1
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Dhillon N, Kamakaka RT. Transcriptional silencing in Saccharomyces cerevisiae: known unknowns. Epigenetics Chromatin 2024; 17:28. [PMID: 39272151 PMCID: PMC11401328 DOI: 10.1186/s13072-024-00553-7] [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: 07/02/2024] [Accepted: 09/02/2024] [Indexed: 09/15/2024] Open
Abstract
Transcriptional silencing in Saccharomyces cerevisiae is a persistent and highly stable form of gene repression. It involves DNA silencers and repressor proteins that bind nucleosomes. The silenced state is influenced by numerous factors including the concentration of repressors, nature of activators, architecture of regulatory elements, modifying enzymes and the dynamics of chromatin.Silencers function to increase the residence time of repressor Sir proteins at silenced domains while clustering of silenced domains enables increased concentrations of repressors and helps facilitate long-range interactions. The presence of an accessible NDR at the regulatory regions of silenced genes, the cycling of chromatin configurations at regulatory sites, the mobility of Sir proteins, and the non-uniform distribution of the Sir proteins across the silenced domain, all result in silenced chromatin that only stably silences weak promoters and enhancers via changes in transcription burst duration and frequency.These data collectively suggest that silencing is probabilistic and the robustness of silencing is achieved through sub-optimization of many different nodes of action such that a stable expression state is generated and maintained even though individual constituents are in constant flux.
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Affiliation(s)
- Namrita Dhillon
- Department of Biomolecular Engineering, University of California, 1156 High Street, Santa Cruz, CA, 95064, USA
| | - Rohinton T Kamakaka
- Department of MCD Biology, University of California, 1156 High Street, Santa Cruz, CA, 95064, USA.
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2
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Segura J, Díaz-Ingelmo O, Martínez-García B, Ayats-Fraile A, Nikolaou C, Roca J. Nucleosomal DNA has topological memory. Nat Commun 2024; 15:4526. [PMID: 38806488 PMCID: PMC11133463 DOI: 10.1038/s41467-024-49023-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 05/21/2024] [Indexed: 05/30/2024] Open
Abstract
One elusive aspect of the chromosome architecture is how it constrains the DNA topology. Nucleosomes stabilise negative DNA supercoils by restraining a DNA linking number difference (∆Lk) of about -1.26. However, whether this capacity is uniform across the genome is unknown. Here, we calculate the ∆Lk restrained by over 4000 nucleosomes in yeast cells. To achieve this, we insert each nucleosome in a circular minichromosome and perform Topo-seq, a high-throughput procedure to inspect the topology of circular DNA libraries in one gel electrophoresis. We show that nucleosomes inherently restrain distinct ∆Lk values depending on their genomic origin. Nucleosome DNA topologies differ at gene bodies (∆Lk = -1.29), intergenic regions (∆Lk = -1.23), rDNA genes (∆Lk = -1.24) and telomeric regions (∆Lk = -1.07). Nucleosomes near the transcription start and termination sites also exhibit singular DNA topologies. Our findings demonstrate that nucleosome DNA topology is imprinted by its native chromatin context and persists when the nucleosome is relocated.
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Affiliation(s)
- Joana Segura
- DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain
- Centro de Biología Molecular Severo Ochoa (CSIC/UAM), Madrid, Spain
| | - Ofelia Díaz-Ingelmo
- DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain
| | - Belén Martínez-García
- DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain
| | - Alba Ayats-Fraile
- DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain
| | | | - Joaquim Roca
- DNA Topology Lab, Molecular Biology Institute of Barcelona (IBMB-CSIC), Barcelona, Spain.
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3
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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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4
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Marinov GK, Chen X, Swaffer MP, Xiang T, Grossman AR, Greenleaf WJ. Genome-wide distribution of 5-hydroxymethyluracil and chromatin accessibility in the Breviolum minutum genome. Genome Biol 2024; 25:115. [PMID: 38711126 PMCID: PMC11071213 DOI: 10.1186/s13059-024-03261-3] [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: 09/23/2023] [Accepted: 04/28/2024] [Indexed: 05/08/2024] Open
Abstract
BACKGROUND In dinoflagellates, a unique and extremely divergent genomic and nuclear organization has evolved. The highly unusual features of dinoflagellate nuclei and genomes include permanently condensed liquid crystalline chromosomes, primarily packaged by proteins other than histones, genes organized in very long unidirectional gene arrays, a general absence of transcriptional regulation, high abundance of the otherwise very rare DNA modification 5-hydroxymethyluracil (5-hmU), and many others. While most of these fascinating properties are originally identified in the 1970s and 1980s, they have not yet been investigated using modern genomic tools. RESULTS In this work, we address some of the outstanding questions regarding dinoflagellate genome organization by mapping the genome-wide distribution of 5-hmU (using both immunoprecipitation-based and basepair-resolution chemical mapping approaches) and of chromatin accessibility in the genome of the Symbiodiniaceae dinoflagellate Breviolum minutum. We find that the 5-hmU modification is preferentially enriched over certain classes of repetitive elements, often coincides with the boundaries between gene arrays, and is generally correlated with decreased chromatin accessibility, the latter otherwise being largely uniform along the genome. We discuss the potential roles of 5-hmU in the functional organization of dinoflagellate genomes and its relationship to the transcriptional landscape of gene arrays. CONCLUSIONS Our results provide the first window into the 5-hmU and chromatin accessibility landscapes in dinoflagellates.
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Affiliation(s)
- Georgi K Marinov
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA.
| | - Xinyi Chen
- Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA
| | - Matthew P Swaffer
- Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Tingting Xiang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, 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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5
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Oyarzún-Cisterna A, Gidi C, Raiqueo F, Amigo R, Rivas C, Torrejón M, Gutiérrez JL. General regulatory factors exert differential effects on nucleosome sliding activity of the ISW1a complex. Biol Res 2024; 57:22. [PMID: 38704609 PMCID: PMC11069190 DOI: 10.1186/s40659-024-00500-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Accepted: 04/15/2024] [Indexed: 05/06/2024] Open
Abstract
BACKGROUND Chromatin dynamics is deeply involved in processes that require access to DNA, such as transcriptional regulation. Among the factors involved in chromatin dynamics at gene regulatory regions are general regulatory factors (GRFs). These factors contribute to establishment and maintenance of nucleosome-depleted regions (NDRs). These regions are populated by nucleosomes through histone deposition and nucleosome sliding, the latter catalyzed by a number of ATP-dependent chromatin remodeling complexes, including ISW1a. It has been observed that GRFs can act as barriers against nucleosome sliding towards NDRs. However, the relative ability of the different GRFs to hinder sliding activity is currently unknown. RESULTS Considering this, we performed a comparative analysis for the main GRFs, with focus in their ability to modulate nucleosome sliding mediated by ISW1a. Among the GRFs tested in nucleosome remodeling assays, Rap1 was the only factor displaying the ability to hinder the activity of ISW1a. This effect requires location of the Rap1 cognate sequence on linker that becomes entry DNA in the nucleosome remodeling process. In addition, Rap1 was able to hinder nucleosome assembly in octamer transfer assays. Concurrently, Rap1 displayed the highest affinity for and longest dwell time from its target sequence, compared to the other GRFs tested. Consistently, through bioinformatics analyses of publicly available genome-wide data, we found that nucleosome occupancy and histone deposition in vivo are inversely correlated with the affinity of Rap1 for its target sequences in the genome. CONCLUSIONS Our findings point to DNA binding affinity, residence time and location at particular translational positions relative to the nucleosome core as the key features of GRFs underlying their roles played in nucleosome sliding and assembly.
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Affiliation(s)
- Andrea Oyarzún-Cisterna
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - Cristián Gidi
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - Fernanda Raiqueo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - Roberto Amigo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - Camila Rivas
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - Marcela Torrejón
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile
| | - José L Gutiérrez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, 4070043, Concepción, Chile.
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6
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Wu K, Dhillon N, Bajor A, Abrahamsson S, Kamakaka RT. Yeast heterochromatin stably silences only weak regulatory elements by altering burst duration. Cell Rep 2024; 43:113983. [PMID: 38517895 PMCID: PMC11141299 DOI: 10.1016/j.celrep.2024.113983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/25/2023] [Accepted: 03/06/2024] [Indexed: 03/24/2024] Open
Abstract
Transcriptional silencing in Saccharomyces cerevisiae involves the generation of a chromatin state that stably represses transcription. Using multiple reporter assays, a diverse set of upstream activating sequence enhancers and core promoters were investigated for their susceptibility to silencing. We show that heterochromatin stably silences only weak and stress-induced regulatory elements but is unable to stably repress housekeeping gene regulatory elements, and the partial repression of these elements did not result in bistable expression states. Permutation analysis of enhancers and promoters indicates that both elements are targets of repression. Chromatin remodelers help specific regulatory elements to resist repression, most probably by altering nucleosome mobility and changing transcription burst duration. The strong enhancers/promoters can be repressed if silencer-bound Sir1 is increased. Together, our data suggest that the heterochromatic locus has been optimized to stably silence the weak mating-type gene regulatory elements but not strong housekeeping gene regulatory sequences.
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Affiliation(s)
- Kenneth Wu
- Department of MCD Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Namrita Dhillon
- Department of MCD Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Antone Bajor
- Electrical Engineering Department, Baskin School of Engineering, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Sara Abrahamsson
- Electrical Engineering Department, Baskin School of Engineering, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA
| | - Rohinton T Kamakaka
- Department of MCD Biology, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
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7
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Oberbeckmann E, Quililan K, Cramer P, Oudelaar AM. In vitro reconstitution of chromatin domains shows a role for nucleosome positioning in 3D genome organization. Nat Genet 2024; 56:483-492. [PMID: 38291333 PMCID: PMC10937381 DOI: 10.1038/s41588-023-01649-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 12/15/2023] [Indexed: 02/01/2024]
Abstract
Eukaryotic genomes are organized into chromatin domains. The molecular mechanisms driving the formation of these domains are difficult to dissect in vivo and remain poorly understood. Here we reconstitute Saccharomyces cerevisiae chromatin in vitro and determine its 3D organization at subnucleosome resolution by micrococcal nuclease-based chromosome conformation capture and molecular dynamics simulations. We show that regularly spaced and phased nucleosome arrays form chromatin domains in vitro that resemble domains in vivo. This demonstrates that neither loop extrusion nor transcription is required for basic domain formation in yeast. In addition, we find that the boundaries of reconstituted domains correspond to nucleosome-free regions and that insulation strength scales with their width. Finally, we show that domain compaction depends on nucleosome linker length, with longer linkers forming more compact structures. Together, our results demonstrate that regular nucleosome positioning is important for the formation of chromatin domains and provide a proof-of-principle for bottom-up 3D genome studies.
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Affiliation(s)
- Elisa Oberbeckmann
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany.
| | - Kimberly Quililan
- Max Planck Institute for Multidisciplinary Sciences, Genome Organization and Regulation, Göttingen, Germany
- The Francis Crick Institute, London, UK
| | - Patrick Cramer
- Max Planck Institute for Multidisciplinary Sciences, Department of Molecular Biology, Göttingen, Germany
| | - A Marieke Oudelaar
- Max Planck Institute for Multidisciplinary Sciences, Genome Organization and Regulation, Göttingen, Germany.
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8
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Ahmad K, Brahma S, Henikoff S. Epigenetic pioneering by SWI/SNF family remodelers. Mol Cell 2024; 84:194-201. [PMID: 38016477 PMCID: PMC10842064 DOI: 10.1016/j.molcel.2023.10.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/20/2023] [Accepted: 10/31/2023] [Indexed: 11/30/2023]
Abstract
In eukaryotic genomes, transcriptional machinery and nucleosomes compete for binding to DNA sequences; thus, a crucial aspect of gene regulatory element function is to modulate chromatin accessibility for transcription factor (TF) and RNA polymerase binding. Recent structural studies have revealed multiple modes of TF engagement with nucleosomes, but how initial "pioneering" results in steady-state DNA accessibility for further TF binding and RNA polymerase II (RNAPII) engagement has been unclear. Even less well understood is how distant sites of open chromatin interact with one another, such as when developmental enhancers activate promoters to release RNAPII for productive elongation. Here, we review evidence for the centrality of the conserved SWI/SNF family of nucleosome remodeling complexes, both in pioneering and in mediating enhancer-promoter contacts. Consideration of the nucleosome unwrapping and ATP hydrolysis activities of SWI/SNF complexes, together with their architectural features, may reconcile steady-state TF occupancy with rapid TF dynamics observed by live imaging.
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Affiliation(s)
- Kami Ahmad
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Sandipan Brahma
- University of Nebraska Medical Center, Department of Genetics, Cell Biology & Anatomy, Omaha, NE, USA
| | - Steven Henikoff
- Basic Sciences Division, Fred Hutchinson Cancer Center, Seattle, WA, USA; Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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9
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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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10
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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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11
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Chanou A, Weiβ M, Holler K, Sajid A, Straub T, Krietsch J, Sanchi A, Ummethum H, Lee CSK, Kruse E, Trauner M, Werner M, Lalonde M, Lopes M, Scialdone A, Hamperl S. Single molecule MATAC-seq reveals key determinants of DNA replication origin efficiency. Nucleic Acids Res 2023; 51:12303-12324. [PMID: 37956271 PMCID: PMC10711542 DOI: 10.1093/nar/gkad1022] [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: 11/25/2022] [Revised: 10/12/2023] [Accepted: 10/20/2023] [Indexed: 11/15/2023] Open
Abstract
Stochastic origin activation gives rise to significant cell-to-cell variability in the pattern of genome replication. The molecular basis for heterogeneity in efficiency and timing of individual origins is a long-standing question. Here, we developed Methylation Accessibility of TArgeted Chromatin domain Sequencing (MATAC-Seq) to determine single-molecule chromatin accessibility of four specific genomic loci. MATAC-Seq relies on preferential modification of accessible DNA by methyltransferases combined with Nanopore-Sequencing for direct readout of methylated DNA-bases. Applying MATAC-Seq to selected early-efficient and late-inefficient yeast replication origins revealed large heterogeneity of chromatin states. Disruption of INO80 or ISW2 chromatin remodeling complexes leads to changes at individual nucleosomal positions that correlate with changes in their replication efficiency. We found a chromatin state with an accessible nucleosome-free region in combination with well-positioned +1 and +2 nucleosomes as a strong predictor for efficient origin activation. Thus, MATAC-Seq identifies the large spectrum of alternative chromatin states that co-exist on a given locus previously masked in population-based experiments and provides a mechanistic basis for origin activation heterogeneity during eukaryotic DNA replication. Consequently, our single-molecule chromatin accessibility assay will be ideal to define single-molecule heterogeneity across many fundamental biological processes such as transcription, replication, or DNA repair in vitro and ex vivo.
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Affiliation(s)
- Anna Chanou
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Matthias Weiβ
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Karoline Holler
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
- Institute of Functional Epigenetics, Helmholtz Zentrum München, Neuherberg, Germany
- Institute of Computational Biology, Helmholtz Zentrum München, Neuherberg, Germany
| | - Atiqa Sajid
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Tobias Straub
- Core Facility Bioinformatics, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, Martinsried, Germany
| | - Jana Krietsch
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Andrea Sanchi
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Henning Ummethum
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Clare S K Lee
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Elisabeth Kruse
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Manuel Trauner
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Marcel Werner
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Maxime Lalonde
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Antonio Scialdone
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
- Institute of Functional Epigenetics, Helmholtz Zentrum München, Neuherberg, Germany
- Institute of Computational Biology, Helmholtz Zentrum München, Neuherberg, Germany
| | - Stephan Hamperl
- Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
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12
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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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13
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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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14
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Khitun A, Brion C, Moqtaderi Z, Geisberg JV, Churchman LS, Struhl K. Elongation rate of RNA polymerase II affects pausing patterns across 3' UTRs. J Biol Chem 2023; 299:105289. [PMID: 37748648 PMCID: PMC10598743 DOI: 10.1016/j.jbc.2023.105289] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/01/2023] [Accepted: 09/20/2023] [Indexed: 09/27/2023] Open
Abstract
Yeast mRNAs are polyadenylated at multiple sites in their 3' untranslated regions (3' UTRs), and poly(A) site usage is regulated by the rate of transcriptional elongation by RNA polymerase II (Pol II). Slow Pol II derivatives favor upstream poly(A) sites, and fast Pol II derivatives favor downstream poly(A) sites. Transcriptional elongation and polyadenylation are linked at the nucleotide level, presumably reflecting Pol II dwell time at each residue that influences the level of polyadenylation. Here, we investigate the effect of Pol II elongation rate on pausing patterns and the relationship between Pol II pause sites and poly(A) sites within 3' UTRs. Mutations that affect Pol II elongation rate alter sequence preferences at pause sites within 3' UTRs, and pausing preferences differ between 3' UTRs and coding regions. In addition, sequences immediately flanking the pause sites show preferences that are largely independent of Pol II speed. In wild-type cells, poly(A) sites are preferentially located < 50 nucleotides upstream from Pol II pause sites, but this spatial relationship is diminished in cells harboring Pol II speed mutants. Based on a random forest classifier, Pol II pause sites are modestly predicted by the distance to poly(A) sites but are better predicted by the chromatin landscape in Pol II speed derivatives. Transcriptional regulatory proteins can influence the relationship between Pol II pausing and polyadenylation but in a manner distinct from Pol II elongation rate derivatives. These results indicate a complex relationship between Pol II pausing and polyadenylation.
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Affiliation(s)
- Alexandra Khitun
- Departments of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Christian Brion
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Zarmik Moqtaderi
- Departments of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Joseph V Geisberg
- Departments of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Kevin Struhl
- Departments of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA.
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15
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Wu K, Dhillon N, Bajor A, Abrahamson S, Kamakaka RT. Yeast Heterochromatin Only Stably Silences Weak Regulatory Elements by Altering Burst Duration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.05.561072. [PMID: 37873261 PMCID: PMC10592971 DOI: 10.1101/2023.10.05.561072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The interplay between nucleosomes and transcription factors leads to programs of gene expression. Transcriptional silencing involves the generation of a chromatin state that represses transcription and is faithfully propagated through DNA replication and cell division. Using multiple reporter assays, including directly visualizing transcription in single cells, we investigated a diverse set of UAS enhancers and core promoters for their susceptibility to heterochromatic gene silencing. These results show that heterochromatin only stably silences weak and stress induced regulatory elements but is unable to stably repress housekeeping gene regulatory elements and the partial repression did not result in bistable expression states. Permutation analysis of different UAS enhancers and core promoters indicate that both elements function together to determine the susceptibility of regulatory sequences to repression. Specific histone modifiers and chromatin remodellers function in an enhancer specific manner to aid these elements to resist repression suggesting that Sir proteins likely function in part by reducing nucleosome mobility. We also show that the strong housekeeping regulatory elements can be repressed if silencer bound Sir1 is increased, suggesting that Sir1 is a limiting component in silencing. Together, our data suggest that the heterochromatic locus has been optimized to stably silence the weak mating type gene regulatory elements but not strong housekeeping gene regulatory sequences which could help explain why these genes are often found at the boundaries of silenced domains.
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Affiliation(s)
- Kenneth Wu
- Department of MCD Biology, 1156 High Street, University of California, Santa Cruz, CA 95064 USA
| | - Namrita Dhillon
- Department of MCD Biology, 1156 High Street, University of California, Santa Cruz, CA 95064 USA
| | - Antone Bajor
- Electrical Engineering Department, Baskin School of Engineering, 1156 High Street, University of California, Santa Cruz, CA 95064 USA
| | - Sara Abrahamson
- Electrical Engineering Department, Baskin School of Engineering, 1156 High Street, University of California, Santa Cruz, CA 95064 USA
| | - Rohinton T. Kamakaka
- Department of MCD Biology, 1156 High Street, University of California, Santa Cruz, CA 95064 USA
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16
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Abdulhay NJ, Hsieh LJ, McNally CP, Ostrowski MS, Moore CM, Ketavarapu M, Kasinathan S, Nanda AS, Wu K, Chio US, Zhou Z, Goodarzi H, Narlikar GJ, Ramani V. Nucleosome density shapes kilobase-scale regulation by a mammalian chromatin remodeler. Nat Struct Mol Biol 2023; 30:1571-1581. [PMID: 37696956 PMCID: PMC10584690 DOI: 10.1038/s41594-023-01093-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 08/09/2023] [Indexed: 09/13/2023]
Abstract
Nearly all essential nuclear processes act on DNA packaged into arrays of nucleosomes. However, our understanding of how these processes (for example, DNA replication, RNA transcription, chromatin extrusion and nucleosome remodeling) occur on individual chromatin arrays remains unresolved. Here, to address this deficit, we present SAMOSA-ChAAT: a massively multiplex single-molecule footprinting approach to map the primary structure of individual, reconstituted chromatin templates subject to virtually any chromatin-associated reaction. We apply this method to distinguish between competing models for chromatin remodeling by the essential imitation switch (ISWI) ATPase SNF2h: nucleosome-density-dependent spacing versus fixed-linker-length nucleosome clamping. First, we perform in vivo single-molecule nucleosome footprinting in murine embryonic stem cells, to discover that ISWI-catalyzed nucleosome spacing correlates with the underlying nucleosome density of specific epigenomic domains. To establish causality, we apply SAMOSA-ChAAT to quantify the activities of ISWI ATPase SNF2h and its parent complex ACF on reconstituted nucleosomal arrays of varying nucleosome density, at single-molecule resolution. We demonstrate that ISWI remodelers operate as density-dependent, length-sensing nucleosome sliders, whose ability to program DNA accessibility is dictated by single-molecule nucleosome density. We propose that the long-observed, context-specific regulatory effects of ISWI complexes can be explained in part by the sensing of nucleosome density within epigenomic domains. More generally, our approach promises molecule-precise views of the essential processes that shape nuclear physiology.
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Affiliation(s)
- Nour J Abdulhay
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | - Laura J Hsieh
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Colin P McNally
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Megan S Ostrowski
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
| | - Camille M Moore
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Tetrad Graduate Program, University of California San Francisco, San Francisco, CA, USA
| | | | - Sivakanthan Kasinathan
- Department of Pediatrics, Lucille Packard Children's Hospital, Stanford University, Palo Alto, CA, USA
| | - Arjun S Nanda
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Ke Wu
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA
| | - Un Seng Chio
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Ziling Zhou
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
| | - Hani Goodarzi
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA
- Bakar Computational Health Sciences Institute, San Francisco, CA, USA
| | - Geeta J Narlikar
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA.
| | - Vijay Ramani
- Gladstone Institute for Data Science and Biotechnology, J. David Gladstone Institutes, San Francisco, CA, USA.
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, USA.
- Bakar Computational Health Sciences Institute, San Francisco, CA, USA.
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17
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Eggers N, Gkountromichos F, Krause S, Campos-Sparr A, Becker P. Physical interaction between MSL2 and CLAMP assures direct cooperativity and prevents competition at composite binding sites. Nucleic Acids Res 2023; 51:9039-9054. [PMID: 37602401 PMCID: PMC10516644 DOI: 10.1093/nar/gkad680] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 07/13/2023] [Accepted: 08/09/2023] [Indexed: 08/22/2023] Open
Abstract
MSL2, the DNA-binding subunit of the Drosophila dosage compensation complex, cooperates with the ubiquitous protein CLAMP to bind MSL recognition elements (MREs) on the X chromosome. We explore the nature of the cooperative binding to these GA-rich, composite sequence elements in reconstituted naïve embryonic chromatin. We found that the cooperativity requires physical interaction between both proteins. Remarkably, disruption of this interaction does not lead to indirect, nucleosome-mediated cooperativity as expected, but to competition. The protein interaction apparently not only increases the affinity for composite binding sites, but also locks both proteins in a defined dimeric state that prevents competition. High Affinity Sites of MSL2 on the X chromosome contain variable numbers of MREs. We find that the cooperation between MSL2/CLAMP is not influenced by MRE clustering or arrangement, but happens largely at the level of individual MREs. The sites where MSL2/CLAMP bind strongly in vitro locate to all chromosomes and show little overlap to an expanded set of X-chromosomal MSL2 in vivo binding sites generated by CUT&RUN. Apparently, the intrinsic MSL2/CLAMP cooperativity is limited to a small selection of potential sites in vivo. This restriction must be due to components missing in our reconstitution, such as roX2 lncRNA.
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Affiliation(s)
- Nikolas Eggers
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
| | | | - Silke Krause
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
| | | | - Peter B Becker
- Biomedical Center, Molecular Biology Division, LMU, Munich, Germany
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18
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Marinov GK, Chen X, Swaffer MP, Xiang T, Grossman AR, Greenleaf WJ. Genome-wide distribution of 5-hydroxymethyluracil and chromatin accessibility in the Breviolum minutum genome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.18.558303. [PMID: 37781619 PMCID: PMC10541103 DOI: 10.1101/2023.09.18.558303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
In dinoflagellates, a unique and extremely divergent genomic and nuclear organization has evolved. The highly unusual features of dinoflagellate nuclei and genomes include permanently condensed liquid crystalline chromosomes, primarily packaged by proteins other than histones, genes organized in very long unidirectional gene arrays, a general absence of transcriptional regulation, high abundance of the otherwise very rare DNA modification 5-hydroxymethyluracil (5-hmU), and many others. While most of these fascinating properties were originally identified in the 1970s and 1980s, they have not yet been investigated using modern genomic tools. In this work, we address some of the outstanding questions regarding dinoflagellate genome organization by mapping the genome-wide distribution of 5-hmU (using both immunoprecipitation-based and basepair-resolution chemical mapping approaches) and of chromatin accessibility in the genome of the Symbiodiniaceae dinoflagellate Breviolum minutum. We find that the 5-hmU modification is preferentially enriched over certain classes of repetitive elements, often coincides with the boundaries between gene arrays, and is generally correlated with decreased chromatin accessibility, the latter otherwise being largely uniform along the genome. We discuss the potential roles of 5-hmU in the functional organization of dinoflagellate genomes and its relationship to the transcriptional landscape of gene arrays.
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Affiliation(s)
- Georgi K Marinov
- Department of Genetics, Stanford University, Stanford, California 94305, USA
| | - Xinyi Chen
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | | | - Tingting Xiang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305, USA
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University, Stanford, California 94305, USA
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
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19
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Hook PW, Timp W. Beyond assembly: the increasing flexibility of single-molecule sequencing technology. Nat Rev Genet 2023; 24:627-641. [PMID: 37161088 PMCID: PMC10169143 DOI: 10.1038/s41576-023-00600-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2023] [Indexed: 05/11/2023]
Abstract
The maturation of high-throughput short-read sequencing technology over the past two decades has shaped the way genomes are studied. Recently, single-molecule, long-read sequencing has emerged as an essential tool in deciphering genome structure and function, including filling gaps in the human reference genome, measuring the epigenome and characterizing splicing variants in the transcriptome. With recent technological developments, these single-molecule technologies have moved beyond genome assembly and are being used in a variety of ways, including to selectively sequence specific loci with long reads, measure chromatin state and protein-DNA binding in order to investigate the dynamics of gene regulation, and rapidly determine copy number variation. These increasingly flexible uses of single-molecule technologies highlight a young and fast-moving part of the field that is leading to a more accessible era of nucleic acid sequencing.
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Affiliation(s)
- Paul W Hook
- Department of Biomedical Engineering, Molecular Biology and Genetics, and Genetic Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Winston Timp
- Department of Biomedical Engineering, Molecular Biology and Genetics, and Genetic Medicine, Johns Hopkins University, Baltimore, MD, USA.
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20
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Tan ZY, Cai S, Noble AJ, Chen JK, Shi J, Gan L. Heterogeneous non-canonical nucleosomes predominate in yeast cells in situ. eLife 2023; 12:RP87672. [PMID: 37503920 PMCID: PMC10382156 DOI: 10.7554/elife.87672] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/29/2023] Open
Abstract
Nuclear processes depend on the organization of chromatin, whose basic units are cylinder-shaped complexes called nucleosomes. A subset of mammalian nucleosomes in situ (inside cells) resembles the canonical structure determined in vitro 25 years ago. Nucleosome structure in situ is otherwise poorly understood. Using cryo-electron tomography (cryo-ET) and 3D classification analysis of budding yeast cells, here we find that canonical nucleosomes account for less than 10% of total nucleosomes expected in situ. In a strain in which H2A-GFP is the sole source of histone H2A, class averages that resemble canonical nucleosomes both with and without GFP densities are found ex vivo (in nuclear lysates), but not in situ. These data suggest that the budding yeast intranuclear environment favors multiple non-canonical nucleosome conformations. Using the structural observations here and the results of previous genomics and biochemical studies, we propose a model in which the average budding yeast nucleosome's DNA is partially detached in situ.
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Affiliation(s)
- Zhi Yang Tan
- Department of Biological Sciences and Center for BioImaging Sciences, National University of SingaporeSingaporeSingapore
| | - Shujun Cai
- Department of Biological Sciences and Center for BioImaging Sciences, National University of SingaporeSingaporeSingapore
| | - Alex J Noble
- National Resource for Automated Molecular Microscopy, Simons Electron Microscopy Center, New York Structural Biology CenterNew YorkUnited States
| | - Jon K Chen
- Department of Biological Sciences and Center for BioImaging Sciences, National University of SingaporeSingaporeSingapore
| | - Jian Shi
- Department of Biological Sciences and Center for BioImaging Sciences, National University of SingaporeSingaporeSingapore
| | - Lu Gan
- Department of Biological Sciences and Center for BioImaging Sciences, National University of SingaporeSingaporeSingapore
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21
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Chen J, Basting PJ, Han S, Garfinkel DJ, Bergman CM. Reproducible evaluation of transposable element detectors with McClintock 2 guides accurate inference of Ty insertion patterns in yeast. Mob DNA 2023; 14:8. [PMID: 37452430 PMCID: PMC10347736 DOI: 10.1186/s13100-023-00296-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 06/09/2023] [Indexed: 07/18/2023] Open
Abstract
BACKGROUND Many computational methods have been developed to detect non-reference transposable element (TE) insertions using short-read whole genome sequencing data. The diversity and complexity of such methods often present challenges to new users seeking to reproducibly install, execute, or evaluate multiple TE insertion detectors. RESULTS We previously developed the McClintock meta-pipeline to facilitate the installation, execution, and evaluation of six first-generation short-read TE detectors. Here, we report a completely re-implemented version of McClintock written in Python using Snakemake and Conda that improves its installation, error handling, speed, stability, and extensibility. McClintock 2 now includes 12 short-read TE detectors, auxiliary pre-processing and analysis modules, interactive HTML reports, and a simulation framework to reproducibly evaluate the accuracy of component TE detectors. When applied to the model microbial eukaryote Saccharomyces cerevisiae, we find substantial variation in the ability of McClintock 2 components to identify the precise locations of non-reference TE insertions, with RelocaTE2 showing the highest recall and precision in simulated data. We find that RelocaTE2, TEMP, TEMP2 and TEBreak provide consistent estimates of [Formula: see text]50 non-reference TE insertions per strain and that Ty2 has the highest number of non-reference TE insertions in a species-wide panel of [Formula: see text]1000 yeast genomes. Finally, we show that best-in-class predictors for yeast applied to resequencing data have sufficient resolution to reveal a dyad pattern of integration in nucleosome-bound regions upstream of yeast tRNA genes for Ty1, Ty2, and Ty4, allowing us to extend knowledge about fine-scale target preferences revealed previously for experimentally-induced Ty1 insertions to spontaneous insertions for other copia-superfamily retrotransposons in yeast. CONCLUSION McClintock ( https://github.com/bergmanlab/mcclintock/ ) provides a user-friendly pipeline for the identification of TEs in short-read WGS data using multiple TE detectors, which should benefit researchers studying TE insertion variation in a wide range of different organisms. Application of the improved McClintock system to simulated and empirical yeast genome data reveals best-in-class methods and novel biological insights for one of the most widely-studied model eukaryotes and provides a paradigm for evaluating and selecting non-reference TE detectors in other species.
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Affiliation(s)
- Jingxuan Chen
- Institute of Bioinformatics, University of Georgia, Athens, GA USA
| | | | - Shunhua Han
- Institute of Bioinformatics, University of Georgia, Athens, GA USA
| | - David J. Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA USA
| | - Casey M. Bergman
- Institute of Bioinformatics, University of Georgia, Athens, GA USA
- Department of Genetics, University of Georgia, Athens, GA USA
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22
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Chen H, Yan C, Dhasarathy A, Kladde M, Bai L. Investigating pioneer factor activity and its coordination with chromatin remodelers using integrated synthetic oligo assay. STAR Protoc 2023; 4:102279. [PMID: 37289591 PMCID: PMC10323128 DOI: 10.1016/j.xpro.2023.102279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/24/2023] [Accepted: 04/07/2023] [Indexed: 06/10/2023] Open
Abstract
Chromatin accessibility is regulated by pioneer factors (PFs) and chromatin remodelers (CRs). Here, we present a protocol, based on integrated synthetic oligonucleotide libraries in yeast, to systematically interrogate the nucleosome-displacing activities of PFs and their coordination with CRs. We describe steps for designing oligonucleotide sequences, constructing yeast libraries, measuring nucleosome configurations, and data analyses. This approach potentially can be adapted for use in higher eukaryotes to investigate the activities of many types of chromatin-associated factors. For complete details on the use and execution of this protocol, please refer to Yan et al.,1 and Chen et al.2.
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Affiliation(s)
- Hengye Chen
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Chao Yan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA
| | - Archana Dhasarathy
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND 58201, USA
| | - Michael Kladde
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Florida, Gainesville, FL 32610, USA; UF Health Cancer Center, University of Florida, Gainesville, FL 32610, USA
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA; Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, PA 16802, USA; Department of Physics, The Pennsylvania State University, University Park, PA 16802, USA.
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23
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Torres DE, Reckard AT, Klocko AD, Seidl MF. Nuclear genome organization in fungi: from gene folding to Rabl chromosomes. FEMS Microbiol Rev 2023; 47:fuad021. [PMID: 37197899 PMCID: PMC10246852 DOI: 10.1093/femsre/fuad021] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 04/28/2023] [Accepted: 05/08/2023] [Indexed: 05/19/2023] Open
Abstract
Comparative genomics has recently provided unprecedented insights into the biology and evolution of the fungal lineage. In the postgenomics era, a major research interest focuses now on detailing the functions of fungal genomes, i.e. how genomic information manifests into complex phenotypes. Emerging evidence across diverse eukaryotes has revealed that the organization of DNA within the nucleus is critically important. Here, we discuss the current knowledge on the fungal genome organization, from the association of chromosomes within the nucleus to topological structures at individual genes and the genetic factors required for this hierarchical organization. Chromosome conformation capture followed by high-throughput sequencing (Hi-C) has elucidated how fungal genomes are globally organized in Rabl configuration, in which centromere or telomere bundles are associated with opposite faces of the nuclear envelope. Further, fungal genomes are regionally organized into topologically associated domain-like (TAD-like) chromatin structures. We discuss how chromatin organization impacts the proper function of DNA-templated processes across the fungal genome. Nevertheless, this view is limited to a few fungal taxa given the paucity of fungal Hi-C experiments. We advocate for exploring genome organization across diverse fungal lineages to ensure the future understanding of the impact of nuclear organization on fungal genome function.
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Affiliation(s)
- David E Torres
- Theoretical Biology and Bioinformatics, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
- Laboratory of Phytopathology, Wageningen University and Research,Droevendaalsesteeg 4, 6708 PB Wageningen, The Netherlands
| | - Andrew T Reckard
- Department of Chemistry and Biochemistry, University of Colorado Colorado Springs, 234 Centennial Hall, 1420 Austin Bluffs Pkwy, Colorado Springs, CO 80918 USA
| | - Andrew D Klocko
- Department of Chemistry and Biochemistry, University of Colorado Colorado Springs, 234 Centennial Hall, 1420 Austin Bluffs Pkwy, Colorado Springs, CO 80918 USA
| | - Michael F Seidl
- Theoretical Biology and Bioinformatics, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
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24
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Pan Y, Hu C, Hou LJ, Chen YL, Shi J, Liu JC, Zhou JQ. Swc4 protects nucleosome-free rDNA, tDNA and telomere loci to inhibit genome instability. DNA Repair (Amst) 2023; 127:103512. [PMID: 37230009 DOI: 10.1016/j.dnarep.2023.103512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 04/17/2023] [Accepted: 05/11/2023] [Indexed: 05/27/2023]
Abstract
In the baker's yeast Saccharomyces cerevisiae, NuA4 and SWR1-C, two multisubunit complexes, are involved in histone acetylation and chromatin remodeling, respectively. Eaf1 is the assembly platform subunit of NuA4, Swr1 is the assembly platform and catalytic subunit of SWR1-C, while Swc4, Yaf9, Arp4 and Act1 form a functional module, and is present in both NuA4 and SWR1 complexes. ACT1 and ARP4 are essential for cell survival. Deletion of SWC4, but not YAF9, EAF1 or SWR1 results in a severe growth defect, but the underlying mechanism remains largely unknown. Here, we show that swc4Δ, but not yaf9Δ, eaf1Δ, or swr1Δ cells display defects in DNA ploidy and chromosome segregation, suggesting that the defects observed in swc4Δ cells are independent of NuA4 or SWR1-C integrity. Swc4 is enriched in the nucleosome-free regions (NFRs) of the genome, including characteristic regions of RDN5s, tDNAs and telomeres, independently of Yaf9, Eaf1 or Swr1. In particular, rDNA, tDNA and telomere loci are more unstable and prone to recombination in the swc4Δ cells than in wild-type cells. Taken together, we conclude that the chromatin associated Swc4 protects nucleosome-free chromatin of rDNA, tDNA and telomere loci to ensure genome integrity.
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Affiliation(s)
- Yue Pan
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Can Hu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Lin-Jun Hou
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yu-Long Chen
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jiantao Shi
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jia-Cheng Liu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
| | - Jin-Qiu Zhou
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai 200031, China; Key Laboratory of Systems Health Science of Zhejiang Province, School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China.
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25
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Chacin E, Reusswig KU, Furtmeier J, Bansal P, Karl LA, Pfander B, Straub T, Korber P, Kurat CF. Establishment and function of chromatin organization at replication origins. Nature 2023; 616:836-842. [PMID: 37020028 DOI: 10.1038/s41586-023-05926-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 03/03/2023] [Indexed: 04/07/2023]
Abstract
The origin recognition complex (ORC) is essential for initiation of eukaryotic chromosome replication as it loads the replicative helicase-the minichromosome maintenance (MCM) complex-at replication origins1. Replication origins display a stereotypic nucleosome organization with nucleosome depletion at ORC-binding sites and flanking arrays of regularly spaced nucleosomes2-4. However, how this nucleosome organization is established and whether this organization is required for replication remain unknown. Here, using genome-scale biochemical reconstitution with approximately 300 replication origins, we screened 17 purified chromatin factors from budding yeast and found that the ORC established nucleosome depletion over replication origins and flanking nucleosome arrays by orchestrating the chromatin remodellers INO80, ISW1a, ISW2 and Chd1. The functional importance of the nucleosome-organizing activity of the ORC was demonstrated by orc1 mutations that maintained classical MCM-loader activity but abrogated the array-generation activity of ORC. These mutations impaired replication through chromatin in vitro and were lethal in vivo. Our results establish that ORC, in addition to its canonical role as the MCM loader, has a second crucial function as a master regulator of nucleosome organization at the replication origin, a crucial prerequisite for efficient chromosome replication.
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Affiliation(s)
- Erika Chacin
- Biomedical Center Munich (BMC), Division of Molecular Biology, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Karl-Uwe Reusswig
- Max Planck Institute of Biochemistry, DNA Replication and Genome Integrity, Martinsried, Germany
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Jessica Furtmeier
- Biomedical Center Munich (BMC), Division of Molecular Biology, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Priyanka Bansal
- Biomedical Center Munich (BMC), Division of Molecular Biology, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Leonhard A Karl
- Max Planck Institute of Biochemistry, DNA Replication and Genome Integrity, Martinsried, Germany
| | - Boris Pfander
- Max Planck Institute of Biochemistry, DNA Replication and Genome Integrity, Martinsried, Germany
- Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
- Institute of Genome Stability in Aging and Disease, CECAD, University of Cologne, Medical Faculty, Cologne, Germany
| | - Tobias Straub
- Core Facility Bioinformatics, BMC, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Philipp Korber
- Biomedical Center Munich (BMC), Division of Molecular Biology, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany
| | - Christoph F Kurat
- Biomedical Center Munich (BMC), Division of Molecular Biology, Faculty of Medicine, Ludwig-Maximilians-Universität in Munich, Martinsried, Germany.
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26
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Chen J, Basting PJ, Han S, Garfinkel DJ, Bergman CM. Reproducible evaluation of transposable element detectors with McClintock 2 guides accurate inference of Ty insertion patterns in yeast. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.13.528343. [PMID: 36824955 PMCID: PMC9948991 DOI: 10.1101/2023.02.13.528343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
BACKGROUND Many computational methods have been developed to detect non-reference transposable element (TE) insertions using short-read whole genome sequencing data. The diversity and complexity of such methods often present challenges to new users seeking to reproducibly install, execute, or evaluate multiple TE insertion detectors. RESULTS We previously developed the McClintock meta-pipeline to facilitate the installation, execution, and evaluation of six first-generation short-read TE detectors. Here, we report a completely re-implemented version of McClintock written in Python using Snakemake and Conda that improves its installation, error handling, speed, stability, and extensibility. McClintock 2 now includes 12 short-read TE detectors, auxiliary pre-processing and analysis modules, interactive HTML reports, and a simulation framework to reproducibly evaluate the accuracy of component TE detectors. When applied to the model microbial eukaryote Saccharomyces cerevisiae, we find substantial variation in the ability of McClintock 2 components to identify the precise locations of non-reference TE insertions, with RelocaTE2 showing the highest recall and precision in simulated data. We find that RelocaTE2, TEMP, TEMP2 and TEBreak provide a consistent and biologically meaningful view of non-reference TE insertions in a species-wide panel of ∼1000 yeast genomes, as evaluated by coverage-based abundance estimates and expected patterns of tRNA promoter targeting. Finally, we show that best-in-class predictors for yeast have sufficient resolution to reveal a dyad pattern of integration in nucleosome-bound regions upstream of yeast tRNA genes for Ty1, Ty2, and Ty4, allowing us to extend knowledge about fine-scale target preferences first revealed experimentally for Ty1 to natural insertions and related copia-superfamily retrotransposons in yeast. CONCLUSION McClintock (https://github.com/bergmanlab/mcclintock/) provides a user-friendly pipeline for the identification of TEs in short-read WGS data using multiple TE detectors, which should benefit researchers studying TE insertion variation in a wide range of different organisms. Application of the improved McClintock system to simulated and empirical yeast genome data reveals best-in-class methods and novel biological insights for one of the most widely-studied model eukaryotes and provides a paradigm for evaluating and selecting non-reference TE detectors for other species.
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Affiliation(s)
- Jingxuan Chen
- Institute of Bioinformatics, University of Georgia, Athens, GA
| | | | - Shunhua Han
- Institute of Bioinformatics, University of Georgia, Athens, GA
| | - David J. Garfinkel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA
| | - Casey M. Bergman
- Institute of Bioinformatics, University of Georgia, Athens, GA
- Department of Genetics, University of Georgia, Athens, GA
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27
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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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28
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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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29
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Parab L, Pal S, Dhar R. Transcription factor binding process is the primary driver of noise in gene expression. PLoS Genet 2022; 18:e1010535. [PMID: 36508455 PMCID: PMC9779669 DOI: 10.1371/journal.pgen.1010535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 12/22/2022] [Accepted: 11/16/2022] [Indexed: 12/14/2022] Open
Abstract
Noise in expression of individual genes gives rise to variations in activity of cellular pathways and generates heterogeneity in cellular phenotypes. Phenotypic heterogeneity has important implications for antibiotic persistence, mutation penetrance, cancer growth and therapy resistance. Specific molecular features such as the presence of the TATA box sequence and the promoter nucleosome occupancy have been associated with noise. However, the relative importance of these features in noise regulation is unclear and how well these features can predict noise has not yet been assessed. Here through an integrated statistical model of gene expression noise in yeast we found that the number of regulating transcription factors (TFs) of a gene was a key predictor of noise, whereas presence of the TATA box and the promoter nucleosome occupancy had poor predictive power. With an increase in the number of regulatory TFs, there was a rise in the number of cooperatively binding TFs. In addition, an increased number of regulatory TFs meant more overlaps in TF binding sites, resulting in competition between TFs for binding to the same region of the promoter. Through modeling of TF binding to promoter and application of stochastic simulations, we demonstrated that competition and cooperation among TFs could increase noise. Thus, our work uncovers a process of noise regulation that arises out of the dynamics of gene regulation and is not dependent on any specific transcription factor or specific promoter sequence.
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Affiliation(s)
- Lavisha Parab
- Department of Biotechnology, Indian Institute of Technology (IIT) Kharagpur, Kharagpur, West Bengal, India
- Max-Planck-Institute for Evolutionary Biology, Plön, Germany
| | - Sampriti Pal
- Department of Biotechnology, Indian Institute of Technology (IIT) Kharagpur, Kharagpur, West Bengal, India
| | - Riddhiman Dhar
- Department of Biotechnology, Indian Institute of Technology (IIT) Kharagpur, Kharagpur, West Bengal, India
- * E-mail:
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30
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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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31
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Malinina DK, Sivkina AL, Korovina AN, McCullough LL, Formosa T, Kirpichnikov MP, Studitsky VM, Feofanov AV. Hmo1 Protein Affects the Nucleosome Structure and Supports the Nucleosome Reorganization Activity of Yeast FACT. Cells 2022; 11:cells11192931. [PMID: 36230893 PMCID: PMC9564320 DOI: 10.3390/cells11192931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 09/06/2022] [Accepted: 09/15/2022] [Indexed: 12/05/2022] Open
Abstract
Yeast Hmo1 is a high mobility group B (HMGB) protein that participates in the transcription of ribosomal protein genes and rDNA, and also stimulates the activities of some ATP-dependent remodelers. Hmo1 binds both DNA and nucleosomes and has been proposed to be a functional yeast analog of mammalian linker histones. We used EMSA and single particle Förster resonance energy transfer (spFRET) microscopy to characterize the effects of Hmo1 on nucleosomes alone and with the histone chaperone FACT. Hmo1 induced a significant increase in the distance between the DNA gyres across the nucleosomal core, and also caused the separation of linker segments. This was opposite to the effect of the linker histone H1, which enhanced the proximity of linkers. Similar to Nhp6, another HMGB factor, Hmo1, was able to support large-scale, ATP-independent, reversible unfolding of nucleosomes by FACT in the spFRET assay and partially support FACT function in vivo. However, unlike Hmo1, Nhp6 alone does not affect nucleosome structure. These results suggest physiological roles for Hmo1 that are distinct from Nhp6 and possibly from other HMGB factors and linker histones, such as H1.
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Affiliation(s)
- Daria K. Malinina
- Biology Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
| | | | - Anna N. Korovina
- Biology Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
| | - Laura L. McCullough
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Tim Formosa
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Mikhail P. Kirpichnikov
- Biology Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Vasily M. Studitsky
- Biology Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
- Correspondence: (V.M.S.); (A.V.F.)
| | - Alexey V. Feofanov
- Biology Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Correspondence: (V.M.S.); (A.V.F.)
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32
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Couvillion M, Harlen KM, Lachance KC, Trotta KL, Smith E, Brion C, Smalec BM, Churchman LS. Transcription elongation is finely tuned by dozens of regulatory factors. eLife 2022; 11:e78944. [PMID: 35575476 PMCID: PMC9154744 DOI: 10.7554/elife.78944] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/15/2022] [Indexed: 11/30/2022] Open
Abstract
Understanding the complex network that regulates transcription elongation requires the quantitative analysis of RNA polymerase II (Pol II) activity in a wide variety of regulatory environments. We performed native elongating transcript sequencing (NET-seq) in 41 strains of Saccharomyces cerevisiae lacking known elongation regulators, including RNA processing factors, transcription elongation factors, chromatin modifiers, and remodelers. We found that the opposing effects of these factors balance transcription elongation and antisense transcription. Different sets of factors tightly regulate Pol II progression across gene bodies so that Pol II density peaks at key points of RNA processing. These regulators control where Pol II pauses with each obscuring large numbers of potential pause sites that are primarily determined by DNA sequence and shape. Antisense transcription varies highly across the regulatory landscapes analyzed, but antisense transcription in itself does not affect sense transcription at the same locus. Our findings collectively show that a diverse array of factors regulate transcription elongation by precisely balancing Pol II activity.
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Affiliation(s)
- Mary Couvillion
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Kevin M Harlen
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Kate C Lachance
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Kristine L Trotta
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Erin Smith
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Christian Brion
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - Brendan M Smalec
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
| | - L Stirling Churchman
- Blavatnik Institute, Department of Genetics, Harvard Medical SchoolBostonUnited States
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33
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Amigo R, Farkas C, Gidi C, Hepp MI, Cartes N, Tarifeño E, Workman JL, Gutiérrez JL. The linker histone Hho1 modulates the activity of ATP-dependent chromatin remodeling complexes. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2022; 1865:194781. [PMID: 34963628 DOI: 10.1016/j.bbagrm.2021.194781] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 11/30/2021] [Accepted: 12/12/2021] [Indexed: 02/07/2023]
Abstract
Diverse factors play roles in chromatin dynamics, including linker proteins. Among them are high mobility group (HMG) box family proteins and linker histones. In the yeast Saccharomyces cerevisiae, Hmo1 has been identified as an HMG-box protein. This protein displays properties that are in agreement with this allocation. However, a number of studies have postulated that Hmo1 functions as a linker histone in yeast. On the other hand, when discovered, the Hho1 protein was identified as a linker histone. While multiple studies support this classification, some findings point to characteristics of Hho1 that are dissimilar to those commonly assigned to linker histones. In order to better understand the roles played by Hmo1 and Hho1 in chromatin dynamics and transcriptional regulation, we performed several analyses directly comparing these two proteins. Our analyses of genome-wide binding profiles support the belonging of Hmo1 to the HMGB family and Hho1 to the linker histones family. Interestingly, by performing protein-protein interaction analyses we found that both Hmo1 and Hho1 display physical interaction with the ATP-dependent chromatin remodeling complexes RSC, ISW1a and SWI/SNF. Moreover, by carrying out nucleosome remodeling assays, we found that both proteins stimulate the activity of the ISW1a complex. However, in the case of RSC, Hmo1 and Hho1 displayed differential properties, with Hho1 mainly showing an inhibitory effect. Our results are in agreement with the opposite roles played by RSC and ISW1a in chromatin dynamics and transcriptional regulation, and expand the view for the roles played by Hho1 and linker histones.
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Affiliation(s)
- Roberto Amigo
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Carlos Farkas
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Cristian Gidi
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Matias I Hepp
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Natalia Cartes
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Estefanía Tarifeño
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile
| | - Jerry L Workman
- Stowers Institute for Medical Research, 1000 E 50(th) Street, Kansas City, MO 64110, USA
| | - José L Gutiérrez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Barrio Universitario s/n, Concepción 4070043, Chile.
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34
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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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35
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Kleinendorst RWD, Barzaghi G, Smith ML, Zaugg JB, Krebs AR. Genome-wide quantification of transcription factor binding at single-DNA-molecule resolution using methyl-transferase footprinting. Nat Protoc 2021; 16:5673-5706. [PMID: 34773120 PMCID: PMC7613001 DOI: 10.1038/s41596-021-00630-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 09/06/2021] [Indexed: 01/16/2023]
Abstract
Precise control of gene expression requires the coordinated action of multiple factors at cis-regulatory elements. We recently developed single-molecule footprinting to simultaneously resolve the occupancy of multiple proteins including transcription factors, RNA polymerase II and nucleosomes on single DNA molecules genome-wide. The technique combines the use of cytosine methyltransferases to footprint the genome with bisulfite sequencing to resolve transcription factor binding patterns at cis-regulatory elements. DNA footprinting is performed by incubating permeabilized nuclei with recombinant methyltransferases. Upon DNA extraction, whole-genome or targeted bisulfite libraries are prepared and loaded on Illumina sequencers. The protocol can be completed in 4-5 d in any laboratory with access to high-throughput sequencing. Analysis can be performed in 2 d using a dedicated R package and requires access to a high-performance computing system. Our method can be used to analyze how transcription factors cooperate and antagonize to regulate transcription.
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Affiliation(s)
| | - Guido Barzaghi
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
- Faculty of Biosciences, Collaboration for Joint PhD Degree between EMBL and Heidelberg University, Heidelberg, Germany
| | - Mike L Smith
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany
| | - Judith B Zaugg
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany
| | - Arnaud R Krebs
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, Heidelberg, Germany.
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Singh AK, Schauer T, Pfaller L, Straub T, Mueller-Planitz F. The biogenesis and function of nucleosome arrays. Nat Commun 2021; 12:7011. [PMID: 34853297 PMCID: PMC8636622 DOI: 10.1038/s41467-021-27285-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 11/09/2021] [Indexed: 11/24/2022] Open
Abstract
Numerous chromatin remodeling enzymes position nucleosomes in eukaryotic cells. Aside from these factors, transcription, DNA sequence, and statistical positioning of nucleosomes also shape the nucleosome landscape. The precise contributions of these processes remain unclear due to their functional redundancy in vivo. By incisive genome engineering, we radically decreased their redundancy in Saccharomyces cerevisiae. The transcriptional machinery strongly disrupts evenly spaced nucleosomes. Proper nucleosome density and DNA sequence are critical for their biogenesis. The INO80 remodeling complex helps space nucleosomes in vivo and positions the first nucleosome over genes in an H2A.Z-independent fashion. INO80 requires its Arp8 subunit but unexpectedly not the Nhp10 module for spacing. Cells with irregularly spaced nucleosomes suffer from genotoxic stress including DNA damage, recombination and transpositions. We derive a model of the biogenesis of the nucleosome landscape and suggest that it evolved not only to regulate but also to protect the genome.
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Affiliation(s)
- Ashish Kumar Singh
- grid.5252.00000 0004 1936 973XMolecular Biology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, München, Germany
| | - Tamás Schauer
- grid.5252.00000 0004 1936 973XBioinformatics Unit, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, München, Germany
| | - Lena Pfaller
- grid.5252.00000 0004 1936 973XMolecular Biology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, München, Germany ,grid.419481.10000 0001 1515 9979Present Address: Novartis Institutes for BioMedical Research, 4056 Basel, Switzerland
| | - Tobias Straub
- grid.5252.00000 0004 1936 973XBioinformatics Unit, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, München, Germany
| | - Felix Mueller-Planitz
- Molecular Biology, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, München, Germany. .,Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Fetscherstraße 74, 01307, Dresden, Germany.
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37
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Krebs AR. Studying transcription factor function in the genome at molecular resolution. Trends Genet 2021; 37:798-806. [DOI: 10.1016/j.tig.2021.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 12/11/2022]
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38
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Barnes T, Korber P. The Active Mechanism of Nucleosome Depletion by Poly(dA:dT) Tracts In Vivo. Int J Mol Sci 2021; 22:ijms22158233. [PMID: 34360997 PMCID: PMC8347975 DOI: 10.3390/ijms22158233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/27/2021] [Accepted: 07/29/2021] [Indexed: 12/16/2022] Open
Abstract
Poly(dA:dT) tracts cause nucleosome depletion in many species, e.g., at promoters and replication origins. Their intrinsic biophysical sequence properties make them stiff and unfavorable for nucleosome assembly, as probed by in vitro nucleosome reconstitution. The mere correlation between nucleosome depletion over poly(dA:dT) tracts in in vitro reconstituted and in in vivo chromatin inspired an intrinsic nucleosome exclusion mechanism in vivo that is based only on DNA and histone properties. However, we compile here published and new evidence that this correlation does not reflect mechanistic causation. (1) Nucleosome depletion over poly(dA:dT) in vivo is not universal, e.g., very weak in S. pombe. (2) The energy penalty for incorporating poly(dA:dT) tracts into nucleosomes is modest (<10%) relative to ATP hydrolysis energy abundantly invested by chromatin remodelers. (3) Nucleosome depletion over poly(dA:dT) is much stronger in vivo than in vitro if monitored without MNase and (4) actively maintained in vivo. (5) S. cerevisiae promoters evolved a strand-biased poly(dA) versus poly(dT) distribution. (6) Nucleosome depletion over poly(dA) is directional in vivo. (7) The ATP dependent chromatin remodeler RSC preferentially and directionally displaces nucleosomes towards 5′ of poly(dA). Especially distribution strand bias and displacement directionality would not be expected for an intrinsic mechanism. Together, this argues for an in vivo mechanism where active and species-specific read out of intrinsic sequence properties, e.g., by remodelers, shapes nucleosome organization.
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Donczew R, Hahn S. BET family members Bdf1/2 modulate global transcription initiation and elongation in Saccharomyces cerevisiae. eLife 2021; 10:e69619. [PMID: 34137374 PMCID: PMC8266393 DOI: 10.7554/elife.69619] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 06/16/2021] [Indexed: 01/10/2023] Open
Abstract
Human bromodomain and extra-terminal domain (BET) family members are promising targets for therapy of cancer and immunoinflammatory diseases, but their mechanisms of action and functional redundancies are poorly understood. Bdf1/2, yeast homologues of the human BET factors, were previously proposed to target transcription factor TFIID to acetylated histone H4, analogous to bromodomains that are present within the largest subunit of metazoan TFIID. We investigated the genome-wide roles of Bdf1/2 and found that their important contributions to transcription extend beyond TFIID function as transcription of many genes is more sensitive to Bdf1/2 than to TFIID depletion. Bdf1/2 co-occupy the majority of yeast promoters and affect preinitiation complex formation through recruitment of TFIID, Mediator, and basal transcription factors to chromatin. Surprisingly, we discovered that hypersensitivity of genes to Bdf1/2 depletion results from combined defects in transcription initiation and early elongation, a striking functional similarity to human BET proteins, most notably Brd4. Our results establish Bdf1/2 as critical for yeast transcription and provide important mechanistic insights into the function of BET proteins in all eukaryotes.
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Affiliation(s)
- Rafal Donczew
- Fred Hutchinson Cancer Research Center, Division of Basic SciencesSeattleUnited States
| | - Steven Hahn
- Fred Hutchinson Cancer Research Center, Division of Basic SciencesSeattleUnited States
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40
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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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Barbier J, Vaillant C, Volff JN, Brunet FG, Audit B. Coupling between Sequence-Mediated Nucleosome Organization and Genome Evolution. Genes (Basel) 2021; 12:genes12060851. [PMID: 34205881 PMCID: PMC8228248 DOI: 10.3390/genes12060851] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 05/27/2021] [Accepted: 05/27/2021] [Indexed: 12/12/2022] Open
Abstract
The nucleosome is a major modulator of DNA accessibility to other cellular factors. Nucleosome positioning has a critical importance in regulating cell processes such as transcription, replication, recombination or DNA repair. The DNA sequence has an influence on the position of nucleosomes on genomes, although other factors are also implicated, such as ATP-dependent remodelers or competition of the nucleosome with DNA binding proteins. Different sequence motifs can promote or inhibit the nucleosome formation, thus influencing the accessibility to the DNA. Sequence-encoded nucleosome positioning having functional consequences on cell processes can then be selected or counter-selected during evolution. We review the interplay between sequence evolution and nucleosome positioning evolution. We first focus on the different ways to encode nucleosome positions in the DNA sequence, and to which extent these mechanisms are responsible of genome-wide nucleosome positioning in vivo. Then, we discuss the findings about selection of sequences for their nucleosomal properties. Finally, we illustrate how the nucleosome can directly influence sequence evolution through its interactions with DNA damage and repair mechanisms. This review aims to provide an overview of the mutual influence of sequence evolution and nucleosome positioning evolution, possibly leading to complex evolutionary dynamics.
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Affiliation(s)
- Jérémy Barbier
- Institut de Génomique Fonctionnelle de Lyon, Univ Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Univ Claude Bernard Lyon 1, F-69364 Lyon, France; (J.B.); (F.G.B.)
- Laboratoire de Physique, Univ Lyon, ENS de Lyon, CNRS, F-69342 Lyon, France;
| | - Cédric Vaillant
- Laboratoire de Physique, Univ Lyon, ENS de Lyon, CNRS, F-69342 Lyon, France;
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle de Lyon, Univ Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Univ Claude Bernard Lyon 1, F-69364 Lyon, France; (J.B.); (F.G.B.)
- Correspondence: (J.-N.V.); (B.A.)
| | - Frédéric G. Brunet
- Institut de Génomique Fonctionnelle de Lyon, Univ Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Univ Claude Bernard Lyon 1, F-69364 Lyon, France; (J.B.); (F.G.B.)
| | - Benjamin Audit
- Laboratoire de Physique, Univ Lyon, ENS de Lyon, CNRS, F-69342 Lyon, France;
- Correspondence: (J.-N.V.); (B.A.)
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42
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Oberbeckmann E, Niebauer V, Watanabe S, Farnung L, Moldt M, Schmid A, Cramer P, Peterson CL, Eustermann S, Hopfner KP, Korber P. Ruler elements in chromatin remodelers set nucleosome array spacing and phasing. Nat Commun 2021; 12:3232. [PMID: 34050140 PMCID: PMC8163753 DOI: 10.1038/s41467-021-23015-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 03/13/2021] [Indexed: 01/09/2023] Open
Abstract
Arrays of regularly spaced nucleosomes dominate chromatin and are often phased by alignment to reference sites like active promoters. How the distances between nucleosomes (spacing), and between phasing sites and nucleosomes are determined remains unclear, and specifically, how ATP-dependent chromatin remodelers impact these features. Here, we used genome-wide reconstitution to probe how Saccharomyces cerevisiae ATP-dependent remodelers generate phased arrays of regularly spaced nucleosomes. We find that remodelers bear a functional element named the 'ruler' that determines spacing and phasing in a remodeler-specific way. We use structure-based mutagenesis to identify and tune the ruler element residing in the Nhp10 and Arp8 modules of the INO80 remodeler complex. Generally, we propose that a remodeler ruler regulates nucleosome sliding direction bias in response to (epi)genetic information. This finally conceptualizes how remodeler-mediated nucleosome dynamics determine stable steady-state nucleosome positioning relative to other nucleosomes, DNA bound factors, DNA ends and DNA sequence elements.
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Affiliation(s)
- Elisa Oberbeckmann
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Vanessa Niebauer
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Shinya Watanabe
- Program of Molecular Medicine, University of Massachusetts, Worcester, MA, USA
| | - Lucas Farnung
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, USA
| | - Manuela Moldt
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Andrea Schmid
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Craig L Peterson
- Program of Molecular Medicine, University of Massachusetts, Worcester, MA, USA
| | - Sebastian Eustermann
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany.
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany.
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, Germany.
| | - Karl-Peter Hopfner
- Gene Center, Ludwig-Maximilians-Universität München, Munich, Germany.
- Department of Biochemistry, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany.
| | - Philipp Korber
- Division of Molecular Biology, Biomedical Center (BMC), Faculty of Medicine, LMU Munich, Martinsried, Germany.
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43
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Salimi D, Moeini A. Incorporating K-mers Highly Correlated to Epigenetic Modifications for Bayesian Inference of Gene Interactions. Curr Bioinform 2021. [DOI: 10.2174/1574893615999200728193621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Objective::
A gene interaction network, along with its related biological features, has an
important role in computational biology. Bayesian network, as an efficient model, based on
probabilistic concepts is able to exploit known and novel biological casual relationships between
genes. The success of Bayesian networks in predicting the relationships greatly depends on
selecting priors.
Methods::
K-mers have been applied as the prominent features to uncover the similarity between
genes in a specific pathway, suggesting that this feature can be applied to study genes
dependencies. In this study, we propose k-mers (4,5 and 6-mers) highly correlated with epigenetic
modifications, including 17 modifications, as a new prior for Bayesian inference in the gene
interaction network.
Result::
Employing this model on a network of 23 human genes and on a network based on 27
genes related to yeast resulted in F-measure improvements in different biological networks.
Conclusion::
The improvements in the best case are 12%, 36%, and 10% in the pathway, coexpression,
and physical interaction, respectively.
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Affiliation(s)
- Dariush Salimi
- Department of Animal Science, Faculty of Agriculture, University of Zanjan, Zanjan, Iran
| | - Ali Moeini
- Department of Algorithms and Computation, Faculty of Engineering Science, College of Engineering, University of Tehran, Tehran, Iran
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44
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McGlincy NJ, Meacham ZA, Reynaud KK, Muller R, Baum R, Ingolia NT. A genome-scale CRISPR interference guide library enables comprehensive phenotypic profiling in yeast. BMC Genomics 2021; 22:205. [PMID: 33757429 PMCID: PMC7986282 DOI: 10.1186/s12864-021-07518-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Accepted: 03/08/2021] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND CRISPR/Cas9-mediated transcriptional interference (CRISPRi) enables programmable gene knock-down, yielding loss-of-function phenotypes for nearly any gene. Effective, inducible CRISPRi has been demonstrated in budding yeast, and genome-scale guide libraries enable systematic, genome-wide genetic analysis. RESULTS We present a comprehensive yeast CRISPRi library, based on empirical design rules, containing 10 distinct guides for most genes. Competitive growth after pooled transformation revealed strong fitness defects for most essential genes, verifying that the library provides comprehensive genome coverage. We used the relative growth defects caused by different guides targeting essential genes to further refine yeast CRISPRi design rules. In order to obtain more accurate and robust guide abundance measurements in pooled screens, we link guides with random nucleotide barcodes and carry out linear amplification by in vitro transcription. CONCLUSIONS Taken together, we demonstrate a broadly useful platform for comprehensive, high-precision CRISPRi screening in yeast.
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Affiliation(s)
| | - Zuriah A Meacham
- Department of Molecular and Cell Biology, Berkeley, CA, 94720, USA
| | - Kendra K Reynaud
- Department of Molecular and Cell Biology, Berkeley, CA, 94720, USA
- Biophysics Graduate Group, University of California, Berkeley, CA, 94720, USA
| | - Ryan Muller
- Department of Molecular and Cell Biology, Berkeley, CA, 94720, USA
| | - Rachel Baum
- Department of Molecular and Cell Biology, Berkeley, CA, 94720, USA
| | - Nicholas T Ingolia
- Department of Molecular and Cell Biology, Berkeley, CA, 94720, USA.
- Biophysics Graduate Group, University of California, Berkeley, CA, 94720, USA.
- California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, 94720, USA.
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45
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Wolff MR, Schmid A, Korber P, Gerland U. Effective dynamics of nucleosome configurations at the yeast PHO5 promoter. eLife 2021; 10:58394. [PMID: 33666171 PMCID: PMC8004102 DOI: 10.7554/elife.58394] [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: 04/29/2020] [Accepted: 03/04/2021] [Indexed: 12/11/2022] Open
Abstract
Chromatin dynamics are mediated by remodeling enzymes and play crucial roles in gene regulation, as established in a paradigmatic model, the Saccharomyces cerevisiae PHO5 promoter. However, effective nucleosome dynamics, that is, trajectories of promoter nucleosome configurations, remain elusive. Here, we infer such dynamics from the integration of published single-molecule data capturing multi-nucleosome configurations for repressed to fully active PHO5 promoter states with other existing histone turnover and new chromatin accessibility data. We devised and systematically investigated a new class of 'regulated on-off-slide' models simulating global and local nucleosome (dis)assembly and sliding. Only seven of 68,145 models agreed well with all data. All seven models involve sliding and the known central role of the N-2 nucleosome, but regulate promoter state transitions by modulating just one assembly rather than disassembly process. This is consistent with but challenges common interpretations of previous observations at the PHO5 promoter and suggests chromatin opening by binding competition.
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Affiliation(s)
| | - Andrea Schmid
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany
| | - Philipp Korber
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, Planegg-Martinsried, Germany
| | - Ulrich Gerland
- Department of Physics, Technical University of Munich, Garching, Germany
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46
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Peritore M, Reusswig KU, Bantele SCS, Straub T, Pfander B. Strand-specific ChIP-seq at DNA breaks distinguishes ssDNA versus dsDNA binding and refutes single-stranded nucleosomes. Mol Cell 2021; 81:1841-1853.e4. [PMID: 33651987 DOI: 10.1016/j.molcel.2021.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 12/30/2020] [Accepted: 01/29/2021] [Indexed: 02/07/2023]
Abstract
In a first step of DNA double-strand break (DSB) repair by homologous recombination, DNA ends are resected such that single-stranded DNA (ssDNA) overhangs are generated. ssDNA is specifically bound by RPA and other factors, which constitutes a ssDNA-domain on damaged chromatin. The molecular organization of this ssDNA and the adjacent dsDNA domain is crucial during DSB signaling and repair. However, data regarding the presence of nucleosomes, the most basic chromatin components, in the ssDNA domain have been contradictory. Here, we use site-specific induction of DSBs and chromatin immunoprecipitation followed by strand-specific sequencing to analyze in vivo binding of key DSB repair and signaling proteins to either the ssDNA or dsDNA domain. In the case of nucleosomes, we show that recently proposed ssDNA nucleosomes are not a major, persistent species, but that nucleosome eviction and DNA end resection are intrinsically coupled. These results support a model of separated dsDNA-nucleosome and ssDNA-RPA domains during DSB repair.
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Affiliation(s)
- Martina Peritore
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Karl-Uwe Reusswig
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Susanne C S Bantele
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Tobias Straub
- Biomedizinisches Centrum, Core Facility Bioinformatics, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany
| | - Boris Pfander
- Research Group DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
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47
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Liu G, Zhao H, Meng H, Xing Y, Cai L. A deformation energy model reveals sequence-dependent property of nucleosome positioning. Chromosoma 2021; 130:27-40. [PMID: 33452566 PMCID: PMC7889546 DOI: 10.1007/s00412-020-00750-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 12/24/2020] [Accepted: 12/29/2020] [Indexed: 11/18/2022]
Abstract
We present a deformation energy model for predicting nucleosome positioning, in which a position-dependent structural parameter set derived from crystal structures of nucleosomes was used to calculate the DNA deformation energy. The model is successful in predicting nucleosome occupancy genome-wide in budding yeast, nucleosome free energy, and rotational positioning of nucleosomes. Our model also indicates that the genomic regions underlying the MNase-sensitive nucleosomes in budding yeast have high deformation energy and, consequently, low nucleosome-forming ability, while the MNase-sensitive non-histone particles are characterized by much lower DNA deformation energy and high nucleosome preference. In addition, we also revealed that remodelers, SNF2 and RSC8, are likely to act in chromatin remodeling by binding to broad nucleosome-depleted regions that are intrinsically favorable for nucleosome positioning. Our data support the important role of position-dependent physical properties of DNA in nucleosome positioning.
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Affiliation(s)
- Guoqing Liu
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, 014010, China.
- Inner Mongolia Key Lab of Functional Genome Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, 014010, China.
| | - Hongyu Zhao
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, 014010, China
- Inner Mongolia Key Lab of Functional Genome Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, 014010, China
| | - Hu Meng
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, 014010, China
- Inner Mongolia Key Lab of Functional Genome Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, 014010, China
| | - Yongqiang Xing
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, 014010, China
- Inner Mongolia Key Lab of Functional Genome Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, 014010, China
| | - Lu Cai
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, 014010, China
- Inner Mongolia Key Lab of Functional Genome Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, 014010, China
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48
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Nucleosome Positioning and Spacing: From Mechanism to Function. J Mol Biol 2021; 433:166847. [PMID: 33539878 DOI: 10.1016/j.jmb.2021.166847] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Revised: 01/16/2021] [Accepted: 01/22/2021] [Indexed: 02/08/2023]
Abstract
Eukaryotes associate their genomes with histone proteins, forming nucleosome particles. Nucleosomes regulate and protect the genetic information. They often assemble into evenly spaced arrays of nucleosomes. These regular nucleosome arrays cover significant portions of the genome, in particular over genes. The presence of these evenly spaced nucleosome arrays is highly conserved throughout the entire eukaryotic domain. Here, we review the mechanisms behind the establishment of this primary structure of chromatin with special emphasis on the biogenesis of evenly spaced nucleosome arrays. We highlight the roles that transcription, nucleosome remodelers, DNA sequence, and histone density play towards the formation of evenly spaced nucleosome arrays and summarize our current understanding of their cellular functions. We end with key unanswered questions that remain to be explored to obtain an in-depth understanding of the biogenesis and function of the nucleosome landscape.
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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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Kharerin H, Bai L. Thermodynamic modeling of genome-wide nucleosome depleted regions in yeast. PLoS Comput Biol 2021; 17:e1008560. [PMID: 33428627 PMCID: PMC7822557 DOI: 10.1371/journal.pcbi.1008560] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 01/22/2021] [Accepted: 11/25/2020] [Indexed: 01/09/2023] Open
Abstract
Nucleosome positioning in the genome is essential for the regulation of many nuclear processes. We currently have limited capability to predict nucleosome positioning in vivo, especially the locations and sizes of nucleosome depleted regions (NDRs). Here, we present a thermodynamic model that incorporates the intrinsic affinity of histones, competitive binding of sequence-specific factors, and nucleosome remodeling to predict nucleosome positioning in budding yeast. The model shows that the intrinsic affinity of histones, at near-saturating histone concentration, is not sufficient in generating NDRs in the genome. However, the binding of a few factors, especially RSC towards GC-rich and poly(A/T) sequences, allows us to predict ~ 66% of genome-wide NDRs. The model also shows that nucleosome remodeling activity is required to predict the correct NDR sizes. The validity of the model was further supported by the agreement between the predicted and the measured nucleosome positioning upon factor deletion or on exogenous sequences introduced into yeast. Overall, our model quantitatively evaluated the impact of different genetic components on NDR formation and illustrated the vital roles of sequence-specific factors and nucleosome remodeling in this process. Nucleosome is the basic unit of chromatin, containing 147 base-pairs of DNA wrapped around a histone core. The positioning of nucleosomes, i.e., which parts of DNA are inside nucleosome and which parts are nucleosome-free, is highly regulated. In particular, regulatory sequences tend to be exposed in nucleosome-depleted regions (NDRs), and such exposure is crucial for a variety of processes including DNA replication, repair, and gene expression. Here, we used a thermodynamics model to predict nucleosome positioning on the yeast genome. The model shows that the intrinsic sequence preference of histones is not sufficient in generating NDRs. In contrast, binding of a few transcription factors, especially RSC, is largely responsible for NDR formation. Nucleosome remodeling activity is also required in the model to recapitulate the NDR sizes. This model contributes to our understanding of the mechanisms that regulate nucleosome positioning. It can also be used to predict nucleosome positioning in mutant yeast or on novel DNA sequences.
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Affiliation(s)
- Hungyo Kharerin
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Lu Bai
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Center for Eukaryotic Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
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