1
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Hao Q, Liu M, Daulatabad SV, Gaffari S, Song YJ, Srivastava R, Bhaskar S, Moitra A, Mangan H, Tseng E, Gilmore RB, Frier SM, Chen X, Wang C, Huang S, Chamberlain S, Jin H, Korlach J, McStay B, Sinha S, Janga SC, Prasanth SG, Prasanth KV. Monoallelically expressed noncoding RNAs form nucleolar territories on NOR-containing chromosomes and regulate rRNA expression. eLife 2024; 13:e80684. [PMID: 38240312 PMCID: PMC10852677 DOI: 10.7554/elife.80684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 01/18/2024] [Indexed: 02/07/2024] Open
Abstract
Out of the several hundred copies of rRNA genes arranged in the nucleolar organizing regions (NOR) of the five human acrocentric chromosomes, ~50% remain transcriptionally inactive. NOR-associated sequences and epigenetic modifications contribute to the differential expression of rRNAs. However, the mechanism(s) controlling the dosage of active versus inactive rRNA genes within each NOR in mammals is yet to be determined. We have discovered a family of ncRNAs, SNULs (Single NUcleolus Localized RNA), which form constrained sub-nucleolar territories on individual NORs and influence rRNA expression. Individual members of the SNULs monoallelically associate with specific NOR-containing chromosomes. SNULs share sequence similarity to pre-rRNA and localize in the sub-nucleolar compartment with pre-rRNA. Finally, SNULs control rRNA expression by influencing pre-rRNA sorting to the DFC compartment and pre-rRNA processing. Our study discovered a novel class of ncRNAs influencing rRNA expression by forming constrained nucleolar territories on individual NORs.
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Affiliation(s)
- Qinyu Hao
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Minxue Liu
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Swapna Vidhur Daulatabad
- Department of BioHealth Informatics, School of Informatics and Computing, IUPUIIndianapolisUnited States
| | - Saba Gaffari
- Department of Computer Science, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - You Jin Song
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Rajneesh Srivastava
- Department of BioHealth Informatics, School of Informatics and Computing, IUPUIIndianapolisUnited States
| | - Shivang Bhaskar
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Anurupa Moitra
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Hazel Mangan
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland GalwayGalwayIreland
| | | | - Rachel B Gilmore
- Department of Genetics and Genome Sciences, University of Connecticut School of MedicineFarmingtonUnited States
| | | | - Xin Chen
- Department of Biophysics and Quantitative Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Chengliang Wang
- Department of Biochemistry, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Sui Huang
- Department of Cell and Molecular Biology, Northwestern UniversityChicagoUnited States
| | - Stormy Chamberlain
- Department of Genetics and Genome Sciences, University of Connecticut School of MedicineFarmingtonUnited States
| | - Hong Jin
- Department of Biophysics and Quantitative Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
- Department of Biochemistry, University of Illinois at Urbana-ChampaignUrbanaUnited States
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | | | - Brian McStay
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland GalwayGalwayIreland
| | - Saurabh Sinha
- Department of Computer Science, University of Illinois at Urbana-ChampaignUrbanaUnited States
- Department of Biomedical Engineering, Georgia TechAtlantaUnited States
| | - Sarath Chandra Janga
- Department of BioHealth Informatics, School of Informatics and Computing, IUPUIIndianapolisUnited States
| | - Supriya G Prasanth
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
- Cancer Center at Illinois, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Kannanganattu V Prasanth
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
- Cancer Center at Illinois, University of Illinois at Urbana-ChampaignUrbanaUnited States
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2
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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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3
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Ballmer D, Tardat M, Ortiz R, Graff-Meyer A, Ozonov E, Genoud C, Peters A, Fanourgakis G. HP1 proteins regulate nucleolar structure and function by secluding pericentromeric constitutive heterochromatin. Nucleic Acids Res 2022; 51:117-143. [PMID: 36533441 PMCID: PMC9841413 DOI: 10.1093/nar/gkac1159] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 10/29/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Nucleoli are nuclear compartments regulating ribosome biogenesis and cell growth. In embryonic stem cells (ESCs), nucleoli containing transcriptionally active ribosomal genes are spatially separated from pericentromeric satellite repeat sequences packaged in largely repressed constitutive heterochromatin (PCH). To date, mechanisms underlying such nuclear partitioning and the physiological relevance thereof are unknown. Here we show that repressive chromatin at PCH ensures structural integrity and function of nucleoli during cell cycle progression. Loss of heterochromatin proteins HP1α and HP1β causes deformation of PCH, with reduced H3K9 trimethylation (H3K9me3) and HP1γ levels, absence of H4K20me3 and upregulated major satellites expression. Spatially, derepressed PCH aberrantly associates with nucleoli accumulating severe morphological defects during S/G2 cell cycle progression. Hp1α/β deficiency reduces cell proliferation, ribosomal RNA biosynthesis and mobility of Nucleophosmin, a major nucleolar component. Nucleolar integrity and function require HP1α/β proteins to be recruited to H3K9me3-marked PCH and their ability to dimerize. Correspondingly, ESCs deficient for both Suv39h1/2 H3K9 HMTs display similar nucleolar defects. In contrast, Suv4-20h1/2 mutant ESCs lacking H4K20me3 at PCH do not. Suv39h1/2 and Hp1α/β deficiency-induced nucleolar defects are reminiscent of those defining human ribosomopathy disorders. Our results reveal a novel role for SUV39H/HP1-marked repressive constitutive heterochromatin in regulating integrity, function and physiology of nucleoli.
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Affiliation(s)
- Daniel Ballmer
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland,Faculty of Sciences, University of Basel, 4056 Basel, Switzerland
| | - Mathieu Tardat
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Raphael Ortiz
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Alexandra Graff-Meyer
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Evgeniy A Ozonov
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Christel Genoud
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | | | - Grigorios Fanourgakis
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
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4
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Yan D, Hua L. Nucleolar stress: Friend or foe in cardiac function? Front Cardiovasc Med 2022; 9:1045455. [PMID: 36386352 PMCID: PMC9659567 DOI: 10.3389/fcvm.2022.1045455] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 10/17/2022] [Indexed: 03/14/2024] Open
Abstract
Studies in the past decades have uncovered an emerging role of the nucleolus in stress response and human disease progression. The disruption of ribosome biogenesis in the nucleolus causes aberrant nucleolar architecture and function, termed nucleolar stress, to initiate stress-responsive pathways via nucleolar release sequestration of various proteins. While data obtained from both clinical and basic investigations have faithfully demonstrated an involvement of nucleolar stress in the pathogenesis of cardiomyopathy, much remains unclear regarding its precise role in the progression of cardiac diseases. On the one hand, the initiation of nucleolar stress following acute myocardial damage leads to the upregulation of various cardioprotective nucleolar proteins, including nucleostemin (NS), nucleophosmin (NPM) and nucleolin (NCL). As a result, nucleolar stress plays an important role in facilitating the survival and repair of cardiomyocytes. On the other hand, abnormalities in nucleolar architecture and function are correlated with the deterioration of cardiac diseases. Notably, the cardiomyocytes of advanced ischemic and dilated cardiomyopathy display impaired silver-stained nucleolar organiser regions (AgNORs) and enlarged nucleoli, resembling the characteristics of tissue aging. Collectively, nucleolar abnormalities are critically involved in the development of cardiac diseases.
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Affiliation(s)
- Daliang Yan
- Department of Cardiovascular Surgery, Taizhou People’s Hospital, Taizhou, China
| | - Lu Hua
- Department of Oncology, Taizhou People’s Hospital, Taizhou, China
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5
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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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6
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Archambault V, Li J, Emond-Fraser V, Larouche M. Dephosphorylation in nuclear reassembly after mitosis. Front Cell Dev Biol 2022; 10:1012768. [PMID: 36268509 PMCID: PMC9576876 DOI: 10.3389/fcell.2022.1012768] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 08/31/2022] [Indexed: 11/13/2022] Open
Abstract
In most animal cell types, the interphase nucleus is largely disassembled during mitotic entry. The nuclear envelope breaks down and chromosomes are compacted into separated masses. Chromatin organization is also mostly lost and kinetochores assemble on centromeres. Mitotic protein kinases play several roles in inducing these transformations by phosphorylating multiple effector proteins. In many of these events, the mechanistic consequences of phosphorylation have been characterized. In comparison, how the nucleus reassembles at the end of mitosis is less well understood in mechanistic terms. In recent years, much progress has been made in deciphering how dephosphorylation of several effector proteins promotes nuclear envelope reassembly, chromosome decondensation, kinetochore disassembly and interphase chromatin organization. The precise roles of protein phosphatases in this process, in particular of the PP1 and PP2A groups, are emerging. Moreover, how these enzymes are temporally and spatially regulated to ensure that nuclear reassembly progresses in a coordinated manner has been partly uncovered. This review provides a global view of nuclear reassembly with a focus on the roles of dephosphorylation events. It also identifies important open questions and proposes hypotheses.
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Affiliation(s)
- Vincent Archambault
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, Canada
- Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, QC, Canada
- *Correspondence: Vincent Archambault,
| | - Jingjing Li
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, Canada
- Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, QC, Canada
| | - Virginie Emond-Fraser
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, Canada
- Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, QC, Canada
| | - Myreille Larouche
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, QC, Canada
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7
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The Image Data Explorer: Interactive exploration of image-derived data. PLoS One 2022; 17:e0273698. [PMID: 36107835 PMCID: PMC9477257 DOI: 10.1371/journal.pone.0273698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/12/2022] [Indexed: 11/24/2022] Open
Abstract
Many bioimage analysis projects produce quantitative descriptors of regions of interest in images. Associating these descriptors with visual characteristics of the objects they describe is a key step in understanding the data at hand. However, as many bioimage data and their analysis workflows are moving to the cloud, addressing interactive data exploration in remote environments has become a pressing issue. To address it, we developed the Image Data Explorer (IDE) as a web application that integrates interactive linked visualization of images and derived data points with exploratory data analysis methods, annotation, classification and feature selection functionalities. The IDE is written in R using the shiny framework. It can be easily deployed on a remote server or on a local computer. The IDE is available at https://git.embl.de/heriche/image-data-explorer and a cloud deployment is accessible at https://shiny-portal.embl.de/shinyapps/app/01_image-data-explorer.
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8
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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: 39] [Impact Index Per Article: 19.5] [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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9
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Matsumori H, Watanabe K, Tachiwana H, Fujita T, Ito Y, Tokunaga M, Sakata-Sogawa K, Osakada H, Haraguchi T, Awazu A, Ochiai H, Sakata Y, Ochiai K, Toki T, Ito E, Goldberg IG, Tokunaga K, Nakao M, Saitoh N. Ribosomal protein L5 facilitates rDNA-bundled condensate and nucleolar assembly. Life Sci Alliance 2022; 5:5/7/e202101045. [PMID: 35321919 PMCID: PMC8942980 DOI: 10.26508/lsa.202101045] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/01/2022] [Accepted: 03/02/2022] [Indexed: 11/24/2022] Open
Abstract
High content image analysis, single molecule tracking, modeling, and DBA patient analysis revealed that ribosomal protein L5 facilitates rDNA-bundled condensate and nucleolar assembly. The nucleolus is the site of ribosome assembly and formed through liquid–liquid phase separation. Multiple ribosomal DNA (rDNA) arrays are bundled in the nucleolus, but the underlying mechanism and significance are unknown. In the present study, we performed high-content screening followed by image profiling with the wndchrm machine learning algorithm. We revealed that cells lacking a specific 60S ribosomal protein set exhibited common nucleolar disintegration. The depletion of RPL5 (also known as uL18), the liquid–liquid phase separation facilitator, was most effective, and resulted in an enlarged and un-separated sub-nucleolar compartment. Single-molecule tracking analysis revealed less-constrained mobility of its components. rDNA arrays were also unbundled. These results were recapitulated by a coarse-grained molecular dynamics model. Transcription and processing of ribosomal RNA were repressed in these aberrant nucleoli. Consistently, the nucleoli were disordered in peripheral blood cells from a Diamond–Blackfan anemia patient harboring a heterozygous, large deletion in RPL5. Our combinatorial analyses newly define the role of RPL5 in rDNA array bundling and the biophysical properties of the nucleolus, which may contribute to the etiology of ribosomopathy.
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Affiliation(s)
- Haruka Matsumori
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Kenji Watanabe
- Cancer Institute of Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Hiroaki Tachiwana
- Cancer Institute of Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Tomoko Fujita
- Cancer Institute of Japanese Foundation for Cancer Research, Tokyo, Japan
| | - Yuma Ito
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Makio Tokunaga
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Kumiko Sakata-Sogawa
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Hiroko Osakada
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe, Japan
| | - Tokuko Haraguchi
- Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe, Japan.,Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Akinori Awazu
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan.,Research Center for the Mathematics on Chromatin Live Dynamics (RcMcD), Hiroshima University, Higashi-Hiroshima, Japan
| | - Hiroshi Ochiai
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan
| | - Yuka Sakata
- Cancer Institute of Japanese Foundation for Cancer Research, Tokyo, Japan
| | | | - Tsutomu Toki
- Department of Pediatrics, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Etsuro Ito
- Department of Pediatrics, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Ilya G Goldberg
- Image Informatics and Computational Biology Unit, Laboratory of Genetics, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Kazuaki Tokunaga
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Mitsuyoshi Nakao
- Department of Medical Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Noriko Saitoh
- Cancer Institute of Japanese Foundation for Cancer Research, Tokyo, Japan
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10
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Musacchio A. On the role of phase separation in the biogenesis of membraneless compartments. EMBO J 2022; 41:e109952. [PMID: 35107832 PMCID: PMC8886532 DOI: 10.15252/embj.2021109952] [Citation(s) in RCA: 99] [Impact Index Per Article: 49.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 12/16/2022] Open
Abstract
Molecular mechanistic biology has ushered us into the world of life’s building blocks, revealing their interactions in macromolecular complexes and inspiring strategies for detailed functional interrogations. The biogenesis of membraneless cellular compartments, functional mesoscale subcellular locales devoid of strong internal order and delimiting membranes, is among mechanistic biology’s most demanding current challenges. A developing paradigm, biomolecular phase separation, emphasizes solvation of the building blocks through low‐affinity, weakly adhesive unspecific interactions as the driver of biogenesis of membraneless compartments. Here, I discuss the molecular underpinnings of the phase separation paradigm and demonstrate that validating its assumptions is much more challenging than hitherto appreciated. I also discuss that highly specific interactions, rather than unspecific ones, appear to be the main driver of biogenesis of subcellular compartments, while phase separation may be harnessed locally in selected instances to generate material properties tailored for specific functions, as exemplified by nucleocytoplasmic transport.
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Affiliation(s)
- Andrea Musacchio
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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11
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Castro C, Carvalho A, Pavia I, Bacelar E, Lima-Brito J. Development of grapevine plants under hydroponic copper-enriched solutions induced morpho-histological, biochemical and cytogenetic changes. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 166:887-901. [PMID: 34243016 DOI: 10.1016/j.plaphy.2021.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 06/14/2021] [Accepted: 07/02/2021] [Indexed: 06/13/2023]
Abstract
Copper (Cu) is an essential micronutrient for plants, but when present in excess, it induces toxicity. In this study, cuttings of four wine-producing varieties of Vitis vinifera L. were used: 'Tinta Barroca', 'Tinto Cão', 'Malvasia Fina' and 'Viosinho'. The grapevine cuttings were distributed by hydroponic solutions enriched with different Cu concentrations (1, 10, 25 and 50 μM) plus control. At the end of the experiment, the root growth was evaluated, and individual roots were collected, fixed, and used for histological sections and chromosome spreads preparation. The higher Cu concentrations induced toxicity and inhibited root growth. However, the grapevine varieties responded with the thickening of the root exodermis and endodermis. In the chromosome spreads, normal and abnormal interphase and mitotic cells were observed in all varieties and treatments. The increase of Cu concentration decreased the nucleolar activity, as seen by reducing the nucleolar number and area. It increased the frequency of interphase cells with anomalies (ICA), but it did not influence total soluble protein concentration. The augment of Cu concentration also decreased the mitotic index (MI) and increased the percentage of dividing cells with anomalies (DCA). Different types of chromosomal anomalies in all mitotic phases, treatments and varieties were found. Overall, the white wine varieties, 'Malvasia Fina' and 'Viosinho', appeared to be more tolerant to the Cu-induced stress because they showed higher root growth and mean MI and lower mean DCA than the red wine varieties.
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Affiliation(s)
- Cláudia Castro
- Plant Cytogenomics Laboratory, Department of Genetics and Biotechnology, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal.
| | - Ana Carvalho
- Plant Cytogenomics Laboratory, Department of Genetics and Biotechnology, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Inov4Agro -Institute for Innovation, Capacity Building and Sustainability of Agri-food Production, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal.
| | - Ivo Pavia
- Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Inov4Agro -Institute for Innovation, Capacity Building and Sustainability of Agri-food Production, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal.
| | - Eunice Bacelar
- Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Inov4Agro -Institute for Innovation, Capacity Building and Sustainability of Agri-food Production, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Department of Biology and Environment, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal.
| | - José Lima-Brito
- Plant Cytogenomics Laboratory, Department of Genetics and Biotechnology, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences (CITAB), University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal; Inov4Agro -Institute for Innovation, Capacity Building and Sustainability of Agri-food Production, University of Tras-os-Montes and Alto Douro, Quinta de Prados, 5000-801, Vila Real, Portugal.
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12
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G-patch domain-containing protein 4 localizes to both the nucleoli and Cajal bodies and regulates cell growth and nucleolar structure. Biochem Biophys Res Commun 2021; 559:99-105. [PMID: 33933995 DOI: 10.1016/j.bbrc.2021.04.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 04/08/2021] [Indexed: 11/20/2022]
Abstract
Ribosome formation occurs in the nucleolus through interaction with various trans-acting factors. Therefore, hundreds of nucleolar proteins have a function in ribosome formation, although the precise function of each nucleolar protein in ribosome formation is largely unclear. We have previously identified an uncharacterized protein, G-patch domain-containing protein 4 (GPATCH4 or G4), as a component of the pre-ribosomes purified with either nucleolin (NCL) or NPM1. In this present study, we sought to clarify the localization and function of G4. We identified that G4 localizes to both the nucleolus and the Cajal body. Although knockdown of G4 did not have a significant effect on pre-ribosomal RNA processing, cell growth did decrease. Interestingly, G4 knockdown also decreased the number of fibrillar center and dense fibrillar component regions inside the nucleolus. This data has identified G4 as a novel nucleolar protein involved in the regulation of cell growth and nucleolar structure.
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13
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Fernandes N, Buchan JR. RNAs as Regulators of Cellular Matchmaking. Front Mol Biosci 2021; 8:634146. [PMID: 33898516 PMCID: PMC8062979 DOI: 10.3389/fmolb.2021.634146] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/22/2021] [Indexed: 12/30/2022] Open
Abstract
RNA molecules are increasingly being identified as facilitating or impeding the interaction of proteins and nucleic acids, serving as so-called scaffolds or decoys. Long non-coding RNAs have been commonly implicated in such roles, particularly in the regulation of nuclear processes including chromosome topology, regulation of chromatin state and gene transcription, and assembly of nuclear biomolecular condensates such as paraspeckles. Recently, an increased awareness of cytoplasmic RNA scaffolds and decoys has begun to emerge, including the identification of non-coding regions of mRNAs that can also function in a scaffold-like manner to regulate interactions of nascently translated proteins. Collectively, cytoplasmic RNA scaffolds and decoys are now implicated in processes such as mRNA translation, decay, protein localization, protein degradation and assembly of cytoplasmic biomolecular condensates such as P-bodies. Here, we review examples of RNA scaffolds and decoys in both the nucleus and cytoplasm, illustrating common themes, the suitability of RNA to such roles, and future challenges in identifying and better understanding RNA scaffolding and decoy functions.
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Affiliation(s)
| | - J. Ross Buchan
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, United States
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14
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Puente-Bedia A, Berciano MT, Tapia O, Martínez-Cué C, Lafarga M, Rueda N. Nuclear Reorganization in Hippocampal Granule Cell Neurons from a Mouse Model of Down Syndrome: Changes in Chromatin Configuration, Nucleoli and Cajal Bodies. Int J Mol Sci 2021; 22:ijms22031259. [PMID: 33514010 PMCID: PMC7865916 DOI: 10.3390/ijms22031259] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Revised: 01/16/2021] [Accepted: 01/22/2021] [Indexed: 01/05/2023] Open
Abstract
Down syndrome (DS) or trisomy of chromosome 21 (Hsa21) is characterized by impaired hippocampal-dependent learning and memory. These alterations are due to defective neurogenesis and to neuromorphological and functional anomalies of numerous neuronal populations, including hippocampal granular cells (GCs). It has been proposed that the additional gene dose in trisomic cells induces modifications in nuclear compartments and on the chromatin landscape, which could contribute to some DS phenotypes. The Ts65Dn (TS) mouse model of DS carries a triplication of 92 genes orthologous to those found in Hsa21, and shares many phenotypes with DS individuals, including cognitive and neuromorphological alterations. Considering its essential role in hippocampal memory formation, we investigated whether the triplication of this set of Hsa21 orthologous genes in TS mice modifies the nuclear architecture of their GCs. Our results show that the TS mouse presents alterations in the nuclear architecture of its GCs, affecting nuclear compartments involved in transcription and pre-rRNA and pre-mRNA processing. In particular, the GCs of the TS mouse show alterations in the nucleolar fusion pattern and the molecular assembly of Cajal bodies (CBs). Furthermore, hippocampal GCs of TS mice present an epigenetic dysregulation of chromatin that results in an increased heterochromatinization and reduced global transcriptional activity. These nuclear alterations could play an important role in the neuromorphological and/or functional alterations of the hippocampal GCs implicated in the cognitive dysfunction characteristic of TS mice.
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Affiliation(s)
- Alba Puente-Bedia
- Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, 39011 Santander, Spain; (A.P.-B.); (C.M.-C.)
| | - María T. Berciano
- Department of Molecular Biology, “Red sobre Enfermedades Neurodegenerativas (CIBERNED)” and University of Cantabria-IDIVAL, 39011 Santander, Spain;
| | - Olga Tapia
- Instituto de Investigación Sanitaria Valdecilla (IDIVAL), “Red sobre Enfermedades Neurodegenerativas (CIBERNED)” and Universidad Europea del Atlántico, 39011 Santander, Spain;
| | - Carmen Martínez-Cué
- Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, 39011 Santander, Spain; (A.P.-B.); (C.M.-C.)
| | - Miguel Lafarga
- Department of Anatomy and Cell Biology, “Red sobre Enfermedades Neurodegenerativas (CIBERNED)” and University of Cantabria-IDIVAL, 39011 Santander, Spain
- Correspondence: (M.L.); (N.R.); Tel.: +34-942201966 (N.R.); Fax: +34-942201903 (N.R.)
| | - Noemí Rueda
- Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, 39011 Santander, Spain; (A.P.-B.); (C.M.-C.)
- Correspondence: (M.L.); (N.R.); Tel.: +34-942201966 (N.R.); Fax: +34-942201903 (N.R.)
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15
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Gilloteaux J, Bouchat J, Brion JP, Nicaise C. The osmotic demyelination syndrome: the resilience of thalamic neurons is verified with transmission electron microscopy. Ultrastruct Pathol 2021; 44:450-480. [DOI: 10.1080/01913123.2020.1853865] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Jacques Gilloteaux
- Unit of Research in Molecular Physiology (Urphym- NARILIS), Department of Medicine, Université de Namur, Namur, Belgium
- Department of Anatomical Sciences, St George’s University School of Medicine, KB Taylor Global Scholar’s Program at UNN, School of Health and Life Sciences, Newcastle upon Tyne, UK
| | - Joanna Bouchat
- Unit of Research in Molecular Physiology (Urphym- NARILIS), Department of Medicine, Université de Namur, Namur, Belgium
| | - Jean-Pierre Brion
- Laboratory of Histology, Neuroanatomy and Neuropathology, Faculté de Médecine Université Libre de Bruxelles, Brussels, Belgium
| | - Charles Nicaise
- Unit of Research in Molecular Physiology (Urphym- NARILIS), Department of Medicine, Université de Namur, Namur, Belgium
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16
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Stenström L, Mahdessian D, Gnann C, Cesnik AJ, Ouyang W, Leonetti MD, Uhlén M, Cuylen‐Haering S, Thul PJ, Lundberg E. Mapping the nucleolar proteome reveals a spatiotemporal organization related to intrinsic protein disorder. Mol Syst Biol 2020; 16:e9469. [PMID: 32744794 PMCID: PMC7397901 DOI: 10.15252/msb.20209469] [Citation(s) in RCA: 78] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 07/02/2020] [Accepted: 07/03/2020] [Indexed: 01/01/2023] Open
Abstract
The nucleolus is essential for ribosome biogenesis and is involved in many other cellular functions. We performed a systematic spatiotemporal dissection of the human nucleolar proteome using confocal microscopy. In total, 1,318 nucleolar proteins were identified; 287 were localized to fibrillar components, and 157 were enriched along the nucleoplasmic border, indicating a potential fourth nucleolar subcompartment: the nucleoli rim. We found 65 nucleolar proteins (36 uncharacterized) to relocate to the chromosomal periphery during mitosis. Interestingly, we observed temporal partitioning into two recruitment phenotypes: early (prometaphase) and late (after metaphase), suggesting phase-specific functions. We further show that the expression of MKI67 is critical for this temporal partitioning. We provide the first proteome-wide analysis of intrinsic protein disorder for the human nucleolus and show that nucleolar proteins in general, and mitotic chromosome proteins in particular, have significantly higher intrinsic disorder level compared to cytosolic proteins. In summary, this study provides a comprehensive and essential resource of spatiotemporal expression data for the nucleolar proteome as part of the Human Protein Atlas.
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Affiliation(s)
- Lovisa Stenström
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
| | - Diana Mahdessian
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
| | - Christian Gnann
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
- Chan Zuckerberg BiohubSan FranciscoCAUSA
| | - Anthony J Cesnik
- Chan Zuckerberg BiohubSan FranciscoCAUSA
- Department of GeneticsStanford UniversityStanfordCAUSA
| | - Wei Ouyang
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
| | | | - Mathias Uhlén
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
| | - Sara Cuylen‐Haering
- Cell Biology and Biophysics UnitEuropean Molecular Biology LaboratoryHeidelbergGermany
| | - Peter J Thul
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
| | - Emma Lundberg
- Science for Life LaboratorySchool of Engineering Sciences in Chemistry, Biotechnology and HealthKTH Royal Institute of TechnologyStockholmSweden
- Chan Zuckerberg BiohubSan FranciscoCAUSA
- Department of GeneticsStanford UniversityStanfordCAUSA
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17
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Gemble S, Buhagiar-Labarchède G, Onclercq-Delic R, Fontaine G, Lambert S, Amor-Guéret M. Topoisomerase IIα prevents ultrafine anaphase bridges by two mechanisms. Open Biol 2020; 10:190259. [PMID: 32400307 PMCID: PMC7276528 DOI: 10.1098/rsob.190259] [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] [Indexed: 12/23/2022] Open
Abstract
Topoisomerase IIα (Topo IIα), a well-conserved double-stranded DNA (dsDNA)-specific decatenase, processes dsDNA catenanes resulting from DNA replication during mitosis. Topo IIα defects lead to an accumulation of ultrafine anaphase bridges (UFBs), a type of chromosome non-disjunction. Topo IIα has been reported to resolve DNA anaphase threads, possibly accounting for the increase in UFB frequency upon Topo IIα inhibition. We hypothesized that the excess UFBs might also result, at least in part, from an impairment of the prevention of UFB formation by Topo IIα. We found that Topo IIα inhibition promotes UFB formation without affecting the global disappearance of UFBs during mitosis, but leads to an aberrant UFB resolution generating DNA damage within the next G1. Moreover, we demonstrated that Topo IIα inhibition promotes the formation of two types of UFBs depending on cell cycle phase. Topo IIα inhibition during S-phase compromises complete DNA replication, leading to the formation of UFB-containing unreplicated DNA, whereas Topo IIα inhibition during mitosis impedes DNA decatenation at metaphase–anaphase transition, leading to the formation of UFB-containing DNA catenanes. Thus, Topo IIα activity is essential to prevent UFB formation in a cell-cycle-dependent manner and to promote DNA damage-free resolution of UFBs.
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Affiliation(s)
- Simon Gemble
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
| | - Géraldine Buhagiar-Labarchède
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
| | - Rosine Onclercq-Delic
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
| | - Gaëlle Fontaine
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
| | - Sarah Lambert
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
| | - Mounira Amor-Guéret
- Institut Curie, PSL Research University, UMR 3348, Centre de Recherche, Orsay, France.,CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France.,Université Paris Saclay, UMR 3348, Centre Universitaire d'Orsay, France
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18
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Caragine CM, Haley SC, Zidovska A. Nucleolar dynamics and interactions with nucleoplasm in living cells. eLife 2019; 8:47533. [PMID: 31769409 PMCID: PMC6879204 DOI: 10.7554/elife.47533] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 10/13/2019] [Indexed: 01/25/2023] Open
Abstract
Liquid-liquid phase separation (LLPS) has been recognized as one of the key cellular organizing principles and was shown to be responsible for formation of membrane-less organelles such as nucleoli. Although nucleoli were found to behave like liquid droplets, many ramifications of LLPS including nucleolar dynamics and interactions with the surrounding liquid remain to be revealed. Here, we study the motion of human nucleoli in vivo, while monitoring the shape of the nucleolus-nucleoplasm interface. We reveal two types of nucleolar pair dynamics: an unexpected correlated motion prior to coalescence and an independent motion otherwise. This surprising kinetics leads to a nucleolar volume distribution, [Formula: see text], unaccounted for by any current theory. Moreover, we find that nucleolus-nucleoplasm interface is maintained by ATP-dependent processes and susceptible to changes in chromatin transcription and packing. Our results extend and enrich the LLPS framework by showing the impact of the surrounding nucleoplasm on nucleoli in living cells.
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Affiliation(s)
- Christina M Caragine
- Center for Soft Matter Research, Department of Physics, New York University, New York, United States
| | - Shannon C Haley
- Center for Soft Matter Research, Department of Physics, New York University, New York, United States
| | - Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, United States
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19
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Nucleolar Division in the Promastigote Stage of Leishmania major Parasite: A Nop56 Point of View. BIOMED RESEARCH INTERNATIONAL 2018; 2018:1641839. [PMID: 30406129 PMCID: PMC6199852 DOI: 10.1155/2018/1641839] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 08/14/2018] [Accepted: 09/13/2018] [Indexed: 11/23/2022]
Abstract
Nucleogenesis is the cellular event responsible for the formation of the new nucleoli at the end of mitosis. This process depends on the synthesis and processing of ribosomal RNA (rRNA) and, in some eukaryotes, the transfer of nucleolar material contained in prenucleolar bodies (PNBs) to active transcription sites. The lack of a comprehensive description of the nucleolus throughout the cell cycle of the human pathogen Leishmania major prompted us to analyze the distribution of nucleolar protein 56 (Nop56) during interphase and mitosis in the promastigote stage of the parasite. By in silico analysis we show that the orthologue of Nop56 in L. major (LmNop56) contains the three characteristic Nop56 domains and that its predicted three-dimensional structure is also conserved. Fluorescence microscopy observations indicate that the nucleolar localization of LmNop56 is similar, but not identical, to that of the nucleolar protein Elp3b. Notably, unlike other nucleolar proteins, LmNop56 remains associated with the nucleolus in nonproliferative cells. Moreover, epifluorescent images indicate the preservation of the nucleolar structure throughout the closed nuclear division. Experiments performed with the related parasite Trypanosoma brucei show that nucleolar division is carried out by an analogous mechanism.
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20
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Caragine CM, Haley SC, Zidovska A. Surface Fluctuations and Coalescence of Nucleolar Droplets in the Human Cell Nucleus. PHYSICAL REVIEW LETTERS 2018; 121:148101. [PMID: 30339413 PMCID: PMC6452643 DOI: 10.1103/physrevlett.121.148101] [Citation(s) in RCA: 88] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 07/01/2018] [Indexed: 05/19/2023]
Abstract
The nucleolus is a membraneless organelle embedded in chromatin solution inside the cell nucleus. By analyzing surface dynamics and fusion kinetics of human nucleoli in vivo, we find that the nucleolar surface exhibits subtle, but measurable, shape fluctuations and that the radius of the neck connecting two fusing nucleoli grows in time as r(t)∼t^{1/2}. This is consistent with liquid droplets with low surface tension ∼10^{-6} N m^{-1} coalescing within an outside fluid of high viscosity ∼10^{3} Pa s. Our study presents a noninvasive approach of using natural probes and their dynamics to investigate material properties of the cell and its constituents.
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Affiliation(s)
- Christina M. Caragine
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY 10003, United States of America
| | - Shannon C. Haley
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY 10003, United States of America
| | - Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY 10003, United States of America
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21
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Chen J, Teo BHD, Cai Y, Wee SYK, Lu J. The linker histone H1.2 is a novel component of the nucleolar organizer regions. J Biol Chem 2018; 293:2358-2369. [PMID: 29301938 DOI: 10.1074/jbc.m117.810184] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 12/18/2017] [Indexed: 01/27/2023] Open
Abstract
The nucleoli accumulate rRNA genes and are the sites of rRNA synthesis and rRNA assembly into ribosomes. During mitosis, nucleoli dissociate, but nucleolar remnants remain on the rRNA gene loci, forming distinct nucleolar organizer regions (NORs). Little is known about the composition and structure of NORs, but upstream binding factor (UBF) has been established as its master organizer. In this study, we sought to establish new proteins in NORs. Using UBF-Sepharose to isolate UBF-binding proteins, we identified histone H1.2 as a candidate partner but were puzzled by this observation, given that UBF is known to be located predominantly in nucleoli, whereas H1.2 distributed broadly among the chromatins in interphase nuclei. We then examined cells undergoing mitosis and saw that both H1.2 and UBF were recruited into NORs in this state, reconciling the results of our UBF pulldowns. Inhibiting rRNA synthesis in interphase nuclei also induced NOR-like structures containing both UBF and H1.2. When chromosomes were isolated and spread on coverslips, NORs appeared separated from the chromosomes containing both UBF and H1.2. After chromosomes were fragmented by homogenization, intact NORs remained visible. Results collectively suggest that NORs are independent structures and that the linker histone H1.2 is a novel component of this structure.
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Affiliation(s)
- Junjie Chen
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Boon Heng Dennis Teo
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Yitian Cai
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Seng Yin Kelly Wee
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
| | - Jinhua Lu
- From the Department of Microbiology and Immunology, Yong Loo Lin School of Medicine and Immunology Programme, National University of Singapore, Singapore 117697
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22
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Nucleolar reorganization in response to rDNA damage. Curr Opin Cell Biol 2017; 46:81-86. [PMID: 28431265 DOI: 10.1016/j.ceb.2017.03.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 02/06/2017] [Accepted: 03/07/2017] [Indexed: 11/24/2022]
Abstract
Nucleoli, sites of ribosome biogenesis, form around nucleolar organizer regions (NORs) comprising rDNA arrays, located on human acrocentric chromosome p-arms. NORs provide an opportunity to investigate the DNA double strand break (DSB) response at highly transcribed, repetitive, essential loci. Targeted introduction of DSBs into rDNA results in ATM-dependent inhibition of RNA-polymerase I transcription, coupled with movement of rDNA from the nucleolar interior to anchoring points at the periphery. Reorganization renders rDNA accessible to repair factors, normally excluded from nucleoli. Importantly, rDNA DSBs recruit the accurate homologous recombination (HR) repair machinery throughout the cell cycle, suggesting that HR can be templated in cis. We discuss recent findings regarding the biophysical properties of nucleoli and suggest a mechanism for stress-induced nucleolar reorganization.
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23
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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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24
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Chiker S, Pennaneach V, Loew D, Dingli F, Biard D, Cordelières FP, Gemble S, Vacher S, Bieche I, Hall J, Fernet M. Cdk5 promotes DNA replication stress checkpoint activation through RPA-32 phosphorylation, and impacts on metastasis free survival in breast cancer patients. Cell Cycle 2016; 14:3066-78. [PMID: 26237679 DOI: 10.1080/15384101.2015.1078020] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cyclin dependent kinase 5 (Cdk5) is a determinant of PARP inhibitor and ionizing radiation (IR) sensitivity. Here we show that Cdk5-depleted (Cdk5-shRNA) HeLa cells show higher sensitivity to S-phase irradiation, chronic hydroxyurea exposure, and 5-fluorouracil and 6-thioguanine treatment, with hydroxyurea and IR sensitivity also seen in Cdk5-depleted U2OS cells. As Cdk5 is not directly implicated in DNA strand break repair we investigated in detail its proposed role in the intra-S checkpoint activation. While Cdk5-shRNA HeLa cells showed altered basal S-phase dynamics with slower replication velocity and fewer active origins per DNA megabase, checkpoint activation was impaired after a hydroxyurea block. Cdk5 depletion was associated with reduced priming phosphorylations of RPA32 serines 29 and 33 and SMC1-Serine 966 phosphorylation, lower levels of RPA serine 4 and 8 phosphorylation and DNA damage measured using the alkaline Comet assay, gamma-H2AX signal intensity, RPA and Rad51 foci, and sister chromatid exchanges resulting in impaired intra-S checkpoint activation and subsequently higher numbers of chromatin bridges. In vitro kinase assays coupled with mass spectrometry demonstrated that Cdk5 can carry out the RPA32 priming phosphorylations on serines 23, 29, and 33 necessary for this checkpoint activation. In addition we found an association between lower Cdk5 levels and longer metastasis free survival in breast cancer patients and survival in Cdk5-depleted breast tumor cells after treatment with IR and a PARP inhibitor. Taken together, these results show that Cdk5 is necessary for basal replication and replication stress checkpoint activation and highlight clinical opportunities to enhance tumor cell killing.
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Affiliation(s)
- Sara Chiker
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,b Inserm; U612; Centre Universitaire ; Orsay Cedex , France.,c Université Paris-XI; Faculté de Médecine ; Le Kremlin Bicêtre , France
| | - Vincent Pennaneach
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,b Inserm; U612; Centre Universitaire ; Orsay Cedex , France
| | - Damarys Loew
- d Institut Curie; Centre de Recherche; Laboratoire de Spectrométrie de Masse Protéomique ; Paris , France
| | - Florent Dingli
- d Institut Curie; Centre de Recherche; Laboratoire de Spectrométrie de Masse Protéomique ; Paris , France
| | - Denis Biard
- e Commissariat à l'Energie Atomique; DSV; iMETI; SEPIA; Team Cellular Engineering and Human Syndromes ; Fontenay aux Roses , France
| | - Fabrice P Cordelières
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,f CNRS; UMR3348; Centre Universitaire ; Orsay Cedex , France.,g Plateforme IBiSA d'Imagerie Cellulaire et Tissulaire; Institut Curie; Centre Universitaire ; Orsay , France
| | - Simon Gemble
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,f CNRS; UMR3348; Centre Universitaire ; Orsay Cedex , France
| | - Sophie Vacher
- h Pharmacogenetics Unit; Genetics Service ; Department of Tumour Biology ; Institut Curie ; Paris , France
| | - Ivan Bieche
- h Pharmacogenetics Unit; Genetics Service ; Department of Tumour Biology ; Institut Curie ; Paris , France
| | - Janet Hall
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,b Inserm; U612; Centre Universitaire ; Orsay Cedex , France.,i Centre de Recherche en Cancérologie de Lyon -UMR Inserm 1052 - CNRS 5286 ; Lyon , France
| | - Marie Fernet
- a Institut Curie; Centre de Recherche; Centre Universitaire ; Orsay Cedex , France.,b Inserm; U612; Centre Universitaire ; Orsay Cedex , France
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25
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Abstract
Nucleoli form around tandem arrays of a ribosomal gene repeat, termed nucleolar organizer regions (NORs). During metaphase, active NORs adopt a characteristic undercondensed morphology. Recent evidence indicates that the HMG-box-containing DNA-binding protein UBF (upstream binding factor) is directly responsible for this morphology and provides a mitotic bookmark to ensure rapid nucleolar formation beginning in telophase in human cells. This is likely to be a widely employed strategy, as UBF is present throughout metazoans. In higher eukaryotes, NORs are typically located within regions of chromosomes that form perinucleolar heterochromatin during interphase. Typically, the genomic architecture of NORs and the chromosomal regions within which they lie is very poorly described, yet recent evidence points to a role for context in their function. In Arabidopsis, NOR silencing appears to be controlled by sequences outside the rDNA (ribosomal DNA) array. Translocations reveal a role for context in the expression of the NOR on the X chromosome in Drosophila Recent work has begun on characterizing the genomic architecture of human NORs. A role for distal sequences located in perinucleolar heterochromatin has been inferred, as they exhibit a complex transcriptionally active chromatin structure. Links between rDNA genomic stability and aging in Saccharomyces cerevisiae are now well established, and indications are emerging that this is important in aging and replicative senescence in higher eukaryotes. This, combined with the fact that rDNA arrays are recombinational hot spots in cancer cells, has focused attention on DNA damage responses in NORs. The introduction of DNA double-strand breaks into rDNA arrays leads to a dramatic reorganization of nucleolar structure. Damaged rDNA repeats move from the nucleolar interior to form caps at the nucleolar periphery, presumably to facilitate repair, suggesting that the chromosomal context of human NORs contributes to their genomic stability. The inclusion of NORs and their surrounding chromosomal environments in future genome drafts now becomes a priority.
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Affiliation(s)
- Brian McStay
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Ireland
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26
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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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Moriuchi T, Kuroda M, Kusumoto F, Osumi T, Hirose F. Lamin A reassembly at the end of mitosis is regulated by its SUMO-interacting motif. Exp Cell Res 2016; 342:83-94. [DOI: 10.1016/j.yexcr.2016.02.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Revised: 02/22/2016] [Accepted: 02/23/2016] [Indexed: 02/01/2023]
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28
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Abstract
Nucleoli are formed on the basis of ribosomal genes coding for RNAs of ribosomal particles, but also include a great variety of other DNA regions. In this article, we discuss the characteristics of ribosomal DNA: the structure of the rDNA locus, complex organization and functions of the intergenic spacer, multiplicity of gene copies in one cell, selective silencing of genes and whole gene clusters, relation to components of nucleolar ultrastructure, specific problems associated with replication. We also review current data on the role of non-ribosomal DNA in the organization and function of nucleoli. Finally, we discuss probable causes preventing efficient visualization of DNA in nucleoli.
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29
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Gemble S, Buhagiar-Labarchède G, Onclercq-Delic R, Biard D, Lambert S, Amor-Guéret M. A balanced pyrimidine pool is required for optimal Chk1 activation to prevent ultrafine anaphase bridge formation. J Cell Sci 2016; 129:3167-77. [DOI: 10.1242/jcs.187781] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 06/27/2016] [Indexed: 01/05/2023] Open
Abstract
Cytidine deaminase (CDA) deficiency induces an excess of cellular dCTP, which reduces basal PARP-1 activity, thereby compromising complete DNA replication, leading to ultrafine anaphase bridge (UFB) formation. CDA dysfunction has pathological implications, notably in cancer and in Bloom syndrome. It remains unknown how reduced levels of PARP-1 activity and pyrimidine pool imbalance lead to the accumulation of unreplicated DNA during mitosis. We report that a decrease in PARP-1 activity in CDA-deficient cells impairs DNA damage-induced Chk1 activation, and, thus, the downstream checkpoints. Chemical inhibition of the ATR-Chk1 pathway leads to UFB accumulation, and we found that this pathway was compromised in CDA-deficient cells. Our data demonstrate that ATR-Chk1 acts downstream from PARP-1, preventing the accumulation of unreplicated DNA in mitosis, and, thus, UFB formation. Finally, delaying entry into mitosis is sufficient to prevent UFB formation in both CDA-deficient and CDA-proficient cells, suggesting that both physiological and pathological UFBs are derived from unreplicated DNA. Our findings demonstrate an unsuspected requirement for a balanced nucleotide pool for optimal Chk1 activation both in unchallenged cells and in response to genotoxic stress.
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Affiliation(s)
- Simon Gemble
- Institut Curie, PSL Research University, UMR 3348, Unité Stress Génotoxiques et Cancer, Centre de Recherche, Orsay, France
- CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France
- Université Paris Sud, Université Paris Saclay, UMR3348, Centre Universitaire d'Orsay, France
| | - Géraldine Buhagiar-Labarchède
- Institut Curie, PSL Research University, UMR 3348, Unité Stress Génotoxiques et Cancer, Centre de Recherche, Orsay, France
- CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France
- Université Paris Sud, Université Paris Saclay, UMR3348, Centre Universitaire d'Orsay, France
| | - Rosine Onclercq-Delic
- Institut Curie, PSL Research University, UMR 3348, Unité Stress Génotoxiques et Cancer, Centre de Recherche, Orsay, France
- CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France
- Université Paris Sud, Université Paris Saclay, UMR3348, Centre Universitaire d'Orsay, France
| | - Denis Biard
- CEA, DSV, iMETI, SEPIA, 18, route du Panorama. Bât. 60, BP6, 92265 Fontenay-aux-Roses Cedex, France
| | - Sarah Lambert
- Institut Curie, PSL Research University, UMR 3348, Unité Stress Génotoxiques et Cancer, Centre de Recherche, Orsay, France
- CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France
- Université Paris Sud, Université Paris Saclay, UMR3348, Centre Universitaire d'Orsay, France
| | - Mounira Amor-Guéret
- Institut Curie, PSL Research University, UMR 3348, Unité Stress Génotoxiques et Cancer, Centre de Recherche, Orsay, France
- CNRS UMR 3348, Centre Universitaire, Bât. 110. 91405, Orsay, France
- Université Paris Sud, Université Paris Saclay, UMR3348, Centre Universitaire d'Orsay, France
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30
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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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31
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Abstract
Our current view of the nucleolus has been shaped by the concept that the organization of this prominent compartment within the nucleus is primarily dictated by its function, the making of ribosome subunits. Whether ribosome biogenesis is framed by a dedicated nucleolar scaffold has remained unclear. In this issue of The EMBO Journal, Caudron‐Herger and colleagues present evidence for a nucleolar skeleton composed of non‐coding RNA enriched in Alu repeat elements.
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Affiliation(s)
- Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
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32
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The NF45/NF90 Heterodimer Contributes to the Biogenesis of 60S Ribosomal Subunits and Influences Nucleolar Morphology. Mol Cell Biol 2015; 35:3491-503. [PMID: 26240280 DOI: 10.1128/mcb.00306-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/21/2015] [Indexed: 01/06/2023] Open
Abstract
The interleukin enhancer binding factors ILF2 (NF45) and ILF3 (NF90/NF110) have been implicated in various cellular pathways, such as transcription, microRNA (miRNA) processing, DNA repair, and translation, in mammalian cells. Using tandem affinity purification, we identified human NF45 and NF90 as components of precursors to 60S (pre-60S) ribosomal subunits. NF45 and NF90 are enriched in nucleoli and cosediment with pre-60S ribosomal particles in density gradient analysis. We show that association of the NF45/NF90 heterodimer with pre-60S ribosomal particles requires the double-stranded RNA binding domains of NF90, while depletion of NF45 and NF90 by RNA interference leads to a defect in 60S biogenesis. Nucleoli of cells depleted of NF45 and NF90 have altered morphology and display a characteristic spherical shape. These effects are not due to impaired rRNA transcription or processing of the precursors to 28S rRNA. Consistent with a role of the NF45/NF90 heterodimer in nucleolar steps of 60S subunit biogenesis, downregulation of NF45 and NF90 leads to a p53 response, accompanied by induction of the cyclin-dependent kinase inhibitor p21/CIP1, which can be counteracted by depletion of RPL11. Together, these data indicate that NF45 and NF90 are novel higher-eukaryote-specific factors required for the maturation of 60S ribosomal subunits.
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33
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Yoshikawa H, Ishikawa H, Izumikawa K, Miura Y, Hayano T, Isobe T, Simpson RJ, Takahashi N. Human nucleolar protein Nop52 (RRP1/NNP-1) is involved in site 2 cleavage in internal transcribed spacer 1 of pre-rRNAs at early stages of ribosome biogenesis. Nucleic Acids Res 2015; 43:5524-36. [PMID: 25969445 PMCID: PMC4477673 DOI: 10.1093/nar/gkv470] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 04/29/2015] [Indexed: 01/02/2023] Open
Abstract
During the early steps of ribosome biogenesis in mammals, the two ribosomal subunits 40S and 60S are produced via splitting of the large 90S pre-ribosomal particle (90S) into pre-40S and pre-60S pre-ribosomal particles (pre-40S and pre-60S). We previously proposed that replacement of fibrillarin by Nop52 (RRP1/NNP-1) for the binding to p32 (C1QBP) is a key event that drives this splitting process. However, how the replacement by RRP1 is coupled with the endo- and/or exo-ribonucleolytic cleavage of pre-rRNA remains unknown. In this study, we demonstrate that RRP1 deficiency suppressed site 2 cleavage on ITS1 of 47S/45S, 41S and 36S pre-rRNAs in human cells. RRP1 was also present in 90S and was localized in the dense fibrillar component of the nucleolus dependently on active RNA polymerase I transcription. In addition, double knockdown of XRN2 and RRP1 revealed that RRP1 accelerated the site 2 cleavage of 47S, 45S and 41S pre-rRNAs. These data suggest that RRP1 is involved not only in competitive binding with fibrillarin to C1QBP on 90S but also in site 2 cleavage in ITS1 of pre-rRNAs at early stages of human ribosome biogenesis; thus, it is likely that RRP1 integrates the cleavage of site 2 with the physical split of 90S into pre-40S and pre-60S.
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Affiliation(s)
- Harunori Yoshikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Centre for Gene Regulation & Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Hideaki Ishikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Keiichi Izumikawa
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
| | - Yutaka Miura
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Toshiya Hayano
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan
| | - Toshiaki Isobe
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan Department of Chemistry, Graduate School of Sciences and Engineering, Tokyo Metropolitan University, 1-1 Minamiosawa, Hachiouji-shi, Tokyo 192-0397, Japan
| | - Richard J Simpson
- La Trobe Institute for Molecular Science (LIMS), LIMS Building 1, Room 412 La Trobe University, Bundoora Victoria 3086, Australia
| | - Nobuhiro Takahashi
- Department of Applied Life Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-shi, Tokyo, 183-8509, Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Sanbancho 5, Chiyoda-ku, Tokyo, 102-0075, Japan
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Liu W, Zhou B, Niu G, Ge J, Wu J, Zhang H, Xu H, Wang P. Deep-red emissive crescent-shaped fluorescent dyes: substituent effect on live cell imaging. ACS APPLIED MATERIALS & INTERFACES 2015; 7:7421-7427. [PMID: 25785397 DOI: 10.1021/acsami.5b01429] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A series of crescent-shaped fluorescent dyes (CP1-CP6) were synthesized by hybridizing coumarin and pyronin moieties with different amino substituents at both ends. The molecular structures and photophysical properties of these fluorescent dyes were investigated through X-ray diffraction, absorption spectroscopy, and fluorescence spectroscopy. Results show that the fluorescent dyes exhibited crescent-shaped structures, deep-red emissions (approximately 650 nm), and significant Stokes shifts. In live-cell-imaging experiments, CP1 stains mitochondria, whereas CP3 and CP6 stain the lysosomes in a cytoplasm and the RNA in nucleoli. The relationships between different amino substituent groups and the imaging properties of CP dyes were discussed as well. Additionally, findings from the cytotoxicity and photostability experiments on living cells indicated the favorable biocompatibility and high photostability of the CP dyes.
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Affiliation(s)
- Weimin Liu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Bingjiang Zhou
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Guangle Niu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Jiechao Ge
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Jiasheng Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Hongyan Zhang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Haitao Xu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Pengfei Wang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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35
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Lam YW, Trinkle-Mulcahy L. New insights into nucleolar structure and function. F1000PRIME REPORTS 2015; 7:48. [PMID: 26097721 PMCID: PMC4447046 DOI: 10.12703/p7-48] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The nucleolus is a non-membrane-bound nuclear organelle found in all eukaryotes. It is the quintessential ‘RNA-seeded’ nuclear body, forming around specific chromosomal features called nucleolar organizing regions that contain arrays of ribosomal DNA. Assembly is triggered by activation of RNA polymerase I-mediated transcription and regulated in mammalian cells in a cell cycle-dependent manner. Although the nucleolus is best known for its role in coordinating ribosome biogenesis, biochemical and proteomic analyses have revealed a much wider functional complexity than previously appreciated, including roles in cell cycle regulation, DNA damage sensing and repair, pre-mRNA processing, telomere metabolism, processing of non-coding RNAs, and coordination of the cellular response to various stresses. Despite these advances, much remains to be learned about the full range of biological processes that occur within, or involve, this organelle and how its assembly/disassembly and functional reorganization in response to various stimuli are regulated. Here, we review the impact of recent studies that provide major insights into these fundamental questions, and we highlight the therapeutic potential of targeting nucleolar pathways.
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Affiliation(s)
- Yun Wah Lam
- Department of Biology and Chemistry, City University of Hong KongTat Chee Avenue, KowloonHong Kong
| | - Laura Trinkle-Mulcahy
- Department of Cellular & Molecular Medicine and Ottawa Institute of Systems Biology, University of Ottawa451 Smyth Road, Ottawa, ON, K1H 8M5Canada
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36
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Wang H, Luo X, You W, Dong Y, Ke C. Cytogenetic analysis and chromosomal characteristics of the polymorphic 18S rDNA of Haliotis discus hannai from Fujian, China. PLoS One 2015; 10:e0113816. [PMID: 25699679 PMCID: PMC4336138 DOI: 10.1371/journal.pone.0113816] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 10/31/2014] [Indexed: 11/27/2022] Open
Abstract
We report on novel chromosomal characteristics of Haliotis discus hannai from a breeding population at Fujian, China. The karyotypes of H. discus hannai we obtained from an abalone farm include a common type 2n = 36 = 10M + 8SM (82%) and two rare types 2n = 36 = 11M + 7SM (14%) and 2n = 36 = 10M + 7SM + 1ST (4%). The results of silver staining showed that the NORs of H. discus hannai were usually located terminally on the long arms of chromosome pairs 14 and 17, NORs were also sometimes located terminally on the short arms of other chromosomes, either metacentric or submetacentric pairs. The number of Ag-nucleoli ranged from 2 to 8, and the mean number was 3.61 ± 0.93. Among the scored interphase cells, 41% had 3 detectable nucleoli and 37% had 4 nucleoli. The 18S rDNA FISH result is the first report of the location of 18S rDNA genes in H. discus hannai. The 18S rDNA locations were highly polymorphic in this species. Copies of the gene were observed in the terminal of long or/and short arms of submetacentric or/and metacentric chromosomes. Using FISH with probe for vertebrate-like telomeric sequences (CCCTAA)3 displayed positive green FITC signals at telomere regions of all analyzed chromosome types. We found about 7% of chromosomes had breaks in prophase. A special form of nucleolus not previously described from H. discus hannai was observed in some interphase cells. It consists of many small silver-stained nucleoli gathered together to form a larger nucleolus and may correspond to prenucleolar bodies.
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Affiliation(s)
- Haishan Wang
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
- Colleges of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Xuan Luo
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
- Colleges of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Weiwei You
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
- Colleges of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Yunwei Dong
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
- Colleges of Ocean and Earth Sciences, Xiamen University, Xiamen, China
| | - Caihuan Ke
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
- Colleges of Ocean and Earth Sciences, Xiamen University, Xiamen, China
- * E-mail:
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37
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Farley KI, Surovtseva Y, Merkel J, Baserga SJ. Determinants of mammalian nucleolar architecture. Chromosoma 2015; 124:323-31. [PMID: 25670395 DOI: 10.1007/s00412-015-0507-z] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/22/2015] [Accepted: 01/26/2015] [Indexed: 11/30/2022]
Abstract
The nucleolus is responsible for the production of ribosomes, essential machines which synthesize all proteins needed by the cell. The structure of human nucleoli is highly dynamic and is directly related to its functions in ribosome biogenesis. Despite the importance of this organelle, the intricate relationship between nucleolar structure and function remains largely unexplored. How do cells control nucleolar formation and function? What are the minimal requirements for making a functional nucleolus? Here we review what is currently known regarding mammalian nucleolar formation at nucleolar organizer regions (NORs), which can be studied by observing the dissolution and reformation of the nucleolus during each cell division. Additionally, the nucleolus can be examined by analyzing how alterations in nucleolar function manifest in differences in nucleolar architecture. Furthermore, changes in nucleolar structure and function are correlated with cancer, highlighting the importance of studying the determinants of nucleolar formation.
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Affiliation(s)
- Katherine I Farley
- Department of Molecular Biophysics & Biochemistry, Yale University School of Medicine, New Haven, CT, 06520, USA
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38
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Zhou B, Liu W, Zhang H, Wu J, Liu S, Xu H, Wang P. Imaging of nucleolar RNA in living cells using a highly photostable deep-red fluorescent probe. Biosens Bioelectron 2014; 68:189-196. [PMID: 25569876 DOI: 10.1016/j.bios.2014.12.055] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 12/23/2014] [Accepted: 12/24/2014] [Indexed: 10/24/2022]
Abstract
A new crescent-shape fluorescent probe (named here as CP) that selectively stains RNA in nucleoli of living cells is prepared. CP shows a deep-red emission (658 nm) and a large Stokes shift because of the introduction of rigid-conjugated coumarin moiety into the molecular structure. Cell imaging experiments indicate that CP can rapidly stain nucleoli in living cells by binding with nucleolar RNA, showing performance superior to commercially available nucleoli dye SYTO RNASelect in terms of high photostability and selectivity. More significantly, these excellent properties together with low cytotoxicity enable CP to monitor nucleolar RNA changes during mitosis, and after treating with anti-cancer drugs cisplatin, actinomycin D and α-amanitin. Thus, CP could be a potential tool for real-time, long-term visualization of the dynamic changes for nucleolar RNA and evaluation of the therapeutic effect for anti-cancer drugs that targeted RNA polymerase I (Pol I).
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Affiliation(s)
- Bingjiang Zhou
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Weimin Liu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongyan Zhang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiasheng Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Sha Liu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Haitao Xu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Pengfei Wang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
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39
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Stępiński D. Functional ultrastructure of the plant nucleolus. PROTOPLASMA 2014; 251:1285-306. [PMID: 24756369 PMCID: PMC4209244 DOI: 10.1007/s00709-014-0648-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 04/08/2014] [Indexed: 05/23/2023]
Abstract
Nucleoli are nuclear domains present in almost all eukaryotic cells. They not only specialize in the production of ribosomal subunits but also play roles in many fundamental cellular activities. Concerning ribosome biosynthesis, particular stages of this process, i.e., ribosomal DNA transcription, primary RNA transcript processing, and ribosome assembly proceed in precisely defined nucleolar subdomains. Although eukaryotic nucleoli are conservative in respect of their main function, clear morphological differences between these structures can be noticed between individual kingdoms. In most cases, a plant nucleolus shows well-ordered structure in which four main ultrastructural components can be distinguished: fibrillar centers, dense fibrillar component, granular component, and nucleolar vacuoles. Nucleolar chromatin is an additional crucial structural component of this organelle. Nucleolonema, although it is not always an unequivocally distinguished nucleolar domain, has often been described as a well-grounded morphological element, especially of plant nucleoli. The ratios and morphology of particular subcompartments of a nucleolus can change depending on its metabolic activity which in turn is correlated with the physiological state of a cell, cell type, cell cycle phase, as well as with environmental influence. Precise attribution of functions to particular nucleolar subregions in the process of ribosome biosynthesis is now possible using various approaches. The presented description of plant nucleolar morphology summarizes previous knowledge regarding the function of nucleoli as well as of their particular subdomains not only in the course of ribosome biosynthesis.
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Affiliation(s)
- Dariusz Stępiński
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236, Łódź, Poland,
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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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41
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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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42
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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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43
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Abstract
In this issue of Genes & Development, Grob and colleagues (pp. 220-230) identify the minimal molecular requirements to assemble a fully functional nucleolus in human cells and demonstrate the importance of the nucleolar transcription factor upstream binding factor (UBF) as a mitotic bookmark at the ribosomal DNA (rDNA).
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Grob A, Colleran C, McStay B. Construction of synthetic nucleoli in human cells reveals how a major functional nuclear domain is formed and propagated through cell division. Genes Dev 2014; 28:220-30. [PMID: 24449107 PMCID: PMC3923965 DOI: 10.1101/gad.234591.113] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 12/17/2013] [Indexed: 01/22/2023]
Abstract
Human cell nuclei are functionally organized into structurally stable yet dynamic bodies whose cell cycle inheritance is poorly understood. Here, we investigate the biogenesis and propagation of nucleoli, sites of ribosome biogenesis and key regulators of cellular growth. Nucleolar and cell cycles are intimately connected. Nucleoli disappear during mitosis, reforming around prominent uncharacterized chromosomal features, nucleolar organizer regions (NORs). By examining the effects of UBF depletion on both endogenous NORs and synthetic pseudo-NORs, we reveal its essential role in maintaining competency and establishing a bookmark on mitotic NORs. Furthermore, we demonstrate that neo-NORs, UBF-binding site arrays coupled with rDNA transcription units, direct the de novo biogenesis of functional compartmentalized neonucleoli irrespective of their site of chromosomal integration. For the first time, we establish the sequence requirements for nucleolar biogenesis and provide proof that this is a staged process where UBF-dependent mitotic bookmarking precedes function-dependent nucleolar assembly.
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Affiliation(s)
- Alice Grob
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Christine Colleran
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Brian McStay
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Ireland
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Michel G, Matthes HWD, Hachet-Haas M, El Baghdadi K, de Mey J, Pepperkok R, Simpson JC, Galzi JL, Lecat S. Plasma membrane translocation of REDD1 governed by GPCRs contributes to mTORC1 activation. J Cell Sci 2013; 127:773-87. [PMID: 24338366 DOI: 10.1242/jcs.136432] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The mTORC1 kinase promotes cell growth in response to growth factors by activation of receptor tyrosine kinase. It is regulated by the cellular energy level and the availability of nutrients. mTORC1 activity is also inhibited by cellular stresses through overexpression of REDD1 (regulated in development and DNA damage responses). We report the identification of REDD1 in a fluorescent live-imaging screen aimed at discovering new proteins implicated in G-protein-coupled receptor signaling, based on translocation criteria. Using a sensitive and quantitative plasma membrane localization assay based on bioluminescent resonance energy transfer, we further show that a panel of endogenously expressed GPCRs, through a Ca(2+)/calmodulin pathway, triggers plasma membrane translocation of REDD1 but not of its homolog REDD2. REDD1 and REDD2 share a conserved mTORC1-inhibitory motif characterized at the functional and structural level and differ most in their N-termini. We show that the N-terminus of REDD1 and its mTORC1-inhibitory motif participate in the GPCR-evoked dynamic interaction of REDD1 with the plasma membrane. We further identify REDD1 as a novel effector in GPCR signaling. We show that fast activation of mTORC1 by GPCRs correlates with fast and maximal translocation of REDD1 to the plasma membrane. Overexpression of functional REDD1 leads to a reduction of mTORC1 activation by GPCRs. By contrast, depletion of endogenous REDD1 protein unleashes mTORC1 activity. Thus, translocation to the plasma membrane appears to be an inactivation mechanism of REDD1 by GPCRs, which probably act by sequestering its functional mTORC1-inhibitory motif that is necessary for plasma membrane targeting.
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Affiliation(s)
- Grégory Michel
- GPCRs, Pain and Inflammation Team, UMR7242, CNRS-University of Strasbourg, LabEx Medalis, 67412 Illkirch, France
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Floutsakou I, Agrawal S, Nguyen TT, Seoighe C, Ganley ARD, McStay B. The shared genomic architecture of human nucleolar organizer regions. Genome Res 2013; 23:2003-12. [PMID: 23990606 PMCID: PMC3847771 DOI: 10.1101/gr.157941.113] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The short arms of the five acrocentric human chromosomes harbor sequences that direct the assembly and function of the nucleolus, one of the key functional domains of the nucleus, yet they are absent from the current human genome assembly. Here we describe the genomic architecture of these human nucleolar organizers. Sequences distal and proximal to ribosomal gene arrays are conserved among the acrocentric chromosomes, suggesting they are sites of frequent recombination. Although previously believed to be heterochromatic, characterization of these two flanking regions reveals that they share a complex genomic architecture similar to other euchromatic regions of the genome, but they have distinct genomic characteristics. Proximal sequences are almost entirely segmentally duplicated, similar to the regions bordering centromeres. In contrast, the distal sequence is predominantly unique to the acrocentric short arms and is dominated by a very large inverted repeat. We show that the distal element is localized to the periphery of the nucleolus, where it appears to anchor the ribosomal gene repeats. This, combined with its complex chromatin structure and transcriptional activity, suggests that this region is involved in nucleolar organization. Our results provide a platform for investigating the role of NORs in nucleolar formation and function, and open the door for determining the role of these regions in the well-known empirical association of nucleoli with pathology.
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Affiliation(s)
- Ioanna Floutsakou
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland, Galway, Galway, Ireland
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47
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Sarshad A, Sadeghifar F, Louvet E, Mori R, Böhm S, Al-Muzzaini B, Vintermist A, Fomproix N, Östlund AK, Percipalle P. Nuclear myosin 1c facilitates the chromatin modifications required to activate rRNA gene transcription and cell cycle progression. PLoS Genet 2013; 9:e1003397. [PMID: 23555303 PMCID: PMC3605103 DOI: 10.1371/journal.pgen.1003397] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/04/2013] [Indexed: 11/18/2022] Open
Abstract
Actin and nuclear myosin 1c (NM1) cooperate in RNA polymerase I (pol I) transcription. NM1 is also part of a multiprotein assembly, B-WICH, which is involved in transcription. This assembly contains the chromatin remodeling complex WICH with its subunits WSTF and SNF2h. We report here that NM1 binds SNF2h with enhanced affinity upon impairment of the actin-binding function. ChIP analysis revealed that NM1, SNF2h, and actin gene occupancies are cell cycle-dependent and require intact motor function. At the onset of cell division, when transcription is temporarily blocked, B-WICH is disassembled due to WSTF phosphorylation, to be reassembled on the active gene at exit from mitosis. NM1 gene knockdown and motor function inhibition, or stable expression of NM1 mutants that do not interact with actin or chromatin, overall repressed rRNA synthesis by stalling pol I at the gene promoter, led to chromatin alterations by changing the state of H3K9 acetylation at gene promoter, and delayed cell cycle progression. These results suggest a unique structural role for NM1 in which the interaction with SNF2h stabilizes B-WICH at the gene promoter and facilitates recruitment of the HAT PCAF. This leads to a permissive chromatin structure required for transcription activation.
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Affiliation(s)
- Aishe Sarshad
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
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48
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Hernandez-Verdun D, Louvet E, Muro E. Time-lapse, photoactivation, and photobleaching imaging of nucleolar assembly after mitosis. Methods Mol Biol 2013; 1042:337-350. [PMID: 23980017 DOI: 10.1007/978-1-62703-526-2_22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nucleolus assembly starts in telophase with the benefit of building blocks passing through mitosis and lasts until cytokinesis generating the two independent interphasic cells. Several approaches make it possible to follow the dynamics of fluorescent molecules in live cells. Here, three complementary approaches are described to measure the dynamics of proteins during nucleolar assembly after mitosis: (1) rapid two-color 4-D imaging time-lapse microscopy that demonstrates the relative localization and movement of two proteins, (2) photoactivation that reveals the directionality of migration from the activated area, and (3) fluorescence recovery after photobleaching (FRAP) that measures the renewing of proteins in the bleached area. We demonstrate that the order of recruitment of the processing machineries into nucleoli results from differential sorting of intermediate structures assembled during telophase, the prenucleolar bodies.
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Affiliation(s)
- Danièle Hernandez-Verdun
- Nuclei and Cell Cycle and Macromolecular Complexes in Live Cells, Institut Jacques Monod - UMR 7592 CNRS - Université Paris Diderot-Paris 7, Paris, France
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Carron C, Balor S, Delavoie F, Plisson-Chastang C, Faubladier M, Gleizes PE, O'Donohue MF. Post-mitotic dynamics of pre-nucleolar bodies is driven by pre-rRNA processing. J Cell Sci 2012; 125:4532-42. [PMID: 22767511 DOI: 10.1242/jcs.106419] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Understanding the relationship between the topological dynamics of nuclear subdomains and their molecular function is a central issue in nucleus biology. Pre-nucleolar bodies (PNBs) are transient nuclear subdomains, which form at telophase and contain nucleolar proteins, snoRNPs and pre-ribosomal RNAs (pre-rRNAs). These structures gradually disappear in early G1 phase and are currently regarded as reservoirs of nucleolar factors that participate to post-mitotic reassembly of the nucleolus. Here, we provide evidence from fluorescence in situ hybridization and loss-of-function experiments in HeLa cells that PNBs are in fact active ribosome factories in which maturation of the pre-rRNAs transiting through mitosis resumes at telophase. We show that the pre-rRNA spacers are sequentially removed in PNBs when cells enter G1 phase, indicating regular pre-rRNA processing as in the nucleolus. Accordingly, blocking pre-rRNA maturation induces accumulation in PNBs of stalled pre-ribosomes characterised by specific pre-rRNAs and pre-ribosomal factors. The presence of pre-ribosomal particles in PNBs is corroborated by observation of these domains by correlative electron tomography. Most importantly, blocking pre-rRNA maturation also prevents the gradual disappearance of PNBs, which persist for several hours in the nucleoplasm. In a revised model, we propose that PNBs are autonomous extra-nucleolar ribosome maturation sites, whose orderly disassembly in G1 phase is driven by the maturation and release of their pre-ribosome content.
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Affiliation(s)
- Coralie Carron
- Université de Toulouse, UPS, Laboratoire de Biologie Moléculaire Eucaryote, F-31000 Toulouse, France
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50
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Azzarello A, Hoest T, Mikkelsen AL. The impact of pronuclei morphology and dynamicity on live birth outcome after time-lapse culture. Hum Reprod 2012; 27:2649-57. [DOI: 10.1093/humrep/des210] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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