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Atia L, Fredberg JJ. A life off the beaten track in biomechanics: Imperfect elasticity, cytoskeletal glassiness, and epithelial unjamming. BIOPHYSICS REVIEWS 2023; 4:041304. [PMID: 38156333 PMCID: PMC10751956 DOI: 10.1063/5.0179719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 11/17/2023] [Indexed: 12/30/2023]
Abstract
Textbook descriptions of elasticity, viscosity, and viscoelasticity fail to account for certain mechanical behaviors that typify soft living matter. Here, we consider three examples. First, strong empirical evidence suggests that within lung parenchymal tissues, the frictional stresses expressed at the microscale are fundamentally not of viscous origin. Second, the cytoskeleton (CSK) of the airway smooth muscle cell, as well as that of all eukaryotic cells, is more solid-like than fluid-like, yet its elastic modulus is softer than the softest of soft rubbers by a factor of 104-105. Moreover, the eukaryotic CSK expresses power law rheology, innate malleability, and fluidization when sheared. For these reasons, taken together, the CSK of the living eukaryotic cell is reminiscent of the class of materials called soft glasses, thus likening it to inert materials such as clays, pastes slurries, emulsions, and foams. Third, the cellular collective comprising a confluent epithelial layer can become solid-like and jammed, fluid-like and unjammed, or something in between. Esoteric though each may seem, these discoveries are consequential insofar as they impact our understanding of bronchospasm and wound healing as well as cancer cell invasion and embryonic development. Moreover, there are reasons to suspect that certain of these phenomena first arose in the early protist as a result of evolutionary pressures exerted by the primordial microenvironment. We have hypothesized, further, that each then became passed down virtually unchanged to the present day as a conserved core process. These topics are addressed here not only because they are interesting but also because they track the journey of one laboratory along a path less traveled by.
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Affiliation(s)
- Lior Atia
- Ben Gurion University of the Negev, Beer Sheva, Israel
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2
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Pujadas EM, Wei X, Acosta N, Carter L, Yang J, Almassalha L, Daneshkhah A, Rao SSP, Agrawal V, Seker-Polat F, Aiden EL, Kanemaki MT, Backman V, Adli M. Depletion of lamins B1 and B2 alters chromatin mobility and induces differential gene expression by a mesoscale-motion dependent mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546573. [PMID: 37425796 PMCID: PMC10326988 DOI: 10.1101/2023.06.26.546573] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
BACKGROUND B-type lamins are critical nuclear envelope proteins that interact with the 3D genomic architecture. However, identifying the direct roles of B-lamins on dynamic genome organization has been challenging as their joint depletion severely impacts cell viability. To overcome this, we engineered mammalian cells to rapidly and completely degrade endogenous B-type lamins using Auxin-inducible degron (AID) technology. RESULTS Paired with a suite of novel technologies, live-cell Dual Partial Wave Spectroscopic (Dual-PWS) microscopy, in situ Hi-C, and CRISPR-Sirius, we demonstrate that lamin B1 and lamin B2 depletion transforms chromatin mobility, heterochromatin positioning, gene expression, and loci-positioning with minimal disruption to mesoscale chromatin folding. Using the AID system, we show that the disruption of B-lamins alters gene expression both within and outside lamin associated domains, with distinct mechanistic patterns depending on their localization. Critically, we demonstrate that chromatin dynamics, positioning of constitutive and facultative heterochromatic markers, and chromosome positioning near the nuclear periphery are significantly altered, indicating that the mechanism of action of B-type lamins is derived from their role in maintaining chromatin dynamics and spatial positioning. CONCLUSIONS Our findings suggest that the mechanistic role of B-type lamins is stabilization of heterochromatin and chromosomal positioning along the nuclear periphery. We conclude that degrading lamin B1 and lamin B2 has several functional consequences related to both structural disease and cancer.
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Chen P, Levy DL. Regulation of organelle size and organization during development. Semin Cell Dev Biol 2023; 133:53-64. [PMID: 35148938 PMCID: PMC9357868 DOI: 10.1016/j.semcdb.2022.02.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/20/2022] [Accepted: 02/01/2022] [Indexed: 12/11/2022]
Abstract
During early embryogenesis, as cells divide in the developing embryo, the size of intracellular organelles generally decreases to scale with the decrease in overall cell size. Organelle size scaling is thought to be important to establish and maintain proper cellular function, and defective scaling may lead to impaired development and disease. However, how the cell regulates organelle size and organization are largely unanswered questions. In this review, we summarize the process of size scaling at both the cell and organelle levels and discuss recently discovered mechanisms that regulate this process during early embryogenesis. In addition, we describe how some recently developed techniques and Xenopus as an animal model can be used to investigate the underlying mechanisms of size regulation and to uncover the significance of proper organelle size scaling and organization.
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Affiliation(s)
- Pan Chen
- Institute of Biochemistry and Molecular Biology, School of Medicine, Ningbo University, Ningbo, Zhejiang 315211, China.
| | - Daniel L Levy
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA.
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4
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Muñiz‐Chicharro A, Votapka LW, Amaro RE, Wade RC. Brownian dynamics simulations of biomolecular diffusional association processes. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Abraham Muñiz‐Chicharro
- Molecular and Cellular Modeling Group Heidelberg Institute for Theoretical Studies (HITS) Heidelberg Germany
- Faculty of Biosciences and Heidelberg Graduate School of Mathematical and Computational Methods for the Sciences (HGS MathComp) Heidelberg University Heidelberg Germany
| | | | | | - Rebecca C. Wade
- Molecular and Cellular Modeling Group Heidelberg Institute for Theoretical Studies (HITS) Heidelberg Germany
- Center for Molecular Biology (ZMBH), DKFZ‐ZMBH Alliance, and Interdisciplinary Center for Scientific Computing (IWR) Heidelberg University Heidelberg Germany
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5
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Li C, Zhang X, Dong M, Han X. Progress on Crowding Effect in Cell-like Structures. MEMBRANES 2022; 12:593. [PMID: 35736300 PMCID: PMC9228500 DOI: 10.3390/membranes12060593] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 05/27/2022] [Accepted: 05/30/2022] [Indexed: 12/10/2022]
Abstract
Several biological macromolecules, such as proteins, nucleic acids, and polysaccharides, occupy about 30% of the space in cells, resulting in a crowded macromolecule environment. The crowding effect within cells exerts an impact on the functions of biological components, the assembly behavior of biomacromolecules, and the thermodynamics and kinetics of metabolic reactions. Cell-like structures provide confined and independent compartments for studying the working mechanisms of cells, which can be used to study the physiological functions arising from the crowding effect of macromolecules in cells. This article mainly summarizes the progress of research on the macromolecular crowding effects in cell-like structures. It includes the effects of this crowding on actin assembly behavior, tubulin aggregation behavior, and gene expression. The challenges and future trends in this field are presented at the end of the paper.
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Affiliation(s)
- Chao Li
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
| | - Xiangxiang Zhang
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
| | - Mingdong Dong
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Xiaojun Han
- State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, 92 West Da-Zhi Street, Harbin 150001, China; (C.L.); (X.Z.)
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6
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Lecinski S, Shepherd JW, Frame L, Hayton I, MacDonald C, Leake MC. Investigating molecular crowding during cell division and hyperosmotic stress in budding yeast with FRET. CURRENT TOPICS IN MEMBRANES 2021; 88:75-118. [PMID: 34862033 PMCID: PMC7612257 DOI: 10.1016/bs.ctm.2021.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cell division, aging, and stress recovery triggers spatial reorganization of cellular components in the cytoplasm, including membrane bound organelles, with molecular changes in their compositions and structures. However, it is not clear how these events are coordinated and how they integrate with regulation of molecular crowding. We use the budding yeast Saccharomyces cerevisiae as a model system to study these questions using recent progress in optical fluorescence microscopy and crowding sensing probe technology. We used a Förster Resonance Energy Transfer (FRET) based sensor, illuminated by confocal microscopy for high throughput analyses and Slimfield microscopy for single-molecule resolution, to quantify molecular crowding. We determine crowding in response to cellular growth of both mother and daughter cells, in addition to osmotic stress, and reveal hot spots of crowding across the bud neck in the burgeoning daughter cell. This crowding might be rationalized by the packing of inherited material, like the vacuole, from mother cells. We discuss recent advances in understanding the role of crowding in cellular regulation and key current challenges and conclude by presenting our recent advances in optimizing FRET-based measurements of crowding while simultaneously imaging a third color, which can be used as a marker that labels organelle membranes. Our approaches can be combined with synchronized cell populations to increase experimental throughput and correlate molecular crowding information with different stages in the cell cycle.
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Affiliation(s)
- Sarah Lecinski
- Department of Physics, University of York, York, United Kingdom
| | - Jack W Shepherd
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom
| | - Lewis Frame
- School of Natural Sciences, University of York, York, United Kingdom
| | - Imogen Hayton
- Department of Biology, University of York, York, United Kingdom
| | - Chris MacDonald
- Department of Biology, University of York, York, United Kingdom
| | - Mark C Leake
- Department of Physics, University of York, York, United Kingdom; Department of Biology, University of York, York, United Kingdom.
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Zannino L, Casali C, Siciliani S, Biggiogera M. The dynamics of the nuclear environment and their impact on gene function. J Biochem 2021; 169:259-264. [PMID: 32745171 DOI: 10.1093/jb/mvaa091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/15/2020] [Indexed: 01/04/2023] Open
Abstract
In the last decades, it has become increasingly clear how the modulation of spatial organization of chromatin over time and through the cell cycle is closely connected to gene function regulation. Different physicochemical stimuli contribute to the realization of specific transcriptional programs and finally to a specific cellular phenotype. In this review, we aim to describe the current knowledge about the dynamics regulating the movements and the interactions of molecules within the nucleus and their impact on gene functions. In particular, taking into account that these forces exert their effect in a nuclear environment characterized by a high concentration of molecules, we will discuss the role of proteins and structures that regulate these movements and transduce physicochemical signals acting on the cell to the nucleus.
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Affiliation(s)
- Lorena Zannino
- Laboratory of Cell Biology and Neurobiology, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | | | - Stella Siciliani
- Laboratory of Cell Biology and Neurobiology, Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
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Matityahu A, Onn I. Hit the brakes - a new perspective on the loop extrusion mechanism of cohesin and other SMC complexes. J Cell Sci 2021; 134:jcs247577. [PMID: 33419949 DOI: 10.1242/jcs.247577] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The three-dimensional structure of chromatin is determined by the action of protein complexes of the structural maintenance of chromosome (SMC) family. Eukaryotic cells contain three SMC complexes, cohesin, condensin, and a complex of Smc5 and Smc6. Initially, cohesin was linked to sister chromatid cohesion, the process that ensures the fidelity of chromosome segregation in mitosis. In recent years, a second function in the organization of interphase chromatin into topologically associated domains has been determined, and loop extrusion has emerged as the leading mechanism of this process. Interestingly, fundamental mechanistic differences exist between mitotic tethering and loop extrusion. As distinct molecular switches that aim to suppress loop extrusion in different biological contexts have been identified, we hypothesize here that loop extrusion is the default biochemical activity of cohesin and that its suppression shifts cohesin into a tethering mode. With this model, we aim to provide an explanation for how loop extrusion and tethering can coexist in a single cohesin complex and also apply it to the other eukaryotic SMC complexes, describing both similarities and differences between them. Finally, we present model-derived molecular predictions that can be tested experimentally, thus offering a new perspective on the mechanisms by which SMC complexes shape the higher-order structure of chromatin.
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Affiliation(s)
- Avi Matityahu
- 8 Henrietta Szold St., The Azrieli Faculty of Medicine, Bar-Ilan University, P.O. Box 1589 Safed, Israel
| | - Itay Onn
- 8 Henrietta Szold St., The Azrieli Faculty of Medicine, Bar-Ilan University, P.O. Box 1589 Safed, Israel
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9
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Lin SN, Wuite GJ, Dame RT. Effect of Different Crowding Agents on the Architectural Properties of the Bacterial Nucleoid-Associated Protein HU. Int J Mol Sci 2020; 21:ijms21249553. [PMID: 33334011 PMCID: PMC7765392 DOI: 10.3390/ijms21249553] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/31/2022] Open
Abstract
HU is a nucleoid-associated protein expressed in most eubacteria at a high amount of copies (tens of thousands). The protein is believed to bind across the genome to organize and compact the DNA. Most of the studies on HU have been carried out in a simple in vitro system, and to what extent these observations can be extrapolated to a living cell is unclear. In this study, we investigate the DNA binding properties of HU under conditions approximating physiological ones. We report that these properties are influenced by both macromolecular crowding and salt conditions. We use three different crowding agents (blotting grade blocker (BGB), bovine serum albumin (BSA), and polyethylene glycol 8000 (PEG8000)) as well as two different MgCl2 conditions to mimic the intracellular environment. Using tethered particle motion (TPM), we show that the transition between two binding regimes, compaction and extension of the HU protein, is strongly affected by crowding agents. Our observations suggest that magnesium ions enhance the compaction of HU–DNA and suppress filamentation, while BGB and BSA increase the local concentration of the HU protein by more than 4-fold. Moreover, BGB and BSA seem to suppress filament formation. On the other hand, PEG8000 is not a good crowding agent for concentrations above 9% (w/v), because it might interact with DNA, the protein, and/or surfaces. Together, these results reveal a complex interplay between the HU protein and the various crowding agents that should be taken into consideration when using crowding agents to mimic an in vivo system.
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Affiliation(s)
- Szu-Ning Lin
- Leiden Institute of Chemistry, Leiden University, 2333 CC Leiden, The Netherlands;
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
| | - Gijs J.L. Wuite
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
- LaserLaB Amsterdam, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
- Correspondence: (G.J.L.W.); (R.T.D.)
| | - Remus T. Dame
- Leiden Institute of Chemistry, Leiden University, 2333 CC Leiden, The Netherlands;
- Centre for Microbial Cell Biology, Leiden University, 2333 CC Leiden, The Netherlands
- Correspondence: (G.J.L.W.); (R.T.D.)
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10
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Shaban HA, Barth R, Bystricky K. Navigating the crowd: visualizing coordination between genome dynamics, structure, and transcription. Genome Biol 2020; 21:278. [PMID: 33203432 PMCID: PMC7670612 DOI: 10.1186/s13059-020-02185-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 10/19/2020] [Indexed: 12/12/2022] Open
Abstract
The eukaryotic genome is hierarchically structured yet highly dynamic. Regulating transcription in this environment demands a high level of coordination to permit many proteins to interact with chromatin fiber at appropriate sites in a timely manner. We describe how recent advances in quantitative imaging techniques overcome caveats of sequencing-based methods (Hi-C and related) by enabling direct visualization of transcription factors and chromatin at high resolution, from single genes to the whole nucleus. We discuss the contribution of fluorescence imaging to deciphering the principles underlying this coordination within the crowded nuclear space in living cells and discuss challenges ahead.
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Affiliation(s)
- Haitham A Shaban
- Spectroscopy Department, Physics Division, National Research Centre, Dokki, Cairo, 12622, Egypt.
- Current Address: Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
| | - Roman Barth
- Department of Bionanoscience, Delft University of Technology, 2628 CJ, Delft, The Netherlands
| | - Kerstin Bystricky
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), CNRS, UPS, University of Toulouse, 31062, Toulouse, France.
- Institut Universitaire de France (IUF), Paris, France.
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11
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Modeling the nucleoporins that form the hairy pores. Biochem Soc Trans 2020; 48:1447-1461. [DOI: 10.1042/bst20190941] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/03/2020] [Accepted: 07/16/2020] [Indexed: 11/17/2022]
Abstract
Sitting on the nuclear envelope, nuclear pore complexes (NPCs) control the molecular transport between the nucleus and the cytoplasm. Without definite open or close states, the NPC uses a family of intrinsically disordered nucleoporins called FG-Nups to construct a selective permeability barrier whose functional structure is unclear. Experimental advances have offered high-resolution molecular knowledge of the NPC scaffold and docking of the unfolded FG-Nups, however, the ‘hairy’ barrier structure still appears as blurred lobes even under the state-of-the-art microscopy. Without accurate experimental visualization, the molecular mechanism for the NPC-mediated transport remains a matter of debate. Modeling provides an alternative way to resolve this long-standing mystery. Here, we briefly review different methods employed in modeling the FG-Nups, arranging from all-atom molecular dynamics to mean-field theories. We discuss the advantage and limit of each modeling technique, and summarize the theoretical insights that, despite certain controversy, deepened our understanding of the hairy pore.
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12
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Zidovska A. The self-stirred genome: large-scale chromatin dynamics, its biophysical origins and implications. Curr Opin Genet Dev 2020; 61:83-90. [PMID: 32497955 DOI: 10.1016/j.gde.2020.03.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 01/02/2023]
Abstract
The organization and dynamics of human genome govern all cellular processes - directly impacting the central dogma of biology - yet are poorly understood, especially at large length scales. Chromatin, the functional form of DNA in cells, undergoes frequent local remodeling and rearrangements to accommodate processes such as transcription, replication and DNA repair. How these local activities contribute to nucleus-wide coherent chromatin motion, where micron-scale regions of chromatin move together over several seconds, remains unclear. Activity of nuclear enzymes was found to drive the coherent chromatin dynamics, however, its biological nature and physical mechanism remain to be revealed. The coherent dynamics leads to a perpetual stirring of the genome, leading to collective gene dynamics over microns and seconds, thus likely contributing to local and global gene-expression patterns. Hence, a possible biological role of chromatin coherence may involve gene regulation.
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Affiliation(s)
- Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY, 10003, USA.
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Schlick T. Multiscale Genome Organization: Dazzling Subject and Inventive Methods. Biophys J 2020; 118:E1-E3. [PMID: 32305070 PMCID: PMC7161524 DOI: 10.1016/j.bpj.2020.04.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 04/10/2020] [Indexed: 01/20/2023] Open
Affiliation(s)
- Tamar Schlick
- Department of Chemistry, Courant Institute of Mathematical Sciences, New York University, New York, New York.
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