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Membrane proteins structures: A review on computational modeling tools. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2021-2039. [DOI: 10.1016/j.bbamem.2017.07.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 07/04/2017] [Accepted: 07/13/2017] [Indexed: 01/02/2023]
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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: 142] [Impact Index Per Article: 20.3] [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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EED-associated overgrowth in a second male patient. J Hum Genet 2016; 61:831-4. [PMID: 27193220 DOI: 10.1038/jhg.2016.51] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 03/30/2016] [Accepted: 04/13/2016] [Indexed: 01/03/2023]
Abstract
Following our discovery that constitutional mutations in EED can cause overgrowth, we screened our cohort of patients with Weaver-like features for mutations in this gene. Here we describe a second patient with a different, rare and de novo mutation in EED. Phenotypic overlap with our first case of EED-associated overgrowth is significant. Now that we have found two unrelated families of different ethnicities, with a similar rare phenotype, both associated with de novo mutations in this member of the PRC2 complex, we are confident that EED is indeed a novel overgrowth gene.
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PINK1 regulates histone H3 trimethylation and gene expression by interaction with the polycomb protein EED/WAIT1. Proc Natl Acad Sci U S A 2013; 110:14729-34. [PMID: 23959866 DOI: 10.1073/pnas.1216844110] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Mutations in PTEN-induced putative kinase 1 (PINK1) gene are associated to early-onset recessive forms of Parkinson disease. PINK1 function is related to mitochondria homeostasis, but the molecular pathways in which PINK1 is involved are largely unknown. Here, we report the identification of the embryonic ectoderm development polycomb histone-methylation modulator (EED/WAIT1) as a PINK1-interacting and -regulated protein. The PINK1:EED/WAIT1 physical interaction was mediated by the PINK1 kinase domain and the EED/WAIT1 40 amino acid ending with tryptophan and aspartate (WD40)-repeat region, and PINK1 phosphorylated EED/WAIT1 in vitro. PINK1 associated with EED/WAIT1 in cells and relocated EED/WAIT1 to the mitochondria. This interaction reduced the trimethylation of lysine 27 from histone H3, which affected polycomb-regulated gene transcription during RA differentiation of SH-SY5Y human neuroblastoma cells. Our findings unveil a pathway by which PINK1 regulates histone methylation and gene expression through the polycomb repressor complex.
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Liu DD, Dong QL, Fang MJ, Chen KQ, Hao YJ. Ectopic expression of an apple apomixis-related gene MhFIE induces co-suppression and results in abnormal vegetative and reproductive development in tomato. JOURNAL OF PLANT PHYSIOLOGY 2012; 169:1866-73. [PMID: 23000466 DOI: 10.1016/j.jplph.2012.07.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 07/11/2012] [Accepted: 07/16/2012] [Indexed: 05/10/2023]
Abstract
It has been well documented that FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) plays important regulatory roles in diverse developmental processes in model plant Arabidopsis thaliana. However, it is largely unknown how FIE genes function in economically important crops. In this study, MhFIE gene, which was previously isolated from apomictic tea crabapple (Malus hupehensis Redh. var. pingyiensis), was introduced into tomato. The hemizygous transgenic tomato lines produced curly leaves and decreased in seed germination. In addition, the co-suppression of the transgenic MhFIE and endogenous (SlFIE) genes occurred in homozygous transgenic tomatoes. As a result, FIE silencing brought about abnormal phenotypes during reproductive development in tomato, such as increased sepal and petal numbers in flower, a fused ovule and pistil and parthenocarpic fruit formation. A yeast two-hybrid assay and bimolecular fluorescence complementation (BiFC) demonstrated that MhFIE interacted with a tomato protein, EZ2 (SlEZ2). Its ectopic expression and SlFIE co-suppression notably influenced the expression of genes associated with leaf, flower, and fruit development. Therefore, together with other PcG proteins, FIE was involved in the regulation of vegetative and reproductive development by modulating the expression of related genes in plants.
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Affiliation(s)
- Dan-Dan Liu
- National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong 271018, China
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Almada R, Cabrera N, Casaretto JA, Peña-Cortés H, Ruiz-Lara S, González Villanueva E. Epigenetic repressor-like genes are differentially regulated during grapevine (Vitis vinifera L.) development. PLANT CELL REPORTS 2011; 30:1959-1968. [PMID: 21681473 DOI: 10.1007/s00299-011-1104-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 05/18/2011] [Accepted: 06/02/2011] [Indexed: 05/28/2023]
Abstract
Grapevine sexual reproduction involves a seasonal separation between inflorescence primordia (flowering induction) and flower development. We hypothesized that a repression mechanism implicating epigenetic changes could play a role in the seasonal separation of these two developmental processes in grapevine. Therefore, the expression of five grapevine genes with homology to the Arabidopsis epigenetic repressor genes FERTILIZATION INDEPENDENT ENDOSPERM (FIE), EMBRYONIC FLOWER 2 (EMF2), CURLY LEAF (CLF), MULTICOPY SUPPRESSOR OF IRA 1 (MSI1) and SWINGER (SWN) was analyzed during the development of buds and vegetative and reproductive organs. During bud development, the putative grapevine epigenetic repressor genes VvCLF, VvEMF2, VvMSI1, VvSWN and VvFIE are mainly expressed in latent buds at the flowering induction period, but also detected during bud burst and inflorescence/flower development. The overlapping expression patterns of grapevine PcG-like genes in buds suggest that chromatin remodeling mechanisms could be operating during grapevine bud development for controlling processes such as seasonal flowering, dormancy and bud burst. Furthermore, the expression of grapevine PcG-like genes was also detected in fruits and vegetative organs, suggesting that epigenetic changes could be at the basis of the regulation of various proliferation-differentiation cell transitions that occur during grapevine development.
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Affiliation(s)
- Rubén Almada
- Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Talca, Chile.
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Rodrigues JCM, Tucker MR, Johnson SD, Hrmova M, Koltunow AMG. Sexual and apomictic seed formation in Hieracium requires the plant polycomb-group gene FERTILIZATION INDEPENDENT ENDOSPERM. THE PLANT CELL 2008; 20:2372-86. [PMID: 18812497 PMCID: PMC2570734 DOI: 10.1105/tpc.108.059287] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 09/02/2008] [Accepted: 09/10/2008] [Indexed: 05/21/2023]
Abstract
A Polycomb-Group (PcG) complex, FERTILIZATION INDEPENDENT SEED (FIS), represses endosperm development in Arabidopsis thaliana until fertilization occurs. The Hieracium genus contains apomictic species that form viable seeds asexually. To investigate FIS function during apomictic seed formation, FERTILIZATION INDEPENDENT ENDOSPERM (FIE), encoding a WD-repeat member of the FIS complex, was isolated and downregulated in sexual and apomictic Hieracium species. General downregulation led to defects in leaf and seed development, consistent with a role in developmental transitions and cell fate. PcG-like activity of Hieracium FIE was also supported by its interaction in vitro with the Arabidopsis CURLY LEAF PcG protein. By contrast, specific downregulation of FIE in developing seeds of sexual Hieracium did not result in autonomous endosperm proliferation but led to seed abortion after cross-pollination. Furthermore, in apomictic Hieracium, specific FIE downregulation inhibited autonomous embryo and endosperm initiation, and most autonomous seeds displayed defective embryo and endosperm growth. Therefore, FIE is required for both apomictic and fertilization-induced seed initiation in Hieracium. Since Hieracium FIE failed to interact with FIS class proteins in vitro, its partner proteins might differ from those in the FIS complex of Arabidopsis. These differences in protein interaction were attributed to structural modifications predicted from comparisons of Arabidopsis and Hieracium FIE molecular models.
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Affiliation(s)
- Julio C M Rodrigues
- Commonwealth Scientific and Industrial Research Organization Plant Industry, Glen Osmond, South Australia 5064, Australia
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Rakotobe D, Violot S, Hong SS, Gouet P, Boulanger P. Mapping of immunogenic and protein-interacting regions at the surface of the seven-bladed beta-propeller domain of the HIV-1 cellular interactor EED. Virol J 2008; 5:32. [PMID: 18302803 PMCID: PMC2292171 DOI: 10.1186/1743-422x-5-32] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Accepted: 02/27/2008] [Indexed: 11/29/2022] Open
Abstract
Background The human EED protein, a member of the superfamily of Polycomb group proteins, is involved in multiple cellular protein complexes. Its C-terminal domain, which is common to the four EED isoforms, contains seven repeats of a canonical WD-40 motif. EED is an interactor of three HIV-1 proteins, matrix (MA), integrase (IN) and Nef. An antiviral activity has been found to be associated with isoforms EED3 and EED4 at the late stage of HIV-1 replication, due to a negative effect on virus assembly and genomic RNA packaging. The aim of the present study was to determine the regions of the EED C-terminal core domain which were accessible and available to protein interactions, using three-dimensional (3D) protein homology modelling with a WD-40 protein of known structure, and epitope mapping of anti-EED antibodies. Results Our data suggested that the C-terminal domain of EED was folded as a seven-bladed β-propeller protein. During the completion of our work, crystallographic data of EED became available from co-crystals of the EED C-terminal core with the N-terminal domain of its cellular partner EZH2. Our 3D-model was in good congruence with the refined structural model determined from crystallographic data, except for a unique α-helix in the fourth β-blade. More importantly, the position of flexible loops and accessible β-strands on the β-propeller was consistent with our mapping of immunogenic epitopes and sites of interaction with HIV-1 MA and IN. Certain immunoreactive regions were found to overlap with the EZH2, MA and IN binding sites, confirming their accessibility and reactivity at the surface of EED. Crystal structure of EED showed that the two discrete regions of interaction with MA and IN did not overlap with each other, nor with the EZH2 binding pocket, but were contiguous, and formed a continuous binding groove running along the lateral face of the β-propeller. Conclusion Identification of antibody-, MA-, IN- and EZH2-binding sites at the surface of the EED isoform 3 provided a global picture of the immunogenic and protein-protein interacting regions in the EED C-terminal domain, organized as a seven-bladed β-propeller protein. Mapping of the HIV-1 MA and IN binding sites on the 3D-model of EED core predicted that EED-bound MA and IN ligands would be in close vicinity at the surface of the β-propeller, and that the occurrence of a ternary complex MA-EED-IN would be possible.
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Affiliation(s)
- Dina Rakotobe
- Laboratoire de Virologie & Pathologie Humaine, Université Lyon I & CNRS FRE-3011, Faculté de Médecine Laennec, 7 rue Guillaume Paradin, 69372 Lyon Cedex 08, France.
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Han Z, Xing X, Hu M, Zhang Y, Liu P, Chai J. Structural basis of EZH2 recognition by EED. Structure 2007; 15:1306-15. [PMID: 17937919 DOI: 10.1016/j.str.2007.08.007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2007] [Revised: 08/20/2007] [Accepted: 08/21/2007] [Indexed: 11/30/2022]
Abstract
The WD-repeat domain is a highly conserved recognition module in eukaryotes involved in diverse cellular processes. It is still not well understood how the bottom of a WD-repeat domain recognizes its binding partners. The WD-repeat-containing protein EED is one component of the PRC2 complex that possesses histone methyltransferase activity required for gene repression. Here we report the crystal structure of EED in complex with a 30 residue peptide from EZH2. The structure reveals that the peptide binds to the bottom of the WD-repeat domain of EED. The structural determinants of EZH2-EED interaction are present not only in EZH2 and EZH1 but also in its Drosophila homolog E(Z), suggesting that the recognition of ESC by E(Z) in Drosophila employs similar structural motifs. Structure-based mutagenesis identified critical residues from both EED and EZH2 for their interaction. The structure presented here may provide a template for understanding of how WD-repeat proteins recognize their interacting proteins.
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Affiliation(s)
- Zhifu Han
- National Institute of Biological Sciences, Beijing 102206, China
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Molecular and functional mapping of EED motifs required for PRC2-dependent histone methylation. J Mol Biol 2007; 374:1145-57. [PMID: 17997413 DOI: 10.1016/j.jmb.2007.10.040] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 10/15/2007] [Accepted: 10/16/2007] [Indexed: 01/07/2023]
Abstract
Polycomb group proteins represent a conserved family of developmental regulators that mediate heritable transcriptional silencing by modifying chromatin states. One Polycomb group complex, the PRC2 complex, is composed of several proteins, including the histone H3 lysine 27 (H3K27) methyltransferase enhancer of zeste homolog 2 and the WD-repeat protein embryonic ectoderm development (EED). Histone H3K27 can be monomethylated (H3K27me1), dimethylated (H3K27me2), or trimethylated (H3K27me3). However, it remains unclear what regulates the number of methyl groups added to H3K27 in a particular nucleosome. In mammalian cells, EED is present as four distinct isoforms, which are believed to be produced by utilizing four distinct, in-frame translation start sites in a common Eed mRNA. A mutation that disables all four EED isoforms produces defects in H3K27 methylation [Montgomery, N.D., Yee, D., Chen, A., Kalantry, S., Chamberlain, S.J., Otte, A.P. & Magnuson, T. (2005). The murine polycomb group protein Eed is required for global histone H3 lysine-27 methylation. Curr. Biol., 15, 942-947]. To assess the roles of individual EED isoforms in H3K27 methylation, we first characterized three of the four EED isoform start sites and then demonstrated that individual isoforms are not necessary for H3K27me1, H3K27me2, or H3K27me3. Instead, we show that the core WD-40 motifs and the histone-binding region of EED alone are sufficient for the generation of all three marks, demonstrating that EED isoforms do not control the number of methyl groups added to H3K27.
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Al-Mawsawi LQ, Neamati N. Blocking interactions between HIV-1 integrase and cellular cofactors: an emerging anti-retroviral strategy. Trends Pharmacol Sci 2007; 28:526-35. [PMID: 17888520 DOI: 10.1016/j.tips.2007.09.005] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2007] [Accepted: 09/07/2007] [Indexed: 12/17/2022]
Abstract
HIV-1 integrase (IN) executes the insertion of proviral DNA into the host cell genome, an essential step in the retroviral life cycle. This is a multi-step process that starts in the cytosol and culminates in the nucleus of the infected cell. It is becoming increasingly clear that IN interacts with a wide range of different host-cell proteins throughout the viral life cycle. These cellular cofactors are exploited for various functions, including nuclear import, DNA target-site selection and virion assembly. The disruption of key interactions between IN and direct cellular cofactors affords a novel therapeutic approach for the design and development of new classes of anti-retroviral agents. Here, we will discuss the rationale behind this emerging and promising therapeutic strategy for HIV drug discovery. Our discussion includes the identified IN cellular cofactors, key research developments in the field and the implications this approach will have on the current HIV treatment regimen.
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Affiliation(s)
- Laith Q Al-Mawsawi
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90089, USA
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Rakotobe D, Tardy JC, André P, Hong SS, Darlix JL, Boulanger P. Human Polycomb group EED protein negatively affects HIV-1 assembly and release. Retrovirology 2007; 4:37. [PMID: 17547741 PMCID: PMC1899515 DOI: 10.1186/1742-4690-4-37] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Accepted: 06/04/2007] [Indexed: 11/30/2022] Open
Abstract
Background The human EED protein, a member of the superfamily of Polycomb group (PcG) proteins with WD-40 repeats, has been found to interact with three HIV-1 components, namely the structural Gag matrix protein (MA), the integrase enzyme (IN) and the Nef protein. The aim of the present study was to analyze the possible biological role of EED in HIV-1 replication, using the HIV-1-based vector HIV-Luc and EED protein expressed by DNA transfection of 293T cells. Results During the early phase of HIV-1 infection, a slight negative effect on virus infectivity occurred in EED-expressing cells, which appeared to be dependent on EED-MA interaction. At late times post infection, EED caused an important reduction of virus production, from 20- to 25-fold as determined by CAp24 immunoassay, to 10- to 80-fold based on genomic RNA levels, and this decrease was not due to a reduction of Gag protein synthesis. Coexpression of WTNef, or the non-N-myristoylated mutant NefG2A, restored virus yields to levels obtained in the absence of exogenous EED protein. This effect was not observed with mutant NefΔ57 mimicking the Nef core, or with the lipid raft-retargeted fusion protein LAT-Nef. LATAA-Nef, a mutant defective in the lipid raft addressing function, had the same anti-EED effect as WTNef. Cell fractionation and confocal imaging showed that, in the absence of Nef, EED mainly localized in membrane domains different from the lipid rafts. Upon co-expression with WTNef, NefG2A or LATAA-Nef, but not with NefΔ57 or LAT-Nef, EED was found to relocate into an insoluble fraction along with Nef protein. Electron microscopy of HIV-Luc producer cells overexpressing EED showed significant less virus budding at the cell surface compared to control cells, and ectopic assembly and clustering of nuclear pore complexes within the cytoplasm. Conclusion Our data suggested that EED exerted an antiviral activity at the late stage of HIV-1 replication, which included genomic RNA packaging and virus assembly, resulting possibly from a mistrafficking of viral genomic RNA (gRNA) or gRNA/Gag complex. Nef reversed the EED negative effect on virus production, a function which required the integrity of the Nef N-terminal domain, but not its N-myristoyl group. The antagonistic effect of Nef correlated with a cellular redistribution of both EED and Nef.
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Affiliation(s)
- Dina Rakotobe
- Laboratoire de Virologie & Pathologie Humaine, Université Lyon I & CNRS FRE-3011, Faculté de Médecine Laennec, 7, rue Guillaume Paradin, 69372 Lyon Cedex 08, France
| | - Jean-Claude Tardy
- Laboratoire de Virologie & Pathologie Humaine, Université Lyon I & CNRS FRE-3011, Faculté de Médecine Laennec, 7, rue Guillaume Paradin, 69372 Lyon Cedex 08, France
- Laboratoire de Virologie Médicale-Nord, Hôpital de la Croix-Rousse, Hospices Civils de Lyon, 103, Grand'Rue de la Croix-Rousse, 69317 Lyon Cedex 04, France
| | - Patrice André
- Laboratoire de Virologie Médicale-Nord, Hôpital de la Croix-Rousse, Hospices Civils de Lyon, 103, Grand'Rue de la Croix-Rousse, 69317 Lyon Cedex 04, France
| | - Saw See Hong
- Laboratoire de Virologie & Pathologie Humaine, Université Lyon I & CNRS FRE-3011, Faculté de Médecine Laennec, 7, rue Guillaume Paradin, 69372 Lyon Cedex 08, France
| | - Jean-Luc Darlix
- LaboRétro, Unité de Virologie Humaine, INSERM U-758 & IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure, 46, allée d'Italie, 69364 Lyon Cedex 07, France
| | - Pierre Boulanger
- Laboratoire de Virologie & Pathologie Humaine, Université Lyon I & CNRS FRE-3011, Faculté de Médecine Laennec, 7, rue Guillaume Paradin, 69372 Lyon Cedex 08, France
- Laboratoire de Virologie Médicale, Hospices Civils de Lyon, CBPE, 59, Boulevard Pinel, 69677 Bron Cedex, France
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Tie F, Stratton CA, Kurzhals RL, Harte PJ. The N terminus of Drosophila ESC binds directly to histone H3 and is required for E(Z)-dependent trimethylation of H3 lysine 27. Mol Cell Biol 2007; 27:2014-26. [PMID: 17210640 PMCID: PMC1820504 DOI: 10.1128/mcb.01822-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Polycomb group proteins mediate heritable transcriptional silencing and function through multiprotein complexes that methylate and ubiquitinate histones. The 600-kDa E(Z)/ESC complex, also known as Polycomb repressive complex 2 (PRC2), specifically methylates histone H3 lysine 27 (H3 K27) through the intrinsic histone methyltransferase (HMTase) activity of the E(Z) SET domain. By itself, E(Z) exhibits no detectable HMTase activity and requires ESC for methylation of H3 K27. The molecular basis for this requirement is unknown. ESC binds directly, via its C-terminal WD repeats (beta-propeller domain), to E(Z). Here, we show that the N-terminal region of ESC that precedes its beta-propeller domain interacts directly with histone H3, thereby physically linking E(Z) to its substrate. We show that when expressed in stable S2 cell lines, an N-terminally truncated ESC (FLAG-ESC61-425), like full-length ESC, is incorporated into complexes with E(Z) and binds to a Ubx Polycomb response element in a chromatin immunoprecipitation assay. However, incorporation of this N-terminally truncated ESC into E(Z) complexes prevents trimethylation of histone H3 by E(Z). We also show that a closely related Drosophila melanogaster paralog of ESC, ESC-like (ESCL), and the mammalian homolog of ESC, EED, also interact with histone H3 via their N termini, indicating that the interaction of ESC with histone H3 is evolutionarily conserved, reflecting its functional importance. Our data suggest that one of the roles of ESC (and ESCL and EED) in PRC2 complexes is to enable E(Z) to utilize histone H3 as a substrate by physically linking enzyme and substrate.
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Affiliation(s)
- Feng Tie
- Department of Genetics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4955, USA
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Kim SY, Paylor SW, Magnuson T, Schumacher A. Juxtaposed Polycomb complexes co-regulate vertebral identity. Development 2006; 133:4957-68. [PMID: 17107999 DOI: 10.1242/dev.02677] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Best known as epigenetic repressors of developmental Hox gene transcription, Polycomb complexes alter chromatin structure by means of post-translational modification of histone tails. Depending on the cellular context, Polycomb complexes of diverse composition and function exhibit cooperative interaction or hierarchical interdependency at target loci. The present study interrogated the genetic, biochemical and molecular interaction of BMI1 and EED, pivotal constituents of heterologous Polycomb complexes, in the regulation of vertebral identity during mouse development. Despite a significant overlap in dosage-sensitive homeotic phenotypes and co-repression of a similar set of Hox genes, genetic analysis implicated eed and Bmi1 in parallel pathways, which converge at the level of Hox gene regulation. Whereas EED and BMI1 formed separate biochemical entities with EzH2 and Ring1B, respectively, in mid-gestation embryos, YY1 engaged in both Polycomb complexes. Strikingly, methylated lysine 27 of histone H3 (H3-K27), a mediator of Polycomb complex recruitment to target genes, stably associated with the EED complex during the maintenance phase of Hox gene repression. Juxtaposed EED and BMI1 complexes, along with YY1 and methylated H3-K27, were detected in upstream regulatory regions of Hoxc8 and Hoxa5. The combined data suggest a model wherein epigenetic and genetic elements cooperatively recruit and retain juxtaposed Polycomb complexes in mammalian Hox gene clusters toward co-regulation of vertebral identity.
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Affiliation(s)
- Se Young Kim
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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15
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Wang L, Jahren N, Vargas ML, Andersen EF, Benes J, Zhang J, Miller EL, Jones RS, Simon JA. Alternative ESC and ESC-like subunits of a polycomb group histone methyltransferase complex are differentially deployed during Drosophila development. Mol Cell Biol 2006; 26:2637-47. [PMID: 16537908 PMCID: PMC1430321 DOI: 10.1128/mcb.26.7.2637-2647.2006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Extra sex combs (ESC) protein is a Polycomb group (PcG) repressor that is a key noncatalytic subunit in the ESC-Enhancer of zeste [E(Z)] histone methyltransferase complex. Survival of esc homozygotes to adulthood based solely on maternal product and peak ESC expression during embryonic stages indicate that ESC is most critical during early development. In contrast, two other PcG repressors in the same complex, E(Z) and Suppressor of zeste-12 [SU(Z)12], are required throughout development for viability and Hox gene repression. Here we describe a novel fly PcG repressor, called ESC-Like (ESCL), whose biochemical, molecular, and genetic properties can explain the long-standing paradox of ESC dispensability during postembryonic times. Developmental Western blots show that ESCL, which is 60% identical to ESC, is expressed with peak abundance during postembryonic stages. Recombinant complexes containing ESCL in place of ESC can methylate histone H3 with activity levels, and lysine specificity for K27, similar to that of the ESC-containing complex. Coimmunoprecipitations show that ESCL associates with E(Z) in postembryonic cells and chromatin immunoprecipitations show that ESCL tracks closely with E(Z) on Ubx regulatory DNA in wing discs. Furthermore, reduced escl+ dosage enhances esc loss-of-function phenotypes and double RNA interference knockdown of ESC/ESCL in wing disc-derived cells causes Ubx derepression. These results suggest that ESCL and ESC have similar functions in E(Z) methyltransferase complexes but are differentially deployed as development proceeds.
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Affiliation(s)
- Liangjun Wang
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275, USA
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16
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Bejarano F, González I, Vidal M, Busturia A. The Drosophila RYBP gene functions as a Polycomb-dependent transcriptional repressor. Mech Dev 2006; 122:1118-29. [PMID: 16125914 DOI: 10.1016/j.mod.2005.06.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Revised: 06/07/2005] [Accepted: 06/07/2005] [Indexed: 10/25/2022]
Abstract
The Polycomb and trithorax groups of genes control the maintenance of homeotic gene expression in a variety of organisms. A putative participant in the regulation of this process is the murine RYBP (Ring and YY1 Binding Protein) gene. Sequence comparison between different species has identified the homologous gene in Drosophila, the dRYBP gene. We have investigated whether dRYBP participates in the mechanisms of silencing of homeotic genes expression. We first studied its expression by RNA in situ hybridisation and detected dRYBP expression ubiquitously and throughout development. Moreover, we generated a polyclonal anti-dRYBP antibody that recognises the dRYBP protein. dRYBP protein is nuclear and expressed maternally and ubiquitously throughout development. To study the transcriptional activity of dRYBP, we generated a fusion protein containing the entire dRYBP protein and the GAL4 DNA binding domain. This fusion protein functions, in vivo, as a transcriptional repressor throughout development. Importantly, this repression is dependent on the function of the Polycomb group genes. Furthermore, using the GAL4/UAS system, we have over expressed dRYBP in the haltere and the wing imaginal discs. In the haltere discs, high levels of dRYBP repress the expression of the homeotic Ultrabithorax gene. This repression is Polycomb dependent. In the wing discs, dRYBP over expression produces a variety of phenotypes suggesting the overall miss regulation of the many putative genes affected by high levels of dRYBP. Taking together, our results indicate that dRYBP is able to interact with PcG proteins to repress transcription suggesting that the dRYBP gene might belong to the Polycomb group of genes in Drosophila.
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Affiliation(s)
- Fernando Bejarano
- Centro de Biología Molecular CSIC-UAM, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
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17
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Ketel CS, Andersen EF, Vargas ML, Suh J, Strome S, Simon JA. Subunit contributions to histone methyltransferase activities of fly and worm polycomb group complexes. Mol Cell Biol 2005; 25:6857-68. [PMID: 16055700 PMCID: PMC1190254 DOI: 10.1128/mcb.25.16.6857-6868.2005] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The ESC-E(Z) complex of Drosophila melanogaster Polycomb group (PcG) repressors is a histone H3 methyltransferase (HMTase). This complex silences fly Hox genes, and related HMTases control germ line development in worms, flowering in plants, and X inactivation in mammals. The fly complex contains a catalytic SET domain subunit, E(Z), plus three noncatalytic subunits, SU(Z)12, ESC, and NURF-55. The four-subunit complex is >1,000-fold more active than E(Z) alone. Here we show that ESC and SU(Z)12 play key roles in potentiating E(Z) HMTase activity. We also show that loss of ESC disrupts global methylation of histone H3-lysine 27 in fly embryos. Subunit mutations identify domains required for catalytic activity and/or binding to specific partners. We describe missense mutations in surface loops of ESC, in the CXC domain of E(Z), and in the conserved VEFS domain of SU(Z)12, which each disrupt HMTase activity but preserve complex assembly. Thus, the E(Z) SET domain requires multiple partner inputs to produce active HMTase. We also find that a recombinant worm complex containing the E(Z) homolog, MES-2, has robust HMTase activity, which depends upon both MES-6, an ESC homolog, and MES-3, a pioneer protein. Thus, although the fly and mammalian PcG complexes absolutely require SU(Z)12, the worm complex generates HMTase activity from a distinct partner set.
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Affiliation(s)
- Carrie S Ketel
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, 55455, USA
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18
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Tie F, Siebold AP, Harte PJ. The N-terminus of Drosophila ESC mediates its phosphorylation and dimerization. Biochem Biophys Res Commun 2005; 332:622-32. [PMID: 15896722 DOI: 10.1016/j.bbrc.2005.04.157] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Accepted: 04/29/2005] [Indexed: 11/17/2022]
Abstract
The ESC protein, like other Polycomb Group proteins, is required for heritable silencing of the homeotic genes. ESC is phosphorylated in vivo, but the region of ESC that is phosphorylated and its consequences are not known. Here, we show that the amino-terminal region of ESC (residues 1-60) mediates its phosphorylation and dimerization. Phosphorylation of ESC1-60 in vitro by CK1 and CK2 strongly enhances its dimerization. Both phosphorylation and dimerization are conserved in the mammalian ESC homolog EED, suggesting that they play important roles in vivo. One role is suggested by the effect of phosphatase treatment on native ESC complexes, which does not affect the integrity of the 600 kDa ESC/E(Z) complex, but eliminates the 1 MDa ESC/E(Z) complex, which is distinguished from the former by the presence of the additional subunits PCL and RPD3. Thus, stability and perhaps assembly of larger ESC complexes may depend on ESC phosphorylation.
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Affiliation(s)
- Feng Tie
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA
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19
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Violot S, Hong SS, Rakotobe D, Petit C, Gay B, Moreau K, Billaud G, Priet S, Sire J, Schwartz O, Mouscadet JF, Boulanger P. The human polycomb group EED protein interacts with the integrase of human immunodeficiency virus type 1. J Virol 2003; 77:12507-22. [PMID: 14610174 PMCID: PMC262565 DOI: 10.1128/jvi.77.23.12507-12522.2003] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2003] [Accepted: 08/23/2003] [Indexed: 11/20/2022] Open
Abstract
Human EED, a member of the superfamily of WD-40 repeat proteins and of the Polycomb group proteins, has been identified as a cellular partner of the human immunodeficiency virus type 1 (HIV-1) matrix (MA) protein (R. Peytavi et al., J. Biol. Chem. 274:1635-1645, 1999). In the present study, EED was found to interact with HIV-1 integrase (IN) both in vitro and in vivo in yeast. In vitro, data from mutagenesis studies, pull-down assays, and phage biopanning suggested that EED-binding site(s) are located in the C-terminal domain of IN, between residues 212 and 264. In EED, two putative discrete IN-binding sites were mapped to its N-terminal moiety, at a distance from the MA-binding site, but EED-IN interaction also required the integrity of the EED last two WD repeats. EED showed an apparent positive effect on IN-mediated DNA integration reaction in vitro, in a dose-dependent manner. In situ analysis by immunoelectron microscopy (IEM) of cellular distribution of IN and EED in HIV-1-infected cells (HeLa CD4(+) cells or MT4 lymphoid cells) showed that IN and EED colocalized in the nucleus and near nuclear pores, with maximum colocalization events occurring at 6 h postinfection (p.i.). Triple colocalizations of IN, EED, and MA were also observed in the nucleoplasm of infected cells at 6 h p.i., suggesting the ocurrence of multiprotein complexes involving these three proteins at early steps of the HIV-1 virus life cycle. Such IEM patterns were not observed with a noninfectious, envelope deletion mutant of HIV-1.
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Affiliation(s)
- Sébastien Violot
- Laboratoire de Virologie and Pathogénèse Virale, Faculté de Médecine RTH Laennec, CNRS UMR-5537, France
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20
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Enünlü I, Pápai G, Cserpán I, Udvardy A, Jeang KT, Boros I. Different isoforms of PRIP-interacting protein with methyltransferase domain/trimethylguanosine synthase localizes to the cytoplasm and nucleus. Biochem Biophys Res Commun 2003; 309:44-51. [PMID: 12943661 DOI: 10.1016/s0006-291x(03)01514-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A protein family including the recently identified PIMT/Tgs1 (PRIP-interacting protein with methyltransferase domain/trimethylguanosine synthase) was identified by searching databases for homologues of a newly identified Drosophila protein with RNA-binding activity and methyltransferase domain. Antibodies raised against a short peptide of the mammalian homologue show a 90-kDa isoform expressed specifically in rat brain and testis and a 55-kDa form expressed ubiquitously. In HeLa cells, the larger isoform of the protein is nuclear and associated with a 600-kDa complex, while the smaller isoform is mainly cytoplasmic and co-localizes to the tubulin network. Inhibition of PIMT/Tgs1 expression by siRNA in HeLa cells resulted in an increase in the percentage of cells in G2/M phases. In yeast two-hybrid and in vitro GST pull down experiments, the conserved C-terminal region of PIMT/Tgs1 interacted with the WD domain containing EED/WAIT-1 that acts as a polycomb-type repressor in the nucleus and also binds to integrins in the cytoplasm. Our experiments, together with earlier data, indicate that isoforms of the PIMT/Tgs1 protein with an RNA methyltransferase domain function both in the nucleus and in the cytoplasm and associate with both elements of the cytoskeletal network and nuclear factors known to be involved in gene regulation.
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21
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Jin Q, van Eynde A, Beullens M, Roy N, Thiel G, Stalmans W, Bollen M. The protein phosphatase-1 (PP1) regulator, nuclear inhibitor of PP1 (NIPP1), interacts with the polycomb group protein, embryonic ectoderm development (EED), and functions as a transcriptional repressor. J Biol Chem 2003; 278:30677-85. [PMID: 12788942 DOI: 10.1074/jbc.m302273200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nuclear protein NIPP1 (nuclear inhibitor of protein Ser/Thr phosphatase-1) interacts with the splicing factors SAP155 and CDC5L and is involved in a late step of spliceosome assembly. In addition, NIPP1 is an interactor of protein phosphatase-1 and a COOH-terminal NIPP1 fragment displays an RNase E like endoribonuclease activity. A yeast two-hybrid screening resulted in the identification of the Polycomb group protein EED (embryonic ectoderm development), an established transcriptional repressor, as a novel NIPP1 interactor. NIPP1 only interacted with full-length EED, whereas two EED interaction domains were mapped to the central and COOH-terminal thirds of NIPP1. The NIPP1-EED interaction was potentiated by the binding of (d)G-rich nucleic acids to the central domain of NIPP1. Nucleic acids also decreased the potency of NIPP1 as an inhibitor of PP1, but they did not prevent the formation of a ternary NIPP1.EED.PP1 complex. EED had no effect on the function of NIPP1 as a splicing factor or as an endoribonuclease. However, similar to EED, NIPP1 acted as a transcriptional repressor of targeted genes and this NIPP1 effect was mediated by the EED interaction domain. Also, the histone deacetylase 2 was present in a complex with NIPP1. Our data are in accordance with a role for NIPP1 as a DNA-targeting protein for EED and associated chromatin-modifying enzymes.
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Affiliation(s)
- Qiming Jin
- Division of Biochemistry, Faculty of Medicine, University of Leuven, B-3000 Leuven, Belgium
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22
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Salvaing J, Lopez A, Boivin A, Deutsch JS, Peronnet F. The Drosophila Corto protein interacts with Polycomb-group proteins and the GAGA factor. Nucleic Acids Res 2003; 31:2873-82. [PMID: 12771214 PMCID: PMC156716 DOI: 10.1093/nar/gkg381] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Drosophila, PcG complexes provide heritable transcriptional silencing of target genes. Among them, the ESC/E(Z) complex is thought to play a role in the initiation of silencing whereas other complexes such as the PRC1 complex are thought to maintain it. PcG complexes are thought to be recruited to DNA through interaction with DNA binding proteins such as the GAGA factor, but no direct interactions between the constituents of PcG complexes and the GAGA factor have been reported so far. The Drosophila corto gene interacts with E(z) as well as with genes encoding members of maintenance complexes, suggesting that it could play a role in the transition between the initiation and maintenance of PcG silencing. Moreover, corto also interacts genetically with Trl, which encodes the GAGA factor, suggesting that it may serve as a mediator in recruiting PcG complexes. Here, we show that Corto bears a chromo domain and we provide evidence for in vivo association of Corto with ESC and with PC in embryos. Moreover, we show by GST pull-down and two-hybrid experiments that Corto binds to E(Z), ESC, PH, SCM and GAGA and co-localizes with these proteins on a few sites on polytene chromosomes. These results reinforce the idea that Corto plays a role in PcG silencing, perhaps by confering target specificity.
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Affiliation(s)
- Juliette Salvaing
- UMR 7622-Biologie du Développement, CNRS et Université Paris VI, 9 Quai Saint-Bernard, F-75252 Paris cedex 05, France
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23
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Danilevskaya ON, Hermon P, Hantke S, Muszynski MG, Kollipara K, Ananiev EV. Duplicated fie genes in maize: expression pattern and imprinting suggest distinct functions. THE PLANT CELL 2003; 15:425-38. [PMID: 12566582 PMCID: PMC141211 DOI: 10.1105/tpc.006759] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2002] [Accepted: 11/06/2002] [Indexed: 05/17/2023]
Abstract
Two maize genes with predicted translational similarity to the Arabidopsis FIE (Fertilization-Independent Endosperm) protein, a repressor of endosperm development in the absence of fertilization, were cloned and analyzed. Genomic sequences of fie1 and fie2 show significant homology within coding regions but none within introns or 5' upstream. The fie1 gene is expressed exclusively in the endosperm of developing kernels starting at approximately 6 days after pollination. fie1 is an imprinted gene showing no detectable expression of the paternally derived fie1 allele during kernel development. Conversely, fie2 is expressed in the embryo sac before pollination. After pollination, its expression persists, predominantly in the embryo and at lower levels in the endosperm. The paternal fie2 allele is not expressed early in kernel development, but its transcription is activated at 5 days after pollination. fie2 is likely to be a functional ortholog of the Arabidopsis FIE gene, whereas fie1 has evolved a distinct function. The maize FIE2 and sorghum FIE proteins form a monophyletic group, sharing a closer relationship to each other than to the FIE1 protein, suggesting that maize fie genes originated from two different ancestral genomes.
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Affiliation(s)
- Olga N Danilevskaya
- Pioneer Hi-Bred International, Inc., 7250 NW 62nd Avenue, Johnston, Iowa 50131, USA.
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24
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Showell C, Cunliffe VT. Identification of putative interaction partners for the Xenopus Polycomb-group protein Xeed. Gene 2002; 291:95-104. [PMID: 12095683 DOI: 10.1016/s0378-1119(02)00588-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The extra sex combs (esc) gene of Drosophila and its mammalian homologue embryonic ectoderm development (eed) play pivotal roles in establishing Polycomb-group (Pc-G) mediated transcriptional silencing of regulatory genes during early development. We have carried out a two-hybrid screen in yeast to identify maternally expressed proteins that interact directly with the product of the Xenopus eed homologue, Xeed. Xeed-interacting proteins that were recovered in this screen included a maternal Xenopus histone deacetylase (HDACm), the Xeed protein itself, and a Xenopus homologue of Enhancer of zeste (XEZ) - a second member of the Pc-G that is closely related by sequence similarity to histone methyltransferases. We have also identified a novel interaction between Xeed and a component of the Xenopus basal transcription machinery, TAF(II)32. We show for the first time that each of these proteins interacts with the Xeed polypeptide, both in the yeast two-hybrid assay and in vitro using purified recombinant proteins. XEZ, HDACm and TAF(II)32 mRNAs are all strongly co-expressed with Xeed mRNA in the fertilized egg, further suggesting that their encoded proteins could interact with Xeed during early embryonic development. Our observations support a multi-step model for the onset of transcriptional silencing in which Xeed binds to and inhibits the function of the transcription initiation complex and also recruits proteins that mediate the acquisition by associated chromatin of epigenetically heritable, post-translational modifications.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Northern
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- Embryo, Nonmammalian/metabolism
- Embryonic Development
- Enhancer of Zeste Homolog 2 Protein
- Female
- Gene Expression Regulation, Developmental
- Histone Deacetylases/genetics
- Histone Deacetylases/metabolism
- Molecular Sequence Data
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Polycomb Repressive Complex 2
- Polycomb-Group Proteins
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Repressor Proteins/genetics
- Repressor Proteins/metabolism
- Saccharomyces cerevisiae/genetics
- Sequence Homology, Amino Acid
- TATA-Binding Protein Associated Factors
- Transcription Factor TFIID
- Transcription Factors, TFII/genetics
- Transcription Factors, TFII/metabolism
- Two-Hybrid System Techniques
- Xenopus Proteins
- Xenopus laevis/genetics
- Xenopus laevis/metabolism
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Affiliation(s)
- Christopher Showell
- Centre for Developmental Genetics, School of Medicine and Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
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25
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Springer NM, Danilevskaya ON, Hermon P, Helentjaris TG, Phillips RL, Kaeppler HF, Kaeppler SM. Sequence relationships, conserved domains, and expression patterns for maize homologs of the polycomb group genes E(z), esc, and E(Pc). PLANT PHYSIOLOGY 2002; 128:1332-45. [PMID: 11950982 PMCID: PMC154261 DOI: 10.1104/pp.010742] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2001] [Revised: 11/28/2001] [Accepted: 12/21/2001] [Indexed: 05/17/2023]
Abstract
Polycomb group (PcG) proteins play an important role in developmental and epigenetic regulation of gene expression in fruit fly (Drosophila melanogaster) and mammals. Recent evidence has shown that Arabidopsis homologs of PcG proteins are also important for the regulation of plant development. The objective of this study was to characterize the PcG homologs in maize (Zea mays). The 11 cloned PcG proteins from fruit fly and the Enhancer of zeste [E(z)], extra sex combs (esc), and Enhancer of Polycomb [E(Pc)] homologs from Arabidopsis were used as queries to perform TBLASTN searches against the public maize expressed sequence tag database and the Pioneer Hi-Bred database. Maize homologs were found for E(z), esc, and E(Pc), but not for Polycomb, pleiohomeotic, Posterior sex combs, Polycomblike, Additional sex combs, Sex combs on midleg, polyhometoic, or multi sex combs. Transcripts of the three maize Enhancer of zeste-like genes, Mez1, Mez2, and Mez3, were detected in all tissues tested, and the Mez2 transcript is alternatively spliced in a tissue-dependent pattern. Zea mays fertilization independent endosperm1 (ZmFie1) expression was limited to developing embryos and endosperms, whereas ZmFie2 expression was found throughout plant development. The conservation of E(z) and esc homologs across kingdoms indicates that these genes likely play a conserved role in repressing gene expression.
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Affiliation(s)
- Nathan M Springer
- Department of Agronomy, University of Wisconsin, Madison, WI 53706, USA
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26
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Richie ER, Schumacher A, Angel JM, Holloway M, Rinchik EM, Magnuson T. The Polycomb-group gene eed regulates thymocyte differentiation and suppresses the development of carcinogen-induced T-cell lymphomas. Oncogene 2002; 21:299-306. [PMID: 11803473 DOI: 10.1038/sj.onc.1205051] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2001] [Revised: 09/25/2001] [Accepted: 10/09/2001] [Indexed: 11/08/2022]
Abstract
The mouse Polycomb-group gene, embryonic ectoderm development (eed), appears to regulate cellular growth and differentiation in a developmental and tissue specific manner. During embryogenesis, eed regulates axial patterning, whereas in the adult eed represses proliferation of myeloid and B cell precursors. The present report demonstrates two novel functional activities of eed: alteration of thymocyte maturation and suppression of thymic lymphoma development. Mice that inherit the viable hypomorphic 17Rn5(1989SB) eed allele sustain a partial developmental block at or before the CD4(-)CD8(-)CD44(-)CD25(+) stage of thymocyte differentiation. Furthermore, mice that are homozygous or heterozygous for the hypomorphic eed allele have an increased incidence and decreased latency of N-methyl-N-nitrosourea-induced thymic lymphoma compared to wild-type littermates. These findings support the notion that Polycomb-group genes exert pleiotropic effects dictated by developmental stage and cellular context.
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Affiliation(s)
- Ellen R Richie
- Department of Carcinogenesis, The University of Texas, M.D. Anderson Cancer Center, Science Park-Research Division, Smithville, Texas 78957, USA.
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27
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Roseman RR, Morgan K, Mallin DR, Roberson R, Parnell TJ, Bornemann DJ, Simon JA, Geyer PK. Long-range repression by multiple polycomb group (PcG) proteins targeted by fusion to a defined DNA-binding domain in Drosophila. Genetics 2001; 158:291-307. [PMID: 11333237 PMCID: PMC1461647 DOI: 10.1093/genetics/158.1.291] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A tethering assay was developed to study the effects of Polycomb group (PcG) proteins on gene expression in vivo. This system employed the Su(Hw) DNA-binding domain (ZnF) to direct PcG proteins to transposons that carried the white and yellow reporter genes. These reporters constituted naive sensors of PcG effects, as bona fide PcG response elements (PREs) were absent from the constructs. To assess the effects of different genomic environments, reporter transposons integrated at nearly 40 chromosomal sites were analyzed. Three PcG fusion proteins, ZnF-PC, ZnF-SCM, and ZnF-ESC, were studied, since biochemical analyses place these PcG proteins in distinct complexes. Tethered ZnF-PcG proteins repressed white and yellow expression at the majority of sites tested, with each fusion protein displaying a characteristic degree of silencing. Repression by ZnF-PC was stronger than ZnF-SCM, which was stronger than ZnF-ESC, as judged by the percentage of insertion lines affected and the magnitude of the conferred repression. ZnF-PcG repression was more effective at centric and telomeric reporter insertion sites, as compared to euchromatic sites. ZnF-PcG proteins tethered as far as 3.0 kb away from the target promoter produced silencing, indicating that these effects were long range. Repression by ZnF-SCM required a protein interaction domain, the SPM domain, which suggests that this domain is not primarily used to direct SCM to chromosomal loci. This targeting system is useful for studying protein domains and mechanisms involved in PcG repression in vivo.
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Affiliation(s)
- R R Roseman
- Department of Biochemistry, The University of Iowa, Iowa City, IA 52242, USA
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28
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Yadegari R, Kinoshita T, Lotan O, Cohen G, Katz A, Choi Y, Katz A, Nakashima K, Harada JJ, Goldberg RB, Fischer RL, Ohad N. Mutations in the FIE and MEA genes that encode interacting polycomb proteins cause parent-of-origin effects on seed development by distinct mechanisms. THE PLANT CELL 2000; 12:2367-2382. [PMID: 11148284 PMCID: PMC102224 DOI: 10.1105/tpc.12.12.2367] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2000] [Accepted: 10/19/2000] [Indexed: 05/17/2023]
Abstract
In flowering plants, two cells are fertilized in the haploid female gametophyte. Egg and sperm nuclei fuse to form the embryo. A second sperm nucleus fuses with the central cell nucleus, which replicates to generate the endosperm, a tissue that supports embryo development. The FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) and MEDEA (MEA) genes encode WD and SET domain polycomb proteins, respectively. In the absence of fertilization, a female gametophyte with a loss-of-function fie or mea allele initiates endosperm development without fertilization. fie and mea mutations also cause parent-of-origin effects, in which the wild-type maternal allele is essential and the paternal allele is dispensable for seed viability. Here, we show that FIE and MEA polycomb proteins interact physically, suggesting that the molecular partnership of WD and SET domain polycomb proteins has been conserved during the evolution of flowering plants. The overlapping expression patterns of FIE and MEA are consistent with their suppression of gene transcription and endosperm development in the central cell as well as their control of seed development after fertilization. Although FIE and MEA interact, differences in maternal versus paternal patterns of expression, as well as the effect of a recessive mutation in the DECREASE IN DNA METHYLATION1 (DDM1) gene on mutant allele transmission, indicate that fie and mea mutations cause parent-of-origin effects on seed development by distinct mechanisms.
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Affiliation(s)
- R Yadegari
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA
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29
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Spillane C, MacDougall C, Stock C, Köhler C, Vielle-Calzada JP, Nunes SM, Grossniklaus U, Goodrich J. Interaction of the Arabidopsis polycomb group proteins FIE and MEA mediates their common phenotypes. Curr Biol 2000; 10:1535-8. [PMID: 11114524 DOI: 10.1016/s0960-9822(00)00839-3] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Genes of the FERTILISATION INDEPENDENT SEED (FIS) class regulate cell proliferation during reproductive development in Arabidopsis [1-5]. The FIS genes FERTILISATION INDEPENDENT ENDOSPERM (FIE) and MEDEA (MEA) encode homologs of animal Polycomb group (Pc-G) proteins, transcriptional regulators that modify chromatin structure and are thought to form multimeric complexes [3-11]. To test whether similarities in fis mutant phenotypes reflect interactions between their protein products, we characterised FIE RNA and protein localisation in vivo, and FIE protein interactions in yeast and in vitro. Expression of FIE mRNA overlaps with that of MEA during embryo sac and seed development and is unaffected in mea mutants. Results from the yeast two-hybrid system and an in vitro pull-down assay indicate that MEA and FIE proteins interact. The relevance of this interaction in vivo is supported by the finding that FIE and MEA co-localise in the nucleus in transfected plant cells. Interaction of MEA and FIE is mediated by the amino-terminal region of MEA. Despite sequence divergence in this domain, MEA can interact with its corresponding animal partner Extrasexcombs (ESC) in the yeast two-hybrid system. We conclude that FIE and MEA act together as part of a multimeric complex and that this accounts for the similarities in mutant phenotypes. We propose that an ancient mechanism for chromatin modification has been independently recruited to different developmental processes in the two kingdoms.
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Affiliation(s)
- C Spillane
- Institute of Plant Biology, University of Zürich, CH-8008,., Zürich, Switzerland
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30
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Lukowiak AA, Granneman S, Mattox SA, Speckmann WA, Jones K, Pluk H, Venrooij WJ, Terns RM, Terns MP. Interaction of the U3-55k protein with U3 snoRNA is mediated by the box B/C motif of U3 and the WD repeats of U3-55k. Nucleic Acids Res 2000; 28:3462-71. [PMID: 10982864 PMCID: PMC110750 DOI: 10.1093/nar/28.18.3462] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
U3 small nucleolar RNA (snoRNA) is a member of the Box C/D family of snoRNAs which functions in ribosomal RNA processing. U3-55k is a protein that has been found to interact with U3 but not other members of the Box C/D snoRNA family. We have found that interaction of the U3-55k protein with U3 RNA in vivo is mediated by the conserved Box B/C motif which is unique to U3 snoRNA. Mutation of Box B and Box C, but not of other conserved sequence elements, disrupted interaction of U3-55k with U3 RNA. Furthermore, a fragment of U3 containing only these two conserved elements was bound by U3-55k in vivo. RNA binding assays performed in vitro indicate that Box C may be the primary determinant of the interaction. We have cloned the cDNA encoding the Xenopus laevis U3-55k protein and find strong homology to the human sequence, including six WD repeats. Deletion of WD repeats or sequences near the C-terminus of U3-55k resulted in loss of association with U3 RNA and also loss of localization of U3-55k to the nucleolus, suggesting that protein-protein interactions contribute to the localization and RNA binding of U3-55k in vivo.
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Affiliation(s)
- A A Lukowiak
- Department of Biochemistry and Molecular Biology and Department of Genetics, University of Georgia, Life Science Building, Athens, GA 30602, USA
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31
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Abstract
The Drosophila Groucho (Gro) protein is the prototype for a large family of corepressors, examples of which are found in most metazoans. This family includes the human transducin-like Enhancer of split (TLE) proteins. As corepressors, Gro/TLE family proteins do not bind to DNA directly, but rather are recruited to the template by DNA-bound repressor proteins. Gro/TLE family proteins are required for many developmental processes, including lateral inhibition, segmentation, sex determination, dorsal/ventral pattern formation, terminal pattern formation, and eye development. These proteins are characterized by a conserved N-terminal glutamine-rich domain and a conserved C-terminal WD-repeat domain. The primary role of the glutamine-rich domain is apparently to mediate tetramerization, while the WD-repeat domain may mediate interactions with DNA-bound repressors. The glutamine rich and WD-repeat domains are separated by a less conserved region containing domains that have been implicated in transcriptional repression and nuclear localization. In addition to encoding full-length Gro/TLE family proteins, most metazoan genomes encode truncated family members that contain the N-terminal oligomerization domain, but lack the C-terminal WD-repeat domain. These truncated proteins may negatively regulate full-length Gro/TLE proteins, perhaps by sequestering them in non-productive complexes. Gro/TLE family proteins probably repress transcription by multiple mechanisms. For example, a glycine/proline-rich domain in the central variable region functions to recruit the histone deacetylase Rpd3 to the template. This histone deacetylase then presumably silences transcription by altering local chromatin structure. Other repression domains in Gro may function in a histone deacetylase-independent manner. Many aspects of Gro/TLE protein function remain to be explored, including the possible post-translational regulation of Gro/TLE activity as well as the mechanisms by which Gro/TLE proteins direct repression at a distance.
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Affiliation(s)
- G Chen
- Department of Chemistry and Biochemistry University of California, Los Angeles 90095-1569, USA
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32
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Ng J, Hart CM, Morgan K, Simon JA. A Drosophila ESC-E(Z) protein complex is distinct from other polycomb group complexes and contains covalently modified ESC. Mol Cell Biol 2000; 20:3069-78. [PMID: 10757791 PMCID: PMC85591 DOI: 10.1128/mcb.20.9.3069-3078.2000] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The extra sex combs (ESC) and Enhancer of zeste [E(Z)] proteins, members of the Polycomb group (PcG) of transcriptional repressors, interact directly and are coassociated in fly embryos. We report that these two proteins are components of a 600-kDa complex in embryos. Using gel filtration and affinity chromatography, we show that this complex is biochemically distinct from previously described complexes containing the PcG proteins Polyhomeotic, Polycomb, and Sex comb on midleg. In addition, we present evidence that ESC is phosphorylated in vivo and that this modified ESC is preferentially associated in the complex with E(Z). Modified ESC accumulates between 2 and 6 h of embryogenesis, which is the developmental time when esc function is first required. We find that mutations in E(z) reduce the ratio of modified to unmodified ESC in vivo. We have also generated germ line transformants that express ESC proteins bearing site-directed mutations that disrupt ESC-E(Z) binding in vitro. These mutant ESC proteins fail to provide esc function, show reduced levels of modification in vivo, and are still assembled into complexes. Taken together, these results suggest that ESC phosphorylation normally occurs after assembly into ESC-E(Z) complexes and that it contributes to the function or regulation of these complexes. We discuss how biochemically separable ESC-E(Z) and PC-PH complexes might work together to provide PcG repression.
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Affiliation(s)
- J Ng
- Department of Genetics, University of Minnesota, Minneapolis, Minnesota 55455, USA
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33
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Wang J, Tie F, Jane E, Schumacher A, Harte PJ, Magnuson T. Mouse homolog of theDrosophila Pc-G geneesc exerts a dominant negative effect inDrosophila. Genesis 2000. [DOI: 10.1002/(sici)1526-968x(200001)26:1<67::aid-gene9>3.0.co;2-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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34
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Seydoux G, Strome S. Launching the germline in Caenorhabditis elegans: regulation of gene expression in early germ cells. Development 1999; 126:3275-83. [PMID: 10393107 DOI: 10.1242/dev.126.15.3275] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
One hundred years after Weismann's seminal observations, the mechanisms that distinguish the germline from the soma still remain poorly understood. This review describes recent studies in Caenorhabditis elegans, which suggest that germ cells utilize unique mechanisms to regulate gene expression. In particular, mechanisms that repress the production of mRNAs appear to be essential to maintain germ cell fate and viability.
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Affiliation(s)
- G Seydoux
- Department of Molecular Biology and Genetics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
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35
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Vasiliauskas D, Hancock S, Stern CD. SWiP-1: novel SOCS box containing WD-protein regulated by signalling centres and by Shh during development. Mech Dev 1999; 82:79-94. [PMID: 10354473 DOI: 10.1016/s0925-4773(99)00014-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We describe a novel chick WD-protein, cSWiP-1, expressed in somitic mesoderm and developing limb buds as well as in other embryonic structures where Hedgehog signalling has been shown to play a role. Using embryonic manipulations we show that in somites cSWiP-1 expression integrates two signals originating from structures adjacent to the segmental mesoderm: a positive signal from the notochord and a negative signal from intermediate and/or lateral mesoderm. In explant cultures of somitic mesoderm, Shh protein induces cSWiP-1, while a blocking antibody to Shh inhibits the induction of cSWiP-1 by the notochord. These results show that the positive signal from the notochord is mediated by Shh. We also show that in limb buds cSWiP-1 is upregulated by ectopic Shh. This occurs in about the same time period as upregulation of BMP2, placing cSWiP-1 among the earliest markers for the change of limb pattern caused by ectopic Shh. We also describe a human homologue of cSWiP-1 and a mouse gene, mSWiP-2, that is more distantly related to SWiP-1, suggesting that SWiP-1 belongs to a novel subfamily of WD-proteins.
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Affiliation(s)
- D Vasiliauskas
- Department of Genetics and Development, College of Physicians and Surgeons of Columbia University, 701 West 168th Street, New York, NY 10032, USA
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36
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Ohad N, Yadegari R, Margossian L, Hannon M, Michaeli D, Harada JJ, Goldberg RB, Fischer RL. Mutations in FIE, a WD polycomb group gene, allow endosperm development without fertilization. THE PLANT CELL 1999; 11:407-16. [PMID: 10072400 PMCID: PMC144179 DOI: 10.1105/tpc.11.3.407] [Citation(s) in RCA: 300] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A fundamental problem in biology is to understand how fertilization initiates reproductive development. Higher plant reproduction is unique because two fertilization events are required for sexual reproduction. First, a sperm must fuse with the egg to form an embryo. A second sperm must then fuse with the adjacent central cell nucleus that replicates to form an endosperm, which is the support tissue required for embryo and/or seedling development. Here, we report cloning of the Arabidopsis FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) gene. The FIE protein is a homolog of the WD motif-containing Polycomb proteins from Drosophila and mammals. These proteins function as repressors of homeotic genes. A female gametophyte with a loss-of-function allele of fie undergoes replication of the central cell nucleus and initiates endosperm development without fertilization. These results suggest that the FIE Polycomb protein functions to suppress a critical aspect of early plant reproduction, namely, endosperm development, until fertilization occurs.
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Affiliation(s)
- N Ohad
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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37
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Schumacher A, Lichtarge O, Schwartz S, Magnuson T. The murine Polycomb-group gene eed and its human orthologue: functional implications of evolutionary conservation. Genomics 1998; 54:79-88. [PMID: 9806832 DOI: 10.1006/geno.1998.5509] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Similar to Drosophila, murine Polycomb-group (PcG) genes regulate anterior-posterior patterning of segmented axial structures by transcriptional repression of homeotic gene expression. The murine PcG gene eed (embryonic ectoderm development) encodes a 441-amino-acid protein with five WD motifs which, except for the amino terminus, is highly homologous to Drosophila ESC (Extra Sex Combs). Here, sequence and expression analysis as well as chromosomal mapping of the human orthologue of eed is described. Absolute conservation of the human eed protein along with significant divergence at the nucleotide level reveals functional constraints operating on all residues. The human orthologue appears to be ubiquitously expressed and maps to chromsome 11q14.2-q22.3. Using the first WD motif of the beta-subunit of the bovine G protein as a structural reference, the predicted locations of two previously identified eed point mutations (A. Schumacher et al., 1996, Nature 383: 250-253) are also reported herein. The proline substitution (L196P) in the second WD motif of the l7Rn5(3354SB) null allele maps to the internal core of the inner end of the beta-propeller blade and is likely to disrupt protein folding. In contrast, the asparagine substitution (I193N) in the second WD motif of the hypomorphic l7Rn5(1989SB) allele maps onto the surface of the beta-propeller blade near the central cavity and may affect surface interactions without compromising propeller packing. These results illustrate the critical importance of all residues for eed function in mammals and support a model whereby the amino terminus might implement function(s) related to embryonic development in higher organisms.
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Affiliation(s)
- A Schumacher
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio, 44106-4955, USA
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38
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Denisenko O, Shnyreva M, Suzuki H, Bomsztyk K. Point mutations in the WD40 domain of Eed block its interaction with Ezh2. Mol Cell Biol 1998; 18:5634-42. [PMID: 9742080 PMCID: PMC109149 DOI: 10.1128/mcb.18.10.5634] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/1998] [Accepted: 07/06/1998] [Indexed: 01/08/2023] Open
Abstract
The Polycomb group proteins are involved in maintenance of the silenced state of several developmentally regulated genes. These proteins form large aggregates with different subunit compositions. To explore the nature of these complexes and their function, we used the full-length Eed (embryonic ectoderm development) protein, a mammalian homolog of the Drosophila Polycomb group protein Esc, as a bait in the yeast two-hybrid screen. Several strongly interacting cDNA clones were isolated. The cloned cDNAs all encoded the 150- to 200-amino-acid N-terminal fragment of the mammalian homolog of the Drosophila Enhancer of zeste [E(z)] protein, Ezh2. The full-length Ezh2 bound strongly to Eed in vitro, and Eed coimmunoprecipitated with Ezh2 from murine 70Z/3 cell extracts, confirming the interaction between these proteins observed in yeast. Mutations T1031A and T1040C in one of the WD40 repeats of Eed, which account for the hypomorphic and lethal phenotype of eed in mouse development, blocked binding of Ezh2 to Eed in a two-hybrid interaction in yeast and in mammalian cells. These mutations also blocked the interaction between these proteins in vitro. In mammalian cells, the Gal4-Eed fusion protein represses the activity of a promoter bearing Gal4 DNA elements. The N-terminal fragment of the Ezh2 protein abolished the transcriptional repressor activity of Gal4-Eed protein when they were coexpressed in mammalian cells. Eed and Ezh2 were also found to bind RNA in vitro, and RNA altered the interaction between these proteins. These findings suggest that Polycomb group proteins Eed and Ezh2 functionally interact in mammalian cells, an interaction that is mediated by the WD40-containing domain of Eed protein.
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Affiliation(s)
- O Denisenko
- Department of Medicine, University of Washington, Seattle, Washington 98195, USA
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39
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Tie F, Furuyama T, Harte PJ. The Drosophila Polycomb Group proteins ESC and E(Z) bind directly to each other and co-localize at multiple chromosomal sites. Development 1998; 125:3483-96. [PMID: 9693151 DOI: 10.1242/dev.125.17.3483] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Polycomb Group gene esc encodes an evolutionarily conserved protein required for transcriptional silencing of the homeotic genes. Unlike other Polycomb Group genes, esc is expressed and apparently required only during early embryogenesis, suggesting it is required for the initial establishment of silencing but not for its subsequent maintenance. We present evidence that the ESC protein interacts directly with E(Z), another Polycomb Group protein required for silencing of the homeotic genes. We show that the most highly conserved region of ESC, containing seven WD motifs that are predicted to fold into a beta-propeller structure, mediate its binding to a conserved N-terminal region of E(Z). Mutations in the WD region that perturb ESC silencing function in vivo also perturb binding to E(Z) in vitro. The entire WD region forms a trypsin-resistant structure, like known beta -propeller domains, and mutations that would affect the predicted ESC beta-propeller perturb its trypsin-resistance, while a putative structure-conserving mutation does not. We show by co-immunoprecipitation that ESC and E(Z) are directly associated in vivo and that they also co-localize at many chromosomal binding sites. Since E(Z) is required for binding of other Polycomb Group proteins to chromosomes, these results suggest that formation of an E(Z):ESC complex at Polycomb Response Elements may be an essential prerequisite for the establishment of silencing.
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Affiliation(s)
- F Tie
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio 44106-4955, USA
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40
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Korf I, Fan Y, Strome S. The Polycomb group in Caenorhabditis elegans and maternal control of germline development. Development 1998; 125:2469-78. [PMID: 9609830 DOI: 10.1242/dev.125.13.2469] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Four Caenorhabditis elegans genes, mes-2, mes-3, mes-4 and mes-6, are essential for normal proliferation and viability of the germline. Mutations in these genes cause a maternal-effect sterile (i.e. mes) or grandchildless phenotype. We report that the mes-6 gene is in an unusual operon, the second example of this type of operon in C. elegans, and encodes the nematode homolog of Extra sex combs, a WD-40 protein in the Polycomb group in Drosophila. mes-2 encodes another Polycomb group protein (see paper by Holdeman, R., Nehrt, S. and Strome, S. (1998). Development 125, 2457–2467). Consistent with the known role of Polycomb group proteins in regulating gene expression, MES-6 is a nuclear protein. It is enriched in the germline of larvae and adults and is present in all nuclei of early embryos. Molecular epistasis results predict that the MES proteins, like Polycomb group proteins in Drosophila, function as a complex to regulate gene expression. Database searches reveal that there are considerably fewer Polycomb group genes in C. elegans than in Drosophila or vertebrates, and our studies suggest that their primary function is in controlling gene expression in the germline and ensuring the survival and proliferation of that tissue.
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Affiliation(s)
- I Korf
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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41
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Jones CA, Ng J, Peterson AJ, Morgan K, Simon J, Jones RS. The Drosophila esc and E(z) proteins are direct partners in polycomb group-mediated repression. Mol Cell Biol 1998; 18:2825-34. [PMID: 9566901 PMCID: PMC110661 DOI: 10.1128/mcb.18.5.2825] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/1997] [Accepted: 02/05/1998] [Indexed: 02/07/2023] Open
Abstract
The extra sex combs (esc) and Enhancer of zeste [E(z)] proteins are members of the Drosophila Polycomb group (Pc-G) of transcriptional repressors. Here we present evidence for direct physical interaction between the esc and E(z) proteins using yeast two-hybrid and in vitro binding assays. In addition, coimmunoprecipitation from embryo extracts demonstrates association of esc and E(z) in vivo. We have delimited the esc-binding domain of E(z) to an N-terminal 33-amino-acid region. Furthermore, we demonstrate that site-directed mutations in the esc protein previously shown to impair esc function in vivo disrupt esc-E(z) interactions in vitro. We also show an in vitro interaction between the heed and EZH1 proteins, which are human homologs of esc and E(z), respectively. These results suggest that the esc-E(z) molecular partnership has been conserved in evolution. Previous studies suggested that esc is primarily involved in the early stages of Pc-G-mediated silencing during embryogenesis. However, E(z) is continuously required in order to maintain chromosome binding by other Pc-G proteins. In light of these earlier observations and the molecular data presented here, we discuss how esc-E(z) protein complexes may contribute to transcriptional silencing by the Pc-G.
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Affiliation(s)
- C A Jones
- Department of Biological Sciences, Southern Methodist University, Dallas, Texas 75275-0376, USA
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