101
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Farley-Barnes KI, Ogawa LM, Baserga SJ. Ribosomopathies: Old Concepts, New Controversies. Trends Genet 2019; 35:754-767. [PMID: 31376929 PMCID: PMC6852887 DOI: 10.1016/j.tig.2019.07.004] [Citation(s) in RCA: 109] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/02/2019] [Accepted: 07/09/2019] [Indexed: 12/30/2022]
Abstract
Ribosomopathies are a diverse subset of diseases caused by reduced expression of, or mutations in, factors necessary for making ribosomes, the protein translation machinery in the cell. Despite the ubiquitous need for ribosomes in all cell types, ribosomopathies manifest with tissue-specific defects and sometimes increased cancer susceptibility, but few treatments target the underlying cause. By highlighting new research in the field, we review current hypotheses for the basis of this tissue specificity. Based on new work, we broaden our understanding of the role of ribosome biogenesis in diverse tissue types throughout embryonic development. We also pose the question of whether previously described human conditions such as aging can be at least partially attributed to defects in making ribosomes.
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Affiliation(s)
- Katherine I Farley-Barnes
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Lisa M Ogawa
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Susan J Baserga
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA.
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102
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Yao RW, Xu G, Wang Y, Shan L, Luan PF, Wang Y, Wu M, Yang LZ, Xing YH, Yang L, Chen LL. Nascent Pre-rRNA Sorting via Phase Separation Drives the Assembly of Dense Fibrillar Components in the Human Nucleolus. Mol Cell 2019; 76:767-783.e11. [PMID: 31540874 DOI: 10.1016/j.molcel.2019.08.014] [Citation(s) in RCA: 163] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 02/04/2019] [Accepted: 08/13/2019] [Indexed: 12/21/2022]
Abstract
Fibrillar centers (FCs) and dense fibrillar components (DFCs) are essential morphologically distinct sub-regions of mammalian cell nucleoli for rDNA transcription and pre-rRNA processing. Here, we report that a human nucleolus consists of several dozen FC/DFC units, each containing 2-3 transcriptionally active rDNAs at the FC/DFC border. Pre-rRNA processing factors, such as fibrillarin (FBL), form 18-24 clusters that further assemble into the DFC surrounding the FC. Mechanistically, the 5' end of nascent 47S pre-rRNA binds co-transcriptionally to the RNA-binding domain of FBL. FBL diffuses to the DFC, where local self-association via its glycine- and arginine-rich (GAR) domain forms phase-separated clusters to immobilize FBL-interacting pre-rRNA, thus promoting directional traffic of nascent pre-rRNA while facilitating pre-rRNA processing and DFC formation. These results unveil FC/DFC ultrastructures in nucleoli and suggest a conceptual framework for considering nascent RNA sorting using multivalent interactions of their binding proteins.
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Affiliation(s)
- Run-Wen Yao
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Guang Xu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Ying Wang
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Lin Shan
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Peng-Fei Luan
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Yang Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Man Wu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Liang-Zhong Yang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Yu-Hang Xing
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Li Yang
- CAS Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institute of Nutrition and Health, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China
| | - Ling-Ling Chen
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China.
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103
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Linsenmeier M, Kopp MRG, Grigolato F, Emmanoulidis L, Liu D, Zürcher D, Hondele M, Weis K, Capasso Palmiero U, Arosio P. Dynamics of Synthetic Membraneless Organelles in Microfluidic Droplets. Angew Chem Int Ed Engl 2019; 58:14489-14494. [DOI: 10.1002/anie.201907278] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Miriam Linsenmeier
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Marie R. G. Kopp
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Fulvio Grigolato
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Leonidas Emmanoulidis
- Institute of Molecular Biology and Biophysics Department of Biology ETH Zurich 8093 Zurich Switzerland
| | - Dany Liu
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Dominik Zürcher
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Maria Hondele
- Department of Biology Institute of Biochemistry ETH Zürich 8093 Zurich Switzerland
| | - Karsten Weis
- Department of Biology Institute of Biochemistry ETH Zürich 8093 Zurich Switzerland
| | - Umberto Capasso Palmiero
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Paolo Arosio
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
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104
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Linsenmeier M, Kopp MRG, Grigolato F, Emmanoulidis L, Liu D, Zürcher D, Hondele M, Weis K, Capasso Palmiero U, Arosio P. Dynamics of Synthetic Membraneless Organelles in Microfluidic Droplets. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907278] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Miriam Linsenmeier
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Marie R. G. Kopp
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Fulvio Grigolato
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Leonidas Emmanoulidis
- Institute of Molecular Biology and Biophysics Department of Biology ETH Zurich 8093 Zurich Switzerland
| | - Dany Liu
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Dominik Zürcher
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Maria Hondele
- Department of Biology Institute of Biochemistry ETH Zürich 8093 Zurich Switzerland
| | - Karsten Weis
- Department of Biology Institute of Biochemistry ETH Zürich 8093 Zurich Switzerland
| | - Umberto Capasso Palmiero
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
| | - Paolo Arosio
- Department of Chemistry and Applied Biosciences Institute for Chemical and Bioengineering ETH Zürich 8093 Zurich Switzerland
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105
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Do Cellular Condensates Accelerate Biochemical Reactions? Lessons from Microdroplet Chemistry. Biophys J 2019; 115:3-8. [PMID: 29972809 DOI: 10.1016/j.bpj.2018.05.023] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 05/03/2018] [Accepted: 05/23/2018] [Indexed: 01/20/2023] Open
Abstract
Cellular condensates-phase-separated concentrates of proteins and nucleic acids-provide organizational structure for biochemistry that is distinct from membrane-bound compartments. It has been suggested that one major function of cellular condensates is to accelerate biochemical processes that are normally slow or thermodynamically unfavorable. Yet, the mechanisms leading to increased reaction rates within cellular condensates remain poorly understood. In this article, we highlight recent advances in microdroplet chemistry that accelerate reaction rates by many orders of magnitude as compared to bulk and suggest that similar mechanisms may also affect reaction kinetics in cellular condensates.
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106
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Taylor NO, Wei MT, Stone HA, Brangwynne CP. Quantifying Dynamics in Phase-Separated Condensates Using Fluorescence Recovery after Photobleaching. Biophys J 2019; 117:1285-1300. [PMID: 31540706 DOI: 10.1016/j.bpj.2019.08.030] [Citation(s) in RCA: 169] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 07/20/2019] [Accepted: 08/22/2019] [Indexed: 12/22/2022] Open
Abstract
Cells contain numerous membraneless organelles that assemble by intracellular liquid-liquid phase separation. The viscous properties and associated biomolecular mobility within these condensed phase droplets, or condensates, are increasingly recognized as important for cellular function and also dysfunction, for example, in protein aggregation pathologies. Fluorescence recovery after photobleaching (FRAP) is widely used to assess condensate fluidity and to estimate protein diffusion coefficients. However, the models and assumptions utilized in FRAP analysis of protein condensates are often not carefully considered. Here, we combine FRAP experiments on both in vitro reconstituted droplets and intracellular condensates with systematic examination of different models that can be used to fit the data and evaluate the impact of model choice on measured values. A key finding is that model boundary conditions can give rise to widely divergent measured values. This has important implications, for example, in experiments that bleach subregions versus the entire condensate, two commonly employed experimental approaches. We suggest guidelines for determining the appropriate modeling framework and highlight emerging questions about the molecular dynamics at the droplet interface. The ability to accurately determine biomolecular mobility both in the condensate interior and at the interface is important for obtaining quantitative insights into condensate function, a key area for future research.
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Affiliation(s)
| | - Ming-Tzo Wei
- Department of Chemical and Biological Engineering
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey.
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering; Howard Hughes Medical Institute, Princeton University, Princeton, New Jersey.
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107
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Abstract
RNA localization mechanisms have been intensively studied and include localized protection of mRNA from degradation, diffusion-coupled local entrapment of mRNA, and directed transport of mRNAs along the cytoskeleton. While it is well understood how cells utilize these three mechanisms to organize mRNAs within the cytoplasm, a newly appreciated mechanism of RNA localization has emerged in recent years in which mRNAs phase-separate and form liquid-like droplets. mRNAs both contribute to condensation of proteins into liquid-like structures and are themselves regulated by being incorporated into membraneless organelles. This ability to condense into droplets is in many instances contributing to previously appreciated mRNA localization phenomena. Here we review how phase separation enables mRNAs to selectively and efficiently colocalize and be coregulated, allowing control of gene expression in time and space.
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Affiliation(s)
- Erin M Langdon
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA;
| | - Amy S Gladfelter
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA; .,Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
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108
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Controlling the material properties and rRNA processing function of the nucleolus using light. Proc Natl Acad Sci U S A 2019; 116:17330-17335. [PMID: 31399547 DOI: 10.1073/pnas.1903870116] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The nucleolus is a prominent nuclear condensate that plays a central role in ribosome biogenesis by facilitating the transcription and processing of nascent ribosomal RNA (rRNA). A number of studies have highlighted the active viscoelastic nature of the nucleolus, whose material properties and phase behavior are a consequence of underlying molecular interactions. However, the ways in which the material properties of the nucleolus impact its function in rRNA biogenesis are not understood. Here we utilize the Cry2olig optogenetic system to modulate the viscoelastic properties of the nucleolus. We show that above a threshold concentration of Cry2olig protein, the nucleolus can be gelled into a tightly linked, low mobility meshwork. Gelled nucleoli no longer coalesce and relax into spheres but nonetheless permit continued internal molecular mobility of small proteins. These changes in nucleolar material properties manifest in specific alterations in rRNA processing steps, including a buildup of larger rRNA precursors and a depletion of smaller rRNA precursors. We propose that the flux of processed rRNA may be actively tuned by the cell through modulating nucleolar material properties, which suggests the potential of materials-based approaches for therapeutic intervention in ribosomopathies.
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109
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Martin N. Dynamic Synthetic Cells Based on Liquid-Liquid Phase Separation. Chembiochem 2019; 20:2553-2568. [PMID: 31039282 DOI: 10.1002/cbic.201900183] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Indexed: 12/16/2022]
Abstract
Living cells have long been a source of inspiration for chemists. Their capacity of performing complex tasks relies on the spatiotemporal coordination of matter and energy fluxes. Recent years have witnessed growing interest in the bottom-up construction of cell-like models capable of reproducing aspects of such dynamic organisation. Liquid-liquid phase-separation (LLPS) processes in water are increasingly recognised as representing a viable compartmentalisation strategy through which to produce dynamic synthetic cells. Herein, we highlight examples of the dynamic properties of LLPS used to assemble synthetic cells, including their biocatalytic activity, reversible condensation and dissolution, growth and division, and recent directions towards the design of higher-order structures and behaviour.
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Affiliation(s)
- Nicolas Martin
- Université de Bordeaux, CNRS, Centre de Recherche Paul Pascal, UMR 5031, 115 Avenue du Dr. Albert Schweitzer, 33600, Pessac, France
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110
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Garcia-Jove Navarro M, Kashida S, Chouaib R, Souquere S, Pierron G, Weil D, Gueroui Z. RNA is a critical element for the sizing and the composition of phase-separated RNA-protein condensates. Nat Commun 2019; 10:3230. [PMID: 31324804 PMCID: PMC6642089 DOI: 10.1038/s41467-019-11241-6] [Citation(s) in RCA: 128] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 06/27/2019] [Indexed: 01/01/2023] Open
Abstract
Liquid-liquid phase separation is thought to be a key organizing principle in eukaryotic cells to generate highly concentrated dynamic assemblies, such as the RNP granules. Numerous in vitro approaches have validated this model, yet a missing aspect is to take into consideration the complex molecular mixture and promiscuous interactions found in vivo. Here we report the versatile scaffold ArtiG to generate concentration-dependent RNA-protein condensates within living cells, as a bottom-up approach to study the impact of co-segregated endogenous components on phase separation. We demonstrate that intracellular RNA seeds the nucleation of the condensates, as it provides molecular cues to locally coordinate the formation of endogenous high-order RNP assemblies. Interestingly, the co-segregation of intracellular components ultimately impacts the size of the phase-separated condensates. Thus, RNA arises as an architectural element that can influence the composition and the morphological outcome of the condensate phases in an intracellular context.
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Affiliation(s)
- Marina Garcia-Jove Navarro
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Shunnichi Kashida
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Racha Chouaib
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire de Biologie du Développement, F-75005, Paris, France.,School of Arts and Sciences, Lebanese International University (LIU), Beirut, Lebanon.,Faculty of Sciences, Lebanese University, Beirut, Lebanon
| | - Sylvie Souquere
- CNRS UMR-9196, Institut Gustave Roussy, F-94800, Villejuif, France
| | - Gérard Pierron
- CNRS UMR-9196, Institut Gustave Roussy, F-94800, Villejuif, France
| | - Dominique Weil
- Sorbonne Université, CNRS, Institut de Biologie Paris-Seine (IBPS), Laboratoire de Biologie du Développement, F-75005, Paris, France
| | - Zoher Gueroui
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France.
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111
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Mohapatra L, Lagny TJ, Harbage D, Jelenkovic PR, Kondev J. The Limiting-Pool Mechanism Fails to Control the Size of Multiple Organelles. Cell Syst 2019; 4:559-567.e14. [PMID: 28544883 DOI: 10.1016/j.cels.2017.04.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 01/31/2017] [Accepted: 04/26/2017] [Indexed: 10/24/2022]
Abstract
How the size of micrometer-scale cellular structures such as the mitotic spindle, cytoskeletal filaments, the nucleus, the nucleolus, and other non-membrane bound organelles is controlled despite a constant turnover of their constituent parts is a central problem in biology. Experiments have implicated the limiting-pool mechanism: structures grow by stochastic addition of molecular subunits from a finite pool until the rates of subunit addition and removal are balanced, producing a structure of well-defined size. Here, we consider these dynamics when multiple filamentous structures are assembled stochastically from a shared pool of subunits. Using analytical calculations and computer simulations, we show that robust size control can be achieved only when a single filament is assembled. When multiple filaments compete for monomers, filament lengths exhibit large fluctuations. These results extend to three-dimensional structures and reveal the physical limitations of the limiting-pool mechanism of size control when multiple organelles are assembled from a shared pool of subunits.
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Affiliation(s)
| | - Thibaut J Lagny
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, 75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 06, 75005 Paris, France; Institut Curie, PSL Research University, CNRS, UMR 144, 75005 Paris, France
| | - David Harbage
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
| | - Predrag R Jelenkovic
- Department of Electrical Engineering, Columbia University, New York, NY 10027, USA
| | - Jane Kondev
- Department of Physics, Brandeis University, Waltham, MA 02454, USA
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112
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Abstract
Individual cell types have characteristic sizes, suggesting that size sensing mechanisms may coordinate transcription, translation, and metabolism with cell growth rates. Two types of size-sensing mechanisms have been proposed: spatial sensing of the location or dimensions of a signal, subcellular structure or organelle; or titration-based sensing of the intracellular concentrations of key regulators. Here we propose that size sensing in animal cells combines both titration and spatial sensing elements in a dynamic mechanism whereby microtubule motor-dependent localization of RNA encoding importin β1 and mTOR, coupled with regulated local protein synthesis, enable cytoskeleton length sensing for cell growth regulation.
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Affiliation(s)
- Ida Rishal
- Department of Biomolecular Sciences, Weizmann Institute of Science, 76100, Rehovot, Israel
| | - Mike Fainzilber
- Department of Biomolecular Sciences, Weizmann Institute of Science, 76100, Rehovot, Israel.
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113
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Shayegan M, Tahvildari R, Metera K, Kisley L, Michnick SW, Leslie SR. Probing Inhomogeneous Diffusion in the Microenvironments of Phase-Separated Polymers under Confinement. J Am Chem Soc 2019; 141:7751-7757. [DOI: 10.1021/jacs.8b13349] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Marjan Shayegan
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Radin Tahvildari
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Kimberly Metera
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - Lydia Kisley
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Stephen W. Michnick
- Département de Biochimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Sabrina R. Leslie
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
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114
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Nuclear Scaling Is Coordinated among Individual Nuclei in Multinucleated Muscle Fibers. Dev Cell 2019; 49:48-62.e3. [PMID: 30905770 DOI: 10.1016/j.devcel.2019.02.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 11/28/2018] [Accepted: 02/22/2019] [Indexed: 12/22/2022]
Abstract
Optimal cell performance depends on cell size and the appropriate relative size, i.e., scaling, of the nucleus. How nuclear scaling is regulated and contributes to cell function is poorly understood, especially in skeletal muscle fibers, which are among the largest cells, containing hundreds of nuclei. Here, we present a Drosophila in vivo system to analyze nuclear scaling in whole multinucleated muscle fibers, genetically manipulate individual components, and assess muscle function. Despite precise global coordination, we find that individual nuclei within a myofiber establish different local scaling relationships by adjusting their size and synthetic activity in correlation with positional or spatial cues. While myonuclei exhibit compensatory potential, even minor changes in global nuclear size scaling correlate with reduced muscle function. Our study provides the first comprehensive approach to unraveling the intrinsic regulation of size in multinucleated muscle fibers. These insights to muscle cell biology will accelerate the development of interventions for muscle diseases.
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115
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Yoo H, Triandafillou C, Drummond DA. Cellular sensing by phase separation: Using the process, not just the products. J Biol Chem 2019; 294:7151-7159. [PMID: 30877200 DOI: 10.1074/jbc.tm118.001191] [Citation(s) in RCA: 127] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Phase separation creates two distinct liquid phases from a single mixed liquid phase, like oil droplets separating from water. Considerable attention has focused on how the products of phase separation-the resulting condensates-might act as biological compartments, bioreactors, filters, and membraneless organelles in cells. Here, we expand this perspective, reviewing recent results showing how cells instead use the process of phase separation to sense intracellular and extracellular changes. We review case studies in phase separation-based sensing and discuss key features, such as extraordinary sensitivity, which make the process of phase separation ideally suited to meet a range of sensory challenges cells encounter.
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Affiliation(s)
- Haneul Yoo
- From the Department of Biochemistry and Molecular Biology
| | | | - D Allan Drummond
- From the Department of Biochemistry and Molecular Biology, .,Department of Human Genetics, University of Chicago, Chicago, Illinois 60637
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116
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Mao S, Kuldinow D, Haataja MP, Košmrlj A. Phase behavior and morphology of multicomponent liquid mixtures. SOFT MATTER 2019; 15:1297-1311. [PMID: 30506078 DOI: 10.1039/c8sm02045k] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Multicomponent systems are ubiquitous in nature and industry. While the physics of few-component liquid mixtures (i.e., binary and ternary ones) is well-understood and routinely taught in undergraduate courses, the thermodynamic and kinetic properties of N-component mixtures with N > 3 have remained relatively unexplored. An example of such a mixture is provided by the intracellular fluid, in which protein-rich droplets phase separate into distinct membraneless organelles. In this work, we investigate equilibrium phase behavior and morphology of N-component liquid mixtures within the Flory-Huggins theory of regular solutions. In order to determine the number of coexisting phases and their compositions, we developed a new algorithm for constructing complete phase diagrams, based on numerical convexification of the discretized free energy landscape. Together with a Cahn-Hilliard approach for kinetics, we employ this method to study mixtures with N = 4 and 5 components. We report on both the coarsening behavior of such systems, as well as the resulting morphologies in three spatial dimensions. We discuss how the number of coexisting phases and their compositions can be extracted with Principal Component Analysis (PCA) and K-means clustering algorithms. Finally, we discuss how one can reverse engineer the interaction parameters and volume fractions of components in order to achieve a range of desired packing structures, such as nested "Russian dolls" and encapsulated Janus droplets.
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Affiliation(s)
- Sheng Mao
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
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117
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Rieloff E, Tully MD, Skepö M. Assessing the Intricate Balance of Intermolecular Interactions upon Self-Association of Intrinsically Disordered Proteins. J Mol Biol 2019; 431:511-523. [DOI: 10.1016/j.jmb.2018.11.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 11/12/2018] [Accepted: 11/28/2018] [Indexed: 12/01/2022]
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118
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Boire A, Renard D, Bouchoux A, Pezennec S, Croguennec T, Lechevalier V, Le Floch-Fouéré C, Bouhallab S, Menut P. Soft-Matter Approaches for Controlling Food Protein Interactions and Assembly. Annu Rev Food Sci Technol 2019; 10:521-539. [PMID: 30633568 DOI: 10.1146/annurev-food-032818-121907] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Animal- and plant-based proteins are present in a wide variety of raw and processed foods. They play an important role in determining the final structure of food matrices. Food proteins are diverse in terms of their biological origin, molecular structure, and supramolecular assembly. This diversity has led to segmented experimental studies that typically focus on one or two proteins but hinder a more general understanding of food protein structuring as a whole. In this review, we propose a unified view of how soft-matter physics can be used to control food protein assembly. We discuss physical models from polymer and colloidal science that best describe and predict the phase behavior of proteins. We explore the occurrence of phase transitions along two axes: increasing protein concentration and increasing molecular attraction. This review provides new perspectives on the link between the interactions, phase transitions, and assembly of proteins that can help in designing new food products and innovative food processing operations.
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Affiliation(s)
- Adeline Boire
- Biopolymères Interactions Assemblages, INRA UR1268, F-44300 Nantes, France;
| | - Denis Renard
- Biopolymères Interactions Assemblages, INRA UR1268, F-44300 Nantes, France;
| | - Antoine Bouchoux
- LISBP, Université de Toulouse, CNRS, INRA, INSA, F-31077 Toulouse, France
| | | | | | | | | | - Saïd Bouhallab
- STLO, INRA UMR1253, Agrocampus Ouest, F-35042 Rennes, France
| | - Paul Menut
- Montpellier SupAgro, 34060 Montpellier, France; .,Ingénierie Procédés Aliments, AgroParisTech, INRA, Université Paris-Saclay, 91300 Massy, France
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119
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The nucleolar transcriptome regulates Piwi shuttling between the nucleolus and the nucleoplasm. Chromosome Res 2018; 27:141-152. [DOI: 10.1007/s10577-018-9595-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 11/25/2018] [Accepted: 11/29/2018] [Indexed: 01/25/2023]
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120
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Langdon EM, Gladfelter AS. Probing RNA Structure in Liquid-Liquid Phase Separation Using SHAPE-MaP. Methods Enzymol 2018; 611:67-79. [PMID: 30471703 DOI: 10.1016/bs.mie.2018.09.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
RNA is an integral component of many biological condensates. A variety of features of RNAs are linked to their function in biological phase separation. Length and negative charge provide fairly generic chemical inputs that drive condensation while sequence has been shown to influence both the molecular identity and biophysical properties of droplets. mRNA sequence guides the secondary structure of the polymers and RNA secondary structure licenses-specific RNA-RNA interactions and the recruitment of RNA-binding proteins. Here, we describe a method for directly probing the structure of mRNAs in the context of RNP-droplets formed via LLPS.
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Affiliation(s)
- Erin M Langdon
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Amy S Gladfelter
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Marine Biological Laboratory, Woods Hole, MA, United States.
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121
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Ma TH, Chen PH, Tan BCM, Lo SJ. Size scaling of nucleolus in Caenorhabditis elegans embryos. Biomed J 2018; 41:333-336. [PMID: 30580798 PMCID: PMC6306298 DOI: 10.1016/j.bj.2018.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 07/20/2018] [Accepted: 07/31/2018] [Indexed: 11/13/2022] Open
Abstract
Nucleolus is viewed as a plurifunctional center in the cell, tightly linked to ribosome biosynthesis. As a non-membranous structure, how the size of nucleolus is determined is a long outstanding question, and the possibility of “direct size scaling to the nucleus” was raised by genetic studies in fission yeast. Here, we used the model organism Caenorhabditis elegans to test this hypothesis in multi-cellular organisms. We depleted ani-2, ima-3, or C27D9.1 by RNAi feeding, which altered embryo sizes to different extents in ncl-1 mutant worms. DIC imaging provided evidence that in size-altering embryo nucleolar size decreases in small cells and increases in large cells. Furthermore, analyses of nucleolar size in four blastomeres (ABa, ABp, EMS, and P2) within the same embryo of ncl-1 mutants consistently demonstrated the correspondence between cell and nucleolar sizes – the small cells (EMS and P2) have smaller nucleoli in comparison to the large cells (ABa).
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Affiliation(s)
- Tian-Hsiang Ma
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Po-Hsiang Chen
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Bertrand Chin-Ming Tan
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Department of Neurosurgery, Chang Gung Memorial Hospital at Linlou, Taoyuan, Taiwan; Research Center for Emerging Viral Infections, Chang Gung Memorial Hospital at Linlou, Taoyuan, Taiwan.
| | - Szecheng J Lo
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan; Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
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122
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Mitrea DM, Chandra B, Ferrolino MC, Gibbs EB, Tolbert M, White MR, Kriwacki RW. Methods for Physical Characterization of Phase-Separated Bodies and Membrane-less Organelles. J Mol Biol 2018; 430:4773-4805. [PMID: 30017918 PMCID: PMC6503534 DOI: 10.1016/j.jmb.2018.07.006] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/04/2018] [Accepted: 07/09/2018] [Indexed: 12/17/2022]
Abstract
Membrane-less organelles are cellular structures which arise through the phenomenon of phase separation. This process enables compartmentalization of specific sets of macromolecules (e.g., proteins, nucleic acids), thereby regulating cellular processes by increasing local concentration, and modulating the structure and dynamics of their constituents. Understanding the connection between structure, material properties and function of membrane-less organelles requires inter-disciplinary approaches, which address length and timescales that span several orders of magnitude (e.g., Ångstroms to micrometer, picoseconds to hours). In this review, we discuss the wide variety of methods that have been applied to characterize the morphology, rheology, structure and dynamics of membrane-less organelles and their components, in vitro and in live cells.
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Affiliation(s)
- Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| | - Bappaditya Chandra
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Mylene C Ferrolino
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Eric B Gibbs
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michele Tolbert
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Michael R White
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN 38163, USA.
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123
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Ditlev JA, Case LB, Rosen MK. Who's In and Who's Out-Compositional Control of Biomolecular Condensates. J Mol Biol 2018; 430:4666-4684. [PMID: 30099028 PMCID: PMC6204295 DOI: 10.1016/j.jmb.2018.08.003] [Citation(s) in RCA: 221] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 08/01/2018] [Accepted: 08/05/2018] [Indexed: 02/06/2023]
Abstract
Biomolecular condensates are two- and three-dimensional compartments in eukaryotic cells that concentrate specific collections of molecules without an encapsulating membrane. Many condensates behave as dynamic liquids and appear to form through liquid-liquid phase separation driven by weak, multivalent interactions between macromolecules. In this review, we discuss current models and data regarding the control of condensate composition, and we describe our current understanding of the composition of representative condensates including PML nuclear bodies, P-bodies, stress granules, the nucleolus, and two-dimensional membrane localized LAT and nephrin clusters. Specific interactions, such as interactions between modular binding domains, weaker interactions between intrinsically disorder regions and nucleic acid base pairing, and nonspecific interactions, such as electrostatic interactions and hydrophobic interactions, influence condensate composition. Understanding how specific condensate composition is determined is essential to understanding condensates as biochemical entities and ultimately discerning their cellular and organismic functions.
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Affiliation(s)
- Jonathon A Ditlev
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Lindsay B Case
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Michael K Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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124
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Advances in Understanding Stimulus-Responsive Phase Behavior of Intrinsically Disordered Protein Polymers. J Mol Biol 2018; 430:4619-4635. [DOI: 10.1016/j.jmb.2018.06.031] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/12/2018] [Accepted: 06/18/2018] [Indexed: 12/20/2022]
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125
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Use of the iNo score to discriminate normal from altered nucleolar morphology, with applications in basic cell biology and potential in human disease diagnostics. Nat Protoc 2018; 13:2387-2406. [DOI: 10.1038/s41596-018-0044-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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126
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Mittag T, Parker R. Multiple Modes of Protein-Protein Interactions Promote RNP Granule Assembly. J Mol Biol 2018; 430:4636-4649. [PMID: 30099026 DOI: 10.1016/j.jmb.2018.08.005] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 08/01/2018] [Accepted: 08/02/2018] [Indexed: 12/21/2022]
Abstract
Eukaryotic cells are known to contain a wide variety of RNA-protein assemblies, collectively referred to as RNP granules. RNP granules form from a combination of RNA-RNA, protein-RNA, and protein-protein interactions. In addition, RNP granules are enriched in proteins with intrinsically disordered regions (IDRs), which are frequently appended to a well-folded domain of the same protein. This structural organization of RNP granule components allows for a diverse set of protein-protein interactions including traditional structured interactions between well-folded domains, interactions of short linear motifs in IDRs with the surface of well-folded domains, interactions of short motifs within IDRs that weakly interact with related motifs, and weak interactions involving at most transient ordering of IDRs and folded domains with other components. In addition, both well-folded domains and IDRs in granule components frequently interact with RNA and thereby can contribute to RNP granule assembly. We discuss the contribution of these interactions to liquid-liquid phase separation and the possible role of phase separation in the assembly of RNP granules. We expect that these principles also apply to other non-membrane bound organelles and large assemblies in the cell.
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Affiliation(s)
- Tanja Mittag
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
| | - Roy Parker
- Department of Chemistry and Biochemistry & Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80303, United States.
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127
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Mutlu B, Chen HM, Moresco JJ, Orelo BD, Yang B, Gaspar JM, Keppler-Ross S, Yates JR, Hall DH, Maine EM, Mango SE. Regulated nuclear accumulation of a histone methyltransferase times the onset of heterochromatin formation in C. elegans embryos. SCIENCE ADVANCES 2018; 4:eaat6224. [PMID: 30140741 PMCID: PMC6105299 DOI: 10.1126/sciadv.aat6224] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 07/18/2018] [Indexed: 05/19/2023]
Abstract
Heterochromatin formation during early embryogenesis is timed precisely, but how this process is regulated remains elusive. We report the discovery of a histone methyltransferase complex whose nuclear accumulation and activation establish the onset of heterochromatin formation in Caenorhabditis elegans embryos. We find that the inception of heterochromatin generation coincides with the accumulation of the histone H3 lysine 9 (H3K9) methyltransferase MET-2 (SETDB) into nuclear hubs. The absence of MET-2 results in delayed and disturbed heterochromatin formation, whereas accelerated nuclear localization of the methyltransferase leads to precocious H3K9 methylation. We identify two factors that bind to and function with MET-2: LIN-65, which resembles activating transcription factor 7-interacting protein (ATF7IP) and localizes MET-2 into nuclear hubs, and ARLE-14, which is orthologous to adenosine 5'-diphosphate-ribosylation factor-like 14 effector protein (ARL14EP) and promotes stable association of MET-2 with chromatin. These data reveal that nuclear accumulation of MET-2 in conjunction with LIN-65 and ARLE-14 regulates timing of heterochromatin domains during embryogenesis.
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Affiliation(s)
- Beste Mutlu
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Huei-Mei Chen
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - James J. Moresco
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - Barbara D. Orelo
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - Bing Yang
- Department of Biology, Syracuse University, Syracuse, NY 13244, USA
| | - John M. Gaspar
- Informatics Group, Faculty of Arts and Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Sabine Keppler-Ross
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - John R. Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, San Diego, CA 92037, USA
| | - David H. Hall
- Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Eleanor M. Maine
- Department of Biology, Syracuse University, Syracuse, NY 13244, USA
| | - Susan E. Mango
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
- Corresponding author.
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128
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Distinct regions of the intrinsically disordered protein MUT-16 mediate assembly of a small RNA amplification complex and promote phase separation of Mutator foci. PLoS Genet 2018; 14:e1007542. [PMID: 30036386 PMCID: PMC6072111 DOI: 10.1371/journal.pgen.1007542] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 08/02/2018] [Accepted: 07/06/2018] [Indexed: 12/26/2022] Open
Abstract
In C. elegans, efficient RNA silencing requires small RNA amplification mediated by RNA-dependent RNA polymerases (RdRPs). RRF-1, an RdRP, and other Mutator complex proteins localize to Mutator foci, which are perinuclear germline foci that associate with nuclear pores and P granules to facilitate small RNA amplification. The Mutator complex protein MUT-16 is critical for Mutator foci assembly. By analyzing small deletions of MUT-16, we identify specific regions of the protein that recruit other Mutator complex components and demonstrate that it acts as a scaffolding protein. We further determine that the C-terminal region of MUT-16, a portion of which contains predicted intrinsic disorder, is necessary and sufficient to promote Mutator foci formation. Finally, we establish that MUT-16 foci have many properties consistent with a phase-separated condensate and propose that Mutator foci form through liquid-liquid phase separation of MUT-16. P granules, which contain additional RNA silencing proteins, have previously been shown to have liquid-like properties. Thus, RNA silencing in C. elegans germ cells may rely on multiple phase-separated compartments through which sorting, processing, and silencing of mRNAs occurs. Small RNAs are a driving force behind the regulation of both essential genes and deleterious transcripts. The Mutator complex is critical to the amplification of high levels of small RNAs and it requires the protein MUT-16 for its assembly. Here we investigate the function of MUT-16 by generating small deletions in the mut-16 gene. Through analysis of the subsequently altered protein, we demonstrate that MUT-16 functions as a scaffold, bringing together many other proteins required for small RNA biogenesis and amplification. Furthermore, we identified a fragment of MUT-16 that is sufficient to promote assembly of MUT-16 into foci that are dynamic and responsive to environmental conditions. We propose that these Mutator foci behave like liquid droplets within the cell, similar to the immiscibility of oil droplets in water. Mutator foci localize to the periphery of germ cell nuclei near P granules, which also have liquid-like properties and contain many factors involved in RNA silencing. Thus, our data suggest that RNA silencing is mediated by compartments of RNAs and proteins in liquid-like assemblies at the periphery of germ cell nuclei.
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129
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Tiku V, Antebi A. Nucleolar Function in Lifespan Regulation. Trends Cell Biol 2018; 28:662-672. [PMID: 29779866 DOI: 10.1016/j.tcb.2018.03.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/26/2018] [Accepted: 03/29/2018] [Indexed: 12/12/2022]
Abstract
The nucleolus is a prominent membraneless organelle residing within the nucleus. The nucleolus has been regarded as a housekeeping structure mainly known for its role in ribosomal RNA (rRNA) production and ribosome assembly. However, accumulating evidence has revealed its functions in numerous cellular processes that control organismal physiology, thereby taking the nucleolus much beyond its conventional role in ribosome biogenesis. Perturbations in nucleolar functions have been associated with severe diseases such as cancer and progeria. Recent studies have also uncovered the role of the nucleolus in development and aging. In this review we discuss major nucleolar functions that impact organismal aging.
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Affiliation(s)
- Varnesh Tiku
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Present Address: Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Adam Antebi
- Max Planck Institute for Biology of Ageing, Joseph Stelzmann Strasse 9b, 50931 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50674 Cologne, Germany.
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130
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Gerhold AR, Poupart V, Labbé JC, Maddox PS. Spindle assembly checkpoint strength is linked to cell fate in the Caenorhabditis elegans embryo. Mol Biol Cell 2018; 29:1435-1448. [PMID: 29688794 PMCID: PMC6014101 DOI: 10.1091/mbc.e18-04-0215] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The spindle assembly checkpoint (SAC) is a conserved mitotic regulator that preserves genome stability by monitoring kinetochore-microtubule attachments and blocking anaphase onset until chromosome biorientation is achieved. Despite its central role in maintaining mitotic fidelity, the ability of the SAC to delay mitotic exit in the presence of kinetochore-microtubule attachment defects (SAC "strength") appears to vary widely. How different cellular aspects drive this variation remains largely unknown. Here we show that SAC strength is correlated with cell fate during development of Caenorhabditis elegans embryos, with germline-fated cells experiencing longer mitotic delays upon spindle perturbation than somatic cells. These differences are entirely dependent on an intact checkpoint and only partially attributable to differences in cell size. In two-cell embryos, cell size accounts for half of the difference in SAC strength between the larger somatic AB and the smaller germline P1 blastomeres. The remaining difference requires asymmetric cytoplasmic partitioning downstream of PAR polarity proteins, suggesting that checkpoint-regulating factors are distributed asymmetrically during early germ cell divisions. Our results indicate that SAC activity is linked to cell fate and reveal a hitherto unknown interaction between asymmetric cell division and the SAC.
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Affiliation(s)
- Abigail R Gerhold
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Vincent Poupart
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Jean-Claude Labbé
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada.,Department of Pathology and Cell Biology, Université de Montréal, Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
| | - Paul S Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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131
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Dzuricky M, Roberts S, Chilkoti A. Convergence of Artificial Protein Polymers and Intrinsically Disordered Proteins. Biochemistry 2018; 57:2405-2414. [PMID: 29683665 DOI: 10.1021/acs.biochem.8b00056] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A flurry of research in recent years has revealed the molecular origins of many membraneless organelles to be the liquid phase separation of intrinsically disordered proteins (IDPs). Consequently, protein disorder has emerged as an important driver of intracellular compartmentalization by providing specialized microenvironments chemically distinct from the surrounding medium. Though the importance of protein disorder and its relationship to intracellular phase behavior are clear, a detailed understanding of how such phase behavior can be predicted and controlled remains elusive. While research in IDPs has largely focused on the implications of structural disorder on cellular function and disease, another field, that of artificial protein polymers, has focused on the de novo design of protein polymers with controllable material properties. A subset of these polymers, specifically those derived from structural proteins such as elastin and resilin, are also disordered sequences that undergo liquid-liquid phase separation. This phase separation has been used in a variety of biomedical applications, and researchers studying these polymers have developed methods to precisely characterize and tune their phase behavior. Despite their disparate origins, both fields are complementary as they study the phase behavior of intrinsically disordered polypeptides. This Perspective hopes to stimulate collaborative efforts by highlighting the similarities between these two fields and by providing examples of how such collaboration could be mutually beneficial.
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Affiliation(s)
- Michael Dzuricky
- Department of Biomedical Engineering , Duke University , Durham , North Carolina 27708-0281 , United States
| | - Stefan Roberts
- Department of Biomedical Engineering , Duke University , Durham , North Carolina 27708-0281 , United States
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering , Duke University , Durham , North Carolina 27708-0281 , United States
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132
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Erdel F, Rippe K. Formation of Chromatin Subcompartments by Phase Separation. Biophys J 2018; 114:2262-2270. [PMID: 29628210 DOI: 10.1016/j.bpj.2018.03.011] [Citation(s) in RCA: 236] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 02/19/2018] [Accepted: 03/06/2018] [Indexed: 10/17/2022] Open
Abstract
Chromatin is partitioned on multiple length scales into subcompartments that differ from each other with respect to their molecular composition and biological function. It is a key question how these compartments can form even though diffusion constantly mixes the nuclear interior and rapidly balances concentration gradients of soluble nuclear components. Different biophysical concepts are currently used to explain the formation of "chromatin bodies" in a self-organizing manner and without consuming energy. They rationalize how soluble protein factors that are dissolved in the liquid nuclear phase, the nucleoplasm, bind and organize transcriptionally active or silenced chromatin domains. In addition to cooperative binding of proteins to a preformed chromatin structure, two different mechanisms for the formation of phase-separated chromatin subcompartments have been proposed. One is based on bridging proteins that cross-link polymer segments with particular properties. Bridging can induce a collapse of the nucleosome chain and associated factors into an ordered globular phase. The other mechanism is based on multivalent interactions among soluble molecules that bind to chromatin. These interactions can induce liquid-liquid phase separation, which drives the assembly of liquid-like nuclear bodies around the respective binding sites on chromatin. Both phase separation mechanisms can explain that chromatin bodies are dynamic spherical structures, which can coalesce and are in constant and rapid exchange with the surrounding nucleoplasm. However, they make distinct predictions about how the size, density, and stability of chromatin bodies depends on the concentration and interaction behavior of the molecules involved. Here, we compare the different biophysical mechanisms for the assembly of chromatin bodies and discuss experimental strategies to distinguish them from each other. Furthermore, we outline the implications for the establishment and memory of functional chromatin state patterns.
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Affiliation(s)
- Fabian Erdel
- Division of Chromatin Networks, German Cancer Research Center (DKFZ) and Bioquant, Heidelberg, Germany.
| | - Karsten Rippe
- Division of Chromatin Networks, German Cancer Research Center (DKFZ) and Bioquant, Heidelberg, Germany.
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133
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Berry J, Brangwynne CP, Haataja M. Physical principles of intracellular organization via active and passive phase transitions. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:046601. [PMID: 29313527 DOI: 10.1088/1361-6633/aaa61e] [Citation(s) in RCA: 246] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Exciting recent developments suggest that phase transitions represent an important and ubiquitous mechanism underlying intracellular organization. We describe key experimental findings in this area of study, as well as the application of classical theoretical approaches for quantitatively understanding these data. We also discuss the way in which equilibrium thermodynamic driving forces may interface with the fundamentally out-of-equilibrium nature of living cells. In particular, time and/or space-dependent concentration profiles may modulate the phase behavior of biomolecules in living cells. We suggest future directions for both theoretical and experimental work that will shed light on the way in which biological activity modulates the assembly, properties, and function of viscoelastic states of living matter.
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Affiliation(s)
- Joel Berry
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, United States of America. Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, United States of America
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134
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Emulsion patterns in the wake of a liquid-liquid phase separation front. Proc Natl Acad Sci U S A 2018; 115:3599-3604. [PMID: 29563232 DOI: 10.1073/pnas.1716330115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Miscible liquids can phase separate in response to a composition change. In bulk fluids, the demixing begins on molecular-length scales, which coarsen into macroscopic phases. By contrast, confining a mixture in microfluidic droplets causes sequential phase separation bursts, which self-organize into rings of oil and water to make multilayered emulsions. The spacing in these nonequilibrium patterns is self-similar and scale-free over a range of droplet sizes. We develop a modified Cahn-Hilliard model, in which an immiscibility front with stretched exponential dynamics quantitatively predicts the spacing of the layers. In addition, a scaling law predicts the lifetime of each layer, giving rise to a stepwise release of inner droplets. Analogously, in long rectangular capillaries, a diffusive front yields large-scale oil and water stripes on the time scale of hours. The same theory relates their characteristic length scale to the speed of the front and the rate of mass transport. Control over liquid-liquid phase separation into large-scale patterns finds potential material applications in living cells, encapsulation, particulate design, and surface patterning.
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135
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Björkegren C, Baranello L. DNA Supercoiling, Topoisomerases, and Cohesin: Partners in Regulating Chromatin Architecture? Int J Mol Sci 2018; 19:E884. [PMID: 29547555 PMCID: PMC5877745 DOI: 10.3390/ijms19030884] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 03/09/2018] [Accepted: 03/13/2018] [Indexed: 01/25/2023] Open
Abstract
Although our knowledge of chromatin organization has advanced significantly in recent years, much about the relationships between different features of genome architecture is still unknown. Folding of mammalian genomes into spatial domains is thought to depend on architectural proteins, other DNA-binding proteins, and different forms of RNA. In addition, emerging evidence points towards the possibility that the three-dimensional organisation of the genome is controlled by DNA topology. In this scenario, cohesin, CCCTC-binding factor (CTCF), transcription, DNA supercoiling, and topoisomerases are integrated to dictate different layers of genome organization, and the contribution of all four to gene control is an important direction of future studies. In this perspective, we review recent studies that give new insight on how DNA supercoiling shape chromatin structure.
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Affiliation(s)
- Camilla Björkegren
- Department of Cell and Molecular Biology, Karolinska Institutet, 17177 Stockholm, Sweden.
- Department of Biosciences and Nutrition, Karolinska Institutet, 141 43 Huddinge, Sweden.
| | - Laura Baranello
- Department of Cell and Molecular Biology, Karolinska Institutet, 17177 Stockholm, Sweden.
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136
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Abstract
Liquid-liquid phase separation seems to play critical roles in the compartmentalization of cells through the formation of biomolecular condensates. Many proteins with low-complexity regions are found in these condensates, and they can undergo phase separation in vitro in response to changes in temperature, pH, and ion concentration. Low-complexity regions are thus likely important players in mediating compartmentalization in response to stress. However, how the phase behavior is encoded in their amino acid composition and patterning is only poorly understood. We discuss here that polymer physics provides a powerful framework for our understanding of the thermodynamics of mixing and demixing and for how the phase behavior is encoded in the primary sequence. We propose to classify low-complexity regions further into subcategories based on their sequence properties and phase behavior. Ongoing research promises to improve our ability to link the primary sequence of low-complexity regions to their phase behavior as well as the emerging miscibility and material properties of the resulting biomolecular condensates, providing mechanistic insight into this fundamental biological process across length scales.
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Affiliation(s)
- Erik W Martin
- Department of Structural Biology , St. Jude Children's Research Hospital , Memphis , Tennessee 38105-3678 , United States
| | - Tanja Mittag
- Department of Structural Biology , St. Jude Children's Research Hospital , Memphis , Tennessee 38105-3678 , United States
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137
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Shin Y, Brangwynne CP. Liquid phase condensation in cell physiology and disease. Science 2018; 357:357/6357/eaaf4382. [PMID: 28935776 DOI: 10.1126/science.aaf4382] [Citation(s) in RCA: 2242] [Impact Index Per Article: 373.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Phase transitions are ubiquitous in nonliving matter, and recent discoveries have shown that they also play a key role within living cells. Intracellular liquid-liquid phase separation is thought to drive the formation of condensed liquid-like droplets of protein, RNA, and other biomolecules, which form in the absence of a delimiting membrane. Recent studies have elucidated many aspects of the molecular interactions underlying the formation of these remarkable and ubiquitous droplets and the way in which such interactions dictate their material properties, composition, and phase behavior. Here, we review these exciting developments and highlight key remaining challenges, particularly the ability of liquid condensates to both facilitate and respond to biological function and how their metastability may underlie devastating protein aggregation diseases.
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Affiliation(s)
- Yongdae Shin
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, USA.
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138
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Bräuer S, Zimyanin V, Hermann A. Prion-like properties of disease-relevant proteins in amyotrophic lateral sclerosis. J Neural Transm (Vienna) 2018; 125:591-613. [PMID: 29417336 DOI: 10.1007/s00702-018-1851-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 01/30/2018] [Indexed: 02/07/2023]
Abstract
The hallmark of age-related neurodegenerative diseases is the appearance of cellular protein deposits and spreading of this pathology throughout the central nervous system. Growing evidence has shown the involvement and critical role of proteins with prion-like properties in the formation of these characteristic cellular aggregates. Prion-like domains of such proteins with their proposed function in the organization of membraneless organelles are prone for misfolding and promoting further aggregation. Spreading of these toxic aggregates between cells and across tissues can explain the progression of clinical phenotypes and pathology in a stereotypical manner, characteristic for almost every neurodegenerative disease. Here, we want to review the current evidence for the role of prion-like mechanisms in classical neurodegenerative diseases and ALS in particular. We will also discuss an intriguingly central role of the protein TDP-43 in the majority of cases of this devastating disease.
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Affiliation(s)
- S Bräuer
- Department of Neurology, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany
- Department of Neurology, Städtisches Klinikum Dresden, 01129, Dresden, Germany
| | - V Zimyanin
- Department of Neurology, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany
| | - A Hermann
- Department of Neurology, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany.
- Center for Regenerative Therapies Dresden (CRTD), Technische Universität Dresden and German Center for Neurodegenerative Diseases (DZNE), 01307, Dresden, Germany.
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139
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Nakashima KK, Baaij JF, Spruijt E. Reversible generation of coacervate droplets in an enzymatic network. SOFT MATTER 2018; 14:361-367. [PMID: 29199758 DOI: 10.1039/c7sm01897e] [Citation(s) in RCA: 110] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Cells can control the assembly and disassembly of membraneless organelles by enzymatic processes, but similar control has not been achieved in vitro yet. Here we develop ATP-based coacervate droplets as artificial membraneless organelles that can be fully controlled by two cooperating enzymes. Droplets can be generated within a minute following the addition of phosphoenolpyruvate as a substrate, and they can be dissolved within tens of seconds by adding glucose as the second substrate. We show how the rates of droplet generation and dissolution can be tuned by varying the enzyme and substrate concentrations, and we support our findings with a kinetic model of the underlying enzymatic reaction network. As all steps of the coacervate droplet life cycle, including nucleation, coarsening, and dissolution, occur under the same reaction conditions, the cycle can be repeated multiple times. In addition, by carefully balancing the rates of both enzymatic reactions, our system can be programmed to either form or dissolve droplets at specified times, acting as a chemical timer.
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Affiliation(s)
- Karina K Nakashima
- Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
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140
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Woodruff JB, Hyman AA, Boke E. Organization and Function of Non-dynamic Biomolecular Condensates. Trends Biochem Sci 2017; 43:81-94. [PMID: 29258725 DOI: 10.1016/j.tibs.2017.11.005] [Citation(s) in RCA: 117] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/19/2017] [Accepted: 11/20/2017] [Indexed: 11/29/2022]
Abstract
Cells compartmentalize biochemical reactions using organelles. Organelles can be either membrane-bound compartments or supramolecular assemblies of protein and ribonucleic acid known as 'biomolecular condensates'. Biomolecular condensates, such as nucleoli and germ granules, have been described as liquid like, as they have the ability to fuse, flow, and undergo fission. Recent experiments have revealed that some liquid-like condensates can mature over time to form stable gels. In other cases, biomolecular condensates solidify into amyloid-like fibers. Here we discuss the assembly, organization, and physiological roles of these more stable condensates in cells, focusing on Balbiani bodies, centrosomes, nuclear pores, and amyloid bodies. We discuss how the material properties of these condensates can be explained by the principles of liquid-liquid phase separation and maturation.
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Affiliation(s)
- Jeffrey B Woodruff
- Department of Cell Biology, Department of Biophysics, UT Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Elvan Boke
- Centre for Genomic Regulation (CRG), Barcelona Institute for Science and Technology, Dr. Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain
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141
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Hierarchical Size Scaling during Multicellular Growth and Development. Cell Rep 2017; 17:345-352. [PMID: 27705784 DOI: 10.1016/j.celrep.2016.09.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 07/12/2016] [Accepted: 09/01/2016] [Indexed: 01/09/2023] Open
Abstract
Multicellular organisms must regulate their growth across the diverse length scales of biological organization, but how this growth is controlled from organelle to body, while coordinating interdependent functions at each scale, remains poorly understood. We utilized the C. elegans worm intestine as a model system to identify distinct allometric scaling laws, revealing that the growth of individual structures is differentially regulated during development. We show that the volume of the nucleolus, a subcellular organelle, is directly proportional (isometric) to cell size during larval development. In contrast to findings in a variety of other systems, the size of the nucleus grows more slowly and is hypoallometric to the cell. We further demonstrate that the relative size of the nucleolus, the site of ribosome biogenesis, is predictive of the growth rate of the entire worm. These results highlight the importance of subcellular size for organism-level function in multicellular organisms.
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142
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There Is an Inclusion for That: Material Properties of Protein Granules Provide a Platform for Building Diverse Cellular Functions. Trends Biochem Sci 2017; 42:765-776. [DOI: 10.1016/j.tibs.2017.08.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/26/2017] [Accepted: 08/03/2017] [Indexed: 12/30/2022]
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143
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Brady JP, Farber PJ, Sekhar A, Lin YH, Huang R, Bah A, Nott TJ, Chan HS, Baldwin AJ, Forman-Kay JD, Kay LE. Structural and hydrodynamic properties of an intrinsically disordered region of a germ cell-specific protein on phase separation. Proc Natl Acad Sci U S A 2017; 114:E8194-E8203. [PMID: 28894006 PMCID: PMC5625912 DOI: 10.1073/pnas.1706197114] [Citation(s) in RCA: 321] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Membrane encapsulation is frequently used by the cell to sequester biomolecules and compartmentalize their function. Cells also concentrate molecules into phase-separated protein or protein/nucleic acid "membraneless organelles" that regulate a host of biochemical processes. Here, we use solution NMR spectroscopy to study phase-separated droplets formed from the intrinsically disordered N-terminal 236 residues of the germ-granule protein Ddx4. We show that the protein within the concentrated phase of phase-separated Ddx4, [Formula: see text], diffuses as a particle of 600-nm hydrodynamic radius dissolved in water. However, NMR spectra reveal sharp resonances with chemical shifts showing [Formula: see text] to be intrinsically disordered. Spin relaxation measurements indicate that the backbone amides of [Formula: see text] have significant mobility, explaining why high-resolution spectra are observed, but motion is reduced compared with an equivalently concentrated nonphase-separating control. Observation of a network of interchain interactions, as established by NOE spectroscopy, shows the importance of Phe and Arg interactions in driving the phase separation of Ddx4, while the salt dependence of both low- and high-concentration regions of phase diagrams establishes an important role for electrostatic interactions. The diffusion of a series of small probes and the compact but disordered 4E binding protein 2 (4E-BP2) protein in [Formula: see text] are explained by an excluded volume effect, similar to that found for globular protein solvents. No changes in structural propensities of 4E-BP2 dissolved in [Formula: see text] are observed, while changes to DNA and RNA molecules have been reported, highlighting the diverse roles that proteinaceous solvents play in dictating the properties of dissolved solutes.
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Affiliation(s)
- Jacob P Brady
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - Patrick J Farber
- Division of Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada M5G 0A4
| | - Ashok Sekhar
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - Yi-Hsuan Lin
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Division of Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada M5G 0A4
| | - Rui Huang
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - Alaji Bah
- Division of Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada M5G 0A4
| | - Timothy J Nott
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - Hue Sun Chan
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
| | - Andrew J Baldwin
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - Julie D Forman-Kay
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8;
- Division of Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada M5G 0A4
| | - Lewis E Kay
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8;
- Department of Chemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8
- Division of Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, ON, Canada M5G 0A4
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144
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Lin Y, Currie SL, Rosen MK. Intrinsically disordered sequences enable modulation of protein phase separation through distributed tyrosine motifs. J Biol Chem 2017; 292:19110-19120. [PMID: 28924037 PMCID: PMC5704491 DOI: 10.1074/jbc.m117.800466] [Citation(s) in RCA: 256] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2017] [Revised: 09/12/2017] [Indexed: 01/04/2023] Open
Abstract
Liquid–liquid phase separation (LLPS) is thought to contribute to the establishment of many biomolecular condensates, eukaryotic cell structures that concentrate diverse macromolecules but lack a bounding membrane. RNA granules control RNA metabolism and comprise a large class of condensates that are enriched in RNA-binding proteins and RNA molecules. Many RNA granule proteins are composed of both modular domains and intrinsically disordered regions (IDRs) having low amino acid sequence complexity. Phase separation of these molecules likely plays an important role in the generation and stability of RNA granules. To understand how folded domains and IDRs can cooperate to modulate LLPS, we generated a series of engineered proteins. These were based on fusions of an IDR derived from the RNA granule protein FUS (fused in sarcoma) to a multivalent poly-Src homology 3 (SH3) domain protein that phase-separates when mixed with a poly-proline–rich-motif (polyPRM) ligand. We found that the wild-type IDR promotes LLPS of the polySH3–polyPRM system, decreasing the phase separation threshold concentration by 8-fold. Systematic mutation of tyrosine residues in Gly/Ser-Tyr-Gly/Ser motifs of the IDR reduced this effect, depending on the number but not on the position of these substitutions. Mutating all tyrosines to non-aromatic residues or phosphorylating the IDR raised the phase separation threshold above that of the unmodified polySH3–polyPRM pair. These results show that low-complexity IDRs can modulate LLPS both positively and negatively, depending on the degree of aromaticity and phosphorylation status. Our findings provide plausible mechanisms by which these sequences could alter RNA granule properties on evolutionary and cellular timescales.
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Affiliation(s)
- Yuan Lin
- From the Department of Biophysics, University of Texas Southwestern Medical Center and.,the Howard Hughes Medical Institute, Dallas, Texas 75390
| | - Simon L Currie
- From the Department of Biophysics, University of Texas Southwestern Medical Center and.,the Howard Hughes Medical Institute, Dallas, Texas 75390
| | - Michael K Rosen
- From the Department of Biophysics, University of Texas Southwestern Medical Center and .,the Howard Hughes Medical Institute, Dallas, Texas 75390
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145
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Ambadipudi S, Biernat J, Riedel D, Mandelkow E, Zweckstetter M. Liquid-liquid phase separation of the microtubule-binding repeats of the Alzheimer-related protein Tau. Nat Commun 2017; 8:275. [PMID: 28819146 PMCID: PMC5561136 DOI: 10.1038/s41467-017-00480-0] [Citation(s) in RCA: 475] [Impact Index Per Article: 67.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 06/30/2017] [Indexed: 02/08/2023] Open
Abstract
The protein Tau aggregates into tangles in the brain of patients with Alzheimer’s disease. In solution, however, Tau is intrinsically disordered, highly soluble, and binds to microtubules. It is still unclear what initiates the conversion from an innocuous phase of high solubility and functionality to solid-like neurotoxic deposits. Here, we show that the microtubule-binding repeats of Tau, which are lysine-rich, undergo liquid–liquid phase separation in solution. Liquid–liquid demixing causes molecular crowding of amyloid-promoting elements of Tau and drives electrostatic coacervation. Furthermore, we demonstrate that three-repeat and four-repeat isoforms of Tau differ in their ability for demixing. Alternative splicing of Tau can thus regulate the formation of Tau-containing membrane-less compartments. In addition, phosphorylation of Tau repeats promotes liquid–liquid phase separation at cellular protein conditions. The combined data propose a mechanism in which liquid droplets formed by the positively charged microtubule-binding domain of Tau undergo coacervation with negatively charged molecules to promote amyloid formation. Tau forms aggregates in the brains of Alzheimer patients. Here, the authors identify conditions, where the microtubule-binding repeats of Tau undergo a phosphorylation-dependent liquid–liquid phase separation, leading to molecular crowding in the formed Tau liquid droplets and characterize them by NMR and other biophysical methods.
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Affiliation(s)
- Susmitha Ambadipudi
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), von-Siebold-Str. 3a, 37075, Göttingen, Germany
| | - Jacek Biernat
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany
| | - Dietmar Riedel
- Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077, Göttingen, Germany
| | - Eckhard Mandelkow
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.,CAESAR Research Center, Bonn, and MPI for Metabolism Research, Hamburg Outstation, 22607, Hamburg, Germany
| | - Markus Zweckstetter
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), von-Siebold-Str. 3a, 37075, Göttingen, Germany. .,Max-Planck-Institut für Biophysikalische Chemie, Am Fassberg 11, 37077, Göttingen, Germany. .,Department of Neurology, University Medical Center Göttingen, University of Göttingen, Waldweg 33, 37073, Göttingen, Germany.
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146
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Kapeli K, Martinez FJ, Yeo GW. Genetic mutations in RNA-binding proteins and their roles in ALS. Hum Genet 2017; 136:1193-1214. [PMID: 28762175 PMCID: PMC5602095 DOI: 10.1007/s00439-017-1830-7] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Accepted: 07/17/2017] [Indexed: 12/11/2022]
Abstract
Mutations in genes that encode RNA-binding proteins (RBPs) have emerged as critical determinants of neurological diseases, especially motor neuron disorders such as amyotrophic lateral sclerosis (ALS). RBPs are involved in all aspects of RNA processing, controlling the life cycle of RNAs from synthesis to degradation. Hallmark features of RBPs in neuron dysfunction include misregulation of RNA processing, mislocalization of RBPs to the cytoplasm, and abnormal aggregation of RBPs. Much progress has been made in understanding how ALS-associated mutations in RBPs drive pathogenesis. Here, we focus on several key RBPs involved in ALS—TDP-43, HNRNP A2/B1, HNRNP A1, FUS, EWSR1, and TAF15—and review our current understanding of how mutations in these proteins cause disease.
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Affiliation(s)
- Katannya Kapeli
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore
| | - Fernando J Martinez
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Gene W Yeo
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117593, Singapore.
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
- Molecular Engineering Laboratory, A*STAR, Singapore, 138673, Singapore.
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147
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Reduction in chromosome mobility accompanies nuclear organization during early embryogenesis in Caenorhabditis elegans. Sci Rep 2017. [PMID: 28623274 PMCID: PMC5473868 DOI: 10.1038/s41598-017-03483-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In differentiated cells, chromosomes are packed inside the cell nucleus in an organised fashion. In contrast, little is known about how chromosomes are packed in undifferentiated cells and how nuclear organization changes during development. To assess changes in nuclear organization during the earliest stages of development, we quantified the mobility of a pair of homologous chromosomal loci in the interphase nuclei of Caenorhabditis elegans embryos. The distribution of distances between homologous loci was consistent with a random distribution up to the 8-cell stage but not at later stages. The mobility of the loci was significantly reduced from the 2-cell to the 48-cell stage. Nuclear foci corresponding to epigenetic marks as well as heterochromatin and the nucleolus also appeared around the 8-cell stage. We propose that the earliest global transformation in nuclear organization occurs at the 8-cell stage during C. elegans embryogenesis.
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148
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Sugawara T, Kimura A. Physical properties of the chromosomes and implications for development. Dev Growth Differ 2017; 59:405-414. [PMID: 28573677 DOI: 10.1111/dgd.12363] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/13/2017] [Accepted: 04/13/2017] [Indexed: 01/15/2023]
Abstract
Remarkable progress has been made in understanding chromosome structures inside the cell nucleus. Recent advances in Hi-C technologies enable the detection of genome-wide chromatin interactions, providing insight into three-dimensional (3D) genome organization. Advancements in the spatial and temporal resolutions of imaging as well as in molecular biological techniques allow the tracking of specific chromosomal loci, improving our understanding of chromosome movements. From these data, we are beginning to understand how the intra-nuclear locations of chromatin loci and the 3D genome structure change during development and differentiation. This emerging field of genome structure and dynamics research requires an interdisciplinary approach including efficient collaborations between experimental biologists and physicists, informaticians, or engineers. Quantitative and mathematical analyses based on polymer physics are becoming increasingly important for processing and interpreting experimental data on 3D chromosome structures and dynamics. In this review, we aim to provide an overview of recent research on the physical aspects of chromosome structure and dynamics oriented for biologists. These studies have mainly focused on chromosomes at the cellular level, using unicellular organisms and cultured cells. However, physical parameters that change during development, such as nuclear size, may impact genome structure and dynamics. Here, we discuss how chromatin dynamics and genome structures in early embryos change during development, which we expect will be a hot topic in the field of chromatin dynamics in the near future. We hope this review helps developmental biologists to quantitatively investigate the physical natures of chromosomes in developmental biology research.
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Affiliation(s)
- Takeshi Sugawara
- Research Center for the Mathematics on Chromatin Live Dynamics (RcMcD), Hiroshima University, Higashi-Hiroshima, 739-8530, Japan.,Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima, 411-8540, Japan
| | - Akatsuki Kimura
- Cell Architecture Laboratory, Structural Biology Center, National Institute of Genetics, Mishima, 411-8540, Japan.,Department of Genetics, School of Life Science, The Graduate University for Advanced Studies (Sokendai), Mishima, 411-8540, Japan
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149
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Banani SF, Lee HO, Hyman AA, Rosen MK. Biomolecular condensates: organizers of cellular biochemistry. Nat Rev Mol Cell Biol 2017; 18:285-298. [PMID: 28225081 PMCID: PMC7434221 DOI: 10.1038/nrm.2017.7] [Citation(s) in RCA: 3245] [Impact Index Per Article: 463.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Biomolecular condensates are micron-scale compartments in eukaryotic cells that lack surrounding membranes but function to concentrate proteins and nucleic acids. These condensates are involved in diverse processes, including RNA metabolism, ribosome biogenesis, the DNA damage response and signal transduction. Recent studies have shown that liquid-liquid phase separation driven by multivalent macromolecular interactions is an important organizing principle for biomolecular condensates. With this physical framework, it is now possible to explain how the assembly, composition, physical properties and biochemical and cellular functions of these important structures are regulated.
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Affiliation(s)
- Salman F. Banani
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hyun O. Lee
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Anthony A. Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Michael K. Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Geometric Asymmetry Induces Upper Limit of Mitotic Spindle Size. Biophys J 2017; 112:1503-1516. [PMID: 28402892 DOI: 10.1016/j.bpj.2017.02.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 02/10/2017] [Accepted: 02/23/2017] [Indexed: 01/10/2023] Open
Abstract
Proper organelle size is critical for many cell functions. However, how cells sense and control their organelle size remains elusive. Here, we develop a general model to study the size control of mitotic spindles by considering both extrinsic and intrinsic factors, such as the limited number of building blocks of the spindle, the interaction between the spindle and cell boundary, the DNA content, the forces generated by various molecular motors, and the dynamics of microtubules. We show that multiple pairs of chromatids, two centrosomes, and microtubules can self-assemble to form a mitotic spindle robustly. We also show that the boundary-sensing and volume-sensing mechanisms coexist in small cells, but both break down in large cells. Strikingly, we find that the upper limit of spindle length naturally arises from the geometric asymmetry of the spindle structure. Thus, our findings reveal, to our knowledge, a novel intrinsic mechanism that limits the organelle size.
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