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Hikmat WM, Sievers A, Hausmann M, Hildenbrand G. Peculiar k-mer Spectra Are Correlated with 3D Contact Frequencies and Breakpoint Regions in the Human Genome. Genes (Basel) 2024; 15:1247. [PMID: 39457371 PMCID: PMC11506876 DOI: 10.3390/genes15101247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2024] [Revised: 09/23/2024] [Accepted: 09/24/2024] [Indexed: 10/28/2024] Open
Abstract
BACKGROUND It is widely accepted that the 3D chromatin organization in human cell nuclei is not random and recent investigations point towards an interactive relation of epigenetic functioning and chromatin (re-)organization. Although chromatin organization seems to be the result of self-organization of the entirety of all molecules available in the cell nucleus, a general question remains open as to what extent chromatin organization might additionally be predetermined by the DNA sequence and, if so, if there are characteristic differences that distinguish typical regions involved in dysfunction-related aberrations from normal ones, since typical DNA breakpoint regions involved in disease-related chromosome aberrations are not randomly distributed along the DNA sequence. METHODS Highly conserved k-mer patterns in intronic and intergenic regions have been reported in eukaryotic genomes. In this article, we search and analyze regions deviating from average spectra (ReDFAS) of k-mer word frequencies in the human genome. This includes all assembled regions, e.g., telomeric, centromeric, genic as well as intergenic regions. RESULTS A positive correlation between k-mer spectra and 3D contact frequencies, obtained exemplarily from given Hi-C datasets, has been found indicating a relation of ReDFAS to chromatin organization and interactions. We also searched and found correlations of known functional annotations, e.g., genes correlating with ReDFAS. Selected regions known to contain typical breakpoints on chromosomes 9 and 5 that are involved in cancer-related chromosomal aberrations appear to be enriched in ReDFAS. Since transposable elements like ALUs are often assigned as major players in 3D genome organization, we also studied their impact on our examples but could not find a correlation between ALU regions and breakpoints comparable to ReDFAS. CONCLUSIONS Our findings might show that ReDFAS are associated with instable regions of the genome and regions with many chromatin contacts which is in line with current research indicating that chromatin loop anchor points lead to genomic instability.
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Affiliation(s)
- Wisam Mohammed Hikmat
- Kirchhoff-Institute for Physics, Heidelberg University, INF 227, 69117 Heidelberg, Germany; (W.M.H.); (A.S.)
| | - Aaron Sievers
- Kirchhoff-Institute for Physics, Heidelberg University, INF 227, 69117 Heidelberg, Germany; (W.M.H.); (A.S.)
- Institute for Human Genetics, University Hospital Heidelberg, INF 366, 69117 Heidelberg, Germany
| | - Michael Hausmann
- Kirchhoff-Institute for Physics, Heidelberg University, INF 227, 69117 Heidelberg, Germany; (W.M.H.); (A.S.)
| | - Georg Hildenbrand
- Kirchhoff-Institute for Physics, Heidelberg University, INF 227, 69117 Heidelberg, Germany; (W.M.H.); (A.S.)
- Faculty of Engineering, University of Applied Science Aschaffenburg, Würzburger Str. 45, 63743 Aschaffenburg, Germany
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2
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Brändle F, Frühbauer B, Jagannathan M. Principles and functions of pericentromeric satellite DNA clustering into chromocenters. Semin Cell Dev Biol 2022; 128:26-39. [PMID: 35144860 DOI: 10.1016/j.semcdb.2022.02.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/03/2022] [Accepted: 02/03/2022] [Indexed: 12/29/2022]
Abstract
Simple non-coding tandem repeats known as satellite DNA are observed widely across eukaryotes. These repeats occupy vast regions at the centromere and pericentromere of chromosomes but their contribution to cellular function has remained incompletely understood. Here, we review the literature on pericentromeric satellite DNA and discuss its organization and functions across eukaryotic species. We specifically focus on chromocenters, DNA-dense nuclear foci that contain clustered pericentromeric satellite DNA repeats from multiple chromosomes. We first discuss chromocenter formation and the roles that epigenetic modifications, satellite DNA transcripts and sequence-specific satellite DNA-binding play in this process. We then review the newly emerging functions of chromocenters in genome encapsulation, the maintenance of cell fate and speciation. We specifically highlight how the rapid divergence of satellite DNA repeats impacts reproductive isolation between closely related species. Together, we underline the importance of this so-called 'junk DNA' in fundamental biological processes.
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Affiliation(s)
- Franziska Brändle
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland
| | - Benjamin Frühbauer
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland
| | - Madhav Jagannathan
- Institute of Biochemistry, ETH Zürich, Otto-Stern-Weg 3, Zürich CH-8093, Switzerland.
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Gil L, Niño SA, Guerrero C, Jiménez-Capdeville ME. Phospho-Tau and Chromatin Landscapes in Early and Late Alzheimer's Disease. Int J Mol Sci 2021; 22:ijms221910283. [PMID: 34638632 PMCID: PMC8509045 DOI: 10.3390/ijms221910283] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/17/2021] [Accepted: 09/18/2021] [Indexed: 12/25/2022] Open
Abstract
Cellular identity is determined through complex patterns of gene expression. Chromatin, the dynamic structure containing genetic information, is regulated through epigenetic modulators, mainly by the histone code. One of the main challenges for the cell is maintaining functionality and identity, despite the accumulation of DNA damage throughout the aging process. Replicative cells can remain in a senescent state or develop a malign cancer phenotype. In contrast, post-mitotic cells such as pyramidal neurons maintain extraordinary functionality despite advanced age, but they lose their identity. This review focuses on tau, a protein that protects DNA, organizes chromatin, and plays a crucial role in genomic stability. In contrast, tau cytosolic aggregates are considered hallmarks of Alzheimer´s disease (AD) and other neurodegenerative disorders called tauopathies. Here, we explain AD as a phenomenon of chromatin dysregulation directly involving the epigenetic histone code and a progressive destabilization of the tau–chromatin interaction, leading to the consequent dysregulation of gene expression. Although this destabilization could be lethal for post-mitotic neurons, tau protein mediates profound cellular transformations that allow for their temporal survival.
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Affiliation(s)
- Laura Gil
- Departamento de Genética, Escuela de Medicina, Universidad “Alfonso X el Sabio”, 28691 Madrid, Spain;
| | - Sandra A. Niño
- Departamento de Bioquímica, Facultad de Medicina, Universidad Autónoma, de San Luis Potosí 78210, Mexico;
| | - Carmen Guerrero
- Banco de Cerebros (Biobanco), Hospital Universitario Fundación Alcorcón, Alcorcón, 28922 Madrid, Spain;
| | - María E. Jiménez-Capdeville
- Departamento de Bioquímica, Facultad de Medicina, Universidad Autónoma, de San Luis Potosí 78210, Mexico;
- Correspondence: ; Tel.: +52-444-826-2366
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4
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Llorens-Giralt P, Camilleri-Robles C, Corominas M, Climent-Cantó P. Chromatin Organization and Function in Drosophila. Cells 2021; 10:cells10092362. [PMID: 34572010 PMCID: PMC8465611 DOI: 10.3390/cells10092362] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/03/2021] [Accepted: 09/06/2021] [Indexed: 12/25/2022] Open
Abstract
Eukaryotic genomes are packaged into high-order chromatin structures organized in discrete territories inside the cell nucleus, which is surrounded by the nuclear envelope acting as a barrier. This chromatin organization is complex and dynamic and, thus, determining the spatial and temporal distribution and folding of chromosomes within the nucleus is critical for understanding the role of chromatin topology in genome function. Primarily focusing on the regulation of gene expression, we review here how the genome of Drosophila melanogaster is organized into the cell nucleus, from small scale histone–DNA interactions to chromosome and lamina interactions in the nuclear space.
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5
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Pappalardo XG, Barra V. Losing DNA methylation at repetitive elements and breaking bad. Epigenetics Chromatin 2021; 14:25. [PMID: 34082816 PMCID: PMC8173753 DOI: 10.1186/s13072-021-00400-z] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 05/21/2021] [Indexed: 02/08/2023] Open
Abstract
Background DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome. Main body Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually methylated to maintain a heterochromatic, repressed state. Notably, there is increasing evidence showing that repetitive elements (satellites, long interspersed nuclear elements (LINEs), Alus) are frequently hypomethylated in various of human pathologies, from cancer to psychiatric disorders. Repetitive sequences’ hypomethylation correlates with chromatin relaxation and unscheduled transcription. If these alterations are directly involved in human diseases aetiology and how, is still under investigation. Conclusions Hypomethylation of different families of repetitive sequences is recurrent in many different human diseases, suggesting that the methylation status of these elements can be involved in preservation of human health. This provides a promising point of view towards the research of therapeutic strategies focused on specifically tuning DNA methylation of DNA repeats.
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Affiliation(s)
- Xena Giada Pappalardo
- Department of Biomedical and Biotechnological Sciences (BIOMETEC), University of Catania, 95125, Catania, Italy.,National Council of Research, Institute for Biomedical Research and Innovation (IRIB), Unit of Catania, 95125, Catania, Italy
| | - Viviana Barra
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, 90128, Palermo, Italy.
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Kundu S, Ray MD, Sharma A. Interplay between genome organization and epigenomic alterations of pericentromeric DNA in cancer. J Genet Genomics 2021; 48:184-197. [PMID: 33840602 DOI: 10.1016/j.jgg.2021.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 02/07/2021] [Accepted: 02/20/2021] [Indexed: 12/16/2022]
Abstract
In eukaryotic genome biology, the genomic organization inside the three-dimensional (3D) nucleus is highly complex, and whether this organization governs gene expression is poorly understood. Nuclear lamina (NL) is a filamentous meshwork of proteins present at the lining of inner nuclear membrane that serves as an anchoring platform for genome organization. Large chromatin domains termed as lamina-associated domains (LADs), play a major role in silencing genes at the nuclear periphery. The interaction of the NL and genome is dynamic and stochastic. Furthermore, many genes change their positions during developmental processes or under disease conditions such as cancer, to activate certain sorts of genes and/or silence others. Pericentromeric heterochromatin (PCH) is mostly in the silenced region within the genome, which localizes at the nuclear periphery. Studies show that several genes located at the PCH are aberrantly expressed in cancer. The interesting question is that despite being localized in the pericentromeric region, how these genes still manage to overcome pericentromeric repression. Although epigenetic mechanisms control the expression of the pericentromeric region, recent studies about genome organization and genome-nuclear lamina interaction have shed light on a new aspect of pericentromeric gene regulation through a complex and coordinated interplay between epigenomic remodeling and genomic organization in cancer.
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Affiliation(s)
- Subhadip Kundu
- Laboratory of Chromatin and Cancer Epigenetics, Department of Biochemistry, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - M D Ray
- Department of Surgical Oncology, IRCH, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
| | - Ashok Sharma
- Laboratory of Chromatin and Cancer Epigenetics, Department of Biochemistry, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
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Topoisomerase IIβ targets DNA crossovers formed between distant homologous sites to induce chromatin opening. Sci Rep 2020; 10:18550. [PMID: 33122676 PMCID: PMC7596052 DOI: 10.1038/s41598-020-75004-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Accepted: 10/09/2020] [Indexed: 11/08/2022] Open
Abstract
Type II DNA topoisomerases (topo II) flip the spatial positions of two DNA duplexes, called G- and T- segments, by a cleavage-passage-resealing mechanism. In living cells, these DNA segments can be derived from distant sites on the same chromosome. Due to lack of proper methodology, however, no direct evidence has been described so far. The beta isoform of topo II (topo IIβ) is essential for transcriptional regulation of genes expressed in the final stage of neuronal differentiation. Here we devise a genome-wide mapping technique (eTIP-seq) for topo IIβ target sites that can measure the genomic distance between G- and T-segments. It revealed that the enzyme operates in two distinctive modes, termed proximal strand passage (PSP) and distal strand passage (DSP). PSP sites are concentrated around transcription start sites, whereas DSP sites are heavily clustered in small number of hotspots. While PSP represent the conventional topo II targets that remove local torsional stresses, DSP sites have not been described previously. Most remarkably, DSP is driven by the pairing between homologous sequences or repeats located in a large distance. A model-building approach suggested that topo IIβ acts on crossovers to unknot the intertwined DSP sites, leading to chromatin decondensation.
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Feodorova Y, Falk M, Mirny LA, Solovei I. Viewing Nuclear Architecture through the Eyes of Nocturnal Mammals. Trends Cell Biol 2020; 30:276-289. [PMID: 31980345 DOI: 10.1016/j.tcb.2019.12.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/10/2019] [Accepted: 12/19/2019] [Indexed: 01/09/2023]
Abstract
The cell nucleus is a remarkably well-organized organelle with membraneless but distinct compartments of various functions. The largest of them, euchromatin and heterochromatin, are spatially segregated in such a way that the transcriptionally active genome occupies the nuclear interior, whereas silent genomic loci are preferentially associated with the nuclear envelope. This rule is broken by rod photoreceptor cells of nocturnal mammals, in which the two major compartments have inverted positions. The inversion and dense compaction of heterochromatin converts these nuclei into microlenses that focus light and facilitate nocturnal vision. As is often the case in biology, when a mutation helps to understand normal processes and structures, inverted nuclei have served as a tool to unravel general principles of nuclear organization, including mechanisms of heterochromatin tethering to the nuclear envelope, autonomous behavior of small genomic segments, and euchromatin-heterochromatin segregation.
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Affiliation(s)
- Yana Feodorova
- Biozentrum, Ludwig-Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany; Department of Medical Biology, Medical University-Plovdiv, Boulevard Vasil Aprilov 15A, Plovdiv 4000, Bulgaria
| | - Martin Falk
- Institute for Medical Engineering and Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Department of Physics, University of Chicago, 929 E 57th St, Chicago, IL 60637, USA
| | - Leonid A Mirny
- Institute for Medical Engineering and Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Irina Solovei
- Biozentrum, Ludwig-Maximilians University Munich, Grosshadernerstrasse 2, 82152 Planegg-Martinsried, Germany.
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9
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Heterochromatin drives compartmentalization of inverted and conventional nuclei. Nature 2019; 570:395-399. [PMID: 31168090 DOI: 10.1038/s41586-019-1275-3] [Citation(s) in RCA: 382] [Impact Index Per Article: 63.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 04/26/2019] [Indexed: 01/18/2023]
Abstract
The nucleus of mammalian cells displays a distinct spatial segregation of active euchromatic and inactive heterochromatic regions of the genome1,2. In conventional nuclei, microscopy shows that euchromatin is localized in the nuclear interior and heterochromatin at the nuclear periphery1,2. Genome-wide chromosome conformation capture (Hi-C) analyses show this segregation as a plaid pattern of contact enrichment within euchromatin and heterochromatin compartments3, and depletion between them. Many mechanisms for the formation of compartments have been proposed, such as attraction of heterochromatin to the nuclear lamina2,4, preferential attraction of similar chromatin to each other1,4-12, higher levels of chromatin mobility in active chromatin13-15 and transcription-related clustering of euchromatin16,17. However, these hypotheses have remained inconclusive, owing to the difficulty of disentangling intra-chromatin and chromatin-lamina interactions in conventional nuclei18. The marked reorganization of interphase chromosomes in the inverted nuclei of rods in nocturnal mammals19,20 provides an opportunity to elucidate the mechanisms that underlie spatial compartmentalization. Here we combine Hi-C analysis of inverted rod nuclei with microscopy and polymer simulations. We find that attractions between heterochromatic regions are crucial for establishing both compartmentalization and the concentric shells of pericentromeric heterochromatin, facultative heterochromatin and euchromatin in the inverted nucleus. When interactions between heterochromatin and the lamina are added, the same model recreates the conventional nuclear organization. In addition, our models allow us to rule out mechanisms of compartmentalization that involve strong euchromatin interactions. Together, our experiments and modelling suggest that attractions between heterochromatic regions are essential for the phase separation of the active and inactive genome in inverted and conventional nuclei, whereas interactions of the chromatin with the lamina are necessary to build the conventional architecture from these segregated phases.
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10
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Tobar-Tosse F, Veléz PE, Ocampo-Toro E, Moreno PA. Structure, clustering and functional insights of repeats configurations in the upstream promoter region of the human coding genes. BMC Genomics 2018; 19:862. [PMID: 30537933 PMCID: PMC6288848 DOI: 10.1186/s12864-018-5196-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Background Repetitive DNA sequences (Repeats) are significant regions in the human genome that have a specific genomic distribution, structure, and several binding sites for genome architecture and function. In consequence, the possible configurations of Repeats in specific and dynamic regions like the gene promoters could define footprints for molecular mechanisms, pathways, and cell function beyond their density in the genome. Here we explored the distribution of Repeats in the upstream promoter region of the human coding genes with the aim to identify specific configurations, clusters and functional meaning of those elements. Our method includes structural descriptions, hierarchical clustering, pathway association, and functional enrichment analysis. Results We report here several configurations of Repeats in the upstream promoter region (UPR), which define 2729 patterns for the 80% of the human coding genes. There are 47 types of Repeats in these configurations, where the most frequent were Alu, Low_complexity, MIR, Simple_repeat, LINE/L2, LINE/L1, hAT-Charlie, and ERV1. The distribution, length, and the high frequency of Repeats in the UPR defines several patterns and clusters, where the minimum frequency of configuration among Repeats was higher than 0.7. We found those clusters associated with cellular pathways and ontologies; thus, it was plausible to determine groups of Repeats to specific functional insights, for example, pathways for Genetic Information Processing or Metabolism shows particular groups of Repeats with specific configurations. Conclusion Based on these findings, we propose that specific configurations of repetitive elements describe frequent patterns in the upstream promoter for sets of human coding genes, which those correlated to specific and essential cell pathways and functions. Electronic supplementary material The online version of this article (10.1186/s12864-018-5196-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fabian Tobar-Tosse
- Departamento de Ciencias Básicas de la Salud, Pontificia Universidad Javeriana Cali, Cali, Colombia
| | - Patricia E Veléz
- Departamento de Biología, FACNED, Universidad del Cauca, Popayán, Colombia
| | - Eliana Ocampo-Toro
- Especialización en Hematología y Oncología Clínica, Universidad Libre Seccional Cali, Cali, Colombia
| | - Pedro A Moreno
- Escuela de Ingeniería de Sistemas y Computación, Universidad del Valle, Cali, Colombia.
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Tang SJ. Potential Role of Phase Separation of Repetitive DNA in Chromosomal Organization. Genes (Basel) 2017; 8:genes8100279. [PMID: 29057826 PMCID: PMC5664129 DOI: 10.3390/genes8100279] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 10/07/2017] [Accepted: 10/13/2017] [Indexed: 01/19/2023] Open
Abstract
The basic principles of chromosomal organization in eukaryotic cells remain elusive. Current mainstream research efforts largely concentrate on searching for critical packaging proteins involved in organizing chromosomes. I have taken a different perspective, by considering the role of genomic information in chromatins. In particular, I put forward the concept that repetitive DNA elements are key chromosomal packaging modules, and their intrinsic property of homology-based interaction can drive chromatin folding. Many repetitive DNA families have high copy numbers and clustered distribution patterns in the linear genomes. These features may facilitate the interactions among members in the same repeat families. In this paper, the potential liquid–liquid phase transition of repetitive DNAs that is induced by their extensive interaction in chromosomes will be considered. I propose that the interaction among repetitive DNAs may lead to phase separation of interacting repetitive DNAs from bulk chromatins. Phase separation of repetitive DNA may provide a physical mechanism that drives rapid massive changes of chromosomal conformation.
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Affiliation(s)
- Shao-Jun Tang
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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12
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Chechetkin VR, Lobzin VV. Large-scale chromosome folding versus genomic DNA sequences: A discrete double Fourier transform technique. J Theor Biol 2017; 426:162-179. [PMID: 28552553 DOI: 10.1016/j.jtbi.2017.05.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 04/23/2017] [Accepted: 05/23/2017] [Indexed: 12/15/2022]
Abstract
Using state-of-the-art techniques combining imaging methods and high-throughput genomic mapping tools leaded to the significant progress in detailing chromosome architecture of various organisms. However, a gap still remains between the rapidly growing structural data on the chromosome folding and the large-scale genome organization. Could a part of information on the chromosome folding be obtained directly from underlying genomic DNA sequences abundantly stored in the databanks? To answer this question, we developed an original discrete double Fourier transform (DDFT). DDFT serves for the detection of large-scale genome regularities associated with domains/units at the different levels of hierarchical chromosome folding. The method is versatile and can be applied to both genomic DNA sequences and corresponding physico-chemical parameters such as base-pairing free energy. The latter characteristic is closely related to the replication and transcription and can also be used for the assessment of temperature or supercoiling effects on the chromosome folding. We tested the method on the genome of E. coli K-12 and found good correspondence with the annotated domains/units established experimentally. As a brief illustration of further abilities of DDFT, the study of large-scale genome organization for bacteriophage PHIX174 and bacterium Caulobacter crescentus was also added. The combined experimental, modeling, and bioinformatic DDFT analysis should yield more complete knowledge on the chromosome architecture and genome organization.
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Affiliation(s)
- V R Chechetkin
- Engelhardt Institute of Molecular Biology of Russian Academy of Sciences, Vavilov str., 32, Moscow 119334, Russia; Theoretical Department of Division for Perspective Investigations, Troitsk Institute of Innovation and Thermonuclear Investigations (TRINITI), Moscow, Troitsk District 108840, Russia.
| | - V V Lobzin
- School of Physics, University of Sydney, Sydney, NSW 2006, Australia.
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13
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Tang SJ. New Evidence for the Theory of Chromosome Organization by Repetitive Elements (CORE). Genes (Basel) 2017; 8:genes8020081. [PMID: 28230735 PMCID: PMC5333070 DOI: 10.3390/genes8020081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 02/17/2017] [Indexed: 11/16/2022] Open
Abstract
Repetitive DNA elements were proposed to coordinate chromatin folding and interaction in chromosomes by their intrinsic homology-based clustering ability. A recent analysis of the data sets from chromosome-conformation-capture experiments confirms the spatial clustering of DNA repeats of the same family in the nuclear space, and thus provides strong new support for the CORE theory.
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Affiliation(s)
- Shao-Jun Tang
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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14
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A repetitive DNA-directed program of chromosome packaging during mitosis. J Genet Genomics 2016; 43:471-6. [PMID: 27567067 DOI: 10.1016/j.jgg.2016.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 03/26/2016] [Accepted: 04/04/2016] [Indexed: 11/20/2022]
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15
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Mourad R, Cuvier O. Computational Identification of Genomic Features That Influence 3D Chromatin Domain Formation. PLoS Comput Biol 2016; 12:e1004908. [PMID: 27203237 PMCID: PMC4874696 DOI: 10.1371/journal.pcbi.1004908] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 04/07/2016] [Indexed: 12/17/2022] Open
Abstract
Recent advances in long-range Hi-C contact mapping have revealed the importance of the 3D structure of chromosomes in gene expression. A current challenge is to identify the key molecular drivers of this 3D structure. Several genomic features, such as architectural proteins and functional elements, were shown to be enriched at topological domain borders using classical enrichment tests. Here we propose multiple logistic regression to identify those genomic features that positively or negatively influence domain border establishment or maintenance. The model is flexible, and can account for statistical interactions among multiple genomic features. Using both simulated and real data, we show that our model outperforms enrichment test and non-parametric models, such as random forests, for the identification of genomic features that influence domain borders. Using Drosophila Hi-C data at a very high resolution of 1 kb, our model suggests that, among architectural proteins, BEAF-32 and CP190 are the main positive drivers of 3D domain borders. In humans, our model identifies well-known architectural proteins CTCF and cohesin, as well as ZNF143 and Polycomb group proteins as positive drivers of domain borders. The model also reveals the existence of several negative drivers that counteract the presence of domain borders including P300, RXRA, BCL11A and ELK1. Chromosomal DNA is tightly packed up in 3D such that around 2 meters of this long molecule fits into the microscopic nucleus of every cell. The genome packing is not random, but instead structured in 3D domains that are essential to numerous key processes in the cell, such as for the regulation of gene expression or for the replication of DNA. A current challenge is to identify the key molecular drivers of this higher-order chromosome organization. Here we propose a novel computational integrative approach to identify proteins and DNA elements that positively or negatively influence the establishment or maintenance of 3D domains. Analysis of Drosophila data at very high resolution suggests that among architectural proteins, BEAF-32 and CP190 are the main positive drivers of 3D domains. In humans, our results highlight the roles of CTCF, cohesin, ZNF143 and Polycomb group proteins as positive drivers of 3D domains, in contrast to P300, RXRA, BCL11A and ELK1 that act as negative drivers.
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Affiliation(s)
- Raphaël Mourad
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), CNRS, Université Paul Sabatier (UPS), Toulouse, France
- * E-mail:
| | - Olivier Cuvier
- Laboratoire de Biologie Moléculaire Eucaryote (LBME), CNRS, Université Paul Sabatier (UPS), Toulouse, France
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Tang SJ. The R-Operon: A Model of Repetitive DNA-Organized Transcriptional Compartmentation of Eukaryotic Chromosomes for Coordinated Gene Expression. Genes (Basel) 2016; 7:genes7040016. [PMID: 27110825 PMCID: PMC4846846 DOI: 10.3390/genes7040016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 03/20/2016] [Accepted: 04/05/2016] [Indexed: 11/29/2022] Open
Abstract
In eukaryotic genomes, it is essential to coordinate the activity of genes that function together to fulfill the same biological processes. Genomic organization likely plays a key role in coordinating transcription of different genes. However, little is known about how co-regulated genes are organized in the cell nucleus and how the chromosomal organization facilitates the co-regulation of different genes. I propose that eukaryotic genomes are organized into repeat assembly (RA)-based structural domains (“R-operons”) in the nuclear space. R-operons result from the interaction of homologous DNA repeats. In an R-operon, genes in different loci of the linear genome are brought into spatial vicinity and co-regulated by the same pool of transcription factors. This type of large-scale chromosomal organization may provide a mechanism for functional compartmentation of chromosomes to facilitate the transcriptional coordination of gene expression.
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Affiliation(s)
- Shao-Jun Tang
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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Hussein SMI, Puri MC, Tonge PD, Benevento M, Corso AJ, Clancy JL, Mosbergen R, Li M, Lee DS, Cloonan N, Wood DLA, Munoz J, Middleton R, Korn O, Patel HR, White CA, Shin JY, Gauthier ME, Cao KAL, Kim JI, Mar JC, Shakiba N, Ritchie W, Rasko JEJ, Grimmond SM, Zandstra PW, Wells CA, Preiss T, Seo JS, Heck AJR, Rogers IM, Nagy A. Genome-wide characterization of the routes to pluripotency. Nature 2014; 516:198-206. [DOI: 10.1038/nature14046] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 11/10/2014] [Indexed: 12/24/2022]
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18
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Ebert G, Steininger A, Weißmann R, Boldt V, Lind-Thomsen A, Grune J, Badelt S, Heßler M, Peiser M, Hitzler M, Jensen LR, Müller I, Hu H, Arndt PF, Kuss AW, Tebel K, Ullmann R. Distribution of segmental duplications in the context of higher order chromatin organisation of human chromosome 7. BMC Genomics 2014; 15:537. [PMID: 24973960 PMCID: PMC4092221 DOI: 10.1186/1471-2164-15-537] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 06/17/2014] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Segmental duplications (SDs) are not evenly distributed along chromosomes. The reasons for this biased susceptibility to SD insertion are poorly understood. Accumulation of SDs is associated with increased genomic instability, which can lead to structural variants and genomic disorders such as the Williams-Beuren syndrome. Despite these adverse effects, SDs have become fixed in the human genome. Focusing on chromosome 7, which is particularly rich in interstitial SDs, we have investigated the distribution of SDs in the context of evolution and the three dimensional organisation of the chromosome in order to gain insights into the mutual relationship of SDs and chromatin topology. RESULTS Intrachromosomal SDs preferentially accumulate in those segments of chromosome 7 that are homologous to marmoset chromosome 2. Although this formerly compact segment has been re-distributed to three different sites during primate evolution, we can show by means of public data on long distance chromatin interactions that these three intervals, and consequently the paralogous SDs mapping to them, have retained their spatial proximity in the nucleus. Focusing on SD clusters implicated in the aetiology of the Williams-Beuren syndrome locus we demonstrate by cross-species comparison that these SDs have inserted at the borders of a topological domain and that they flank regions with distinct DNA conformation. CONCLUSIONS Our study suggests a link of nuclear architecture and the propagation of SDs across chromosome 7, either by promoting regional SD insertion or by contributing to the establishment of higher order chromatin organisation themselves. The latter could compensate for the high risk of structural rearrangements and thus may have contributed to their evolutionary fixation in the human genome.
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Affiliation(s)
- Grit Ebert
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
- />Department of Biology, Chemistry and Pharmacy, Free University Berlin, 14195 Berlin, Germany
| | - Anne Steininger
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
- />Department of Biology, Chemistry and Pharmacy, Free University Berlin, 14195 Berlin, Germany
| | - Robert Weißmann
- />Department of Human Genetics, University Medicine Greifswald, and Interfaculty Institute of Genetics and Functional Genomics, University of Greifswald, Fleischmannstraße 42-44, 17475 Greifswald, Germany
| | - Vivien Boldt
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
- />Department of Biology, Chemistry and Pharmacy, Free University Berlin, 14195 Berlin, Germany
| | - Allan Lind-Thomsen
- />Wilhelm Johannsen Centre for Functional Genome Research, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark
| | - Jana Grune
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Stefan Badelt
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
- />Institute for Theoretical Chemistry, University of Vienna, Waehringer Straße 17, A-1090 Vienna, Austria
| | - Melanie Heßler
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Matthias Peiser
- />Unit Experimental Research, Department of Product Safety, Federal Institute for Bundeswehr Institute of Radiobiology affiliated, the University of Ulm, Neuherbergstraße 11, 80937 Munich, Germany
| | - Manuel Hitzler
- />Unit Experimental Research, Department of Product Safety, Federal Institute for Bundeswehr Institute of Radiobiology affiliated, the University of Ulm, Neuherbergstraße 11, 80937 Munich, Germany
| | - Lars R Jensen
- />Department of Human Genetics, University Medicine Greifswald, and Interfaculty Institute of Genetics and Functional Genomics, University of Greifswald, Fleischmannstraße 42-44, 17475 Greifswald, Germany
| | - Ines Müller
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Hao Hu
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Peter F Arndt
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Andreas W Kuss
- />Department of Human Genetics, University Medicine Greifswald, and Interfaculty Institute of Genetics and Functional Genomics, University of Greifswald, Fleischmannstraße 42-44, 17475 Greifswald, Germany
| | - Katrin Tebel
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
| | - Reinhard Ullmann
- />Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195 Berlin, Germany
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A Study of Fractality and Long-Range Order in the Distribution of Transposable Elements in Eukaryotic Genomes Using the Scaling Properties of Block Entropy and Box-Counting. ENTROPY 2014. [DOI: 10.3390/e16041860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
Fractal characteristics of chromatin, revealed by light or electron microscopy, have been reported during the last 20 years. Fractal features can easily be estimated in digitalized microscopic images and are helpful for diagnosis and prognosis of neoplasias. During carcinogenesis and tumor progression, an increase of the fractal dimension (FD) of stained nuclei has been shown in intraepithelial lesions of the uterine cervix and the anus, oral squamous cell carcinomas or adenocarcinomas of the pancreas. Furthermore, an increased FD of chromatin is an unfavorable prognostic factor in squamous cell carcinomas of the oral cavity and the larynx, melanomas and multiple myelomas. High goodness-of-fit of the regression line of the FD is a favorable prognostic factor in acute leukemias and multiple myelomas. The nucleus has fractal and power-law organization in several different levels, which might in part be interrelated. Some possible relations between modifications of the chromatin organization during carcinogenesis and tumor progression and an increase of the FD of stained chromatin are suggested. Furthermore, increased complexity of the chromatin structure, loss of heterochromatin and a less-perfect self-organization of the nucleus in aggressive neoplasias are discussed.
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Affiliation(s)
- Konradin Metze
- Department of Pathology, Faculty of Medical Sciences Research Group, 'Analytical Cellular Pathology' and National Institute of Photonics Applied to Cell Biology, University of Campinas, Campinas, Brazil +55 19 32893897 kmetze.at.fcm.unicamp.br
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Nishikawa JI, Ohyama T. Selective association between nucleosomes with identical DNA sequences. Nucleic Acids Res 2012; 41:1544-54. [PMID: 23254334 PMCID: PMC3561984 DOI: 10.1093/nar/gks1269] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Self-assembly is the autonomous organization of constituents into higher order structures or assemblages and is a fundamental mechanism in biological systems. There has been an unfounded idea that self-assembly may be used in the sensing and pairing of homologous chromosomes or chromatin, including meiotic chromosome pairing, polytene chromosome formation in Diptera and transvection. Recent studies proved that double-stranded DNA molecules have a sequence-sensing property and can self-assemble, which may play a role in the above phenomena. However, to explain these processes in terms of self-assembly, it first must be proved that nucleosomes retain a DNA sequence-sensing property and can self-assemble. Here, using atomic force microscopy (AFM)-based analyses and a quantitative interaction assay, we show that nucleosomes with identical DNA sequences preferentially associate with each other in the presence of Mg(2+) ions. Using Xenopus borealis 5S rDNA nucleosome-positioning sequence and 601 and 603 sequences, homomeric or heteromeric octa- or tetranucleosomes were reconstituted in vitro and induced to form weak intracondensates by MgCl(2). AFM clearly showed that DNA sequence-based selective association occurs between nucleosomes with identical DNA sequences. Selective association was also detected between mononucleosomes. We propose that nucleosome self-assembly and DNA self-assembly constitute the mechanism underlying sensing and pairing of homologous chromosomes or chromatin.
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Affiliation(s)
- Jun-ichi Nishikawa
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2, Tokyo 162-8480, Japan
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Tang SJ. A Model of Repetitive-DNA-Organized Chromatin Network of Interphase Chromosomes. Genes (Basel) 2012; 3:167-75. [PMID: 24704848 PMCID: PMC3902797 DOI: 10.3390/genes3010167] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Revised: 02/21/2012] [Accepted: 02/28/2012] [Indexed: 11/16/2022] Open
Abstract
During interphase, chromosomes are relatively de-condensed in the nuclear space. Interphase chromosomes are known to occupy nuclear space in a non-random manner (chromosome territory); however, their internal structures are poorly defined. In particular, little is understood about the molecular mechanisms that govern the internal organization of interphase chromosomes. The author recently proposed that pairing (or interaction) of repetitive DNA-containing chromatin regions is a critical driving force that specifies the higher-order organization of eukaryotic chromosomes. Guided by this theoretical framework and published experimental data on the structure of interphase chromosomes and the spatial distribution of repetitive DNA in interphase nuclei, I postulate here a molecular structure of chromatin organization in interphase chromosomes. According to this model, an interphase chromosome is a chromatin mesh (or lattice) that is formed by repeat pairing (RP). The mesh consists of two types of structural components: chromosome nodes and loose chromatin fibers. Chromosome nodes are DNA repeat assemblies (RAs) that are formed via RP, while loose fibers include chromatin loops that radiate from the nodes. Different loops crosslink by RPs and form a large integrated chromatin network. I suggest that the organization of the chromatin network of a given interphase chromosome is intrinsically specified by the distribution of repetitive DNA elements on the linear chromatin. The stability of the organization is governed by the collection of RA-formed nodes, and the dynamics of the organization is driven by the assembling and disassembling of the nodes.
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Affiliation(s)
- Shao-Jun Tang
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
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Klimopoulos A, Sellis D, Almirantis Y. Widespread occurrence of power-law distributions in inter-repeat distances shaped by genome dynamics. Gene 2012; 499:88-98. [PMID: 22370293 DOI: 10.1016/j.gene.2012.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 02/05/2012] [Accepted: 02/06/2012] [Indexed: 11/25/2022]
Abstract
Repetitive DNA sequences derived from transposable elements (TE) are distributed in a non-random way, co-clustering with other classes of repeat elements, genes and other genomic components. In a previous work we reported power-law-like size distributions (linearity in log-log scale) in the spatial arrangement of Alu and LINE1 elements in the human genome. Here we investigate the large-scale features of the spatial arrangement of all principal classes of TEs in 14 genomes from phylogenetically distant organisms by studying the size distribution of inter-repeat distances. Power-law-like size distributions are found to be widespread, extending up to several orders of magnitude. In order to understand the emergence of this distributional pattern, we introduce an evolutionary scenario, which includes (i) Insertions of DNA segments (e.g., more recent repeats) into the considered sequence and (ii) Eliminations of members of the studied TE family. In the proposed model we also incorporate the potential for transposition events (characteristic of the DNA transposons' life-cycle) and segmental duplications. Simulations reproduce the main features of the observed size distributions. Furthermore, we investigate the effects of various genomic features on the presence and extent of power-law size distributions including TE class and age, mode of parental TE transmission, GC content, deletion and recombination rates in the studied genomic region, etc. Our observations corroborate the hypothesis that insertions of genomic material and eliminations of repeats are at the basis of power-laws in inter-repeat distances. The existence of these power-laws could facilitate the formation of the recently proposed "fractal globule" for the confined chromatin organization.
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Affiliation(s)
- Alexandros Klimopoulos
- National Center for Scientific Research "Demokritos," Institute of Biology, 153 10 Athens, Greece.
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A model of DNA repeat-assembled mitotic chromosomal skeleton. Genes (Basel) 2011; 2:661-70. [PMID: 24710285 PMCID: PMC3927603 DOI: 10.3390/genes2040661] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 09/15/2011] [Accepted: 09/21/2011] [Indexed: 01/01/2023] Open
Abstract
Despite intensive investigation for decades, the principle of higher-order organization of mitotic chromosomes is unclear. Here, I describe a novel model that emphasizes a critical role of interactions of homologous DNA repeats (repetitive elements; repetitive sequences) in mitotic chromosome architecture. According to the model, DNA repeats are assembled, via repeat interactions (pairing), into compact core structures that govern the arrangement of chromatins in mitotic chromosomes. Tandem repeat assemblies form a chromosomal axis to coordinate chromatins in the longitudinal dimension, while dispersed repeat assemblies form chromosomal nodes around the axis to organize chromatins in the halo. The chromosomal axis and nodes constitute a firm skeleton on which non-skeletal chromatins can be anchored, folded, and supercoiled.
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