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Luchsinger-Morcelle SJ, Gribnau J, Mira-Bontenbal H. Orchestrating Asymmetric Expression: Mechanisms behind Xist Regulation. EPIGENOMES 2024; 8:6. [PMID: 38390897 PMCID: PMC10885031 DOI: 10.3390/epigenomes8010006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 01/19/2024] [Accepted: 01/22/2024] [Indexed: 02/24/2024] Open
Abstract
Compensation for the gene dosage disequilibrium between sex chromosomes in mammals is achieved in female cells by repressing one of its X chromosomes through a process called X chromosome inactivation (XCI), exemplifying the control of gene expression by epigenetic mechanisms. A critical player in this mechanism is Xist, a long, non-coding RNA upregulated from a single X chromosome during early embryonic development in female cells. Over the past few decades, many factors involved at different levels in the regulation of Xist have been discovered. In this review, we hierarchically describe and analyze the different layers of Xist regulation operating concurrently and intricately interacting with each other to achieve asymmetric and monoallelic upregulation of Xist in murine female cells. We categorize these into five different classes: DNA elements, transcription factors, other regulatory proteins, long non-coding RNAs, and the chromatin and topological landscape surrounding Xist.
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Affiliation(s)
| | - Joost Gribnau
- Department of Developmental Biology, Erasmus MC, University Medical Center, 3015 GD Rotterdam, The Netherlands
| | - Hegias Mira-Bontenbal
- Department of Developmental Biology, Erasmus MC, University Medical Center, 3015 GD Rotterdam, The Netherlands
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2
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Bauer M, Payer B, Filion GJ. Causality in transcription and genome folding: Insights from X inactivation. Bioessays 2022; 44:e2200105. [PMID: 36028473 DOI: 10.1002/bies.202200105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 08/11/2022] [Accepted: 08/14/2022] [Indexed: 11/10/2022]
Abstract
The spatial organization of genomes is becoming increasingly understood. In mammals, where it is most investigated, this organization ties in with transcription, so an important research objective is to understand whether gene activity is a cause or a consequence of genome folding in space. In this regard, the phenomena of X-chromosome inactivation and reactivation open a unique window of investigation because of the singularities of the inactive X chromosome. Here we focus on the cause-consequence nexus between genome conformation and transcription and explain how recent results about the structural changes associated with inactivation and reactivation of the X chromosome shed light on this problem.
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Affiliation(s)
- Moritz Bauer
- Oncode Institute, Hubrecht Institute-KNAW and University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bernhard Payer
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Guillaume J Filion
- Dept. Biological Sciences, University of Toronto Scarborough, Toronto, ON, Canada
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3
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Gene regulation in time and space during X-chromosome inactivation. Nat Rev Mol Cell Biol 2022; 23:231-249. [PMID: 35013589 DOI: 10.1038/s41580-021-00438-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2021] [Indexed: 12/21/2022]
Abstract
X-chromosome inactivation (XCI) is the epigenetic mechanism that ensures X-linked dosage compensation between cells of females (XX karyotype) and males (XY). XCI is essential for female embryos to survive through development and requires the accurate spatiotemporal regulation of many different factors to achieve remarkable chromosome-wide gene silencing. As a result of XCI, the active and inactive X chromosomes are functionally and structurally different, with the inactive X chromosome undergoing a major conformational reorganization within the nucleus. In this Review, we discuss the multiple layers of genetic and epigenetic regulation that underlie initiation of XCI during development and then maintain it throughout life, in light of the most recent findings in this rapidly advancing field. We discuss exciting new insights into the regulation of X inactive-specific transcript (XIST), the trigger and master regulator of XCI, and into the mechanisms and dynamics that underlie the silencing of nearly all X-linked genes. Finally, given the increasing interest in understanding the impact of chromosome organization on gene regulation, we provide an overview of the factors that are thought to reshape the 3D structure of the inactive X chromosome and of the relevance of such structural changes for XCI establishment and maintenance.
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4
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Chromosome compartments on the inactive X guide TAD formation independently of transcription during X-reactivation. Nat Commun 2021; 12:3499. [PMID: 34108480 PMCID: PMC8190187 DOI: 10.1038/s41467-021-23610-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 05/10/2021] [Indexed: 12/21/2022] Open
Abstract
A hallmark of chromosome organization is the partition into transcriptionally active A and repressed B compartments, and into topologically associating domains (TADs). Both structures were regarded to be absent from the inactive mouse X chromosome, but to be re-established with transcriptional reactivation and chromatin opening during X-reactivation. Here, we combine a tailor-made mouse iPSC reprogramming system and high-resolution Hi-C to produce a time course combining gene reactivation, chromatin opening and chromosome topology during X-reactivation. Contrary to previous observations, we observe A/B-like compartments on the inactive X harbouring multiple subcompartments. While partial X-reactivation initiates within a compartment rich in X-inactivation escapees, it then occurs rapidly along the chromosome, concomitant with downregulation of Xist. Importantly, we find that TAD formation precedes transcription and initiates from Xist-poor compartments. Here, we show that TAD formation and transcriptional reactivation are causally independent during X-reactivation while establishing Xist as a common denominator.
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5
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Crippa M, Zhan Y, Tiana G. Effective model of loop extrusion predicts chromosomal domains. Phys Rev E 2020; 102:032414. [PMID: 33076010 DOI: 10.1103/physreve.102.032414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 09/03/2020] [Indexed: 11/07/2022]
Abstract
An active loop-extrusion mechanism is regarded as the main out-of-equilibrium mechanism responsible for the structuring of megabase-sized domains in chromosomes. We developed a model to study the dynamics of the chromosome fiber by solving the kinetic equations associated with the motion of the extruder. By averaging out the position of the extruder along the chain, we build an effective equilibrium model capable of reproducing experimental contact maps based solely on the positions of extrusion-blocking proteins. We assessed the quality of the effective model using numerical simulations of chromosomal segments and comparing the results with explicit-extruder models and experimental data.
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Affiliation(s)
- Martina Crippa
- Department of Physics, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy and Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
| | - Yinxiu Zhan
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Guido Tiana
- Department of Physics and Center for Complexity and Biosystems, Università degli Studi di Milano and INFN, via Celoria 16, 20133 Milano, Italy
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6
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Aeby E, Lee HG, Lee YW, Kriz A, del Rosario BC, Oh HJ, Boukhali M, Haas W, Lee JT. Decapping enzyme 1A breaks X-chromosome symmetry by controlling Tsix elongation and RNA turnover. Nat Cell Biol 2020; 22:1116-1129. [PMID: 32807903 DOI: 10.1038/s41556-020-0558-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/09/2020] [Indexed: 12/27/2022]
Abstract
How allelic asymmetry is generated remains a major unsolved problem in epigenetics. Here we model the problem using X-chromosome inactivation by developing "BioRBP", an enzymatic RNA-proteomic method that enables probing of low-abundance interactions and an allelic RNA-depletion and -tagging system. We identify messenger RNA-decapping enzyme 1A (DCP1A) as a key regulator of Tsix, a noncoding RNA implicated in allelic choice through X-chromosome pairing. DCP1A controls Tsix half-life and transcription elongation. Depleting DCP1A causes accumulation of X-X pairs and perturbs the transition to monoallelic Tsix expression required for Xist upregulation. While ablating DCP1A causes hyperpairing, forcing Tsix degradation resolves pairing and enables Xist upregulation. We link pairing to allelic partitioning of CCCTC-binding factor (CTCF) and show that tethering DCP1A to one Tsix allele is sufficient to drive monoallelic Xist expression. Thus, DCP1A flips a bistable switch for the mutually exclusive determination of active and inactive Xs.
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7
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Campbell MJ. Tales from topographic oceans: topologically associated domains and cancer. Endocr Relat Cancer 2019; 26:R611-R626. [PMID: 31505466 PMCID: PMC7664306 DOI: 10.1530/erc-19-0348] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 09/09/2019] [Indexed: 01/03/2023]
Abstract
The 3D organization of the genome within the cell nucleus has come into sharp focus over the last decade. This has largely arisen because of the application of genomic approaches that have revealed numerous levels of genomic and chromatin interactions, including topologically associated domains (TADs). The current review examines how these domains were identified, are organized, how their boundaries arise and are regulated, and how genes within TADs are coordinately regulated. There are many examples of the disruption to TAD structure in cancer and the altered regulation, structure and function of TADs are discussed in the context of hormone responsive cancers, including breast, prostate and ovarian cancer. Finally, some aspects of the statistical insight and computational skills required to interrogate TAD organization are considered and future directions discussed.
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Affiliation(s)
- Moray J Campbell
- Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University, Columbus, Ohio, USA
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8
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The bipartite TAD organization of the X-inactivation center ensures opposing developmental regulation of Tsix and Xist. Nat Genet 2019; 51:1024-1034. [PMID: 31133748 PMCID: PMC6551226 DOI: 10.1038/s41588-019-0412-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 04/04/2019] [Indexed: 01/08/2023]
Abstract
The mouse X-inactivation center (Xic) locus represents a powerful model for understanding the links between genome architecture and gene regulation, with the non-coding genes Xist and Tsix showing opposite developmental expression patterns while being organized as an overlapping sense/antisense unit. The Xic is organized into two topologically associating domains (TADs) but the role of this architecture in orchestrating cis-regulatory information remains elusive. To explore this, we generated genomic inversions that swap the Xist/Tsix transcriptional unit and place their promoters in each other’s TAD. We found that this led to a switch in their expression dynamics: Xist became precociously and ectopically up-regulated, both in male and female pluripotent cells, while Tsix expression aberrantly persisted during differentiation. The topological partitioning of the Xic is thus critical to ensure proper developmental timing of X inactivation. Our study illustrates how the genomic architecture of cis-regulatory landscapes can affect the regulation of mammalian developmental processes.
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9
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Del Rosario BC, Kriz AJ, Del Rosario AM, Anselmo A, Fry CJ, White FM, Sadreyev RI, Lee JT. Exploration of CTCF post-translation modifications uncovers Serine-224 phosphorylation by PLK1 at pericentric regions during the G2/M transition. eLife 2019; 8:e42341. [PMID: 30676316 PMCID: PMC6361588 DOI: 10.7554/elife.42341] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 01/23/2019] [Indexed: 01/05/2023] Open
Abstract
The zinc finger CCCTC-binding protein (CTCF) carries out many functions in the cell. Although previous studies sought to explain CTCF multivalency based on sequence composition of binding sites, few examined how CTCF post-translational modification (PTM) could contribute to function. Here, we performed CTCF mass spectrometry, identified a novel phosphorylation site at Serine 224 (Ser224-P), and demonstrate that phosphorylation is carried out by Polo-like kinase 1 (PLK1). CTCF Ser224-P is chromatin-associated, mapping to at least a subset of known CTCF sites. CTCF Ser224-P accumulates during the G2/M transition of the cell cycle and is enriched at pericentric regions. The phospho-obviation mutant, S224A, appeared normal. However, the phospho-mimic mutant, S224E, is detrimental to mouse embryonic stem cell colonies. While ploidy and chromatin architecture appear unaffected, S224E mutants differentially express hundreds of genes, including p53 and p21. We have thus identified a new CTCF PTM and provided evidence of biological function.
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Affiliation(s)
- Brian C Del Rosario
- Department of Molecular BiologyHoward Hughes Medical Institute, Massachusetts General HospitalBostonUnited States
- Department of GeneticsHarvard Medical SchoolBostonUnited States
| | - Andrea J Kriz
- Department of Molecular BiologyHoward Hughes Medical Institute, Massachusetts General HospitalBostonUnited States
- Department of GeneticsHarvard Medical SchoolBostonUnited States
| | - Amanda M Del Rosario
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeUnited States
| | - Anthony Anselmo
- Department of Molecular BiologyMassachusetts General HospitalBostonUnited States
| | | | - Forest M White
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeUnited States
| | - Ruslan I Sadreyev
- Department of Molecular BiologyMassachusetts General HospitalBostonUnited States
| | - Jeannie T Lee
- Department of Molecular BiologyHoward Hughes Medical Institute, Massachusetts General HospitalBostonUnited States
- Department of GeneticsHarvard Medical SchoolBostonUnited States
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10
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Foamy Virus Vector Carries a Strong Insulator in Its Long Terminal Repeat Which Reduces Its Genotoxic Potential. J Virol 2017; 92:JVI.01639-17. [PMID: 29046446 DOI: 10.1128/jvi.01639-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 09/29/2017] [Indexed: 12/11/2022] Open
Abstract
Strong viral enhancers in gammaretrovirus vectors have caused cellular proto-oncogene activation and leukemia, necessitating the use of cellular promoters in "enhancerless" self-inactivating integrating vectors. However, cellular promoters result in relatively low transgene expression, often leading to inadequate disease phenotype correction. Vectors derived from foamy virus, a nonpathogenic retrovirus, show higher preference for nongenic integrations than gammaretroviruses/lentiviruses and preferential integration near transcriptional start sites, like gammaretroviruses. We found that strong viral enhancers/promoters placed in foamy viral vectors caused extremely low immortalization of primary mouse hematopoietic stem/progenitor cells compared to analogous gammaretrovirus/lentivirus vectors carrying the same enhancers/promoters, an effect not explained solely by foamy virus' modest insertional site preference for nongenic regions compared to gammaretrovirus/lentivirus vectors. Using CRISPR/Cas9-mediated targeted insertion of analogous proviral sequences into the LMO2 gene and then measuring LMO2 expression, we demonstrate a sequence-specific effect of foamy virus, independent of insertional bias, contributing to reduced genotoxicity. We show that this effect is mediated by a 36-bp insulator located in the foamy virus long terminal repeat (LTR) that has high-affinity binding to the CCCTC-binding factor. Using our LMO2 activation assay, LMO2 expression was significantly increased when this insulator was removed from foamy virus and significantly reduced when the insulator was inserted into the lentiviral LTR. Our results elucidate a mechanism underlying the low genotoxicity of foamy virus, identify a novel insulator, and support the use of foamy virus as a vector for gene therapy, especially when strong enhancers/promoters are required.IMPORTANCE Understanding the genotoxic potential of viral vectors is important in designing safe and efficacious vectors for gene therapy. Self-inactivating vectors devoid of viral long-terminal-repeat enhancers have proven safe; however, transgene expression from cellular promoters is often insufficient for full phenotypic correction. Foamy virus is an attractive vector for gene therapy. We found foamy virus vectors to be remarkably less genotoxic, well below what was expected from their integration site preferences. We demonstrate that the foamy virus long terminal repeats contain an insulator element that binds CCCTC-binding factor and reduces its insertional genotoxicity. Our study elucidates a mechanism behind the low genotoxic potential of foamy virus, identifies a unique insulator, and supports the use of foamy virus as a vector for gene therapy.
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11
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Genetic Intersection of Tsix and Hedgehog Signaling during the Initiation of X-Chromosome Inactivation. Dev Cell 2017; 43:359-371.e6. [PMID: 29107559 DOI: 10.1016/j.devcel.2017.09.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 08/27/2017] [Accepted: 09/29/2017] [Indexed: 01/20/2023]
Abstract
X-chromosome inactivation (XCI) silences one X chromosome in the female mammal and is essential to peri-implantation development. XCI is thought to be cell autonomous, with all factors required being produced within each cell. Nevertheless, external cues may exist. Here, we search for such developmental signals by combining bioinformatic, biochemical, and genetic approaches. Using ex vivo and in vivo models, we identify the Hedgehog (HH) paracrine system as a candidate signaling cascade. HH signaling keeps XCI in check in pluripotent cells and is transduced by GLI transcription factors to binding sites in Tsix, the antisense repressor of XCI. GLI potentiates Tsix expression and impedes XCI. In vivo, mutating Indian Hedgehog results in a sex ratio bias against females, and the female lethality is rescued by a second-site mutation in Tsix. These data demonstrate a genetic and functional intersection between HH and XCI and support a role for intercellular signaling during XCI.
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12
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Abstract
Extensive 3D folding is required to package a genome into the tiny nuclear space, and this packaging must be compatible with proper gene expression. Thus, in the well-hierarchized nucleus, chromosomes occupy discrete territories and adopt specific 3D organizational structures that facilitate interactions between regulatory elements for gene expression. The mammalian X chromosome exemplifies this structure-function relationship. Recent studies have shown that, upon X-chromosome inactivation, active and inactive X chromosomes localize to different subnuclear positions and adopt distinct chromosomal architectures that reflect their activity states. Here, we review the roles of long non-coding RNAs, chromosomal organizational structures and the subnuclear localization of chromosomes as they relate to X-linked gene expression.
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13
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Furlan G, Rougeulle C. Function and evolution of the long noncoding RNA circuitry orchestrating X-chromosome inactivation in mammals. WILEY INTERDISCIPLINARY REVIEWS-RNA 2016; 7:702-22. [PMID: 27173581 DOI: 10.1002/wrna.1359] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 03/30/2016] [Accepted: 03/31/2016] [Indexed: 12/20/2022]
Abstract
X-chromosome inactivation (XCI) is a chromosome-wide regulatory process that ensures dosage compensation for X-linked genes in Theria. XCI is established during early embryogenesis and is developmentally regulated. Different XCI strategies exist in mammalian infraclasses and the regulation of this process varies also among closely related species. In Eutheria, initiation of XCI is orchestrated by a cis-acting locus, the X-inactivation center (Xic), which is particularly enriched in genes producing long noncoding RNAs (lncRNAs). Among these, Xist generates a master transcript that coats and propagates along the future inactive X-chromosome in cis, establishing X-chromosome wide transcriptional repression through interaction with several protein partners. Other lncRNAs also participate to the regulation of X-inactivation but the extent to which their function has been maintained in evolution is still poorly understood. In Metatheria, Xist is not conserved, but another, evolutionary independent lncRNA with similar properties, Rsx, has been identified, suggesting that lncRNA-mediated XCI represents an evolutionary advantage. Here, we review current knowledge on the interplay of X chromosome-encoded lncRNAs in ensuring proper establishment and maintenance of chromosome-wide silencing, and discuss the evolutionary implications of the emergence of species-specific lncRNAs in the control of XCI within Theria. WIREs RNA 2016, 7:702-722. doi: 10.1002/wrna.1359 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Giulia Furlan
- Sorbonne Paris Cité, Epigenetics and Cell Fate, UMR7216 CNRS, Université Paris Diderot, Paris, France
| | - Claire Rougeulle
- Sorbonne Paris Cité, Epigenetics and Cell Fate, UMR7216 CNRS, Université Paris Diderot, Paris, France
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14
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How Many Non-coding RNAs Does It Take to Compensate Male/Female Genetic Imbalance? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 886:33-49. [PMID: 26659486 DOI: 10.1007/978-94-017-7417-8_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Genetic sex determination in mammals relies on dimorphic sex chromosomes that confer phenotypic/physiologic differences between males and females. In this heterogametic system, X and Y chromosomes diverged from an ancestral pair of autosomes, creating a genetic disequilibrium between XX females and XY males. Dosage compensation mechanisms alleviate intrinsic gene dosage imbalance, leading to equal expression levels of most X-linked genes in the two sexes. In therian mammals, this is achieved through inactivation of one of the two X chromosomes in females. Failure to undergo X-chromosome inactivation (XCI) results in developmental arrest and death. Although fundamental for survival, a surprising loose conservation in the mechanisms to achieve XCI during development in therian lineage has been, and continues, to be uncovered. XCI involves the concerted action of non-coding RNAs (ncRNAs), including the well-known Xist RNA, and has thus become a classical paradigm to study the mode of action of this particular class of transcripts. In this chapter, we will describe the processes coping with sex chromosome genetic imbalance and how ncRNAs underlie dosage compensation mechanisms and influence male-female differences in mammals. Moreover, we will discuss how ncRNAs have been tinkered with during therian evolution to adapt XCI mechanistic to species-specific constraints.
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15
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Guo F, Jiao F, Song Z, Li S, Liu B, Yang H, Zhou Q, Li Z. Regulation of MALAT1 expression by TDP43 controls the migration and invasion of non-small cell lung cancer cells in vitro. Biochem Biophys Res Commun 2015; 465:293-8. [PMID: 26265046 DOI: 10.1016/j.bbrc.2015.08.027] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 08/06/2015] [Indexed: 11/17/2022]
Abstract
MALAT1 is a non-coding RNA overexpressed in non-small cell lung cancer (NSCLC). TDP-43 is a ubiquitously expressed, MALAT1-binding protein implicated in cancer development. We hypothesized that MALAT1 expression level is regulated in lung cancer by TDP-43. We analyzed their functions in cultured NSCLC cells. Downregulation of MALAT1 or TDP-43 expression by siRNA not only markedly suppressed NSCLC cell growth, as measured by the MTT assay in vitro cultured NSCLC cells (P < 0.05), but also noticeably impaired the migration and invasion of NSCLC cells, as analyzed by the migration and invasion assay. We also confirm that TDP-43 directly bound to MALAT1 RNA by a RNA immunoprecipitation (RIP) assay and by luciferase reporter activity assay. In a RT-PCR assay, silencing TDP-43 expression effectively decreased MALAT1 RNA transcript level. In contrast, TDP-43 overexpression markedly increased MALAT1 transcript level. In summary, these findings demonstrated that MALAT1 expression by regulation of TDP-43 controls cellular growth, migration, and invasion of NSCLCs.
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MESH Headings
- Base Sequence
- Binding Sites
- Carcinoma, Non-Small-Cell Lung/genetics
- Carcinoma, Non-Small-Cell Lung/metabolism
- Carcinoma, Non-Small-Cell Lung/pathology
- Cell Line, Tumor
- Cell Movement
- Cell Proliferation
- DNA-Binding Proteins/antagonists & inhibitors
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Gene Expression Regulation, Neoplastic
- Genes, Reporter
- Humans
- Luciferases/genetics
- Luciferases/metabolism
- Molecular Sequence Data
- Protein Binding
- RNA, Long Noncoding/antagonists & inhibitors
- RNA, Long Noncoding/genetics
- RNA, Long Noncoding/metabolism
- RNA, Messenger/antagonists & inhibitors
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Signal Transduction
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Affiliation(s)
- Fengjie Guo
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China
| | - Feng Jiao
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China
| | - Zuoqing Song
- Department of Lung Cancer Surgery, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China
| | - Shujun Li
- The Second Hospital, Hebei Medical University, 215 Heping West Road, Shijiazhuang 050000, Hebei, PR China
| | - Bin Liu
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China
| | - Hongwei Yang
- Geriatric Ward of Neurology, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China
| | - Qinghua Zhou
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China; Department of Lung Cancer Surgery, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China.
| | - Zhigang Li
- Tianjin Key Laboratory of Lung Cancer Metastasis and Tumor Microenvironment, Tianjin Lung Cancer Institute, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China; Department of Lung Cancer Surgery, Tianjin Medical University General Hospital, 154 Anshan Rd, Tianjin 300052, PR China.
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16
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Yue M, Charles Richard JL, Ogawa Y. Dynamic interplay and function of multiple noncoding genes governing X chromosome inactivation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:112-20. [PMID: 26260844 DOI: 10.1016/j.bbagrm.2015.07.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 07/07/2015] [Accepted: 07/14/2015] [Indexed: 12/17/2022]
Abstract
There is increasing evidence for the emergence of long noncoding RNAs (lncRNAs) as important components, especially in the regulation of gene expression. In the event of X chromosome inactivation, robust epigenetic marks are established in a long noncoding Xist RNA-dependent manner, giving rise to a distinct epigenetic landscape on the inactive X chromosome (Xi). The X inactivation center (Xic) is essential for induction of X chromosome inactivation and harbors two topologically associated domains (TADs) to regulate monoallelic Xist expression: one at the noncoding Xist gene and its upstream region, and the other at the antisense Tsix and its upstream region. The monoallelic expression of Xist is tightly regulated by these two functionally distinct TADs as well as their constituting lncRNAs and proteins. In this review, we summarize recent updates in our knowledge of lncRNAs found at the Xic and discuss their overall mechanisms of action. We also discuss our current understanding of the molecular mechanism behind Xist RNA-mediated induction of the repressive epigenetic landscape at the Xi. This article is part of a Special Issue entitled: Clues to long noncoding RNA taxonomy1, edited by Dr. Tetsuro Hirose and Dr. Shinichi Nakagawa.
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Affiliation(s)
- Minghui Yue
- Division of Reproductive Sciences, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
| | - John Lalith Charles Richard
- Division of Reproductive Sciences, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
| | - Yuya Ogawa
- Division of Reproductive Sciences, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
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17
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Abstract
Recent investigations on 3D chromatin folding revealed that the eukaryote genomes are both highly compartmentalized and extremely dynamic. This review presents the most recent advances in topological domains' organization of the eukaryote genomes and discusses the relationship to chromatin loop formation. CTCF protein appears as a central factor of these two organization levels having either a strong insulating role at TAD borders, or a weaker architectural role in chromatin loop formation. TAD borders directly impact on chromatin dynamics by restricting contacts within specific genomic portions thus confining chromatin loop formation within TADs. We discuss how sub-TAD chromatin dynamics, constrained into a recently described statistical helix conformation, can produce functional interactions by contact stabilization.
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Abstract
Female mammalian cells compensate dosage of X-linked gene expression through the inactivation of one of their two X chromosomes. X chromosome inactivation (XCI) in eutherians is dependent on the non-coding RNA Xist that is up-regulated from the future inactive X chromosome, coating it and recruiting factors involved in silencing and altering its chromatin state. Xist lies within the X-inactivation center (Xic), a region on the X that is required for XCI, and is regulated in cis by elements on the X chromosome and in trans by diffusible factors. In this review, we summarize the latest results in cis- and trans-regulation of the Xic. We discuss how the organization of the Xic in topologically associating domains is important for XCI (cis-regulation) and how proteins in the pluripotent state and upon development or differentiation of embryonic stem cells control proper inactivation of one X chromosome (trans-regulation).
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Massah S, Beischlag TV, Prefontaine GG. Epigenetic events regulating monoallelic gene expression. Crit Rev Biochem Mol Biol 2015; 50:337-58. [PMID: 26155735 DOI: 10.3109/10409238.2015.1064350] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In mammals, generally it is assumed that the genes inherited from each parent are expressed to similar levels. However, it is now apparent that in non-sex chromosomes, 6-10% of genes are selected for monoallelic expression. Monoallelic expression or allelic exclusion is established either in an imprinted (parent-of-origin) or a stochastic manner. The stochastic model explains random selection while the imprinted model describes parent-of-origin specific selection of alleles for expression. Allelic exclusion occurs during X chromosome inactivation, parent-of-origin expression of imprinted genes and stochastic monoallelic expression of cell surface molecules, clustered protocadherin (PCDH) genes. Mis-regulation or loss of allelic exclusion contributes to developmental diseases. Epigenetic mechanisms are fundamental players that determine this type of expression despite a homogenous genetic background. DNA methylation and histone modifications are two mediators of the epigenetic phenomena. The majority of DNA methylation is found on cytosines of the CpG dinucleotide in mammals. Several covalent modifications of histones change the electrostatic forces between DNA and histones modifying gene expression. Long-range chromatin interactions organize chromatin into transcriptionally permissive and prohibitive regions leading to simultaneous regulation of gene expression and repression. Non-coding RNAs (ncRNAs) are also players in regulating gene expression. Together, these epigenetic mechanisms fine-tune gene expression levels essential for normal development and survival. In this review, first we discuss what is known about monoallelic gene expression. Then, we focus on the molecular mechanisms that regulate expression of three monoallelically expressed gene classes: the X-linked genes, selected imprinted genes and PCDH genes.
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Affiliation(s)
- Shabnam Massah
- a The Faculty of Health Sciences , Simon Fraser University , Burnaby , BC , Canada
| | - Timothy V Beischlag
- a The Faculty of Health Sciences , Simon Fraser University , Burnaby , BC , Canada
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20
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Galupa R, Heard E. X-chromosome inactivation: new insights into cis and trans regulation. Curr Opin Genet Dev 2015; 31:57-66. [PMID: 26004255 DOI: 10.1016/j.gde.2015.04.002] [Citation(s) in RCA: 107] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 04/02/2015] [Indexed: 12/19/2022]
Abstract
X-chromosome inactivation (XCI) is a developmentally associated process that evolved in mammals to enable gene dosage compensation between XX and XY individuals. In placental mammals, it is triggered by the long noncoding RNA Xist, which is produced from a complex regulatory locus, the X-inactivation centre (Xic). Recent insights into the regulatory landscape of the Xic, including its partitioning into topological associating domains (TADs) and its genetic dissection, have important implications for the monoallelic regulation of Xist. Here, we present some of the latest studies on X inactivation with a special focus on the regulation of Xist, its various functions and the putative role of chromosome conformation in regulating the dynamics of this locus during development and differentiation.
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Affiliation(s)
- Rafael Galupa
- Mammalian Developmental Epigenetics Group, Institut Curie, PSL University, CNRS UMR3215, INSERM U934, 26, rue d'Ulm, 75005 Paris, France
| | - Edith Heard
- Mammalian Developmental Epigenetics Group, Institut Curie, PSL University, CNRS UMR3215, INSERM U934, 26, rue d'Ulm, 75005 Paris, France.
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21
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Kung JT, Kesner B, An JY, Ahn JY, Cifuentes-Rojas C, Colognori D, Jeon Y, Szanto A, del Rosario BC, Pinter SF, Erwin JA, Lee JT. Locus-specific targeting to the X chromosome revealed by the RNA interactome of CTCF. Mol Cell 2015; 57:361-75. [PMID: 25578877 PMCID: PMC4316200 DOI: 10.1016/j.molcel.2014.12.006] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 10/28/2014] [Accepted: 11/25/2014] [Indexed: 12/27/2022]
Abstract
CTCF is a master regulator that plays important roles in genome architecture and gene expression. How CTCF is recruited in a locus-specific manner is not fully understood. Evidence from epigenetic processes, such as X chromosome inactivation (XCI), indicates that CTCF associates functionally with RNA. Using genome-wide approaches to investigate the relationship between its RNA interactome and epigenomic landscape, here we report that CTCF binds thousands of transcripts in mouse embryonic stem cells, many in close proximity to CTCF's genomic binding sites. CTCF is a specific and high-affinity RNA-binding protein (Kd < 1 nM). During XCI, CTCF differentially binds the active and inactive X chromosomes and interacts directly with Tsix, Xite, and Xist RNAs. Tsix and Xite RNAs target CTCF to the X inactivation center, thereby inducing homologous X chromosome pairing. Our work elucidates one mechanism by which CTCF is recruited in a locus-specific manner and implicates CTCF-RNA interactions in long-range chromosomal interactions.
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Affiliation(s)
- Johnny T Kung
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Barry Kesner
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Jee Young An
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Janice Y Ahn
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138 USA
| | - Catherine Cifuentes-Rojas
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - David Colognori
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Yesu Jeon
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Attila Szanto
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Brian C del Rosario
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Stefan F Pinter
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Jennifer A Erwin
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA
| | - Jeannie T Lee
- Howard Hughes Medical Institute; Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114 USA; Department of Genetics, Harvard Medical School, Boston, MA 02115 USA; Department of Pathology, Massachusetts General Hospital, Boston, MA 02114 USA.
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22
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A prominent and conserved role for YY1 in Xist transcriptional activation. Nat Commun 2014; 5:4878. [PMID: 25209548 PMCID: PMC4172967 DOI: 10.1038/ncomms5878] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 08/01/2014] [Indexed: 01/21/2023] Open
Abstract
Accumulation of the non-coding RNA Xist on one X chromosome in female cells is a hallmark of X-chromosome inactivation in eutherians. Here, we uncovered an essential function for the ubiquitous autosomal transcription factor Yin-Yang 1 (YY1) in the transcriptional activation of Xist in both human and mouse. We show that loss of YY1 prevents Xist up-regulation during the initiation and maintenance of X-inactivation, and that YY1 binds directly the Xist 5′ region to trigger the activity of the Xist promoter. Binding of YY1 to the Xist 5′ region prior to X-chromosome inactivation competes with the Xist repressor REX1 while DNA methylation controls mono-allelic fixation of YY1 to Xist at the onset of X-chromosome inactivation. YY1 is thus the first autosomal activating factor involved in a fundamental and conserved pathway of Xist regulation that ensures the asymmetric transcriptional up-regulation of the master regulator of X-chromosome inactivation.
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23
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Payer B, Lee JT. Coupling of X-chromosome reactivation with the pluripotent stem cell state. RNA Biol 2014; 11:798-807. [PMID: 25137047 DOI: 10.4161/rna.29779] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
X-chromosome inactivation (XCI) in female mammals is a dramatic example of epigenetic gene regulation, which entails the silencing of an entire chromosome through a wide range of mechanisms involving noncoding RNAs, chromatin-modifications, and DNA-methylation. While XCI is associated with the differentiated cell state, it is reversed by X-chromosome reactivation (XCR) ex vivo in pluripotent stem cells and in vivo in the early mouse embryo and the germline. Critical in the regulation of XCI vs. XCR is the X-inactivation center, a multigene locus on the X-chromosome harboring several long noncoding RNA genes including, most prominently, Xist and Tsix. These genes, which sit at the top of the XCI hierarchy, are by themselves controlled by pluripotency factors, coupling XCR with the naïve pluripotent stem cell state. In this point-of-view article we review the latest findings regarding this intricate relationship between cell differentiation state and epigenetic control of the X-chromosome. In particular, we discuss the emerging picture of complex multifactorial regulatory mechanisms, ensuring both a fine-tuned and robust X-reactivation process.
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Affiliation(s)
- Bernhard Payer
- Howard Hughes Medical Institute; Department of Molecular Biology; Massachusetts General Hospital; Department of Genetics; Harvard Medical School; Boston, MA USA
| | - Jeannie T Lee
- Howard Hughes Medical Institute; Department of Molecular Biology; Massachusetts General Hospital; Department of Genetics; Harvard Medical School; Boston, MA USA
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24
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Krawczyk M, Emerson BM. p50-associated COX-2 extragenic RNA (PACER) activates COX-2 gene expression by occluding repressive NF-κB complexes. eLife 2014; 3:e01776. [PMID: 24843008 PMCID: PMC4017649 DOI: 10.7554/elife.01776] [Citation(s) in RCA: 232] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Deregulated expression of COX-2 has been causally linked to development, progression, and outcome of several types of human cancer. We describe a novel fundamental level of transcriptional control of COX-2 expression. Using primary human mammary epithelial cells and monocyte/macrophage cell lines, we show that the chromatin boundary/insulator factor CTCF establishes an open chromatin domain and induces expression of a long non-coding RNA within the upstream promoter region of COX-2. Upon induction of COX-2 expression, the lncRNA associates with p50, a repressive subunit of NF-κB, and occludes it from the COX-2 promoter, potentially facilitating interaction with activation-competent NF-κB p65/p50 dimers. This enables recruitment of the p300 histone acetyltransferase, a domain-wide increase in histone acetylation and assembly of RNA Polymerase II initiation complexes. Our findings reveal an unexpected mechanism of gene control by lncRNA-mediated repressor occlusion and identify the COX-2-lncRNA, PACER, as a new potential target for COX-2-modulation in inflammation and cancer. DOI:http://dx.doi.org/10.7554/eLife.01776.001 To produce a protein a cell must first transcribe the DNA in a gene to make a messenger RNA molecule, which is then translated to make the protein. However, cells also produce other types of RNA molecules which do not become proteins. MicroRNAs, for example, regulate the expression of genes as proteins, while the role of other RNA molecules called long non-coding RNAs (lncRNAs) is not well understood. Now Krawczyk and Emerson have found an lncRNA that controls a gene called COX-2 that is often implicated in breast, colon, prostate, and lung cancer. This RNA molecule, which is called PACER, originates near the start of the COX-2 gene, but it cannot be messenger RNA because it does not contain the instructions to make the COX-2 protein, and it is too long to be a microRNA. Further experiments showed that the newly discovered lncRNA activates the expression of the COX-2 gene. Krawczyk and Emerson found that PACER attracts enzymes that spotlight genes that need to be activated, thus increasing the transcription of these genes to make messenger RNA. Genes can also be switched on and off by various molecules binding to nearby DNA, and PACER encourages the activation of COX-2 by keeping away the molecules that might switch it off. In addition to shedding new light on the role of lncRNAs, these results suggest that PACER could be a suitable therapeutic target in cancers that involve the COX-2 gene. DOI:http://dx.doi.org/10.7554/eLife.01776.002
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Affiliation(s)
- Michal Krawczyk
- Regulatory Biology Laboratory, Salk Institute for Biological Studies, La Jolla, United States
| | - Beverly M Emerson
- Regulatory Biology Laboratory, Salk Institute for Biological Studies, La Jolla, United States
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25
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Wood AM, Garza-Gongora AG, Kosak ST. A Crowdsourced nucleus: understanding nuclear organization in terms of dynamically networked protein function. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1839:178-90. [PMID: 24412853 PMCID: PMC3954575 DOI: 10.1016/j.bbagrm.2014.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 12/30/2013] [Accepted: 01/02/2014] [Indexed: 01/14/2023]
Abstract
The spatial organization of the nucleus results in a compartmentalized structure that affects all aspects of nuclear function. This compartmentalization involves genome organization as well as the formation of nuclear bodies and plays a role in many functions, including gene regulation, genome stability, replication, and RNA processing. Here we review the recent findings associated with the spatial organization of the nucleus and reveal that a common theme for nuclear proteins is their ability to participate in a variety of functions and pathways. We consider this multiplicity of function in terms of Crowdsourcing, a recent phenomenon in the world of information technology, and suggest that this model provides a novel way to synthesize the many intersections between nuclear organization and function. This article is part of a Special Issue entitled: Chromatin and epigenetic regulation of animal development.
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Affiliation(s)
- Ashley M Wood
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Arturo G Garza-Gongora
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Steven T Kosak
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
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26
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Marshall AD, Bailey CG, Rasko JEJ. CTCF and BORIS in genome regulation and cancer. Curr Opin Genet Dev 2013; 24:8-15. [PMID: 24657531 DOI: 10.1016/j.gde.2013.10.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 10/18/2013] [Accepted: 10/19/2013] [Indexed: 10/25/2022]
Abstract
CTCF plays a vital role in chromatin structure and function. CTCF is ubiquitously expressed and plays diverse roles in gene regulation, imprinting, insulation, intra/interchromosomal interactions, nuclear compartmentalisation, and alternative splicing. CTCF has a single paralogue, the testes-specific CTCF-like gene (CTCFL)/BORIS. CTCF and BORIS can be deregulated in cancer. The tumour suppressor gene CTCF can be mutated or deleted in cancer, or CTCF DNA binding can be altered by epigenetic changes. BORIS is aberrantly expressed frequently in cancer, leading some to propose a pro-tumourigenic role for BORIS. However, BORIS can inhibit cell proliferation, and is mutated in cancer similarly to CTCF suggesting BORIS activation in cancer may be due to global genetic or epigenetic changes typical of malignant transformation.
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Affiliation(s)
- Amy D Marshall
- Gene and Stem Cell Therapy Program, Centenary Institute, Missenden Road, Camperdown 2050, NSW, Australia; Sydney Medical School, University of Sydney, Sydney 2006, NSW, Australia
| | - Charles G Bailey
- Gene and Stem Cell Therapy Program, Centenary Institute, Missenden Road, Camperdown 2050, NSW, Australia; Sydney Medical School, University of Sydney, Sydney 2006, NSW, Australia
| | - John E J Rasko
- Gene and Stem Cell Therapy Program, Centenary Institute, Missenden Road, Camperdown 2050, NSW, Australia; Sydney Medical School, University of Sydney, Sydney 2006, NSW, Australia; Cell and Molecular Therapies, Royal Prince Alfred Hospital, Camperdown 2050, NSW, Australia.
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27
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Jpx RNA activates Xist by evicting CTCF. Cell 2013; 153:1537-51. [PMID: 23791181 DOI: 10.1016/j.cell.2013.05.028] [Citation(s) in RCA: 231] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 03/05/2013] [Accepted: 05/05/2013] [Indexed: 11/21/2022]
Abstract
In mammals, dosage compensation between XX and XY individuals occurs through X chromosome inactivation (XCI). The noncoding Xist RNA is expressed and initiates XCI only when more than one X chromosome is present. Current models invoke a dependency on the X-to-autosome ratio (X:A), but molecular factors remain poorly defined. Here, we demonstrate that molecular titration between an X-encoded RNA and an autosomally encoded protein dictates Xist induction. In pre-XCI cells, CTCF protein represses Xist transcription. At the onset of XCI, Jpx RNA is upregulated, binds CTCF, and extricates CTCF from one Xist allele. We demonstrate that CTCF is an RNA-binding protein and is titrated away from the Xist promoter by Jpx RNA. Thus, Jpx activates Xist by evicting CTCF. The functional antagonism via molecular titration reveals a role for long noncoding RNA in epigenetic regulation.
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28
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Phillips-Cremins JE, Corces VG. Chromatin insulators: linking genome organization to cellular function. Mol Cell 2013; 50:461-74. [PMID: 23706817 DOI: 10.1016/j.molcel.2013.04.018] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A growing body of evidence suggests that insulators have a primary role in orchestrating the topological arrangement of higher-order chromatin architecture. Insulator-mediated long-range interactions can influence the epigenetic status of the genome and, in certain contexts, may have important effects on gene expression. Here we discuss higher-order chromatin organization as a unifying mechanism for diverse insulator actions across the genome.
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29
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Merkenschlager M, Odom DT. CTCF and cohesin: linking gene regulatory elements with their targets. Cell 2013; 152:1285-97. [PMID: 23498937 DOI: 10.1016/j.cell.2013.02.029] [Citation(s) in RCA: 265] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 02/11/2013] [Accepted: 02/12/2013] [Indexed: 12/11/2022]
Abstract
Current epigenomics approaches have facilitated the genome-wide identification of regulatory elements based on chromatin features and transcriptional regulator binding and have begun to map long-range interactions between regulatory elements and their targets. Here, we focus on the emerging roles of CTCF and the cohesin in coordinating long-range interactions between regulatory elements. We discuss how species-specific transposable elements may influence such interactions by remodeling the CTCF binding repertoire and suggest that cohesin's association with enhancers, promoters, and sites defined by CTCF binding has the potential to form developmentally regulated networks of long-range interactions that reflect and promote cell-type-specific transcriptional programs.
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Affiliation(s)
- Matthias Merkenschlager
- Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College London, Du Cane Road, London W12 0NN, UK.
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30
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Lipovich L, Tarca AL, Cai J, Jia H, Chugani HT, Sterner KN, Grossman LI, Uddin M, Hof PR, Sherwood CC, Kuzawa CW, Goodman M, Wildman DE. Developmental changes in the transcriptome of human cerebral cortex tissue: long noncoding RNA transcripts. ACTA ACUST UNITED AC 2013; 24:1451-9. [PMID: 23377288 DOI: 10.1093/cercor/bhs414] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The human neocortex is characterized by protracted developmental intervals of synaptogenesis and myelination, which allow for an extended period of learning. The molecular basis of these and other postnatal developmental changes in the human cerebral cortex remain incompletely understood. Recently, a new large class of mammalian genes, encoding nonmessenger, long nonprotein-coding ribonucleic acid (lncRNA) molecules has been discovered. Although their function remains uncertain, numerous lncRNAs have primate-specific sequences and/or show evidence of rapid, lineage-specific evolution, making them potentially relevant to the evolution of unique human neural properties. To examine the hypothesis that lncRNA expression varies with age, potentially paralleling known developmental trends in synaptogenesis, myelination, and energetics, we quantified levels of nearly 6000 lncRNAs in 36 surgically resected human neocortical samples (primarily derived from temporal cortex) spanning infancy to adulthood. Our analysis identified 8 lncRNA genes with distinct developmental expression patterns. These lncRNA genes contained anthropoid-specific exons, as well as splice sites and polyadenylation signals that resided in primate-specific sequences. To our knowledge, our study is the first to describe developmental expression profiles of lncRNA in surgically resected in vivo human brain tissue. Future analysis of the functional relevance of these transcripts to neural development and energy metabolism is warranted.
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31
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Abstract
A variety of important cellular processes require, for functional purposes, the colocalization of multiple DNA loci at specific time points. In most cases, the physical mechanisms responsible for bringing them in close proximity are still elusive. Here we show that the interaction of DNA loci with a concentration of diffusing molecular factors can induce spontaneously their colocalization, through a mechanism based on a thermodynamic phase transition. We consider up to four DNA loci and different valencies for diffusing molecular factors. In particular, our analysis illustrates that a variety of nontrivial stable spatial configurations is allowed in the system, depending on the details of the molecular factor/DNA binding-sites interaction. Finally, we discuss as a case study an application of our model to the pairing of X chromosome at X inactivation, one of the best-known examples of DNA colocalization. We also speculate on the possible links between X colocalization and inactivation.
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32
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Singh P, Lee DH, Szabó PE. More than insulator: multiple roles of CTCF at the H19-Igf2 imprinted domain. Front Genet 2012; 3:214. [PMID: 23087708 PMCID: PMC3471092 DOI: 10.3389/fgene.2012.00214] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 09/27/2012] [Indexed: 12/28/2022] Open
Abstract
CTCF (CCCTC-binding factor)-mediated insulation at the H19-Insulin-like growth factor 2 (Igf2) imprinted domain is a classic example for imprinted gene regulation. DNA methylation difference in the imprinting control region (ICR) is inherited from the gametes and subsequently determines parental allele-specific enhancer blocking and imprinted expression in the soma. Recent genetic studies showed that proper monoallelic enhancer blocking at the H19-Igf2 ICR is critical for development. Strict biallelic insulation at this locus causes perinatal lethality, whereas leaky biallelic insulation results in smaller size but no lethality. Apart from enhancer blocking, CTCF is also the master organizer of chromatin composition in the maternal allele along this imprinted domain, affecting not only histone tail covalent modifications but also those in the histone core. Additionally, CTCF binding in the soma protects the maternal allele from de novo DNA methylation. CTCF binding is not involved in the establishment of the gametic marks at the ICR, but it slightly delays de novo methylation in the maternally inherited ICR allele in prospermatogonia. This review focuses on the developmental and epigenetic consequences of CTCF binding at the H19-Igf2 ICR.
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Affiliation(s)
- Purnima Singh
- Department of Molecular and Cellular Biology, Beckman Research Institute Duarte, CA, USA
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33
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Son J, Min NY, Choi JH, Ko YJ, Liang W, Rhee S, Lee KH. Direct evidence of allele-specific binding of CTCF and MeCP2 to Tsix in a HPRT-deficient female F₁ hybrid mouse cell line. Cytogenet Genome Res 2012; 138:11-8. [PMID: 22889989 DOI: 10.1159/000341503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2012] [Indexed: 11/19/2022] Open
Abstract
Mammalian dosage compensation requires silencing of one of the two X chromosomes in females and is controlled by the X inactivation center (Xic). Xic contains many of the regulatory elements for the mutual interplay of X-inactive specific transcript (Xist) and Tsix, the antisense counterpart of Xist. The regulatory elements control X chromosome inactivation (XCI) via the formation of DNA-DNA and DNA-protein complexes with cis- and trans-acting factors. However, the process-dependent regulation of Xist/Tsix by these elements in each XCI process remains largely unknown. In this study, a 6-thioguanine-resistant female F(1) hybrid mouse cell line (designated HOBMSKI2) was constructed from a cross between a female HPRT-deficient transgenic mouse (designated BM3) and a male wild type Mus spretus mouse (designated MS), which enabled the direct discrimination of both allele-specific expression of X-linked genes and allele-specific binding of proteins associated with XCI due to DNA polymorphisms between BM3 and MS. Using this cell line, we found that Tsix on the active X chromosome (Xa) was not expressed in somatic cells despite the fact that CTCF, which ensures Tsix expression in embryonic stem cells, was still bound to the 5' end of Tsix on Xa, implying that CTCF may function differently during each XCI process and its trans-activating activity for Tsix expression may be lost in the maintenance process. In addition, the monoallelic expression of Tsix on Xa was inhibited by epigenetic modification of the chromatin in the maintenance process, which was mediated by protein complexes recruited by MeCP2. The results indicate the value of HOBMSKI2 in directly detecting the allele-specific binding of CTCF and MeCP2 to the 5' end of Tsix. The HOBMSKI2 mouse line is a versatile and useful resource for studying the molecular mechanism of the XCI process.
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Affiliation(s)
- J Son
- School of Life Sciences, College of Natural Science, Chung-Ang University, Seoul, Republic of Korea
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34
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Nora EP, Lajoie BR, Schulz EG, Giorgetti L, Okamoto I, Servant N, Piolot T, van Berkum NL, Meisig J, Sedat J, Gribnau J, Barillot E, Blüthgen N, Dekker J, Heard E. Spatial partitioning of the regulatory landscape of the X-inactivation centre. Nature 2012; 485:381-5. [PMID: 22495304 DOI: 10.1038/nature11049] [Citation(s) in RCA: 2002] [Impact Index Per Article: 166.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 03/22/2012] [Indexed: 12/21/2022]
Abstract
In eukaryotes transcriptional regulation often involves multiple long-range elements and is influenced by the genomic environment. A prime example of this concerns the mouse X-inactivation centre (Xic), which orchestrates the initiation of X-chromosome inactivation (XCI) by controlling the expression of the non-protein-coding Xist transcript. The extent of Xic sequences required for the proper regulation of Xist remains unknown. Here we use chromosome conformation capture carbon-copy (5C) and super-resolution microscopy to analyse the spatial organization of a 4.5-megabases (Mb) region including Xist. We discover a series of discrete 200-kilobase to 1 Mb topologically associating domains (TADs), present both before and after cell differentiation and on the active and inactive X. TADs align with, but do not rely on, several domain-wide features of the epigenome, such as H3K27me3 or H3K9me2 blocks and lamina-associated domains. TADs also align with coordinately regulated gene clusters. Disruption of a TAD boundary causes ectopic chromosomal contacts and long-range transcriptional misregulation. The Xist/Tsix sense/antisense unit illustrates how TADs enable the spatial segregation of oppositely regulated chromosomal neighbourhoods, with the respective promoters of Xist and Tsix lying in adjacent TADs, each containing their known positive regulators. We identify a novel distal regulatory region of Tsix within its TAD, which produces a long intervening RNA, Linx. In addition to uncovering a new principle of cis-regulatory architecture of mammalian chromosomes, our study sets the stage for the full genetic dissection of the X-inactivation centre.
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Jeon Y, Sarma K, Lee JT. New and Xisting regulatory mechanisms of X chromosome inactivation. Curr Opin Genet Dev 2012; 22:62-71. [PMID: 22424802 PMCID: PMC3361064 DOI: 10.1016/j.gde.2012.02.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 02/07/2012] [Indexed: 01/30/2023]
Abstract
Equalization of X linked gene expression is necessary in mammalian cells due to the presence of two X chromosomes in females and one in males. To achieve this, all female cells inactivate one of the two X chromosomes during development. This process, termed X chromosome inactivation (XCI), is a quintessential epigenetic phenomenon and involves a complex interplay between noncoding RNAs and protein factors. Progress in this area of study has consequently resulted in new approaches to study epigenetics and regulatory RNA function. Here we will discuss recent developments in the field that have advanced our understanding of XCI and its regulatory mechanisms.
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Affiliation(s)
- Yesu Jeon
- Howard Hughes Medical Institute, Dept. of Molecular Biology, Massachusetts General Hospital, Dept. of Genetics, Harvard Medical School, Boston, MA 02114, USA
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Gribnau J, Grootegoed JA. Origin and evolution of X chromosome inactivation. Curr Opin Cell Biol 2012; 24:397-404. [PMID: 22425180 DOI: 10.1016/j.ceb.2012.02.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 02/17/2012] [Accepted: 02/17/2012] [Indexed: 10/28/2022]
Abstract
Evolution of the mammalian sex chromosomes heavily impacts on the expression of X-encoded genes, both in marsupials and placental mammals. The loss of genes from the Y chromosome forced a two-fold upregulation of dose sensitive X-linked homologues. As a corollary, female cells would experience a lethal dose of X-linked genes, if this upregulation was not counteracted by evolution of X chromosome inactivation (XCI) that allows for only one active X chromosome per diploid genome. Marsupials rely on imprinted XCI, which inactivates always the paternally inherited X chromosome. In placental mammals, random XCI (rXCI) is the predominant form, inactivating either the maternal or paternal X. In this review, we discuss recent new insights in the regulation of XCI. Based on these findings, we propose an X inactivation center (Xic), composed of a cis-Xic and trans-Xic that encompass all elements and factors acting to control rXCI either in cis or in trans. We also highlight that XCI may have evolved from a very small nucleation site on the X chromosome in the vicinity of the Sox3 gene. Finally, we discuss the possible evolutionary road maps that resulted in imprinted XCI and rXCI as observed in present day mammals.
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Affiliation(s)
- Joost Gribnau
- Department of Reproduction and Development, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
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Herold M, Bartkuhn M, Renkawitz R. CTCF: insights into insulator function during development. Development 2012; 139:1045-57. [PMID: 22354838 DOI: 10.1242/dev.065268] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
The genome of higher eukaryotes exhibits a patchwork of inactive and active genes. The nuclear protein CCCTC-binding factor (CTCF) when bound to insulator sequences can prevent undesirable crosstalk between active and inactive genomic regions, and it can also shield particular genes from enhancer function, a role that has many applications in development. Exciting recent work has demonstrated roles for CTCF in, for example, embryonic, neuronal and haematopoietic development. Here, we discuss the underlying mechanisms of developmentally regulated CTCF-dependent transcription in relation to model genes, and highlight genome-wide results indicating that CTCF might play a master role in regulating both activating and repressive transcription events at sites throughout the genome.
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Affiliation(s)
- Martin Herold
- Institut für Genetik, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58-62, 35392 Giessen, Germany
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