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Melnikova L, Golovnin A. Multiple Roles of dXNP and dADD1- Drosophila Orthologs of ATRX Chromatin Remodeler. Int J Mol Sci 2023; 24:16486. [PMID: 38003676 PMCID: PMC10671109 DOI: 10.3390/ijms242216486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/11/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023] Open
Abstract
The Drosophila melanogaster dADD1 and dXNP proteins are orthologues of the ADD and SNF2 domains of the vertebrate ATRX (Alpha-Thalassemia with mental Retardation X-related) protein. ATRX plays a role in general molecular processes, such as regulating chromatin status and gene expression, while dADD1 and dXNP have similar functions in the Drosophila genome. Both ATRX and dADD1/dXNP interact with various protein partners and participate in various regulatory complexes. Disruption of ATRX expression in humans leads to the development of α-thalassemia and cancer, especially glioma. However, the mechanisms that allow ATRX to regulate various cellular processes are poorly understood. Studying the functioning of dADD1/dXNP in the Drosophila model may contribute to understanding the mechanisms underlying the multifunctional action of ATRX and its connection with various cellular processes. This review provides a brief overview of the currently available information in mammals and Drosophila regarding the roles of ATRX, dXNP, and dADD1. It discusses possible mechanisms of action of complexes involving these proteins.
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Affiliation(s)
- Larisa Melnikova
- Department of Drosophila Molecular Genetics, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., 119334 Moscow, Russia
| | - Anton Golovnin
- Department of Drosophila Molecular Genetics, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov St., 119334 Moscow, Russia
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2
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Identification of the Telomere elongation Mutation in Drosophila. Cells 2022; 11:cells11213484. [DOI: 10.3390/cells11213484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/31/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Telomeres in Drosophila melanogaster, which have inspired a large part of Sergio Pimpinelli work, are similar to those of other eukaryotes in terms of their function. Yet, their length maintenance relies on the transposition of the specialized retrotransposons Het-A, TART, and TAHRE, rather than on the activity of the enzyme telomerase as it occurs in most other eukaryotic organisms. The length of the telomeres in Drosophila thus depends on the number of copies of these transposable elements. Our previous work has led to the isolation of a dominant mutation, Tel1, that caused a several-fold elongation of telomeres. In this study, we molecularly identified the Tel1 mutation by a combination of transposon-induced, site-specific recombination and next-generation sequencing. Recombination located Tel1 to a 15 kb region in 92A. Comparison of the DNA sequence in this region with the Drosophila Genetic Reference Panel of wild-type genomic sequences delimited Tel1 to a 3 bp deletion inside intron 8 of Ino80. Furthermore, CRISPR/Cas9-induced deletions surrounding the same region exhibited the Tel1 telomere phenotype, confirming a strict requirement of this intron 8 gene sequence for a proper regulation of Drosophila telomere length.
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Different transcriptional responses by the CRISPRa system in distinct types of heterochromatin in Drosophila melanogaster. Sci Rep 2022; 12:11702. [PMID: 35810197 PMCID: PMC9271074 DOI: 10.1038/s41598-022-15944-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 07/01/2022] [Indexed: 11/09/2022] Open
Abstract
Transcription factors (TFs) activate gene expression by binding to elements close to promoters or enhancers. Some TFs can bind to heterochromatic regions to initiate gene activation, suggesting that if a TF is able to bind to any type of heterochromatin, it can activate transcription. To investigate this possibility, we used the CRISPRa system based on dCas9-VPR as an artificial TF in Drosophila. dCas9-VPR was targeted to the TAHRE telomeric element, an example of constitutive heterochromatin, and to promoters and enhancers of the HOX Ultrabithorax (Ubx) and Sex Combs Reduced (Scr) genes in the context of facultative heterochromatin. dCas9-VPR robustly activated TAHRE transcription, showing that although this element is heterochromatic, dCas9-VPR was sufficient to activate its expression. In the case of HOX gene promoters, although Polycomb complexes epigenetically silence these genes, both were ectopically activated. When the artificial TF was directed to enhancers, we found that the expression pattern was different compared to the effect on the promoters. In the case of the Scr upstream enhancer, dCas9-VPR activated the gene ectopically but with less expressivity; however, ectopic activation also occurred in different cells. In the case of the bxI enhancer located in the third intron of Ubx, the presence of dCas9-VPR is capable of increasing transcription initiation while simultaneously blocking transcription elongation, generating a lack of functional phenotype. Our results show that CRISPRa system is able to activate transcription in any type of heterochromatin; nevertheless, its effect on transcription is subject to the intrinsic characteristics of each gene or regulatory element.
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Zinshteyn D, Barbash DA. Stonewall prevents expression of ectopic genes in the ovary and accumulates at insulator elements in D. melanogaster. PLoS Genet 2022; 18:e1010110. [PMID: 35324887 PMCID: PMC8982855 DOI: 10.1371/journal.pgen.1010110] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 04/05/2022] [Accepted: 02/18/2022] [Indexed: 11/29/2022] Open
Abstract
Germline stem cells (GSCs) are the progenitor cells of the germline for the lifetime of an animal. In Drosophila, these cells reside in a cellular niche that is required for both their maintenance (self-renewal) and differentiation (asymmetric division resulting in a daughter cell that differs from the GSC). The stem cell—daughter cell transition is tightly regulated by a number of processes, including an array of proteins required for genome stability. The germline stem-cell maintenance factor Stonewall (Stwl) associates with heterochromatin, but its molecular function is poorly understood. We performed RNA-Seq on stwl mutant ovaries and found significant derepression of many transposon families but not heterochromatic genes. We also discovered inappropriate expression of multiple classes of genes. Most prominent are testis-enriched genes, including the male germline sex-determination switch Phf7, the differentiation factor bgcn, and a large testis-specific gene cluster on chromosome 2, all of which are upregulated or ectopically expressed in stwl mutant ovaries. Surprisingly, we also found that RNAi knockdown of stwl in somatic S2 cells results in ectopic expression of these testis genes. Using parallel ChIP-Seq and RNA-Seq experiments in S2 cells, we discovered that Stwl localizes upstream of transcription start sites and at heterochromatic sequences including repetitive sequences associated with telomeres. Stwl is also enriched at bgcn, suggesting that it directly regulates this essential differentiation factor. Finally, we identify Stwl binding motifs that are shared with known insulator binding proteins. We propose that Stwl affects gene regulation, including repression of male transcripts in the female germline, by binding insulators and establishing chromatin boundaries. Stem cells are defined by their ability to divide asymmetrically, resulting in a differentiated cell and a stem cell daughter. In fruit flies, sperm and egg production begins with germline stem cells (GSCs). The ability of a GSC to differentiate or self-renew is tightly regulated by a myriad of factors. Some of these are transcription factors, which are responsible for activating or suppressing other genes to promote one state in favor of another. Stonewall is an ovarian nuclear protein required for GSC self-renewal, whose molecular function is poorly understood. Here we show that Stonewall is responsible for preventing the activation of “male” molecular programming in the fruit fly ovary. When Stonewall is absent from the ovary, egg production is terminated and testis-specific genes become highly expressed, including the male transcript of Phf7, which induces male sexual identity in female germ cells. We also show that Stonewall is likely localizing to genomic insulators, which are regions of the genome that shield genes from nearby regulators. Our findings suggest that Stonewall helps to organize the genome in ovarian germ cells and prevent expression of male genes.
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Affiliation(s)
- Daniel Zinshteyn
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Daniel A. Barbash
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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El-Sappah AH, Yan K, Huang Q, Islam MM, Li Q, Wang Y, Khan MS, Zhao X, Mir RR, Li J, El-Tarabily KA, Abbas M. Comprehensive Mechanism of Gene Silencing and Its Role in Plant Growth and Development. FRONTIERS IN PLANT SCIENCE 2021; 12:705249. [PMID: 34589097 PMCID: PMC8475493 DOI: 10.3389/fpls.2021.705249] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 08/10/2021] [Indexed: 05/19/2023]
Abstract
Gene silencing is a negative feedback mechanism that regulates gene expression to define cell fate and also regulates metabolism and gene expression throughout the life of an organism. In plants, gene silencing occurs via transcriptional gene silencing (TGS) and post-transcriptional gene silencing (PTGS). TGS obscures transcription via the methylation of 5' untranslated region (5'UTR), whereas PTGS causes the methylation of a coding region to result in transcript degradation. In this review, we summarized the history and molecular mechanisms of gene silencing and underlined its specific role in plant growth and crop production.
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Affiliation(s)
- Ahmed H. El-Sappah
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Genetics Department, Faculty of Agriculture, Zagazig University, Zagazig, Egypt
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
| | - Kuan Yan
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
| | - Qiulan Huang
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
- College of Tea Science, Yibin University, Yibin, China
| | | | - Quanzi Li
- State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China
- Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China
| | - Yu Wang
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
| | - Muhammad Sarwar Khan
- Center of Agriculture Biochemistry and Biotechnology, University of Agriculture, Faisalabad, Pakistan
| | - Xianming Zhao
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
| | - Reyazul Rouf Mir
- Division of Genetics and Plant Breeding, Faculty of Agriculture (FoA), Sher-e-Kashmir University of Agricultural Sciences and Technology (SKUAST–K), Sopore, India
| | - Jia Li
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
| | - Khaled A. El-Tarabily
- Department of Biology, College of Science, United Arab Emirates University, Al-Ain, United Arab Emirates
- Harry Butler Institute, Murdoch University, Murdoch, WA, Australia
| | - Manzar Abbas
- School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, China
- Key Laboratory of Sichuan Province for Refining Sichuan Tea, Yibin, China
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Albig C, Wang C, Dann GP, Wojcik F, Schauer T, Krause S, Maenner S, Cai W, Li Y, Girton J, Muir TW, Johansen J, Johansen KM, Becker PB, Regnard C. JASPer controls interphase histone H3S10 phosphorylation by chromosomal kinase JIL-1 in Drosophila. Nat Commun 2019; 10:5343. [PMID: 31767855 PMCID: PMC6877644 DOI: 10.1038/s41467-019-13174-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 10/22/2019] [Indexed: 01/02/2023] Open
Abstract
In flies, the chromosomal kinase JIL-1 is responsible for most interphase histone H3S10 phosphorylation and has been proposed to protect active chromatin from acquiring heterochromatic marks, such as dimethylated histone H3K9 (H3K9me2) and HP1. Here, we show that JIL-1's targeting to chromatin depends on a PWWP domain-containing protein JASPer (JIL-1 Anchoring and Stabilizing Protein). JASPer-JIL-1 (JJ)-complex is the major form of kinase in vivo and is targeted to active genes and telomeric transposons via binding of the PWWP domain of JASPer to H3K36me3 nucleosomes, to modulate transcriptional output. JIL-1 and JJ-complex depletion in cycling cells lead to small changes in H3K9me2 distribution at active genes and telomeric transposons. Finally, we identify interactors of the endogenous JJ-complex and propose that JIL-1 not only prevents heterochromatin formation but also coordinates chromatin-based regulation in the transcribed part of the genome.
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Affiliation(s)
- Christian Albig
- Molecular Biology Division, Biomedical Center, Faculty of Medicine and Center for Integrated Protein Science Munich (CIPSM), LMU Munich, 82152, Martinsried, Germany
- Graduate School for Quantitative Biosciences (QBM), LMU Munich, 81377, Munich, Germany
| | - Chao Wang
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Geoffrey P Dann
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, NJ, 08544, USA
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Felix Wojcik
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, NJ, 08544, USA
| | - Tamás Schauer
- Bioinformatics Unit, Biomedical Center, Faculty of Medicine, LMU Munich, 82152, Martinsried, Germany
| | - Silke Krause
- Molecular Biology Division, Biomedical Center, Faculty of Medicine and Center for Integrated Protein Science Munich (CIPSM), LMU Munich, 82152, Martinsried, Germany
| | - Sylvain Maenner
- Molecular Biology Division, Biomedical Center, Faculty of Medicine and Center for Integrated Protein Science Munich (CIPSM), LMU Munich, 82152, Martinsried, Germany
- UMR7365 CNRS-UL, IMoPA, University of Lorraine, 54505, Vandoeuvre-lès-Nancy, France
| | - Weili Cai
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Yeran Li
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Jack Girton
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Tom W Muir
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, NJ, 08544, USA
| | - Jørgen Johansen
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Kristen M Johansen
- Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Peter B Becker
- Molecular Biology Division, Biomedical Center, Faculty of Medicine and Center for Integrated Protein Science Munich (CIPSM), LMU Munich, 82152, Martinsried, Germany.
| | - Catherine Regnard
- Molecular Biology Division, Biomedical Center, Faculty of Medicine and Center for Integrated Protein Science Munich (CIPSM), LMU Munich, 82152, Martinsried, Germany.
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Radion E, Morgunova V, Ryazansky S, Akulenko N, Lavrov S, Abramov Y, Komarov PA, Glukhov SI, Olovnikov I, Kalmykova A. Key role of piRNAs in telomeric chromatin maintenance and telomere nuclear positioning in Drosophila germline. Epigenetics Chromatin 2018; 11:40. [PMID: 30001204 PMCID: PMC6043984 DOI: 10.1186/s13072-018-0210-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 07/06/2018] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Telomeric small RNAs related to PIWI-interacting RNAs (piRNAs) have been described in various eukaryotes; however, their role in germline-specific telomere function remains poorly understood. Using a Drosophila model, we performed an in-depth study of the biogenesis of telomeric piRNAs and their function in telomere homeostasis in the germline. RESULTS To fully characterize telomeric piRNA clusters, we integrated the data obtained from analysis of endogenous telomeric repeats, as well as transgenes inserted into different telomeric and subtelomeric regions. The small RNA-seq data from strains carrying telomeric transgenes demonstrated that all transgenes belong to a class of dual-strand piRNA clusters; however, their capacity to produce piRNAs varies significantly. Rhino, a paralog of heterochromatic protein 1 (HP1) expressed exclusively in the germline, is associated with all telomeric transgenes, but its enrichment correlates with the abundance of transgenic piRNAs. It is likely that this heterogeneity is determined by the sequence peculiarities of telomeric retrotransposons. In contrast to the heterochromatic non-telomeric germline piRNA clusters, piRNA loss leads to a dramatic decrease in HP1, Rhino, and trimethylated histone H3 lysine 9 in telomeric regions. Therefore, the presence of piRNAs is required for the maintenance of telomere chromatin in the germline. Moreover, piRNA loss causes telomere translocation from the nuclear periphery toward the nuclear interior but does not affect telomere end capping. Analysis of the telomere-associated sequences (TASs) chromatin revealed strong tissue specificity. In the germline, TASs are enriched with HP1 and Rhino, in contrast to somatic tissues, where they are repressed by Polycomb group proteins. CONCLUSIONS piRNAs play an essential role in the assembly of telomeric chromatin, as well as in nuclear telomere positioning in the germline. Telomeric arrays and TASs belong to a unique type of Rhino-dependent piRNA clusters with transcripts that serve simultaneously as piRNA precursors and as their only targets. Telomeric chromatin is highly sensitive to piRNA loss, implying the existence of a novel developmental checkpoint that depends on telomere integrity in the germline.
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Affiliation(s)
- Elizaveta Radion
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Valeriya Morgunova
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Sergei Ryazansky
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Natalia Akulenko
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Sergey Lavrov
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Yuri Abramov
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Pavel A Komarov
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182.,Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia, 119991
| | - Sergey I Glukhov
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Ivan Olovnikov
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182
| | - Alla Kalmykova
- Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow, Russia, 123182.
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8
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Asif-Laidin A, Delmarre V, Laurentie J, Miller WJ, Ronsseray S, Teysset L. Short and long-term evolutionary dynamics of subtelomeric piRNA clusters in Drosophila. DNA Res 2017; 24:459-472. [PMID: 28459978 PMCID: PMC5737368 DOI: 10.1093/dnares/dsx017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 03/29/2017] [Indexed: 12/31/2022] Open
Abstract
Two Telomeric Associated Sequences, TAS-R and TAS-L, form the principal subtelomeric repeat families identified in Drosophila melanogaster. They are PIWI-interacting RNA (piRNA) clusters involved in repression of Transposable Elements. In this study, we revisited TAS structural and functional dynamics in D. melanogaster and in related species. In silico analysis revealed that TAS-R family members are composed of previously uncharacterized domains. This analysis also showed that TAS-L repeats are composed of arrays of a region we have named "TAS-L like" (TLL) identified specifically in one TAS-R family member, X-TAS. TLL were also present in other species of the melanogaster subgroup. Therefore, it is possible that TLL represents an ancestral subtelomeric piRNA core-cluster. Furthermore, all D. melanogaster genomes tested possessed at least one TAS-R locus, whereas TAS-L can be absent. A screen of 110 D. melanogaster lines showed that X-TAS is always present in flies living in the wild, but often absent in long-term laboratory stocks and that natural populations frequently lost their X-TAS within 2 years upon lab conditioning. Therefore, the unexpected structural and temporal dynamics of subtelomeric piRNA clusters demonstrated here suggests that genome organization is subjected to distinct selective pressures in the wild and upon domestication in the laboratory.
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Affiliation(s)
- Amna Asif-Laidin
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Valérie Delmarre
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Jeanne Laurentie
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Wolfgang J. Miller
- Lab Genome Dynamics, Department for Cell & Developmental Biology, Center of Anatomy and Cell Biology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Stéphane Ronsseray
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
| | - Laure Teysset
- Sorbonne Universités, UPMC University of Paris 06, CNRS, Biologie du Développement Paris-Seine, Institut de Biologie Paris-Seine (LBD-IBPS), 75005 Paris, France
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9
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Widespread colocalization of the Drosophila histone acetyltransferase homolog MYST5 with DREF and insulator proteins at active genes. Chromosoma 2016; 126:165-178. [PMID: 26894919 DOI: 10.1007/s00412-016-0582-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 01/18/2016] [Accepted: 02/10/2016] [Indexed: 12/28/2022]
Abstract
MYST family histone acetyltransferases play important roles in gene regulation. Here, we have characterized the Drosophila MYST histone acetyltransferase (HAT) encoded by cg1894, whose closest homolog is Drosophila MOF, and which we have termed MYST5. We found it localized to a large number of interbands as well as to the telomeres of polytene chromosomes, and it showed strong colocalization with the interband protein Z4/Putzig and RNA polymerase II. Accordingly, genome-wide location analysis by ChIP-seq showed co-occurrence of MYST5 with the Z4-interacting partner Chriz/Chromator. Interestingly, MYST5 bound to the promoter of actively transcribed genes, and about half of MYST5 sites colocalized with the transcription factor DNA replication-related element-binding factor (DREF), indicating a role for MYST5 in gene expression. Moreover, we observed substantial overlap of MYST5 binding with that of the insulator proteins CP190, dCTCF, and BEAF-32, which mediate the organization of the genome into functionally distinct topological domains. Altogether, our data suggest a broad role for MYST5 both in gene-specific transcriptional regulation and in the organization of the genome into chromatin domains, with the two roles possibly being functionally interconnected.
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10
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Targeting of P-Element Reporters to Heterochromatic Domains by Transposable Element 1360 in Drosophila melanogaster. Genetics 2015; 202:565-82. [PMID: 26680659 DOI: 10.1534/genetics.115.183228] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/10/2015] [Indexed: 11/18/2022] Open
Abstract
Heterochromatin is a common DNA packaging form employed by eukaryotes to constitutively silence transposable elements. Determining which sequences to package as heterochromatin is vital for an organism. Here, we use Drosophila melanogaster to study heterochromatin formation, exploiting position-effect variegation, a process whereby a transgene is silenced stochastically if inserted in proximity to heterochromatin, leading to a variegating phenotype. Previous studies identified the transposable element 1360 as a target for heterochromatin formation. We use transgene reporters with either one or four copies of 1360 to determine if increasing local repeat density can alter the fraction of the genome supporting heterochromatin formation. We find that including 1360 in the reporter increases the frequency with which variegating phenotypes are observed. This increase is due to a greater recovery of insertions at the telomere-associated sequences (∼50% of variegating inserts). In contrast to variegating insertions elsewhere, the phenotype of telomere-associated sequence insertions is largely independent of the presence of 1360 in the reporter. We find that variegating and fully expressed transgenes are located in different types of chromatin and that variegating reporters in the telomere-associated sequences differ from those in pericentric heterochromatin. Indeed, chromatin marks at the transgene insertion site can be used to predict the eye phenotype. Our analysis reveals that increasing the local repeat density (via the transgene reporter) does not enlarge the fraction of the genome supporting heterochromatin formation. Rather, additional copies of 1360 appear to target the reporter to the telomere-associated sequences with greater efficiency, thus leading to an increased recovery of variegating insertions.
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11
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Singh AK, Lakhotia SC. The hnRNP A1 homolog Hrb87F/Hrp36 is important for telomere maintenance in Drosophila melanogaster. Chromosoma 2015; 125:373-88. [PMID: 26373285 DOI: 10.1007/s00412-015-0540-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 08/25/2015] [Accepted: 09/07/2015] [Indexed: 10/23/2022]
Abstract
Unlike the telomerase-dependent mammalian telomeres, HeT-A, TART, and TAHRE (HTT) retroposon arrays regulate Drosophila telomere length. Cap prevents telomeric associations (TAs) and telomeric fusions (TFs). Our results suggest important roles of Hrb87F in telomeric HTT array and cap maintenance in Drosophila. All chromosome arms, except 2L, in Df(3R)Hrb87F homozygotes (Hrb87F-null) displayed significantly elongated telomeres with amplified HTT arrays and high TAs, all of which resolved without damage. Presence of FLAG-tagged Hrb87F (FLAG-Hrb87F) on cap and subtelomeric regions following hsFLAG-Hrb87F transgene expression in Df(3R)Hrb87F homozygotes suppressed TAs without affecting telomere length. A normal X-chromosome telomere expanded within five generations in Hrb87F-null background and displayed high TAs, but not when hsFLAG-Hrb87F was co-expressed. Tel (1) /Gaiano line or HP1 loss-of-function mutant-derived expanded telomeres carry Hrb87F on cap and HTT arrays while Hrb87F-null telomeres have HP1 and HOAP on caps and expanded HTT arrays. ISWI, seen only on cap on normal telomeres, was abundant on Hrb87F-null expanded HTT arrays. Extended telomeres derived from Tel (1) (Gaiano) or HP1-null mutation background interact with those from Hrb87F-null, since while the end association frequency was negligible in Df(3R)Hrb87F/+ nuclei, it increased significantly in co-presence of Tel (1) or HP1-null-based expanded telomere/s. Together, these suggest complex interactions between members of the proteome of telomere so that absence of any key member leads to telomere expansion and/or enhanced TAs/TFs. HTT expansion in Hrb87F-null condition is not developmental but a germline event presumably because absence of Hrb87F in germline may deregulate HTT retroposition/replication leading to telomere elongation.
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Affiliation(s)
- Anand K Singh
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India
| | - Subhash C Lakhotia
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India.
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12
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Zimmermann M, Kugler SJ, Schulz A, Nagel AC. Loss of putzig Activity Results in Apoptosis during Wing Imaginal Development in Drosophila. PLoS One 2015; 10:e0124652. [PMID: 25894556 PMCID: PMC4403878 DOI: 10.1371/journal.pone.0124652] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/17/2015] [Indexed: 12/22/2022] Open
Abstract
The Drosophila gene putzig (pzg) encodes a nuclear protein that is an integral component of the Trf2/Dref complex involved in the transcription of proliferation-related genes. Moreover, Pzg is found in a complex together with the nucleosome remodeling factor NURF, where it promotes Notch target gene activation. Here we show that downregulation of pzg activity in the developing wing imaginal discs induces an apoptotic response, accompanied by the induction of the pro-apoptotic gene reaper, repression of Drosophila inhibitor of apoptosis protein accumulation and the activation of the caspases Drice, Caspase3 and Dcp1. As a further consequence ‘Apoptosis induced Proliferation’ (AiP) and ‘Apoptosis induced Apoptosis’ (AiA) are triggered. As expected, the activity of the stress kinase Jun N-terminal kinase (JNK), proposed to mediate both processes, is ectopically induced in response to pzg loss. In addition, the expression of the mitogen wingless (wg) but not of decapentaplegic (dpp) is observed. We present evidence that downregulation of Notch activates Dcp1 caspase and JNK signaling, however, neither induces ectopic wg nor dpp expression. In contrast, the consequences of Dref-RNAi were largely indistinguishable from pzg-RNAi with regard to apoptosis induction. Moreover, overexpression of Dref ameliorated the downregulation of pzg compatible with the notion that the two are required together to maintain cell and tissue homeostasis in Drosophila.
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Affiliation(s)
- Mirjam Zimmermann
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Sabrina J. Kugler
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Adriana Schulz
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
| | - Anja C. Nagel
- Institute of Genetics, University of Hohenheim, 70599 Stuttgart, Germany
- * E-mail:
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13
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Nordman JT, Kozhevnikova EN, Verrijzer CP, Pindyurin AV, Andreyeva EN, Shloma VV, Zhimulev IF, Orr-Weaver TL. DNA copy-number control through inhibition of replication fork progression. Cell Rep 2014; 9:841-9. [PMID: 25437540 DOI: 10.1016/j.celrep.2014.10.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 08/29/2014] [Accepted: 09/30/2014] [Indexed: 01/15/2023] Open
Abstract
Proper control of DNA replication is essential to ensure faithful transmission of genetic material and prevent chromosomal aberrations that can drive cancer progression and developmental disorders. DNA replication is regulated primarily at the level of initiation and is under strict cell-cycle regulation. Importantly, DNA replication is highly influenced by developmental cues. In Drosophila, specific regions of the genome are repressed for DNA replication during differentiation by the SNF2 domain-containing protein SUUR through an unknown mechanism. We demonstrate that SUUR is recruited to active replication forks and mediates the repression of DNA replication by directly inhibiting replication fork progression instead of functioning as a replication fork barrier. Mass spectrometry identification of SUUR-associated proteins identified the replicative helicase member CDC45 as a SUUR-associated protein, supporting a role for SUUR directly at replication forks. Our results reveal that control of eukaryotic DNA copy number can occur through the inhibition of replication fork progression.
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Affiliation(s)
- Jared T Nordman
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Elena N Kozhevnikova
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands; Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 10, Novosibirsk 630090, Russia
| | - C Peter Verrijzer
- Erasmus University Medical Centre, P.O. Box 1738, 3000 DR Rotterdam, the Netherlands
| | - Alexey V Pindyurin
- Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Victor V Shloma
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 8/2, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russia
| | - Terry L Orr-Weaver
- Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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14
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Abstract
Drosophila telomeres are maintained as a result of transpositions of specialized telomeric retrotransposons. The abundance of telomeric retroelement transcripts, as well as the frequency of their transpositions onto the chromosome ends, is controlled by a PIWI-interacting RNA (piRNA) pathway. In our recent report, we demonstrate strong evidence of piRNA-mediated transcriptional silencing of telomeric repeats in the Drosophila germline. Telomerase-generated repeats serve as a platform for recruiting specialized DNA-binding proteins which are involved in chromosome end protection and in the telomere length control. No specific proteins are known to bind to heterogeneous long sequences of the Drosophila telomeric retrotransposons. The importance of the piRNA silencing mechanism in the formation of telomeric chromatin along the region of the retrotransposon array will be discussed. We propose that Drosophila telomeric retrotransposon HeT-A serves as a template for the piRNA-mediated assembly of the specific protein complex, which is functionally similar to the recruiting of the DNA-binding telomeric proteins by the telomerase-generated repeats. The role of the piRNA pathway components in the assembly of the telomere capping complex was recently unveiled. Taken together, these data elucidate the importance of the piRNA pathway in the Drosophila telomere homeostasis.
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Affiliation(s)
- Sergey Shpiz
- Institute of Molecular Genetics; Russian Academy of Sciences; Moscow, Russia
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15
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Satyaki PRV, Cuykendall TN, Wei KHC, Brideau NJ, Kwak H, Aruna S, Ferree PM, Ji S, Barbash DA. The Hmr and Lhr hybrid incompatibility genes suppress a broad range of heterochromatic repeats. PLoS Genet 2014; 10:e1004240. [PMID: 24651406 PMCID: PMC3961192 DOI: 10.1371/journal.pgen.1004240] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/30/2014] [Indexed: 11/19/2022] Open
Abstract
Hybrid incompatibilities (HIs) cause reproductive isolation between species and thus contribute to speciation. Several HI genes encode adaptively evolving proteins that localize to or interact with heterochromatin, suggesting that HIs may result from co-evolution with rapidly evolving heterochromatic DNA. Little is known, however, about the intraspecific function of these HI genes, the specific sequences they interact with, or the evolutionary forces that drive their divergence. The genes Hmr and Lhr genetically interact to cause hybrid lethality between Drosophila melanogaster and D. simulans, yet mutations in both genes are viable. Here, we report that Hmr and Lhr encode proteins that form a heterochromatic complex with Heterochromatin Protein 1 (HP1a). Using RNA-Seq analyses we discovered that Hmr and Lhr are required to repress transcripts from satellite DNAs and many families of transposable elements (TEs). By comparing Hmr and Lhr function between D. melanogaster and D. simulans we identify several satellite DNAs and TEs that are differentially regulated between the species. Hmr and Lhr mutations also cause massive overexpression of telomeric TEs and significant telomere lengthening. Hmr and Lhr therefore regulate three types of heterochromatic sequences that are responsible for the significant differences in genome size and structure between D. melanogaster and D. simulans and have high potential to cause genetic conflicts with host fitness. We further find that many TEs are overexpressed in hybrids but that those specifically mis-expressed in lethal hybrids do not closely correlate with Hmr function. Our results therefore argue that adaptive divergence of heterochromatin proteins in response to repetitive DNAs is an important underlying force driving the evolution of hybrid incompatibility genes, but that hybrid lethality likely results from novel epistatic genetic interactions that are distinct to the hybrid background. Sister species capable of mating often produce hybrids that are sterile or die during development. This reproductive isolation is caused by incompatibilities between the two sister species' genomes. Some hybrid incompatibilities involve genes that encode rapidly evolving proteins that localize to heterochromatin. Heterochromatin is largely made up of highly repetitive transposable elements and satellite DNAs. It has been hypothesized that rapid changes in heterochromatic DNA drives the changes in these HI genes and thus the evolution of reproductive isolation. In support of this model, we show that two rapidly evolving HI proteins, Lhr and Hmr, which reproductively isolate the fruit fly sister species D. melanogaster and D. simulans, repress transposable elements and satellite DNAs. These proteins also help regulate the length of the atypical Drosophila telomeres, which are themselves made of domesticated transposable elements. Our data suggest that these proteins are part of the adaptive machinery that allows the host to respond to changes and increases in heterochromatin and to maintain the activity of genes located within or adjacent to heterochromatin.
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Affiliation(s)
- P. R. V. Satyaki
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Tawny N. Cuykendall
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Kevin H-C. Wei
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Nicholas J. Brideau
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Hojoong Kwak
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - S. Aruna
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Patrick M. Ferree
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Shuqing Ji
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Daniel A. Barbash
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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16
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Silva-Sousa R, Casacuberta E. The JIL-1 kinase affects telomere expression in the different telomere domains of Drosophila. PLoS One 2013; 8:e81543. [PMID: 24244743 DOI: 10.1371/journal.pone.0081543] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/23/2013] [Indexed: 11/17/2022] Open
Abstract
In Drosophila, the non-LTR retrotransposons HeT-A, TART and TAHRE build a head-to-tail array of repetitions that constitute the telomere domain by targeted transposition at the end of the chromosome whenever needed. As a consequence, Drosophila telomeres have the peculiarity to harbor the genes in charge of telomere elongation. Understanding telomere expression is important in Drosophila since telomere homeostasis depends in part on the expression of this genomic compartment. We have recently shown that the essential kinase JIL-1 is the first positive regulator of the telomere retrotransposons. JIL-1 mediates chromatin changes at the promoter of the HeT-A retrotransposon that are necessary to obtain wild type levels of expression of these telomere transposons. With the present study, we show how JIL-1 is also needed for the expression of a reporter gene embedded in the telomere domain. Our analysis, using different reporter lines from the telomere and subtelomere domains of different chromosomes, indicates that JIL-1 likely acts protecting the telomere domain from the spreading of repressive chromatin from the adjacent subtelomere domain. Moreover, the analysis of the 4R telomere suggests a slightly different chromatin structure at this telomere. In summary, our results strongly suggest that the action of JIL-1 depends on which telomere domain, which chromosome and which promoter is embedded in the telomere chromatin.
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Affiliation(s)
- Rute Silva-Sousa
- Institute of Evolutionary Biology, IBE (CSIC-UPF), Barcelona, Spain
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17
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Silva-Sousa R, Varela MD, Casacuberta E. The Putzig partners DREF, TRF2 and KEN are involved in the regulation of the Drosophila telomere retrotransposons, HeT-A and TART. Mob DNA 2013; 4:18. [PMID: 23822164 PMCID: PMC3726405 DOI: 10.1186/1759-8753-4-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 06/28/2013] [Indexed: 12/26/2022] Open
Abstract
Background Telomere maintenance in Drosophila relies on the targeted transposition of three very special non-LTR retrotransposons, HeT-A, TART, and TAHRE (HTT). The sequences of the retrotransposon array build up the telomere chromatin in this organism. We have recently reported the role of the chromosomal protein Putzig/Z4 in maintaining a proper chromatin structure at the telomere domain of Drosophila. Because the Putzig protein has been found in different cellular complexes related with cell proliferation, development, and immunity, we decided to investigate whether the previously described Putzig partners, DREF/TRF2 and KEN, could also be involved in the telomere function in this organism. Results We have found that mutant alleles for Dref/Trf2 and Ken show alterations in HeT-A and TART expression, suggesting a possible role of these protein complexes in the regulation of the telomere retrotransposons. In agreement, both HeT-A and TART contain the specific DNA binding sequences for the DREF and the KEN protein proteins. Conclusions We have identified three new negative regulators involved in the control of the expression of the telomeric retrotransposons, Dref, Trf2, and Ken. Our results offer some clues on which other chromatin-related proteins might be involved in telomere regulation and retrotransposon control.
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Affiliation(s)
- Rute Silva-Sousa
- Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Passeig de la Barceloneta, 37-49, Barcelona 08003, Spain.
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18
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Effete, a Drosophila chromatin-associated ubiquitin-conjugating enzyme that affects telomeric and heterochromatic position effect variegation. Genetics 2013; 195:147-58. [PMID: 23821599 DOI: 10.1534/genetics.113.153320] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Drosophila telomeres are elongated by the transposition of telomere-specific retrotransposons rather than telomerase activity. Proximal to the terminal transposon array, Drosophila chromosomes contain several kilobases of a complex satellite DNA termed telomere-associated sequences (TASs). Reporter genes inserted into or next to the TAS are silenced through a mechanism called telomere position effect (TPE). TPE is reminiscent of the position effect variegation (PEV) induced by Drosophila constitutive heterochromatin. However, most genes that modulate PEV have no effect on TPE, and systematic searches for TPE modifiers have so far identified only a few dominant suppressors. Surprisingly, only a few of the genes required to prevent telomere fusion have been tested for their effect on TPE. Here, we show that with the exception of the effete (eff; also called UbcD1) mutant alleles, none of the tested mutations at the other telomere fusion genes affects TPE. We also found that mutations in eff, which encodes a class I ubiquitin-conjugating enzyme, act as suppressors of PEV. Thus, eff is one of the rare genes that can modulate both TPE and PEV. Immunolocalization experiments showed that Eff is a major constituent of polytene chromosomes. Eff is enriched at several euchromatic bands and interbands, the TAS regions, and the chromocenter. Our results suggest that Eff associates with different types of chromatin affecting their abilities to regulate gene expression.
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19
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Giraud-Panis MJ, Pisano S, Benarroch-Popivker D, Pei B, Le Du MH, Gilson E. One identity or more for telomeres? Front Oncol 2013; 3:48. [PMID: 23509004 PMCID: PMC3598436 DOI: 10.3389/fonc.2013.00048] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 02/23/2013] [Indexed: 12/19/2022] Open
Abstract
A major issue in telomere research is to understand how the integrity of chromosome ends is controlled. The fact that different types of nucleoprotein complexes have been described at the telomeres of different organisms raises the question of whether they have in common a structural identity that explains their role in chromosome protection. We will review here how telomeric nucleoprotein complexes are structured, comparing different organisms and trying to link these structures to telomere biology. It emerges that telomeres are formed by a complex and specific network of interactions between DNA, RNA, and proteins. The fact that these interactions and associated activities are reinforcing each other might help to guarantee the robustness of telomeric functions across the cell cycle and in the event of cellular perturbations. We will also discuss the recent notion that telomeres have evolved specific systems to overcome the DNA topological stress generated during their replication and transcription. This will lead to revisit the way we envisage the functioning of telomeric complexes since the regulation of topology is central to DNA stability, replication, recombination, and transcription as well as to chromosome higher-order organization.
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Affiliation(s)
- Marie-Josèphe Giraud-Panis
- Faculté de Médecine de Nice, Université de Nice-Sophia Antipolis, Institute for Research on Cancer and Aging Nice, UMR 7284 CNRS, U1081 INSERM Nice, France
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20
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Silva-Sousa R, López-Panadès E, Piñeyro D, Casacuberta E. The chromosomal proteins JIL-1 and Z4/Putzig regulate the telomeric chromatin in Drosophila melanogaster. PLoS Genet 2012; 8:e1003153. [PMID: 23271984 PMCID: PMC3521665 DOI: 10.1371/journal.pgen.1003153] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 10/24/2012] [Indexed: 12/28/2022] Open
Abstract
Drosophila telomere maintenance depends on the transposition of the specialized retrotransposons HeT-A, TART, and TAHRE. Controlling the activation and silencing of these elements is crucial for a precise telomere function without compromising genomic integrity. Here we describe two chromosomal proteins, JIL-1 and Z4 (also known as Putzig), which are necessary for establishing a fine-tuned regulation of the transcription of the major component of Drosophila telomeres, the HeT-A retrotransposon, thus guaranteeing genome stability. We found that mutant alleles of JIL-1 have decreased HeT-A transcription, putting forward this kinase as the first positive regulator of telomere transcription in Drosophila described to date. We describe how the decrease in HeT-A transcription in JIL-1 alleles correlates with an increase in silencing chromatin marks such as H3K9me3 and HP1a at the HeT-A promoter. Moreover, we have detected that Z4 mutant alleles show moderate telomere instability, suggesting an important role of the JIL-1-Z4 complex in establishing and maintaining an appropriate chromatin environment at Drosophila telomeres. Interestingly, we have detected a biochemical interaction between Z4 and the HeT-A Gag protein, which could explain how the Z4-JIL-1 complex is targeted to the telomeres. Accordingly, we demonstrate that a phenotype of telomere instability similar to that observed for Z4 mutant alleles is found when the gene that encodes the HeT-A Gag protein is knocked down. We propose a model to explain the observed transcriptional and stability changes in relation to other heterochromatin components characteristic of Drosophila telomeres, such as HP1a.
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Affiliation(s)
- Rute Silva-Sousa
- Institute of Evolutionary Biology, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
| | - Elisenda López-Panadès
- Institute of Evolutionary Biology, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
| | - David Piñeyro
- Institute of Evolutionary Biology, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
| | - Elena Casacuberta
- Institute of Evolutionary Biology, Institut de Biologia Evolutiva (CSIC-UPF), Barcelona, Spain
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Takács S, Biessmann H, Reddy HM, Mason JM, Török T. Protein interactions on telomeric retrotransposons in Drosophila. Int J Biol Sci 2012; 8:1055-61. [PMID: 22949888 PMCID: PMC3432853 DOI: 10.7150/ijbs.4460] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/04/2012] [Indexed: 12/02/2022] Open
Abstract
Telomere length in Drosophila is maintained by targeted transposition of three non-LTR retrotransposons: HeT-A, TART and TAHRE (HTT), but understanding the regulation of this process is hindered by our poor knowledge of HTT associated proteins. We have identified new protein components of the HTT array: Chromator (Chro), the TRF2/DREF complex and the sumoylation machinery. Chro was localized on telomeric HTT arrays by immunostaining, where it may interact with Prod directly, as indicated by yeast two-hybrid interaction, co-IP, and colocalization on polytene chromosomes. The TRF2/DREF complex may promote the open structure of HTT chromatin. The protein interactions controlling HTT chromatin structure and telomere length may be modulated by sumoylation.
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Affiliation(s)
- Sándor Takács
- Department of Genetics, University of Szeged, H-6701 Szeged, Hungary
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22
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Ectopic assembly of heterochromatin in Drosophila melanogaster triggered by transposable elements. Proc Natl Acad Sci U S A 2012; 109:14104-9. [PMID: 22891327 DOI: 10.1073/pnas.1207036109] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
A persistent question in biology is how cis-acting sequence elements influence trans-acting factors and the local chromatin environment to modulate gene expression. We reported previously that the DNA transposon 1360 can enhance silencing of a reporter in a heterochromatic domain of Drosophila melanogaster. We have now generated a collection of variegating phiC31 landing-pad insertion lines containing 1360 and a heat-shock protein 70 (hsp70)-driven white reporter to explore the mechanism of 1360-sensitive silencing. Many 1360-sensitive sites were identified, some in apparently euchromatic domains, although all are close to heterochromatic masses. One such site (line 1198; insertion near the base of chromosome arm 2L) has been investigated in detail. ChIP analysis shows 1360-dependent Heterochromatin Protein 1a (HP1a) accumulation at this otherwise euchromatic site. The phiC31 landing pad system allows different 1360 constructs to be swapped with the full-length element at the same genomic site to identify the sequences that mediate 1360-sensitive silencing. Short deletions over sites with homology to PIWI-interacting RNAs (piRNAs) are sufficient to compromise 1360-sensitive silencing. Similar results were obtained on replacing 1360 with Invader4 (a retrotransposon), suggesting that this phenomenon likely applies to a broader set of transposable elements. Our results suggest a model in which piRNA sequence elements behave as cis-acting targets for heterochromatin assembly, likely in the early embryo, where piRNA pathway components are abundant, with the heterochromatic state subsequently propagated by chromatin modifiers present in somatic tissue.
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23
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Protein landscape at Drosophila melanogaster telomere-associated sequence repeats. Mol Cell Biol 2012; 32:2170-82. [PMID: 22493064 DOI: 10.1128/mcb.00010-12] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The specific set of proteins bound at each genomic locus contributes decisively to regulatory processes and to the identity of a cell. Understanding of the function of a particular locus requires the knowledge of what factors interact with that locus and how the protein composition changes in different cell types or during the response to internal and external signals. Proteomic analysis of isolated chromatin segments (PICh) was developed as a tool to target, purify, and identify proteins associated with a defined locus and was shown to allow the purification of human telomeric chromatin. Here we have developed this method to identify proteins that interact with the Drosophila telomere-associated sequence (TAS) repeats. Several of the purified factors were validated as novel TAS-bound proteins by chromatin immunoprecipitation, and the Brahma complex was confirmed as a dominant modifier of telomeric position effect through the use of a genetic test. These results offer information on the efficacy of applying the PICh protocol to loci with sequence more complex than that found at human telomeres and identify proteins that bind to the TAS repeats, which might contribute to TAS biology and chromatin silencing.
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A high-resolution whole-genome map of key chromatin modifications in the adult Drosophila melanogaster. PLoS Genet 2011; 7:e1002380. [PMID: 22194694 PMCID: PMC3240582 DOI: 10.1371/journal.pgen.1002380] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 09/27/2011] [Indexed: 01/21/2023] Open
Abstract
Epigenetic research has been focused on cell-type-specific regulation; less is known about common features of epigenetic programming shared by diverse cell types within an organism. Here, we report a modified method for chromatin immunoprecipitation and deep sequencing (ChIP–Seq) and its use to construct a high-resolution map of the Drosophila melanogaster key histone marks, heterochromatin protein 1a (HP1a) and RNA polymerase II (polII). These factors are mapped at 50-bp resolution genome-wide and at 5-bp resolution for regulatory sequences of genes, which reveals fundamental features of chromatin modification landscape shared by major adult Drosophila cell types: the enrichment of both heterochromatic and euchromatic marks in transposons and repetitive sequences, the accumulation of HP1a at transcription start sites with stalled polII, the signatures of histone code and polII level/position around the transcriptional start sites that predict both the mRNA level and functionality of genes, and the enrichment of elongating polII within exons at splicing junctions. These features, likely conserved among diverse epigenomes, reveal general strategies for chromatin modifications. Just as a genome sequence map is indispensible to genetic studies, an epigenome map is crucial for epigenetic research. This is especially true for a sophisticated genetic model such as Drosophila melanogaster, where the wealth of information on genetics and developmental biology awaits systematic epigenetic interpretation on a whole-genome scale. In this manuscript, we report a high-resolution map of key chromatin modifications in the Drosophila genome constructed by the ChIP–Seq approach. This map is derived from all cell types in the adult Drosophila weighted by their natural abundance. It contains key histone marks, HP1a and RNA polymerase II, mapped at 50-bp resolution throughout the genome and at 5-bp resolution for regulatory sequences of genes. It reveals striking features of chromatin modification and transcriptional regulation shared by major adult Drosophila cell types. We anticipate that this map and the salient chromatin modification landscapes revealed by this map should have broad utility to the fields of epigenetics, developmental biology, and stem cell biology.
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Shpiz S, Olovnikov I, Sergeeva A, Lavrov S, Abramov Y, Savitsky M, Kalmykova A. Mechanism of the piRNA-mediated silencing of Drosophila telomeric retrotransposons. Nucleic Acids Res 2011; 39:8703-11. [PMID: 21764773 PMCID: PMC3203600 DOI: 10.1093/nar/gkr552] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In the Drosophila germline, retrotransposons are silenced by the PIWI-interacting RNA (piRNA) pathway. Telomeric retroelements HeT-A, TART and TAHRE, which are involved in telomere maintenance in Drosophila, are also the targets of piRNA-mediated silencing. We have demonstrated that expression of reporter genes driven by the HeT-A promoter is under the control of the piRNA silencing pathway independent of the transgene location. In order to test directly whether piRNAs affect the transcriptional state of retrotransposons we performed a nuclear run-on (NRO) assay and revealed increased density of the active RNA polymerase complexes at the sequences of endogenous HeT-A and TART telomeric retroelements as well as HeT-A-containing constructs in the ovaries of spn-E mutants and in flies with piwi knockdown. This strongly correlates with enrichment of two histone H3 modifications (dimethylation of lysine 79 and dimethylation of lysine 4), which mark transcriptionally active chromatin, on the same sequences in the piRNA pathway mutants. spn-E mutation and piwi knockdown results in transcriptional activation of some other non-telomeric retrotransposons in the ovaries, such as I-element and HMS Beagle. Therefore piRNA-mediated transcriptional mode of silencing is involved in the control of retrotransposon expression in the Drosophila germline.
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Affiliation(s)
- Sergey Shpiz
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russia
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Burgio G, Cipressa F, Ingrassia AMR, Cenci G, Corona DFV. The histone deacetylase Rpd3 regulates the heterochromatin structure of Drosophila telomeres. J Cell Sci 2011; 124:2041-8. [DOI: 10.1242/jcs.078261] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Telomeres are specialized structures at the end of eukaryotic chromosomes that are required to preserve genome integrity, chromosome stability and nuclear architecture. Telomere maintenance and function are established epigenetically in several eukaryotes. However, the exact chromatin enzymatic modifications regulating telomere homeostasis are poorly understood. In Drosophila melanogaster, telomere length and stability are maintained through the retrotransposition of specialized telomeric sequences and by the specific loading of protecting capping proteins, respectively. Here, we show that the loss of the essential and evolutionarily conserved histone deacetylase Rpd3, the homolog of mammalian HDAC1, causes aberrant telomeric fusions on polytene chromosome ends. Remarkably, these telomere fusion defects are associated with a marked decrease of histone H4 acetylation, as well as an accumulation of heterochromatic epigenetic marks at telomeres, including histone H3K9 trimethylation and the heterochromatic protein HP2. Our work suggests that Drosophila telomere structure is epigenetically regulated by the histone deacetylase Rpd3.
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Affiliation(s)
- Giosalba Burgio
- Istituto Telethon Dulbecco, c/o STEMBIO, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
- Università degli Studi di Palermo–Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari – Sezione di Biologia Cellulare, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
| | - Francesca Cipressa
- Dipartimento di Biologia di Base ed Applicata, Università dell'Aquila, 67100 Coppito, L'Aquila, Italy
| | - Antonia Maria Rita Ingrassia
- Istituto Telethon Dulbecco, c/o STEMBIO, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
- Università degli Studi di Palermo–Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari – Sezione di Biologia Cellulare, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
| | - Giovanni Cenci
- Dipartimento di Biologia di Base ed Applicata, Università dell'Aquila, 67100 Coppito, L'Aquila, Italy
| | - Davide F. V. Corona
- Istituto Telethon Dulbecco, c/o STEMBIO, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
- Università degli Studi di Palermo–Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari – Sezione di Biologia Cellulare, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy
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Todeschini AL, Teysset L, Delmarre V, Ronsseray S. The epigenetic trans-silencing effect in Drosophila involves maternally-transmitted small RNAs whose production depends on the piRNA pathway and HP1. PLoS One 2010; 5:e11032. [PMID: 20559422 PMCID: PMC2885412 DOI: 10.1371/journal.pone.0011032] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Accepted: 05/21/2010] [Indexed: 11/18/2022] Open
Abstract
Background The study of P transposable element repression in Drosophila melanogaster led to the discovery of the Trans-Silencing Effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin (Telomeric Associated Sequences, “TAS”) has the capacity to repress in trans, in the female germline, a homologous P-lacZ transgene located in euchromatin. Phenotypic and genetic analysis have shown that TSE exhibits variegation in ovaries, displays a maternal effect as well as epigenetic transmission through meiosis and involves heterochromatin (including HP1) and RNA silencing. Principal Findings Here, we show that mutations in squash and zucchini, which are involved in the piwi-interacting RNA (piRNA) silencing pathway, strongly affect TSE. In addition, we carried out a molecular analysis of TSE and show that silencing is correlated to the accumulation of lacZ small RNAs in ovaries. Finally, we show that the production of these small RNAs is sensitive to mutations affecting squash and zucchini, as well as to the dose of HP1. Conclusions and Significance Thus, our results indicate that the TSE represents a bona fide piRNA-based repression. In addition, the sensitivity of TSE to HP1 dose suggests that in Drosophila, as previously shown in Schizosaccharomyces pombe, a RNA silencing pathway can depend on heterochromatin components.
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Affiliation(s)
- Anne-Laure Todeschini
- Laboratoire Biologie du Développement, UMR7622, CNRS-Université Pierre et Marie Curie, Paris, France
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Smith MB, Weiler KS. Drosophila D1 overexpression induces ectopic pairing of polytene chromosomes and is deleterious to development. Chromosoma 2010; 119:287-309. [PMID: 20127347 DOI: 10.1007/s00412-010-0257-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Revised: 12/24/2009] [Accepted: 01/06/2010] [Indexed: 11/30/2022]
Abstract
Eukaryotic genomes function in the context of chromatin, but the roles of most nonhistone chromosomal proteins are far from understood. The D1 protein of Drosophila is an example of a chromosomal protein that has been fairly well characterized biochemically, but has nevertheless eluded functional description. To this end, we have undertaken a gain-of-function genetical analysis of D1, utilizing the GAL4-UAS system. We determined that ubiquitous overexpression of D1 using the Act5C- or tubP-GAL4 drivers was lethal to the organism during larval growth. We also ectopically expressed D1 in a tissue-limited manner using other GAL4 drivers. In general, ectopic D1 was observed to inhibit differentiation and/or development. We observed effects on pattern formation of the adult eye, bristle morphogenesis, and spermatogenesis. These phenotypes may be the consequence of misregulation of D1 target genes. A surprising result was obtained when D1 was overexpressed in the third instar salivary gland. The polytene chromosomes exhibited numerous ectopic associations such that spreading of the chromosome arms was precluded. We mapped the sites of ectopic pairing along the polytene chromosome arms, and found a correlation with sites of intercalary heterochromatin. We speculate that these sites comprise the natural targets of D1 protein activity and that D1 is involved in the ectopic pairing observed for wild-type chromosomes. Together, our data suggest that D1 may influence multiple biochemical activities within the nucleus.
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Affiliation(s)
- Marissa B Smith
- Department of Biology, West Virginia University, Morgantown, WV 26506, USA
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29
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Andreyenkova NG, Kokoza EB, Semeshin VF, Belyaeva ES, Demakov SA, Pindyurin AV, Andreyeva EN, Volkova EI, Zhimulev IF. Localization and characteristics of DNA underreplication zone in the 75C region of intercalary heterochromatin in Drosophila melanogaster polytene chromosomes. Chromosoma 2009; 118:747-61. [PMID: 19685068 DOI: 10.1007/s00412-009-0232-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Revised: 07/16/2009] [Accepted: 07/22/2009] [Indexed: 10/20/2022]
Abstract
In Drosophila polytene chromosomes, regions of intercalary heterochromatin are scattered throughout the euchromatic arms. Here, we present data on the first fine analysis of the individual intercalary heterochromatin region, 75C1-2, located in the 3L chromosome. By using electron microscopy, we demonstrated that this region appears as three closely adjacent condensed bands. Mapping of the region on the physical map by means of the chromosomal rearrangements with known breakpoints showed that the length of the region is about 445 kb. Although it seems that the SUUR protein binds to the whole 75C1-2 region, the proximal part of the region is fully polytenized, so the DNA underreplication zone is asymmetric and located in the distal half of the region. Finally, we speculate that intercalary heterochromatin regions of Drosophila polytene chromosomes are organized into three different types with respect to the localization of the underreplication zone.
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Affiliation(s)
- Natalya G Andreyenkova
- Department of Molecular and Cellular Biology, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
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30
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A 'higher order' of telomere regulation: telomere heterochromatin and telomeric RNAs. EMBO J 2009; 28:2323-36. [PMID: 19629032 PMCID: PMC2722253 DOI: 10.1038/emboj.2009.197] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 06/24/2009] [Indexed: 01/20/2023] Open
Abstract
Protection of chromosome ends from DNA repair and degradation activities is mediated by specialized protein complexes bound to telomere repeats. Recently, it has become apparent that epigenetic regulation of the telomric chromatin template critically impacts on telomere function and telomere-length homeostasis from yeast to man. Across all species, telomeric repeats as well as the adjacent subtelomeric regions carry features of repressive chromatin. Disruption of this silent chromatin environment results in loss of telomere-length control and increased telomere recombination. In turn, progressive telomere loss reduces chromatin compaction at telomeric and subtelomeric domains. The recent discoveries of telomere chromatin regulation during early mammalian development, as well as during nuclear reprogramming, further highlights a central role of telomere chromatin changes in ontogenesis. In addition, telomeres were recently shown to generate long, non-coding RNAs that remain associated to telomeric chromatin and will provide new insights into the regulation of telomere length and telomere chromatin. In this review, we will discuss the epigenetic regulation of telomeres across species, with special emphasis on mammalian telomeres. We will also discuss the links between epigenetic alterations at mammalian telomeres and telomere-associated diseases.
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31
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Umbrea, a chromo shadow domain protein in Drosophila melanogaster heterochromatin, interacts with Hip, HP1 and HOAP. Chromosome Res 2009; 17:19-36. [PMID: 19190990 PMCID: PMC2758380 DOI: 10.1007/s10577-008-9002-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 10/09/2008] [Accepted: 10/09/2008] [Indexed: 01/10/2023]
Abstract
Drosophila melanogaster HP1-interacting protein (Hip) is a partner of heterochromatin protein 1 (HP1) and is involved in transcriptional epigenetic gene silencing and the formation of heterochromatin. Recently, it has been shown that HP1 interacts with the telomere capping factor HP1/ORC (origin recognition complex)-associated protein (HOAP). Telomeres, complexes of DNA and proteins at the end of linear chromosomes, have been recognized to protect chromosome ends from degradation and fusion events. Both proteins are located at telomeres and prevent telomere fusions. Here, we report the identification and characterization of the Hip-interacting protein Umbrea. We found that Umbrea interacts directly with Hip, HP1 and HOAP in vitro. Umbrea, Hip and HP1 are partners in a protein complex in vivo and completely co-localize in the pericentric heterochromatin and at telomeres. Using a Gal4-induced RNA interference system, we found that after depletion of Umbrea in salivary gland polytene chromosomes, they exhibit multiple telomeric fusions. Taken together, these results suggest that Umbrea cooperates with Hip, HP1 and HOAP and plays a functional role in mediating normal telomere behaviour in Drosophila.
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32
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Capkova Frydrychova R, Biessmann H, Mason JM. Regulation of telomere length in Drosophila. Cytogenet Genome Res 2009; 122:356-64. [PMID: 19188706 DOI: 10.1159/000167823] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2008] [Indexed: 01/20/2023] Open
Abstract
Telomeres in all organisms must perform the same vital functions to ensure cell viability: to act as a protective chromosome cap that distinguishes natural chromosome ends from DNA double strand breaks, and to balance the loss of DNA from the chromosome end due to incomplete DNA replication. Most eukaryotes rely on a specialized reverse transcriptase, telomerase, to generate short repeats at the chromosome end to maintain chromosome length. Drosophila, however, uses retrotransposons that target telomeres. Transposition of these elements may be controlled by small RNAs and spreading of silent chromatin from the telomere associated sequence, both of which limit the retrotransposon expression level. Proteins binding to the retrotransposon array, such as HP1 and PROD, may also modulate transcription. It is not clear however, that simply increasing transcript levels of the telomeric retrotransposons is sufficient to increase transposition. The chromosome cap may control the ability of the telomere-specific elements to attach to chromosome ends. As in other organisms, chromosomes can be elongated by gene conversion. Although the mechanism is not known, HP1, a component of the cap, and the Ku proteins are key components in this pathway.
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Affiliation(s)
- R Capkova Frydrychova
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709-2233, USA
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33
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Doheny JG, Mottus R, Grigliatti TA. Telomeric position effect--a third silencing mechanism in eukaryotes. PLoS One 2008; 3:e3864. [PMID: 19057646 PMCID: PMC2587703 DOI: 10.1371/journal.pone.0003864] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Accepted: 10/20/2008] [Indexed: 12/29/2022] Open
Abstract
Eukaryotic chromosomes terminate in telomeres, complex nucleoprotein structures that are required for chromosome integrity that are implicated in cellular senescence and cancer. The chromatin at the telomere is unique with characteristics of both heterochromatin and euchromatin. The end of the chromosome is capped by a structure that protects the end and is required for maintaining proper chromosome length. Immediately proximal to the cap are the telomere associated satellite-like (TAS) sequences. Genes inserted into the TAS sequences are silenced indicating the chromatin environment is incompatible with transcription. This silencing phenomenon is called telomeric position effect (TPE). Two other silencing mechanisms have been identified in eukaryotes, suppressors position effect variegation [Su(var)s, greater than 30 members] and Polycomb group proteins (PcG, approximately 15 members). We tested a large number of each group for their ability to suppress TPE [Su(TPE)]. Our results showed that only three Su(var)s and only one PcG member are involved in TPE, suggesting silencing in the TAS sequences occurs via a novel silencing mechanism. Since, prior to this study, only five genes have been identified that are Su(TPE)s, we conducted a candidate screen for Su(TPE) in Drosophila by testing point mutations in, and deficiencies for, proteins involved in chromatin metabolism. Screening with point mutations identified seven new Su(TPE)s and the deficiencies identified 19 regions of the Drosophila genome that harbor suppressor mutations. Chromatin immunoprecipitation experiments on a subset of the new Su(TPE)s confirm they act directly on the gene inserted into the telomere. Since the Su(TPE)s do not overlap significantly with either PcGs or Su(var)s, and the candidates were selected because they are involved generally in chromatin metabolism and act at a wide variety of sites within the genome, we propose that the Su(TPE) represent a third, widely used, silencing mechanism in the eukaryotic genome.
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Affiliation(s)
- J. Greg Doheny
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Randy Mottus
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Thomas A. Grigliatti
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
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34
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Telomeric trans-silencing in Drosophila melanogaster: tissue specificity, development and functional interactions between non-homologous telomeres. PLoS One 2008; 3:e3249. [PMID: 18813361 PMCID: PMC2547894 DOI: 10.1371/journal.pone.0003249] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 09/02/2008] [Indexed: 12/03/2022] Open
Abstract
Background The study of P element repression in Drosophila melanogaster led to the discovery of the telomeric Trans-Silencing Effect (TSE), a homology-dependent repression mechanism by which a P-transgene inserted in subtelomeric heterochromatin (Telomeric Associated Sequences, “TAS”) has the capacity to repress in trans, in the female germline, a homologous P-lacZ transgene located in euchromatin. TSE can show variegation in ovaries, displays a maternal effect as well as an epigenetic transmission through meiosis and involves heterochromatin and RNA silencing pathways. Principal Findings Here, we analyze phenotypic and genetic properties of TSE. We report that TSE does not occur in the soma at the adult stage, but appears restricted to the female germline. It is detectable during development at the third instar larvae where it presents the same tissue specificity and maternal effect as in adults. Transgenes located in TAS at the telomeres of the main chromosomes can be silencers which in each case show the maternal effect. Silencers located at non-homologous telomeres functionally interact since they stimulate each other via the maternally-transmitted component. All germinally-expressed euchromatic transgenes tested, located on all major chromosomes, were found to be repressed by a telomeric silencer: thus we detected no TSE escaper. The presence of the euchromatic target transgene is not necessary to establish the maternal inheritance of TSE, responsible for its epigenetic behavior. A single telomeric silencer locus can simultaneously repress two P-lacZ targets located on different chromosomal arms. Conclusions and Significance Therefore TSE appears to be a widespread phenomenon which can involve different telomeres and work across the genome. It can explain the P cytotype establishment by telomeric P elements in natural Drosophila populations.
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35
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Abstract
Telomeric regions in Drosophila are composed of three subdomains. A chromosome cap distinguishes the chromosome end from a DNA double-strand break; an array of retrotransposons, HeT-A, TART, and TAHRE (HTT), maintains telomere length by targeted transposition to chromosome ends; and telomere-associated sequence (TAS), which consists of a mosaic of complex repeated sequences, has been identified as a source of gene silencing. Heterochromatin protein 1 (HP1) and HP1-ORC-associated protein (HOAP) are major protein components of the telomere cap in Drosophila and are required for telomere stability. Besides the chromosome cap, HP1 is also localized along the HTT array and in TAS. Mutants for Su(var)205, the gene encoding HP1, have decreased the HP1 level in the HTT array and increased transcription of individual HeT-A elements. This suggests that HP1 levels directly affect HeT-A activity along the HTT array, although they have little or no effect on transcription of a white reporter gene in the HTT. Chromatin immunoprecipitation to identify other heterochromatic proteins indicates that TAS and the HTT array may be distinct from either heterochromatin or euchromatin.
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36
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Mason JM, Frydrychova RC, Biessmann H. Drosophila telomeres: an exception providing new insights. Bioessays 2008; 30:25-37. [PMID: 18081009 DOI: 10.1002/bies.20688] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Drosophila telomeres comprise DNA sequences that differ dramatically from those of other eukaryotes. Telomere functions, however, are similar to those found in telomerase-based telomeres, even though the underlying mechanisms may differ. Drosophila telomeres use arrays of retrotransposons to maintain chromosome length, while nearly all other eukaryotes rely on telomerase-generated short repeats. Regardless of the DNA sequence, several end-binding proteins are evolutionarily conserved. Away from the end, the Drosophila telomeric and subtelomeric DNA sequences are complexed with unique combinations of proteins that also modulate chromatin structure elsewhere in the genome. Maintaining and regulating the transcriptional activity of the telomeric retrotransposons in Drosophila requires specific chromatin structures and, while telomeric silencing spreads from the terminal repeats in yeast, the source of telomeric silencing in Drosophila is the subterminal arrays. However, the subterminal arrays in both species may be involved in telomere-telomere associations and/or communication.
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Affiliation(s)
- James M Mason
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
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37
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Rong YS. Telomere capping in Drosophila: dealing with chromosome ends that most resemble DNA breaks. Chromosoma 2008; 117:235-42. [PMID: 18193446 DOI: 10.1007/s00412-007-0144-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 11/30/2007] [Accepted: 12/11/2007] [Indexed: 01/03/2023]
Abstract
Telomere caps prevent chromosome ends from being recognized as DNA double-strand breaks (DSBs). Unlike most organisms studied, the telomere-capping function of Drosophila does not require a specific sequence. Without this sequence component, Drosophila telomeres most resemble DNA breaks and, thus, represent a simpler system for the study of telomere capping. I review recent progress in Drosophila telomere studies, and challenge the notion that Drosophila may not be a relevant model for the study of telomere maintenance.
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Affiliation(s)
- Yikang S Rong
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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38
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Krauss V. Glimpses of evolution: heterochromatic histone H3K9 methyltransferases left its marks behind. Genetica 2007; 133:93-106. [PMID: 17710556 DOI: 10.1007/s10709-007-9184-z] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 07/19/2007] [Indexed: 01/01/2023]
Abstract
In eukaryotes, histone methylation is an epigenetic mechanism associated with a variety of functions related to gene regulation or genomic stability. Recently analyzed H3K9 methyltransferases (HMTases) as SUV39H1, Clr4p, DIM-5, Su(var)3-9 or SUVH2 are responsible for the establishment of histone H3 lysine 9 methylation (H3K9me), which is intimately connected with heterochromatinization. In this review, available data will be evaluated concerning (1) the phylogenetic distribution of H3K9me as heterochromatin-specific histone modification and its evolutionary stability in relation to other epigenetic marks, (2) known families of H3K9 methyltransferases, (3) their responsibility for the formation of constitutive heterochromatin and (4) the evolution of Su(var)3-9-like and SUVH-like H3K9 methyltransferases. Compilation and parsimony analysis reveal that histone H3K9 methylation is, next to histone deacetylation, the evolutionary most stable heterochromatic mark, which is established by at least two subfamilies of specialized heterochromatic HMTases in almost all studied eukaryotes.
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Affiliation(s)
- Veiko Krauss
- Department of Genetics, Institute for Biology II, University of Leipzig, Johannisallee 21-23, 04103 Leipzig, Germany.
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39
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Josse T, Teysset L, Todeschini AL, Sidor CM, Anxolabéhère D, Ronsseray S. Telomeric trans-silencing: an epigenetic repression combining RNA silencing and heterochromatin formation. PLoS Genet 2007; 3:1633-43. [PMID: 17941712 PMCID: PMC1976332 DOI: 10.1371/journal.pgen.0030158] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Accepted: 07/31/2007] [Indexed: 12/02/2022] Open
Abstract
The study of P-element repression in Drosophila melanogaster led to the discovery of the telomeric Trans-Silencing Effect (TSE), a repression mechanism by which a transposon or a transgene inserted in subtelomeric heterochromatin (Telomeric Associated Sequence or TAS) has the capacity to repress in trans in the female germline, a homologous transposon, or transgene located in euchromatin. TSE shows variegation among egg chambers in ovaries when silencing is incomplete. Here, we report that TSE displays an epigenetic transmission through meiosis, which involves an extrachromosomal maternally transmitted factor. We show that this silencing is highly sensitive to mutations affecting both heterochromatin formation (Su(var)205 encoding Heterochromatin Protein 1 and Su(var)3–7) and the repeat-associated small interfering RNA (or rasiRNA) silencing pathway (aubergine, homeless, armitage, and piwi). In contrast, TSE is not sensitive to mutations affecting r2d2, which is involved in the small interfering RNA (or siRNA) silencing pathway, nor is it sensitive to a mutation in loquacious, which is involved in the micro RNA (or miRNA) silencing pathway. These results, taken together with the recent discovery of TAS homologous small RNAs associated to PIWI proteins, support the proposition that TSE involves a repeat-associated small interfering RNA pathway linked to heterochromatin formation, which was co-opted by the P element to establish repression of its own transposition after its recent invasion of the D. melanogaster genome. Therefore, the study of TSE provides insight into the genetic properties of a germline-specific small RNA silencing pathway. The genome of the fruitfly was invaded in the last century by a mobile DNA element called the P element. After a transient period of genetic disorders due to P mobility, the P element established a repressive state for its transposition. We have shown that a major component of this repression comes from P copies inserted close to telomeres, the ends of linear chromosomes. One or two P copies inserted in subtelomeric heterochromatin (the DNA region highly compacted by protein complexes) can stabilize around 80 P copies. This finding allowed the discovery of a more general phenomenon called the “Trans-silencing effect” in which a transgene inserted in this subtelomeric heterochromatin represses, in the female germline, a homologous transgene, irrespective of the genetic location of the latter. We show that Trans-silencing requires not only the chromosomal copy of the telomeric silencer, but also a maternally transmitted factor whose influence can persist over generations. We have found that this epigenetic silencing is sensitive to mutations in genes involved in heterochromatin formation and in a recently discovered silencing pathway based on small RNAs. Trans-silencing thus provides a tool for mechanistic analysis of gene repression on the basis of chromatin changes combined with small RNA pathways in the germline.
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Affiliation(s)
- Thibaut Josse
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
| | - Laure Teysset
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
| | - Anne-Laure Todeschini
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
| | - Clara M Sidor
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
| | - Dominique Anxolabéhère
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
| | - Stéphane Ronsseray
- Laboratoire Dynamique du Génome et Evolution, Institut Jacques Monod, Paris, France
- CNRS, UMR7592, Paris, France
- Université Paris 6, Paris, France
- Université Paris 7, Paris, France
- * To whom correspondence should be addressed. E-mail:
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Abstract
The telomeric nucleoprotein complex protects linear chromosome ends from degradation. In contrast to most eukaryotes in which telomerase is responsible for telomere elongation by adding short DNA repeats synthesized using an RNA template, the telomere elongation in Drosophila involves transposition of specialized telomeric retroelements onto chromosome ends. Proteins that bind telomeric and subtelomeric sequences form specific telomeric chromatin, and its components are highly conserved among organisms employing different mechanisms of telomere elongation. This review is focused on the analysis of components of the Drosophila telomeric complex and its comparison with telomeric proteins in telomerase-encoded organisms. Structural and functional analysis of Drosophila telomeres suggests that there are three distinct chromatin regions: protective structure at the very end of chromosome (cap), subtelomeric region which is characterized by condensed chromatin structure, and the terminal retrotransposon array whose expression is under the control of an RNAi (RNA interference)-based mechanism. The link between RNAi and telomeric chromatin formation in germinal tissues is discussed.
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Affiliation(s)
- S G Shpiz
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia
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41
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Frydrychova RC, Biessmann H, Konev AY, Golubovsky MD, Johnson J, Archer TK, Mason JM. Transcriptional activity of the telomeric retrotransposon HeT-A in Drosophila melanogaster is stimulated as a consequence of subterminal deficiencies at homologous and nonhomologous telomeres. Mol Cell Biol 2007; 27:4991-5001. [PMID: 17470550 PMCID: PMC1951507 DOI: 10.1128/mcb.00515-07] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drosophila melanogaster telomeres have two DNA domains: a terminal array of retrotransposons and a subterminal repetitive telomere-associated sequence (TAS), a source of telomere position effect (TPE). We reported previously that deletion of the 2L TAS array leads to dominant suppression of TPE by stimulating in trans expression of a telomeric transgene. Here, we compared the transcript activities of a w transgene inserted between the retrotransposon and TAS arrays at the 2L telomere in genotypes with different lengths of the 2L TAS. In contrast to individuals bearing a wild-type 2L homologue, flies with a TAS deficiency showed a significant increase in the level of telomeric w transcript during development, especially in pupae. Moreover, we identified a read-through w transcript initiated from a retrotransposon promoter in the terminal array. Read-through transcript levels also significantly increased with the presence of a 2L TAS deficiency in trans, indicating a stimulating force of the TAS deficiency on retrotransposon promoter activity. The read-through transcript contributes to total w transcript, although most w transcript originates at the w promoter. While silencing of transgenes in nonhomologous telomeres is suppressed by 2L TAS deficiencies, suggesting a global effect, the overall level of HeT-A transcripts is not increased under similar conditions.
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Affiliation(s)
- Radmila Capkova Frydrychova
- Laboratory of Molecular Genetics, D3-01, P.O. Box 12233, 111 T. W. Alexander Drive, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709-2233, USA
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Török T, Benitez C, Takács S, Biessmann H. The protein encoded by the gene proliferation disrupter (prod) is associated with the telomeric retrotransposon array in Drosophila melanogaster. Chromosoma 2006; 116:185-95. [PMID: 17186256 DOI: 10.1007/s00412-006-0090-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 11/10/2006] [Accepted: 11/13/2006] [Indexed: 01/07/2023]
Abstract
We report in this paper that the PROD protein, encoded by the gene proliferation disrupter (prod), is associated with the telomeric chromatin in Drosophila melanogaster. It binds to a region just upstream of the promoter of the telomere-specific retrotransposon HeT-A, which is located in the long 3'untranslated region of the element near its oligo(A) tail. Reduction of PROD in prod heterozygote flies results in elevated levels of HeT-A RNA in the ovaries, suggesting that PROD functions as a repressor of HeT-A transcriptional activity at the telomeres.
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Affiliation(s)
- Tibor Török
- Department of Genetics and Molecular Biology, University of Szeged, Szeged, Hungary
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Demakova OV, Pokholkova GV, Kolesnikova TD, Demakov SA, Andreyeva EN, Belyaeva ES, Zhimulev IF. The SU(VAR)3-9/HP1 complex differentially regulates the compaction state and degree of underreplication of X chromosome pericentric heterochromatin in Drosophila melanogaster. Genetics 2006; 175:609-20. [PMID: 17151257 PMCID: PMC1800617 DOI: 10.1534/genetics.106.062133] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In polytene chromosomes of Drosophila melanogaster, regions of pericentric heterochromatin coalesce to form a compact chromocenter and are highly underreplicated. Focusing on study of X chromosome heterochromatin, we demonstrate that loss of either SU(VAR)3-9 histone methyltransferase activity or HP1 protein differentially affects the compaction of different pericentric regions. Using a set of inversions breaking X chromosome heterochromatin in the background of the Su(var)3-9 mutations, we show that distal heterochromatin (blocks h26-h29) is the only one within the chromocenter to form a big "puff"-like structure. The "puffed" heterochromatin has not only unique morphology but also very special protein composition as well: (i) it does not bind proteins specific for active chromatin and should therefore be referred to as a pseudopuff and (ii) it strongly associates with heterochromatin-specific proteins SU(VAR)3-7 and SUUR, despite the fact that HP1 and HP2 are depleted particularly from this polytene structure. The pseudopuff completes replication earlier than when it is compacted as heterochromatin, and underreplication of some DNA sequences within the pseudopuff is strongly suppressed. So, we show that pericentric heterochromatin is heterogeneous in its requirement for SU(VAR)3-9 with respect to the establishment of the condensed state, time of replication, and DNA polytenization.
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Affiliation(s)
- Olga V Demakova
- Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk 630090, Russia
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Kolesnikova TD, Andreeva EN, Pindyurin AV, Ananko NG, Belyakin SN, Shloma VV, Yurlova AA, Makunin IV, Pokholkova GV, Volkova EI, Zarutskaya EA, Kokoza EB, Semeshin VF, Belyaeva ES, Zhimulev IF. Contribution of the SuUR gene to the organization of epigenetically repressed regions of Drosophila melanogaster chromosomes. RUSS J GENET+ 2006. [DOI: 10.1134/s1022795406080011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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