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Jangam S, Briere LC, Jay K, Andrews JC, Walker MA, Rodan LH, High FA, Yamamoto S, Sweetser DA, Wangler M. A de novo missense variant in EZH1 associated with developmental delay exhibits functional deficits in Drosophila melanogaster. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.01.31.23285113. [PMID: 36778246 PMCID: PMC9915809 DOI: 10.1101/2023.01.31.23285113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
EZH1 ( Enhancer of Zeste, homolog 1) , a Polycomb Repressive Complex-2 (PRC2) component, is involved in a myriad of cellular processes through modifying histone 3 lysine27 (H3K27) residues. EZH1 represses transcription of downstream target genes through H3K27 trimethylation (H3K27me3). Genetic mutations in histone modifiers have been associated with developmental disorders, while EZH1 has not yet been linked to any human disease. However, the paralog EZH2 is associated with Weaver syndrome. Here we report a previously undiagnosed individual with a novel neurodevelopmental phenotype identified to have a de novo variant in EZH1 , p.Ala678Gly, through exome sequencing. The individual presented in infancy with neurodevelopmental delay and hypotonia and was later noted to have proximal muscle weakness. The variant, p.A678G, is in the SET domain, known for its methyltransferase activity, and was the best candidate variant found in the exome. Human EZH1 / 2 are homologous to fly Enhancer of zeste E(z) , an essential gene in flies, and the residue (A678 in humans, A691 in Drosophila ) is conserved. To further study this variant, we obtained Drosophila null alleles and generated transgenic flies expressing wild-type (E(z) WT ) and the variant (E(z) A691G ) . The E(z) A691G variant led to hyper H3K27me3 while the E(z) WT did not, suggesting this is as a gain-of-function allele. When expressed under the tubulin promotor in vivo the variant rescued null-lethality similar to wild-type but the E(z) A691G flies exhibit bang sensitivity and shortened lifespan. In conclusion, here we present a novel EZH1 de novo variant associated with a neurodevelopmental disorder. Furthermore, we found that this variant has a functional impact in Drosophila . Biochemically this allele leads to increased H3K27me3 suggesting gain-of-function, but when expressed in adult flies the E(z) A691G has some characteristics of partial loss-of-function which may suggest it is a more complex allele in vivo .
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Affiliation(s)
- Sharayu Jangam
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, 77030 USA
| | - Lauren C Briere
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Kristy Jay
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, 77030 USA
- Genetics and Genomics program, Baylor College of Medicine, Houston, Texas, 77030 USA
| | - Jonathan C Andrews
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, 77030 USA
| | - Melissa A Walker
- Department of Neurology, Division of Neurogenetics, Child Neurology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Lance H Rodan
- Department of Neurology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Frances A High
- Division of Medical Genetics & Metabolism, Massachusetts General Hospital for Children, Boston, MA 02114, USA
| | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, 77030 USA
- Genetics and Genomics program, Baylor College of Medicine, Houston, Texas, 77030 USA
| | - David A Sweetser
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Division of Medical Genetics & Metabolism, Massachusetts General Hospital for Children, Boston, MA 02114, USA
| | - Michael Wangler
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, 77030 USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, 77030 USA
- Genetics and Genomics program, Baylor College of Medicine, Houston, Texas, 77030 USA
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Ruchert JM, Brady MM, McMahan S, Lacey KJ, Latta LC, Sekelsky J, Stoffregen EP. Blm helicase facilitates rapid replication of repetitive DNA sequences in early Drosophila development. Genetics 2022; 220:iyab169. [PMID: 34849849 PMCID: PMC8733427 DOI: 10.1093/genetics/iyab169] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 09/18/2021] [Indexed: 11/12/2022] Open
Abstract
The absence of functional BLM DNA helicase, a member of the RecQ family of helicases, is responsible for the rare human disorder Bloom Syndrome, which results in developmental abnormalities, DNA repair defects, genomic instability, and a predisposition to cancer. In Drosophila melanogaster, the orthologous Blm protein is essential during early development when the embryo is under the control of maternal gene products. We show that lack of functional maternal Blm during the syncytial cell cycles of Drosophila embryonic development results in severe nuclear defects and lethality. Amongst the small fraction of embryos from Blm mutant mothers that survive to adulthood, a prominent sex-bias favors the class that inherits less repetitive DNA content, which serves as an endogenous source of replication stress. This selection against repetitive DNA content reflects a role for Blm in facilitating replication through repetitive sequences during the rapid S-phases of syncytial cell cycles. During these syncytial cycles, Blm is not required for complex DNA double-strand break repair; however, the progeny sex-bias resulting from the absence of maternal Blm is exacerbated by repetitive DNA sequences and by the slowing of replication fork progression, suggesting that the essential role for Blm during this stage is to manage replication fork stress brought about by impediments to fork progression. Additionally, our data suggest that Blm is only required to manage this replication stress during embryonic development, and likely only during the early, rapid syncytial cell cycles, and not at later developmental stages. These results provide novel insights into Blm function throughout development.
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Affiliation(s)
- Jolee M Ruchert
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Morgan M Brady
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Susan McMahan
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Karly J Lacey
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Leigh C Latta
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
| | - Jeff Sekelsky
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
- Integrative Program for Biological and Genome Sciences, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Eric P Stoffregen
- Physical, Life, Movement & Sport Sciences, Lewis-Clark State College, Lewiston, ID 83501, USA
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
- SPIRE Postdoctoral Fellowship Program, University of North Carolina, Chapel Hill, NC 27599, USA
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3
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Simonini S, Bemer M, Bencivenga S, Gagliardini V, Pires ND, Desvoyes B, van der Graaff E, Gutierrez C, Grossniklaus U. The Polycomb group protein MEDEA controls cell proliferation and embryonic patterning in Arabidopsis. Dev Cell 2021; 56:1945-1960.e7. [PMID: 34192526 PMCID: PMC8279741 DOI: 10.1016/j.devcel.2021.06.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/22/2021] [Accepted: 06/07/2021] [Indexed: 12/13/2022]
Abstract
Establishing the embryonic body plan of multicellular organisms relies on precisely orchestrated cell divisions coupled with pattern formation, which, in animals, are regulated by Polycomb group (PcG) proteins. The conserved Polycomb Repressive Complex 2 (PRC2) mediates H3K27 trimethylation and comes in different flavors in Arabidopsis. The PRC2 catalytic subunit MEDEA is required for seed development; however, a role for PRC2 in embryonic patterning has been dismissed. Here, we demonstrate that embryos derived from medea eggs abort because MEDEA is required for patterning and cell lineage determination in the early embryo. Similar to PcG proteins in mammals, MEDEA regulates embryonic patterning and growth by controlling cell-cycle progression through repression of CYCD1;1, which encodes a core cell-cycle component. Thus, Arabidopsis embryogenesis is epigenetically regulated by PcG proteins, revealing that the PRC2-dependent modulation of cell-cycle progression was independently recruited to control embryonic cell proliferation and patterning in animals and plants.
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Affiliation(s)
- Sara Simonini
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Marian Bemer
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Stefano Bencivenga
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Valeria Gagliardini
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Nuno D Pires
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Bénédicte Desvoyes
- Centro de Biología Molecular Severo Ochoa CSIC-UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Eric van der Graaff
- BIOSS Centre for Biological Signaling Studies, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany
| | - Crisanto Gutierrez
- Centro de Biología Molecular Severo Ochoa CSIC-UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Ueli Grossniklaus
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, 8008 Zurich, Switzerland.
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PRC1 Prevents Replication Stress during Chondrogenic Transit Amplification. EPIGENOMES 2017. [DOI: 10.3390/epigenomes1030022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Kassis JA, Kennison JA, Tamkun JW. Polycomb and Trithorax Group Genes in Drosophila. Genetics 2017; 206:1699-1725. [PMID: 28778878 PMCID: PMC5560782 DOI: 10.1534/genetics.115.185116] [Citation(s) in RCA: 149] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/15/2017] [Indexed: 01/08/2023] Open
Abstract
Polycomb group (PcG) and Trithorax group (TrxG) genes encode important regulators of development and differentiation in metazoans. These two groups of genes were discovered in Drosophila by their opposing effects on homeotic gene (Hox) expression. PcG genes collectively behave as genetic repressors of Hox genes, while the TrxG genes are necessary for HOX gene expression or function. Biochemical studies showed that many PcG proteins are present in two protein complexes, Polycomb repressive complexes 1 and 2, which repress transcription via chromatin modifications. TrxG proteins activate transcription via a variety of mechanisms. Here we summarize the large body of genetic and biochemical experiments in Drosophila on these two important groups of genes.
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Affiliation(s)
- Judith A Kassis
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - James A Kennison
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - John W Tamkun
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California 95064
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Coordinating Cell Cycle Remodeling with Transcriptional Activation at the Drosophila MBT. Curr Top Dev Biol 2015; 113:113-48. [DOI: 10.1016/bs.ctdb.2015.06.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Luna, a Drosophila KLF6/KLF7, is maternally required for synchronized nuclear and centrosome cycles in the preblastoderm embryo. PLoS One 2014; 9:e96933. [PMID: 24915236 PMCID: PMC4051582 DOI: 10.1371/journal.pone.0096933] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 04/11/2014] [Indexed: 11/20/2022] Open
Abstract
Krüppel like factors (KLFs) are conserved transcription factors that have been implicated in many developmental processes including differentiation, organ patterning, or regulation of stem cell pluripotency. We report the generation and analysis of loss-of-function mutants of Drosophila Klf6/7, the luna gene. We demonstrate that luna mutants are associated with very early embryonic defects prior to cellularization at the syncytial stage and cause DNA separation defects during the rapid mitotic cycles resulting in un-coupled DNA and centrosome cycles. These defects manifest themselves, both in animals that are maternally homozygous and heterozygous mutant. Surprisingly, luna is only required during the syncytial stages and not later in development, suggesting that the DNA segregation defect is linked to centrosomes, since centrosomes are dispensable for later cell divisions.
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Pushpavalli SNCVL, Sarkar A, Bag I, Hunt CR, Ramaiah MJ, Pandita TK, Bhadra U, Pal-Bhadra M. Argonaute-1 functions as a mitotic regulator by controlling Cyclin B during Drosophila early embryogenesis. FASEB J 2013; 28:655-66. [PMID: 24165481 DOI: 10.1096/fj.13-231167] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The role of Ago-1 in microRNA (miRNA) biogenesis has been thoroughly studied, but little is known about its involvement in mitotic cell cycle progression. In this study, we established evidence of the regulatory role of Ago-1 in cell cycle control in association with the G2/M cyclin, cyclin B. Immunostaining of early embryos revealed that the maternal effect gene Ago-1 is essential for proper chromosome segregation, mitotic cell division, and spindle fiber assembly during early embryonic development. Ago-1 mutation resulted in the up-regulation of cyclin B-Cdk1 activity and down-regulation of p53, grp, mei-41, and wee1. The increased expression of cyclin B in Ago-1 mutants caused less stable microtubules and probably does not produce enough force to push the nuclei to the cortex, resulting in a decreased number of pole cells. The role of cyclin B in mitotic defects was further confirmed by suppressing the defects in the presence of one mutant copy of cyclin B. We identified involvement of 2 novel embryonic miRNAs--miR-981 and miR--317-for spatiotemporal regulation of cyclin B. In summary, our results demonstrate that the haploinsufficiency of maternal Ago-1 disrupts mitotic chromosome segregation and spindle fiber assembly via miRNA-guided control during early embryogenesis in Drosophila. The increased expression of cyclin B-Cdk1 and decreased activity of the Cdk1 inhibitor and cell cycle checkpoint proteins (mei-41 and grp) in Ago-1 mutant embryos allow the nuclei to enter into mitosis prematurely, even before completion of DNA replication. Thus, our results have established a novel role of Ago-1 as a regulator of the cell cycle.
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Pushpavalli SNCVL, Sarkar A, Ramaiah MJ, Chowdhury DR, Bhadra U, Pal-Bhadra M. Drosophila MOF controls Checkpoint protein2 and regulates genomic stability during early embryogenesis. BMC Mol Biol 2013; 14:1. [PMID: 23347679 PMCID: PMC3566930 DOI: 10.1186/1471-2199-14-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/18/2013] [Indexed: 01/01/2023] Open
Abstract
Background In Drosophila embryos, checkpoints maintain genome stability by delaying cell cycle progression that allows time for damage repair or to complete DNA synthesis. Drosophila MOF, a member of MYST histone acetyl transferase is an essential component of male X hyperactivation process. Until recently its involvement in G2/M cell cycle arrest and defects in ionizing radiation induced DNA damage pathways was not well established. Results Drosophila MOF is highly expressed during early embryogenesis. In the present study we show that haplo-insufficiency of maternal MOF leads to spontaneous mitotic defects like mitotic asynchrony, mitotic catastrophe and chromatid bridges in the syncytial embryos. Such abnormal nuclei are eliminated and digested in the yolk tissues by nuclear fall out mechanism. MOF negatively regulates Drosophila checkpoint kinase 2 tumor suppressor homologue. In response to DNA damage the checkpoint gene Chk2 (Drosophila mnk) is activated in the mof mutants, there by causing centrosomal inactivation suggesting its role in response to genotoxic stress. A drastic decrease in the fall out nuclei in the syncytial embryos derived from mof1/+; mnkp6/+ females further confirms the role of DNA damage response gene Chk2 to ensure the removal of abnormal nuclei from the embryonic precursor pool and maintain genome stability. The fact that mof mutants undergo DNA damage has been further elucidated by the increased number of single and double stranded DNA breaks. Conclusion mof mutants exhibited genomic instability as evidenced by the occurance of frequent mitotic bridges in anaphase, asynchronous nuclear divisions, disruption of cytoskeleton, inactivation of centrosomes finally leading to DNA damage. Our findings are consistent to what has been reported earlier in mammals that; reduced levels of MOF resulted in increased genomic instability while total loss resulted in lethality. The study can be further extended using Drosophila as model system and carry out the interaction of MOF with the known components of the DNA damage pathway.
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Mohd-Sarip A, Lagarou A, Doyen CM, van der Knaap JA, Aslan U, Bezstarosti K, Yassin Y, Brock HW, Demmers JAA, Verrijzer CP. Transcription-Independent Function of Polycomb Group Protein PSC in Cell Cycle Control. Science 2012; 336:744-7. [DOI: 10.1126/science.1215927] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Touma JJ, Weckerle FF, Cleary MD. Drosophila Polycomb complexes restrict neuroblast competence to generate motoneurons. Development 2012; 139:657-66. [DOI: 10.1242/dev.071589] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Similar to mammalian neural progenitors, Drosophila neuroblasts progressively lose competence to make early-born neurons. In neuroblast 7-1 (NB7-1), Kruppel (Kr) specifies the third-born U3 motoneuron and Kr misexpression induces ectopic U3 cells. However, competence to generate U3 cells is limited to early divisions, when the Eve+ U motoneurons are produced, and competence is lost when NB7-1 transitions to making interneurons. We have found that Polycomb repressor complexes (PRCs) are necessary and sufficient to restrict competence in NB7-1. PRC loss of function extends the ability of Kr to induce U3 fates and PRC gain of function causes precocious loss of competence to make motoneurons. PRCs also restrict competence to make HB9+ Islet+ motoneurons in another neuroblast that undergoes a motoneuron-to-interneuron transition, NB3-1. In contrast to the regulation of motoneuron competence, PRC activity does not affect the production of Eve+ interneurons by NB3-3, HB9+ Islet+ interneurons by NB7-3, or Dbx+ interneurons by multiple neuroblasts. These findings support a model in which PRCs establish motoneuron-specific competence windows in neuroblasts that transition from motoneuron to interneuron production.
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Affiliation(s)
- Johnny J. Touma
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
| | - Frank F. Weckerle
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
| | - Michael D. Cleary
- School of Natural Sciences, University of California Merced, Merced, CA 95343, USA
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Strübbe G, Popp C, Schmidt A, Pauli A, Ringrose L, Beisel C, Paro R. Polycomb purification by in vivo biotinylation tagging reveals cohesin and Trithorax group proteins as interaction partners. Proc Natl Acad Sci U S A 2011; 108:5572-7. [PMID: 21415365 PMCID: PMC3078387 DOI: 10.1073/pnas.1007916108] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The maintenance of specific gene expression patterns during cellular proliferation is crucial for the identity of every cell type and the development of tissues in multicellular organisms. Such a cellular memory function is conveyed by the complex interplay of the Polycomb and Trithorax groups of proteins (PcG/TrxG). These proteins exert their function at the level of chromatin by establishing and maintaining repressed (PcG) and active (TrxG) chromatin domains. Past studies indicated that a core PcG protein complex is potentially associated with cell type or even cell stage-specific sets of accessory proteins. In order to better understand the dynamic aspects underlying PcG composition and function we have established an inducible version of the biotinylation tagging approach to purify Polycomb and associated factors from Drosophila embryos. This system enabled fast and efficient isolation of Polycomb containing complexes under near physiological conditions, thereby preserving substoichiometric interactions. Novel interacting proteins were identified by highly sensitive mass spectrometric analysis. We found many TrxG related proteins, suggesting a previously unrecognized extent of molecular interaction of the two counteracting chromatin regulatory protein groups. Furthermore, our analysis revealed an association of PcG protein complexes with the cohesin complex and showed that Polycomb-dependent silencing of a transgenic reporter depends on cohesin function.
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Affiliation(s)
- Gero Strübbe
- Department of Biosystems Science and Engineering, Swiss Federal Institute of Technology Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Christian Popp
- The Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, United Kingdom
| | - Alexander Schmidt
- Institute of Molecular Systems Biology, Swiss Federal Institute of Technology Zürich, Wolfgang-Pauli-Strasse 16, 8093 Zürich, Switzerland
| | - Andrea Pauli
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom
| | - Leonie Ringrose
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, 1030 Vienna, Austria; and
| | - Christian Beisel
- Department of Biosystems Science and Engineering, Swiss Federal Institute of Technology Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Renato Paro
- Department of Biosystems Science and Engineering, Swiss Federal Institute of Technology Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
- Faculty of Sciences, University of Basel, 4056 Basel, Switzerland
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Sauvageau M, Sauvageau G. Polycomb group proteins: multi-faceted regulators of somatic stem cells and cancer. Cell Stem Cell 2010; 7:299-313. [PMID: 20804967 PMCID: PMC4959883 DOI: 10.1016/j.stem.2010.08.002] [Citation(s) in RCA: 543] [Impact Index Per Article: 36.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/30/2010] [Accepted: 08/06/2010] [Indexed: 02/06/2023]
Abstract
Polycomb Group (PcG) proteins are transcriptional repressors that epigenetically modify chromatin and participate in the establishment and maintenance of cell fates. These proteins play important roles in both stem cell self-renewal and in cancer development. Our understanding of their mechanism of action has greatly advanced over the past 10 years, but many unanswered questions remain. In this review, we present the currently available experimental data that connect PcG protein function with some of the key processes which govern somatic stem cell activity. We also highlight recent studies suggesting that a delicate balance in PcG gene dosage is crucial for proper stem cell homeostasis and prevention of cancer stem cell development.
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Affiliation(s)
- Martin Sauvageau
- Molecular Genetics of Stem Cells Laboratory, Institute of Research in Immunology and Cancer, University of Montreal, Montreal, QC H3C 3J7, Canada.
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Beck SA, Falconer E, Catching A, Hodgson JW, Brock HW. Cell cycle defects in polyhomeotic mutants are caused by abrogation of the DNA damage checkpoint. Dev Biol 2010; 339:320-8. [PMID: 20045683 DOI: 10.1016/j.ydbio.2009.12.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 10/30/2009] [Accepted: 12/19/2009] [Indexed: 12/31/2022]
Abstract
Polycomb group (PcG) genes are required for heritable silencing of target genes. Many PcG mutants have chromatin bridges and other mitotic defects in early embryos. These phenotypes can arise from defects in S phase or mitosis, so the phenotype does not show when PcG proteins act in cell cycle regulation. We analyzed the cell cycle role of the proximal subunit of Polyhomeotic (PhP) in Drosophila. Time-lapse imaging reveals that chromatin bridges formed during mitosis are able to resolve but sometimes result in chromosome breakage. Chromosome bridging is also observed in canonical cell cycles occurring in larval brains and is therefore not unique to the rapid embryonic cycles. PhP colocalizes with chromatin in S phase but not in mitosis in early embryos, indicating a direct role in DNA synthesis. Time lapse imaging of ph(p) mutants reveals an acceleration of S phase, showing that ph(p) regulates S phase length. Like ph(p) mutations, mutations in DNA damage checkpoints result in S phase acceleration. Consistent with this model, mutations in ph do not affect DNA synthesis rates, but exhibit impaired ability to block cell cycle progression following exposure to gamma-rays. Our data show that the mitotic defects of ph(p) are caused by defects in the DNA damage response that occurs after DNA replication in S phase, and we propose that PhP has a direct role in DNA damage repair.
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Affiliation(s)
- Samantha A Beck
- Molecular Epigenetics Group, Department of Zoology, University of BC, Life Sciences Centre, 2350 Health Sciences Mall Vancouver, BC, Canada V6T 1Z3
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Polycomb group complexes--many combinations, many functions. Trends Cell Biol 2009; 19:692-704. [PMID: 19889541 DOI: 10.1016/j.tcb.2009.10.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 10/05/2009] [Accepted: 10/05/2009] [Indexed: 11/21/2022]
Abstract
Polycomb Group (PcG) proteins are transcription regulatory proteins that control the expression of a variety of genes from early embryogenesis through birth to adulthood. PcG proteins form several complexes that are thought to collaborate to repress gene transcription. Individual PcG proteins have unique characteristics, and mutations in genes encoding different PcG proteins cause distinct phenotypes. Histone modifications have important roles in some PcG protein functions, but they are not universally required. The mechanisms of gene-specific recruitment, transcription repression, and selective derepression of genes by vertebrate PcG proteins are incompletely understood. Future studies of this enigmatic group of developmental regulators are certain to produce unanticipated discoveries.
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Meagher RB, Kandasamy MK, McKinney EC, Roy E. Chapter 5. Nuclear actin-related proteins in epigenetic control. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 277:157-215. [PMID: 19766970 PMCID: PMC2800988 DOI: 10.1016/s1937-6448(09)77005-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The nuclear actin-related proteins (ARPs) share overall structure and low-level sequence homology with conventional actin. They are indispensable subunits of macromolecular machines that control chromatin remodeling and modification leading to dynamic changes in DNA structure, transcription, and DNA repair. Cellular, genetic, and biochemical studies suggest that the nuclear ARPs are essential to the epigenetic control of the cell cycle and cell proliferation in all eukaryotes, while in plants and animals they also exert epigenetic controls over most stages of multicellular development including organ initiation, the switch to reproductive development, and senescence and programmed cell death. A theme emerging from plants and animals is that in addition to their role in controlling the general compaction of DNA and gene silencing, isoforms of nuclear ARP-containing chromatin complexes have evolved to exert dynamic epigenetic control over gene expression and different phases of multicellular development. Herein, we explore this theme by examining nuclear ARP phylogeny, activities of ARP-containing chromatin remodeling complexes that lead to epigenetic control, expanding developmental roles assigned to several animal and plant ARP-containing complexes, the evidence that thousands of ARP complex isoforms may have evolved in concert with multicellular development, and ARPs in human disease.
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Affiliation(s)
- Richard B Meagher
- Department of Genetics, Davison Life Sciences Building, University of Georgia, Athens, GA 30602, USA
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Hallson G, Syrzycka M, Beck SA, Kennison JA, Dorsett D, Page SL, Hunter SM, Keall R, Warren WD, Brock HW, Sinclair DAR, Honda BM. The Drosophila cohesin subunit Rad21 is a trithorax group (trxG) protein. Proc Natl Acad Sci U S A 2008; 105:12405-10. [PMID: 18713858 PMCID: PMC2527924 DOI: 10.1073/pnas.0801698105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Indexed: 12/19/2022] Open
Abstract
The cohesin complex is a key player in regulating cell division. Cohesin proteins SMC1, SMC3, Rad21, and stromalin (SA), along with associated proteins Nipped-B, Pds5, and EcoI, maintain sister chromatid cohesion before segregation to daughter cells during anaphase. Recent chromatin immunoprecipitation (ChIP) data reveal extensive overlap of Nipped-B and cohesin components with RNA polymerase II binding at active genes in Drosophila. These and other data strongly suggest a role for cohesion in transcription; however, there is no clear evidence for any specific mechanisms by which cohesin and associated proteins regulate transcription. We report here a link between cohesin components and trithorax group (trxG) function, thus implicating these proteins in transcription activation and/or elongation. We show that the Drosophila Rad21 protein is encoded by verthandi (vtd), a member of the trxG gene family that is also involved in regulating the hedgehog (hh) gene. In addition, mutations in the associated protein Nipped-B show similar trxG activity i.e., like vtd, they act as dominant suppressors of Pc and hh(Mrt) without impairing cell division. Our results provide a framework to further investigate how cohesin and associated components might regulate transcription.
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Affiliation(s)
- Graham Hallson
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | - Monika Syrzycka
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | - Samantha A. Beck
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - James A. Kennison
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-2785
| | - Dale Dorsett
- Department of Biochemistry and Molecular Biology, School of Medicine, St. Louis University, St. Louis, MO 63104; and
| | - Scott L. Page
- Comparative Genomics Centre, James Cook University, Townsville 4811, Queensland, Australia
| | - Sally M. Hunter
- Comparative Genomics Centre, James Cook University, Townsville 4811, Queensland, Australia
| | - Rebecca Keall
- Comparative Genomics Centre, James Cook University, Townsville 4811, Queensland, Australia
| | - William D. Warren
- Comparative Genomics Centre, James Cook University, Townsville 4811, Queensland, Australia
| | - Hugh W. Brock
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Donald A. R. Sinclair
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | - Barry M. Honda
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
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Joshi P, Carrington EA, Wang L, Ketel CS, Miller EL, Jones RS, Simon JA. Dominant alleles identify SET domain residues required for histone methyltransferase of Polycomb repressive complex 2. J Biol Chem 2008; 283:27757-27766. [PMID: 18693240 DOI: 10.1074/jbc.m804442200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycomb gene silencing requires histone methyltransferase activity of Polycomb repressive complex 2 (PRC2), which methylates lysine 27 of histone H3. Information on how PRC2 works is limited by lack of structural data on the catalytic subunit, Enhancer of zeste (E(Z)), and the paucity of E(z) mutant alleles that alter its SET domain. Here we analyze missense alleles of Drosophila E(z), selected for molecular study because of their dominant genetic effects. Four missense alleles identify key E(Z) SET domain residues, and a fifth is located in the adjacent CXC domain. Analysis of mutant PRC2 complexes in vitro, and H3-K27 methylation in vivo, shows that each SET domain mutation disrupts PRC2 histone methyltransferase. Based on known SET domain structures, the mutations likely affect either the lysine-substrate binding pocket, the binding site for the adenosylmethionine methyl donor, or a critical tyrosine predicted to interact with the substrate lysine epsilon-amino group. In contrast, the CXC mutant retains catalytic activity, Lys-27 specificity, and trimethylation capacity. Deletion analysis also reveals a functional requirement for a conserved E(Z) domain N-terminal to CXC and SET. These results identify critical SET domain residues needed for PRC2 enzyme function, and they also emphasize functional inputs from outside the SET domain.
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Affiliation(s)
- Preeti Joshi
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minneapolis 55455
| | | | - Liangjun Wang
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minneapolis 55455
| | - Carrie S Ketel
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minneapolis 55455
| | - Ellen L Miller
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minneapolis 55455
| | - Richard S Jones
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275.
| | - Jeffrey A Simon
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minneapolis 55455.
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Abstract
The Drosophila dRYBP gene has been described to function as a Polycomb-dependent transcriptional repressor. To determine the in vivo function of the dRYBP gene, we have generated mutations and analyzed the associated phenotypes. Homozygous null mutants die progressively throughout development and present phenotypes variable both in their penetrance and in their expressivity, including disrupted oogenesis, a disorganized pattern of the syncytial nuclear divisions, defects in pattern formation, and decreased wing size. Although dRYBP mutations do not show the homeotic-like phenotypes typical of mutations in the PcG and trxG genes, they enhance the phenotypes of mutations of either the Sex comb extra gene (PcG) or the trithorax gene (trxG). Finally, the dRYBP protein interacts physically with the Sex comb extra and the Pleiohomeotic proteins, and the homeotic-like phenotypes produced by the high levels of the dRYBP protein are mediated through its C-terminal domain. Our results indicate that the dRYBP gene functions in the control of cell identity together with the PcG/trxG proteins. Furthermore, they also indicate that dRYBP participates in the control of cell proliferation and cell differentiation and we propose that its functional requirement may well depend on the robustness of the animal.
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The enhancer of trithorax and polycomb corto interacts with cyclin G in Drosophila. PLoS One 2008; 3:e1658. [PMID: 18286205 PMCID: PMC2243016 DOI: 10.1371/journal.pone.0001658] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Accepted: 01/21/2008] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Polycomb (PcG) and trithorax (trxG) genes encode proteins involved in the maintenance of gene expression patterns, notably Hox genes, throughout development. PcG proteins are required for long-term gene repression whereas TrxG proteins are positive regulators that counteract PcG action. PcG and TrxG proteins form large complexes that bind chromatin at overlapping sites called Polycomb and Trithorax Response Elements (PRE/TRE). A third class of proteins, so-called "Enhancers of Trithorax and Polycomb" (ETP), interacts with either complexes, behaving sometimes as repressors and sometimes as activators. The role of ETP proteins is largely unknown. METHODOLOGY/PRINCIPAL FINDINGS In a two-hybrid screen, we identified Cyclin G (CycG) as a partner of the Drosophila ETP Corto. Inactivation of CycG by RNA interference highlights its essential role during development. We show here that Corto and CycG directly interact and bind to each other in embryos and S2 cells. Moreover, CycG is targeted to polytene chromosomes where it co-localizes at multiple sites with Corto and with the PcG factor Polyhomeotic (PH). We observed that corto is involved in maintaining Abd-B repression outside its normal expression domain in embryos. This could be achieved by association between Corto and CycG since both proteins bind the regulatory element iab-7 PRE and the promoter of the Abd-B gene. CONCLUSIONS/SIGNIFICANCE Our results suggest that CycG could regulate the activity of Corto at chromatin and thus be involved in changing Corto from an Enhancer of TrxG into an Enhancer of PcG.
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Breiling A, Sessa L, Orlando V. Biology of polycomb and trithorax group proteins. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 258:83-136. [PMID: 17338920 DOI: 10.1016/s0074-7696(07)58002-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cellular phenotypes can be ascribed to different patterns of gene expression. Epigenetic mechanisms control the generation of different phenotypes from the same genotype. Thus differentiation is basically a process driven by changes in gene activity during development, often in response to transient factors or environmental stimuli. To keep the specific characteristics of cell types, tissue-specific gene expression patterns must be transmitted stably from one cell to the daughter cells, also in the absence of the early-acting determination factors. This heritability of patterns of active and inactive genes is enabled by epigenetic mechanisms that create a layer of information on top of the DNA sequence that ensures mitotic and sometimes also meiotic transmission of expression patterns. The proteins of the Polycomb and Trithorax group comprise such a cellular memory mechanism that preserves gene expression patterns through many rounds of cell division. This review provides an overview of the genetics and molecular biology of these maintenance proteins, concentrating mainly on mechanisms of Polycomb group-mediated repression.
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Affiliation(s)
- Achim Breiling
- Dulbecco Telethon Institute, Institute of Genetics and Biophysics, CNR, 80131 Naples, Italy
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