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Cervenak M, Molnár OR, Horváth P, Smeller L. Stabilization of G-Quadruplex Structures of the SARS-CoV-2 Genome by TMPyP4, BRACO19, and PhenDC3. Int J Mol Sci 2024; 25:2482. [PMID: 38473730 DOI: 10.3390/ijms25052482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/14/2024] [Accepted: 02/16/2024] [Indexed: 03/14/2024] Open
Abstract
The G-quadruplex is one of the non-canonical structures formed by nucleic acids, which can be formed by guanine-rich sequences. They became the focus of much research when they were found in several oncogene promoter regions and also in the telomeres. Later on, they were discovered in viruses as well. Various ligands have been developed in order to stabilize DNA G-quadruplexes, which were believed to have an anti-cancer or antiviral effect. We investigated three of these ligands, and whether they can also affect the stability of the G-quadruplex-forming sequences of the RNA genome of SARS-CoV-2. All three investigated oligonucleotides showed the G-quadruplex form. We characterized their stability and measured their thermodynamic parameters using the Förster resonance energy transfer method. The addition of the ligands caused an increase in the unfolding temperature, but this effect was smaller compared to that found earlier in the case of G-quadruplexes of the hepatitis B virus, which has a DNA genome.
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Affiliation(s)
- Miklós Cervenak
- Department of Biophysics and Radiation Biology, Semmelweis University, 1094 Budapest, Hungary
| | - Orsolya Réka Molnár
- Department of Biophysics and Radiation Biology, Semmelweis University, 1094 Budapest, Hungary
| | - Péter Horváth
- Department of Pharmaceutical Chemistry, Semmelweis University, 1092 Budapest, Hungary
| | - László Smeller
- Department of Biophysics and Radiation Biology, Semmelweis University, 1094 Budapest, Hungary
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Iida S, Ide S, Tamura S, Tani T, Goto T, Shribak M, Maeshima K. Orientation-Independent-DIC imaging reveals that a transient rise in depletion force contributes to mitotic chromosome condensation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.11.11.566679. [PMID: 37986866 PMCID: PMC10659371 DOI: 10.1101/2023.11.11.566679] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Genomic information must be faithfully transmitted into two daughter cells during mitosis. To ensure the transmission process, interphase chromatin is further condensed into mitotic chromosomes. Although protein factors like condensins and topoisomerase IIα are involved in the assembly of mitotic chromosomes, the physical bases of the condensation process remain unclear. Depletion force/macromolecular crowding, an effective attractive force that arises between large structures in crowded environments around chromosomes, may contribute to the condensation process. To approach this issue, we investigated the "chromosome milieu" during mitosis of living human cells using orientation-independent-differential interference contrast (OI-DIC) module combined with a confocal laser scanning microscope, which is capable of precisely mapping optical path differences and estimating molecular densities. We found that the molecular density surrounding chromosomes increased with the progression from prometaphase to anaphase, concurring with chromosome condensation. However, the molecular density went down in telophase, when chromosome decondensation began. Changes in the molecular density around chromosomes by hypotonic or hypertonic treatment consistently altered the condensation levels of chromosomes. In vitro, native chromatin was converted into liquid droplets of chromatin in the presence of cations and a macromolecular crowder. Additional crowder made the chromatin droplets stiffer and more solid-like, with further condensation. These results suggest that a transient rise in depletion force, likely triggered by the relocation of macromolecules (proteins, RNAs and others) via nuclear envelope breakdown and also by a subsequent decrease in cell-volumes, contributes to mitotic chromosome condensation, shedding light on a new aspect of the condensation mechanism in living human cells.
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Affiliation(s)
- Shiori Iida
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
| | - Satoru Ide
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Tomomi Tani
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan
| | - Tatsuhiko Goto
- Research Center for Global Agromedicine and Department of Life and Food Sciences, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Michael Shribak
- Marine Biological Laboratory, 7 MBL St, Woods Hole, MA 02543, USA
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
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3
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Fritz AJ, Ghule PN, Toor R, Dillac L, Perelman J, Boyd J, Lian JB, Gordon JA, Frietze S, Van Wijnen A, Stein JL, Stein GS. Spatiotemporal Epigenetic Control of the Histone Gene Chromatin Landscape during the Cell Cycle. Crit Rev Eukaryot Gene Expr 2023; 33:85-97. [PMID: 37017672 PMCID: PMC10826887 DOI: 10.1615/critreveukaryotgeneexpr.2022046190] [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: 12/23/2022]
Abstract
Higher-order genomic organization supports the activation of histone genes in response to cell cycle regulatory cues that epigenetically mediates stringent control of transcription at the G1/S-phase transition. Histone locus bodies (HLBs) are dynamic, non-membranous, phase-separated nuclear domains where the regulatory machinery for histone gene expression is organized and assembled to support spatiotemporal epigenetic control of histone genes. HLBs provide molecular hubs that support synthesis and processing of DNA replication-dependent histone mRNAs. These regulatory microenvironments support long-range genomic interactions among non-contiguous histone genes within a single topologically associating domain (TAD). HLBs respond to activation of the cyclin E/CDK2/NPAT/HINFP pathway at the G1/S transition. HINFP and its coactivator NPAT form a complex within HLBs that controls histone mRNA transcription to support histone protein synthesis and packaging of newly replicated DNA. Loss of HINFP compromises H4 gene expression and chromatin formation, which may result in DNA damage and impede cell cycle progression. HLBs provide a paradigm for higher-order genomic organization of a subnuclear domain that executes an obligatory cell cycle-controlled function in response to cyclin E/CDK2 signaling. Understanding the coordinately and spatiotemporally organized regulatory programs in focally defined nuclear domains provides insight into molecular infrastructure for responsiveness to cell signaling pathways that mediate biological control of growth, differentiation phenotype, and are compromised in cancer.
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Affiliation(s)
- Andrew J. Fritz
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Prachi N. Ghule
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Rabail Toor
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Louis Dillac
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Jonah Perelman
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
| | - Joseph Boyd
- College of Nursing and Health Sciences, University of Vermont, Burlington, Vermont, USA
| | - Jane B. Lian
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Johnathan A.R. Gordon
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Seth Frietze
- University of Vermont Cancer Center, Burlington, Vermont, USA
- College of Nursing and Health Sciences, University of Vermont, Burlington, Vermont, USA
| | - Andre Van Wijnen
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
| | - Janet L. Stein
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
| | - Gary S. Stein
- Department of Biochemistry, University of Vermont, Burlington, Vermont, USA
- University of Vermont Cancer Center, Burlington, Vermont, USA
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4
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Huertas J, Woods EJ, Collepardo-Guevara R. Multiscale modelling of chromatin organisation: Resolving nucleosomes at near-atomistic resolution inside genes. Curr Opin Cell Biol 2022; 75:102067. [DOI: 10.1016/j.ceb.2022.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/24/2022] [Accepted: 02/04/2022] [Indexed: 12/15/2022]
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5
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Fritz AJ, El Dika M, Toor RH, Rodriguez PD, Foley SJ, Ullah R, Nie D, Banerjee B, Lohese D, Glass KC, Frietze S, Ghule PN, Heath JL, Imbalzano AN, van Wijnen A, Gordon J, Lian JB, Stein JL, Stein GS, Stein GS. Epigenetic-Mediated Regulation of Gene Expression for Biological Control and Cancer: Cell and Tissue Structure, Function, and Phenotype. Results Probl Cell Differ 2022; 70:339-373. [PMID: 36348114 PMCID: PMC9753575 DOI: 10.1007/978-3-031-06573-6_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epigenetic gene regulatory mechanisms play a central role in the biological control of cell and tissue structure, function, and phenotype. Identification of epigenetic dysregulation in cancer provides mechanistic into tumor initiation and progression and may prove valuable for a variety of clinical applications. We present an overview of epigenetically driven mechanisms that are obligatory for physiological regulation and parameters of epigenetic control that are modified in tumor cells. The interrelationship between nuclear structure and function is not mutually exclusive but synergistic. We explore concepts influencing the maintenance of chromatin structures, including phase separation, recognition signals, factors that mediate enhancer-promoter looping, and insulation and how these are altered during the cell cycle and in cancer. Understanding how these processes are altered in cancer provides a potential for advancing capabilities for the diagnosis and identification of novel therapeutic targets.
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Affiliation(s)
- Andrew J. Fritz
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Mohammed El Dika
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Rabail H. Toor
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | | | - Stephen J. Foley
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Rahim Ullah
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Daijing Nie
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Bodhisattwa Banerjee
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Dorcas Lohese
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Karen C. Glass
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Pharmacology, Burlington, VT 05405
| | - Seth Frietze
- University of Vermont, College of Nursing and Health Sciences, Burlington, VT 05405
| | - Prachi N. Ghule
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Jessica L. Heath
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405,University of Vermont, Larner College of Medicine, Department of Pediatrics, Burlington, VT 05405
| | - Anthony N. Imbalzano
- UMass Chan Medical School, Department of Biochemistry and Molecular Biotechnology, Worcester, MA 01605
| | - Andre van Wijnen
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Jonathan Gordon
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Jane B. Lian
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Janet L. Stein
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
| | - Gary S. Stein
- University of Vermont, UVM Cancer Center, Larner College of Medicine, Department of Biochemistry, Burlington, VT 05405
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Pliss A, Kuzmin AN, Lita A, Kumar R, Celiku O, Atilla-Gokcumen GE, Gokcumen O, Chandra D, Larion M, Prasad PN. A Single-Organelle Optical Omics Platform for Cell Science and Biomarker Discovery. Anal Chem 2021; 93:8281-8290. [PMID: 34048235 DOI: 10.1021/acs.analchem.1c01131] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Research in fundamental cell biology and pathology could be revolutionized by developing the capacity for quantitative molecular analysis of subcellular structures. To that end, we introduce the Ramanomics platform, based on confocal Raman microspectrometry coupled to a biomolecular component analysis algorithm, which together enable us to molecularly profile single organelles in a live-cell environment. This emerging omics approach categorizes the entire molecular makeup of a sample into about a dozen of general classes and subclasses of biomolecules and quantifies their amounts in submicrometer volumes. A major contribution of our study is an attempt to bridge Raman spectrometry with big-data analysis in order to identify complex patterns of biomolecules in a single cellular organelle and leverage discovery of disease biomarkers. Our data reveal significant variations in organellar composition between different cell lines. We also demonstrate the merits of Ramanomics for identifying diseased cells by using prostate cancer as an example. We report large-scale molecular transformations in the mitochondria, Golgi apparatus, and endoplasmic reticulum that accompany the development of prostate cancer. Based on these findings, we propose that Ramanomics datasets in distinct organelles constitute signatures of cellular metabolism in healthy and diseased states.
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Affiliation(s)
- Artem Pliss
- Institute for Lasers, Photonics and Biophotonics and Department of Chemistry, Natural Science Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Andrey N Kuzmin
- Institute for Lasers, Photonics and Biophotonics and Department of Chemistry, Natural Science Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Adrian Lita
- Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Rahul Kumar
- Department of Pharmacology and Therapeutics, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, United States
| | - Orieta Celiku
- Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - G Ekin Atilla-Gokcumen
- Department of Chemistry, Natural Science Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Omer Gokcumen
- Department of Biological Sciences, Cooke Hall, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
| | - Dhyan Chandra
- Department of Pharmacology and Therapeutics, Roswell Park Comprehensive Cancer Center, Buffalo, New York 14263, United States
| | - Mioara Larion
- Neuro-Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Paras N Prasad
- Institute for Lasers, Photonics and Biophotonics and Department of Chemistry, Natural Science Complex, University at Buffalo, The State University of New York, Buffalo, New York 14260, United States
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7
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Farr SE, Woods EJ, Joseph JA, Garaizar A, Collepardo-Guevara R. Nucleosome plasticity is a critical element of chromatin liquid-liquid phase separation and multivalent nucleosome interactions. Nat Commun 2021; 12:2883. [PMID: 34001913 PMCID: PMC8129070 DOI: 10.1038/s41467-021-23090-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 03/23/2021] [Indexed: 12/19/2022] Open
Abstract
Liquid-liquid phase separation (LLPS) is an important mechanism that helps explain the membraneless compartmentalization of the nucleus. Because chromatin compaction and LLPS are collective phenomena, linking their modulation to the physicochemical features of nucleosomes is challenging. Here, we develop an advanced multiscale chromatin model-integrating atomistic representations, a chemically-specific coarse-grained model, and a minimal model-to resolve individual nucleosomes within sub-Mb chromatin domains and phase-separated systems. To overcome the difficulty of sampling chromatin at high resolution, we devise a transferable enhanced-sampling Debye-length replica-exchange molecular dynamics approach. We find that nucleosome thermal fluctuations become significant at physiological salt concentrations and destabilize the 30-nm fiber. Our simulations show that nucleosome breathing favors stochastic folding of chromatin and promotes LLPS by simultaneously boosting the transient nature and heterogeneity of nucleosome-nucleosome contacts, and the effective nucleosome valency. Our work puts forward the intrinsic plasticity of nucleosomes as a key element in the liquid-like behavior of nucleosomes within chromatin, and the regulation of chromatin LLPS.
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Affiliation(s)
- Stephen E Farr
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | - Esmae J Woods
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | - Jerelle A Joseph
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
- Department of Genetics, University of Cambridge, Cambridge, UK
| | - Adiran Garaizar
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | - Rosana Collepardo-Guevara
- Maxwell Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK.
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
- Department of Genetics, University of Cambridge, Cambridge, UK.
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8
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Abstract
Dehydration of cells by acute hyperosmotic stress has profound effects upon cell structure and function. Interphase chromatin and mitotic chromosomes collapse ("congelation"). HL-60/S4 cells remain ~100% viable for, at least, 1 hour, exhibiting shrinkage to ~2/3 their original volume, when placed in 300mM sucrose in tissue culture medium. Fixed cells were imaged by immunostaining confocal and STED microscopy. At a "global" structural level (μm), mitotic chromosomes congeal into a residual gel with apparent (phase) separations of Ki67, CTCF, SMC2, RAD21, H1 histones and HMG proteins. At an "intermediate" level (sub-μm), radial distribution analysis of STED images revealed a most probable peak DNA density separation of ~0.16 μm, essentially unchanged by hyperosmotic stress. At a "local" structural level (~1-2 nm), in vivo crosslinking revealed essentially unchanged crosslinked products between H1, HMG and inner histones. Hyperosmotic cellular stress is discussed in terms of concepts of mitotic chromosome structure and liquid-liquid phase separation.
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Affiliation(s)
- Ada L Olins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, ME, USA
| | - Travis J Gould
- Department of Physics & Astronomy, Bates College, Lewiston, ME,USA
| | - Logan Boyd
- Department of Physics & Astronomy, Bates College, Lewiston, ME,USA
| | - Bettina Sarg
- Division of Clinical Biochemistry, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Donald E Olins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, ME, USA
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Tsai A, Galupa R, Crocker J. Robust and efficient gene regulation through localized nuclear microenvironments. Development 2020; 147:147/19/dev161430. [PMID: 33020073 DOI: 10.1242/dev.161430] [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] [Indexed: 12/26/2022]
Abstract
Developmental enhancers drive gene expression in specific cell types during animal development. They integrate signals from many different sources mediated through the binding of transcription factors, producing specific responses in gene expression. Transcription factors often bind low-affinity sequences for only short durations. How brief, low-affinity interactions drive efficient transcription and robust gene expression is a central question in developmental biology. Localized high concentrations of transcription factors have been suggested as a possible mechanism by which to use these enhancer sites effectively. Here, we discuss the evidence for such transcriptional microenvironments, mechanisms for their formation and the biological consequences of such sub-nuclear compartmentalization for developmental decisions and evolution.
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Affiliation(s)
- Albert Tsai
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Rafael Galupa
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Justin Crocker
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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10
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Pliss A, Prasad PN. High resolution mapping of subcellular refractive index by Fluorescence Lifetime Imaging: a next frontier in quantitative cell science? Methods Appl Fluoresc 2020; 8:032001. [PMID: 32235079 DOI: 10.1088/2050-6120/ab8571] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Intracellular refractive index (RI) is an essential biophysical parameter, which best represents the mass and the distribution of proteins in the cell interior, including high-density accumulations in membraneless organelles. For RI measurements, a number of sophisticated techniques have been developed; however most of the new approaches are either insufficiently sensitive to intracellular variations of proteins distribution or are not compatible with live cell studies. Here, we outline the fluorescence lifetime imaging (FLIM) strategy for high resolution mapping of subcellular RI. We provide an example of our recent studies in which we utilize FLIM for measurements and monitoring of local RI in the major membraneless organelles within live cultured cells.
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11
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Sjakste T, Leonova E, Petrovs R, Trapina I, Röder MS, Sjakste N. Tight DNA-protein complexes isolated from barley seedlings are rich in potential guanine quadruplex sequences. PeerJ 2020; 8:e8569. [PMID: 32110488 PMCID: PMC7034378 DOI: 10.7717/peerj.8569] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 01/15/2020] [Indexed: 11/20/2022] Open
Abstract
Background The concept of chromatin domains attached to the nuclear matrix is being revisited, with nucleus described as a set of topologically associating domains. The significance of the tightly bound to DNA proteins (TBP), a protein group that remains attached to DNA after its deproteinization should be also revisited, as the existence of these interactions is in good agreement with the concept of the topologically associating domain. The work aimed to characterize the DNA component of TBP isolated from barley seedlings. Methods The tight DNA-protein complexes from the first leaves, coleoptiles, and roots of barley seedlings were isolated by purification with chromatography on nitrocellulose or exhaustive digestion of DNA with DNase I. Cloning and transformation were performed using pMOSBBlue Blunt Ended Cloning Kit. Inserts were amplified by PCR, and sequencing was performed on the MegaBace 1000 Sequencing System. The BLAST search was performed using sequence databases at NCBI, CR-EST, and TREP and Ensembl Plants databases. Comparison to MAR/SAR sequences was performed using http://smartdb.bioinf.med.uni-goettingen.de/cgi-bin/SMARtDB/smar.cgi database. The prediction of G quadruplexes (GQ) was performed with the aid of R-studio library pqsfinder. CD spectra were recorded on a Chirascan CS/3D spectrometer. Results Although the barley genome is AT-rich (43% of GC pairs), most DNA fragments associated with TBP were GC-rich (up to 70% in some fractions). Both fractionation procedures yielded a high proportion of CT-motif sequences presented predominantly by the 16-bp CC(TCTCCC)2 TC fragment present in clones derived from the TBP-bound DNA and absent in free DNA. BLAST analysis revealed alignment with different barley repeats. Some clones, however, aligned with both nuclear and chloroplast structural genes. Alignments with MAR/SAR motifs were very few. The analysis produced by the pqsfinder program revealed numerous potential quadruplex-forming sites in the TBP-bound sequences. A set of oligonucleotides containing sites of possible GQs were designed and ordered. Three of them represented the minus strand of the CT-repeat. Two were derived from sequences of two clones of nitrocellulose retained fraction from leaves and contained GC-rich motifs different from the CT motif. Circular dichroism spectroscopy revealed profound changes in spectra when oligonucleotides were incubated with 100 mM KCl. There was either an increase of positive band in the area of 260 nm or the formation of a positive band at 290 nm. In the former case, changes are typical for parallel G-quadruplexes and, in the latter, 3 + 1 structures. Discussion The G-quadruplexes anchor proteins are probably involved in the maintenance of the topologically associated domain structure.
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Affiliation(s)
- Tatjana Sjakste
- Genomics and Bioinformatics Group, Institute of Biology, University of Latvia, Riga, Latvia
| | - Elina Leonova
- Faculty of Medicine, University of Latvia, Riga, Latvia
| | | | - Ilva Trapina
- Genomics and Bioinformatics Group, Institute of Biology, University of Latvia, Riga, Latvia
| | - Marion S Röder
- Leibniz Institute for Plant Genetics and Crop Research, Gatersleben, Germany
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12
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Erenpreisa J, Giuliani A. Resolution of Complex Issues in Genome Regulation and Cancer Requires Non-Linear and Network-Based Thermodynamics. Int J Mol Sci 2019; 21:E240. [PMID: 31905791 PMCID: PMC6981914 DOI: 10.3390/ijms21010240] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/22/2019] [Accepted: 12/27/2019] [Indexed: 02/06/2023] Open
Abstract
The apparent lack of success in curing cancer that was evidenced in the last four decades of molecular medicine indicates the need for a global re-thinking both its nature and the biological approaches that we are taking in its solution. The reductionist, one gene/one protein method that has served us well until now, and that still dominates in biomedicine, requires complementation with a more systemic/holistic approach, to address the huge problem of cross-talk between more than 20,000 protein-coding genes, about 100,000 protein types, and the multiple layers of biological organization. In this perspective, the relationship between the chromatin network organization and gene expression regulation plays a fundamental role. The elucidation of such a relationship requires a non-linear thermodynamics approach to these biological systems. This change of perspective is a necessary step for developing successful 'tumour-reversion' therapeutic strategies.
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Affiliation(s)
- Jekaterina Erenpreisa
- Cancer Research Division, Latvian Biomedicine Research and Study Centre, LV1067 Riga, Latvia
| | - Alessandro Giuliani
- Environmental and Health Department, Istituto Superiore di Sanità, 00161 Rome, Italy;
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13
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Somkuti J, Adányi M, Smeller L. Self-crowding influences the temperature - pressure stability of the human telomere G-quadruplex. Biophys Chem 2019; 254:106248. [PMID: 31470349 DOI: 10.1016/j.bpc.2019.106248] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/07/2019] [Accepted: 08/09/2019] [Indexed: 01/22/2023]
Abstract
We measured the effect of crowded environment on G-quadruplex structures, formed by guanine rich DNA sequences. Fluorescence and infrared spectroscopy were used to determine the temperature stability of G-quadruplex structure formed by the human telomere sequence. We determined the T-p phase diagram of Htel aptamer up to 1 GPa at different self-crowding conditions. The unfolding volume change was determined from the pressure induced shift of the unfolding temperature of the quadruplex form. The unfolding volume change decreased in magnitude, and even its sign changed from negative (-19 ml/mol) to positive (7 ml/mol) under self-crowded conditions. The possible explanations are the appearance of the parallel GQ structure at high concentration or the fact that the volume decrease caused by the released central K+ ion during the unfolding is less significant in crowded environment.
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Affiliation(s)
- J Somkuti
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - M Adányi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - L Smeller
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.
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14
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Fritz AJ, Gillis NE, Gerrard DL, Rodriguez PD, Hong D, Rose JT, Ghule PN, Bolf EL, Gordon JA, Tye CE, Boyd JR, Tracy KM, Nickerson JA, van Wijnen AJ, Imbalzano AN, Heath JL, Frietze SE, Zaidi SK, Carr FE, Lian JB, Stein JL, Stein GS. Higher order genomic organization and epigenetic control maintain cellular identity and prevent breast cancer. Genes Chromosomes Cancer 2019; 58:484-499. [PMID: 30873710 DOI: 10.1002/gcc.22731] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/07/2019] [Accepted: 01/07/2019] [Indexed: 12/24/2022] Open
Abstract
Cells establish and sustain structural and functional integrity of the genome to support cellular identity and prevent malignant transformation. In this review, we present a strategic overview of epigenetic regulatory mechanisms including histone modifications and higher order chromatin organization (HCO) that are perturbed in breast cancer onset and progression. Implications for dysfunctions that occur in hormone regulation, cell cycle control, and mitotic bookmarking in breast cancer are considered, with an emphasis on epithelial-to-mesenchymal transition and cancer stem cell activities. The architectural organization of regulatory machinery is addressed within the contexts of translating cancer-compromised genomic organization to advances in breast cancer risk assessment, diagnosis, prognosis, and identification of novel therapeutic targets with high specificity and minimal off target effects.
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Affiliation(s)
- A J Fritz
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - N E Gillis
- University of Vermont Cancer Center, Burlington, Vermont.,Department of Pharmacology, Larner college of Medicine, University of Vermont, Burlington, Vermont
| | - D L Gerrard
- Cellular Molecular Biomedical Sciences Program, University of Vermont, Burlington, Vermont.,Department of Biomedical and Health Sciences, University of Vermont, Burlington, Vermont
| | - P D Rodriguez
- Cellular Molecular Biomedical Sciences Program, University of Vermont, Burlington, Vermont.,Department of Biomedical and Health Sciences, University of Vermont, Burlington, Vermont
| | - D Hong
- Department of Medical Oncology, Dana Farber Cancer Institute, Boston, Massachusetts
| | - J T Rose
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - P N Ghule
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - E L Bolf
- University of Vermont Cancer Center, Burlington, Vermont.,Department of Pharmacology, Larner college of Medicine, University of Vermont, Burlington, Vermont
| | - J A Gordon
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - C E Tye
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - J R Boyd
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - K M Tracy
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - J A Nickerson
- Division of Genes and Development of the Department of Pediatrics, University of Massachusetts Medical School, Worcester, Massachusetts
| | - A J van Wijnen
- Orthopedic Surgery and Biochemistry and Molecular Biology, Mayo Clinic Minnesota, Rochester, Minnesota
| | - A N Imbalzano
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts
| | - J L Heath
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont.,Department of Pediatrics, Larner College of Medicine, University of Vermont, Burlington, Vermont
| | - S E Frietze
- Cellular Molecular Biomedical Sciences Program, University of Vermont, Burlington, Vermont.,Department of Biomedical and Health Sciences, University of Vermont, Burlington, Vermont
| | - S K Zaidi
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - F E Carr
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont.,Department of Pharmacology, Larner college of Medicine, University of Vermont, Burlington, Vermont
| | - J B Lian
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - J L Stein
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
| | - G S Stein
- Department of Biochemistry, Larner College of Medicine, University of Vermont, Burlington, Vermont.,University of Vermont Cancer Center, Burlington, Vermont
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15
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Lemetti L, Hirvonen SP, Fedorov D, Batys P, Sammalkorpi M, Tenhu H, Linder MB, Aranko AS. Molecular crowding facilitates assembly of spidroin-like proteins through phase separation. Eur Polym J 2019. [DOI: 10.1016/j.eurpolymj.2018.10.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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16
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Cycles of protein condensation and discharge in nuclear organelles studied by fluorescence lifetime imaging. Nat Commun 2019; 10:455. [PMID: 30692529 PMCID: PMC6349932 DOI: 10.1038/s41467-019-08354-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 01/03/2019] [Indexed: 02/07/2023] Open
Abstract
Nuclear organelles are viscous droplets, created by concentration-dependent condensation and liquid–liquid phase separation of soluble proteins. Nuclear organelles have been actively investigated for their role in cellular regulation and disease. However, these studies are highly challenging to perform in live cells, and therefore, their physico-chemical properties are still poorly understood. In this study, we describe a fluorescence lifetime imaging approach for real-time monitoring of protein condensation in nuclear organelles of live cultured cells. This approach unravels surprisingly large cyclic changes in concentration of proteins in major nuclear organelles including nucleoli, nuclear speckles, Cajal bodies, as well as in the clusters of heterochromatin. Remarkably, protein concentration changes are synchronous for different organelles of the same cells. We propose a molecular mechanism responsible for synchronous accumulations of proteins in the nuclear organelles. This mechanism can serve for general regulation of cellular metabolism and contribute to coordination of gene expression. Studying the condensation of proteins into membraneless organelles in live cells is highly challenging. Here the authors develop a fluorescence lifetime imaging approach to monitor the condensation of proteins in nuclear organelles and report coordinated and cyclic changes in several nuclear organelles.
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17
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Abstract
The nucleolus as site of ribosome biogenesis holds a pivotal role in cell metabolism. It is composed of ribosomal DNA (rDNA), which is present as tandem arrays located in nucleolus organizer regions (NORs). In interphase cells, rDNA can be found inside and adjacent to nucleoli and the location is indicative for transcriptional activity of ribosomal genes-inactive rDNA (outside) versus active one (inside). Moreover, the nucleolus itself acts as a spatial organizer of non-nucleolar chromatin. Microscopy-based approaches offer the possibility to explore the spatially distinct localization of the different DNA populations in relation to the nucleolar structure. Recent technical developments in microscopy and preparatory methods may further our understanding of the functional architecture of nucleoli. This review will attempt to summarize the current understanding of mammalian nucleolar chromatin organization as seen from a microscopist's perspective.
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Affiliation(s)
- Christian Schöfer
- Division of Cell and Developmental Biology, Center for Anatomy and Cell Biology, Medical University of Vienna, Schwarzspanierstr. 17, 1090, Vienna, Austria.
| | - Klara Weipoltshammer
- Division of Cell and Developmental Biology, Center for Anatomy and Cell Biology, Medical University of Vienna, Schwarzspanierstr. 17, 1090, Vienna, Austria
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18
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Zaidi SK, Fritz AJ, Tracy KM, Gordon JA, Tye CE, Boyd J, Van Wijnen AJ, Nickerson JA, Imbalzano AN, Lian JB, Stein JL, Stein GS. Nuclear organization mediates cancer-compromised genetic and epigenetic control. Adv Biol Regul 2018; 69:1-10. [PMID: 29759441 PMCID: PMC6102062 DOI: 10.1016/j.jbior.2018.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 04/13/2018] [Accepted: 05/02/2018] [Indexed: 12/19/2022]
Abstract
Nuclear organization is functionally linked to genetic and epigenetic regulation of gene expression for biological control and is modified in cancer. Nuclear organization supports cell growth and phenotypic properties of normal and cancer cells by facilitating physiologically responsive interactions of chromosomes, genes and regulatory complexes at dynamic three-dimensional microenvironments. We will review nuclear structure/function relationships that include: 1. Epigenetic bookmarking of genes by phenotypic transcription factors to control fidelity and plasticity of gene expression as cells enter and exit mitosis; 2. Contributions of chromatin remodeling to breast cancer nuclear morphology, metabolism and effectiveness of chemotherapy; 3. Relationships between fidelity of nuclear organization and metastasis of breast cancer to bone; 4. Dynamic modifications of higher-order inter- and intra-chromosomal interactions in breast cancer cells; 5. Coordinate control of cell growth and phenotype by tissue-specific transcription factors; 6. Oncofetal epigenetic control by bivalent histone modifications that are functionally related to sustaining the stem cell phenotype; and 7. Noncoding RNA-mediated regulation in the onset and progression of breast cancer. The discovery of components to nuclear organization that are functionally related to cancer and compromise gene expression have the potential for translation to innovative cancer diagnosis and targeted therapy.
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Affiliation(s)
- Sayyed K Zaidi
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Andrew J Fritz
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Kirsten M Tracy
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Jonathan A Gordon
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Coralee E Tye
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Joseph Boyd
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Andre J Van Wijnen
- Departments of Orthopedic Surgery, Biochemistry & Molecular Biology, Mayo Clinic, Rochester, MN, United States
| | - Jeffrey A Nickerson
- Department of Pediatrics, UMass Medical School, Worcester, MA, United States
| | - Antony N Imbalzano
- Graduate Program in Cell Biology and Department of Biochemistry and Molecular Pharmacology, UMass Medical School, Worcester, MA, United States
| | - Jane B Lian
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States
| | - Janet L Stein
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States.
| | - Gary S Stein
- Department of Biochemistry and University of Vermont Cancer Center, University of Vermont, Burlington, VT, United States.
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19
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Strom AR, Emelyanov AV, Mir M, Fyodorov DV, Darzacq X, Karpen GH. Phase separation drives heterochromatin domain formation. Nature 2017; 547:241-245. [PMID: 28636597 PMCID: PMC6022742 DOI: 10.1038/nature22989] [Citation(s) in RCA: 1151] [Impact Index Per Article: 164.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 05/31/2017] [Indexed: 12/13/2022]
Abstract
Constitutive heterochromatin is an important component of eukaryotic genomes that has essential roles in nuclear architecture, DNA repair and genome stability, and silencing of transposon and gene expression. Heterochromatin is highly enriched for repetitive sequences, and is defined epigenetically by methylation of histone H3 at lysine 9 and recruitment of its binding partner heterochromatin protein 1 (HP1). A prevalent view of heterochromatic silencing is that these and associated factors lead to chromatin compaction, resulting in steric exclusion of regulatory proteins such as RNA polymerase from the underlying DNA. However, compaction alone does not account for the formation of distinct, multi-chromosomal, membrane-less heterochromatin domains within the nucleus, fast diffusion of proteins inside the domain, and other dynamic features of heterochromatin. Here we present data that support an alternative hypothesis: that the formation of heterochromatin domains is mediated by phase separation, a phenomenon that gives rise to diverse non-membrane-bound nuclear, cytoplasmic and extracellular compartments. We show that Drosophila HP1a protein undergoes liquid-liquid demixing in vitro, and nucleates into foci that display liquid properties during the first stages of heterochromatin domain formation in early Drosophila embryos. Furthermore, in both Drosophila and mammalian cells, heterochromatin domains exhibit dynamics that are characteristic of liquid phase-separation, including sensitivity to the disruption of weak hydrophobic interactions, and reduced diffusion, increased coordinated movement and inert probe exclusion at the domain boundary. We conclude that heterochromatic domains form via phase separation, and mature into a structure that includes liquid and stable compartments. We propose that emergent biophysical properties associated with phase-separated systems are critical to understanding the unusual behaviours of heterochromatin, and how chromatin domains in general regulate essential nuclear functions.
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Affiliation(s)
- Amy R Strom
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Alexander V Emelyanov
- Albert Einstein College of Medicine, Department of Cell Biology, New York, New York, USA
| | - Mustafa Mir
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Dmitry V Fyodorov
- Albert Einstein College of Medicine, Department of Cell Biology, New York, New York, USA
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
| | - Gary H Karpen
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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20
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Pederson T, King MC, Marko JF. Forces, fluctuations, and self-organization in the nucleus. Mol Biol Cell 2016; 26:3915-9. [PMID: 26543199 PMCID: PMC4710223 DOI: 10.1091/mbc.e15-06-0357] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We address several processes and domains in the nucleus wherein holding the perspective of physics either reveals a conundrum or is likely to enable progress.
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Affiliation(s)
- Thoru Pederson
- Program in Cell and Developmental Dynamics, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Megan C King
- Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520
| | - John F Marko
- Department of Molecular Biosciences and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208
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21
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Vasquez PA, Hult C, Adalsteinsson D, Lawrimore J, Forest MG, Bloom K. Entropy gives rise to topologically associating domains. Nucleic Acids Res 2016; 44:5540-9. [PMID: 27257057 PMCID: PMC4937343 DOI: 10.1093/nar/gkw510] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 05/06/2016] [Accepted: 05/25/2016] [Indexed: 12/15/2022] Open
Abstract
We investigate chromosome organization within the nucleus using polymer models whose formulation is closely guided by experiments in live yeast cells. We employ bead-spring chromosome models together with loop formation within the chains and the presence of nuclear bodies to quantify the extent to which these mechanisms shape the topological landscape in the interphase nucleus. By investigating the genome as a dynamical system, we show that domains of high chromosomal interactions can arise solely from the polymeric nature of the chromosome arms due to entropic interactions and nuclear confinement. In this view, the role of bio-chemical related processes is to modulate and extend the duration of the interacting domains.
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Affiliation(s)
- Paula A Vasquez
- Department of Mathematics, University of South Carolina, Columbia, SC 29808, USA
| | - Caitlin Hult
- Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - David Adalsteinsson
- Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Josh Lawrimore
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Mark G Forest
- Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Kerry Bloom
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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22
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Abstract
Nucleoli are formed on the basis of ribosomal genes coding for RNAs of ribosomal particles, but also include a great variety of other DNA regions. In this article, we discuss the characteristics of ribosomal DNA: the structure of the rDNA locus, complex organization and functions of the intergenic spacer, multiplicity of gene copies in one cell, selective silencing of genes and whole gene clusters, relation to components of nucleolar ultrastructure, specific problems associated with replication. We also review current data on the role of non-ribosomal DNA in the organization and function of nucleoli. Finally, we discuss probable causes preventing efficient visualization of DNA in nucleoli.
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23
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Abstract
Gene expression control is a fundamental determinant of cellular life with transcription being the most important step. The spatial nuclear arrangement of the transcription process driven by RNA polymerases II and III is nonrandomly organized in foci, which is believed to add another regulatory layer on gene expression control. RNA polymerase I transcription takes place within a specialized organelle, the nucleolus. Transcription of ribosomal RNA directly responds to metabolic requirements, which in turn is reflected in the architecture of nucleoli. It differs from that of the other polymerases with respect to the gene template organization, transcription rate, and epigenetic expression control, whereas other features are shared like the formation of DNA loops bringing genes and components of the transcription machinery in close proximity. In recent years, significant advances have been made in the understanding of the structural prerequisites of nuclear transcription, of the arrangement in the nuclear volume, and of the dynamics of these entities. Here, we compare ribosomal RNA and mRNA transcription side by side and review the current understanding focusing on structural aspects of transcription foci, of their constituents, and of the dynamical behavior of these components with respect to foci formation, disassembly, and cell cycle.
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Affiliation(s)
- Klara Weipoltshammer
- Department for Cell and Developmental Biology, Medical University of Vienna, Schwarzspanierstr. 17, 1090, Vienna, Austria
| | - Christian Schöfer
- Department for Cell and Developmental Biology, Medical University of Vienna, Schwarzspanierstr. 17, 1090, Vienna, Austria.
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24
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Aranda-Anzaldo A. The interphase mammalian chromosome as a structural system based on tensegrity. J Theor Biol 2016; 393:51-9. [PMID: 26780650 DOI: 10.1016/j.jtbi.2016.01.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Revised: 12/11/2015] [Accepted: 01/04/2016] [Indexed: 10/22/2022]
Abstract
Each mammalian chromosome is constituted by a DNA fiber of macroscopic length that needs to be fitted in a microscopic nucleus. The DNA fiber is subjected at physiological temperature to random thermal bending and looping that must be constrained so as achieve structural stability thus avoiding spontaneous rupturing of the fiber. Standard textbooks assume that chromatin proteins are primarily responsible for the packaging of DNA and so of its protection against spontaneous breakage. Yet the dynamic nature of the interactions between chromatin proteins and DNA is unlikely to provide the necessary long-term structural stability for the chromosomal DNA. On the other hand, longstanding evidence indicates that stable interactions between DNA and constituents of a nuclear compartment commonly known as the nuclear matrix organize the chromosomal DNA as a series of topologically constrained, supercoiled loops during interphase. This results in a primary level of DNA condensation and packaging within the nucleus, as well as in protection against spontaneous DNA breakage, independently of chromatin proteins which nevertheless increase and dynamically modulate the degree of DNA packaging and its role in the regulation of DNA function. Thus current evidence, presented hereunder, supports a model for the organization of the interphase chromosome as resilient system that satisfies the principles of structural tensegrity.
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Affiliation(s)
- Armando Aranda-Anzaldo
- Laboratorio de Biología Molecular y Neurociencias, Facultad de Medicina, Universidad Autónoma del Estado de México, Paseo Tollocan y Jesús Carranza s/n, Toluca, 50180 Edo. Méx., México.
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25
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Maeso I, Tena JJ. Favorable genomic environments for cis-regulatory evolution: A novel theoretical framework. Semin Cell Dev Biol 2015; 57:2-10. [PMID: 26673387 DOI: 10.1016/j.semcdb.2015.12.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/02/2015] [Accepted: 12/05/2015] [Indexed: 12/22/2022]
Abstract
Cis-regulatory changes are arguably the primary evolutionary source of animal morphological diversity. With the recent explosion of genome-wide comparisons of the cis-regulatory content in different animal species is now possible to infer general principles underlying enhancer evolution. However, these studies have also revealed numerous discrepancies and paradoxes, suggesting that the mechanistic causes and modes of cis-regulatory evolution are still not well understood and are probably much more complex than generally appreciated. Here, we argue that the mutational mechanisms and genomic regions generating new regulatory activities must comply with the constraints imposed by the molecular properties of cis-regulatory elements (CREs) and the organizational features of long-range chromatin interactions. Accordingly, we propose a new integrative evolutionary framework for cis-regulatory evolution based on two major premises for the origin of novel enhancer activity: (i) an accessible chromatin environment and (ii) compatibility with the 3D structure and interactions of pre-existing CREs. Mechanisms and DNA sequences not fulfilling these premises, will be less likely to have a measurable impact on gene expression and as such, will have a minor contribution to the evolution of gene regulation. Finally, we discuss current comparative cis-regulatory data under the light of this new evolutionary model, and propose that the two most prominent mechanisms for the evolution of cis-regulatory changes are the overprinting of ancestral CREs and the exaptation of transposable elements.
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Affiliation(s)
- Ignacio Maeso
- Centro Andaluz de Biología del Desarrollo (CSIC/UPO/JA), Universidad Pablo de Olavide, 41013 Seville, Spain.
| | - Juan J Tena
- Centro Andaluz de Biología del Desarrollo (CSIC/UPO/JA), Universidad Pablo de Olavide, 41013 Seville, Spain.
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26
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Bosse JB, Hogue IB, Feric M, Thiberge SY, Sodeik B, Brangwynne CP, Enquist LW. Remodeling nuclear architecture allows efficient transport of herpesvirus capsids by diffusion. Proc Natl Acad Sci U S A 2015; 112:E5725-33. [PMID: 26438852 PMCID: PMC4620878 DOI: 10.1073/pnas.1513876112] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The nuclear chromatin structure confines the movement of large macromolecular complexes to interchromatin corrals. Herpesvirus capsids of approximately 125 nm assemble in the nucleoplasm and must reach the nuclear membranes for egress. Previous studies concluded that nuclear herpesvirus capsid motility is active, directed, and based on nuclear filamentous actin, suggesting that large nuclear complexes need metabolic energy to escape nuclear entrapment. However, this hypothesis has recently been challenged. Commonly used microscopy techniques do not allow the imaging of rapid nuclear particle motility with sufficient spatiotemporal resolution. Here, we use a rotating, oblique light sheet, which we dubbed a ring-sheet, to image and track viral capsids with high temporal and spatial resolution. We do not find any evidence for directed transport. Instead, infection with different herpesviruses induced an enlargement of interchromatin domains and allowed particles to diffuse unrestricted over longer distances, thereby facilitating nuclear egress for a larger fraction of capsids.
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Affiliation(s)
- Jens B Bosse
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544; Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544
| | - Ian B Hogue
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544; Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544
| | - Marina Feric
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544
| | - Stephan Y Thiberge
- Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544
| | - Beate Sodeik
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544
| | - Lynn W Enquist
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544; Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08544;
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27
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Golov AK, Gavrilov AA, Razin SV. The Role of Crowding Forces in Juxtaposing β-Globin Gene Domain Remote Regulatory Elements in Mouse Erythroid Cells. PLoS One 2015; 10:e0139855. [PMID: 26436546 PMCID: PMC4593578 DOI: 10.1371/journal.pone.0139855] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 09/11/2015] [Indexed: 01/03/2023] Open
Abstract
The extremely high concentration of macromolecules in a eukaryotic cell nucleus indicates that the nucleoplasm is a crowded macromolecular solution in which large objects tend to gather together due to crowding forces. It has been shown experimentally that crowding forces support the integrity of various nuclear compartments. However, little is known about their role in control of chromatin dynamics in vivo. Here, we experimentally addressed the possible role of crowding forces in spatial organization of the eukaryotic genome. Using the mouse β-globin domain as a model, we demonstrated that spatial juxtaposition of the remote regulatory elements of this domain in globin-expressing cells may be lost and restored by manipulation of the level of macromolecular crowding. In addition to proving the role of crowding forces in shaping interphase chromatin, our results suggest that the folding of the chromatin fiber is a major determinant in juxtaposing remote genomic elements.
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Affiliation(s)
- Arkadiy K. Golov
- Institute of Gene Biology of the Russian Academy of Sciences, Vavilov Street 34/5, 119334, Moscow, Russia
| | - Alexey A. Gavrilov
- Institute of Gene Biology of the Russian Academy of Sciences, Vavilov Street 34/5, 119334, Moscow, Russia
| | - Sergey V. Razin
- Institute of Gene Biology of the Russian Academy of Sciences, Vavilov Street 34/5, 119334, Moscow, Russia
- Molecular Biology Department, Biological Faculty, Lomonosov Moscow State University, 119992, Moscow, Russia
- * E-mail:
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28
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Abstract
In aging societies increasing cases of neurodegenerative protein deposit diseases urge for the identification of the underlying mechanisms. Expectations are that in 2050 the percentage of population over age 60 is 42% in Japan, 34% in China, and 27% in the US. The cell nucleus is a major target of amyloid-like protein fibrillation in a variety of disorders that are characterized by widespread aggregation of proteins with instable homopolymeric amino acid repeats, ubiquitin, and other proteinaceous components. Additionally, accumulation of insoluble, SDS-resistant proteins has been identified as an intrinsic property of organismal aging. This review collects current knowledge about the composition and function of insoluble, nuclear protein inclusions from the protein homeostasis perspective. It discusses the occurrence and role of nuclear amyloid in the diseased as well as the healthy cell. Features of nuclear inclusions such as protein composition and locally active protein degradation may predict neural fitness and survival in a variety of health or disease settings.
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Affiliation(s)
- Anna von Mikecz
- a IUF - Leibniz Research Institute for Environmental Medicine at Heinrich-Heine-University; Duesseldorf, Germany
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29
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The substrate matters in the Raman spectroscopy analysis of cells. Sci Rep 2015; 5:13150. [PMID: 26310910 PMCID: PMC4550836 DOI: 10.1038/srep13150] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 07/21/2015] [Indexed: 11/08/2022] Open
Abstract
Raman spectroscopy is a powerful analytical method that allows deposited and/or immobilized cells to be evaluated without complex sample preparation or labeling. However, a main limitation of Raman spectroscopy in cell analysis is the extremely weak Raman intensity that results in low signal to noise ratios. Therefore, it is important to seize any opportunity that increases the intensity of the Raman signal and to understand whether and how the signal enhancement changes with respect to the substrate used. Our experimental results show clear differences in the spectroscopic response from cells on different surfaces. This result is partly due to the difference in spatial distribution of electric field at the substrate/cell interface as shown by numerical simulations. We found that the substrate also changes the spatial location of maximum field enhancement around the cells. Moreover, beyond conventional flat surfaces, we introduce an efficient nanostructured silver substrate that largely enhances the Raman signal intensity from a single yeast cell. This work contributes to the field of vibrational spectroscopy analysis by providing a fresh look at the significance of the substrate for Raman investigations in cell research.
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30
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Abstract
The nucleus is physically distinct from the cytoplasm in ways that suggest new ideas and approaches for interrogating the operation of this organelle. Chemical bond formation and breakage underlie the lives of cells, but as this special issue of Molecular Biology of the Cell attests, the nonchemical aspects of cell nuclei present a new frontier to biologists and biophysicists.
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Affiliation(s)
- Thoru Pederson
- Program in Cell and Developmental Dynamics, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - John F Marko
- Department of Molecular Biosciences and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208
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Nolin F, Ploton D, Wortham L, Tchelidze P, Bobichon H, Banchet V, Lalun N, Terryn C, Michel J. Targeted nano analysis of water and ions in the nucleus using cryo-correlative microscopy. Methods Mol Biol 2015; 1228:145-58. [PMID: 25311128 DOI: 10.1007/978-1-4939-1680-1_12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
The cell nucleus is a crowded volume in which the concentration of macromolecules is high. These macromolecules sequester most of the water molecules and ions which, together, are very important for stabilization and folding of proteins and nucleic acids. To better understand how the localization and quantity of water and ions vary with nuclear activity, it is necessary to study them simultaneously by using newly developed cell imaging approaches. Some years ago, we showed that dark-field cryo-Scanning Transmission Electron Microscopy (cryo-STEM) allows quantification of the mass percentages of water, dry matter, and elements (among which are ions) in freeze-dried ultrathin sections. To overcome the difficulty of clearly identifying nuclear subcompartments imaged by STEM in ultrathin cryo-sections, we developed a new cryo correlative light and STEM imaging procedure. This combines fluorescence imaging of nuclear GFP-tagged proteins to identify, within cryo ultrathin sections, regions of interest which are then analyzed by STEM for quantification of water and identification and quantification of ions. In this chapter we describe the new setup we have developed to perform this cryo-correlative light and STEM imaging approach, which allows a targeted nano analysis of water and ions in nuclear compartments.
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Affiliation(s)
- Frédérique Nolin
- Laboratoire de Recherche en Nanosciences EA 4682, UFR Sciences Exactes et Naturelles, Université de Reims Champagne Ardenne, Reims, France
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32
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Pliss A, Peng X, Liu L, Kuzmin A, Wang Y, Qu J, Li Y, Prasad PN. Single Cell Assay for Molecular Diagnostics and Medicine: Monitoring Intracellular Concentrations of Macromolecules by Two-photon Fluorescence Lifetime Imaging. Theranostics 2015; 5:919-30. [PMID: 26155309 PMCID: PMC4493531 DOI: 10.7150/thno.11863] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/03/2015] [Indexed: 02/01/2023] Open
Abstract
Molecular organization of a cell is dynamically transformed along the course of cellular physiological processes, pathologic developments or derived from interactions with drugs. The capability to measure and monitor concentrations of macromolecules in a single cell would greatly enhance studies of cellular processes in heterogeneous populations. In this communication, we introduce and experimentally validate a bio-analytical single-cell assay, wherein the overall concentration of macromolecules is estimated in specific subcellular domains, such as structure-function compartments of the cell nucleus as well as in nucleoplasm. We describe quantitative mapping of local biomolecular concentrations, either intrinsic relating to the functional and physiological state of a cell, or altered by a therapeutic drug action, using two-photon excited fluorescence lifetime imaging (FLIM). The proposed assay utilizes a correlation between the fluorescence lifetime of fluorophore and the refractive index of its microenvironment varying due to changes in the concentrations of macromolecules, mainly proteins. Two-photon excitation in Near-Infra Red biological transparency window reduced the photo-toxicity in live cells, as compared with a conventional single-photon approach. Using this new assay, we estimated average concentrations of proteins in the compartments of nuclear speckles and in the nucleoplasm at ~150 mg/ml, and in the nucleolus at ~284 mg/ml. Furthermore, we show a profound influence of pharmaceutical inhibitors of RNA synthesis on intracellular protein density. The approach proposed here will significantly advance theranostics, and studies of drug-cell interactions at the single-cell level, aiding development of personal molecular medicine.
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33
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Gavrilov AA, Razin SV. Compartmentalization of the cell nucleus and spatial organization of the genome. Mol Biol 2015. [DOI: 10.1134/s0026893315010033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Ulianov SV, Gavrilov AA, Razin SV. Nuclear Compartments, Genome Folding, and Enhancer-Promoter Communication. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:183-244. [DOI: 10.1016/bs.ircmb.2014.11.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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35
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What macromolecular crowding can do to a protein. Int J Mol Sci 2014; 15:23090-140. [PMID: 25514413 PMCID: PMC4284756 DOI: 10.3390/ijms151223090] [Citation(s) in RCA: 355] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/04/2014] [Accepted: 12/05/2014] [Indexed: 01/17/2023] Open
Abstract
The intracellular environment represents an extremely crowded milieu, with a limited amount of free water and an almost complete lack of unoccupied space. Obviously, slightly salted aqueous solutions containing low concentrations of a biomolecule of interest are too simplistic to mimic the “real life” situation, where the biomolecule of interest scrambles and wades through the tightly packed crowd. In laboratory practice, such macromolecular crowding is typically mimicked by concentrated solutions of various polymers that serve as model “crowding agents”. Studies under these conditions revealed that macromolecular crowding might affect protein structure, folding, shape, conformational stability, binding of small molecules, enzymatic activity, protein-protein interactions, protein-nucleic acid interactions, and pathological aggregation. The goal of this review is to systematically analyze currently available experimental data on the variety of effects of macromolecular crowding on a protein molecule. The review covers more than 320 papers and therefore represents one of the most comprehensive compendia of the current knowledge in this exciting area.
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36
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Slattery M, Zhou T, Yang L, Dantas Machado AC, Gordân R, Rohs R. Absence of a simple code: how transcription factors read the genome. Trends Biochem Sci 2014; 39:381-99. [PMID: 25129887 DOI: 10.1016/j.tibs.2014.07.002] [Citation(s) in RCA: 337] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 07/11/2014] [Accepted: 07/15/2014] [Indexed: 12/21/2022]
Abstract
Transcription factors (TFs) influence cell fate by interpreting the regulatory DNA within a genome. TFs recognize DNA in a specific manner; the mechanisms underlying this specificity have been identified for many TFs based on 3D structures of protein-DNA complexes. More recently, structural views have been complemented with data from high-throughput in vitro and in vivo explorations of the DNA-binding preferences of many TFs. Together, these approaches have greatly expanded our understanding of TF-DNA interactions. However, the mechanisms by which TFs select in vivo binding sites and alter gene expression remain unclear. Recent work has highlighted the many variables that influence TF-DNA binding, while demonstrating that a biophysical understanding of these many factors will be central to understanding TF function.
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Affiliation(s)
- Matthew Slattery
- Department of Biomedical Sciences, University of Minnesota Medical School, Duluth, MN 55812, USA; Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Tianyin Zhou
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Lin Yang
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Ana Carolina Dantas Machado
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, CA 90089, USA
| | - Raluca Gordân
- Center for Genomic and Computational Biology, Departments of Biostatistics and Bioinformatics, Computer Science, and Molecular Genetics and Microbiology, Duke University, Durham, NC 27708, USA.
| | - Remo Rohs
- Molecular and Computational Biology Program, Departments of Biological Sciences, Chemistry, Physics, and Computer Science, University of Southern California, Los Angeles, CA 90089, USA.
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37
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Razin SV, Iarovaia OV, Vassetzky YS. A requiem to the nuclear matrix: from a controversial concept to 3D organization of the nucleus. Chromosoma 2014; 123:217-24. [PMID: 24664318 DOI: 10.1007/s00412-014-0459-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/10/2014] [Accepted: 03/14/2014] [Indexed: 12/13/2022]
Abstract
The first papers coining the term "nuclear matrix" were published 40 years ago. Here, we review the data obtained during the nuclear matrix studies and discuss the contribution of this controversial concept to our current understanding of nuclear architecture and three-dimensional organization of genome.
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Affiliation(s)
- S V Razin
- Institute of Gene Biology of the Russian Academy of Sciences, 119334, Moscow, Russia
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38
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Lavelle C. Pack, unpack, bend, twist, pull, push: the physical side of gene expression. Curr Opin Genet Dev 2014; 25:74-84. [PMID: 24576847 DOI: 10.1016/j.gde.2014.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/03/2014] [Indexed: 12/31/2022]
Abstract
Molecular motors such as polymerases produce physical constraints on DNA and chromatin. Recent techniques, in particular single-molecule micromanipulation, provide estimation of the forces and torques at stake. These biophysical approaches have improved our understanding of chromatin behaviour under physiological physical constraints and should, in conjunction with genome wide and in vivo studies, help to build more realistic mechanistic models of transcription in the context of chromatin. Here, we wish to provide a brief overview of our current knowledge in the field, and emphasize at the same time the importance of DNA supercoiling as a major parameter in gene regulation.
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Affiliation(s)
- Christophe Lavelle
- National Museum of Natural History, Paris, France; CNRS UMR7196, Paris, France; INSERM U1154, Paris, France; Nuclear Architecture and Dynamics, CNRS GDR3536, Paris, France.
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