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Liu J, Fan H, Liang X, Chen Y. Polycomb repressor complex: Its function in human cancer and therapeutic target strategy. Biomed Pharmacother 2023; 169:115897. [PMID: 37981459 DOI: 10.1016/j.biopha.2023.115897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/07/2023] [Accepted: 11/13/2023] [Indexed: 11/21/2023] Open
Abstract
The Polycomb Repressor Complex (PRC) plays a pivotal role in gene regulation during development and disease, with dysregulation contributing significantly to various human cancers. The intricate interplay between PRC and cellular signaling pathways sheds light on cancer complexity. PRC presents promising therapeutic opportunities, with inhibitors undergoing rigorous evaluation in preclinical and clinical studies. In this review, we emphasize the critical role of PRC complex in gene regulation, particularly PcG proteins mediated chromatin compaction through phase separation. We also highlight the pathological implications of PRC complex dysregulation in various tumors, elucidating underlying mechanisms driving cancer progression. The burgeoning field of therapeutic strategies targeting PRC complexes, notably EZH2 inhibitors, has advanced significantly. However, we explore the need for combination therapies to enhance PRC targeted treatments efficacy, providing a glimpse into the future of cancer therapeutics.
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Affiliation(s)
- Jingrong Liu
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China
| | - Hongjie Fan
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China
| | - Xinmiao Liang
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China; CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
| | - Yang Chen
- Ganjiang Chinese Medicine Innovation Center, Nanchang 330000, China; CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
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2
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Bi CL, Cheng Q, Yan LY, Wu HY, Wang Q, Wang P, Cheng L, Wang R, Yang L, Li J, Tie F, Xie H, Fang M. A prominent gene activation role for C-terminal binding protein in mediating PcG/trxG proteins through Hox gene regulation. Development 2022; 149:275613. [DOI: 10.1242/dev.200153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 04/28/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
The evolutionarily conserved C-terminal binding protein (CtBP) has been well characterized as a transcriptional co-repressor. Herein, we report a previously unreported function for CtBP, showing that lowering CtBP dosage genetically suppresses Polycomb group (PcG) loss-of-function phenotypes while enhancing that of trithorax group (trxG) in Drosophila, suggesting that the role of CtBP in gene activation is more pronounced in fly development than previously thought. In fly cells, we show that CtBP is required for the derepression of the most direct PcG target genes, which are highly enriched by homeobox transcription factors, including Hox genes. Using ChIP and co-IP assays, we demonstrate that CtBP is directly required for the molecular switch between H3K27me3 and H3K27ac in the derepressed Hox loci. In addition, CtBP physically interacts with many proteins, such as UTX, CBP, Fs(1)h and RNA Pol II, that have activation roles, potentially assisting in their recruitment to promoters and Polycomb response elements that control Hox gene expression. Therefore, we reveal a prominent activation function for CtBP that confers a major role for the epigenetic program of fly segmentation and development.
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Affiliation(s)
- Cai-Li Bi
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
- Institute of Translational Medicine 2 , , , Yangzhou 225001 , China
- Medical College 2 , , , Yangzhou 225001 , China
- Yangzhou University 2 , , , Yangzhou 225001 , China
| | - Qian Cheng
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Ling-Yue Yan
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Hong-Yan Wu
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Qiang Wang
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Ping Wang
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Lin Cheng
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Rui Wang
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Lin Yang
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Jian Li
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Feng Tie
- Case Western Reserve University 3 Department of Genetics and Genome Sciences , , Cleveland, OH 44106, USA
| | - Hao Xie
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
| | - Ming Fang
- School of Life Science and Technology, MOE Key Laboratory of Developmental Genes and Human Diseases, Southeast University 1 , Nanjing 210096 , China
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3
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Erokhin M, Gorbenko F, Lomaev D, Mazina MY, Mikhailova A, Garaev AK, Parshikov A, Vorobyeva NE, Georgiev P, Schedl P, Chetverina D. Boundaries potentiate polycomb response element-mediated silencing. BMC Biol 2021; 19:113. [PMID: 34078365 PMCID: PMC8170967 DOI: 10.1186/s12915-021-01047-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 05/07/2021] [Indexed: 12/21/2022] Open
Abstract
Background Epigenetic memory plays a critical role in the establishment and maintenance of cell identities in multicellular organisms. Polycomb and trithorax group (PcG and TrxG) proteins are responsible for epigenetic memory, and in flies, they are recruited to specialized DNA regulatory elements termed polycomb response elements (PREs). Previous transgene studies have shown that PREs can silence reporter genes outside of their normal context, often by pairing sensitive (PSS) mechanism; however, their silencing activity is non-autonomous and depends upon the surrounding chromatin context. It is not known why PRE activity depends on the local environment or what outside factors can induce silencing. Results Using an attP system in Drosophila, we find that the so-called neutral chromatin environments vary substantially in their ability to support the silencing activity of the well-characterized bxdPRE. In refractory chromosomal contexts, factors required for PcG-silencing are unable to gain access to the PRE. Silencing activity can be rescued by linking the bxdPRE to a boundary element (insulator). When placed next to the PRE, the boundaries induce an alteration in chromatin structure enabling factors critical for PcG silencing to gain access to the bxdPRE. When placed at a distance from the bxdPRE, boundaries induce PSS by bringing the bxdPREs on each homolog in close proximity. Conclusion This proof-of-concept study demonstrates that the repressing activity of PREs can be induced or enhanced by nearby boundary elements. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01047-8.
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Affiliation(s)
- Maksim Erokhin
- Group of Chromatin Biology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia.
| | - Fedor Gorbenko
- Group of Chromatin Biology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia.,Present address: Department of Biology, ETH Zurich, Zurich, Switzerland
| | - Dmitry Lomaev
- Group of Epigenetics, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia
| | - Marina Yu Mazina
- Group of Transcriptional Complexes Dynamics, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Anna Mikhailova
- Group of Chromatin Biology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia
| | - Azat K Garaev
- Laboratory of Structural and Functional Organization of Chromosomes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia
| | - Aleksander Parshikov
- Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia
| | - Nadezhda E Vorobyeva
- Group of Transcriptional Complexes Dynamics, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - Pavel Georgiev
- Department of the Control of Genetic Processes, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia
| | - Paul Schedl
- Department of Molecular Biology Princeton University, Princeton, NJ, 08544, USA.
| | - Darya Chetverina
- Group of Epigenetics, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., Moscow, 119334, Russia.
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4
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Piunti A, Shilatifard A. The roles of Polycomb repressive complexes in mammalian development and cancer. Nat Rev Mol Cell Biol 2021; 22:326-345. [PMID: 33723438 DOI: 10.1038/s41580-021-00341-1] [Citation(s) in RCA: 195] [Impact Index Per Article: 65.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2021] [Indexed: 12/14/2022]
Abstract
More than 80 years ago, the first Polycomb-related phenotype was identified in Drosophila melanogaster. Later, a group of diverse genes collectively called Polycomb group (PcG) genes were identified based on common mutant phenotypes. PcG proteins, which are well-conserved in animals, were originally characterized as negative regulators of gene transcription during development and subsequently shown to function in various biological processes; their deregulation is associated with diverse phenotypes in development and in disease, especially cancer. PcG proteins function on chromatin and can form two distinct complexes with different enzymatic activities: Polycomb repressive complex 1 (PRC1) is a histone ubiquitin ligase and PRC2 is a histone methyltransferase. Recent studies have revealed the existence of various mutually exclusive PRC1 and PRC2 variants. In this Review, we discuss new concepts concerning the biochemical and molecular functions of these new PcG complex variants, and how their epigenetic activities are involved in mammalian development and cancer.
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Affiliation(s)
- Andrea Piunti
- Simpson Querrey Institute for Epigenetics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Ali Shilatifard
- Simpson Querrey Institute for Epigenetics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA. .,Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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Reinig J, Ruge F, Howard M, Ringrose L. A theoretical model of Polycomb/Trithorax action unites stable epigenetic memory and dynamic regulation. Nat Commun 2020; 11:4782. [PMID: 32963223 PMCID: PMC7508846 DOI: 10.1038/s41467-020-18507-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 08/24/2020] [Indexed: 12/12/2022] Open
Abstract
Polycomb and Trithorax group proteins maintain stable epigenetic memory of gene expression states for some genes, but many targets show highly dynamic regulation. Here we combine experiment and theory to examine the mechanistic basis of these different modes of regulation. We present a mathematical model comprising a Polycomb/Trithorax response element (PRE/TRE) coupled to a promoter and including Drosophila developmental timing. The model accurately recapitulates published studies of PRE/TRE mediated epigenetic memory of both silencing and activation. With minimal parameter changes, the same model can also recapitulate experimental data for a different PRE/TRE that allows dynamic regulation of its target gene. The model predicts that both cell cycle length and PRE/TRE identity are critical for determining whether the system gives stable memory or dynamic regulation. Our work provides a simple unifying framework for a rich repertoire of PRE/TRE functions, and thus provides insights into genome-wide Polycomb/Trithorax regulation. Polycomb (PcG) and Trithorax (TrxG) group regulate several hundred target genes with important roles in development and disease. Here the authors combine experiment and theory to provide evidence that the Polycomb/Trithorax system has the potential for a rich repertoire of regulatory modes beyond simple epigenetic memory.
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Affiliation(s)
- Jeannette Reinig
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany
| | - Frank Ruge
- IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria
| | - Martin Howard
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Leonie Ringrose
- Humboldt Universität zu Berlin, IRI- Lifesciences, Philippstr. 13, 10115, Berlin, Germany. .,IMBA, Institute of Molecular Biotechnology, Dr. Bohr- Gasse 3, 1030, Vienna, Austria.
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6
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Lim JH, Kang YJ, Bak HJ, Kim MS, Lee HJ, Kwak DW, Han YJ, Kim MY, Boo H, Kim SY, Ryu HM. Epigenome-wide DNA methylation profiling of preeclamptic placenta according to severe features. Clin Epigenetics 2020; 12:128. [PMID: 32831145 PMCID: PMC7444072 DOI: 10.1186/s13148-020-00918-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/13/2020] [Indexed: 11/17/2022] Open
Abstract
Background Preeclampsia (PE) is an obstetric disorder with significant morbidities for both the mother and fetus possibly caused by a failure of the placental trophoblast invasion. However, its pathophysiology largely remains unclear. Here, we performed DNA methylation profiling to determine whether differential patterns of DNA methylation correlate with PE and severe features of PE. Materials and methods We extracted DNA from placental tissues of 13 normal, five PE, and eight PE pregnant women with severe features. Genome-wide DNA methylation analysis was performed using the Illumina HumanMethylation 850K BeadChip. New functional annotations of differentially methylated CpGs (DMCs) in PE were predicted using bioinformatics tools. Results Significant differences were evident for 398 DMCs, including 243 DMCs in PE and 155 DMCs in PE with severe features, compared with normal placental tissues. Of these, 12 hypermethylated DMCs and three hypomethylated DMCs were observed in both PE groups, thus were independent from severe features. Three hundred seventy-nine DMCs were identified by the presence or absence of severe features. Two hundred genes containing these DMCs were associated with developmental processes and cell morphogenesis. These genes were significantly associated with various PE complications such as disease susceptibility, viral infections, immune system diseases, endocrine disturbance, seizures, hematologic diseases, and thyroid diseases. Conclusions This is the first study to investigate the genome-scale DNA methylation profiles of PE placentas according to severe features. The epigenetic variation in the placentas probably resulted in altered developmental processes and immune dysregulation, contributing to PE. This study provides basic information to refine the clinical and pathological mechanisms of the severe features in placenta-mediated PE.
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Affiliation(s)
- Ji Hyae Lim
- Center for Prenatal Biomarker Research, CHA Advanced Research Institute, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, Republic of Korea
| | - Yu-Jung Kang
- Center for Prenatal Biomarker Research, CHA Advanced Research Institute, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, Republic of Korea
| | - Hye Jin Bak
- Center for Prenatal Biomarker Research, CHA Advanced Research Institute, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, Republic of Korea
| | - Mi Sun Kim
- Department of Obstetrics & Gynecology, CHA Bundang Medical Center, CHA University, 59, Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea
| | - Hyun Jung Lee
- Department of Obstetrics & Gynecology, CHA Bundang Medical Center, CHA University, 59, Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea
| | - Dong Wook Kwak
- Department of Obstetrics and Gynecology, Ajou University School of Medicine, Suwon, Republic of Korea
| | - You Jung Han
- Department of Obstetrics & Gynecology, CHA Gangnam Medical Center, CHA University, Seoul, Republic of Korea
| | - Moon Young Kim
- Department of Obstetrics & Gynecology, CHA Gangnam Medical Center, CHA University, Seoul, Republic of Korea
| | - Hyeyeon Boo
- Department of Obstetrics & Gynecology, CHA Ilsan Medical Center, CHA University, Pocheon-si, Gyeonggi-do, Republic of Korea
| | - Shin Young Kim
- Laboratory of Medical Genetics, Medical Research Institute, Cheil General Hospital and Women's Healthcare Center, Seoul, Republic of Korea
| | - Hyun Mee Ryu
- Center for Prenatal Biomarker Research, CHA Advanced Research Institute, CHA Bundang Medical Center, Seongnam-si, Gyeonggi-do, Republic of Korea. .,Department of Obstetrics & Gynecology, CHA Bundang Medical Center, CHA University, 59, Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 13496, Republic of Korea.
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7
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Wang Q, Zhang Q, Gan Z, Li H, Yang Y, Zhang Y, Zhao X. Screening for reproductive biomarkers in Bactrian camel via iTRAQ analysis of proteomes. Reprod Domest Anim 2020; 55:189-199. [PMID: 31840896 DOI: 10.1111/rda.13607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 12/04/2019] [Indexed: 12/20/2022]
Abstract
Bactrian camel is an ancient and precious species of livestock; that is, unique resources exist in the desert and have important economic and scientific value. In recent years, the number of Bactrian camels has declined sharply. Due to its long reproductive cycle and seasonal oestrus, the mechanism of oestrus is unknown. To identify candidate biomarkers of reproduction, we performed a comprehensive proteomic analysis of serum from Bactrian camel in oestrus and non-oestrus, using isobaric tags for relative and absolute quantitation (iTRAQ) coupled with tandem mass spectrometry. We identified 359 proteins, of which 32 were differentially expressed: 11 were up-regulated and 21 were down-regulated in samples from camels in oestrus. We validated the differential expression of a subset of these proteins using qPCR and Western blot. Gene ontology annotation identified that the differentially expressed proteins function in cellular processes, metabolic processes and immune system processes. Notably, five of the differentially expressed proteins, PCGF5, histone H1.2, RBP4, FOLR1 and ANTXR2, are involved in reproductive regulatory processes in other animals. KEGG enrichment analysis demonstrated significant enrichment in several cardiac-related pathways, such as 'dilated cardiomyopathy', 'hypertrophic cardiomyopathy', 'cardiac muscle contraction' and 'adrenergic signalling in cardiomyopathy'. Our results suggest that candidate biomarker (PCGF5, histone H1.2, RBP4, FOLR1 and ANTXR2) discovery can aid in understanding reproduction in Bactrian camels. We conclude that the profiling of serum proteomes, followed by the measurement of selected proteins using more targeted methods, offers a promising approach for studying mechanisms of oestrus.
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Affiliation(s)
- Qi Wang
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China
| | - Quanwei Zhang
- College of Life Science and Technology, Gansu Agriculture University, Lanzhou, China
| | - Ze Gan
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China
| | - Haijiang Li
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China
| | - Yang Yang
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China
| | - Yong Zhang
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China.,College of Life Science and Technology, Gansu Agriculture University, Lanzhou, China
| | - Xingxu Zhao
- College of Veterinary Medicine, Gansu Agriculture University, Lanzhou, China.,College of Life Science and Technology, Gansu Agriculture University, Lanzhou, China
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8
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Serpent/dGATAb regulates Laminin B1 and Laminin B2 expression during Drosophila embryogenesis. Sci Rep 2019; 9:15910. [PMID: 31685844 PMCID: PMC6828711 DOI: 10.1038/s41598-019-52210-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 10/15/2019] [Indexed: 12/15/2022] Open
Abstract
Transcriptional regulation of Laminin expression during embryogenesis is a key step required for proper ECM assembly. We show, that in Drosophila the Laminin B1 and Laminin B2 genes share expression patterns in mesodermal cells as well as in endodermal and ectodermal gut primordia, yolk and amnioserosa. In the absence of the GATA transcription factor Serpent, the spatial extend of Laminin reporter gene expression was strongly limited, indicating that Laminin expression in many tissues depends on Serpent activity. We demonstrate a direct binding of Serpent to the intronic enhancers of Laminin B1 and Laminin B2. In addition, ectopically expressed Serpent activated enhancer elements of Laminin B1 and Laminin B2. Our results reveal Serpent as an important regulator of Laminin expression across tissues.
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9
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Du J, Kirk B, Zeng J, Ma J, Wang Q. Three classes of response elements for human PRC2 and MLL1/2-Trithorax complexes. Nucleic Acids Res 2018; 46:8848-8864. [PMID: 29992232 PMCID: PMC6158500 DOI: 10.1093/nar/gky595] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/19/2018] [Accepted: 06/21/2018] [Indexed: 12/15/2022] Open
Abstract
Polycomb group (PcG) and Trithorax group (TrxG) proteins are essential for maintaining epigenetic memory in both embryonic stem cells and differentiated cells. To date, how they are localized to hundreds of specific target genes within a vertebrate genome had remained elusive. Here, by focusing on short cis-acting DNA elements of single functions, we discovered three classes of response elements in human genome: Polycomb response elements (PREs), Trithorax response elements (TREs) and Polycomb/Trithorax response elements (P/TREs). In particular, the four PREs (PRE14, 29, 39 and 48) are the first set of, to our knowledge, bona fide vertebrate PREs ever discovered, while many previously reported Drosophila or vertebrate PREs are likely P/TREs. We further demonstrated that YY1 and CpG islands are specifically enriched in the four TREs (PRE30, 41, 44 and 55), but not in the PREs. The three classes of response elements as unraveled in this study should guide further global investigation and open new doors for a deeper understanding of PcG and TrxG mechanisms in vertebrates.
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Affiliation(s)
- Junqing Du
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Brian Kirk
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Jia Zeng
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Jianpeng Ma
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
- Department of Bioengineering, Rice University, 6500 Main Street, Houston, TX 77030, USA
| | - Qinghua Wang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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10
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Erceg J, Pakozdi T, Marco-Ferreres R, Ghavi-Helm Y, Girardot C, Bracken AP, Furlong EEM. Dual functionality of cis-regulatory elements as developmental enhancers and Polycomb response elements. Genes Dev 2017; 31:590-602. [PMID: 28381411 PMCID: PMC5393054 DOI: 10.1101/gad.292870.116] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 03/03/2017] [Indexed: 11/24/2022]
Abstract
Here, Erceg et al. studied the occupancy of the Drosophila PhoRC during embryogenesis and revealed extensive co-occupancy at developmental enhancers. By using an established in vivo assay for Polycomb response element (PRE) activity, they show that a subset of characterized developmental enhancers can function as PREs and silence transcription in a Polycomb-dependent manner, thereby suggesting that reuse of the same elements by the PcG system may help fine-tune gene expression and ensure the timely maintenance of cell identities. Developmental gene expression is tightly regulated through enhancer elements, which initiate dynamic spatio–temporal expression, and Polycomb response elements (PREs), which maintain stable gene silencing. These two cis-regulatory functions are thought to operate through distinct dedicated elements. By examining the occupancy of the Drosophila pleiohomeotic repressive complex (PhoRC) during embryogenesis, we revealed extensive co-occupancy at developmental enhancers. Using an established in vivo assay for PRE activity, we demonstrated that a subset of characterized developmental enhancers can function as PREs, silencing transcription in a Polycomb-dependent manner. Conversely, some classic Drosophila PREs can function as developmental enhancers in vivo, activating spatio–temporal expression. This study therefore uncovers elements with dual function: activating transcription in some cells (enhancers) while stably maintaining transcriptional silencing in others (PREs). Given that enhancers initiate spatio–temporal gene expression, reuse of the same elements by the Polycomb group (PcG) system may help fine-tune gene expression and ensure the timely maintenance of cell identities.
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Affiliation(s)
- Jelena Erceg
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
| | - Tibor Pakozdi
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
| | - Raquel Marco-Ferreres
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
| | - Yad Ghavi-Helm
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
| | - Charles Girardot
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
| | - Adrian P Bracken
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Eileen E M Furlong
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg D69117, Germany
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11
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Piunti A, Shilatifard A. Epigenetic balance of gene expression by Polycomb and COMPASS families. Science 2016; 352:aad9780. [PMID: 27257261 DOI: 10.1126/science.aad9780] [Citation(s) in RCA: 331] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Epigenetic regulation of gene expression in metazoans is central for establishing cellular diversity, and its deregulation can result in pathological conditions. Although transcription factors are essential for implementing gene expression programs, they do not function in isolation and require the recruitment of various chromatin-modifying and -remodeling machineries. A classic example of developmental chromatin regulation is the balanced activities of the Polycomb group (PcG) proteins within the PRC1 and PRC2 complexes, and the Trithorax group (TrxG) proteins within the COMPASS family, which are highly mutated in a large number of human diseases. In this review, we will discuss the latest findings regarding the properties of the PcG and COMPASS families and the insight they provide into the epigenetic control of transcription under physiological and pathological settings.
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Affiliation(s)
- Andrea Piunti
- Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Chicago, IL 60611, USA
| | - Ali Shilatifard
- Department of Biochemistry and Molecular Genetics, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Chicago, IL 60611, USA.
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12
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Sadasivam DA, Huang DH. Maintenance of Tissue Pluripotency by Epigenetic Factors Acting at Multiple Levels. PLoS Genet 2016; 12:e1005897. [PMID: 26926299 PMCID: PMC4771708 DOI: 10.1371/journal.pgen.1005897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 02/04/2016] [Indexed: 01/24/2023] Open
Abstract
Pluripotent stem cells often adopt a unique developmental program while retaining certain flexibility. The molecular basis of such properties remains unclear. Using differentiation of pluripotent Drosophila imaginal tissues as assays, we examined the contribution of epigenetic factors in ectopic activation of Hox genes. We found that over-expression of Trithorax H3K4 methyltransferase can induce ectopic adult appendages by selectively activating the Hox genes Ultrabithorax and Sex comb reduced in wing and leg discs, respectively. This tissue-specific inducibility correlates with the presence of paused RNA polymerase II in the promoter-proximal region of these genes. Although the Antennapedia promoter is paused in eye-antenna discs, it cannot be induced by Trx without a reduction in histone variants or their chaperones, suggesting additional control by the nucleosomal architecture. Lineage tracing and pulse-chase experiments revealed that the active state of Hox genes is maintained substantially longer in mutants deficient for HIRA, a chaperone for the H3.3 variant. In addition, both HIRA and H3.3 appeared to act cooperatively with the Polycomb group of epigenetic repressors. These results support the involvement of H3.3-mediated nucleosome turnover in restoring the repressed state. We propose a regulatory framework integrating transcriptional pausing, histone modification, nucleosome architecture and turnover for cell lineage maintenance. During animal development, the primordia of different body parts undergo a series of transitions in which their developmental potency becomes more restricted. Hox genes encode a family of evolutionarily conserved transcriptional factors that are crucial for choosing different paths during transitions. Thus, the transcriptional status of Hox genes is directly linked to the maintenance and developmental direction of pluripotent tissues. As post-translational methylation of histone H3 is pivotal for transcriptional control, we could activate Hox genes and alter the subsequent development of some pluripotent Drosophila imaginal tissues by increasing the level of Trithorax that catalyzes activation-related methylation. However, other imaginal tissues remain refractory unless histone variants or their chaperones that directly affect nucleosome dynamics are simultaneously depleted. By monitoring the duration of Hox expression under these conditions, we found that the active state of Hox genes is substantially prolonged, resulting from effective conversion of promoter-associated paused RNA polymerase II into active transcription. Further analyses indicate that these factors are functionally linked to the Polycomb group of epigenetic factors that bestow long-term repression. Our studies demonstrate that developmental constraints are modulated by factors acting at multiple levels, offering a useful approach to tissue re-programming in regeneration medicine and stem cell research.
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Affiliation(s)
- Devendran A. Sadasivam
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Der-Hwa Huang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
- * E-mail:
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13
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Elizar’ev PV, Lomaev DV, Chetverina DA, Georgiev PG, Erokhin MM. Role of Transcriptional Read-Through in PRE Activity in Drosophila melanogaster. Acta Naturae 2016; 8:79-86. [PMID: 27446595 PMCID: PMC4954543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Maintenance of the individual patterns of gene expression in different cell types is required for the differentiation and development of multicellular organisms. Expression of many genes is controlled by Polycomb (PcG) and Trithorax (TrxG) group proteins that act through association with chromatin. PcG/TrxG are assembled on the DNA sequences termed PREs (Polycomb Response Elements), the activity of which can be modulated and switched from repression to activation. In this study, we analyzed the influence of transcriptional read-through on PRE activity switch mediated by the yeast activator GAL4. We show that a transcription terminator inserted between the promoter and PRE doesn't prevent switching of PRE activity from repression to activation. We demonstrate that, independently of PRE orientation, high levels of transcription fail to dislodge PcG/TrxG proteins from PRE in the absence of a terminator. Thus, transcription is not the main factor required for PRE activity switch.
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Affiliation(s)
- P. V. Elizar’ev
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov str. 34/5, 119334, Moscow, Russia
| | - D. V. Lomaev
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov str. 34/5, 119334, Moscow, Russia
| | - D. A. Chetverina
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov str. 34/5, 119334, Moscow, Russia
| | - P. G. Georgiev
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov str. 34/5, 119334, Moscow, Russia
| | - M. M. Erokhin
- Institute of Gene Biology, Russian Academy of Sciences, Vavilov str. 34/5, 119334, Moscow, Russia
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14
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Abstract
Chromatin immunoprecipitation (ChIP) is a valuable method to investigate protein-DNA interactions in vivo. Since its discovery it has been indispensable to identify binding sites and patterns of a variety of DNA-interacting proteins, such as transcription factors and regulators, modified histones, and epigenetic modifiers. The Polycomb repressors were the first proteins that have been mapped using this technique, which provided the mechanistic basis for the understanding of their biological function. Cross-linked (XChIP) or native (NChIP) chromatin from tissues or cultured cells is fragmented and the protein of interest is immunoprecipitated using a specific antibody. The co-precipitated DNA is then purified and subjected to analysis by region-specific PCR, DNA microarray (ChIP-on-chip), or next-generation sequencing (ChIP-seq). The assay can therefore produce information about the localization of the analyzed protein at specific candidate loci or throughout the entire genome. In this chapter, we provide a detailed protocol of the basic standard ChIP assay and some remarks about variations.
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Affiliation(s)
- Laura Wiehle
- Division of Epigenetics, DKFZ-ZMBH Alliance, German Cancer Research Center, Im Neuenheimer Feld 580, 69120, Heidelberg, Germany.
| | - Achim Breiling
- Division of Epigenetics, DKFZ-ZMBH Alliance, German Cancer Research Center, Im Neuenheimer Feld 580, 69120, Heidelberg, Germany
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15
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The quest for mammalian Polycomb response elements: are we there yet? Chromosoma 2015; 125:471-96. [PMID: 26453572 PMCID: PMC4901126 DOI: 10.1007/s00412-015-0539-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 08/31/2015] [Accepted: 09/02/2015] [Indexed: 12/12/2022]
Abstract
A long-standing mystery in the field of Polycomb and Trithorax regulation is how these proteins, which are highly conserved between flies and mammals, can regulate several hundred equally highly conserved target genes, but recognise these targets via cis-regulatory elements that appear to show no conservation in their DNA sequence. These elements, termed Polycomb/Trithorax response elements (PRE/TREs or PREs), are relatively well characterised in flies, but their mammalian counterparts have proved to be extremely difficult to identify. Recent progress in this endeavour has generated a wealth of data and raised several intriguing questions. Here, we ask why and to what extent mammalian PREs are so different to those of the fly. We review recent advances, evaluate current models and identify open questions in the quest for mammalian PREs.
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16
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Chromatin analyses of Zymoseptoria tritici: Methods for chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq). Fungal Genet Biol 2015; 79:63-70. [PMID: 25857259 DOI: 10.1016/j.fgb.2015.03.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/19/2015] [Accepted: 03/25/2015] [Indexed: 02/05/2023]
Abstract
The presence or absence of specific transcription factors, chromatin remodeling machineries, chromatin modification enzymes, post-translational histone modifications and histone variants all play crucial roles in the regulation of pathogenicity genes. Chromatin immunoprecipitation (ChIP) followed by high-throughput sequencing (ChIP-seq) provides an important tool to study genome-wide protein-DNA interactions to help understand gene regulation in the context of native chromatin. ChIP-seq is a convenient in vivo technique to identify, map and characterize occupancy of specific DNA fragments with proteins against which specific antibodies exist or which can be epitope-tagged in vivo. We optimized existing ChIP protocols for use in the wheat pathogen Zymoseptoria tritici and closely related sister species. Here, we provide a detailed method, underscoring which aspects of the technique are organism-specific. Library preparation for Illumina sequencing is described, as this is currently the most widely used ChIP-seq method. One approach for the analysis and visualization of representative sequence is described; improved tools for these analyses are constantly being developed. Using ChIP-seq with antibodies against H3K4me2, which is considered a mark for euchromatin or H3K9me3 and H3K27me3, which are considered marks for heterochromatin, the overall distribution of euchromatin and heterochromatin in the genome of Z. tritici can be determined. Our ChIP-seq protocol was also successfully applied to Z. tritici strains with high levels of melanization or aberrant colony morphology, and to different species of the genus (Z. ardabiliae and Z. pseudotritici), suggesting that our technique is robust. The methods described here provide a powerful framework to study new aspects of chromatin biology and gene regulation in this prominent wheat pathogen.
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17
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Ruden DM, Cingolani PE, Sen A, Qu W, Wang L, Senut MC, Garfinkel MD, Sollars VE, Lu X. Epigenetics as an answer to Darwin's "special difficulty," Part 2: natural selection of metastable epialleles in honeybee castes. Front Genet 2015; 6:60. [PMID: 25759717 PMCID: PMC4338822 DOI: 10.3389/fgene.2015.00060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 02/08/2015] [Indexed: 11/15/2022] Open
Abstract
In a recent perspective in this journal, Herb (2014) discussed how epigenetics is a possible mechanism to circumvent Charles Darwin's "special difficulty" in using natural selection to explain the existence of the sterile-fertile dimorphism in eusocial insects. Darwin's classic book "On the Origin of Species by Means of Natural Selection" explains how natural selection of the fittest individuals in a population can allow a species to adapt to a novel or changing environment. However, in bees and other eusocial insects, such as ants and termites, there exist two or more castes of genetically similar females, from fertile queens to multiple sub-castes of sterile workers, with vastly different phenotypes, lifespans, and behaviors. This necessitates the selection of groups (or kin) rather than individuals in the evolution of honeybee hives, but group and kin selection theories of evolution are controversial and mechanistically uncertain. Also, group selection would seem to be prohibitively inefficient because the effective population size of a colony is reduced from thousands to a single breeding queen. In this follow-up perspective, we elaborate on possible mechanisms for how a combination of both epigenetics, specifically, the selection of metastable epialleles, and genetics, the selection of mutations generated by the selected metastable epialleles, allows for a combined means for selection amongst the fertile members of a species to increase colony fitness. This "intra-caste evolution" hypothesis is a variation of the epigenetic directed genetic error hypothesis, which proposes that selected metastable epialleles increase genetic variability by directing mutations specifically to the epialleles. Natural selection of random metastable epialleles followed by a second round of natural selection of random mutations generated by the metastable epialleles would allow a way around the small effective population size of eusocial insects.
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Affiliation(s)
- Douglas M. Ruden
- Department of Obstetrics and Gynecology, C. S. Mott Center for Human Growth and Development and Center for Urban Responses to Environmental Stressors, Institute of Environmental Health Sciences, Wayne State UniversityDetroit, MI, USA
| | - Pablo E. Cingolani
- School of Computer Science and Genome Quebec Innovation Centre, McGill UniversityMontreal, QC, Canada
| | - Arko Sen
- Department of Pharmacology, Wayne State UniversityDetroit, MI, USA
| | - Wen Qu
- Department of Pharmacology, Wayne State UniversityDetroit, MI, USA
| | - Luan Wang
- Institute of Environmental Health Sciences, Wayne State UniversityDetroit, MI, USA
| | - Marie-Claude Senut
- Institute of Environmental Health Sciences, Wayne State UniversityDetroit, MI, USA
| | - Mark D. Garfinkel
- Department of Biological Sciences, University of Alabama in HuntsvilleHuntsville, AL, USA
| | - Vincent E. Sollars
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall UniversityHuntington, WV, USA
| | - Xiangyi Lu
- Institute of Environmental Health Sciences, Wayne State UniversityDetroit, MI, USA
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18
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Magbanua JP, Runneburger E, Russell S, White R. A variably occupied CTCF binding site in the ultrabithorax gene in the Drosophila bithorax complex. Mol Cell Biol 2015; 35:318-30. [PMID: 25368383 PMCID: PMC4295388 DOI: 10.1128/mcb.01061-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/10/2014] [Accepted: 10/25/2014] [Indexed: 11/20/2022] Open
Abstract
Although the majority of genomic binding sites for the insulator protein CCCTC-binding factor (CTCF) are constitutively occupied, a subset show variable occupancy. Such variable sites provide an opportunity to assess context-specific CTCF functions in gene regulation. Here, we have identified a variably occupied CTCF site in the Drosophila Ultrabithorax (Ubx) gene. This site is occupied in tissues where Ubx is active (third thoracic leg imaginal disc) but is not bound in tissues where the Ubx gene is repressed (first thoracic leg imaginal disc). Using chromatin conformation capture, we show that this site preferentially interacts with the Ubx promoter region in the active state. The site lies close to Ubx enhancer elements and is also close to the locations of several gypsy transposon insertions that disrupt Ubx expression, leading to the bx mutant phenotype. gypsy insertions carry the Su(Hw)-dependent gypsy insulator and were found to affect both CTCF binding at the variable site and the chromatin topology. This suggests that insertion of the gypsy insulator in this region interferes with CTCF function and supports a model for the normal function of the variable CTCF site as a chromatin loop facilitator, promoting interaction between Ubx enhancers and the Ubx transcription start site.
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Affiliation(s)
- Jose Paolo Magbanua
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Estelle Runneburger
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Steven Russell
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Robert White
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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19
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Herzog VA, Lempradl A, Trupke J, Okulski H, Altmutter C, Ruge F, Boidol B, Kubicek S, Schmauss G, Aumayr K, Ruf M, Pospisilik A, Dimond A, Senergin HB, Vargas ML, Simon JA, Ringrose L. A strand-specific switch in noncoding transcription switches the function of a Polycomb/Trithorax response element. Nat Genet 2014; 46:973-981. [PMID: 25108384 DOI: 10.1038/ng.3058] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 07/14/2014] [Indexed: 12/14/2022]
Abstract
Polycomb/Trithorax response elements (PRE/TREs) can switch their function reversibly between silencing and activation by mechanisms that are poorly understood. Here we show that a switch in forward and reverse noncoding transcription from the Drosophila melanogaster vestigial (vg) PRE/TRE switches the status of the element between silencing (induced by the forward strand) and activation (induced by the reverse strand). In vitro, both noncoding RNAs inhibit PRC2 histone methyltransferase activity, but, in vivo, only the reverse strand binds PRC2. Overexpression of the reverse strand evicts PRC2 from chromatin and inhibits its enzymatic activity. We propose that the interaction of RNAs with PRC2 is differentially regulated in vivo, allowing regulated inhibition of local PRC2 activity. Genome-wide analysis shows that strand switching of noncoding RNAs occurs at several hundred Polycomb-binding sites in fly and vertebrate genomes. This work identifies a previously unreported and potentially widespread class of PRE/TREs that switch function by switching the direction of noncoding RNA transcription.
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Affiliation(s)
- Veronika A Herzog
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Adelheid Lempradl
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria.,Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
| | - Johanna Trupke
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Helena Okulski
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Christina Altmutter
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Frank Ruge
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Bernd Boidol
- CeMM, Research Center for Molecular Medicine, Lazarettgasse 14, 1090 Vienna, Austria
| | - Stefan Kubicek
- CeMM, Research Center for Molecular Medicine, Lazarettgasse 14, 1090 Vienna, Austria
| | - Gerald Schmauss
- IMP, Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Karin Aumayr
- IMP, Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria
| | - Marius Ruf
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
| | - Andrew Pospisilik
- Max Planck Institute of Immunobiology and Epigenetics, Stübeweg 51, 79108 Freiburg, Germany
| | - Andrew Dimond
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria.,The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, United Kingdom
| | - Hasene Basak Senergin
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Marcus L Vargas
- Department of Genetics, Cell Biology and Development, University of Minnesota. Minneapolis, Minnesota, USA
| | - Jeffrey A Simon
- Department of Genetics, Cell Biology and Development, University of Minnesota. Minneapolis, Minnesota, USA
| | - Leonie Ringrose
- IMBA, Institute of Molecular Biotechnology GmBH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
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20
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Bengani H, Mendiratta S, Maini J, Vasanthi D, Sultana H, Ghasemi M, Ahluwalia J, Ramachandran S, Mishra RK, Brahmachari V. Identification and Validation of a Putative Polycomb Responsive Element in the Human Genome. PLoS One 2013; 8:e67217. [PMID: 23805300 PMCID: PMC3689693 DOI: 10.1371/journal.pone.0067217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 05/20/2013] [Indexed: 12/31/2022] Open
Abstract
Epigenetic cellular memory mechanisms that involve polycomb and trithorax group of proteins are well conserved across metazoans. The cis-acting elements interacting with these proteins, however, are poorly understood in mammals. In a directed search we identified a potential polycomb responsive element with 25 repeats of YY1 binding motifthatwe designate PRE-PIK3C2B as it occurs in the first intron of human PIK3C2B gene. It down regulates reporter gene expression in HEK cells and the repression is dependent on polycomb group of proteins (PcG). We demonstrate that PRE-PIK3C2B interacts directly with YY1 in vitro and recruits PRC2 complex in vivo. The localization of PcG proteins including YY1 to PRE-PIK3C2B in HEK cells is decreased on knock-down of either YY1 or SUZ12. Endogenous PRE-PIK3C2B shows bivalent marking having H3K27me3 and H3K4me3 for repressed and active state respectively. In transgenic Drosophila, PRE-PIK3C2B down regulates mini-white expression, exhibits variegation and pairing sensitive silencing (PSS), which has not been previously demonstrated for mammalian PRE. Taken together, our results strongly suggest that PRE-PIK3C2B functions as a site of interaction for polycomb proteins.
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Affiliation(s)
- Hemant Bengani
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Shweta Mendiratta
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Jayant Maini
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Dasari Vasanthi
- Centre for Cellular and Molecular Biology (CSIR), Hyderabad, Andhra Pradesh, India
| | - Hina Sultana
- Centre for Cellular and Molecular Biology (CSIR), Hyderabad, Andhra Pradesh, India
| | - Mohsen Ghasemi
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Jasmine Ahluwalia
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Sowmya Ramachandran
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
| | - Rakesh K. Mishra
- Centre for Cellular and Molecular Biology (CSIR), Hyderabad, Andhra Pradesh, India
| | - Vani Brahmachari
- Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, Delhi, India
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21
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Steffen PA, Fonseca JP, Gänger C, Dworschak E, Kockmann T, Beisel C, Ringrose L. Quantitative in vivo analysis of chromatin binding of Polycomb and Trithorax group proteins reveals retention of ASH1 on mitotic chromatin. Nucleic Acids Res 2013; 41:5235-50. [PMID: 23580551 PMCID: PMC3664806 DOI: 10.1093/nar/gkt217] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Polycomb (PcG) and Trithorax (TrxG) group proteins work antagonistically on several hundred developmentally important target genes, giving stable mitotic memory, but also allowing flexibility of gene expression states. How this is achieved in quantitative terms is poorly understood. Here, we present a quantitative kinetic analysis in living Drosophila of the PcG proteins Enhancer of Zeste, (E(Z)), Pleiohomeotic (PHO) and Polycomb (PC) and the TrxG protein absent, small or homeotic discs 1 (ASH1). Fluorescence recovery after photobleaching and fluorescence correlation spectroscopy reveal highly dynamic chromatin binding behaviour for all proteins, with exchange occurring within seconds. We show that although the PcG proteins substantially dissociate from mitotic chromatin, ASH1 remains robustly associated with chromatin throughout mitosis. Finally, we show that chromatin binding by ASH1 and PC switches from an antagonistic relationship in interphase, to a cooperative one during mitosis. These results provide quantitative insights into PcG and TrxG chromatin-binding dynamics and have implications for our understanding of the molecular nature of epigenetic memory.
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Affiliation(s)
- Philipp A Steffen
- Institute of Molecular Biotechnology, Dr Bohr-Gasse 3, 1030 Vienna, Austria
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22
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Abstract
The first genes composing the Polycomb group (PcG) were identified 50 years ago in Drosophila melanogaster as essential developmental functions that regulate the correct segmental expression of homeotic selector genes. In the past two decades, what was initially described as a large family of chromatin-associated proteins involved in the maintenance of transcriptional repression to maintain cellular memory of homeotic genes turned out to be a highly conserved and sophisticated network of epigenetic regulators that play key roles in multiple aspects of cell physiology and identity, including regulation of all developmental genes, cell differentiation, stem and somatic cell reprogramming and response to environmental stimuli. These myriad phenotypes further spread interest for the contribution that PcG proteins revealed in the pathogenesis and progression of cancer and other complex diseases. Recent novel insights have increasingly clarified the molecular regulatory mechanisms at the basis of PcG-mediated epigenetic silencing and opened new visions about PcG functions in cells. In this review, we focus on the multiple modes of action of the PcG complexes and describe their biological roles.
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Affiliation(s)
- Chiara Lanzuolo
- Dulbecco Telethon Institute, Epigenetics and Genome Reprogramming, IRCCS Santa Lucia Foundation, 00143 Rome, Italy
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23
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Srivastava S, Mishra RK, Dhawan J. Regulation of cellular chromatin state: insights from quiescence and differentiation. Organogenesis 2012; 6:37-47. [PMID: 20592864 DOI: 10.4161/org.6.1.11337] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2009] [Revised: 01/19/2010] [Accepted: 01/29/2010] [Indexed: 11/19/2022] Open
Abstract
The identity and functionality of eukaryotic cells is defined not just by their genomic sequence which remains constant between cell types, but by their gene expression profiles governed by epigenetic mechanisms. Epigenetic controls maintain and change the chromatin state throughout development, as exemplified by the setting up of cellular memory for the regulation and maintenance of homeotic genes in proliferating progenitors during embryonic development. Higher order chromatin structure in reversibly arrested adult stem cells also involves epigenetic regulation and in this review we highlight common trends governing chromatin states, focusing on quiescence and differentiation during myogenesis. Together, these diverse developmental modules reveal the dynamic nature of chromatin regulation providing fresh insights into the role of epigenetic mechanisms in potentiating development and differentiation.
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Affiliation(s)
- Surabhi Srivastava
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India.
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24
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Lanzuolo C, Lo Sardo F, Orlando V. Concerted epigenetic signatures inheritance at PcG targets through replication. Cell Cycle 2012; 11:1296-300. [PMID: 22421150 PMCID: PMC3527071 DOI: 10.4161/cc.19710] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Polycomb group of proteins (PcG), by controlling gene silencing transcriptional programs through cell cycle, lock cell identity and memory. Recent chromatin genome-wide studies indicate that PcG targets sites are bivalent domains with overlapping repressive H3K27me3 and active H3K4me3 mark domains. During S phase, the stability of epigenetic signatures is challenged by the replication fork passage. Hence, specific mechanisms of epigenetic inheritance might be provided to preserve epigenome structures. Recently, we have identified a critical time window before replication, during which high levels of PcG binding and histone marks on BX-C PRE target sites set the stage for subsequent dilution of epigenomic components, allowing proper transmission of epigenetic signatures to the next generation. Here, we extended this analysis to promoter elements, showing the same mechanism of inheritance. Furthermore, to gain insight into the inheritance of PREs bivalent marks, we analyzed dynamics of H3K4me3 deposition, a mark that correlates with transcriptionally active chromatin. Likewise, we found an early S-phase enrichment of H3K4me3 mark preceding the replication-dependent dilution. This evidence suggests that all epigenetic marks are inherited simultaneously to ensure their correct propagation through replication and to protect the “bivalency” of PREs.
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Affiliation(s)
- Chiara Lanzuolo
- Dulbecco Telethon Institute at IRCCS Santa Lucia Foundation, Epigenetics and Genome Reprogramming, Rome, Italy.
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25
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Smith ER, Lin C, Garrett AS, Thornton J, Mohaghegh N, Hu D, Jackson J, Saraf A, Swanson SK, Seidel C, Florens L, Washburn MP, Eissenberg JC, Shilatifard A. The little elongation complex regulates small nuclear RNA transcription. Mol Cell 2012; 44:954-65. [PMID: 22195968 DOI: 10.1016/j.molcel.2011.12.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 11/28/2011] [Accepted: 12/06/2011] [Indexed: 01/09/2023]
Abstract
Eleven-nineteen lysine-rich leukemia (ELL) participates in the super elongation complex (SEC) with the RNA polymerase II (Pol II) CTD kinase P-TEFb. SEC is a key regulator in the expression of HOX genes in mixed lineage leukemia (MLL)-based hematological malignancies, in the control of induced gene expression early in development, and in immediate early gene transcription. Here, we identify an SEC-like complex in Drosophila, as well as a distinct ELL-containing complex that lacks P-TEFb and other components of SEC named the "little elongation complex" (LEC). LEC subunits are highly enriched at RNA Pol II-transcribed small nuclear RNA (snRNA) genes, and the loss of LEC results in decreased snRNA expression in both flies and mammals. The specialization of the SEC and LEC complexes for mRNA and snRNA-containing genes, respectively, suggests the presence of specific classes of elongation factors for each class of genes transcribed by RNA polymerase II.
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Affiliation(s)
- Edwin R Smith
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
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Rappailles A, Decoville M, Locker D. DSP1, a Drosophila HMG protein, is involved in spatiotemporal expression of the homoeotic gene Sex combs reduced. Biol Cell 2012; 97:779-85. [PMID: 15610064 DOI: 10.1042/bc20040508] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION The Pc-G (Polycomb group) and trx-G (trithorax group) genes play a key role in the regulation of the homoeotic genes. The homoeotic gene Scr (Sex combs reduced) contained in the Antennapedia complex specifies segmental identity of the labial and prothoracic segments in Drosophila. Regulation of Scr requires the action of different enhancer elements spread over several kilobases. We previously identified an HMGB (high mobility group)-like protein DSP1 (dorsal switch protein 1), which works like a trx-G protein for the normal Scr expression. RESULTS In the present study, we attempted to characterize the regulatory sequences involved in the maintenance of the Scr activation by DSP1. We report here, using a transgenic line for the Scr10.0XbaI-regulatory element, that lack of DSP1 affects the function of a reporter gene in legs' imaginal discs but not in embryos. We show by immunolocalization that DSP1 is recruited on polytene chromosomes to the insertion site of the transgene. Moreover, using chromatin immunoprecipitation experiments, we identify two regions of 1 kb in Scr10.0XbaI as the main DSP1 targets. CONCLUSION These results provide strong evidence that the Scr gene expression is influenced by direct interaction between DSP1 and two Scr regulation elements. In addition, our results show that this interaction undergoes dynamic changes during development.
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Affiliation(s)
- Aurélien Rappailles
- Centre de Biophysique Moléculaire, CNRS UPR 4301, conventionnée avec l'Université d'Orléans, rue C. Sadron, 45071 Orléans, France.
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Li J, Poi MJ, Tsai MD. Regulatory mechanisms of tumor suppressor P16(INK4A) and their relevance to cancer. Biochemistry 2011; 50:5566-82. [PMID: 21619050 PMCID: PMC3127263 DOI: 10.1021/bi200642e] [Citation(s) in RCA: 222] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
P16(INK4A) (also known as P16 and MTS1), a protein consisting exclusively of four ankyrin repeats, is recognized as a tumor suppressor mainly because of the prevalence of genetic inactivation of the p16(INK4A) (or CDKN2A) gene in virtually all types of human cancers. However, it has also been shown that an elevated level of expression (upregulation) of P16 is involved in cellular senescence, aging, and cancer progression, indicating that the regulation of P16 is critical for its function. Here, we discuss the regulatory mechanisms of P16 function at the DNA level, the transcription level, and the posttranscriptional level, as well as their implications for the structure-function relationship of P16 and for human cancers.
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Affiliation(s)
- Junan Li
- Division of Environmental Health Sciences, College of Public Health, The Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, The Ohio State University, Columbus, Ohio 43210, USA.
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Schwartz YB, Kahn TG, Stenberg P, Ohno K, Bourgon R, Pirrotta V. Alternative epigenetic chromatin states of polycomb target genes. PLoS Genet 2010; 6:e1000805. [PMID: 20062800 PMCID: PMC2799325 DOI: 10.1371/journal.pgen.1000805] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 12/09/2009] [Indexed: 11/18/2022] Open
Abstract
Polycomb (PcG) regulation has been thought to produce stable long-term gene silencing. Genomic analyses in Drosophila and mammals, however, have shown that it targets many genes, which can switch state during development. Genetic evidence indicates that critical for the active state of PcG target genes are the histone methyltransferases Trithorax (TRX) and ASH1. Here we analyze the repertoire of alternative states in which PcG target genes are found in different Drosophila cell lines and the role of PcG proteins TRX and ASH1 in controlling these states. Using extensive genome-wide chromatin immunoprecipitation analysis, RNAi knockdowns, and quantitative RT-PCR, we show that, in addition to the known repressed state, PcG targets can reside in a transcriptionally active state characterized by formation of an extended domain enriched in ASH1, the N-terminal, but not C-terminal moiety of TRX and H3K27ac. ASH1/TRX N-ter domains and transcription are not incompatible with repressive marks, sometimes resulting in a "balanced" state modulated by both repressors and activators. Often however, loss of PcG repression results instead in a "void" state, lacking transcription, H3K27ac, or binding of TRX or ASH1. We conclude that PcG repression is dynamic, not static, and that the propensity of a target gene to switch states depends on relative levels of PcG, TRX, and activators. N-ter TRX plays a remarkable role that antagonizes PcG repression and preempts H3K27 methylation by acetylation. This role is distinct from that usually attributed to TRX/MLL proteins at the promoter. These results have important implications for Polycomb gene regulation, the "bivalent" chromatin state of embryonic stem cells, and gene expression in development.
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Affiliation(s)
- Yuri B. Schwartz
- Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Laboratories, Piscataway, New Jersey, United States of America
| | - Tatyana G. Kahn
- Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Laboratories, Piscataway, New Jersey, United States of America
| | - Per Stenberg
- Department of Molecular Biology, Umeå University, Umeå, Sweden
- Computational Life Science Cluster, Umeå University, Umeå, Sweden
| | - Katsuhito Ohno
- Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Laboratories, Piscataway, New Jersey, United States of America
| | - Richard Bourgon
- European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Vincenzo Pirrotta
- Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Laboratories, Piscataway, New Jersey, United States of America
- * E-mail:
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Cierpicki T, Risner LE, Grembecka J, Lukasik SM, Popovic R, Omonkowska M, Shultis DD, Zeleznik-Le NJ, Bushweller JH. Structure of the MLL CXXC domain-DNA complex and its functional role in MLL-AF9 leukemia. Nat Struct Mol Biol 2009; 17:62-8. [PMID: 20010842 DOI: 10.1038/nsmb.1714] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2009] [Accepted: 10/05/2009] [Indexed: 02/02/2023]
Abstract
The gene MLL (encoding the protein mixed-lineage leukemia) is the target of chromosomal translocations that cause leukemias with poor prognosis. All leukemogenic MLL fusion proteins retain the CXXC domain, which binds to nonmethylated CpG DNA sites. We present the solution structure of the MLL CXXC domain in complex with DNA, showing how the CXXC domain distinguishes nonmethylated from methylated CpG DNA. On the basis of the structure, we generated point mutations that disrupt DNA binding. Introduction of these mutations into the MLL-AF9 fusion protein resulted in increased DNA methylation of specific CpG nucleotides in Hoxa9, increased H3K9 methylation, decreased expression of Hoxa9-locus transcripts, loss of immortalization potential, and inability to induce leukemia in mice. These results establish that DNA binding by the CXXC domain and protection against DNA methylation is essential for MLL fusion leukemia. They also provide support for viewing this interaction as a potential target for therapeutic intervention.
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Affiliation(s)
- Tomasz Cierpicki
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
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Senthilkumar R, Mishra RK. Novel motifs distinguish multiple homologues of Polycomb in vertebrates: expansion and diversification of the epigenetic toolkit. BMC Genomics 2009; 10:549. [PMID: 19930571 PMCID: PMC2784810 DOI: 10.1186/1471-2164-10-549] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 11/20/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Polycomb group (PcG) proteins maintain expression pattern of genes set early during development. Although originally isolated as regulators of homeotic genes, PcG members play a key role in epigenetic mechanism that maintains the expression state of a large number of genes. Polycomb (PC) is conserved during evolution and while invertebrates have one PC gene, vertebrates have five or more homologues. It remains unclear if different vertebrate PC homologues have distinct or overlapping functions. We have identified and compared the sequence of PC homologues in various organisms to analyze similarities and differences that shaped the evolutionary history of this key regulatory protein. RESULTS All PC homologues have an N-terminal chromodomain and a C-terminal Polycomb Repressor box. We searched the protein and genome sequence database of various organisms for these signatures and identified approximately 100 PC homologues. Comparative analysis of these sequences led to the identification of a novel insect specific motif and several novel and signature motifs in the vertebrate homologue: two in CBX2 (Cx2.1 and Cx2.2), four in CBX4 (Cx4.1, Cx4.2, Cx4.3 and Cx4.4), three in CBX6 (Cx6.1, Cx6.2 and Cx6.3) and one in CBX8 (Cx8.1). Additionally, adjacent to the chromodomain, all the vertebrate homologues have a DNA binding motif - AT-Hook in case of CBX2, which was known earlier, and 'AT-Hook Like' motif, from this study, in other PC homologues. CONCLUSION Our analysis shows that PC is an ancient gene dating back to pre bilaterian origin that has not only been conserved but has also expanded during the evolution of complexity. Unique motifs acquired by each homologue have been maintained for more than 500 millions years indicating their functional relevance in boosting the epigenetic 'tool kit'. We report the presence of a DNA interaction motif adjacent to chromodomain in all vertebrate PC homologues and suggest a three-way 'PC-histoneH3-DNA' interaction that can restrict nucleosome dynamics. The signature motifs of PC homologues and insect specific motif identified in this study pave the way to understand the molecular basis of epigenetic mechanisms.
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Hauenschild A, Ringrose L, Altmutter C, Paro R, Rehmsmeier M. Evolutionary plasticity of polycomb/trithorax response elements in Drosophila species. PLoS Biol 2008; 6:e261. [PMID: 18959483 PMCID: PMC2573935 DOI: 10.1371/journal.pbio.0060261] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Accepted: 09/15/2008] [Indexed: 12/22/2022] Open
Abstract
cis-Regulatory DNA elements contain multiple binding sites for activators and repressors of transcription. Among these elements are enhancers, which establish gene expression states, and Polycomb/Trithorax response elements (PREs), which take over from enhancers and maintain transcription states of several hundred developmentally important genes. PREs are essential to the correct identities of both stem cells and differentiated cells. Evolutionary differences in cis-regulatory elements are a rich source of phenotypic diversity, and functional binding sites within regulatory elements turn over rapidly in evolution. However, more radical evolutionary changes that go beyond motif turnover have been difficult to assess. We used a combination of genome-wide bioinformatic prediction and experimental validation at specific loci, to evaluate PRE evolution across four Drosophila species. Our results show that PRE evolution is extraordinarily dynamic. First, we show that the numbers of PREs differ dramatically between species. Second, we demonstrate that functional binding sites within PREs at conserved positions turn over rapidly in evolution, as has been observed for enhancer elements. Finally, although it is theoretically possible that new elements can arise out of nonfunctional sequence, evidence that they do so is lacking. We show here that functional PREs are found at nonorthologous sites in conserved gene loci. By demonstrating that PRE evolution is not limited to the adaptation of preexisting elements, these findings document a novel dimension of cis-regulatory evolution.
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Affiliation(s)
- Arne Hauenschild
- Universität Bielefeld, Center for Biotechnology (CeBiTec),
Bielefeld, Germany
| | - Leonie Ringrose
- Institute of Molecular Biotechnology (IMBA), Vienna, Austria
- Zentrum für Molekulare Biologie der Universität
Heidelberg (ZMBH), Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail:
(MR); (LR)
| | | | - Renato Paro
- Zentrum für Molekulare Biologie der Universität
Heidelberg (ZMBH), Heidelberg, Germany
- Department of Biosystems Science and Engineering, ETH Zurich,
Basel, Switzerland
| | - Marc Rehmsmeier
- Universität Bielefeld, Center for Biotechnology (CeBiTec),
Bielefeld, Germany
- Gregor Mendel Institute of Molecular Plant Biology (GMI), Vienna,
Austria
- * To whom correspondence should be addressed. E-mail:
(MR); (LR)
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32
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Schwartz YB, Pirrotta V. Polycomb Complexes and the Role of Epigenetic Memory in Development. Epigenomics 2008. [DOI: 10.1007/978-1-4020-9187-2_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Abstract
Genomic imprinting results in the expression of genes in a parent-of-origin-dependent manner. The mechanism and developmental consequences of genomic imprinting are most well characterized in mammals, plants, and certain insect species (e.g., sciarid flies and coccid insects). However, researchers have observed imprinting phenomena in species in which imprinting of endogenous genes is not known to exist or to be developmentally essential. In this review, I survey the known mechanisms of imprinting, focusing primarily on examples from mammals, where imprinting is relatively well characterized. Where appropriate, I draw attention to imprinting mechanisms in other organisms to compare and contrast how diverse organisms employ different strategies to perform the same process. I discuss how the various mechanisms come into play in the context of the imprint life cycle. Finally, I speculate why imprinting may be more widely prevalent than previously thought.
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Affiliation(s)
- Ky Sha
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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Garaulet DL, Foronda D, Calleja M, Sánchez-Herrero E. Polycomb-dependentUltrabithoraxHox gene silencing induced by high Ultrabithorax levels inDrosophila. Development 2008; 135:3219-28. [DOI: 10.1242/dev.025809] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Ultrabithorax (Ubx) gene of Drosophilaspecifies the third thoracic and first abdominal segments. Ubxexpression is controlled by several mechanisms, including negative regulation by its own product. We show here that if Ubx expression levels are inappropriately elevated, overriding the auto-regulatory control, a permanent repression of Ubx is established. This continuous repression becomes independent of the presence of exogenous Ubx and leads to the paradoxical result that an excess of Ubx results in a phenotype of Ubx loss. The mechanism of permanent repression depends on Polycomb-group genes. Absence of endogenous Ubxtranscription when Ubx levels are highly elevated probably activates Polycomb complexes on a Polycomb response element located in the Ubx major intron. This, in turn, brings about permanent repression of Ubx transcription. Similar results are obtained with the gene engrailed, showing that this mechanism of permanent repression may be a general one for genes with negative auto-regulation when levels of expression are transitorily elevated.
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Affiliation(s)
- Daniel L. Garaulet
- Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.),Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco,28049 Madrid, Spain
| | - David Foronda
- Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.),Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco,28049 Madrid, Spain
| | - Manuel Calleja
- Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.),Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco,28049 Madrid, Spain
| | - Ernesto Sánchez-Herrero
- Centro de Biología Molecular Severo Ochoa (C.S.I.C.-U.A.M.),Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco,28049 Madrid, Spain
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Kwong C, Adryan B, Bell I, Meadows L, Russell S, Manak JR, White R. Stability and dynamics of polycomb target sites in Drosophila development. PLoS Genet 2008; 4:e1000178. [PMID: 18773083 PMCID: PMC2525605 DOI: 10.1371/journal.pgen.1000178] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Accepted: 07/18/2008] [Indexed: 11/25/2022] Open
Abstract
Polycomb-group (PcG) and Trithorax-group proteins together form a maintenance machinery that is responsible for stable heritable states of gene activity. While the best-studied target genes are the Hox genes of the Antennapedia and Bithorax complexes, a large number of key developmental genes are also Polycomb (Pc) targets, indicating a widespread role for this maintenance machinery in cell fate determination. We have studied the linkage between the binding of PcG proteins and the developmental regulation of gene expression using whole-genome mapping to identify sites bound by the PcG proteins, Pc and Pleiohomeotic (Pho), in the Drosophila embryo and in a more restricted tissue, the imaginal discs of the third thoracic segment. Our data provide support for the idea that Pho is a general component of the maintenance machinery, since the majority of Pc targets are also associated with Pho binding. We find, in general, considerable developmental stability of Pc and Pho binding at target genes and observe that Pc/Pho binding can be associated with both expressed and inactive genes. In particular, at the Hox complexes, both active and inactive genes have significant Pc and Pho binding. However, in comparison to inactive genes, the active Hox genes show reduced and altered binding profiles. During development, Pc target genes are not simply constantly associated with Pc/Pho binding, and we identify sets of genes with clear differential binding between embryo and imaginal disc. Using existing datasets, we show that for specific fate-determining genes of the haemocyte lineage, the active state is characterised by lack of Pc binding. Overall, our analysis suggests a dynamic relationship between Pc/Pho binding and gene transcription. Pc/Pho binding does not preclude transcription, but levels of Pc/Pho binding change during development, and loss of Pc/Pho binding can be associated with both stable gene activity and inactivity. Cells make fate decisions as they progressively differentiate into specific cell types during development. The stability of these decisions is important and is achieved, in part, by changes to the chromatin that packages DNA in the nucleus. A key set of protein complexes that together constitute the Polycomb-group/Trithorax-group (PcG/TrxG) machinery is involved in chromatin modification and is known to operate at a large number of genes involved in developmental decisions. The PcG proteins establish stable gene repression, whereas the TrxG counteract the PcG to enable gene activation. How this PcG/TrxG balance works is not understood. By mapping PcG protein binding to chromatin in vivo, we show, in general, a relatively constant association of PcG protein at target genes during development. However, we also find changes in binding at specific genes. While some of these changes are consistent with a loss of PcG proteins associated with gene expression, we also find examples where PcG proteins are present at active genes and not present at inactive genes. Our analysis supports the idea that simply the presence of PcG proteins at a target gene does not necessarily result in gene repression and suggests a more dynamic balance between PcG protein binding and gene expression.
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Affiliation(s)
- Camilla Kwong
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Boris Adryan
- Theoretical and Computational Biology Group, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Ian Bell
- Affymetrix Inc., Affy Labs–Transcriptome, Santa Clara, California, United States of America
| | - Lisa Meadows
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Steven Russell
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - J. Robert Manak
- Affymetrix Inc., Affy Labs–Transcriptome, Santa Clara, California, United States of America
| | - Robert White
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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A mono-allelic bivalent chromatin domain controls tissue-specific imprinting at Grb10. EMBO J 2008; 27:2523-32. [PMID: 18650936 DOI: 10.1038/emboj.2008.142] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 06/27/2008] [Indexed: 02/04/2023] Open
Abstract
Genomic imprinting is a developmental mechanism that mediates parent-of-origin-specific expression in a subset of genes. How the tissue specificity of imprinted gene expression is controlled remains poorly understood. As a model to address this question, we studied Grb10, a gene that displays brain-specific expression from the paternal chromosome. Here, we show in the mouse that the paternal promoter region is marked by allelic bivalent chromatin enriched in both H3K4me2 and H3K27me3, from early embryonic stages onwards. This is maintained in all somatic tissues, but brain. The bivalent domain is resolved upon neural commitment, during the developmental window in which paternal expression is activated. Our data indicate that bivalent chromatin, in combination with neuronal factors, controls the paternal expression of Grb10 in brain. This finding highlights a novel mechanism to control tissue-specific imprinting.
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Vasanthi D, Mishra RK. Epigenetic regulation of genes during development: A conserved theme from flies to mammals. J Genet Genomics 2008; 35:413-29. [DOI: 10.1016/s1673-8527(08)60059-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 06/04/2008] [Accepted: 06/05/2008] [Indexed: 01/16/2023]
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Petruk S, Smith ST, Sedkov Y, Mazo A. Association of trxG and PcG proteins with the bxd maintenance element depends on transcriptional activity. Development 2008; 135:2383-90. [PMID: 18550707 DOI: 10.1242/dev.023275] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Polycomb group (PcG) and trithorax group (trxG) proteins act in an epigenetic fashion to maintain active and repressive states of expression of the Hox and other target genes by altering their chromatin structure. Genetically, mutations in trxG and PcG genes can antagonize each other's function, whereas mutations of genes within each group have synergistic effects. Here, we show in Drosophila that multiple trxG and PcG proteins act through the same or juxtaposed sequences in the maintenance element (ME) of the homeotic gene Ultrabithorax. Surprisingly, trxG or PcG proteins, but not both, associate in vivo in any one cell in a salivary gland with the ME of an activated or repressed Ultrabithorax transgene, respectively. Among several trxG and PcG proteins, only Ash1 and Asx require Trithorax in order to bind to their target genes. Together, our data argue that at the single-cell level, association of repressors and activators correlates with gene silencing and activation, respectively. There is, however, no overall synergism or antagonism between and within the trxG and PcG proteins and, instead, only subsets of trxG proteins act synergistically.
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Affiliation(s)
- Svetlana Petruk
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
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39
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Fedorova E, Sadoni N, Dahlsveen IK, Koch J, Kremmer E, Eick D, Paro R, Zink D. The nuclear organization of Polycomb/Trithorax group response elements in larval tissues of Drosophila melanogaster. Chromosome Res 2008; 16:649-73. [PMID: 18560994 DOI: 10.1007/s10577-008-1218-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/27/2008] [Accepted: 02/27/2008] [Indexed: 01/28/2023]
Abstract
We analysed the nuclear organization of the Polycomb/Trithorax group response element (PRE/TRE) Fab-7 and of other PRE/TREs in larval tissues of D. melanogaster. The results show that pairing/clustering of transgenic and endogenous Fab-7 elements and of other endogenous PRE/TREs occurs only to a limited degree in a highly locus-specific and tissue-specific manner. However, transgenic Fab-7 elements as well as the Fab-7-regulated Abd-B gene and other endogenous loci preferentially occupied defined nuclear regions. Preferred association with the nuclear periphery was observed in the inactive state. However, also in the active state, Fab-7 was often found associated with the nuclear periphery as well as with the boundary of heterochromatin in a fly line- and tissue-specific manner. The boundary between heterochromatin and euchromatin revealed a highly complex architecture in the three-dimensional nuclear space with a close juxtaposition of active and repressed domains. The results suggest that such complex architectures create nuclear microenvironments sustaining specific states of activity of defined PRE/TREs. However, the data also show that the positional behaviour of the transgenic Fab-7 element does not apply to PRE/TREs in general. Altogether, this finding and the highly locus-, tissue-, and fly line-specific behaviour with regard to nuclear positioning and pairing/clustering suggest that the relationships between nuclear organization and functional regulation of PRE/TREs are highly complex and that simple models making general predictions might not be appropriate.
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Affiliation(s)
- Elena Fedorova
- Department Biologie II, Ludwig-Maximilians-Universität München, Grosshaderner Str. 2, 82152, Planegg-Martinsried, Germany
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Abstract
Noncoding RNA has arrived at centre stage in recent years with the discovery of "hidden transcriptomes" in many higher organisms. Over two decades ago, noncoding transcripts were discovered in Drosophila Hox complexes, but their function has remained elusive. Recent studies1-3 have examined the role of these noncoding RNAs in Hox gene regulation, and have generated a fierce debate as to whether the noncoding transcripts are important for silencing or activation. Here we review the evidence, and show that, by taking developmental timing into account, some of these apparently conflicting results can be resolved. We examine current models that explain these data and explore alternative interpretations.
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41
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Mavrich TN, Jiang C, Ioshikhes IP, Li X, Venters BJ, Zanton SJ, Tomsho LP, Qi J, Glaser RL, Schuster SC, Gilmour DS, Albert I, Pugh BF. Nucleosome organization in the Drosophila genome. Nature 2008; 453:358-62. [PMID: 18408708 PMCID: PMC2735122 DOI: 10.1038/nature06929] [Citation(s) in RCA: 541] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Accepted: 03/26/2008] [Indexed: 01/22/2023]
Abstract
Comparative genomics of nucleosome positions provides a powerful means for understanding how the organization of chromatin and the transcription machinery co-evolve. Here we produce a high-resolution reference map of H2A.Z and bulk nucleosome locations across the genome of the fly Drosophila melanogaster and compare it to that from the yeast Saccharomyces cerevisiae. Like Saccharomyces, Drosophila nucleosomes are organized around active transcription start sites in a canonical -1, nucleosome-free region, +1 arrangement. However, Drosophila does not incorporate H2A.Z into the -1 nucleosome and does not bury its transcriptional start site in the +1 nucleosome. At thousands of genes, RNA polymerase II engages the +1 nucleosome and pauses. How the transcription initiation machinery contends with the +1 nucleosome seems to be fundamentally different across major eukaryotic lines.
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Affiliation(s)
- Travis N Mavrich
- Center for Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Comparing active and repressed expression states of genes controlled by the Polycomb/Trithorax group proteins. Proc Natl Acad Sci U S A 2007; 104:16615-20. [PMID: 17921257 DOI: 10.1073/pnas.0701538104] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Drosophila Polycomb group (PcG) and Trithorax group (TrxG) proteins are responsible for the maintenance of stable transcription patterns of many developmental regulators, such as the homeotic genes. We have used ChIP-on-chip to compare the distribution of several PcG/TrxG proteins, as well as histone modifications in active and repressed genes across the two homeotic complexes ANT-C and BX-C. Our data indicate the colocalization of the Polycomb repressive complex 1 (PRC1) with Trx and the DNA binding protein Pleiohomeotic (Pho) at discrete sequence elements as well as significant chromatin assembly differences in active and inactive regions. Trx binds to the promoters of active genes and noncoding transcripts. Most strikingly, in the active state, Pho covers extended chromatin domains over many kilobases. This feature of Pho, observed on many polytene chromosome puffs, reflects a previously undescribed function. At the hsp70 gene, we demonstrate in mutants that Pho is required for transcriptional recovery after heat shock. Besides its presumptive function in recruiting PcG complexes to their site of action, our results now uncover that Pho plays an additional role in the repression of already induced genes.
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Rajasekhar VK, Begemann M. Concise Review: Roles of Polycomb Group Proteins in Development and Disease: A Stem Cell Perspective. Stem Cells 2007; 25:2498-510. [PMID: 17600113 DOI: 10.1634/stemcells.2006-0608] [Citation(s) in RCA: 155] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The acquisition and maintenance of cell fate are essential for metazoan growth and development. A strict coordination between genetic and epigenetic programs regulates cell fate determination and maintenance. Polycomb group (PcG) genes are identified as essential in these epigenetic developmental processes. These genes encode components of multimeric transcriptional repressor complexes that are crucial in maintaining cell fate. PcG proteins have also been shown to play a central role in stem cell maintenance and lineage specification. PcG proteins, together with a battery of components including sequence-specific DNA binding/accessory factors, chromatin remodeling factors, signaling pathway intermediates, noncoding small RNAs, and RNA interference machinery, generally define a dynamic cellular identity through tight regulation of specific gene expression patterns. Epigenetic modification of chromatin structure that results in expression silencing of specific genes is now emerging as an important molecular mechanism in this process. In embryonic stem (ES) cells and adult stem cells, such specific genes represent those associated with differentiation and development, and silencing of these genes in a PcG protein-dependent manner confers stemness. ES cells also contain novel chromatin motifs enriched in epigenetic modifications associated with both activation and repression of genes, suggesting that certain genes are poised for activation or repression. Interestingly, these chromatin domains are highly coincident with the promoters of developmental regulators, which are also found to be occupied by PcG proteins. The epigenetic integrity is compromised, however, by mutations or other alterations that affect the function of PcG proteins in stem cells leading to aberrant cell proliferation and tissue transformation, a hallmark of cancer. Disclosure of potential conflicts of interest is found at the end of this article.
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Affiliation(s)
- Vinagolu K Rajasekhar
- Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Rockefeller Research Laboratories, Room #945, New York, New York 10021, USA.
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Lanzuolo C, Roure V, Dekker J, Bantignies F, Orlando V. Polycomb response elements mediate the formation of chromosome higher-order structures in the bithorax complex. Nat Cell Biol 2007; 9:1167-74. [PMID: 17828248 DOI: 10.1038/ncb1637] [Citation(s) in RCA: 230] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 07/26/2007] [Indexed: 12/12/2022]
Abstract
In Drosophila, the function of the Polycomb group genes (PcGs) and their target sequences (Polycomb response elements (PREs)) is to convey mitotic heritability of transcription programmes--in particular, gene silencing. As part of the mechanisms involved, PREs are thought to mediate this transcriptional memory function by building up higher-order structures in the nucleus. To address this question, we analysed in vivo the three-dimensional structure of the homeotic locus bithorax complex (BX-C) by combining chromosome conformation capture (3C) with fluorescent in situ hybridization (FISH) and FISH immunostaining (FISH-I) analysis. We found that, in the repressed state, all major elements that have been shown to bind PcG proteins, including PREs and core promoters, interact at a distance, giving rise to a topologically complex structure. We show that this structure is important for epigenetic silencing of the BX-C, as we find that major changes in higher-order structures must occur to stably maintain alternative transcription states, whereas histone modification and reduced levels of PcG proteins determine an epigenetic switch that is only partially heritable.
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Affiliation(s)
- Chiara Lanzuolo
- Dulbecco Telethon Institute at IGB CNR, Epigenetics and Genome Reprogramming, Via Pietro Castellino 111, 80131 Naples, Italy
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Sipos L, Kozma G, Molnár E, Bender W. In situ dissection of a Polycomb response element in Drosophila melanogaster. Proc Natl Acad Sci U S A 2007; 104:12416-21. [PMID: 17640916 PMCID: PMC1941339 DOI: 10.1073/pnas.0703144104] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Genes of the Polycomb group maintain long-term, segment-specific repression of the homeotic genes in Drosophila. DNA targets of Polycomb group proteins, called Polycomb response elements (PREs), have been defined by several assays, but they have not been dissected in their original chromosomal context. An enhanced method of gene conversion was developed to generate a series of small, targeted deletions encompassing the best-studied PRE, upstream of the Ultrabithorax (Ubx) transcription unit in the bithorax complex. Deletions that removed an essential 185-bp core of the PRE caused anterior misexpression of Ubx and posterior segmental transformations, including the conversion of the third thoracic segment toward a duplicate first abdominal segment. These phenotypes were variable, suggesting some cooperation between this PRE and others in the bithorax complex. Larger deletions up to 3 kb were also created, which removed DNA sites reportedly needed for Ubx activation, including putative trithorax response elements. These deletions resulted in neither loss of Ubx expression nor loss-of-function phenotypes. Thus, the 3-kb region including the PRE is required for repression, but not for activation, of Ubx.
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Affiliation(s)
- László Sipos
- Institute of Genetics, Biological Research Center of Hungarian Academy of Sciences, H-6701 Szeged, Hungary
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Wang X, Lee C, Gilmour DS, Gergen JP. Transcription elongation controls cell fate specification in the Drosophila embryo. Genes Dev 2007; 21:1031-6. [PMID: 17473169 PMCID: PMC1855229 DOI: 10.1101/gad.1521207] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The simple combinatorial rules for regulation of the sloppy-paired-1 (slp1) gene by the pair-rule transcription factors during early Drosophila embryogenesis offer a unique opportunity to investigate the molecular mechanisms of developmentally regulated transcription repression. We find that the initial repression of slp1 in response to Runt and Fushi-tarazu (Ftz) does not involve chromatin remodeling, or histone modification. Chromatin immunoprecipitation and in vivo footprinting experiments indicate RNA polymerase II (Pol II) initiates transcription in slp1-repressed cells and pauses downstream from the promoter in a complex that includes the negative elongation factor NELF. The finding that NELF also associates with the promoter regions of wingless (wg) and engrailed (en), two other pivotal targets of the pair-rule transcription factors, strongly suggests that developmentally regulated transcriptional elongation is central to the process of cell fate specification during this critical stage of embryonic development.
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Affiliation(s)
- Xiaoling Wang
- Department of Biochemistry and Cell Biology and the Center for Developmental Genetics, Stony Brook University, Stony Brook, New York 11794, USA
- Graduate Program in Biochemistry and Structural Biology, Stony Brook University, Stony Brook, New York 11794, USA
| | - Chanhyo Lee
- Center for Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - David S. Gilmour
- Center for Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - J. Peter Gergen
- Department of Biochemistry and Cell Biology and the Center for Developmental Genetics, Stony Brook University, Stony Brook, New York 11794, USA
- Corresponding author.E-MAIL ; FAX (631) 632-8575
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Ringrose L. Polycomb comes of age: genome-wide profiling of target sites. Curr Opin Cell Biol 2007; 19:290-7. [PMID: 17481880 DOI: 10.1016/j.ceb.2007.04.010] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 04/16/2007] [Indexed: 10/23/2022]
Abstract
The Polycomb group proteins are best known for their role as epigenetic regulators of the fly homeotic (Hox) gene clusters, but it has long been clear that these well conserved proteins have many other targets. For example, they are vital for maintaining both the pluripotency of stem cells and the identity of differentiated cells. However, a comprehensive list of experimentally defined targets has been lacking. Six new studies use genome wide profiling techniques to map Polycomb targets in stem cells and differentiated cells in vertebrates and flies. The findings of these studies demand that we rethink some of our current assumptions about Polycomb function.
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Affiliation(s)
- Leonie Ringrose
- IMBA - Institute of Molecular Biotechnology GmbH, Dr. Bohr-Gasse 3, 1030 Vienna, Austria.
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Chang YL, King B, Lin SC, Kennison JA, Huang DH. A double-bromodomain protein, FSH-S, activates the homeotic gene ultrabithorax through a critical promoter-proximal region. Mol Cell Biol 2007; 27:5486-98. [PMID: 17526731 PMCID: PMC1952094 DOI: 10.1128/mcb.00692-07] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
More than a dozen trithorax group (trxG) proteins are involved in activation of Drosophila HOX genes. How they act coordinately to integrate signals from distantly located enhancers is not fully understood. The female sterile (1) homeotic (fs(1)h) gene is one of the trxG genes that is most critical for Ultrabithorax (Ubx) activation. We show that one of the two double-bromodomain proteins encoded by fs(1)h acts as an essential factor in the Ubx proximal promoter. First, overexpression of the small isoform FSH-S, but not the larger one, can induce ectopic expression of HOX genes and cause body malformation. Second, FSH-S can stimulate Ubx promoter in cultured cells through a critical proximal region in a bromodomain-dependent manner. Third, purified FSH-S can bind specifically to a motif within this region that was previously known as the ZESTE site. The physiological relevance of FSH-S is ascertained using transgenic embryos containing a modified Ubx proximal promoter and chromatin immunoprecipitation. In addition, we show that FSH-S is involved in phosphorylation of itself and other regulatory factors. We suggest that FSH-S acts as a critical component of a regulatory circuitry mediating long-range effects of distant enhancers.
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Affiliation(s)
- Yuh-Long Chang
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan 115, Republic of China
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Nakayama T, Nishioka K, Dong YX, Shimojima T, Hirose S. Drosophila GAGA factor directs histone H3.3 replacement that prevents the heterochromatin spreading. Genes Dev 2007; 21:552-61. [PMID: 17344416 PMCID: PMC1820897 DOI: 10.1101/gad.1503407] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Epigenetic maintenance of the expression state of the genome is critical for development. Drosophila GAGA factor interacts with FACT and modulates chromatin structure for the maintenance of gene expression. Here we show that the GAGA factor-FACT complex and its binding site just downstream from the white gene are crucial for position effect variegation. Interestingly there is a dip of histone H3 Lys 9 methylation and a peak of H3 Lys 4 methylation at this site. The GAGA factor and FACT direct replacement of histone H3 by H3.3 through association of HIRA at this site, and maintain white expression under the heterochromatin environment. Based on these findings we propose that the GAGA factor and FACT-dependent replacement of Lys 9-methylated histone H3 by H3.3 counteracts the spreading of silent chromatin.
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Affiliation(s)
- Takahiro Nakayama
- Department of Developmental Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka-ken 411-8540, Japan
| | - Kenichi Nishioka
- Department of Developmental Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka-ken 411-8540, Japan
| | - Yi-Xin Dong
- Department of Developmental Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka-ken 411-8540, Japan
| | - Tsukasa Shimojima
- Department of Developmental Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka-ken 411-8540, Japan
| | - Susumu Hirose
- Department of Developmental Genetics, National Institute of Genetics, and Department of Genetics, SOKENDAI, Mishima, Shizuoka-ken 411-8540, Japan
- Corresponding author.E-MAIL ; FAX 81-55-981-6776
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Abstract
Chemical modifications to DNA and histone proteins form a complex regulatory network that modulates chromatin structure and genome function. The epigenome refers to the complete description of these potentially heritable changes across the genome. The composition of the epigenome within a given cell is a function of genetic determinants, lineage, and environment. With the sequencing of the human genome completed, investigators now seek a comprehensive view of the epigenetic changes that determine how genetic information is made manifest across an incredibly varied background of developmental stages, tissue types, and disease states. Here we review current research efforts, with an emphasis on large-scale studies, emerging technologies, and challenges ahead.
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Affiliation(s)
- Bradley E Bernstein
- Molecular Pathology Unit and Center for Cancer Research, Massachusetts General Hospital, Charlestown, MA 02129, USA.
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