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Bornens M. Centrosome organization and functions. Curr Opin Struct Biol 2020; 66:199-206. [PMID: 33338884 DOI: 10.1016/j.sbi.2020.11.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 10/23/2020] [Accepted: 11/03/2020] [Indexed: 02/06/2023]
Abstract
The centrosome, discovered near 1875, was named by Boveri when proposing the chromosomal theory of heredity. After a long eclipse, a considerable amount of molecular data has been accumulated on the centrosome and its biogenesis in the last 30 years, summarized regularly in excellent reviews. Major questions are still at stake in 2021 however, as we lack a comprehensive view of the centrosome functions. I will first try to see how progress towards a unified view of the role of centrosomes during evolution is possible, and then review recent data on only some of the many important questions raised by this organelle.
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Affiliation(s)
- Michel Bornens
- Institut Curie, PSL University, CNRS - UMR 144, 75005 Paris, France.
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52
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Woodruff JB. The material state of centrosomes: lattice, liquid, or gel? Curr Opin Struct Biol 2020; 66:139-147. [PMID: 33248427 DOI: 10.1016/j.sbi.2020.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 09/24/2020] [Accepted: 10/01/2020] [Indexed: 12/25/2022]
Abstract
Centrosomes are micron-scale structures that nucleate microtubule arrays for chromosome segregation and mitotic spindle positioning. For these jobs, centrosomes must be dynamic enough to grow, yet stable enough to resist microtubule-mediated forces. How do centrosomes achieve such seemingly contradictory features? While much is understood about the molecular parts of centrosomes, very little is known about their functional material properties. Two prevalent hypotheses pose that the centrosome is either a liquid droplet or a solid lattice. However, many material states exist between a pure Newtonian liquid and a crystalline solid, and it is not clear where centrosomes lie along this spectrum. Furthermore, broad terms like "liquid" or "solid" do not reveal functional properties like strength, ductility, elasticity, and toughness, which are more relevant to understand how centrosomes resist forces. This review covers recent findings and new rheology techniques that reveal the material characteristics of centrosomes and how they are regulated.
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Affiliation(s)
- Jeffrey B Woodruff
- Department of Cell Biology, Department of Biophysics, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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53
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Ryder PV, Fang J, Lerit DA. centrocortin RNA localization to centrosomes is regulated by FMRP and facilitates error-free mitosis. J Cell Biol 2020; 219:211538. [PMID: 33196763 PMCID: PMC7716377 DOI: 10.1083/jcb.202004101] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 09/12/2020] [Accepted: 10/14/2020] [Indexed: 02/06/2023] Open
Abstract
Centrosomes are microtubule-organizing centers required for error-free mitosis and embryonic development. The microtubule-nucleating activity of centrosomes is conferred by the pericentriolar material (PCM), a composite of numerous proteins subject to cell cycle-dependent oscillations in levels and organization. In diverse cell types, mRNAs localize to centrosomes and may contribute to changes in PCM abundance. Here, we investigate the regulation of mRNA localization to centrosomes in the rapidly cycling Drosophila melanogaster embryo. We find that RNA localization to centrosomes is regulated during the cell cycle and developmentally. We identify a novel role for the fragile-X mental retardation protein in the posttranscriptional regulation of a model centrosomal mRNA, centrocortin (cen). Further, mistargeting cen mRNA is sufficient to alter cognate protein localization to centrosomes and impair spindle morphogenesis and genome stability.
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54
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Tarczewska A, Wycisk K, Orłowski M, Waligórska A, Dobrucki J, Drewniak-Świtalska M, Berlicki Ł, Ożyhar A. Nuclear immunophilin FKBP39 from Drosophila melanogaster drives spontaneous liquid-liquid phase separation. Int J Biol Macromol 2020; 163:108-119. [PMID: 32615218 DOI: 10.1016/j.ijbiomac.2020.06.255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 06/25/2020] [Accepted: 06/26/2020] [Indexed: 11/27/2022]
Abstract
The FKBP39 from Drosophila melanogaster is a multifunctional regulatory immunophilin. It contains two globular domains linked by a highly charged disordered region. The N-terminal domain shows homology to the nucleoplasmin core domain, and the C-terminal domain is characteristic for the family of the FKBP immunophilin ligand binding domain. The specific partially disordered structure of the protein inspired us to investigate whether FKBP39 can drive spontaneous liquid-liquid phase separation (LLPS). Preliminary analyses using CatGranule and Pi-Pi contact predictors suggested a propensity for LLPS. Microscopy observations revealed that FKBP39 can self-concentrate to form liquid condensates. We also found that FKBP39 can lead to LLPS in the presence of RNA and peptides containing Arg-rich linear motifs derived from selected nuclear and nucleolar proteins. These heterotypic interactions have a stronger propensity for driving LLPS when compared to the interactions mediated by self-associating FKBP39 molecules. To investigate whether FKBP39 can drive LLPS in the cellular environment, we analysed it in fusion with YFP in COS-7 cells. The specific distribution and diffusion kinetics of FKBP39 examined by FRAP experiments provided evidence that immunophilin is an important driver of phase separation. The ability of FKBP39 to go into heterotypic interaction may be fundamental for ribosome subunits assembly.
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Affiliation(s)
- Aneta Tarczewska
- Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland.
| | - Krzysztof Wycisk
- Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
| | - Marek Orłowski
- Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
| | - Agnieszka Waligórska
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Jurek Dobrucki
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, Poland
| | - Magda Drewniak-Świtalska
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
| | - Łukasz Berlicki
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
| | - Andrzej Ożyhar
- Department of Biochemistry, Molecular Biology and Biotechnology, Faculty of Chemistry, Wroclaw University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wroclaw, Poland
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55
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Adame-Arana O, Weber CA, Zaburdaev V, Prost J, Jülicher F. Liquid Phase Separation Controlled by pH. Biophys J 2020; 119:1590-1605. [PMID: 33010236 DOI: 10.1016/j.bpj.2020.07.044] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 06/27/2020] [Accepted: 07/06/2020] [Indexed: 12/31/2022] Open
Abstract
We present a minimal model to study the effects of pH on liquid phase separation of macromolecules. Our model describes a mixture composed of water and macromolecules that exist in three different charge states and have a tendency to phase separate. This phase separation is affected by pH via a set of chemical reactions describing protonation and deprotonation of macromolecules, as well as self-ionization of water. We consider the simple case in which interactions are captured by Flory-Huggins interaction parameters corresponding to Debye screening lengths shorter than a nanometer, which is relevant to proteins inside biological cells under physiological conditions. We identify the conjugate thermodynamic variables at chemical equilibrium and discuss the effective free energy at fixed pH. First, we study phase diagrams as a function of macromolecule concentration and temperature at the isoelectric point of the macromolecules. We find a rich variety of phase diagram topologies, including multiple critical points, triple points, and first-order transition points. Second, we change the pH relative to the isoelectric point of the macromolecules and study how phase diagrams depend on pH. We find that these phase diagrams as a function of pH strongly depend on whether oppositely charged macromolecules or neutral macromolecules have a stronger tendency to phase separate. One key finding is that we predict the existence of a reentrant behavior as a function of pH. In addition, our model predicts that the region of phase separation is typically broader at the isoelectric point. This model could account for both in vitro phase separation of proteins as a function of pH and protein phase separation in yeast cells for pH values close to the isoelectric point of many cytosolic proteins.
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Affiliation(s)
- Omar Adame-Arana
- Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany
| | - Christoph A Weber
- Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany
| | - Vasily Zaburdaev
- Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany
| | - Jacques Prost
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France; Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Frank Jülicher
- Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany; Center for Systems Biology Dresden, Dresden, Germany; Cluster of Excellence Physics of Life, Technische Universität Dresden, Dresden, Germany.
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56
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Guilhas B, Walter JC, Rech J, David G, Walliser NO, Palmeri J, Mathieu-Demaziere C, Parmeggiani A, Bouet JY, Le Gall A, Nollmann M. ATP-Driven Separation of Liquid Phase Condensates in Bacteria. Mol Cell 2020; 79:293-303.e4. [PMID: 32679076 DOI: 10.1016/j.molcel.2020.06.034] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 04/08/2020] [Accepted: 06/22/2020] [Indexed: 12/18/2022]
Abstract
Liquid-liquid phase-separated (LLPS) states are key to compartmentalizing components in the absence of membranes; however, it is unclear whether LLPS condensates are actively and specifically organized in the subcellular space and by which mechanisms. Here, we address this question by focusing on the ParABS DNA segregation system, composed of a centromeric-like sequence (parS), a DNA-binding protein (ParB), and a motor (ParA). We show that parS and ParB associate to form nanometer-sized, round condensates. ParB molecules diffuse rapidly within the nucleoid volume but display confined motions when trapped inside ParB condensates. Single ParB molecules are able to rapidly diffuse between different condensates, and nucleation is strongly favored by parS. Notably, the ParA motor is required to prevent the fusion of ParB condensates. These results describe a novel active mechanism that splits, segregates, and localizes non-canonical LLPS condensates in the subcellular space.
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Affiliation(s)
- Baptiste Guilhas
- Centre de Biochimie Structurale, CNRS UMR 5048, INSERM U1054, Université de Montpellier, 60 rue de Navacelles, 34090 Montpellier, France
| | - Jean-Charles Walter
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France
| | - Jerome Rech
- LMGM, CBI, CNRS, Université de Toulouse, UPS, Toulouse, France
| | - Gabriel David
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France
| | - Nils Ole Walliser
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France
| | - John Palmeri
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France
| | | | - Andrea Parmeggiani
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, Montpellier, France; LPHI, CNRS, Université de Montpellier, Montpellier, France
| | - Jean-Yves Bouet
- LMGM, CBI, CNRS, Université de Toulouse, UPS, Toulouse, France
| | - Antoine Le Gall
- Centre de Biochimie Structurale, CNRS UMR 5048, INSERM U1054, Université de Montpellier, 60 rue de Navacelles, 34090 Montpellier, France.
| | - Marcelo Nollmann
- Centre de Biochimie Structurale, CNRS UMR 5048, INSERM U1054, Université de Montpellier, 60 rue de Navacelles, 34090 Montpellier, France.
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57
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Liu X, Liu X, Wang H, Dou Z, Ruan K, Hill DL, Li L, Shi Y, Yao X. Phase separation drives decision making in cell division. J Biol Chem 2020; 295:13419-13431. [PMID: 32699013 DOI: 10.1074/jbc.rev120.011746] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 07/22/2020] [Indexed: 12/11/2022] Open
Abstract
Liquid-liquid phase separation (LLPS) of biomolecules drives the formation of subcellular compartments with distinct physicochemical properties. These compartments, free of lipid bilayers and therefore called membraneless organelles, include nucleoli, centrosomes, heterochromatin, and centromeres. These have emerged as a new paradigm to account for subcellular organization and cell fate decisions. Here we summarize recent studies linking LLPS to mitotic spindle, heterochromatin, and centromere assembly and their plasticity controls in the context of the cell division cycle, highlighting a functional role for phase behavior and material properties of proteins assembled onto heterochromatin, centromeres, and central spindles via LLPS. The techniques and tools for visualizing and harnessing membraneless organelle dynamics and plasticity in mitosis are also discussed, as is the potential for these discoveries to promote new research directions for investigating chromosome dynamics, plasticity, and interchromosome interactions in the decision-making process during mitosis.
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Affiliation(s)
- Xing Liu
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China; Keck Center for Cellular Dynamics and Organoids Plasticity, Morehouse School of Medicine, Atlanta, Georgia, USA
| | - Xu Liu
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China; Keck Center for Cellular Dynamics and Organoids Plasticity, Morehouse School of Medicine, Atlanta, Georgia, USA
| | - Haowei Wang
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China
| | - Zhen Dou
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China
| | - Ke Ruan
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China
| | - Donald L Hill
- Comprehensive Cancer Center, University of Alabama, Birmingham, Alabama, USA
| | - Lin Li
- CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Shanghai, China
| | - Yunyu Shi
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China
| | - Xuebiao Yao
- MOE Key Laboratory for Membraneless Organelles and Cellular Dynamics and CAS Center for Excellence in Molecular Cell Science, University of Science and Technology of China School of Life Science, Hefei, China; Anhui Key Laboratory for Cellular Dynamics & Chemical Biology, Hefei National Center for Physical Sciences at Nanoscale, Hefei, China; Keck Center for Cellular Dynamics and Organoids Plasticity, Morehouse School of Medicine, Atlanta, Georgia, USA; Comprehensive Cancer Center, University of Alabama, Birmingham, Alabama, USA; CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Shanghai, China.
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58
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Vidal-Henriquez E, Zwicker D. Theory of droplet ripening in stiffness gradients. SOFT MATTER 2020; 16:5898-5905. [PMID: 32525198 DOI: 10.1039/d0sm00182a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Liquid droplets embedded in soft solids are a new composite material whose properties are not very well explored. In particular, it is unclear how the elastic properties of the matrix affect the dynamics of the droplets. Here, we study theoretically how stiffness gradients influence droplet growth and arrangement. We show that stiffness gradients imply concentration gradients in the dilute phase, which transport droplet material from stiff to soft regions. Consequently, droplets dissolve in the stiff region, creating a dissolution front. Using a mean-field theory, we predict that the front emerges where the curvature of the elasticity profile is large and that it propagates diffusively. This elastic ripening can occur at much higher rates than classical Ostwald ripening, thus driving the dynamics. Our work shows how gradients in elastic properties control the arrangement of droplets, which has potential applications in soft matter physics and biological cells.
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59
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Rosowski KA, Vidal-Henriquez E, Zwicker D, Style RW, Dufresne ER. Elastic stresses reverse Ostwald ripening. SOFT MATTER 2020; 16:5892-5897. [PMID: 32519711 DOI: 10.1039/d0sm00628a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
When liquid droplets nucleate and grow in a polymer network, compressive stresses can significantly increase their internal pressure, reaching values that far exceed the Laplace pressure. When droplets have grown in a polymer network with a stiffness gradient, droplets in relatively stiff regions of the network tend to dissolve, favoring growth of droplets in softer regions. Here, we show that this elastic ripening can be strong enough to reverse the direction of Ostwald ripening: large droplets can shrink to feed the growth of smaller ones. To numerically model these experiments, we generalize the theory of elastic ripening to account for gradients in solubility alongside gradients in mechanical stiffness.
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Affiliation(s)
| | | | - David Zwicker
- Max Planck Institute for Dynamics and Self-Organization, 37077, Göttingen, Germany
| | - Robert W Style
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland.
| | - Eric R Dufresne
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland.
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60
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Sapkota H, Wren JD, Gorbsky GJ. CSAG1 maintains the integrity of the mitotic centrosome in cells with defective p53. J Cell Sci 2020; 133:jcs.239723. [PMID: 32295846 DOI: 10.1242/jcs.239723] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 03/26/2020] [Indexed: 02/06/2023] Open
Abstract
Centrosomes focus microtubules to promote mitotic spindle bipolarity, a critical requirement for balanced chromosome segregation. Comprehensive understanding of centrosome function and regulation requires a complete inventory of components. While many centrosome components have been identified, others yet remain undiscovered. We have used a bioinformatics approach, based on 'guilt by association' expression to identify novel mitotic components among the large group of predicted human proteins that have yet to be functionally characterized. Here, we identify chondrosarcoma-associated gene 1 protein (CSAG1) in maintaining centrosome integrity during mitosis. Depletion of CSAG1 disrupts centrosomes and leads to multipolar spindles, particularly in cells with compromised p53 function. Thus, CSAG1 may reflect a class of 'mitotic addiction' genes, whose expression is more essential in transformed cells.
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Affiliation(s)
- Hem Sapkota
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Jonathan D Wren
- Genes and Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
| | - Gary J Gorbsky
- Cell Cycle and Cancer Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104, USA
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61
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Bressloff PC. Active suppression of Ostwald ripening: Beyond mean-field theory. Phys Rev E 2020; 101:042804. [PMID: 32422749 DOI: 10.1103/physreve.101.042804] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Accepted: 04/01/2020] [Indexed: 12/29/2022]
Abstract
Active processes play a major role in the formation of membraneless cellular structures (biological condensates). Classical coarsening theory predicts that only a single droplet remains following Ostwald ripening. However, in both the cell nucleus and cytoplasm there coexist several membraneless organelles of the same basic composition, suggesting that there is some mechanism for suppressing Ostwald ripening. One potential candidate is the active regulation of liquid-liquid phase separation by enzymatic reactions that switch proteins between different conformational states (e.g., different levels of phosphorylation). Recent theoretical studies have used mean-field methods to analyze the suppression of Ostwald ripening in three-dimensional (3D) systems consisting of a solute that switches between two different conformational states, an S state that does not phase separate and a P state that does. However, mean-field theory breaks down in the case of 2D systems, since the concentration around a droplet varies as lnR rather than R^{-1}, where R is the distance from the center of the droplet. It also fails to capture finite-size effects. In this paper we show how to go beyond mean-field theory by using the theory of diffusion in domains with small holes or exclusions (strongly localized perturbations). In particular, we use asymptotic methods to study the suppression of Ostwald ripening in a 2D or 3D solution undergoing active liquid-liquid phase separation. We proceed by partitioning the region outside the droplets into a set of inner regions around each droplet together with an outer region where mean-field interactions occur. Asymptotically matching the inner and outer solutions, we derive leading-order conditions for the existence and stability of a multidroplet steady state. We also show how finite-size effects can be incorporated into the theory by including higher-order terms in the asymptotic expansion, which depend on the positions of the droplets and the boundary of the 2D or 3D domain. The theoretical framework developed in this paper provides a general method for analyzing active phase separation for dilute droplets in bounded domains such as those found in living cells.
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Affiliation(s)
- Paul C Bressloff
- Department of Mathematics, University of Utah, Salt Lake City, Utah 84112, USA
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62
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Abstract
Many biomolecular condensates appear to form via spontaneous or driven processes that have the hallmarks of intracellular phase transitions. This suggests that a common underlying physical framework might govern the formation of functionally and compositionally unrelated biomolecular condensates. In this review, we summarize recent work that leverages a stickers-and-spacers framework adapted from the field of associative polymers for understanding how multivalent protein and RNA molecules drive phase transitions that give rise to biomolecular condensates. We discuss how the valence of stickers impacts the driving forces for condensate formation and elaborate on how stickers can be distinguished from spacers in different contexts. We touch on the impact of sticker- and spacer-mediated interactions on the rheological properties of condensates and show how the model can be mapped to known drivers of different types of biomolecular condensates.
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Affiliation(s)
- Jeong-Mo Choi
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63130, USA; , ,
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri, 63130, USA
- Natural Science Research Institute, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea
| | - Alex S Holehouse
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63130, USA; , ,
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri, 63130, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, 63130, USA; , ,
- Center for Science & Engineering of Living Systems (CSELS), Washington University in St. Louis, St. Louis, Missouri, 63130, USA
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63
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Skuodas S, Clemons A, Hayes M, Goll A, Zora B, Weeks DL, Phillips BT, Fassler JS. The ABCF gene family facilitates disaggregation during animal development. Mol Biol Cell 2020; 31:1324-1345. [PMID: 32320318 PMCID: PMC7353142 DOI: 10.1091/mbc.e19-08-0443] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Protein aggregation, once believed to be a harbinger and/or consequence of stress, age, and pathological conditions, is emerging as a novel concept in cellular regulation. Normal versus pathological aggregation may be distinguished by the capacity of cells to regulate the formation, modification, and dissolution of aggregates. We find that Caenorhabditis elegans aggregates are observed in large cells/blastomeres (oocytes, embryos) and in smaller, further differentiated cells (primordial germ cells), and their analysis using cell biological and genetic tools is straightforward. These observations are consistent with the hypothesis that aggregates are involved in normal development. Using cross-platform analysis in Saccharomyces cerevisiae, C. elegans, and Xenopus laevis, we present studies identifying a novel disaggregase family encoded by animal genomes and expressed embryonically. Our initial analysis of yeast Arb1/Abcf2 in disaggregation and animal ABCF proteins in embryogenesis is consistent with the possibility that members of the ABCF gene family may encode disaggregases needed for aggregate processing during the earliest stages of animal development.
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Affiliation(s)
- Sydney Skuodas
- Department of Biology, University of Iowa, Iowa City, IA 52242
| | - Amy Clemons
- Department of Biology, University of Iowa, Iowa City, IA 52242
| | - Michael Hayes
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242
| | - Ashley Goll
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242
| | - Betul Zora
- Department of Biology, University of Iowa, Iowa City, IA 52242
| | - Daniel L Weeks
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242
| | | | - Jan S Fassler
- Department of Biology, University of Iowa, Iowa City, IA 52242
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64
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Rosowski KA, Sai T, Vidal-Henriquez E, Zwicker D, Style RW, Dufresne ER. Elastic ripening and inhibition of liquid-liquid phase separation. NATURE PHYSICS 2020; 16:422-425. [PMID: 32273899 PMCID: PMC7145441 DOI: 10.1038/s41567-019-0767-2] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 12/02/2019] [Indexed: 05/07/2023]
Abstract
Phase separation is a central concept of materials physics [1-3] and has recently emerged as an important route to compartmentalization within living cells [4-6]. Biological phase separation features activity [7], complex compositions [8], and elasticity [9], which reveal important gaps in our understanding of this universal physical phenomenon. Here, we explore the impact of elasticity on phase separation in synthetic polymer networks. We show that compressive stresses in a polymer network can suppress phase separation of the solvent that swells it, stabilizing mixtures well beyond the liquid-liquid phase separation boundary. Network stresses also drive a new form of ripening, driven by transport of solute down stiffness gradients. This elastic ripening can be much faster than conventional surface tension driven Ostwald ripening.
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Affiliation(s)
| | - Tianqi Sai
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | | | - David Zwicker
- Max Planck Institute for Dynamics and Self-Organization, 37077, Göttingen, Germany
| | - Robert W. Style
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
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65
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Brackley CA, Marenduzzo D. Bridging-induced microphase separation: photobleaching experiments, chromatin domains and the need for active reactions. Brief Funct Genomics 2020; 19:111-118. [DOI: 10.1093/bfgp/elz032] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 10/09/2019] [Accepted: 10/15/2019] [Indexed: 01/11/2023] Open
Abstract
Abstract
We review the mechanism and consequences of the ‘bridging-induced attraction’, a generic biophysical principle that underpins some existing models for chromosome organization in 3D. This attraction, which was revealed in polymer physics-inspired computer simulations, is a generic clustering tendency arising in multivalent chromatin-binding proteins, and it provides an explanation for the biogenesis of nuclear bodies and transcription factories via microphase separation. Including post-translational modification reactions involving these multivalent proteins can account for the fast dynamics of the ensuing clusters, as is observed via microscopy and photobleaching experiments. The clusters found in simulations also give rise to chromatin domains that conform well with the observation of A/B compartments in HiC experiments.
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66
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Lesne A, Baudement MO, Rebouissou C, Forné T. Exploring Mammalian Genome within Phase-Separated Nuclear Bodies: Experimental Methods and Implications for Gene Expression. Genes (Basel) 2019; 10:E1049. [PMID: 31861077 PMCID: PMC6947181 DOI: 10.3390/genes10121049] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 12/11/2019] [Accepted: 12/13/2019] [Indexed: 01/05/2023] Open
Abstract
The importance of genome organization at the supranucleosomal scale in the control of gene expression is increasingly recognized today. In mammals, Topologically Associating Domains (TADs) and the active/inactive chromosomal compartments are two of the main nuclear structures that contribute to this organization level. However, recent works reviewed here indicate that, at specific loci, chromatin interactions with nuclear bodies could also be crucial to regulate genome functions, in particular transcription. They moreover suggest that these nuclear bodies are membrane-less organelles dynamically self-assembled and disassembled through mechanisms of phase separation. We have recently developed a novel genome-wide experimental method, High-salt Recovered Sequences sequencing (HRS-seq), which allows the identification of chromatin regions associated with large ribonucleoprotein (RNP) complexes and nuclear bodies. We argue that the physical nature of such RNP complexes and nuclear bodies appears to be central in their ability to promote efficient interactions between distant genomic regions. The development of novel experimental approaches, including our HRS-seq method, is opening new avenues to understand how self-assembly of phase-separated nuclear bodies possibly contributes to mammalian genome organization and gene expression.
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Affiliation(s)
- Annick Lesne
- IGMM, Univ. Montpellier, CNRS, F-34293 Montpellier, France; (M.-O.B.); (C.R.)
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée, LPTMC, F-75252 Paris, France
| | - Marie-Odile Baudement
- IGMM, Univ. Montpellier, CNRS, F-34293 Montpellier, France; (M.-O.B.); (C.R.)
- Centre for Integrative Genetics (CIGENE), Faculty of Biosciences, Norwegian University of Life Sciences, 1430 Ås, Norway
| | - Cosette Rebouissou
- IGMM, Univ. Montpellier, CNRS, F-34293 Montpellier, France; (M.-O.B.); (C.R.)
| | - Thierry Forné
- IGMM, Univ. Montpellier, CNRS, F-34293 Montpellier, France; (M.-O.B.); (C.R.)
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67
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Michieletto D, Colì D, Marenduzzo D, Orlandini E. Nonequilibrium Theory of Epigenomic Microphase Separation in the Cell Nucleus. PHYSICAL REVIEW LETTERS 2019; 123:228101. [PMID: 31868408 DOI: 10.1103/physrevlett.123.228101] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 08/05/2019] [Indexed: 06/10/2023]
Abstract
Understanding the spatial organization of the genome in the cell nucleus is one of the current grand challenges in biophysics. Certain biochemical-or epigenetic-marks that are deposited along the genome are thought to play an important, yet poorly understood, role in determining genome organization and cell identity. The physical principles underlying the interplay between epigenetic dynamics and genome folding remain elusive. Here we propose and study a theory that assumes a coupling between epigenetic mark and genome densities, and which can be applied at the scale of the whole nucleus. We show that equilibrium models are not compatible with experiments and a qualitative agreement is recovered by accounting for nonequilibrium processes that can stabilize microphase separated epigenomic domains. We finally discuss the potential biophysical origin of these terms.
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Affiliation(s)
- Davide Michieletto
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
- Centre for Mathematical Biology, and Department of Mathematical Sciences, University of Bath, North Rd, Bath BA2 7AY, United Kingdom
| | - Davide Colì
- Dipartimento di Fisica e Astronomia and Sezione INFN, Università degli Studi di Padova, I-35131 Padova, Italy
| | - Davide Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - Enzo Orlandini
- Dipartimento di Fisica e Astronomia and Sezione INFN, Università degli Studi di Padova, I-35131 Padova, Italy
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68
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Söding J, Zwicker D, Sohrabi-Jahromi S, Boehning M, Kirschbaum J. Mechanisms for Active Regulation of Biomolecular Condensates. Trends Cell Biol 2019; 30:4-14. [PMID: 31753533 DOI: 10.1016/j.tcb.2019.10.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 10/17/2019] [Accepted: 10/18/2019] [Indexed: 12/31/2022]
Abstract
Liquid-liquid phase separation is a key organizational principle in eukaryotic cells, on par with intracellular membranes. It allows cells to concentrate specific proteins into condensates, increasing reaction rates and achieving switch-like regulation. We propose two active mechanisms that can explain how cells regulate condensate formation and size. In both, the cell regulates the activity of an enzyme, often a kinase, that adds post-translational modifications to condensate proteins. In enrichment inhibition, the enzyme enriches in the condensate and weakens interactions, as seen in stress granules (SGs), Cajal bodies, and P granules. In localization-induction, condensates form around immobilized enzymes that strengthen interactions, as observed in DNA repair, transmembrane signaling, and microtubule assembly. These models can guide studies into the many emerging roles of biomolecular condensates.
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Affiliation(s)
- Johannes Söding
- Quantitative Biology and Bioinformatics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
| | - David Zwicker
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, 37077 Göttingen, Germany
| | - Salma Sohrabi-Jahromi
- Quantitative Biology and Bioinformatics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Marc Boehning
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Jan Kirschbaum
- Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, 37077 Göttingen, Germany
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69
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Abstract
Asymmetric cell division (ACD) is a conserved strategy for achieving cell diversity. A cell can undergo an intrinsic ACD through asymmetric segregation of cell fate determinants or cellular organelles. Recently, a new biophysical concept known as biomolecular phase separation, through which proteins and/or RNAs autonomously form a highly concentrated non-membrane-enclosed compartment via multivalent interactions, has provided new insights into the assembly and regulation of many membrane-less or membrane-attached organelles. Intriguingly, biomolecular phase separation is suggested to drive asymmetric condensation of cell fate determinants during ACD as well as organization of cellular organelles involved in ACD. In this Perspective, I first summarize recent findings on the molecular basis governing intrinsic ACD. Then I will discuss how ACD might be regulated by formation of dense molecular assemblies via phase separation.
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Affiliation(s)
- Wenyu Wen
- Department of Neurosurgery, Huashan Hospital, Institutes of Biomedical Sciences, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, School of Basic Medical Sciences , Shanghai Medical College of Fudan University , Shanghai 200032 , China
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70
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Pessina F, Giavazzi F, Yin Y, Gioia U, Vitelli V, Galbiati A, Barozzi S, Garre M, Oldani A, Flaus A, Cerbino R, Parazzoli D, Rothenberg E, d'Adda di Fagagna F. Functional transcription promoters at DNA double-strand breaks mediate RNA-driven phase separation of damage-response factors. Nat Cell Biol 2019; 21:1286-1299. [PMID: 31570834 PMCID: PMC6859070 DOI: 10.1038/s41556-019-0392-4] [Citation(s) in RCA: 203] [Impact Index Per Article: 40.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 08/16/2019] [Indexed: 12/31/2022]
Abstract
Damage-induced long non-coding RNAs (dilncRNA) synthesized at DNA double-strand breaks (DSBs) by RNA polymerase II are necessary for DNA-damage-response (DDR) focus formation. We demonstrate that induction of DSBs results in the assembly of functional promoters that include a complete RNA polymerase II preinitiation complex, MED1 and CDK9. Absence or inactivation of these factors causes a reduction in DDR foci both in vivo and in an in vitro system that reconstitutes DDR events on nucleosomes. We also show that dilncRNAs drive molecular crowding of DDR proteins, such as 53BP1, into foci that exhibit liquid-liquid phase-separation condensate properties. We propose that the assembly of DSB-induced transcriptional promoters drives RNA synthesis, which stimulates phase separation of DDR factors in the shape of foci.
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Affiliation(s)
- Fabio Pessina
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | - Fabio Giavazzi
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Segrate, Italy
| | - Yandong Yin
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Ubaldo Gioia
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | - Valerio Vitelli
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | | | - Sara Barozzi
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | | | - Amanda Oldani
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | - Andrew Flaus
- Centre for Chromosome Biology, Biochemistry, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Roberto Cerbino
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Segrate, Italy
| | - Dario Parazzoli
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy
| | - Eli Rothenberg
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Fabrizio d'Adda di Fagagna
- IFOM, The FIRC Institute of Molecular Oncology, Milan, Italy.
- Istituto di Genetica Molecolare, CNR-Consiglio Nazionale delle Ricerche, Pavia, Italy.
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71
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Alvarez-Rodrigo I, Steinacker TL, Saurya S, Conduit PT, Baumbach J, Novak ZA, Aydogan MG, Wainman A, Raff JW. Evidence that a positive feedback loop drives centrosome maturation in fly embryos. eLife 2019; 8:e50130. [PMID: 31498081 PMCID: PMC6733597 DOI: 10.7554/elife.50130] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 08/21/2019] [Indexed: 01/26/2023] Open
Abstract
Centrosomes are formed when mother centrioles recruit pericentriolar material (PCM) around themselves. The PCM expands dramatically as cells prepare to enter mitosis (a process termed centrosome maturation), but it is unclear how this expansion is achieved. In flies, Spd-2 and Cnn are thought to form a scaffold around the mother centriole that recruits other components of the mitotic PCM, and the Polo-dependent phosphorylation of Cnn at the centrosome is crucial for scaffold assembly. Here, we show that, like Cnn, Spd-2 is specifically phosphorylated at centrosomes. This phosphorylation appears to create multiple phosphorylated S-S/T(p) motifs that allow Spd-2 to recruit Polo to the expanding scaffold. If the ability of Spd-2 to recruit Polo is impaired, the scaffold is initially assembled around the mother centriole, but it cannot expand outwards, and centrosome maturation fails. Our findings suggest that interactions between Spd-2, Polo and Cnn form a positive feedback loop that drives the dramatic expansion of the mitotic PCM in fly embryos.
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Affiliation(s)
- Ines Alvarez-Rodrigo
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Thomas L Steinacker
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Saroj Saurya
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Paul T Conduit
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Janina Baumbach
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Zsofia A Novak
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Mustafa G Aydogan
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Alan Wainman
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
| | - Jordan W Raff
- The Sir William Dunn School of PathologyUniversity of OxfordOxfordUnited Kingdom
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72
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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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73
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Mapping Local and Global Liquid Phase Behavior in Living Cells Using Photo-Oligomerizable Seeds. Cell 2019; 175:1467-1480.e13. [PMID: 30500534 DOI: 10.1016/j.cell.2018.10.048] [Citation(s) in RCA: 266] [Impact Index Per Article: 53.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 08/10/2018] [Accepted: 10/23/2018] [Indexed: 11/24/2022]
Abstract
Liquid-liquid phase separation plays a key role in the assembly of diverse intracellular structures. However, the biophysical principles by which phase separation can be precisely localized within subregions of the cell are still largely unclear, particularly for low-abundance proteins. Here, we introduce an oligomerizing biomimetic system, "Corelets," and utilize its rapid and quantitative light-controlled tunability to map full intracellular phase diagrams, which dictate the concentrations at which phase separation occurs and the transition mechanism, in a protein sequence dependent manner. Surprisingly, both experiments and simulations show that while intracellular concentrations may be insufficient for global phase separation, sequestering protein ligands to slowly diffusing nucleation centers can move the cell into a different region of the phase diagram, resulting in localized phase separation. This diffusive capture mechanism liberates the cell from the constraints of global protein abundance and is likely exploited to pattern condensates associated with diverse biological processes. VIDEO ABSTRACT.
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74
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Bodakuntla S, Jijumon AS, Villablanca C, Gonzalez-Billault C, Janke C. Microtubule-Associated Proteins: Structuring the Cytoskeleton. Trends Cell Biol 2019; 29:804-819. [PMID: 31416684 DOI: 10.1016/j.tcb.2019.07.004] [Citation(s) in RCA: 165] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 11/27/2022]
Abstract
Microtubule-associated proteins (MAPs) were initially discovered as proteins that bind to and stabilize microtubules. Today, an ever-growing number of MAPs reveals a more complex picture of these proteins as organizers of the microtubule cytoskeleton that have a large variety of functions. MAPs enable microtubules to participate in a plethora of cellular processes such as the assembly of mitotic and meiotic spindles, neuronal development, and the formation of the ciliary axoneme. Although some subgroups of MAPs have been exhaustively characterized, a strikingly large number of MAPs remain barely characterized other than their interactions with microtubules. We provide a comprehensive view on the currently known MAPs in mammals. We discuss their molecular mechanisms and functions, as well as their physiological role and links to pathologies.
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Affiliation(s)
- Satish Bodakuntla
- Institut Curie, Paris Sciences et Lettres (PSL) Research University, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche (UMR) 3348, F-91405 Orsay, France; Université Paris Sud, Université Paris-Saclay, CNRS UMR 3348, F-91405 Orsay, France
| | - A S Jijumon
- Institut Curie, Paris Sciences et Lettres (PSL) Research University, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche (UMR) 3348, F-91405 Orsay, France; Université Paris Sud, Université Paris-Saclay, CNRS UMR 3348, F-91405 Orsay, France
| | - Cristopher Villablanca
- Center for Geroscience, Brain Health, and Metabolism (GERO), Santiago, Chile; Department of Biology, Faculty of Sciences, University of Chile, Santiago, Chile
| | - Christian Gonzalez-Billault
- Center for Geroscience, Brain Health, and Metabolism (GERO), Santiago, Chile; Department of Biology, Faculty of Sciences, University of Chile, Santiago, Chile.
| | - Carsten Janke
- Institut Curie, Paris Sciences et Lettres (PSL) Research University, Centre National de la Recherche Scientifique (CNRS) Unité Mixte de Recherche (UMR) 3348, F-91405 Orsay, France; Université Paris Sud, Université Paris-Saclay, CNRS UMR 3348, F-91405 Orsay, France.
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75
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Differential Requirements for Centrioles in Mitotic Centrosome Growth and Maintenance. Dev Cell 2019; 50:355-366.e6. [DOI: 10.1016/j.devcel.2019.06.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/29/2019] [Accepted: 06/10/2019] [Indexed: 10/26/2022]
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76
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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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77
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Quarantotti V, Chen J, Tischer J, Gonzalez Tejedo C, Papachristou EK, D'Santos CS, Kilmartin JV, Miller ML, Gergely F. Centriolar satellites are acentriolar assemblies of centrosomal proteins. EMBO J 2019; 38:e101082. [PMID: 31304626 PMCID: PMC6627235 DOI: 10.15252/embj.2018101082] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 04/24/2019] [Accepted: 05/06/2019] [Indexed: 12/02/2022] Open
Abstract
Centrioles are core structural elements of both centrosomes and cilia. Although cytoplasmic granules called centriolar satellites have been observed around these structures, lack of a comprehensive inventory of satellite proteins impedes our understanding of their ancestry. To address this, we performed mass spectrometry (MS)-based proteome profiling of centriolar satellites obtained by affinity purification of their key constituent, PCM1, from sucrose gradient fractions. We defined an interactome consisting of 223 proteins, which showed striking enrichment in centrosome components. The proteome also contained new structural and regulatory factors with roles in ciliogenesis. Quantitative MS on whole-cell and centriolar satellite proteomes of acentriolar cells was performed to reveal dependencies of satellite composition on intact centrosomes. Although most components remained associated with PCM1 in acentriolar cells, reduced cytoplasmic and satellite levels were observed for a subset of centrosomal proteins. These results demonstrate that centriolar satellites and centrosomes form independently but share a substantial fraction of their proteomes. Dynamic exchange of proteins between these organelles could facilitate their adaptation to changing cellular environments during development, stress response and tissue homeostasis.
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Affiliation(s)
- Valentina Quarantotti
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | - Jia‐Xuan Chen
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | - Julia Tischer
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | - Carmen Gonzalez Tejedo
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | | | - Clive S D'Santos
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | - John V Kilmartin
- MRC Laboratory of Molecular BiologyCambridge Biomedical CampusCambridgeUK
| | - Martin L Miller
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
| | - Fanni Gergely
- Cancer Research UK Cambridge InstituteLi Ka Shing CentreUniversity of CambridgeCambridgeUK
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78
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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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79
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Oh D, Houston DW. RNA Localization in the Vertebrate Oocyte: Establishment of Oocyte Polarity and Localized mRNA Assemblages. Results Probl Cell Differ 2019; 63:189-208. [PMID: 28779319 PMCID: PMC6538070 DOI: 10.1007/978-3-319-60855-6_9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
RNA localization is a fundamental mechanism for controlling cell structure and function. Early development in fish and amphibians requires the localization of specific mRNAs to establish the initial differences in cell fates prior to the onset of zygotic genome activation. RNA localization in these oocytes (e.g., Xenopus and zebrafish) requires that animal-vegetal polarity be established early in oogenesis, mediated by formation of the Balbiani body/mitochondrial cloud. This structure serves as a platform for assembly and transport of germline determinants to the future vegetal pole and also sets up the machinery for the localization of non-germline transcripts later in oogenesis. Understanding these polarization and localization mechanisms is critical for understanding the basis for early embryonic development in these organisms and also for understanding the role of RNA compartmentalization in animal gametogenesis. Here we outline recent advances in elucidating the molecular basis for the establishment of oocyte polarity at the level of Balbiani body assembly as well as the formation of RNP assemblies for early and late pathway mRNA localization in the oocyte.
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Affiliation(s)
- Denise Oh
- Department of Biology, The University of Iowa, 257 BB, Iowa City, IA, 52242, USA
| | - Douglas W Houston
- Department of Biology, The University of Iowa, 257 BB, Iowa City, IA, 52242, USA.
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80
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Weber CA, Zwicker D, Jülicher F, Lee CF. Physics of active emulsions. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2019; 82:064601. [PMID: 30731446 DOI: 10.1088/1361-6633/ab052b] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phase separating systems that are maintained away from thermodynamic equilibrium via molecular processes represent a class of active systems, which we call active emulsions. These systems are driven by external energy input, for example provided by an external fuel reservoir. The external energy input gives rise to novel phenomena that are not present in passive systems. For instance, concentration gradients can spatially organise emulsions and cause novel droplet size distributions. Another example are active droplets that are subject to chemical reactions such that their nucleation and size can be controlled, and they can divide spontaneously. In this review, we discuss the physics of phase separation and emulsions and show how the concepts that govern such phenomena can be extended to capture the physics of active emulsions. This physics is relevant to the spatial organisation of the biochemistry in living cells, for the development of novel applications in chemical engineering and models for the origin of life.
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Affiliation(s)
- Christoph A Weber
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, Germany. Center for Systems Biology Dresden, CSBD, Dresden, Germany. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, United States of America
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81
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Weber C, Michaels T, Mahadevan L. Spatial control of irreversible protein aggregation. eLife 2019; 8:e42315. [PMID: 31084715 PMCID: PMC6516824 DOI: 10.7554/elife.42315] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 04/01/2019] [Indexed: 12/19/2022] Open
Abstract
Liquid cellular compartments form in the cyto- or nucleoplasm and can regulate aberrant protein aggregation. Yet, the mechanisms by which these compartments affect protein aggregation remain unknown. Here, we combine kinetic theory of protein aggregation and liquid-liquid phase separation to study the spatial control of irreversible protein aggregation in the presence of liquid compartments. We find that even for weak interactions aggregates strongly partition into the liquid compartment. Aggregate partitioning is caused by a positive feedback mechanism of aggregate nucleation and growth driven by a flux maintaining the phase equilibrium between the compartment and its surrounding. Our model establishes a link between specific aggregating systems and the physical conditions maximizing aggregate partitioning into the compartment. The underlying mechanism of aggregate partitioning could be used to confine cytotoxic protein aggregates inside droplet-like compartments but may also represent a common mechanism to spatially control irreversible chemical reactions in general.
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Affiliation(s)
- Christoph Weber
- School of Engineering and Applied SciencesHarvard UniversityCambridgeUnited States
| | - Thomas Michaels
- School of Engineering and Applied SciencesHarvard UniversityCambridgeUnited States
| | - L Mahadevan
- Department of PhysicsHarvard UniversityCambridgeUnited States
- Department of Organismic and Evolutionary BiologyHarvard UniversityCambridgeUnited States
- Kavli Institute for NanoBio Science and TechnologyHarvard UniversityCambridgeUnited States
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82
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Raff JW. Phase Separation and the Centrosome: A Fait Accompli? Trends Cell Biol 2019; 29:612-622. [PMID: 31076235 DOI: 10.1016/j.tcb.2019.04.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/08/2019] [Accepted: 04/08/2019] [Indexed: 12/28/2022]
Abstract
There is currently intense interest in the idea that many membraneless organelles might assemble through phase separation of their constituent molecules into biomolecular 'condensates' that have liquid-like properties. This idea is intuitively appealing, especially for complex organelles such as centrosomes, where a liquid-like structure would allow the many constituent molecules to diffuse and interact with one another efficiently. I discuss here recent studies that either support the concept of a liquid-like centrosome or suggest that centrosomes are assembled upon a more solid, stable scaffold. I suggest that it may be difficult to distinguish between these possibilities. I argue that the concept of biomolecular condensates is an important advance in cell biology, with potentially wide-ranging implications, but it seems premature to conclude that centrosomes, and perhaps other membraneless organelles, are necessarily best described as liquid-like phase-separated condensates.
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Affiliation(s)
- Jordan W Raff
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK.
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83
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Michieletto D, Gilbert N. Role of nuclear RNA in regulating chromatin structure and transcription. Curr Opin Cell Biol 2019; 58:120-125. [PMID: 31009871 PMCID: PMC6694202 DOI: 10.1016/j.ceb.2019.03.007] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 03/10/2019] [Accepted: 03/13/2019] [Indexed: 12/31/2022]
Abstract
The importance of three-dimensional chromatin organisation in genome regulation has never been clearer. But in spite of the enormous technological advances to probe chromatin organisation in vivo, there is still a lack of mechanistic understanding of how such an arrangement is achieved. Here we review emerging evidence pointing to an intriguing role of nuclear RNA in shaping large-scale chromatin structure and regulating genome function. We suggest this role may be achieved through the formation of a dynamic nuclear mesh that can exploit ATP-driven processes and phase separation of RNA-binding proteins to tune its assembly and material properties.
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Affiliation(s)
- Davide Michieletto
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK; School of Physics and Astronomy, University of Edinburgh, EH9 3FD, UK
| | - Nick Gilbert
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK.
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84
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Bentley EP, Frey BB, Deniz AA. Physical Chemistry of Cellular Liquid-Phase Separation. Chemistry 2019; 25:5600-5610. [PMID: 30589142 PMCID: PMC6551525 DOI: 10.1002/chem.201805093] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 12/11/2018] [Indexed: 01/05/2023]
Abstract
Compartmentalization of biochemical processes is essential for cell function. Although membrane-bound organelles are well studied in this context, recent work has shown that phase separation is a key contributor to cellular compartmentalization through the formation of liquid-like membraneless organelles (MLOs). In this Minireview, the key mechanistic concepts that underlie MLO dynamics and function are first briefly discussed, including the relevant noncovalent interaction chemistry and polymer physical chemistry. Next, a few examples of MLOs and relevant proteins are given, along with their functions, which highlight the relevance of the above concepts. The developing area of active matter and non-equilibrium systems, which can give rise to unexpected effects in fluctuating cellular conditions, are also discussed. Finally, our thoughts for emerging and future directions in the field are discussed, including in vitro and in vivo studies of MLO physical chemistry and function.
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Affiliation(s)
- Emily P Bentley
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
| | - Benjamin B Frey
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
| | - Ashok A Deniz
- The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA, 92037, USA
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85
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Ganier O, Schnerch D, Nigg EA. Structural centrosome aberrations sensitize polarized epithelia to basal cell extrusion. Open Biol 2019; 8:rsob.180044. [PMID: 29899122 PMCID: PMC6030118 DOI: 10.1098/rsob.180044] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/11/2018] [Indexed: 12/17/2022] Open
Abstract
Centrosome aberrations disrupt tissue architecture and may confer invasive properties to cancer cells. Here we show that structural centrosome aberrations, induced by overexpression of either Ninein-like protein (NLP) or CEP131/AZI1, sensitize polarized mammalian epithelia to basal cell extrusion. While unperturbed epithelia typically dispose of damaged cells through apical dissemination into luminal cavities, certain oncogenic mutations cause a switch in directionality towards basal cell extrusion, raising the potential for metastatic cell dissemination. Here we report that NLP-induced centrosome aberrations trigger the preferential extrusion of damaged cells towards the basal surface of epithelial monolayers. This switch in directionality from apical to basal dissemination coincides with a profound reorganization of the microtubule cytoskeleton, which in turn prevents the contractile ring repositioning that is required to support extrusion towards the apical surface. While the basal extrusion of cells harbouring NLP-induced centrosome aberrations requires exogenously induced cell damage, structural centrosome aberrations induced by excess CEP131 trigger the spontaneous dissemination of dying cells towards the basal surface from MDCK cysts. Thus, similar to oncogenic mutations, structural centrosome aberrations can favour basal extrusion of damaged cells from polarized epithelia. Assuming that additional mutations may promote cell survival, this process could sensitize epithelia to disseminate potentially metastatic cells.
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Affiliation(s)
- Olivier Ganier
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Dominik Schnerch
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Erich A Nigg
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
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86
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Falahati H, Haji-Akbari A. Thermodynamically driven assemblies and liquid-liquid phase separations in biology. SOFT MATTER 2019; 15:1135-1154. [PMID: 30672955 DOI: 10.1039/c8sm02285b] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The sustenance of life depends on the high degree of organization that prevails through different levels of living organisms, from subcellular structures such as biomolecular complexes and organelles to tissues and organs. The physical origin of such organization is not fully understood, and even though it is clear that cells and organisms cannot maintain their integrity without consuming energy, there is growing evidence that individual assembly processes can be thermodynamically driven and occur spontaneously due to changes in thermodynamic variables such as intermolecular interactions and concentration. Understanding the phase separation in vivo requires a multidisciplinary approach, integrating the theory and physics of phase separation with experimental and computational techniques. This paper aims at providing a brief overview of the physics of phase separation and its biological implications, with a particular focus on the assembly of membraneless organelles. We discuss the underlying physical principles of phase separation from its thermodynamics to its kinetics. We also overview the wide range of methods utilized for experimental verification and characterization of phase separation of membraneless organelles, as well as the utility of molecular simulations rooted in thermodynamics and statistical physics in understanding the governing principles of thermodynamically driven biological self-assembly processes.
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Affiliation(s)
- Hanieh Falahati
- Department of Neuroscience, Yale School of Medicine, New Haven, CT 06510, USA.
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87
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Pintard L, Bowerman B. Mitotic Cell Division in Caenorhabditis elegans. Genetics 2019; 211:35-73. [PMID: 30626640 PMCID: PMC6325691 DOI: 10.1534/genetics.118.301367] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/24/2018] [Indexed: 11/18/2022] Open
Abstract
Mitotic cell divisions increase cell number while faithfully distributing the replicated genome at each division. The Caenorhabditis elegans embryo is a powerful model for eukaryotic cell division. Nearly all of the genes that regulate cell division in C. elegans are conserved across metazoan species, including humans. The C. elegans pathways tend to be streamlined, facilitating dissection of the more redundant human pathways. Here, we summarize the virtues of C. elegans as a model system and review our current understanding of centriole duplication, the acquisition of pericentriolar material by centrioles to form centrosomes, the assembly of kinetochores and the mitotic spindle, chromosome segregation, and cytokinesis.
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Affiliation(s)
- Lionel Pintard
- Equipe labellisée Ligue contre le Cancer, Institut Jacques Monod, Team Cell Cycle and Development UMR7592, Centre National de la Recherche Scientifique - Université Paris Diderot, Sorbonne Paris Cité, 75013 Paris, France
| | - Bruce Bowerman
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403
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88
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Zwicker D, Baumgart J, Redemann S, Müller-Reichert T, Hyman AA, Jülicher F. Positioning of Particles in Active Droplets. PHYSICAL REVIEW LETTERS 2018; 121:158102. [PMID: 30362788 DOI: 10.1103/physrevlett.121.158102] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 08/06/2018] [Indexed: 05/12/2023]
Abstract
Chemically active droplets are nonequilibrium systems that combine phase separation with chemical reactions. We here investigate how the activity introduced by the chemical reactions influences solid particles inside such droplets. We find that passive particles are centered in active droplets governed by first-order reactions. In autocatalytic active droplets, only catalytically active particles can be centered. An example of such systems in biology are centrosomes. Our study can account for the observed positioning of centrioles and provides a general mechanism to control the position of particles within chemically active droplets.
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Affiliation(s)
- David Zwicker
- Max Planck Institute for Dynamics and Self-Organization, 37077 Göttingen, Germany
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - Johannes Baumgart
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
| | - Stefanie Redemann
- Technische Universität Dresden, Experimental Center, Faculty of Medicine Carl Gustav Carus, Fiedlerstraße 42, 01307 Dresden, Germany
- Center for Membrane and Cell Physiology and Department of Molecular Physiology and Biological Physics, University of Virginia, School of Medicine, Charlottesville, Virginia 22903, USA
| | - Thomas Müller-Reichert
- Technische Universität Dresden, Experimental Center, Faculty of Medicine Carl Gustav Carus, Fiedlerstraße 42, 01307 Dresden, Germany
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Frank Jülicher
- Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany
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89
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Gavilan MP, Gandolfo P, Balestra FR, Arias F, Bornens M, Rios RM. The dual role of the centrosome in organizing the microtubule network in interphase. EMBO Rep 2018; 19:embr.201845942. [PMID: 30224411 DOI: 10.15252/embr.201845942] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 08/27/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022] Open
Abstract
Here, we address the regulation of microtubule nucleation during interphase by genetically ablating one, or two, of three major mammalian γ-TuRC-binding factors namely pericentrin, CDK5Rap2, and AKAP450. Unexpectedly, we find that while all of them participate in microtubule nucleation at the Golgi apparatus, they only modestly contribute at the centrosome where CEP192 has a more predominant function. We also show that inhibiting microtubule nucleation at the Golgi does not affect centrosomal activity, whereas manipulating the number of centrosomes with centrinone modifies microtubule nucleation activity of the Golgi apparatus. In centrosome-free cells, inhibition of Golgi-based microtubule nucleation triggers pericentrin-dependent formation of cytoplasmic-nucleating structures. Further depletion of pericentrin under these conditions leads to the generation of individual microtubules in a γ-tubulin-dependent manner. In all cases, a conspicuous MT network forms. Strikingly, centrosome loss increases microtubule number independently of where they were growing from. Our results lead to an unexpected view of the interphase centrosome that would control microtubule network organization not only by nucleating microtubules, but also by modulating the activity of alternative microtubule-organizing centers.
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Affiliation(s)
- Maria P Gavilan
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Pablo Gandolfo
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Fernando R Balestra
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | - Francisco Arias
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
| | | | - Rosa M Rios
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain
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90
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Revisiting Centrioles in Nematodes-Historic Findings and Current Topics. Cells 2018; 7:cells7080101. [PMID: 30096824 PMCID: PMC6115991 DOI: 10.3390/cells7080101] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 01/02/2023] Open
Abstract
Theodor Boveri is considered as the “father” of centrosome biology. Boveri’s fundamental findings have laid the groundwork for decades of research on centrosomes. Here, we briefly review his early work on centrosomes and his first description of the centriole. Mainly focusing on centriole structure, duplication, and centriole assembly factors in C. elegans, we will highlight the role of this model in studying germ line centrosomes in nematodes. Last but not least, we will point to future directions of the C. elegans centrosome field.
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91
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Nigg EA, Holland AJ. Once and only once: mechanisms of centriole duplication and their deregulation in disease. Nat Rev Mol Cell Biol 2018; 19:297-312. [PMID: 29363672 PMCID: PMC5969912 DOI: 10.1038/nrm.2017.127] [Citation(s) in RCA: 301] [Impact Index Per Article: 50.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Centrioles are conserved microtubule-based organelles that form the core of the centrosome and act as templates for the formation of cilia and flagella. Centrioles have important roles in most microtubule-related processes, including motility, cell division and cell signalling. To coordinate these diverse cellular processes, centriole number must be tightly controlled. In cycling cells, one new centriole is formed next to each pre-existing centriole in every cell cycle. Advances in imaging, proteomics, structural biology and genome editing have revealed new insights into centriole biogenesis, how centriole numbers are controlled and how alterations in these processes contribute to diseases such as cancer and neurodevelopmental disorders. Moreover, recent work has uncovered the existence of surveillance pathways that limit the proliferation of cells with numerical centriole aberrations. Owing to this progress, we now have a better understanding of the molecular mechanisms governing centriole biogenesis, opening up new possibilities for targeting these pathways in the context of human disease.
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Affiliation(s)
- Erich A. Nigg
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Andrew J. Holland
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
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92
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Abstract
To survive, organisms must orchestrate competing biochemical and regulatory processes in time and space. Recent work has suggested that the underlying chemical properties of some biomolecules allow them to self-organize and that life may have exploited this property to organize biochemistry in space and time. Such phase separation is ubiquitous, particularly among the many regulatory proteins that harbor prion-like intrinsically disordered domains. And yet, despite evident regulation by post-translational modification and myriad other stimuli, the biological significance of many phase-separated compartments remains uncertain. Many potential functions have been proposed, but far fewer have been demonstrated. A burgeoning subfield at the intersection of cell biology and polymer physics has defined the biophysical underpinnings that govern the genesis and stability of these particles. The picture is complex: many assemblies are composed of multiple proteins that each have the capacity to phase separate. Here, we briefly discuss this foundational work and survey recent efforts combining targeted biochemical perturbations and quantitative modeling to specifically address the diverse roles that phase separation processes may play in biology.
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Affiliation(s)
- Alan K. Itakura
- Department of Biology, Stanford University, 269 Campus Drive, Stanford, CA 94305
| | - Raymond A. Futia
- Department of Biology, Stanford University, 269 Campus Drive, Stanford, CA 94305
| | - Daniel F. Jarosz
- Department of Chemical and Systems Biology, Stanford University, 269 Campus Drive, Stanford, CA 94305
- Department of Developmental Biology, Stanford University, 269 Campus Drive, Stanford, CA 94305
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93
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Milin AN, Deniz AA. Reentrant Phase Transitions and Non-Equilibrium Dynamics in Membraneless Organelles. Biochemistry 2018; 57:2470-2477. [PMID: 29569441 DOI: 10.1021/acs.biochem.8b00001] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Compartmentalization of biochemical components, interactions, and reactions is critical for the function of cells. While intracellular partitioning of molecules via membranes has been extensively studied, there has been an expanding focus in recent years on the critical cellular roles and biophysical mechanisms of action of membraneless organelles (MLOs) such as the nucleolus. In this context, a substantial body of recent work has demonstrated that liquid-liquid phase separation plays a key role in MLO formation. However, less is known about MLO dissociation, with phosphorylation being the primary mechanism demonstrated thus far. In this Perspective, we focus on another mechanism for MLO dissociation that has been described in recent work, namely a reentrant phase transition (RPT). This concept, which emerges from the polymer physics field, provides a mechanistic basis for both formation and dissolution of MLOs by monotonic tuning of RNA concentration, which is an outcome of cellular processes such as transcription. Furthermore, the RPT model also predicts the formation of dynamic substructures (vacuoles) of the kind that have been observed in cellular MLOs. We end with a discussion of future directions in terms of open questions and methods that can be used to answer them, including further exploration of RPTs in vitro, in cells, and in vivo using ensemble and single-molecule methods as well as theory and computation. We anticipate that continued studies will further illuminate the important roles of reentrant phase transitions and associated non-equilibrium dynamics in the spatial patterning of the biochemistry and biology of the cell.
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Affiliation(s)
- Anthony N Milin
- Department of Integrative Structural and Computational Biology , The Scripps Research Institute , La Jolla , California 92037 , United States
| | - Ashok A Deniz
- Department of Integrative Structural and Computational Biology , The Scripps Research Institute , La Jolla , California 92037 , United States
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94
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Mahen R. Stable centrosomal roots disentangle to allow interphase centriole independence. PLoS Biol 2018; 16:e2003998. [PMID: 29649211 PMCID: PMC5918241 DOI: 10.1371/journal.pbio.2003998] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 04/24/2018] [Accepted: 03/19/2018] [Indexed: 11/23/2022] Open
Abstract
The centrosome is a non-membrane-bound cellular compartment consisting of 2 centrioles surrounded by a protein coat termed the pericentriolar material (PCM). Centrioles generally remain physically associated together (a phenomenon called centrosome cohesion), yet how this occurs in the absence of a bounding lipid membrane is unclear. One model posits that pericentriolar fibres formed from rootletin protein directly link centrioles, yet little is known about the structure, biophysical properties, or assembly kinetics of such fibres. Here, I combine live-cell imaging of endogenously tagged rootletin with cell fusion and find previously unrecognised plasticity in centrosome cohesion. Rootletin forms large, diffusionally stable bifurcating fibres, which amass slowly on mature centrioles over many hours from anaphase. Nascent centrioles (procentrioles), in contrast, do not form roots and must be licensed to do so through polo-like kinase 1 (PLK1) activity. Transient separation of roots accompanies centriolar repositioning during the interphase, suggesting that centrioles organize as independent units, each containing discrete roots. Indeed, forced induction of duplicate centriole pairs allows independent reshuffling of individual centrioles between the pairs. Therefore collectively, these findings suggest that progressively nucleated polymers mediate the dynamic association of centrioles as either 1 or 2 interphase centrosomes, with implications for the understanding of how non-membrane-bound organelles self-organise.
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Affiliation(s)
- Robert Mahen
- Photonics Group, Department of Physics, Imperial College London, London, United Kingdom
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Cambridge, United Kingdom
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95
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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: 244] [Impact Index Per Article: 40.7] [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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96
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Coming into Focus: Mechanisms of Microtubule Minus-End Organization. Trends Cell Biol 2018; 28:574-588. [PMID: 29571882 DOI: 10.1016/j.tcb.2018.02.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/17/2018] [Accepted: 02/27/2018] [Indexed: 11/22/2022]
Abstract
Microtubule organization has a crucial role in regulating cell architecture. The geometry of microtubule arrays strongly depends on the distribution of sites responsible for microtubule nucleation and minus-end attachment. In cycling animal cells, the centrosome often represents a dominant microtubule-organizing center (MTOC). However, even in cells with a radial microtubule system, many microtubules are not anchored at the centrosome, but are instead linked to the Golgi apparatus or other structures. Non-centrosomal microtubules predominate in many types of differentiated cell and in mitotic spindles. In this review, we discuss recent advances in understanding how the organization of centrosomal and non-centrosomal microtubule networks is controlled by proteins involved in microtubule nucleation and specific factors that recognize free microtubule minus ends and regulate their localization and dynamics.
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97
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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: 2184] [Impact Index Per Article: 364.0] [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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98
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Abstract
Just like all matter, proteins can also switch between gas, liquid and solid phases. Protein phase transition has claimed the spotlight in recent years as a novel way of how cells compartmentalize and regulate biochemical reactions. Moreover, this discovery has provided a new framework for the study of membrane-less organelle biogenesis and protein aggregation in neurodegenerative disorders. We now argue that this framework could be useful in the study of cell cycle regulation and cancer. Based on our work on phase transitions of arginine-rich proteins in neurodegeneration, via combining mass spectroscopy with bioinformatics analyses, we found that also numerous proteins involved in the regulation of the cell cycle can undergo protein phase separation. Indeed, several proteins whose function affects the cell cycle or are associated with cancer, have been recently found to phase separate from the test tube to cells. Investigating the role of this process for cell cycle proteins and understanding its molecular underpinnings will provide pivotal insights into the biology of cell cycle progression and cancer.
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Affiliation(s)
- Steven Boeynaems
- Department of Neurosciences, Experimental Neurology and Leuven Research Institute for Neuroscience and Disease (LIND), KU Leuven-University of Leuven, 3000 Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain and Disease Research, 3000 Leuven, Belgium
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305 USA
| | - Peter Tompa
- VIB, Center for Structural Biology (CSB), Vrije Universiteit Brussel (VUB), Brussels, Belgium
- Institute of Enzymology, Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Budapest, Hungary
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology and Leuven Research Institute for Neuroscience and Disease (LIND), KU Leuven-University of Leuven, 3000 Leuven, Belgium
- Laboratory of Neurobiology, VIB, Center for Brain and Disease Research, 3000 Leuven, Belgium
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99
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Loncarek J, Bettencourt-Dias M. Building the right centriole for each cell type. J Cell Biol 2017; 217:823-835. [PMID: 29284667 PMCID: PMC5839779 DOI: 10.1083/jcb.201704093] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Revised: 09/14/2017] [Accepted: 11/27/2017] [Indexed: 12/22/2022] Open
Abstract
Loncarek and Bettencourt-Dias review molecular mechanisms of centriole biogenesis amongst different organisms and cell types. The centriole is a multifunctional structure that organizes centrosomes and cilia and is important for cell signaling, cell cycle progression, polarity, and motility. Defects in centriole number and structure are associated with human diseases including cancer and ciliopathies. Discovery of the centriole dates back to the 19th century. However, recent advances in genetic and biochemical tools, development of high-resolution microscopy, and identification of centriole components have accelerated our understanding of its assembly, function, evolution, and its role in human disease. The centriole is an evolutionarily conserved structure built from highly conserved proteins and is present in all branches of the eukaryotic tree of life. However, centriole number, size, and organization varies among different organisms and even cell types within a single organism, reflecting its cell type–specialized functions. In this review, we provide an overview of our current understanding of centriole biogenesis and how variations around the same theme generate alternatives for centriole formation and function.
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Affiliation(s)
- Jadranka Loncarek
- Cell Cycle Regulation Lab, Gulbenkian Institute of Science, Oeiras, Portugal
| | - Mónica Bettencourt-Dias
- Laboratory of Protein Dynamics and Signaling, National Institutes of Health/Center for Cancer Research/National Cancer Institute-Frederick, Frederick, MD
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100
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Rale MJ, Kadzik RS, Petry S. Phase Transitioning the Centrosome into a Microtubule Nucleator. Biochemistry 2017; 57:30-37. [PMID: 29256606 DOI: 10.1021/acs.biochem.7b01064] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Centrosomes are self-assembling, micron-scale, nonmembrane bound organelles that nucleate microtubules (MTs) and organize the microtubule cytoskeleton of the cell. They orchestrate critical cellular processes such as ciliary-based motility, vesicle trafficking, and cell division. Much is known about the role of the centrosome in these contexts, but we have a less comprehensive understanding of how the centrosome assembles and generates microtubules. Studies over the past 10 years have fundamentally shifted our view of these processes. Subdiffraction imaging has probed the amorphous haze of material surrounding the core of the centrosome revealing a complex, hierarchically organized structure whose composition and size changes profoundly during the transition from interphase to mitosis. New biophysical insights into protein phase transitions, where a diffuse protein spontaneously separates into a locally concentrated, nonmembrane bounded compartment, have provided a fresh perspective into how the centrosome might rapidly condense from diffuse cytoplasmic components. In this Perspective, we focus on recent findings that identify several centrosomal proteins that undergo phase transitions. We discuss how to reconcile these results with the current model of the underlying organization of proteins in the centrosome. Furthermore, we reflect on how these findings impact our understanding of how the centrosome undergoes self-assembly and promotes MT nucleation.
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Affiliation(s)
- Michael J Rale
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Rachel S Kadzik
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Sabine Petry
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
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