1
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Sarıyer OS, Erbaş A. Polymer physics view of peripheral chromatin: de Gennes' self-similar carpet. Phys Rev E 2024; 109:054403. [PMID: 38907468 DOI: 10.1103/physreve.109.054403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Accepted: 04/09/2024] [Indexed: 06/24/2024]
Abstract
Using scaling arguments to model peripheral chromatin localized near the inner surface of the nuclear envelope (NE) as a flexible polymer chain, we discuss the structural properties of the peripheral chromatin composed of alternating lamin-associated domains (LADs) and inter-LADs. Modeling the attraction of LADs to NE by de Gennes' self-similar carpet, which treats the chromatin layer as a polymer fractal, explains two major experimental observations. (i) The high density of chromatin close to the nuclear periphery decays to a constant density as the distance to the periphery increases. (ii) Due to the decreasing mesh size towards the nuclear periphery, the chromatin carpet inside NE excludes molecules (via nonspecific interactions) above a threshold size that depends on the distance from the nuclear periphery.
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Affiliation(s)
- Ozan S Sarıyer
- Pîrî Reis University, School of Arts and Sciences, Tuzla 34940, Istanbul, Turkey
| | - Aykut Erbaş
- UNAM National Nanotechnology Research Center and Institute of Materials Science & Nanotechnology, Bilkent University, Ankara 06800, Turkey and University of Silesia, Institute of Physics, 41-500 Katowice, Poland
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2
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Park J, Kim JJ, Ryu JK. Mechanism of phase condensation for chromosome architecture and function. Exp Mol Med 2024; 56:809-819. [PMID: 38658703 PMCID: PMC11059216 DOI: 10.1038/s12276-024-01226-x] [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] [Received: 11/09/2023] [Revised: 02/23/2024] [Accepted: 02/28/2024] [Indexed: 04/26/2024] Open
Abstract
Chromosomal phase separation is involved in a broad spectrum of chromosome organization and functional processes. Nonetheless, the intricacy of this process has left its molecular mechanism unclear. Here, we introduce the principles governing phase separation and its connections to physiological roles in this context. Our primary focus is contrasting two phase separation mechanisms: self-association-induced phase separation (SIPS) and bridging-induced phase separation (BIPS). We provide a comprehensive discussion of the distinct features characterizing these mechanisms and offer illustrative examples that suggest their broad applicability. With a detailed understanding of these mechanisms, we explore their associations with nucleosomes and chromosomal biological functions. This comprehensive review contributes to the exploration of uncharted territory in the intricate interplay between chromosome architecture and function.
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Affiliation(s)
- Jeongveen Park
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea
| | - Jeong-Jun Kim
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea
| | - Je-Kyung Ryu
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea.
- Institute of Applied Physics of Seoul National University, Seoul, 08826, South Korea.
- Institute of Molecular Biology and Genetics, Seoul National University, Seoul, 08826, South Korea.
- Department of Biological Sciences, Seoul National University, Seoul, 08826, South Korea.
- Interdisciplinary Program in Neuroscience, Seoul National University, Seoul, 08826, South Korea.
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3
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Wei J, Xue Y, Liu Y, Tian H, Shao Y, Gao YQ. Steric repulsion introduced by loop constraints modulates the microphase separation of chromatins. J Chem Phys 2024; 160:054904. [PMID: 38341710 DOI: 10.1063/5.0189692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 01/15/2024] [Indexed: 02/13/2024] Open
Abstract
Within the confines of a densely populated cell nucleus, chromatin undergoes intricate folding, forming loops, domains, and compartments under the governance of topological constraints and phase separation. This coordinated process inevitably introduces interference between different folding strategies. In this study, we model interphase chromatins as block copolymers with hetero-hierarchical loops within a confined system. Employing dissipative particle dynamics simulations and scaling analysis, we aim to explain how the structure and distribution of loop domains modulate the microphase separation of chromatins. Our results highlight the correlation between the microphase separation of the copolymer and the length, heterogeneity, and hierarchically nested levels of the loop domains. This correlation arises from steric repulsion intrinsic to loop domains. The steric repulsion induces variations in chain stiffness (including local orientation correlations and the persistence length), thereby influencing the degree of phase separation. Through simulations of block copolymers with distinct groups of hetero-hierarchical loop anchors, we successfully reproduce changes in phase separation across diverse cell lines, under fixed interaction parameters. These findings, in qualitative alignment with Hi-C data, suggest that the variations of loop constraints alone possess the capacity to regulate higher-order structures and the gene expressions of interphase chromatins.
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Affiliation(s)
| | - Yue Xue
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China
| | - Yawei Liu
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
| | - Hao Tian
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China
| | - Yingfeng Shao
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yi Qin Gao
- Changping Laboratory, Beijing 102206, China
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China
- Shenzhen Bay Laboratory, 5F, No. 9 Duxue Rd., Nanshan District, Shenzhen 518055, Guangdong, China
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4
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Hertzog M, Erdel F. The Material Properties of the Cell Nucleus: A Matter of Scale. Cells 2023; 12:1958. [PMID: 37566037 PMCID: PMC10416959 DOI: 10.3390/cells12151958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/26/2023] [Accepted: 07/26/2023] [Indexed: 08/12/2023] Open
Abstract
Chromatin regulatory processes physically take place in the environment of the cell nucleus, which is filled with the chromosomes and a plethora of smaller biomolecules. The nucleus contains macromolecular assemblies of different sizes, from nanometer-sized protein complexes to micrometer-sized biomolecular condensates, chromosome territories, and nuclear bodies. This multiscale organization impacts the transport processes within the nuclear interior, the global mechanical properties of the nucleus, and the way the nucleus senses and reacts to mechanical stimuli. Here, we discuss recent work on these aspects, including microrheology and micromanipulation experiments assessing the material properties of the nucleus and its subcomponents. We summarize how the properties of multiscale media depend on the time and length scales probed in the experiment, and we reconcile seemingly contradictory observations made on different scales. We also revisit the concept of liquid-like and solid-like material properties for complex media such as the nucleus. We propose that the nucleus can be considered a multiscale viscoelastic medium composed of three major components with distinct properties: the lamina, the chromatin network, and the nucleoplasmic fluid. This multicomponent organization enables the nucleus to serve its different functions as a reaction medium on the nanoscale and as a mechanosensor and structural scaffold on the microscale.
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Affiliation(s)
| | - Fabian Erdel
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, 169 Avenue Marianne Grunberg-Manago, 31062 Toulouse, France
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5
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Erdel F. Phase transitions in heterochromatin organization. Curr Opin Struct Biol 2023; 80:102597. [PMID: 37087823 DOI: 10.1016/j.sbi.2023.102597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/13/2023] [Accepted: 03/20/2023] [Indexed: 04/25/2023]
Abstract
Heterochromatin formation has been proposed to involve phase transitions on the level of the three-dimensional folding of heterochromatin regions and the liquid-liquid demixing of heterochromatin proteins. Here, I outline the hallmarks of such transitions and the current challenges to detect them in living cells. I further discuss the abundance and properties of prominent heterochromatin proteins and relate them to their potential role in driving phase transitions. Recent data from mouse fibroblasts indicate that pericentric heterochromatin is organized via a reordering transition on the level of heterochromatin regions that does not necessarily involve liquid-liquid demixing of heterochromatin proteins. Evaluating key hallmarks of the different candidate phase transition mechanisms across cell types and species will be needed to complete the current picture.
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Affiliation(s)
- Fabian Erdel
- MCD, Center for Integrative Biology (CBI), CNRS, UPS, Toulouse, France.
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6
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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: 27] [Impact Index Per Article: 27.0] [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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7
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Gupta A, Joshi A, Arora K, Mukhopadhyay S, Guptasarma P. The bacterial nucleoid-associated proteins, HU, and Dps, condense DNA into context-dependent biphasic or multiphasic complex coacervates. J Biol Chem 2023; 299:104637. [PMID: 36963493 PMCID: PMC10141540 DOI: 10.1016/j.jbc.2023.104637] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 02/27/2023] [Accepted: 03/08/2023] [Indexed: 03/26/2023] Open
Abstract
The bacterial chromosome, known as its nucleoid, is an amorphous assemblage of globular nucleoprotein domains. It exists in a state of phase separation from the cell's cytoplasm, as an irregularly-shaped, membrane-less, intracellular compartment. This state (the nature of which remains largely unknown) is maintained through bacterial generations ad infinitum. Here, we show that HU, and Dps, two of the most abundant nucleoid-associated proteins (NAPs) of Escherichia coli, undergo spontaneous complex coacervation with different forms of DNA/RNA, both individually and in each other's presence, to cause accretion and compaction of DNA/RNA into liquid-liquid phase separated (LLPS) condensates in vitro. Upon mixing with nucleic acids, HU-A and HU-B form (a) bi-phasic heterotypic mixed condensates in which HU-B helps to lower the Csat of HU-A; and also (b) multi-phasic heterotypic condensates, with Dps, in which de-mixed domains display different contents of HU and Dps. We believe that these modes of complex coacervation that are seen in vitro can serve as models for the in vivo relationships amongst NAPs in nucleoids, involving local and global variations in the relative abundances of the different NAPs, especially in de-mixed sub-domains that are characterized by differing grades of phase separation. Our results clearly demonstrate some quantitative, and some qualitative, differences in the coacervating abilities of different NAPs with DNA, potentially explaining (i) why E. coli has two isoforms of HU, and (ii) why changes in the abundances of HU and Dps facilitate the lag, logarithmic and stationary phases of E. coli growth.
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Affiliation(s)
- Archit Gupta
- Centre for Protein Science, Design and Engineering, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India.
| | - Ashish Joshi
- Centre for Protein Science, Design and Engineering, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Kanika Arora
- Centre for Protein Science, Design and Engineering, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Samrat Mukhopadhyay
- Centre for Protein Science, Design and Engineering, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Chemical Sciences; Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India
| | - Purnananda Guptasarma
- Centre for Protein Science, Design and Engineering, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India; Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Punjab 140306, India.
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8
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Li X, An Z, Zhang W, Li F. Phase Separation: Direct and Indirect Driving Force for High-Order Chromatin Organization. Genes (Basel) 2023; 14:499. [PMID: 36833426 PMCID: PMC9956262 DOI: 10.3390/genes14020499] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 02/09/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023] Open
Abstract
The multi-level spatial chromatin organization in the nucleus is closely related to chromatin activity. The mechanism of chromatin organization and remodeling attract much attention. Phase separation describes the biomolecular condensation which is the basis for membraneless compartments in cells. Recent research shows that phase separation is a key aspect to drive high-order chromatin structure and remodeling. In addition, chromatin functional compartmentalization in the nucleus which is formed by phase separation also plays an important role in overall chromatin structure. In this review, we summarized the latest work about the role of phase separation in spatial chromatin organization, focusing on direct and indirect effects of phase separation on 3D chromatin organization and its impact on transcription regulation.
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Affiliation(s)
- Xiaoli Li
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China
- Department of Cell Biology and Genetics, Core Facility of Developmental Biology, Chongqing Medical University, Chongqing 400016, China
| | - Ziyang An
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Wenqing Zhang
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China
| | - Feifei Li
- Division of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, China
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9
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Roemer A, Mohammed L, Strickfaden H, Underhill DA, Hendzel MJ. Mechanisms governing the accessibility of DNA damage proteins to constitutive heterochromatin. Front Genet 2022; 13:876862. [PMID: 36092926 PMCID: PMC9458887 DOI: 10.3389/fgene.2022.876862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 07/18/2022] [Indexed: 12/05/2022] Open
Abstract
Chromatin is thought to regulate the accessibility of the underlying DNA sequence to machinery that transcribes and repairs the DNA. Heterochromatin is chromatin that maintains a sufficiently high density of DNA packing to be visible by light microscopy throughout the cell cycle and is thought to be most restrictive to transcription. Several studies have suggested that larger proteins and protein complexes are attenuated in their access to heterochromatin. In addition, heterochromatin domains may be associated with phase separated liquid condensates adding further complexity to the regulation of protein concentration within chromocenters. This provides a solvent environment distinct from the nucleoplasm, and proteins that are not size restricted in accessing this liquid environment may partition between the nucleoplasm and heterochromatin based on relative solubility. In this study, we assessed the accessibility of constitutive heterochromatin in mouse cells, which is organized into large and easily identifiable chromocenters, to fluorescently tagged DNA damage response proteins. We find that proteins larger than the expected 10 nm size limit can access the interior of heterochromatin. We find that the sensor proteins Ku70 and PARP1 enrich in mouse chromocenters. At the same time, MRE11 shows variability within an asynchronous population that ranges from depleted to enriched but is primarily homogeneously distribution between chromocenters and the nucleoplasm. While larger downstream proteins such as ATM, BRCA1, and 53BP1 are commonly depleted in chromocenters, they show a wide range of concentrations, with none being depleted beyond approximately 75%. Contradicting exclusively size-dependent accessibility, many smaller proteins, including EGFP, are also depleted in chromocenters. Our results are consistent with minimal size-dependent selectivity but a distinct solvent environment explaining reduced concentrations of diffusing nucleoplasmic proteins within the volume of the chromocenter.
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10
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Iida S, Shinkai S, Itoh Y, Tamura S, Kanemaki MT, Onami S, Maeshima K. Single-nucleosome imaging reveals steady-state motion of interphase chromatin in living human cells. SCIENCE ADVANCES 2022; 8:eabn5626. [PMID: 35658044 PMCID: PMC9166292 DOI: 10.1126/sciadv.abn5626] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Dynamic chromatin behavior plays a critical role in various genome functions. However, it remains unclear how chromatin behavior changes during interphase, where the nucleus enlarges and genomic DNA doubles. While the previously reported chromatin movements varied during interphase when measured using a minute or longer time scale, we unveil that local chromatin motion captured by single-nucleosome imaging/tracking on a second time scale remained steady throughout G1, S, and G2 phases in live human cells. This motion mode appeared to change beyond this time scale. A defined genomic region also behaved similarly. Combined with Brownian dynamics modeling, our results suggest that this steady-state chromatin motion was mainly driven by thermal fluctuations. Steady-state motion temporarily increased following a DNA damage response. Our findings support the viscoelastic properties of chromatin. We propose that the observed steady-state chromatin motion allows cells to conduct housekeeping functions, such as transcription and DNA replication, under similar environments during interphase.
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Affiliation(s)
- Shiori Iida
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
- Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
| | - Soya Shinkai
- Laboratory for Developmental Dynamics, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Yuji Itoh
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
| | - Masato T. Kanemaki
- Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
- Molecular Cell Engineering Laboratory, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
| | - Shuichi Onami
- Laboratory for Developmental Dynamics, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Japan
- Department of Genetics, School of Life Science, SOKENDAI, Mishima, Japan
- Corresponding author.
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11
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Ide S, Tamura S, Maeshima K. Chromatin behavior in living cells: Lessons from single‐nucleosome imaging and tracking. Bioessays 2022; 44:e2200043. [DOI: 10.1002/bies.202200043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/24/2022] [Accepted: 04/26/2022] [Indexed: 11/05/2022]
Affiliation(s)
- Satoru Ide
- Genome Dynamics Laboratory National Institute of Genetics, ROIS Mishima Shizuoka Japan
- Department of Genetics School of Life Science SOKENDAI Mishima Shizuoka Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory National Institute of Genetics, ROIS Mishima Shizuoka Japan
| | - Kazuhiro Maeshima
- Genome Dynamics Laboratory National Institute of Genetics, ROIS Mishima Shizuoka Japan
- Department of Genetics School of Life Science SOKENDAI Mishima Shizuoka Japan
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12
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Hammonds EF, Harwig MC, Paintsil EA, Tillison EA, Hill RB, Morrison EA. Histone H3 and H4 tails play an important role in nucleosome phase separation. Biophys Chem 2022; 283:106767. [PMID: 35158124 PMCID: PMC8963862 DOI: 10.1016/j.bpc.2022.106767] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/19/2022] [Accepted: 01/24/2022] [Indexed: 11/28/2022]
Abstract
Chromatin organization and its dynamic regulation are crucial in governing the temporal and spatial accessibility of DNA for proper gene expression. Disordered chains of nucleosomes comprise the basis of eukaryotic chromatin, forming higher-level organization across a range of length scales. Models of chromatin organization involving phase separation driven by chromatin-associating proteins have been proposed. More recently, evidence has emerged that nucleosome arrays can phase separate in the absence of other protein factors, yet questions remain regarding the molecular basis of chromatin phase separation that governs this dynamic nuclear organization. Here, we break chromatin down into its most basic subunit, the nucleosome core particle, and investigate phase separation using turbidity assays in conjunction with differential interference contrast microscopy. We show that, at physiologically-relevant concentrations, this fundamental subunit of chromatin undergoes phase separation. Individually removing the H3 and H4 tails abrogates phase separation under the same conditions. Taking a reductionist approach to investigate H3 and H4 tail peptide interactions in-trans with DNA and nucleosome core particles supports the direct involvement of these tails in chromatin phase separation. These results provide insight into fundamental mechanisms underlying phase separation of chromatin, which starts at the level of the nucleosome core particle, and support that long-range inter-nucleosomal interactions are sufficient to drive phase separation at nuclear concentrations. Additionally, our data have implications for understanding crosstalk between histone tails and provide a lens through which to interpret the effect of histone post-translational modifications and sequence variants. STATEMENT OF SIGNIFICANCE: Emerging models propose that chromatin organization is based in phase separation, however, mechanisms that drive this dynamic nuclear organization are only beginning to be understood. Previous focus has been on phase separation driven by chromatin-associating proteins, but this has recently shifted to recognize a direct role of chromatin in phase separation. Here, we take a fundamental approach in understanding chromatin phase separation and present new findings that the basic subunit of chromatin, the nucleosome core particle, undergoes phase separation under physiological concentrations of nucleosome and monovalent salt. Furthermore, the histone H3 and H4 tails are involved in phase separation in a manner independent of histone-associating proteins. These data suggest that H3 and H4 tail epigenetic factors may modulate chromatin phase separation.
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Affiliation(s)
- Erin F Hammonds
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America
| | - Megan Cleland Harwig
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America
| | - Emeleeta A Paintsil
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America
| | - Emma A Tillison
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America; Medical Scientist Training Program, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America
| | - R Blake Hill
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America
| | - Emma A Morrison
- Department of Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, United States of America.
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13
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Laghmach R, Di Pierro M, Potoyan D. A Liquid State Perspective on Dynamics of Chromatin Compartments. Front Mol Biosci 2022; 8:781981. [PMID: 35096966 PMCID: PMC8793688 DOI: 10.3389/fmolb.2021.781981] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 12/22/2021] [Indexed: 12/11/2022] Open
Abstract
The interior of the eukaryotic cell nucleus has a crowded and heterogeneous environment packed with chromatin polymers, regulatory proteins, and RNA molecules. Chromatin polymer, assisted by epigenetic modifications, protein and RNA binders, forms multi-scale compartments which help regulate genes in response to cellular signals. Furthermore, chromatin compartments are dynamic and tend to evolve in size and composition in ways that are not fully understood. The latest super-resolution imaging experiments have revealed a much more dynamic and stochastic nature of chromatin compartments than was appreciated before. An emerging mechanism explaining chromatin compartmentalization dynamics is the phase separation of protein and nucleic acids into membraneless liquid condensates. Consequently, concepts and ideas from soft matter and polymer systems have been rapidly entering the lexicon of cell biology. In this respect, the role of computational models is crucial for establishing a rigorous and quantitative foundation for the new concepts and disentangling the complex interplay of forces that contribute to the emergent patterns of chromatin dynamics and organization. Several multi-scale models have emerged to address various aspects of chromatin dynamics, ranging from equilibrium polymer simulations, hybrid non-equilibrium simulations coupling protein binding and chromatin folding, and mesoscopic field-theoretic models. Here, we review these emerging theoretical paradigms and computational models with a particular focus on chromatin’s phase separation and liquid-like properties as a basis for nuclear organization and dynamics.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, IA, United States
| | - Michele Di Pierro
- Department of Physics, Northeastern University, Boston, MA, United States
| | - Davit Potoyan
- Department of Chemistry, Iowa State University, Ames, IA, United States
- *Correspondence: Davit Potoyan,
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14
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Laghmach R, Di Pierro M, Potoyan DA. The interplay of chromatin phase separation and lamina interactions in nuclear organization. Biophys J 2021; 120:5005-5017. [PMID: 34653387 DOI: 10.1016/j.bpj.2021.10.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 09/28/2021] [Accepted: 10/08/2021] [Indexed: 12/12/2022] Open
Abstract
The genetic material of eukaryotes is segregated into transcriptionally active euchromatin and silent heterochromatin compartments. The spatial arrangement of chromatin compartments evolves over the course of cellular life in a process that remains poorly understood. The latest nuclear imaging experiments reveal a number of dynamical signatures of chromatin that are reminiscent of active multiphase liquids. This includes the observations of viscoelastic response, coherent motions, Ostwald ripening, and coalescence of chromatin compartments. There is also growing evidence that liquid-liquid phase separation of protein and nucleic acid components is the underlying mechanism for the dynamical behavior of chromatin. To dissect the organizational and dynamical implications of chromatin's liquid behavior, we have devised a phenomenological field-theoretic model of the nucleus as a multiphase condensate of liquid chromatin types. Employing the liquid chromatin model of the Drosophila nucleus, we have carried out an extensive set of simulations with an objective to shed light on the dynamics and chromatin patterning observed in the latest nuclear imaging experiments. Our simulations reveal the emergence of experimentally detected mesoscale chromatin channels and spheroidal droplets which arise from the dynamic interplay of chromatin type to type interactions and intermingling of chromosomal territories. We also quantitatively reproduce coherent motions of chromatin domains observed in displacement correlation spectroscopy measurements which are explained within the framework of our model by phase separation of chromatin types operating within constrained intrachromosomal and interchromosomal boundaries. Finally, we illuminate the role of heterochromatin-lamina interactions in the nuclear organization by showing that these interactions enhance the mobility of euchromatin and indirectly introduce correlated motions of heterochromatin droplets.
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Affiliation(s)
- Rabia Laghmach
- Department of Chemistry, Iowa State University, Ames, Iowa.
| | - Michele Di Pierro
- Department of Physics, Northeastern University, Boston, Massachusetts
| | - Davit A Potoyan
- Department of Chemistry, Iowa State University, Ames, Iowa; Department of Biochemistry and Molecular Biology, Ames, Iowa; Bioinformatics and Computational Biology Program, Iowa State University, Ames, Iowa.
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15
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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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16
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Wei J, Tian H, Zhou R, Shao Y, Song F, Gao YQ. Topological Constraints with Optimal Length Promote the Formation of Chromosomal Territories at Weakened Degree of Phase Separation. J Phys Chem B 2021; 125:9092-9101. [PMID: 34351763 DOI: 10.1021/acs.jpcb.1c03523] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is generally agreed that the nuclei of eukaryotic cells at interphase are partitioned into disjointed territories, with distinct regions occupied by certain chromosomes. However, the underlying mechanism for such territorialization is still under debate. Here we model chromosomes as coarse-grained block copolymers and to investigate the effect of loop domains (LDs) on the formation of compartments and territories based on dissipative particle dynamics. A critical length of LDs, which depends sensitively on the length of polymeric blocks, is obtained to minimize the degree of phase separation. This also applies to the two-polymer system: The critical length not only maximizes the degree of territorialization but also minimizes the degree of phase separation. Interestingly, by comparing with experimental data, we find the critical length for LDs and the corresponding length of blocks to be respectively very close to the mean length of topologically associating domains (TADs) and chromosomal segments with different densities of CpG islands for human chromosomes. The results indicate that topological constraints with optimal length can contribute to the formation of territories by weakening the degree of phase separation, which likely promotes the chromosomal flexibility in response to genetic regulations.
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Affiliation(s)
- Jiachen Wei
- State Key Laboratory of Nonlinear Mechanics and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.,Shenzhen Bay Laboratory, 5F, No. 9 Duxue Road, Nanshan District, 518055 Shenzhen, Guangdong, China
| | - Hao Tian
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.,Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China.,Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing 100871, China
| | - Rui Zhou
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.,Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China.,Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing 100871, China
| | - Yingfeng Shao
- State Key Laboratory of Nonlinear Mechanics and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fan Song
- State Key Laboratory of Nonlinear Mechanics and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.,School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Qin Gao
- Shenzhen Bay Laboratory, 5F, No. 9 Duxue Road, Nanshan District, 518055 Shenzhen, Guangdong, China.,Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.,Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing 100871, China.,Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing 100871, China
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17
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Daban JR. Soft-matter properties of multilayer chromosomes. Phys Biol 2021; 18. [PMID: 34126606 DOI: 10.1088/1478-3975/ac0aff] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 06/14/2021] [Indexed: 12/17/2022]
Abstract
This perspective aims to identify the relationships between the structural and dynamic properties of chromosomes and the fundamental properties of soft-matter systems. Chromatin is condensed into metaphase chromosomes during mitosis. The resulting structures are elongated cylinders having micrometer-scale dimensions. Our previous studies, using transmission electron microscopy, atomic force microscopy, and cryo-electron tomography, suggested that metaphase chromosomes have a multilayered structure, in which each individual layer has the width corresponding to a mononucleosome sheet. The self-assembly of multilayer chromatin plates from small chromatin fragments suggests that metaphase chromosomes are self-organized hydrogels (in which a single DNA molecule crosslinks the whole structure) with an internal liquid-crystal order produced by the stacking of chromatin layers along the chromosome axis. This organization of chromatin was unexpected, but the spontaneous assembly of large structures has been studied in different soft-matter systems and, according to these studies, the self-organization of chromosomes could be justified by the interplay between weak interactions of repetitive nucleosome building blocks and thermal fluctuations. The low energy of interaction between relatively large building blocks also justifies the easy deformation and structural fluctuations of soft-matter structures and the changes of phase caused by diverse external factors. Consistent with these properties of soft matter, different experimental results show that metaphase chromosomes are easily deformable. Furthermore, at the end of mitosis, condensed chromosomes undergo a phase transition into a more fluid structure, which can be correlated to the decrease in the Mg2+concentration and to the dissociation of condensins from chromosomes. Presumably, the unstacking of layers and chromatin fluctuations driven by thermal energy facilitate gene expression during interphase.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193-Bellaterra (Barcelona), Spain
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18
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Muzzopappa F, Hertzog M, Erdel F. DNA length tunes the fluidity of DNA-based condensates. Biophys J 2021; 120:1288-1300. [PMID: 33640380 PMCID: PMC8059207 DOI: 10.1016/j.bpj.2021.02.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/31/2021] [Accepted: 02/15/2021] [Indexed: 02/09/2023] Open
Abstract
Living organisms typically store their genomic DNA in a condensed form. Mechanistically, DNA condensation can be driven by macromolecular crowding, multivalent cations, or positively charged proteins. At low DNA concentration, condensation triggers the conformational change of individual DNA molecules into a compacted state, with distinct morphologies. Above a critical DNA concentration, condensation goes along with phase separation into a DNA-dilute and a DNA-dense phase. The latter DNA-dense phase can have different material properties and has been reported to be rather liquid-like or solid-like depending on the characteristics of the DNA and the solvent composition. Here, we systematically assess the influence of DNA length on the properties of the resulting condensates. We show that short DNA molecules with sizes below 1 kb can form dynamic liquid-like assemblies when condensation is triggered by polyethylene glycol and magnesium ions, binding of linker histone H1, or nucleosome reconstitution in combination with linker histone H1. With increasing DNA length, molecules preferentially condense into less dynamic more solid-like assemblies, with phage λ-DNA with 48.5 kb forming mostly solid-like assemblies under the conditions assessed here. The transition from liquid-like to solid-like condensates appears to be gradual, with DNA molecules of roughly 1–10 kb forming condensates with intermediate properties. Titration experiments with linker histone H1 suggest that the fluidity of condensates depends on the net number of attractive interactions established by each DNA molecule. We conclude that DNA molecules that are much shorter than a typical human gene are able to undergo liquid-liquid phase separation, whereas longer DNA molecules phase separate by default into rather solid-like condensates. We speculate that the local distribution of condensing factors can modulate the effective length of chromosomal domains in the cell. We anticipate that the link between DNA length and fluidity established here will improve our understanding of biomolecular condensates involving DNA.
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Affiliation(s)
- Fernando Muzzopappa
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, Toulouse, France
| | - Maud Hertzog
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, Toulouse, France
| | - Fabian Erdel
- MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, Toulouse, France.
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19
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Bitman-Lotan E, Orian A. Nuclear organization and regulation of the differentiated state. Cell Mol Life Sci 2021; 78:3141-3158. [PMID: 33507327 PMCID: PMC8038961 DOI: 10.1007/s00018-020-03731-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/01/2020] [Accepted: 12/04/2020] [Indexed: 12/22/2022]
Abstract
Regulation of the differentiated identity requires active and continued supervision. Inability to maintain the differentiated state is a hallmark of aging and aging-related disease. To maintain cellular identity, a network of nuclear regulators is devoted to silencing previous and non-relevant gene programs. This network involves transcription factors, epigenetic regulators, and the localization of silent genes to heterochromatin. Together, identity supervisors mold and maintain the unique nuclear environment of the differentiated cell. This review describes recent discoveries regarding mechanisms and regulators that supervise the differentiated identity and protect from de-differentiation, tumorigenesis, and attenuate forced somatic cell reprograming. The review focuses on mechanisms involved in H3K9me3-decorated heterochromatin and the importance of nuclear lamins in cell identity. We outline how the biophysical properties of these factors are involved in self-compartmentalization of heterochromatin and cell identity. Finally, we discuss the relevance of these regulators to aging and age-related disease.
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Affiliation(s)
- Eliya Bitman-Lotan
- Rappaport Research Institute and Faculty of Medicine, The Rappaport Faculty of Medicine Technion-IIT, Technion Integrative Cancer Center (TICC), Technion-Israel Institute of Technology, Bat-Galim, 3109610, Haifa, Israel
| | - Amir Orian
- Rappaport Research Institute and Faculty of Medicine, The Rappaport Faculty of Medicine Technion-IIT, Technion Integrative Cancer Center (TICC), Technion-Israel Institute of Technology, Bat-Galim, 3109610, Haifa, Israel.
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20
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Lobbia VR, Trueba Sanchez MC, van Ingen H. Beyond the Nucleosome: Nucleosome-Protein Interactions and Higher Order Chromatin Structure. J Mol Biol 2021; 433:166827. [PMID: 33460684 DOI: 10.1016/j.jmb.2021.166827] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/20/2022]
Abstract
The regulation of chromatin biology ultimately depends on the manipulation of its smallest subunit, the nucleosome. The proteins that bind and operate on the nucleosome do so, while their substrate is part of a polymer embedded in the dense nuclear environment. Their molecular interactions must in some way be tuned to deal with this complexity. Due to the rapid increase in the number of high-resolution structures of nucleosome-protein complexes and the increasing understanding of the cellular chromatin structure, it is starting to become clearer how chromatin factors operate in this complex environment. In this review, we analyze the current literature on the interplay between nucleosome-protein interactions and higher-order chromatin structure. We examine in what way nucleosomes-protein interactions can affect and can be affected by chromatin organization at the oligonucleosomal level. In addition, we review the characteristics of nucleosome-protein interactions that can cause phase separation of chromatin. Throughout, we hope to illustrate the exciting challenges in characterizing nucleosome-protein interactions beyond the nucleosome.
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Affiliation(s)
- Vincenzo R Lobbia
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Maria Cristina Trueba Sanchez
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Hugo van Ingen
- NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands.
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21
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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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22
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Villaseñor R, Baubec T. Regulatory mechanisms governing chromatin organization and function. Curr Opin Cell Biol 2020; 70:10-17. [PMID: 33276273 DOI: 10.1016/j.ceb.2020.10.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 10/26/2020] [Accepted: 10/30/2020] [Indexed: 12/12/2022]
Abstract
Nucleosomes, the basic structures used to package genetic information into chromatin, are subject to a diverse array of chemical modifications. A large number of these marks serve as interaction hubs for many nuclear proteins and provide critical structural features for protein recruitment. Dynamic deposition and removal of chromatin modifications by regulatory proteins ensure their correct deposition to the genome, which is essential for DNA replication, transcription, chromatin compaction, or DNA damage repair. The spatiotemporal regulation and maintenance of chromatin marks relies on coordinated activities of writer, eraser, and reader enzymes and often depends on complex multicomponent regulatory circuits. In recent years, the field has made enormous advances in uncovering the mechanisms that regulate chromatin modifications. Here, we discuss well-established and emerging concepts in chromatin biology ranging from cooperativity and multivalent interactions to regulatory feedback loops and increased local concentration of chromatin-modifying enzymes.
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Affiliation(s)
- Rodrigo Villaseñor
- Department of Molecular Mechanisms of Disease, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
| | - Tuncay Baubec
- Department of Molecular Mechanisms of Disease, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland.
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23
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Editorial overview: Diving into the Genome. Curr Opin Genet Dev 2020; 61:iii-vi. [PMID: 32950132 DOI: 10.1016/j.gde.2020.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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