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Jangam SV, Briere LC, Jay KL, Andrews JC, Walker MA, Rodan LH, High FA, Yamamoto S, Sweetser DA, Wangler MF. A de novo missense variant in EZH1 associated with developmental delay exhibits functional deficits in Drosophila melanogaster. Genetics 2023; 224:iyad110. [PMID: 37314226 PMCID: PMC10411565 DOI: 10.1093/genetics/iyad110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 01/13/2023] [Accepted: 05/31/2023] [Indexed: 06/15/2023] Open
Abstract
EZH1, a polycomb repressive complex-2 component, is involved in a myriad of cellular processes. EZH1 represses transcription of downstream target genes through histone 3 lysine27 (H3K27) trimethylation (H3K27me3). Genetic variants 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 missense variant in EZH1 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 an analogous somatic or germline mutation in EZH2 has been reported in patients with B-cell lymphoma or Weaver syndrome, respectively. Human EZH1/2 are homologous to fly Enhancer of zeste (E(z)), an essential gene in Drosophila, and the affected residue (p.A678 in humans, p.A691 in flies) is conserved. To further study this variant, we obtained null alleles and generated transgenic flies expressing wildtype [E(z)WT] and the variant [E(z)A691G]. When expressed ubiquitously the variant rescues null-lethality similar to the wildtype. Overexpression of E(z)WT induces homeotic patterning defects but notably the E(z)A691G variant leads to dramatically stronger morphological phenotypes. We also note a dramatic loss of H3K27me2 and a corresponding increase in H3K27me3 in flies expressing E(z)A691G, suggesting this acts as a gain-of-function allele. 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.
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Affiliation(s)
- Sharayu V Jangam
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Lauren C Briere
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Kristy L Jay
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
| | - Jonathan C Andrews
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 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 and Metabolism, Massachusetts General Hospital for Children, Boston, MA 02114, USA
| | | | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX 77030, USA
| | - David A Sweetser
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
- Division of Medical Genetics and Metabolism, Massachusetts General Hospital for Children, Boston, MA 02114, USA
| | - Michael F Wangler
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX 77030, USA
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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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Epigenetic Regulation in Breast Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021. [PMID: 33983575 DOI: 10.1007/978-981-32-9620-6_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2023]
Abstract
Aberrant epigenetic alteration has been associated with development of various cancers, including breast cancer. Since epigenetic modifications such as DNA methylation and histone modification are reversible, epigenetic enzymes, including histone modifying enzymes and DNA methyltransferases, emerge as attractive targets for cancer therapy. Although epi-drugs targeting histone deacetylation or DNA methylation have received FDA approval for cancer therapy, a very modest anti-tumor activity has been observed with monotherapy in clinical studies of breast cancer. To improve efficacy of epi-drugs in breast cancer, combination of epi-drugs with other therapies currently has been investigated. Additionally, basic researches to elucidate molecular causes of cancer should be extensively and intensively conducted in order to find novel epigenetic druggable targets. In this chapter, we summarize how epigenetic regulation affects the development of breast cancer and how to control cancer phenotype by modulating abnormal epigenetic modifications, and then suggest future research directions in epigenetics for breast cancer treatment.
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Moutaoufik MT, Tanguay RM. Analysis of insect nuclear small heat shock proteins and interacting proteins. Cell Stress Chaperones 2021; 26:265-274. [PMID: 32888179 PMCID: PMC7736433 DOI: 10.1007/s12192-020-01156-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Revised: 08/13/2020] [Accepted: 08/19/2020] [Indexed: 10/23/2022] Open
Abstract
The small heat shock proteins (sHsps) are a ubiquitous family of ATP-independent stress proteins found in all domains of life. Drosophila melanogaster Hsp27 (DmHsp27) is the only known nuclear sHsp in insect. Here analyzing sequences from HMMER, we identified 56 additional insect sHsps with conserved arginine-rich nuclear localization signal (NLS) in the N-terminal region. At this time, the exact role of nuclear sHsps remains unknown. DmHsp27 protein-protein interaction analysis from iRefIndex database suggests that this protein, in addition to a putative role of molecular chaperone, is likely involved in other nuclear processes (i.e., chromatin remodeling and transcription). Identification of DmHsp27 interactors should provide key insights on the cellular and molecular functions of this nuclear chaperone.
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Affiliation(s)
- Mohamed Taha Moutaoufik
- Lab of Cell & Developmental Genetics, Department of Cellular and Molecular Biology, Medical Biochemistry & Pathology, Medical School, Université Laval, Quebec, G1K 7P4, Canada
- Department of Biochemistry, University of Regina, Regina, SK, S4S 0A2, Canada
| | - Robert M Tanguay
- Lab of Cell & Developmental Genetics, Department of Cellular and Molecular Biology, Medical Biochemistry & Pathology, Medical School, Université Laval, Quebec, G1K 7P4, Canada.
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Epigenetic Regulation of Notch Signaling During Drosophila Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1218:59-75. [PMID: 32060871 DOI: 10.1007/978-3-030-34436-8_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Notch signaling exerts multiple important functions in various developmental processes, including cell differentiation and cell proliferation, while mis-regulation of this pathway results in a variety of complex diseases, such as cancer and developmental defects. The simplicity of the Notch pathway in Drosophila melanogaster, in combination with the availability of powerful genetics, makes this an attractive model for studying the fundamental mechanisms of how Notch signaling is regulated and how it functions in various cellular contexts. Recently, increasing evidence for epigenetic control of Notch signaling reveals the intimate link between epigenetic regulators and Notch signaling pathway. In this chapter, we summarize the research advances of Notch and CAF-1 in Drosophila development and the epigenetic regulation mechanisms of Notch signaling activity by CAF-1 as well as other epigenetic modification machineries, which enables Notch to orchestrate different biological inputs and outputs in specific cellular contexts.
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A Role for Monomethylation of Histone H3-K27 in Gene Activity in Drosophila. Genetics 2017; 208:1023-1036. [PMID: 29242288 DOI: 10.1534/genetics.117.300585] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/07/2017] [Indexed: 01/09/2023] Open
Abstract
Polycomb repressive complex 2 (PRC2) is a conserved chromatin-modifying enzyme that methylates histone H3 on lysine-27 (K27). PRC2 can add one, two, or three methyl groups and the fully methylated product, H3-K27me3, is a hallmark of Polycomb-silenced chromatin. Less is known about functions of K27me1 and K27me2 and the dynamics of flux through these states. These modifications could serve mainly as intermediates to produce K27me3 or they could each convey distinct epigenetic information. To investigate this, we engineered a variant of Drosophila melanogaster PRC2 which is converted into a monomethyltransferase. A single substitution, F738Y, in the lysine-substrate binding pocket of the catalytic subunit, E(Z), creates an enzyme that retains robust K27 monomethylation but dramatically reduced di- and trimethylation. Overexpression of E(Z)-F738Y in fly cells triggers desilencing of Polycomb target genes significantly more than comparable overexpression of catalytically deficient E(Z), suggesting that H3-K27me1 contributes positively to gene activity. Consistent with this, normal genomic distribution of H3-K27me1 is enriched on actively transcribed Drosophila genes, with localization overlapping the active H3-K36me2/3 chromatin marks. Thus, distinct K27 methylation states link to either repression or activation depending upon the number of added methyl groups. If so, then H3-K27me1 deposition may involve alternative methyltransferases beyond PRC2, which is primarily repressive. Indeed, assays on fly embryos with PRC2 genetically inactivated, and on fly cells with PRC2 chemically inhibited, show that substantial H3-K27me1 accumulates independently of PRC2. These findings imply distinct roles for K27me1 vs. K27me3 in transcriptional control and an expanded machinery for methylating H3-K27.
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Calvo-Martín JM, Librado P, Aguadé M, Papaceit M, Segarra C. Adaptive selection and coevolution at the proteins of the Polycomb repressive complexes in Drosophila. Heredity (Edinb) 2016; 116:213-23. [PMID: 26486609 PMCID: PMC4806890 DOI: 10.1038/hdy.2015.91] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 07/23/2015] [Accepted: 08/10/2015] [Indexed: 11/08/2022] Open
Abstract
Polycomb group (PcG) proteins are important epigenetic regulatory proteins that modulate the chromatin state through posttranslational histone modifications. These interacting proteins form multimeric complexes that repress gene expression. Thus, PcG proteins are expected to evolve coordinately, which might be reflected in their phylogenetic trees by concordant episodes of positive selection and by a correlation in evolutionary rates. In order to detect these signals of coevolution, the molecular evolution of 17 genes encoding the subunits of five Polycomb repressive complexes has been analyzed in the Drosophila genus. The observed distribution of divergence differs substantially among and along proteins. Indeed, CAF1 is uniformly conserved, whereas only the established protein domains are conserved in other proteins, such as PHO, PHOL, PSC, PH-P and ASX. Moreover, regions with a low divergence not yet described as protein domains are present, for instance, in SFMBT and SU(Z)12. Maximum likelihood methods indicate an acceleration in the nonsynonymous substitution rate at the lineage ancestral to the obscura group species in most genes encoding subunits of the Pcl-PRC2 complex and in genes Sfmbt, Psc and Kdm2. These methods also allow inferring the action of positive selection in this lineage at genes E(z) and Sfmbt. Finally, the protein interaction network predicted from the complete proteomes of 12 Drosophila species using a coevolutionary approach shows two tight PcG clusters. These clusters include well-established binary interactions among PcG proteins as well as new putative interactions.
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Affiliation(s)
- J M Calvo-Martín
- Facultat de Biologia, Departament de Genètica, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - P Librado
- Facultat de Biologia, Departament de Genètica, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - M Aguadé
- Facultat de Biologia, Departament de Genètica, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - M Papaceit
- Facultat de Biologia, Departament de Genètica, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
| | - C Segarra
- Facultat de Biologia, Departament de Genètica, and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Spain
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8
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Biagioli M, Ferrari F, Mendenhall EM, Zhang Y, Erdin S, Vijayvargia R, Vallabh SM, Solomos N, Manavalan P, Ragavendran A, Ozsolak F, Lee JM, Talkowski ME, Gusella JF, Macdonald ME, Park PJ, Seong IS. Htt CAG repeat expansion confers pleiotropic gains of mutant huntingtin function in chromatin regulation. Hum Mol Genet 2015; 24:2442-57. [PMID: 25574027 DOI: 10.1093/hmg/ddv006] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 01/06/2015] [Indexed: 12/15/2022] Open
Abstract
The CAG repeat expansion in the Huntington's disease gene HTT extends a polyglutamine tract in mutant huntingtin that enhances its ability to facilitate polycomb repressive complex 2 (PRC2). To gain insight into this dominant gain of function, we mapped histone modifications genome-wide across an isogenic panel of mouse embryonic stem cell (ESC) and neuronal progenitor cell (NPC) lines, comparing the effects of Htt null and different size Htt CAG mutations. We found that Htt is required in ESC for the proper deposition of histone H3K27me3 at a subset of 'bivalent' loci but in NPC it is needed at 'bivalent' loci for both the proper maintenance and the appropriate removal of this mark. In contrast, Htt CAG size, though changing histone H3K27me3, is prominently associated with altered histone H3K4me3 at 'active' loci. The sets of ESC and NPC genes with altered histone marks delineated by the lack of huntingtin or the presence of mutant huntingtin, though distinct, are enriched in similar pathways with apoptosis specifically highlighted for the CAG mutation. Thus, the manner by which huntingtin function facilitates PRC2 may afford mutant huntingtin with multiple opportunities to impinge upon the broader machinery that orchestrates developmentally appropriate chromatin status.
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Affiliation(s)
- Marta Biagioli
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | | | | | - Yijing Zhang
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Serkan Erdin
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Ravi Vijayvargia
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Sonia M Vallabh
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Nicole Solomos
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Poornima Manavalan
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Ashok Ragavendran
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Fatih Ozsolak
- RaNA Therapeutics, 790 Memorial Drive, Cambridge, MA 02139, USA
| | - Jong Min Lee
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Department of Neurology, Harvard Medical School, Boston, MA 02114, USA
| | - Michael E Talkowski
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
| | - James F Gusella
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA, Department of Genetics, Harvard Medical School, Boston, MA 02115, USA and
| | - Marcy E Macdonald
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Department of Neurology, Harvard Medical School, Boston, MA 02114, USA, Department of Genetics, Harvard Medical School, Boston, MA 02115, USA and
| | - Peter J Park
- Center for Biomedical Informatics, Boston, MA 02114, USA Division of Genetics, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Ihn Sik Seong
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA, Department of Neurology, Harvard Medical School, Boston, MA 02114, USA,
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Elements of the polycomb repressor SU(Z)12 needed for histone H3-K27 methylation, the interface with E(Z), and in vivo function. Mol Cell Biol 2013; 33:4844-56. [PMID: 24100017 DOI: 10.1128/mcb.00307-13] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Polycomb repressive complex 2 (PRC2) is an essential chromatin-modifying enzyme that implements gene silencing. PRC2 methylates histone H3 on lysine-27 and is conserved from plants to flies to humans. In Drosophila melanogaster, PRC2 contains four core subunits: E(Z), SU(Z)12, ESC, and NURF55. E(Z) bears a SET domain that houses the enzyme active site. However, PRC2 activity depends upon critical inputs from SU(Z)12 and ESC. The stimulatory mechanisms are not understood. We present here functional dissection of the SU(Z)12 subunit. SU(Z)12 contains two highly conserved domains: an ∼140-amino-acid VEFS domain and a Cys2-His2 zinc finger (ZnF). Analysis of recombinant PRC2 bearing VEFS domain alterations, including some modeled after leukemia mutations, identifies distinct elements needed for SU(Z)12 assembly with E(Z) and stimulation of histone methyltransferase. The results define an extensive VEFS subdomain that organizes the SU(Z)12-E(Z) interface. Although the SU(Z)12 ZnF is not needed for methyltransferase in vitro, genetic rescue assays show that the ZnF is required in vivo. Chromatin immunoprecipitations reveal that this ZnF facilitates PRC2 binding to a genomic target. This study defines functionally critical SU(Z)12 elements, including key determinants of SU(Z)12-E(Z) communication. Together with recent findings, this illuminates PRC2 modulation by conserved inputs from its noncatalytic subunits.
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EZH2 generates a methyl degron that is recognized by the DCAF1/DDB1/CUL4 E3 ubiquitin ligase complex. Mol Cell 2012; 48:572-86. [PMID: 23063525 DOI: 10.1016/j.molcel.2012.09.004] [Citation(s) in RCA: 175] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/14/2012] [Accepted: 09/06/2012] [Indexed: 12/22/2022]
Abstract
Ubiquitination plays a major role in protein degradation. Although phosphorylation-dependent ubiquitination is well known for the regulation of protein stability, methylation-dependent ubiquitination machinery has not been characterized. Here, we provide evidence that methylation-dependent ubiquitination is carried out by damage-specific DNA binding protein 1 (DDB1)/cullin4 (CUL4) E3 ubiquitin ligase complex and a DDB1-CUL4-associated factor 1 (DCAF1) adaptor, which recognizes monomethylated substrates. Molecular modeling and binding affinity studies reveal that the putative chromo domain of DCAF1 directly recognizes monomethylated substrates, whereas critical binding pocket mutations of the DCAF1 chromo domain ablated the binding from the monomethylated substrates. Further, we discovered that enhancer of zeste homolog 2 (EZH2) methyltransferase has distinct substrate specificities for histone H3K27 and nonhistones exemplified by an orphan nuclear receptor, RORα. We propose that EZH2-DCAF1/DDB1/CUL4 represents a previously unrecognized methylation-dependent ubiquitination machinery specifically recognizing "methyl degron"; through this, nonhistone protein stability can be dynamically regulated in a methylation-dependent manner.
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11
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Fedorova EV, Pindyurin AV, Baricheva EM. Maintenance of the patterns of expression of homeotic genes in the development of Drosophila melanogaster by proteins of the polycomb, trithorax, and ETP groups. RUSS J GENET+ 2009. [DOI: 10.1134/s1022795409100019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Shen X, Liu Y, Hsu YJ, Fujiwara Y, Kim J, Mao X, Yuan GC, Orkin SH. EZH1 mediates methylation on histone H3 lysine 27 and complements EZH2 in maintaining stem cell identity and executing pluripotency. Mol Cell 2009; 32:491-502. [PMID: 19026780 PMCID: PMC2630502 DOI: 10.1016/j.molcel.2008.10.016] [Citation(s) in RCA: 736] [Impact Index Per Article: 49.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 07/20/2008] [Accepted: 10/16/2008] [Indexed: 01/04/2023]
Abstract
Trimethylation on H3K27 (H3K27me3) mediated by Polycomb repressive complex 2 (PRC2) has been linked to embryonic stem cell (ESC) identity and pluripotency. EZH2, the catalytic subunit of PRC2, has been reported as the sole histone methyltransferase that methylates H3K27 and mediates transcriptional silencing. Analysis of Ezh2(-/-) ESCs suggests existence of an additional enzyme(s) catalyzing H3K27 methylation. We have identified EZH1, a homolog of EZH2 that is physically present in a noncanonical PRC2 complex, as an H3K27 methyltransferase in vivo and in vitro. EZH1 colocalizes with the H3K27me3 mark on chromatin and preferentially preserves this mark on development-related genes in Ezh2(-/-) ESCs. Depletion of Ezh1 in cells lacking Ezh2 abolishes residual methylation on H3K27 and derepresses H3K27me3 target genes, demonstrating a role of EZH1 in safeguarding ESC identity. Ezh1 partially complements Ezh2 in executing pluripotency during ESC differentiation, suggesting that cell-fate transitions require epigenetic specificity.
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Affiliation(s)
- Xiaohua Shen
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Margueron R, Li G, Sarma K, Blais A, Zavadil J, Woodcock CL, Dynlacht BD, Reinberg D. Ezh1 and Ezh2 maintain repressive chromatin through different mechanisms. Mol Cell 2009; 32:503-18. [PMID: 19026781 PMCID: PMC3641558 DOI: 10.1016/j.molcel.2008.11.004] [Citation(s) in RCA: 644] [Impact Index Per Article: 42.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Revised: 09/01/2008] [Accepted: 11/05/2008] [Indexed: 12/14/2022]
Abstract
Polycomb group proteins are critical to maintaining gene repression established during Drosophila development. Part of this group forms the PRC2 complex containing Ez that catalyzes di- and trimethylation of histone H3 lysine 27 (H3K37me2/3), marks repressive to transcription. We report that the mammalian homologs Ezh1 and Ezh2 form similar PRC2 complexes but exhibit contrasting repressive roles. While PRC2-Ezh2 catalyzes H3K27me2/3 and its knockdown affects global H3K27me2/3 levels, PRC2-Ezh1 performs this function weakly. In accordance, Ezh1 knockdown was ineffectual on global H3K27me2/3 levels. Instead, PRC2-Ezh1 directly and robustly represses transcription from chromatinized templates and compacts chromatin in the absence of the methyltransferase cofactor SAM, as evidenced by electron microscopy. Ezh1 targets a subset of Ezh2 genes, yet Ezh1 is more abundant in nonproliferative adult organs while Ezh2 expression is tightly associated with proliferation, as evidenced when analyzing aging mouse kidney. These results might reflect subfunctionalization of a PcG protein during evolution.
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Affiliation(s)
- Raphael Margueron
- Department of Biochemistry NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Guohong Li
- Howard Hughes Medical Institute NYU-Medical School 522 First Av., New York, NY 10016, USA
- Department of Biochemistry NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Kavitha Sarma
- Department of Biochemistry NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Alexandre Blais
- Department of Pathology and NYU Cancer Institute NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Jiri Zavadil
- Department of Pathology and NYU Cancer Institute NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Christopher L. Woodcock
- Department of Biology, Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Brian D. Dynlacht
- Department of Pathology and NYU Cancer Institute NYU-Medical School 522 First Av., New York, NY 10016, USA
| | - Danny Reinberg
- Howard Hughes Medical Institute NYU-Medical School 522 First Av., New York, NY 10016, USA
- Department of Biochemistry NYU-Medical School 522 First Av., New York, NY 10016, USA
- Corresponding author: Howard Hughes Medical Institute NYU School of Medicine-Smilow Research Center Biochemistry Department 522 First Avenue, 2nd Floor, Room 211 New York, New York 10016 () Tel: 212-263-9036 Fax: 212-263-9040
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14
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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: 2.8] [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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15
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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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16
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Parrish JZ, Emoto K, Jan LY, Jan YN. Polycomb genes interact with the tumor suppressor genes hippo and warts in the maintenance of Drosophila sensory neuron dendrites. Genes Dev 2007; 21:956-72. [PMID: 17437999 PMCID: PMC1847713 DOI: 10.1101/gad.1514507] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Dendritic fields are important determinants of neuronal function. However, how neurons establish and then maintain their dendritic fields is not well understood. Here we show that Polycomb group (PcG) genes are required for maintenance of complete and nonoverlapping dendritic coverage of the larval body wall by Drosophila class IV dendrite arborization (da) neurons. In esc, Su(z)12, or Pc mutants, dendritic fields are established normally, but class IV neurons display a gradual loss of dendritic coverage, while axons remain normal in appearance, demonstrating that PcG genes are specifically required for dendrite maintenance. Both multiprotein Polycomb repressor complexes (PRCs) involved in transcriptional silencing are implicated in regulation of dendrite arborization in class IV da neurons, likely through regulation of homeobox (Hox) transcription factors. We further show genetic interactions and association between PcG proteins and the tumor suppressor kinase Warts (Wts), providing evidence for their cooperation in multiple developmental processes including dendrite maintenance.
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Affiliation(s)
- Jay Z. Parrish
- Howard Hughes Medical Institute, Department of Physiology, and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Kazuo Emoto
- Howard Hughes Medical Institute, Department of Physiology, and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Lily Yeh Jan
- Howard Hughes Medical Institute, Department of Physiology, and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
| | - Yuh Nung Jan
- Howard Hughes Medical Institute, Department of Physiology, and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143, USA
- Corresponding author.E-MAIL ; FAX (415) 476-5774
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17
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Grimaud C, Nègre N, Cavalli G. From genetics to epigenetics: the tale of Polycomb group and trithorax group genes. Chromosome Res 2006; 14:363-75. [PMID: 16821133 DOI: 10.1007/s10577-006-1069-y] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The Polycomb gene was discovered 60 years ago as a mutation inducing a particular homeotic phenotype. Subsequent work showed that Polycomb is a general repressor of homeotic genes. Other genes with similar function were identified and named Polycomb group (PcG) genes, while trithorax group (trxG) genes were shown to counteract PcG-mediated repression of homeotic genes. We now know that PcG and trxG proteins are conserved factors that regulate hundreds of different genomic loci. A sophisticated pathway is responsible for recruitment of these proteins at regulatory regions that were named PcG and trxG response elements (PRE and TRE). Once recruited to their targets, multimeric PcG and trxG protein complexes regulate transcription by modulating chromatin structure, in particular via deposition of specific post-translational histone modification marks and control of chromatin accessibility, as well as regulation of the three-dimensional nuclear organization of PRE and TRE. Here, we recapitulate the history of PcG and trxG gene discovery, we review the current evidence on their molecular function and, based on this evidence, we propose a revised classification of genes involved in PcG and trxG regulatory pathways.
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Affiliation(s)
- Charlotte Grimaud
- Institute of Human Genetics, CNRS, 141, rue de la Cardonille, 34396, Montpellier Cedex 5, France
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18
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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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19
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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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20
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Nekrasov M, Wild B, Müller J. Nucleosome binding and histone methyltransferase activity of Drosophila PRC2. EMBO Rep 2005; 6:348-53. [PMID: 15776017 PMCID: PMC1299286 DOI: 10.1038/sj.embor.7400376] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 02/10/2005] [Accepted: 02/15/2005] [Indexed: 11/08/2022] Open
Abstract
The Drosophila Polycomb group protein E(z) is a histone methyltransferase (HMTase) that is essential for maintaining HOX gene silencing during development. E(z) exists in a multiprotein complex called Polycomb repressive complex 2 (PRC2) that also contains Su(z)12, Esc and Nurf55. Reconstituted recombinant PRC2 methylates nucleosomes in vitro, but recombinant E(z) on its own shows only poor HMTase activity on nucleosomes. Here, we investigate the function of the PRC2 subunits. We show that PRC2 binds to nucleosomes in vitro but that individual PRC2 subunits alone do not bind to nucleosomes. By analysing PRC2 subcomplexes, we show that Su(z)12-Nurf55 is the minimal nucleosome-binding module of PRC2 and that Esc contributes to high-affinity binding of PRC2 nucleosomes. We find that nucleosome binding of PRC2 is not sufficient for histone methylation and that only complexes that contain Esc protein show robust HMTase activity. These observations suggest that different subunits provide mechanistically distinct functions within the PRC2 HMTase: the nucleosome-binding subunits Su(z)12 and Nurf55 anchor the E(z) enzyme on chromatin substrates, whereas Esc is needed to boost enzymatic activity.
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Affiliation(s)
- Maxim Nekrasov
- Gene Expression Programme, EMBL, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Brigitte Wild
- Gene Expression Programme, EMBL, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Jürg Müller
- Gene Expression Programme, EMBL, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Tel: +49 6221 387 629; Fax: +49 6221 387 424; E-mail:
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21
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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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22
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Qiao F, Bowie JU. The many faces of SAM. SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2005; 2005:re7. [PMID: 15928333 DOI: 10.1126/stke.2862005re7] [Citation(s) in RCA: 200] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Protein-protein interactions are essential for the assembly, regulation, and localization of functional protein complexes in the cell. SAM domains are among the most abundant protein-protein interaction motifs in organisms from yeast to humans. Although SAM domains adopt similar folds, they are remarkably versatile in their binding properties. Some identical SAM domains can interact with each other to form homodimers or polymers. In other cases, SAM domains can bind to other related SAM domains, to non-SAM domain-containing proteins, and even to RNA. Such versatility earns them functional roles in myriad biological processes, from signal transduction to transcriptional and translational regulation. In this review, we describe the structural basis of SAM domain interactions and highlight their roles in the scaffolding of protein complexes in normal and pathological processes.
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Affiliation(s)
- Feng Qiao
- U.S. Department of Energy (UCLA-DOE) Institute of Genomics and Proteomics, Molecular Biology Institute, Department of Chemistry and Biochemistry, UCLA, CA 90095, USA
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23
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Shindo N, Sakai A, Arai D, Matsuoka O, Yamasaki Y, Higashinakagawa T. The ESC-E(Z) complex participates in the hedgehog signaling pathway. Biochem Biophys Res Commun 2005; 327:1179-87. [PMID: 15652519 DOI: 10.1016/j.bbrc.2004.12.125] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2004] [Indexed: 11/22/2022]
Abstract
Polycomb group (PcG) genes are required for stable inheritance of epigenetic states throughout development, a phenomenon termed cellular memory. In Drosophila and mice, the product of the E(z) gene, one of the PcG genes, constitutes the ESC-E(Z) complex and specifically methylates histone H3. It has been argued that this methylation sets the stage for appropriate repression of certain genes. Here, we report the isolation of a well-conserved homolog of E(z), olezh2, in medaka. Hypomorphic knock-down of olezh2 resulted in a cyclopia phenotype and markedly perturbed hedgehog signaling, consistent with our previous report on oleed, a medaka esc. We also found cyclopia in embryos treated with trichostatin A, an inhibitor of histone deacetylase, which is a transient component of the ESC-E(Z) complex. The level of tri-methylation at lysine 27 of histone H3 was substantially decreased in both olezh2 and oleed knock-down embryos, and in embryos with hedgehog signaling perturbed by forskolin. We conclude that the ESC-E(Z) complex per se participates in hedgehog signaling.
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Affiliation(s)
- Norihisa Shindo
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Major in Integrated Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 1-6-1 Nishi-Waseda, Shinjuku-ku, Tokyo 169-8050, Japan
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24
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Attwooll C, Oddi S, Cartwright P, Prosperini E, Agger K, Steensgaard P, Wagener C, Sardet C, Moroni MC, Helin K. A novel repressive E2F6 complex containing the polycomb group protein, EPC1, that interacts with EZH2 in a proliferation-specific manner. J Biol Chem 2004; 280:1199-208. [PMID: 15536069 DOI: 10.1074/jbc.m412509200] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transcriptional repressor E2F6 has been identified as a component of two distinct polycomb group protein (PcG)-containing complexes, suggesting a mechanism for the recruitment of repressive complexes to target sequences in DNA. Whereas one complex is involved in the repression of classic E2F target genes in G0, a role for E2F6 within the cell cycle has yet to be defined. We searched for novel E2F6-binding proteins using a yeast two-hybrid screen and identified the PcG protein, EPC1. We showed that, both in vitro and in vivo, E2F6, DP1, and EPC1 form a stable core complex with repressive activity. Furthermore, we identified the proliferation-specific PcG, EZH2, as an EPC1-interacting protein. Using affinity purification, we showed that E2F6, DP1, EPC1, EZH2, and Sin3B co-elute, suggesting the identification of a novel E2F6 complex that exists in vivo in both normal and transformed human cell lines. EZH2 is required for cellular proliferation and consistent with this, EZH2 elutes with the E2F6-EPC1 complex only in proliferating cells. Thus we have identified a novel E2F6-PcG complex (E2F6-EPC1) that interacts with EZH2 and may regulate genes required for cell cycle progression.
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Affiliation(s)
- Claire Attwooll
- European Institute of Oncology, Department of Experimental Oncology, Via Ripamonti 435, Milan, 20141, Italy
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25
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Tang X, Milyavsky M, Shats I, Erez N, Goldfinger N, Rotter V. Activated p53 suppresses the histone methyltransferase EZH2 gene. Oncogene 2004; 23:5759-69. [PMID: 15208672 DOI: 10.1038/sj.onc.1207706] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Replicative senescence is an irreversible cell cycle arrest that limits the proliferation of damaged cells and may be an important tumor suppression mechanism in vivo. This process is regulated at critical steps by the tumor suppressor p53. To identify genes that may regulate the senescence process, we performed cDNA microarray analysis of gene expression in senescent, young proliferating, and hTERT-immortalized primary human fibroblasts. The histone methyltransferase (HMTase), EZH2, was specifically downregulated in senescent cells. Activated p53 suppressed EZH2 gene expression through repression of the EZH2 gene promoter. This activity of p53 requires intact p53 transactivation and DNA binding domains. Furthermore, the repression of EZH2 promoter by p53 is dependent on p53 transcriptional target p21(Waf1) inactivating RB/E2F pathways. In addition, the knockdown of EZH2 expression retards cell proliferation and induces G2/M arrest. We suggest that the p53-dependent suppression of EZH2 expression is a novel pathway that contributes to p53-mediated G2/M arrest. EZH2 associated complex possesses HMTase activity and is involved in epigenetic regulation. Activated p53 suppresses EZH2 expression, suggesting a further role for p53 in epigenetic regulation and in the maintenance of genetic stability. Suppression of EZH2 expression in tumors by p53 may lead to novel approaches to control cancer progression.
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Affiliation(s)
- Xiaohu Tang
- Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel
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26
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Wang L, Brown JL, Cao R, Zhang Y, Kassis JA, Jones RS. Hierarchical recruitment of polycomb group silencing complexes. Mol Cell 2004; 14:637-46. [PMID: 15175158 DOI: 10.1016/j.molcel.2004.05.009] [Citation(s) in RCA: 413] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2004] [Revised: 04/28/2004] [Accepted: 05/03/2004] [Indexed: 11/22/2022]
Abstract
Polycomb group (PcG) proteins maintain the transcriptional silence of target genes through many cycles of cell division. Here, we provide evidence for the sequential binding of PcG proteins at a Polycomb response element (PRE) in proliferating cells in which the sequence-specific DNA binding Pho and Phol proteins directly recruit E(z)-containing complexes, which in turn methylate histone H3 at lysine 27 (H3mK27). This provides a tag that facilitates binding by a Pc-containing complex. In wing imaginal discs, these PcG proteins also are present at discrete locations at or downstream of the promoter of a silenced target gene, Ubx. E(z)-dependent H3mK27 is also present near the Ubx promoter and is needed for Pc binding. The location of E(z)- and Pc-containing complexes downstream of the Ubx transcription start site suggests that they may inhibit transcription by interfering with assembly of the preinitiation complex or by blocking transcription initiation or elongation.
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Affiliation(s)
- Liangjun Wang
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, USA
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27
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Weeraratna AT, Becker D, Carr KM, Duray PH, Rosenblatt KP, Yang S, Chen Y, Bittner M, Strausberg RL, Riggins GJ, Wagner U, Kallioniemi OP, Trent JM, Morin PJ, Meltzer PS. Generation and analysis of melanoma SAGE libraries: SAGE advice on the melanoma transcriptome. Oncogene 2004; 23:2264-74. [PMID: 14755246 DOI: 10.1038/sj.onc.1207337] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this study, we generated three SAGE libraries from melanoma tissues. Using bioinformatics tools usually applied to microarray data, we identified several genes, including novel transcripts, which are preferentially expressed in melanoma. SAGE results converged with previous microarray analysis on the importance of intracellular calcium and G-protein signaling, and the Wnt/Frizzled family. We also examined the expression of CD74, which was specifically, albeit not abundantly, expressed in the melanoma libraries using a melanoma progression tissue microarray, and demonstrate that this protein is expressed by melanoma cells but not by benign melanocytes. Many genes involved in intracellular calcium and G-protein signaling were highly expressed in melanoma, results we had observed earlier from microarray studies (Bittner et al., 2000). One of the genes most highly expressed in our melanoma SAGE libraries was a calcium-regulated gene, calpain 3 (p94). Immunohistochemical analysis demonstrated that calpain 3 moves from the nuclei of non-neoplastic cells to the cytoplasm of malignant cells, suggesting activation of this intracellular proteinase. Our SAGE results and the clinical validation data demonstrate how SAGE profiles can highlight specific links between signaling pathways as well as associations with tumor progression. This may provide insights into new genes that may be useful for the diagnosis and therapy of melanoma.
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Affiliation(s)
- Ashani T Weeraratna
- Laboratory of Immunology, National Institutes of Health, The National Institute on Aging, Baltimore, MD 21224, USA.
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28
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Raaphorst FM, Meijer CJLM, Fieret E, Blokzijl T, Mommers E, Buerger H, Packeisen J, Sewalt RAB, Otte AP, van Diest PJ. Poorly differentiated breast carcinoma is associated with increased expression of the human polycomb group EZH2 gene. Neoplasia 2004; 5:481-8. [PMID: 14965441 PMCID: PMC1502571 DOI: 10.1016/s1476-5586(03)80032-5] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Polycomb group (PcG) genes contribute to the maintenance of cell identity, cell cycle regulation, and oncogenesis. We describe the expression of five PcG genes (BMI-1, RING1, HPC1, HPC2, and EZH2) innormal breast tissues, invasive breast carcinomas, and their precursors. Members of the HPC-HPH/PRC1 PcG complex, including BMI-1, RING1, HPC1, and HPC2, were detected in normal resting and cycling breast cells. The EED-EZH/PRC2 PcG complex protein EZH2 was only found in rare cycling cells, whereas normal resting breast cells were negative for EZH2. PcG gene expression patterns in ductal hyperplasia (DH), well-differentiated ductal carcinoma in situ (DCIS), and well-differentiated invasive carcinomas closely resembled the pattern in healthy cells. However, poorly differentiated DCIS and invasive carcinomas frequently expressed EZH2 in combination with HPC-HPH/PRC1 proteins. Most BMI-1/EZH2 double-positive cells in poorly differentiated DCIS were resting. Poorly differentiated invasive carcinoma displayed an enhanced rate of cell division within BMI-1/EZH2 double-positive cells. We propose that the enhanced expression of EZH2 in BMI-1(+) cells contributes to the loss of cell identity in poorly differentiated breast carcinomas, and that increased EZH2 expression precedes high frequencies of proliferation. These observations suggest that deregulated expression of EZH2 is associated with loss of differentiation and development of poorly differentiated breast cancer in humans.
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Affiliation(s)
- Frank M Raaphorst
- Department of Pathology, VU University Medical Center, BioCentrum Amsterdam, University of Amsterdam, Amsterdam, The Netherlands.
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29
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Raaphorst FM, Vermeer M, Fieret E, Blokzijl T, Dukers D, Sewalt RGAB, Otte AP, Willemze R, Meijer CJLM. Site-specific expression of polycomb-group genes encoding the HPC-HPH/PRC1 complex in clinically defined primary nodal and cutaneous large B-cell lymphomas. THE AMERICAN JOURNAL OF PATHOLOGY 2004; 164:533-42. [PMID: 14742259 PMCID: PMC1602277 DOI: 10.1016/s0002-9440(10)63143-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polycomb-group (PcG) genes preserve cell identity by gene silencing, and contribute to regulation of lymphopoiesis and malignant transformation. We show that primary nodal large B-cell lymphomas (LBCLs), and secondary cutaneous deposits from such lymphomas, abnormally express the BMI-1, RING1, and HPH1 PcG genes in cycling neoplastic cells. By contrast, tumor cells in primary cutaneous LBCLs lacked BMI-1 expression, whereas RING1 was variably detected. Lack of BMI-1 expression was characteristic for primary cutaneous LBCLs, because other primary extranodal LBCLs originating from brain, testes, and stomach were BMI-1-positive. Expression of HPH1 was rarely detected in primary cutaneous LBCLs of the head or trunk and abundant in primary cutaneous LBCLs of the legs, which fits well with its earlier recognition as a distinct clinical pathological entity with different clinical behavior. We conclude that clinically defined subclasses of primary LBCLs display site-specific abnormal expression patterns of PcG genes of the HPC-HPH/PRC1 PcG complex. Some of these patterns (such as the expression profile of BMI-1) may be diagnostically relevant. We propose that distinct expression profiles of PcG genes results in abnormal formation of HPC-HPH/PRC1 PcG complexes, and that this contributes to lymphomagenesis and different clinical behavior of clinically defined LBCLs.
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Affiliation(s)
- Frank M Raaphorst
- Department of Pathology, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
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30
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Katz A, Oliva M, Mosquna A, Hakim O, Ohad N. FIE and CURLY LEAF polycomb proteins interact in the regulation of homeobox gene expression during sporophyte development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 37:707-19. [PMID: 14871310 DOI: 10.1111/j.1365-313x.2003.01996.x] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Arabidopsis FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) polycomb group (PcG) protein, a WD40 homologue of Drosophila extra sex comb (ESC), regulates endosperm and embryo development and represses flowering during embryo and seedling development. As fie alleles are not transmitted maternally, homozygous mutant plants cannot be obtained. To study FIE function during the entire plant life cycle, we used Arabidopsis FIE co-suppressed plants. Low FIE level in these plants produced dramatic morphological aberrations, including loss of apical dominance, curled leaves, early flowering and homeotic conversion of leaves, flower organs and ovules into carpel-like structures. These morphological aberrations are similar to those exhibited by plants overexpressing AGAMOUS (AG) or CURLY LEAF (clf) mutants. Furthermore, the aberrant leaf morphology of FIE-silenced and clf plants correlates with de-repression of the class I KNOTTED-like homeobox (KNOX) genes including KNOTTED-like from Arabidopsis thaliana 2 (KNAT2) and SHOOTMERISTEMLESS (STM), whereas BREVIPEDICELLUS (BP) was upregulated in FIE-silenced plants, but not in the clf mutant. Thus, FIE is essential for the control of shoot and leaf development. Yeast two-hybrid and pull-down assays demonstrate that FIE interacts with CLF. Collectively, the morphological characteristics, together with the molecular and biochemical data presented in this work, strongly suggest that in plants, as in mammals and insects, PcG proteins control expression of homeobox genes. Our findings demonstrate that the versatility of the plant FIE function, which is derived from association with different SET (SU (VAR)3-9, E (Z), Trithorax) domain PcG proteins, results in differential regulation of gene expression throughout the plant life cycle.
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Affiliation(s)
- Aviva Katz
- Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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31
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Thakur JK, Malik MR, Bhatt V, Reddy MK, Sopory SK, Tyagi AK, Khurana JP. A POLYCOMB group gene of rice (Oryza sativa L. subspecies indica), OsiEZ1, codes for a nuclear-localized protein expressed preferentially in young seedlings and during reproductive development. Gene 2003; 314:1-13. [PMID: 14527713 DOI: 10.1016/s0378-1119(03)00723-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The SET domains are conserved amino acid sequences present in chromosomal proteins that contribute to the epigenetic control of gene expression by altering regional organization of the chromatin structure. The SET domain proteins are divided into four subgroups as categorized by their Drosophila members; enhancer of zeste (E(Z)), trithorax (TRX), absent small or homeotic 1 (ASH1) and supressor of variegation (SU(VAR)3-9). Homologs of all four classes have been characterized in yeast, mammals and plants. We report here the isolation and characterization of rice (Oryza sativa L. subspecies indica) cDNA, OsiEZ1, as a monocot member of this family. The OsiEZ1 cDNA is 3133 bp long with an ORF of 2799 bp, and the predicted amino acid sequence (895 residues) corresponds to a protein of ca. 98 kDa. All the characteristic domains known to be conserved in E(Z) homologs (subgroup I) of SET domain containing proteins are present in OsiEZ1. In the rice genome, a 7499 bp long OsiEZ1 sequence is split into 17 exons interrupted by 16 introns. Southern analysis indicates that OsiEZ1 is represented as single copy in the rice genome. Expression studies revealed that the OsiEZ1 transcript level was highest in rice flowers, almost undetectable in developing seeds of 1-2 days post-fertilization but increased significantly in young seeds of 3-5 days post-fertilization. The OsiEZ1 transcript was barely detectable in mature zygotic embryos, but its levels were significantly higher in callus derived from rice scutellum, somatic embryos and young seedlings. The OsiEZ1/GUS recombinant protein was confined to the nucleus in living cells of particle-bombarded onion peels. The expression of OsiEZ1 complemented a set1Delta Saccharomyces cerevisiae mutant that is impaired in telomeric silencing. We suggest that the nuclear-localized OsiEZ1 has a role in regulating various aspects of plant development, and this control is most likely brought about by repressing the activity of downstream regulatory genes.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Blotting, Northern
- Chromosome Mapping
- Chromosomes, Plant/genetics
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Flowers/genetics
- Flowers/growth & development
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Plant
- Genetic Complementation Test
- Molecular Sequence Data
- Mutation
- Nuclear Proteins/genetics
- Oryza/genetics
- Oryza/growth & development
- Phylogeny
- Plant Proteins/genetics
- Polycomb-Group Proteins
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Repressor Proteins/genetics
- Reproduction/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Saccharomyces cerevisiae/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Telomere/genetics
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Affiliation(s)
- Jitendra K Thakur
- Department of Plant Molecular Biology, University of Delhi South Campus, Benito Juarez Road, 110021, New Delhi, India
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32
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Sathyamurthy A, Allen MD, Murzin AG, Bycroft M. Crystal structure of the malignant brain tumor (MBT) repeats in Sex Comb on Midleg-like 2 (SCML2). J Biol Chem 2003; 278:46968-73. [PMID: 12952983 DOI: 10.1074/jbc.m306469200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sex Comb on Midleg (SCM) belongs to the Polycomb group of proteins, which are involved in transcriptional regulation in Drosophila. It is one of the components of Polycomb repressive complex 1, a multiprotein complex of Polycomb group proteins involved in the maintenance of repression and the blocking of chromatin remodeling. SCM contains two approximately 100-residue malignant brain tumor (MBT) repeats at the N terminus. These repeats are also found in other proteins involved in transcriptional repression. Here, we report the 1.78-A crystal structure of the two MBT repeats of SCM-like 2 (SCML2), a human homologue of SCM. Each repeat consists of an extended arm and a beta-barrel core. There are significant structural similarities to the Tudor, PWWP, and chromo domains, suggesting probable evolutionary relationships and functional similarities between the MBT repeats and these domains.
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Affiliation(s)
- Aruna Sathyamurthy
- Medical Research Council Centre for Protein Engineering, Hills Road, Cambridge CB2 2QH, United Kingdom
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33
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Köhler C, Hennig L, Bouveret R, Gheyselinck J, Grossniklaus U, Gruissem W. Arabidopsis MSI1 is a component of the MEA/FIE Polycomb group complex and required for seed development. EMBO J 2003; 22:4804-14. [PMID: 12970192 PMCID: PMC212713 DOI: 10.1093/emboj/cdg444] [Citation(s) in RCA: 316] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Seed development in angiosperms initiates after double fertilization, leading to the formation of a diploid embryo and a triploid endosperm. The active repression of precocious initiation of certain aspects of seed development in the absence of fertilization requires the Polycomb group proteins MEDEA (MEA), FERTILIZATION-INDEPENDENT ENDOSPERM (FIE) and FERTILIZATION-INDEPENDENT SEED2. Here we show that the Arabidopsis WD-40 domain protein MSI1 is present together with MEA and FIE in a 600 kDa complex and interacts directly with FIE. Mutant plants heterozygous for msi1 show a seed abortion ratio of 50% with seeds aborting when the mutant allele is maternally inherited, irrespective of a paternal wild-type or mutant MSI1 allele. Further more, msi1 mutant gametophytes initiate endosperm development in the absence of fertilization at a high penetrance. After pollination, only the egg cell becomes fertilized, the central cell starts dividing prior to fertilization, resulting in the formation of seeds containing embryos surrounded by diploid endosperm. Our results establish that MSI1 has an essential function in the correct initiation and progression of seed development.
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Affiliation(s)
- Claudia Köhler
- Institute of Plant Biology and Zurich-Basel Plant Science Centre, University of Zurich, Zollikerstrasse 107, CH-8050 Zurich, Switzerland
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34
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Ayyar S, Jiang J, Collu A, White-Cooper H, White RAH. Drosophila TGIF is essential for developmentally regulated transcription in spermatogenesis. Development 2003; 130:2841-52. [PMID: 12756169 DOI: 10.1242/dev.00513] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have investigated the role of TGIF, a TALE-class homeodomain transcription factor, in Drosophila development. In vertebrates, TGIF has been implicated, by in vitro analysis, in several pathways, most notably as a repressor modulating the response to TGFbeta signalling. Human TGIF has been associated with the developmental disorder holoprosencephaly. Drosophila TGIF is represented by the products of two tandemly repeated highly similar genes, achintya and vismay. We have generated mutations that delete both genes. Homozygous mutant flies are viable and appear morphologically normal, but the males are completely sterile. The defect lies at the primary spermatocyte stage and differentiation is blocked prior to the onset of the meiotic divisions. We show that mutants lacking TGIF function fail to activate transcription of many genes required for sperm manufacture and of some genes required for entry into the meiotic divisions. This groups TGIF together with two other genes producing similar phenotypes, always early and cookie monster, as components of the machinery required for the activation of the spermatogenic programme of transcription. TGIF is the first sequence-specific transcription factor identified in this pathway. By immunolabelling in mouse testes we show that TGIF is expressed in the early stages of spermatogenesis consistent with a conserved role in the activation of the spermatogenesis transcription programme.
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Affiliation(s)
- Savita Ayyar
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK
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35
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Lessard J, Sauvageau G. Polycomb group genes as epigenetic regulators of normal and leukemic hemopoiesis. Exp Hematol 2003; 31:567-85. [PMID: 12842702 DOI: 10.1016/s0301-472x(03)00081-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Epigenetic modification of chromatin structure underlies the differentiation of pluripotent hemopoietic stem cells (HSCs) into their committed/differentiated progeny. Compelling evidence indicates that Polycomb group (PcG) genes play a key role in normal and leukemic hemopoiesis through epigenetic regulation of HSC self-renewal/proliferation and commitment. The PcG proteins are constituents of evolutionary highly conserved molecular pathways regulating cell fate in several other tissues through diverse mechanisms, including 1) regulation of self-renewal/proliferation, 2) regulation of senescence/immortalization, 3) interaction with the initiation transcription machinery, 4) interaction with chromatin-condensation proteins, 5) modification of histones, 6) inactivation of paternal X chromosome, and 7) regulation of cell death. It is therefore not surprising that PcG genes lead to pleiotropic phenotypes when mutated and have been associated with malignancies in several systems in both mice and humans. Although much remains to be learned regarding the PcG mechanism(s) of action, advances in identifying the functional domains and enzymatic activities of these multimeric protein complexes have provided insights into how PcG proteins accomplish such processes. Some of the new insights into a role for the PcG cellular memory system in regulating normal and leukemic hemopoiesis are reviewed here, with special emphasis on their potential involvement in epigenetic regulation of gene expression through modification of chromatin structure.
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Affiliation(s)
- Julie Lessard
- Laboratory of Molecular Genetics of Hemopoietic Stem Cells, Clinical Research Institute of Montreal, Montreal, Quebec, Canada
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36
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Erhardt S, Lyko F, Ainscough JFX, Surani MA, Paro R. Polycomb-group proteins are involved in silencing processes caused by a transgenic element from the murine imprinted H19/Igf2 region in Drosophila. Dev Genes Evol 2003; 213:336-44. [PMID: 12750886 DOI: 10.1007/s00427-003-0331-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2002] [Accepted: 03/20/2003] [Indexed: 12/22/2022]
Abstract
A subset of autosomal genes undergo genomic imprinting which results in expression from only the paternal or maternal chromosome. While this phenomenon is restricted to mammals and angiosperms, the underlying silencing mechanisms appear to be evolutionarily conserved. A biallelically unmethylated DNaseI hypersensitive region (A6-A4) between the imprinted Igf2 and H19 genes is conserved in humans and mice and functions as a tissue-specific maintenance element for the imprinted growth factor IGF2. In order to analyse A6-A4 for potentially conserved transcriptional maintenance properties, we have generated transgenic Drosophila harbouring the element in a reporter construct. These flies depicted silencing of the reporter genes lacZ and mini -white. The silenced state of the mini -white gene showed variegation and sensitivity to temperature changes. In addition, two members of the conserved Polycomb group, Enhancer of zeste and Posterior sex combs, were needed for repression. Polycomb group proteins are essential for gene silencing during development. Our results indicate that Polycomb group proteins may also be involved in the regulation of mammalian imprinted genes.
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Affiliation(s)
- Sylvia Erhardt
- ZMBH, University of Heidelberg, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany
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37
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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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38
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Silva J, Mak W, Zvetkova I, Appanah R, Nesterova TB, Webster Z, Peters AHFM, Jenuwein T, Otte AP, Brockdorff N. Establishment of histone h3 methylation on the inactive X chromosome requires transient recruitment of Eed-Enx1 polycomb group complexes. Dev Cell 2003; 4:481-95. [PMID: 12689588 DOI: 10.1016/s1534-5807(03)00068-6] [Citation(s) in RCA: 496] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Previous studies have implicated the Eed-Enx1 Polycomb group complex in the maintenance of imprinted X inactivation in the trophectoderm lineage in mouse. Here we show that recruitment of Eed-Enx1 to the inactive X chromosome (Xi) also occurs in random X inactivation in the embryo proper. Localization of Eed-Enx1 complexes to Xi occurs very early, at the onset of Xist expression, but then disappears as differentiation and development progress. This transient localization correlates with the presence of high levels of the complex in totipotent cells and during early differentiation stages. Functional analysis demonstrates that Eed-Enx1 is required to establish methylation of histone H3 at lysine 9 and/or lysine 27 on Xi and that this, in turn, is required to stabilize the Xi chromatin structure.
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Affiliation(s)
- Jose Silva
- X Inactivation Group, MRC Clinical Sciences Centre, ICSM, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom
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39
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Atchison L, Ghias A, Wilkinson F, Bonini N, Atchison ML. Transcription factor YY1 functions as a PcG protein in vivo. EMBO J 2003; 22:1347-58. [PMID: 12628927 PMCID: PMC151054 DOI: 10.1093/emboj/cdg124] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Polycomb group (PcG) proteins function as high molecular weight complexes that maintain transcriptional repression patterns during embryogenesis. The vertebrate DNA binding protein and transcriptional repressor, YY1, shows sequence homology with the Drosophila PcG protein, pleiohomeotic (PHO). YY1 might therefore be a vertebrate PcG protein. We used Drosophila embryo and larval/imaginal disc transcriptional repression systems to determine whether YY1 repressed transcription in a manner consistent with PcG function in vivo. YY1 repressed transcription in Drosophila, and this repression was stable on a PcG-responsive promoter, but not on a PcG-non-responsive promoter. PcG mutants ablated YY1 repression, and YY1 could substitute for PHO in repressing transcription in wing imaginal discs. YY1 functionally compensated for loss of PHO in pho mutant flies and partially corrected mutant phenotypes. Taken together, these results indicate that YY1 functions as a PcG protein. Finally, we found that YY1, as well as Polycomb, required the co-repressor protein CtBP for repression in vivo. These results provide a mechanism for recruitment of vertebrate PcG complexes to DNA and demonstrate new functions for YY1.
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Affiliation(s)
| | - Ayesha Ghias
- Department of Biology, Chestnut Hill College, 9601 Germantown Avenue, Philadelphia, PA 19118,
Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104 and Department of Biology, Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Frank Wilkinson
- Department of Biology, Chestnut Hill College, 9601 Germantown Avenue, Philadelphia, PA 19118,
Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104 and Department of Biology, Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Nancy Bonini
- Department of Biology, Chestnut Hill College, 9601 Germantown Avenue, Philadelphia, PA 19118,
Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104 and Department of Biology, Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, PA 19104, USA Corresponding author e-mail:
| | - Michael L. Atchison
- Department of Biology, Chestnut Hill College, 9601 Germantown Avenue, Philadelphia, PA 19118,
Department of Animal Biology, University of Pennsylvania, School of Veterinary Medicine, 3800 Spruce Street, Philadelphia, PA 19104 and Department of Biology, Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, PA 19104, USA Corresponding author e-mail:
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40
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Reyes JC, Grossniklaus U. Diverse functions of Polycomb group proteins during plant development. Semin Cell Dev Biol 2003; 14:77-84. [PMID: 12524010 DOI: 10.1016/s1084-9521(02)00139-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polycomb group (PcG) proteins play essential roles in animal and plant life cycles by controlling the expression of important developmental regulators. These structurally heterogeneous proteins form multimeric protein complexes that control higher order chromatin structure and, thereby, the expression state of their target genes. Once established, PcG proteins maintain silent gene expression states over many cell divisions providing a molecular basis for a cellular 'memory.' PcG proteins are best known for their role in the control of homeotic genes in Drosophila and mammals. In addition, they play important roles in the control of cell proliferation in vertebrate and invertebrate systems. Recent studies in plants have shown that PcG proteins regulate diverse developmental processes and, as in animals, they affect both homeotic gene expression and cell proliferation. Thus, the function of PcG proteins has been widely conserved between the plant and animal kingdoms.
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Affiliation(s)
- José C Reyes
- Instituto de Bioquimica Vegetal y Fotosintesis, Centro de Investigaciones Isla de la Cartuja, Av. Americo Vespucio s/n, E-41092 Sevilla, Spain
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41
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Faucheux M, Roignant JY, Netter S, Charollais J, Antoniewski C, Théodore L. batman Interacts with polycomb and trithorax group genes and encodes a BTB/POZ protein that is included in a complex containing GAGA factor. Mol Cell Biol 2003; 23:1181-95. [PMID: 12556479 PMCID: PMC141128 DOI: 10.1128/mcb.23.4.1181-1195.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polycomb and trithorax group genes maintain the appropriate repressed or activated state of homeotic gene expression throughout Drosophila melanogaster development. We have previously identified the batman gene as a Polycomb group candidate since its function is necessary for the repression of Sex combs reduced. However, our present genetic analysis indicates functions of batman in both activation and repression of homeotic genes. The 127-amino-acid Batman protein is almost reduced to a BTB/POZ domain, an evolutionary conserved protein-protein interaction domain found in a large protein family. We show that this domain is involved in the interaction between Batman and the DNA binding GAGA factor encoded by the Trithorax-like gene. The GAGA factor and Batman codistribute on polytene chromosomes, coimmunoprecipitate from nuclear embryonic and larval extracts, and interact in the yeast two-hybrid assay. Batman, together with the GAGA factor, binds to MHS-70, a 70-bp fragment of the bithoraxoid Polycomb response element. This binding, like that of the GAGA factor, requires the presence of d(GA)n sequences. Together, our results suggest that batman belongs to a subset of the Polycomb/trithorax group of genes that includes Trithorax-like, whose products are involved in both activation and repression of homeotic genes.
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Affiliation(s)
- M Faucheux
- Laboratoire d'Embryologie Moléculaire et Expérimentale, Chromatine et Développement, CNRS ESA 8080, Université Paris Sud, Orsay, France
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42
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Fujisaki S, Ninomiya Y, Ishihara H, Miyazaki M, Kanno R, Asahara T, Kanno M. Dimerization of the Polycomb-group protein Mel-18 is regulated by PKC phosphorylation. Biochem Biophys Res Commun 2003; 300:135-40. [PMID: 12480532 DOI: 10.1016/s0006-291x(02)02791-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The Polycomb-group (Pc-G) gene products form complexes via protein-protein interactions and maintain the transcriptional repression of genes involved in embryogenesis, cell cycle, and tumorigenesis. Previously, we have shown that mouse Mel-18, a Pc-G protein, has tumor suppressor gene-like activity and negatively regulates transcription. Here, we show in vitro by pull-down assays and in vivo in transiently transfected COS-7 cells that Mel-18 forms homodimers. Deletion analysis revealed that the N-terminal RING-finger and alpha-helix domains are required for homodimer formation. In addition, we demonstrated that Mel-18 homo-dimerization is regulated by protein kinase C (PKC) and protein phosphatases, such that dephosphorylated Mel-18 is able to homo-dimerize. These results suggest that the stoichiometry and/or equilibrium of subunits of the class II Polycomb complex containing Mel-18 might be regulated by changes in phosphorylation status via the PKC signaling pathway.
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Affiliation(s)
- Seiji Fujisaki
- Department of Immunology, Graduate School of Science, Hiroshima University, 1-2-3, Kasumi, Minami-ku, Japan
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43
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Müller J, Hart CM, Francis NJ, Vargas ML, Sengupta A, Wild B, Miller EL, O'Connor MB, Kingston RE, Simon JA. Histone methyltransferase activity of a Drosophila Polycomb group repressor complex. Cell 2002; 111:197-208. [PMID: 12408864 DOI: 10.1016/s0092-8674(02)00976-5] [Citation(s) in RCA: 1181] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Polycomb group (PcG) proteins maintain transcriptional repression during development, likely by creating repressive chromatin states. The Extra Sex Combs (ESC) and Enhancer of Zeste [E(Z)] proteins are partners in an essential PcG complex, but its full composition and biochemical activities are not known. A SET domain in E(Z) suggests this complex might methylate histones. We purified an ESC-E(Z) complex from Drosophila embryos and found four major subunits: ESC, E(Z), NURF-55, and the PcG repressor, SU(Z)12. A recombinant complex reconstituted from these four subunits methylates lysine-27 of histone H3. Mutations in the E(Z) SET domain disrupt methyltransferase activity in vitro and HOX gene repression in vivo. These results identify E(Z) as a PcG protein with enzymatic activity and implicate histone methylation in PcG-mediated silencing.
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Affiliation(s)
- Jürg Müller
- EMBL, Gene Expression Programme, Meyerhofstr. 1, 69117 Heidelberg, Germany.
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Jacobs JJL, van Lohuizen M. Polycomb repression: from cellular memory to cellular proliferation and cancer. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1602:151-61. [PMID: 12020801 DOI: 10.1016/s0304-419x(02)00052-5] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The transcriptional repressors of the Polycomb group (PcG), together with the counteracting Trithorax group (TrxG) proteins, establish a form of cellular memory by regulating gene expression in a heritable fashion at the level of chromatin. This cellular memory function is required for a correct cell fate/behavior, which is not only crucial during development for the generation of a correct body plan but also later in life to prevent cellular transformation. Here, we summarize the rapidly accumulating data that implicate several mammalian PcG members in the control of cellular proliferation and tumorigenesis.
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Affiliation(s)
- Jacqueline J L Jacobs
- Department of Molecular Genetics, The Netherlands Cancer Institute, H5, Plesmanlaan 121, Amsterdam, The Netherlands
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45
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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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46
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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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Tuckfield A, Clouston DR, Wilanowski TM, Zhao LL, Cunningham JM, Jane SM. Binding of the RING polycomb proteins to specific target genes in complex with the grainyhead-like family of developmental transcription factors. Mol Cell Biol 2002; 22:1936-46. [PMID: 11865070 PMCID: PMC135618 DOI: 10.1128/mcb.22.6.1936-1946.2002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2001] [Accepted: 12/14/2001] [Indexed: 01/01/2023] Open
Abstract
The Polycomb group (PcG) of proteins represses homeotic gene expression through the assembly of multiprotein complexes on key regulatory elements. The mechanisms mediating complex assembly have remained enigmatic since most PcG proteins fail to bind DNA. We now demonstrate that the human PcG protein dinG interacts with CP2, a mammalian member of the grainyhead-like family of transcription factors, in vitro and in vivo. The functional consequence of this interaction is repression of CP2-dependent transcription. The CP2-dinG interaction is conserved in evolution with the Drosophila factor grainyhead binding to dring, the fly homologue of dinG. Electrophoretic mobility shift assays demonstrate that the grh-dring complex forms on regulatory elements of genes whose expression is repressed by grh but not on elements where grh plays an activator role. These observations reveal a novel mechanism by which PcG proteins may be anchored to specific regulatory elements in developmental genes.
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Affiliation(s)
- Annabel Tuckfield
- Rotary Bone Marrow Research Laboratory, Royal Melbourne Hospital Research Foundation, c/o RMH Post Office, Grattan Street, Parkville, Victoria 3050, Australia
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48
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Abstract
The Drosophila Enhancer of zeste [E(z)] gene encodes a member of the Polycomb group of transcriptional repressors. Here we report evidence for direct physical interaction between E(Z) and dSAP18, which previously has been shown to interact with Drosophila GAGA factor and BICOID proteins. dSAP18 shares extensive sequence similarity with a human polypeptide originally identified as a subunit of the SIN3A-HDAC (switch-independent 3-histone deacetylase) co-repressor complex. Yeast two-hybrid and in vitro binding assays demonstrate direct E(Z)-dSAP18 interaction and show that dSAP18 is capable of interacting with itself. Co-immunoprecipitation experiments provide evidence for in vivo association of E(Z) and dSAP18. Gel filtration analysis of embryo nuclear extracts shows that dSAP18 is present in native protein complexes ranging from approximately 1100 to approximately 450 kDa in molecular mass. These studies provide support for a model in which dSAP18 contributes to the activities of multiple protein complexes, and potentially may mediate interactions between distinct proteins and/or protein complexes.
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Affiliation(s)
- Liangjun Wang
- Department of Biological Sciences, Southern Methodist University, Fondren Science Building, Dallas, TX 75275-0376, USA
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49
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Abstract
SET-domain (SET: Su(var)3-9, E(z) and Trithorax)-containing proteins were collected through sequence searches of the available databases. After removing redundancies, the proteins belonging to three families, SU(VAR)3-9, E(Z) and Trithorax, were selected. Analysis of the relationship between the different members is based on pairwise alignment, compilation, and comparison of their SET-domains. The level of homology of the SET-domains defined the distribution of the proteins into families and into clades within the families. The architecture of the entire protein supported the distribution pattern built upon SET-domain similarity. Parallel cladistic and protein-architecture analyses outlined two plausible criteria for predicting function.
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Affiliation(s)
- Raul Alvarez-Venegas
- Department of Biological Sciences, Lilly Hall of Life Sciences, Purdue University, West Lafayette, IN 47907-1392, USA
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50
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Lohe AR, Chaudhury A. Genetic and epigenetic processes in seed development. CURRENT OPINION IN PLANT BIOLOGY 2002; 5:19-25. [PMID: 11788303 DOI: 10.1016/s1369-5266(01)00224-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Seed development has emerged as an important area of research in plant development. Recent research has highlighted the divergent reproductive strategies of the male and female genomes and interaction between genetic and epigenetic control mechanisms. Isolation of genes involved in embryo and endosperm development is leading to an understanding of the regulation of these processes at the molecular level. A thorough grasp of these processes will not only illuminate an important area of plant development but will also have an impact on agronomy by helping to facilitate food production. An understanding of seed development is also likely to clarify the molecular mechanisms of apomixis, a fascinating process of asexual seed production present in many plants.
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Affiliation(s)
- Allan R Lohe
- CSIRO Division of Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia.
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