1
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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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2
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Che X, Wu J, Liu H, Su J, Chen X. Cellular liquid-liquid phase separation: Concept, functions, regulations, and detections. J Cell Physiol 2023; 238:847-865. [PMID: 36870067 DOI: 10.1002/jcp.30980] [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: 06/06/2022] [Revised: 10/05/2022] [Accepted: 02/08/2023] [Indexed: 03/06/2023]
Abstract
Liquid-liquid phase separation is a multicomponent system separated into phases with different compositions and structures. It has been identified and explored in organisms after being introduced from the thermodynamic field. Condensate, the product of phase separation, exists in different scales of cellular structures, such as nucleolus, stress granules, and other organelles in nuclei or cytoplasm. And also play critical roles in different cellular behaviors. Here, we review the concept, thermodynamical and biochemical principles of phase separation. We summarized the main functions including the adjustment of biochemical reaction rates, the regulation of macromolecule folding state, subcellular structural support, the mediation of subcellular location, and intimately linked to different kinds of diseases, such as cancer and neurodegeneration. Advanced detection methods to investigate phase separation are collected and analyzed. We conclude with the discussion of anxiety of phase separation, and thought about how progress can be made to develop precise detection methods and disclose the potential application of condensates.
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Affiliation(s)
- Xuanlin Che
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
| | - Jiajun Wu
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Hua Liu
- Department of Orthopaedics, Xiangya Hospital, Central South University, Changsha, China
| | - Juan Su
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
| | - Xiang Chen
- Department of Dermatology, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Skin Cancer and Psoriasis, Xiangya Hospital, Changsha, Hunan, China.,Hunan Engineering Research Center of Skin Health and Disease, Xiangya Hospital, Changsha, Hunan, China.,Xiangya Clinical Research Center for Cancer Immunotherapy, Central South University, Changsha, Hunan, China
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3
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Miyake T, McDermott JC. Re-organization of nucleolar architecture in myogenic differentiation. J Cell Sci 2023; 136:286887. [PMID: 36727534 DOI: 10.1242/jcs.260496] [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: 08/08/2022] [Accepted: 01/19/2023] [Indexed: 02/03/2023] Open
Abstract
Myogenesis, the process of muscle differentiation, requires an extensive remodeling of the cellular transcriptome and proteome. Whereas the transcriptional program underpinning myogenesis is well characterized, the required adaptation in protein synthesis is incompletely understood. Enhanced protein synthesis necessitates ribosome biogenesis at the nucleolus. Nucleolar size and activity are inextricably linked with altered gene expression. Here, we report changes in nucleolar morphology and function during myogenic differentiation. Immunofluorescence analysis revealed alterations in nucleolar morphology that were dependent on the cellular state - proliferative or quiescent myogenic progenitors (myoblasts or reserve cells) contained multiple small nucleoli with a characteristic spherical shape, whereas multinucleated myotubes typically contained one large, often irregularly shaped nucleolus. These morphological alterations are consistent with changes to nucleolar phase separation properties. Re-organization of the nucleolar structure was correlated with enhanced rRNA production and protein translation. Inhibition of mTOR signaling with rapamycin perturbed nucleolar re-organization. Conversely, hyperactivated mTOR enhanced alterations in nucleolar morphology. These findings support the idea that there is an mTOR dependent re-organization of nucleolar structure during myogenesis, enhancing our understanding of myogenesis and possibly facilitating new approaches to therapeutic interventions in muscle pathologies.
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Affiliation(s)
- Tetsuaki Miyake
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada.,Muscle Health Research Centre (MHRC), York University, Toronto, ON M3J 1P3, Canada.,Centre for Research in Biomolecular Interactions (CRBI), York University, Toronto, ON M3J 1P3, Canada
| | - John C McDermott
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada.,Muscle Health Research Centre (MHRC), York University, Toronto, ON M3J 1P3, Canada.,Centre for Research in Biomolecular Interactions (CRBI), York University, Toronto, ON M3J 1P3, Canada
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4
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Islas-Morales PF, Cárdenas A, Mosqueira MJ, Jiménez-García LF, Voolstra CR. Ultrastructural and proteomic evidence for the presence of a putative nucleolus in an Archaeon. Front Microbiol 2023; 14:1075071. [PMID: 36819014 PMCID: PMC9932318 DOI: 10.3389/fmicb.2023.1075071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 01/02/2023] [Indexed: 02/05/2023] Open
Abstract
Nucleoli are subcellular compartments where transcription and maturation of pre-ribosomal RNAs occur. While the transcription of ribosomal RNAs is common to all living cells, the presence and ultrastructure of nucleoli has been only documented in eukaryotes. Asgard-Archaea, the closest prokaryotic relatives of eukaryotes, and their near relatives TACK-Archaea have homologs of nucleolar proteins and RNAs in their genome, but the cellular organization of both is largely unexplored. Here we provide ultrastructural and molecular evidence for the presence of putative nucleolus-like subcellular domains in the TACK crenarchaeon Saccharolobus solfataricus (formerly known as Sulfolobus solfataricus). Transmission electron microscopy (TEM) revealed consistent electron-dense fibro-granular compartments, also positive to the specific silver staining for nucleolar organizer regions (AgNOR). TEM also confirmed that ribosomal DNA (rDNA) is spatially distributed in non-random, clustered arrays underlying fine structures, as observed by ultrastructural in situ hybridization (UISH). To further explore these observations, proteomic sequencing of isolated bands from AgNOR-stained protein gels was conducted and compared against a compiled inventory of putative nucleolar homologs from the S. solfataricus P1 genome. Sequenced AgNOR-sensitive peptides encoded homologs of eukaryotic nucleoli proteins, enriched for nucleolus-related functions. Our results provide first evidence that subcellular domains of nucleolar-like nature are not exclusive to eukaryotes. Based on our data, we propose a model for a putative nucleolus in S. solfataricus. Whereas technical limitations and further aspects remain a matter for future functional studies, our data supports the origin of nucleoli within the common ancestor of Eukarya and TACK-Archaea, based on a two-domain tree of life.
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Affiliation(s)
- Parsifal F. Islas-Morales
- Programa de Doctorado en Ciencias Biomédicas, Facultad de Medicina, UNAM, Mexico City, Mexico,UNESCO Chair on Science Diplomacy and Scientific Heritage, Instituto de Biología, UNAM, Mexico City, Mexico,Red Sea Research Center (RSRC), Biological, Environmental Sciences, and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Anny Cárdenas
- Red Sea Research Center (RSRC), Biological, Environmental Sciences, and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia,Department of Biology, University of Konstanz, Konstanz, Germany,Department of Biology, American University, Washington, DC, United States
| | - María J. Mosqueira
- Red Sea Research Center (RSRC), Biological, Environmental Sciences, and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia,NEOM, Saudi Arabia
| | - Luis Felipe Jiménez-García
- Programa de Doctorado en Ciencias Biomédicas, Facultad de Medicina, UNAM, Mexico City, Mexico,Department of Cell Biology, Faculty of Sciences, UNAM, Mexico City, Mexico,*Correspondence: Luis Felipe Jiménez-García, ✉
| | - Christian R. Voolstra
- Red Sea Research Center (RSRC), Biological, Environmental Sciences, and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia,Department of Biology, University of Konstanz, Konstanz, Germany,Christian R. Voolstra, ✉
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5
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Tani I, Oikawa Y, Doi S, Janairo JIB, Kamada R, Sakaguchi K. Ribosomal protein uL30 undergoes phase separation with nucleophosmin and regulates nucleolar formation in the absence of RNA. Biochem Biophys Res Commun 2023; 642:35-40. [PMID: 36543022 DOI: 10.1016/j.bbrc.2022.12.041] [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: 12/02/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
The nucleolus is a membrane-less structure that exists in the nucleus of cells and plays a crucial role in ribosome biogenesis. It is known to be formed through liquid-liquid phase separation (LLPS) caused by the interaction of various nucleolar proteins and nucleic acids. Recently, many studies on LLPS with nucleolar proteins in the presence of RNA showed the importance of electrostatic interactions and cation-pi interactions among RNA and intrinsically disordered regions of proteins. However, it is reported that the initiation of nucleolar formation is RNA polymerase I-independent. The mechanism of nucleolar formation in the early stage remains obscure. In this study, we showed for the first time that the ribosomal protein uL30 and a major nucleolar protein, nucleophosmin (NPM) formed liquid droplets in vitro in the absence of RNA. The liquid droplet formation with uL30 and NPM may be derived from the interaction between the basic regions of uL30 and acidic regions of the oligomeric NPM. The knockdown of uL30 in cells significantly reduced the number of nucleoli, while it did not alter the protein level of NPM. The results showed that LLPS and nucleolar formation were affected by changes in uL30 levels. Our results suggest that the protein-protein interaction between nucleolar proteins may play an important role in nucleolar formation in the early stages when the rRNA content is very low.
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Affiliation(s)
- Itsumi Tani
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Yui Oikawa
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Seiyo Doi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Jose Isagani B Janairo
- Department of Biology, College of Science, De La Salle University, Manila, 0922, Philippines
| | - Rui Kamada
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Kazuyasu Sakaguchi
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan.
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6
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Stamatiou K, Chmielewska A, Ohta S, Earnshaw WC, Vagnarelli P. CCDC86 is a novel Ki-67-interacting protein important for cell division. J Cell Sci 2023; 136:286751. [PMID: 36695333 PMCID: PMC10022746 DOI: 10.1242/jcs.260391] [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: 07/04/2022] [Accepted: 12/08/2022] [Indexed: 01/26/2023] Open
Abstract
The chromosome periphery is a network of proteins and RNAs that coats the outer surface of mitotic chromosomes. Despite the identification of new components, the functions of this complex compartment are poorly characterised. In this study, we identified a novel chromosome periphery-associated protein, CCDC86 (also known as cyclon). Using a combination of RNA interference, microscopy and biochemistry, we studied the functions of CCDC86 in mitosis. CCDC86 depletion resulted in partial disorganisation of the chromosome periphery with alterations in the localisation of Ki-67 (also known as MKI67) and nucleolin (NCL), and the formation of abnormal cytoplasmic aggregates. Furthermore, CCDC86-depleted cells displayed errors in chromosome alignment, altered spindle length and increased apoptosis. These results suggest that, within the chromosome periphery, different subcomplexes that include CCDC86, nucleolin and B23 (nucleophosmin or NPM1) are required for mitotic spindle regulation and correct kinetochore-microtubule attachments, thus contributing to chromosome segregation in mitosis. Moreover, we identified CCDC86 as a MYCN-regulated gene, the expression levels of which represent a powerful marker for prognostic outcomes in neuroblastoma.
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Affiliation(s)
- Konstantinos Stamatiou
- College of Health, Medicine and Life Sciences, Department of Life Sciences, Brunel University London, London UB8 3PH, UK
| | - Aldona Chmielewska
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Shinya Ohta
- Institute for Genetic Medicine, Hokkaido University, Kita-15, Nishi-7, Kita-Ku, Sapporo 060-0815, Japan
| | - William C Earnshaw
- Wellcome Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Paola Vagnarelli
- College of Health, Medicine and Life Sciences, Department of Life Sciences, Brunel University London, London UB8 3PH, UK
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7
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Sakthivel D, Brown-Suedel A, Bouchier-Hayes L. The role of the nucleolus in regulating the cell cycle and the DNA damage response. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2023; 135:203-241. [PMID: 37061332 DOI: 10.1016/bs.apcsb.2023.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The nucleolus has long been perceived as the site for ribosome biogenesis, but numerous studies suggest that the nucleolus carefully sequesters crucial proteins involved in multiple cellular functions. Among these, the role of nucleolus in cell cycle regulation is the most evident. The nucleolus is the first responder of growth-related signals to mediate normal cell cycle progression. The nucleolus also senses different cellular stress insults by activating diverse pathways that arrest the cell cycle, promote DNA repair, or initiate apoptosis. Here, we review the emerging concepts on how the ribosomal and nonribosomal nucleolar proteins mediate such cellular effects.
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8
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van Schaik T, Manzo SG, Vouzas AE, Liu NQ, Teunissen H, de Wit E, Gilbert DM, van Steensel B. Dynamic chromosomal interactions and control of heterochromatin positioning by Ki-67. EMBO Rep 2022; 23:e55782. [PMID: 36245428 PMCID: PMC9724667 DOI: 10.15252/embr.202255782] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/26/2022] [Accepted: 09/29/2022] [Indexed: 11/05/2022] Open
Abstract
Ki-67 is a chromatin-associated protein with a dynamic distribution pattern throughout the cell cycle and is thought to be involved in chromatin organization. The lack of genomic interaction maps has hampered a detailed understanding of its roles, particularly during interphase. By pA-DamID mapping in human cell lines, we find that Ki-67 associates with large genomic domains that overlap mostly with late-replicating regions. Early in interphase, when Ki-67 is present in pre-nucleolar bodies, it interacts with these domains on all chromosomes. However, later in interphase, when Ki-67 is confined to nucleoli, it shows a striking shift toward small chromosomes. Nucleolar perturbations indicate that these cell cycle dynamics correspond to nucleolar maturation during interphase, and suggest that nucleolar sequestration of Ki-67 limits its interactions with larger chromosomes. Furthermore, we demonstrate that Ki-67 does not detectably control chromatin-chromatin interactions during interphase, but it competes with the nuclear lamina for interaction with late-replicating DNA, and it controls replication timing of (peri)centromeric regions. Together, these results reveal a highly dynamic choreography of genome interactions and roles for Ki-67 in heterochromatin organization.
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Affiliation(s)
- Tom van Schaik
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands
| | - Stefano G Manzo
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands
| | - Athanasios E Vouzas
- Department of Biological ScienceThe Florida State UniversityTallahasseeFLUSA,San Diego Biomedical Research InstituteSan DiegoCAUSA
| | - Ning Qing Liu
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands
| | - Hans Teunissen
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands
| | - Elzo de Wit
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands
| | - David M Gilbert
- Department of Biological ScienceThe Florida State UniversityTallahasseeFLUSA,San Diego Biomedical Research InstituteSan DiegoCAUSA
| | - Bas van Steensel
- Division of Gene Regulation and Oncode InstituteNetherlands Cancer InstituteAmsterdamThe Netherlands,Department of Cell BiologyErasmus University Medical CentreRotterdamThe Netherlands
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9
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Belmont AS. Nuclear Compartments: An Incomplete Primer to Nuclear Compartments, Bodies, and Genome Organization Relative to Nuclear Architecture. Cold Spring Harb Perspect Biol 2022; 14:a041268. [PMID: 34400557 PMCID: PMC9248822 DOI: 10.1101/cshperspect.a041268] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This work reviews nuclear compartments, defined broadly to include distinct nuclear structures, bodies, and chromosome domains. It first summarizes original cytological observations before comparing concepts of nuclear compartments emerging from microscopy versus genomic approaches and then introducing new multiplexed imaging approaches that promise in the future to meld both approaches. I discuss how previous models of radial distribution of chromosomes or the binary division of the genome into A and B compartments are now being refined by the recognition of more complex nuclear compartmentalization. The poorly understood question of how these nuclear compartments are established and maintained is then discussed, including through the modern perspective of phase separation, before moving on to address possible functions of nuclear compartments, using the possible role of nuclear speckles in modulating gene expression as an example. Finally, the review concludes with a discussion of future questions for this field.
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Affiliation(s)
- Andrew S Belmont
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA
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10
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Ribosomal RNA regulates chromosome clustering during mitosis. Cell Discov 2022; 8:51. [PMID: 35637200 PMCID: PMC9151767 DOI: 10.1038/s41421-022-00400-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 02/21/2022] [Indexed: 11/18/2022] Open
Abstract
Noncoding RNAs are known to associate with mitotic chromosomes, but the identities and functions of chromosome-associated RNAs in mitosis remain elusive. Here, we show that rRNA species associate with condensed chromosomes during mitosis. In particular, pre-rRNAs such as 45S, 32S, and 30S are highly enriched on mitotic chromosomes. Immediately following nucleolus disassembly in mitotic prophase, rRNAs are released and associate with and coat each condensed chromosome at prometaphase. Using unbiased mass spectrometry analysis, we further demonstrate that chromosome-bound rRNAs are associated with Ki-67. Moreover, the FHA domain and the repeat region of Ki-67 recognize and anchor rRNAs to chromosomes. Finally, suppression of chromosome-bound rRNAs by RNA polymerase I inhibition or by using rRNA-binding-deficient Ki-67 mutants impair mitotic chromosome dispersion during prometaphase. Our study thus reveals an important role of rRNAs in preventing chromosome clustering during mitosis.
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11
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Kadzik RS, Homa KE, Kovar DR. F-Actin Cytoskeleton Network Self-Organization Through Competition and Cooperation. Annu Rev Cell Dev Biol 2021; 36:35-60. [PMID: 33021819 DOI: 10.1146/annurev-cellbio-032320-094706] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many fundamental cellular processes such as division, polarization, endocytosis, and motility require the assembly, maintenance, and disassembly of filamentous actin (F-actin) networks at specific locations and times within the cell. The particular function of each network is governed by F-actin organization, size, and density as well as by its dynamics. The distinct characteristics of different F-actin networks are determined through the coordinated actions of specific sets of actin-binding proteins (ABPs). Furthermore, a cell typically assembles and uses multiple F-actin networks simultaneously within a common cytoplasm, so these networks must self-organize from a common pool of shared globular actin (G-actin) monomers and overlapping sets of ABPs. Recent advances in multicolor imaging and analysis of ABPs and their associated F-actin networks in cells, as well as the development of sophisticated in vitro reconstitutions of networks with ensembles of ABPs, have allowed the field to start uncovering the underlying principles by which cells self-organize diverse F-actin networks to execute basic cellular functions.
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Affiliation(s)
- Rachel S Kadzik
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA; , .,Department of Molecular BioSciences, Northwestern University, Evanston, Illinois 60208, USA;
| | - Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA; ,
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA; , .,Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637, USA
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12
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Commuting to Work: Nucleolar Long Non-Coding RNA Control Ribosome Biogenesis from Near and Far. Noncoding RNA 2021; 7:ncrna7030042. [PMID: 34287370 PMCID: PMC8293466 DOI: 10.3390/ncrna7030042] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 07/09/2021] [Accepted: 07/11/2021] [Indexed: 12/26/2022] Open
Abstract
Gene expression is an essential process for cellular growth, proliferation, and differentiation. The transcription of protein-coding genes and non-coding loci depends on RNA polymerases. Interestingly, numerous loci encode long non-coding (lnc)RNA transcripts that are transcribed by RNA polymerase II (RNAPII) and fine-tune the RNA metabolism. The nucleolus is a prime example of how different lncRNA species concomitantly regulate gene expression by facilitating the production and processing of ribosomal (r)RNA for ribosome biogenesis. Here, we summarise the current findings on how RNAPII influences nucleolar structure and function. We describe how RNAPII-dependent lncRNA can both promote nucleolar integrity and inhibit ribosomal (r)RNA synthesis by modulating the availability of rRNA synthesis factors in trans. Surprisingly, some lncRNA transcripts can directly originate from nucleolar loci and function in cis. The nucleolar intergenic spacer (IGS), for example, encodes nucleolar transcripts that counteract spurious rRNA synthesis in unperturbed cells. In response to DNA damage, RNAPII-dependent lncRNA originates directly at broken ribosomal (r)DNA loci and is processed into small ncRNA, possibly to modulate DNA repair. Thus, lncRNA-mediated regulation of nucleolar biology occurs by several modes of action and is more direct than anticipated, pointing to an intimate crosstalk of RNA metabolic events.
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13
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Chin MY, Espinosa JA, Pohan G, Markossian S, Arkin MR. Reimagining dots and dashes: Visualizing structure and function of organelles for high-content imaging analysis. Cell Chem Biol 2021; 28:320-337. [PMID: 33600764 PMCID: PMC7995685 DOI: 10.1016/j.chembiol.2021.01.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 12/18/2020] [Accepted: 01/20/2021] [Indexed: 12/16/2022]
Abstract
Organelles are responsible for biochemical and cellular processes that sustain life and their dysfunction causes diseases from cancer to neurodegeneration. While researchers are continuing to appreciate new roles of organelles in disease, the rapid development of specifically targeted fluorescent probes that report on the structure and function of organelles will be critical to accelerate drug discovery. Here, we highlight four organelles that collectively exemplify the progression of phenotypic discovery, starting with mitochondria, where many functional probes have been described, then continuing with lysosomes and Golgi and concluding with nascently described membraneless organelles. We introduce emerging probe designs to explore organelle-specific morphology and dynamics and highlight recent case studies using high-content analysis to stimulate further development of probes and approaches for organellar high-throughput screening.
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Affiliation(s)
- Marcus Y Chin
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Jether Amos Espinosa
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Grace Pohan
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Sarine Markossian
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Michelle R Arkin
- Small Molecule Discovery Center and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA.
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14
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Abstract
The nucleolus is the most prominent nuclear body and serves a fundamentally important biological role as a site of ribonucleoprotein particle assembly, primarily dedicated to ribosome biogenesis. Despite being one of the first intracellular structures visualized historically, the biophysical rules governing its assembly and function are only starting to become clear. Recent studies have provided increasing support for the concept that the nucleolus represents a multilayered biomolecular condensate, whose formation by liquid-liquid phase separation (LLPS) facilitates the initial steps of ribosome biogenesis and other functions. Here, we review these biophysical insights in the context of the molecular and cell biology of the nucleolus. We discuss how nucleolar function is linked to its organization as a multiphase condensate and how dysregulation of this organization could provide insights into still poorly understood aspects of nucleolus-associated diseases, including cancer, ribosomopathies and neurodegeneration as well as ageing. We suggest that the LLPS model provides the starting point for a unifying quantitative framework for the assembly, structural maintenance and function of the nucleolus, with implications for gene regulation and ribonucleoprotein particle assembly throughout the nucleus. The LLPS concept is also likely useful in designing new therapeutic strategies to target nucleolar dysfunction.
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15
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Hassine S, Bonnet-Magnaval F, Benoit Bouvrette LP, Doran B, Ghram M, Bouthillette M, Lecuyer E, DesGroseillers L. Staufen1 localizes to the mitotic spindle and controls the localization of RNA populations to the spindle. J Cell Sci 2020; 133:jcs247155. [PMID: 32576666 DOI: 10.1242/jcs.247155] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/07/2020] [Indexed: 12/20/2022] Open
Abstract
Staufen1 (STAU1) is an RNA-binding protein involved in the post-transcriptional regulation of mRNAs. We report that a large fraction of STAU1 localizes to the mitotic spindle in colorectal cancer HCT116 cells and in non-transformed hTERT-RPE1 cells. Spindle-associated STAU1 partly co-localizes with ribosomes and active sites of translation. We mapped the molecular determinant required for STAU1-spindle association within the first 88 N-terminal amino acids, a domain that is not required for RNA binding. Interestingly, transcriptomic analysis of purified mitotic spindles revealed that 1054 mRNAs and the precursor ribosomal RNA (pre-rRNA), as well as the long non-coding RNAs and small nucleolar RNAs involved in ribonucleoprotein assembly and processing, are enriched on spindles compared with cell extracts. STAU1 knockout causes displacement of the pre-rRNA and of 154 mRNAs coding for proteins involved in actin cytoskeleton organization and cell growth, highlighting a role for STAU1 in mRNA trafficking to spindle. These data demonstrate that STAU1 controls the localization of subpopulations of RNAs during mitosis and suggests a novel role of STAU1 in pre-rRNA maintenance during mitosis, ribogenesis and/or nucleoli reassembly.
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Affiliation(s)
- Sami Hassine
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
| | - Florence Bonnet-Magnaval
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
| | - Louis Philip Benoit Bouvrette
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
- Institut de Recherches Cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Bellastrid Doran
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
| | - Mehdi Ghram
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
| | - Mathieu Bouthillette
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
| | - Eric Lecuyer
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
- Institut de Recherches Cliniques de Montréal, 110 Avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Luc DesGroseillers
- Département de biochimie et médecine moléculaire, Faculté de médecine, Université de Montréal, 2900 Édouard Montpetit, Montréal, QC H3T 1J4, Canada
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16
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Esgleas M, Falk S, Forné I, Thiry M, Najas S, Zhang S, Mas-Sanchez A, Geerlof A, Niessing D, Wang Z, Imhof A, Götz M. Trnp1 organizes diverse nuclear membrane-less compartments in neural stem cells. EMBO J 2020; 39:e103373. [PMID: 32627867 PMCID: PMC7429739 DOI: 10.15252/embj.2019103373] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 05/18/2020] [Accepted: 05/20/2020] [Indexed: 11/09/2022] Open
Abstract
TMF1‐regulated nuclear protein 1 (Trnp1) has been shown to exert potent roles in neural development affecting neural stem cell self‐renewal and brain folding, but its molecular function in the nucleus is still unknown. Here, we show that Trnp1 is a low complexity protein with the capacity to phase separate. Trnp1 interacts with factors located in several nuclear membrane‐less organelles, the nucleolus, nuclear speckles, and condensed chromatin. Importantly, Trnp1 co‐regulates the architecture and function of these nuclear compartments in vitro and in the developing brain in vivo. Deletion of a highly conserved region in the N‐terminal intrinsic disordered region abolishes the capacity of Trnp1 to regulate nucleoli and heterochromatin size, proliferation, and M‐phase length; decreases the capacity to phase separate; and abrogates most of Trnp1 protein interactions. Thus, we identified Trnp1 as a novel regulator of several nuclear membrane‐less compartments, a function important to maintain cells in a self‐renewing proliferative state.
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Affiliation(s)
- Miriam Esgleas
- Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians Universitaet Muenchen, Planegg/Munich, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Sven Falk
- Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians Universitaet Muenchen, Planegg/Munich, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Ignasi Forné
- Protein Analysis Unit, BioMedical Center (BMC), Ludwig-Maximilians-Universitaet Muenchen, Planegg/Munich, Germany
| | - Marc Thiry
- Cell and Tissue Biology Unit, GIGA-Neurosciences, University of Liege, C.H.U. Sart Tilman, Liege, Belgium
| | - Sonia Najas
- Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians Universitaet Muenchen, Planegg/Munich, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Sirui Zhang
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Aina Mas-Sanchez
- Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians Universitaet Muenchen, Planegg/Munich, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany
| | - Arie Geerlof
- Institute of Structural Biology, Helmholtz Zentrum Muenchen, Neuherberg, Germany
| | - Dierk Niessing
- Group Intracellular Transport and RNA Biology at the Institute of Structural Biology, Helmholtz Zentrum Muenchen, Neuherberg, Germany.,Department of Cell Biology, BioMedical Center (BMC), Ludwig-Maximilians-Universitaet Muenchen, Planegg/Munich, Germany
| | - Zefeng Wang
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Axel Imhof
- Protein Analysis Unit, BioMedical Center (BMC), Ludwig-Maximilians-Universitaet Muenchen, Planegg/Munich, Germany.,SYNERGY, Excellence Cluster of Systems Neurology, BioMedical Center (BMC), Ludwig-Maximilians-Universitaet Muenchen, Planegg/Munich, Germany
| | - Magdalena Götz
- Physiological Genomics, Biomedical Center (BMC), Ludwig-Maximilians Universitaet Muenchen, Planegg/Munich, Germany.,Institute for Stem Cell Research, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany.,SYNERGY, Excellence Cluster of Systems Neurology, BioMedical Center (BMC), Ludwig-Maximilians-Universitaet Muenchen, Planegg/Munich, Germany
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17
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Iyer-Bierhoff A, Krogh N, Tessarz P, Ruppert T, Nielsen H, Grummt I. SIRT7-Dependent Deacetylation of Fibrillarin Controls Histone H2A Methylation and rRNA Synthesis during the Cell Cycle. Cell Rep 2019; 25:2946-2954.e5. [PMID: 30540930 DOI: 10.1016/j.celrep.2018.11.051] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/17/2018] [Accepted: 11/12/2018] [Indexed: 12/31/2022] Open
Abstract
Fibrillarin (FBL) is a dual-function nucleolar protein that catalyzes 2'-O methylation of pre-rRNA and methylation of histone H2A at glutamine 104 (H2AQ104me). The mechanisms that regulate FBL activity are unexplored. Here, we show that FBL is acetylated at several lysine residues by the acetyltransferase CBP and deacetylated by SIRT7. While reversible acetylation does not impact FBL-mediated pre-rRNA methylation, hyperacetylation impairs the interaction of FBL with histone H2A and chromatin, thereby compromising H2AQ104 methylation (H2AQ104me) and rDNA transcription. SIRT7-dependent deacetylation of FBL ensures H2AQ104me and high levels of rRNA synthesis during interphase. At the onset of mitosis, nucleolar disassembly is accompanied by hyperacetylation of FBL, loss of H2AQ104me, and repression of polymerase I (Pol I) transcription. Overexpression of an acetylation-deficient, but not an acetylation-mimicking, FBL mutant restores H2AQ104me and transcriptional activity. The results reveal that SIRT7-dependent deacetylation impacts nucleolar activity by an FBL-driven circuitry that mediates cell-cycle-dependent fluctuation of rDNA transcription.
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Affiliation(s)
- Aishwarya Iyer-Bierhoff
- Molecular Biology of the Cell II, German Cancer Research Centre (DKFZ), DKFZ-Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Alliance, 69120 Heidelberg, Germany
| | - Nicolai Krogh
- Department of Cellular and Molecular Medicine, University of Copenhagen, 2200N Copenhagen, Denmark
| | - Peter Tessarz
- Department of Chromatin and Ageing, Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Thomas Ruppert
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Henrik Nielsen
- Department of Cellular and Molecular Medicine, University of Copenhagen, 2200N Copenhagen, Denmark
| | - Ingrid Grummt
- Molecular Biology of the Cell II, German Cancer Research Centre (DKFZ), DKFZ-Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Alliance, 69120 Heidelberg, Germany.
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18
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Kim TK, Lee BW, Fujii F, Kim JK, Pack CG. Physicochemical Properties of Nucleoli in Live Cells Analyzed by Label-Free Optical Diffraction Tomography. Cells 2019; 8:cells8070699. [PMID: 31295945 PMCID: PMC6679011 DOI: 10.3390/cells8070699] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/27/2019] [Accepted: 07/09/2019] [Indexed: 12/15/2022] Open
Abstract
The cell nucleus is three-dimensionally and dynamically organized by nuclear components with high molecular density, such as chromatin and nuclear bodies. The structure and functions of these components are represented by the diffusion and interaction of related factors. Recent studies suggest that the nucleolus can be assessed using various protein probes, as the probes are highly mobile in this organelle, although it is known that they have a densely packed structure. However, physicochemical properties of the nucleolus itself, such as molecular density and volume when cellular conditions are changed, are not yet fully understood. In this study, physical parameters such as the refractive index (RI) and volume of the nucleoli in addition to the diffusion coefficient (D) of fluorescent probe protein inside the nucleolus are quantified and compared by combining label-free optical diffraction tomography (ODT) with confocal laser scanning microscopy (CLSM)-based fluorescence correlation spectroscopy (FCS). 3D evaluation of RI values and corresponding RI images of nucleoli in live HeLa cells successfully demonstrated varying various physiological conditions. Our complimentary method suggests that physical property of the nucleolus in live cell is sensitive to ATP depletion and transcriptional inhibition, while it is insensitive to hyper osmotic pressure when compared with the cytoplasm and nucleoplasm. The result demonstrates that the nucleolus has unique physicochemical properties when compared with other cellular components.
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Affiliation(s)
- Tae-Keun Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea
| | - Byong-Wook Lee
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea
| | - Fumihiko Fujii
- Division of Physical Pharmacy, Faculty of Pharmaceutical Sciences, Kobe Gakuin University, Kobe 650-8586, Japan
| | - Jun Ki Kim
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
| | - Chan-Gi Pack
- Asan Institute for Life Sciences, Asan Medical Center, Seoul 05505, Korea.
- Department of Convergence Medicine, University of Ulsan College of Medicine, Seoul 05505, Korea.
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19
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Iarovaia OV, Minina EP, Sheval EV, Onichtchouk D, Dokudovskaya S, Razin SV, Vassetzky YS. Nucleolus: A Central Hub for Nuclear Functions. Trends Cell Biol 2019; 29:647-659. [PMID: 31176528 DOI: 10.1016/j.tcb.2019.04.003] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 12/19/2022]
Abstract
The nucleolus is the largest and most studied nuclear body, but its role in nuclear function is far from being comprehensively understood. Much work on the nucleolus has focused on its role in regulating RNA polymerase I (RNA Pol I) transcription and ribosome biogenesis; however, emerging evidence points to the nucleolus as an organizing hub for many nuclear functions, accomplished via the shuttling of proteins and nucleic acids between the nucleolus and nucleoplasm. Here, we discuss the cellular mechanisms affected by shuttling of nucleolar components, including the 3D organization of the genome, stress response, DNA repair and recombination, transcription regulation, telomere maintenance, and other essential cellular functions.
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Affiliation(s)
- Olga V Iarovaia
- Institute of Gene Biology of the Russian Academy of Sciences, 119334 Moscow, Russia; LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805 Villejuif, France
| | - Elizaveta P Minina
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Eugene V Sheval
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805 Villejuif, France; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Daria Onichtchouk
- Developmental Biology Unit, Department of Biology I, University of Freiburg, Hauptstrasse 1, D-79104 Freiburg, Germany
| | - Svetlana Dokudovskaya
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805 Villejuif, France; UMR8126, Université Paris-Sud, CNRS, Institut Gustave Roussy, 94805 Villejuif, France
| | - Sergey V Razin
- Institute of Gene Biology of the Russian Academy of Sciences, 119334 Moscow, Russia; LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805 Villejuif, France; Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Yegor S Vassetzky
- LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, 94805 Villejuif, France; Koltzov Institute of Developmental Biology of the Russian Academy of Sciences, 119334 Moscow, Russia; UMR8126, Université Paris-Sud, CNRS, Institut Gustave Roussy, 94805 Villejuif, France.
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20
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Iyer-Bierhoff A, Grummt I. Stop-and-Go: Dynamics of Nucleolar Transcription During the Cell Cycle. Epigenet Insights 2019; 12:2516865719849090. [PMID: 31206100 PMCID: PMC6537492 DOI: 10.1177/2516865719849090] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/09/2019] [Indexed: 12/25/2022] Open
Abstract
Entry into mitosis correlates with nucleolar disassembly and shutdown of ribosomal RNA (rRNA) gene (rDNA) transcription. In telophase, nucleoli reform and transcription is reactivated. The molecular mechanisms underlying the dynamics of nucleolar transcription during the cell cycle are manifold. Although mitotic inactivation of the RNA polymerase I (Pol I) transcription machinery by posttranslational modifications has been extensively studied, little is known about the structure of rDNA chromatin during progression through mitosis. Methylation of histone H2A at glutamine 104 (H2AQ104me), a dedicated nucleolar histone modification, is lost in prometaphase, leading to chromatin compaction, which enforces mitotic repression of rRNA genes. At telophase, restoration of H2AQ104me is required for the activation of transcription. H2AQ104 methylation and chromatin dynamics are regulated by fibrillarin (FBL) and the NAD+-dependent nucleolar deacetylase sirtuin 7 (SIRT7). Deacetylation of FBL is required for the methylation of H2AQ104 and high levels of rDNA transcription during interphase. At the entry into mitosis, nucleoli disassemble and FBL is hyperacetylated, leading to loss of H2AQ104me, chromatin compaction, and shutdown of Pol I transcription. These results reveal that reversible acetylation of FBL regulates methylation of nucleolar H2AQ104, thereby reinforcing oscillation of Pol I transcription during the cell cycle.
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Affiliation(s)
| | - Ingrid Grummt
- German Cancer Research Centre, DKFZ-ZMBH Alliance, Heidelberg, Germany
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21
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Rashidi M, Jebali A. Liposomal prodigiosin and plasmid encoding serial GCA nucleotides reduce inflammation in microglial and astrocyte cells by ATM/ATR signaling. J Neuroimmunol 2018; 326:75-78. [PMID: 30530109 DOI: 10.1016/j.jneuroim.2018.11.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/17/2018] [Accepted: 11/30/2018] [Indexed: 10/27/2022]
Abstract
The aim of this study was to use liposomal structure consisting prodigiosin and plasmid encoding serial GCA nucleotides (LP/pSGCAN) to reduce inflammation in microglial cells (MGCs) and astrocyte cells (ACCs) by ATM/ATR signaling. Here, it was shown that LP/pSGCAN decreased cell viability and total RNA level. Importantly, LP/pSGCAN had more effect on ACCs than MGCs (P < 0.05). Moreover, increase of apoptosis was seen with increase of concentration. The expression of IL-1 and IL-6 were decreased and the expression of ATM and ATR were increased in treated MGCs and ACCs, which showed LP/pSGCAN could inhibit inflammation by activation of ATM/ATR pathway.
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Affiliation(s)
- Mohsen Rashidi
- Department of Physiology and Pharmacology, Faculty of medicine, Mazandaran University of Medical Science, Sari, Iran
| | - Ali Jebali
- Department of Laboratory Sciences, School of Paramedicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran; Medical Biotechnology Research Center, Ashkezar Branch, Islamic Azad University, Ashkezar, Yazd, Iran.
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22
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Mitrea DM, Chandra B, Ferrolino MC, Gibbs EB, Tolbert M, White MR, Kriwacki RW. Methods for Physical Characterization of Phase-Separated Bodies and Membrane-less Organelles. J Mol Biol 2018; 430:4773-4805. [PMID: 30017918 PMCID: PMC6503534 DOI: 10.1016/j.jmb.2018.07.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/04/2018] [Accepted: 07/09/2018] [Indexed: 12/17/2022]
Abstract
Membrane-less organelles are cellular structures which arise through the phenomenon of phase separation. This process enables compartmentalization of specific sets of macromolecules (e.g., proteins, nucleic acids), thereby regulating cellular processes by increasing local concentration, and modulating the structure and dynamics of their constituents. Understanding the connection between structure, material properties and function of membrane-less organelles requires inter-disciplinary approaches, which address length and timescales that span several orders of magnitude (e.g., Ångstroms to micrometer, picoseconds to hours). In this review, we discuss the wide variety of methods that have been applied to characterize the morphology, rheology, structure and dynamics of membrane-less organelles and their components, in vitro and in live cells.
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Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| | - Bappaditya Chandra
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mylene C Ferrolino
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Eric B Gibbs
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michele Tolbert
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michael R White
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA.
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23
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Sawyer IA, Sturgill D, Dundr M. Membraneless nuclear organelles and the search for phases within phases. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 10:e1514. [DOI: 10.1002/wrna.1514] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/20/2018] [Accepted: 09/27/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Iain A. Sawyer
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - David Sturgill
- Laboratory of Receptor Biology and Gene Expression National Cancer Institute, National Institutes of Health Bethesda Maryland
| | - Miroslav Dundr
- Department of Cell Biology and Anatomy, Chicago Medical School Rosalind Franklin University of Medicine and Science North Chicago Illinois
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24
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Petrović A, Petrović V, Jovanović D, Antović A, Milić M, Kocić H. LIGHT - MICROSCOPIC AND MORP HOMETRIC PROPERTIES OF ARGYROPHILIC NUCLEOL AR ORGANIZING REGION S IN DEEP EPIDERMAL RIDGES OF HUMAN THICK SKIN. ACTA MEDICA MEDIANAE 2018. [DOI: 10.5633/amm.2018.0118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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25
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Sen Gupta A, Sengupta K. Lamin B2 Modulates Nucleolar Morphology, Dynamics, and Function. Mol Cell Biol 2017; 37:e00274-17. [PMID: 28993479 PMCID: PMC5705821 DOI: 10.1128/mcb.00274-17] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/05/2017] [Accepted: 09/29/2017] [Indexed: 01/11/2023] Open
Abstract
The nucleolus is required for ribosome biogenesis. Human cells have 2 or 3 nucleoli associated with nucleolar organizer region (NOR)-bearing chromosomes. An increase in number and altered nucleolar morphology define cancer cells. However, the mechanisms that modulate nucleolar morphology and function are unclear. Here we show that in addition to localizing at the nuclear envelope, lamin B2 localizes proximal to nucleolin at the granular component (GC) of the nucleolus and associates with the nucleolar proteins nucleolin and nucleophosmin. Lamin B2 knockdown severely disrupted the nucleolar morphology, which was rescued to intact and discrete nucleoli upon lamin B2 overexpression. Furthermore, two mutually exclusive lamin B2 deletion mutants, ΔHead and ΔSLS, rescued nuclear and nucleolar morphology defects, respectively, induced upon lamin B2 depletion, suggesting independent roles for lamin B2 at the nucleolus and nuclear envelope. Lamin B2 depletion increased nucleolin aggregation in the nucleoplasm, implicating lamin B2 in stabilizing nucleolin within the nucleolus. Lamin B2 knockdown upregulated nucleolus-specific 45S rRNA and upstream intergenic sequence (IGS) transcripts. The IGS transcripts colocalized with aggregates of nucleolin speckles, which were sustained in the nucleoplasm upon lamin B2 depletion. Taken together, these studies uncover a novel role for lamin B2 in modulating the morphology, dynamics, and function of the nucleolus.
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Affiliation(s)
- Ayantika Sen Gupta
- Biology, Indian Institute of Science Education and Research, Pune, India
| | - Kundan Sengupta
- Biology, Indian Institute of Science Education and Research, Pune, India
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26
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Tchelidze P, Benassarou A, Kaplan H, O’Donohue MF, Lucas L, Terryn C, Rusishvili L, Mosidze G, Lalun N, Ploton D. Nucleolar sub-compartments in motion during rRNA synthesis inhibition: Contraction of nucleolar condensed chromatin and gathering of fibrillar centers are concomitant. PLoS One 2017; 12:e0187977. [PMID: 29190286 PMCID: PMC5708645 DOI: 10.1371/journal.pone.0187977] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 10/30/2017] [Indexed: 12/26/2022] Open
Abstract
The nucleolus produces the large polycistronic transcript (47S precursor) containing the 18S, 5.8S and 28S rRNA sequences and hosts most of the nuclear steps of pre-rRNA processing. Among numerous components it contains condensed chromatin and active rRNA genes which adopt a more accessible conformation. For this reason, it is a paradigm of chromosome territory organization. Active rRNA genes are clustered within several fibrillar centers (FCs), in which they are maintained in an open configuration by Upstream Binding Factor (UBF) molecules. Here, we used the reproducible reorganization of nucleolar components induced by the inhibition of rRNA synthesis by Actinomycin D (AMD) to address the steps of the spatiotemporal reorganization of FCs and nucleolar condensed chromatin. To reach that goal, we used two complementary approaches: i) time-lapse confocal imaging of cells expressing one or several GFP-tagged proteins (fibrillarin, UBF, histone H2B) and ii) ultrastructural identification of nucleolar components involved in the reorganization. Data obtained by time lapse confocal microscopy were analyzed through detailed 3D imaging. This allowed us to demonstrate that AMD treatment induces no fusion and no change in the relative position of the different nucleoli contained in one nucleus. In contrast, for each nucleolus, we observed step by step gathering and fusion of both FCs and nucleolar condensed chromatin. To analyze the reorganization of FCs and condensed chromatin at a higher resolution, we performed correlative light and electron microscopy electron microscopy (CLEM) imaging of the same cells. We demonstrated that threads of intranucleolar condensed chromatin are localized in a complex 3D network of vacuoles. Upon AMD treatment, these structures coalesce before migrating toward the perinucleolar condensed chromatin, to which they finally fuse. During their migration, FCs, which are all linked to ICC, are pulled by the latter to gather as caps disposed at the periphery of nucleoli.
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Affiliation(s)
- Pavel Tchelidze
- Faculty of Exact and Life Sciences, Department of Morphology, Tbilisi State University, Tbilisi, Georgia
| | - Aassif Benassarou
- EA 3804 (CRESTIC), Université de Reims Champagne Ardenne, Reims, France
| | - Hervé Kaplan
- Université de Reims Champagne Ardenne, Reims, France
| | - Marie-Françoise O’Donohue
- Laboratoire de Biologie Moléculaire Eukaryote, Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, UPS, Toulouse, France
| | - Laurent Lucas
- EA 3804 (CRESTIC), Université de Reims Champagne Ardenne, Reims, France
| | - Christine Terryn
- Platform of Cellular and Tissular Imaging (PICT), Université de Reims Champagne Ardenne, Reims, France
| | - Levan Rusishvili
- Faculty of Exact and Life Sciences, Department of Morphology, Tbilisi State University, Tbilisi, Georgia
| | - Giorgi Mosidze
- Faculty of Exact and Life Sciences, Department of Morphology, Tbilisi State University, Tbilisi, Georgia
| | - Nathalie Lalun
- CNRS UMR 7369, Université de Reims Champagne Ardenne, Reims, France
| | - Dominique Ploton
- CNRS UMR 7369, Université de Reims Champagne Ardenne, Reims, France
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27
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Roberts B, Haupt A, Tucker A, Grancharova T, Arakaki J, Fuqua MA, Nelson A, Hookway C, Ludmann SA, Mueller IA, Yang R, Horwitz R, Rafelski SM, Gunawardane RN. Systematic gene tagging using CRISPR/Cas9 in human stem cells to illuminate cell organization. Mol Biol Cell 2017; 28:2854-2874. [PMID: 28814507 PMCID: PMC5638588 DOI: 10.1091/mbc.e17-03-0209] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 08/09/2017] [Accepted: 08/10/2017] [Indexed: 12/12/2022] Open
Abstract
The generation of a collection of human induced pluripotent stem cell (hiPSC) lines expressing endogenously GFP-tagged proteins using CRISPR/Cas9 methods is described. The methods used and the genomic and cell biological data validating the GFP-tagged hiPSC lines are also presented. We present a CRISPR/Cas9 genome-editing strategy to systematically tag endogenous proteins with fluorescent tags in human induced pluripotent stem cells (hiPSC). To date, we have generated multiple hiPSC lines with monoallelic green fluorescent protein tags labeling 10 proteins representing major cellular structures. The tagged proteins include alpha tubulin, beta actin, desmoplakin, fibrillarin, nuclear lamin B1, nonmuscle myosin heavy chain IIB, paxillin, Sec61 beta, tight junction protein ZO1, and Tom20. Our genome-editing methodology using Cas9/crRNA ribonuclear protein and donor plasmid coelectroporation, followed by fluorescence-based enrichment of edited cells, typically resulted in <0.1–4% homology-directed repair (HDR). Twenty-five percent of clones generated from each edited population were precisely edited. Furthermore, 92% (36/39) of expanded clonal lines displayed robust morphology, genomic stability, expression and localization of the tagged protein to the appropriate subcellular structure, pluripotency-marker expression, and multilineage differentiation. It is our conclusion that, if cell lines are confirmed to harbor an appropriate gene edit, pluripotency, differentiation potential, and genomic stability are typically maintained during the clonal line–generation process. The data described here reveal general trends that emerged from this systematic gene-tagging approach. Final clonal lines corresponding to each of the 10 cellular structures are now available to the research community.
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Affiliation(s)
| | - Amanda Haupt
- Allen Institute for Cell Science, Seattle, WA 98109
| | | | | | - Joy Arakaki
- Allen Institute for Cell Science, Seattle, WA 98109
| | | | | | | | | | | | - Ruian Yang
- Allen Institute for Cell Science, Seattle, WA 98109
| | - Rick Horwitz
- Allen Institute for Cell Science, Seattle, WA 98109
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28
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Musinova YR, Lisitsyna OM, Sorokin DV, Arifulin EA, Smirnova TA, Zinovkin RA, Potashnikova DM, Vassetzky YS, Sheval EV. RNA-dependent disassembly of nuclear bodies. J Cell Sci 2016; 129:4509-4520. [PMID: 27875271 DOI: 10.1242/jcs.189142] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Accepted: 11/02/2016] [Indexed: 12/17/2022] Open
Abstract
Nuclear bodies are membraneless organelles that play important roles in genome functioning. A specific type of nuclear bodies known as interphase prenucleolar bodies (iPNBs) are formed in the nucleoplasm after hypotonic stress from partially disassembled nucleoli. iPNBs are then disassembled, and the nucleoli are reformed simultaneously. Here, we show that diffusion of B23 molecules (also known as nucleophosmin, NPM1) from iPNBs, but not fusion of iPNBs with the nucleoli, contributes to the transfer of B23 from iPNBs to the nucleoli. Maturation of pre-ribosomal RNAs (rRNAs) and the subsequent outflow of mature rRNAs from iPNBs led to the disassembly of iPNBs. We found that B23 transfer was dependent on the synthesis of pre-rRNA molecules in nucleoli; these pre-rRNA molecules interacted with B23 and led to its accumulation within nucleoli. The transfer of B23 between iPNBs and nucleoli was accomplished through a nucleoplasmic pool of B23, and increased nucleoplasmic B23 content retarded disassembly, whereas B23 depletion accelerated disassembly. Our results suggest that iPNB disassembly and nucleolus assembly might be coupled through RNA-dependent exchange of nucleolar proteins, creating a highly dynamic system with long-distance correlations between spatially distinct processes.
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Affiliation(s)
- Yana R Musinova
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia.,LIA1066 French-Russian Joint Cancer Research Laboratory, Villejuif 94805, France
| | - Olga M Lisitsyna
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Dmitry V Sorokin
- Centre for Biomedical Image Analysis, Faculty of Informatics, Masaryk University, Botanická 68a, Brno 602 00, Czech Republic.,Laboratory of Mathematical Methods of Image Processing, Faculty of Computational Mathematics and Cybernetics, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Eugene A Arifulin
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Tatiana A Smirnova
- Department of Cell Biology and Histology, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Roman A Zinovkin
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Daria M Potashnikova
- Department of Cell Biology and Histology, Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia
| | - Yegor S Vassetzky
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia.,LIA1066 French-Russian Joint Cancer Research Laboratory, Villejuif 94805, France.,UMR8126, Université Paris-Sud, CNRS, Institut de cancérologie Gustave Roussy, Villejuif 94805, France
| | - Eugene V Sheval
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Moscow 119992, Russia .,LIA1066 French-Russian Joint Cancer Research Laboratory, Villejuif 94805, France
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29
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Kashida H, Morimoto K, Asanuma H. A stem-less probe using spontaneous pairing between Cy3 and quencher for RNA detection. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2016; 17:267-273. [PMID: 27877879 PMCID: PMC5101869 DOI: 10.1080/14686996.2016.1182412] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 03/30/2016] [Accepted: 04/05/2016] [Indexed: 05/26/2023]
Abstract
We herein report a stem-less probe for the detection of RNA that depends on pairing between Cy3 and nitro methyl red. In our design, two Cy3 residues and two nitro methyl red residues were introduced into an oligonucleotide. In the absence of the target, these dyes formed a complex, and emission of Cy3 was efficiently quenched. Hybridization with the target RNA disrupted this interaction and resulted in Cy3 emission. Under optimized conditions, the signal to background ratio was as high as 180. We demonstrated specific detection of target RNA in cells using a wash-free FISH protocol.
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Affiliation(s)
- Hiromu Kashida
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8603, Japan
- Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama332-0012, Japan
| | - Kazuhiro Morimoto
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8603, Japan
| | - Hiroyuki Asanuma
- Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8603, Japan
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30
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Martin RM, Ter-Avetisyan G, Herce HD, Ludwig AK, Lättig-Tünnemann G, Cardoso MC. Principles of protein targeting to the nucleolus. Nucleus 2016; 6:314-25. [PMID: 26280391 PMCID: PMC4615656 DOI: 10.1080/19491034.2015.1079680] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The nucleolus is the hallmark of nuclear compartmentalization and has been shown to exert multiple roles in cellular metabolism besides its main function as the place of rRNA synthesis and assembly of ribosomes. Nucleolar proteins dynamically localize and accumulate in this nuclear compartment relative to the surrounding nucleoplasm. In this study, we have assessed the molecular requirements that are necessary and sufficient for the localization and accumulation of peptides and proteins inside the nucleoli of living cells. The data showed that positively charged peptide entities composed of arginines alone and with an isoelectric point at and above 12.6 are necessary and sufficient for mediating significant nucleolar accumulation. A threshold of 6 arginines is necessary for peptides to accumulate in nucleoli, but already 4 arginines are sufficient when fused within 15 amino acid residues of a nuclear localization signal of a protein. Using a pH sensitive dye, we found that the nucleolar compartment is particularly acidic when compared to the surrounding nucleoplasm and, hence, provides the ideal electrochemical environment to bind poly-arginine containing proteins. In fact, we found that oligo-arginine peptides and GFP fusions bind RNA in vitro. Consistent with RNA being the main binding partner for arginines in the nucleolus, we found that the same principles apply to cells from insects to man, indicating that this mechanism is highly conserved throughout evolution.
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Affiliation(s)
- Robert M Martin
- a Instituto de Medicina Molecular ; Faculdade de Medicina ; Universidade de Lisboa ; Lisboa , Portugal
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31
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Nepomuceno-Mejía T, Lara-Martínez R, Hernández R, Segura-Valdez MDL, Jiménez-García LF. Nucleologenesis in Trypanosoma cruzi. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2016; 22:621-629. [PMID: 27126372 DOI: 10.1017/s1431927616000623] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Nucleolar assembly is a cellular event that requires the synthesis and processing of ribosomal RNA, in addition to the participation of pre-nucleolar bodies (PNBs) at the end of mitosis. In mammals and plants, nucleolar biogenesis has been described in detail, but in unicellular eukaryotes it is a poorly understood process. In this study, we used light and electron microscopy cytochemical techniques to investigate the distribution of nucleolar components in the pathway of nucleolus rebuilding during closed cell division in epimastigotes of Trypanosoma cruzi, the etiologic agent of American trypanosomiasis. Silver impregnation specific for nucleolar organizer regions and an ethylenediaminetetraacetic acid regressive procedure to preferentially stain ribonucleoprotein revealed the conservation and dispersion of nucleolar material throughout the nucleoplasm during cell division. Furthermore, at the end of mitosis, the argyrophilic proteins were concentrated in the nucleolar organizer region. Unexpectedly, accumulation of nucleolar material in the form of PNBs was not visualized. We suggest that formation of the nucleolus in epimastigotes of T. cruzi occurs by a process that does not require the concentration of nucleolar material within intermediate nuclear bodies such as mammalian and plant PNBs.
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Affiliation(s)
- Tomás Nepomuceno-Mejía
- 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México
| | - Reyna Lara-Martínez
- 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México
| | - Roberto Hernández
- 2Department of Molecular Biology and Biotechnology,Biomedical Research Institute,National Autonomous University of Mexico,México Cd. Mx. 04510,México
| | - María de Lourdes Segura-Valdez
- 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México
| | - Luis F Jiménez-García
- 1Laboratory of Electron Microscopy, Faculty of Science,National Autonomous University of Mexico,México Cd. Mx. 04510,México
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32
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Dynamic Nucleolar Targeting of Dengue Virus Polymerase NS5 in Response to Extracellular pH. J Virol 2016; 90:5797-5807. [PMID: 27076639 DOI: 10.1128/jvi.02727-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 02/29/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED The nucleolar subcompartment of the nucleus is increasingly recognized as an important target of RNA viruses. Here we document for the first time the ability of dengue virus (DENV) polymerase, nonstructural protein 5 (NS5), to accumulate within the nucleolus of infected cells and to target green fluorescent protein (GFP) to the nucleolus of live transfected cells. Intriguingly, NS5 exchange between the nucleus and nucleolus is dynamically modulated by extracellular pH, responding rapidly and reversibly to pH change, in contrast to GFP alone or other nucleolar and non-nucleolar targeted protein controls. The minimal pH-sensitive nucleolar targeting region (pHNTR), sufficient to target GFP to the nucleolus in a pH-sensitive fashion, was mapped to NS5 residues 1 to 244, with mutation of key hydrophobic residues, Leu-165, Leu-167, and Val-168, abolishing pHNTR function in NS5-transfected cells, and severely attenuating DENV growth in infected cells. This is the first report of a viral protein whose nucleolar targeting ability is rapidly modulated by extracellular stimuli, suggesting that DENV has the ability to detect and respond dynamically to the extracellular environment. IMPORTANCE Infections by dengue virus (DENV) threaten 40% of the world's population yet there is no approved vaccine or antiviral therapeutic to treat infections. Understanding the molecular details that govern effective viral replication is key for the development of novel antiviral strategies. Here, we describe for the first time dynamic trafficking of DENV nonstructural protein 5 (NS5) to the subnuclear compartment, the nucleolus. We demonstrate that NS5's targeting to the nucleolus occurs in response to acidic pH, identify the key amino acid residues within NS5 that are responsible, and demonstrate that their mutation severely impairs production of infectious DENV. Overall, this study identifies a unique subcellular trafficking event and suggests that DENV is able to detect and respond dynamically to environmental changes.
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33
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Negi SS, Brown P. rRNA synthesis inhibitor, CX-5461, activates ATM/ATR pathway in acute lymphoblastic leukemia, arrests cells in G2 phase and induces apoptosis. Oncotarget 2016; 6:18094-104. [PMID: 26061708 PMCID: PMC4627237 DOI: 10.18632/oncotarget.4093] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 05/23/2015] [Indexed: 12/13/2022] Open
Abstract
Ribosome biogenesis is a fundamental cellular process and is elevated in cancer cells. As one of the most energy consuming cellular processes, it is highly regulated by signaling pathways in response to changing cellular conditions. Many of the regulators of this process are aberrantly activated in various cancers. Recently two novel rRNA synthesis inhibitors, CX-5461 and BMH-21, have been shown to selectively kill cancer cells while sparing normal cells. Here, we tested the effectiveness of pre-rRNA synthesis inhibitor CX-5461 on acute lymphoblastic leukemia cells with different cytogenetic abnormalities. Acute lymphoblastic leukemia cells are more sensitive to rRNA synthesis inhibition compared to normal bone marrow cells. CX-5461 treated cells undergo caspase-dependent apoptosis independent of their p53 status. More-over, CX5461, activates checkpoint kinases and arrests cells in G2 phase of cell cycle. Finally, overcoming this G2 arrest by inhibiting ATR kinase leads to robust cell killing. These results show that CX-5461 can be even more potent in combination with ATR inhibitors.
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Affiliation(s)
- Sandeep S Negi
- Department of Oncology and Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Patrick Brown
- Department of Oncology and Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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34
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Todd MAM, Huh MS, Picketts DJ. The sub-nucleolar localization of PHF6 defines its role in rDNA transcription and early processing events. Eur J Hum Genet 2016; 24:1453-9. [PMID: 27165002 PMCID: PMC5027685 DOI: 10.1038/ejhg.2016.40] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 03/30/2016] [Accepted: 04/12/2016] [Indexed: 12/20/2022] Open
Abstract
Ribosomal RNA synthesis occurs in the nucleolus and is a tightly regulated process that is targeted in some developmental diseases and hyperactivated in multiple cancers. Subcellular localization and immunoprecipitation coupled mass spectrometry demonstrated that a proportion of plant homeodomain (PHD) finger protein 6 (PHF6) protein is localized within the nucleolus and interacts with proteins involved in ribosomal processing. PHF6 sequence variants cause Börjeson–Forssman–Lehmann syndrome (BFLS, MIM#301900) and are also associated with a female-specific phenotype overlapping with Coffin–Siris syndrome (MIM#135900), T-cell acute lymphoblastic leukemia (MIM#613065), and acute myeloid leukemia (MIM#601626); however, very little is known about its cellular function, including its nucleolar role. HEK 293T cells were treated with RNase A, DNase I, actinomycin D, or 5,6-dichloro-β-D-ribofuranosylbenzimadole, followed by immunocytochemistry to determine PHF6 sub-nucleolar localization. We observed RNA-dependent localization of PHF6 to the sub-nucleolar fibrillar center (FC) and dense fibrillar component (DFC), at whose interface rRNA transcription occurs. Subsequent ChIP-qPCR analysis revealed strong enrichment of PHF6 across the entire rDNA-coding sequence but not along the intergenic spacer (IGS) region. When rRNA levels were quantified in a PHF6 gain-of-function model, we observed an overall decrease in rRNA transcription, accompanied by a modest increase in repressive promoter-associated RNA (pRNA) and a significant increase in the expression levels of the non-coding IGS36RNA and IGS39RNA transcripts. Collectively, our results demonstrate a role for PHF6 in carefully mediating the overall levels of ribosome biogenesis within a cell.
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Affiliation(s)
- Matthew A M Todd
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.,Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Michael S Huh
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - David J Picketts
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.,Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.,Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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35
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Lara-Martínez R, De Lourdes Segura-Valdez M, De La Mora-De La Mora I, López-Velázquez G, JimÉnez-García LF. Morphological Studies of Nucleologenesis inGiardia lamblia. Anat Rec (Hoboken) 2016; 299:549-56. [DOI: 10.1002/ar.23323] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 11/30/2015] [Accepted: 12/07/2015] [Indexed: 11/05/2022]
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36
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Falahati H, Pelham-Webb B, Blythe S, Wieschaus E. Nucleation by rRNA Dictates the Precision of Nucleolus Assembly. Curr Biol 2016; 26:277-85. [PMID: 26776729 PMCID: PMC5866055 DOI: 10.1016/j.cub.2015.11.065] [Citation(s) in RCA: 131] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 10/27/2015] [Accepted: 11/25/2015] [Indexed: 02/05/2023]
Abstract
Membrane-less organelles are intracellular compartments specialized to carry out specific cellular functions. There is growing evidence supporting the possibility that such organelles form as a new phase, separating from cytoplasm or nucleoplasm. However, a main challenge to such phase separation models is that the initial assembly, or nucleation, of the new phase is typically a highly stochastic process and does not allow for the spatiotemporal precision observed in biological systems. Here, we investigate the initial assembly of the nucleolus, a membrane-less organelle involved in different cellular functions including ribosomal biogenesis. We demonstrate that the nucleolus formation is precisely timed in D. melanogaster embryos and follows the transcription of rRNA. We provide evidence that transcription of rRNA is necessary for overcoming the highly stochastic nucleation step in the formation of the nucleolus, through a seeding mechanism. In the absence of rDNA, the nucleolar proteins studied are able to form high-concentration assemblies. However, unlike the nucleolus, these assemblies are highly variable in number, location, and time at which they form. In addition, quantitative study of the changes in the nucleoplasmic concentration and distribution of these nucleolar proteins in the wild-type embryos is consistent with the role of rRNA in seeding the nucleolus formation.
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Affiliation(s)
- Hanieh Falahati
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Bobbie Pelham-Webb
- Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065, USA
| | - Shelby Blythe
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA
| | - Eric Wieschaus
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA; Howard Hughes Medical Institute, Princeton University, Princeton, NJ 08544, USA.
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37
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Abstract
The nucleolus is the largest nuclear organelle and is the primary site of ribosome subunit biogenesis in eukaryotic cells. It is assembled around arrays of ribosomal DNA genes, forming specific chromosomal features known as nucleolar organizing regions (NORs) which are the sites of ribosomal DNA transcription. While the nucleolus main activity involve different steps of ribosome biogenesis, the presence of proteins with no obvious relationship with ribosome subunit production suggests additional functions for the nucleolus, such as regulation of mitosis, cell cycle progression, stress response and biogenesis of multiple ribonucleoprotein complexes. The many novel factors and separate classes of proteins identified within the nucleolus support this view that the nucleolus may perform additional functions beyond its known role in ribosome subunit biogenesis. Here we review our knowledge of the nucleolar functions and will provide a detailed picture of how the nucleolus is involved in many cellular pathways.
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Affiliation(s)
- David P. Bazett-Jones
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario Canada
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38
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Martin RM, Herce HD, Ludwig AK, Cardoso MC. Visualization of the Nucleolus in Living Cells with Cell-Penetrating Fluorescent Peptides. Methods Mol Biol 2016; 1455:71-82. [PMID: 27576711 DOI: 10.1007/978-1-4939-3792-9_6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The nucleolus is the hallmark of nuclear compartmentalization and has been shown to exert multiple roles in cellular metabolism besides its main function as the place of ribosomal RNA synthesis and assembly of ribosomes. The nucleolus plays also a major role in nuclear organization as the largest compartment within the nucleus. The prominent structure of the nucleolus can be detected using contrast light microscopy providing an approximate localization of the nucleolus, but this approach does not allow to determine accurately the three-dimensional structure of the nucleolus in cells and tissues. Immunofluorescence staining with antibodies specific to nucleolar proteins albeit very useful is time consuming, normally antibodies recognize their epitopes only within a small range of species and is applicable only in fixed cells. Here, we present a simple method to selectively and accurately label this ubiquitous subnuclear compartment in living cells of a large range of species using a fluorescently labeled cell-penetrating peptide.
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Affiliation(s)
- Robert M Martin
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028, Lisbon, Portugal
| | - Henry D Herce
- Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287, Darmstadt, Germany
| | - Anne K Ludwig
- Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287, Darmstadt, Germany
| | - M Cristina Cardoso
- Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287, Darmstadt, Germany.
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39
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Sirri V, Jourdan N, Hernandez-Verdun D, Roussel P. Sharing the mitotic pre-ribosomal particles between daughter cells. J Cell Sci 2016; 129:1592-604. [DOI: 10.1242/jcs.180521] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 02/20/2016] [Indexed: 01/05/2023] Open
Abstract
Ribosome biogenesis is a fundamental multistep process initiated by the synthesis of 90S pre-ribosomal particles in the nucleoli of higher eukaryotes. Even though synthesis of ribosomes stops during mitosis while nucleoli disappear, mitotic pre-ribosomal particles persist as observed in prenucleolar bodies (PNBs) during telophase. To further understand the relationship between the nucleolus and the PNBs, the presence and the fate of the mitotic pre-ribosomal particles during cell division was investigated. We demonstrate that the recently synthesized 45S precursor ribosomal RNAs (pre-rRNAs) but also the 32S and 30S pre-rRNAs are maintained during mitosis and associated with the chromosome periphery together with pre-rRNA processing factors. Maturation of the mitotic pre-ribosomal particles, as assessed by the stability of the mitotic pre-rRNAs, is transiently arrested during mitosis by a cyclin-dependent kinase (CDK)1-cyclin B-dependent mechanism and may be restored by CDK inhibitor treatments. At the M/G1 transition, the resumption of mitotic pre-rRNA processing in PNBs does not induce the disappearance of PNBs that only occurs when functional nucleoli reform. Strikingly, during their maturation process, mitotic pre-rRNAs localize in reforming nucleoli.
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Affiliation(s)
- Valentina Sirri
- Univ. Paris Diderot, Unit of Functional and Adaptive Biology, UMR 8251 CNRS, 4 rue Marie-Andrée Lagroua Weill-Hallé, F-75205 Paris, France
| | - Nathalie Jourdan
- UPMC Univ. Paris 06, Institut de Biologie Paris Seine, UMR 8256 CNRS, 9 quai St Bernard, F-75252 Paris, France
| | - Danièle Hernandez-Verdun
- Univ. Paris Diderot, Institut Jacques Monod, UMR 7592 CNRS, 15 rue Hélène Brion, F‑75205 Paris, France
| | - Pascal Roussel
- Univ. Paris Diderot, Unit of Functional and Adaptive Biology, UMR 8251 CNRS, 4 rue Marie-Andrée Lagroua Weill-Hallé, F-75205 Paris, France
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Salomon-Kent R, Marom R, John S, Dundr M, Schiltz LR, Gutierrez J, Workman J, Benayahu D, Hager GL. New Face for Chromatin-Related Mesenchymal Modulator: n-CHD9 Localizes to Nucleoli and Interacts With Ribosomal Genes. J Cell Physiol 2015; 230:2270-80. [PMID: 25689118 DOI: 10.1002/jcp.24960] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 02/11/2015] [Indexed: 01/01/2023]
Abstract
Mesenchymal stem cells' differentiation into several lineages is coordinated by a complex of transcription factors and co-regulators which bind to specific gene promoters. The Chromatin-Related Mesenchymal Modulator, CHD9 demonstrated in vitro its ability for remodeling activity to reposition nucleosomes in an ATP-dependent manner. Epigenetically, CHD9 binds with modified H3-(K9me2/3 and K27me3). Previously, we presented a role for CHD9 with RNA Polymerase II (Pol II)-dependent transcription of tissue specific genes. Far less is known about CHD9 function in RNA Polymerase I (Pol I) related transcription of the ribosomal locus that also drives specific cell fate. We here describe a new form, the nucleolar CHD9 (n-CHD9) that is dynamically associated with Pol I, fibrillarin, and upstream binding factor (UBF) in the nucleoli, as shown by imaging and molecular approaches. Inhibitors of transcription disorganized the nucleolar compartment of transcription sites where rDNA is actively transcribed. Collectively, these findings link n-CHD9 with RNA pol I transcription in fibrillar centers. Using chromatin immunoprecipitation (ChIP) and tilling arrays (ChIP- chip), we find an association of n-CHD9 with Pol I related to rRNA biogenesis. Our new findings support the role for CHD9 in chromatin regulation and association with rDNA genes, in addition to its already known function in transcription control of tissue specific genes.
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Affiliation(s)
- Ronit Salomon-Kent
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
| | - Ronit Marom
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel.,Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
| | - Sam John
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
| | - Miroslav Dundr
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
| | - Louis R Schiltz
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
| | - Jose Gutierrez
- Stowers Institute for Medical Research, Kansas City, Missouri
| | - Jerry Workman
- Stowers Institute for Medical Research, Kansas City, Missouri
| | - Dafna Benayahu
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel
| | - Gordon L Hager
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, Maryland
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Muro E, Gébrane-Younès J, Jobart-Malfait A, Louvet E, Roussel P, Hernandez-Verdun D. The traffic of proteins between nucleolar organizer regions and prenucleolar bodies governs the assembly of the nucleolus at exit of mitosis. Nucleus 2014. [DOI: 10.4161/nucl.11334] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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42
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Booth DG, Takagi M, Sanchez-Pulido L, Petfalski E, Vargiu G, Samejima K, Imamoto N, Ponting CP, Tollervey D, Earnshaw WC, Vagnarelli P. Ki-67 is a PP1-interacting protein that organises the mitotic chromosome periphery. eLife 2014; 3:e01641. [PMID: 24867636 PMCID: PMC4032110 DOI: 10.7554/elife.01641] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Accepted: 04/27/2014] [Indexed: 12/23/2022] Open
Abstract
When the nucleolus disassembles during open mitosis, many nucleolar proteins and RNAs associate with chromosomes, establishing a perichromosomal compartment coating the chromosome periphery. At present nothing is known about the function of this poorly characterised compartment. In this study, we report that the nucleolar protein Ki-67 is required for the assembly of the perichromosomal compartment in human cells. Ki-67 is a cell-cycle regulated protein phosphatase 1-binding protein that is involved in phospho-regulation of the nucleolar protein B23/nucleophosmin. Following siRNA depletion of Ki-67, NIFK, B23, nucleolin, and four novel chromosome periphery proteins all fail to associate with the periphery of human chromosomes. Correlative light and electron microscopy (CLEM) images suggest a near-complete loss of the entire perichromosomal compartment. Mitotic chromosome condensation and intrinsic structure appear normal in the absence of the perichromosomal compartment but significant differences in nucleolar reassembly and nuclear organisation are observed in post-mitotic cells.DOI: http://dx.doi.org/10.7554/eLife.01641.001.
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Affiliation(s)
- Daniel G Booth
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Masatoshi Takagi
- Cellular Dynamics Laboratory, Riken Advanced Science Institute, Wako Saitama, Japan
| | - Luis Sanchez-Pulido
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Elizabeth Petfalski
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Giulia Vargiu
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Kumiko Samejima
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - Naoko Imamoto
- Cellular Dynamics Laboratory, Riken Advanced Science Institute, Wako Saitama, Japan
| | - Chris P Ponting
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - David Tollervey
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
| | - William C Earnshaw
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, United Kingdom
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Louvet E, Yoshida A, Kumeta M, Takeyasu K. Probing the stiffness of isolated nucleoli by atomic force microscopy. Histochem Cell Biol 2014; 141:365-81. [PMID: 24297448 DOI: 10.1007/s00418-013-1167-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2013] [Indexed: 11/24/2022]
Abstract
In eukaryotic cells, ribosome biogenesis occurs in the nucleolus, a membraneless nuclear compartment. Noticeably, the nucleolus is also involved in several nuclear functions, such as cell cycle regulation, non-ribosomal ribonucleoprotein complex assembly, aggresome formation and some virus assembly. The most intriguing question about the nucleolus is how such dynamics processes can occur in such a compact compartment. We hypothesized that its structure may be rather flexible. To investigate this, we used atomic force microscopy (AFM) on isolated nucleoli. Surface topography imaging revealed the beaded structure of the nucleolar surface. With the AFM's ability to measure forces, we were able to determine the stiffness of isolated nucleoli. We could establish that the nucleolar stiffness varies upon drastic morphological changes induced by transcription and proteasome inhibition. Furthermore, upon ribosomal proteins and LaminB1 knockdowns, the nucleolar stiffness was increased. This led us to propose a model where the nucleolus has steady-state stiffness dependent on ribosome biogenesis activity and requires LaminB1 for its flexibility.
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Affiliation(s)
- Emilie Louvet
- Graduate School of Biostudies, Kyoto University, Kyoto, 606-8501, Japan,
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44
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Lisitsyna OM, Musinova YR, Shubina MY, Polyakov VY, Sheval EV. The role of interphase prenucleolar bodies in the recovery of the nucleolar structure after reversible hypotonic treatment. BIOL BULL+ 2013. [DOI: 10.1134/s1062359013060083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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45
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Hirai Y, Louvet E, Oda T, Kumeta M, Watanabe Y, Horigome T, Takeyasu K. Nucleolar scaffold protein, WDR46, determines the granular compartmental localization of nucleolin and DDX21. Genes Cells 2013; 18:780-97. [PMID: 23848194 DOI: 10.1111/gtc.12077] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Accepted: 05/16/2013] [Indexed: 12/01/2022]
Abstract
The nuclear scaffold is an insoluble nuclear structure that contributes to the inner nuclear organization. In this study, we showed that one of the nuclear scaffold proteins, WDR46, plays a role as a fundamental scaffold component of the nucleolar structure. WDR46 is a highly insoluble nucleolar protein, and its subcellular localization is dependent on neither DNA nor RNA. The N- and C-terminal regions of WDR46 are predicted to be intrinsically disordered, and both regions are critical for the nucleolar localization of WDR46 and the association with its binding partners. When WDR46 was knocked down, two of its binding partners, nucleolin and DDX21 (involved in 18S rRNA processing), were mislocalized from the granular component to the edges of the nucleoli, whereas other binding partners, NOP2 and EBP2 (involved in 28S rRNA processing), were not affected. This is because the proper recruitment of nucleolin and DDX21 to the nucleoli in daughter cells after cell division is ensured by WDR46. These findings suggest a structural role for WDR46 in organizing the 18S ribosomal RNA processing machinery. This role of WDR46 is enabled by its interaction property via intrinsically disordered regions.
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Affiliation(s)
- Yuya Hirai
- Graduate School of Biostudies, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan
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46
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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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Nucleolar trafficking of the mouse mammary tumor virus gag protein induced by interaction with ribosomal protein L9. J Virol 2012; 87:1069-82. [PMID: 23135726 DOI: 10.1128/jvi.02463-12] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mouse mammary tumor virus (MMTV) Gag protein directs the assembly in the cytoplasm of immature viral capsids, which subsequently bud from the plasma membranes of infected cells. MMTV Gag localizes to discrete cytoplasmic foci in mouse mammary epithelial cells, consistent with the formation of cytosolic capsids. Unexpectedly, we also observed an accumulation of Gag in the nucleoli of infected cells derived from mammary gland tumors. To detect Gag-interacting proteins that might influence its subcellular localization, a yeast two-hybrid screen was performed. Ribosomal protein L9 (RPL9 or L9), an essential component of the large ribosomal subunit and a putative tumor suppressor, was identified as a Gag binding partner. Overexpression of L9 in cells expressing the MMTV(C3H) provirus resulted in specific, robust accumulation of Gag in nucleoli. Förster resonance energy transfer (FRET) and coimmunoprecipitation analyses demonstrated that Gag and L9 interact within the nucleolus, and the CA domain was the major site of interaction. In addition, the isolated NC domain of Gag localized to the nucleolus, suggesting that it contains a nucleolar localization signal (NoLS). To determine whether L9 plays a role in virus assembly, small interfering RNA (siRNA)-mediated knockdown was performed. Although Gag expression was not reduced with L9 knockdown, virus production was significantly impaired. Thus, our data support the hypothesis that efficient MMTV particle assembly is dependent upon the interaction of Gag and L9 in the nucleoli of infected cells.
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48
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NC-mediated nucleolar localization of retroviral gag proteins. Virus Res 2012; 171:304-18. [PMID: 23036987 DOI: 10.1016/j.virusres.2012.09.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 08/13/2012] [Accepted: 09/22/2012] [Indexed: 11/21/2022]
Abstract
The assembly and release of retrovirus particles from the cell membrane is directed by the Gag polyprotein. The Gag protein of Rous sarcoma virus (RSV) traffics through the nucleus prior to plasma membrane localization. We previously reported that nuclear localization of RSV Gag is linked to efficient packaging of viral genomic RNA, however the intranuclear activities of RSV Gag are not well understood. To gain insight into the properties of the RSV Gag protein within the nucleus, we examined the subnuclear localization and dynamic trafficking of RSV Gag. Restriction of RSV Gag to the nucleus by mutating its nuclear export signal (NES) in the p10 domain or interfering with CRM1-mediated nuclear export of Gag by leptomycin B (LMB) treatment led to the accumulation of Gag in nucleoli and discrete nucleoplasmic foci. Retention of RSV Gag in nucleoli was reduced with cis-expression of the 5' untranslated RU5 region of the viral RNA genome, suggesting the psi (Ψ) packaging signal may alter the subnuclear localization of Gag. Fluorescence recovery after photobleaching (FRAP) demonstrated that the nucleolar fraction of Gag was highly mobile, indicating that there was rapid exchange with Gag proteins in the nucleoplasm. RSV Gag is targeted to nucleoli by a nucleolar localization signal (NoLS) in the NC domain, and similarly, the human immunodeficiency virus type 1 (HIV-1) NC protein also contains an NoLS consisting of basic residues. Interestingly, co-expression of HIV-1 NC or Rev with HIV-1 Gag resulted in accumulation of Gag in nucleoli. Moreover, a subpopulation of HIV-1 Gag was detected in the nucleoli of HeLa cells stably expressing the entire HIV-1 genome in a Rev-dependent fashion. These findings suggest that the RSV and HIV-1 Gag proteins undergo nucleolar trafficking in the setting of viral infection.
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Jády BE, Ketele A, Kiss T. Human intron-encoded Alu RNAs are processed and packaged into Wdr79-associated nucleoplasmic box H/ACA RNPs. Genes Dev 2012; 26:1897-910. [PMID: 22892240 PMCID: PMC3435494 DOI: 10.1101/gad.197467.112] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 07/16/2012] [Indexed: 11/25/2022]
Abstract
Alu repetitive sequences are the most abundant short interspersed DNA elements in the human genome. Full-length Alu elements are composed of two tandem sequence monomers, the left and right Alu arms, both derived from the 7SL signal recognition particle RNA. Since Alu elements are common in protein-coding genes, they are frequently transcribed into pre-mRNAs. Here, we demonstrate that the right arms of nascent Alu transcripts synthesized within pre-mRNA introns are processed into metabolically stable small RNAs. The intron-encoded Alu RNAs, termed AluACA RNAs, are structurally highly reminiscent of box H/ACA small Cajal body (CB) RNAs (scaRNAs). They are composed of two hairpin units followed by the essential H (AnAnnA) and ACA box motifs. The mature AluACA RNAs associate with the four H/ACA core proteins: dyskerin, Nop10, Nhp2, and Gar1. Moreover, the 3' hairpin of AluACA RNAs carries two closely spaced CB localization motifs, CAB boxes (UGAG), which bind Wdr79 in a cumulative fashion. In contrast to canonical H/ACA scaRNPs, which concentrate in CBs, the AluACA RNPs accumulate in the nucleoplasm. Identification of 348 human AluACA RNAs demonstrates that intron-encoded AluACA RNAs represent a novel, large subgroup of H/ACA RNAs, which are apparently confined to human or primate cells.
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Affiliation(s)
- Beáta E Jády
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, 31062 Toulouse Cedex 9, France
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50
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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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