1
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Dennis AF, Xu Z, Clark DJ. Examining chromatin heterogeneity through PacBio long-read sequencing of M.EcoGII methylated genomes: an m6A detection efficiency and calling bias correcting pipeline. Nucleic Acids Res 2024; 52:e45. [PMID: 38634798 PMCID: PMC11109960 DOI: 10.1093/nar/gkae288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/23/2024] [Accepted: 04/04/2024] [Indexed: 04/19/2024] Open
Abstract
Recent studies have combined DNA methyltransferase footprinting of genomic DNA in nuclei with long-read sequencing, resulting in detailed chromatin maps for multi-kilobase stretches of genomic DNA from one cell. Theoretically, nucleosome footprints and nucleosome-depleted regions can be identified using M.EcoGII, which methylates adenines in any sequence context, providing a high-resolution map of accessible regions in each DNA molecule. Here, we report PacBio long-read sequence data for budding yeast nuclei treated with M.EcoGII and a bioinformatic pipeline which corrects for three key challenges undermining this promising method. First, detection of m6A in individual DNA molecules by the PacBio software is inefficient, resulting in false footprints predicted by random gaps of seemingly unmethylated adenines. Second, there is a strong bias against m6A base calling as AT content increases. Third, occasional methylation occurs within nucleosomes, breaking up their footprints. After correcting for these issues, our pipeline calculates a correlation coefficient-based score indicating the extent of chromatin heterogeneity within the cell population for every gene. Although the population average is consistent with that derived using other techniques, we observe a wide range of heterogeneity in nucleosome positions at the single-molecule level, probably reflecting cellular chromatin dynamics.
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Affiliation(s)
- Allison F Dennis
- Division of Developmental Biology, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Zhuwei Xu
- Division of Developmental Biology, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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2
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Peng Y, Song W, Teif VB, Ovcharenko I, Landsman D, Panchenko AR. Detection of new pioneer transcription factors as cell-type-specific nucleosome binders. eLife 2024; 12:RP88936. [PMID: 38293962 PMCID: PMC10945518 DOI: 10.7554/elife.88936] [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] [Indexed: 02/01/2024] Open
Abstract
Wrapping of DNA into nucleosomes restricts accessibility to DNA and may affect the recognition of binding motifs by transcription factors. A certain class of transcription factors, the pioneer transcription factors, can specifically recognize their DNA binding sites on nucleosomes, initiate local chromatin opening, and facilitate the binding of co-factors in a cell-type-specific manner. For the majority of human pioneer transcription factors, the locations of their binding sites, mechanisms of binding, and regulation remain unknown. We have developed a computational method to predict the cell-type-specific ability of transcription factors to bind nucleosomes by integrating ChIP-seq, MNase-seq, and DNase-seq data with details of nucleosome structure. We have demonstrated the ability of our approach in discriminating pioneer from canonical transcription factors and predicted new potential pioneer transcription factors in H1, K562, HepG2, and HeLa-S3 cell lines. Last, we systematically analyzed the interaction modes between various pioneer transcription factors and detected several clusters of distinctive binding sites on nucleosomal DNA.
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Affiliation(s)
- Yunhui Peng
- Institute of Biophysics and Department of Physics, Central China Normal UniversityWuhanChina
- National Library of Medicine, National Institutes of HealthBethesdaUnited States
| | - Wei Song
- National Library of Medicine, National Institutes of HealthBethesdaUnited States
| | - Vladimir B Teif
- School of Life Sciences, University of Essex, Wivenhoe ParkColchesterUnited Kingdom
| | - Ivan Ovcharenko
- National Library of Medicine, National Institutes of HealthBethesdaUnited States
| | - David Landsman
- National Library of Medicine, National Institutes of HealthBethesdaUnited States
| | - Anna R Panchenko
- Department of Pathology and Molecular Medicine, Queen’s UniversityKingstonCanada
- Department of Biology and Molecular Sciences, Queen’s UniversityKingstonCanada
- School of Computing, Queen’s UniversityKingstonCanada
- Ontario Institute of Cancer ResearchTorontoCanada
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3
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Boltengagen M, Verhagen D, Wolff MR, Oberbeckmann E, Hanke M, Gerland U, Korber P, Mueller-Planitz F. A single fiber view of the nucleosome organization in eukaryotic chromatin. Nucleic Acids Res 2024; 52:166-185. [PMID: 37994698 PMCID: PMC10783498 DOI: 10.1093/nar/gkad1098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 10/13/2023] [Accepted: 10/31/2023] [Indexed: 11/24/2023] Open
Abstract
Eukaryotic cells are thought to arrange nucleosomes into extended arrays with evenly spaced nucleosomes phased at genomic landmarks. Here we tested to what extent this stereotypic organization describes the nucleosome organization in Saccharomyces cerevisiae using Fiber-Seq, a long-read sequencing technique that maps entire nucleosome arrays on individual chromatin fibers in a high throughput manner. With each fiber coming from a different cell, Fiber-Seq uncovers cell-to-cell heterogeneity. The long reads reveal the nucleosome architecture even over repetitive DNA such as the ribosomal DNA repeats. The absolute nucleosome occupancy, a parameter that is difficult to obtain with conventional sequencing approaches, is a direct readout of Fiber-Seq. We document substantial deviations from the stereotypical nucleosome organization with unexpectedly long linker DNAs between nucleosomes, gene bodies missing entire nucleosomes, cell-to-cell heterogeneity in nucleosome occupancy, heterogeneous phasing of arrays and irregular nucleosome spacing. Nucleosome array structures are indistinguishable throughout the gene body and with respect to the direction of transcription arguing against transcription promoting array formation. Acute nucleosome depletion destroyed most of the array organization indicating that nucleosome remodelers cannot efficiently pack nucleosomes under those conditions. Given that nucleosomes are cis-regulatory elements, the cell-to-cell heterogeneity uncovered by Fiber-Seq provides much needed information to understand chromatin structure and function.
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Affiliation(s)
- Mark Boltengagen
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
| | - Daan Verhagen
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
- Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Michael Roland Wolff
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
- Physics of Complex Biosystems, Physics Department, Technical University of Munich, Garching, Germany
| | - Elisa Oberbeckmann
- Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Matthias Hanke
- Physics of Complex Biosystems, Physics Department, Technical University of Munich, Garching, Germany
| | - Ulrich Gerland
- Physics of Complex Biosystems, Physics Department, Technical University of Munich, Garching, Germany
| | - Philipp Korber
- Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Felix Mueller-Planitz
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
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4
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Brahma S, Henikoff S. The BAF chromatin remodeler synergizes with RNA polymerase II and transcription factors to evict nucleosomes. Nat Genet 2024; 56:100-111. [PMID: 38049663 PMCID: PMC10786724 DOI: 10.1038/s41588-023-01603-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 10/30/2023] [Indexed: 12/06/2023]
Abstract
Chromatin accessibility is a hallmark of active transcription and entails ATP-dependent nucleosome remodeling, which is carried out by complexes such as Brahma-associated factor (BAF). However, the mechanistic links between transcription, nucleosome remodeling and chromatin accessibility are unclear. Here, we used a chemical-genetic approach coupled with time-resolved chromatin profiling to dissect the interplay between RNA Polymerase II (RNAPII), BAF and DNA-sequence-specific transcription factors in mouse embryonic stem cells. We show that BAF dynamically unwraps and evicts nucleosomes at accessible chromatin regions, while RNAPII promoter-proximal pausing stabilizes BAF chromatin occupancy and enhances ATP-dependent nucleosome eviction by BAF. We find that although RNAPII and BAF dynamically probe both transcriptionally active and Polycomb-repressed genomic regions, pluripotency transcription factor chromatin binding confers locus specificity for productive chromatin remodeling and nucleosome eviction by BAF. Our study suggests a paradigm for how functional synergy between dynamically acting chromatin factors regulates locus-specific nucleosome organization and chromatin accessibility.
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Affiliation(s)
- Sandipan Brahma
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA.
- Department of Genetics, Cell Biology & Anatomy, University of Nebraska Medical Center, Omaha, NE, USA.
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA.
- Howard Hughes Medical Institute, Seattle, WA, USA.
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5
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Maeshima K, Iida S, Shimazoe MA, Tamura S, Ide S. Is euchromatin really open in the cell? Trends Cell Biol 2024; 34:7-17. [PMID: 37385880 DOI: 10.1016/j.tcb.2023.05.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 07/01/2023]
Abstract
Genomic DNA is wrapped around a core histone octamer and forms a nucleosome. In higher eukaryotic cells, strings of nucleosomes are irregularly folded as chromatin domains that act as functional genome units. According to a typical textbook model, chromatin can be categorized into two types, euchromatin and heterochromatin, based on its degree of compaction. Euchromatin is open, while heterochromatin is closed and condensed. However, is euchromatin really open in the cell? New evidence from genomics and advanced imaging studies has revealed that euchromatin consists of condensed liquid-like domains. Condensed chromatin seems to be the default chromatin state in higher eukaryotic cells. We discuss this novel view of euchromatin in the cell and how the revealed organization is relevant to genome functions.
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Affiliation(s)
- Kazuhiro Maeshima
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan.
| | - Shiori Iida
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
| | - Masa A Shimazoe
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
| | - Sachiko Tamura
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
| | - Satoru Ide
- Genome Dynamics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Graduate Institute for Advanced Studies, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
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6
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Dahl H, Ballangby J, Tengs T, Wojewodzic MW, Eide DM, Brede DA, Graupner A, Duale N, Olsen AK. Dose rate dependent reduction in chromatin accessibility at transcriptional start sites long time after exposure to gamma radiation. Epigenetics 2023; 18:2193936. [PMID: 36972203 PMCID: PMC10054331 DOI: 10.1080/15592294.2023.2193936] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023] Open
Abstract
Ionizing radiation (IR) impact cellular and molecular processes that require chromatin remodelling relevant for cellular integrity. However, the cellular implications of ionizing radiation (IR) delivered per time unit (dose rate) are still debated. This study investigates whether the dose rate is relevant for inflicting changes to the epigenome, represented by chromatin accessibility, or whether it is the total dose that is decisive. CBA/CaOlaHsd mice were whole-body exposed to either chronic low dose rate (2.5 mGy/h for 54 d) or the higher dose rates (10 mGy/h for 14 d and 100 mGy/h for 30 h) of gamma radiation (60Co, total dose: 3 Gy). Chromatin accessibility was analysed in liver tissue samples using Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-Seq), both one day after and over three months post-radiation (>100 d). The results show that the dose rate contributes to radiation-induced epigenomic changes in the liver at both sampling timepoints. Interestingly, chronic low dose rate exposure to a high total dose (3 Gy) did not inflict long-term changes to the epigenome. In contrast to the acute high dose rate given to the same total dose, reduced accessibility at transcriptional start sites (TSS) was identified in genes relevant for the DNA damage response and transcriptional activity. Our findings link dose rate to essential biological mechanisms that could be relevant for understanding long-term changes after ionizing radiation exposure. However, future studies are needed to comprehend the biological consequence of these findings.
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Affiliation(s)
- Hildegunn Dahl
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Jarle Ballangby
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Torstein Tengs
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
- Division for Aquaculture, Department of breeding and genetics, Nofima, Ås, Norway
| | - Marcin W Wojewodzic
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
- Department of Research, Section Molecular Epidemiology and Infections, Cancer Registry of Norway, Oslo, Norway
| | - Dag M Eide
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Dag Anders Brede
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
- Faculty of Environmental Sciences and Natural Resource Management (MINA), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Anne Graupner
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Nur Duale
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Ann-Karin Olsen
- Division of Climate and Environmental Health, Department of Chemical Toxicology, Norwegian Institute of Public Health, Oslo, Norway
- Centre for Environmental Radiation (CERAD), Norwegian University of Life Sciences (NMBU), Ås, Norway
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7
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Dennis AF, Xu Z, Clark DJ. Examining chromatin heterogeneity through PacBio long-read sequencing of M.EcoGII methylated genomes: an m 6A detection efficiency and calling bias correcting pipeline. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.28.569045. [PMID: 38076871 PMCID: PMC10705563 DOI: 10.1101/2023.11.28.569045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2023]
Abstract
Recent studies have combined DNA methyltransferase footprinting of genomic DNA in nuclei with long-read sequencing, resulting in detailed chromatin maps for multi-kilobase stretches of genomic DNA from one cell. Theoretically, nucleosome footprints and nucleosome-depleted regions can be identified using M.EcoGII, which methylates adenines in any sequence context, providing a high-resolution map of accessible regions in each DNA molecule. Here we report PacBio long-read sequence data for budding yeast nuclei treated with M.EcoGII and a bioinformatic pipeline which corrects for three key challenges undermining this promising method. First, detection of m6A in individual DNA molecules by the PacBio software is inefficient, resulting in false footprints predicted by random gaps of seemingly unmethylated adenines. Second, there is a strong bias against m6A base calling as AT content increases. Third, occasional methylation occurs within nucleosomes, breaking up their footprints. After correcting for these issues, our pipeline calculates a correlation coefficient-based score indicating the extent of chromatin heterogeneity within the cell population for every gene. Although the population average is consistent with that derived using other techniques, we observe a wide range of heterogeneity in nucleosome positions at the single-molecule level, probably reflecting cellular chromatin dynamics.
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Affiliation(s)
| | | | - David J. Clark
- Division of Developmental Biology, Eunice Kennedy-Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda MD 20892, USA
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8
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Peng Y, Song W, Teif VB, Ovcharenko I, Landsman D, Panchenko AR. Detection of new pioneer transcription factors as cell-type specific nucleosome binders. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.10.540098. [PMID: 37425841 PMCID: PMC10327179 DOI: 10.1101/2023.05.10.540098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Wrapping of DNA into nucleosomes restricts accessibility to the DNA and may affect the recognition of binding motifs by transcription factors. A certain class of transcription factors, the pioneer transcription factors, can specifically recognize their DNA binding sites on nucleosomes, may initiate local chromatin opening and facilitate the binding of co-factors in a cell-type-specific manner. For the majority of human pioneer transcription factors, the locations of their binding sites, mechanisms of binding and regulation remain unknown. We have developed a computational method to predict the cell-type-specific ability of transcription factors to bind nucleosomes by integrating ChIP-seq, MNase-seq and DNase-seq data with details of nucleosome structure. We have demonstrated the ability of our approach in discriminating pioneer from canonical transcription factors and predicted new potential pioneer transcription factors in H1, K562, HepG2 and HeLa cell lines. Lastly, we systemically analyzed the interaction modes between various pioneer transcription factors and detected several clusters of distinctive binding sites on nucleosomal DNA.
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Affiliation(s)
- Yunhui Peng
- current address: Institute of Biophysics and Department of Physics, Central China Normal University, Wuhan 430079, China
- National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Wei Song
- National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Vladimir B. Teif
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | - Ivan Ovcharenko
- National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - David Landsman
- National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
| | - Anna R. Panchenko
- Department of Pathology and Molecular Medicine, Queen’s University, ON, Canada
- Department of Biology and Molecular Sciences, Queen’s University, ON, Canada
- School of Computing, Queen’s University, ON, Canada
- Ontario Institute of Cancer Research, Toronto, ON, Canada
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9
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Beati P, Massimino Stepñicka M, Vilchez Larrea SC, Smircich P, Alonso GD, Ocampo J. Improving genome-wide mapping of nucleosomes in Trypanosome cruzi. PLoS One 2023; 18:e0293809. [PMID: 37988351 PMCID: PMC10662739 DOI: 10.1371/journal.pone.0293809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 10/19/2023] [Indexed: 11/23/2023] Open
Abstract
In Trypanosoma cruzi DNA is packaged into chromatin by octamers of histone proteins that form nucleosomes. Transcription of protein coding genes in trypanosomes is constitutive producing polycistronic units and gene expression is primarily regulated post-transcriptionally. However, chromatin organization influences DNA dependent processes. Hence, determining nucleosome position is of uppermost importance to understand the peculiarities found in trypanosomes. To map nucleosomes genome-wide in several organisms, digestion of chromatin with micrococcal nuclease followed by deep sequencing has been applied. Nonetheless, the special requirements for cell manipulation and the uniqueness of the chromatin organization in trypanosomes entails a customized analytical approach. In this work, we adjusted this broadly used method to the hybrid reference strain, CL Brener. Particularly, we implemented an exhaustive and thorough computational workflow to overcome the difficulties imposed by this complex genome. We tested the performance of two aligners, Bowtie2 and HISAT2, and discuss their advantages and caveats. Specifically, we highlight the relevance of using the whole genome as a reference instead of the commonly used Esmeraldo-like haplotype to avoid spurious alignments. Additionally, we show that using the whole genome refines the average nucleosome representation, but also the quality of mapping for every region represented. Moreover, we show that the average nucleosome organization around trans-splicing acceptor site described before, is not just an average since the same chromatin pattern is detected for most of the represented regions. In addition, we extended the study to a non-hybrid strain applying the experimental and analytical approach to Sylvio-X10 strain. Furthermore, we provide a source code for the construction of 2D plots and heatmaps which are easy to adapt to any T. cruzi strain.
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Affiliation(s)
- Paula Beati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Milena Massimino Stepñicka
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Salomé C. Vilchez Larrea
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Pablo Smircich
- Laboratorio de Bioinformática, Departamento de Genómica, Instituto de Investigaciones Biológicas Clemente Estable (IIBCE), Montevideo, Uruguay
- Sección Genómica Funcional, Facultad de Ciencias, Universidad de la República (UdelaR), Montevideo, Uruguay
| | - Guillermo D. Alonso
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Josefina Ocampo
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
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10
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Marinov GK, Bagdatli ST, Wu T, He C, Kundaje A, Greenleaf WJ. The chromatin landscape of the euryarchaeon Haloferax volcanii. Genome Biol 2023; 24:253. [PMID: 37932847 PMCID: PMC10626798 DOI: 10.1186/s13059-023-03095-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 10/24/2023] [Indexed: 11/08/2023] Open
Abstract
BACKGROUND Archaea, together with Bacteria, represent the two main divisions of life on Earth, with many of the defining characteristics of the more complex eukaryotes tracing their origin to evolutionary innovations first made in their archaeal ancestors. One of the most notable such features is nucleosomal chromatin, although archaeal histones and chromatin differ significantly from those of eukaryotes, not all archaea possess histones and it is not clear if histones are a main packaging component for all that do. Despite increased interest in archaeal chromatin in recent years, its properties have been little studied using genomic tools. RESULTS Here, we adapt the ATAC-seq assay to archaea and use it to map the accessible landscape of the genome of the euryarchaeote Haloferax volcanii. We integrate the resulting datasets with genome-wide maps of active transcription and single-stranded DNA (ssDNA) and find that while H. volcanii promoters exist in a preferentially accessible state, unlike most eukaryotes, modulation of transcriptional activity is not associated with changes in promoter accessibility. Applying orthogonal single-molecule footprinting methods, we quantify the absolute levels of physical protection of H. volcanii and find that Haloferax chromatin is similarly or only slightly more accessible, in aggregate, than that of eukaryotes. We also evaluate the degree of coordination of transcription within archaeal operons and make the unexpected observation that some CRISPR arrays are associated with highly prevalent ssDNA structures. CONCLUSIONS Our results provide the first comprehensive maps of chromatin accessibility and active transcription in Haloferax across conditions and thus a foundation for future functional studies of archaeal chromatin.
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Affiliation(s)
- Georgi K Marinov
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA.
| | - S Tansu Bagdatli
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
| | - Tong Wu
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
| | - Chuan He
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
- Howard Hughes Medical Institute, The University of Chicago, Chicago, IL, 60637, USA
| | - Anshul Kundaje
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
- Department of Computer Science, Stanford University, Stanford, CA, 94305, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, CA, 94305, USA
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
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11
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ORE-Seq: Genome-Wide Absolute Occupancy Measurement by Restriction Enzyme Accessibilities. Methods Mol Biol 2023; 2611:121-152. [PMID: 36807068 DOI: 10.1007/978-1-0716-2899-7_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Digestion with restriction enzymes is a classical approach for probing DNA accessibility in chromatin. It allows to monitor both the cut and the uncut fraction and thereby the determination of accessibility or occupancy (= 1 - accessibility) in absolute terms as the percentage of cut or uncut molecules, respectively, out of all molecules. The protocol presented here takes this classical approach to the genome-wide level. After exhaustive restriction enzyme digestion of chromatin, DNA is purified, sheared, and converted into libraries for high-throughput sequencing. Bioinformatic analysis counts uncut DNA fragments as well as DNA ends generated by restriction enzyme digest and derives thereof the fraction of accessible DNA. This straightforward principle is technically challenged as preparation and sequencing of the libraries leads to biased scoring of DNA fragments. Our protocol includes two orthogonal approaches to correct for this bias, the "corrected cut-uncut" and the "cut-all cut" method, so that accurate measurements of absolute accessibility or occupancy at restriction sites throughout a genome are possible. The protocol is presented for the example of S. cerevisiae chromatin but may be adapted for any other species.
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12
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Brahma S, Henikoff S. RNA Polymerase II, the BAF remodeler and transcription factors synergize to evict nucleosomes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.22.525083. [PMID: 36711459 PMCID: PMC9882304 DOI: 10.1101/2023.01.22.525083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Chromatin accessibility is a hallmark of active transcription and requires ATP-dependent nucleosome remodeling by Brahma-Associated Factor (BAF). However, the mechanistic link between transcription, nucleosome remodeling, and chromatin accessibility is unclear. Here, we used a chemical-genetic approach to dissect the interplay between RNA Polymerase II (RNAPII), BAF, and DNA-sequence-specific transcription factors (TFs) in mouse embryonic stem cells. By time-resolved chromatin profiling with acute transcription block at distinct stages, we show that RNAPII promoter-proximal pausing stabilizes BAF chromatin occupancy and enhances nucleosome eviction by BAF. We find that RNAPII and BAF probe both transcriptionally active and Polycomb-repressed genomic regions and provide evidence that TFs capture transient site exposure due to nucleosome unwrapping by BAF to confer locus specificity for persistent chromatin remodeling. Our study reveals the mechanistic basis of cell-type-specific chromatin accessibility. We propose a new paradigm for how functional synergy between dynamically acting chromatin factors regulates nucleosome organization.
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Affiliation(s)
- Sandipan Brahma
- Basic Sciences Division, Fred Hutchinson Cancer Center, 1100 Fairview Ave North, Seattle, WA, 98109
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, 1100 Fairview Ave North, Seattle, WA, 98109
- Howard Hughes Medical Institute, USA
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13
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Mansisidor AR, Risca VI. Chromatin accessibility: methods, mechanisms, and biological insights. Nucleus 2022; 13:236-276. [PMID: 36404679 PMCID: PMC9683059 DOI: 10.1080/19491034.2022.2143106] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/23/2022] [Accepted: 10/30/2022] [Indexed: 11/22/2022] Open
Abstract
Access to DNA is a prerequisite to the execution of essential cellular processes that include transcription, replication, chromosomal segregation, and DNA repair. How the proteins that regulate these processes function in the context of chromatin and its dynamic architectures is an intensive field of study. Over the past decade, genome-wide assays and new imaging approaches have enabled a greater understanding of how access to the genome is regulated by nucleosomes and associated proteins. Additional mechanisms that may control DNA accessibility in vivo include chromatin compaction and phase separation - processes that are beginning to be understood. Here, we review the ongoing development of accessibility measurements, we summarize the different molecular and structural mechanisms that shape the accessibility landscape, and we detail the many important biological functions that are linked to chromatin accessibility.
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Affiliation(s)
- Andrés R. Mansisidor
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
| | - Viviana I. Risca
- Laboratory of Genome Architecture and Dynamics, The Rockefeller University, New York, NY
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14
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Bhat JA, Balliano AJ, Hayes JJ. Histone protein surface accessibility dictates direction of RSC-dependent nucleosome mobilization. Nucleic Acids Res 2022; 50:10376-10384. [PMID: 36161493 PMCID: PMC9561379 DOI: 10.1093/nar/gkac790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/23/2022] [Accepted: 09/21/2022] [Indexed: 11/21/2022] Open
Abstract
Chromatin remodeling enzymes use energy derived from ATP hydrolysis to mobilize nucleosomes and alter their structure to facilitate DNA access. The Remodels the Structure of Chromatin (RSC) complex has been extensively studied, yet aspects of how this complex functionally interacts with nucleosomes remain unclear. We introduce a steric mapping approach to determine how RSC activity depends on interaction with specific surfaces within the nucleosome. We find that blocking SHL + 4.5/–4.5 via streptavidin binding to the H2A N-terminal tail domains results in inhibition of RSC nucleosome mobilization. However, restriction enzyme assays indicate that remodeling-dependent exposure of an internal DNA site near the nucleosome dyad is not affected. In contrast, occlusion of both protein faces of the nucleosome by streptavidin attachment near the acidic patch completely blocks both remodeling-dependent nucleosome mobilization and internal DNA site exposure. However, we observed partial inhibition when only one protein surface is occluded, consistent with abrogation of one of two productive RSC binding orientations. Our results indicate that nucleosome mobilization requires RSC access to the trailing but not the leading protein surface, and reveals a mechanism by which RSC and related complexes may drive unidirectional movement of nucleosomes to regulate cis-acting DNA sequences in vivo.
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Affiliation(s)
- Javeed Ahmad Bhat
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Angela J Balliano
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY 14642, USA
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15
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Zhu J, Chen S, Sun L, Liu S, Bai X, Li D, Zhang F, Qiao Z, Li L, Yao H, Xia Y, Xu P, Jiang X, Chen Z, Yan Y, Ma F. LincRNA‐EPS impairs host antiviral immunity by antagonizing viral RNA–PKR interaction. EMBO Rep 2022; 23:e53937. [PMID: 35312140 PMCID: PMC9066075 DOI: 10.15252/embr.202153937] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 03/03/2022] [Accepted: 03/07/2022] [Indexed: 11/15/2022] Open
Abstract
LincRNA‐EPS is an important regulator in inflammation. However, the role of lincRNA‐EPS in the host response against viral infection is unexplored. Here, we show that lincRNA‐EPS is downregulated in macrophages infected with different viruses including VSV, SeV, and HSV‐1. Overexpression of lincRNA‐EPS facilitates viral infection, while deficiency of lincRNA‐EPS protects the host against viral infection in vitro and in vivo. LincRNA‐EPS−/− macrophages show elevated expression of antiviral interferon‐stimulated genes (ISGs) such as Mx1, Oas2, and Ifit2 at both basal and inducible levels. However, IFN‐β, the key upstream inducer of these ISGs, is downregulated in lincRNA‐EPS−/− macrophages compared with control cells. RNA pulldown and mass spectrometry results indicate that lincRNA‐EPS binds to PKR and antagonizes the viral RNA–PKR interaction. PKR activates STAT1 and induces antiviral ISGs independent of IFN‐I induction. LincRNA‐EPS inhibits PKR‐STAT1‐ISGs signaling and thus facilitates viral infection. Our study outlines an alternative antiviral pathway, with downregulation of lincRNA‐EPS promoting the induction of PKR‐STAT1‐dependent ISGs, and reveals a potential therapeutic target for viral infectious diseases.
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Affiliation(s)
- Jingfei Zhu
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Shengchuan Chen
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
- Department of Hepatopancreatobiliary Surgery The First Affiliated Hospital of Wenzhou Medical University Wenzhou China
| | - Li‐Qiong Sun
- Institute of Chinese Medicinal Materials Nanjing Agricultural University Nanjing China
| | - Siying Liu
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Xue Bai
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Dapei Li
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Fan Zhang
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Zigang Qiao
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Liang Li
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Haiping Yao
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
| | - Yu Xia
- Suzhou Center for Disease Control and Prevention Suzhou China
| | - Ping Xu
- Department of Laboratory Medicine The Fifth People’s Hospital of Suzhou Suzhou China
| | - Xiaohui Jiang
- Department of Pulmonary Medicine Children’s Hospital of Soochow University Suzhou China
| | - Zhengrong Chen
- Department of Pulmonary Medicine Children’s Hospital of Soochow University Suzhou China
| | - Yongdong Yan
- Department of Pulmonary Medicine Children’s Hospital of Soochow University Suzhou China
| | - Feng Ma
- CAMS Key Laboratory of Synthetic Biology Regulatory Elements Institute of Systems Medicine Chinese Academy of Medical Sciences & Peking Union Medical College Beijing China
- Suzhou Institute of Systems Medicine Suzhou China
- Department of Hepatopancreatobiliary Surgery The First Affiliated Hospital of Wenzhou Medical University Wenzhou China
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16
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Rajendran A, Krishnamurthy K, Park S, Nakata E, Kwon Y, Morii T. Topologically‐Interlocked Minicircles as Probes of DNA Topology and DNA‐Protein Interactions. Chemistry 2022; 28:e202200108. [DOI: 10.1002/chem.202200108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Indexed: 12/30/2022]
Affiliation(s)
| | | | - Seojeong Park
- College of Pharmacy Ewha Womans University Seoul 120-750 Republic of Korea
| | - Eiji Nakata
- Institute of Advanced Energy Kyoto University Uji Kyoto, 611–0011 Japan
| | - Youngjoo Kwon
- College of Pharmacy Ewha Womans University Seoul 120-750 Republic of Korea
| | - Takashi Morii
- Institute of Advanced Energy Kyoto University Uji Kyoto, 611–0011 Japan
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17
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Whole-genome methods to define DNA and histone accessibility and long-range interactions in chromatin. Biochem Soc Trans 2022; 50:199-212. [PMID: 35166326 PMCID: PMC9847230 DOI: 10.1042/bst20210959] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/30/2021] [Accepted: 01/24/2022] [Indexed: 02/08/2023]
Abstract
Defining the genome-wide chromatin landscape has been a goal of experimentalists for decades. Here we review highlights of these efforts, from seminal experiments showing discontinuities in chromatin structure related to gene activation to extensions of these methods elucidating general features of chromatin related to gene states by exploiting deep sequencing methods. We also review chromatin conformational capture methods to identify patterns in long-range interactions between genomic loci.
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18
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Marinov GK, Shipony Z, Kundaje A, Greenleaf WJ. Single-Molecule Multikilobase-Scale Profiling of Chromatin Accessibility Using m6A-SMAC-Seq and m6A-CpG-GpC-SMAC-Seq. Methods Mol Biol 2022; 2458:269-298. [PMID: 35103973 PMCID: PMC9531602 DOI: 10.1007/978-1-0716-2140-0_15] [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] [Indexed: 06/14/2023]
Abstract
A hallmark feature of active cis-regulatory elements (CREs) in eukaryotes is their nucleosomal depletion and, accordingly, higher accessibility to enzymatic treatment. This property has been the basis of a number of sequencing-based assays for genome-wide identification and tracking the activity of CREs across different biological conditions, such as DNAse-seq, ATAC-seq , NOMeseq, and others. However, the fragmentation of DNA inherent to many of these assays and the limited read length of short-read sequencing platforms have so far not allowed the simultaneous measurement of the chromatin accessibility state of CREs located distally from each other. The combination of labeling accessible DNA with DNA modifications and nanopore sequencing has made it possible to develop such assays. Here, we provide a detailed protocol for carrying out the SMAC-seq assay (Single-Molecule long-read Accessible Chromatin mapping sequencing), in its m6A-SMAC-seq and m6A-CpG-GpC-SMAC-seq variants, together with methods for data processing and analysis, and discuss key experimental and analytical considerations for working with SMAC-seq datasets.
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Affiliation(s)
| | - Zohar Shipony
- Department of Genetics, Stanford University, Stanford, CA, USA.
| | - Anshul Kundaje
- Department of Genetics, Stanford University, Stanford, CA, USA
- Department of Computer Science, Stanford University, Stanford, CA, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University, Stanford, CA, USA
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, CA, USA
- Department of Applied Physics, Stanford University, Stanford, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
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19
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Coey CT, Clark DJ. A systematic genome-wide account of binding sites for the model transcription factor Gcn4. Genome Res 2021; 32:367-377. [PMID: 34916251 PMCID: PMC8805717 DOI: 10.1101/gr.276080.121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Accepted: 12/15/2021] [Indexed: 12/04/2022]
Abstract
Sequence-specific DNA-binding transcription factors are central to gene regulation. They are often associated with consensus binding sites that predict far more genomic sites than are bound in vivo. One explanation is that most sites are blocked by nucleosomes, such that only sites in nucleosome-depleted regulatory regions are bound. We compared the binding of the yeast transcription factor Gcn4 in vivo using published ChIP-seq data (546 sites) and in vitro, using a modified SELEX method (“G-SELEX”), which utilizes short genomic DNA fragments to quantify binding at all sites. We confirm that Gcn4 binds strongly to an AP-1-like sequence (TGACTCA) and weakly to half-sites. However, Gcn4 binds only some of the 1078 exact matches to this sequence, even in vitro. We show that there are only 166 copies of the high-affinity RTGACTCAY site (exact match) in the yeast genome, all occupied in vivo, largely independently of whether they are located in nucleosome-depleted or nucleosomal regions. Generally, RTGACTCAR/YTGACTCAY sites are bound much more weakly and YTGACTCAR sites are unbound, with biological implications for determining induction levels. We conclude that, to a first approximation, Gcn4 binding can be predicted using the high-affinity site, without reference to chromatin structure. We propose that transcription factor binding sites should be defined more precisely using quantitative data, allowing more accurate genome-wide prediction of binding sites and greater insight into gene regulation.
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Affiliation(s)
- Christopher T Coey
- National Institute of Child Health and Human Development, National Institutes of Health
| | - David J Clark
- National Institute of Child Health and Human Development, National Institutes of Health
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20
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Wang L, Peng Q, Yin N, Xie Y, Xu J, Chen A, Yi J, Tang J, Xiang J. Chromatin accessibility regulates chemotherapy-induced dormancy and reactivation. MOLECULAR THERAPY. NUCLEIC ACIDS 2021; 26:269-279. [PMID: 34513309 PMCID: PMC8413835 DOI: 10.1016/j.omtn.2021.07.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 07/26/2021] [Indexed: 12/14/2022]
Abstract
Cisplatin-based chemotherapy remains the standard care for non-small cell lung cancer (NSCLC) patients. Relapse after chemotherapy-induced dormancy affects the overall survival of patients. The evolution of cancer cells under chemotherapy stress is regulated by transcription factors (TFs) with binding sites initially buried deep within inaccessible chromatin. The transcription machinery and dynamic epigenetic alterations during the process of dormancy-reactivation of lung cancer cells after chemotherapy need to be investigated. Here, we investigated the chromatin accessibility of lung cancer cells after cisplatin treatment, using an assay for transposase-accessible chromatin sequencing (ATAC-seq). We observed that global chromatin accessibility was extensively improved. Transcriptional Regulatory Relationships Unraveled by Sentence-based Text mining (TRRUST) v.2 was used to elucidate TF-target interaction during the process of dormancy and reactivation. Enhancer regions and motifs specific to key TFs including JUN, MYC, SMAD3, E2F1, SP1, CTCF, SMAD4, STAT3, NFKB1, and KLF4 were enriched in differential loci ATAC-seq peaks of dormant and reactivated cancer cells induced by chemotherapy. The findings suggest that these key TFs regulated gene expressions during the process of dormancy and reactivation of cancer cells through altering promoter accessibility of target genes. Our study helps advance understanding of how cancer cells adapt to the stress induced by chemotherapy through TF binding motif accessibility.
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Affiliation(s)
- Lujuan Wang
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
| | - Qiu Peng
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
| | - Na Yin
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
| | - Yaohuan Xie
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
| | - Jiaqi Xu
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
| | - Anqi Chen
- Department of Thoracic Surgery, the Second Xiangya Hospital, Central South University, Changsha, Hunan 410013, China.,Hunan Key Laboratory of Early Diagnosis and Precise Treatment of Lung Cancer, Central South University, Changsha, Hunan, China
| | - Junqi Yi
- Department of Thoracic Surgery, the Second Xiangya Hospital, Central South University, Changsha, Hunan 410013, China.,Hunan Key Laboratory of Early Diagnosis and Precise Treatment of Lung Cancer, Central South University, Changsha, Hunan, China
| | - Jingqun Tang
- Department of Thoracic Surgery, the Second Xiangya Hospital, Central South University, Changsha, Hunan 410013, China.,Hunan Key Laboratory of Early Diagnosis and Precise Treatment of Lung Cancer, Central South University, Changsha, Hunan, China
| | - Juanjuan Xiang
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, Changsha, Hunan, China.,Cancer Research Institute, School of Basic Medical Science, Central South University, Changsha, Hunan, China.,NHC Key Laboratory of Carcinogenesis and the Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Xiangya Hospital, Central South University, Changsha, Hunan, China.,Hunan Key Laboratory of Nonresolving Inflammation and Cancer, Changsha, Hunan 410013, China
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21
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Nair VD, Vasoya M, Nair V, Smith GR, Pincas H, Ge Y, Douglas CM, Esser KA, Sealfon SC. Differential analysis of chromatin accessibility and gene expression profiles identifies cis-regulatory elements in rat adipose and muscle. Genomics 2021; 113:3827-3841. [PMID: 34547403 DOI: 10.1016/j.ygeno.2021.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 09/08/2021] [Accepted: 09/15/2021] [Indexed: 01/04/2023]
Abstract
Chromatin accessibility is a key factor influencing gene expression. We optimized the Omni-ATAC-seq protocol and used it together with RNA-seq to investigate cis-regulatory elements in rat white adipose and skeletal muscle, two tissues with contrasting metabolic functions. While promoter accessibility correlated with RNA expression, integration of the two datasets identified tissue-specific differentially accessible regions (DARs) that predominantly localized in intergenic and intron regions. DARs were mapped to differentially expressed (DE) genes enriched in distinct biological processes in each tissue. Randomly selected DE genes were validated by qPCR. Top enriched motifs in DARs predicted binding sites for transcription factors (TFs) showing tissue-specific up-regulation. The correlation between differential chromatin accessibility at a given TF binding motif and differential expression of target genes further supported the functional relevance of that motif. Our study identified cis-regulatory regions that likely play a major role in the regulation of tissue-specific gene expression in adipose and muscle.
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Affiliation(s)
- Venugopalan D Nair
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
| | - Mital Vasoya
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Vishnu Nair
- Department of Computer Sciences, Columbia University, New York, NY 10027, USA
| | - Gregory R Smith
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Hanna Pincas
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Yongchao Ge
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Collin M Douglas
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610, USA
| | - Karyn A Esser
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL 32610, USA
| | - Stuart C Sealfon
- Department of Neurology, Center for Advanced Research on Diagnostic Assays, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
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22
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Ishihara S, Sasagawa Y, Kameda T, Yamashita H, Umeda M, Kotomura N, Abe M, Shimono Y, Nikaido I. Local states of chromatin compaction at transcription start sites control transcription levels. Nucleic Acids Res 2021; 49:8007-8023. [PMID: 34233004 PMCID: PMC8373074 DOI: 10.1093/nar/gkab587] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 06/12/2021] [Accepted: 06/30/2021] [Indexed: 11/16/2022] Open
Abstract
The ‘open’ and ‘compact’ regions of chromatin are considered to be regions of active and silent transcription, respectively. However, individual genes produce transcripts at different levels, suggesting that transcription output does not depend on the simple open-compact conversion of chromatin, but on structural variations in chromatin itself, which so far have remained elusive. In this study, weakly crosslinked chromatin was subjected to sedimentation velocity centrifugation, which fractionated the chromatin according to its degree of compaction. Open chromatin remained in upper fractions, while compact chromatin sedimented to lower fractions depending on the level of nucleosome assembly. Although nucleosomes were evenly detected in all fractions, histone H1 was more highly enriched in the lower fractions. H1 was found to self-associate and crosslinked to histone H3, suggesting that H1 bound to H3 interacts with another H1 in an adjacent nucleosome to form compact chromatin. Genome-wide analyses revealed that nearly the entire genome consists of compact chromatin without differences in compaction between repeat and non-repeat sequences; however, active transcription start sites (TSSs) were rarely found in compact chromatin. Considering the inverse correlation between chromatin compaction and RNA polymerase binding at TSSs, it appears that local states of chromatin compaction determine transcription levels.
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Affiliation(s)
- Satoru Ishihara
- Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan
| | - Yohei Sasagawa
- Laboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama 351-0198, Japan.,Functional Genome Informatics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Takeru Kameda
- Laboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama 351-0198, Japan.,Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Hayato Yamashita
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Mana Umeda
- Laboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama 351-0198, Japan
| | - Naoe Kotomura
- Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan
| | - Masayuki Abe
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yohei Shimono
- Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan
| | - Itoshi Nikaido
- Laboratory for Bioinformatics Research, RIKEN Center for Biosystems Dynamics Research, Wako, Saitama 351-0198, Japan.,Functional Genome Informatics, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan.,Master's/Doctoral Program in Life Science Innovation (Bioinformatics), Degree Programs in Systems and Information Engineering, Graduate School of Science and Technology, University of Tsukuba, Wako, Saitama 351-0198, Japan
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23
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Ni P, Su Z. Accurate prediction of cis-regulatory modules reveals a prevalent regulatory genome of humans. NAR Genom Bioinform 2021; 3:lqab052. [PMID: 34159315 PMCID: PMC8210889 DOI: 10.1093/nargab/lqab052] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 05/01/2021] [Accepted: 06/14/2021] [Indexed: 02/07/2023] Open
Abstract
cis-regulatory modules(CRMs) formed by clusters of transcription factor (TF) binding sites (TFBSs) are as important as coding sequences in specifying phenotypes of humans. It is essential to categorize all CRMs and constituent TFBSs in the genome. In contrast to most existing methods that predict CRMs in specific cell types using epigenetic marks, we predict a largely cell type agonistic but more comprehensive map of CRMs and constituent TFBSs in the gnome by integrating all available TF ChIP-seq datasets. Our method is able to partition 77.47% of genome regions covered by available 6092 datasets into a CRM candidate (CRMC) set (56.84%) and a non-CRMC set (43.16%). Intriguingly, the predicted CRMCs are under strong evolutionary constraints, while the non-CRMCs are largely selectively neutral, strongly suggesting that the CRMCs are likely cis-regulatory, while the non-CRMCs are not. Our predicted CRMs are under stronger evolutionary constraints than three state-of-the-art predictions (GeneHancer, EnhancerAtlas and ENCODE phase 3) and substantially outperform them for recalling VISTA enhancers and non-coding ClinVar variants. We estimated that the human genome might encode about 1.47M CRMs and 68M TFBSs, comprising about 55% and 22% of the genome, respectively; for both of which, we predicted 80%. Therefore, the cis-regulatory genome appears to be more prevalent than originally thought.
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Affiliation(s)
- Pengyu Ni
- Department of Bioinformatics and Genomics, the University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA
| | - Zhengchang Su
- Department of Bioinformatics and Genomics, the University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA
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Henikoff S, Henikoff JG, Ahmad K. Simplified Epigenome Profiling Using Antibody-tethered Tagmentation. Bio Protoc 2021; 11:e4043. [PMID: 34250209 PMCID: PMC8250384 DOI: 10.21769/bioprotoc.4043] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 03/24/2021] [Accepted: 04/29/2021] [Indexed: 12/02/2022] Open
Abstract
We previously introduced Cleavage Under Targets & Tagmentation (CUT&Tag), an epigenomic profiling method in which antibody tethering of the Tn5 transposase to a chromatin epitope of interest maps specific chromatin features in small samples and single cells. With CUT&Tag, intact cells or nuclei are permeabilized, followed by successive addition of a primary antibody, a secondary antibody, and a chimeric Protein A-Transposase fusion protein that binds to the antibody. Addition of Mg++ activates the transposase and inserts sequencing adapters into adjacent DNA in situ. We have since adapted CUT&Tag to also map chromatin accessibility by simply modifying the transposase activation conditions when using histone H3K4me2, H3K4me3, or Serine-5-phosphorylated RNA Polymerase II antibodies. Using these antibodies, we redirect the tagmentation of accessible DNA sites to produce chromatin accessibility maps with exceptionally high signal-to-noise and resolution. All steps from nuclei to amplified sequencing-ready libraries are performed in single PCR tubes using non-toxic reagents and inexpensive equipment, making our simplified strategy for simultaneous chromatin profiling and accessibility mapping suitable for the lab, home workbench, or classroom.
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Affiliation(s)
- Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, Washington 98109, USA.,Howard Hughes Medical Institute, Seattle WA, USA
| | - Jorja G Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, Washington 98109, USA
| | - Kami Ahmad
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, Washington 98109, USA
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25
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Pagani CA, Huber AK, Hwang C, Marini S, Padmanabhan K, Livingston N, Nunez J, Sun Y, Edwards N, Cheng YH, Visser N, Yu P, Patel N, Greenstein JA, Rasheed H, Nelson R, Kessel K, Vasquez K, Strong AL, Hespe GE, Song JY, Wellik DM, Levi B. Novel Lineage-Tracing System to Identify Site-Specific Ectopic Bone Precursor Cells. Stem Cell Reports 2021; 16:626-640. [PMID: 33606989 PMCID: PMC7940250 DOI: 10.1016/j.stemcr.2021.01.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 01/19/2021] [Accepted: 01/21/2021] [Indexed: 11/30/2022] Open
Abstract
Heterotopic ossification (HO) is a form of pathological cell-fate change of mesenchymal stem/precursor cells (MSCs) that occurs following traumatic injury, limiting range of motion in extremities and causing pain. MSCs have been shown to differentiate to form bone; however, their lineage and aberrant processes after trauma are not well understood. Utilizing a well-established mouse HO model and inducible lineage-tracing mouse (Hoxa11-CreERT2;ROSA26-LSL-TdTomato), we found that Hoxa11-lineage cells represent HO progenitors specifically in the zeugopod. Bioinformatic single-cell transcriptomic and epigenomic analyses showed Hoxa11-lineage cells are regionally restricted mesenchymal cells that, after injury, gain the potential to undergo differentiation toward chondrocytes, osteoblasts, and adipocytes. This study identifies Hoxa11-lineage cells as zeugopod-specific ectopic bone progenitors and elucidates the fate specification and multipotency that mesenchymal cells acquire after injury. Furthermore, this highlights homeobox patterning genes as useful tools to trace region-specific progenitors and enable location-specific gene deletion. Lineage tracing, single-cell RNA-seq and single cell ATAC enable cell specific analysis of in vivo cell fate Hoxa11 lineage marks distinct mesenchymal precursors in the zeugopod Hoxa11 lineage mesenchymal precursors undergo an aberrant cell fate change towards ectopic bone and cartilage
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Affiliation(s)
- Chase A Pagani
- Center for Organogenesis and Trauma, Department of Surgery, University of Texas Southwestern, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA
| | - Amanda K Huber
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Charles Hwang
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Simone Marini
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | | | - Nicholas Livingston
- Center for Organogenesis and Trauma, Department of Surgery, University of Texas Southwestern, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA
| | - Johanna Nunez
- Center for Organogenesis and Trauma, Department of Surgery, University of Texas Southwestern, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA
| | - Yuxiao Sun
- Center for Organogenesis and Trauma, Department of Surgery, University of Texas Southwestern, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA
| | - Nicole Edwards
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Yu-Hao Cheng
- Institute for Cell Engineering, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Noelle Visser
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Pauline Yu
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nicole Patel
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Joseph A Greenstein
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Husain Rasheed
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Reagan Nelson
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Karen Kessel
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Kaetlin Vasquez
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amy L Strong
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Geoffrey E Hespe
- Section of Plastic Surgery, Department of Surgery, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jane Y Song
- Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA
| | - Deneen M Wellik
- Department of Cell and Regenerative Biology, University of Wisconsin, Madison, WI 53705, USA
| | - Benjamin Levi
- Center for Organogenesis and Trauma, Department of Surgery, University of Texas Southwestern, 6000 Harry Hines Boulevard, Dallas, TX 75235, USA.
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Gamarra N, Narlikar GJ. Collaboration through chromatin: motors of transcription and chromatin structure. J Mol Biol 2021; 433:166876. [PMID: 33556407 DOI: 10.1016/j.jmb.2021.166876] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 01/09/2023]
Abstract
Packaging of the eukaryotic genome into chromatin places fundamental physical constraints on transcription. Clarifying how transcription operates within these constraints is essential to understand how eukaryotic gene expression programs are established and maintained. Here we review what is known about the mechanisms of transcription on chromatin templates. Current models indicate that transcription through chromatin is accomplished by the combination of an inherent nucleosome disrupting activity of RNA polymerase and the action of ATP-dependent chromatin remodeling motors. Collaboration between these two types of molecular motors is proposed to occur at all stages of transcription through diverse mechanisms. Further investigation of how these two motors combine their basic activities is essential to clarify the interdependent relationship between genome structure and transcription.
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Affiliation(s)
- Nathan Gamarra
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States; TETRAD Graduate Program, University of California, San Francisco, San Francisco, United States
| | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States.
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Minnoye L, Marinov GK, Krausgruber T, Pan L, Marand AP, Secchia S, Greenleaf WJ, Furlong EEM, Zhao K, Schmitz RJ, Bock C, Aerts S. Chromatin accessibility profiling methods. NATURE REVIEWS. METHODS PRIMERS 2021; 1:10. [PMID: 38410680 PMCID: PMC10895463 DOI: 10.1038/s43586-020-00008-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/01/2020] [Indexed: 02/06/2023]
Abstract
Chromatin accessibility, or the physical access to chromatinized DNA, is a widely studied characteristic of the eukaryotic genome. As active regulatory DNA elements are generally 'accessible', the genome-wide profiling of chromatin accessibility can be used to identify candidate regulatory genomic regions in a tissue or cell type. Multiple biochemical methods have been developed to profile chromatin accessibility, both in bulk and at the single-cell level. Depending on the method, enzymatic cleavage, transposition or DNA methyltransferases are used, followed by high-throughput sequencing, providing a view of genome-wide chromatin accessibility. In this Primer, we discuss these biochemical methods, as well as bioinformatics tools for analysing and interpreting the generated data, and insights into the key regulators underlying developmental, evolutionary and disease processes. We outline standards for data quality, reproducibility and deposition used by the genomics community. Although chromatin accessibility profiling is invaluable to study gene regulation, alone it provides only a partial view of this complex process. Orthogonal assays facilitate the interpretation of accessible regions with respect to enhancer-promoter proximity, functional transcription factor binding and regulatory function. We envision that technological improvements including single-molecule, multi-omics and spatial methods will bring further insight into the secrets of genome regulation.
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Affiliation(s)
- Liesbeth Minnoye
- Center for Brain & Disease Research, VIB-KU Leuven, Leuven, Belgium
- Department of Human Genetics, KU Leuven, Leuven, Belgium
| | | | - Thomas Krausgruber
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Lixia Pan
- Laboratory of Epigenome Biology, Systems Biology Center, Division of Intramural Research, National Heart, Lung and Blood Institute, NIH, Bethesda, MD, USA
| | | | - Stefano Secchia
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | | | - Eileen E M Furlong
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Keji Zhao
- Laboratory of Epigenome Biology, Systems Biology Center, Division of Intramural Research, National Heart, Lung and Blood Institute, NIH, Bethesda, MD, USA
| | | | - Christoph Bock
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
- Institute of Artificial Intelligence and Decision Support, Center for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria
| | - Stein Aerts
- Center for Brain & Disease Research, VIB-KU Leuven, Leuven, Belgium
- Department of Human Genetics, KU Leuven, Leuven, Belgium
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28
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Marr LT, Ocampo J, Clark DJ, Hayes JJ. Global histone protein surface accessibility in yeast indicates a uniformly loosely packed genome with canonical nucleosomes. Epigenetics Chromatin 2021; 14:5. [PMID: 33430969 PMCID: PMC7802155 DOI: 10.1186/s13072-020-00381-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/28/2020] [Indexed: 01/09/2023] Open
Abstract
Background The vast majority of methods available to characterize genome-wide chromatin structure exploit differences in DNA accessibility to nucleases or chemical crosslinking. We developed a novel method to gauge genome-wide accessibility of histone protein surfaces within nucleosomes by assessing reactivity of engineered cysteine residues with a thiol-specific reagent, biotin-maleimide (BM). Results Yeast nuclei were obtained from cells expressing the histone mutant H2B S116C, in which a cysteine resides near the center of the external flat protein surface of the nucleosome. BM modification revealed that nucleosomes are generally equivalently accessible throughout the S. cerevisiae genome, including heterochromatic regions, suggesting limited, higher-order chromatin structures in which this surface is obstructed by tight nucleosome packing. However, we find that nucleosomes within 500 bp of transcription start sites exhibit the greatest range of accessibility, which correlates with the density of chromatin remodelers. Interestingly, accessibility is not well correlated with RNA polymerase density and thus the level of gene expression. We also investigated the accessibility of cysteine mutations designed to detect exposure of histone surfaces internal to the nucleosome thought to be accessible in actively transcribed genes: H3 102, is at the H2A–H2B dimer/H3–H4 tetramer interface, and H3 A110C, resides at the H3–H3 interface. However, in contrast to the external surface site, we find that neither of these internal sites were found to be appreciably exposed. Conclusions Overall, our finding that nucleosomes surfaces within S. cerevisiae chromatin are equivalently accessible genome-wide is consistent with a globally uncompacted chromatin structure lacking substantial higher-order organization. However, we find modest differences in accessibility that correlate with chromatin remodelers but not transcription, suggesting chromatin poised for transcription is more accessible than actively transcribed or intergenic regions. In contrast, we find that two internal sites remain inaccessible, suggesting that such non-canonical nucleosome species generated during transcription are rapidly and efficiently converted to canonical nucleosome structure and thus not widely present in native chromatin.
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Affiliation(s)
- Luke T Marr
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Josefina Ocampo
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI-CONICET), C1428ADN, Buenos Aires, Argentina
| | - David J Clark
- Division of Developmental Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, 20892, USA
| | - Jeffrey J Hayes
- Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, NY, 14642, USA.
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Jana T, Brodsky S, Barkai N. Speed-Specificity Trade-Offs in the Transcription Factors Search for Their Genomic Binding Sites. Trends Genet 2021; 37:421-432. [PMID: 33414013 DOI: 10.1016/j.tig.2020.12.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 12/17/2022]
Abstract
Transcription factors (TFs) regulate gene expression by binding DNA sequences recognized by their DNA-binding domains (DBDs). DBD-recognized motifs are short and highly abundant in genomes. The ability of TFs to bind a specific subset of motif-containing sites, and to do so rapidly upon activation, is fundamental for gene expression in all eukaryotes. Despite extensive interest, our understanding of the TF-target search process is fragmented; although binding specificity and detection speed are two facets of this same process, trade-offs between them are rarely addressed. In this opinion article, we discuss potential speed-specificity trade-offs in the context of existing models. We further discuss the recently described 'distributed specificity' paradigm, suggesting that intrinsically disordered regions (IDRs) promote specificity while reducing the TF-target search time.
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Affiliation(s)
- Tamar Jana
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sagie Brodsky
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naama Barkai
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
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30
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Abstract
The ATAC-seq assay has emerged as the most useful, versatile, and widely adaptable method for profiling accessible chromatin regions and tracking the activity of cis-regulatory elements (cREs) in eukaryotes. Thanks to its great utility, it is now being applied to map active chromatin in the context of a very wide diversity of biological systems and questions. In the course of these studies, considerable experience working with ATAC-seq data has accumulated and a standard set of computational tasks that need to be carried for most ATAC-seq analyses has emerged. Here, we review and provide examples of common such analytical procedures (including data processing, quality control, peak calling, identifying differentially accessible open chromatin regions, and variable transcription factor (TF) motif accessibility) and discuss recommended optimal practices.
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31
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Henikoff S, Henikoff JG, Kaya-Okur HS, Ahmad K. Efficient chromatin accessibility mapping in situ by nucleosome-tethered tagmentation. eLife 2020; 9:e63274. [PMID: 33191916 PMCID: PMC7721439 DOI: 10.7554/elife.63274] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 11/13/2020] [Indexed: 12/27/2022] Open
Abstract
Chromatin accessibility mapping is a powerful approach to identify potential regulatory elements. A popular example is ATAC-seq, whereby Tn5 transposase inserts sequencing adapters into accessible DNA ('tagmentation'). CUT&Tag is a tagmentation-based epigenomic profiling method in which antibody tethering of Tn5 to a chromatin epitope of interest profiles specific chromatin features in small samples and single cells. Here, we show that by simply modifying the tagmentation conditions for histone H3K4me2 or H3K4me3 CUT&Tag, antibody-tethered tagmentation of accessible DNA sites is redirected to produce chromatin accessibility maps that are indistinguishable from the best ATAC-seq maps. Thus, chromatin accessibility maps can be produced in parallel with CUT&Tag maps of other epitopes with all steps from nuclei to amplified sequencing-ready libraries performed in single PCR tubes in the laboratory or on a home workbench. As H3K4 methylation is produced by transcription at promoters and enhancers, our method identifies transcription-coupled accessible regulatory sites.
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Affiliation(s)
- Steven Henikoff
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
- Howard Hughes Medical InstituteSeattleUnited States
| | - Jorja G Henikoff
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Hatice S Kaya-Okur
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Kami Ahmad
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
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Hammelman J, Krismer K, Banerjee B, Gifford DK, Sherwood RI. Identification of determinants of differential chromatin accessibility through a massively parallel genome-integrated reporter assay. Genome Res 2020; 30:1468-1480. [PMID: 32973041 PMCID: PMC7605270 DOI: 10.1101/gr.263228.120] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 08/26/2020] [Indexed: 12/20/2022]
Abstract
A key mechanism in cellular regulation is the ability of the transcriptional machinery to physically access DNA. Transcription factors interact with DNA to alter the accessibility of chromatin, which enables changes to gene expression during development or disease or as a response to environmental stimuli. However, the regulation of DNA accessibility via the recruitment of transcription factors is difficult to study in the context of the native genome because every genomic site is distinct in multiple ways. Here we introduce the multiplexed integrated accessibility assay (MIAA), an assay that measures chromatin accessibility of synthetic oligonucleotide sequence libraries integrated into a controlled genomic context with low native accessibility. We apply MIAA to measure the effects of sequence motifs on cell type-specific accessibility between mouse embryonic stem cells and embryonic stem cell-derived definitive endoderm cells, screening 7905 distinct DNA sequences. MIAA recapitulates differential accessibility patterns of 100-nt sequences derived from natively differential genomic regions, identifying E-box motifs common to epithelial-mesenchymal transition driver transcription factors in stem cell-specific accessible regions that become repressed in endoderm. We show that a single binding motif for a key regulatory transcription factor is sufficient to open chromatin, and classify sets of stem cell-specific, endoderm-specific, and shared accessibility-modifying transcription factor motifs. We also show that overexpression of two definitive endoderm transcription factors, T and Foxa2, results in changes to accessibility in DNA sequences containing their respective DNA-binding motifs and identify preferential motif arrangements that influence accessibility.
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Affiliation(s)
- Jennifer Hammelman
- Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Konstantin Krismer
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Budhaditya Banerjee
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
| | - David K Gifford
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Richard I Sherwood
- Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
- Hubrecht Institute, 3584 CT Utrecht, Netherlands
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Baier T, Jacobebbinghaus N, Einhaus A, Lauersen KJ, Kruse O. Introns mediate post-transcriptional enhancement of nuclear gene expression in the green microalga Chlamydomonas reinhardtii. PLoS Genet 2020; 16:e1008944. [PMID: 32730252 PMCID: PMC7419008 DOI: 10.1371/journal.pgen.1008944] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/11/2020] [Accepted: 06/19/2020] [Indexed: 12/13/2022] Open
Abstract
Efficient nuclear transgene expression in the green microalga Chlamydomonas reinhardtii is generally hindered by low transcription rates. Introns can increase transcript abundance by a process called Intron-Mediated Enhancement (IME) in this alga and has been broadly observed in other eukaryotes. However, the mechanisms of IME in microalgae are poorly understood. Here, we identified 33 native introns from highly expressed genes in C. reinhardtii selected from transcriptome studies as well as 13 non-native introns. We investigated their IME capacities and probed the mechanism of action by modification of splice sites, internal sequence motifs, and position within transgenes. Several introns were found to elicit strong IME and found to be broadly applicable in different expression constructs. We determined that IME in C. reinhardtii exclusively occurs from introns within transcribed ORFs regardless of the promoter and is not induced by traditional enhancers of transcription. Our results elucidate some mechanistic details of IME in C. reinhardtii, which are similar to those observed in higher plants yet underly distinctly different induction processes. Our findings narrow the focus of targets responsible for algal IME and provides evidence that introns are underestimated regulators of C. reinhardtii nuclear gene expression. Although many genetic tools and basic transformation strategies exist for the model microalga Chlamydomonas reinhardtii, high-level genetic engineering with this organism is hindered by its inherent recalcitrance to foreign gene expression and limited knowledge of responsible expression regulators. In this work, we characterized the dynamics of 33 endogenous and 13 non-native introns and their effect on gene expression as artificial insertions into codon optimized transgenes. We found that introns from different origins have the capacity to increase gene expression rates. Intron-mediated enhancement was observed exclusively when these elements were placed in transcripts but not outside of transcribed mRNA regions. Insertion of different endogenous introns into coding sequences was found to positively affect expression rates through a synergy of additive transcription enhancement and exon length reduction, similar to those natively found in the C. reinhardtii genome. Our results indicate that intensive mRNA processing plays an underestimated role in the regulation of native gene expression in C. reinhardtii. In addition to internal sequence motifs, the location of artificially introduced introns greatly affected transgene expression levels. This work is highly valuable to the greater microalgal and synthetic biology research communities and contributes to broadening our understanding of eukaryotic intron-mediated enhancement.
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Affiliation(s)
- Thomas Baier
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse, Bielefeld, Germany
| | - Nick Jacobebbinghaus
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse, Bielefeld, Germany
| | - Alexander Einhaus
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse, Bielefeld, Germany
| | - Kyle J. Lauersen
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse, Bielefeld, Germany
- Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Olaf Kruse
- Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse, Bielefeld, Germany
- * E-mail:
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Interplay among ATP-Dependent Chromatin Remodelers Determines Chromatin Organisation in Yeast. BIOLOGY 2020; 9:biology9080190. [PMID: 32722483 PMCID: PMC7466152 DOI: 10.3390/biology9080190] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 07/15/2020] [Accepted: 07/21/2020] [Indexed: 02/06/2023]
Abstract
Cellular DNA is packaged into chromatin, which is composed of regularly-spaced nucleosomes with occasional gaps corresponding to active regulatory elements, such as promoters and enhancers, called nucleosome-depleted regions (NDRs). This chromatin organisation is primarily determined by the activities of a set of ATP-dependent remodeling enzymes that are capable of moving nucleosomes along DNA, or of evicting nucleosomes altogether. In yeast, the nucleosome-spacing enzymes are ISW1 (Imitation SWitch protein 1), Chromodomain-Helicase-DNA-binding (CHD)1, ISW2 (Imitation SWitch protein 2) and INOsitol-requiring 80 (INO80); the nucleosome eviction enzymes are the SWItching/Sucrose Non-Fermenting (SWI/SNF) family, the Remodeling the Structure of Chromatin (RSC) complexes and INO80. We discuss the contributions of each set of enzymes to chromatin organisation. ISW1 and CHD1 are the major spacing enzymes; loss of both enzymes results in major chromatin disruption, partly due to the appearance of close-packed di-nucleosomes. ISW1 and CHD1 compete to set nucleosome spacing on most genes. ISW1 is dominant, setting wild type spacing, whereas CHD1 sets short spacing and may dominate on highly-transcribed genes. We propose that the competing remodelers regulate spacing, which in turn controls the binding of linker histone (H1) and therefore the degree of chromatin folding. Thus, genes with long spacing bind more H1, resulting in increased chromatin compaction. RSC, SWI/SNF and INO80 are involved in NDR formation, either directly by nucleosome eviction or repositioning, or indirectly by affecting the size of the complex that resides in the NDR. The nature of this complex is controversial: some suggest that it is a RSC-bound “fragile nucleosome”, whereas we propose that it is a non-histone transcription complex. In either case, this complex appears to serve as a barrier to nucleosome formation, resulting in the formation of phased nucleosomal arrays on both sides.
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Chandradoss KR, Guthikonda PK, Kethavath S, Dass M, Singh H, Nayak R, Kurukuti S, Sandhu KS. Biased visibility in Hi-C datasets marks dynamically regulated condensed and decondensed chromatin states genome-wide. BMC Genomics 2020; 21:175. [PMID: 32087673 PMCID: PMC7036197 DOI: 10.1186/s12864-020-6580-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 02/13/2020] [Indexed: 01/29/2023] Open
Abstract
Background Proximity ligation based techniques, like Hi-C, involve restriction digestion followed by ligation of formaldehyde cross-linked chromatin. Distinct chromatin states can impact the restriction digestion, and hence the visibility in the contact maps, of engaged loci. Yet, the extent and the potential impact of digestion bias remain obscure and under-appreciated in the literature. Results Through analysis of 45 Hi-C datasets, lamina-associated domains (LADs), inactive X-chromosome in mammals, and polytene bands in fly, we first established that the DNA in condensed chromatin had lesser accessibility to restriction endonucleases used in Hi-C as compared to that in decondensed chromatin. The observed bias was independent of known systematic biases, was not appropriately corrected by existing computational methods, and needed an additional optimization step. We then repurposed this bias to identify novel condensed domains outside LADs, which were bordered by insulators and were dynamically associated with the polycomb mediated epigenetic and transcriptional states during development. Conclusions Our observations suggest that the corrected one-dimensional read counts of existing Hi-C datasets can be reliably repurposed to study the gene-regulatory dynamics associated with chromatin condensation and decondensation, and that the existing Hi-C datasets should be interpreted with cautions.
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Affiliation(s)
- Keerthivasan Raanin Chandradoss
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) - Mohali, Knowledge City, Sector 81, SAS Nagar, 140306, India
| | - Prashanth Kumar Guthikonda
- Department of Animal Biology, School of Life Sciences, University of Hyderabad (UoH), Central University, Prof. CN Rao Road, P O, Gachibowli, Hyderabad, Telangana, 500046, India
| | - Srinivas Kethavath
- Department of Animal Biology, School of Life Sciences, University of Hyderabad (UoH), Central University, Prof. CN Rao Road, P O, Gachibowli, Hyderabad, Telangana, 500046, India
| | - Monika Dass
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) - Mohali, Knowledge City, Sector 81, SAS Nagar, 140306, India
| | - Harpreet Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) - Mohali, Knowledge City, Sector 81, SAS Nagar, 140306, India
| | - Rakhee Nayak
- Department of Animal Biology, School of Life Sciences, University of Hyderabad (UoH), Central University, Prof. CN Rao Road, P O, Gachibowli, Hyderabad, Telangana, 500046, India
| | - Sreenivasulu Kurukuti
- Department of Animal Biology, School of Life Sciences, University of Hyderabad (UoH), Central University, Prof. CN Rao Road, P O, Gachibowli, Hyderabad, Telangana, 500046, India.
| | - Kuljeet Singh Sandhu
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) - Mohali, Knowledge City, Sector 81, SAS Nagar, 140306, India.
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Oberbeckmann E, Wolff M, Krietenstein N, Heron M, Ellins JL, Schmid A, Krebs S, Blum H, Gerland U, Korber P. Absolute nucleosome occupancy map for the Saccharomyces cerevisiae genome. Genome Res 2019; 29:1996-2009. [PMID: 31694866 PMCID: PMC6886505 DOI: 10.1101/gr.253419.119] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/31/2019] [Indexed: 12/23/2022]
Abstract
Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation because nucleosomes modulate DNA access by their positioning along the genome. A cell-population nucleosome map requires two observables: nucleosome positions along the DNA ("Where?") and nucleosome occupancies across the population ("In how many cells?"). All available genome-wide nucleosome mapping techniques are yield methods because they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or nonnucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions, but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby cross-validating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9-bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (±SD). Depending on nucleosome position calling procedures, there are 57,000 to 60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but correlate with increased presence of the nucleosome-evicting chromatin structure remodeling (RSC) complex, and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
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Affiliation(s)
- Elisa Oberbeckmann
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Michael Wolff
- Physik Department, Technische Universität München, 85748 Garching, Germany
| | - Nils Krietenstein
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Mark Heron
- Quantitative and Computational Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.,Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Jessica L Ellins
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, United Kingdom
| | - Andrea Schmid
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Stefan Krebs
- Laboratory of Functional Genome Analysis (LAFUGA), Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Helmut Blum
- Laboratory of Functional Genome Analysis (LAFUGA), Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Ulrich Gerland
- Physik Department, Technische Universität München, 85748 Garching, Germany
| | - Philipp Korber
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
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