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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: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Velanis CN, Perera P, Thomson B, de Leau E, Liang SC, Hartwig B, Förderer A, Thornton H, Arede P, Chen J, Webb KM, Gümüs S, De Jaeger G, Page CA, Hancock CN, Spanos C, Rappsilber J, Voigt P, Turck F, Wellmer F, Goodrich J. The domesticated transposase ALP2 mediates formation of a novel Polycomb protein complex by direct interaction with MSI1, a core subunit of Polycomb Repressive Complex 2 (PRC2). PLoS Genet 2020; 16:e1008681. [PMID: 32463832 PMCID: PMC7282668 DOI: 10.1371/journal.pgen.1008681] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 06/09/2020] [Accepted: 02/18/2020] [Indexed: 12/17/2022] Open
Abstract
A large fraction of plant genomes is composed of transposable elements (TE), which provide a potential source of novel genes through “domestication”–the process whereby the proteins encoded by TE diverge in sequence, lose their ability to catalyse transposition and instead acquire novel functions for their hosts. In Arabidopsis, ANTAGONIST OF LIKE HETEROCHROMATIN PROTEIN 1 (ALP1) arose by domestication of the nuclease component of Harbinger class TE and acquired a new function as a component of POLYCOMB REPRESSIVE COMPLEX 2 (PRC2), a histone H3K27me3 methyltransferase involved in regulation of host genes and in some cases TE. It was not clear how ALP1 associated with PRC2, nor what the functional consequence was. Here, we identify ALP2 genetically as a suppressor of Polycomb-group (PcG) mutant phenotypes and show that it arose from the second, DNA binding component of Harbinger transposases. Molecular analysis of PcG compromised backgrounds reveals that ALP genes oppose silencing and H3K27me3 deposition at key PcG target genes. Proteomic analysis reveals that ALP1 and ALP2 are components of a variant PRC2 complex that contains the four core components but lacks plant-specific accessory components such as the H3K27me3 reader LIKE HETEROCHROMATION PROTEIN 1 (LHP1). We show that the N-terminus of ALP2 interacts directly with ALP1, whereas the C-terminus of ALP2 interacts with MULTICOPY SUPPRESSOR OF IRA1 (MSI1), a core component of PRC2. Proteomic analysis reveals that in alp2 mutant backgrounds ALP1 protein no longer associates with PRC2, consistent with a role for ALP2 in recruitment of ALP1. We suggest that the propensity of Harbinger TE to insert in gene-rich regions of the genome, together with the modular two component nature of their transposases, has predisposed them for domestication and incorporation into chromatin modifying complexes. A large part of the genomes of plants and animals consists of transposable elements (TE), which are usually considered as selfish or parasitic as they encode proteins (transposases) which promote TE proliferation but not functions useful for their hosts. As a result, hosts have evolved ways of reducing TE proliferation, usually by modifying the DNA or chromatin of TE so that their transposases are no longer produced. Once the TE are inactivated they can no longer proliferate and over time they accumulate mutations and can evolve new functions, often beneficial for their hosts. This process is known as domestication and is increasingly recognised as a potent source of evolutionary novelty. For example, the CRISPR/Cas system that has provided the basis for a revolution in genetic engineering (“genome editing”) has evolved via domestication of transposons in bacteria. We have identified the ALP proteins, two domesticated transposases which function as components of an enzyme complex (PRC2) involved in modifying chromatin and regulating host gene activity in plants. Here we show how ALPs contact PRC2 and direct formation of a novel complex that lacks several of the usual components. The ALPs and related proteins will provide valuable tools for manipulating plant chromatin.
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Affiliation(s)
- Christos N. Velanis
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Pumi Perera
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Bennett Thomson
- Smurfit Institute of Genetics, Trinity College Dublin, Ireland
| | - Erica de Leau
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Shih Chieh Liang
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Ben Hartwig
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | - Alexander Förderer
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | - Harry Thornton
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Pedro Arede
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Jiawen Chen
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
| | - Kimberly M. Webb
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh, United Kingdom
| | - Serin Gümüs
- Department of Biotechnology, Mannheim University of Applied Science, Mannheim, Germany
| | - Geert De Jaeger
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, Belgium
- VIB Center for Plant Systems Biology, Gent, Belgium
| | - Clinton A. Page
- Department of Biology & Geology, University of South Carolina Aiken, Aiken, South Carolina, United States of America
| | - C. Nathan Hancock
- Department of Biology & Geology, University of South Carolina Aiken, Aiken, South Carolina, United States of America
| | - Christos Spanos
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh, United Kingdom
| | - Juri Rappsilber
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh, United Kingdom
- Bioanalytics Unit, Institute of Biotechnology, Technische Universität Berlin, Berlin, Germany
| | - Philipp Voigt
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Max Born Crescent, Edinburgh, United Kingdom
| | - Franziska Turck
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Köln, Germany
| | - Frank Wellmer
- Smurfit Institute of Genetics, Trinity College Dublin, Ireland
| | - Justin Goodrich
- Institute of Molecular Plant Science, School of Biological Sciences, University of Edinburgh, Daniel Rutherford Building, Max Born Crescent, Edinburgh, United Kingdom
- * E-mail:
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