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Peggion C, Massimino ML, Pereira D, Granuzzo S, Righetto F, Bortolotto R, Agostini J, Sartori G, Bertoli A, Lopreiato R. Structural Integrity of Nucleolin Is Required to Suppress TDP-43-Mediated Cytotoxicity in Yeast and Human Cell Models. Int J Mol Sci 2023; 24:17466. [PMID: 38139294 PMCID: PMC10744044 DOI: 10.3390/ijms242417466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 11/28/2023] [Accepted: 12/09/2023] [Indexed: 12/24/2023] Open
Abstract
The Transactivating response (TAR) element DNA-binding of 43 kDa (TDP-43) is mainly implicated in the regulation of gene expression, playing multiple roles in RNA metabolism. Pathologically, it is implicated in amyotrophic lateral sclerosis and in a class of neurodegenerative diseases broadly going under the name of frontotemporal lobar degeneration (FTLD). A common hallmark of most forms of such diseases is the presence of TDP-43 insoluble inclusions in the cell cytosol. The molecular mechanisms of TDP-43-related cell toxicity are still unclear, and the contribution to cell damage from either loss of normal TDP-43 function or acquired toxic properties of protein aggregates is yet to be established. Here, we investigate the effects on cell viability of FTLD-related TDP-43 mutations in both yeast and mammalian cell models. Moreover, we focus on nucleolin (NCL) gene, recently identified as a genetic suppressor of TDP-43 toxicity, through a thorough structure/function characterization aimed at understanding the role of NCL domains in rescuing TDP-43-induced cytotoxicity. Using functional and biochemical assays, our data demonstrate that the N-terminus of NCL is necessary, but not sufficient, to exert its antagonizing effects on TDP-43, and further support the relevance of the DNA/RNA binding central region of the protein. Concurrently, data suggest the importance of the NCL nuclear localization for TDP-43 trafficking, possibly related to both TDP-43 physiology and toxicity.
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Affiliation(s)
- Caterina Peggion
- Department of Biology, University of Padova, 35131 Padova, Italy
| | | | - Daniel Pereira
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
- Department of Bioengineering, iBB—Institute for Bioengineering and Biosciences, Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal
| | - Sara Granuzzo
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Francesca Righetto
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Raissa Bortolotto
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Jessica Agostini
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Geppo Sartori
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Alessandro Bertoli
- Neuroscience Institute, Consiglio Nazionale Delle Ricerche, 35131 Padova, Italy
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
- Padova Neuroscience Center, University of Padova, 35131 Padova, Italy
| | - Raffaele Lopreiato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
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2
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Dash S, Lamb MC, Lange JJ, McKinney MC, Tsuchiya D, Guo F, Zhao X, Corbin TJ, Kirkman M, Delventhal K, Moore EL, McKinney S, Shiang R, Trainor PA. rRNA transcription is integral to phase separation and maintenance of nucleolar structure. PLoS Genet 2023; 19:e1010854. [PMID: 37639467 PMCID: PMC10513380 DOI: 10.1371/journal.pgen.1010854] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 09/21/2023] [Accepted: 07/03/2023] [Indexed: 08/31/2023] Open
Abstract
Transcription of ribosomal RNA (rRNA) by RNA Polymerase (Pol) I in the nucleolus is necessary for ribosome biogenesis, which is intimately tied to cell growth and proliferation. Perturbation of ribosome biogenesis results in tissue specific disorders termed ribosomopathies in association with alterations in nucleolar structure. However, how rRNA transcription and ribosome biogenesis regulate nucleolar structure during normal development and in the pathogenesis of disease remains poorly understood. Here we show that homozygous null mutations in Pol I subunits required for rRNA transcription and ribosome biogenesis lead to preimplantation lethality. Moreover, we discovered that Polr1a-/-, Polr1b-/-, Polr1c-/- and Polr1d-/- mutants exhibit defects in the structure of their nucleoli, as evidenced by a decrease in number of nucleolar precursor bodies and a concomitant increase in nucleolar volume, which results in a single condensed nucleolus. Pharmacological inhibition of Pol I in preimplantation and midgestation embryos, as well as in hiPSCs, similarly results in a single condensed nucleolus or fragmented nucleoli. We find that when Pol I function and rRNA transcription is inhibited, the viscosity of the granular compartment of the nucleolus increases, which disrupts its phase separation properties, leading to a single condensed nucleolus. However, if a cell progresses through mitosis, the absence of rRNA transcription prevents reassembly of the nucleolus and manifests as fragmented nucleoli. Taken together, our data suggests that Pol I function and rRNA transcription are required for maintaining nucleolar structure and integrity during development and in the pathogenesis of disease.
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Affiliation(s)
- Soma Dash
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Maureen C. Lamb
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Jeffrey J. Lange
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Mary C. McKinney
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Dai Tsuchiya
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Fengli Guo
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Xia Zhao
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Timothy J. Corbin
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - MaryEllen Kirkman
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Kym Delventhal
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Emma L. Moore
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Sean McKinney
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Rita Shiang
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Paul A. Trainor
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
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3
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Muñoz-Díaz E, Sáez-Vásquez J. Nuclear dynamics: Formation of bodies and trafficking in plant nuclei. FRONTIERS IN PLANT SCIENCE 2022; 13:984163. [PMID: 36082296 PMCID: PMC9445803 DOI: 10.3389/fpls.2022.984163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/04/2022] [Indexed: 06/01/2023]
Abstract
The existence of the nucleus distinguishes prokaryotes and eukaryotes. Apart from containing most of the genetic material, the nucleus possesses several nuclear bodies composed of protein and RNA molecules. The nucleus is separated from the cytoplasm by a double membrane, regulating the trafficking of molecules in- and outwards. Here, we investigate the composition and function of the different plant nuclear bodies and molecular clues involved in nuclear trafficking. The behavior of the nucleolus, Cajal bodies, dicing bodies, nuclear speckles, cyclophilin-containing bodies, photobodies and DNA damage foci is analyzed in response to different abiotic stresses. Furthermore, we research the literature to collect the different protein localization signals that rule nucleocytoplasmic trafficking. These signals include the different types of nuclear localization signals (NLSs) for nuclear import, and the nuclear export signals (NESs) for nuclear export. In contrast to these unidirectional-movement signals, the existence of nucleocytoplasmic shuttling signals (NSSs) allows bidirectional movement through the nuclear envelope. Likewise, nucleolar signals are also described, which mainly include the nucleolar localization signals (NoLSs) controlling nucleolar import. In contrast, few examples of nucleolar export signals, called nucleoplasmic localization signals (NpLSs) or nucleolar export signals (NoESs), have been reported. The existence of consensus sequences for these localization signals led to the generation of prediction tools, allowing the detection of these signals from an amino acid sequence. Additionally, the effect of high temperatures as well as different post-translational modifications in nuclear and nucleolar import and export is discussed.
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Affiliation(s)
- Eduardo Muñoz-Díaz
- Centre National de la Recherche Scientifique (CNRS), Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
- Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
| | - Julio Sáez-Vásquez
- Centre National de la Recherche Scientifique (CNRS), Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
- Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, Perpignan, France
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4
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Sheikh TI, Harripaul R, Vasli N, Ghadami M, Santangelo SL, Ayub M, Sasanfar R, Vincent JB. Heterozygous De Novo Truncating Mutation of Nucleolin in an ASD Individual Disrupts Its Nucleolar Localization. Genes (Basel) 2021; 13:51. [PMID: 35052391 PMCID: PMC8774667 DOI: 10.3390/genes13010051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 12/10/2021] [Accepted: 12/14/2021] [Indexed: 11/16/2022] Open
Abstract
Nucleolin (NCL/C23; OMIM: 164035) is a major nucleolar protein that plays a critical role in multiple processes, including ribosome assembly and maturation, chromatin decondensation, and pre-rRNA transcription. Due to its diverse functions, nucleolin has frequently been implicated in pathological processes, including cancer and viral infection. We recently identified a de novo frameshifting indel mutation of NCL, p.Gly664Glufs*70, through whole-exome sequencing of autism spectrum disorder trios. Through the transfection of constructs encoding either a wild-type human nucleolin or a mutant nucleolin with the same C-terminal sequence predicted for the autism proband, and by using co-localization with the nucleophosmin (NPM; B23) protein, we have shown that the nucleolin mutation leads to mislocalization of the NCL protein from the nucleolus to the nucleoplasm. Moreover, a construct with a nonsense mutation at the same residue, p.Gly664*, shows a very similar effect on the location of the NCL protein, thus confirming the presence of a predicted nucleolar location signal in this region of the NCL protein. Real-time fluorescence recovery experiments show significant changes in the kinetics and mobility of mutant NCL protein in the nucleoplasm of HEK293Tcells. Several other studies also report de novoNCL mutations in ASD or neurodevelopmental disorders. The altered mislocalization and dynamics of mutant NCL (p.G664Glufs*70/p.G664*) may have relevance to the etiopathlogy of NCL-related ASD and other neurodevelopmental phenotypes.
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Affiliation(s)
- Taimoor I. Sheikh
- Molecular Neuropsychiatry & Development (MiND) Lab, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (T.I.S.); (R.H.)
| | - Ricardo Harripaul
- Molecular Neuropsychiatry & Development (MiND) Lab, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (T.I.S.); (R.H.)
- Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Nasim Vasli
- Department of Pediatric Laboratory Medicine, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada;
| | - Majid Ghadami
- Department of Educational Sciences, Farhangian University, Tehran 19989-63341, Iran;
| | - Susan L. Santangelo
- Center for Psychiatric Research, Maine Medical Center Research Institute, Portland, ME 04101, USA;
- Department of Psychiatry, Tufts University School of Medicine, Boston, MA 02110, USA
- Department of Psychiatry, Maine Medical Center, Portland, ME 04102, USA
| | - Muhammad Ayub
- Department of Psychiatry, Queen’s University, Kingston, ON K7L 7X3, Canada;
- Department of Academic Psychiatry, University College London, London WC1E 6BT, UK
| | - Roksana Sasanfar
- Department of Psychiatry, Harvard Medical School, Boston, MA 02215, USA;
- Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - John B. Vincent
- Molecular Neuropsychiatry & Development (MiND) Lab, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON M5T 1R8, Canada; (T.I.S.); (R.H.)
- Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON M5T 1R8, Canada
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5
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Doron‐Mandel E, Koppel I, Abraham O, Rishal I, Smith TP, Buchanan CN, Sahoo PK, Kadlec J, Oses‐Prieto JA, Kawaguchi R, Alber S, Zahavi EE, Di Matteo P, Di Pizio A, Song D, Okladnikov N, Gordon D, Ben‐Dor S, Haffner‐Krausz R, Coppola G, Burlingame AL, Jungwirth P, Twiss JL, Fainzilber M. The glycine arginine-rich domain of the RNA-binding protein nucleolin regulates its subcellular localization. EMBO J 2021; 40:e107158. [PMID: 34515347 PMCID: PMC8521312 DOI: 10.15252/embj.2020107158] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 07/29/2021] [Accepted: 08/03/2021] [Indexed: 12/31/2022] Open
Abstract
Nucleolin is a multifunctional RNA Binding Protein (RBP) with diverse subcellular localizations, including the nucleolus in all eukaryotic cells, the plasma membrane in tumor cells, and the axon in neurons. Here we show that the glycine arginine rich (GAR) domain of nucleolin drives subcellular localization via protein-protein interactions with a kinesin light chain. In addition, GAR sequences mediate plasma membrane interactions of nucleolin. Both these modalities are in addition to the already reported involvement of the GAR domain in liquid-liquid phase separation in the nucleolus. Nucleolin transport to axons requires the GAR domain, and heterozygous GAR deletion mice reveal reduced axonal localization of nucleolin cargo mRNAs and enhanced sensory neuron growth. Thus, the GAR domain governs axonal transport of a growth controlling RNA-RBP complex in neurons, and is a versatile localization determinant for different subcellular compartments. Localization determination by GAR domains may explain why GAR mutants in diverse RBPs are associated with neurodegenerative disease.
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Affiliation(s)
- Ella Doron‐Mandel
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
- Present address:
Department of Biological SciencesColumbia UniversityNew YorkNYUSA
| | - Indrek Koppel
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
- Present address:
Department of Chemistry and BiotechnologyTallinn University of TechnologyTallinnEstonia
| | - Ofri Abraham
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Ida Rishal
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Terika P Smith
- Department of Biological SciencesUniversity of South CarolinaColumbiaSCUSA
| | | | - Pabitra K Sahoo
- Department of Biological SciencesUniversity of South CarolinaColumbiaSCUSA
| | - Jan Kadlec
- Institute of Organic Chemistry and BiochemistryCzech Academy of SciencesPragueCzech Republic
| | - Juan A Oses‐Prieto
- Department of Pharmaceutical ChemistryUniversity of California San FranciscoSan FranciscoCAUSA
| | - Riki Kawaguchi
- Departments of Psychiatry and NeurologySemel Institute for Neuroscience and Human BehaviorUniversity of California Los AngelesLos AngelesCAUSA
| | - Stefanie Alber
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Eitan Erez Zahavi
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Pierluigi Di Matteo
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Agostina Di Pizio
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Didi‐Andreas Song
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Nataliya Okladnikov
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Dalia Gordon
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
| | - Shifra Ben‐Dor
- Bioinformatics UnitLife Sciences Core FacilitiesWeizmann Institute of ScienceRehovotIsrael
| | | | - Giovanni Coppola
- Departments of Psychiatry and NeurologySemel Institute for Neuroscience and Human BehaviorUniversity of California Los AngelesLos AngelesCAUSA
| | - Alma L Burlingame
- Department of Pharmaceutical ChemistryUniversity of California San FranciscoSan FranciscoCAUSA
| | - Pavel Jungwirth
- Institute of Organic Chemistry and BiochemistryCzech Academy of SciencesPragueCzech Republic
| | - Jeffery L Twiss
- Department of Biological SciencesUniversity of South CarolinaColumbiaSCUSA
| | - Mike Fainzilber
- Departments of Biomolecular Sciences and Molecular NeuroscienceWeizmann Institute of ScienceRehovotIsrael
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6
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Live-Cell Imaging and Analysis of Nuclear Body Mobility. Methods Mol Biol 2020. [PMID: 32681479 DOI: 10.1007/978-1-0716-0763-3_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The cell nucleus contains different domains and nuclear bodies, whose position relative to each other inside the nucleus can vary depending on the physiological state of the cell. Changes in the three-dimensional organization are associated with the mobility of individual components of the nucleus. In this chapter, we present a protocol for live-cell imaging and analysis of nuclear body mobility. Unlike other similar protocols, our image analysis pipeline includes non-rigid compensation for global motion of the nucleus before particle tracking and trajectory analysis, leading to precise detection of intranuclear movements. The protocol described can be easily adapted to work with most cell lines and nuclear bodies.
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7
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Arifulin EA, Sorokin DV, Tvorogova AV, Kurnaeva MA, Musinova YR, Zhironkina OA, Golyshev SA, Abramchuk SS, Vassetzky YS, Sheval EV. Heterochromatin restricts the mobility of nuclear bodies. Chromosoma 2018; 127:529-537. [PMID: 30291421 DOI: 10.1007/s00412-018-0683-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/25/2018] [Accepted: 09/26/2018] [Indexed: 12/24/2022]
Abstract
Nuclear bodies are relatively immobile organelles. Here, we investigated the mechanisms underlying their movement using experimentally induced interphase prenucleolar bodies (iPNBs). Most iPNBs demonstrated constrained diffusion, exhibiting infrequent fusions with other iPNBs and nucleoli. Fusion events were actin-independent and appeared to be the consequence of stochastic collisions between iPNBs. Most iPNBs were surrounded by condensed chromatin, while fusing iPNBs were usually found in a single heterochromatin-delimited compartment ("cage"). The experimentally induced over-condensation of chromatin significantly decreased the frequency of iPNB fusion. Thus, the data obtained indicate that the mobility of nuclear bodies is restricted by heterochromatin.
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Affiliation(s)
- Eugene A Arifulin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Dmitry V Sorokin
- Laboratory of Mathematical Methods of Image Processing, Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Anna V Tvorogova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Margarita A Kurnaeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Yana R Musinova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
- Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Vavilov str. 26, 119334, Moscow, Russia
| | - Oxana A Zhironkina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Sergey A Golyshev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Sergey S Abramchuk
- Faculty of Chemistry, Lomonosov Moscow State University, 119991, Moscow, Russia
| | - Yegor S Vassetzky
- Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Vavilov str. 26, 119334, Moscow, Russia.
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France.
- UMR8126, CNRS, Institut de Cancérologie Gustave Roussy, Université Paris-Sud, 94805, Villejuif, France.
| | - Eugene V Sheval
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991, Moscow, Russia.
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France.
- Department of Cell Biology and Histology, Faculty of Biology, Lomonosov Moscow State University, 119991, Moscow, Russia.
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8
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Caudron-Herger M, Pankert T, Rippe K. Regulation of nucleolus assembly by non-coding RNA polymerase II transcripts. Nucleus 2017; 7:308-18. [PMID: 27416361 DOI: 10.1080/19491034.2016.1190890] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The nucleolus is a nuclear subcompartment for tightly regulated rRNA production and ribosome subunit biogenesis. It also acts as a cellular stress sensor and can release enriched factors in response to cellular stimuli. Accordingly, the content and structure of the nucleolus change dynamically, which is particularly evident during cell cycle progression: the nucleolus completely disassembles during mitosis and reassembles in interphase. Although the mechanisms that drive nucleolar (re)organization have been the subject of a number of studies, they are only partly understood. Recently, we identified Alu element-containing RNA polymerase II transcripts (aluRNAs) as important for nucleolar structure and rRNA synthesis. Integrating these findings with studies on the liquid droplet-like nature of the nucleolus leads us to propose a model on how RNA polymerase II transcripts could regulate the assembly of the nucleolus in response to external stimuli and during cell cycle progression.
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Affiliation(s)
- Maïwen Caudron-Herger
- a RNA Biology and Cancer, German Cancer Research Center (DKFZ) , Heidelberg , Germany
| | - Teresa Pankert
- b Genome Organization & Function, German Cancer Research Center (DKFZ) and BioQuant Center , Heidelberg , Germany
| | - Karsten Rippe
- b Genome Organization & Function, German Cancer Research Center (DKFZ) and BioQuant Center , Heidelberg , Germany
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9
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Durut N, Sáez-Vásquez J. Nucleolin: dual roles in rDNA chromatin transcription. Gene 2015; 556:7-12. [PMID: 25225127 DOI: 10.1016/j.gene.2014.09.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 09/08/2014] [Accepted: 09/09/2014] [Indexed: 01/17/2023]
Abstract
Nucleolin is a major nucleolar protein conserved in all eukaryotic organisms. It is a multifunctional protein involved in different cellular aspects like chromatin organization and stability, DNA and RNA metabolism, assembly of ribonucleoprotein complexes, cytokinesis, cell proliferation and stress response. The multifunctionality of nucleolin is linked to its tripartite structure, post-translational modifications and its ability of shuttling from and to the nucleolus/nucleoplasm and cytoplasm. Nucleolin has been now studied for many years and its activities and properties have been described in a number of excellent reviews. Here, we overview the role of nucleolin in RNA polymerase I (RNAPI) transcription and describe recent results concerning its functional interaction with rDNA chromatin organization. For a long time, nucleolin has been associated with rRNA gene expression and pre-rRNA processing. However, the functional connection between nucleolin and active versus inactive rRNA genes is still not fully understood. Novel evidence indicates that the nucleolin protein might be required for controlling the transcriptional ON/OFF states of rDNA chromatin in both mammals and plants.
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Affiliation(s)
- Nathalie Durut
- CNRS, Laboratoire Génome et Développement des Plantes, UMR 5096, 66860 Perpignan, France; Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, F-66860 Perpignan, France
| | - Julio Sáez-Vásquez
- CNRS, Laboratoire Génome et Développement des Plantes, UMR 5096, 66860 Perpignan, France; Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, F-66860 Perpignan, France.
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10
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Chen YL, Liu CD, Cheng CP, Zhao B, Hsu HJ, Shen CL, Chiu SJ, Kieff E, Peng CW. Nucleolin is important for Epstein-Barr virus nuclear antigen 1-mediated episome binding, maintenance, and transcription. Proc Natl Acad Sci U S A 2014; 111:243-8. [PMID: 24344309 PMCID: PMC3890893 DOI: 10.1073/pnas.1321800111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) is essential for EBV episome maintenance, replication, and transcription. These effects are mediated by EBNA1 binding to cognate oriP DNA, which comprise 20 imperfect copies of a 30-bp dyad symmetry enhancer and an origin for DNA replication. To identify cell proteins essential for these EBNA1 functions, EBNA1 associated cell proteins were immune precipitated and analyzed by liquid chromatography-tandem mass spectrometry. Nucleolin (NCL) was identified to be EBNA1 associated. EBNA1's N-terminal 100 aa and NCL's RNA-binding domains were critical for EBNA1/NCL interaction. Lentivirus shRNA-mediated NCL depletion substantially reduced EBNA1 recruitment to oriP DNA, EBNA1-dependent transcription of an EBV oriP luciferase reporter, and EBV genome maintenance in lymphoblastoid cell lines. NCL RNA-binding domain K429 was critical for ATP and EBNA1 binding. NCL overexpression increased EBNA1 binding to oriP and transcription, whereas NCL K429A was deficient. Moreover, NCL silencing impaired lymphoblastoid cell line growth. These experiments reveal a surprisingly critical role for NCL K429 in EBNA1 episome maintenance and transcription, which may be a target for therapeutic intervention.
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Affiliation(s)
- Ya-Lin Chen
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Cheng-Der Liu
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Chi-Ping Cheng
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Bo Zhao
- Department of Medicine, Brigham and Women’s Hospital, and Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Hao-Jen Hsu
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Chih-Long Shen
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Shu-Jun Chiu
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
| | - Elliott Kieff
- Department of Medicine, Brigham and Women’s Hospital, and Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Chih-wen Peng
- Department of Life Sciences, Tzu-Chi University, Hualien 97004, Taiwan; and
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11
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Abstract
Motifs rich in arginines and glycines were recognized several decades ago to play functional roles and were termed glycine-arginine-rich (GAR) domains and/or RGG boxes. We review here the evolving functions of the RGG box along with several sequence variations that we collectively term the RGG/RG motif. Greater than 1,000 human proteins harbor the RGG/RG motif, and these proteins influence numerous physiological processes such as transcription, pre-mRNA splicing, DNA damage signaling, mRNA translation, and the regulation of apoptosis. In particular, we discuss the role of the RGG/RG motif in mediating nucleic acid and protein interactions, a function that is often regulated by arginine methylation and partner-binding proteins. The physiological relevance of the RGG/RG motif is highlighted by its association with several diseases including neurological and neuromuscular diseases and cancer. Herein, we discuss the evidence for the emerging diverse functionality of this important motif.
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Affiliation(s)
- Palaniraja Thandapani
- Terry Fox Molecular Oncology Group and Bloomfield Center for Research on Aging, Lady Davis Institute for Medical Research and Departments of Oncology and Medicine, McGill University, Montreal, Quebec H3T 1E2, Canada
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12
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de Melo IS, Jimenez-Nuñez MD, Iglesias C, Campos-Caro A, Moreno-Sanchez D, Ruiz FA, Bolívar J. NOA36 protein contains a highly conserved nucleolar localization signal capable of directing functional proteins to the nucleolus, in mammalian cells. PLoS One 2013; 8:e59065. [PMID: 23516598 PMCID: PMC3596294 DOI: 10.1371/journal.pone.0059065] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 02/11/2013] [Indexed: 11/18/2022] Open
Abstract
NOA36/ZNF330 is an evolutionarily well-preserved protein present in the nucleolus and mitochondria of mammalian cells. We have previously reported that the pro-apoptotic activity of this protein is mediated by a characteristic cysteine-rich domain. We now demonstrate that the nucleolar localization of NOA36 is due to a highly-conserved nucleolar localization signal (NoLS) present in residues 1-33. This NoLS is a sequence containing three clusters of two or three basic amino acids. We fused the amino terminal of NOA36 to eGFP in order to characterize this putative NoLS. We show that a cluster of three lysine residues at positions 3 to 5 within this sequence is critical for the nucleolar localization. We also demonstrate that the sequence as found in human is capable of directing eGFP to the nucleolus in several mammal, fish and insect cells. Moreover, this NoLS is capable of specifically directing the cytosolic yeast enzyme polyphosphatase to the target of the nucleolus of HeLa cells, wherein its enzymatic activity was detected. This NoLS could therefore serve as a very useful tool as a nucleolar marker and for directing particular proteins to the nucleolus in distant animal species.
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Affiliation(s)
- Ivan S. de Melo
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain
| | - Maria D. Jimenez-Nuñez
- Unidad de Investigación, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain
| | - Concepción Iglesias
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain
| | - Antonio Campos-Caro
- Unidad de Investigación, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain
| | - David Moreno-Sanchez
- Unidad de Investigación, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain
| | - Felix A. Ruiz
- Unidad de Investigación, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Medicina, Universidad de Cádiz, Cádiz, Spain
| | - Jorge Bolívar
- Departamento de Biomedicina, Biotecnología y Salud Pública - Facultad de Ciencias, Universidad de Cádiz, Cádiz, Spain
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13
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Stępiński D. Nucleolin level in plant root meristematic cells under chilling stress and recovery. Micron 2012; 43:870-5. [PMID: 22483616 DOI: 10.1016/j.micron.2012.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 10/28/2022]
Abstract
Nucleolin and its homologues are multifunctional proteins which reside mainly in nucleoli of yeast, animal and plant cells. Hence, they are generally implicated in many stages of ribosome biosynthesis. In this study nucleolin was identified in root meristematic cell nucleoli of soybean plants subjected to chilling stress, recovered after chilling and under control conditions with the use of the immunogold electron microscopy technique. Soybean nucleoli exhibited various metabolic activities under these conditions (Stępiński, 2004). Current studies showed that the level of nucleolin, expressed as a number of gold grains per μm(2), varied in particular subnucleolar regions in the soybean root meristematic cell nucleoli. Labeling density changed in these regions when plants were subjected to the given treatment. Most abundantly this protein was present in dense fibrillar component (DFC) around fibrillar centers (FCs) in the nucleoli of recovered plants, while in the nucleoli of stressed plants this region contained the lowest level of nucleolin. It can be supposed that nucleolin participates in ribosome biogenesis and its level is correlated with metabolic activity of soybean nucleoli - the more active nucleoli, the higher level of nucleolin and vice versa.
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Affiliation(s)
- Dariusz Stępiński
- Department of Cytophysiology, University of Łódź, Pomorska 141/143, 90-236 Łódź, Poland.
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14
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Abstract
Nucleolin is a multifunctional protein localized primarily in the nucleolus, but also found in the nucleoplasm, cytoplasm and cell membrane. It is involved in several aspects of DNA metabolism, and participates extensively in RNA regulatory mechanisms, including transcription, ribosome assembly, mRNA stability and translation, and microRNA processing. Nucleolin's implication in disease is linked to its ability to associate with target RNAs via its four RNA-binding domains and its arginine/glycin-rich domain. By modulating the post-transcriptional fate of target mRNAs, which typically bear AU-rich and/or G-rich elements, nucleolin has been linked to cellular events that influence disease, notably cell proliferation and protection against apoptotic death. Through its diverse RNA functions, nucleolin is increasingly implicated in pathological processes, particularly cancer and viral infection. Here, we review the RNA-binding activities of nucleolin, its influence on gene expression patterns, and its impact upon diseases. We also discuss the rising interest in targeting nucleolin therapeutically.
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Affiliation(s)
- Kotb Abdelmohsen
- Laboratory of Molecular Biology and Immunology, National Institute on Aging-Intramural Research Program, National Institutes of Health, Baltimore, MD, USA.
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15
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Losfeld ME, Khoury DE, Mariot P, Carpentier M, Krust B, Briand JP, Mazurier J, Hovanessian AG, Legrand D. The cell surface expressed nucleolin is a glycoprotein that triggers calcium entry into mammalian cells. Exp Cell Res 2009; 315:357-69. [PMID: 19026635 DOI: 10.1016/j.yexcr.2008.10.039] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 10/16/2008] [Accepted: 10/23/2008] [Indexed: 11/24/2022]
Abstract
Nucleolin is an ubiquitous nucleolar phosphoprotein involved in fundamental aspects of transcription regulation, cell proliferation and growth. It has also been described as a shuttling molecule between nucleus, cytosol and the cell surface. Several studies have demonstrated that surface nucleolin serves as a receptor for various extracellular ligands implicated in cell proliferation, differentiation, adhesion, mitogenesis and angiogenesis. Previously, we reported that nucleolin in the extranuclear cell compartment is a glycoprotein containing N- and O-glycans. In the present study, we show that glycosylation is an essential requirement for surface nucleolin expression, since it is prevented when cells are cultured in the presence of tunicamycin, an inhibitor of N-glycosylation. Accordingly, surface but not nuclear nucleolin is radioactively labeled upon metabolic labeling of cells with [(3)H]glucosamine. Besides its well-demonstrated role in the internalization of specific ligands, here we show that ligand binding to surface nucleolin could also induce Ca(2+) entry into cells. Indeed, by flow cytometry, microscopy and patch-clamp experiments, we show that the HB-19 pseudopeptide, which binds specifically surface nucleolin, triggers rapid and intense membrane Ca(2+) fluxes in various types of cells. The use of several drugs then indicated that Store-Operated Ca(2+) Entry (SOCE)-like channels are involved in the generation of these fluxes. Taken together, our findings suggest that binding of an extracellular ligand to surface nucleolin could be involved in the activation of signaling pathways by promoting Ca(2+) entry into cells.
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Affiliation(s)
- Marie-Estelle Losfeld
- Unité de Glycobiologie Structurale et Fonctionnelle, Unité Mixte de Recherche no 8576 du Centre National de la Recherche Scientifique, France
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16
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Nucleolin – Characteristics of Protein and its Role in Biology of Cancers and Viral Infections. ACTA ACUST UNITED AC 2008. [DOI: 10.2478/v10052-008-0003-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Teng Y, Girvan AC, Casson LK, Pierce WM, Qian M, Thomas SD, Bates PJ. AS1411 alters the localization of a complex containing protein arginine methyltransferase 5 and nucleolin. Cancer Res 2007; 67:10491-500. [PMID: 17974993 DOI: 10.1158/0008-5472.can-06-4206] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
AS1411 is a quadruplex-forming oligonucleotide aptamer that targets nucleolin. It is currently in clinical trials as a treatment for various cancers. We have proposed that AS1411 inhibits cancer cell proliferation by affecting the activities of certain nucleolin-containing complexes. Here, we report that protein arginine methyltransferase 5 (PRMT5), an enzyme that catalyzes the formation of symmetrical dimethylarginine (sDMA), is a nucleolin-associated protein whose localization and activity are altered by AS1411. Levels of PRMT5 were found to be decreased in the nucleus of AS1411-treated DU145 human prostate cancer cells, but increased in the cytoplasm. These changes were dependent on nucleolin and were not observed in cells pretreated with nucleolin-specific small interfering RNA. Treatment with AS1411 altered levels of PRMT5 activity (assessed by sDMA levels) in accord with changes in its localization. In addition, our data indicate that nucleolin itself is a substrate for PRMT5 and that distribution of sDMA-modified nucleolin is altered by AS1411. Because histone arginine methylation by PRMT5 causes transcriptional repression, we also examined expression of selected PRMT5 target genes in AS1411-treated cells. For some genes, including cyclin E2 and tumor suppressor ST7, a significant up-regulation was noted, which corresponded with decreased PRMT5 association with the gene promoter. We conclude that nucleolin is a novel binding partner and substrate for PRMT5, and that AS1411 causes relocalization of the nucleolin-PRMT5 complex from the nucleus to the cytoplasm. Consequently, the nuclear activity of PRMT5 is decreased, leading to derepression of some PRMT5 target genes, which may contribute to the biological effects of AS1411.
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Affiliation(s)
- Yun Teng
- Department of Medicine, James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202-1756, USA
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18
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Abstract
Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) is a newly identified anti-apoptotic molecule. Our previous studies have demonstrated that CIAPIN1 is ubiquitously expressed in normal fetal and adult human tissues and confers multidrug resistance in gastric cancer cells, possibly by upregulating the expression of multidrug resistance gene 1 and multidrug resistance-related protein 1. However, fundamental biological functions of CIAPIN1 have not been elucidated. In this study, we first predicted the subcellular localization of CIAPIN1 with bioinformatic approaches and then characterized the intracellular localization of CIAPIN1 in both human and mouse cells by a combination of techniques including (a)immunohistochemistry and immunofluorescence, (b) His-tagged CIAPIN1 expression, and (c)subcellular fractionation and analysis of CIAPIN1 in the fractions by Western blotting. All methods produced consistent results; CIAPIN1 was localized in both the cytoplasm and the nucleus and was accumulated in the nucleolus. Bioinformatic prediction disclosed a putative nuclear localization signal and a putative nuclear export signal within both human and mouse CIAPIN1. These findings suggest that CIAPIN1 may undergo a cytoplasm-nucleus-nucleolus translocation.
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Affiliation(s)
- Zhiming Hao
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Xiaohua Li
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Taidong Qiao
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Rui Du
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Guoyun Zhang
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
| | - Daiming Fan
- State Key Laboratory of Cancer Biology, Institute of Digestive Diseases, Xijing Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, China
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19
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3 Diverse roles of protein arginine methyltransferases. PROTEIN METHYLTRANSFERASES 2006; 24:51-103. [DOI: 10.1016/s1874-6047(06)80005-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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20
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McBride AE, Cook JT, Stemmler EA, Rutledge KL, McGrath KA, Rubens JA. Arginine Methylation of Yeast mRNA-binding Protein Npl3 Directly Affects Its Function, Nuclear Export, and Intranuclear Protein Interactions. J Biol Chem 2005; 280:30888-98. [PMID: 15998636 DOI: 10.1074/jbc.m505831200] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arginine methylation can affect both nucleocytoplasmic transport and protein-protein interactions of RNA-binding proteins. These effects are seen in cells that lack the yeast hnRNP methyltransferase (HMT1), raising the question of whether effects on specific proteins are direct or indirect. The presence of multiple arginines in individual methylated proteins also raises the question of whether overall methylation or methylation of a subset of arginines affects protein function. We have used the yeast mRNA-binding protein Npl3 to address these questions in vivo. Matrix-assisted laser desorption/ionization Fourier transform mass spectrometry was used to identify 17 methylated arginines in Npl3 purified from yeast: whereas 10 Arg-Gly-Gly (RGG) tripeptides were exclusively dimethylated, variable levels of methylation were found for 5 RGG and 2 RG motif arginines. We constructed a set of Npl3 proteins in which subsets of the RGG arginines were mutated to lysine. Expression of these mutant proteins as the sole form of Npl3 specifically affected growth of a strain that requires Hmt1. Although decreased growth generally correlated with increased numbers of Arg-to-Lys mutations, lysine substitutions in the N terminus of the RGG domain showed more severe effects. Npl3 with all 15 RGG arginines mutated to lysine exited the nucleus independent of Hmt1, indicating a direct effect of methylation on Npl3 transport. These mutations also resulted in a decreased, methylation-independent interaction of Npl3 with transcription elongation factor Tho2 and inhibited Npl3 self-association. These results support a model in which arginine methylation facilitates Npl3 export directly by weakening contacts with nuclear proteins.
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Affiliation(s)
- Anne E McBride
- Department of Biology, Bowdoin College, Brunswick, Maine 04011, USA.
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21
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Alex D, Lee KAW. RGG-boxes of the EWS oncoprotein repress a range of transcriptional activation domains. Nucleic Acids Res 2005; 33:1323-31. [PMID: 15743974 PMCID: PMC552958 DOI: 10.1093/nar/gki270] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Ewings Sarcoma Oncoprotein (EWS) interacts with several components of the mammalian transcriptional and pre-mRNA splicing machinery and is also found in the cytoplasm and even on the cell surface. The apparently diverse cellular functions of EWS are, however, not well characterized. EWS harbours a potent N-terminal transcriptional activation domain (the EAD) that is revealed in the context of oncogenic EWS-fusion proteins (EFPs) and a C-terminal RNA-binding domain (RBD) that recruits pre-mRNA splicing factors and may couple transcription and splicing. In contrast to EFPs, the presumed transcriptional role of normal EWS remains enigmatic. Here, we report that multiple RGG-boxes within the RBD are necessary and sufficient for cis-repression of the EAD and that RGG-boxes can also repress in-trans, within dimeric partners. Lys can functionally substitute for Arg, indicating that the basic nature of the Arg side chain is the critical determinant of RGG-box-mediated repression. In addition to the EAD, RGG-boxes can repress a broad range of activation domains (including those of VP16, E1a and CREB), but repression can be alleviated by the simultaneous presence of more than one activation domain. We therefore propose that a key function of RGG boxes within native EWS is to restrict promiscuous activation by the EAD while still allowing EWS to enter functional transcription complexes and participate in other transactions involving pre-mRNAs.
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Affiliation(s)
| | - Kevin A. W. Lee
- To whom correspondence should be addressed. Tel: +852 2358 8636; Fax: +852 2358 1559;
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22
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Horke S, Reumann K, Schweizer M, Will H, Heise T. Nuclear trafficking of La protein depends on a newly identified nucleolar localization signal and the ability to bind RNA. J Biol Chem 2004; 279:26563-70. [PMID: 15060081 DOI: 10.1074/jbc.m401017200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Here we provide evidence for an interaction-dependent subnuclear trafficking of the human La (hLa) protein, known as transient interaction partner of a variety of RNAs. Among these, precursor transcripts of certain RNAs are located in the nucleoplasm or nucleolus. Here we examined which functional domains of hLa are involved in its nuclear trafficking. By using green fluorescent-hLa fusion proteins, we discovered a nucleolar localization signal and demonstrated its functionality in a heterologous context. In addition, we revealed that the RRM2 motif of hLa is essential both for its RNA binding competence in vitro and in vivo and its exit from the nucleolus. Our data imply that hLa traffics between different subnuclear compartments, which depend decisively on a functional nucleolar localization signal as well as on RNA binding. Directed trafficking of hLa is fully consistent with its function in the maturation of precursor RNAs located in different subnuclear compartments.
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Affiliation(s)
- Sven Horke
- Heinrich-Pette-Institut fur Experimentelle Virologie und Immunologie an der Universitaat Hamburg, Martinistrasse 52, D-20251 Hamburg, Germany
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23
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Dimario PJ. Cell and Molecular Biology of Nucleolar Assembly and Disassembly. INTERNATIONAL REVIEW OF CYTOLOGY 2004; 239:99-178. [PMID: 15464853 DOI: 10.1016/s0074-7696(04)39003-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nucleoli disassemble in prophase of the metazoan mitotic cycle, and they begin their reassembly (nucleologenesis) in late anaphase?early telophase. Nucleolar disassembly and reassembly were obvious to the early cytologists of the eighteenth and nineteenth centuries, and although this has lead to a plethora of literature describing these events, our understanding of the molecular mechanisms regulating nucleolar assembly and disassembly has expanded immensely just within the last 10-15 years. We briefly survey the findings of nineteenth-century cytologists on nucleolar assembly and disassembly, followed by the work of Heitz and McClintock on nucleolar organizers. A primer review of nucleolar structure and functions precedes detailed descriptions of modern molecular and microscopic studies of nucleolar assembly and disassembly. Nucleologenesis is concurrent with the reinitiation of rDNA transcription in telophase. The perichromosomal sheath, prenucleolar bodies, and nucleolar-derived foci serve as repositories for nucleolar processing components used in the previous interphase. Disassembly of the perichromosomal sheath along with the dynamic movements and compositional changes of the prenucleolar bodies and nucleolus-derived foci coincide with reactivation of rDNA synthesis within the chromosomal nucleolar organizers during telophase. Nucleologenesis is considered in various model organisms to provide breadth to our understanding. Nucleolar disassembly occurs at the onset of mitosis primarily as a result of the mitosis-specific phosphorylation of Pol I transcription factors and processing components. Although we have learned much regarding nucleolar assembly and disassembly, many questions still remain, and these questions are as vibrant for us today as early questions were for nineteenth- and early twentieth-century cytologists.
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Affiliation(s)
- Patrick J Dimario
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803-1715, USA
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