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Dwiranti A, Mualifah M, Kartapradja RHDH, Abinawanto A, Salamah A, Fukui K. Insight into magnesium ions effect on chromosome banding and ultrastructure. Microsc Res Tech 2022; 85:3356-3364. [PMID: 35765224 DOI: 10.1002/jemt.24190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 06/04/2022] [Accepted: 06/20/2022] [Indexed: 11/08/2022]
Abstract
Magnesium ion (Mg2+ ) plays a fundamental role in chromosome condensation which is important for genetic material segregation. Studies about the effects of Mg2+ on the overall chromosome structure have been reported. Nevertheless, its effects on the distribution of heterochromatin and euchromatin region have yet to be investigated. The aim of this study was to evaluate the effects of Mg2+ on the banding pattern and ultrastructure of the chromosome. Chromosome analysis was performed using the synchronized HeLa cells. The effect of Mg2+ was evaluated by subjecting the chromosomes to three different solutions, namely XBE5 (containing 5 mM Mg2+ ) as a control, XBE (0 mM Mg2+ ), and 1 mM EDTA as cations-chelator. Chromosome banding was carried out using the GTL-banding technique. The ultrastructure of the chromosomes treated with and without Mg2+ was further obtained using SEM. The results showed a condensed chromosome structure with a clear banding pattern when the chromosomes were treated with a buffer containing 5 mM Mg2+ . In contrast, chromosomes treated with a buffer containing no Mg2+ and those treated with a cations-chelator showed an expanded and fibrous structure with the lower intensity of the banding pattern. Elongation of the chromosome caused by decondensation resulted in the band splitting. The different ultrastructure of the chromosomes treated with and without Mg2+ was obvious under SEM. The results of this study further emphasized the role of Mg2+ on chromosome structure and gave insights into Mg2+ effects on the banding distribution and ultrastructure of the chromosome.
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Affiliation(s)
- Astari Dwiranti
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Mualifah Mualifah
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | | | - Abinawanto Abinawanto
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Andi Salamah
- Cellular and Molecular Mechanisms in Biological System Research Group, Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, Indonesia
| | - Kiichi Fukui
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
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2
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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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3
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Dwiranti A, Arifudin FS, Takata H, Ohmido N, Fukui K. Application of the Chromosome Image Analyzing System (CHIAS) for Straightening Cation-treated Bent Chromosomes. Microsc Res Tech 2020; 83:1411-1416. [PMID: 32648619 DOI: 10.1002/jemt.23533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/18/2020] [Accepted: 06/02/2020] [Indexed: 11/11/2022]
Abstract
Divalent cations, mainly calcium and magnesium ions, are known to play a major role in the maintenance of chromosomes. The depletion of both ions using ethylenediaminetetraacetic acid (EDTA) results in a bent chromosome structure with extended arms and dispersed chromatin fibers. The importance of divalent cations for the maintenance of chromosome structure has been reported previously; nevertheless, previous studies were limited to qualitative data only. Straightening the bent image of the chromosome would provide quantitative data. Thus, this study aimed to evaluate the effects of cation depletion by the application of the Chromosome Image Analyzing System (CHIAS) to straighten bent chromosomes. Human HeLa chromosomes were treated with EDTA as a known chelating agent in order to investigate the importance of divalent cations on the maintenance of chromosome structure. Chromosomes were stained and directly observed with a fluorescence microscope. Images were then analyzed using CHIAS. The results revealed that EDTA-treated chromosomes showed longer arms than those without EDTA treatment, and most of them tended to bend-out. By straightening the image using CHIAS, the bent chromosomes were successfully straightened. The average lengths of the chromosomes treated with and without EDTA were 4.97 and 0.96 μm, respectively. These results signify the advantages of CHIAS for chromosome analysis and highlight the fundamental effects of cations on chromosome condensation.
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Affiliation(s)
- Astari Dwiranti
- Department of Biology, Faculty of Mathematics and Natural Sciences, University of Indonesia, Depok Campus, West Java, Indonesia
| | - Fendi Sofyan Arifudin
- Department of Biology, Faculty of Mathematics and Natural Sciences, University of Indonesia, Depok Campus, West Java, Indonesia
| | - Hideaki Takata
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ikeda, Osaka, Japan
| | - Nobuko Ohmido
- Department of Human Environmental Science, Graduate School of Human Development and Environment, Kobe University, Kobe, Hyogo, Japan
| | - Kiichi Fukui
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
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4
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Daban JR. Supramolecular multilayer organization of chromosomes: possible functional roles of planar chromatin in gene expression and DNA replication and repair. FEBS Lett 2020; 594:395-411. [PMID: 31879954 DOI: 10.1002/1873-3468.13724] [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: 09/03/2019] [Revised: 11/25/2019] [Accepted: 12/12/2019] [Indexed: 01/16/2023]
Abstract
Experimental evidence indicates that the chromatin filament is self-organized into a multilayer planar structure that is densely stacked in metaphase and unstacked in interphase. This chromatin organization is unexpected, but it is shown that diverse supramolecular assemblies, including dinoflagellate chromosomes, are multilayered. The mechanical strength of planar chromatin protects the genome integrity, even when double-strand breaks are produced. Here, it is hypothesized that the chromatin filament in the loops and topologically associating domains is folded within the thin layers of the multilaminar chromosomes. It is also proposed that multilayer chromatin has two states: inactive when layers are stacked and active when layers are unstacked. Importantly, the well-defined topology of planar chromatin may facilitate DNA replication without entanglements and DNA repair by homologous recombination.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Spain
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5
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Ohyama T. New Aspects of Magnesium Function: A Key Regulator in Nucleosome Self-Assembly, Chromatin Folding and Phase Separation. Int J Mol Sci 2019; 20:ijms20174232. [PMID: 31470631 PMCID: PMC6747271 DOI: 10.3390/ijms20174232] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 08/21/2019] [Accepted: 08/26/2019] [Indexed: 02/07/2023] Open
Abstract
Metal cations are associated with many biological processes. The effects of these cations on nucleic acids and chromatin were extensively studied in the early stages of nucleic acid and chromatin research. The results revealed that some monovalent and divalent metal cations, including Mg2+, profoundly affect the conformations and stabilities of nucleic acids, the folding of chromatin fibers, and the extent of chromosome condensation. Apart from these effects, there have only been a few reports on the functions of these cations. In 2007 and 2013, however, Mg2+-implicated novel phenomena were found: Mg2+ facilitates or enables both self-assembly of identical double-stranded (ds) DNA molecules and self-assembly of identical nucleosomes in vitro. These phenomena may be deeply implicated in the heterochromatin domain formation and chromatin-based phase separation. Furthermore, a recent study showed that elevation of the intranuclear Mg2+ concentration causes unusual differentiation of mouse ES (embryonic stem) cells. All of these phenomena seem to be closely related to one another. Mg2+ seems to be a key regulator of chromatin dynamics and chromatin-based biological processes.
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Affiliation(s)
- Takashi Ohyama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
- Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan.
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Dwiranti A, Takata H, Fukui K. Reversible Changes of Chromosome Structure upon Different Concentrations of Divalent Cations. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2019; 25:817-821. [PMID: 30992092 DOI: 10.1017/s1431927619000266] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The structural details of chromosomes have been of interest to researchers for many years, but how the metaphase chromosome is constructed remains unsolved. Divalent cations have been suggested to be required for the organization of chromosomes. However, detailed information about the role of these cations in chromosome organization is still limited. In the current study, we investigated the effects of Ca2+ and Mg2+ depletion and the reversibility upon re-addition of one of the two ions. Human chromosomes were treated with different concentrations of Ca2+and Mg2+. Depletion of Ca2+ and both Ca2+ and Mg2+ were carried out using 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and ethylenediaminetetraacetic acid (EDTA), respectively. Chromosome structure was examined by fluorescence microscopy and scanning electron microscopy. The results indicated that chromosome structures after treatment with a buffer without Mg2+, after Ca2+ depletion, as well as after depletion of both Mg2+, and Ca2+, yielded fewer compact structures with fibrous chromatin than those without cation depletion. Interestingly, the chromatin of EDTA-treated chromosomes reversed to their original granular diameters after re-addition of either Mg2+ or Ca2+ only. These findings signify the importance of divalent cations on the chromosome structure and suggest the interchangeable role of Ca2+ and Mg2+.
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Affiliation(s)
- Astari Dwiranti
- Department of Biology, Faculty of Mathematics and Natural Sciences,Universitas Indonesia,Depok Campus, 16404 West Java,Indonesia
| | - Hideaki Takata
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology,Midorigaoka, Ikeda, Osaka 563-8577,Japan
| | - Kiichi Fukui
- Graduate School of Pharmaceutical Sciences,Osaka University,Suita, Osaka 565-0871,Japan
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7
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Chromatin plates in the interphase nucleus. FEBS Lett 2019; 593:810-819. [DOI: 10.1002/1873-3468.13370] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/12/2019] [Accepted: 03/19/2019] [Indexed: 12/14/2022]
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Chicano A, Crosas E, Otón J, Melero R, Engel BD, Daban JR. Frozen-hydrated chromatin from metaphase chromosomes has an interdigitated multilayer structure. EMBO J 2019; 38:embj.201899769. [PMID: 30609992 DOI: 10.15252/embj.201899769] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 11/29/2018] [Accepted: 12/05/2018] [Indexed: 12/20/2022] Open
Abstract
Cryo-electron tomography and small-angle X-ray scattering were used to investigate the chromatin folding in metaphase chromosomes. The tomographic 3D reconstructions show that frozen-hydrated chromatin emanated from chromosomes is planar and forms multilayered plates. The layer thickness was measured accounting for the contrast transfer function fringes at the plate edges, yielding a width of ~ 7.5 nm, which is compatible with the dimensions of a monolayer of nucleosomes slightly tilted with respect to the layer surface. Individual nucleosomes are visible decorating distorted plates, but typical plates are very dense and nucleosomes are not identifiable as individual units, indicating that they are tightly packed. Two layers in contact are ~ 13 nm thick, which is thinner than the sum of two independent layers, suggesting that nucleosomes in the layers interdigitate. X-ray scattering of whole chromosomes shows a main scattering peak at ~ 6 nm, which can be correlated with the distance between layers and between interdigitating nucleosomes interacting through their faces. These observations support a model where compact chromosomes are composed of many chromatin layers stacked along the chromosome axis.
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Affiliation(s)
- Andrea Chicano
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Eva Crosas
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Barcelona, Spain.,NCD Beamline, ALBA Synchrotron Light Source, Cerdanyola del Vallès, Barcelona, Spain
| | - Joaquín Otón
- National Center of Biotechnology (CSIC), Campus Univ. Autónoma de Madrid, Madrid, Spain
| | - Roberto Melero
- National Center of Biotechnology (CSIC), Campus Univ. Autónoma de Madrid, Madrid, Spain
| | - Benjamin D Engel
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany
| | - Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Barcelona, Spain
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9
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Kuznetsova MA, Sheval EV. Chromatin fibers: from classical descriptions to modern interpretation. Cell Biol Int 2016; 40:1140-1151. [PMID: 27569720 DOI: 10.1002/cbin.10672] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Accepted: 08/20/2016] [Indexed: 12/14/2022]
Abstract
The first description of intrachromosomal fibers was made by Baranetzky in 1880. Since that time, a plethora of fibrillar substructures have been described inside the mitotic chromosomes, and published data indicate that chromosomes may be formed as a result of the hierarchical folding of chromatin fibers. In this review, we examine the evolution and the current state of research on the morphological organization of mitotic chromosomes.
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Affiliation(s)
- Maria A Kuznetsova
- Faculty of Bioengineering and Bioinformatics, M.V. Lomonosov Moscow State University, 119992, Moscow, Russia.,A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, 119992, Moscow, Russia
| | - Eugene V Sheval
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, 119992, Moscow, Russia. .,LIA1066 French-Russian Joint Cancer Research Laboratory, 119334, Moscow, Russia.
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10
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Daban JR. Stacked thin layers of metaphase chromatin explain the geometry of chromosome rearrangements and banding. Sci Rep 2015; 5:14891. [PMID: 26446309 PMCID: PMC4597206 DOI: 10.1038/srep14891] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 08/21/2015] [Indexed: 01/02/2023] Open
Abstract
The three-dimensional organization of tightly condensed chromatin within metaphase chromosomes has been one of the most challenging problems in structural biology since the discovery of the nucleosome. This study shows that chromosome images obtained from typical banded karyotypes and from different multicolour cytogenetic analyses can be used to gain information about the internal structure of chromosomes. Chromatin bands and the connection surfaces in sister chromatid exchanges and in cancer translocations are planar and orthogonal to the chromosome axis. Chromosome stretching produces band splitting and even the thinnest bands are orthogonal and well defined, indicating that short stretches of DNA can occupy completely the chromosome cross-section. These observations impose strong physical constraints on models that attempt to explain chromatin folding in chromosomes. The thin-plate model, which consists of many stacked layers of planar chromatin perpendicular to the chromosome axis, is compatible with the observed orientation of bands, with the existence of thin bands, and with band splitting; it is also compatible with the orthogonal orientation and planar geometry of the connection surfaces in chromosome rearrangements. The results obtained provide a consistent interpretation of the chromosome structural properties that are used in clinical cytogenetics for the diagnosis of hereditary diseases and cancers.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193-Bellaterra, Spain
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11
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Daban JR. The energy components of stacked chromatin layers explain the morphology, dimensions and mechanical properties of metaphase chromosomes. J R Soc Interface 2014; 11:20131043. [PMID: 24402918 PMCID: PMC3899872 DOI: 10.1098/rsif.2013.1043] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 12/11/2013] [Indexed: 12/17/2022] Open
Abstract
The measurement of the dimensions of metaphase chromosomes in different animal and plant karyotypes prepared in different laboratories indicates that chromatids have a great variety of sizes which are dependent on the amount of DNA that they contain. However, all chromatids are elongated cylinders that have relatively similar shape proportions (length to diameter ratio approx. 13). To explain this geometry, it is considered that chromosomes are self-organizing structures formed by stacked layers of planar chromatin and that the energy of nucleosome-nucleosome interactions between chromatin layers inside the chromatid is approximately 3.6 × 10(-20) J per nucleosome, which is the value reported by other authors for internucleosome interactions in chromatin fibres. Nucleosomes in the periphery of the chromatid are in contact with the medium; they cannot fully interact with bulk chromatin within layers and this generates a surface potential that destabilizes the structure. Chromatids are smooth cylinders because this morphology has a lower surface energy than structures having irregular surfaces. The elongated shape of chromatids can be explained if the destabilizing surface potential is higher in the telomeres (approx. 0.16 mJ m(-2)) than in the lateral surface (approx. 0.012 mJ m(-2)). The results obtained by other authors in experimental studies of chromosome mechanics have been used to test the proposed supramolecular structure. It is demonstrated quantitatively that internucleosome interactions between chromatin layers can justify the work required for elastic chromosome stretching (approx. 0.1 pJ for large chromosomes). The high amount of work (up to approx. 10 pJ) required for large chromosome extensions is probably absorbed by chromatin layers through a mechanism involving nucleosome unwrapping.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain
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12
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Dwiranti A, Hamano T, Takata H, Nagano S, Guo H, Onishi K, Wako T, Uchiyama S, Fukui K. The effect of magnesium ions on chromosome structure as observed by helium ion microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2014; 20:184-188. [PMID: 24229477 DOI: 10.1017/s1431927613013792] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
One of the few conclusions known about chromosome structure is that Mg2+ is required for the organization of chromosomes. Scanning electron microscopy is a powerful tool for studying chromosome morphology, but being nonconductive, chromosomes require metal/carbon coating that may conceal information about the detailed surface structure of the sample. Helium ion microscopy (HIM), which has recently been developed, does not require sample coating due to its charge compensation system. Here we investigated the structure of isolated human chromosomes under different Mg2+ concentrations by HIM. High-contrast and resolution images from uncoated samples obtained by HIM enabled investigation on the effects of Mg2+ on chromosome structure. Chromatin fiber information was obtained more clearly with uncoated than coated chromosomes. Our results suggest that both overall features and detailed structure of chromatin are significantly affected by different Mg2+ concentrations. Chromosomes were more condensed and a globular structure of chromatin with 30 nm diameter was visualized with 5 mM Mg2+ treatment, while 0 mM Mg2+ resulted in a less compact and more fibrous structure 11 nm in diameter. We conclude that HIM is a powerful tool for investigating chromosomes and other biological samples without requiring metal/carbon coating.
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Affiliation(s)
- Astari Dwiranti
- Laboratory of Dynamic Cell Biology, Department of Biotechnology, Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Tohru Hamano
- Laboratory of Dynamic Cell Biology, Department of Biotechnology, Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hideaki Takata
- Laboratory of Dynamic Cell Biology, Department of Biotechnology, Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shoko Nagano
- Surface Characterization Group, Nano Characterization Unit, Advanced Key Technologies Division, National Institute for Materials Science, Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - Hongxuan Guo
- Global Research Center for Environment and Energy Based on Nanomaterials Science, National Institute for Materials Science, Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - Keiko Onishi
- Surface Characterization Group, Nano Characterization Unit, Advanced Key Technologies Division, National Institute for Materials Science, Sengen, Tsukuba, Ibaraki 305-0047, Japan
| | - Toshiyuki Wako
- Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki 305-8602, Japan
| | - Susumu Uchiyama
- Laboratory of Dynamic Cell Biology, Department of Biotechnology, Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kiichi Fukui
- Laboratory of Dynamic Cell Biology, Department of Biotechnology, Graduate School of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
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13
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Caravaca JM, Donahue G, Becker JS, He X, Vinson C, Zaret KS. Bookmarking by specific and nonspecific binding of FoxA1 pioneer factor to mitotic chromosomes. Genes Dev 2013; 27:251-60. [PMID: 23355396 DOI: 10.1101/gad.206458.112] [Citation(s) in RCA: 160] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
While most transcription factors exit the chromatin during mitosis and the genome becomes silent, a subset of factors remains and "bookmarks" genes for rapid reactivation as cells progress through the cell cycle. However, it is unknown whether such bookmarking factors bind to chromatin similarly in mitosis and how different binding capacities among them relate to function. We compared a diverse set of transcription factors involved in liver differentiation and found markedly different extents of mitotic chromosome binding. Among them, the pioneer factor FoxA1 exhibits the greatest extent of mitotic chromosome binding. Genomically, ~15% of the FoxA1 interphase target sites are bound in mitosis, including at genes that are important for liver differentiation. Biophysical, genome mapping, and mutagenesis studies of FoxA1 reveals two different modes of binding to mitotic chromatin. Specific binding in mitosis occurs at sites that continue to be bound from interphase. Nonspecific binding in mitosis occurs across the chromosome due to the intrinsic chromatin affinity of FoxA1. Both specific and nonspecific binding contribute to timely reactivation of target genes post-mitosis. These studies reveal an unexpected diversity in the mechanisms by which transcription factors help retain cell identity during mitosis.
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Affiliation(s)
- Juan Manuel Caravaca
- Epigenetics Program, Department of Cell and Developmental Biology, University of Pennsylvania, Perelman School of Medicine, Smilow Center for Translation Research, Philadelphia, PA 19104, USA
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14
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Self-assembly of thin plates from micrococcal nuclease-digested chromatin of metaphase chromosomes. Biophys J 2013; 103:567-575. [PMID: 22947873 DOI: 10.1016/j.bpj.2012.06.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 06/12/2012] [Accepted: 06/20/2012] [Indexed: 12/13/2022] Open
Abstract
The three-dimensional organization of the enormously long DNA molecules packaged within metaphase chromosomes has been one of the most elusive problems in structural biology. Chromosomal DNA is associated with histones and different structural models consider that the resulting long chromatin fibers are folded forming loops or more irregular three-dimensional networks. Here, we report that fragments of chromatin fibers obtained from human metaphase chromosomes digested with micrococcal nuclease associate spontaneously forming multilaminar platelike structures. These self-assembled structures are identical to the thin plates found previously in partially denatured chromosomes. Under metaphase ionic conditions, the fragments that are initially folded forming the typical 30-nm chromatin fibers are untwisted and incorporated into growing plates. Large plates can be self-assembled from very short chromatin fragments, indicating that metaphase chromatin has a high tendency to generate plates even when there are many discontinuities in the DNA chain. Self-assembly at 37°C favors the formation of thick plates having many layers. All these results demonstrate conclusively that metaphase chromatin has the intrinsic capacity to self-organize as a multilayered planar structure. A chromosome structure consistent of many stacked layers of planar chromatin avoids random entanglement of DNA, and gives compactness and a high physical consistency to chromatids.
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15
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Abstract
Eukaryotic genomic DNA is combined with histones, nonhistone proteins, and RNA to form chromatin, which is extensively packaged hierarchically to fit inside a cell's nucleus. The nucleosome-comprising a histone octamer with 147 base pairs of DNA wrapped around it-is the initial level and the repeating unit of chromatin packaging, which electron microscopy first made visible to the human eye as "beads on a string" nearly four decades ago. The mechanism and nature of chromatin packaging are still under intense research. Recently, classic methods like chromatin immunoprecipitation and digestion with deoxyribonuclease and micrococcal nuclease have been combined with high-throughput sequencing to provide detailed nucleosome occupancy maps, and chromosome conformation capture and its variants have revealed that higher-order chromatin structure involves long-range loop formation between distant genomic elements. This review discusses the methods for identifying higher-order chromatin structure and the information they have provided on this important topic.
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Affiliation(s)
- Samin A Sajan
- Department of Medicine, Division of Human Genetics, University of Washington, Seattle, WA 98195, USA
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16
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Daban JR. Electron microscopy and atomic force microscopy studies of chromatin and metaphase chromosome structure. Micron 2011; 42:733-50. [PMID: 21703860 DOI: 10.1016/j.micron.2011.05.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 05/01/2011] [Indexed: 11/26/2022]
Abstract
The folding of the chromatin filament and, in particular, the organization of genomic DNA within metaphase chromosomes has attracted the interest of many laboratories during the last five decades. This review discusses our current understanding of chromatin higher-order structure based on results obtained with transmission electron microscopy (TEM), cryo-electron microscopy (cryo-EM), and different atomic force microscopy (AFM) techniques. Chromatin isolated from different cell types in buffers without cations form extended filaments with nucleosomes visible as separated units. In presence of low concentrations of Mg(2+), chromatin filaments are folded into fibers having a diameter of ∼ 30 nm. Highly compact fibers were obtained with isolated chromatin fragments in solutions containing 1-2mM Mg(2+). The high density of these fibers suggested that the successive turns of the chromatin filament are interdigitated. Similar results were obtained with reconstituted nucleosome arrays under the same ionic conditions. This led to the proposal of compact interdigitated solenoid models having a helical pitch of 4-5 nm. These findings, together with the observation of columns of stacked nucleosomes in different liquid crystal phases formed by aggregation of nucleosome core particles at high concentration, and different experimental evidences obtained using other approaches, indicate that face-to-face interactions between nucleosomes are very important for the formation of dense chromatin structures. Chromatin fibers were observed in metaphase chromosome preparations in deionized water and in buffers containing EDTA, but chromosomes in presence of the Mg(2+) concentrations found in metaphase (5-22 mM) are very compact, without visible fibers. Moreover, a recent cryo-electron microscopy analysis of vitreous sections of mitotic cells indicated that chromatin has a disordered organization, which does not support the existence of 30-nm fibers in condensed chromosomes. TEM images of partially denatured chromosomes obtained using different procedures that maintain the ionic conditions of metaphase showed that bulk chromatin in chromosomes is organized forming multilayered plate-like structures. The structure and mechanical properties of these plates were studied using cryo-EM, electron tomography, AFM imaging in aqueous media, and AFM-based nanotribology and force spectroscopy. The results obtained indicated that the chromatin filament forms a flexible two-dimensional network, in which DNA is the main component responsible for the mechanical strength observed in friction force measurements. The discovery of this unexpected structure based on a planar geometry has opened completely new possibilities for the understanding of chromatin folding in metaphase chromosomes. It was proposed that chromatids are formed by many stacked thin chromatin plates oriented perpendicular to the chromatid axis. Different experimental evidences indicated that nucleosomes in the plates are irregularly oriented, and that the successive layers are interdigitated (the apparent layer thickness is 5-6 nm), allowing face-to-face interactions between nucleosomes of adjacent layers. The high density of this structure is in agreement with the high concentration of DNA observed in metaphase chromosomes of different species, and the irregular orientation of nucleosomes within the plates make these results compatible with those obtained with mitotic cell cryo-sections. The multilaminar chromatin structure proposed for chromosomes allows an easy explanation of chromosome banding and of the band splitting observed in stretched chromosomes.
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Affiliation(s)
- Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
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Gállego I, Oncins G, Sisquella X, Fernàndez-Busquets X, Daban JR. Nanotribology results show that DNA forms a mechanically resistant 2D network in metaphase chromatin plates. Biophys J 2011; 99:3951-8. [PMID: 21156137 DOI: 10.1016/j.bpj.2010.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 10/18/2010] [Accepted: 11/10/2010] [Indexed: 10/18/2022] Open
Abstract
In a previous study, we found that metaphase chromosomes are formed by thin plates, and here we have applied atomic force microscopy (AFM) and friction force measurements at the nanoscale (nanotribology) to analyze the properties of these planar structures in aqueous media at room temperature. Our results show that high concentrations of NaCl and EDTA and extensive digestion with protease and nuclease enzymes cause plate denaturation. Nanotribology studies show that native plates under structuring conditions (5 mM Mg2+) have a relatively high friction coefficient (μ≈0.3), which is markedly reduced when high concentrations of NaCl or EDTA are added (μ≈0.1). This lubricant effect can be interpreted considering the electrostatic repulsion between DNA phosphate groups and the AFM tip. Protease digestion increases the friction coefficient (μ≈0.5), but the highest friction is observed when DNA is cleaved by micrococcal nuclease (μ≈0.9), indicating that DNA is the main structural element of plates. Whereas nuclease-digested plates are irreversibly damaged after the friction measurement, native plates can absorb kinetic energy from the AFM tip without suffering any damage. These results suggest that plates are formed by a flexible and mechanically resistant two-dimensional network which allows the safe storage of DNA during mitosis.
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Affiliation(s)
- Isaac Gállego
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, Bellaterra, Spain
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Castro-Hartmann P, Milla M, Daban JR. Irregular Orientation of Nucleosomes in the Well-Defined Chromatin Plates of Metaphase Chromosomes. Biochemistry 2010; 49:4043-50. [DOI: 10.1021/bi100125f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Pablo Castro-Hartmann
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Maria Milla
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Joan-Ramon Daban
- Departament de Bioquímica i Biologia Molecular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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Dense chromatin plates in metaphase chromosomes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 38:503-22. [DOI: 10.1007/s00249-008-0401-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 12/11/2008] [Accepted: 12/19/2008] [Indexed: 10/21/2022]
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Zhou J, Fan JY, Rangasamy D, Tremethick DJ. The nucleosome surface regulates chromatin compaction and couples it with transcriptional repression. Nat Struct Mol Biol 2007; 14:1070-6. [PMID: 17965724 DOI: 10.1038/nsmb1323] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2007] [Accepted: 09/24/2007] [Indexed: 11/09/2022]
Abstract
Although it is believed that the interconversion between permissive and refractory chromatin structures is important in regulating gene transcription, this process is poorly understood. Central to addressing this issue is to elucidate how a nucleosomal array folds into higher-order chromatin structures. Such findings can then provide new insights into how the folding process is regulated to yield different functional states. Using well-defined in vitro chromatin-assembly and transcription systems, we show that a small acidic region on the surface of the nucleosome is crucial both for the folding of a nucleosomal template into the 30-nm chromatin fiber and for the efficient repression of transcription, thereby providing a mechanistic link between these two essential processes. This structure-function relationship has been exploited by complex eukaryotic cells through the replacement of H2A with the specific variant H2A.Bbd, which naturally lacks an acidic patch.
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Affiliation(s)
- Jiansheng Zhou
- The John Curtin School of Medical Research, The Australian National University, PO Box 334, Canberra, Australian Capital Territory 2601, Australia
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Caño S, Caravaca JM, Martín M, Daban JR. Highly compact folding of chromatin induced by cellular cation concentrations. Evidence from atomic force microscopy studies in aqueous solution. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2006; 35:495-501. [PMID: 16572269 DOI: 10.1007/s00249-006-0057-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/10/2006] [Accepted: 03/14/2006] [Indexed: 11/29/2022]
Abstract
We have performed a very extensive investigation of chromatin folding in different buffers over a wide range of ionic conditions similar to those found in eukaryotic cells. Our results show that in the presence of physiological concentrations of monovalent cations and/or low concentrations of divalent cations, small chicken erythrocyte chromatin fragments and chromatin from HeLa cells observed by transmission electron microscopy (TEM) show a compact folding, forming circular bodies of approximately 35 nm in diameter that were found previously in our laboratory in studies performed under very limited conditions. Since TEM images are obtained with dehydrated samples, we have performed atomic force microscopy (AFM) experiments to analyze chromatin structure in the presence of solutions containing different cation concentrations. The highly compact circular structures (in which individual nucleosomes are not visible as separated units) produced by small chromatin fragments in interphase ionic conditions observed by AFM are equivalent to the structures observed by TEM with chromatin samples prepared under the same ionic conditions. We have also carried out experiments of sedimentation and trypsin digestion of chromatin fragments; the results obtained confirm our AFM observations. Our results suggest that the compaction of bulk interphase chromatin in solution at room temperature is considerably higher than that generally considered in current literature. The dense chromatin folding observed in this study is consistent with the requirement of compact chromatin structures as starting elements for the building of metaphase chromosomes, but poses a difficult physical problem for gene expression during interphase.
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Affiliation(s)
- Silvia Caño
- Departament de Bioquímica i Biologia Molecular, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
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