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Bell CC, Faulkner GJ, Gilan O. Chromatin-based memory as a self-stabilizing influence on cell identity. Genome Biol 2024; 25:320. [PMID: 39736786 DOI: 10.1186/s13059-024-03461-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2024] [Accepted: 12/16/2024] [Indexed: 01/01/2025] Open
Abstract
Cell types are traditionally thought to be specified and stabilized by gene regulatory networks. Here, we explore how chromatin memory contributes to the specification and stabilization of cell states. Through pervasive, local, feedback loops, chromatin memory enables cell states that were initially unstable to become stable. Deeper appreciation of this self-stabilizing role for chromatin broadens our perspective of Waddington's epigenetic landscape from a static surface with islands of stability shaped by evolution, to a plasticine surface molded by experience. With implications for the evolution of cell types, stabilization of resistant states in cancer, and the widespread plasticity of complex life.
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Affiliation(s)
- Charles C Bell
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD, 4102, Australia.
| | - Geoffrey J Faulkner
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD, 4102, Australia
- Queensland Brain Institute, University of Queensland, Brisbane, QLD, 4169, Australia
| | - Omer Gilan
- Australian Centre for Blood Diseases, Monash University, Melbourne, VIC, 3004, Australia
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2
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Pease NA, Denecke KM, Chen L, Gerges PH, Kueh HY. A timed epigenetic switch balances T and ILC lineage proportions in the thymus. Development 2024; 151:dev203016. [PMID: 39655434 PMCID: PMC11664168 DOI: 10.1242/dev.203016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2024] [Accepted: 11/04/2024] [Indexed: 01/11/2025]
Abstract
How multipotent progenitors give rise to multiple cell types in defined numbers is a central question in developmental biology. Epigenetic switches, acting at single gene loci, can generate extended delays in the activation of lineage-specifying genes and impact lineage decisions and cell type output. Here, we analyzed a timed epigenetic switch controlling expression of mouse Bcl11b, a transcription factor that drives T-cell commitment, but only after a multi-day delay. To investigate roles for this delay in controlling lineage decision making, we analyzed progenitors with a deletion in a distal Bcl11b enhancer, which extends this delay by ∼3 days. Strikingly, delaying Bcl11b activation reduces T-cell output but enhances innate lymphoid cell (ILC) generation in the thymus by redirecting uncommitted progenitors to the ILC lineages. Mechanistically, delaying Bcl11b activation promoted ILC redirection by enabling upregulation of the ILC-specifying transcription factor PLZF. Despite the upregulation of PLZF, committed ILC progenitors could subsequently express Bcl11b, which is also needed for type 2 ILC differentiation. These results show that epigenetic switches can control the activation timing and order of lineage-specifying genes to modulate cell type numbers and proportions.
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Affiliation(s)
- Nicholas A. Pease
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98105, USA
| | - Kathryn M. Denecke
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA
| | - Lihua Chen
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA
| | - Peter Habib Gerges
- Department of Immunology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Hao Yuan Kueh
- Department of Bioengineering, University of Washington, Seattle, WA 98105, USA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98105, USA
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3
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Movilla Miangolarra A, Howard M. Theory of epigenetic switching due to stochastic histone mark loss during DNA replication. Phys Biol 2024; 22:016005. [PMID: 39556945 PMCID: PMC11605279 DOI: 10.1088/1478-3975/ad942c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2024] [Revised: 11/12/2024] [Accepted: 11/18/2024] [Indexed: 11/20/2024]
Abstract
How much information does a cell inherit from its ancestors beyond its genetic sequence? What are the epigenetic mechanisms that allow this? Despite the rise in available epigenetic data, how such information is inherited through the cell cycle is still not fully understood. Often, epigenetic marks can display bistable behaviour and their bistable state is transmitted to daughter cells through the cell cycle, providing the cell with a form of memory. However, loss-of-memory events also take place, where a daughter cell switches epigenetic state (with respect to the mother cell). Here, we develop a framework to compute these epigenetic switching rates, for the case when they are driven by DNA replication, i.e. the frequency of loss-of-memory events due to replication. We consider the dynamics of histone modifications during the cell cycle deterministically, except at DNA replication, where nucleosomes are randomly distributed between the two daughter DNA strands, which is therefore implemented stochastically. This hybrid stochastic-deterministic approach enables an analytic derivation of the replication-driven switching rate. While retaining great simplicity, this framework can explain experimental switching rate data, establishing its biological importance as a framework to quantitatively study epigenetic inheritance.
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Affiliation(s)
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom
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4
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Conneely LJ, Hurgobin B, Ng S, Tamiru-Oli M, Lewsey MG. Characterization of the Cannabis sativa glandular trichome epigenome. BMC PLANT BIOLOGY 2024; 24:1075. [PMID: 39538149 PMCID: PMC11562870 DOI: 10.1186/s12870-024-05787-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2024] [Accepted: 11/05/2024] [Indexed: 11/16/2024]
Abstract
BACKGROUND The relationship between epigenomics and plant specialised metabolism remains largely unexplored despite the fundamental importance of epigenomics in gene regulation and, potentially, yield of products of plant specialised metabolic pathways. The glandular trichomes of Cannabis sativa are an emerging model system that produce large quantities of cannabinoid and terpenoid specialised metabolites with known medicinal and commercial value. To address this lack of epigenomic data, we mapped H3K4 trimethylation, H3K56 acetylation, H3K27 trimethylation post-translational modifications and the histone variant H2A.Z, using chromatin immunoprecipitation, in C. sativa glandular trichomes, leaf, and stem tissues. Corresponding transcriptomic (RNA-seq) datasets were integrated, and tissue-specific analyses conducted to relate chromatin states to glandular trichome specific gene expression. RESULTS The promoters of cannabinoid and terpenoid biosynthetic genes, specialised metabolite transporter genes, defence related genes, and starch and sucrose metabolism were enriched specifically in trichomes for histone marks H3K4me3 and H3K56ac, consistent with active transcription. We identified putative trichome-specific enhancer elements by identifying intergenic regions of H3K56ac enrichment, a histone mark that maintains enhancer accessibility, then associated these to putative target genes using the tissue specific gene transcriptomic data. Bi-valent chromatin loci specific to glandular trichomes, marked with H3K4 trimethylation and H3K27 trimethylation, were associated with genes of MAPK signalling pathways and plant specialised metabolism pathways, supporting recent hypotheses that implicate bi-valent chromatin in plant defence. The histone variant H2A.Z was largely found in intergenic regions and enriched in chromatin that contained genes involved in DNA homeostasis. CONCLUSION We report the first genome-wide histone post-translational modification maps for C. sativa glandular trichomes, and more broadly for glandular trichomes in plants. Our findings have implications in plant adaptation and stress responses and provide a basis for enhancer-mediated, targeted, gene transformation studies in plant glandular trichomes.
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Affiliation(s)
- Lee J Conneely
- La Trobe Institute for Sustainable Agriculture and Food, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
- Australian Research Council Research Hub for Medicinal Agriculture, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
- Australian Research Council Centre of Excellence in Plants for Space, La Trobe University, Bundoora, VIC, Australia
| | - Bhavna Hurgobin
- La Trobe Institute for Sustainable Agriculture and Food, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
- Australian Research Council Research Hub for Medicinal Agriculture, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
| | - Sophia Ng
- La Trobe Institute for Sustainable Agriculture and Food, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
- Australian Research Council Research Hub for Medicinal Agriculture, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
| | - Muluneh Tamiru-Oli
- La Trobe Institute for Sustainable Agriculture and Food, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
- Australian Research Council Research Hub for Medicinal Agriculture, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia
| | - Mathew G Lewsey
- La Trobe Institute for Sustainable Agriculture and Food, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia.
- Australian Research Council Research Hub for Medicinal Agriculture, La Trobe University, AgriBio Building, Bundoora, VIC, 3086, Australia.
- Australian Research Council Centre of Excellence in Plants for Space, La Trobe University, Bundoora, VIC, Australia.
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5
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Wighard S, Sommer RJ. The Role of Epigenetic Switches in Polyphenism Control: Implications from a Nematode Model for the Developmental Regulation of Alternative Phenotypes. BIOLOGY 2024; 13:922. [PMID: 39596877 PMCID: PMC11591871 DOI: 10.3390/biology13110922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2024] [Revised: 11/05/2024] [Accepted: 11/11/2024] [Indexed: 11/29/2024]
Abstract
Polyphenisms, the capability of organisms to form two or more alternative phenotypes in response to environmental variation, are prevalent in nature. However, associated molecular mechanisms and potential general principles of polyphenisms among major organismal groups remain currently unknown. This review focuses on an emerging model system for developmental plasticity and polyphenism research, the nematode Pristionchus pacificus and explores mechanistic insight obtained through unbiased genetic, experimental and natural variation studies. Resulting findings identify a central role for epigenetic switches in the environmental control of alternative phenotypes and their micro-and macroevolution. Several features observed in P. pacificus are shared with insects and plants and might become general principles for the control of polyphenisms during development.
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Affiliation(s)
- Sara Wighard
- Max Planck Institute for Biology Tuebingen, Department for Integrative Evolutionary Biology, 72076 Tuebingen, Germany;
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Ralf J. Sommer
- Max Planck Institute for Biology Tuebingen, Department for Integrative Evolutionary Biology, 72076 Tuebingen, Germany;
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6
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Karin O. EnhancerNet: a predictive model of cell identity dynamics through enhancer selection. Development 2024; 151:dev202997. [PMID: 39289870 PMCID: PMC11488642 DOI: 10.1242/dev.202997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 09/06/2024] [Indexed: 09/19/2024]
Abstract
Understanding how cell identity is encoded by the genome and acquired during differentiation is a central challenge in cell biology. I have developed a theoretical framework called EnhancerNet, which models the regulation of cell identity through the lens of transcription factor-enhancer interactions. I demonstrate that autoregulation in these interactions imposes a constraint on the model, resulting in simplified dynamics that can be parameterized from observed cell identities. Despite its simplicity, EnhancerNet recapitulates a broad range of experimental observations on cell identity dynamics, including enhancer selection, cell fate induction, hierarchical differentiation through multipotent progenitor states and direct reprogramming by transcription factor overexpression. The model makes specific quantitative predictions, reproducing known reprogramming recipes and the complex haematopoietic differentiation hierarchy without fitting unobserved parameters. EnhancerNet provides insights into how new cell types could evolve and highlights the functional importance of distal regulatory elements with dynamic chromatin in multicellular evolution.
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Affiliation(s)
- Omer Karin
- Department of Mathematics, Imperial College London, London, SW7 2AZ, UK
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7
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Manivannan V, Inamdar MM, Padinhateeri R. Role of diffusion and reaction of the constituents in spreading of histone modification marks. PLoS Comput Biol 2024; 20:e1012235. [PMID: 38991050 PMCID: PMC11265668 DOI: 10.1371/journal.pcbi.1012235] [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: 12/29/2023] [Revised: 07/23/2024] [Accepted: 06/06/2024] [Indexed: 07/13/2024] Open
Abstract
Cells switch genes ON or OFF by altering the state of chromatin via histone modifications at specific regulatory locations along the chromatin polymer. These gene regulation processes are carried out by a network of reactions in which the histone marks spread to neighboring regions with the help of enzymes. In the literature, this spreading has been studied as a purely kinetic, non-diffusive process considering the interactions between neighboring nucleosomes. In this work, we go beyond this framework and study the spreading of modifications using a reaction-diffusion (RD) model accounting for the diffusion of the constituents. We quantitatively segregate the modification profiles generated from kinetic and RD models. The diffusion and degradation of enzymes set a natural length scale for limiting the domain size of modification spreading, and the resulting enzyme limitation is inherent in our model. We also demonstrate the emergence of confined modification domains without the explicit requirement of a nucleation site. We explore polymer compaction effects on spreading and show that single-cell domains may differ from averaged profiles. We find that the modification profiles from our model are comparable with existing H3K9me3 data of S. pombe.
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Affiliation(s)
- Vinoth Manivannan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Mandar M. Inamdar
- Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
- Sunita Sanghi Centre of Aging and Neurodegenerative Diseases, Indian Institute of Technology Bombay, Mumbai, India
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8
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Briffa A, Menon G, Movilla Miangolarra A, Howard M. Dissecting Mechanisms of Epigenetic Memory Through Computational Modeling. ANNUAL REVIEW OF PLANT BIOLOGY 2024; 75:265-290. [PMID: 38424070 DOI: 10.1146/annurev-arplant-070523-041445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Understanding the mechanistic basis of epigenetic memory has proven to be a difficult task due to the underlying complexity of the systems involved in its establishment and maintenance. Here, we review the role of computational modeling in helping to unlock this complexity, allowing the dissection of intricate feedback dynamics. We focus on three forms of epigenetic memory encoded in gene regulatory networks, DNA methylation, and histone modifications and discuss the important advantages offered by plant systems in their dissection. We summarize the main modeling approaches involved and highlight the principal conceptual advances that the modeling has enabled through iterative cycles of predictive modeling and experiments. Lastly, we discuss remaining gaps in our understanding and how intertwined theory and experimental approaches might help in their resolution.
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Affiliation(s)
- Amy Briffa
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom;
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Govind Menon
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom;
| | - Ander Movilla Miangolarra
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom;
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom;
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9
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Menon G, Mateo-Bonmati E, Reeck S, Maple R, Wu Z, Ietswaart R, Dean C, Howard M. Proximal termination generates a transcriptional state that determines the rate of establishment of Polycomb silencing. Mol Cell 2024; 84:2255-2271.e9. [PMID: 38851186 DOI: 10.1016/j.molcel.2024.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 02/28/2024] [Accepted: 05/14/2024] [Indexed: 06/10/2024]
Abstract
The mechanisms and timescales controlling de novo establishment of chromatin-mediated transcriptional silencing by Polycomb repressive complex 2 (PRC2) are unclear. Here, we investigate PRC2 silencing at Arabidopsis FLOWERING LOCUS C (FLC), known to involve co-transcriptional RNA processing, histone demethylation activity, and PRC2 function, but so far not mechanistically connected. We develop and test a computational model describing proximal polyadenylation/termination mediated by the RNA-binding protein FCA that induces H3K4me1 removal by the histone demethylase FLD. H3K4me1 removal feeds back to reduce RNA polymerase II (RNA Pol II) processivity and thus enhance early termination, thereby repressing productive transcription. The model predicts that this transcription-coupled repression controls the level of transcriptional antagonism to PRC2 action. Thus, the effectiveness of this repression dictates the timescale for establishment of PRC2/H3K27me3 silencing. We experimentally validate these mechanistic model predictions, revealing that co-transcriptional processing sets the level of productive transcription at the locus, which then determines the rate of the ON-to-OFF switch to PRC2 silencing.
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Affiliation(s)
- Govind Menon
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Eduardo Mateo-Bonmati
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Svenja Reeck
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Robert Maple
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Zhe Wu
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Robert Ietswaart
- Harvard Medical School, Department of Genetics, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Caroline Dean
- Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
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10
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Movilla Miangolarra A, Saxton DS, Yan Z, Rine J, Howard M. Two-way feedback between chromatin compaction and histone modification state explains Saccharomyces cerevisiae heterochromatin bistability. Proc Natl Acad Sci U S A 2024; 121:e2403316121. [PMID: 38593082 PMCID: PMC11032488 DOI: 10.1073/pnas.2403316121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Accepted: 03/02/2024] [Indexed: 04/11/2024] Open
Abstract
Compact chromatin is closely linked with gene silencing in part by sterically masking access to promoters, inhibiting transcription factor binding and preventing polymerase from efficiently transcribing a gene. However, a broader hypothesis suggests that chromatin compaction can be both a cause and a consequence of the locus histone modification state, with a tight bidirectional interaction underpinning bistable transcriptional states. To rigorously test this hypothesis, we developed a mathematical model for the dynamics of the HMR locus in Saccharomyces cerevisiae, that incorporates activating histone modifications, silencing proteins, and a dynamic, acetylation-dependent, three-dimensional locus size. Chromatin compaction enhances silencer protein binding, which in turn feeds back to remove activating histone modifications, leading to further compaction. The bistable output of the model was in good agreement with prior quantitative data, including switching rates from expressed to silent states (and vice versa), and protein binding/histone modification levels within the locus. We then tested the model by predicting changes in switching rates as the genetic length of the locus was increased, which were then experimentally verified. Such bidirectional feedback between chromatin compaction and the histone modification state may be a widespread and important regulatory mechanism given the hallmarks of many heterochromatic regions: physical chromatin compaction and dimerizing (or multivalent) silencing proteins.
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Affiliation(s)
| | - Daniel S. Saxton
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - Zhi Yan
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - Jasper Rine
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, NorwichNR4 7UH, United Kingdom
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11
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Faivre L, Kinscher NF, Kuhlmann AB, Xu X, Kaufmann K, Schubert D. Cold stress induces rapid gene-specific changes in the levels of H3K4me3 and H3K27me3 in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2024; 15:1390144. [PMID: 38685963 PMCID: PMC11056581 DOI: 10.3389/fpls.2024.1390144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 03/27/2024] [Indexed: 05/02/2024]
Abstract
When exposed to low temperatures, plants undergo a drastic reprogramming of their transcriptome in order to adapt to their new environmental conditions, which primes them for potential freezing temperatures. While the involvement of transcription factors in this process, termed cold acclimation, has been deeply investigated, the potential contribution of chromatin regulation remains largely unclear. A large proportion of cold-inducible genes carries the repressive mark histone 3 lysine 27 trimethylation (H3K27me3), which has been hypothesized as maintaining them in a silenced state in the absence of stress, but which would need to be removed or counteracted upon stress perception. However, the fate of H3K27me3 during cold exposure has not been studied genome-wide. In this study, we offer an epigenome profiling of H3K27me3 and its antagonistic active mark H3K4me3 during short-term cold exposure. Both chromatin marks undergo rapid redistribution upon cold exposure, however, the gene sets undergoing H3K4me3 or H3K27me3 differential methylation are distinct, refuting the simplistic idea that gene activation relies on a switch from an H3K27me3 repressed chromatin to an active form enriched in H3K4me3. Coupling the ChIP-seq experiments with transcriptome profiling reveals that differential histone methylation only weakly correlates with changes in expression. Interestingly, only a subset of cold-regulated genes lose H3K27me3 during their induction, indicating that H3K27me3 is not an obstacle to transcriptional activation. In the H3K27me3 methyltransferase curly leaf (clf) mutant, many cold regulated genes display reduced H3K27me3 levels but their transcriptional activity is not altered prior or during a cold exposure, suggesting that H3K27me3 may serve a more intricate role in the cold response than simply repressing the cold-inducible genes in naïve conditions.
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Affiliation(s)
- Léa Faivre
- Epigenetics of Plants, Freie Universität Berlin, Berlin, Germany
| | | | | | - Xiaocai Xu
- Department for Plant Cell and Molecular Biology, Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Kerstin Kaufmann
- Department for Plant Cell and Molecular Biology, Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Daniel Schubert
- Epigenetics of Plants, Freie Universität Berlin, Berlin, Germany
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12
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Murphy SE, Boettiger AN. Polycomb repression of Hox genes involves spatial feedback but not domain compaction or phase transition. Nat Genet 2024; 56:493-504. [PMID: 38361032 DOI: 10.1038/s41588-024-01661-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 01/10/2024] [Indexed: 02/17/2024]
Abstract
Polycomb group proteins have a critical role in silencing transcription during development. It is commonly proposed that Polycomb-dependent changes in genome folding, which compact chromatin, contribute directly to repression by blocking the binding of activating complexes. Recently, it has also been argued that liquid-liquid demixing of Polycomb proteins facilitates this compaction and repression by phase-separating target genes into a membraneless compartment. To test these models, we used Optical Reconstruction of Chromatin Architecture to trace the Hoxa gene cluster, a canonical Polycomb target, in thousands of single cells. Across multiple cell types, we find that Polycomb-bound chromatin frequently explores decompact states and partial mixing with neighboring chromatin, while remaining uniformly repressed, challenging the repression-by-compaction or phase-separation models. Using polymer simulations, we show that these observed flexible ensembles can be explained by 'spatial feedback'-transient contacts that contribute to the propagation of the epigenetic state (epigenetic memory), without inducing a globular organization.
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Affiliation(s)
- Sedona Eve Murphy
- Department of Genetics, Stanford University, Stanford, CA, USA
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Cell Biology, Yale University, New Haven, CT, USA
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13
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Owen JA, Osmanović D, Mirny L. Design principles of 3D epigenetic memory systems. Science 2023; 382:eadg3053. [PMID: 37972190 PMCID: PMC11075759 DOI: 10.1126/science.adg3053] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 09/28/2023] [Indexed: 11/19/2023]
Abstract
Cells remember their identities, in part, by using epigenetic marks-chemical modifications placed along the genome. How can mark patterns remain stable over cell generations despite their constant erosion by replication and other processes? We developed a theoretical model that reveals that three-dimensional (3D) genome organization can stabilize epigenetic memory as long as (i) there is a large density difference between chromatin compartments, (ii) modifying "reader-writer" enzymes spread marks in three dimensions, and (iii) the enzymes are limited in abundance relative to their histone substrates. Analogous to an associative memory that encodes memory in neuronal connectivity, mark patterns are encoded in a 3D network of chromosomal contacts. Our model provides a unified account of diverse observations and reveals a key role of 3D genome organization in epigenetic memory.
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Affiliation(s)
- Jeremy A. Owen
- Department of Physics, Massachusetts Institute of Technology; Cambridge, USA
| | - Dino Osmanović
- Department of Mechanical and Aeronautical Engineering, UCLA; Los Angeles, USA
| | - Leonid Mirny
- Department of Physics, Massachusetts Institute of Technology; Cambridge, USA
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14
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Depierre D, Perrois C, Schickele N, Lhoumaud P, Abdi-Galab M, Fosseprez O, Heurteau A, Margueron R, Cuvier O. Chromatin in 3D distinguishes dMes-4/NSD and Hypb/dSet2 in protecting genes from H3K27me3 silencing. Life Sci Alliance 2023; 6:e202302038. [PMID: 37684044 PMCID: PMC10491495 DOI: 10.26508/lsa.202302038] [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: 03/14/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 09/10/2023] Open
Abstract
Cell type-specific barcoding of genomes requires the establishment of hundreds of heterochromatin domains where heterochromatin-associated repressive complexes hinder chromatin accessibility thereby silencing genes. At heterochromatin-euchromatin borders, regulation of accessibility not only depends on the delimitation of heterochromatin but may also involve interplays with nearby genes and their transcriptional activity, or alternatively on histone modifiers, chromatin barrier insulators, and more global demarcation of chromosomes into 3D compartmentalized domains and topological-associating domain (TADs). Here, we show that depletion of H3K36 di- or tri-methyl histone methyltransferases dMes-4/NSD or Hypb/dSet2 induces reproducible increasing levels of H3K27me3 at heterochromatin borders including in nearby promoters, thereby repressing hundreds of genes. Furthermore, dMes-4/NSD influences genes demarcated by insulators and TAD borders, within chromatin hubs, unlike transcription-coupled action of Hypb/dSet2 that protects genes independently of TADs. Insulator mutants recapitulate the increase of H3K27me3 upon dMes-4/NSD depletion unlike Hypb/dSet2. Hi-C data demonstrate how dMes-4/NSD blocks propagation of long-range interactions onto active regions. Our data highlight distinct mechanisms protecting genes from H3K27me3 silencing, highlighting a direct influence of H3K36me on repressive TADs.
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Affiliation(s)
- David Depierre
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Charlène Perrois
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Naomi Schickele
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Priscillia Lhoumaud
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Mahdia Abdi-Galab
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Olivier Fosseprez
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Alexandre Heurteau
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
| | - Raphaël Margueron
- Institut Curie, Paris Sciences et Lettres Research University; INSERM U934/ CNRS UMR3215, Paris, France
| | - Olivier Cuvier
- Chromatin Dynamics and Cell Proliferation, Center of Integrative Biology, Molecular, Cellular and Developmental Biology (MCD/UMR5087), CNRS, Université Paul Sabatier de Toulouse, Toulouse, France
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15
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Franco-Echevarría E, Nielsen M, Schulten A, Cheema J, Morgan TE, Bienz M, Dean C. Distinct accessory roles of Arabidopsis VEL proteins in Polycomb silencing. Genes Dev 2023; 37:801-817. [PMID: 37734835 PMCID: PMC7615239 DOI: 10.1101/gad.350814.123] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/31/2023] [Indexed: 09/23/2023]
Abstract
Polycomb repressive complex 2 (PRC2) mediates epigenetic silencing of target genes in animals and plants. In Arabidopsis, PRC2 is required for the cold-induced epigenetic silencing of the FLC floral repressor locus to align flowering with spring. During this process, PRC2 relies on VEL accessory factors, including the constitutively expressed VRN5 and the cold-induced VIN3. The VEL proteins are physically associated with PRC2, but their individual functions remain unclear. Here, we show an intimate association between recombinant VRN5 and multiple components within a reconstituted PRC2, dependent on a compact conformation of VRN5 central domains. Key residues mediating this compact conformation are conserved among VRN5 orthologs across the plant kingdom. In contrast, VIN3 interacts with VAL1, a transcriptional repressor that binds directly to FLC These associations differentially affect their role in H3K27me deposition: Both proteins are required for H3K27me3, but only VRN5 is necessary for H3K27me2. Although originally defined as vernalization regulators, VIN3 and VRN5 coassociate with many targets in the Arabidopsis genome that are modified with H3K27me3. Our work therefore reveals the distinct accessory roles for VEL proteins in conferring cold-induced silencing on FLC, with broad relevance for PRC2 targets generally.
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Affiliation(s)
- Elsa Franco-Echevarría
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Mathias Nielsen
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Anna Schulten
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Jitender Cheema
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Tomos E Morgan
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom
| | - Mariann Bienz
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom;
| | - Caroline Dean
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom;
- John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
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16
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Miangolarra AM, Saxton DS, Yan Z, Rine J, Howard M. Two-way feedback between chromatin compaction and histone modification state explains S. cerevisiae heterochromatin bistability. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.12.552948. [PMID: 37645983 PMCID: PMC10461966 DOI: 10.1101/2023.08.12.552948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Compact chromatin is closely linked with gene silencing in part by sterically masking access to promoters, inhibiting transcription factor binding and preventing polymerase from efficiently transcribing a gene. Here, we propose a broader view: chromatin compaction can be both a cause and a consequence of the histone modification state, and this tight bidirectional interaction can underpin bistable transcriptional states. To test this theory, we developed a mathematical model for the dynamics of the HMR locus in S. cerevisiae, that incorporates activating histone modifications, silencing proteins and a dynamic, acetylation-dependent, three-dimensional locus size. Chromatin compaction enhances silencer protein binding, which in turn feeds back to remove activating histone modifications, leading to further compaction. The bistable output of the model was in good agreement with prior quantitative data, including switching rates from expressed to silent states, and vice versa, and protein binding levels within the locus. We then tested the model by predicting changes in switching rates as the genetic length of the locus was increased, which were then experimentally verified. This bidirectional feedback between chromatin compaction and the histone modification state may be an important regulatory mechanism at many loci.
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Affiliation(s)
- Ander Movilla Miangolarra
- Dept. of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Daniel S Saxton
- Dept. of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Zhi Yan
- Dept. of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Jasper Rine
- Dept. of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Martin Howard
- Dept. of Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
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17
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Antoniou-Kourounioti RL, Meschichi A, Reeck S, Berry S, Menon G, Zhao Y, Fozard J, Holmes T, Zhao L, Wang H, Hartley M, Dean C, Rosa S, Howard M. Integrating analog and digital modes of gene expression at Arabidopsis FLC. eLife 2023; 12:e79743. [PMID: 37466633 DOI: 10.7554/elife.79743] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/25/2023] [Indexed: 07/20/2023] Open
Abstract
Quantitative gene regulation at the cell population level can be achieved by two fundamentally different modes of regulation at individual gene copies. A 'digital' mode involves binary ON/OFF expression states, with population-level variation arising from the proportion of gene copies in each state, while an 'analog' mode involves graded expression levels at each gene copy. At the Arabidopsis floral repressor FLOWERING LOCUS C (FLC), 'digital' Polycomb silencing is known to facilitate quantitative epigenetic memory in response to cold. However, whether FLC regulation before cold involves analog or digital modes is unknown. Using quantitative fluorescent imaging of FLC mRNA and protein, together with mathematical modeling, we find that FLC expression before cold is regulated by both analog and digital modes. We observe a temporal separation between the two modes, with analog preceding digital. The analog mode can maintain intermediate expression levels at individual FLC gene copies, before subsequent digital silencing, consistent with the copies switching OFF stochastically and heritably without cold. This switch leads to a slow reduction in FLC expression at the cell population level. These data present a new paradigm for gradual repression, elucidating how analog transcriptional and digital epigenetic memory pathways can be integrated.
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Affiliation(s)
- Rea L Antoniou-Kourounioti
- Department of Computational and Systems Biology, John Innes Centre, Norwich, United Kingdom
- School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anis Meschichi
- Swedish University of Agricultural Sciences, Plant Biology Department, Uppsala, Sweden
| | - Svenja Reeck
- Department of Cell and Developmental Biology, John Innes Centre, Norwich, United Kingdom
| | - Scott Berry
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Govind Menon
- Department of Computational and Systems Biology, John Innes Centre, Norwich, United Kingdom
| | - Yusheng Zhao
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - John Fozard
- Department of Computational and Systems Biology, John Innes Centre, Norwich, United Kingdom
| | - Terri Holmes
- Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia, Norwich, United Kingdom
| | - Lihua Zhao
- Swedish University of Agricultural Sciences, Plant Biology Department, Uppsala, Sweden
| | - Huamei Wang
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Matthew Hartley
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI), Wellcome Genome Campus, Cambridge, United Kingdom
| | - Caroline Dean
- Department of Cell and Developmental Biology, John Innes Centre, Norwich, United Kingdom
| | - Stefanie Rosa
- Swedish University of Agricultural Sciences, Plant Biology Department, Uppsala, Sweden
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich, United Kingdom
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18
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Auge G, Hankofer V, Groth M, Antoniou-Kourounioti R, Ratikainen I, Lampei C. Plant environmental memory: implications, mechanisms and opportunities for plant scientists and beyond. AOB PLANTS 2023; 15:plad032. [PMID: 37415723 PMCID: PMC10321398 DOI: 10.1093/aobpla/plad032] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 06/01/2023] [Indexed: 07/08/2023]
Abstract
Plants are extremely plastic organisms. They continuously receive and integrate environmental information and adjust their growth and development to favour fitness and survival. When this integration of information affects subsequent life stages or the development of subsequent generations, it can be considered an environmental memory. Thus, plant memory is a relevant mechanism by which plants respond adaptively to different environments. If the cost of maintaining the response is offset by its benefits, it may influence evolutionary trajectories. As such, plant memory has a sophisticated underlying molecular mechanism with multiple components and layers. Nonetheless, when mathematical modelling is combined with knowledge of ecological, physiological, and developmental effects as well as molecular mechanisms as a tool for understanding plant memory, the combined potential becomes unfathomable for the management of plant communities in natural and agricultural ecosystems. In this review, we summarize recent advances in the understanding of plant memory, discuss the ecological requirements for its evolution, outline the multilayered molecular network and mechanisms required for accurate and fail-proof plant responses to variable environments, point out the direct involvement of the plant metabolism and discuss the tremendous potential of various types of models to further our understanding of the plant's environmental memory. Throughout, we emphasize the use of plant memory as a tool to unlock the secrets of the natural world.
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Affiliation(s)
| | - Valentin Hankofer
- Institute of Biochemical Plant Pathology, Helmholtz Munich, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Neuherberg, Germany
| | - Martin Groth
- Institute of Functional Epigenetics, Helmholtz Munich, Ingolstädter Landstraße 1, 85764 Oberschleißheim, Neuherberg, Germany
| | - Rea Antoniou-Kourounioti
- School of Molecular Biosciences, University of Glasgow, Sir James Black Building, University Ave, Glasgow G12 8QQ, UK
| | - Irja Ratikainen
- Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, Realfagbygget, NO-7491 Trondheim, Norway
| | - Christian Lampei
- Department of Biology (FB17), Plant Ecology and Geobotany Group, University of Marburg, Karl-von-Frisch-Straße 8, 35032 Marburg, Germany
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19
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Noviello G, Gjaltema RAF, Schulz EG. CasTuner is a degron and CRISPR/Cas-based toolkit for analog tuning of endogenous gene expression. Nat Commun 2023; 14:3225. [PMID: 37270532 DOI: 10.1038/s41467-023-38909-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 05/22/2023] [Indexed: 06/05/2023] Open
Abstract
Certain cellular processes are dose-dependent, requiring specific quantities or stoichiometries of gene products, as exemplified by haploinsufficiency and sex-chromosome dosage compensation. Understanding dosage-sensitive processes requires tools to quantitatively modulate protein abundance. Here we present CasTuner, a CRISPR-based toolkit for analog tuning of endogenous gene expression. The system exploits Cas-derived repressors that are quantitatively tuned by ligand titration through a FKBP12F36V degron domain. CasTuner can be applied at the transcriptional or post-transcriptional level using a histone deacetylase (hHDAC4) fused to dCas9, or the RNA-targeting CasRx, respectively. We demonstrate analog tuning of gene expression homogeneously across cells in mouse and human cells, as opposed to KRAB-dependent CRISPR-interference systems, which exhibit digital repression. Finally, we quantify the system's dynamics and use it to measure dose-response relationships of NANOG and OCT4 with their target genes and with the cellular phenotype. CasTuner thus provides an easy-to-implement tool to study dose-responsive processes in their physiological context.
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Affiliation(s)
- Gemma Noviello
- Systems Epigenetics, Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, 14195, Berlin, Germany
| | - Rutger A F Gjaltema
- Systems Epigenetics, Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, 14195, Berlin, Germany
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Edda G Schulz
- Systems Epigenetics, Otto Warburg Laboratories, Max Planck Institute for Molecular Genetics, 14195, Berlin, Germany.
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20
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Abdulla AZ, Salari H, Tortora MMC, Vaillant C, Jost D. 4D epigenomics: deciphering the coupling between genome folding and epigenomic regulation with biophysical modeling. Curr Opin Genet Dev 2023; 79:102033. [PMID: 36893485 DOI: 10.1016/j.gde.2023.102033] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/25/2023] [Accepted: 02/20/2023] [Indexed: 03/09/2023]
Abstract
Recent experimental observations suggest a strong coupling between the 3D nuclear chromosome organization and epigenomics. However, the mechanistic and functional bases of such interplay remain elusive. In this review, we describe how biophysical modeling has been instrumental in characterizing how genome folding may impact the formation of epigenomic domains and, conversely, how epigenomic marks may affect chromosome conformation. Finally, we discuss how this mutual feedback loop between chromatin organization and epigenome regulation, via the formation of physicochemical nanoreactors, may represent a key functional role of 3D compartmentalization in the assembly and maintenance of stable - but yet plastic - epigenomic landscapes.
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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. https://twitter.com/@AmithZafal
| | - Hossein Salari
- 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. https://twitter.com/@hosseinsalari65
| | - Maxime M C Tortora
- 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
| | - Cédric Vaillant
- École Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, 46 Allée d'Italie, 69007 Lyon, France.
| | - Daniel Jost
- 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.
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21
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Macrae TA, Fothergill-Robinson J, Ramalho-Santos M. Regulation, functions and transmission of bivalent chromatin during mammalian development. Nat Rev Mol Cell Biol 2023; 24:6-26. [PMID: 36028557 DOI: 10.1038/s41580-022-00518-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/05/2022] [Indexed: 12/25/2022]
Abstract
Cells differentiate and progress through development guided by a dynamic chromatin landscape that mediates gene expression programmes. During development, mammalian cells display a paradoxical chromatin state: histone modifications associated with gene activation (trimethylated histone H3 Lys4 (H3K4me3)) and with gene repression (trimethylated H3 Lys27 (H3K27me3)) co-occur at promoters of developmental genes. This bivalent chromatin modification state is thought to poise important regulatory genes for expression or repression during cell-lineage specification. In this Review, we discuss recent work that has expanded our understanding of the molecular basis of bivalent chromatin and its contributions to mammalian development. We describe the factors that establish bivalency, especially histone-lysine N-methyltransferase 2B (KMT2B) and Polycomb repressive complex 2 (PRC2), and consider evidence indicating that PRC1 shapes bivalency and may contribute to its transmission between generations. We posit that bivalency is a key feature of germline and embryonic stem cells, as well as other types of stem and progenitor cells. Finally, we discuss the relevance of bivalent chromtin to human development and cancer, and outline avenues of future research.
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Affiliation(s)
- Trisha A Macrae
- Medical Scientist Training Program, University of California, San Francisco, San Francisco, CA, USA.
| | - Julie Fothergill-Robinson
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Miguel Ramalho-Santos
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
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22
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Mikulski P, Wolff P, Lu T, Nielsen M, Echevarria EF, Zhu D, Questa JI, Saalbach G, Martins C, Dean C. VAL1 acts as an assembly platform co-ordinating co-transcriptional repression and chromatin regulation at Arabidopsis FLC. Nat Commun 2022; 13:5542. [PMID: 36130923 PMCID: PMC9492735 DOI: 10.1038/s41467-022-32897-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 08/23/2022] [Indexed: 12/04/2022] Open
Abstract
Polycomb (PcG) silencing is crucial for development, but how targets are specified remains incompletely understood. The cold-induced Polycomb Repressive Complex 2 (PRC2) silencing of Arabidopsis thaliana FLOWERING LOCUS C (FLC) provides an excellent system to elucidate PcG regulation. Association of the DNA binding protein VAL1 to FLC PcG nucleation regionis an important step. VAL1 co-immunoprecipitates APOPTOSIS AND SPLICING ASSOCIATED PROTEIN (ASAP) complex and PRC1. Here, we show that ASAP and PRC1 are necessary for co-transcriptional repression and chromatin regulation at FLC. ASAP mutants affect FLC transcription in warm conditions, but the rate of FLC silencing in the cold is unaffected. PRC1-mediated H2Aub accumulation increases at the FLC nucleation region during cold, but unlike the PRC2-delivered H3K27me3, does not spread across the locus. H2Aub thus involved in the transition to epigenetic silencing at FLC, facilitating H3K27me3 accumulation and long-term epigenetic memory. Overall, our work highlights the importance of VAL1 as an assembly platform co-ordinating activities necessary for epigenetic silencing at FLC.
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Affiliation(s)
- Pawel Mikulski
- Cell and Developmental Biology, John Innes Centre, Norwich, UK. .,Department of Biochemistry, University of Oxford, Oxford, UK.
| | - Philip Wolff
- Cell and Developmental Biology, John Innes Centre, Norwich, UK
| | - Tiancong Lu
- Cell and Developmental Biology, John Innes Centre, Norwich, UK.,State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Mathias Nielsen
- Cell and Developmental Biology, John Innes Centre, Norwich, UK
| | | | - Danling Zhu
- Cell and Developmental Biology, John Innes Centre, Norwich, UK.,SUSTech-PKU Institute of Plant and Food Science, Department of Biology, Southern University of Science and Technology, Shenzhen, China
| | - Julia I Questa
- Cell and Developmental Biology, John Innes Centre, Norwich, UK.,Centre for Research in Agricultural Genomics, Barcelona, Spain
| | | | - Carlo Martins
- Biological Chemistry, John Innes Centre, Norwich, UK
| | - Caroline Dean
- Cell and Developmental Biology, John Innes Centre, Norwich, UK. .,MRC Laboratory of Molecular Biology, Cambridge, UK.
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23
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Newar K, Abdulla AZ, Salari H, Fanchon E, Jost D. Dynamical modeling of the H3K27 epigenetic landscape in mouse embryonic stem cells. PLoS Comput Biol 2022; 18:e1010450. [PMID: 36054209 PMCID: PMC9477427 DOI: 10.1371/journal.pcbi.1010450] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 09/15/2022] [Accepted: 07/28/2022] [Indexed: 01/02/2023] Open
Abstract
The Polycomb system via the methylation of the lysine 27 of histone H3 (H3K27) plays central roles in the silencing of many lineage-specific genes during development. Recent experimental evidence suggested that the recruitment of histone modifying enzymes like the Polycomb repressive complex 2 (PRC2) at specific sites and their spreading capacities from these sites are key to the establishment and maintenance of a proper epigenomic landscape around Polycomb-target genes. Here, to test whether such mechanisms, as a minimal set of qualitative rules, are quantitatively compatible with data, we developed a mathematical model that can predict the locus-specific distributions of H3K27 modifications based on previous biochemical knowledge. Within the biological context of mouse embryonic stem cells, our model showed quantitative agreement with experimental profiles of H3K27 acetylation and methylation around Polycomb-target genes in wild-type and mutants. In particular, we demonstrated the key role of the reader-writer module of PRC2 and of the competition between the binding of activating and repressing enzymes in shaping the H3K27 landscape around transcriptional start sites. The predicted dynamics of establishment and maintenance of the repressive trimethylated H3K27 state suggest a slow accumulation, in perfect agreement with experiments. Our approach represents a first step towards a quantitative description of PcG regulation in various cellular contexts and provides a generic framework to better characterize epigenetic regulation in normal or disease situations.
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Affiliation(s)
- Kapil Newar
- Univ Grenoble Alpes, CNRS, TIMC laboratory, UMR 5525, Grenoble, France
| | - Amith Zafal Abdulla
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Université Claude Bernard Lyon 1, Lyon, France
| | - Hossein Salari
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Université Claude Bernard Lyon 1, Lyon, France
| | - Eric Fanchon
- Univ Grenoble Alpes, CNRS, TIMC laboratory, UMR 5525, Grenoble, France
| | - Daniel Jost
- Univ Grenoble Alpes, CNRS, TIMC laboratory, UMR 5525, Grenoble, France
- Laboratoire de Biologie et Modélisation de la Cellule, École Normale Supérieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Université Claude Bernard Lyon 1, Lyon, France
- * E-mail:
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24
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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: 11] [Impact Index Per Article: 3.7] [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.
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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;
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25
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Yang D, Zhao F, Zhu D, Chen X, Kong X, Wu Y, Chen M, Du J, Qu LJ, Wu Z. Progressive chromatin silencing of ABA biosynthesis genes permits seed germination in Arabidopsis. THE PLANT CELL 2022; 34:2871-2891. [PMID: 35522002 PMCID: PMC9338806 DOI: 10.1093/plcell/koac134] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 04/28/2022] [Indexed: 05/08/2023]
Abstract
Seed germination represents a major developmental switch in plants that is vital to agriculture, but how this process is controlled at the chromatin level remains obscure. Here we demonstrate that successful germination in Arabidopsis thaliana requires a chromatin mechanism that progressively silences 9-CIS-EPOXYCAROTENOID DIOXYGENASE 6 (NCED6), which encodes a rate-limiting enzyme in abscisic acid (ABA) biosynthesis, through the cooperative action of the RNA-binding protein RZ-1 and the polycomb repressive complex 2 (PRC2). Simultaneous inactivation of RZ-1 and PRC2 blocked germination and synergistically derepressed NCEDs and hundreds of genes. At NCED6, in part by promoting H3 deacetylation and suppressing H3K4me3, RZ-1 facilitates transcriptional silencing and also an H3K27me3 accumulation process that occurs during seed germination and early seedling growth. Genome-wide analysis revealed that RZ-1 is preferentially required for transcriptional silencing of many PRC2 targets early during seed germination, when H3K27me3 is not yet established. We propose RZ-1 confers a novel silencing mechanism to compensate for and synergize with PRC2. Our work highlights the progressive chromatin silencing of ABA biosynthesis genes via the RNA-binding protein RZ-1 and PRC2 acting in synergy, a process that is vital for seed germination.
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Affiliation(s)
| | | | - Danling Zhu
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xi Chen
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xiangxiong Kong
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yufeng Wu
- National Key Laboratory for Crop Genetics and Germplasm Enhancement, Bioinformatics Center, Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University, Nanjing 210095, China
| | - Min Chen
- State Key Laboratory of Crop Stress Adaptation and Improvement, Henan University, Kaifeng 475000, China
| | - Jiamu Du
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Li-Jia Qu
- State Key Laboratory of Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, College of Life Sciences, Peking University, Beijing 100871, China
| | - Zhe Wu
- Author for correspondence:
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26
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Katava M, Shi G, Thirumalai D. Chromatin dynamics controls epigenetic domain formation. Biophys J 2022; 121:2895-2905. [PMID: 35799447 PMCID: PMC9388564 DOI: 10.1016/j.bpj.2022.07.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 04/17/2022] [Accepted: 06/30/2022] [Indexed: 11/28/2022] Open
Abstract
In multicellular organisms, nucleosomes carry epigenetic information that defines distinct patterns of gene expression, which are inherited over multiple generations. The enhanced capacity for information storage arises by nucleosome modifications, which are triggered by enzymes. Modified nucleosomes can transfer the mark to others that are in proximity by a positive-feedback (modification begets modification) mechanism. We created a generic polymer model, referred to as 3DSpreader, in which each bead, representing a nucleosome, stochastically switches between unmodified (U) and modified (M) states depending on the states of the neighbors. Modification begins at a specific nucleation site (NS) that is permanently in the M state, and could spread to other loci that is dictated by chromatin dynamics. Transfer of marks among the non-nucleation loci occurs stochastically as chromatin evolves in time. If the spreading rate is slower than the chromatin relaxation rate, which is biologically pertinent, then finite-sized domains form, driven by contacts between nucleosomes through a three-dimensional looping mechanism. Surprisingly, simulations based on the 3DSpreader model result in finite bounded domains that arise without the need for any boundary elements. Maintenance of spatially and temporally stable domains requires the presence of the NS, whose removal eliminates finite-sized modified domains. The theoretical predictions are in excellent agreement with experimental data for H3K9me3 spreading in mouse embryonic stem cells.
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Affiliation(s)
- Marina Katava
- Laboratoire de Biochimie Théorique, CNRS, Université de Paris, Paris, France
| | - Guang Shi
- Department of Chemistry, The University of Texas, Austin, Texas
| | - D Thirumalai
- Department of Chemistry, The University of Texas, Austin, Texas.
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27
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DNA sequence-dependent formation of heterochromatin nanodomains. Nat Commun 2022; 13:1861. [PMID: 35387992 PMCID: PMC8986797 DOI: 10.1038/s41467-022-29360-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 03/03/2022] [Indexed: 01/08/2023] Open
Abstract
The mammalian epigenome contains thousands of heterochromatin nanodomains (HNDs) marked by di- and trimethylation of histone H3 at lysine 9 (H3K9me2/3), which have a typical size of 3–10 nucleosomes. However, what governs HND location and extension is only partly understood. Here, we address this issue by introducing the chromatin hierarchical lattice framework (ChromHL) that predicts chromatin state patterns with single-nucleotide resolution. ChromHL is applied to analyse four HND types in mouse embryonic stem cells that are defined by histone methylases SUV39H1/2 or GLP, transcription factor ADNP or chromatin remodeller ATRX. We find that HND patterns can be computed from PAX3/9, ADNP and LINE1 sequence motifs as nucleation sites and boundaries that are determined by DNA sequence (e.g. CTCF binding sites), cooperative interactions between nucleosomes as well as nucleosome-HP1 interactions. Thus, ChromHL rationalizes how patterns of H3K9me2/3 are established and changed via the activity of protein factors in processes like cell differentiation. The ability to predict epigenetic regulation is an important challenge in biology. Here the authors describe heterochromatin nanodomains (HNDs) and compare four different types of H3K9me2/3-marked HNDs in mouse embryonic stem cells. They further develop a computational framework to predict genome-wide HND maps from DNA sequence and protein concentrations, at single-nucleotide resolution.
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28
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Chen L, Wang Y, Liu J, Wang H. Coloured noise induces phenotypic diversity with energy dissipation. Biosystems 2022; 214:104648. [PMID: 35218875 DOI: 10.1016/j.biosystems.2022.104648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 02/17/2022] [Accepted: 02/20/2022] [Indexed: 11/02/2022]
Abstract
Genes integrate many different sources of noise to adapt their survival strategy with energy costs, but how this noise impacts gene phenotype switching is not fully understood. Here, we refine a mechanistic model with multiplicative and additive coloured noise and analyse the influence of noise strength (NS) and autocorrelation time (AT) on gene phenotypic diversity. Different from white noise, we found that in the autocorrelation time-scale plane, increasing the multiplicative noise will broaden the bimodal region of the gene product, and additive noise will induce bimodal region drift from the lower level to the higher level, while the AT will promote this transition. Specifically, the effect of AT on gene expression is similar to a feedback loop; that is, the AT of multiplicative noise will elongate the mean first passage time (MFPT) from the low stable state to the high stable state, but it will reduce the MFPT from the high stable state to the low stable state, and the opposite is true for additive noise. Moreover, these transitions will violate the detailed equilibrium and then consume energy. By effective topology network reconstruction, we found that when the NS is small, the more obvious the bimodality is, the lower the energy dissipation; however, when the NS is large, it will consume more energy with a tendency for bimodality. The overall analysis implies that living organisms will utilize noise strength and its autocorrelation time for better survival in complex and fluctuating environments.
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Affiliation(s)
- Leiyan Chen
- School of Sciences, Hainan University, Haikou, 570228, Hainan, People's Republic of China
| | - Yan Wang
- Department of Neurology, The First Affiliated Hospital, University of South China, HengYang, 421001, Hunan, People's Republic of China
| | - Jinrong Liu
- School of Sciences, Hainan University, Haikou, 570228, Hainan, People's Republic of China
| | - Haohua Wang
- School of Sciences, Hainan University, Haikou, 570228, Hainan, People's Republic of China; Hainan University, Coll Forestry, Key Laboratory of Genetics & Germplasm Innovation Tropical Special Fo, Ministry of Education, Haikou, 570228, Hainan, People's Republic of China; Hainan University, Key Laboratory of Engineering Modeling and Statistical Computation of Hainan Province, Haikou, 570228, Hainan, People's Republic of China.
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29
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Ramakrishnan N, Pillai SRB, Padinhateeri R. High fidelity epigenetic inheritance: Information theoretic model predicts threshold filling of histone modifications post replication. PLoS Comput Biol 2022; 18:e1009861. [PMID: 35176029 PMCID: PMC8903295 DOI: 10.1371/journal.pcbi.1009861] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 03/08/2022] [Accepted: 01/24/2022] [Indexed: 02/06/2023] Open
Abstract
During cell devision, maintaining the epigenetic information encoded in histone modification patterns is crucial for survival and identity of cells. The faithful inheritance of the histone marks from the parental to the daughter strands is a puzzle, given that each strand gets only half of the parental nucleosomes. Mapping DNA replication and reconstruction of modifications to equivalent problems in communication of information, we ask how well enzymes can recover the parental modifications, if they were ideal computing machines. Studying a parameter regime where realistic enzymes can function, our analysis predicts that enzymes may implement a critical threshold filling algorithm which fills unmodified regions of length at most k. This algorithm, motivated from communication theory, is derived from the maximum à posteriori probability (MAP) decoding which identifies the most probable modification sequence based on available observations. Simulations using our method produce modification patterns similar to what has been observed in recent experiments. We also show that our results can be naturally extended to explain inheritance of spatially distinct antagonistic modifications.
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Affiliation(s)
- Nithya Ramakrishnan
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Sibi Raj B. Pillai
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Ranjith Padinhateeri
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
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30
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Menon G, Howard M. Investigating Histone Modification Dynamics by Mechanistic Computational Modeling. Methods Mol Biol 2022; 2529:441-473. [PMID: 35733026 DOI: 10.1007/978-1-0716-2481-4_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The maintenance of transcriptional states regulated by histone modifications and controlled switching between these states are fundamental concepts in our understanding of nucleosome-mediated epigenetic memory. Any approach relying on genome-wide bioinformatic analyses alone offers limited scope for dissecting the molecular mechanisms involved in maintenance and switching. Mechanistic mathematical models-describing the dynamics of histone modifications at individual genomic loci-offer an alternative way to investigate these mechanisms. These models, in conjunction with quantitative experimental data-ChIP data, quantification of mRNA levels, and single-cell fluorescence tracking in clonal lineages-can generate predictions that drive more targeted experiments, allowing us to understand mechanisms that would be challenging to unravel by a purely experimental approach. In this chapter, we describe a generic stochastic modeling framework that can be used to capture histone modification dynamics and associated molecular processes-including transcription and read-write feedback by chromatin modifying complexes-at individual genomic loci. Using a specific example-transcriptional silencing by Polycomb-mediated H3K27 methylation-we demonstrate how to construct and simulate a stochastic histone modification model. We provide a step-by-step guide to programming simulations for such a model and discuss how to analyze the simulation output.
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Affiliation(s)
- Govind Menon
- Department of Computational and Systems Biology, John Innes Centre, Norwich, UK
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich, UK.
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31
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Kumar S, Kaur S, Seem K, Kumar S, Mohapatra T. Understanding 3D Genome Organization and Its Effect on Transcriptional Gene Regulation Under Environmental Stress in Plant: A Chromatin Perspective. Front Cell Dev Biol 2021; 9:774719. [PMID: 34957106 PMCID: PMC8692796 DOI: 10.3389/fcell.2021.774719] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 11/23/2021] [Indexed: 01/17/2023] Open
Abstract
The genome of a eukaryotic organism is comprised of a supra-molecular complex of chromatin fibers and intricately folded three-dimensional (3D) structures. Chromosomal interactions and topological changes in response to the developmental and/or environmental stimuli affect gene expression. Chromatin architecture plays important roles in DNA replication, gene expression, and genome integrity. Higher-order chromatin organizations like chromosome territories (CTs), A/B compartments, topologically associating domains (TADs), and chromatin loops vary among cells, tissues, and species depending on the developmental stage and/or environmental conditions (4D genomics). Every chromosome occupies a separate territory in the interphase nucleus and forms the top layer of hierarchical structure (CTs) in most of the eukaryotes. While the A and B compartments are associated with active (euchromatic) and inactive (heterochromatic) chromatin, respectively, having well-defined genomic/epigenomic features, TADs are the structural units of chromatin. Chromatin architecture like TADs as well as the local interactions between promoter and regulatory elements correlates with the chromatin activity, which alters during environmental stresses due to relocalization of the architectural proteins. Moreover, chromatin looping brings the gene and regulatory elements in close proximity for interactions. The intricate relationship between nucleotide sequence and chromatin architecture requires a more comprehensive understanding to unravel the genome organization and genetic plasticity. During the last decade, advances in chromatin conformation capture techniques for unravelling 3D genome organizations have improved our understanding of genome biology. However, the recent advances, such as Hi-C and ChIA-PET, have substantially increased the resolution, throughput as well our interest in analysing genome organizations. The present review provides an overview of the historical and contemporary perspectives of chromosome conformation capture technologies, their applications in functional genomics, and the constraints in predicting 3D genome organization. We also discuss the future perspectives of understanding high-order chromatin organizations in deciphering transcriptional regulation of gene expression under environmental stress (4D genomics). These might help design the climate-smart crop to meet the ever-growing demands of food, feed, and fodder.
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Affiliation(s)
- Suresh Kumar
- Division of Biochemistry, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Simardeep Kaur
- Division of Biochemistry, ICAR-Indian Agricultural Research Institute, New Delhi, India
| | - Karishma Seem
- Division of Biochemistry, ICAR-Indian Agricultural Research Institute, New Delhi, India
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32
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Blackledge NP, Klose RJ. The molecular principles of gene regulation by Polycomb repressive complexes. Nat Rev Mol Cell Biol 2021; 22:815-833. [PMID: 34400841 PMCID: PMC7612013 DOI: 10.1038/s41580-021-00398-y] [Citation(s) in RCA: 254] [Impact Index Per Article: 63.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2021] [Indexed: 12/12/2022]
Abstract
Precise control of gene expression is fundamental to cell function and development. Although ultimately gene expression relies on DNA-binding transcription factors to guide the activity of the transcription machinery to genes, it has also become clear that chromatin and histone post-translational modification have fundamental roles in gene regulation. Polycomb repressive complexes represent a paradigm of chromatin-based gene regulation in animals. The Polycomb repressive system comprises two central protein complexes, Polycomb repressive complex 1 (PRC1) and PRC2, which are essential for normal gene regulation and development. Our early understanding of Polycomb function relied on studies in simple model organisms, but more recently it has become apparent that this system has expanded and diverged in mammals. Detailed studies are now uncovering the molecular mechanisms that enable mammalian PRC1 and PRC2 to identify their target sites in the genome, communicate through feedback mechanisms to create Polycomb chromatin domains and control transcription to regulate gene expression. In this Review, we discuss and contextualize the emerging principles that define how this fascinating chromatin-based system regulates gene expression in mammals.
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Affiliation(s)
| | - Robert J Klose
- Department of Biochemistry, University of Oxford, Oxford, UK.
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33
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Holoch D, Wassef M, Lövkvist C, Zielinski D, Aflaki S, Lombard B, Héry T, Loew D, Howard M, Margueron R. A cis-acting mechanism mediates transcriptional memory at Polycomb target genes in mammals. Nat Genet 2021; 53:1686-1697. [PMID: 34782763 DOI: 10.1038/s41588-021-00964-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 10/05/2021] [Indexed: 11/09/2022]
Abstract
Epigenetic inheritance of gene expression states enables a single genome to maintain distinct cellular identities. How histone modifications contribute to this process remains unclear. Using global chromatin perturbations and local, time-controlled modulation of transcription, we establish the existence of epigenetic memory of transcriptional activation for genes that can be silenced by the Polycomb group. This property emerges during cell differentiation and allows genes to be stably switched after a transient transcriptional stimulus. This transcriptional memory state at Polycomb targets operates in cis; however, rather than relying solely on read-and-write propagation of histone modifications, the memory is also linked to the strength of activating inputs opposing Polycomb proteins, and therefore varies with the cellular context. Our data and computational simulations suggest a model whereby transcriptional memory arises from double-negative feedback between Polycomb-mediated silencing and active transcription. Transcriptional memory at Polycomb targets thus depends not only on histone modifications but also on the gene-regulatory network and underlying identity of a cell.
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Affiliation(s)
- Daniel Holoch
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Michel Wassef
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Cecilia Lövkvist
- John Innes Centre, Norwich Research Park, Norwich, UK. .,Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark.
| | - Dina Zielinski
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France.,INSERM U900, Mines ParisTech, Paris, France
| | - Setareh Aflaki
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Bérangère Lombard
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,Proteomics Mass Spectrometry Laboratory, Paris, France
| | - Tiphaine Héry
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,INSERM U934/CNRS UMR 3215, Paris, France
| | - Damarys Loew
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France.,Proteomics Mass Spectrometry Laboratory, Paris, France
| | - Martin Howard
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Raphaël Margueron
- Institut Curie, Paris Sciences et Lettres Research University, Sorbonne University, Paris, France. .,INSERM U934/CNRS UMR 3215, Paris, France.
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34
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Lövkvist C, Mikulski P, Reeck S, Hartley M, Dean C, Howard M. Hybrid protein assembly-histone modification mechanism for PRC2-based epigenetic switching and memory. eLife 2021; 10:66454. [PMID: 34473050 PMCID: PMC8412945 DOI: 10.7554/elife.66454] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 08/03/2021] [Indexed: 12/31/2022] Open
Abstract
The histone modification H3K27me3 plays a central role in Polycomb-mediated epigenetic silencing. H3K27me3 recruits and allosterically activates Polycomb Repressive Complex 2 (PRC2), which adds this modification to nearby histones, providing a read/write mechanism for inheritance through DNA replication. However, for some PRC2 targets, a purely histone-based system for epigenetic inheritance may be insufficient. We address this issue at the Polycomb target FLOWERING LOCUS C (FLC) in Arabidopsis thaliana, as a narrow nucleation region of only ~three nucleosomes within FLC mediates epigenetic state switching and subsequent memory over many cell cycles. To explain the memory's unexpected persistence, we introduce a mathematical model incorporating extra protein memory storage elements with positive feedback that persist at the locus through DNA replication, in addition to histone modifications. Our hybrid model explains many features of epigenetic switching/memory at FLC and encapsulates generic mechanisms that may be widely applicable.
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Affiliation(s)
- Cecilia Lövkvist
- Computational and Systems Biology, John Innes Centre, Norwich Research Park, United Kingdom
| | - Pawel Mikulski
- Cell and Developmental Biology, John Innes Centre, Norwich Research Park, United Kingdom
| | - Svenja Reeck
- Computational and Systems Biology, John Innes Centre, Norwich Research Park, United Kingdom.,Cell and Developmental Biology, John Innes Centre, Norwich Research Park, United Kingdom
| | - Matthew Hartley
- Computational and Systems Biology, John Innes Centre, Norwich Research Park, United Kingdom
| | - Caroline Dean
- Cell and Developmental Biology, John Innes Centre, Norwich Research Park, United Kingdom
| | - Martin Howard
- Computational and Systems Biology, John Innes Centre, Norwich Research Park, United Kingdom
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35
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Nguyen P, Pease NA, Kueh HY. Scalable control of developmental timetables by epigenetic switching networks. J R Soc Interface 2021; 18:20210109. [PMID: 34283940 DOI: 10.1098/rsif.2021.0109] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
During development, progenitor cells follow timetables for differentiation that span many cell generations. These developmental timetables are robustly encoded by the embryo, yet scalably adjustable by evolution, facilitating variation in organism size and form. Epigenetic switches, involving rate-limiting activation steps at regulatory gene loci, control gene activation timing in diverse contexts, and could profoundly impact the dynamics of gene regulatory networks controlling developmental lineage specification. Here, we develop a mathematical framework to model regulatory networks with genes controlled by epigenetic switches. Using this framework, we show that such epigenetic switching networks uphold developmental timetables that robustly span many cell generations, and enable the generation of differentiated cells in precisely defined numbers and fractions. Changes to epigenetic switching networks can readily alter the timing of developmental events within a timetable, or alter the overall speed at which timetables unfold, enabling scalable control over differentiated population sizes. With their robust, yet flexibly adjustable nature, epigenetic switching networks could represent central targets on which evolution acts to manufacture diversity in organism size and form.
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Affiliation(s)
- Phuc Nguyen
- Molecular Engineering and Sciences Program, University of Washington, Seattle, WA, USA
| | - Nicholas A Pease
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA
| | - Hao Yuan Kueh
- Department of Bioengineering, University of Washington, Seattle, WA, USA.,Institute of Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, USA
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36
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Zhao W, Qiao L, Yan S, Nie Q, Zhang L. Mathematical modeling of histone modifications reveals the formation mechanism and function of bivalent chromatin. iScience 2021; 24:102732. [PMID: 34278251 PMCID: PMC8261666 DOI: 10.1016/j.isci.2021.102732] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 05/23/2021] [Accepted: 06/08/2021] [Indexed: 01/09/2023] Open
Abstract
Bivalent chromatin is characterized by occupation of both activating and repressive histone modifications. Here, we develop a mathematical model that involves antagonistic histone modifications H3K4me3 and H3K27me3 to capture the key features of bivalent chromatin. Three necessary conditions for the emergence of bivalent chromatin are identified, including advantageous methylating activity over demethylating activity, frequent noise conversions of modifications, and sufficient nonlinearity. The first condition is further confirmed by analyzing the existing experimental data. Investigation of the composition of bivalent chromatin reveals that bivalent nucleosomes carrying both H3K4me3 and H3K27me3 account for no more than half of nucleosomes at the bivalent chromatin domain. We identify that bivalent chromatin not only allows transitions to multiple states but also serves as a stepping stone to facilitate a stepwise transition between repressive chromatin state and activating chromatin state and thus elucidate crucial roles of bivalent chromatin in mediating phenotypical plasticity during cell fate determination. Emergence of bivalency needs advantageous writing activity over erasing activity Emergence of bivalency is facilitated by noise and nonlinearity The proportion of bivalent nucleosomes at bivalent chromatin is no more than 50% Bivalent chromatin facilitates chromatin state transitions
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Affiliation(s)
- Wei Zhao
- Beijing International Center for Mathematical Research, Peking University, Beijing 100871, China.,Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Lingxia Qiao
- Beijing International Center for Mathematical Research, Peking University, Beijing 100871, China
| | - Shiyu Yan
- Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Qing Nie
- Department of Mathematics and Department of Developmental and Cell Biology, University of California Irvine, Irvine, CA 92697, USA
| | - Lei Zhang
- Beijing International Center for Mathematical Research, Peking University, Beijing 100871, China.,Center for Quantitative Biology, Peking University, Beijing 100871, China
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37
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Menon G, Schulten A, Dean C, Howard M. Digital paradigm for Polycomb epigenetic switching and memory. CURRENT OPINION IN PLANT BIOLOGY 2021; 61:102012. [PMID: 33662809 PMCID: PMC8250048 DOI: 10.1016/j.pbi.2021.102012] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 01/21/2021] [Accepted: 01/24/2021] [Indexed: 05/04/2023]
Abstract
How epigenetic memory states are established and maintained is a central question in gene regulation. A major epigenetic process important for developmental biology involves Polycomb-mediated chromatin silencing. Significant progress has recently been made on elucidating Polycomb silencing in plant systems through analysis of Arabidopsis FLOWERING LOCUS C (FLC). Quantitative silencing of FLC by prolonged cold exposure was shown to represent an ON to OFF switch in an increasing proportion of cells. Here, we review the underlying all-or-nothing, digital paradigm for Polycomb epigenetic silencing. We then examine other Arabidopsis Polycomb-regulated targets where digital regulation may also be relevant.
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Affiliation(s)
- Govind Menon
- Department of Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Anna Schulten
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Caroline Dean
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Martin Howard
- Department of Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK.
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38
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Pease NA, Nguyen PHB, Woodworth MA, Ng KKH, Irwin B, Vaughan JC, Kueh HY. Tunable, division-independent control of gene activation timing by a polycomb switch. Cell Rep 2021; 34:108888. [PMID: 33761349 PMCID: PMC8024876 DOI: 10.1016/j.celrep.2021.108888] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 12/17/2020] [Accepted: 03/01/2021] [Indexed: 01/09/2023] Open
Abstract
During development, progenitors often differentiate many cell generations after receiving signals. These delays must be robust yet tunable for precise population size control. Polycomb repressive mechanisms, involving histone H3 lysine-27 trimethylation (H3K27me3), restrain the expression of lineage-specifying genes in progenitors and may delay their activation and ensuing differentiation. Here, we elucidate an epigenetic switch controlling the T cell commitment gene Bcl11b that holds its locus in a heritable inactive state for multiple cell generations before activation. Integrating experiments and modeling, we identify a mechanism where H3K27me3 levels at Bcl11b, regulated by methyltransferase and demethylase activities, set the time delay at which the locus switches from a compacted, silent state to an extended, active state. This activation delay robustly spans many cell generations, is tunable by chromatin modifiers and transcription factors, and is independent of cell division. With their regulatory flexibility, such timed epigenetic switches may broadly control timing in development.
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Affiliation(s)
- Nicholas A Pease
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Phuc H B Nguyen
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Molecular Engineering and Sciences Institute, University of Washington, Seattle, WA 98195, USA
| | - Marcus A Woodworth
- Biological Physics, Structure and Design Program, University of Washington, Seattle, WA 98195, USA; Department of Chemistry, University of Washington, Seattle, WA 98195, USA
| | - Kenneth K H Ng
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Blythe Irwin
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA
| | - Joshua C Vaughan
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA; Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - Hao Yuan Kueh
- Department of Bioengineering, University of Washington, Seattle, WA 98195, USA; Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195, USA.
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39
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Ancona M, Michieletto D, Marenduzzo D. Competition between local erasure and long-range spreading of a single biochemical mark leads to epigenetic bistability. Phys Rev E 2021; 101:042408. [PMID: 32422714 DOI: 10.1103/physreve.101.042408] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/19/2020] [Indexed: 11/07/2022]
Abstract
The mechanism through which cells determine their fate is intimately related to the spreading of certain biochemical (so-called epigenetic) marks along their genome. The mechanisms behind mark spreading and maintenance are not yet fully understood, and current models often assume a long-range infectionlike process for the dynamics of marks, due to the polymeric nature of the chromatin fiber which allows looping between distant sites. While these existing models typically consider antagonizing marks, here we propose a qualitatively different scenario which analyses the spreading of a single mark. We define a one-dimensional stochastic model in which mark spreading/infection occurs as a long-range process whereas mark erasure/recovery is a local process, with an enhanced rate at boundaries of infected domains. In the limiting case where our model exhibits absorbing states, we find a first-order-like transition separating the marked/infected phase from the unmarked/recovered phase. This suggests that our model, in this limit, belongs to the long-range compact directed percolation universality class. The abrupt nature of the transition is retained in a more biophysically realistic situation when a basal infection/recovery rate is introduced (thereby removing absorbing states). Close to the transition there is a range of bistability where both the marked/infected and unmarked/recovered states are metastable and long lived, which provides a possible avenue for controlling fate decisions in cells. Increasing the basal infection/recovery rate, we find a second transition between a coherent (marked or unmarked) phase, and a mixed, or random, one.
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Affiliation(s)
- Marco Ancona
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - Davide Michieletto
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom.,MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom.,Centre for Mathematical Biology, and Department of Mathematical Sciences, University of Bath, North Road, Bath BA2 7AY, United Kingdom
| | - Davide Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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40
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Using computational modelling to reveal mechanisms of epigenetic Polycomb control. Biochem Soc Trans 2021; 49:71-77. [PMID: 33616630 PMCID: PMC7925002 DOI: 10.1042/bst20190955] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 11/17/2022]
Abstract
The Polycomb system is essential for stable gene silencing in many organisms. This regulation is achieved in part through addition of the histone modifications H3K27me2/me3 by Polycomb Repressive Complex 2 (PRC2). These modifications are believed to be the causative epigenetic memory elements of PRC2-mediated silencing. As these marks are stored locally in the chromatin, PRC2-based memory is a cis-acting system. A key feature of stable epigenetic memory in cis is PRC2-mediated, self-reinforcing feedback from K27-methylated histones onto nearby histones in a read-write paradigm. However, it was not clear under what conditions such feedback can lead to stable memory, able, for example, to survive the perturbation of histone dilution at DNA replication. In this context, computational modelling has allowed a rigorous exploration of possible underlying memory mechanisms and has also greatly accelerated our understanding of switching between active and silenced states. Specifically, modelling has predicted that switching and memory at Polycomb loci is digital, with a locus being either active or inactive, rather than possessing intermediate, smoothly varying levels of activation. Here, we review recent advances in models of Polycomb control, focusing on models of epigenetic switching through nucleation and spreading of H3K27me2/me3. We also examine models that incorporate transcriptional feedback antagonism and those including bivalent chromatin states. With more quantitative experimental data on histone modification kinetics, as well as single-cell resolution data on transcription and protein levels for PRC2 targets, we anticipate an expanded need for modelling to help dissect increasingly interconnected and complex memory mechanisms.
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41
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Abstract
Determining whether and how a gene is transcribed are two of the central processes of life. The conceptual basis for understanding such gene regulation arose from pioneering biophysical studies in eubacteria. However, eukaryotic genomes exhibit vastly greater complexity, which raises questions not addressed by this bacterial paradigm. First, how is information integrated from many widely separated binding sites to determine how a gene is transcribed? Second, does the presence of multiple energy-expending mechanisms, which are absent from eubacterial genomes, indicate that eukaryotes are capable of improved forms of genetic information processing? An updated biophysical foundation is needed to answer such questions. We describe the linear framework, a graph-based approach to Markov processes, and show that it can accommodate many previous studies in the field. Under the assumption of thermodynamic equilibrium, we introduce a language of higher-order cooperativities and show how it can rigorously quantify gene regulatory properties suggested by experiment. We point out that fundamental limits to information processing arise at thermodynamic equilibrium and can only be bypassed through energy expenditure. Finally, we outline some of the mathematical challenges that must be overcome to construct an improved biophysical understanding of gene regulation.
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Affiliation(s)
- Felix Wong
- Institute for Medical Engineering & Science, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Jeremy Gunawardena
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA;
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42
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Domain Model Explains Propagation Dynamics and Stability of Histone H3K27 and H3K36 Methylation Landscapes. Cell Rep 2020; 30:1223-1234.e8. [PMID: 31995760 DOI: 10.1016/j.celrep.2019.12.060] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/25/2019] [Accepted: 12/16/2019] [Indexed: 01/12/2023] Open
Abstract
Chromatin states must be maintained during cell proliferation to uphold cellular identity and genome integrity. Inheritance of histone modifications is central in this process. However, the histone modification landscape is challenged by incorporation of new unmodified histones during each cell cycle, and the principles governing heritability remain unclear. We take a quantitative computational modeling approach to describe propagation of histone H3K27 and H3K36 methylation states. We measure combinatorial H3K27 and H3K36 methylation patterns by quantitative mass spectrometry on subsequent generations of histones. Using model comparison, we reject active global demethylation and invoke the existence of domains defined by distinct methylation endpoints. We find that H3K27me3 on pre-existing histones stimulates the rate of de novo H3K27me3 establishment, supporting a read-write mechanism in timely chromatin restoration. Finally, we provide a detailed quantitative picture of the mutual antagonism between H3K27 and H3K36 methylation and propose that it stabilizes epigenetic states across cell division.
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43
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Nishio H, Iwayama K, Kudoh H. Duration of cold exposure defines the rate of reactivation of a perennial FLC orthologue via H3K27me3 accumulation. Sci Rep 2020; 10:16056. [PMID: 32994432 PMCID: PMC7525499 DOI: 10.1038/s41598-020-72566-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 08/31/2020] [Indexed: 12/15/2022] Open
Abstract
Vernalisation is the process in which long-term cold exposure makes plants competent to flower. In vernalisation of Arabidopsis thaliana, a floral repressor, AtFLC, undergoes epigenetic silencing. Although the silencing of AtFLC is maintained under warm conditions after a sufficient duration of cold, FLC orthologues are reactivated under the same conditions in perennial plants, such as A. halleri. In contrast to the abundant knowledge on cold requirements in AtFLC silencing, it has remained unknown how cold duration affects the reactivation of perennial FLC. Here, we analysed the dynamics of A. halleri FLC (AhgFLC) mRNA, H3K4me3, and H3K27me3 over 8 weeks and 14 weeks cold followed by warm conditions. We showed that the minimum levels of AhgFLC mRNA and H3K4me3 were similar between 8 and 14 weeks vernalisation; however, the maximum level of H3K27me3 was higher after 14 weeks than after 8 weeks vernalisation. Combined with mathematical modelling, we showed that H3K27me3 prevents a rapid increase in AhgFLC expression in response to warm temperatures after vernalisation, which controls AhgFT expression and the initiation of flowering. Thus, the duration of cold defines the rate of AhgFLC reactivation via the buffering function of H3K27me3 against temperature increase.
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Affiliation(s)
- Haruki Nishio
- Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, 520-2113, Japan.
| | - Koji Iwayama
- Faculty of Data Science, Shiga University, 1-1-1 Bamba, Hikone, Shiga, 522-8522, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan
| | - Hiroshi Kudoh
- Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, 520-2113, Japan.
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44
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Reinig J, Ruge F, Howard M, Ringrose L. A theoretical model of Polycomb/Trithorax action unites stable epigenetic memory and dynamic regulation. Nat Commun 2020; 11:4782. [PMID: 32963223 PMCID: PMC7508846 DOI: 10.1038/s41467-020-18507-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 08/24/2020] [Indexed: 12/12/2022] Open
Abstract
Polycomb and Trithorax group proteins maintain stable epigenetic memory of gene expression states for some genes, but many targets show highly dynamic regulation. Here we combine experiment and theory to examine the mechanistic basis of these different modes of regulation. We present a mathematical model comprising a Polycomb/Trithorax response element (PRE/TRE) coupled to a promoter and including Drosophila developmental timing. The model accurately recapitulates published studies of PRE/TRE mediated epigenetic memory of both silencing and activation. With minimal parameter changes, the same model can also recapitulate experimental data for a different PRE/TRE that allows dynamic regulation of its target gene. The model predicts that both cell cycle length and PRE/TRE identity are critical for determining whether the system gives stable memory or dynamic regulation. Our work provides a simple unifying framework for a rich repertoire of PRE/TRE functions, and thus provides insights into genome-wide Polycomb/Trithorax regulation. Polycomb (PcG) and Trithorax (TrxG) group regulate several hundred target genes with important roles in development and disease. Here the authors combine experiment and theory to provide evidence that the Polycomb/Trithorax system has the potential for a rich repertoire of regulatory modes beyond simple epigenetic memory.
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Affiliation(s)
- Jeannette Reinig
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany
| | - Frank Ruge
- IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria
| | - Martin Howard
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Leonie Ringrose
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany. .,IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria.
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45
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Perrella G, Zioutopoulou A, Headland LR, Kaiserli E. The impact of light and temperature on chromatin organization and plant adaptation. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:5247-5255. [PMID: 32215554 DOI: 10.1093/jxb/eraa154] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 03/24/2020] [Indexed: 05/23/2023]
Abstract
Light and temperature shape the developmental trajectory and morphology of plants. Changes in chromatin organization and nuclear architecture can modulate gene expression and lead to short- and long-term plant adaptation to the environment. Here, we review recent reports investigating how changes in chromatin composition, structure, and topology modulate gene expression in response to fluctuating light and temperature conditions resulting in developmental and physiological responses. Furthermore, the potential application of novel revolutionary techniques, such Hi-C, RNA fluorescence in situ hybridization (FISH) and padlock-FISH, to study the impact of environmental stimuli such as light and temperature on nuclear compartmentalization in plants is discussed.
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Affiliation(s)
- Giorgio Perrella
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- ENEA-Trisaia Research Centre 75026, Rotondella (Matera), Italy
| | - Anna Zioutopoulou
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Lauren R Headland
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Eirini Kaiserli
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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46
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Quadrana L. The contribution of transposable elements to transcriptional novelty in plants: the FLC affair. Transcription 2020; 11:192-198. [PMID: 32783496 PMCID: PMC7714446 DOI: 10.1080/21541264.2020.1803031] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are repetitive DNA sequences with the ability to replicate across genomes and generate mutations with major transcriptional effects. Epigenetic silencing mechanisms that target TEs to limit their activity, including DNA methylation, add to the range of gene expression variants generated by TEs. Here, using the iconic gene flowering locus C (FLC) as a case study I discuss the multiple ways by which TEs can affect the expression of genes and contribute to the adaptation of plants to changing environments
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Affiliation(s)
- Leandro Quadrana
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Centre National de la Recherche Scientifique (CNRS), Institut National de la Santé et de la Recherche Médicale (INSERM), Ecole Normale Supérieure, PSL Research University , Paris, France
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47
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Bloomer RH, Hutchison CE, Bäurle I, Walker J, Fang X, Perera P, Velanis CN, Gümüs S, Spanos C, Rappsilber J, Feng X, Goodrich J, Dean C. The Arabidopsis epigenetic regulator ICU11 as an accessory protein of Polycomb Repressive Complex 2. Proc Natl Acad Sci U S A 2020; 117:16660-16666. [PMID: 32601198 PMCID: PMC7368280 DOI: 10.1073/pnas.1920621117] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Molecular mechanisms enabling the switching and maintenance of epigenetic states are not fully understood. Distinct histone modifications are often associated with ON/OFF epigenetic states, but how these states are stably maintained through DNA replication, yet in certain situations switch from one to another remains unclear. Here, we address this problem through identification of Arabidopsis INCURVATA11 (ICU11) as a Polycomb Repressive Complex 2 accessory protein. ICU11 robustly immunoprecipitated in vivo with PRC2 core components and the accessory proteins, EMBRYONIC FLOWER 1 (EMF1), LIKE HETEROCHROMATIN PROTEIN1 (LHP1), and TELOMERE_REPEAT_BINDING FACTORS (TRBs). ICU11 encodes a 2-oxoglutarate-dependent dioxygenase, an activity associated with histone demethylation in other organisms, and mutant plants show defects in multiple aspects of the Arabidopsis epigenome. To investigate its primary molecular function we identified the Arabidopsis FLOWERING LOCUS C (FLC) as a direct target and found icu11 disrupted the cold-induced, Polycomb-mediated silencing underlying vernalization. icu11 prevented reduction in H3K36me3 levels normally seen during the early cold phase, supporting a role for ICU11 in H3K36me3 demethylation. This was coincident with an attenuation of H3K27me3 at the internal nucleation site in FLC, and reduction in H3K27me3 levels across the body of the gene after plants were returned to the warm. Thus, ICU11 is required for the cold-induced epigenetic switching between the mutually exclusive chromatin states at FLC, from the active H3K36me3 state to the silenced H3K27me3 state. These data support the importance of physical coupling of histone modification activities to promote epigenetic switching between opposing chromatin states.
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Affiliation(s)
- Rebecca H Bloomer
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - Claire E Hutchison
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - Isabel Bäurle
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - James Walker
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - Xiaofeng Fang
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - Pumi Perera
- Institute of Molecular Plant Sciences, University of Edinburgh, Max Born Crescent, EH9 3BF Edinburgh, United Kingdom
| | - Christos N Velanis
- Institute of Molecular Plant Sciences, University of Edinburgh, Max Born Crescent, EH9 3BF Edinburgh, United Kingdom
| | - Serin Gümüs
- Faculty of Biotechnology, Hochschule Mannheim, 68163 Mannheim, Germany
| | - Christos Spanos
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, EH9 3BF Edinburgh, United Kingdom
| | - Juri Rappsilber
- Wellcome Centre for Cell Biology, University of Edinburgh, Max Born Crescent, EH9 3BF Edinburgh, United Kingdom
- Institute of Biotechnology, Technische Universität Berlin, 13355 Berlin, Germany
| | - Xiaoqi Feng
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom
| | - Justin Goodrich
- Institute of Molecular Plant Sciences, University of Edinburgh, Max Born Crescent, EH9 3BF Edinburgh, United Kingdom
| | - Caroline Dean
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, NR47UH Norwich, United Kingdom;
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48
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Jarad M, Antoniou-Kourounioti R, Hepworth J, Qüesta JI. Unique and contrasting effects of light and temperature cues on plant transcriptional programs. Transcription 2020; 11:134-159. [PMID: 33016207 PMCID: PMC7714439 DOI: 10.1080/21541264.2020.1820299] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/26/2020] [Accepted: 08/31/2020] [Indexed: 12/12/2022] Open
Abstract
Plants have adapted to tolerate and survive constantly changing environmental conditions by reprogramming gene expression in response to stress or to drive developmental transitions. Among the many signals that plants perceive, light and temperature are of particular interest due to their intensely fluctuating nature which is combined with a long-term seasonal trend. Whereas specific receptors are key in the light-sensing mechanism, the identity of plant thermosensors for high and low temperatures remains far from fully addressed. This review aims at discussing common as well as divergent characteristics of gene expression regulation in plants, controlled by light and temperature. Light and temperature signaling control the abundance of specific transcription factors, as well as the dynamics of co-transcriptional processes such as RNA polymerase elongation rate and alternative splicing patterns. Additionally, sensing both types of cues modulates gene expression by altering the chromatin landscape and through the induction of long non-coding RNAs (lncRNAs). However, while light sensing is channeled through dedicated receptors, temperature can broadly affect chemical reactions inside plant cells. Thus, direct thermal modifications of the transcriptional machinery add another level of complexity to plant transcriptional regulation. Besides the rapid transcriptome changes that follow perception of environmental signals, plant developmental transitions and acquisition of stress tolerance depend on long-term maintenance of transcriptional states (active or silenced genes). Thus, the rapid transcriptional response to the signal (Phase I) can be distinguished from the long-term memory of the acquired transcriptional state (Phase II - remembering the signal). In this review we discuss recent advances in light and temperature signal perception, integration and memory in Arabidopsis thaliana, focusing on transcriptional regulation and highlighting the contrasting and unique features of each type of cue in the process.
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Affiliation(s)
- Mai Jarad
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Barcelona, Spain
| | | | - Jo Hepworth
- John Innes Centre, Norwich Research Park, Norwich, UK
| | - Julia I. Qüesta
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Barcelona, Spain
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49
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Bheda P, Aguilar-Gómez D, Becker NB, Becker J, Stavrou E, Kukhtevich I, Höfer T, Maerkl S, Charvin G, Marr C, Kirmizis A, Schneider R. Single-Cell Tracing Dissects Regulation of Maintenance and Inheritance of Transcriptional Reinduction Memory. Mol Cell 2020; 78:915-925.e7. [DOI: 10.1016/j.molcel.2020.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 02/15/2020] [Accepted: 04/15/2020] [Indexed: 10/24/2022]
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50
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Nishio H, Buzas DM, Nagano AJ, Iwayama K, Ushio M, Kudoh H. Repressive chromatin modification underpins the long-term expression trend of a perennial flowering gene in nature. Nat Commun 2020; 11:2065. [PMID: 32358518 PMCID: PMC7195410 DOI: 10.1038/s41467-020-15896-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 04/01/2020] [Indexed: 11/17/2022] Open
Abstract
Natural environments require organisms to possess robust mechanisms allowing responses to seasonal trends. In Arabidopsis halleri, the flowering regulator AhgFLC shows upregulation and downregulation phases along with long-term past temperature, but the underlying machinery remains elusive. Here, we investigate the seasonal dynamics of histone modifications, H3K27me3 and H3K4me3, at AhgFLC in a natural population. Our advanced modelling and transplant experiments reveal that H3K27me3-mediated chromatin regulation at AhgFLC provides two essential properties. One is the ability to respond to the long-term temperature trends via bidirectional interactions between H3K27me3 and H3K4me3; the other is the ratchet-like character of the AhgFLC system, i.e. reversible in the entire perennial life cycle but irreversible during the upregulation phase. Furthermore, we show that the long-term temperature trends are locally indexed at AhgFLC in the form of histone modifications. Our study provides a more comprehensive understanding of H3K27me3 function at AhgFLC in a complex natural environment. The flowering regulator FLC shows upregulation and downregulation phases along with long-term past temperature in Arabidopsishalleri. Here, the authors reveal that H3K27me3-mediated chromatin regulation at AhgFLC provides the ability to respond to both the seasonal temperature trends and the perennial life cycle.
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Affiliation(s)
- Haruki Nishio
- Center for Ecological Research, Kyoto University, Otsu, 520-2113, Japan.
| | - Diana M Buzas
- Tsukuba-Plant Innovation Research Center and Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8572, Japan
| | - Atsushi J Nagano
- Center for Ecological Research, Kyoto University, Otsu, 520-2113, Japan.,Faculty of Agriculture, Ryukoku University, Seta Oe-cho, Otsu, 520-2194, Japan
| | - Koji Iwayama
- Faculty of Data Science, Shiga University, Hikone, 522-8522, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan
| | - Masayuki Ushio
- Center for Ecological Research, Kyoto University, Otsu, 520-2113, Japan.,PRESTO, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan.,Hakubi Center, Kyoto University, Yoshida-honmachi, Kyoto, 606-8501, Japan
| | - Hiroshi Kudoh
- Center for Ecological Research, Kyoto University, Otsu, 520-2113, Japan.
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