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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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A study of strong nucleosomes in the human genome. iScience 2022; 25:104593. [PMID: 35789840 PMCID: PMC9249913 DOI: 10.1016/j.isci.2022.104593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 03/03/2022] [Accepted: 06/08/2022] [Indexed: 11/30/2022] Open
Abstract
Micrococcal nuclease (MNase) is widely used to map nucleosomes. However, nucleosomes are highly dynamic and susceptible to experimental conditions, resulting in extreme variability across nucleosome maps, which complicates the generation of accurate nucleosome organization data. We mapped nucleosomes from different individuals using improved MNase-seq. The improvements included setting different digestion levels (low, medium, high) and naked DNA correction to remove the noise caused by experimental manipulation and comparing maps to obtain the accurate position and occupancy of strong nucleosomes (SNs) in the whole genome. In addition, the characteristics of SNs were further excavated. SNs were enriched in Alu elements and near the centromere of Chr12. SNs contain some specific sequences, and the GC content of SNs is different from that of dynamic nucleosomes. The findings suggest that nucleosome location in the genome and the DNA sequence may affect nucleosome stability. Naked DNA correction improved the accuracy of nucleosome map in partial digestion Level of MNase digestion has effects on nucleosome organization A type of strong nucleosomes (SNs) exist across different nucleosome maps Nucleosome stability may be related to its location and the DNA sequence
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Burnham P, Chen F, Cheng AP, Srivatana V, Zhang LT, Edusei E, Albakry S, Botticelli B, Guo X, Renaghan A, Silberzweig J, Dadhania DM, Lenz JS, Heyang M, Iliev ID, Hayden JA, Westblade LF, De Vlaminck I, Lee JR. Peritoneal Effluent Cell-Free DNA Sequencing in Peritoneal Dialysis Patients With and Without Peritonitis. Kidney Med 2022; 4:100383. [PMID: 35072047 PMCID: PMC8767090 DOI: 10.1016/j.xkme.2021.08.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Rationale & Objective Conventional culture can be insensitive for the detection of rare infections and for the detection of common infections in the setting of recent antibiotic usage. Patients receiving peritoneal dialysis (PD) with suspected peritonitis have a significant proportion of negative conventional cultures. This study examines the utility of metagenomic sequencing of peritoneal effluent cell-free DNA (cfDNA) for evaluating the peritoneal effluent in PD patients with and without peritonitis. Study Design Prospective cohort study. Setting & Participants We prospectively characterized cfDNA in 68 peritoneal effluent samples obtained from 33 patients receiving PD at a single center from September 2016 to July 2018. Outcomes Peritoneal effluent, microbial, and human cfDNA characteristics were evaluated in culture-confirmed peritonitis and culture-negative peritonitis. Analytical Approach Descriptive statistics were analyzed and microbial cfDNA was detected in culture-confirmed peritonitis and culture-negative peritonitis. Results Metagenomic sequencing of cfDNA was able to detect and identify bacterial, viral, and eukaryotic pathogens in the peritoneal effluent from PD patients with culture-confirmed peritonitis, as well as patients with recent antibiotic usage and in cases of culture-negative peritonitis. Limitations Parallel cultures were not obtained in all the peritoneal effluent specimens. Conclusions Metagenomic cfDNA sequencing of the peritoneal effluent can identify pathogens in PD patients with peritonitis, including culture-negative peritonitis.
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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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5
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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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6
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Klein-Brill A, Joseph-Strauss D, Appleboim A, Friedman N. Dynamics of Chromatin and Transcription during Transient Depletion of the RSC Chromatin Remodeling Complex. Cell Rep 2020; 26:279-292.e5. [PMID: 30605682 PMCID: PMC6315372 DOI: 10.1016/j.celrep.2018.12.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/19/2018] [Accepted: 12/04/2018] [Indexed: 12/03/2022] Open
Abstract
Nucleosome organization has a key role in transcriptional regulation, yet the precise mechanisms establishing nucleosome locations and their effect on transcription are unclear. Here, we use an induced degradation system to screen all yeast ATP-dependent chromatin remodelers. We characterize how rapid clearance of the remodeler affects nucleosome locations. Specifically, depletion of Sth1, the catalytic subunit of the RSC (remodel the structure of chromatin) complex, leads to rapid fill-in of nucleosome-free regions at gene promoters. These changes are reversible upon reintroduction of Sth1 and do not depend on DNA replication. RSC-dependent nucleosome positioning is pivotal in maintaining promoters of lowly expressed genes free from nucleosomes. In contrast, we observe that upon acute stress, the RSC is not necessary for the transcriptional response. Moreover, RSC-dependent nucleosome positions are tightly related to usage of specific transcription start sites. Our results suggest organizational principles that determine nucleosome positions with and without RSC and how these interact with the transcriptional process. Screen of all yeast ATP-dependent remodelers with a conditional degradation system RSC depletion leads to rapid replication-independent NFR fill-in Recovery of RSC fully reverses NFR fill-in and transcriptional changes RSC-dependent nucleosome positioning directly affect transcription start site choice
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Affiliation(s)
- Avital Klein-Brill
- School of Engineering and Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Daphna Joseph-Strauss
- School of Engineering and Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Alon Appleboim
- School of Engineering and Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Nir Friedman
- School of Engineering and Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
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7
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Beltran B, Kannan D, MacPherson Q, Spakowitz AJ. Geometrical Heterogeneity Dominates Thermal Fluctuations in Facilitating Chromatin Contacts. PHYSICAL REVIEW LETTERS 2019; 123:208103. [PMID: 31809067 DOI: 10.1103/physrevlett.123.208103] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Indexed: 06/10/2023]
Abstract
Within a living cell, the myriad of proteins that bind DNA introduce heterogeneously spaced kinks into an otherwise semiflexible DNA double helix. To investigate the effects of heterogeneous nucleosome binding on chromatin organization, we extend the wormlike chain model to include statistically spaced, rigid kinks. On timescales where nucleosome positions are fixed, we find that the probability of chromatin loop formation can vary by up to six orders of magnitude between two sets of nucleosome positions drawn from the same distribution. On longer timescales, we show that continuous rerandomization due to nucleosome turnover results in chromatin tracing out an effective WLC with a dramatically smaller Kuhn length than bare DNA. Together, these observations demonstrate that nucleosome spacing acts as the primary source of the structural heterogeneity that dominates local and global chromatin organization.
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Affiliation(s)
- Bruno Beltran
- Biophysics Program, Stanford University, Stanford, California 94305, USA
| | - Deepti Kannan
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Quinn MacPherson
- Department of Physics, Stanford University, Stanford, California 94305, USA
| | - Andrew J Spakowitz
- Chemical Engineering Department, Stanford University, Stanford, California 94305, USA
- Department of Materials Science and Engineering, Stanford University Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
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8
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Oberbeckmann E, Wolff M, Krietenstein N, Heron M, Ellins JL, Schmid A, Krebs S, Blum H, Gerland U, Korber P. Absolute nucleosome occupancy map for the Saccharomyces cerevisiae genome. Genome Res 2019; 29:1996-2009. [PMID: 31694866 PMCID: PMC6886505 DOI: 10.1101/gr.253419.119] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/31/2019] [Indexed: 12/23/2022]
Abstract
Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation because nucleosomes modulate DNA access by their positioning along the genome. A cell-population nucleosome map requires two observables: nucleosome positions along the DNA ("Where?") and nucleosome occupancies across the population ("In how many cells?"). All available genome-wide nucleosome mapping techniques are yield methods because they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or nonnucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions, but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby cross-validating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9-bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (±SD). Depending on nucleosome position calling procedures, there are 57,000 to 60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but correlate with increased presence of the nucleosome-evicting chromatin structure remodeling (RSC) complex, and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
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Affiliation(s)
- Elisa Oberbeckmann
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Michael Wolff
- Physik Department, Technische Universität München, 85748 Garching, Germany
| | - Nils Krietenstein
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Mark Heron
- Quantitative and Computational Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.,Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Jessica L Ellins
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, United Kingdom
| | - Andrea Schmid
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Stefan Krebs
- Laboratory of Functional Genome Analysis (LAFUGA), Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Helmut Blum
- Laboratory of Functional Genome Analysis (LAFUGA), Gene Center, Faculty of Chemistry and Pharmacy, Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Ulrich Gerland
- Physik Department, Technische Universität München, 85748 Garching, Germany
| | - Philipp Korber
- Molecular Biology Division, Biomedical Center, Faculty of Medicine, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
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9
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van Eijk P, Nandi SP, Yu S, Bennett M, Leadbitter M, Teng Y, Reed SH. Nucleosome remodeling at origins of global genome-nucleotide excision repair occurs at the boundaries of higher-order chromatin structure. Genome Res 2018; 29:74-84. [PMID: 30552104 PMCID: PMC6314166 DOI: 10.1101/gr.237198.118] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 11/07/2018] [Indexed: 11/24/2022]
Abstract
Repair of UV-induced DNA damage requires chromatin remodeling. How repair is initiated in chromatin remains largely unknown. We recently demonstrated that global genome–nucleotide excision repair (GG-NER) in chromatin is organized into domains in relation to open reading frames. Here, we define these domains, identifying the genomic locations from which repair is initiated. By examining DNA damage–induced changes in the linear structure of nucleosomes at these sites, we demonstrate how chromatin remodeling is initiated during GG-NER. In undamaged cells, we show that the GG-NER complex occupies chromatin, establishing the nucleosome structure at these genomic locations, which we refer to as GG-NER complex binding sites (GCBSs). We demonstrate that these sites are frequently located at genomic boundaries that delineate chromosomally interacting domains (CIDs). These boundaries define domains of higher-order nucleosome–nucleosome interaction. We demonstrate that initiation of GG-NER in chromatin is accompanied by the disruption of dynamic nucleosomes that flank GCBSs by the GG-NER complex.
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Affiliation(s)
- Patrick van Eijk
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Shuvro Prokash Nandi
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Shirong Yu
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Mark Bennett
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Matthew Leadbitter
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Yumin Teng
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
| | - Simon H Reed
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, United Kingdom
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10
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Reconstruction of a Global Transcriptional Regulatory Network for Control of Lipid Metabolism in Yeast by Using Chromatin Immunoprecipitation with Lambda Exonuclease Digestion. mSystems 2018; 3:mSystems00215-17. [PMID: 30073202 PMCID: PMC6068829 DOI: 10.1128/msystems.00215-17] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 07/04/2018] [Indexed: 11/20/2022] Open
Abstract
To build transcription regulatory networks, transcription factor binding must be analyzed in cells grown under different conditions because their responses and targets differ depending on environmental conditions. We performed whole-genome analysis of the DNA binding of five Saccharomyces cerevisiae transcription factors involved in lipid metabolism, Ino2, Ino4, Hap1, Oaf1, and Pip2, in response to four different environmental conditions in chemostat cultures, which allowed us to keep the specific growth rate constant. Chromatin immunoprecipitation with lambda exonuclease digestion (ChIP-exo) enabled the detection of binding events at a high resolution. We discovered a large number of unidentified targets and thus expanded functions for each transcription factor (e.g., glutamate biosynthesis as a target of Oaf1 and Pip2). Moreover, condition-dependent binding of transcription factors in response to cell metabolic state (e.g., differential binding of Ino2 between fermentative and respiratory metabolic conditions) was clearly suggested. Combining the new binding data with previously published data from transcription factor deletion studies revealed the high complexity of the transcriptional regulatory network for lipid metabolism in yeast, which involves the combinatorial and complementary regulation by multiple transcription factors. We anticipate that our work will provide insights into transcription factor binding dynamics that will prove useful for the understanding of transcription regulatory networks. IMPORTANCE Transcription factors play a crucial role in the regulation of gene expression and adaptation to different environments. To better understand the underlying roles of these adaptations, we performed experiments that give us high-resolution binding of transcription factors to their targets. We investigated five transcription factors involved in lipid metabolism in yeast, and we discovered multiple novel targets and condition-specific responses that allow us to draw a better regulatory map of the lipid metabolism.
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11
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Systematic Study of Nucleosome-Displacing Factors in Budding Yeast. Mol Cell 2018; 71:294-305.e4. [PMID: 30017582 DOI: 10.1016/j.molcel.2018.06.017] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 05/04/2018] [Accepted: 06/07/2018] [Indexed: 12/11/2022]
Abstract
Nucleosomes present a barrier for the binding of most transcription factors (TFs). However, special TFs known as nucleosome-displacing factors (NDFs) can access embedded sites and cause the depletion of the local nucleosomes as well as repositioning of the neighboring nucleosomes. Here, we developed a novel high-throughput method in yeast to identify NDFs among 104 TFs and systematically characterized the impact of orientation, affinity, location, and copy number of their binding motifs on the nucleosome occupancy. Using this assay, we identified 29 NDF motifs and divided the nuclear TFs into three groups with strong, weak, and no nucleosome-displacing activities. Further studies revealed that tight DNA binding is the key property that underlies NDF activity, and the NDFs may partially rely on the DNA replication to compete with nucleosome. Overall, our study presents a framework to functionally characterize NDFs and elucidate the mechanism of nucleosome invasion.
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12
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Jeffers TE, Lieb JD. Nucleosome fragility is associated with future transcriptional response to developmental cues and stress in C. elegans. Genome Res 2016; 27:75-86. [PMID: 27979995 PMCID: PMC5204346 DOI: 10.1101/gr.208173.116] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Accepted: 11/14/2016] [Indexed: 02/03/2023]
Abstract
Nucleosomes have structural and regulatory functions in all eukaryotic DNA-templated processes. The position of nucleosomes on DNA and the stability of the underlying histone–DNA interactions affect the access of regulatory proteins to DNA. Both stability and position are regulated through DNA sequence, histone post-translational modifications, histone variants, chromatin remodelers, and transcription factors. Here, we explored the functional implications of nucleosome properties on gene expression and development in Caenorhabditis elegans embryos. We performed a time-course of micrococcal nuclease (MNase) digestion and measured the relative sensitivity or resistance of nucleosomes throughout the genome. Fragile nucleosomes were defined by nucleosomal DNA fragments that were recovered preferentially in early MNase-digestion time points. Nucleosome fragility was strongly and positively correlated with the AT content of the underlying DNA sequence. There was no correlation between promoter nucleosome fragility and the levels of histone modifications or histone variants. Genes with fragile nucleosomes in their promoters tended to be lowly expressed and expressed in a context-specific way, operating in neuronal response, the immune system, and stress response. In addition to DNA-encoded nucleosome fragility, we also found fragile nucleosomes at locations where we expected to find destabilized nucleosomes, for example, at transcription factor binding sites where nucleosomes compete with DNA-binding factors. Our data suggest that in C. elegans promoters, nucleosome fragility is in large part DNA-encoded and that it poises genes for future context-specific activation in response to environmental stress and developmental cues.
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Affiliation(s)
- Tess E Jeffers
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
| | - Jason D Lieb
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
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13
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Yu S, Evans K, van Eijk P, Bennett M, Webster RM, Leadbitter M, Teng Y, Waters R, Jackson SP, Reed SH. Global genome nucleotide excision repair is organized into domains that promote efficient DNA repair in chromatin. Genome Res 2016; 26:1376-1387. [PMID: 27470111 PMCID: PMC5052058 DOI: 10.1101/gr.209106.116] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 07/27/2016] [Indexed: 01/08/2023]
Abstract
The rates at which lesions are removed by DNA repair can vary widely throughout the genome, with important implications for genomic stability. To study this, we measured the distribution of nucleotide excision repair (NER) rates for UV-induced lesions throughout the budding yeast genome. By plotting these repair rates in relation to genes and their associated flanking sequences, we reveal that, in normal cells, genomic repair rates display a distinctive pattern, suggesting that DNA repair is highly organized within the genome. Furthermore, by comparing genome-wide DNA repair rates in wild-type cells and cells defective in the global genome-NER (GG-NER) subpathway, we establish how this alters the distribution of NER rates throughout the genome. We also examined the genomic locations of GG-NER factor binding to chromatin before and after UV irradiation, revealing that GG-NER is organized and initiated from specific genomic locations. At these sites, chromatin occupancy of the histone acetyl-transferase Gcn5 is controlled by the GG-NER complex, which regulates histone H3 acetylation and chromatin structure, thereby promoting efficient DNA repair of UV-induced lesions. Chromatin remodeling during the GG-NER process is therefore organized into these genomic domains. Importantly, loss of Gcn5 significantly alters the genomic distribution of NER rates; this has implications for the effects of chromatin modifiers on the distribution of mutations that arise throughout the genome.
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Affiliation(s)
- Shirong Yu
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Katie Evans
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Patrick van Eijk
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Mark Bennett
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Richard M Webster
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Matthew Leadbitter
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Yumin Teng
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Raymond Waters
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
| | - Stephen P Jackson
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, CB2 1QN, United Kingdom
| | - Simon H Reed
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff, CF14 4XN, United Kingdom
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14
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Jin H, Rube HT, Song JS. Categorical spectral analysis of periodicity in nucleosomal DNA. Nucleic Acids Res 2016; 44:2047-57. [PMID: 26893354 PMCID: PMC4797311 DOI: 10.1093/nar/gkw101] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/09/2016] [Indexed: 12/26/2022] Open
Abstract
DNA helical twist imposes geometric constraints on the location of histone–DNA interaction sites along nucleosomal DNA. Certain 10.5-bp periodic nucleotides in phase with these geometric constraints have been suggested to facilitate nucleosome positioning. However, the extent of nucleotide periodicity in nucleosomal DNA and its significance in directing nucleosome positioning still remain unclear. We clarify these issues by applying categorical spectral analysis to high-resolution nucleosome maps in two yeast species. We find that only a small fraction of nucleosomal sequences contain significant 10.5-bp periodicity. We further develop a spectral decomposition method to show that the previously observed periodicity in aligned nucleosomal sequences mainly results from proper phasing among nucleosomal sequences, and not from a preponderant occurrence of periodicity within individual sequences. Importantly, we show that this phasing may arise from the histones’ proclivity for putting preferred nucleotides at some of the evenly spaced histone–DNA contact points with respect to the dyad axis. We demonstrate that 10.5-bp periodicity, when present, significantly facilitates rotational, but not translational, nucleosome positioning. Finally, although periodicity only moderately affects nucleosome occupancy genome wide, reduced periodicity is an evolutionarily conserved signature of nucleosome-depleted regions around transcription start/termination sites.
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Affiliation(s)
- Hu Jin
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA Institute for Genomic Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
| | - H Tomas Rube
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA Institute for Genomic Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
| | - Jun S Song
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA Institute for Genomic Biology, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA Department of Bioengineering, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
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15
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Wu WS, Lai FJ. Functional redundancy of transcription factors explains why most binding targets of a transcription factor are not affected when the transcription factor is knocked out. BMC SYSTEMS BIOLOGY 2015; 9 Suppl 6:S2. [PMID: 26678747 PMCID: PMC4674858 DOI: 10.1186/1752-0509-9-s6-s2] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background Biologists are puzzled by the extremely low percentage (3%) of the binding targets of a yeast transcription factor (TF) affected when the TF is knocked out, a phenomenon observed by comparing the TF binding dataset and TF knockout effect dataset. Results This study gives a plausible biological explanation of this counterintuitive phenomenon. Our analyses find that TFs with high functional redundancy show significantly lower percentage than do TFs with low functional redundancy. This suggests that functional redundancy may lead to one TF compensating for another, thus masking the TF knockout effect on the binding targets of the knocked-out TF. In addition, we show that seven classes of genes (lowly expressed genes, TATA box-less genes, genes containing a nucleosome-free region immediately upstream of the transcriptional start site (TSS), genes with low transcriptional plasticity, genes with a low number of bound TFs, genes with a low number of TFBSs, and genes with a short average distance of TFBSs to the TSS) are insensitive to the knockout of their promoter-binding TFs, providing clues for finding other biological explanations of the surprisingly low percentage of the binding targets of a TF affected when the TF is knocked out. Conclusions This study shows that one property of TFs (functional redundancy) and seven properties of genes (expression level, TATA box, nucleosome, transcriptional plasticity, the number of bound TFs, the number of TFBSs, and the average distance of TFBSs to the TSS) may be useful for explaining a counterintuitive phenomenon: most binding targets of a yeast transcription factor are not affected when the transcription factor is knocked out.
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16
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Sarda S, Hannenhalli S. High-Throughput Identification of Cis-Regulatory Rewiring Events in Yeast. Mol Biol Evol 2015; 32:3047-63. [PMID: 26399482 DOI: 10.1093/molbev/msv203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A coregulated module of genes ("regulon") can have evolutionarily conserved expression patterns and yet have diverged upstream regulators across species. For instance, the ribosomal genes regulon is regulated by the transcription factor (TF) TBF1 in Candida albicans, while in Saccharomyces cerevisiae it is regulated by RAP1. Only a handful of such rewiring events have been established, and the prevalence or conditions conducive to such events are not well known. Here, we develop a novel probabilistic scoring method to comprehensively screen for regulatory rewiring within regulons across 23 yeast species. Investigation of 1,713 regulons and 176 TFs yielded 5,353 significant rewiring events at 5% false discovery rate (FDR). Besides successfully recapitulating known rewiring events, our analyses also suggest TF candidates for certain processes reported to be under distinct regulatory controls in S. cerevisiae and C. albicans, for which the implied regulators are not known: 1) Oxidative stress response (Sc-MSN2 to Ca-FKH2) and 2) nutrient modulation (Sc-RTG1 to Ca-GCN4/Ca-UME6). Furthermore, a stringent screen to detect TF rewiring at individual genes identified 1,446 events at 10% FDR. Overall, these events are supported by strong coexpression between the predicted regulator and its target gene(s) in a species-specific fashion (>50-fold). Independent functional analyses of rewiring TF pairs revealed greater functional interactions and shared biological processes between them (P = 1 × 10(-3)).Our study represents the first comprehensive assessment of regulatory rewiring; with a novel approach that has generated a unique high-confidence resource of several specific events, suggesting that evolutionary rewiring is relatively frequent and may be a significant mechanism of regulatory innovation.
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Affiliation(s)
- Shrutii Sarda
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park
| | - Sridhar Hannenhalli
- Center for Bioinformatics and Computational Biology, University of Maryland, College Park
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17
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Peeters E, Driessen RPC, Werner F, Dame RT. The interplay between nucleoid organization and transcription in archaeal genomes. Nat Rev Microbiol 2015; 13:333-41. [PMID: 25944489 DOI: 10.1038/nrmicro3467] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The archaeal genome is organized by either eukaryotic-like histone proteins or bacterial-like nucleoid-associated proteins. Recent studies have revealed novel insights into chromatin dynamics and their effect on gene expression in archaeal model organisms. In this Progress article, we discuss the interplay between chromatin proteins, such as histones and Alba, and components of the basal transcription machinery, as well as between chromatin structure and gene-specific transcription factors in archaea. Such an interplay suggests that chromatin might have a role in regulating gene expression on both a global and a gene-specific level. Moreover, several archaeal transcription factors combine a global gene regulatory role with an architectural role, thus contributing to chromatin organization and compaction, as well as gene expression. We describe the emerging principles underlying how these factors cooperate in nucleoid structuring and gene regulation.
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Affiliation(s)
- Eveline Peeters
- 1] Research Group of Microbiology, Department of Bio-engineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. [2]
| | - Rosalie P C Driessen
- 1] Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands. [2]
| | - Finn Werner
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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18
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Menconi G, Bedini A, Barale R, Sbrana I. Global mapping of DNA conformational flexibility on Saccharomyces cerevisiae. PLoS Comput Biol 2015; 11:e1004136. [PMID: 25860149 PMCID: PMC4393290 DOI: 10.1371/journal.pcbi.1004136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/16/2015] [Indexed: 11/25/2022] Open
Abstract
In this study we provide the first comprehensive map of DNA conformational flexibility in Saccharomyces cerevisiae complete genome. Flexibility plays a key role in DNA supercoiling and DNA/protein binding, regulating DNA transcription, replication or repair. Specific interest in flexibility analysis concerns its relationship with human genome instability. Enrichment in flexible sequences has been detected in unstable regions of human genome defined fragile sites, where genes map and carry frequent deletions and rearrangements in cancer. Flexible sequences have been suggested to be the determinants of fragile gene proneness to breakage; however, their actual role and properties remain elusive. Our in silico analysis carried out genome-wide via the StabFlex algorithm, shows the conserved presence of highly flexible regions in budding yeast genome as well as in genomes of other Saccharomyces sensu stricto species. Flexibile peaks in S. cerevisiae identify 175 ORFs mapping on their 3'UTR, a region affecting mRNA translation, localization and stability. (TA)n repeats of different extension shape the central structure of peaks and co-localize with polyadenylation efficiency element (EE) signals. ORFs with flexible peaks share common features. Transcripts are characterized by decreased half-life: this is considered peculiar of genes involved in regulatory systems with high turnover; consistently, their function affects biological processes such as cell cycle regulation or stress response. Our findings support the functional importance of flexibility peaks, suggesting that the flexible sequence may be derived by an expansion of canonical TAYRTA polyadenylation efficiency element. The flexible (TA)n repeat amplification could be the outcome of an evolutionary neofunctionalization leading to a differential 3'-end processing and expression regulation in genes with peculiar function. Our study provides a new support to the functional role of flexibility in genomes and a strategy for its characterization inside human fragile sites.
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Affiliation(s)
- Giulia Menconi
- Dip. Informatica, Università di Pisa, Largo Pontecorvo, Pisa, Italy
- Istituto Nazionale di Alta Matematica “Francesco Severi”, Piazzale Aldo Moro, Città Universitaria, Roma, Italy
| | - Andrea Bedini
- Dept. Mathematics and Statistics, The University of Melbourne Victoria, Australia
| | - Roberto Barale
- Dip. Biologia, Università di Pisa, Via Derna, Pisa, Italy
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19
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Nucleosome positioning in yeasts: methods, maps, and mechanisms. Chromosoma 2014; 124:131-51. [PMID: 25529773 DOI: 10.1007/s00412-014-0501-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 01/23/2023]
Abstract
Eukaryotic nuclear DNA is packaged into nucleosomes. During the past decade, genome-wide nucleosome mapping across species revealed the high degree of order in nucleosome positioning. There is a conserved stereotypical nucleosome organization around transcription start sites (TSSs) with a nucleosome-depleted region (NDR) upstream of the TSS and a TSS-aligned regular array of evenly spaced nucleosomes downstream over the gene body. As nucleosomes largely impede access to DNA and thereby provide an important level of genome regulation, it is of general interest to understand the mechanisms generating nucleosome positioning and especially the stereotypical NDR-array pattern. We focus here on the most advanced models, unicellular yeasts, and review the progress in mapping nucleosomes and which nucleosome positioning mechanisms are discussed. There are four mechanistic aspects: How are NDRs generated? How are individual nucleosomes positioned, especially those flanking the NDRs? How are nucleosomes evenly spaced leading to regular arrays? How are regular arrays aligned at TSSs? The main candidates for nucleosome positioning determinants are intrinsic DNA binding preferences of the histone octamer, specific DNA binding factors, nucleosome remodeling enzymes, transcription, and statistical positioning. We summarize the state of the art in an integrative model where nucleosomes are positioned by a combination of all these candidate determinants. We highlight the predominance of active mechanisms involving nucleosome remodeling enzymes which may be recruited by DNA binding factors and the transcription machinery. While this mechanistic framework emerged clearly during recent years, the involved factors and their mechanisms are still poorly understood and require future efforts combining in vivo and in vitro approaches.
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20
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Grzechnik P, Tan-Wong SM, Proudfoot NJ. Terminate and make a loop: regulation of transcriptional directionality. Trends Biochem Sci 2014; 39:319-27. [PMID: 24928762 PMCID: PMC4085477 DOI: 10.1016/j.tibs.2014.05.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 04/24/2014] [Accepted: 05/12/2014] [Indexed: 01/28/2023]
Abstract
Transcriptional directionality is controlled by premature transcription termination. Transcriptional directionality is enforced by gene looping. mRNA-specific termination signals and factors are required for gene looping.
Bidirectional promoters are a common feature of many eukaryotic organisms from yeast to humans. RNA Polymerase II that is recruited to this type of promoter can start transcribing in either direction using alternative DNA strands as the template. Such promiscuous transcription can lead to the synthesis of unwanted transcripts that may have negative effects on gene expression. Recent studies have identified transcription termination and gene looping as critical players in the enforcement of promoter directionality. Interestingly, both mechanisms share key components. Here, we focus on recent findings relating to the transcriptional output of bidirectional promoters.
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Affiliation(s)
- Pawel Grzechnik
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sue Mei Tan-Wong
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Nick J Proudfoot
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
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21
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Flores O, Deniz Ö, Soler-López M, Orozco M. Fuzziness and noise in nucleosomal architecture. Nucleic Acids Res 2014; 42:4934-46. [PMID: 24586063 PMCID: PMC4005669 DOI: 10.1093/nar/gku165] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Nucleosome organization plays a key role in the regulation of gene expression. However, despite the striking advances in the accuracy of nucleosome maps, there are still severe discrepancies on individual nucleosome positioning and how this influences gene regulation. The variability among nucleosome maps, which precludes the fine analysis of nucleosome positioning, might emerge from diverse sources. We have carefully inspected the extrinsic factors that may induce diversity by the comparison of microccocal nuclease (MNase)-Seq derived nucleosome maps generated under distinct conditions. Furthermore, we have also explored the variation originated from intrinsic nucleosome dynamics by generating additional maps derived from cell cycle synchronized and asynchronous yeast cultures. Taken together, our study has enabled us to measure the effect of noise in nucleosome occupancy and positioning and provides insights into the underlying determinants. Furthermore, we present a systematic approach that may guide the standardization of MNase-Seq experiments in order to generate reproducible genome-wide nucleosome patterns.
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Affiliation(s)
- Oscar Flores
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac 10-12, 08028 Barcelona, Spain, Joint IRB-BSC Program in Computational Biology, Baldiri Reixac 10-12, 08028 Barcelona, Spain and Department of Biochemistry and Molecular Biology. University of Barcelona, 08028 Barcelona, Spain
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