1
|
Teplitz GM, Pasquier E, Bonnell E, De Laurentiis E, Bartle L, Lucier JF, Sholes S, Greider CW, Wellinger RJ. A mechanism for telomere-specific telomere length regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.12.598646. [PMID: 38915611 PMCID: PMC11195199 DOI: 10.1101/2024.06.12.598646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
Telomeric DNA, composed of short, direct repeats, is of crucial importance for chromosome stability. Due to intrinsic problems with replicating this DNA, the repeat tracts shorten at each cell division. Once repeat tracts become critically short, a telomeric stress signal induces cellular senescence and division arrest, which eventually may lead to devastating age-related degenerative diseases associated with dysfunctional telomers. Conversely, maintenance of telomere length by telomerase upregulation is a hallmark of cancer. Therefore, telomere length is a critical determinant of telomere function. How telomere length is established and molecular mechanisms for telomere-specific length regulation remained unknown. Here we show that subtelomeric chromatin is a determinant for how telomere equilibrium set-length is established in cis. The results demonstrate that telomerase recruitment mediated by the telomere-associated Sir4 protein is modulated on chromosome 3L in a telomere-specific way. Increased Sir4 abundance on subtelomeric heterochromatin of this specific telomere leads to telomere lengthening of only that telomere in cis, but not at other telomeres. Therefore, this work describes a mechanism for a how telomere-specific repeat tract length can be established. Further, our results will force the evaluation of telomere length away from a generalized view to a more telomere-specific consideration.
Collapse
Affiliation(s)
- Gabriela M. Teplitz
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | - Emeline Pasquier
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
- Current Address: CNRS-UMR9019, Gustave Roussy Institute, Villejuif, France
| | - Erin Bonnell
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | - Evelina De Laurentiis
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
| | - Louise Bartle
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
- Current Address: School of Agriculture, Food and Wine, The University of Adelaide, Urrbrae, Australia
| | - Jean-François Lucier
- Department of Biology, Faculty of Sciences, Université de Sherbrooke, Sherbrooke Canada
| | - Samantha Sholes
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, USA
- Biochemistry, Cellular and Molecular Biology Graduate Program, Johns Hopkins University School of Medicine, Baltimore, USA
- Current Address: Merck & Co., 770 Sumneytown Pike, West Point, USA
| | - Carol W. Greider
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, USA
- Department of Molecular Cell and Developmental Biology, University of California, Santa Cruz, USA
| | - Raymund J. Wellinger
- Department of Microbiology and Infectiology, Faculty of Medicine and Sciences, Université de Sherbrooke, Sherbrooke, Canada
| |
Collapse
|
2
|
Sosa Ponce ML, Remedios MH, Moradi-Fard S, Cobb JA, Zaremberg V. SIR telomere silencing depends on nuclear envelope lipids and modulates sensitivity to a lysolipid. J Cell Biol 2023; 222:e202206061. [PMID: 37042812 PMCID: PMC10103788 DOI: 10.1083/jcb.202206061] [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: 06/13/2022] [Revised: 11/29/2022] [Accepted: 03/24/2023] [Indexed: 04/13/2023] Open
Abstract
The nuclear envelope (NE) is important in maintaining genome organization. The role of lipids in communication between the NE and telomere regulation was investigated, including how changes in lipid composition impact gene expression and overall nuclear architecture. Yeast was treated with the non-metabolizable lysophosphatidylcholine analog edelfosine, known to accumulate at the perinuclear ER. Edelfosine induced NE deformation and disrupted telomere clustering but not anchoring. Additionally, the association of Sir4 at telomeres decreased. RNA-seq analysis showed altered expression of Sir-dependent genes located at sub-telomeric (0-10 kb) regions, consistent with Sir4 dispersion. Transcriptomic analysis revealed that two lipid metabolic circuits were activated in response to edelfosine, one mediated by the membrane sensing transcription factors, Spt23/Mga2, and the other by a transcriptional repressor, Opi1. Activation of these transcriptional programs resulted in higher levels of unsaturated fatty acids and the formation of nuclear lipid droplets. Interestingly, cells lacking Sir proteins displayed resistance to unsaturated-fatty acids and edelfosine, and this phenotype was connected to Rap1.
Collapse
Affiliation(s)
| | | | - Sarah Moradi-Fard
- Departments of Biochemistry and Molecular Biology and Oncology, Cumming School of Medicine, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Calgary, Canada
| | - Jennifer A. Cobb
- Departments of Biochemistry and Molecular Biology and Oncology, Cumming School of Medicine, Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, Calgary, Canada
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Vanina Zaremberg
- Department of Biological Sciences, University of Calgary, Calgary, Canada
| |
Collapse
|
3
|
He F, Yu Q, Wang M, Wang R, Gong X, Ge F, Yu X, Li S. SESAME-catalyzed H3T11 phosphorylation inhibits Dot1-catalyzed H3K79me3 to regulate autophagy and telomere silencing. Nat Commun 2022; 13:7526. [PMID: 36473858 PMCID: PMC9726891 DOI: 10.1038/s41467-022-35182-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022] Open
Abstract
The glycolytic enzyme, pyruvate kinase Pyk1 maintains telomere heterochromatin by phosphorylating histone H3T11 (H3pT11), which promotes SIR (silent information regulator) complex binding at telomeres and prevents autophagy-mediated Sir2 degradation. However, the exact mechanism of action for H3pT11 is poorly understood. Here, we report that H3pT11 directly inhibits Dot1-catalyzed H3K79 tri-methylation (H3K79me3) and uncover how this histone crosstalk regulates autophagy and telomere silencing. Mechanistically, Pyk1-catalyzed H3pT11 directly reduces the binding of Dot1 to chromatin and inhibits Dot1-catalyzed H3K79me3, which leads to transcriptional repression of autophagy genes and reduced autophagy. Despite the antagonism between H3pT11 and H3K79me3, they work together to promote the binding of SIR complex at telomeres to maintain telomere silencing. Furthermore, we identify Reb1 as a telomere-associated factor that recruits Pyk1-containing SESAME (Serine-responsive SAM-containing Metabolic Enzyme) complex to telomere regions to phosphorylate H3T11 and prevent the invasion of H3K79me3 from euchromatin into heterochromatin to maintain telomere silencing. Together, these results uncover a histone crosstalk and provide insights into dynamic regulation of silent heterochromatin and autophagy in response to cell metabolism.
Collapse
Affiliation(s)
- Fei He
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| | - Qi Yu
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| | - Min Wang
- grid.9227.e0000000119573309Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 China
| | - Rongsha Wang
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| | - Xuanyunjing Gong
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| | - Feng Ge
- grid.9227.e0000000119573309Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072 China
| | - Xilan Yu
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| | - Shanshan Li
- grid.34418.3a0000 0001 0727 9022State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, Hubei 430062 China
| |
Collapse
|
4
|
Abdulla AZ, Vaillant C, Jost D. Painters in chromatin: a unified quantitative framework to systematically characterize epigenome regulation and memory. Nucleic Acids Res 2022; 50:9083-9104. [PMID: 36018799 PMCID: PMC9458448 DOI: 10.1093/nar/gkac702] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/03/2022] [Indexed: 12/24/2022] Open
Abstract
In eukaryotes, many stable and heritable phenotypes arise from the same DNA sequence, owing to epigenetic regulatory mechanisms relying on the molecular cooperativity of 'reader-writer' enzymes. In this work, we focus on the fundamental, generic mechanisms behind the epigenome memory encoded by post-translational modifications of histone tails. Based on experimental knowledge, we introduce a unified modeling framework, the painter model, describing the mechanistic interplay between sequence-specific recruitment of chromatin regulators, chromatin-state-specific reader-writer processes and long-range spreading mechanisms. A systematic analysis of the model building blocks highlights the crucial impact of tridimensional chromatin organization and state-specific recruitment of enzymes on the stability of epigenomic domains and on gene expression. In particular, we show that enhanced 3D compaction of the genome and enzyme limitation facilitate the formation of ultra-stable, confined chromatin domains. The model also captures how chromatin state dynamics impact the intrinsic transcriptional properties of the region, slower kinetics leading to noisier expression. We finally apply our framework to analyze experimental data, from the propagation of γH2AX around DNA breaks in human cells to the maintenance of heterochromatin in fission yeast, illustrating how the painter model can be used to extract quantitative information on epigenomic molecular processes.
Collapse
Affiliation(s)
- Amith Z Abdulla
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR5239, Inserm U1293, Université Claude Bernard Lyon 1, 46 Allée d’Italie, 69007 Lyon, France,École Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, 46 Allée d’Italie, 69007 Lyon, France
| | - Cédric Vaillant
- Correspondence may also be addressed to Cédric Vaillant. Tel: +33 4 72 72 81 54; Fax: +33 4 72 72 80 00;
| | - Daniel Jost
- To whom correspondence should be addressed. Tel: +33 4 72 72 86 30; Fax: +33 4 72 72 80 00;
| |
Collapse
|
5
|
Dutta S, Polavaram NS, Islam R, Bhattacharya S, Bodas S, Mayr T, Roy S, Albala SAY, Toma MI, Darehshouri A, Borkowetz A, Conrad S, Fuessel S, Wirth M, Baretton GB, Hofbauer LC, Ghosh P, Pienta KJ, Klinkebiel DL, Batra SK, Muders MH, Datta K. Neuropilin-2 regulates androgen-receptor transcriptional activity in advanced prostate cancer. Oncogene 2022; 41:3747-3760. [PMID: 35754042 PMCID: PMC9979947 DOI: 10.1038/s41388-022-02382-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 06/03/2022] [Accepted: 06/10/2022] [Indexed: 01/22/2023]
Abstract
Aberrant transcriptional activity of androgen receptor (AR) is one of the dominant mechanisms for developing of castration-resistant prostate cancer (CRPC). Analyzing AR-transcriptional complex related to CRPC is therefore important towards understanding the mechanism of therapy resistance. While studying its mechanism, we observed that a transmembrane protein called neuropilin-2 (NRP2) plays a contributory role in forming a novel AR-transcriptional complex containing nuclear pore proteins. Using immunogold electron microscopy, high-resolution confocal microscopy, chromatin immunoprecipitation, proteomics, and other biochemical techniques, we delineated the molecular mechanism of how a specific splice variant of NRP2 becomes sumoylated upon ligand stimulation and translocates to the inner nuclear membrane. This splice variant of NRP2 then stabilizes the complex between AR and nuclear pore proteins to promote CRPC specific gene expression. Both full-length and splice variants of AR have been identified in this specific transcriptional complex. In vitro cell line-based assays indicated that depletion of NRP2 not only destabilizes the AR-nuclear pore protein interaction but also inhibits the transcriptional activities of AR. Using an in vivo bone metastasis model, we showed that the inhibition of NRP2 led to the sensitization of CRPC cells toward established anti-AR therapies such as enzalutamide. Overall, our finding emphasize the importance of combinatorial inhibition of NRP2 and AR as an effective therapeutic strategy against treatment refractory prostate cancer.
Collapse
Affiliation(s)
- Samikshan Dutta
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA.
| | - Navatha Shree Polavaram
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Ridwan Islam
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Sreyashi Bhattacharya
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Sanika Bodas
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Thomas Mayr
- Rudolf Becker Laboratory for Prostate Cancer Research, Medical Faculty, University of Bonn, Germany,Institute of Pathology, Medical Faculty, University of Bonn, Germany,Institute of Pathology, Technische Universitaet Dresden, Dresden, Germany
| | - Sohini Roy
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | | | - Marieta I. Toma
- Institute of Pathology, Medical Faculty, University of Bonn, Germany,Institute of Pathology, Technische Universitaet Dresden, Dresden, Germany
| | - Anza Darehshouri
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Angelika Borkowetz
- Department of Urology, Technische Universitaet Dresden, Dresden, Germany
| | - Stefanie Conrad
- Division of Endocrinology and Metabolic Bone Diseases, Department of Medicine III, Technische Universitaet Dresden, Dresden, Germany,Center for Healthy Aging, Technische Universitaet Dresden, Dresden, Germany
| | - Susanne Fuessel
- Department of Urology, Technische Universitaet Dresden, Dresden, Germany
| | - Manfred Wirth
- Department of Urology, Technische Universitaet Dresden, Dresden, Germany
| | - Gustavo B. Baretton
- Institute of Pathology, Technische Universitaet Dresden, Dresden, Germany,German Cancer Consortium (DKTK), partner site Dresden and German Research Center (DKFZ), Heidelberg, Germany,Tumor and Normal Tissue Bank of the University Cancer Center (UCC), University Hospital and Faculty of Medicine, Technische Universitaet Dresden, Germany
| | - Lorenz C. Hofbauer
- Division of Endocrinology and Metabolic Bone Diseases, Department of Medicine III, Technische Universitaet Dresden, Dresden, Germany,Center for Healthy Aging, Technische Universitaet Dresden, Dresden, Germany,German Cancer Consortium (DKTK), partner site Dresden and German Research Center (DKFZ), Heidelberg, Germany
| | - Paramita Ghosh
- Department of Biochemistry and Molecular Medicine, University of California Davis
| | - Kenneth J. Pienta
- The Brady Urological Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - David L Klinkebiel
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Surinder K. Batra
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Michael H. Muders
- Rudolf Becker Laboratory for Prostate Cancer Research, Medical Faculty, University of Bonn, Germany,Institute of Pathology, Medical Faculty, University of Bonn, Germany,Institute of Pathology, Technische Universitaet Dresden, Dresden, Germany
| | - Kaustubh Datta
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE, USA.
| |
Collapse
|
6
|
Lister-Shimauchi EH, McCarthy B, Lippincott M, Ahmed S. Genetic and Epigenetic Inheritance at Telomeres. EPIGENOMES 2022; 6:9. [PMID: 35323213 PMCID: PMC8947350 DOI: 10.3390/epigenomes6010009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 02/21/2022] [Accepted: 03/08/2022] [Indexed: 12/17/2022] Open
Abstract
Transgenerational inheritance can occur at telomeres in distinct contexts. Deficiency for telomerase or telomere-binding proteins in germ cells can result in shortened or lengthened chromosome termini that are transmitted to progeny. In human families, altered telomere lengths can result in stem cell dysfunction or tumor development. Genetic inheritance of altered telomeres as well as mutations that alter telomeres can result in progressive telomere length changes over multiple generations. Telomeres of yeast can modulate the epigenetic state of subtelomeric genes in a manner that is mitotically heritable, and the effects of telomeres on subtelomeric gene expression may be relevant to senescence or other human adult-onset disorders. Recently, two novel epigenetic states were shown to occur at C. elegans telomeres, where very low or high levels of telomeric protein foci can be inherited for multiple generations through a process that is regulated by histone methylation.Together, these observations illustrate that information relevant to telomere biology can be inherited via genetic and epigenetic mechanisms, although the broad impact of epigenetic inheritance to human biology remains unclear.
Collapse
Affiliation(s)
- Evan H. Lister-Shimauchi
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599-3280, USA; (E.H.L.-S.); (B.M.); (M.L.)
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA
| | - Benjamin McCarthy
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599-3280, USA; (E.H.L.-S.); (B.M.); (M.L.)
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA
| | - Michael Lippincott
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599-3280, USA; (E.H.L.-S.); (B.M.); (M.L.)
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA
| | - Shawn Ahmed
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599-3280, USA; (E.H.L.-S.); (B.M.); (M.L.)
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA
| |
Collapse
|
7
|
Brothers M, Rine J. Distinguishing between recruitment and spread of silent chromatin structures in Saccharomyces cerevisiae. eLife 2022; 11:75653. [PMID: 35073254 PMCID: PMC8830885 DOI: 10.7554/elife.75653] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 01/21/2022] [Indexed: 11/13/2022] Open
Abstract
The formation of heterochromatin at HML, HMR, and telomeres in Saccharomyces cerevisiae involves two main steps: Recruitment of Sir proteins to silencers and their spread throughout the silenced domain. We developed a method to study these two processes at single base-pair resolution. Using a fusion protein between the heterochromatin protein Sir3 and the non-site-specific bacterial adenine methyltransferase M.EcoGII, we mapped sites of Sir3-chromatin interactions genome-wide using long-read Nanopore sequencing to detect adenines methylated by the fusion protein and by ChIP-seq to map the distribution of Sir3-M.EcoGII. A silencing-deficient mutant of Sir3 lacking its Bromo-Adjacent Homology (BAH) domain, sir3-bah∆, was still recruited to HML, HMR, and telomeres. However, in the absence of the BAH domain, it was unable to spread away from those recruitment sites. Overexpression of Sir3 did not lead to further spreading at HML, HMR, and most telomeres. A few exceptional telomeres, like 6R, exhibited a small amount of Sir3 spreading, suggesting that boundaries at telomeres responded variably to Sir3 overexpression. Finally, by using a temperature-sensitive allele of SIR3 fused to M.ECOGII, we tracked the positions first methylated after induction and found that repression of genes at HML and HMR began before Sir3 occupied the entire locus.
Collapse
Affiliation(s)
- Molly Brothers
- Department of Molecular and Cell Biology, University of California, Berkeley
| | - Jasper Rine
- Department of Molecular and Cell Biology, University of California, Berkeley
| |
Collapse
|
8
|
Measuring the buffering capacity of gene silencing in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2021; 118:2111841118. [PMID: 34857629 PMCID: PMC8670432 DOI: 10.1073/pnas.2111841118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2021] [Indexed: 11/18/2022] Open
Abstract
Gene silencing, once established, is stably maintained for several generations. Despite the high fidelity of the inheritance of the silent state, individual components of silenced chromatin are in constant flux. Models suggest that silent loci can tolerate fluctuations in Sir proteins and histone acetylation levels, but the level of tolerance is unknown. To understand the quantitative relationships between H4K16 acetylation, Sir proteins, and silencing, we developed assays to quantitatively alter a H4K16 acetylation mimic allele and Sir protein levels and measure the effects of these changes on silencing. Our data suggest that a two- to threefold change in levels of histone marks and specific Sir proteins affects the stability of the silent state of a large chromatin domain. Gene silencing in budding yeast is mediated by Sir protein binding to unacetylated nucleosomes to form a chromatin structure that inhibits transcription. Transcriptional silencing is characterized by the high-fidelity transmission of the silent state. Despite its relative stability, the constituent parts of the silent state are in constant flux, giving rise to a model that silent loci can tolerate such fluctuations without functional consequences. However, the level of tolerance is unknown, and we developed methods to measure the threshold of histone acetylation that causes the silent chromatin state to switch to the active state as well as to measure the levels of the enzymes and structural proteins necessary for silencing. We show that loss of silencing required 50 to 75% acetyl-mimic histones, though the precise levels were influenced by silencer strength and upstream activating sequence (UAS) enhancer/promoter strength. Measurements of repressor protein levels necessary for silencing showed that reducing SIR4 gene dosage two- to threefold significantly weakened silencing, though reducing the gene copy numbers for Sir2 or Sir3 to the same extent did not significantly affect silencing suggesting that Sir4 was a limiting component in gene silencing. Calculations suggest that a mere twofold reduction in the ability of acetyltransferases to acetylate nucleosomes across a large array of nucleosomes may be sufficient to generate a transcriptionally silent domain.
Collapse
|
9
|
Jethmalani Y, Tran K, Negesse MY, Sun W, Ramos M, Jaiswal D, Jezek M, Amos S, Garcia EJ, Park D, Green EM. Set4 regulates stress response genes and coordinates histone deacetylases within yeast subtelomeres. Life Sci Alliance 2021; 4:e202101126. [PMID: 34625508 PMCID: PMC8507492 DOI: 10.26508/lsa.202101126] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 09/28/2021] [Accepted: 09/29/2021] [Indexed: 12/25/2022] Open
Abstract
The yeast chromatin protein Set4 is a member of the Set3-subfamily of SET domain proteins which play critical roles in the regulation of gene expression in diverse developmental and environmental contexts. We previously reported that Set4 promotes survival during oxidative stress and regulates expression of stress response genes via stress-dependent chromatin localization. In this study, global gene expression analysis and investigation of histone modification status identified a role for Set4 in maintaining gene repressive mechanisms within yeast subtelomeres under both normal and stress conditions. We show that Set4 works in a partially overlapping pathway to the SIR complex and the histone deacetylase Rpd3 to maintain proper levels of histone acetylation and expression of stress response genes encoded in subtelomeres. This role for Set4 is particularly critical for cells under hypoxic conditions, where the loss of Set4 decreases cell fitness and cell wall integrity. These findings uncover a new regulator of subtelomeric chromatin that is key to stress defense pathways and demonstrate a function for Set4 in regulating repressive, heterochromatin-like environments.
Collapse
Affiliation(s)
- Yogita Jethmalani
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Khoa Tran
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Maraki Y Negesse
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Winny Sun
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Mark Ramos
- Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Deepika Jaiswal
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Meagan Jezek
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Shandon Amos
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Eric Joshua Garcia
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| | - DoHwan Park
- Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD, USA
| | - Erin M Green
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA
| |
Collapse
|
10
|
Loïodice I, Garnier M, Nikolov I, Taddei A. An Inducible System for Silencing Establishment Reveals a Stepwise Mechanism in Which Anchoring at the Nuclear Periphery Precedes Heterochromatin Formation. Cells 2021; 10:cells10112810. [PMID: 34831033 PMCID: PMC8616196 DOI: 10.3390/cells10112810] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/11/2021] [Accepted: 10/13/2021] [Indexed: 12/02/2022] Open
Abstract
In eukaryotic cells, silent chromatin is mainly found at the nuclear periphery forming subnuclear compartments that favor silencing establishment. Here, we set up an inducible system to monitor silencing establishment at an ectopic locus in relation with its subnuclear localization in budding yeast. We previously showed that introducing LacI bound lacO arrays in proximity to gene flanked by HML silencers favors the recruitment of the yeast silencing complex SIR at this locus, leading to its silencing and anchoring at the nuclear periphery. Using an inducible version of this system, we show that silencing establishment is a stepwise process occurring over several cell cycles, with the progressive recruitment of the SIR complex. In contrast, we observed a rapid, SIR-independent perinuclear anchoring, induced by the high amount of LacI binding at the lacO array leading to nucleosome eviction at this array and to the phosphorylation of H2A in the neighboring nucleosomes by Mec1 kinase. While the initial phosphorylation of H2A (H2A-P) and perinuclear anchoring are independent of the SIR complex, its latter recruitment stabilizes H2A-P and reinforces the perinuclear anchoring. Finally, we showed that Sir3 spreading stabilizes nucleosomes and limits the access of specific DNA-binding protein to DNA.
Collapse
Affiliation(s)
- Isabelle Loïodice
- Nuclear Dynamics Unit, CNRS, Institut Curie, PSL University, Sorbonne Université, 75005 Paris, France; (I.L.); (M.G.); (I.N.)
| | - Mickael Garnier
- Nuclear Dynamics Unit, CNRS, Institut Curie, PSL University, Sorbonne Université, 75005 Paris, France; (I.L.); (M.G.); (I.N.)
| | - Ivaylo Nikolov
- Nuclear Dynamics Unit, CNRS, Institut Curie, PSL University, Sorbonne Université, 75005 Paris, France; (I.L.); (M.G.); (I.N.)
| | - Angela Taddei
- Nuclear Dynamics Unit, CNRS, Institut Curie, PSL University, Sorbonne Université, 75005 Paris, France; (I.L.); (M.G.); (I.N.)
- Cogitamus Laboratory, F-75005 Paris, France
- Correspondence:
| |
Collapse
|
11
|
Doughty TW, Yu R, Chao LFI, Qin Z, Siewers V, Nielsen J. A single chromosome strain of S. cerevisiae exhibits diminished ethanol metabolism and tolerance. BMC Genomics 2021; 22:688. [PMID: 34551706 PMCID: PMC8456624 DOI: 10.1186/s12864-021-07947-x] [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: 03/22/2021] [Accepted: 08/25/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Eukaryotic organisms, like the model yeast S. cerevisiae, have linear chromosomes that facilitate organization and protection of nuclear DNA. A recent work described a stepwise break/repair method that enabled fusion of the 16 chromosomes of S. cerevisiae into a single large chromosome. Construction of this strain resulted in the removal of 30 of 32 telomeres, over 300 kb of subtelomeric DNA, and 107 subtelomeric ORFs. Despite these changes, characterization of the single chromosome strain uncovered modest phenotypes compared to a reference strain. RESULTS This study further characterized the single chromosome strain and found that it exhibited a longer lag phase, increased doubling time, and lower final biomass concentration compared with a reference strain when grown on YPD. These phenotypes were amplified when ethanol was added to the medium or used as the sole carbon source. RNAseq analysis showed poor induction of genes involved in diauxic shift, ethanol metabolism, and fatty-acid ß-oxidation during growth on ethanol compared to the reference strain. Enzyme-constrained metabolic modeling identified decreased flux through the enzymes that are encoded by these poorly induced genes as a likely cause of diminished biomass accumulation. The diminished growth on ethanol for the single chromosome strain was rescued by nicotinamide, an inhibitor of sirtuin family deacetylases, which have been shown to silence gene expression in heterochromatic regions. CONCLUSIONS Our results indicate that sirtuin-mediated silencing in the single chromosome strain interferes with growth on non-fermentable carbon sources. We propose that the removal of subtelomeric DNA that would otherwise be bound by sirtuins leads to silencing at other loci in the single chromosome strain. Further, we hypothesize that the poorly induced genes in the single chromosome strain during ethanol growth could be silenced by sirtuins in wildtype S. cerevisiae during growth on glucose.
Collapse
Affiliation(s)
- Tyler W Doughty
- Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Rosemary Yu
- Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Lucy Fang-I Chao
- Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Zhongjun Qin
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Verena Siewers
- Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden
| | - Jens Nielsen
- Department of Biology and Biological Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden.
- Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden.
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark.
- BioInnovation Institute, DK-2200, Copenhagen N, Denmark.
| |
Collapse
|
12
|
Hoggard T, Hollatz AJ, Cherney RE, Seman MR, Fox CA. The Fkh1 Forkhead associated domain promotes ORC binding to a subset of DNA replication origins in budding yeast. Nucleic Acids Res 2021; 49:10207-10220. [PMID: 34095951 PMCID: PMC8501964 DOI: 10.1093/nar/gkab450] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 05/03/2021] [Accepted: 06/02/2021] [Indexed: 12/14/2022] Open
Abstract
The pioneer event in eukaryotic DNA replication is binding of chromosomal DNA by the origin recognitioncomplex (ORC). The ORC-DNA complex directs the formation of origins, the specific chromosomal regions where DNA synthesis initiates. In all eukaryotes, incompletely understood features of chromatin promote ORC-DNA binding. Here, we uncover a role for the Fkh1 (Forkhead homolog) protein and its forkhead associated (FHA) domain in promoting ORC-origin binding and origin activity at a subset of origins in Saccharomyces cerevisiae. Several of the FHA-dependent origins examined required a distinct Fkh1 binding site located 5′ of and proximal to their ORC sites (5′-FKH-T site). Genetic and molecular experiments provided evidence that the Fkh1-FHA domain promoted origin activity directly through Fkh1 binding to this 5′ FKH-T site. Nucleotide substitutions within two relevant origins that enhanced their ORC-DNA affinity bypassed the requirement for their 5′ FKH-T sites and for the Fkh1-FHA domain. Significantly, assessment of ORC-origin binding by ChIPSeq provided evidence that this mechanism was relevant at ∼25% of yeast origins. Thus, the FHA domain of the conserved cell-cycle transcription factor Fkh1 enhanced origin selection in yeast at the level of ORC-origin binding.
Collapse
Affiliation(s)
- Timothy Hoggard
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA
| | - Allison J Hollatz
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA.,Integrated Program in Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Rachel E Cherney
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA
| | - Melissa R Seman
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA
| | - Catherine A Fox
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, WI 53706, USA.,Integrated Program in Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| |
Collapse
|
13
|
Ruault M, Scolari VF, Lazar-Stefanita L, Hocher A, Loïodice I, Koszul R, Taddei A. Sir3 mediates long-range chromosome interactions in budding yeast. Genome Res 2021; 31:411-425. [PMID: 33579753 PMCID: PMC7919453 DOI: 10.1101/gr.267872.120] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 12/30/2020] [Indexed: 11/24/2022]
Abstract
Physical contacts between distant loci contribute to regulate genome function. However, the molecular mechanisms responsible for settling and maintaining such interactions remain poorly understood. Here, we investigate the well-conserved interactions between heterochromatin loci. In budding yeast, the 32 telomeres cluster in 3–5 foci in exponentially growing cells. This clustering is functionally linked to the formation of heterochromatin in subtelomeric regions through the recruitment of the silencing SIR complex composed of Sir2/3/4. Combining microscopy and Hi-C on strains expressing different alleles of SIR3, we show that the binding of Sir3 directly promotes long-range contacts between distant regions, including the rDNA, telomeres, and internal Sir3-bound sites. Furthermore, we unveil a new property of Sir3 in promoting rDNA compaction. Finally, using a synthetic approach, we demonstrate that Sir3 can bond loci belonging to different chromosomes together, when targeted to these loci, independently of its interaction with its known partners (Rap1, Sir4), Sir2 activity, or chromosome context. Altogether, these data suggest that Sir3 acts as a molecular bridge that stabilizes long-range interactions.
Collapse
Affiliation(s)
- Myriam Ruault
- Institut Curie, PSL University, Sorbonne Université, CNRS, Nuclear Dynamics, 75005 Paris, France
| | - Vittore F Scolari
- Institut Curie, PSL University, Sorbonne Université, CNRS, Nuclear Dynamics, 75005 Paris, France.,Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS, UMR 3525, C3BI USR 3756, F-75015 Paris, France
| | - Luciana Lazar-Stefanita
- Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS, UMR 3525, C3BI USR 3756, F-75015 Paris, France.,Sorbonne Université, collège Doctoral, F-75005 Paris, France
| | - Antoine Hocher
- Institut Curie, PSL University, Sorbonne Université, CNRS, Nuclear Dynamics, 75005 Paris, France
| | - Isabelle Loïodice
- Institut Curie, PSL University, Sorbonne Université, CNRS, Nuclear Dynamics, 75005 Paris, France
| | - Romain Koszul
- Institut Pasteur, Unité Régulation Spatiale des Génomes, CNRS, UMR 3525, C3BI USR 3756, F-75015 Paris, France.,Cogitamus Laboratory, F-75005 Paris, France
| | - Angela Taddei
- Institut Curie, PSL University, Sorbonne Université, CNRS, Nuclear Dynamics, 75005 Paris, France.,Cogitamus Laboratory, F-75005 Paris, France
| |
Collapse
|
14
|
Sir2 mitigates an intrinsic imbalance in origin licensing efficiency between early- and late-replicating euchromatin. Proc Natl Acad Sci U S A 2020; 117:14314-14321. [PMID: 32513739 PMCID: PMC7322022 DOI: 10.1073/pnas.2004664117] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
A eukaryotic chromosome relies on the function of multiple spatially distributed DNA replication origins for its stable inheritance. The spatial location of an origin is determined by the chromosomal position of an MCM complex, the inactive form of the DNA replicative helicase that is assembled onto DNA in G1-phase (also known as origin licensing). While the biochemistry of origin licensing is understood, the mechanisms that promote an adequate spatial distribution of MCM complexes across chromosomes are not. We have elucidated a role for the Sir2 histone deacetylase in establishing the normal distribution of MCM complexes across Saccharomyces cerevisiae chromosomes. In the absence of Sir2, MCM complexes accumulated within both early-replicating euchromatin and telomeric heterochromatin, and replication activity within these regions was enhanced. Concomitantly, the duplication of several regions of late-replicating euchromatin were delayed. Thus, Sir2-mediated attenuation of origin licensing within both euchromatin and telomeric heterochromatin established the normal spatial distribution of origins across yeast chromosomes important for normal genome duplication.
Collapse
|
15
|
Hocher A, Ruault M, Kaferle P, Descrimes M, Garnier M, Morillon A, Taddei A. Expanding heterochromatin reveals discrete subtelomeric domains delimited by chromatin landscape transitions. Genome Res 2018; 28:1867-1881. [PMID: 30355601 PMCID: PMC6280759 DOI: 10.1101/gr.236554.118] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 10/20/2018] [Indexed: 01/20/2023]
Abstract
The eukaryotic genome is divided into chromosomal domains of heterochromatin and euchromatin. Transcriptionally silent heterochromatin is found at subtelomeric regions, leading to the telomeric position effect (TPE) in yeast, fly, and human. Heterochromatin generally initiates and spreads from defined loci, and diverse mechanisms prevent the ectopic spread of heterochromatin into euchromatin. Here, we overexpressed the silencing factor Sir3 at varying levels in yeast and found that Sir3 spreads into extended silent domains (ESDs), eventually reaching saturation at subtelomeres. We observed the spread of Sir3 into subtelomeric domains associated with specific histone marks in wild-type cells, and stopping at zones of histone mark transitions including H3K79 trimethylation levels. Our study shows that the conserved H3K79 methyltransferase Dot1 is essential in restricting Sir3 spread beyond ESDs, thus ensuring viability upon overexpression of Sir3. Last, our analyses of published data demonstrate how ESDs unveil uncharacterized discrete domains isolating structural and functional subtelomeric features from the rest of the genome. Our work offers a new approach on how to separate subtelomeres from the core chromosome.
Collapse
Affiliation(s)
- Antoine Hocher
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Myriam Ruault
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Petra Kaferle
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Marc Descrimes
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Mickaël Garnier
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Antonin Morillon
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| | - Angela Taddei
- Institut Curie, PSL Research University, CNRS, UMR3664, F-75005 Paris, France.,Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR3664, F-75005 Paris, France
| |
Collapse
|
16
|
A Heterochromatin Domain Forms Gradually at a New Telomere and Is Dynamic at Stable Telomeres. Mol Cell Biol 2018; 38:MCB.00393-17. [PMID: 29784772 PMCID: PMC6048312 DOI: 10.1128/mcb.00393-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 05/09/2018] [Indexed: 02/03/2023] Open
Abstract
Heterochromatin domains play important roles in chromosome biology, organismal development, and aging, including centromere function, mammalian female X chromosome inactivation, and senescence-associated heterochromatin foci. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. Heterochromatin domains play important roles in chromosome biology, organismal development, and aging, including centromere function, mammalian female X chromosome inactivation, and senescence-associated heterochromatin foci. In the fission yeast Schizosaccharomyces pombe and metazoans, heterochromatin contains histone H3 that is dimethylated at lysine 9. While factors required for heterochromatin have been identified, the dynamics of heterochromatin formation are poorly understood. Telomeres convert adjacent chromatin into heterochromatin. To form a new heterochromatic region in S. pombe, an inducible DNA double-strand break (DSB) was engineered next to 48 bp of telomere repeats in euchromatin, which caused formation of a new telomere and the establishment and gradual spreading of a new heterochromatin domain. However, spreading was dynamic even after the telomere had reached its stable length, with reporter genes within the heterochromatin domain showing variegated expression. The system also revealed the presence of repeats located near the boundaries of euchromatin and heterochromatin that are oriented to allow the efficient healing of a euchromatic DSB to cap the chromosome end with a new telomere. Telomere formation in S. pombe therefore reveals novel aspects of heterochromatin dynamics and fail-safe mechanisms to repair subtelomeric breaks, with implications for similar processes in metazoan genomes.
Collapse
|
17
|
Hoggard TA, Chang F, Perry KR, Subramanian S, Kenworthy J, Chueng J, Shor E, Hyland EM, Boeke JD, Weinreich M, Fox CA. Yeast heterochromatin regulators Sir2 and Sir3 act directly at euchromatic DNA replication origins. PLoS Genet 2018; 14:e1007418. [PMID: 29795547 PMCID: PMC5991416 DOI: 10.1371/journal.pgen.1007418] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 06/06/2018] [Accepted: 05/15/2018] [Indexed: 01/23/2023] Open
Abstract
Most active DNA replication origins are found within euchromatin, while origins within heterochromatin are often inactive or inhibited. In yeast, origin activity within heterochromatin is negatively controlled by the histone H4K16 deacetylase, Sir2, and at some heterochromatic loci also by the nucleosome binding protein, Sir3. The prevailing view has been that direct functions of Sir2 and Sir3 are confined to heterochromatin. However, growth defects in yeast mutants compromised for loading the MCM helicase, such as cdc6-4, are suppressed by deletion of either SIR2 or SIR3. While these and other observations indicate that SIR2,3 can have a negative impact on at least some euchromatic origins, the genomic scale of this effect was unknown. It was also unknown whether this suppression resulted from direct functions of Sir2,3 within euchromatin, or was an indirect effect of their previously established roles within heterochromatin. Using MCM ChIP-Seq, we show that a SIR2 deletion rescued MCM complex loading at ~80% of euchromatic origins in cdc6-4 cells. Therefore, Sir2 exhibited a pervasive effect at the majority of euchromatic origins. Using MNase-H4K16ac ChIP-Seq, we show that origin-adjacent nucleosomes were depleted for H4K16 acetylation in a SIR2-dependent manner in wild type (i.e. CDC6) cells. In addition, we present evidence that both Sir2 and Sir3 bound to nucleosomes adjacent to euchromatic origins. The relative levels of each of these molecular hallmarks of yeast heterochromatin–SIR2-dependent H4K16 hypoacetylation, Sir2, and Sir3 –correlated with how strongly a SIR2 deletion suppressed the MCM loading defect in cdc6-4 cells. Finally, a screen for histone H3 and H4 mutants that could suppress the cdc6-4 growth defect identified amino acids that map to a surface of the nucleosome important for Sir3 binding. We conclude that heterochromatin proteins directly modify the local chromatin environment of euchromatic DNA replication origins. When a cell divides, it must copy or “replicate” its DNA. DNA replication starts at chromosomal regions called origins when a collection of replication proteins gains local access to unwind the two DNA strands. Chromosomal DNA is packaged into a protein-DNA complex called chromatin and there are two major structurally and functionally distinct types. Euchromatin allows DNA replication proteins to access origin DNA, while heterochromatin inhibits their access. The prevalent view has been that the heterochromatin proteins required to inhibit origins are confined to heterochromatin. In this study, the conserved heterochromatin proteins, Sir2 and Sir3, were shown to both physically and functionally associate with the majority of origins in euchromatin. This observation raises important questions about the chromosomal targets of heterochromatin proteins, and how and why the majority of origins exist within a potentially repressive chromatin structure.
Collapse
Affiliation(s)
- Timothy A. Hoggard
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
| | - FuJung Chang
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Kelsey Rae Perry
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
| | - Sandya Subramanian
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Jessica Kenworthy
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
| | - Julie Chueng
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
| | - Erika Shor
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, New Jersey, United States of America
| | - Edel M. Hyland
- School of Biological Sciences, Medical Biology Center, Queen’s University, Belfast, United Kingdom
| | - Jef D. Boeke
- Department of Biochemistry and Molecular Pharmacology, Institute for Systems Genetics and NYU Langone Health, New York, NY, United States of America
| | - Michael Weinreich
- Laboratory of Genome Integrity and Tumorigenesis, Van Andel Research Institute, Grand Rapids, MI, United States of America
- * E-mail: (MW); (CAF)
| | - Catherine A. Fox
- Department of Biomolecular Chemistry, School of Medicine and Public Health, Madison, WI, United States of America
- Integrated Program in Biochemistry, School of Medicine and Public Health and College of Agricultural Sciences, University of Wisconsin, Madison, WI, United States of America
- * E-mail: (MW); (CAF)
| |
Collapse
|
18
|
Guintini L, Tremblay M, Toussaint M, D'Amours A, Wellinger RE, Wellinger RJ, Conconi A. Repair of UV-induced DNA lesions in natural Saccharomyces cerevisiae telomeres is moderated by Sir2 and Sir3, and inhibited by yKu-Sir4 interaction. Nucleic Acids Res 2017; 45:4577-4589. [PMID: 28334768 PMCID: PMC5416773 DOI: 10.1093/nar/gkx123] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 02/10/2017] [Indexed: 01/28/2023] Open
Abstract
Ultraviolet light (UV) causes DNA damage that is removed by nucleotide excision repair (NER). UV-induced DNA lesions must be recognized and repaired in nucleosomal DNA, higher order structures of chromatin and within different nuclear sub-compartments. Telomeric DNA is made of short tandem repeats located at the ends of chromosomes and their maintenance is critical to prevent genome instability. In Saccharomyces cerevisiae the chromatin structure of natural telomeres is distinctive and contingent to telomeric DNA sequences. Namely, nucleosomes and Sir proteins form the heterochromatin like structure of X-type telomeres, whereas a more open conformation is present at Y’-type telomeres. It is proposed that there are no nucleosomes on the most distal telomeric repeat DNA, which is bound by a complex of proteins and folded into higher order structure. How these structures affect NER is poorly understood. Our data indicate that the X-type, but not the Y’-type, sub-telomeric chromatin modulates NER, a consequence of Sir protein-dependent nucleosome stability. The telomere terminal complex also prevents NER, however, this effect is largely dependent on the yKu–Sir4 interaction, but Sir2 and Sir3 independent.
Collapse
Affiliation(s)
- Laetitia Guintini
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| | - Maxime Tremblay
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| | - Martin Toussaint
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| | - Annie D'Amours
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| | - Ralf E Wellinger
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, CSIC, Avda Américo Vespucio s/n, Sevilla 41092, Spain
| | - Raymund J Wellinger
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| | - Antonio Conconi
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, 3201 rue Jean-Mignault, Sherbrooke J1E 4K8, Canada
| |
Collapse
|
19
|
The Nuts and Bolts of Transcriptionally Silent Chromatin in Saccharomyces cerevisiae. Genetics 2017; 203:1563-99. [PMID: 27516616 DOI: 10.1534/genetics.112.145243] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/30/2016] [Indexed: 12/31/2022] Open
Abstract
Transcriptional silencing in Saccharomyces cerevisiae occurs at several genomic sites including the silent mating-type loci, telomeres, and the ribosomal DNA (rDNA) tandem array. Epigenetic silencing at each of these domains is characterized by the absence of nearly all histone modifications, including most prominently the lack of histone H4 lysine 16 acetylation. In all cases, silencing requires Sir2, a highly-conserved NAD(+)-dependent histone deacetylase. At locations other than the rDNA, silencing also requires additional Sir proteins, Sir1, Sir3, and Sir4 that together form a repressive heterochromatin-like structure termed silent chromatin. The mechanisms of silent chromatin establishment, maintenance, and inheritance have been investigated extensively over the last 25 years, and these studies have revealed numerous paradigms for transcriptional repression, chromatin organization, and epigenetic gene regulation. Studies of Sir2-dependent silencing at the rDNA have also contributed to understanding the mechanisms for maintaining the stability of repetitive DNA and regulating replicative cell aging. The goal of this comprehensive review is to distill a wide array of biochemical, molecular genetic, cell biological, and genomics studies down to the "nuts and bolts" of silent chromatin and the processes that yield transcriptional silencing.
Collapse
|
20
|
Behrouzi R, Lu C, Currie MA, Jih G, Iglesias N, Moazed D. Heterochromatin assembly by interrupted Sir3 bridges across neighboring nucleosomes. eLife 2016; 5. [PMID: 27835568 PMCID: PMC5106214 DOI: 10.7554/elife.17556] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 10/18/2016] [Indexed: 01/05/2023] Open
Abstract
Heterochromatin is a conserved feature of eukaryotic chromosomes with central roles in regulation of gene expression and maintenance of genome stability. Heterochromatin formation involves spreading of chromatin-modifying factors away from initiation points over large DNA domains by poorly understood mechanisms. In Saccharomyces cerevisiae, heterochromatin formation requires the SIR complex, which contains subunits with histone-modifying, histone-binding, and self-association activities. Here, we analyze binding of the Sir proteins to reconstituted mono-, di-, tri-, and tetra-nucleosomal chromatin templates and show that key Sir-Sir interactions bridge only sites on different nucleosomes but not sites on the same nucleosome, and are therefore 'interrupted' with respect to sites on the same nucleosome. We observe maximal binding affinity and cooperativity to unmodified di-nucleosomes and propose that nucleosome pairs bearing unmodified histone H4-lysine16 and H3-lysine79 form the fundamental units of Sir chromatin binding and that cooperative binding requiring two appropriately modified nucleosomes mediates selective Sir recruitment and spreading.
Collapse
Affiliation(s)
- Reza Behrouzi
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Chenning Lu
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Mark A Currie
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Gloria Jih
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Nahid Iglesias
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| | - Danesh Moazed
- Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States
| |
Collapse
|
21
|
Duan YM, Zhou BO, Peng J, Tong XJ, Zhang QD, Zhou JQ. Molecular dynamics of de novo telomere heterochromatin formation in budding yeast. J Genet Genomics 2016; 43:451-65. [DOI: 10.1016/j.jgg.2016.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 03/09/2016] [Accepted: 03/17/2016] [Indexed: 11/26/2022]
|
22
|
Mitsumori R, Ohashi T, Kugou K, Ichino A, Taniguchi K, Ohta K, Uchida H, Oki M. Analysis of novel Sir3 binding regions in Saccharomyces cerevisiae. J Biochem 2016; 160:11-7. [PMID: 26957548 DOI: 10.1093/jb/mvw021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 12/27/2015] [Indexed: 01/25/2023] Open
Abstract
In Saccharomyces cerevisiae, the HMR, HML, telomere and rDNA regions are silenced. Silencing at the rDNA region requires Sir2, and silencing at the HMR, HML and telomere regions requires binding of a protein complex, consisting of Sir2, Sir3 and Sir4, that mediates repression of gene expression. Here, several novel Sir3 binding domains, termed CN domains (Chromosomal Novel Sir3 binding region), were identified using chromatin immunoprecipitation (ChIP) on chip analysis of S. cerevisiae chromosomes. Furthermore, analysis of G1-arrested cells demonstrated that Sir3 binding was elevated in G1-arrested cells compared with logarithmically growing asynchronous cells, and that Sir3 binding varied with the cell cycle. In addition to 14 CN regions identified from analysis of logarithmically growing asynchronous cells (CN1-14), 11 CN regions were identified from G1-arrested cells (CN15-25). Gene expression at some CN regions did not differ between WT and sir3Δ strains. Sir3 at conventional heterochromatic regions is thought to be recruited to chromosomes by Sir2 and Sir4; however, in this study, Sir3 binding occurred at some CN regions even in sir2Δ and sir4Δ backgrounds. Taken together, our results suggest that Sir3 exhibits novel binding parameters and gene regulatory functions at the CN binding domains.
Collapse
Affiliation(s)
- Risa Mitsumori
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Tomoe Ohashi
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Kazuto Kugou
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan; Department of Frontier Research, Kazusa DNA Research Institute, Kisarazu, Chiba 292-0818, Japan
| | - Ayako Ichino
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Kei Taniguchi
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Kunihiro Ohta
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan
| | - Hiroyuki Uchida
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
| | - Masaya Oki
- Department of Applied Chemistry & Biotechnology, Graduate School of Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan; Research and Education Program for Life Science, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan and PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| |
Collapse
|
23
|
Ellahi A, Thurtle DM, Rine J. The Chromatin and Transcriptional Landscape of Native Saccharomyces cerevisiae Telomeres and Subtelomeric Domains. Genetics 2015; 200:505-21. [PMID: 25823445 PMCID: PMC4492376 DOI: 10.1534/genetics.115.175711] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 03/22/2015] [Indexed: 12/18/2022] Open
Abstract
Saccharomyces cerevisiae telomeres have been a paradigm for studying telomere position effects on gene expression. Telomere position effect was first described in yeast by its effect on the expression of reporter genes inserted adjacent to truncated telomeres. The reporter genes showed variable silencing that depended on the Sir2/3/4 complex. Later studies examining subtelomeric reporter genes inserted at natural telomeres hinted that telomere position effects were less pervasive than previously thought. Additionally, more recent data using the sensitive technology of chromatin immunoprecipitation and massively parallel sequencing (ChIP-Seq) revealed a discrete and noncontinuous pattern of coenrichment for all three Sir proteins at a few telomeres, calling the generality of these conclusions into question. Here we combined the ChIP-Seq of the Sir proteins with RNA sequencing (RNA-Seq) of messenger RNAs (mRNAs) in wild-type and in SIR2, SIR3, and SIR4 deletion mutants to characterize the chromatin and transcriptional landscape of all native S. cerevisiae telomeres at the highest achievable resolution. Most S. cerevisiae chromosomes had subtelomeric genes that were expressed, with only ∼6% of subtelomeric genes silenced in a SIR-dependent manner. In addition, we uncovered 29 genes with previously unknown cell-type-specific patterns of expression. These detailed data provided a comprehensive assessment of the chromatin and transcriptional landscape of the subtelomeric domains of a eukaryotic genome.
Collapse
Affiliation(s)
- Aisha Ellahi
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California at Berkeley, Berkeley, California 94720
| | - Deborah M Thurtle
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California at Berkeley, Berkeley, California 94720
| | - Jasper Rine
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California at Berkeley, Berkeley, California 94720
| |
Collapse
|
24
|
Sir2 is involved in the transcriptional modulation of NHP6A in Saccharomyces cerevisiae. Biochem Biophys Res Commun 2015; 461:42-6. [PMID: 25858320 DOI: 10.1016/j.bbrc.2015.03.165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 03/29/2015] [Indexed: 11/22/2022]
Abstract
The Sir proteins, namely Sir2, 3 and 4, have roles related to heterochromatin, but genome-wide studies have revealed their presence at many euchromatic loci, although the functional meaning of this is still not clear. Nhp6a is an abundant HMG-like protein in yeast, which has a role in transcription by modulating chromatin structure and nucleosome number. Although much is known about its structure and function, information regarding its regulation is scarce. NHP6A, among other genes, emerges in ChIP-on chip studies of global Sir proteins binding, suggesting it could be regulated by SIR. We have investigated NHP6A expression in sir deletion mutants as well as in SIR2 overexpressing conditions. In addition, we have asked if the Sir2 deacetylation activity is involved by using conditions that either inhibit (treatment with nicotinamide) or enhance (calorie restriction conditions) Sir2 activity. We have found that, consistent with previous microarray studies, NHP6A expression undergoes a slight increase in sir mutant strains, but is strongly repressed when SIR2 is overexpressed. In a sir3 mutant strain the gene continues to be transcribed, even in SIR2 overexpressing conditions. In addition, treating the cells with nicotinamide counteracts the SIR2 overexpressing effect. Finally, conditions that are known to potentiate Sir2 deacetylation activity seem to mimic the effect of SIR2 overexpression on NHP6A. Our results suggest that Sir2 is involved in the regulation of NHP6A promoter, acting more as a specific repressor, rather than a long-range silencer. This effect is specific, and the Sir2 deacetylase activity is required for the Sir2 mediated repression of NHP6A. Moreover, the presence of the SIR complex seems required for Sir2 to silence NHP6A.
Collapse
|
25
|
Weiner A, Hsieh THS, Appleboim A, Chen HV, Rahat A, Amit I, Rando OJ, Friedman N. High-resolution chromatin dynamics during a yeast stress response. Mol Cell 2015; 58:371-86. [PMID: 25801168 PMCID: PMC4405355 DOI: 10.1016/j.molcel.2015.02.002] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 12/16/2014] [Accepted: 01/29/2015] [Indexed: 11/22/2022]
Abstract
Covalent histone modifications are highly conserved and play multiple roles in eukaryotic transcription regulation. Here, we mapped 26 histone modifications genome-wide in exponentially growing yeast and during a dramatic transcriptional reprogramming—the response to diamide stress. We extend prior studies showing that steady-state histone modification patterns reflect genomic processes, especially transcription, and display limited combinatorial complexity. Interestingly, during the stress response we document a modest increase in the combinatorial complexity of histone modification space, resulting from roughly 3% of all nucleosomes transiently populating rare histone modification states. Most of these rare histone states result from differences in the kinetics of histone modification that transiently uncouple highly correlated marks, with slow histone methylation changes often lagging behind the more rapid acetylation changes. Explicit analysis of modification dynamics uncovers ordered sequences of events in gene activation and repression. Together, our results provide a comprehensive view of chromatin dynamics during a massive transcriptional upheaval. Comprehensive map of 26 histone marks during a transcriptional response in yeast Stress does not alter global relationships between marks and transcription Limited combinatorial complexity with transient modest increase during response Ordered waves of histone modifications during transcriptional reprogramming
Collapse
Affiliation(s)
- Assaf Weiner
- School of Computer Science and Engineering, The Hebrew University, Jerusalem 9190401, Israel; Institute of Life Sciences, The Hebrew University, Jerusalem 9190401, Israel
| | - Tsung-Han S Hsieh
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Alon Appleboim
- School of Computer Science and Engineering, The Hebrew University, Jerusalem 9190401, Israel; Institute of Life Sciences, The Hebrew University, Jerusalem 9190401, Israel
| | - Hsiuyi V Chen
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ayelet Rahat
- School of Computer Science and Engineering, The Hebrew University, Jerusalem 9190401, Israel; Institute of Life Sciences, The Hebrew University, Jerusalem 9190401, Israel
| | - Ido Amit
- Department of Immunology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Oliver J Rando
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Nir Friedman
- School of Computer Science and Engineering, The Hebrew University, Jerusalem 9190401, Israel; Institute of Life Sciences, The Hebrew University, Jerusalem 9190401, Israel.
| |
Collapse
|
26
|
Nagaraj VH, Mukhopadhyay S, Dayarian A, Sengupta AM. Breaking an epigenetic chromatin switch: curious features of hysteresis in Saccharomyces cerevisiae telomeric silencing. PLoS One 2014; 9:e113516. [PMID: 25536038 PMCID: PMC4275178 DOI: 10.1371/journal.pone.0113516] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 10/29/2014] [Indexed: 11/18/2022] Open
Abstract
In addition to gene network switches, local epigenetic modifications to DNA and histones play an important role in all-or-none cellular decision-making. Here, we study the dynamical design of a well-characterized epigenetic chromatin switch: the yeast SIR system, in order to understand the origin of the stability of epigenetic states. We study hysteresis in this system by perturbing it with a histone deacetylase inhibitor. We find that SIR silencing has many characteristics of a non-linear bistable system, as observed in conventional genetic switches, which are based on activities of a few promoters affecting each other through the abundance of their gene products. Quite remarkably, our experiments in yeast telomeric silencing show a very distinctive pattern when it comes to the transition from bistability to monostability. In particular, the loss of the stable silenced state, upon increasing the inhibitor concentration, does not seem to show the expected saddle node behavior, instead looking like a supercritical pitchfork bifurcation. In other words, the 'off' state merges with the 'on' state at a threshold concentration leading to a single state, as opposed to the two states remaining distinct up to the threshold and exhibiting a discontinuous jump from the 'off' to the 'on' state. We argue that this is an inevitable consequence of silenced and active regions coexisting with dynamic domain boundaries. The experimental observations in our study therefore have broad implications for the understanding of chromatin silencing in yeast and beyond.
Collapse
Affiliation(s)
| | | | - Adel Dayarian
- Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA, United States of America
| | - Anirvan M. Sengupta
- BioMaPS Institute, Rutgers University, Piscataway, NJ, United States of America
- Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, United States of America
- * E-mail:
| |
Collapse
|
27
|
Abstract
Telomeres protect chromosome ends from degradation and inappropriate DNA damage response activation through their association with specific factors. Interestingly, these telomeric factors are able to localize outside telomeric regions, where they can regulate the transcription of genes involved in metabolism, immunity and differentiation. These findings delineate a signalling pathway by which telomeric changes control the ability of their associated factors to regulate transcription. This mechanism is expected to enable a greater diversity of cellular responses that are adapted to specific cell types and telomeric changes, and may therefore represent a pivotal aspect of development, ageing and telomere-mediated diseases.
Collapse
|
28
|
Affiliation(s)
- Amanda L. Hughes
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605;
| | - Oliver J. Rando
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605;
| |
Collapse
|
29
|
Abstract
Heterochromatin imparts regional, promoter-independent repression of genes and is epigenetically heritable. Understanding how silencing achieves this regional repression is a fundamental problem in genetics and development. Current models of yeast silencing posit that Sir proteins, recruited by transcription factors bound to the silencers, spread throughout the silenced region. To test this model directly at high resolution, we probed the silenced chromatin architecture by chromatin immunoprecipitation (ChIP) followed by next-generation sequencing (ChIP-seq) of Sir proteins, histones, and a key histone modification, H4K16-acetyl. These analyses revealed that Sir proteins are strikingly concentrated at and immediately adjacent to the silencers, with lower levels of enrichment over the promoters at HML and HMR, the critical targets for transcriptional repression. The telomeres also showed discrete peaks of Sir enrichment yet a continuous domain of hypoacetylated histone H4K16. Surprisingly, ChIP-seq of cross-linked chromatin revealed a distribution of nucleosomes at silenced loci that was similar to Sir proteins, whereas native nucleosome maps showed a regular distribution throughout silenced loci, indicating that cross-linking captured a specialized chromatin organization imposed by Sir proteins. This specialized chromatin architecture observed in yeast informs the importance of a steric contribution to regional repression in other organisms.
Collapse
Affiliation(s)
- Deborah M Thurtle
- Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California at Berkeley, Berkeley, California 94720, USA
| | | |
Collapse
|
30
|
|
31
|
Young TJ, Kirchmaier AL. Cell cycle regulation of silent chromatin formation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1819:303-312. [PMID: 24459732 DOI: 10.1016/j.bbagrm.2011.10.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
Identical genes in two different cells can stably exist in alternate transcriptional states despite the dynamic changes that will occur to chromatin at that locus throughout the cell cycle. In mammals, this is achieved through epigenetic processes that regulate key developmental transitions and ensure stable patterns of gene expression during growth and differentiation. The budding yeast Saccharomyces cerevisiae utilizes silencing to control the expression state of genes encoding key regulatory factors for determining cell-type, ribosomal RNA levels and proper telomere function. Here, we review the composition of silent chromatin in S. cerevisiae, how silent chromatin is influenced by chromatin assembly and histone modifications and highlight several observations that have contributed to our understanding of the interplay between silent chromatin formation and stability and the cell cycle. This article is part of a Special Issue entitled: Histone chaperones and Chromatin assembly.
Collapse
|
32
|
Wierman MB, Smith JS. Yeast sirtuins and the regulation of aging. FEMS Yeast Res 2014; 14:73-88. [PMID: 24164855 PMCID: PMC4365911 DOI: 10.1111/1567-1364.12115] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/09/2013] [Accepted: 10/13/2013] [Indexed: 11/29/2022] Open
Abstract
The sirtuins are a phylogenetically conserved family of NAD(+) -dependent protein deacetylases that consume one molecule of NAD(+) for every deacetylated lysine side chain. Their requirement for NAD(+) potentially makes them prone to regulation by fluctuations in NAD(+) or biosynthesis intermediates, thus linking them to cellular metabolism. The Sir2 protein from Saccharomyces cerevisiae is the founding sirtuin family member and has been well characterized as a histone deacetylase that functions in transcriptional silencing of heterochromatin domains and as a pro-longevity factor for replicative life span (RLS), defined as the number of times a mother cell divides (buds) before senescing. Deleting SIR2 shortens RLS, while increased gene dosage causes extension. Furthermore, Sir2 has been implicated in mediating the beneficial effects of caloric restriction (CR) on life span, not only in yeast, but also in higher eukaryotes. While this paradigm has had its share of disagreements and debate, it has also helped rapidly drive the aging research field forward. S. cerevisiae has four additional sirtuins, Hst1, Hst2, Hst3, and Hst4. This review discusses the function of Sir2 and the Hst homologs in replicative aging and chronological aging, and also addresses how the sirtuins are regulated in response to environmental stresses such as CR.
Collapse
Affiliation(s)
- Margaret B Wierman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA, USA
| | | |
Collapse
|
33
|
Highly expressed loci are vulnerable to misleading ChIP localization of multiple unrelated proteins. Proc Natl Acad Sci U S A 2013; 110:18602-7. [PMID: 24173036 DOI: 10.1073/pnas.1316064110] [Citation(s) in RCA: 284] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Chromatin immunoprecipitation (ChIP) is the gold-standard technique for localizing nuclear proteins in the genome. We used ChIP, in combination with deep sequencing (Seq), to study the genome-wide distribution of the Silent information regulator (Sir) complex in Saccharomyces cerevisiae. We analyzed ChIP-Seq peaks of the Sir2, Sir3, and Sir4 silencing proteins and discovered 238 unexpected euchromatic loci that exhibited enrichment of all three. Surprisingly, published ChIP-Seq datasets for the Ste12 transcription factor and the centromeric Cse4 protein indicated that these proteins were also enriched in the same euchromatic regions with the high Sir protein levels. The 238 loci, termed "hyper-ChIPable", were in highly expressed regions with strong polymerase II and polymerase III enrichment signals, and the correlation between transcription level and ChIP enrichment was not limited to these 238 loci but extended genome-wide. The apparent enrichment of various proteins at hyper-ChIPable loci was not a consequence of artifacts associated with deep sequencing methods, as confirmed by ChIP-quantitative PCR. The localization of unrelated proteins, including the entire silencing complex, to the most highly transcribed genes was highly suggestive of a technical issue with the immunoprecipitations. ChIP-Seq on chromatin immunoprecipitated with a nuclear-localized GFP reproduced the above enrichment in an expression-dependent manner: induction of the GAL genes resulted in an increased ChIP signal of the GFP protein at these loci, with presumably no biological relevance. Whereas ChIP is a broadly valuable technique, some published conclusions based upon ChIP procedures may merit reevaluation in light of these findings.
Collapse
|
34
|
Kueng S, Oppikofer M, Gasser SM. SIR proteins and the assembly of silent chromatin in budding yeast. Annu Rev Genet 2013; 47:275-306. [PMID: 24016189 DOI: 10.1146/annurev-genet-021313-173730] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Saccharomyces cerevisiae provides a well-studied model system for heritable silent chromatin in which a histone-binding protein complex [the SIR (silent information regulator) complex] represses gene transcription in a sequence-independent manner by spreading along nucleosomes, much like heterochromatin in higher eukaryotes. Recent advances in the biochemistry and structural biology of the SIR-chromatin system bring us much closer to a molecular understanding of yeast silent chromatin. Simultaneously, genome-wide approaches have shed light on the biological importance of this form of epigenetic repression. Here, we integrate genetic, structural, and cell biological data into an updated overview of yeast silent chromatin assembly.
Collapse
Affiliation(s)
- Stephanie Kueng
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | | | | |
Collapse
|
35
|
Oppikofer M, Kueng S, Gasser SM. SIR–nucleosome interactions: Structure–function relationships in yeast silent chromatin. Gene 2013; 527:10-25. [DOI: 10.1016/j.gene.2013.05.088] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 05/27/2013] [Accepted: 05/30/2013] [Indexed: 01/09/2023]
|
36
|
Mukhopadhyay S, Sengupta AM. The role of multiple marks in epigenetic silencing and the emergence of a stable bivalent chromatin state. PLoS Comput Biol 2013; 9:e1003121. [PMID: 23874171 PMCID: PMC3715441 DOI: 10.1371/journal.pcbi.1003121] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 05/10/2013] [Indexed: 12/29/2022] Open
Abstract
We introduce and analyze a minimal model of epigenetic silencing in budding yeast, built upon known biomolecular interactions in the system. Doing so, we identify the epigenetic marks essential for the bistability of epigenetic states. The model explicitly incorporates two key chromatin marks, namely H4K16 acetylation and H3K79 methylation, and explores whether the presence of multiple marks lead to a qualitatively different systems behavior. We find that having both modifications is important for the robustness of epigenetic silencing. Besides the silenced and transcriptionally active fate of chromatin, our model leads to a novel state with bivalent (i.e., both active and silencing) marks under certain perturbations (knock-out mutations, inhibition or enhancement of enzymatic activity). The bivalent state appears under several perturbations and is shown to result in patchy silencing. We also show that the titration effect, owing to a limited supply of silencing proteins, can result in counter-intuitive responses. The design principles of the silencing system is systematically investigated and disparate experimental observations are assessed within a single theoretical framework. Specifically, we discuss the behavior of Sir protein recruitment, spreading and stability of silenced regions in commonly-studied mutants (e.g., sas2[Formula: see text], dot1[Formula: see text]) illuminating the controversial role of Dot1 in the systems biology of yeast silencing.
Collapse
|
37
|
Tung SY, Lee KW, Hong JY, Lee SP, Shen HH, Liou GG. Changes in the genome-wide localization pattern of Sir3 in Saccharomyces cerevisiae during different growth stages. Comput Struct Biotechnol J 2013; 7:e201304001. [PMID: 24688731 PMCID: PMC3962127 DOI: 10.5936/csbj.201304001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 05/14/2013] [Accepted: 05/19/2013] [Indexed: 12/03/2022] Open
Abstract
In budding yeast, the Sir2, Sir3 and Sir4 proteins form SIR complexes, required for the assembly of silent heterochromatin domains, and which mediate transcription silencing at the telomeres as well as at silent mating type loci. In this study, under fluorescence microscopy, we found most Sir3-GFP expressions in the logarithmic phase cells appeared as multiple punctations as expected. However, some differences in the distribution of fluorescent signals were detected in the diauxic~early stationary phase cells. To clarify these, we then used ChIP on chip assays to investigate the genome-wide localization of Sir3. In general, Sir3 binds to all 32 telomere proximal regions, the silent mating type loci and also binds to the rDNA region. However, the genome-wide localization patterns of Sir3 are different between these two distinct growth phases. We also confirmed that Sir3 binds to a recently identified secondary binding site, PAU genes, and further identified 349 Sir3-associated cluster regions. These results provide additional support in roles for Sir3 in the modulation of gene expression during physical conditions such as diauxic~early stationary phase growing. Moreover, they imply that Sir3 may be not only involved in the formation of conventional silent heterochromatin, but also able to associate with some other chromatin regions involved in epigenetic regulation.
Collapse
Affiliation(s)
- Shu-Yun Tung
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan, ROC ; These authors contributed equally to this work
| | - Kuan-Wei Lee
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli 35053, Taiwan, ROC ; These authors contributed equally to this work
| | - Jia-Yang Hong
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli 35053, Taiwan, ROC ; These authors contributed equally to this work
| | - Sue-Ping Lee
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan, ROC ; These authors contributed equally to this work
| | - Hsiao-Hsuian Shen
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli 35053, Taiwan, ROC
| | - Gunn-Guang Liou
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli 35053, Taiwan, ROC ; Graduate Institute of Basic Medical Science, China Medical University, Taichung 40402, Taiwan, ROC
| |
Collapse
|
38
|
Li M, Valsakumar V, Poorey K, Bekiranov S, Smith JS. Genome-wide analysis of functional sirtuin chromatin targets in yeast. Genome Biol 2013; 14:R48. [PMID: 23710766 PMCID: PMC4053722 DOI: 10.1186/gb-2013-14-5-r48] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 05/14/2013] [Accepted: 05/27/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The sirtuins are a conserved family of NAD⁺-dependent histone/protein deacetylases that regulate numerous cellular processes, including heterochromatin formation and transcription. Multiple sirtuins are encoded by each eukaryotic genome, raising the possibility of cooperativity or functional overlap. The scope and variety of chromatin binding sites of the sirtuins in any specific organism remain unclear. RESULTS Here we utilize the ChIP-seq technique to identify and functionally characterize the genome-wide targets of the sirtuins, Sir2, Hst1 to Hst4, and the DNA binding partner of Hst1, Sum 1, in Saccharomyces cerevisiae. Unexpectedly, Sir2, Hst1 and Sum1, but not the other sirtuins, exhibit co-enrichment at several classes of chromatin targets. These include telomeric repeat clusters, tRNA genes, and surprisingly, the open reading frames (ORFs) of multiple highly expressed RNA polymerase II-transcribed genes that function in processes such as fermentation, glycolysis, and translation. Repression of these target genes during the diauxic shift is specifically dependent on Sir2/Hst1/Sum1 binding to the ORF and sufficiently high intracellular NAD⁺ concentrations. Sir2 recruitment to the ORFs is independent of the canonical SIR complex and surprisingly requires Sum1. The shared Sir2/Hst1/Sum1 targets also significantly overlap with condensin and cohesin binding sites, where Sir2, Hst1, and Sum1 were found to be important for condensin and cohesin deposition, suggesting a possible mechanistic link between metabolism and chromatin architecture during the diauxic shift. CONCLUSIONS This study demonstrates the existence of overlap in sirtuin function, and advances our understanding of conserved sirtuin-regulated functions, including the regulation of glycolytic gene expression and condensin loading.
Collapse
Affiliation(s)
- Mingguang Li
- Department of Biochemistry and Molecular Genetics, University of Virginia, School of Medicine, 1340 Jefferson Park Ave, Charlottesville, VA 22908, USA
| | - Veena Valsakumar
- Department of Biochemistry and Molecular Genetics, University of Virginia, School of Medicine, 1340 Jefferson Park Ave, Charlottesville, VA 22908, USA
| | - Kunal Poorey
- Department of Biochemistry and Molecular Genetics, University of Virginia, School of Medicine, 1340 Jefferson Park Ave, Charlottesville, VA 22908, USA
| | - Stefan Bekiranov
- Department of Biochemistry and Molecular Genetics, University of Virginia, School of Medicine, 1340 Jefferson Park Ave, Charlottesville, VA 22908, USA
| | - Jeffrey S Smith
- Department of Biochemistry and Molecular Genetics, University of Virginia, School of Medicine, 1340 Jefferson Park Ave, Charlottesville, VA 22908, USA
| |
Collapse
|
39
|
Abstract
Epigenetic mechanisms of silencing via heritable chromatin modifications play a major role in gene regulation and cell fate specification. We consider a model of epigenetic chromatin silencing in budding yeast and study the bifurcation diagram and characterize the bistable and the monostable regimes. The main focus of this paper is to examine how the perturbations altering the activity of histone modifying enzymes affect the epigenetic states. We analyze the implications of having the total number of silencing proteins, given by the sum of proteins bound to the nucleosomes and the ones available in the ambient, to be constant. This constraint couples different regions of chromatin through the shared reservoir of ambient silencing proteins. We show that the response of the system to perturbations depends dramatically on the titration effect caused by the above constraint. In particular, for a certain range of overall abundance of silencing proteins, the hysteresis loop changes qualitatively with certain jump replaced by continuous merger of different states. In addition, we find a nonmonotonic dependence of gene expression on the rate of histone deacetylation activity of Sir2. We discuss how these qualitative predictions of our model could be compared with experimental studies of the yeast system under anti-silencing drugs.
Collapse
Affiliation(s)
- Adel Dayarian
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA, USA
| | | |
Collapse
|
40
|
Hozé N, Ruault M, Amoruso C, Taddei A, Holcman D. Spatial telomere organization and clustering in yeast Saccharomyces cerevisiae nucleus is generated by a random dynamics of aggregation-dissociation. Mol Biol Cell 2013; 24:1791-800, S1-10. [PMID: 23576549 PMCID: PMC3667730 DOI: 10.1091/mbc.e13-01-0031] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The 32 telomeres of budding yeast form clusters, yet whether clusters are due to random localization or telomeric interactions is unclear. Data from live-cell imaging are compared with a biophysical model of telomere dynamics. Direct molecular interaction between telomeres is the key parameter that regulates telomere clustering. Spatial and temporal behavior of chromosomes and their regulatory proteins is a key control mechanism in genomic function. This is exemplified by the clustering of the 32 budding yeast telomeres that form foci in which silencing factors concentrate. To uncover the determinants of telomere distribution, we compare live-cell imaging with a stochastic model of telomere dynamics that we developed. We show that random encounters alone are inadequate to produce the clustering observed in vivo. In contrast, telomere dynamics observed in vivo in both haploid and diploid cells follows a process of dissociation–aggregation. We determine the time that two telomeres spend in the same cluster for the telomere distribution observed in cells expressing different levels of the silencing factor Sir3 protein, limiting for telomere clustering. We conclude that telomere clusters, their dynamics, and their nuclear distribution result from random motion, aggregation, and dissociation of telomeric regions, specifically determined by the amount of Sir3.
Collapse
Affiliation(s)
- Nathanaël Hozé
- Institute of Biology, Group of Computational Biology and Applied Mathematics, Ecole Normale Supérieure, 75005 Paris, France
| | | | | | | | | |
Collapse
|
41
|
Meister P, Taddei A. Building silent compartments at the nuclear periphery: a recurrent theme. Curr Opin Genet Dev 2013; 23:96-103. [PMID: 23312840 DOI: 10.1016/j.gde.2012.12.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 11/29/2012] [Accepted: 12/05/2012] [Indexed: 01/12/2023]
Abstract
In eukaryotes, the genetic material is stored in the nucleus, which is enclosed in a double lipid bilayer, the nuclear envelope (NE). It protects the genome from physical stress and separates it from the rest of the cell. On top of this physical function, growing evidence shows that the nuclear periphery contributes to the 3D organization of the genome. In turn, tridimensional organization of chromatin in the nuclear space influences genome expression. Here we review recent findings on the function of this physical barrier in gene repression and latest models on how silent subnuclear compartments at the NE are built in yeast as well as in the nematode C. elegans and mammalian cells; trying to draw parallels between the three systems.
Collapse
Affiliation(s)
- Peter Meister
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland.
| | | |
Collapse
|
42
|
Weiner A, Chen HV, Liu CL, Rahat A, Klien A, Soares L, Gudipati M, Pfeffner J, Regev A, Buratowski S, Pleiss JA, Friedman N, Rando OJ. Systematic dissection of roles for chromatin regulators in a yeast stress response. PLoS Biol 2012; 10:e1001369. [PMID: 22912562 PMCID: PMC3416867 DOI: 10.1371/journal.pbio.1001369] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 06/20/2012] [Indexed: 01/05/2023] Open
Abstract
Systematic functional and mapping studies of histone modifications in yeast show that most chromatin regulators are more important for dynamic transcriptional reprogramming than for steady-state gene expression. Packaging of eukaryotic genomes into chromatin has wide-ranging effects on gene transcription. Curiously, it is commonly observed that deletion of a global chromatin regulator affects expression of only a limited subset of genes bound to or modified by the regulator in question. However, in many single-gene studies it has become clear that chromatin regulators often do not affect steady-state transcription, but instead are required for normal transcriptional reprogramming by environmental cues. We therefore have systematically investigated the effects of 83 histone mutants, and 119 gene deletion mutants, on induction/repression dynamics of 170 transcripts in response to diamide stress in yeast. Importantly, we find that chromatin regulators play far more pronounced roles during gene induction/repression than they do in steady-state expression. Furthermore, by jointly analyzing the substrates (histone mutants) and enzymes (chromatin modifier deletions) we identify specific interactions between histone modifications and their regulators. Combining these functional results with genome-wide mapping of several histone marks in the same time course, we systematically investigated the correspondence between histone modification occurrence and function. We followed up on one pathway, finding that Set1-dependent H3K4 methylation primarily acts as a gene repressor during multiple stresses, specifically at genes involved in ribosome biosynthesis. Set1-dependent repression of ribosomal genes occurs via distinct pathways for ribosomal protein genes and ribosomal biogenesis genes, which can be separated based on genetic requirements for repression and based on chromatin changes during gene repression. Together, our dynamic studies provide a rich resource for investigating chromatin regulation, and identify a significant role for the “activating” mark H3K4me3 in gene repression. Chromatin packaging of eukaryotic genomes has wideranging, yet poorly understood, effects on gene regulation. Curiously, many histone modifications occur on the majority of genes, yet their loss typically affects a small subset of those genes. Here, we examine gene expression defects in 200 chromatin-related mutants during a stress response, finding that chromatin regulators have far greater effects on the dynamics of gene expression than on the steady-state transcription. By grouping mutants according to their shared defects in the stress response, we systematically recover known chromatin-related complexes and pathways, and predict several novel pathways. Finally, by integrating genome-wide changes in the locations of five prominent histone modifications during the stress response with our functional data, we uncover a novel role for the “activating” histone modification H3K4me3 in gene repression. Surprisingly, H3K4 methylation appears to act in conjunction with H3S10 phosphorylation in the repression of ribosomal biosynthesis genes. Repression of ribosomal protein genes and ribosomal RNA maturation genes occur via distinct pathways. Our results show that steady-state studies miss a great deal of important chromatin biology, and identify a surprising role for H3K4 methylation in ribosomal gene repression in yeast.
Collapse
Affiliation(s)
- Assaf Weiner
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
- Alexander Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Hsiuyi V. Chen
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Chih Long Liu
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Ayelet Rahat
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
- Alexander Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Avital Klien
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
- Alexander Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
| | - Luis Soares
- Department of Biochemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Mohanram Gudipati
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Jenna Pfeffner
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Aviv Regev
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Stephen Buratowski
- Department of Biochemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jeffrey A. Pleiss
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Nir Friedman
- School of Computer Science and Engineering, The Hebrew University, Jerusalem, Israel
- Alexander Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
- * E-mail: (NF); (OJR)
| | - Oliver J. Rando
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail: (NF); (OJR)
| |
Collapse
|
43
|
Kueng S, Tsai-Pflugfelder M, Oppikofer M, Ferreira HC, Roberts E, Tsai C, Roloff TC, Sack R, Gasser SM. Regulating repression: roles for the sir4 N-terminus in linker DNA protection and stabilization of epigenetic states. PLoS Genet 2012; 8:e1002727. [PMID: 22654676 PMCID: PMC3359979 DOI: 10.1371/journal.pgen.1002727] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 04/11/2012] [Indexed: 01/19/2023] Open
Abstract
Silent information regulator proteins Sir2, Sir3, and Sir4 form a heterotrimeric complex that represses transcription at subtelomeric regions and homothallic mating type (HM) loci in budding yeast. We have performed a detailed biochemical and genetic analysis of the largest Sir protein, Sir4. The N-terminal half of Sir4 is dispensable for SIR–mediated repression of HM loci in vivo, except in strains that lack Yku70 or have weak silencer elements. For HM silencing in these cells, the C-terminal domain (Sir4C, residues 747–1,358) must be complemented with an N-terminal domain (Sir4N; residues 1–270), expressed either independently or as a fusion with Sir4C. Nonetheless, recombinant Sir4C can form a complex with Sir2 and Sir3 in vitro, is catalytically active, and has sedimentation properties similar to a full-length Sir4-containing SIR complex. Sir4C-containing SIR complexes bind nucleosomal arrays and protect linker DNA from nucleolytic digestion, but less effectively than wild-type SIR complexes. Consistently, full-length Sir4 is required for the complete repression of subtelomeric genes. Supporting the notion that the Sir4 N-terminus is a regulatory domain, we find it extensively phosphorylated on cyclin-dependent kinase consensus sites, some being hyperphosphorylated during mitosis. Mutation of two major phosphoacceptor sites (S63 and S84) derepresses natural subtelomeric genes when combined with a serendipitous mutation (P2A), which alone can enhance the stability of either the repressed or active state. The triple mutation confers resistance to rapamycin-induced stress and a loss of subtelomeric repression. We conclude that the Sir4 N-terminus plays two roles in SIR–mediated silencing: it contributes to epigenetic repression by stabilizing the SIR–mediated protection of linker DNA; and, as a target of phosphorylation, it can destabilize silencing in a regulated manner. Three Silent Information Regulator (SIR) proteins Sir2, Sir3, and Sir4 are involved in the epigenetic gene silencing of the homothallic mating (HM) loci and of telomere-proximal genes in budding yeast. They bind as a heterotrimeric complex to chromatin, repressing the underlying genes. Sir2 has an essential histone deacetylase activity, and Sir3 binds nucleosomes, with a high specificity for unmodified histones. We explored Sir4, whose role had largely remained a mystery. We report here that Sir4 N- and C-terminal domains have distinct functions: The Sir4 C-terminus binds all proteins essential for SIR–mediated silencing and is sufficient to repress HM loci, but surprisingly it is not sufficient to efficiently repress at telomeres. The Sir4 N-terminus binds DNA, which strengthens the SIR–chromatin interaction and helps target Sir4 to telomeric loci. In addition the Sir4 N-terminus binds sequence-specific factors that recruit Sir4 to sites of repression. We find that the Sir4 N-terminus is a target of mitotic phosphorylation. Mutation of the phosphoacceptor sites indicates that they help fine-tune subtelomeric repression. We propose therefore that phosphorylation of the Sir4 N-terminal domain modulates epigenetic repression at telomeres in response to cell cycle and/or stress situations.
Collapse
Affiliation(s)
- Stephanie Kueng
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | | | - Mariano Oppikofer
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Faculty of Natural Sciences, University of Basel, Basel, Switzerland
| | - Helder C. Ferreira
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Emma Roberts
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Chinyen Tsai
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | | | - Ragna Sack
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Susan M. Gasser
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Faculty of Natural Sciences, University of Basel, Basel, Switzerland
- * E-mail:
| |
Collapse
|
44
|
Abstract
Drosophila Groucho (Gro) is the founding member of a family of metazoan corepressors. Gro mediates repression through interactions with a myriad of DNA-binding repressor proteins to direct the silencing of genes involved in many developmental processes, including neurogenesis and patterning of the main body axis, as well as receptor tyrosine kinase/Ras/MAPK, Notch, Wingless (Wg)/Wnt, and Decapentaplegic (Dpp) signaling. Gro mediates repression by multiple molecular mechanisms, depending on the regulatory context. Because Gro is a broadly expressed nuclear factor, whereas its repressor partners display restricted temporal and spatial distribution, it was presumed that this corepressor played permissive rather than instructive roles in development. However, a wide range of studies demonstrates that this is not the case. Gro can sense and integrate many cellular inputs to modulate the expression of variety of genes, making it a versatile corepressor with crucial instructive roles in development and signaling.
Collapse
Affiliation(s)
- Wiam Turki-Judeh
- Department of Chemistry & Biochemistry and Molecular Biology Institute, University of California, Los Angeles, California, USA
| | | |
Collapse
|
45
|
The Hog1 mitogen-activated protein kinase mediates a hypoxic response in Saccharomyces cerevisiae. Genetics 2011; 188:325-38. [PMID: 21467572 DOI: 10.1534/genetics.111.128322] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
We have studied hypoxic induction of transcription by studying the seripauperin (PAU) genes of Saccharomyces cerevisiae. Previous studies showed that PAU induction requires the depletion of heme and is dependent upon the transcription factor Upc2. We have now identified additional factors required for PAU induction during hypoxia, including Hog1, a mitogen-activated protein kinase (MAPK) whose signaling pathway originates at the membrane. Our results have led to a model in which heme and ergosterol depletion alters membrane fluidity, thereby activating Hog1 for hypoxic induction. Hypoxic activation of Hog1 is distinct from its previously characterized response to osmotic stress, as the two conditions cause different transcriptional consequences. Furthermore, Hog1-dependent hypoxic activation is independent of the S. cerevisiae general stress response. In addition to Hog1, specific components of the SAGA coactivator complex, including Spt20 and Sgf73, are also required for PAU induction. Interestingly, the mammalian ortholog of Spt20, p38IP, has been previously shown to interact with the mammalian ortholog of Hog1, p38. Taken together, our results have uncovered a previously unknown hypoxic-response pathway that may be conserved throughout eukaryotes.
Collapse
|