depleted of macroH2A. At the molecular level, we find that macroH2A is required for the interaction of repeat sequences with the nucleostructural protein lamin B1. Taken together, our results argue that a major function of macroH2A histone variants is to link nucleosome composition to higher-order chromatin architecture.
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Affiliation(s)
- Julien Douet
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias and Pujol Research Institute (PMPPC-IGTP), Campus Can Ruti, Badalona 08916, Spain
| | - David Corujo
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias and Pujol Research Institute (PMPPC-IGTP), Campus Can Ruti, Badalona 08916, Spain
| | - Roberto Malinverni
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias and Pujol Research Institute (PMPPC-IGTP), Campus Can Ruti, Badalona 08916, Spain
| | - Justine Renauld
- Cell and tissue biology unit, GIGA-Neurosciences, University of Liege, C.H.U. Sart Tilman, Liege 4000, Belgium
| | - Viola Sansoni
- BioMedical Center and Center for Integrated Protein Sciences Munich, Ludwig-Maximilians-University of Munich, Großhaderner Straße 9, Planegg-Martinsried 82152, Germany
| | - Melanija Posavec Marjanović
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
| | - Neus Cantariño
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
| | - Vanesa Valero
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias and Pujol Research Institute (PMPPC-IGTP), Campus Can Ruti, Badalona 08916, Spain
| | - Fabien Mongelard
- Université de Lyon, Ecole normale Supérieure de Lyon, Centre de Recherche en Cancérologie de Lyon, Cancer Cell Plasticity Department, UMR INSERM 1052 CNRS5286, Centre Léon Bérard, 69008 Lyon, France
| | - Philippe Bouvet
- Université de Lyon, Ecole normale Supérieure de Lyon, Centre de Recherche en Cancérologie de Lyon, Cancer Cell Plasticity Department, UMR INSERM 1052 CNRS5286, Centre Léon Bérard, 69008 Lyon, France
| | - Axel Imhof
- BioMedical Center and Center for Integrated Protein Sciences Munich, Ludwig-Maximilians-University of Munich, Großhaderner Straße 9, Planegg-Martinsried 82152, Germany
| | - Marc Thiry
- Cell and tissue biology unit, GIGA-Neurosciences, University of Liege, C.H.U. Sart Tilman, Liege 4000, Belgium
| | - Marcus Buschbeck
- Josep Carreras Leukaemia Research Institute (IJC), Campus ICO - Germans Trias i Pujol, Campus Can Ruti, Badalona 08916, Spain
- Program of Predictive and Personalized Medicine of Cancer, Germans Trias and Pujol Research Institute (PMPPC-IGTP), Campus Can Ruti, Badalona 08916, Spain
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206
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Stevens TJ, Lando D, Basu S, Atkinson LP, Cao Y, Lee SF, Leeb M, Wohlfahrt KJ, Boucher W, O'Shaughnessy-Kirwan A, Cramard J, Faure AJ, Ralser M, Blanco E, Morey L, Sansó M, Palayret MGS, Lehner B, Di Croce L, Wutz A, Hendrich B, Klenerman D, Laue ED. 3D structures of individual mammalian genomes studied by single-cell Hi-C. Nature 2017; 544:59-64. [PMID: 28289288 PMCID: PMC5385134 DOI: 10.1038/nature21429] [Citation(s) in RCA: 505] [Impact Index Per Article: 72.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 01/26/2017] [Indexed: 12/19/2022]
Abstract
The folding of genomic DNA from the beads-on-a-string-like structure of nucleosomes into higher-order assemblies is crucially linked to nuclear processes. Here we calculate 3D structures of entire mammalian genomes using data from a new chromosome conformation capture procedure that allows us to first image and then process single cells. The technique enables genome folding to be examined at a scale of less than 100 kb, and chromosome structures to be validated. The structures of individual topological-associated domains and loops vary substantially from cell to cell. By contrast, A and B compartments, lamina-associated domains and active enhancers and promoters are organized in a consistent way on a genome-wide basis in every cell, suggesting that they could drive chromosome and genome folding. By studying genes regulated by pluripotency factor and nucleosome remodelling deacetylase (NuRD), we illustrate how the determination of single-cell genome structure provides a new approach for investigating biological processes.
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Affiliation(s)
- Tim J Stevens
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, United Kingdom
| | - David Lando
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Srinjan Basu
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Liam P Atkinson
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Yang Cao
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Steven F Lee
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Martin Leeb
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Kai J Wohlfahrt
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Wayne Boucher
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Aoife O'Shaughnessy-Kirwan
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Julie Cramard
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Andre J Faure
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
| | - Meryem Ralser
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Enrique Blanco
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
| | - Lluis Morey
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
| | - Miriam Sansó
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
| | - Matthieu G S Palayret
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Ben Lehner
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
- Universitat Pompeu Fabra, 08003 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - Luciano Di Croce
- EMBL-CRG Systems Biology Unit, Centre for Genomic Regulation (CRG), 08003 Barcelona, Spain
- Universitat Pompeu Fabra, 08003 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
| | - Anton Wutz
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Brian Hendrich
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
- Wellcome Trust - MRC Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, United Kingdom
| | - Dave Klenerman
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Ernest D Laue
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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207
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van de Werken HJG, Haan JC, Feodorova Y, Bijos D, Weuts A, Theunis K, Holwerda SJB, Meuleman W, Pagie L, Thanisch K, Kumar P, Leonhardt H, Marynen P, van Steensel B, Voet T, de Laat W, Solovei I, Joffe B. Small chromosomal regions position themselves autonomously according to their chromatin class. Genome Res 2017; 27:922-933. [PMID: 28341771 PMCID: PMC5453326 DOI: 10.1101/gr.213751.116] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 03/22/2017] [Indexed: 11/24/2022]
Abstract
The spatial arrangement of chromatin is linked to the regulation of nuclear processes. One striking aspect of nuclear organization is the spatial segregation of heterochromatic and euchromatic domains. The mechanisms of this chromatin segregation are still poorly understood. In this work, we investigated the link between the primary genomic sequence and chromatin domains. We analyzed the spatial intranuclear arrangement of a human artificial chromosome (HAC) in a xenospecific mouse background in comparison to an orthologous region of native mouse chromosome. The two orthologous regions include segments that can be assigned to three major chromatin classes according to their gene abundance and repeat repertoire: (1) gene-rich and SINE-rich euchromatin; (2) gene-poor and LINE/LTR-rich heterochromatin; and (3) gene-depleted and satellite DNA-containing constitutive heterochromatin. We show, using fluorescence in situ hybridization (FISH) and 4C-seq technologies, that chromatin segments ranging from 0.6 to 3 Mb cluster with segments of the same chromatin class. As a consequence, the chromatin segments acquire corresponding positions in the nucleus irrespective of their chromosomal context, thereby strongly suggesting that this is their autonomous property. Interactions with the nuclear lamina, although largely retained in the HAC, reveal less autonomy. Taken together, our results suggest that building of a functional nucleus is largely a self-organizing process based on mutual recognition of chromosome segments belonging to the major chromatin classes.
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Affiliation(s)
- Harmen J G van de Werken
- Cancer Computational Biology Center, Erasmus MC Cancer Institute & Department of Urology, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3015 CN, Rotterdam, The Netherlands.,Hubrecht Institute-KNAW & University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands
| | - Josien C Haan
- Laboratory of Reproductive Genomics, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Yana Feodorova
- Department of Biology II, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany
| | - Dominika Bijos
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - An Weuts
- Laboratory of Reproductive Genomics, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Koen Theunis
- Laboratory of Reproductive Genomics, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Sjoerd J B Holwerda
- Hubrecht Institute-KNAW & University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands
| | - Wouter Meuleman
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - Ludo Pagie
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - Katharina Thanisch
- Department of Biology II, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany
| | - Parveen Kumar
- Laboratory of Reproductive Genomics, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Heinrich Leonhardt
- Department of Biology II, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany
| | - Peter Marynen
- Human Genome Laboratory, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - Thierry Voet
- Laboratory of Reproductive Genomics, Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
| | - Wouter de Laat
- Hubrecht Institute-KNAW & University Medical Center Utrecht, 3584 CT Utrecht, The Netherlands
| | - Irina Solovei
- Department of Biology II, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany
| | - Boris Joffe
- Department of Biology II, Ludwig Maximilians University Munich, 82152 Planegg-Martinsried, Germany
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208
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Identifying Novel Transcriptional and Epigenetic Features of Nuclear Lamina-associated Genes. Sci Rep 2017; 7:100. [PMID: 28273906 PMCID: PMC5427898 DOI: 10.1038/s41598-017-00176-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 02/13/2017] [Indexed: 01/10/2023] Open
Abstract
Because a large portion of the mammalian genome is associated with the nuclear lamina (NL), it is interesting to study how native genes resided there are transcribed and regulated. In this study, we report unique transcriptional and epigenetic features of nearly 3,500 NL-associated genes (NL genes). Promoter regions of active NL genes are often excluded from NL-association, suggesting that NL-promoter interactions may repress transcription. Active NL genes with higher RNA polymerase II (Pol II) recruitment levels tend to display Pol II promoter-proximal pausing, while Pol II recruitment and Pol II pausing are not correlated among non-NL genes. At the genome-wide scale, NL-association and H3K27me3 distinguishes two large gene classes with low transcriptional activities. Notably, NL-association is anti-correlated with both transcription and active histone mark levels among genes not significantly enriched with H3K9me3 or H3K27me3, suggesting that NL-association may represent a novel gene repression pathway. Interestingly, an NL gene subgroup is not significantly enriched with H3K9me3 or H3K27me3 and is transcribed at higher levels than the rest of NL genes. Furthermore, we identified distal enhancers associated with active NL genes and reported their epigenetic features.
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209
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Thanisch K, Song C, Engelkamp D, Koch J, Wang A, Hallberg E, Foisner R, Leonhardt H, Stewart CL, Joffe B, Solovei I. Nuclear envelope localization of LEMD2 is developmentally dynamic and lamin A/C dependent yet insufficient for heterochromatin tethering. Differentiation 2017; 94:58-70. [PMID: 28056360 DOI: 10.1016/j.diff.2016.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 12/05/2016] [Accepted: 12/06/2016] [Indexed: 11/28/2022]
Abstract
Peripheral heterochromatin in mammalian nuclei is tethered to the nuclear envelope by at least two mechanisms here referred to as the A- and B-tethers. The A-tether includes lamins A/C and additional unknown components presumably INM protein(s) interacting with both lamins A/C and chromatin. The B-tether includes the inner nuclear membrane (INM) protein Lamin B-receptor, which binds B-type lamins and chromatin. Generally, at least one of the tethers is always present in the nuclear envelope of mammalian cells. Deletion of both causes the loss of peripheral heterochromatin and consequently inversion of the entire nuclear architecture, with this occurring naturally in rod photoreceptors of nocturnal mammals. The tethers are differentially utilized during development, regulate gene expression in opposite manners, and play an important role during cell differentiation. Here we aimed to identify the unknown chromatin binding component(s) of the A-tether. We analyzed 10 mouse tissues by immunostaining with antibodies against 7 INM proteins and found that every cell type has specific, although differentially and developmentally regulated, sets of these proteins. In particular, we found that INM protein LEMD2 is concomitantly expressed with A-type lamins in various cell types but is lacking in inverted nuclei of rod cells. Truncation or deletion of Lmna resulted in the downregulation and mislocalization of LEMD2, suggesting that the two proteins interact and pointing at LEMD2 as a potential chromatin binding mediator of the A-tether. Using nuclei of mouse rods as an experimental model lacking peripheral heterochromatin, we expressed a LEMD2 transgene alone or in combination with lamin C in these cells and observed no restoration of peripheral heterochromatin in either case. We conclude that in contrary to the B-tether, the A-tether has a more intricate composition and consists of multiple components that presumably vary, at differing degrees of redundancy, between cell types and differentiation stages.
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Affiliation(s)
- Katharina Thanisch
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Congdi Song
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Dieter Engelkamp
- Transgenic Service Facility, BTE, Franz-Penzoldt-Centre, Friedrich-Alexander-University of Erlangen-Nürnberg, Erwin-Rommel-Str.3, D-91058 Erlangen, Germany
| | - Jeannette Koch
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Audrey Wang
- Institute of Medical Biology, 8A Biomedical Grove and Dept of Biological Sciences, NUS, 138648, Singapore
| | - Einar Hallberg
- Department of Neurochemistry, Stockholm University, Se-106 91 Stockholm, Sweden
| | - Roland Foisner
- Max F. Perutz Laboratories, Medical University of Vienna, Vienna Biocenter (VBC), Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Heinrich Leonhardt
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Colin L Stewart
- Institute of Medical Biology, 8A Biomedical Grove and Dept of Biological Sciences, NUS, 138648, Singapore.
| | - Boris Joffe
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany
| | - Irina Solovei
- Department of Biology II, Ludwig-Maximilians-University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany.
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210
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Ranade D, Koul S, Thompson J, Prasad KB, Sengupta K. Chromosomal aneuploidies induced upon Lamin B2 depletion are mislocalized in the interphase nucleus. Chromosoma 2017; 126:223-244. [PMID: 26921073 PMCID: PMC5371638 DOI: 10.1007/s00412-016-0580-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 01/28/2016] [Accepted: 02/09/2016] [Indexed: 12/31/2022]
Abstract
Chromosome territories assume non-random positions in the interphase nucleus with gene-rich chromosomes localized toward the nuclear interior and gene-poor chromosome territories toward the nuclear periphery. Lamins are intermediate filament proteins of the inner nuclear membrane required for the maintenance of nuclear structure and function. Here, we show using whole-genome expression profiling that Lamin A/C or Lamin B2 depletion in an otherwise diploid colorectal cancer cell line (DLD1) deregulates transcript levels from specific chromosomes. Further, three-dimensional fluorescence in situ hybridization (3D-FISH) analyses of a subset of these transcriptionally deregulated chromosome territories revealed that the diploid chromosome territories in Lamin-depleted cells largely maintain conserved positions in the interphase nucleus in a gene-density-dependent manner. In addition, chromosomal aneuploidies were induced in ~25 % of Lamin A/C or Lamin B2-depleted cells. Sub-populations of these aneuploid cells consistently showed a mislocalization of the gene-rich aneuploid chromosome 19 territory toward the nuclear periphery, while gene-poor aneuploid chromosome 18 territory was mislocalized toward the nuclear interior predominantly upon Lamin B2 than Lamin A/C depletion. In addition, a candidate gene locus ZNF570 (Chr.19q13.12) significantly overexpressed upon Lamin B2 depletion was remarkably repositioned away from the nuclear lamina. Taken together, our studies strongly implicate an overarching role for Lamin B2 in the maintenance of nuclear architecture since loss of Lamin B2 relieves the spatial positional constraints required for maintaining conserved localization of aneuploid chromosome territories in the interphase nucleus.
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Affiliation(s)
- Devika Ranade
- Biology, Indian Institute of Science Education and Research, Pune, Main Building, Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India
| | - Shivsmriti Koul
- Biology, Indian Institute of Science Education and Research, Pune, Main Building, Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India
| | - Joyce Thompson
- Biology, Indian Institute of Science Education and Research, Pune, Main Building, Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India
| | - Kumar Brajesh Prasad
- Biology, Indian Institute of Science Education and Research, Pune, Main Building, Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India
| | - Kundan Sengupta
- Biology, Indian Institute of Science Education and Research, Pune, Main Building, Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India.
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211
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Tissue-specific features of the X chromosome and nucleolus spatial dynamics in a malaria mosquito, Anopheles atroparvus. PLoS One 2017; 12:e0171290. [PMID: 28158219 PMCID: PMC5291520 DOI: 10.1371/journal.pone.0171290] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 01/19/2017] [Indexed: 02/08/2023] Open
Abstract
Spatial organization of chromosome territories is important for maintenance of genomic stability and regulation of gene expression. Recent studies have shown tissue-specific features of chromosome attachments to the nuclear envelope in various organisms including malaria mosquitoes. However, other spatial characteristics of nucleus organization, like volume and shape of chromosome territories, have not been studied in Anopheles. We conducted a thorough analysis of tissue-specific features of the X chromosome and nucleolus volume and shape in follicular epithelium and nurse cells of the Anopheles atroparvus ovaries using a modern open-source software. DNA of the polytene X chromosome from ovarian nurse cells was obtained by microdissection and was used as a template for amplification with degenerate oligo primers. A fluorescently labeled X chromosome painting probe was hybridized with formaldehyde-fixed ovaries of mosquitoes using a 3D-FISH method. The nucleolus was stained by immunostaining with an anti-fibrillarin antibody. The analysis was conducted with TANGO-a software for a chromosome spatial organization analysis. We show that the volume and position of the X chromosome have tissue-specific characteristics. Unlike nurse cell nuclei, the growth of follicular epithelium nuclei is not accompanied with the proportional growth of the X chromosome. However, the shape of the X chromosome does not differ between the tissues. The dynamics of the X chromosome attachment regions location is tissue-specific and it is correlated with the process of nucleus growth in follicular epithelium and nurse cells.
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212
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Sewitz SA, Fahmi Z, Lipkow K. Higher order assembly: folding the chromosome. Curr Opin Struct Biol 2017; 42:162-168. [DOI: 10.1016/j.sbi.2017.02.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 02/13/2017] [Indexed: 11/28/2022]
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213
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Yáñez-Cuna JO, van Steensel B. Genome-nuclear lamina interactions: from cell populations to single cells. Curr Opin Genet Dev 2017; 43:67-72. [PMID: 28107752 DOI: 10.1016/j.gde.2016.12.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 12/07/2016] [Accepted: 12/21/2016] [Indexed: 01/06/2023]
Abstract
Lamina-associated domains (LADs) are large genomic regions that interact with the nuclear lamina (NL) and help to guide the spatial folding of chromosomes in the interphase nucleus. LADs have been linked to gene repression and other functions. Recent studies have begun to uncover some of the molecular players that drive LAD-NL interactions. A picture emerges in which DNA sequence, chromatin components and nuclear lamina proteins play an important role. Complementary to this, imaging and single-cell genomics approaches have revealed that some LAD-NL interactions are variable from cell to cell, while others are very stable. Understanding LADs can provide a unique perspective into the general process of genome organization.
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Affiliation(s)
- J Omar Yáñez-Cuna
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands; Department of Cell Biology, Erasmus University Medical Center, Rotterdam, The Netherlands.
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214
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Zhu Y, Gong K, Denholtz M, Chandra V, Kamps MP, Alber F, Murre C. Comprehensive characterization of neutrophil genome topology. Genes Dev 2017; 31:141-153. [PMID: 28167501 PMCID: PMC5322729 DOI: 10.1101/gad.293910.116] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 01/05/2017] [Indexed: 12/18/2022]
Abstract
Neutrophils are responsible for the first line of defense against invading pathogens. Their nuclei are uniquely structured as multiple lobes that establish a highly constrained nuclear environment. Here we found that neutrophil differentiation was not associated with large-scale changes in the number and sizes of topologically associating domains (TADs). However, neutrophil genomes were enriched for long-range genomic interactions that spanned multiple TADs. Population-based simulation of spherical and toroid genomes revealed declining radii of gyration for neutrophil chromosomes. We found that neutrophil genomes were highly enriched for heterochromatic genomic interactions across vast genomic distances, a process named supercontraction. Supercontraction involved genomic regions located in the heterochromatic compartment in both progenitors and neutrophils or genomic regions that switched from the euchromatic to the heterochromatic compartment during neutrophil differentiation. Supercontraction was accompanied by the repositioning of centromeres, pericentromeres, and long interspersed nuclear elements (LINEs) to the neutrophil nuclear lamina. We found that Lamin B receptor expression was required to attach centromeric and pericentromeric repeats but not LINE-1 elements to the lamina. Differentiating neutrophils also repositioned ribosomal DNA and mininucleoli to the lamina-a process that was closely associated with sharply reduced ribosomal RNA expression. We propose that large-scale chromatin reorganization involving supercontraction and recruitment of heterochromatin and nucleoli to the nuclear lamina facilitates the folding of the neutrophil genome into a confined geometry imposed by a multilobed nuclear architecture.
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Affiliation(s)
- Yina Zhu
- Department of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - Ke Gong
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Matthew Denholtz
- Department of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - Vivek Chandra
- Department of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
| | - Mark P Kamps
- Department of Pathology, University of California at San Diego, La Jolla, California 92093, USA
| | - Frank Alber
- Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
| | - Cornelis Murre
- Department of Molecular Biology, University of California at San Diego, La Jolla, California 92093, USA
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215
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Jabbari K, Bernardi G. An Isochore Framework Underlies Chromatin Architecture. PLoS One 2017; 12:e0168023. [PMID: 28060840 PMCID: PMC5218411 DOI: 10.1371/journal.pone.0168023] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/24/2016] [Indexed: 01/03/2023] Open
Abstract
A recent investigation showed the existence of correlations between the architectural features of mammalian interphase chromosomes and the compositional properties of isochores. This result prompted us to compare maps of the Topologically Associating Domains (TADs) and of the Lamina Associated Domains (LADs) with the corresponding isochore maps of mouse and human chromosomes. This approach revealed that: 1) TADs and LADs correspond to isochores, i.e., isochores are the genomic units that underlie chromatin domains; 2) the conservation of TADs and LADs in mammalian genomes is explained by the evolutionary conservation of isochores; 3) chromatin domains corresponding to GC-poor isochores (e.g., LADs) show not only self-interactions but also intrachromosomal interactions with other domains also corresponding to GC-poor isochores even if located far away; in contrast, chromatin domains corresponding to GC-rich isochores (e.g., TADs) show more localized chromosomal interactions, many of which are inter-chromosomal. In conclusion, this investigation establishes a link between DNA sequences and chromatin architecture, explains the evolutionary conservation of TADs and LADs and provides new information on the spatial distribution of GC-poor/gene-poor and GC-rich/gene-rich chromosomal regions in the interphase nucleus.
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Affiliation(s)
- Kamel Jabbari
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Straße 9B, Köln, Germany
| | - Giorgio Bernardi
- Science Department, Roma Tre University, Viale Marconi, Rome, Italy, and Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, Italy
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216
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Ibarra A, Benner C, Tyagi S, Cool J, Hetzer MW. Nucleoporin-mediated regulation of cell identity genes. Genes Dev 2016; 30:2253-2258. [PMID: 27807035 PMCID: PMC5110992 DOI: 10.1101/gad.287417.116] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Accepted: 10/07/2016] [Indexed: 01/21/2023]
Abstract
Here, Ibarra et al. investigate the contribution of nuclear envelope components to the regulation of cell type-specific gene expression and show a role for NPC components in the regulation of cell type-specific gene expression The authors found that nucleoporin-associated superenhancers localize preferentially to the nuclear periphery, and, in the absence of nucleoporins, transcriptional changes of SE-associated genes were observed. The organization of the genome in the three-dimensional space of the nucleus is coupled with cell type-specific gene expression. However, how nuclear architecture influences transcription that governs cell identity remains unknown. Here, we show that nuclear pore complex (NPC) components Nup93 and Nup153 bind superenhancers (SE), regulatory structures that drive the expression of key genes that specify cell identity. We found that nucleoporin-associated SEs localize preferentially to the nuclear periphery, and absence of Nup153 and Nup93 results in dramatic transcriptional changes of SE-associated genes. Our results reveal a crucial role of NPC components in the regulation of cell type-specifying genes and highlight nuclear architecture as a regulatory layer of genome functions in cell fate.
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Affiliation(s)
- Arkaitz Ibarra
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Chris Benner
- Integrative Genomics and Bioinformatics Core, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Swati Tyagi
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Jonah Cool
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Martin W Hetzer
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
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217
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Abstract
Lamins are major components of the nuclear lamina, a network of proteins that supports the nuclear envelope in metazoan cells. Over the past decade, biochemical studies have provided support for the view that lamins are not passive bystanders providing mechanical stability to the nucleus but play an active role in the organization of the genome and the function of fundamental nuclear processes. It has also become apparent that lamins are critical for human health, as a large number of mutations identified in the gene that encodes for A-type lamins are associated with tissue-specific and systemic genetic diseases, including the accelerated aging disorder known as Hutchinson-Gilford progeria syndrome. Recent years have witnessed great advances in our understanding of the role of lamins in the nucleus and the functional consequences of disease-associated A-type lamin mutations. Many of these findings have been presented in comprehensive reviews. In this mini-review, we discuss recent breakthroughs in the role of lamins in health and disease and what lies ahead in lamin research.
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Affiliation(s)
- Sita Reddy
- Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Lucio Comai
- Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA; Department of Molecular Microbiology and Immunology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
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218
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Abstract
The nucleus is separated from the cytosol by the nuclear envelope, which is a double lipid bilayer composed of the outer nuclear membrane and the inner nuclear membrane. The intermediate filament proteins lamin A, lamin B, and lamin C form a network underlying the inner nuclear membrane. This proteinaceous network provides the nucleus with its strength, rigidity, and elasticity. Positioned within the inner nuclear membrane are more than 150 inner nuclear membrane proteins, many of which interact directly with lamins and require lamins for their inner nuclear membrane localization. Inner nuclear membrane proteins and the nuclear lamins define the nuclear lamina. These inner nuclear membrane proteins have tissue-specific expression and diverse functions including regulating cytoskeletal organization, nuclear architecture, cell cycle dynamics, and genomic organization. Loss or mutations in lamins and inner nuclear membrane proteins cause a wide spectrum of diseases. Here, I will review the functions of the well-studied nuclear lamina proteins and the diseases associated with loss or mutations in these proteins. © 2016 American Physiological Society. Compr Physiol 6:1655-1674, 2016.
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Affiliation(s)
- James M. Holaska
- Department of Pharmaceutical Sciences, University of the Sciences, Philadelphia, Pennsylvania, USA
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219
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Robin JD, Magdinier F. Physiological and Pathological Aging Affects Chromatin Dynamics, Structure and Function at the Nuclear Edge. Front Genet 2016; 7:153. [PMID: 27602048 PMCID: PMC4993774 DOI: 10.3389/fgene.2016.00153] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 08/08/2016] [Indexed: 01/29/2023] Open
Abstract
Lamins are intermediate filaments that form a complex meshwork at the inner nuclear membrane. Mammalian cells express two types of Lamins, Lamins A/C and Lamins B, encoded by three different genes, LMNA, LMNB1, and LMNB2. Mutations in the LMNA gene are associated with a group of phenotypically diverse diseases referred to as laminopathies. Lamins interact with a large number of binding partners including proteins of the nuclear envelope but also chromatin-associated factors. Lamins not only constitute a scaffold for nuclear shape, rigidity and resistance to stress but also contribute to the organization of chromatin and chromosomal domains. We will discuss here the impact of A-type Lamins loss on alterations of chromatin organization and formation of chromatin domains and how disorganization of the lamina contributes to the patho-physiology of premature aging syndromes.
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Affiliation(s)
- Jérôme D Robin
- IRCAN, CNRS UMR 7284/INSERM U1081, Faculté de Médecine Nice, France
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220
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Tomita S, Abdalla MOA, Fujiwara S, Yamamoto T, Iwase H, Nakao M, Saitoh N. Roles of long noncoding RNAs in chromosome domains. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 8. [DOI: 10.1002/wrna.1384] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 06/30/2016] [Accepted: 07/07/2016] [Indexed: 12/26/2022]
Affiliation(s)
- Saori Tomita
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
- Department of Breast and Endocrine Surgery, Graduate School of Medical Sciences; Kumamoto University; Kumamoto Japan
| | - Mohamed Osama Ali Abdalla
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
- Department of Clinical Pathology, Faculty of Medicine; Suez Canal University; Ismailia Egypt
| | - Saori Fujiwara
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
- Department of Breast and Endocrine Surgery, Graduate School of Medical Sciences; Kumamoto University; Kumamoto Japan
| | - Tatsuro Yamamoto
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
| | - Hirotaka Iwase
- Department of Breast and Endocrine Surgery, Graduate School of Medical Sciences; Kumamoto University; Kumamoto Japan
| | - Mitsuyoshi Nakao
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Agency for Medical Research and Development; Tokyo Japan
| | - Noriko Saitoh
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics; Kumamoto University; Kumamoto Japan
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221
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Pueschel R, Coraggio F, Meister P. From single genes to entire genomes: the search for a function of nuclear organization. Development 2016; 143:910-23. [PMID: 26980791 DOI: 10.1242/dev.129007] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The existence of different domains within the nucleus has been clear from the time, in the late 1920s, that heterochromatin and euchromatin were discovered. The observation that heterochromatin is less transcribed than euchromatin suggested that microscopically identifiable structures might correspond to functionally different domains of the nucleus. Until 15 years ago, studies linking gene expression and subnuclear localization were limited to a few genes. As we discuss in this Review, new genome-wide techniques have now radically changed the way nuclear organization is analyzed. These have provided a much more detailed view of functional nuclear architecture, leading to the emergence of a number of new paradigms of chromatin folding and how this folding evolves during development.
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Affiliation(s)
- Ringo Pueschel
- Cell Fate and Nuclear Organization, Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland
| | - Francesca Coraggio
- Cell Fate and Nuclear Organization, Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland
| | - Peter Meister
- Cell Fate and Nuclear Organization, Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
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222
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3D genomics imposes evolution of the domain model of eukaryotic genome organization. Chromosoma 2016; 126:59-69. [DOI: 10.1007/s00412-016-0604-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 05/11/2016] [Accepted: 06/06/2016] [Indexed: 10/21/2022]
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223
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McGregor AL, Hsia CR, Lammerding J. Squish and squeeze-the nucleus as a physical barrier during migration in confined environments. Curr Opin Cell Biol 2016; 40:32-40. [PMID: 26895141 PMCID: PMC4887392 DOI: 10.1016/j.ceb.2016.01.011] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 01/23/2016] [Indexed: 01/22/2023]
Abstract
From embryonic development to cancer metastasis, cell migration plays a central role in health and disease. It is increasingly becoming apparent that cells migrating in three-dimensional (3-D) environments exhibit some striking differences compared with their well-established 2-D counterparts. One key finding is the significant role the nucleus plays during 3-D migration: when cells move in confined spaces, the cell body and nucleus must deform to squeeze through available spaces, and the deformability of the large and relatively rigid nucleus can become rate-limiting. In this review, we highlight recent findings regarding the role of nuclear mechanics in 3-D migration, including factors that govern nuclear deformability, and emerging mechanisms by which cells apply cytoskeletal forces to the nucleus to facilitate nuclear translocation. Intriguingly, the 'physical barrier' imposed by the nucleus also impacts cytoplasmic dynamics that affect cell migration and signaling, and changes in nuclear structure resulting from the mechanical forces acting on the nucleus during 3-D migration could further alter cellular function. These findings have broad relevance to the migration of both normal and cancerous cells inside living tissues, and motivate further research into the molecular details by which cells move their nuclei, as well as the consequences of the mechanical stress on the nucleus.
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Affiliation(s)
- Alexandra Lynn McGregor
- Nancy C. and Peter E. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Chieh-Ren Hsia
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jan Lammerding
- Nancy C. and Peter E. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA; Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.
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224
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Chen H, Zheng X, Xiao D, Zheng Y. Age-associated de-repression of retrotransposons in the Drosophila fat body, its potential cause and consequence. Aging Cell 2016; 15:542-52. [PMID: 27072046 PMCID: PMC4854910 DOI: 10.1111/acel.12465] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2016] [Indexed: 01/07/2023] Open
Abstract
Eukaryotic genomes contain transposable elements (TE) that can move into new locations upon activation. Since uncontrolled transposition of TEs, including the retrotransposons and DNA transposons, can lead to DNA breaks and genomic instability, multiple mechanisms, including heterochromatin‐mediated repression, have evolved to repress TE activation. Studies in model organisms have shown that TEs become activated upon aging as a result of age‐associated deregulation of heterochromatin. Considering that different organisms or cell types may undergo distinct heterochromatin changes upon aging, it is important to identify pathways that lead to TE activation in specific tissues and cell types. Through deep sequencing of isolated RNAs, we report an increased expression of many retrotransposons in the old Drosophila fat body, an organ equivalent to the mammalian liver and adipose tissue. This de‐repression correlates with an increased number of DNA damage foci and decreased level of Drosophila lamin‐B in the old fat body cells. Depletion of the Drosophila lamin‐B in the young or larval fat body results in a reduction of heterochromatin and a corresponding increase in retrotransposon expression and DNA damage. Further manipulations of lamin‐B and retrotransposon expression suggest a role of the nuclear lamina in maintaining the genome integrity of the Drosophila fat body by repressing retrotransposons.
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Affiliation(s)
- Haiyang Chen
- Key Laboratory of Gene Engineering of the Ministry of Education State Key Laboratory of Biocontrol School of Life Sciences Sun Yat‐sen University Guangzhou 510275 China
- Department of Embryology Carnegie Institution for Science Baltimore MD 21218 USA
| | - Xiaobin Zheng
- Department of Embryology Carnegie Institution for Science Baltimore MD 21218 USA
| | - Danqing Xiao
- Key Laboratory of Gene Engineering of the Ministry of Education State Key Laboratory of Biocontrol School of Life Sciences Sun Yat‐sen University Guangzhou 510275 China
| | - Yixian Zheng
- Department of Embryology Carnegie Institution for Science Baltimore MD 21218 USA
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225
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Fotuhi Siahpirani A, Ay F, Roy S. A multi-task graph-clustering approach for chromosome conformation capture data sets identifies conserved modules of chromosomal interactions. Genome Biol 2016; 17:114. [PMID: 27233632 PMCID: PMC4882777 DOI: 10.1186/s13059-016-0962-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 04/22/2016] [Indexed: 01/13/2023] Open
Abstract
Chromosome conformation capture methods are being increasingly used to study three-dimensional genome architecture in multiple cell types and species. An important challenge is to examine changes in three-dimensional architecture across cell types and species. We present Arboretum-Hi-C, a multi-task spectral clustering method, to identify common and context-specific aspects of genome architecture. Compared to standard clustering, Arboretum-Hi-C produced more biologically consistent patterns of conservation. Most clusters are conserved and enriched for either high- or low-activity genomic signals. Most genomic regions diverge between clusters with similar chromatin state except for a few that are associated with lamina-associated domains and open chromatin.
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Affiliation(s)
| | - Ferhat Ay
- La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, 92037, CA, USA
| | - Sushmita Roy
- Wisconsin Institute for Discovery, University of Wisconsin, Madison, 53717, WI, USA. .,Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, 53717, WI, USA.
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226
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Monte E, Rosa-Garrido M, Karbassi E, Chen H, Lopez R, Rau CD, Wang J, Nelson SF, Wu Y, Stefani E, Lusis AJ, Wang Y, Kurdistani SK, Franklin S, Vondriska TM. Reciprocal Regulation of the Cardiac Epigenome by Chromatin Structural Proteins Hmgb and Ctcf: IMPLICATIONS FOR TRANSCRIPTIONAL REGULATION. J Biol Chem 2016; 291:15428-46. [PMID: 27226577 DOI: 10.1074/jbc.m116.719633] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Indexed: 02/05/2023] Open
Abstract
Transcriptome remodeling in heart disease occurs through the coordinated actions of transcription factors, histone modifications, and other chromatin features at pathology-associated genes. The extent to which genome-wide chromatin reorganization also contributes to the resultant changes in gene expression remains unknown. We examined the roles of two chromatin structural proteins, Ctcf (CCCTC-binding factor) and Hmgb2 (high mobility group protein B2), in regulating pathologic transcription and chromatin remodeling. Our data demonstrate a reciprocal relationship between Hmgb2 and Ctcf in controlling aspects of chromatin structure and gene expression. Both proteins regulate each others' expression as well as transcription in cardiac myocytes; however, only Hmgb2 does so in a manner that involves global reprogramming of chromatin accessibility. We demonstrate that the actions of Hmgb2 on local chromatin accessibility are conserved across genomic loci, whereas the effects on transcription are loci-dependent and emerge in concert with histone modification and other chromatin features. Finally, although both proteins share gene targets, Hmgb2 and Ctcf, neither binds these genes simultaneously nor do they physically colocalize in myocyte nuclei. Our study uncovers a previously unknown relationship between these two ubiquitous chromatin proteins and provides a mechanistic explanation for how Hmgb2 regulates gene expression and cellular phenotype. Furthermore, we provide direct evidence for structural remodeling of chromatin on a genome-wide scale in the setting of cardiac disease.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Yong Wu
- From the Departments of Anesthesiology
| | | | - Aldons J Lusis
- Medicine, Human Genetics, Microbiology, Immunology and Molecular Genetics, and
| | - Yibin Wang
- From the Departments of Anesthesiology, Medicine, Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 and
| | | | - Sarah Franklin
- the Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah 84112
| | - Thomas M Vondriska
- From the Departments of Anesthesiology, Medicine, Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095 and
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227
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Abstract
A concern in the field of genomics is the proper interpretation of large, high-throughput sequencing datasets. The use of DNA FISH followed by high-content microscopy is a valuable tool for validation and contextualization of frequently occurring gene pairing events at the single-cell level identified by deep sequencing. However, these techniques possess certain limitations. Firstly, they do not permit the study of colocalization of many gene loci simultaneously. Secondly, the direct assessment of the relative position of many clustered gene loci within their respective chromosome territories is impossible. Thus, methods are required to advance the study of higher-order nuclear and cellular organization. Here, we describe a multiplexed DNA FISH technique combined with indirect immunofluorescence to study the relative position of 6 distinct genomic or cellular structures. This can be achieved in a single hybridization step using spectral imaging during image acquisition and linear unmixing. Here, we detail the use of this method to quantify gene pairing between highly expressed spliceosomal genes and compare these data to randomly positioned in silico simulated gene clusters. This is a potentially universally applicable approach for the validation of 3C-based technologies, deep imaging of spatial organization within the nucleus and global cellular organization.
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Affiliation(s)
- Iain A Sawyer
- a Department of Cell Biology , Rosalind Franklin University of Medicine & Science, Chicago Medical School , North Chicago , IL , USA.,b Laboratory of Receptor Biology and Gene Expression , National Cancer Institute, National Institutes of Health , Bethesda , MD , USA
| | - Sergei P Shevtsov
- a Department of Cell Biology , Rosalind Franklin University of Medicine & Science, Chicago Medical School , North Chicago , IL , USA
| | - Miroslav Dundr
- a Department of Cell Biology , Rosalind Franklin University of Medicine & Science, Chicago Medical School , North Chicago , IL , USA
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228
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Abstract
The nuclear lamina (NL) is a structural component of the nuclear envelope and makes extensive contacts with integral nuclear membrane proteins and chromatin. These interactions are critical for many cellular processes, such as nuclear positioning, perception of mechanical stimuli from the cell surface, nuclear stability, 3-dimensional organization of chromatin and regulation of chromatin-binding proteins, including transcription factors. The NL is present in all nucleated metazoan cells but its composition and interactome differ between tissues. Most likely, this contributes to the broad spectrum of disease manifestations in humans with mutations in NL-related genes, ranging from muscle dystrophies to neurological disorders, lipodystrophies and progeria syndromes. We review here exciting novel insight into NL function at the cellular level, in particular in chromatin organization and mechanosensation. We also present recent observations on the relation between the NL and metabolism and the special relevance of the NL in muscle tissues. Finally, we discuss new therapeutic approaches to treat NL-related diseases.
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Affiliation(s)
- Agnieszka Dobrzynska
- a Andalusian Center for Developmental Biology (CABD) , CSIC/Junta de Andalucia/Universidad Pablo de Olavide , Seville , Spain
| | - Susana Gonzalo
- b Edward A. Doisy Department of Biochemistry and Molecular Biology , St Louis University School of Medicine , St. Louis , MO , USA
| | - Catherine Shanahan
- c BHF Center for Research Excellence , King's College London, Cardiovascular Division, James Black Center , London , UK
| | - Peter Askjaer
- a Andalusian Center for Developmental Biology (CABD) , CSIC/Junta de Andalucia/Universidad Pablo de Olavide , Seville , Spain
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229
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Shachar S, Voss TC, Pegoraro G, Sciascia N, Misteli T. Identification of Gene Positioning Factors Using High-Throughput Imaging Mapping. Cell 2016; 162:911-23. [PMID: 26276637 DOI: 10.1016/j.cell.2015.07.035] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 06/08/2015] [Accepted: 06/27/2015] [Indexed: 10/23/2022]
Abstract
Genomes are arranged non-randomly in the 3D space of the cell nucleus. Here, we have developed HIPMap, a high-precision, high-throughput, automated fluorescent in situ hybridization imaging pipeline, for mapping of the spatial location of genome regions at large scale. High-throughput imaging position mapping (HIPMap) enabled an unbiased siRNA screen for factors involved in genome organization in human cells. We identify 50 cellular factors required for proper positioning of a set of functionally diverse genomic loci. Positioning factors include chromatin remodelers, histone modifiers, and nuclear envelope and pore proteins. Components of the replication and post-replication chromatin re-assembly machinery are prominently represented among positioning factors, and timely progression of cells through replication, but not mitosis, is required for correct gene positioning. Our results establish a method for the large-scale mapping of genome locations and have led to the identification of a compendium of cellular factors involved in spatial genome organization.
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Affiliation(s)
- Sigal Shachar
- National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Ty C Voss
- High Throughput Imaging Facility (HiTIF), National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Gianluca Pegoraro
- High Throughput Imaging Facility (HiTIF), National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | | | - Tom Misteli
- National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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230
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Chandra T, Kirschner K. Chromosome organisation during ageing and senescence. Curr Opin Cell Biol 2016; 40:161-167. [PMID: 27101466 DOI: 10.1016/j.ceb.2016.03.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 03/08/2016] [Accepted: 03/28/2016] [Indexed: 02/01/2023]
Abstract
Acute cellular stress caused by oncogene activation or high levels of DNA damage can engage a tumour suppressive response, which can lead to cellular senescence. Chronic cellular stress evoked by low levels of DNA damage or telomere erosion is involved in the ageing process. In oncogene induced senescence in fibroblasts, a dramatic rearrangement of heterochromatin into foci and accumulation of constitutive heterochromatin is well documented. In contrast, a loss of heterochromatin has been described in replicative senescence and premature ageing syndromes. The distinct nuclear phenotypes that accompany the stress response highlight the differences between acute and chronic stress models, and this review will address the differences and similarities between these models with a focus on chromosome organisation and heterochromatin.
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Affiliation(s)
- Tamir Chandra
- Epigenetics Programme, The Babraham Institute, Cambridge CB22 3AT, UK; The Wellcome Trust Sanger Institute, Cambridge CB10 1SA, UK.
| | - Kristina Kirschner
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Stem Cell Institute and Department of Haematology, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK.
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231
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Pinter SF. A Tale of Two Cities: How Xist and its partners localize to and silence the bicompartmental X. Semin Cell Dev Biol 2016; 56:19-34. [PMID: 27072488 DOI: 10.1016/j.semcdb.2016.03.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 03/30/2016] [Accepted: 03/30/2016] [Indexed: 10/22/2022]
Abstract
Sex chromosomal dosage compensation in mammals takes the form of X chromosome inactivation (XCI), driven by the non-coding RNA Xist. In contrast to dosage compensation systems of flies and worms, mammalian XCI has to restrict its function to the Xist-producing X chromosome, while leaving autosomes and active X untouched. The mechanisms behind the long-range yet cis-specific localization and silencing activities of Xist have long been enigmatic, but genomics, proteomics, super-resolution microscopy, and innovative genetic approaches have produced significant new insights in recent years. In this review, I summarize and integrate these findings with a particular focus on the redundant yet mutually reinforcing pathways that enable long-term transcriptional repression throughout the soma. This includes an exploration of concurrent epigenetic changes acting in parallel within two distinct compartments of the inactive X. I also examine how Polycomb repressive complexes 1 and 2 and macroH2A may bridge XCI establishment and maintenance. XCI is a remarkable phenomenon that operates across multiple scales, combining changes in nuclear architecture, chromosome topology, chromatin compaction, and nucleosome/nucleotide-level epigenetic cues. Learning how these pathways act in concert likely holds the answer to the riddle posed by Cattanach's and other autosomal translocations: What makes the X especially receptive to XCI?
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Affiliation(s)
- Stefan F Pinter
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut Health Center, 263 Farmington Ave, Farmington, CT 06030-6403, USA.
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232
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Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare premature aging disease presenting many features resembling the normal aging process. HGPS patients die before the age of 20 years due to cardiovascular problems and heart failure. HGPS is linked to mutations in the LMNA gene encoding the intermediate filament protein lamin A. Lamin A is a major component of the nuclear lamina, a scaffold structure at the nuclear envelope that defines mechanochemical properties of the nucleus and is involved in chromatin organization and epigenetic regulation. Lamin A is also present in the nuclear interior where it fulfills lamina-independent functions in cell signaling and gene regulation. The most common LMNA mutation linked to HGPS leads to mis-splicing of the LMNA mRNA and produces a mutant lamin A protein called progerin that tightly associates with the inner nuclear membrane and affects the dynamic properties of lamins. Progerin expression impairs many important cellular processes providing insight into potential disease mechanisms. These include changes in mechanosignaling, altered chromatin organization and impaired genome stability, and changes in signaling pathways, leading to impaired regulation of adult stem cells, defective extracellular matrix production and premature cell senescence. In this review, we discuss these pathways and their potential contribution to the disease pathologies as well as therapeutic approaches used in preclinical and clinical tests.
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Affiliation(s)
- Sandra Vidak
- Max F. Perutz Laboratories (MFPL), Department of Medical Biochemistry, Vienna Biocenter (VBC), Medical University Vienna, Dr. Bohr-Gasse 9/3, 1030, Vienna, Austria
| | - Roland Foisner
- Max F. Perutz Laboratories (MFPL), Department of Medical Biochemistry, Vienna Biocenter (VBC), Medical University Vienna, Dr. Bohr-Gasse 9/3, 1030, Vienna, Austria.
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233
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Telorac J, Prykhozhij SV, Schöne S, Meierhofer D, Sauer S, Thomas-Chollier M, Meijsing SH. Identification and characterization of DNA sequences that prevent glucocorticoid receptor binding to nearby response elements. Nucleic Acids Res 2016; 44:6142-56. [PMID: 27016732 PMCID: PMC5291246 DOI: 10.1093/nar/gkw203] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 03/16/2016] [Indexed: 01/13/2023] Open
Abstract
Out of the myriad of potential DNA binding sites of the glucocorticoid receptor (GR) found in the human genome, only a cell-type specific minority is actually bound, indicating that the presence of a recognition sequence alone is insufficient to specify where GR binds. Cooperative interactions with other transcription factors (TFs) are known to contribute to binding specificity. Here, we reasoned that sequence signals preventing GR recruitment to certain loci provide an alternative means to confer specificity. Motif analyses uncovered candidate Negative Regulatory Sequences (NRSs) that interfere with genomic GR binding. Subsequent functional analyses demonstrated that NRSs indeed prevent GR binding to nearby response elements. We show that NRS activity is conserved across species, found in most tissues and that they also interfere with the genomic binding of other TFs. Interestingly, the effects of NRSs appear not to be a simple consequence of changes in chromatin accessibility. Instead, we find that NRSs interact with proteins found at sub-nuclear structures called paraspeckles and that these proteins might mediate the repressive effects of NRSs. Together, our studies suggest that the joint influence of positive and negative sequence signals partition the genome into regions where GR can bind and those where it cannot.
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Affiliation(s)
- Jonas Telorac
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany
| | - Sergey V Prykhozhij
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany Dalhousie University, Halifax, NS B3K 6R8, Canada
| | - Stefanie Schöne
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany
| | - David Meierhofer
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany
| | - Sascha Sauer
- CU Systems Medicine, University of Würzburg, Josef-Schneider-Strasse 2, D-97080 Würzburg, Germany
| | - Morgane Thomas-Chollier
- Computational Systems Biology, Institut de Biologie de l'Ecole Normale, Supérieure (IBENS), CNRS, Inserm, Ecole Normale Supérieure, PSL Research University, F-75005 Paris, France
| | - Sebastiaan H Meijsing
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, D-14195 Berlin, Germany
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234
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Feinberg AP, Koldobskiy MA, Göndör A. Epigenetic modulators, modifiers and mediators in cancer aetiology and progression. Nat Rev Genet 2016; 17:284-99. [PMID: 26972587 DOI: 10.1038/nrg.2016.13] [Citation(s) in RCA: 573] [Impact Index Per Article: 71.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
This year is the tenth anniversary of the publication in this journal of a model suggesting the existence of 'tumour progenitor genes'. These genes are epigenetically disrupted at the earliest stages of malignancies, even before mutations, and thus cause altered differentiation throughout tumour evolution. The past decade of discovery in cancer epigenetics has revealed a number of similarities between cancer genes and stem cell reprogramming genes, widespread mutations in epigenetic regulators, and the part played by chromatin structure in cellular plasticity in both development and cancer. In the light of these discoveries, we suggest here a framework for cancer epigenetics involving three types of genes: 'epigenetic mediators', corresponding to the tumour progenitor genes suggested earlier; 'epigenetic modifiers' of the mediators, which are frequently mutated in cancer; and 'epigenetic modulators' upstream of the modifiers, which are responsive to changes in the cellular environment and often linked to the nuclear architecture. We suggest that this classification is helpful in framing new diagnostic and therapeutic approaches to cancer.
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Affiliation(s)
- Andrew P Feinberg
- Center for Epigenetics, Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Rangos 570, Baltimore, Maryland 21205, USA
| | - Michael A Koldobskiy
- Center for Epigenetics, Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Rangos 570, Baltimore, Maryland 21205, USA
| | - Anita Göndör
- Department of Microbiology, Tumour and Cell Biology, Nobels väg 16, Karolinska Institutet, S-171 77 Stockholm, Sweden
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235
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Deciphering DNA replication dynamics in eukaryotic cell populations in relation with their averaged chromatin conformations. Sci Rep 2016; 6:22469. [PMID: 26935043 PMCID: PMC4776152 DOI: 10.1038/srep22469] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 02/16/2016] [Indexed: 12/16/2022] Open
Abstract
We propose a non-local model of DNA replication that takes into account the observed
uncertainty on the position and time of replication initiation in eukaryote cell
populations. By picturing replication initiation as a two-state system and
considering all possible transition configurations, and by taking into account the
chromatin’s fractal dimension, we derive an analytical expression for
the rate of replication initiation. This model predicts with no free parameter the
temporal profiles of initiation rate, replication fork density and fraction of
replicated DNA, in quantitative agreement with corresponding experimental data from
both S. cerevisiae and human cells and provides a quantitative estimate of
initiation site redundancy. This study shows that, to a large extent, the program
that regulates the dynamics of eukaryotic DNA replication is a collective phenomenon
that emerges from the stochastic nature of replication origins initiation.
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236
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Solovei I, Thanisch K, Feodorova Y. How to rule the nucleus: divide et impera. Curr Opin Cell Biol 2016; 40:47-59. [PMID: 26938331 DOI: 10.1016/j.ceb.2016.02.014] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 02/04/2016] [Accepted: 02/14/2016] [Indexed: 01/14/2023]
Abstract
Genome-wide molecular studies have provided new insights into the organization of nuclear chromatin by revealing the presence of chromatin domains of differing transcriptional activity, frequency of cis-interactions, proximity to scaffolding structures and replication timing. These studies have not only brought our understanding of genome function to a new level, but also offered functional insight for many phenomena observed in microscopic studies. In this review, we discuss the major principles of nuclear organization based on the spatial segregation of euchromatin and heterochromatin, as well as the dynamic genome rearrangements occurring during cell differentiation and development. We hope to unite the existing molecular and microscopic data on genome organization to get a holistic view of the nucleus, and propose a model, in which repeat repertoire together with scaffolding structures blueprint the functional nuclear architecture.
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Affiliation(s)
- Irina Solovei
- Department of Biology II, Ludwig Maximilians University Munich, Grosshadernerstrasse 2, Planegg-Martinsried 82152, Germany.
| | - Katharina Thanisch
- Department of Biology II, Ludwig Maximilians University Munich, Grosshadernerstrasse 2, Planegg-Martinsried 82152, Germany
| | - Yana Feodorova
- Department of Biology II, Ludwig Maximilians University Munich, Grosshadernerstrasse 2, Planegg-Martinsried 82152, Germany; Department of Medical Biology, Medical University-Plovdiv, Boulevard Vasil Aprilov 15A, Plovdiv 4000, Bulgaria
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237
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Marullo F, Cesarini E, Antonelli L, Gregoretti F, Oliva G, Lanzuolo C. Nucleoplasmic Lamin A/C and Polycomb group of proteins: An evolutionarily conserved interplay. Nucleus 2016; 7:103-11. [PMID: 26930442 PMCID: PMC4916880 DOI: 10.1080/19491034.2016.1157675] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Nuclear lamins are the main components of the nuclear lamina at the nuclear periphery, providing mechanical support to the nucleus. However, recent findings suggest that lamins also reside in the nuclear interior, as a distinct and dynamic pool with critical roles in transcriptional regulation. In our work we found a functional and evolutionary conserved crosstalk between Lamin A/C and the Polycomb group (PcG) of proteins, this being required for the maintenance of the PcG repressive functions. Indeed, Lamin A/C knock-down causes PcG foci dispersion and defects in PcG-mediated higher order structures, thereby leading to impaired PcG mediated transcriptional repression. By using ad-hoc algorithms for image analysis and PLA approaches we hereby show that PcG proteins are preferentially located in the nuclear interior where they interact with nucleoplasmic Lamin A/C. Taken together, our findings suggest that nuclear components, such as Lamin A/C, functionally interact with epigenetic factors to ensure the correct transcriptional program maintenance.
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Affiliation(s)
- F Marullo
- a CNR Institute of Cell Biology and Neurobiology, IRCCS Santa Lucia Foundation , Rome , Italy
| | - E Cesarini
- a CNR Institute of Cell Biology and Neurobiology, IRCCS Santa Lucia Foundation , Rome , Italy
| | - L Antonelli
- b CNR Institute for High Performance Computing and Networking (ICAR) , Naples, Italy
| | - F Gregoretti
- b CNR Institute for High Performance Computing and Networking (ICAR) , Naples, Italy
| | - G Oliva
- b CNR Institute for High Performance Computing and Networking (ICAR) , Naples, Italy
| | - C Lanzuolo
- a CNR Institute of Cell Biology and Neurobiology, IRCCS Santa Lucia Foundation , Rome , Italy.,c Istituto Nazionale Genetica Molecolare Romeo ed Enrica Invernizzi , Milan , Italy
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238
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Mita P, Boeke JD. How retrotransposons shape genome regulation. Curr Opin Genet Dev 2016; 37:90-100. [PMID: 26855260 DOI: 10.1016/j.gde.2016.01.001] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/30/2015] [Accepted: 01/17/2016] [Indexed: 12/30/2022]
Abstract
Retrotransposons are mutagenic units able to move within the genome. Despite many defenses deployed by the host to suppress potentially harmful activities of retrotransposons, these genetic units have found ways to meld with normal cellular functions through processes of exaptation and domestication. The same host mechanisms targeting transposon mobility allow for expansion and rewiring of gene regulatory networks on an evolutionary time scale. Recent works demonstrating retrotransposon activity during development, cell differentiation and neurogenesis shed new light on unexpected activities of transposable elements. Moreover, new technological advances illuminated subtler nuances of the complex relationship between retrotransposons and the host genome, clarifying the role of retroelements in evolution, development and impact on human disease.
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Affiliation(s)
- Paolo Mita
- Institute for Systems Genetics, Department of Biochemistry & Molecular Pharmacology, NYU Langone Medical Center, 430 East 29 Street, NY, NY 10016, USA.
| | - Jef D Boeke
- Institute for Systems Genetics, Department of Biochemistry & Molecular Pharmacology, NYU Langone Medical Center, 430 East 29 Street, NY, NY 10016, USA
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239
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Abstract
The role of genome architecture in transcription regulation has become the focus of an increasing number of studies over the past decade. Chromatin organization can have a significant impact on gene expression by promoting or restricting the physical proximity between regulatory DNA elements. Given that any change in chromatin state has the potential to alter DNA folding and the proximity between control elements, the spatial organization of chromatin is inherently linked to its molecular composition. In this review, we explore how modulators of chromatin state and organization might keep gene expression in check. We discuss recent findings and present some of the less well-studied aspects of spatial genome organization such as chromatin dynamics and regulation by non-coding RNAs.
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240
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Abstract
'Epigenome' refers to the panoply of chemical modifications borne by DNA and its associated proteins that locally affect genome function. Epigenomic patterns are thought to be determined by external constraints resulting from development, disease and the environment, but DNA sequence is also a potential influence. We propose that domains of relatively uniform DNA base composition may modulate the epigenome through cell type-specific proteins that recognize short, frequent sequence motifs. Differential recruitment of epigenomic modifiers may adjust gene expression in multigene blocks as an alternative to tuning the activity of each gene separately, thus simplifying gene expression programming.
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241
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Bernardi G. Genome Organization and Chromosome Architecture. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2016; 80:83-91. [PMID: 26801160 DOI: 10.1101/sqb.2015.80.027318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
How the same DNA sequences can function in the three-dimensional architecture of interphase nucleus, fold in the very compact structure of metaphase chromosomes, and go precisely back to the original interphase architecture in the following cell cycle remains an unresolved question to this day. The solution to this question presented here rests on the correlations that were found to hold between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase. The key points are the following: (1) The transition from the looped domains and subdomains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through their unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); (2) the architectural proteins of interphase chromatin, such as CTCF and cohesin subunits, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; and (3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the reversibility of the interphase to mitosis process and the "mitotic memory" of interphase architecture.
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Affiliation(s)
- Giorgio Bernardi
- Science Department, Roma Tre University, 00146 Rome, Italy Stazione Zoologica Anton Dohrn, 80121 Naples, Italy
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242
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Gesson K, Rescheneder P, Skoruppa MP, von Haeseler A, Dechat T, Foisner R. A-type lamins bind both hetero- and euchromatin, the latter being regulated by lamina-associated polypeptide 2 alpha. Genome Res 2016; 26:462-73. [PMID: 26798136 PMCID: PMC4817770 DOI: 10.1101/gr.196220.115] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 01/19/2016] [Indexed: 11/24/2022]
Abstract
Lamins are components of the peripheral nuclear lamina and interact with heterochromatic genomic regions, termed lamina-associated domains (LADs). In contrast to lamin B1 being primarily present at the nuclear periphery, lamin A/C also localizes throughout the nucleus, where it associates with the chromatin-binding protein lamina-associated polypeptide (LAP) 2 alpha. Here, we show that lamin A/C also interacts with euchromatin, as determined by chromatin immunoprecipitation of euchromatin- and heterochromatin-enriched samples. By way of contrast, lamin B1 was only found associated with heterochromatin. Euchromatic regions occupied by lamin A/C overlap with those bound by LAP2alpha, and lack of LAP2alpha in LAP2alpha-deficient cells shifts binding of lamin A/C toward more heterochromatic regions. These alterations in lamin A/C-chromatin interactions correlate with changes in epigenetic histone marks in euchromatin but do not significantly affect gene expression. Loss of lamin A/C in heterochromatic regions in LAP2alpha-deficient cells, however, correlated with increased gene expression. Our data show a novel role of nucleoplasmic lamin A/C and LAP2alpha in regulating euchromatin.
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Affiliation(s)
- Kevin Gesson
- Department of Medical Biochemistry, Medical University of Vienna, A-1030 Vienna, Austria
| | - Philipp Rescheneder
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories (MFPL), Medical University of Vienna and University of Vienna, Vienna Biocenter (VBC), A-1030 Vienna, Austria
| | - Michael P Skoruppa
- Department of Medical Biochemistry, Medical University of Vienna, A-1030 Vienna, Austria
| | - Arndt von Haeseler
- Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories (MFPL), Medical University of Vienna and University of Vienna, Vienna Biocenter (VBC), A-1030 Vienna, Austria; Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, A-1030 Vienna, Austria
| | - Thomas Dechat
- Department of Medical Biochemistry, Medical University of Vienna, A-1030 Vienna, Austria
| | - Roland Foisner
- Department of Medical Biochemistry, Medical University of Vienna, A-1030 Vienna, Austria
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243
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Foti R, Gnan S, Cornacchia D, Dileep V, Bulut-Karslioglu A, Diehl S, Buness A, Klein FA, Huber W, Johnstone E, Loos R, Bertone P, Gilbert DM, Manke T, Jenuwein T, Buonomo SCB. Nuclear Architecture Organized by Rif1 Underpins the Replication-Timing Program. Mol Cell 2016; 61:260-73. [PMID: 26725008 PMCID: PMC4724237 DOI: 10.1016/j.molcel.2015.12.001] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 07/22/2015] [Accepted: 11/13/2015] [Indexed: 02/08/2023]
Abstract
DNA replication is temporally and spatially organized in all eukaryotes, yet the molecular control and biological function of the replication-timing program are unclear. Rif1 is required for normal genome-wide regulation of replication timing, but its molecular function is poorly understood. Here we show that in mouse embryonic stem cells, Rif1 coats late-replicating domains and, with Lamin B1, identifies most of the late-replicating genome. Rif1 is an essential determinant of replication timing of non-Lamin B1-bound late domains. We further demonstrate that Rif1 defines and restricts the interactions between replication-timing domains during the G1 phase, thereby revealing a function of Rif1 as organizer of nuclear architecture. Rif1 loss affects both number and replication-timing specificity of the interactions between replication-timing domains. In addition, during the S phase, Rif1 ensures that replication of interacting domains is temporally coordinated. In summary, our study identifies Rif1 as the molecular link between nuclear architecture and replication-timing establishment in mammals.
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Affiliation(s)
- Rossana Foti
- Mouse Biology Unit, EMBL Monterotondo, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Stefano Gnan
- Mouse Biology Unit, EMBL Monterotondo, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Daniela Cornacchia
- Mouse Biology Unit, EMBL Monterotondo, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Vishnu Dileep
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Aydan Bulut-Karslioglu
- Max Planck Institute of Immunbiology and Epigenetics, Stubeweg 51, 79108 Freiburg, Germany
| | - Sarah Diehl
- Max Planck Institute of Immunbiology and Epigenetics, Stubeweg 51, 79108 Freiburg, Germany
| | - Andreas Buness
- Mouse Biology Unit, EMBL Monterotondo, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Felix A Klein
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Wolfgang Huber
- Genome Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Ewan Johnstone
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SD, UK
| | - Remco Loos
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SD, UK
| | - Paul Bertone
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SD, UK; Genome Biology and Developmental Biology Units, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; Wellcome Trust-Medical Research Council Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA
| | - Thomas Manke
- Max Planck Institute of Immunbiology and Epigenetics, Stubeweg 51, 79108 Freiburg, Germany
| | - Thomas Jenuwein
- Max Planck Institute of Immunbiology and Epigenetics, Stubeweg 51, 79108 Freiburg, Germany
| | - Sara C B Buonomo
- Mouse Biology Unit, EMBL Monterotondo, Via Ramarini 32, 00015 Monterotondo, Italy.
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244
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Harr JC, Gonzalez-Sandoval A, Gasser SM. Histones and histone modifications in perinuclear chromatin anchoring: from yeast to man. EMBO Rep 2016; 17:139-55. [PMID: 26792937 PMCID: PMC4783997 DOI: 10.15252/embr.201541809] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 12/21/2015] [Indexed: 01/01/2023] Open
Abstract
It is striking that within a eukaryotic nucleus, the genome can assume specific spatiotemporal distributions that correlate with the cell's functional states. Cell identity itself is determined by distinct sets of genes that are expressed at a given time. On the level of the individual gene, there is a strong correlation between transcriptional activity and associated histone modifications. Histone modifications act by influencing the recruitment of non-histone proteins and by determining the level of chromatin compaction, transcription factor binding, and transcription elongation. Accumulating evidence also shows that the subnuclear position of a gene or domain correlates with its expression status. Thus, the question arises whether this spatial organization results from or determines a gene's chromatin status. Although the association of a promoter with the inner nuclear membrane (INM) is neither necessary nor sufficient for repression, the perinuclear sequestration of heterochromatin is nonetheless conserved from yeast to man. How does subnuclear localization influence gene expression? Recent work argues that the common denominator between genome organization and gene expression is the modification of histones and in some cases of histone variants. This provides an important link between local chromatin structure and long-range genome organization in interphase cells. In this review, we will evaluate how histones contribute to the latter, and discuss how this might help to regulate genes crucial for cell differentiation.
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Affiliation(s)
- Jennifer C Harr
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Adriana Gonzalez-Sandoval
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland Faculty of Natural Sciences, University of Basel, Basel, Switzerland
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland Faculty of Natural Sciences, University of Basel, Basel, Switzerland
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245
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Cournac A, Koszul R, Mozziconacci J. The 3D folding of metazoan genomes correlates with the association of similar repetitive elements. Nucleic Acids Res 2016; 44:245-55. [PMID: 26609133 PMCID: PMC4705657 DOI: 10.1093/nar/gkv1292] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 10/13/2015] [Accepted: 11/04/2015] [Indexed: 12/11/2022] Open
Abstract
The potential roles of the numerous repetitive elements found in the genomes of multi-cellular organisms remain speculative. Several studies have suggested a role in stabilizing specific 3D genomic contacts. To test this hypothesis, we exploited inter-chromosomal contacts frequencies obtained from Hi-C experiments and show that the folding of the human, mouse and Drosophila genomes is associated with a significant co-localization of several specific repetitive elements, notably many elements of the SINE family. These repeats tend to be the oldest ones and are enriched in transcription factor binding sites. We propose that the co-localization of these repetitive elements may explain the global conservation of genome folding observed between homologous regions of the human and mouse genome. Taken together, these results support a contribution of specific repetitive elements in maintaining and/or reshaping genome architecture over evolutionary times.
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Affiliation(s)
- Axel Cournac
- LPTMC, Université Pierre et Marie Curie, Sorbonne université, 4 Place Jussieu 75005 Paris, France Institut Pasteur, Group Spatial Regulation of Genomes, Department of Genomes and Genetics, F-75015 Paris, France CNRS, UMR3525, F-75015 Paris, France
| | - Romain Koszul
- Institut Pasteur, Group Spatial Regulation of Genomes, Department of Genomes and Genetics, F-75015 Paris, France CNRS, UMR3525, F-75015 Paris, France
| | - Julien Mozziconacci
- LPTMC, Université Pierre et Marie Curie, Sorbonne université, 4 Place Jussieu 75005 Paris, France
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246
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Jabbari K, Nürnberg P. A genomic view on epilepsy and autism candidate genes. Genomics 2016; 108:31-6. [PMID: 26772991 DOI: 10.1016/j.ygeno.2016.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 12/15/2015] [Accepted: 01/01/2016] [Indexed: 01/25/2023]
Abstract
Epilepsy is a common complex disorder most frequently associated with psychiatric and neurological diseases. Massive parallel sequencing of individual or cohort genomes and exomes led the identification of several disease associated genes. We review here the candidate genes in epilepsy genetics with focus on exome and gene panel data. Together with the examination of brain expressed genes and post synaptic proteome the results show that: (1) Non-metabolic epilepsies and autism candidate genes tend to be AT-rich and (2) large transcript size and local AT-richness are characteristic features of genes involved in developmental brain disorders and synaptic functions. These results point to the preferential location of core epilepsy and autism candidate genes in late replicating, GC-poor chromosomal regions (isochores). These results indicate that the genomic alterations leading to some brain disorders are confined to responsive chromatin areas harboring brain critical genes.
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Affiliation(s)
- Kamel Jabbari
- Cologne Center for Genomics, University of Cologne, Cologne, Germany.
| | - Peter Nürnberg
- Cologne Center for Genomics, University of Cologne, Cologne, Germany
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247
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Duband-Goulet I. Lamin ChIP from Chromatin Prepared by Micrococcal Nuclease Digestion. Methods Mol Biol 2016; 1411:325-339. [PMID: 27147052 DOI: 10.1007/978-1-4939-3530-7_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
It is now clearly demonstrated that nuclear lamins interact with the genomic DNA and largely contribute to its three-dimensional organization and transcriptional regulation. Emergence of genome-wide mapping techniques such as DamID technology or chromatin immunoprecipitation (ChIP) followed by array hybridization or high-throughput sequencing has allowed the mapping of large lamin-interacting genomic areas called lamina-associated domains. These cover up to 40 % of the genome and are preferentially located in transcriptionally silent heterochromatin at the nuclear periphery. We recently showed that the use of enzymatic rather than physical fragmentation of chromatin in ChIP experiments uncovers new chromatin compartments with features of euchromatin that interacts with A-type lamins. We describe here a detailed ChIP procedure to covalently cross-link protein-DNA, fragment the chromatin fibers by micrococcal nuclease digestion, and solubilize the lamin network with a short sonication pulse prior to immunoprecipitating the lamin-DNA complexes using specific antibodies. Enriched DNA fragments from the lamin-binding sites are then purified as suitable samples for qPCR analysis or high-throughput sequencing.
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Affiliation(s)
- Isabelle Duband-Goulet
- Pathophysiology of Striated Muscles Laboratory, Unit of Functional and Adaptive Biology, University Paris Diderot-UMR CNRS 8251, Paris, France.
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248
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Mapping Nuclear Lamin-Genome Interactions by Chromatin Immunoprecipitation of Nuclear Lamins. Methods Mol Biol 2016; 1411:315-24. [PMID: 27147051 DOI: 10.1007/978-1-4939-3530-7_20] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The nuclear lamina is a meshwork of A- and B-type lamins which interact with chromatin and regulate many nuclear functions. Recent studies have reported the discovery of chromatin domains interacting with nuclear lamins by chromatin immunoprecipitation (ChIP) of lamin A/C or B1 and identification of the associated DNA sequences by microarray or high-throughput sequencing. ChIP has been used over many years to get a snapshot of interactions between DNA and proteins in cells, including modified histones, transcription factors, chromatin remodelers, and recently, structural proteins such as nuclear lamins. We describe here the procedure we have established in our laboratory for ChIP of lamin A/C and lamin B1 from human cultured cells. The protocol is compatible with polymerase chain reaction and high-throughput sequencing analysis of the co-immunoprecipitated DNA.
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249
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Abstract
How the same DNA sequences can function in the three-dimensional architecture of interphase nucleus, fold in the very compact structure of metaphase chromosomes and go precisely back to the original interphase architecture in the following cell cycle remains an unresolved question to this day. The strategy used to address this issue was to analyze the correlations between chromosome architecture and the compositional patterns of DNA sequences spanning a size range from a few hundreds to a few thousands Kilobases. This is a critical range that encompasses isochores, interphase chromatin domains and boundaries, and chromosomal bands. The solution rests on the following key points: 1) the transition from the looped domains and sub-domains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through the unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); 2) the architectural proteins of interphase chromatin, such as CTCF and cohesin sub-units, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; 3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the "mitotic memory" of interphase architecture and the reversibility of the interphase to mitosis process. The results presented here also lead to a general conclusion which concerns the existence of correlations between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase.
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Affiliation(s)
- Giorgio Bernardi
- Science Department, Roma Tre University, Marconi, Rome, Italy
- Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, Italy
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250
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Lund EG, Duband-Goulet I, Oldenburg A, Buendia B, Collas P. Distinct features of lamin A-interacting chromatin domains mapped by ChIP-sequencing from sonicated or micrococcal nuclease-digested chromatin. Nucleus 2015; 6:30-9. [PMID: 25602132 DOI: 10.4161/19491034.2014.990855] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The nuclear lamina has been shown to interact with the genome through lamina-associated domains (LADs). LADs have been identified by DamID, a proximity labeling assay, and more recently by chromatin immunoprecipitation-sequencing (ChIP-seq) of A- and B-type lamins. LADs form megabase-size domains at the nuclear periphery, they are gene-poor and mostly heterochromatic. Here, we show that the mode of chromatin fragmentation for ChIP, namely bath sonication or digestion with micrococcal nuclease (MNase), leads to the discovery of common but also distinct sets of lamin-interacting domains, or LiDs. Using ChIP-seq, we show the existence of lamin A/C (LMNA) LiDs with distinct gene contents, histone composition enrichment and relationships to lamin B1-interacting domains. The extent of genome coverage of lamin A/C (LMNA) LiDs in sonicated or MNase-digested chromatin is similar (∼730 megabases); however over half of these domains are uniquely detected in sonicated or MNase-digested chromatin. Sonication-specific LMNA LiDs are gene-poor and devoid of a broad panel of histone modifications, while MNase-specific LMNA LiDs are of higher gene density and are enriched in H3K9me3, H3K27me3 and in histone variant H2A.Z. LMNB1 LiDs are gene-poor and show no or little enrichment in these marks. Comparison of published LMNB1 DamID LADs with LMNB1 and LMNA LiDs identified here by ChIP-seq further shows that LMNA can associate with 'open' chromatin domains displaying euchromatin characteristics, and which are not associated with LMNB1. The differential genomic and epigenetic properties of lamin-interacting domains reflect the existence of distinct LiD populations identifiable in different chromatin contexts, including nuclease-accessible regions presumably localized in the nuclear interior.
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Affiliation(s)
- Eivind G Lund
- a Department of Molecular Medicine, Institute of Basic Medical Sciences ; University of Oslo, and Norwegian Center for Stem Cell Research , Oslo , Norway
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