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Lakadamyali M. From feulgen to modern methods: marking a century of DNA imaging advances. Histochem Cell Biol 2024; 162:13-22. [PMID: 38753186 PMCID: PMC11227465 DOI: 10.1007/s00418-024-02291-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2024] [Indexed: 07/07/2024]
Abstract
The mystery of how human DNA is compactly packaged into a nucleus-a space a hundred thousand times smaller-while still allowing for the regulation of gene function, has long been one of the greatest enigmas in cell biology. This puzzle is gradually being solved, thanks in part to the advent of new technologies. Among these, innovative genome-labeling techniques combined with high-resolution imaging methods have been pivotal. These methods facilitate the visualization of DNA within intact nuclei and have significantly contributed to our current understanding of genome organization. This review will explore various labeling and imaging approaches that are revolutionizing our understanding of the three-dimensional organization of the genome, shedding light on the relationship between its structure and function.
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Affiliation(s)
- Melike Lakadamyali
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA.
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA.
- Perelman School of Medicine, Epigenetics Institute, University of Pennsylvania, Philadelphia, USA.
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2
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Lee CSK, Weiβ M, Hamperl S. Where and when to start: Regulating DNA replication origin activity in eukaryotic genomes. Nucleus 2023; 14:2229642. [PMID: 37469113 PMCID: PMC10361152 DOI: 10.1080/19491034.2023.2229642] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/20/2023] [Accepted: 06/21/2023] [Indexed: 07/21/2023] Open
Abstract
In eukaryotic genomes, hundreds to thousands of potential start sites of DNA replication named origins are dispersed across each of the linear chromosomes. During S-phase, only a subset of origins is selected in a stochastic manner to assemble bidirectional replication forks and initiate DNA synthesis. Despite substantial progress in our understanding of this complex process, a comprehensive 'identity code' that defines origins based on specific nucleotide sequences, DNA structural features, the local chromatin environment, or 3D genome architecture is still missing. In this article, we review the genetic and epigenetic features of replication origins in yeast and metazoan chromosomes and highlight recent insights into how this flexibility in origin usage contributes to nuclear organization, cell growth, differentiation, and genome stability.
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Affiliation(s)
- Clare S K Lee
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Matthias Weiβ
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Stephan Hamperl
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
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3
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Pradhan S, Apaydin S, Bucevičius J, Gerasimaitė R, Kostiuk G, Lukinavičius G. Sequence-specific DNA labelling for fluorescence microscopy. Biosens Bioelectron 2023; 230:115256. [PMID: 36989663 DOI: 10.1016/j.bios.2023.115256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 03/04/2023] [Accepted: 03/21/2023] [Indexed: 03/29/2023]
Abstract
The preservation of nucleus structure during microscopy imaging is a top priority for understanding chromatin organization, genome dynamics, and gene expression regulation. In this review, we summarize the sequence-specific DNA labelling methods that can be used for imaging in fixed and/or living cells without harsh treatment and DNA denaturation: (i) hairpin polyamides, (ii) triplex-forming oligonucleotides, (iii) dCas9 proteins, (iv) transcription activator-like effectors (TALEs) and (v) DNA methyltransferases (MTases). All these techniques are capable of identifying repetitive DNA loci and robust probes are available for telomeres and centromeres, but visualizing single-copy sequences is still challenging. In our futuristic vision, we see gradual replacement of the historically important fluorescence in situ hybridization (FISH) by less invasive and non-destructive methods compatible with live cell imaging. Combined with super-resolution fluorescence microscopy, these methods will open the possibility to look into unperturbed structure and dynamics of chromatin in living cells, tissues and whole organisms.
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4
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Nozaki T, Shinkai S, Ide S, Higashi K, Tamura S, Shimazoe MA, Nakagawa M, Suzuki Y, Okada Y, Sasai M, Onami S, Kurokawa K, Iida S, Maeshima K. Condensed but liquid-like domain organization of active chromatin regions in living human cells. SCIENCE ADVANCES 2023; 9:eadf1488. [PMID: 37018405 PMCID: PMC10075990 DOI: 10.1126/sciadv.adf1488] [Citation(s) in RCA: 31] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 03/07/2023] [Indexed: 05/31/2023]
Abstract
In eukaryotes, higher-order chromatin organization is spatiotemporally regulated as domains, for various cellular functions. However, their physical nature in living cells remains unclear (e.g., condensed domains or extended fiber loops; liquid-like or solid-like). Using novel approaches combining genomics, single-nucleosome imaging, and computational modeling, we investigated the physical organization and behavior of early DNA replicated regions in human cells, which correspond to Hi-C contact domains with active chromatin marks. Motion correlation analysis of two neighbor nucleosomes shows that nucleosomes form physically condensed domains with ~150-nm diameters, even in active chromatin regions. The mean-square displacement analysis between two neighbor nucleosomes demonstrates that nucleosomes behave like a liquid in the condensed domain on the ~150 nm/~0.5 s spatiotemporal scale, which facilitates chromatin accessibility. Beyond the micrometers/minutes scale, chromatin seems solid-like, which may contribute to maintaining genome integrity. Our study reveals the viscoelastic principle of the chromatin polymer; chromatin is locally dynamic and reactive but globally stable.
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Affiliation(s)
- Tadasu Nozaki
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Soya Shinkai
- Laboratory for Developmental Dynamics, Center for Biosystems Dynamics Research (BDR), RIKEN, Kobe, Hyogo 650-0047, Japan
| | - Satoru Ide
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
| | - Koichi Higashi
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
- Genome Evolution Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Masa A. Shimazoe
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
| | - Masaki Nakagawa
- Department of Computer Science and Engineering, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan
| | - Yutaka Suzuki
- Department of Computational Biology and Medical Sciences, University of Tokyo, 5-1-5 Kashiwanoha Kashiwa, Chiba 277-8562, Japan
| | - Yasushi Okada
- Laboratory for Cell Polarity Regulation, Center for Biosystems Dynamics Research (BDR), RIKEN, Suita, Osaka 565-0874, Japan
| | - Masaki Sasai
- Department of Complex Systems Science, Nagoya University, Nagoya 464-8601, Japan
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan
| | - Shuichi Onami
- Laboratory for Developmental Dynamics, Center for Biosystems Dynamics Research (BDR), RIKEN, Kobe, Hyogo 650-0047, Japan
| | - Ken Kurokawa
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
- Genome Evolution Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Shiori Iida
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
- Department of Genetics, School of Life Science, SOKENDAI (Graduate University for Advanced Studies), Mishima, Shizuoka 411-8540, Japan
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5
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Burgers TCQ, Vlijm R. Fluorescence-based super-resolution-microscopy strategies for chromatin studies. Chromosoma 2023:10.1007/s00412-023-00792-9. [PMID: 37000292 PMCID: PMC10356683 DOI: 10.1007/s00412-023-00792-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/28/2023] [Accepted: 03/16/2023] [Indexed: 04/01/2023]
Abstract
Super-resolution microscopy (SRM) is a prime tool to study chromatin organisation at near biomolecular resolution in the native cellular environment. With fluorescent labels DNA, chromatin-associated proteins and specific epigenetic states can be identified with high molecular specificity. The aim of this review is to introduce the field of diffraction-unlimited SRM to enable an informed selection of the most suitable SRM method for a specific chromatin-related research question. We will explain both diffraction-unlimited approaches (coordinate-targeted and stochastic-localisation-based) and list their characteristic spatio-temporal resolutions, live-cell compatibility, image-processing, and ability for multi-colour imaging. As the increase in resolution, compared to, e.g. confocal microscopy, leads to a central role of the sample quality, important considerations for sample preparation and concrete examples of labelling strategies applicable to chromatin research are discussed. To illustrate how SRM-based methods can significantly improve our understanding of chromatin functioning, and to serve as an inspiring starting point for future work, we conclude with examples of recent applications of SRM in chromatin research.
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Affiliation(s)
- Thomas C Q Burgers
- Molecular Biophysics, Zernike Institute for Advanced Materials, Rijksuniversiteit Groningen, Groningen, the Netherlands
| | - Rifka Vlijm
- Molecular Biophysics, Zernike Institute for Advanced Materials, Rijksuniversiteit Groningen, Groningen, the Netherlands.
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6
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Safeguarding DNA Replication: A Golden Touch of MiDAS and Other Mechanisms. Int J Mol Sci 2022; 23:ijms231911331. [PMID: 36232633 PMCID: PMC9570362 DOI: 10.3390/ijms231911331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/19/2022] [Accepted: 09/20/2022] [Indexed: 11/21/2022] Open
Abstract
DNA replication is a tightly regulated fundamental process allowing the correct duplication and transfer of the genetic information from the parental cell to the progeny. It involves the coordinated assembly of several proteins and protein complexes resulting in replication fork licensing, firing and progression. However, the DNA replication pathway is strewn with hurdles that affect replication fork progression during S phase. As a result, cells have adapted several mechanisms ensuring replication completion before entry into mitosis and segregating chromosomes with minimal, if any, abnormalities. In this review, we describe the possible obstacles that a replication fork might encounter and how the cell manages to protect DNA replication from S to the next G1.
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7
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Li Y, Agrawal V, Virk RKA, Roth E, Li WS, Eshein A, Frederick J, Huang K, Almassalha L, Bleher R, Carignano MA, Szleifer I, Dravid VP, Backman V. Analysis of three-dimensional chromatin packing domains by chromatin scanning transmission electron microscopy (ChromSTEM). Sci Rep 2022; 12:12198. [PMID: 35842472 PMCID: PMC9288481 DOI: 10.1038/s41598-022-16028-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 07/04/2022] [Indexed: 11/09/2022] Open
Abstract
Chromatin organization over multiple length scales plays a critical role in the regulation of transcription. Deciphering the interplay of these processes requires high-resolution, three-dimensional, quantitative imaging of chromatin structure in vitro. Herein, we introduce ChromSTEM, a method that utilizes high-angle annular dark-field imaging and tomography in scanning transmission electron microscopy combined with DNA-specific staining for electron microscopy. We utilized ChromSTEM for an in-depth quantification of 3D chromatin conformation with high spatial resolution and contrast, allowing for characterization of higher-order chromatin structure almost down to the level of the DNA base pair. Employing mass scaling analysis on ChromSTEM mass density tomograms, we observed that chromatin forms spatially well-defined higher-order domains, around 80 nm in radius. Within domains, chromatin exhibits a polymeric fractal-like behavior and a radially decreasing mass-density from the center to the periphery. Unlike other nanoimaging and analysis techniques, we demonstrate that our unique combination of this high-resolution imaging technique with polymer physics-based analysis enables us to (i) investigate the chromatin conformation within packing domains and (ii) quantify statistical descriptors of chromatin structure that are relevant to transcription. We observe that packing domains have heterogeneous morphological properties even within the same cell line, underlying the potential role of statistical chromatin packing in regulating gene expression within eukaryotic nuclei.
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Affiliation(s)
- Yue Li
- Applied Physics Program, Northwestern University, Evanston, IL, 60208, USA
| | - Vasundhara Agrawal
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Ranya K A Virk
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Eric Roth
- Department of Materials Sciences and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Wing Shun Li
- Applied Physics Program, Northwestern University, Evanston, IL, 60208, USA
| | - Adam Eshein
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Jane Frederick
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Kai Huang
- Shenzhen Bay Laboratory, Institute of Systems and Physical Biology, Shenzhen, 518132, China
| | - Luay Almassalha
- Medical Scientist Training Program, Feinberg School of Medicine, Northwestern University, Evanston, IL, 60611, USA
| | - Reiner Bleher
- Department of Materials Sciences and Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Marcelo A Carignano
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA.,Department of Chemistry, Northwestern University, Evanston, IL, 60208, USA
| | - Vinayak P Dravid
- Department of Materials Sciences and Engineering, Northwestern University, Evanston, IL, 60208, USA.
| | - Vadim Backman
- Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA.
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8
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Hobson CM, Aaron JS. Combining multiple fluorescence imaging techniques in biology: when one microscope is not enough. Mol Biol Cell 2022; 33:tp1. [PMID: 35549314 PMCID: PMC9265156 DOI: 10.1091/mbc.e21-10-0506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
While fluorescence microscopy has proven to be an exceedingly useful tool in bioscience, it is difficult to offer simultaneous high resolution, fast speed, large volume, and good biocompatibility in a single imaging technique. Thus, when determining the image data required to quantitatively test a complex biological hypothesis, it often becomes evident that multiple imaging techniques are necessary. Recent years have seen an explosion in development of novel fluorescence microscopy techniques, each of which features a unique suite of capabilities. In this Technical Perspective, we highlight recent studies to illustrate the benefits, and often the necessity, of combining multiple fluorescence microscopy modalities. We provide guidance in choosing optimal technique combinations to effectively address a biological question. Ultimately, we aim to promote a more well-rounded approach in designing fluorescence microscopy experiments, leading to more robust quantitative insight.
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Affiliation(s)
- Chad M Hobson
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
| | - Jesse S Aaron
- Advanced Imaging Center, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147
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9
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Xue Y, Yang Y, Tian H, Quan H, Liu S, Zhang L, Yang L, Zhu H, Wu H, Gao YQ. Computational characterization of domain-segregated 3D chromatin structure and segmented DNA methylation status in carcinogenesis. Mol Oncol 2022; 16:699-716. [PMID: 34708506 PMCID: PMC8807360 DOI: 10.1002/1878-0261.13127] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 09/17/2021] [Accepted: 10/26/2021] [Indexed: 12/12/2022] Open
Abstract
The high-order chromatin structure, together with DNA methylation and other epigenetic marks, plays a vital role in gene regulation and displays abnormal status in cancer cells. Theoretical analyses are expected to provide a more unified understanding of the multi-omics data on the large variety of samples, and hopefully a common picture of carcinogenesis. In particular, we are interested in the question of whether an underlying origin DNA sequence exists for these epigenetic alterations. The human genome consists of two types of megabase-sized domain based on the distribution of CpG islands (CGIs) that show distinct structural, epigenetic, and transcriptional properties: CGI-rich and CGI-poor domains. Through an integrated analysis of chromatin structure, DNA methylation, and RNA sequencing data, we found that, in carcinogenesis, the two different types of domain display different structural changes and have an increased number of DNA methylation differences and transcriptional-level differences, compared with in noncancer cells. We also compared the structural features among carcinogenesis, senescence, and mitosis, showing the possible connection between chromatin structure and cell state, which could affect vital cancer-related properties. In summary, chromatin structure, DNA methylation, and gene expression, as well as their changes observed in several types of cancers, show a dependence on multiscale DNA sequence heterogeneity.
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Affiliation(s)
- Yue Xue
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Ying Yang
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Hao Tian
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Hui Quan
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Sirui Liu
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Ling Zhang
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
| | - Lu Yang
- The MOE Key Laboratory of Cell Proliferation and DifferentiationSchool of Life SciencesPeking UniversityBeijingChina
- Peking‐Tsinghua Center for Life SciencesPeking UniversityBeijingChina
| | - Haichuan Zhu
- The MOE Key Laboratory of Cell Proliferation and DifferentiationSchool of Life SciencesPeking UniversityBeijingChina
- Peking‐Tsinghua Center for Life SciencesPeking UniversityBeijingChina
| | - Hong Wu
- The MOE Key Laboratory of Cell Proliferation and DifferentiationSchool of Life SciencesPeking UniversityBeijingChina
- Peking‐Tsinghua Center for Life SciencesPeking UniversityBeijingChina
- Peking University Institute of HematologyNational Clinical Research Center for Hematologic DiseasePeking University People’s HospitalBeijingChina
| | - Yi Qin Gao
- Beijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijingChina
- Biomedical Pioneering Innovation Center (BIOPIC)Peking UniversityBeijingChina
- Beijing Advanced Innovation Center for Genomics (ICG)Peking UniversityBeijingChina
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10
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Hansen JC, Maeshima K, Hendzel MJ. The solid and liquid states of chromatin. Epigenetics Chromatin 2021; 14:50. [PMID: 34717733 PMCID: PMC8557566 DOI: 10.1186/s13072-021-00424-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 10/22/2021] [Indexed: 12/14/2022] Open
Abstract
The review begins with a concise description of the principles of phase separation. This is followed by a comprehensive section on phase separation of chromatin, in which we recount the 60 years history of chromatin aggregation studies, discuss the evidence that chromatin aggregation intrinsically is a physiologically relevant liquid-solid phase separation (LSPS) process driven by chromatin self-interaction, and highlight the recent findings that under specific solution conditions chromatin can undergo liquid-liquid phase separation (LLPS) rather than LSPS. In the next section of the review, we discuss how certain chromatin-associated proteins undergo LLPS in vitro and in vivo. Some chromatin-binding proteins undergo LLPS in purified form in near-physiological ionic strength buffers while others will do so only in the presence of DNA, nucleosomes, or chromatin. The final section of the review evaluates the solid and liquid states of chromatin in the nucleus. While chromatin behaves as an immobile solid on the mesoscale, nucleosomes are mobile on the nanoscale. We discuss how this dual nature of chromatin, which fits well the concept of viscoelasticity, contributes to genome structure, emphasizing the dominant role of chromatin self-interaction.
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Affiliation(s)
- Jeffrey C Hansen
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, 80523, USA.
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, and Department of Genetics, Sokendai (Graduate University for Advanced Studies), Mishima, Shizuoka, 411-8540, Japan.
| | - Michael J Hendzel
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
- Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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11
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Yin Y, Lee WTC, Gupta D, Xue H, Tonzi P, Borowiec JA, Huang TT, Modesti M, Rothenberg E. A basal-level activity of ATR links replication fork surveillance and stress response. Mol Cell 2021; 81:4243-4257.e6. [PMID: 34473946 DOI: 10.1016/j.molcel.2021.08.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 03/03/2021] [Accepted: 08/06/2021] [Indexed: 11/27/2022]
Abstract
Mammalian cells use diverse pathways to prevent deleterious consequences during DNA replication, yet the mechanism by which cells survey individual replisomes to detect spontaneous replication impediments at the basal level, and their accumulation during replication stress, remain undefined. Here, we used single-molecule localization microscopy coupled with high-order-correlation image-mining algorithms to quantify the composition of individual replisomes in single cells during unperturbed replication and under replicative stress. We identified a basal-level activity of ATR that monitors and regulates the amounts of RPA at forks during normal replication. Replication-stress amplifies the basal activity through the increased volume of ATR-RPA interaction and diffusion-driven enrichment of ATR at forks. This localized crowding of ATR enhances its collision probability, stimulating the activation of its replication-stress response. Finally, we provide a computational model describing how the basal activity of ATR is amplified to produce its canonical replication stress response.
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Affiliation(s)
- Yandong Yin
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA.
| | - Wei Ting Chelsea Lee
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Dipika Gupta
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Huijun Xue
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Peter Tonzi
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - James A Borowiec
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Tony T Huang
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
| | - Mauro Modesti
- Cancer Research Center of Marseille, CNRS UMR 7258, Inserm U1068, Institut Paoli-Calmettes, Aix-Marseille Université UM105, Marseille, France
| | - Eli Rothenberg
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA.
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12
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Li Y, Xue B, Zhang M, Zhang L, Hou Y, Qin Y, Long H, Su QP, Wang Y, Guan X, Jin Y, Cao Y, Li G, Sun Y. Transcription-coupled structural dynamics of topologically associating domains regulate replication origin efficiency. Genome Biol 2021; 22:206. [PMID: 34253239 PMCID: PMC8276456 DOI: 10.1186/s13059-021-02424-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 06/30/2021] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Metazoan cells only utilize a small subset of the potential DNA replication origins to duplicate the whole genome in each cell cycle. Origin choice is linked to cell growth, differentiation, and replication stress. Although various genetic and epigenetic signatures have been linked to the replication efficiency of origins, there is no consensus on how the selection of origins is determined. RESULTS We apply dual-color stochastic optical reconstruction microscopy (STORM) super-resolution imaging to map the spatial distribution of origins within individual topologically associating domains (TADs). We find that multiple replication origins initiate separately at the spatial boundary of a TAD at the beginning of the S phase. Intriguingly, while both high-efficiency and low-efficiency origins are distributed homogeneously in the TAD during the G1 phase, high-efficiency origins relocate to the TAD periphery before the S phase. Origin relocalization is dependent on both transcription and CTCF-mediated chromatin structure. Further, we observe that the replication machinery protein PCNA forms immobile clusters around TADs at the G1/S transition, explaining why origins at the TAD periphery are preferentially fired. CONCLUSION Our work reveals a new origin selection mechanism that the replication efficiency of origins is determined by their physical distribution in the chromatin domain, which undergoes a transcription-dependent structural re-organization process. Our model explains the complex links between replication origin efficiency and many genetic and epigenetic signatures that mark active transcription. The coordination between DNA replication, transcription, and chromatin organization inside individual TADs also provides new insights into the biological functions of sub-domain chromatin structural dynamics.
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Affiliation(s)
- Yongzheng Li
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Boxin Xue
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
- College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Mengling Zhang
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
| | - Liwei Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Yingping Hou
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Yizhi Qin
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
| | - Haizhen Long
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Qian Peter Su
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
- School of Biomedical Engineering, Faculty of Engineering and Information Technology, University of Technology Sydney, Sydney, NSW, 2007, Australia
| | - Yao Wang
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
| | - Xiaodong Guan
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
| | - Yanyan Jin
- Department of Neurobiology, Beijing Centre of Neural Regeneration and Repair, Capital Medical University, Beijing, 100101, China
| | - Yuan Cao
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yujie Sun
- State Key Laboratory of Membrane Biology, Biomedical Pioneer Innovation Center (BIOPIC), School of Life Sciences, Peking University, Beijing, 100871, China.
- College of Future Technology, Peking University, Beijing, 100871, China.
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13
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Hao X, Parmar JJ, Lelandais B, Aristov A, Ouyang W, Weber C, Zimmer C. Super-resolution visualization and modeling of human chromosomal regions reveals cohesin-dependent loop structures. Genome Biol 2021; 22:150. [PMID: 33975635 PMCID: PMC8111965 DOI: 10.1186/s13059-021-02343-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 04/08/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The 3D organization of the chromatin fiber in cell nuclei plays a key role in the regulation of gene expression. Genome-wide techniques to score DNA-DNA contacts, such as Hi-C, reveal the partitioning of chromosomes into epigenetically defined active and repressed compartments and smaller "topologically associated" domains. These domains are often associated with chromatin loops, which largely disappear upon removal of cohesin. Because most Hi-C implementations average contact frequencies over millions of cells and do not provide direct spatial information, it remains unclear whether and how frequently chromatin domains and loops exist in single cells. RESULTS We combine 3D single-molecule localization microscopy with a low-cost fluorescence labeling strategy that does not denature the DNA, to visualize large portions of single human chromosomes in situ at high resolution. In parallel, we develop multi-scale, whole nucleus polymer simulations, that predict chromatin structures at scales ranging from 5 kb up to entire chromosomes. We image chromosomes in G1 and M phase and examine the effect of cohesin on interphase chromatin structure. Depletion of cohesin leads to increased prevalence of loose chromatin stretches, increased gyration radii, and reduced smoothness of imaged chromatin regions. By comparison to model predictions, we estimate that 6-25 or more purely cohesin-dependent chromatin loops coexist per megabase of DNA in single cells, suggesting that the vast majority of the genome is enclosed in loops. CONCLUSION Our results provide new constraints on chromatin structure and showcase an affordable non-invasive approach to study genome organization in single cells.
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Affiliation(s)
- Xian Hao
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- School of Public Health & Jiangxi Provincial Key Laboratory of Preventive Medicine, Nanchang University, Nanchang, 330006, China
| | - Jyotsana J Parmar
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- Simons Center for the Study of Living Machines, National Center for Biological Sciences (TIFR), Bangalore, Karnataka, 560065, India
| | - Benoît Lelandais
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Andrey Aristov
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Wei Ouyang
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
- Université de Paris, F-75013, Paris, France
| | - Christian Weber
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France
| | - Christophe Zimmer
- Institut Pasteur, Imaging and Modeling Unit, UMR 3691, CNRS, Paris, France.
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14
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Single-molecule imaging reveals replication fork coupled formation of G-quadruplex structures hinders local replication stress signaling. Nat Commun 2021; 12:2525. [PMID: 33953191 PMCID: PMC8099879 DOI: 10.1038/s41467-021-22830-9] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 03/30/2021] [Indexed: 12/19/2022] Open
Abstract
Guanine-rich DNA sequences occur throughout the human genome and can transiently form G-quadruplex (G4) structures that may obstruct DNA replication, leading to genomic instability. Here, we apply multi-color single-molecule localization microscopy (SMLM) coupled with robust data-mining algorithms to quantitatively visualize replication fork (RF)-coupled formation and spatial-association of endogenous G4s. Using this data, we investigate the effects of G4s on replisome dynamics and organization. We show that a small fraction of active replication forks spontaneously form G4s at newly unwound DNA immediately behind the MCM helicase and before nascent DNA synthesis. These G4s locally perturb replisome dynamics and organization by reducing DNA synthesis and limiting the binding of the single-strand DNA-binding protein RPA. We find that the resolution of RF-coupled G4s is mediated by an interplay between RPA and the FANCJ helicase. FANCJ deficiency leads to G4 accumulation, DNA damage at G4-associated replication forks, and silencing of the RPA-mediated replication stress response. Our study provides first-hand evidence of the intrinsic, RF-coupled formation of G4 structures, offering unique mechanistic insights into the interference and regulation of stable G4s at replication forks and their effect on RPA-associated fork signaling and genomic instability.
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15
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Coskun AF, Han G, Ganesh S, Chen SY, Clavé XR, Harmsen S, Jiang S, Schürch CM, Bai Y, Hitzman C, Nolan GP. Nanoscopic subcellular imaging enabled by ion beam tomography. Nat Commun 2021; 12:789. [PMID: 33542220 PMCID: PMC7862654 DOI: 10.1038/s41467-020-20753-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 12/08/2020] [Indexed: 01/30/2023] Open
Abstract
Multiplexed ion beam imaging (MIBI) has been previously used to profile multiple parameters in two dimensions in single cells within tissue slices. Here, a mathematical and technical framework for three-dimensional (3D) subcellular MIBI is presented. Ion-beam tomography (IBT) compiles ion beam images that are acquired iteratively across successive, multiple scans, and later assembled into a 3D format without loss of depth resolution. Algorithmic deconvolution, tailored for ion beams, is then applied to the transformed ion image series, yielding 4-fold enhanced ion beam data cubes. To further generate 3D sub-ion-beam-width precision visuals, isolated ion molecules are localized in the raw ion beam images, creating an approach coined as SILM, secondary ion beam localization microscopy, providing sub-25 nm accuracy in original ion images. Using deep learning, a parameter-free reconstruction method for ion beam tomograms with high accuracy is developed for low-density targets. In cultured cancer cells and tissues, IBT enables accessible visualization of 3D volumetric distributions of genomic regions, RNA transcripts, and protein factors with 5 nm axial resolution using isotope-enrichments and label-free elemental analyses. Multiparameter imaging of subcellular features at near macromolecular resolution is implemented by the IBT tools as a general biocomputation pipeline for imaging mass spectrometry.
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Affiliation(s)
- Ahmet F. Coskun
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA ,grid.168010.e0000000419368956Department of Radiology, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, CA USA ,grid.213917.f0000 0001 2097 4943Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA USA
| | - Guojun Han
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA
| | - Shambavi Ganesh
- grid.213917.f0000 0001 2097 4943Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA USA ,grid.213917.f0000 0001 2097 4943School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Shih-Yu Chen
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA
| | - Xavier Rovira Clavé
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA
| | - Stefan Harmsen
- grid.168010.e0000000419368956Department of Radiology, Molecular Imaging Program at Stanford, Stanford University School of Medicine, Stanford, CA USA ,grid.25879.310000 0004 1936 8972Present Address: Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA USA
| | - Sizun Jiang
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA
| | - Christian M. Schürch
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA ,grid.411544.10000 0001 0196 8249Present Address: Department of Pathology and Neuropathology, University Hospital and Comprehensive Cancer Center Tübingen, Tübingen, Germany
| | - Yunhao Bai
- grid.168010.e0000000419368956Department of Chemistry, Stanford University, Stanford, CA USA
| | - Chuck Hitzman
- grid.168010.e0000000419368956Department of Materials Science and Engineering, Stanford University, Stanford, CA USA
| | - Garry P. Nolan
- grid.168010.e0000000419368956Baxter Laboratory, Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA USA
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16
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Mamberti S, Cardoso MC. Are the processes of DNA replication and DNA repair reading a common structural chromatin unit? Nucleus 2020; 11:66-82. [PMID: 32275847 PMCID: PMC7289585 DOI: 10.1080/19491034.2020.1744415] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Decades of investigation on genomic DNA have brought us deeper insights into its organization within the nucleus and its metabolic mechanisms. This was fueled by the parallel development of experimental techniques and has stimulated model building to simulate genome conformation in agreement with the experimental data. Here, we will discuss our recent discoveries on the chromatin units of DNA replication and DNA damage response. We will highlight their remarkable structural similarities and how both revealed themselves as clusters of nanofocal structures each on the hundred thousand base pair size range corresponding well with chromatin loop sizes. We propose that the function of these two global genomic processes is determined by the loop level organization of chromatin structure with structure dictating function. Abbreviations: 3D-SIM: 3D-structured illumination microscopy; 3C: chromosome conformation capture; DDR: DNA damage response; FISH: fluorescent in situ hybridization; Hi-C: high conformation capture; HiP-HoP: highly predictive heteromorphic polymer model; IOD: inter-origin distance; LAD: lamina associated domain; STED: stimulated emission depletion microscopy; STORM: stochastic optical reconstruction microscopy; SBS: strings and binders switch model; TAD: topologically associated domain
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Affiliation(s)
- Stefania Mamberti
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - M Cristina Cardoso
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
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17
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Strickfaden H, Tolsma TO, Sharma A, Underhill DA, Hansen JC, Hendzel MJ. Condensed Chromatin Behaves like a Solid on the Mesoscale In Vitro and in Living Cells. Cell 2020; 183:1772-1784.e13. [PMID: 33326747 DOI: 10.1016/j.cell.2020.11.027] [Citation(s) in RCA: 156] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/16/2020] [Accepted: 11/16/2020] [Indexed: 12/11/2022]
Abstract
The association of nuclear DNA with histones to form chromatin is essential for temporal and spatial control of eukaryotic genomes. In this study, we examined the physical state of condensed chromatin in vitro and in vivo. Our in vitro studies demonstrate that self-association of nucleosomal arrays under a wide range of solution conditions produces supramolecular condensates in which the chromatin is physically constrained and solid-like. By measuring DNA mobility in living cells, we show that condensed chromatin also exhibits solid-like behavior in vivo. Representative heterochromatin proteins, however, display liquid-like behavior and coalesce around the solid chromatin scaffold. Importantly, euchromatin and heterochromatin show solid-like behavior even under conditions that produce limited interactions between chromatin fibers. Our results reveal that condensed chromatin exists in a solid-like state whose properties resist external forces and create an elastic gel and provides a scaffold that supports liquid-liquid phase separation of chromatin binding proteins.
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Affiliation(s)
- Hilmar Strickfaden
- Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Thomas O Tolsma
- Department of Biochemistry and Molecular Biology, College of Natural Sciences, Colorado State University, Fort Collins, CO, USA
| | - Ajit Sharma
- Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - D Alan Underhill
- Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada; Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Jeffrey C Hansen
- Department of Biochemistry and Molecular Biology, College of Natural Sciences, Colorado State University, Fort Collins, CO, USA.
| | - Michael J Hendzel
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada; Department of Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.
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18
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Strickfaden H. Reflections on the organization and the physical state of chromatin in eukaryotic cells. Genome 2020; 64:311-325. [PMID: 33306433 DOI: 10.1139/gen-2020-0132] [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: 12/25/2022]
Abstract
In recent years, our perception of chromatin structure and organization in the cell nucleus has changed in fundamental ways. The 30 nm chromatin fiber has lost its status as an essential in vivo structure. Hi-C and related biochemical methods, advanced electron and super-resolved fluorescence microscopy, together with concepts from soft matter physics, have revolutionized the field. A comprehensive understanding of the structural and functional interactions that regulate cell cycle and cell type specific nuclear functions appears within reach, but it requires the integration of top-down and bottom-up approachs. In this review, I present an update on nuclear architecture studies with an emphasis on organization and the controversy regarding the physical state of chromatin in cells.
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Affiliation(s)
- Hilmar Strickfaden
- Departments of Cell Biology and Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada.,Departments of Cell Biology and Oncology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
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19
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Cremer M, Brandstetter K, Maiser A, Rao SSP, Schmid VJ, Guirao-Ortiz M, Mitra N, Mamberti S, Klein KN, Gilbert DM, Leonhardt H, Cardoso MC, Aiden EL, Harz H, Cremer T. Cohesin depleted cells rebuild functional nuclear compartments after endomitosis. Nat Commun 2020; 11:6146. [PMID: 33262376 PMCID: PMC7708632 DOI: 10.1038/s41467-020-19876-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 10/28/2020] [Indexed: 01/05/2023] Open
Abstract
Cohesin plays an essential role in chromatin loop extrusion, but its impact on a compartmentalized nuclear architecture, linked to nuclear functions, is less well understood. Using live-cell and super-resolved 3D microscopy, here we find that cohesin depletion in a human colon cancer derived cell line results in endomitosis and a single multilobulated nucleus with chromosome territories pervaded by interchromatin channels. Chromosome territories contain chromatin domain clusters with a zonal organization of repressed chromatin domains in the interior and transcriptionally competent domains located at the periphery. These clusters form microscopically defined, active and inactive compartments, which likely correspond to A/B compartments, which are detected with ensemble Hi-C. Splicing speckles are observed nearby within the lining channel system. We further observe that the multilobulated nuclei, despite continuous absence of cohesin, pass through S-phase with typical spatio-temporal patterns of replication domains. Evidence for structural changes of these domains compared to controls suggests that cohesin is required for their full integrity.
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Affiliation(s)
- Marion Cremer
- Anthropology and Human Genomics, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany.
| | - Katharina Brandstetter
- Human Biology & BioImaging, Center for Molecular Biosystems, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany
| | - Andreas Maiser
- Human Biology & BioImaging, Center for Molecular Biosystems, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany
| | - Suhas S P Rao
- Center for Genome Architecture, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Structural Biology, Stanford University School of Medicine, California, USA
| | - Volker J Schmid
- Bayesian Imaging and Spatial Statistics Group, Department of Statistics, Ludwig-Maximilians-Universität München, München, Germany
| | - Miguel Guirao-Ortiz
- Human Biology & BioImaging, Center for Molecular Biosystems, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany
| | - Namita Mitra
- Center for Genome Architecture, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Stefania Mamberti
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Kyle N Klein
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - David M Gilbert
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Heinrich Leonhardt
- Human Biology & BioImaging, Center for Molecular Biosystems, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany
| | - M Cristina Cardoso
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany
| | - Erez Lieberman Aiden
- Center for Genome Architecture, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- Center for Theoretical Biological Physics, Rice University, Houston, TX, USA
- Broad Institute of the Massachusetts Institute of Technology and Harvard University, Cambridge, MA, USA
- Departments of Computer Science and Computational and Applied Mathematics, Rice University, Houston, TX, USA
| | - Hartmann Harz
- Human Biology & BioImaging, Center for Molecular Biosystems, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany.
| | - Thomas Cremer
- Anthropology and Human Genomics, Department Biology II, Ludwig-Maximilians-Universität München, München, Germany.
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20
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A framework for understanding the functions of biomolecular condensates across scales. Nat Rev Mol Cell Biol 2020; 22:215-235. [PMID: 33169001 DOI: 10.1038/s41580-020-00303-z] [Citation(s) in RCA: 405] [Impact Index Per Article: 101.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2020] [Indexed: 02/07/2023]
Abstract
Biomolecular condensates are found throughout eukaryotic cells, including in the nucleus, in the cytoplasm and on membranes. They are also implicated in a wide range of cellular functions, organizing molecules that act in processes ranging from RNA metabolism to signalling to gene regulation. Early work in the field focused on identifying condensates and understanding how their physical properties and regulation arise from molecular constituents. Recent years have brought a focus on understanding condensate functions. Studies have revealed functions that span different length scales: from molecular (modulating the rates of chemical reactions) to mesoscale (organizing large structures within cells) to cellular (facilitating localization of cellular materials and homeostatic responses). In this Roadmap, we discuss representative examples of biochemical and cellular functions of biomolecular condensates from the recent literature and organize these functions into a series of non-exclusive classes across the different length scales. We conclude with a discussion of areas of current interest and challenges in the field, and thoughts about how progress may be made to further our understanding of the widespread roles of condensates in cell biology.
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21
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Zidovska A. The rich inner life of the cell nucleus: dynamic organization, active flows, and emergent rheology. Biophys Rev 2020; 12:1093-1106. [PMID: 33064286 PMCID: PMC7575674 DOI: 10.1007/s12551-020-00761-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/03/2020] [Accepted: 09/14/2020] [Indexed: 02/07/2023] Open
Abstract
The cell nucleus stores the genetic material essential for life, and provides the environment for transcription, maintenance, and replication of the genome. Moreover, the nucleoplasm is filled with subnuclear bodies such as nucleoli that are responsible for other vital functions. Overall, the nucleus presents a highly heterogeneous and dynamic environment with diverse functionality. Here, we propose that its biophysical complexity can be organized around three inter-related and interactive facets: heterogeneity, activity, and rheology. Most nuclear constituents are sites of active, ATP-dependent processes and are thus inherently dynamic: The genome undergoes constant rearrangement, the nuclear envelope flickers and fluctuates, nucleoli migrate and coalesce, and many of these events are mediated by nucleoplasmic flows and interactions. And yet there is spatiotemporal organization in terms of hierarchical structure of the genome, its coherently moving regions and membrane-less compartmentalization via phase-separated nucleoplasmic constituents. Moreover, the non-equilibrium or activity-driven nature of the nucleus gives rise to emergent rheology and material properties that impact all cellular processes via the central dogma of molecular biology. New biophysical insights into the cell nucleus can come from appreciating this rich inner life.
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Affiliation(s)
- Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY, USA.
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22
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Miron E, Oldenkamp R, Brown JM, Pinto DMS, Xu CS, Faria AR, Shaban HA, Rhodes JDP, Innocent C, de Ornellas S, Hess HF, Buckle V, Schermelleh L. Chromatin arranges in chains of mesoscale domains with nanoscale functional topography independent of cohesin. SCIENCE ADVANCES 2020; 6:eaba8811. [PMID: 32967822 PMCID: PMC7531892 DOI: 10.1126/sciadv.aba8811] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 08/06/2020] [Indexed: 05/05/2023]
Abstract
Three-dimensional (3D) chromatin organization plays a key role in regulating mammalian genome function; however, many of its physical features at the single-cell level remain underexplored. Here, we use live- and fixed-cell 3D super-resolution and scanning electron microscopy to analyze structural and functional nuclear organization in somatic cells. We identify chains of interlinked ~200- to 300-nm-wide chromatin domains (CDs) composed of aggregated nucleosomes that can overlap with individual topologically associating domains and are distinct from a surrounding RNA-populated interchromatin compartment. High-content mapping uncovers confinement of cohesin and active histone modifications to surfaces and enrichment of repressive modifications toward the core of CDs in both hetero- and euchromatic regions. This nanoscale functional topography is temporarily relaxed in postreplicative chromatin but remarkably persists after ablation of cohesin. Our findings establish CDs as physical and functional modules of mesoscale genome organization.
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Affiliation(s)
- Ezequiel Miron
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Roel Oldenkamp
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Jill M Brown
- MRC Weatherall Institute of Molecular Medicine, Haematology Unit, University of Oxford, Oxford OX3 9DS, UK
| | - David M S Pinto
- Micron Oxford Advanced Bioimaging Unit, University of Oxford, Oxford OX1 3QU, UK
| | - C Shan Xu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Ana R Faria
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Haitham A Shaban
- Spectroscopy Department, Physics Division, National Research Centre, 12622 Dokki, Cairo, Egypt
| | - James D P Rhodes
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | | | - Sara de Ornellas
- MRC Weatherall Institute of Molecular Medicine, Haematology Unit, University of Oxford, Oxford OX3 9DS, UK
| | - Harald F Hess
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Veronica Buckle
- MRC Weatherall Institute of Molecular Medicine, Haematology Unit, University of Oxford, Oxford OX3 9DS, UK
| | - Lothar Schermelleh
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
- Micron Oxford Advanced Bioimaging Unit, University of Oxford, Oxford OX1 3QU, UK
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23
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Chromatin and Nuclear Architecture: Shaping DNA Replication in 3D. Trends Genet 2020; 36:967-980. [PMID: 32713597 DOI: 10.1016/j.tig.2020.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/26/2020] [Accepted: 07/02/2020] [Indexed: 12/13/2022]
Abstract
In eukaryotes, DNA replication progresses through a finely orchestrated temporal and spatial program. The 3D genome structure and nuclear architecture have recently emerged as fundamental determinants of the replication program. Factors with established roles in replication have been recognized as genome organization regulators. Exploiting paradigms from yeasts and mammals, we discuss how DNA replication is regulated in time and space through DNA-associated trans-acting factors, diffusible limiting replication initiation factors, higher-order chromatin folding, dynamic origin localization, and specific nuclear microenvironments. We present an integrated model for the regulation of DNA replication in 3D and highlight the importance of accurate spatio-temporal regulation of DNA replication in physiology and disease.
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24
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Barth R, Bystricky K, Shaban HA. Coupling chromatin structure and dynamics by live super-resolution imaging. SCIENCE ADVANCES 2020; 6:6/27/eaaz2196. [PMID: 32937447 PMCID: PMC7458449 DOI: 10.1126/sciadv.aaz2196] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 04/16/2020] [Indexed: 05/30/2023]
Abstract
Chromatin conformation regulates gene expression and thus, constant remodeling of chromatin structure is essential to guarantee proper cell function. To gain insight into the spatiotemporal organization of the genome, we use high-density photoactivated localization microscopy and deep learning to obtain temporally resolved super-resolution images of chromatin in living cells. In combination with high-resolution dense motion reconstruction, we find elongated ~45- to 90-nm-wide chromatin "blobs." A computational chromatin model suggests that these blobs are dynamically associating chromatin fragments in close physical and genomic proximity and adopt topologically associated domain-like interactions in the time-average limit. Experimentally, we found that chromatin exhibits a spatiotemporal correlation over ~4 μm in space and tens of seconds in time, while chromatin dynamics are correlated over ~6 μm and last 40 s. Notably, chromatin structure and dynamics are closely related, which may constitute a mechanism to grant access to regions with high local chromatin concentration.
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Affiliation(s)
- R Barth
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), CNRS, University of Toulouse, UPS, 31062 Toulouse, France
- Department of Bionanoscience, Delft University of Technology, 2628 CJ, Delft, Netherlands
| | - K Bystricky
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), CNRS, University of Toulouse, UPS, 31062 Toulouse, France
- Institut Universitaire de France (IUF), Paris, France
| | - H A Shaban
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), Centre de Biologie Intégrative (CBI), CNRS, University of Toulouse, UPS, 31062 Toulouse, France.
- Spectroscopy Department, Physics Division, National Research Centre, Dokki, 12622 Cairo, Egypt
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25
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Superresolution imaging reveals spatiotemporal propagation of human replication foci mediated by CTCF-organized chromatin structures. Proc Natl Acad Sci U S A 2020; 117:15036-15046. [PMID: 32541019 DOI: 10.1073/pnas.2001521117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Mammalian DNA replication is initiated at numerous replication origins, which are clustered into thousands of replication domains (RDs) across the genome. However, it remains unclear whether the replication origins within each RD are activated stochastically or preferentially near certain chromatin features. To understand how DNA replication in single human cells is regulated at the sub-RD level, we directly visualized and quantitatively characterized the spatiotemporal organization, morphology, and in situ epigenetic signatures of individual replication foci (RFi) across S-phase at superresolution using stochastic optical reconstruction microscopy. Importantly, we revealed a hierarchical radial pattern of RFi propagation dynamics that reverses directionality from early to late S-phase and is diminished upon caffeine treatment or CTCF knockdown. Together with simulation and bioinformatic analyses, our findings point to a "CTCF-organized REplication Propagation" (CoREP) model, which suggests a nonrandom selection mechanism for replication activation at the sub-RD level during early S-phase, mediated by CTCF-organized chromatin structures. Collectively, these findings offer critical insights into the key involvement of local epigenetic environment in coordinating DNA replication across the genome and have broad implications for our conceptualization of the role of multiscale chromatin architecture in regulating diverse cell nuclear dynamics in space and time.
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Liao J, Lu X, Shao X, Zhu L, Fan X. Uncovering an Organ's Molecular Architecture at Single-Cell Resolution by Spatially Resolved Transcriptomics. Trends Biotechnol 2020; 39:43-58. [PMID: 32505359 DOI: 10.1016/j.tibtech.2020.05.006] [Citation(s) in RCA: 119] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 05/11/2020] [Accepted: 05/12/2020] [Indexed: 01/17/2023]
Abstract
Revealing fine-scale cellular heterogeneity among spatial context and the functional and structural foundations of tissue architecture is fundamental within biological research and pharmacology. Unlike traditional approaches involving single molecules or bulk omics, cutting-edge, spatially resolved transcriptomics techniques offer near-single-cell or even subcellular resolution within tissues. Massive information across higher dimensions along with position-coordinating labels can better map the whole 3D transcriptional landscape of tissues. In this review, we focus on developments and strategies in spatially resolved transcriptomics, compare the cell and gene throughput and spatial resolution in detail for existing methods, and highlight the enormous potential in biomedical research.
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Affiliation(s)
- Jie Liao
- Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Xiaoyan Lu
- Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Xin Shao
- Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China
| | - Ling Zhu
- The Save Sight Institute, Faculty of Medicine and Health, the University of Sydney, Sydney, NSW 2000, Australia
| | - Xiaohui Fan
- Pharmaceutical Informatics Institute, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, Zhejiang, China; The Save Sight Institute, Faculty of Medicine and Health, the University of Sydney, Sydney, NSW 2000, Australia.
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27
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Zidovska A. The self-stirred genome: large-scale chromatin dynamics, its biophysical origins and implications. Curr Opin Genet Dev 2020; 61:83-90. [PMID: 32497955 DOI: 10.1016/j.gde.2020.03.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 01/02/2023]
Abstract
The organization and dynamics of human genome govern all cellular processes - directly impacting the central dogma of biology - yet are poorly understood, especially at large length scales. Chromatin, the functional form of DNA in cells, undergoes frequent local remodeling and rearrangements to accommodate processes such as transcription, replication and DNA repair. How these local activities contribute to nucleus-wide coherent chromatin motion, where micron-scale regions of chromatin move together over several seconds, remains unclear. Activity of nuclear enzymes was found to drive the coherent chromatin dynamics, however, its biological nature and physical mechanism remain to be revealed. The coherent dynamics leads to a perpetual stirring of the genome, leading to collective gene dynamics over microns and seconds, thus likely contributing to local and global gene-expression patterns. Hence, a possible biological role of chromatin coherence may involve gene regulation.
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Affiliation(s)
- Alexandra Zidovska
- Center for Soft Matter Research, Department of Physics, New York University, New York, NY, 10003, USA.
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28
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Tosheva KL, Yuan Y, Matos Pereira P, Culley S, Henriques R. Between life and death: strategies to reduce phototoxicity in super-resolution microscopy. JOURNAL OF PHYSICS D: APPLIED PHYSICS 2020; 53:163001. [PMID: 33994582 PMCID: PMC8114953 DOI: 10.1088/1361-6463/ab6b95] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/01/2019] [Accepted: 01/14/2020] [Indexed: 05/23/2023]
Abstract
Super-resolution microscopy (SRM) enables non-invasive, molecule-specific imaging of the internal structure and dynamics of cells with sub-diffraction limit spatial resolution. One of its major limitations is the requirement for high-intensity illumination, generating considerable cellular phototoxicity. This factor considerably limits the capacity for live-cell observations, particularly for extended periods of time. Here, we give an overview of new developments in hardware, software and probe chemistry aiming to reduce phototoxicity. Additionally, we discuss how the choice of biological model and sample environment impacts the capacity for live-cell observations.
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Affiliation(s)
- Kalina L Tosheva
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Yue Yuan
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | | | - Siân Culley
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- The Francis Crick Institute, London, United Kingdom
| | - Ricardo Henriques
- MRC Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- The Francis Crick Institute, London, United Kingdom
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29
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Parker MW, Bell M, Mir M, Kao JA, Darzacq X, Botchan MR, Berger JM. A new class of disordered elements controls DNA replication through initiator self-assembly. eLife 2019; 8:e48562. [PMID: 31560342 PMCID: PMC6764820 DOI: 10.7554/elife.48562] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 08/14/2019] [Indexed: 12/11/2022] Open
Abstract
The initiation of DNA replication in metazoans occurs at thousands of chromosomal sites known as origins. At each origin, the Origin Recognition Complex (ORC), Cdc6, and Cdt1 co-assemble to load the Mcm2-7 replicative helicase onto chromatin. Current replication models envisage a linear arrangement of isolated origins functioning autonomously; the extent of inter-origin organization and communication is unknown. Here, we report that the replication initiation machinery of D. melanogaster unexpectedly undergoes liquid-liquid phase separation (LLPS) upon binding DNA in vitro. We find that ORC, Cdc6, and Cdt1 contain intrinsically disordered regions (IDRs) that drive LLPS and constitute a new class of phase separating elements. Initiator IDRs are shown to regulate multiple functions, including chromosome recruitment, initiator-specific co-assembly, and Mcm2-7 loading. These data help explain how CDK activity controls replication initiation and suggest that replication programs are subject to higher-order levels of inter-origin organization.
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Affiliation(s)
- Matthew W Parker
- Department of Biophysics and Biophysical ChemistryJohns Hopkins School of MedicineBaltimoreUnited States
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Maren Bell
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Mustafa Mir
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Jonchee A Kao
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Xavier Darzacq
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - Michael R Botchan
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
| | - James M Berger
- Department of Biophysics and Biophysical ChemistryJohns Hopkins School of MedicineBaltimoreUnited States
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30
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Control of DNA replication timing in the 3D genome. Nat Rev Mol Cell Biol 2019; 20:721-737. [DOI: 10.1038/s41580-019-0162-y] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2019] [Indexed: 12/27/2022]
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31
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Varga D, Majoros H, Ujfaludi Z, Erdélyi M, Pankotai T. Quantification of DNA damage induced repair focus formation via super-resolution dSTORM localization microscopy. NANOSCALE 2019; 11:14226-14236. [PMID: 31317161 DOI: 10.1039/c9nr03696b] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In eukaryotic cells, each process, in which DNA is involved, should take place in the context of a chromatin structure. DNA double-strand breaks (DSBs) are one of the most deleterious lesions often leading to chromosomal rearrangement. In response to environmental stresses, cells have developed repair mechanisms to eliminate the DSBs. Upon DSB induction, several factors play roles in chromatin relaxation by catalysing the appropriate histone posttranslational modification (PTM) steps, therefore promoting the access of the repair factors to the DSBs. Among these PTMs, the phosphorylation of the histone variant H2AX at its Ser139 residue (also known as γH2AX) could be observed at the break sites. The structure of a DNA double-strand break induced repair focus has to be organized during the repair as it contributes to the accessibility of specific repair proteins to the damaged site. Our aim was to develop a quantitative approach to analyse the morphology of single repair foci by super-resolution dSTORM microscopy to gain insight into chromatin organization in DNA repair. We have established a specific dSTORM measurement process by developing a new analytical algorithm for gaining quantitative information about chromatin morphology and repair foci topology at an individual γH2AX enriched repair focus. Using this method we quantified single repair foci to show the distribution of γH2AX. The image of individual γH2AX referred to as the Single target Molecule response scatter Plot (SMPlot) was obtained by using high lateral resolution dSTORM images. Determination of the average localization numbers in an SMPlot was one of the key steps of quantitative dSTORM. A repair focus is made up of nanofoci. Such a substructure of repair foci can only be resolved and detected with super-resolution microscopy. Determination of the number of γH2AXs in the nanofoci was another key step of quantitative dSTORM. Additionally, based on our new analysis method, we were able to show the number of nucleosomes in each nanofocus that could allow us to define the possible chromatin structure and the nucleosome density around the break sites. This method is one of the first demonstrations of a single-cell based quantitative measurement of a discrete repair focus, which could provide new opportunities to categorize the spatial organization of nanofoci by parametric determination of topological similarity.
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Affiliation(s)
- Dániel Varga
- University of Szeged, Department of Optics and Quantum Electronics, Hungary.
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32
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Hériché JK, Alexander S, Ellenberg J. Integrating Imaging and Omics: Computational Methods and Challenges. Annu Rev Biomed Data Sci 2019. [DOI: 10.1146/annurev-biodatasci-080917-013328] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fluorescence microscopy imaging has long been complementary to DNA sequencing- and mass spectrometry–based omics in biomedical research, but these approaches are now converging. On the one hand, omics methods are moving from in vitro methods that average across large cell populations to in situ molecular characterization tools with single-cell sensitivity. On the other hand, fluorescence microscopy imaging has moved from a morphological description of tissues and cells to quantitative molecular profiling with single-molecule resolution. Recent technological developments underpinned by computational methods have started to blur the lines between imaging and omics and have made their direct correlation and seamless integration an exciting possibility. As this trend continues rapidly, it will allow us to create comprehensive molecular profiles of living systems with spatial and temporal context and subcellular resolution. Key to achieving this ambitious goal will be novel computational methods and successfully dealing with the challenges of data integration and sharing as well as cloud-enabled big data analysis.
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Affiliation(s)
- Jean-Karim Hériché
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Stephanie Alexander
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Jan Ellenberg
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
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33
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Fluorescence fluctuation spectroscopy: an invaluable microscopy tool for uncovering the biophysical rules for navigating the nuclear landscape. Biochem Soc Trans 2019; 47:1117-1129. [DOI: 10.1042/bst20180604] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/03/2019] [Accepted: 06/05/2019] [Indexed: 11/17/2022]
Abstract
Abstract
Nuclear architecture is fundamental to the manner by which molecules traverse the nucleus. The nucleoplasm is a crowded environment where dynamic rearrangements in local chromatin compaction locally redefine the space accessible toward nuclear protein diffusion. Here, we review a suite of methods based on fluorescence fluctuation spectroscopy (FFS) and how they have been employed to interrogate chromatin organization, as well as the impact this structural framework has on nuclear protein target search. From first focusing on a set of studies that apply FFS to an inert fluorescent tracer diffusing inside the nucleus of a living cell, we demonstrate the capacity of this technology to measure the accessibility of the nucleoplasm. Then with a baseline understanding of the exploration volume available to nuclear proteins during target search, we review direct applications of FFS to fluorescently labeled transcription factors (TFs). FFS can detect changes in TF mobility due to DNA binding, as well as the formation of TF complexes via changes in brightness due to oligomerization. Collectively, we find that FFS-based methods can uncover how nuclear proteins in general navigate the nuclear landscape.
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34
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Single-cell approaches to understand genome organisation throughout the cell cycle. Essays Biochem 2019; 63:209-216. [PMID: 31092688 DOI: 10.1042/ebc20180043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/01/2019] [Accepted: 05/03/2019] [Indexed: 01/05/2023]
Abstract
Mammalian genomes are ordered at several scales, ranging from nucleosomes (beads on a string), to topologically associated domains (TADs), laminar associated domains (LADs), and chromosome territories. These are described briefly below and we refer the reader to some recent comprehensive reviews on genome architecture summarising the current state of knowledge of the organisational principles of the nucleus [1,2]. Biological observations from populations of millions of individual cells can reveal consensus behaviour. New methods to study and interpret biological data at the single-cell level have recently been instrumental in revealing new understanding of cell-to-cell variation and novel biology. Here we will summarise the recent advances in single-cell technology that have provided insights into the behaviour of the mammalian genome during a cell cycle. We will focus on the interphase domain structure of chromosomes, including TADs and LADs, and how chromosome architecture changes during the cell cycle. The role of genome architecture relating to gene expression has been reviewed elsewhere [3].
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35
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Dileep V, Wilson KA, Marchal C, Lyu X, Zhao PA, Li B, Poulet A, Bartlett DA, Rivera-Mulia JC, Qin ZS, Robins AJ, Schulz TC, Kulik MJ, McCord RP, Dekker J, Dalton S, Corces VG, Gilbert DM. Rapid Irreversible Transcriptional Reprogramming in Human Stem Cells Accompanied by Discordance between Replication Timing and Chromatin Compartment. Stem Cell Reports 2019; 13:193-206. [PMID: 31231024 PMCID: PMC6627004 DOI: 10.1016/j.stemcr.2019.05.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 05/20/2019] [Accepted: 05/20/2019] [Indexed: 02/02/2023] Open
Abstract
The temporal order of DNA replication is regulated during development and is highly correlated with gene expression, histone modifications and 3D genome architecture. We tracked changes in replication timing, gene expression, and chromatin conformation capture (Hi-C) A/B compartments over the first two cell cycles during differentiation of human embryonic stem cells to definitive endoderm. Remarkably, transcriptional programs were irreversibly reprogrammed within the first cell cycle and were largely but not universally coordinated with replication timing changes. Moreover, changes in A/B compartment and several histone modifications that normally correlate strongly with replication timing showed weak correlation during the early cell cycles of differentiation but showed increased alignment in later differentiation stages and in terminally differentiated cell lines. Thus, epigenetic cell fate transitions during early differentiation can occur despite dynamic and discordant changes in otherwise highly correlated genomic properties.
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Affiliation(s)
- Vishnu Dileep
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Korey A Wilson
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Claire Marchal
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Xiaowen Lyu
- Department of Biology, Emory University, Atlanta, GA 30322, USA
| | - Peiyao A Zhao
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Ben Li
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA
| | - Axel Poulet
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA
| | - Daniel A Bartlett
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Juan Carlos Rivera-Mulia
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA
| | - Zhaohui S Qin
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, 1518 Clifton Road NE, Atlanta, GA 30322, USA
| | | | | | - Michael J Kulik
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Rachel Patton McCord
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Job Dekker
- Program in Systems Biology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Stephen Dalton
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Victor G Corces
- Department of Biology, Emory University, Atlanta, GA 30322, USA
| | - David M Gilbert
- Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL 32306, USA.
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36
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Abstract
DNA replication starts with the opening of DNA at sites called DNA replication origins. From the single sequence-specific DNA replication origin of the small Escherichia coli genome, up to thousands of origins that are necessary to replicate the large human genome, strict sequence specificity has been lost. Nevertheless, genome-wide analyses performed in the recent years, using different mapping methods, demonstrated that there are precise locations along the metazoan genome from which replication initiates. These sites contain relaxed sequence consensus and epigenetic features. There is flexibility in the choice of origins to be used during a given cell cycle, probably imposed by evolution and developmental constraints. Here, we will briefly describe their main features.
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37
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Maeshima K, Ide S, Babokhov M. Dynamic chromatin organization without the 30-nm fiber. Curr Opin Cell Biol 2019; 58:95-104. [DOI: 10.1016/j.ceb.2019.02.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/08/2019] [Accepted: 02/14/2019] [Indexed: 12/24/2022]
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38
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Parmar JJ, Woringer M, Zimmer C. How the Genome Folds: The Biophysics of Four-Dimensional Chromatin Organization. Annu Rev Biophys 2019; 48:231-253. [DOI: 10.1146/annurev-biophys-052118-115638] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The genetic information that instructs transcription and other cellular functions is carried by the chromosomes, polymers of DNA in complex with histones and other proteins. These polymers are folded inside nuclei five orders of magnitude smaller than their linear length, and many facets of this folding correlate with or are causally related to transcription and other cellular functions. Recent advances in sequencing and imaging-based techniques have enabled new views into several layers of chromatin organization. These experimental findings are accompanied by computational modeling efforts based on polymer physics that can provide mechanistic insights and quantitative predictions. Here, we review current knowledge of the main levels of chromatin organization, from the scale of nucleosomes to the entire nucleus, our current understanding of their underlying biophysical and molecular mechanisms, and some of their functional implications.
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Affiliation(s)
- Jyotsana J. Parmar
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
| | - Maxime Woringer
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
- Sorbonne Universités, CNRS, 75005 Paris, France
- Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, and CIRM Center of Excellence in Stem Cell Genomics, University of California, Berkeley, California 94720, USA
| | - Christophe Zimmer
- Unité Imagerie et Modélisation, CNRS UMR 3691, and C3BI (Center of Bioinformatics, Biostatistics and Integrative Biology), CNRS USR 3756, Institut Pasteur, 75015 Paris, France;, ,
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39
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Hiratani I, Takahashi S. DNA Replication Timing Enters the Single-Cell Era. Genes (Basel) 2019; 10:genes10030221. [PMID: 30884743 PMCID: PMC6470765 DOI: 10.3390/genes10030221] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 03/12/2019] [Accepted: 03/12/2019] [Indexed: 12/20/2022] Open
Abstract
In mammalian cells, DNA replication timing is controlled at the level of megabase (Mb)-sized chromosomal domains and correlates well with transcription, chromatin structure, and three-dimensional (3D) genome organization. Because of these properties, DNA replication timing is an excellent entry point to explore genome regulation at various levels and a variety of studies have been carried out over the years. However, DNA replication timing studies traditionally required at least tens of thousands of cells, and it was unclear whether the replication domains detected by cell population analyses were preserved at the single-cell level. Recently, single-cell DNA replication profiling methods became available, which revealed that the Mb-sized replication domains detected by cell population analyses were actually well preserved in individual cells. In this article, we provide a brief overview of our current knowledge on DNA replication timing regulation in mammals based on cell population studies, outline the findings from single-cell DNA replication profiling, and discuss future directions and challenges.
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Affiliation(s)
- Ichiro Hiratani
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Hyogo 650-0047, Japan.
| | - Saori Takahashi
- Laboratory for Developmental Epigenetics, RIKEN Center for Biosystems Dynamics Research (BDR), Kobe, Hyogo 650-0047, Japan.
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40
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Nagashima R, Hibino K, Ashwin SS, Babokhov M, Fujishiro S, Imai R, Nozaki T, Tamura S, Tani T, Kimura H, Shribak M, Kanemaki MT, Sasai M, Maeshima K. Single nucleosome imaging reveals loose genome chromatin networks via active RNA polymerase II. J Cell Biol 2019; 218:1511-1530. [PMID: 30824489 PMCID: PMC6504897 DOI: 10.1083/jcb.201811090] [Citation(s) in RCA: 117] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 01/31/2019] [Accepted: 02/07/2019] [Indexed: 01/01/2023] Open
Abstract
When a gene is activated, chromatin in the transcribed region is thought to be more open and dynamic. However, Nagashima et al. found that this is not necessarily the case—inhibition of transcription globally increases chromatin motion, revealing the existence of loose genome chromatin networks via transcriptional machinery. Although chromatin organization and dynamics play a critical role in gene transcription, how they interplay remains unclear. To approach this issue, we investigated genome-wide chromatin behavior under various transcriptional conditions in living human cells using single-nucleosome imaging. While transcription by RNA polymerase II (RNAPII) is generally thought to need more open and dynamic chromatin, surprisingly, we found that active RNAPII globally constrains chromatin movements. RNAPII inhibition or its rapid depletion released the chromatin constraints and increased chromatin dynamics. Perturbation experiments of P-TEFb clusters, which are associated with active RNAPII, had similar results. Furthermore, chromatin mobility also increased in resting G0 cells and UV-irradiated cells, which are transcriptionally less active. Our results demonstrated that chromatin is globally stabilized by loose connections through active RNAPII, which is compatible with models of classical transcription factories or liquid droplet formation of transcription-related factors. Together with our computational modeling, we propose the existence of loose chromatin domain networks for various intra-/interchromosomal contacts via active RNAPII clusters/droplets.
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Affiliation(s)
- Ryosuke Nagashima
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan.,Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
| | - Kayo Hibino
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan.,Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
| | - S S Ashwin
- Department of Applied Physics, Nagoya University, Nagoya, Japan.,Department of Computational Science and Engineering, Nagoya University, Nagoya, Japan
| | - Michael Babokhov
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan
| | - Shin Fujishiro
- Department of Applied Physics, Nagoya University, Nagoya, Japan.,Department of Computational Science and Engineering, Nagoya University, Nagoya, Japan
| | - Ryosuke Imai
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan.,Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
| | - Tadasu Nozaki
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan
| | - Tomomi Tani
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, MA
| | - Hiroshi Kimura
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Michael Shribak
- Eugene Bell Center for Regenerative Biology and Tissue Engineering, Marine Biological Laboratory, Woods Hole, MA
| | - Masato T Kanemaki
- Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan.,Molecular Cell Engineering Laboratory, National Institute of Genetics, ROIS, Mishima, Japan
| | - Masaki Sasai
- Department of Applied Physics, Nagoya University, Nagoya, Japan.,Department of Computational Science and Engineering, Nagoya University, Nagoya, Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems, Mishima, Japan .,Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
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41
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Cremer M, Cremer T. Nuclear compartmentalization, dynamics, and function of regulatory DNA sequences. Genes Chromosomes Cancer 2019; 58:427-436. [DOI: 10.1002/gcc.22714] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 11/23/2018] [Accepted: 11/27/2018] [Indexed: 12/15/2022] Open
Affiliation(s)
- Marion Cremer
- Biocenter, Department Biology II; Ludwig Maximilians-Universität (LMU Munich); Munich Germany
| | - Thomas Cremer
- Biocenter, Department Biology II; Ludwig Maximilians-Universität (LMU Munich); Munich Germany
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Pękowska A, Klaus B, Xiang W, Severino J, Daigle N, Klein FA, Oleś M, Casellas R, Ellenberg J, Steinmetz LM, Bertone P, Huber W. Gain of CTCF-Anchored Chromatin Loops Marks the Exit from Naive Pluripotency. Cell Syst 2018; 7:482-495.e10. [PMID: 30414923 PMCID: PMC6327227 DOI: 10.1016/j.cels.2018.09.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 03/06/2018] [Accepted: 09/24/2018] [Indexed: 11/30/2022]
Abstract
The genome of pluripotent stem cells adopts a unique three-dimensional architecture featuring weakly condensed heterochromatin and large nucleosome-free regions. Yet, it is unknown whether structural loops and contact domains display characteristics that distinguish embryonic stem cells (ESCs) from differentiated cell types. We used genome-wide chromosome conformation capture and super-resolution imaging to determine nuclear organization in mouse ESC and neural stem cell (NSC) derivatives. We found that loss of pluripotency is accompanied by widespread gain of structural loops. This general architectural change correlates with enhanced binding of CTCF and cohesins and more pronounced insulation of contacts across chromatin boundaries in lineage-committed cells. Reprogramming NSCs to pluripotency restores the unique features of ESC domain topology. Domains defined by the anchors of loops established upon differentiation are enriched for developmental genes. Chromatin loop formation is a pervasive structural alteration to the genome that accompanies exit from pluripotency and delineates the spatial segregation of developmentally regulated genes.
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Affiliation(s)
- Aleksandra Pękowska
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany.
| | - Bernd Klaus
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Wanqing Xiang
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Jacqueline Severino
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Nathalie Daigle
- Genomics & Immunity, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Felix A Klein
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Małgorzata Oleś
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Rafael Casellas
- Genomics & Immunity, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA; Center for Cancer Research, NCI, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jan Ellenberg
- European Molecular Biology Laboratory (EMBL), Cell Biology and Biophysics Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Lars M Steinmetz
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany; Stanford Genome Technology Center, 855 California Ave, Palo Alto, CA 94305, USA; Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Paul Bertone
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany; European Molecular Biology Laboratory (EMBL), European Bioinformatics Institute, Wellcome Trust Genome Campus, Cambridge CB10 1SD, UK; Wellcome Trust - Medical Research Council Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK.
| | - Wolfgang Huber
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Meyerhofstrasse 1, Heidelberg 69117, Germany.
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Abdollahi E, Taucher-Scholz G, Jakob B. Application of fluorescence lifetime imaging microscopy of DNA binding dyes to assess radiation-induced chromatin compaction changes. Int J Mol Sci 2018; 19:E2399. [PMID: 30110966 PMCID: PMC6121443 DOI: 10.3390/ijms19082399] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 08/02/2018] [Accepted: 08/10/2018] [Indexed: 01/19/2023] Open
Abstract
In recent years several approaches have been developed to address the chromatin status and its changes in eukaryotic cells under different conditions-but only few are applicable in living cells. Fluorescence lifetime imaging microscopy (FLIM) is a functional tool that can be used for the inspection of the molecular environment of fluorophores in living cells. Here, we present the use of single organic minor groove DNA binder dyes in FLIM for measuring chromatin changes following modulation of chromatin structure in living cells. Treatment with histone deacetylase inhibitors led to an increased fluorescence lifetime indicating global chromatin decompaction, whereas hyperosmolarity decreased the lifetime of the used dyes, thus reflecting the expected compaction. In addition, we demonstrate that time domain FLIM data based on single photon counting should be optimized using pile-up and counting loss correction, which affect the readout even at moderate average detector count rates in inhomogeneous samples. Using these corrections and utilizing Hoechst 34580 as chromatin compaction probe, we measured a pan nuclear increase in the lifetime following irradiation with X-rays in living NIH/3T3 cells thus providing a method to measure radiation-induced chromatin decompaction.
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Affiliation(s)
- Elham Abdollahi
- Department of Biophysics, GSI Helmholzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.
| | - Gisela Taucher-Scholz
- Department of Biophysics, GSI Helmholzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.
- Department of Biology, Technical University of Darmstadt, 64287 Darmstadt, Germany.
| | - Burkhard Jakob
- Department of Biophysics, GSI Helmholzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany.
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