1
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Gasior KI, Cogan NG. Untangling the Molecular Interactions Underlying Intracellular Phase Separation Using Combined Global Sensitivity Analyses. Bull Math Biol 2024; 86:60. [PMID: 38641666 DOI: 10.1007/s11538-024-01288-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/27/2024] [Indexed: 04/21/2024]
Abstract
Liquid-liquid phase separation is an intracellular mechanism by which molecules, usually proteins and RNAs, interact and then rapidly demix from the surrounding matrix to form membrane-less compartments necessary for cellular function. Occurring in both the cytoplasm and the nucleus, properties of the resulting droplets depend on a variety of characteristics specific to the molecules involved, such as valency, density, and diffusion within the crowded environment. Capturing these complexities in a biologically relevant model is difficult. To understand the nuanced dynamics between proteins and RNAs as they interact and form droplets, as well as the impact of these interactions on the resulting droplet properties, we turn to sensitivity analysis. In this work, we examine a previously published mathematical model of two RNA species competing for the same protein-binding partner. We use the combined analyses of Morris Method and Sobol' sensitivity analysis to understand the impact of nine molecular parameters, subjected to three different initial conditions, on two observable LLPS outputs: the time of phase separation and the composition of the droplet field. Morris Method is a screening method capable of highlighting the most important parameters impacting a given output, while the variance-based Sobol' analysis can quantify both the importance of a given parameter, as well as the other model parameters it interacts with, to produce the observed phenomena. Combining these two techniques allows Morris Method to identify the most important dynamics and circumvent the large computational expense associated with Sobol', which then provides more nuanced information about parameter relationships. Together, the results of these combined methodologies highlight the complicated protein-RNA relationships underlying both the time of phase separation and the composition of the droplet field. Sobol' sensitivity analysis reveals that observed spatial and temporal dynamics are due, at least in part, to high-level interactions between multiple (3+) parameters. Ultimately, this work discourages using a single measurement to extrapolate the value of any single rate or parameter value, while simultaneously establishing a framework in which to analyze and assess the impact of these small-scale molecular interactions on large-scale droplet properties.
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Affiliation(s)
- Kelsey I Gasior
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, IN, USA.
| | - Nicholas G Cogan
- Department of Mathematics, Florida State University, Tallahassee, FL, USA
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2
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Cai L, Wang GG. Through the lens of phase separation: intrinsically unstructured protein and chromatin looping. Nucleus 2023; 14:2179766. [PMID: 36821650 PMCID: PMC9980480 DOI: 10.1080/19491034.2023.2179766] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
The establishment, maintenance and dynamic regulation of three-dimensional (3D) chromatin structures provide an important means for partitioning of genome into functionally distinctive domains, which helps to define specialized gene expression programs associated with developmental stages and cell types. Increasing evidence supports critical roles for intrinsically disordered regions (IDRs) harbored within transcription factors (TFs) and chromatin-modulatory proteins in inducing phase separation, a phenomenon of forming membrane-less condensates through partitioning of biomolecules. Such a process is also critically involved in the establishment of high-order chromatin structures and looping. IDR- and phase separation-driven 3D genome (re)organization often goes wrong in disease such as cancer. This review discusses about recent advances in understanding how phase separation of intrinsically disordered proteins (IDPs) modulates chromatin looping and gene expression.
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Affiliation(s)
- Ling Cai
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,Department of Genetics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,Ling Cai Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC27599, USA
| | - Gang Greg Wang
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA,CONTACT Gang Greg Wang Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC27599, USA
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3
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Vasquez PA, Walker B, Bloom K, Kolbin D, Caughman N, Freeman R, Lysy M, Hult C, Newhall KA, Papanikolas M, Edelmaier C, Forest MG. The power of weak, transient interactions across biology: A paradigm of emergent behavior. PHYSICA D. NONLINEAR PHENOMENA 2023; 454:133866. [PMID: 38274029 PMCID: PMC10806540 DOI: 10.1016/j.physd.2023.133866] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
A growing list of diverse biological systems and their equally diverse functionalities provides realizations of a paradigm of emergent behavior. In each of these biological systems, pervasive ensembles of weak, short-lived, spatially local interactions act autonomously to convey functionalities at larger spatial and temporal scales. In this article, a range of diverse systems and functionalities are presented in a cursory manner with literature citations for further details. Then two systems and their properties are discussed in more detail: yeast chromosome biology and human respiratory mucus.
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Affiliation(s)
- Paula A. Vasquez
- Department of Mathematics, University of South Carolina, United States of America
| | - Ben Walker
- Department of Mathematics, University of California at Irvine, United States of America
| | - Kerry Bloom
- Department of Biology, University of North Carolina at Chapel Hill, United States of America
| | - Daniel Kolbin
- Department of Biology, University of North Carolina at Chapel Hill, United States of America
| | - Neall Caughman
- Department of Mathematics, University of North Carolina at Chapel Hill, United States of America
| | - Ronit Freeman
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, United States of America
| | - Martin Lysy
- Department of Statistics and Actuarial Science, University of Waterloo, Canada
| | - Caitlin Hult
- Department of Mathematics, Gettysburg College, United States of America
| | - Katherine A. Newhall
- Department of Mathematics, University of North Carolina at Chapel Hill, United States of America
| | - Micah Papanikolas
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, United States of America
| | - Christopher Edelmaier
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, United States of America
- Center for Computational Biology, Flatiron Institute, United States of America
| | - M. Gregory Forest
- Department of Mathematics, University of North Carolina at Chapel Hill, United States of America
- Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, United States of America
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4
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Li Y, Chen T, You K, Peng T, Li T. Sequence determinants and solution conditions underlying liquid to solid phase transition. Am J Physiol Cell Physiol 2023; 324:C236-C246. [PMID: 36503242 DOI: 10.1152/ajpcell.00280.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Life consists of numberless functional biomolecules that exist in various states. Besides well-dissolved phases, biomolecules especially proteins and nucleic acids can form liquid droplets through liquid-liquid phase separation (LLPS). Stronger interactions promote a solid-like state of biomolecular condensates, which are also formerly referred to as detergent-insoluble aggregates. Solid-like condensates exist in vivo physiologically and pathologically, and their formation has not been fully understood. Recently, more and more research has proven that liquid to solid phase transition (LST) is an essential way to form solid condensates. In this review, we summarized the regions in the sequence that have different impacts on phase transition and emphasized that the LST is affected by its sequence characteristics. Moreover, increasing evidence unveiled that LST is affected by various solution conditions. We discussed solution conditions like protein concentration, pH, ATP, ions, and small molecules in a solution. Methods have been established to study these solid phase components. Here, we summarized low-throughput experimental techniques and high-throughput omics methods in the study of the LST.
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Affiliation(s)
- Yuxuan Li
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China.,Key Laboratory for Neuroscience, Ministry of Education/National Health Commission of China, Peking University, Beijing, China
| | - Taoyu Chen
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China.,Key Laboratory for Neuroscience, Ministry of Education/National Health Commission of China, Peking University, Beijing, China
| | - Kaiqing You
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China.,Happy Life Technology, Beijing, China
| | - Tao Peng
- Happy Life Technology, Beijing, China
| | - Tingting Li
- Department of Biomedical Informatics, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China.,Key Laboratory for Neuroscience, Ministry of Education/National Health Commission of China, Peking University, Beijing, China
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5
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Zhorabek F, Abesekara MS, Liu J, Dai X, Huang J, Chau Y. Construction of multiphasic membraneless organelles towards spontaneous spatial segregation and directional flow of biochemical reactions. Chem Sci 2023; 14:801-811. [PMID: 36755726 PMCID: PMC9890938 DOI: 10.1039/d2sc05438h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 11/29/2022] [Indexed: 01/15/2023] Open
Abstract
Many intracellular membraneless organelles (MLOs) appear to adapt a hierarchical multicompartment organization for efficient coordination of highly complex reaction networks. Recapitulating such an internal architecture in biomimetic platforms is, therefore, an important step to facilitate the functional understanding of MLOs and to enable the design of advanced microreactors. Herein, we present a modular bottom-up approach for building synthetic multiphasic condensates using a set of engineered multivalent polymer-oligopeptide hybrids. These hybrid constructs exhibit dynamic phase separation behaviour generating membraneless droplets with a subdivided interior featuring distinct chemical and physical properties, whereby a range of functional biomolecules can be spontaneously enriched and spatially segregated. The platform also attains separated confinement of transcription and translation reactions in proximal compartments, while allowing inter-compartment communication via a directional flow of reactants. With advanced structural and functional features attained, this system can be of great value as a MLO model and as a cell-free system for multiplex chemical biosynthesis.
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Affiliation(s)
- Fariza Zhorabek
- Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong SAR China
| | - Manisha Sandupama Abesekara
- Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong SAR China
| | - Jianhui Liu
- Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong SAR China
| | - Xin Dai
- Department of Chemistry, Hong Kong University of Science and TechnologyClear Water Bay, KowloonHong Kong SARChina
| | - Jinqing Huang
- Department of Chemistry, Hong Kong University of Science and TechnologyClear Water Bay, KowloonHong Kong SARChina
| | - Ying Chau
- Department of Chemical and Biological Engineering, Hong Kong University of Science and Technology Clear Water Bay, Kowloon Hong Kong SAR China
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6
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Laghmach R, Malhotra I, Potoyan DA. Multiscale Modeling of Protein-RNA Condensation in and Out of Equilibrium. Methods Mol Biol 2023; 2563:117-133. [PMID: 36227470 PMCID: PMC11186142 DOI: 10.1007/978-1-0716-2663-4_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A vast number of intracellular membraneless bodies also known as biomolecular condensates form through a liquid-liquid phase separation (LLPS) of biomolecules. To date, phase separation has been identified as the main driving force for a membraneless organelles such as nucleoli, Cajal bodies, stress granules, and chromatin compartments. Recently, the protein-RNA condensation is receiving increased attention, because it is closely related to the biological function of cells such as transcription, translation, and RNA metabolism. Despite the multidisciplinary efforts put forth to study the biophysical properties of protein-RNA condensates, there are many fundamental unanswered questions regarding the mechanism of formation and regulation of protein-RNA condensates in eukaryotic cells. Major challenges in studying protein-RNA condensation stem from (i) the molecular heterogeneity and conformational flexibility of RNA and protein chains and (ii) the nonequilibrium nature of transcription and cellular environment. Computer simulations, bioinformatics, and mathematical models are uniquely positioned for shedding light on the microscopic nature of protein-RNA phase separation. To this end, there is an urgent need for innovative models with the right spatiotemporal resolution for confronting the experimental observables in a comprehensive and physics-based manner. In this chapter, we will summarize the currently emerging research efforts, which employ atomistic and coarse-grained molecular models and field theoretical models to understand equilibrium and nonequilibrium aspects of protein-RNA condensation.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Isha Malhotra
- Department of Chemistry, Iowa State University, Ames, IA, USA
| | - Davit A Potoyan
- Department of Chemistry, Iowa State University, Ames, IA, USA.
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7
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Guo H, Ryan JC, Song X, Mallet A, Zhang M, Pabst V, Decrulle AL, Ejsmont P, Wintermute EH, Lindner AB. Spatial engineering of E. coli with addressable phase-separated RNAs. Cell 2022; 185:3823-3837.e23. [PMID: 36179672 DOI: 10.1016/j.cell.2022.09.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 04/25/2022] [Accepted: 09/06/2022] [Indexed: 01/26/2023]
Abstract
Biochemical processes often require spatial regulation and specific microenvironments. The general lack of organelles in bacteria limits the potential of bioengineering complex intracellular reactions. Here, we demonstrate synthetic membraneless organelles in Escherichia coli termed transcriptionally engineered addressable RNA solvent droplets (TEARS). TEARS are assembled from RNA-binding protein recruiting domains fused to poly-CAG repeats that spontaneously drive liquid-liquid phase separation from the bulk cytoplasm. Targeting TEARS with fluorescent proteins revealed multilayered structures with composition and reaction robustness governed by non-equilibrium dynamics. We show that TEARS provide organelle-like bioprocess isolation for sequestering biochemical pathways, controlling metabolic branch points, buffering mRNA translation rates, and scaffolding protein-protein interactions. We anticipate TEARS to be a simple and versatile tool for spatially controlling E. coli biochemistry. Particularly, the modular design of TEARS enables applications without expression fine-tuning, simplifying the design-build-test cycle of bioengineering.
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Affiliation(s)
- Haotian Guo
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France.
| | - Joseph C Ryan
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Xiaohu Song
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Adeline Mallet
- Ultrastructural BioImaging UTechS, C2RT, Institut Pasteur, 28 rue du Dr Roux, 75015 Paris, France
| | - Mengmeng Zhang
- Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Shenzhen, China
| | - Victor Pabst
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Antoine L Decrulle
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Paulina Ejsmont
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Edwin H Wintermute
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France
| | - Ariel B Lindner
- Université de Paris, INSERM U1284, Center for Research and Interdisciplinarity (CRI), 75006 Paris, France.
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8
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Pereira RG. Steady states and coarsening in one-dimensional driven Allen-Cahn system. Phys Rev E 2022; 106:014150. [PMID: 35974652 DOI: 10.1103/physreve.106.014150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
We study the steady states and the coarsening dynamics in a one-dimensional driven nonconserved system modeled by the so-called driven Allen-Cahn equation, which is the standard Allen-Cahn equation with an additional driving force. In particular, we derive equations of motion for the phase boundaries in a phase ordering system obeying this equation using a nearest-neighbor interaction approach. Using the equations of motion we explore kink binary and ternary interactions and analyze how the average domain size scale with respect to time. Further, we employ numerical techniques to perform a bifurcation analysis of the one-period stationary solutions of the equation. We then investigate the linear stability of the two-period solutions and thereby identify and study various coarsening modes.
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Affiliation(s)
- Rajiv G Pereira
- School of Physics, IISER Thiruvananthapuram, Vithura, Kerala 695551, India
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9
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Vweza AO, Song CG, Chong KT. Liquid-Liquid Phase Separation in the Presence of Macromolecular Crowding and State-dependent Kinetics. Int J Mol Sci 2021; 22:6675. [PMID: 34206440 PMCID: PMC8268629 DOI: 10.3390/ijms22136675] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 06/13/2021] [Accepted: 06/14/2021] [Indexed: 12/27/2022] Open
Abstract
Biomolecular condensates formed via liquid-liquid phase separation (LLPS) are increasingly being shown to play major roles in cellular self-organization dynamics in health and disease. It is well established that macromolecular crowding has a profound impact on protein interactions, particularly those that lead to LLPS. Although synthetic crowding agents are used during in vitro LLPS experiments, they are considerably different from the highly crowded nucleo-/cytoplasm and the effects of in vivo crowding remain poorly understood. In this work, we applied computational modeling to investigate the effects of macromolecular crowding on LLPS. To include biologically relevant LLPS dynamics, we extended the conventional Cahn-Hilliard model for phase separation by coupling it to experimentally derived macromolecular crowding dynamics and state-dependent reaction kinetics. Through extensive field-theoretic computer simulations, we show that the inclusion of macromolecular crowding results in late-stage coarsening and the stabilization of relatively smaller condensates. At a high crowding concentration, there is an accelerated growth and late-stage arrest of droplet formation, effectively resulting in anomalous labyrinthine morphologies akin to protein gelation observed in experiments. These results not only elucidate the crowder effects observed in experiments, but also highlight the importance of including state-dependent kinetics in LLPS models, and may help in designing further experiments to probe the intricate roles played by LLPS in self-organization dynamics of cells.
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Affiliation(s)
- Alick-O. Vweza
- Department of Electronics and Information Engineering, Jeonbuk National University, Jeonju 54896, Korea; (A.-O.V.); (C.-G.S.)
| | - Chul-Gyu Song
- Department of Electronics and Information Engineering, Jeonbuk National University, Jeonju 54896, Korea; (A.-O.V.); (C.-G.S.)
- Advanced Biomedical Imaging Center, Jeonbuk National University, Jeonju 54896, Korea
| | - Kil-To Chong
- Department of Electronics and Information Engineering, Jeonbuk National University, Jeonju 54896, Korea; (A.-O.V.); (C.-G.S.)
- Advanced Electronics and Information Research Center, Jeonbuk National University, Jeonju 54896, Korea
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10
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Yu H, Lu S, Gasior K, Singh D, Vazquez-Sanchez S, Tapia O, Toprani D, Beccari MS, Yates JR, Da Cruz S, Newby JM, Lafarga M, Gladfelter AS, Villa E, Cleveland DW. HSP70 chaperones RNA-free TDP-43 into anisotropic intranuclear liquid spherical shells. Science 2021; 371:science.abb4309. [PMID: 33335017 PMCID: PMC8286096 DOI: 10.1126/science.abb4309] [Citation(s) in RCA: 157] [Impact Index Per Article: 52.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 10/05/2020] [Accepted: 12/02/2020] [Indexed: 12/14/2022]
Abstract
The RNA binding protein TDP-43 forms intranuclear or cytoplasmic aggregates in age-related neurodegenerative diseases. In this study, we found that RNA binding-deficient TDP-43 (produced by neurodegeneration-causing mutations or posttranslational acetylation in its RNA recognition motifs) drove TDP-43 demixing into intranuclear liquid spherical shells with liquid cores. These droplets, which we named "anisosomes", have shells that exhibit birefringence, thus indicating liquid crystal formation. Guided by mathematical modeling, we identified the primary components of the liquid core to be HSP70 family chaperones, whose adenosine triphosphate (ATP)-dependent activity maintained the liquidity of shells and cores. In vivo proteasome inhibition within neurons, to mimic aging-related reduction of proteasome activity, induced TDP-43-containing anisosomes. These structures converted to aggregates when ATP levels were reduced. Thus, acetylation, HSP70, and proteasome activities regulate TDP-43 phase separation and conversion into a gel or solid phase.
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Affiliation(s)
- Haiyang Yu
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, CA, USA.
| | - Shan Lu
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA
| | - Kelsey Gasior
- University of North Carolina Chapel Hill, Department of Biology, Chapel Hill, North Carolina, USA, University of North Carolina Chapel Hill, Department of Mathematics, Chapel Hill, North Carolina, USA
| | - Digvijay Singh
- Division of Biological Sciences, University of California, San Diego, San Diego, California, USA
| | - Sonia Vazquez-Sanchez
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA
| | - Olga Tapia
- “Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas” (CIBERNED), Madrid, Spain., “Instituto de Investigación Sanitaria Valdecilla” (IDIVAL), Santander, Spain
| | - Divek Toprani
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA
| | - Melinda S. Beccari
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA, Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, USA
| | - John R. Yates
- Departments of Molecular Medicine and Neurobiology, The Scripps Research Institute, La Jolla, California, USA
| | - Sandrine Da Cruz
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA, VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium, Department of Neurosciences, KU Leuven, Leuven, Belgium
| | - Jay M. Newby
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1
| | - Miguel Lafarga
- “Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas” (CIBERNED), Madrid, Spain., “Instituto de Investigación Sanitaria Valdecilla” (IDIVAL), Santander, Spain, Department of Anatomy and Cell Biology, University of Cantabria, Santander, Spain
| | - Amy S. Gladfelter
- University of North Carolina Chapel Hill, Department of Biology, Chapel Hill, North Carolina, USA, Marine Biological Laboratory, Woods Hole, Massachusetts, USA
| | - Elizabeth Villa
- Division of Biological Sciences, University of California, San Diego, San Diego, California, USA
| | - Don W. Cleveland
- Ludwig Institute for Cancer Research, University of California at San Diego, La Jolla, California, USA, Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California, USA,Corresponding authors: ,
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11
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Laghmach R, Potoyan DA. Liquid-liquid phase separation driven compartmentalization of reactive nucleoplasm. Phys Biol 2021; 18:015001. [PMID: 33113512 PMCID: PMC8201646 DOI: 10.1088/1478-3975/abc5ad] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The nucleus of eukaryotic cells harbors active and out of equilibrium environments conducive to diverse gene regulatory processes. On a molecular scale, gene regulatory processes take place within hierarchically compartmentalized sub-nuclear bodies. While the impact of nuclear structure on gene regulation is widely appreciated, it has remained much less clear whether and how gene regulation is impacting nuclear order itself. Recently, the liquid-liquid phase separation emerged as a fundamental mechanism driving the formation of biomolecular condensates, including membrane-less organelles, chromatin territories, and transcriptional domains. The transience and environmental sensitivity of biomolecular condensation are strongly suggestive of kinetic gene-regulatory control of phase separation. To better understand kinetic aspects controlling biomolecular phase-separation, we have constructed a minimalist model of the reactive nucleoplasm. The model is based on the Cahn-Hilliard formulation of ternary protein-RNA-nucleoplasm components coupled to non-equilibrium and spatially dependent gene expression. We find a broad range of kinetic regimes through an extensive set of simulations where the interplay of phase separation and reactive timescales can generate heterogeneous multi-modal gene expression patterns. Furthermore, the significance of this finding is that heterogeneity of gene expression is linked directly with the heterogeneity of length-scales in phase-separated condensates.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, IA 50011, United States of America. Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, United States of America. Bioinformatics and Computational Biology program, Iowa State University, Ames, IA 50011, United States of America
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12
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Regy RM, Dignon GL, Zheng W, Kim YC, Mittal J. Sequence dependent phase separation of protein-polynucleotide mixtures elucidated using molecular simulations. Nucleic Acids Res 2020; 48:12593-12603. [PMID: 33264400 PMCID: PMC7736803 DOI: 10.1093/nar/gkaa1099] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/21/2020] [Accepted: 10/27/2020] [Indexed: 12/22/2022] Open
Abstract
Ribonucleoprotein (RNP) granules are membraneless organelles (MLOs), which majorly consist of RNA and RNA-binding proteins and are formed via liquid-liquid phase separation (LLPS). Experimental studies investigating the drivers of LLPS have shown that intrinsically disordered proteins (IDPs) and nucleic acids like RNA and other polynucleotides play a key role in modulating protein phase separation. There is currently a dearth of modelling techniques which allow one to delve deeper into how polynucleotides play the role of a modulator/promoter of LLPS in cells using computational methods. Here, we present a coarse-grained polynucleotide model developed to fill this gap, which together with our recently developed HPS model for protein LLPS, allows us to capture the factors driving protein-polynucleotide phase separation. We explore the capabilities of the modelling framework with the LAF-1 RGG system which has been well studied in experiments and also with the HPS model previously. Further taking advantage of the fact that the HPS model maintains sequence specificity we explore the role of charge patterning on controlling polynucleotide incorporation into condensates. With increased charge patterning we observe formation of structured or patterned condensates which suggests the possible roles of polynucleotides in not only shifting the phase boundaries but also introducing microscopic organization in MLOs.
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Affiliation(s)
- Roshan Mammen Regy
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Gregory L Dignon
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
| | - Wenwei Zheng
- College of Integrative Sciences and Arts, Arizona State University, Mesa, AZ 85212, USA
| | - Young C Kim
- Center for Materials Physics and Technology, Naval Research Laboratory, Washington, DC 20375, USA
| | - Jeetain Mittal
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA
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13
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Gasior K, Forest MG, Gladfelter AS, Newby JM. Modeling the Mechanisms by Which Coexisting Biomolecular RNA-Protein Condensates Form. Bull Math Biol 2020; 82:153. [PMID: 33231755 DOI: 10.1007/s11538-020-00823-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 10/21/2020] [Indexed: 11/30/2022]
Abstract
Liquid-liquid phase separation is an emerging mechanism for intracellular organization. This work presents a mathematical model to examine molecular mechanisms that yield phase-separated droplets composed of different RNA-protein complexes. Using a Cahn-Hilliard diffuse interface model with a Flory-Huggins free energy scheme, we explore how multiple (here two, for simplicity) protein-RNA complexes (species) can establish a heterogeneous droplet field where droplets with single or multiple species phase separate and evolve during coarsening. We show that the complex-complex de-mixing energy tunes whether the complexes co-exist or form distinct droplets, while the transient binding kinetics dictate both the timescale of droplet formation and whether distinct species phase separate into droplets simultaneously or sequentially. For specific energetics and kinetics, a field of droplets driven by the formation of only one protein-RNA complex will emerge. Slowly, the other droplet species will accumulate inside the preformed droplets of the other species, allowing them to occupy the same droplet space. Alternatively, unfavorable species mixing creates a parasitic relationship: the slow-to-form protein-RNA complex will accumulate at the surface of a competing droplet species, siphoning off the free protein as it is released. Once this competing protein-RNA complex has sufficiently accumulated on the droplet surface, it can form a new droplet that is capable of sharing an interface with the first complex droplet but is not capable of mixing. These results give insights into a wide range of phase-separation scenarios and heterogeneous droplets that coexist but do not mix within the nucleus and the cytoplasm of cells.
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Affiliation(s)
- K Gasior
- Department of Mathematics, Florida State University, 1017 Academic Way, Tallahassee, FL, 32304, USA.,Department of Mathematics, University of North Carolina at Chapel Hill, 329 Phillips Hall CB #3250, Chapel Hill, NC, 27514, USA
| | - M G Forest
- Department of Mathematics, University of North Carolina at Chapel Hill, 329 Phillips Hall CB #3250, Chapel Hill, NC, 27514, USA.,Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, 333 S Columbia Street, Chapel Hill, NC, 27514, USA.,Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, 1112 Murray Hall, CB #3050, Chapel Hill, NC, 27514, USA
| | - A S Gladfelter
- Department of Biology, University of North Carolina at Chapel Hill, Coker Hall CB #3280, 120 South Road, Chapel Hill, NC, 27514, USA.
| | - J M Newby
- Department of Mathematical and Statistical Sciences, CAB 632, University of Alberta, Edmonton, AB, T6G 2G1, Canada.
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14
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Rhine K, Makurath MA, Liu J, Skanchy S, Lopez C, Catalan KF, Ma Y, Fare CM, Shorter J, Ha T, Chemla YR, Myong S. ALS/FTLD-Linked Mutations in FUS Glycine Residues Cause Accelerated Gelation and Reduced Interactions with Wild-Type FUS. Mol Cell 2020; 80:666-681.e8. [PMID: 33159856 PMCID: PMC7688085 DOI: 10.1016/j.molcel.2020.10.014] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 08/06/2020] [Accepted: 10/09/2020] [Indexed: 12/12/2022]
Abstract
The RNA-binding protein fused in sarcoma (FUS) can form pathogenic inclusions in neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). Over 70 mutations in Fus are linked to ALS/FTLD. In patients, all Fus mutations are heterozygous, indicating that the mutant drives disease progression despite the presence of wild-type (WT) FUS. Here, we demonstrate that ALS/FTLD-linked FUS mutations in glycine (G) strikingly drive formation of droplets that do not readily interact with WT FUS, whereas arginine (R) mutants form mixed condensates with WT FUS. Remarkably, interactions between WT and G mutants are disfavored at the earliest stages of FUS nucleation. In contrast, R mutants physically interact with the WT FUS such that WT FUS recovers the mutant defects by reducing droplet size and increasing dynamic interactions with RNA. This result suggests disparate molecular mechanisms underlying ALS/FTLD pathogenesis and differing recovery potential depending on the type of mutation.
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Affiliation(s)
- Kevin Rhine
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Monika A Makurath
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - James Liu
- Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Medical Genetics and Ophthalmic Genomics Unit, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Sophie Skanchy
- Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Christian Lopez
- Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Kevin F Catalan
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biology, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA
| | - Ye Ma
- Department of Biomedical Engineering, Johns Hopkins Medical Institute, 615 N Wolfe St, Baltimore, MD 21231, USA
| | - Charlotte M Fare
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Taekjip Ha
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Biomedical Engineering, Johns Hopkins Medical Institute, 615 N Wolfe St, Baltimore, MD 21231, USA; Howard Hughes Medical Institute, Baltimore, MD 21218, USA
| | - Yann R Chemla
- Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Sua Myong
- Program in Cell, Molecular, Developmental Biology, and Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA; Department of Physics, Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Biophysics, Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA.
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15
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Ryan VH, Watters S, Amaya J, Khatiwada B, Venditti V, Naik MT, Fawzi NL. Weak binding to the A2RE RNA rigidifies hnRNPA2 RRMs and reduces liquid-liquid phase separation and aggregation. Nucleic Acids Res 2020; 48:10542-10554. [PMID: 32870271 PMCID: PMC7544213 DOI: 10.1093/nar/gkaa710] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/28/2020] [Accepted: 08/24/2020] [Indexed: 12/30/2022] Open
Abstract
hnRNPA2 is a major component of mRNA transport granules in oligodendrocytes and neurons. However, the structural details of how hnRNPA2 binds the A2 recognition element (A2RE) and if this sequence stimulates granule formation by enhancing phase separation of hnRNPA2 has not yet been studied. Using solution NMR and biophysical studies, we find that each of the two individual RRMs retain the domain structure observed in complex with RNA but are not rigidly confined (i.e. they move independently) in solution in the absence of RNA. hnRNPA2 RRMs bind the minimal rA2RE11 weakly but at least, and most likely, two hnRNPA2 molecules are able to simultaneously bind the longer 21mer myelin basic protein A2RE. Upon binding of the RNA, NMR chemical shift deviations are observed in both RRMs, suggesting both play a role in binding the A2RE11. Interestingly, addition of short A2RE RNAs or longer RNAs containing this sequence completely prevents in vitro phase separation of full-length hnRNPA2 and aggregation of the disease-associated mutants. These findings suggest that RRM interactions with specific recognition sequences alone do not account for nucleating granule formation, consistent with models where multivalent protein:RNA and protein:protein contacts form across many sites in granule proteins and long RNA transcripts.
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Affiliation(s)
- Veronica H Ryan
- Neuroscience Graduate Program, Brown University, Providence, RI 02912, USA
| | - Scott Watters
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Joshua Amaya
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | | | | | - Mandar T Naik
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Nicolas L Fawzi
- Department of Molecular Pharmacology, Physiology, and Biotechnology, Brown University, Providence, RI 02912, USA
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16
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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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17
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Abstract
Biological phase separation is known to be important for cellular organization, which has recently been extended to a new class of biomolecules that form liquid-like droplets coexisting with the surrounding cellular or extracellular environment. These droplets are termed membraneless organelles, as they lack a dividing lipid membrane, and are formed through liquid-liquid phase separation (LLPS). Elucidating the molecular determinants of phase separation is a critical challenge for the field, as we are still at the early stages of understanding how cells may promote and regulate functions that are driven by LLPS. In this review, we discuss the role that disorder, perturbations to molecular interactions resulting from sequence, posttranslational modifications, and various regulatory stimuli play on protein LLPS, with a particular focus on insights that may be obtained from simulation and theory. We finally discuss how these molecular driving forces alter multicomponent phase separation and selectivity.
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Affiliation(s)
- Gregory L Dignon
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA;
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, New York 11794, USA;
| | - Robert B Best
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Jeetain Mittal
- Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA;
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18
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Abstract
Liquid-liquid phase separation is emerging as the universal mechanism by which membraneless cellular granules form. Despite many previous studies on condensation of intrinsically disordered proteins and low complexity domains, we lack understanding about the role of RNA, which is the essential component of all ribonucleoprotein (RNP) granules. RNA, as an anionic polymer, is inherently an excellent platform for achieving multivalency and can accommodate many RNA binding proteins. Recent findings have highlighted the diverse function of RNA in tuning phase-separation propensity up or down, altering viscoelastic properties and thereby driving immiscibility between different condensates. In addition to contributing to the biophysical properties of droplets, RNA is a functionally critical constituent that defines the identity of cellular condensates and controls the temporal and spatial distribution of specific RNP granules. In this review, we summarize what we have learned so far about such roles of RNA in the context of in vitro and in vivo studies.
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Affiliation(s)
- Kevin Rhine
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Velinda Vidaurre
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Sua Myong
- Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA; .,Physics Frontier Center (Center for the Physics of Living Cells), University of Illinois, Urbana, Illinois 61801, USA
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19
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Martin N. Dynamic Synthetic Cells Based on Liquid-Liquid Phase Separation. Chembiochem 2019; 20:2553-2568. [PMID: 31039282 DOI: 10.1002/cbic.201900183] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Indexed: 12/16/2022]
Abstract
Living cells have long been a source of inspiration for chemists. Their capacity of performing complex tasks relies on the spatiotemporal coordination of matter and energy fluxes. Recent years have witnessed growing interest in the bottom-up construction of cell-like models capable of reproducing aspects of such dynamic organisation. Liquid-liquid phase-separation (LLPS) processes in water are increasingly recognised as representing a viable compartmentalisation strategy through which to produce dynamic synthetic cells. Herein, we highlight examples of the dynamic properties of LLPS used to assemble synthetic cells, including their biocatalytic activity, reversible condensation and dissolution, growth and division, and recent directions towards the design of higher-order structures and behaviour.
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Affiliation(s)
- Nicolas Martin
- Université de Bordeaux, CNRS, Centre de Recherche Paul Pascal, UMR 5031, 115 Avenue du Dr. Albert Schweitzer, 33600, Pessac, France
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