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Mezentsev Y, Ershov P, Yablokov E, Kaluzhskiy L, Kupriyanov K, Gnedenko O, Ivanov A. Protein Interactome Profiling of Stable Molecular Complexes in Biomaterial Lysate. Int J Mol Sci 2022; 23:15697. [PMID: 36555337 PMCID: PMC9779103 DOI: 10.3390/ijms232415697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/05/2022] [Accepted: 12/07/2022] [Indexed: 12/14/2022] Open
Abstract
Most proteins function as part of various complexes, forming via stable and dynamic protein-protein interactions (PPIs). The profiling of PPIs expands the fundamental knowledge about the structures, functions, and regulation patterns of protein complexes and intracellular molecular machineries. Protein interactomics aims at solving three main tasks: (1) identification of protein partners and parts of complex intracellular structures; (2) analysis of PPIs parameters (affinity, molecular-recognition specificity, kinetic rate constants, and thermodynamic-parameters determination); (3) the study of the functional role of novel PPIs. The purpose of this work is to update the current state and prospects of multi-omics approaches to profiling of proteins involved in the formation of stable complexes. Methodological paradigm includes a development of protein-extraction and -separation techniques from tissues or cellular lysates and subsequent identification of proteins using mass-spectrometry analysis. In addition, some aspects of authors' experimental platforms, based on high-performance size-exclusion chromatography, procedures of molecular fishing, and protein identification, as well as the possibilities of interactomic taxonomy of each protein, are discussed.
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Affiliation(s)
| | | | | | | | | | | | - Alexis Ivanov
- Institute of Biomedical Chemistry (IBMC), 119121 Moscow, Russia
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2
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Abstract
To predict transcription, one needs a mechanistic understanding of how the numerous required transcription factors (TFs) explore the nuclear space to find their target genes, assemble, cooperate, and compete with one another. Advances in fluorescence microscopy have made it possible to visualize real-time TF dynamics in living cells, leading to two intriguing observations: first, most TFs contact chromatin only transiently; and second, TFs can assemble into clusters through their intrinsically disordered regions. These findings suggest that highly dynamic events and spatially structured nuclear microenvironments might play key roles in transcription regulation that are not yet fully understood. The emerging model is that while some promoters directly convert TF-binding events into on/off cycles of transcription, many others apply complex regulatory layers that ultimately lead to diverse phenotypic outputs. Cracking this kinetic code is an ongoing and challenging task that is made possible by combining innovative imaging approaches with biophysical models.
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Affiliation(s)
- Feiyue Lu
- Institute for Systems Genetics and Cell Biology Department, NYU School of Medicine, New York, New York 10016, USA
| | - Timothée Lionnet
- Institute for Systems Genetics and Cell Biology Department, NYU School of Medicine, New York, New York 10016, USA
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3
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Zarębski M, Bosire R, Wesołowska J, Szelest O, Eatmann A, Jasińska-Konior K, Kepp O, Kroemer G, Szabo G, Dobrucki JW. Translocation of chromatin proteins to nucleoli-The influence of protein dynamics on post-fixation localization. Cytometry A 2021; 99:1230-1239. [PMID: 34110091 PMCID: PMC9543561 DOI: 10.1002/cyto.a.24464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/16/2021] [Accepted: 05/19/2021] [Indexed: 11/23/2022]
Abstract
It is expected that the subnuclear localization of a protein in a fixed cell, detected by microscopy, reflects its position in the living cell. We demonstrate, however, that some dynamic nuclear proteins can change their localization upon fixation by either crosslinking or non‐crosslinking methods. We examined the subnuclear localization of the chromatin architectural protein HMGB1, linker histone H1, and core histone H2B in cells fixed by formaldehyde, glutaraldehyde, glyoxal, ethanol, or zinc salts. We demonstrate that some dynamic, weakly binding nuclear proteins, like HMGB1 and H1, may not only be unexpectedly lost from their original binding sites during the fixation process, but they can also diffuse through the nucleus and eventually bind in nucleoli. Such translocation to nucleoli does not occur in the case of core histone H2B, which is more stably bound to DNA and other histones. We suggest that the diminished binding of some dynamic proteins to DNA during fixation, and their subsequent translocation to nucleoli, is induced by changes of DNA structure, arising from interaction with a fixative. Detachment of dynamic proteins from chromatin can also be induced in cells already fixed by non‐crosslinking methods when DNA structure is distorted by intercalating molecules. The proteins translocated during fixation from chromatin to nucleoli bind there to RNA‐containing structures.
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Affiliation(s)
- Mirosław Zarębski
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
| | - Rosevalentine Bosire
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, Debrecen, Hungary
| | - Julita Wesołowska
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
| | - Oskar Szelest
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
| | - Ahmed Eatmann
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
| | - Katarzyna Jasińska-Konior
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
| | - Oliver Kepp
- Centre de Recherche des Cordeliers, Equipe labellisée par la Ligue contre le cancer, Université de Paris, Sorbonne Université, Paris, France.,Metabolomics and Cell Biology Platforms, Institut Gustave Roussy, Villejuif, France
| | - Guido Kroemer
- Centre de Recherche des Cordeliers, Equipe labellisée par la Ligue contre le cancer, Université de Paris, Sorbonne Université, Paris, France.,Metabolomics and Cell Biology Platforms, Institut Gustave Roussy, Villejuif, France.,Pôle de Biologie, Hôpital Européen Georges Pompidou, Paris, AP-HP, France.,Suzhou Institute for Systems Medicine, Chinese Academy of Medical Sciences, Suzhou, China.,Karolinska Institute, Department of Women's and Children's Health, Karolinska University Hospital, Stockholm, Sweden
| | - Gabor Szabo
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Jurek W Dobrucki
- Department of Cell Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Poland
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4
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Ngounou Wetie AG, Sokolowska I, Channaveerappa D, Dupree EJ, Jayathirtha M, Woods AG, Darie CC. Proteomics and Non-proteomics Approaches to Study Stable and Transient Protein-Protein Interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1140:121-142. [DOI: 10.1007/978-3-030-15950-4_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Minic Z, Dahms TES, Babu M. Chromatographic separation strategies for precision mass spectrometry to study protein-protein interactions and protein phosphorylation. J Chromatogr B Analyt Technol Biomed Life Sci 2018; 1102-1103:96-108. [PMID: 30380468 DOI: 10.1016/j.jchromb.2018.10.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/19/2018] [Accepted: 10/22/2018] [Indexed: 11/30/2022]
Abstract
Investigating protein-protein interactions and protein phosphorylation can be of great significance when studying biological processes and human diseases at the molecular level. However, sample complexity, presence of low abundance proteins, and dynamic nature of the proteins often impede in achieving sufficient analytical depth in proteomics research. In this regard, chromatographic separation methodologies have played a vital role in the identification and quantification of proteins in complex sample mixtures. The combination of peptide and protein fractionation techniques with advanced high-performance mass spectrometry has allowed the researchers to successfully study the protein-protein interactions and protein phosphorylation. Several new fractionation strategies for large scale analysis of proteins and peptides have been developed to study protein-protein interactions and protein phosphorylation. These emerging chromatography methodologies have enabled the identification of several hundred protein complexes and even thousands of phosphorylation sites in a single study. In this review, we focus on current workflow strategies and chromatographic tools, highlighting their advantages and disadvantages, and examining their associated challenges and future potential.
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Affiliation(s)
- Zoran Minic
- Department of Chemistry and Biomolecular Science, University of Ottawa, John L. Holmes, Mass Spectrometry Facility, 10 Marie-Curie, Marion Hall, Room 02, Ottawa, ON K1N 1A2, Canada.
| | - Tanya E S Dahms
- Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
| | - Mohan Babu
- Department of Chemistry and Biochemistry, University of Regina, 3737 Wascana Parkway, Regina, SK S4S 0A2, Canada
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6
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Hoischen C, Monajembashi S, Weisshart K, Hemmerich P. Multimodal Light Microscopy Approaches to Reveal Structural and Functional Properties of Promyelocytic Leukemia Nuclear Bodies. Front Oncol 2018; 8:125. [PMID: 29888200 PMCID: PMC5980967 DOI: 10.3389/fonc.2018.00125] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 04/05/2018] [Indexed: 12/11/2022] Open
Abstract
The promyelocytic leukemia (pml) gene product PML is a tumor suppressor localized mainly in the nucleus of mammalian cells. In the cell nucleus, PML seeds the formation of macromolecular multiprotein complexes, known as PML nuclear bodies (PML NBs). While PML NBs have been implicated in many cellular functions including cell cycle regulation, survival and apoptosis their role as signaling hubs along major genome maintenance pathways emerged more clearly. However, despite extensive research over the past decades, the precise biochemical function of PML in these pathways is still elusive. It remains a big challenge to unify all the different previously suggested cellular functions of PML NBs into one mechanistic model. With the advent of genetically encoded fluorescent proteins it became possible to trace protein function in living specimens. In parallel, a variety of fluorescence fluctuation microscopy (FFM) approaches have been developed which allow precise determination of the biophysical and interaction properties of cellular factors at the single molecule level in living cells. In this report, we summarize the current knowledge on PML nuclear bodies and describe several fluorescence imaging, manipulation, FFM, and super-resolution techniques suitable to analyze PML body assembly and function. These include fluorescence redistribution after photobleaching, fluorescence resonance energy transfer, fluorescence correlation spectroscopy, raster image correlation spectroscopy, ultraviolet laser microbeam-induced DNA damage, erythrocyte-mediated force application, and super-resolution microscopy approaches. Since most if not all of the microscopic equipment to perform these techniques may be available in an institutional or nearby facility, we hope to encourage more researches to exploit sophisticated imaging tools for their research in cancer biology.
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7
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Erdel F, Rippe K. Formation of Chromatin Subcompartments by Phase Separation. Biophys J 2018; 114:2262-2270. [PMID: 29628210 DOI: 10.1016/j.bpj.2018.03.011] [Citation(s) in RCA: 236] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 02/19/2018] [Accepted: 03/06/2018] [Indexed: 10/17/2022] Open
Abstract
Chromatin is partitioned on multiple length scales into subcompartments that differ from each other with respect to their molecular composition and biological function. It is a key question how these compartments can form even though diffusion constantly mixes the nuclear interior and rapidly balances concentration gradients of soluble nuclear components. Different biophysical concepts are currently used to explain the formation of "chromatin bodies" in a self-organizing manner and without consuming energy. They rationalize how soluble protein factors that are dissolved in the liquid nuclear phase, the nucleoplasm, bind and organize transcriptionally active or silenced chromatin domains. In addition to cooperative binding of proteins to a preformed chromatin structure, two different mechanisms for the formation of phase-separated chromatin subcompartments have been proposed. One is based on bridging proteins that cross-link polymer segments with particular properties. Bridging can induce a collapse of the nucleosome chain and associated factors into an ordered globular phase. The other mechanism is based on multivalent interactions among soluble molecules that bind to chromatin. These interactions can induce liquid-liquid phase separation, which drives the assembly of liquid-like nuclear bodies around the respective binding sites on chromatin. Both phase separation mechanisms can explain that chromatin bodies are dynamic spherical structures, which can coalesce and are in constant and rapid exchange with the surrounding nucleoplasm. However, they make distinct predictions about how the size, density, and stability of chromatin bodies depends on the concentration and interaction behavior of the molecules involved. Here, we compare the different biophysical mechanisms for the assembly of chromatin bodies and discuss experimental strategies to distinguish them from each other. Furthermore, we outline the implications for the establishment and memory of functional chromatin state patterns.
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Affiliation(s)
- Fabian Erdel
- Division of Chromatin Networks, German Cancer Research Center (DKFZ) and Bioquant, Heidelberg, Germany.
| | - Karsten Rippe
- Division of Chromatin Networks, German Cancer Research Center (DKFZ) and Bioquant, Heidelberg, Germany.
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8
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Tavakoli M, Taylor JN, Li CB, Komatsuzaki T, Pressé S. Single Molecule Data Analysis: An Introduction. ADVANCES IN CHEMICAL PHYSICS 2017. [DOI: 10.1002/9781119324560.ch4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Meysam Tavakoli
- Physics Department; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
| | - J. Nicholas Taylor
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
| | - Chun-Biu Li
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
- Department of Mathematics; Stockholm University; 106 91 Stockholm Sweden
| | - Tamiki Komatsuzaki
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
| | - Steve Pressé
- Physics Department; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
- Department of Chemistry and Chemical Biology; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
- Department of Cell and Integrative Physiology; Indiana University School of Medicine; Indianapolis IN 46202 USA
- Department of Physics and School of Molecular Sciences; Arizona State University; Tempe AZ 85287 USA
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9
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Panamarova M, Cox A, Wicher KB, Butler R, Bulgakova N, Jeon S, Rosen B, Seong RH, Skarnes W, Crabtree G, Zernicka-Goetz M. The BAF chromatin remodelling complex is an epigenetic regulator of lineage specification in the early mouse embryo. Development 2016; 143:1271-83. [PMID: 26952987 PMCID: PMC4852518 DOI: 10.1242/dev.131961] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 02/22/2016] [Indexed: 12/16/2022]
Abstract
Dynamic control of gene expression is essential for the development of a totipotent zygote into an embryo with defined cell lineages. The accessibility of genes responsible for cell specification to transcriptional machinery is dependent on chromatin remodelling complexes such as the SWI\SNF (BAF) complex. However, the role of the BAF complex in early mouse development has remained unclear. Here, we demonstrate that BAF155, a major BAF complex subunit, regulates the assembly of the BAF complex in vivo and regulates lineage specification of the mouse blastocyst. We find that associations of BAF155 with other BAF complex subunits become enriched in extra-embryonic lineages just prior to implantation. This enrichment is attributed to decreased mobility of BAF155 in extra-embryonic compared with embryonic lineages. Downregulation of BAF155 leads to increased expression of the pluripotency marker Nanog and its ectopic expression in extra-embryonic lineages, whereas upregulation of BAF155 leads to the upregulation of differentiation markers. Finally, we show that the arginine methyltransferase CARM1 methylates BAF155, which differentially influences assembly of the BAF complex between the lineages and the expression of pluripotency markers. Together, our results indicate a novel role of BAF-dependent chromatin remodelling in mouse development via regulation of lineage specification. Summary: Associations of BAF155 with other BAF complex subunits are enriched in extra-embryonic lineages prior to implantation, while changes in BAF155 levels modulate the expression of early developmental markers.
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Affiliation(s)
- Maryna Panamarova
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Andy Cox
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Krzysztof B Wicher
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - Richard Butler
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Natalia Bulgakova
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK Bateson Centre and Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Shin Jeon
- Department of Biological Sciences, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-747, South Korea
| | - Barry Rosen
- Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK
| | - Rho H Seong
- Department of Biological Sciences, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-747, South Korea
| | | | - Gerald Crabtree
- Department of Developmental Biology, Stanford University Medical School, Stanford, CA 94305, USA
| | - Magdalena Zernicka-Goetz
- Wellcome Trust Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge CB2 1QN, UK Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
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10
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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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11
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Fritz A, Barutcu AR, Martin-Buley L, vanWijnen AJ, Zaidi SK, Imbalzano AN, Lian JB, Stein JL, Stein GS. Chromosomes at Work: Organization of Chromosome Territories in the Interphase Nucleus. J Cell Biochem 2016; 117:9-19. [PMID: 26192137 PMCID: PMC4715719 DOI: 10.1002/jcb.25280] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 07/17/2015] [Indexed: 12/26/2022]
Abstract
The organization of interphase chromosomes in chromosome territories (CTs) was first proposed more than one hundred years ago. The introduction of increasingly sophisticated microscopic and molecular techniques, now provide complementary strategies for studying CTs in greater depth than ever before. Here we provide an overview of these strategies and how they are being used to elucidate CT interactions and the role of these dynamically regulated, nuclear-structure building blocks in directly supporting nuclear function in a physiologically responsive manner.
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Affiliation(s)
- Andrew Fritz
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
| | - A. Rasim Barutcu
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Lori Martin-Buley
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
| | - André J. vanWijnen
- Departments of Orthopedic Surgery and Biochemistry & Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Sayyed K. Zaidi
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
| | - Anthony N. Imbalzano
- Department of Cell and Developmental Biology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA
| | - Jane B. Lian
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
| | - Janet L. Stein
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
| | - Gary S. Stein
- University of Vermont Cancer Center, Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405, USA
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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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13
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Tsekouras K, Siegel AP, Day RN, Pressé S. Inferring diffusion dynamics from FCS in heterogeneous nuclear environments. Biophys J 2015; 109:7-17. [PMID: 26153697 PMCID: PMC4572512 DOI: 10.1016/j.bpj.2015.05.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 05/20/2015] [Accepted: 05/28/2015] [Indexed: 01/08/2023] Open
Abstract
Fluorescence correlation spectroscopy (FCS) is a noninvasive technique that probes the diffusion dynamics of proteins down to single-molecule sensitivity in living cells. Critical mechanistic insight is often drawn from FCS experiments by fitting the resulting time-intensity correlation function, G(t), to known diffusion models. When simple models fail, the complex diffusion dynamics of proteins within heterogeneous cellular environments can be fit to anomalous diffusion models with adjustable anomalous exponents. Here, we take a different approach. We use the maximum entropy method to show-first using synthetic data-that a model for proteins diffusing while stochastically binding/unbinding to various affinity sites in living cells gives rise to a G(t) that could otherwise be equally well fit using anomalous diffusion models. We explain the mechanistic insight derived from our method. In particular, using real FCS data, we describe how the effects of cell crowding and binding to affinity sites manifest themselves in the behavior of G(t). Our focus is on the diffusive behavior of an engineered protein in 1) the heterochromatin region of the cell's nucleus as well as 2) in the cell's cytoplasm and 3) in solution. The protein consists of the basic region-leucine zipper (BZip) domain of the CCAAT/enhancer-binding protein (C/EBP) fused to fluorescent proteins.
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Affiliation(s)
| | - Amanda P Siegel
- Integrated Nanosystems Development Institute, IUPUI, Indianapolis Indiana
| | - Richard N Day
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Steve Pressé
- Department of Physics, IUPUI, Indianapolis Indiana; Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.
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14
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Cattoni DI, Valeri A, Le Gall A, Nollmann M. A matter of scale: how emerging technologies are redefining our view of chromosome architecture. Trends Genet 2015; 31:454-64. [PMID: 26113398 DOI: 10.1016/j.tig.2015.05.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 11/25/2022]
Abstract
The 3D folding of the genome and its relation to fundamental processes such as gene regulation, replication, and segregation remains one of the most puzzling and exciting questions in genetics. In this review, we describe how the use of new technologies is starting to revolutionize the field of chromosome organization, and to shed light on the mechanisms of transcription, replication, and repair. In particular, we concentrate on recent studies using genome-wide methods, single-molecule technologies, and super-resolution microscopy (SRM). We summarize some of the main concerns when employing these techniques, and discuss potential new and exciting perspectives that illuminate the connection between 3D genomic organization and gene regulation.
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Affiliation(s)
- Diego I Cattoni
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université de Montpellier, 29 rue de Navacelles, 34090 Montpellier, France
| | - Alessandro Valeri
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université de Montpellier, 29 rue de Navacelles, 34090 Montpellier, France
| | - Antoine Le Gall
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université de Montpellier, 29 rue de Navacelles, 34090 Montpellier, France
| | - Marcelo Nollmann
- Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Université de Montpellier, 29 rue de Navacelles, 34090 Montpellier, France.
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15
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Ollion J, Loll F, Cochennec J, Boudier T, Escudé C. Proliferation-dependent positioning of individual centromeres in the interphase nucleus of human lymphoblastoid cell lines. Mol Biol Cell 2015; 26:2550-60. [PMID: 25947134 PMCID: PMC4571307 DOI: 10.1091/mbc.e14-05-1002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 04/27/2015] [Indexed: 01/01/2023] Open
Abstract
Centromeres are not randomly distributed in interphase nuclei. High-throughput imaging provides an accurate characterization of how their organization varies as a function of the proliferation state in human lymphoblastoid cells. The results suggest the existence of mechanisms that drive the nuclear positioning of centromeres. The cell nucleus is a highly organized structure and plays an important role in gene regulation. Understanding the mechanisms that sustain this organization is therefore essential for understanding genome function. Centromeric regions (CRs) of chromosomes have been known for years to adopt specific nuclear positioning patterns, but the significance of this observation is not yet completely understood. Here, using a combination of fluorescence in situ hybridization and immunochemistry on fixed human cells and high-throughput imaging, we directly and quantitatively investigated the nuclear positioning of specific human CRs. We observe differential attraction of individual CRs toward both the nuclear border and the nucleoli, the former being enhanced in nonproliferating cells and the latter being enhanced in proliferating cells. Similar positioning patterns are observed in two different lymphoblastoid cell lines. Moreover, the positioning of CRs differs from that of noncentromeric regions, and CRs display specific orientations within chromosome territories. These results suggest the existence of not-yet-characterized mechanisms that drive the nuclear positioning of CRs and therefore pave the way toward a better understanding of how CRs affect nuclear organization.
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Affiliation(s)
- Jean Ollion
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - François Loll
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Julien Cochennec
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
| | - Thomas Boudier
- Université Pierre et Marie Curie, Sorbonne Universités, 75005 Paris, France
| | - Christophe Escudé
- Institut National de la Santé et de la Recherche Médicale U1154, Centre National de la Recherche Scientifique UMR7196, Muséum National d'Histoire Naturelle, 75231 Paris, France
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16
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Arnhold F, Gührs KH, von Mikecz A. Amyloid domains in the cell nucleus controlled by nucleoskeletal protein lamin B1 reveal a new pathway of mercury neurotoxicity. PeerJ 2015; 3:e754. [PMID: 25699204 PMCID: PMC4327309 DOI: 10.7717/peerj.754] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/19/2015] [Indexed: 01/17/2023] Open
Abstract
Mercury (Hg) is a bioaccumulating trace metal that globally circulates the atmosphere and waters in its elemental, inorganic and organic chemical forms. While Hg represents a notorious neurotoxicant, the underlying cellular pathways are insufficiently understood. We identify amyloid protein aggregation in the cell nucleus as a novel pathway of Hg-bio-interactions. By mass spectrometry of purified protein aggregates, a subset of spliceosomal components and nucleoskeletal protein lamin B1 were detected as constituent parts of an Hg-induced nuclear aggregome network. The aggregome network was located by confocal imaging of amyloid-specific antibodies and dyes to amyloid cores within splicing-speckles that additionally recruit components of the ubiquitin-proteasome system. Hg significantly enhances global proteasomal activity in the nucleus, suggesting that formation of amyloid speckles plays a role in maintenance of protein homeostasis. RNAi knock down showed that lamin B1 for its part regulates amyloid speckle formation and thus likewise participates in nuclear protein homeostasis. As the Hg-induced cascade of interactions between the nucleoskeleton and protein homeostasis reduces neuronal signalling, amyloid fibrillation in the cell nucleus is introduced as a feature of Hg-neurotoxicity that opens new avenues of future research. Similar to protein aggregation events in the cytoplasm that are controlled by the cytoskeleton, amyloid fibrillation of nuclear proteins may be driven by the nucleoskeleton.
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Affiliation(s)
- Florian Arnhold
- IUF-Leibniz Research Institute for Environmental Medicine at Heinrich-Heine-University Duesseldorf , Duesseldorf , Germany
| | - Karl-Heinz Gührs
- CF Proteomics, FLI-Leibniz-Institute for Age Research, Fritz-Lipman-Institute e.V. , Jena , Germany
| | - Anna von Mikecz
- IUF-Leibniz Research Institute for Environmental Medicine at Heinrich-Heine-University Duesseldorf , Duesseldorf , Germany
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17
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Feilke M, Schneider K, Schmid VJ. Bayesian mixed-effects model for the analysis of a series of FRAP images. Stat Appl Genet Mol Biol 2014; 14:35-51. [PMID: 25503866 DOI: 10.1515/sagmb-2014-0013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The binding behavior of molecules in nuclei of living cells can be studied through the analysis of images from fluorescence recovery after photobleaching experiments. However, there is still a lack of methodology for the statistical evaluation of FRAP data, especially for the joint analysis of multiple dynamic images. We propose a hierarchical Bayesian nonlinear model with mixed-effect priors based on local compartment models in order to obtain joint parameter estimates for all nuclei as well as to account for the heterogeneity of the nuclei population. We apply our method to a series of FRAP experiments of DNA methyltransferase 1 tagged to green fluorescent protein expressed in a somatic mouse cell line and compare the results to the application of three different fixed-effects models to the same series of FRAP experiments. With the proposed model, we get estimates of the off-rates of the interactions of the molecules under study together with credible intervals, and additionally gain information about the variability between nuclei. The proposed model is superior to and more robust than the tested fixed-effects models. Therefore, it can be used for the joint analysis of data from FRAP experiments on various similar nuclei.
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18
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Viswanathan R, Hoffman EA, Shetty SJ, Bekiranov S, Auble DT. Analysis of chromatin binding dynamics using the crosslinking kinetics (CLK) method. Methods 2014; 70:97-107. [PMID: 25448301 PMCID: PMC4267959 DOI: 10.1016/j.ymeth.2014.10.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 10/17/2014] [Accepted: 10/27/2014] [Indexed: 02/03/2023] Open
Abstract
Transcription factor binding sites in chromatin are routinely inventoried by the chromatin immunoprecipitation assay, and these binding patterns can provide precise and detailed information about cell state. However, some fundamental molecular questions regarding transcription factor function require an understanding of in vivo binding dynamics as well as location information. Here we describe the crosslinking kinetics (CLK) assay, in which the time-dependence of formaldehyde crosslinking is used to extract on- and off-rates for chromatin binding in vivo.
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Affiliation(s)
- Ramya Viswanathan
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, United States
| | - Elizabeth A Hoffman
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, United States
| | - Savera J Shetty
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, United States
| | - Stefan Bekiranov
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, United States
| | - David T Auble
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, VA 22908, United States.
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19
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Pathak RU, Srinivasan A, Mishra RK. Genome-wide mapping of matrix attachment regions in Drosophila melanogaster. BMC Genomics 2014; 15:1022. [PMID: 25424749 PMCID: PMC4301625 DOI: 10.1186/1471-2164-15-1022] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 11/12/2014] [Indexed: 12/12/2022] Open
Abstract
Background Eukaryotic genome acquires functionality upon proper packaging within the nucleus. This process is facilitated by the structural framework of Nuclear Matrix, a nucleo-proteinaceous meshwork. Matrix Attachment Regions (MARs) in the genome serve as anchoring sites to this framework. Results Here we report direct sequencing of the MAR preparation from Drosophila melanogaster embryos and identify >7350 MARs. This amounts to ~2.5% of the fly genome and often coincide with AT rich non-coding regions. We find significant association of MARs with the origins of replication, transcription start sites, paused RNA Polymerase II sites and exons, but not introns, of highly expressed genes. We also identified sequence motifs and repeats that constitute MARs. Conclusion Our data reveal the contact points of genome to the nuclear architecture and provide a link between nuclear functions and genomic packaging. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1022) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | - Rakesh K Mishra
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India.
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20
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Zhen CY, Duc HN, Kokotovic M, Phiel CJ, Ren X. Cbx2 stably associates with mitotic chromosomes via a PRC2- or PRC1-independent mechanism and is needed for recruiting PRC1 complex to mitotic chromosomes. Mol Biol Cell 2014; 25:3726-39. [PMID: 25232004 PMCID: PMC4230780 DOI: 10.1091/mbc.e14-06-1109] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cbx2 is immobilized at mitotic chromosomes, and the immobilization is independent of PRC1 or PRC2. Cbx2 plays important roles in recruiting PRC1 complex to mitotic chromosomes. This study provides novel insights into the PcG epigenetic memory passing down through cell divisions. Polycomb group (PcG) proteins are epigenetic transcriptional factors that repress key developmental regulators and maintain cellular identity through mitosis via a poorly understood mechanism. Using quantitative live-cell imaging in mouse ES cells and tumor cells, we demonstrate that, although Polycomb repressive complex (PRC) 1 proteins (Cbx-family proteins, Ring1b, Mel18, and Phc1) exhibit variable capacities of association with mitotic chromosomes, Cbx2 overwhelmingly binds to mitotic chromosomes. The recruitment of Cbx2 to mitotic chromosomes is independent of PRC1 or PRC2, and Cbx2 is needed to recruit PRC1 complex to mitotic chromosomes. Quantitative fluorescence recovery after photobleaching analysis indicates that PRC1 proteins rapidly exchange at interphasic chromatin. On entry into mitosis, Cbx2, Ring1b, Mel18, and Phc1 proteins become immobilized at mitotic chromosomes, whereas other Cbx-family proteins dynamically bind to mitotic chromosomes. Depletion of PRC1 or PRC2 protein has no effect on the immobilization of Cbx2 on mitotic chromosomes. We find that the N-terminus of Cbx2 is needed for its recruitment to mitotic chromosomes, whereas the C-terminus is required for its immobilization. Thus these results provide fundamental insights into the molecular mechanisms of epigenetic inheritance.
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Affiliation(s)
- Chao Yu Zhen
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364
| | - Huy Nguyen Duc
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364
| | - Marko Kokotovic
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364
| | - Christopher J Phiel
- Department of Integrative Biology, University of Colorado Denver, Denver, CO 80217-3364
| | - Xiaojun Ren
- Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364
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21
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Hendrix J, van Heertum B, Vanstreels E, Daelemans D, De Rijck J. Dynamics of the ternary complex formed by c-Myc interactor JPO2, transcriptional co-activator LEDGF/p75, and chromatin. J Biol Chem 2014; 289:12494-506. [PMID: 24634210 DOI: 10.1074/jbc.m113.525964] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Lens epithelium-derived growth factor (LEDGF/p75) is a transcriptional co-activator involved in targeting human immunodeficiency virus (HIV) integration and the development of MLL fusion-mediated acute leukemia. A previous study revealed that LEDGF/p75 dynamically scans the chromatin, and upon interaction with HIV-1 integrase, their complex is locked on chromatin. At present, it is not known whether LEDGF/p75-mediated chromatin locking is typical for interacting proteins. Here, we employed continuous photobleaching and fluorescence correlation and cross-correlation spectroscopy to investigate in vivo chromatin binding of JPO2, a LEDGF/p75- and c-Myc-interacting protein involved in transcriptional regulation. In the absence of LEDGF/p75, JPO2 performs chromatin scanning inherent to transcription factors. However, whereas the dynamics of JPO2 chromatin binding are decelerated upon interaction with LEDGF/p75, very strong locking of their complex onto chromatin is absent. Similar results were obtained with the domesticated transposase PogZ, another cellular interaction partner of LEDGF/p75. We furthermore show that diffusive JPO2 can oligomerize; that JPO2 and LEDGF/p75 interact directly and specifically in vivo through the specific interaction domain of JPO2 and the C-terminal domain of LEDGF/p75, comprising the integrase-binding domain; and that modulation of JPO2 dynamics requires a functional PWWP domain in LEDGF/p75. Our results suggest that the dynamics of the LEDGF/p75-chromatin interaction depend on the specific partner and that strong chromatin locking is not a property of all LEDGF/p75-binding proteins.
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Affiliation(s)
- Jelle Hendrix
- From the Laboratory for Photochemistry and Spectroscopy, Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
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22
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Biomolecular dynamics and binding studies in the living cell. Phys Life Rev 2014; 11:1-30. [DOI: 10.1016/j.plrev.2013.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 11/20/2013] [Indexed: 11/22/2022]
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23
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Ngounou Wetie AG, Sokolowska I, Woods AG, Roy U, Deinhardt K, Darie CC. Protein-protein interactions: switch from classical methods to proteomics and bioinformatics-based approaches. Cell Mol Life Sci 2014; 71:205-28. [PMID: 23579629 PMCID: PMC11113707 DOI: 10.1007/s00018-013-1333-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 03/25/2013] [Accepted: 03/26/2013] [Indexed: 11/28/2022]
Abstract
Following the sequencing of the human genome and many other organisms, research on protein-coding genes and their functions (functional genomics) has intensified. Subsequently, with the observation that proteins are indeed the molecular effectors of most cellular processes, the discipline of proteomics was born. Clearly, proteins do not function as single entities but rather as a dynamic network of team players that have to communicate. Though genetic (yeast two-hybrid Y2H) and biochemical methods (co-immunoprecipitation Co-IP, affinity purification AP) were the methods of choice at the beginning of the study of protein-protein interactions (PPI), in more recent years there has been a shift towards proteomics-based methods and bioinformatics-based approaches. In this review, we first describe in depth PPIs and we make a strong case as to why unraveling the interactome is the next challenge in the field of proteomics. Furthermore, classical methods of investigation of PPIs and structure-based bioinformatics approaches are presented. The greatest emphasis is placed on proteomic methods, especially native techniques that were recently developed and that have been shown to be reliable. Finally, we point out the limitations of these methods and the need to set up a standard for the validation of PPI experiments.
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Affiliation(s)
- Armand G. Ngounou Wetie
- Department of Chemistry and Biomolecular Science, Biochemistry and Proteomics Group, Clarkson University, 8 Clarkson Avenue, Potsdam, NY 13699-5810 USA
| | - Izabela Sokolowska
- Department of Chemistry and Biomolecular Science, Biochemistry and Proteomics Group, Clarkson University, 8 Clarkson Avenue, Potsdam, NY 13699-5810 USA
| | - Alisa G. Woods
- Department of Chemistry and Biomolecular Science, Biochemistry and Proteomics Group, Clarkson University, 8 Clarkson Avenue, Potsdam, NY 13699-5810 USA
| | - Urmi Roy
- Department of Chemistry and Biomolecular Science, Biochemistry and Proteomics Group, Clarkson University, 8 Clarkson Avenue, Potsdam, NY 13699-5810 USA
| | - Katrin Deinhardt
- Centre for Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ UK
- Institute for Life Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ UK
| | - Costel C. Darie
- Department of Chemistry and Biomolecular Science, Biochemistry and Proteomics Group, Clarkson University, 8 Clarkson Avenue, Potsdam, NY 13699-5810 USA
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Mass Spectrometric Analysis of Post-translational Modifications (PTMs) and Protein–Protein Interactions (PPIs). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 806:205-35. [DOI: 10.1007/978-3-319-06068-2_9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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25
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Crowded chromatin is not sufficient for heterochromatin formation and not required for its maintenance. J Struct Biol 2013; 184:445-53. [PMID: 24145303 DOI: 10.1016/j.jsb.2013.10.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 09/30/2013] [Accepted: 10/03/2013] [Indexed: 11/22/2022]
Abstract
In contrast to cytoplasmic organelles, which are usually separated from the rest of the cell by phospholipid membranes, nuclear compartments are readily accessible to diffusing proteins and must rely on different mechanisms to maintain their integrity. Specific interactions between scaffolding proteins are known to have important roles for the formation and maintenance of nuclear structures. General physical mechanisms such as molecular crowding, phase separation or colloidal behavior have also been suggested, but their physiological significance remains uncertain. For macromolecular crowding, a role in the maintenance of nucleoli and promyelocytic leukemia (PML) nuclear bodies has been shown. Here, we tested whether a modulation of the compaction state of chromatin, which directly influences the local crowding state, has an impact on the formation and maintenance of densely packed heterochromatin. By osmotic perturbations, we could modify the packing state of chromatin in a controlled manner and show that chromatin compaction, which is associated with increased crowding conditions, is not, per se, sufficient to initiate the formation of new bona fide heterochromatin structures nor is it necessary to maintain already established heterochromatin domains. In consequence, if an increase in crowding induced by chromatin compaction maybe an early step in heterochromatin formation, specific protein-protein interactions are nevertheless required to make heterochromatin long lasting and independent of the crowding state.
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26
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Mueller F, Stasevich TJ, Mazza D, McNally JG. Quantifying transcription factor kinetics: at work or at play? Crit Rev Biochem Mol Biol 2013; 48:492-514. [PMID: 24025032 DOI: 10.3109/10409238.2013.833891] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Transcription factors (TFs) interact dynamically in vivo with chromatin binding sites. Here we summarize and compare the four different techniques that are currently used to measure these kinetics in live cells, namely fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), single molecule tracking (SMT) and competition ChIP (CC). We highlight the principles underlying each of these approaches as well as their advantages and disadvantages. A comparison of data from each of these techniques raises an important question: do measured transcription kinetics reflect biologically functional interactions at specific sites (i.e. working TFs) or do they reflect non-specific interactions (i.e. playing TFs)? To help resolve this dilemma we discuss five key unresolved biological questions related to the functionality of transient and prolonged binding events at both specific promoter response elements as well as non-specific sites. In support of functionality, we review data suggesting that TF residence times are tightly regulated, and that this regulation modulates transcriptional output at single genes. We argue that in addition to this site-specific regulatory role, TF residence times also determine the fraction of promoter targets occupied within a cell thereby impacting the functional status of cellular gene networks. Thus, TF residence times are key parameters that could influence transcription in multiple ways.
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Affiliation(s)
- Florian Mueller
- Institut Pasteur, Computational Imaging and Modeling Unit, CNRS , Paris , France
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27
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Herbomel G, Kloster-Landsberg M, Folco EG, Col E, Usson Y, Vourc’h C, Delon A, Souchier C. Dynamics of the full length and mutated heat shock factor 1 in human cells. PLoS One 2013; 8:e67566. [PMID: 23861773 PMCID: PMC3704536 DOI: 10.1371/journal.pone.0067566] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Accepted: 05/23/2013] [Indexed: 11/24/2022] Open
Abstract
Heat shock factor 1 is the key transcription factor of the heat shock response. Its function is to protect the cell against the deleterious effects of stress. Upon stress, HSF1 binds to and transcribes hsp genes and repeated satellite III (sat III) sequences present at the 9q12 locus. HSF1 binding to pericentric sat III sequences forms structures known as nuclear stress bodies (nSBs). nSBs represent a natural amplification of RNA pol II dependent transcription sites. Dynamics of HSF1 and of deletion mutants were studied in living cells using multi-confocal Fluorescence Correlation Spectroscopy (mFCS) and Fluorescence Recovery After Photobleaching (FRAP). In this paper, we show that HSF1 dynamics modifications upon heat shock result from both formation of high molecular weight complexes and increased HSF1 interactions with chromatin. These interactions involve both DNA binding with Heat Shock Element (HSE) and sat III sequences and a more transient sequence-independent binding likely corresponding to a search for more specific targets. We find that the trimerization domain is required for low affinity interactions with chromatin while the DNA binding domain is required for site-specific interactions of HSF1 with DNA.
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Affiliation(s)
- Gaëtan Herbomel
- INSERM, University Grenoble 1, IAB CRI U823 team 10, La Tronche, France
| | | | - Eric G. Folco
- INSERM, University Grenoble 1, IAB CRI U823 team 10, La Tronche, France
| | - Edwige Col
- INSERM, University Grenoble 1, IAB CRI U823 team 10, La Tronche, France
| | - Yves Usson
- University Grenoble I, CNRS, TIMC-IMAG UMR5525, La Tronche, France
| | - Claire Vourc’h
- INSERM, University Grenoble 1, IAB CRI U823 team 10, La Tronche, France
| | - Antoine Delon
- University Grenoble 1, CNRS, LIPhy UMR 5588, St Martin d’Hères, France
| | - Catherine Souchier
- INSERM, University Grenoble 1, IAB CRI U823 team 10, La Tronche, France
- * E-mail:
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28
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Michel D. Kinetic approaches to lactose operon induction and bimodality. J Theor Biol 2013; 325:62-75. [PMID: 23454080 DOI: 10.1016/j.jtbi.2013.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Revised: 02/08/2013] [Accepted: 02/12/2013] [Indexed: 11/25/2022]
Abstract
The quasi-equilibrium approximation is acceptable when molecular interactions are fast enough compared to circuit dynamics, but is no longer allowed when cellular activities are governed by rare events. A typical example is the lactose operon (lac), one of the most famous paradigms of transcription regulation, for which several theories still coexist to describe its behaviors. The lac system is generally analyzed by using equilibrium constants, contradicting single-event hypotheses long suggested by Novick and Weiner (1957). Enzyme induction as an all-or-none phenomenon. Proc. Natl. Acad. Sci. USA 43, 553-566) and recently refined in the study of (Choi et al., 2008. A stochastic single-molecule event triggers phenotype switching of a bacterial cell. Science 322, 442-446). In the present report, a lac repressor (LacI)-mediated DNA immunoprecipitation experiment reveals that the natural LacI-lac DNA complex built in vivo is extremely tight and long-lived compared to the time scale of lac expression dynamics, which could functionally disconnect the abortive expression bursts and forbid using the standard modes of lac bistability. As alternatives, purely kinetic mechanisms are examined for their capacity to restrict induction through: (i) widely scattered derepression related to the arrival time variance of a predominantly backward asymmetric random walk and (ii) an induction threshold arising in a single window of derepression without recourse to nonlinear multimeric binding and Hill functions. Considering the complete disengagement of the lac repressor from the lac promoter as the probabilistic consequence of a transient stepwise mechanism, is sufficient to explain the sigmoidal lac responses as functions of time and of inducer concentration. This sigmoidal shape can be misleadingly interpreted as a phenomenon of equilibrium cooperativity classically used to explain bistability, but which has been reported to be weak in this system.
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Affiliation(s)
- Denis Michel
- Universite de Rennes1-IRSET, Campus de Beaulieu Bat. 13, 35042 Rennes Cedex, France.
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29
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Brehm MA, Wundenberg T, Williams J, Mayr GW, Shears SB. A non-catalytic role for inositol 1,3,4,5,6-pentakisphosphate 2-kinase in the synthesis of ribosomal RNA. J Cell Sci 2012. [PMID: 23203802 DOI: 10.1242/jcs.110031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Fundamental to the life and destiny of every cell is the regulation of protein synthesis through ribosome biogenesis, which begins in the nucleolus with the production of ribosomal RNA (rRNA). Nucleolar organization is a highly dynamic and tightly regulated process; the structural factors that direct nucleolar assembly and disassembly are just as important in controlling rRNA synthesis as are the catalytic activities that synthesize rRNA. Here, we report that a signaling enzyme, inositol 1,3,4,5,6-pentakisphosphate 2-kinase (IP5K) is also a structural component in the nucleolus. We demonstrate that IP5K has functionally significant interactions with three proteins that regulate rRNA synthesis: protein kinase CK2, TCOF1 and upstream-binding-factor (UBF). Through molecular modeling and mutagenic studies, we identified an Arg-Lys-Lys tripeptide located on the surface of IP5K that mediates its association with UBF. Nucleolar IP5K spatial dynamics were sensitive to experimental procedures (serum starvation or addition of actinomycin D) that inhibited rRNA production. We show that IP5K makes stoichiometrically sensitive contributions to the architecture of the nucleoli in intact cells, thereby influencing the degree of rRNA synthesis. Our study adds significantly to the biological significance of IP5K; previously, it was the kinase activity of this protein that had attracted attention. Our demonstration that IP5K 'moonlights' as a molecular scaffold offers an unexpected new example of how the biological sophistication of higher organisms can arise from gene products acquiring multiple functions, rather than by an increase in gene number.
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Affiliation(s)
- Maria A Brehm
- Inositol Signaling Section, Laboratory of Signal Transduction, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA
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30
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Henderson BR. The BRCA1 Breast Cancer Suppressor: Regulation of Transport, Dynamics, and Function at Multiple Subcellular Locations. SCIENTIFICA 2012; 2012:796808. [PMID: 24278741 PMCID: PMC3820561 DOI: 10.6064/2012/796808] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 09/18/2012] [Indexed: 06/02/2023]
Abstract
Inherited mutations in the BRCA1 gene predispose to a higher risk of breast/ovarian cancer. The BRCA1 tumor suppressor is a 1863 amino acid protein with multiple protein interaction domains that facilitate its roles in regulating DNA repair and maintenance, cell cycle progression, transcription, and cell survival/apoptosis. BRCA1 was first identified as a nuclear phosphoprotein, but has since been shown to contain different transport sequences including nuclear export and nuclear localization signals that enable it to shuttle between specific sites within the nucleus and cytoplasm, including DNA repair foci, centrosomes, and mitochondria. BRCA1 nuclear transport and ubiquitin E3 ligase enzymatic activity are tightly regulated by the BRCA1 dimeric binding partner BARD1 and further modulated by cancer mutations and diverse signaling pathways. This paper will focus on the transport, dynamics, and multiple intracellular destinations of BRCA1 with emphasis on how regulation of these events has impact on, and determines, a broad range of important cellular functions.
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Affiliation(s)
- Beric R. Henderson
- Westmead Institute for Cancer Research, Westmead Millennium Institute at Westmead Hospital, University of Sydney, Darcy Road, P.O. Box 412, Westmead, NSW 2145, Australia
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31
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Ulbricht T, Alzrigat M, Horch A, Reuter N, von Mikecz A, Steimle V, Schmitt E, Krämer OH, Stamminger T, Hemmerich P. PML promotes MHC class II gene expression by stabilizing the class II transactivator. ACTA ACUST UNITED AC 2012; 199:49-63. [PMID: 23007646 PMCID: PMC3461510 DOI: 10.1083/jcb.201112015] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Promyelocytic leukemia (PML) nuclear bodies selectively associate with transcriptionally active genomic regions, including the gene-rich major histocompatibility (MHC) locus. In this paper, we have explored potential links between PML and interferon (IFN)-γ-induced MHC class II expression. IFN-γ induced a substantial increase in the spatial proximity between PML bodies and the MHC class II gene cluster in different human cell types. Knockdown experiments show that PML is required for efficient IFN-γ-induced MHC II gene transcription through regulation of the class II transactivator (CIITA). PML mediates this function through protection of CIITA from proteasomal degradation. We also show that PML isoform II specifically forms a stable complex with CIITA at PML bodies. These observations establish PML as a coregulator of IFN-γ-induced MHC class II expression.
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Affiliation(s)
- Tobias Ulbricht
- Leibniz Institute for Age Research, Fritz-Lipmann Institute, 07745 Jena, Germany
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32
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Eskat A, Deng W, Hofmeister A, Rudolphi S, Emmerth S, Hellwig D, Ulbricht T, Döring V, Bancroft JM, McAinsh AD, Cardoso MC, Meraldi P, Hoischen C, Leonhardt H, Diekmann S. Step-wise assembly, maturation and dynamic behavior of the human CENP-P/O/R/Q/U kinetochore sub-complex. PLoS One 2012; 7:e44717. [PMID: 23028590 PMCID: PMC3445539 DOI: 10.1371/journal.pone.0044717] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 08/06/2012] [Indexed: 11/18/2022] Open
Abstract
Kinetochores are multi-protein megadalton assemblies that are required for attachment of microtubules to centromeres and, in turn, the segregation of chromosomes in mitosis. Kinetochore assembly is a cell cycle regulated multi-step process. The initial step occurs during interphase and involves loading of the 15-subunit constitutive centromere associated complex (CCAN), which contains a 5-subunit (CENP-P/O/R/Q/U) sub-complex. Here we show using a fluorescent three-hybrid (F3H) assay and fluorescence resonance energy transfer (FRET) in living mammalian cells that CENP-P/O/R/Q/U subunits exist in a tightly packed arrangement that involves multifold protein-protein interactions. This sub-complex is, however, not pre-assembled in the cytoplasm, but rather assembled on kinetochores through the step-wise recruitment of CENP-O/P heterodimers and the CENP-P, -O, -R, -Q and -U single protein units. SNAP-tag experiments and immuno-staining indicate that these loading events occur during S-phase in a manner similar to the nucleosome binding components of the CCAN, CENP-T/W/N. Furthermore, CENP-P/O/R/Q/U binding to the CCAN is largely mediated through interactions with the CENP-N binding protein CENP-L as well as CENP-K. Once assembled, CENP-P/O/R/Q/U exchanges slowly with the free nucleoplasmic pool indicating a low off-rate for individual CENP-P/O/R/Q/U subunits. Surprisingly, we then find that during late S-phase, following the kinetochore-binding step, both CENP-Q and -U but not -R undergo oligomerization. We propose that CENP-P/O/R/Q/U self-assembles on kinetochores with varying stoichiometry and undergoes a pre-mitotic maturation step that could be important for kinetochores switching into the correct conformation necessary for microtubule-attachment.
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Affiliation(s)
| | - Wen Deng
- Department of Biology II, Center for Integrated Protein Science, Ludwig Maximilians University Munich, Planegg-Martinsried, Munich, Germany
| | | | | | | | | | | | | | - James M. Bancroft
- Centre for Mechanochemical Cell Biology, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | - Andrew D. McAinsh
- Centre for Mechanochemical Cell Biology, Warwick Medical School, University of Warwick, Coventry, United Kingdom
| | | | | | | | - Heinrich Leonhardt
- Department of Biology II, Center for Integrated Protein Science, Ludwig Maximilians University Munich, Planegg-Martinsried, Munich, Germany
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33
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Geng Y, Monajembashi S, Shao A, Cui D, He W, Chen Z, Hemmerich P, Tang J. Contribution of the C-terminal regions of promyelocytic leukemia protein (PML) isoforms II and V to PML nuclear body formation. J Biol Chem 2012; 287:30729-42. [PMID: 22773875 PMCID: PMC3436317 DOI: 10.1074/jbc.m112.374769] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 06/25/2012] [Indexed: 12/12/2022] Open
Abstract
Promyelocytic leukemia protein (PML) nuclear bodies are dynamic and heterogeneous nuclear protein complexes implicated in various important functions, most notably tumor suppression. PML is the structural component of PML nuclear bodies and has several nuclear splice isoforms that share a common N-terminal region but differ in their C termini. Previous studies have suggested that the coiled-coil motif within the N-terminal region is sufficient for PML nuclear body formation by mediating homo/multi-dimerization of PML molecules. However, it has not been investigated whether any of the C-terminal variants of PML may contribute to PML body assembly. Here we report that the unique C-terminal domains of PML-II and PML-V can target to PML-NBs independent of their N-terminal region. Strikingly, both domains can form nuclear bodies in the absence of endogenous PML. The C-terminal domain of PML-II interacts transiently with unknown binding sites at PML nuclear bodies, whereas the C-terminal domain of PML-V exhibits hyperstable binding to PML bodies via homo-dimerization. This strong interaction is mediated by a putative α-helix in the C terminus of PML-V. Moreover, nuclear bodies assembled from the C-terminal domain of PML-V also recruit additional PML body components, including Daxx and Sp100. These observations establish the C-terminal domain of PML-V as an additional important contributor to the assembly mechanism(s) of PML bodies.
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Affiliation(s)
- Yunyun Geng
- From the State Key Laboratory of Agrobiotechnology and
- College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | | | - Anwen Shao
- College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Di Cui
- From the State Key Laboratory of Agrobiotechnology and
- College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Weiyong He
- College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Zhongzhou Chen
- From the State Key Laboratory of Agrobiotechnology and
- the College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Peter Hemmerich
- the Leibniz Institute for Age Research, 07743 Jena, Germany, and
| | - Jun Tang
- From the State Key Laboratory of Agrobiotechnology and
- College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
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34
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Steffen PA, Fonseca JP, Ringrose L. Epigenetics meets mathematics: towards a quantitative understanding of chromatin biology. Bioessays 2012; 34:901-13. [PMID: 22911103 DOI: 10.1002/bies.201200076] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
How fast? How strong? How many? So what? Why do numbers matter in biology? Chromatin binding proteins are forever in motion, exchanging rapidly between bound and free pools. How do regulatory systems whose components are in constant flux ensure stability and flexibility? This review explores the application of quantitative and mathematical approaches to mechanisms of epigenetic regulation. We discuss methods for measuring kinetic parameters and protein quantities in living cells, and explore the insights that have been gained by quantifying and modelling dynamics of chromatin binding proteins.
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35
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Broderick R, Ramadurai S, Tóth K, Togashi DM, Ryder AG, Langowski J, Nasheuer HP. Cell cycle-dependent mobility of Cdc45 determined in vivo by fluorescence correlation spectroscopy. PLoS One 2012; 7:e35537. [PMID: 22536402 PMCID: PMC3334904 DOI: 10.1371/journal.pone.0035537] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 03/17/2012] [Indexed: 12/31/2022] Open
Abstract
Eukaryotic DNA replication is a dynamic process requiring the co-operation of specific replication proteins. We measured the mobility of eGFP-Cdc45 by Fluorescence Correlation Spectroscopy (FCS) in vivo in asynchronous cells and in cells synchronized at the G1/S transition and during S phase. Our data show that eGFP-Cdc45 mobility is faster in G1/S transition compared to S phase suggesting that Cdc45 is part of larger protein complex formed in S phase. Furthermore, the size of complexes containing Cdc45 was estimated in asynchronous, G1/S and S phase-synchronized cells using gel filtration chromatography; these findings complemented the in vivo FCS data. Analysis of the mobility of eGFP-Cdc45 and the size of complexes containing Cdc45 and eGFP-Cdc45 after UVC-mediated DNA damage revealed no significant changes in diffusion rates and complex sizes using FCS and gel filtration chromatography analyses. This suggests that after UV-damage, Cdc45 is still present in a large multi-protein complex and that its mobility within living cells is consistently similar following UVC-mediated DNA damage.
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Affiliation(s)
- Ronan Broderick
- Systems Biology Ireland and Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Sivaramakrishnan Ramadurai
- Systems Biology Ireland and Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
| | - Katalin Tóth
- Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Denisio M. Togashi
- Nanoscale Biophotonics Laboratory, School of Chemistry, National University of Ireland Galway, Galway, Ireland
| | - Alan G. Ryder
- Nanoscale Biophotonics Laboratory, School of Chemistry, National University of Ireland Galway, Galway, Ireland
| | - Jörg Langowski
- Biophysics of Macromolecules, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Heinz Peter Nasheuer
- Systems Biology Ireland and Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
- * E-mail:
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36
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Golubev A. Genes at work in random bouts: stochastically discontinuous gene activity makes cell cycle duration and cell fate decisions variable, thus providing for stem cells plasticity. Bioessays 2012; 34:311-9. [PMID: 22323313 DOI: 10.1002/bies.201100119] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cell interdivision periods (IDP) in homogenous cell populations vary stochastically. Another aspect of probabilistic cell behavior is randomness in cell differentiation. These features are suggested to result from competing stochastic events of assembly/disassembly of the transcription pre-initiation complex (PIC) at gene promoters. The time needed to assemble a proper PIC from different proteins, which must be numerous enough to make their combination gene specific, may be comparable to the IDP. Nascent mRNA visualization at defined genes and inferences from protein level fluctuations in single cells suggest that some genes do operate in this way. The onset of mRNA production by such genes may miss the time windows provided by the cell cycle, resulting in cells differentiating into those in which the respective mRNAs are either present or absent. This creates a way to generate cell phenotype diversity in multicellular organisms.
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Affiliation(s)
- Alexey Golubev
- Research Institute for Experimental Medicine, Saint-Petersburg, Russia.
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37
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Erdel F, Rippe K. Binding kinetics of human ISWI chromatin-remodelers to DNA repair sites elucidate their target location mechanism. Nucleus 2012; 2:105-12. [PMID: 21738833 DOI: 10.4161/nucl.2.2.15209] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 02/18/2011] [Indexed: 01/08/2023] Open
Abstract
Chromatin remodelers translocate nucleosomes along the DNA chain in an ATP-dependent manner. This catalytic activity is particularly important for DNA replication and repair since both processes require a significant amount of nucleosome translocations and assembly during DNA synthesis. Recently, we have studied the mobility and interactions of the human ISWI family chromatin remodelers Snf2H and Snf2L as well as Acf1, one of the non-catalytic subunits present in the ACF and CHRAC complexes of Snf2H. We proposed that these protein complexes identify their nucleosomal substrates via a continuous sampling mechanism. It rationalizes the relatively high nuclear mobility and abundance observed for all ISWI proteins in terms of fast target location. According to our model a certain type of ISWI complex visits a given nucleosome in the human genome on the timescale of several seconds to a few minutes. Here, we show that the ISWI proteins Snf2H, Snf2L as well as Acf1 accumulate at UV-induced DNA damage sites within tens of seconds and reach a plateau after a few minutes. These findings corroborate the predictions of the continuous sampling mechanism as an efficient way for targeting chromatin remodelers to sites in the genome that require their activity. In comparison to the mobility of PCNA (proliferating cell nuclear antigen) that also accumulates at DNA repair sites the specifics of substrate location by chromatin remodelers are further characterized.
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Affiliation(s)
- Fabian Erdel
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum & BioQuant, Heidelberg, Germany
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38
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Assembly of the transcription machinery: ordered and stable, random and dynamic, or both? Chromosoma 2011; 120:533-45. [PMID: 22048163 DOI: 10.1007/s00412-011-0340-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 08/22/2011] [Accepted: 08/23/2011] [Indexed: 01/12/2023]
Abstract
The assembly of the transcription machinery is a key step in gene activation, but even basic details of this process remain unclear. Here we discuss the apparent discrepancy between the classic sequential assembly model based mostly on biochemistry and an emerging dynamic assembly model based mostly on fluorescence microscopy. The former model favors a stable transcription complex with subunits that cooperatively assemble in order, whereas the latter model favors an unstable complex with subunits that may assemble more randomly. To confront this apparent discrepancy, we review the merits and drawbacks of the different experimental approaches and list potential biasing factors that could be responsible for the different interpretations of assembly. We then discuss how these biases might be overcome in the future with improved experiments or new techniques. Finally, we discuss how kinetic models for assembly may help resolve the ordered and stable vs. random and dynamic assembly debate.
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39
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Erdel F, Müller-Ott K, Baum M, Wachsmuth M, Rippe K. Dissecting chromatin interactions in living cells from protein mobility maps. Chromosome Res 2011; 19:99-115. [PMID: 20848178 DOI: 10.1007/s10577-010-9155-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The genome of eukaryotes is organized into a dynamic nucleoprotein complex referred to as chromatin, which can adopt different functional states. Both the DNA and the protein component of chromatin are subject to various post-translational modifications that define the cell's gene expression program. Their readout and establishment occurs in a spatio-temporally coordinated manner that is controlled by numerous chromatin-interacting proteins. Binding to chromatin in living cells can be measured by a spatially resolved analysis of protein mobility using fluorescence microscopy based approaches. Recent advancements in the acquisition of protein mobility data using fluorescence bleaching and correlation methods provide data sets on diffusion coefficients, binding kinetics, and cellular concentrations on different time and length scales. The combination of different techniques is needed to dissect the complex interplay of diffusive translocations, binding events, and mobility constraints of the chromatin environment. While bleaching techniques have their strength in the characterization of particles that are immobile on the second/minute time scale, a correlation analysis is advantageous to characterize transient binding events with millisecond residence time. The application and synergy effects of the different approaches to obtain protein mobility and interaction maps in the nucleus are illustrated for the analysis of heterochromatin protein 1.
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Affiliation(s)
- Fabian Erdel
- Deutsches Krebsforschungszentrum and BioQuant, Research Group Genome Organization and Function, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
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