1
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Kyriacou E, Heun P. Centromere structure and function: lessons from Drosophila. Genetics 2023; 225:iyad170. [PMID: 37931172 PMCID: PMC10697814 DOI: 10.1093/genetics/iyad170] [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: 06/15/2023] [Accepted: 09/01/2023] [Indexed: 11/08/2023] Open
Abstract
The fruit fly Drosophila melanogaster serves as a powerful model organism for advancing our understanding of biological processes, not just by studying its similarities with other organisms including ourselves but also by investigating its differences to unravel the underlying strategies that evolved to achieve a common goal. This is particularly true for centromeres, specialized genomic regions present on all eukaryotic chromosomes that function as the platform for the assembly of kinetochores. These multiprotein structures play an essential role during cell division by connecting chromosomes to spindle microtubules in mitosis and meiosis to mediate accurate chromosome segregation. Here, we will take a historical perspective on the study of fly centromeres, aiming to highlight not only the important similarities but also the differences identified that contributed to advancing centromere biology. We will discuss the current knowledge on the sequence and chromatin organization of fly centromeres together with advances for identification of centromeric proteins. Then, we will describe both the factors and processes involved in centromere organization and how they work together to provide an epigenetic identity to the centromeric locus. Lastly, we will take an evolutionary point of view of centromeres and briefly discuss current views on centromere drive.
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Affiliation(s)
- Eftychia Kyriacou
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Patrick Heun
- Wellcome Centre of Cell Biology, School of Biological Sciences, University of Edinburgh, EH9 3BF Edinburgh, UK
- Department of Biology, Technische Universität Darmstadt, 64287 Darmstadt, Germany
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2
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Hill HJ, Golic KG. Chromosome Tug of War: Dicentric Chromosomes and the Centromere Strength Hypothesis. Cells 2022; 11:3550. [PMID: 36428979 PMCID: PMC9688759 DOI: 10.3390/cells11223550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 11/09/2022] [Indexed: 11/12/2022] Open
Abstract
It has been 70 years since the concept of varied centromere strengths was introduced based on the behavior of dicentric chromosomes. One of the key conclusions from those early experiments was that some centromeres could pull with sufficient force to break a dicentric chromosome bridge, while others could not. In the ensuing decades there have been numerous studies to characterize strengths of the various components involved, such as the spindle, the kinetochore, and the chromosome itself. We review these various measurements to determine if the conclusions about centromere strength are supported by current evidence, with special attention to characterization of Drosophila melanogaster kinetochores upon which the original conclusions were based.
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Affiliation(s)
| | - Kent G. Golic
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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3
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Zattera ML, Bruschi DP. Transposable Elements as a Source of Novel Repetitive DNA in the Eukaryote Genome. Cells 2022; 11:3373. [PMID: 36359770 PMCID: PMC9659126 DOI: 10.3390/cells11213373] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 12/02/2022] Open
Abstract
The impact of transposable elements (TEs) on the evolution of the eukaryote genome has been observed in a number of biological processes, such as the recruitment of the host's gene expression network or the rearrangement of genome structure. However, TEs may also provide a substrate for the emergence of novel repetitive elements, which contribute to the generation of new genomic components during the course of the evolutionary process. In this review, we examine published descriptions of TEs that give rise to tandem sequences in an attempt to comprehend the relationship between TEs and the emergence of de novo satellite DNA families in eukaryotic organisms. We evaluated the intragenomic behavior of the TEs, the role of their molecular structure, and the chromosomal distribution of the paralogous copies that generate arrays of repeats as a substrate for the emergence of new repetitive elements in the genome. We highlight the involvement and importance of TEs in the eukaryote genome and its remodeling processes.
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Affiliation(s)
- Michelle Louise Zattera
- Departamento de Genética, Programa de Pós-Graduação em Genética, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba 81530-000, PR, Brazil
| | - Daniel Pacheco Bruschi
- Departamento de Genética, Laboratorio de Citogenética Evolutiva e Conservação Animal, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba 81530-000, PR, Brazil
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4
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Lee Y, Ha U, Moon S. Ongoing endeavors to detect mobilization of transposable elements. BMB Rep 2022. [PMID: 35725016 PMCID: PMC9340088 DOI: 10.5483/bmbrep.2022.55.7.088] [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] [Indexed: 11/20/2022] Open
Abstract
Transposable elements (TEs) are DNA sequences capable of mobilization from one location to another in the genome. Since the discovery of ‘Dissociation (Dc) locus’ by Barbara McClintock in maize (1), mounting evidence in the era of genomics indicates that a significant fraction of most eukaryotic genomes is composed of TE sequences, involving in various aspects of biological processes such as development, physiology, diseases and evolution. Although technical advances in genomics have discovered numerous functional impacts of TE across species, our understanding of TEs is still ongoing process due to challenges resulted from complexity and abundance of TEs in the genome. In this mini-review, we briefly summarize biology of TEs and their impacts on the host genome, emphasizing importance of understanding TE landscape in the genome. Then, we introduce recent endeavors especially in vivo retrotransposition assays and long read sequencing technology for identifying de novo insertions/TE polymorphism, which will broaden our knowledge of extraordinary relationship between genomic cohabitants and their host.
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Affiliation(s)
- Yujeong Lee
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
| | - Una Ha
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
| | - Sungjin Moon
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
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5
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Colonna Romano N, Fanti L. Transposable Elements: Major Players in Shaping Genomic and Evolutionary Patterns. Cells 2022; 11:cells11061048. [PMID: 35326499 PMCID: PMC8947103 DOI: 10.3390/cells11061048] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/04/2022] [Accepted: 03/18/2022] [Indexed: 02/04/2023] Open
Abstract
Transposable elements (TEs) are ubiquitous genetic elements, able to jump from one location of the genome to another, in all organisms. For this reason, on the one hand, TEs can induce deleterious mutations, causing dysfunction, disease and even lethality in individuals. On the other hand, TEs can increase genetic variability, making populations better equipped to respond adaptively to environmental change. To counteract the deleterious effects of TEs, organisms have evolved strategies to avoid their activation. However, their mobilization does occur. Usually, TEs are maintained silent through several mechanisms, but they can be reactivated during certain developmental windows. Moreover, TEs can become de-repressed because of drastic changes in the external environment. Here, we describe the ‘double life’ of TEs, being both ‘parasites’ and ‘symbionts’ of the genome. We also argue that the transposition of TEs contributes to two important evolutionary processes: the temporal dynamic of evolution and the induction of genetic variability. Finally, we discuss how the interplay between two TE-dependent phenomena, insertional mutagenesis and epigenetic plasticity, plays a role in the process of evolution.
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6
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Chang CH, Gregory LE, Gordon KE, Meiklejohn CD, Larracuente AM. Unique structure and positive selection promote the rapid divergence of Drosophila Y chromosomes. eLife 2022; 11:e75795. [PMID: 34989337 PMCID: PMC8794474 DOI: 10.7554/elife.75795] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 12/18/2021] [Indexed: 02/06/2023] Open
Abstract
Y chromosomes across diverse species convergently evolve a gene-poor, heterochromatic organization enriched for duplicated genes, LTR retrotransposons, and satellite DNA. Sexual antagonism and a loss of recombination play major roles in the degeneration of young Y chromosomes. However, the processes shaping the evolution of mature, already degenerated Y chromosomes are less well-understood. Because Y chromosomes evolve rapidly, comparisons between closely related species are particularly useful. We generated de novo long-read assemblies complemented with cytological validation to reveal Y chromosome organization in three closely related species of the Drosophila simulans complex, which diverged only 250,000 years ago and share >98% sequence identity. We find these Y chromosomes are divergent in their organization and repetitive DNA composition and discover new Y-linked gene families whose evolution is driven by both positive selection and gene conversion. These Y chromosomes are also enriched for large deletions, suggesting that the repair of double-strand breaks on Y chromosomes may be biased toward microhomology-mediated end joining over canonical non-homologous end-joining. We propose that this repair mechanism contributes to the convergent evolution of Y chromosome organization across organisms.
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Affiliation(s)
- Ching-Ho Chang
- Department of Biology, University of RochesterRochesterUnited States
| | - Lauren E Gregory
- Department of Biology, University of RochesterRochesterUnited States
| | - Kathleen E Gordon
- School of Biological Sciences, University of Nebraska-LincolnLincolnUnited States
| | - Colin D Meiklejohn
- School of Biological Sciences, University of Nebraska-LincolnLincolnUnited States
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7
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McGurk MP, Dion-Côté AM, Barbash DA. Rapid evolution at the Drosophila telomere: transposable element dynamics at an intrinsically unstable locus. Genetics 2021; 217:iyaa027. [PMID: 33724410 PMCID: PMC8045721 DOI: 10.1093/genetics/iyaa027] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/03/2020] [Indexed: 12/26/2022] Open
Abstract
Drosophila telomeres have been maintained by three families of active transposable elements (TEs), HeT-A, TAHRE, and TART, collectively referred to as HTTs, for tens of millions of years, which contrasts with an unusually high degree of HTT interspecific variation. While the impacts of conflict and domestication are often invoked to explain HTT variation, the telomeres are unstable structures such that neutral mutational processes and evolutionary tradeoffs may also drive HTT evolution. We leveraged population genomic data to analyze nearly 10,000 HTT insertions in 85 Drosophila melanogaster genomes and compared their variation to other more typical TE families. We observe that occasional large-scale copy number expansions of both HTTs and other TE families occur, highlighting that the HTTs are, like their feral cousins, typically repressed but primed to take over given the opportunity. However, large expansions of HTTs are not caused by the runaway activity of any particular HTT subfamilies or even associated with telomere-specific TE activity, as might be expected if HTTs are in strong genetic conflict with their hosts. Rather than conflict, we instead suggest that distinctive aspects of HTT copy number variation and sequence diversity largely reflect telomere instability, with HTT insertions being lost at much higher rates than other TEs elsewhere in the genome. We extend previous observations that telomere deletions occur at a high rate, and surprisingly discover that more than one-third do not appear to have been healed with an HTT insertion. We also report that some HTT families may be preferentially activated by the erosion of whole telomeres, implying the existence of HTT-specific host control mechanisms. We further suggest that the persistent telomere localization of HTTs may reflect a highly successful evolutionary strategy that trades away a stable insertion site in order to have reduced impact on the host genome. We propose that HTT evolution is driven by multiple processes, with niche specialization and telomere instability being previously underappreciated and likely predominant.
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Affiliation(s)
- Michael P McGurk
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Anne-Marie Dion-Côté
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
- Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, SE-752 36 Uppsala, Sweden
| | - Daniel A Barbash
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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8
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Leo L, Marchetti M, Giunta S, Fanti L. Epigenetics as an Evolutionary Tool for Centromere Flexibility. Genes (Basel) 2020; 11:genes11070809. [PMID: 32708654 PMCID: PMC7397245 DOI: 10.3390/genes11070809] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/11/2020] [Accepted: 07/13/2020] [Indexed: 12/31/2022] Open
Abstract
Centromeres are the complex structures responsible for the proper segregation of chromosomes during cell division. Structural or functional alterations of the centromere cause aneuploidies and other chromosomal aberrations that can induce cell death with consequences on health and survival of the organism as a whole. Because of their essential function in the cell, centromeres have evolved high flexibility and mechanisms of tolerance to preserve their function following stress, whether it is originating from within or outside the cell. Here, we review the main epigenetic mechanisms of centromeres’ adaptability to preserve their functional stability, with particular reference to neocentromeres and holocentromeres. The centromere position can shift in response to altered chromosome structures, but how and why neocentromeres appear in a given chromosome region are still open questions. Models of neocentromere formation developed during the last few years will be hereby discussed. Moreover, we will discuss the evolutionary significance of diffuse centromeres (holocentromeres) in organisms such as nematodes. Despite the differences in DNA sequences, protein composition and centromere size, all of these diverse centromere structures promote efficient chromosome segregation, balancing genome stability and adaptability, and ensuring faithful genome inheritance at each cellular generation.
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Affiliation(s)
- Laura Leo
- Istituto Pasteur Italia, Dipartimento di Biologia e Biotecnologie “Charles Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy; (L.L.); (M.M.); (S.G.)
| | - Marcella Marchetti
- Istituto Pasteur Italia, Dipartimento di Biologia e Biotecnologie “Charles Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy; (L.L.); (M.M.); (S.G.)
| | - Simona Giunta
- Istituto Pasteur Italia, Dipartimento di Biologia e Biotecnologie “Charles Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy; (L.L.); (M.M.); (S.G.)
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, New York, NY 10065, USA
| | - Laura Fanti
- Istituto Pasteur Italia, Dipartimento di Biologia e Biotecnologie “Charles Darwin”, “Sapienza” University of Rome, 00185 Rome, Italy; (L.L.); (M.M.); (S.G.)
- Correspondence:
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9
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Paço A, Freitas R, Vieira-da-Silva A. Conversion of DNA Sequences: From a Transposable Element to a Tandem Repeat or to a Gene. Genes (Basel) 2019; 10:E1014. [PMID: 31817529 PMCID: PMC6947457 DOI: 10.3390/genes10121014] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 11/18/2019] [Accepted: 11/29/2019] [Indexed: 01/24/2023] Open
Abstract
Eukaryotic genomes are rich in repetitive DNA sequences grouped in two classes regarding their genomic organization: tandem repeats and dispersed repeats. In tandem repeats, copies of a short DNA sequence are positioned one after another within the genome, while in dispersed repeats, these copies are randomly distributed. In this review we provide evidence that both tandem and dispersed repeats can have a similar organization, which leads us to suggest an update to their classification based on the sequence features, concretely regarding the presence or absence of retrotransposons/transposon specific domains. In addition, we analyze several studies that show that a repetitive element can be remodeled into repetitive non-coding or coding sequences, suggesting (1) an evolutionary relationship among DNA sequences, and (2) that the evolution of the genomes involved frequent repetitive sequence reshuffling, a process that we have designated as a "DNA remodeling mechanism". The alternative classification of the repetitive DNA sequences here proposed will provide a novel theoretical framework that recognizes the importance of DNA remodeling for the evolution and plasticity of eukaryotic genomes.
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Affiliation(s)
- Ana Paço
- MED-Mediterranean Institute for Agriculture, Environment and Development, University of Évora, 7002–554 Évora, Portugal;
| | - Renata Freitas
- IBMC-Institute for Molecular and Cell Biology, University of Porto, R. Campo Alegre 823, 4150–180 Porto, Portugal;
- I3S-Institute for Innovation and Health Research, University of Porto, Rua Alfredo Allen, 208, 4200–135 Porto, Portugal
- ICBAS-Institute of Biomedical Sciences Abel Salazar, University of Porto, 4050-313 Porto, Portugal
| | - Ana Vieira-da-Silva
- MED-Mediterranean Institute for Agriculture, Environment and Development, University of Évora, 7002–554 Évora, Portugal;
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10
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Saint-Leandre B, Nguyen SC, Levine MT. Diversification and collapse of a telomere elongation mechanism. Genome Res 2019; 29:920-931. [PMID: 31138619 PMCID: PMC6581046 DOI: 10.1101/gr.245001.118] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 05/14/2019] [Indexed: 12/18/2022]
Abstract
In most eukaryotes, telomerase counteracts chromosome erosion by adding repetitive sequence to terminal ends. Drosophila melanogaster instead relies on specialized retrotransposons that insert exclusively at telomeres. This exchange of goods between host and mobile element-wherein the mobile element provides an essential genome service and the host provides a hospitable niche for mobile element propagation-has been called a "genomic symbiosis." However, these telomere-specialized, jockey family retrotransposons may actually evolve to "selfishly" overreplicate in the genomes that they ostensibly serve. Under this model, we expect rapid diversification of telomere-specialized retrotransposon lineages and, possibly, the breakdown of this ostensibly symbiotic relationship. Here we report data consistent with both predictions. Searching the raw reads of the 15-Myr-old melanogaster species group, we generated de novo jockey retrotransposon consensus sequences and used phylogenetic tree-building to delineate four distinct telomere-associated lineages. Recurrent gains, losses, and replacements account for this retrotransposon lineage diversity. In Drosophila biarmipes, telomere-specialized elements have disappeared completely. De novo assembly of long reads and cytogenetics confirmed this species-specific collapse of retrotransposon-dependent telomere elongation. Instead, telomere-restricted satellite DNA and DNA transposon fragments occupy its terminal ends. We infer that D. biarmipes relies instead on a recombination-based mechanism conserved from yeast to flies to humans. Telomeric retrotransposon diversification and disappearance suggest that persistently "selfish" machinery shapes telomere elongation across Drosophila rather than completely domesticated, symbiotic mobile elements.
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Affiliation(s)
- Bastien Saint-Leandre
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.,Epigenetics Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Son C Nguyen
- Epigenetics Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Mia T Levine
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.,Epigenetics Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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11
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Heterochromatin-Enriched Assemblies Reveal the Sequence and Organization of the Drosophila melanogaster Y Chromosome. Genetics 2018; 211:333-348. [PMID: 30420487 PMCID: PMC6325706 DOI: 10.1534/genetics.118.301765] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 11/05/2018] [Indexed: 12/21/2022] Open
Abstract
Heterochromatic regions of the genome are repeat-rich and poor in protein coding genes, and are therefore underrepresented in even the best genome assemblies. One of the most difficult regions of the genome to assemble are sex-limited chromosomes. The Drosophila melanogaster Y chromosome is entirely heterochromatic, yet has wide-ranging effects on male fertility, fitness, and genome-wide gene expression. The genetic basis of this phenotypic variation is difficult to study, in part because we do not know the detailed organization of the Y chromosome. To study Y chromosome organization in D. melanogaster, we develop an assembly strategy involving the in silico enrichment of heterochromatic long single-molecule reads and use these reads to create targeted de novo assemblies of heterochromatic sequences. We assigned contigs to the Y chromosome using Illumina reads to identify male-specific sequences. Our pipeline extends the D. melanogaster reference genome by 11.9 Mb, closes 43.8% of the gaps, and improves overall contiguity. The addition of 10.6 MB of Y-linked sequence permitted us to study the organization of repeats and genes along the Y chromosome. We detected a high rate of duplication to the pericentric regions of the Y chromosome from other regions in the genome. Most of these duplicated genes exist in multiple copies. We detail the evolutionary history of one sex-linked gene family, crystal-Stellate While the Y chromosome does not undergo crossing over, we observed high gene conversion rates within and between members of the crystal-Stellate gene family, Su(Ste), and PCKR, compared to genome-wide estimates. Our results suggest that gene conversion and gene duplication play an important role in the evolution of Y-linked genes.
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12
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Wei KHC, Lower SE, Caldas IV, Sless TJS, Barbash DA, Clark AG. Variable Rates of Simple Satellite Gains across the Drosophila Phylogeny. Mol Biol Evol 2018; 35:925-941. [PMID: 29361128 PMCID: PMC5888958 DOI: 10.1093/molbev/msy005] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Simple satellites are tandemly repeating short DNA motifs that can span megabases in eukaryotic genomes. Because they can cause genomic instability through nonallelic homologous exchange, they are primarily found in the repressive heterochromatin near centromeres and telomeres where recombination is minimal, and on the Y chromosome, where they accumulate as the chromosome degenerates. Interestingly, the types and abundances of simple satellites often vary dramatically between closely related species, suggesting that they turn over rapidly. However, limited sampling has prevented detailed understanding of their evolutionary dynamics. Here, we characterize simple satellites from whole-genome sequences generated from males and females of nine Drosophila species, spanning 40 Ma of evolution. We show that PCR-free library preparation and postsequencing GC-correction better capture satellite quantities than conventional methods. We find that over half of the 207 simple satellites identified are species-specific, consistent with previous descriptions of their rapid evolution. Based on a maximum parsimony framework, we determined that most interspecific differences are due to lineage-specific gains. Simple satellites gained within a species are typically a single mutation away from abundant existing satellites, suggesting that they likely emerge from existing satellites, especially in the genomes of satellite-rich species. Interestingly, unlike most of the other lineages which experience various degrees of gains, the lineage leading up to the satellite-poor D. pseudoobscura and D. persimilis appears to be recalcitrant to gains, providing a counterpoint to the notion that simple satellites are universally rapidly evolving.
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Affiliation(s)
- Kevin H -C Wei
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
- Department of Integrative Biology, University of California, Berkeley, CA
| | - Sarah E Lower
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
| | - Ian V Caldas
- Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, NY
| | - Trevor J S Sless
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY
| | - Daniel A Barbash
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
| | - Andrew G Clark
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY
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13
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Abstract
The genetic material, contained on chromosomes, is often described as the "blueprint for life." During nuclear division, the chromosomes are pulled into each of the two daughter nuclei by the coordination of spindle microtubules, kinetochores, centromeres, and chromatin. These four functional units must link the chromosomes to the microtubules, signal to the cell when the attachment is made so that division can proceed, and withstand the force generated by pulling the chromosomes to either daughter cell. To perform each of these functions, kinetochores are large protein complexes, approximately 5MDa in size, and they contain at least 45 unique proteins. Many of the central components in the kinetochore are well conserved, yielding a common core of proteins forming consistent structures. However, many of the peripheral subcomplexes vary between different taxonomic groups, including changes in primary sequence and gain or loss of whole proteins. It is still unclear how significant these changes are, and answers to this question may provide insights into adaptation to specific lifestyles or progression of disease that involve chromosome instability.
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14
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Meštrović N, Mravinac B, Pavlek M, Vojvoda-Zeljko T, Šatović E, Plohl M. Structural and functional liaisons between transposable elements and satellite DNAs. Chromosome Res 2016; 23:583-96. [PMID: 26293606 DOI: 10.1007/s10577-015-9483-7] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Transposable elements (TEs) and satellite DNAs (satDNAs) are typically identified as major repetitive DNA components in eukaryotic genomes. TEs are DNA segments able to move throughout a genome while satDNAs are tandemly repeated sequences organized in long arrays. Both classes of repetitive sequences are extremely diverse, and many TEs and satDNAs exist within a genome. Although they differ in structure, genomic organization, mechanisms of spread, and evolutionary dynamics, TEs and satDNAs can share sequence similarity and organizational patterns, thus indicating that complex mutual relationships can determine their evolution, and ultimately define roles they might have on genome architecture and function. Motivated by accumulating data about sequence elements that incorporate features of both TEs and satDNAs, here we present an overview of their structural and functional liaisons.
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Affiliation(s)
| | | | - Martina Pavlek
- Ruđer Bošković Institute, Bijenička 54, HR-10000, Zagreb, Croatia
| | | | - Eva Šatović
- Ruđer Bošković Institute, Bijenička 54, HR-10000, Zagreb, Croatia
| | - Miroslav Plohl
- Ruđer Bošković Institute, Bijenička 54, HR-10000, Zagreb, Croatia.
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15
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Abstract
Contrary to the pattern seen in mammalian sex chromosomes, where most Y-linked genes have X-linked homologs, the Drosophila X and Y chromosomes appear to be unrelated. Most of the Y-linked genes have autosomal paralogs, so autosome-to-Y transposition must be the main source of Drosophila Y-linked genes. Here we show how these genes were acquired. We found a previously unidentified gene (flagrante delicto Y, FDY) that originated from a recent duplication of the autosomal gene vig2 to the Y chromosome of Drosophila melanogaster. Four contiguous genes were duplicated along with vig2, but they became pseudogenes through the accumulation of deletions and transposable element insertions, whereas FDY remained functional, acquired testis-specific expression, and now accounts for ∼20% of the vig2-like mRNA in testis. FDY is absent in the closest relatives of D. melanogaster, and DNA sequence divergence indicates that the duplication to the Y chromosome occurred ∼2 million years ago. Thus, FDY provides a snapshot of the early stages of the establishment of a Y-linked gene and demonstrates how the Drosophila Y has been accumulating autosomal genes.
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16
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Garavís M, Méndez-Lago M, Gabelica V, Whitehead SL, González C, Villasante A. The structure of an endogenous Drosophila centromere reveals the prevalence of tandemly repeated sequences able to form i-motifs. Sci Rep 2015; 5:13307. [PMID: 26289671 PMCID: PMC4542561 DOI: 10.1038/srep13307] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 07/21/2015] [Indexed: 12/21/2022] Open
Abstract
Centromeres are the chromosomal loci at which spindle microtubules attach to mediate chromosome segregation during mitosis and meiosis. In most eukaryotes, centromeres are made up of highly repetitive DNA sequences (satellite DNA) interspersed with middle repetitive DNA sequences (transposable elements). Despite the efforts to establish complete genomic sequences of eukaryotic organisms, the so-called 'finished' genomes are not actually complete because the centromeres have not been assembled due to the intrinsic difficulties in constructing both physical maps and complete sequence assemblies of long stretches of tandemly repetitive DNA. Here we show the first molecular structure of an endogenous Drosophila centromere and the ability of the C-rich dodeca satellite strand to form dimeric i-motifs. The finding of i-motif structures in simple and complex centromeric satellite DNAs leads us to suggest that these centromeric sequences may have been selected not by their primary sequence but by their ability to form noncanonical secondary structures.
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Affiliation(s)
- Miguel Garavís
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain.,Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
| | - María Méndez-Lago
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Valérie Gabelica
- Univ. Bordeaux, ARNA Laboratory, IECB, 2 rue Robert Escarpit, F-33600 Pessac, France.,Inserm ARNA Laboratory, 146 rue Leo Saignat, F-33000 Bordeaux, France
| | - Siobhan L Whitehead
- The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Carlos González
- Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
| | - Alfredo Villasante
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
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17
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Long-Read Single Molecule Sequencing to Resolve Tandem Gene Copies: The Mst77Y Region on the Drosophila melanogaster Y Chromosome. G3-GENES GENOMES GENETICS 2015; 5:1145-50. [PMID: 25858959 PMCID: PMC4478544 DOI: 10.1534/g3.115.017277] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The autosomal gene Mst77F of Drosophila melanogaster is essential for male fertility. In 2010, Krsticevic et al. (Genetics184: 295−307) found 18 Y-linked copies of Mst77F (“Mst77Y”), which collectively account for 20% of the functional Mst77F-like mRNA. The Mst77Y genes were severely misassembled in the then-available genome assembly and were identified by cloning and sequencing polymerase chain reaction products. The genomic structure of the Mst77Y region and the possible existence of additional copies remained unknown. The recent publication of two long-read assemblies of D. melanogaster prompted us to reinvestigate this challenging region of the Y chromosome. We found that the Illumina Synthetic Long Reads assembly failed in the Mst77Y region, most likely because of its tandem duplication structure. The PacBio MHAP assembly of the Mst77Y region seems to be very accurate, as revealed by comparisons with the previously found Mst77Y genes, a bacterial artificial chromosome sequence, and Illumina reads of the same strain. We found that the Mst77Y region spans 96 kb and originated from a 3.4-kb transposition from chromosome 3L to the Y chromosome, followed by tandem duplications inside the Y chromosome and invasion of transposable elements, which account for 48% of its length. Twelve of the 18 Mst77Y genes found in 2010 were confirmed in the PacBio assembly, the remaining six being polymerase chain reaction−induced artifacts. There are several identical copies of some Mst77Y genes, coincidentally bringing the total copy number to 18. Besides providing a detailed picture of the Mst77Y region, our results highlight the utility of PacBio technology in assembling difficult genomic regions such as tandemly repeated genes.
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18
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Zaballos MA, Cantero W, Azpiazu N. The TALE transcription factor homothorax functions to assemble heterochromatin during Drosophila embryogenesis. PLoS One 2015; 10:e0120662. [PMID: 25794008 PMCID: PMC4368669 DOI: 10.1371/journal.pone.0120662] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 02/02/2015] [Indexed: 02/03/2023] Open
Abstract
We have previously identified Homothorax (Hth) as an important factor for the correct assembly of the pericentromeric heterochromatin during the first fast syncytial divisions of the Drosophila embryo. Here we have extended our studies to later stages of embryonic development. We were able to show that hth mutants exhibit a drastic overall reduction in the tri-methylation of H3 in Lys9, with no reduction of the previous di-methylation. One phenotypic outcome of such a reduction is a genome instability visualized by the many DNA breaks observed in the mutant nuclei. Moreover, loss of Hth leads to the opening of closed heterochromatic regions, including the rDNA genomic region. Our data show that the satellite repeats get transcribed in wild type embryos and that this transcription depends on the presence of Hth, which binds to them as well as to the rDNA region. This work indicates that there is an important role of transcription of non-coding RNAs for constitutive heterochromatin assembly in the Drosophila embryo, and suggests that Hth plays an important role in this process.
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Affiliation(s)
- Miguel Angel Zaballos
- Centro de Biología Molecular “Severo Ochoa” CSIC-UAM, C/ Nicolás Cabrera, 1 Universidad Autónoma de Madrid, Madrid, Spain
| | - Walter Cantero
- Centro de Biología Molecular “Severo Ochoa” CSIC-UAM, C/ Nicolás Cabrera, 1 Universidad Autónoma de Madrid, Madrid, Spain
| | - Natalia Azpiazu
- Centro de Biología Molecular “Severo Ochoa” CSIC-UAM, C/ Nicolás Cabrera, 1 Universidad Autónoma de Madrid, Madrid, Spain
- * E-mail:
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19
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Hoskins RA, Carlson JW, Wan KH, Park S, Mendez I, Galle SE, Booth BW, Pfeiffer BD, George RA, Svirskas R, Krzywinski M, Schein J, Accardo MC, Damia E, Messina G, Méndez-Lago M, de Pablos B, Demakova OV, Andreyeva EN, Boldyreva LV, Marra M, Carvalho AB, Dimitri P, Villasante A, Zhimulev IF, Rubin GM, Karpen GH, Celniker SE. The Release 6 reference sequence of the Drosophila melanogaster genome. Genome Res 2015; 25:445-58. [PMID: 25589440 PMCID: PMC4352887 DOI: 10.1101/gr.185579.114] [Citation(s) in RCA: 279] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Drosophila melanogaster plays an important role in molecular,
genetic, and genomic studies of heredity, development, metabolism, behavior, and
human disease. The initial reference genome sequence reported more than a decade ago
had a profound impact on progress in Drosophila research, and
improving the accuracy and completeness of this sequence continues to be important to
further progress. We previously described improvement of the 117-Mb sequence in the
euchromatic portion of the genome and 21 Mb in the heterochromatic portion, using a
whole-genome shotgun assembly, BAC physical mapping, and clone-based finishing. Here,
we report an improved reference sequence of the single-copy and middle-repetitive
regions of the genome, produced using cytogenetic mapping to mitotic and polytene
chromosomes, clone-based finishing and BAC fingerprint verification, ordering of
scaffolds by alignment to cDNA sequences, incorporation of other map and sequence
data, and validation by whole-genome optical restriction mapping. These data
substantially improve the accuracy and completeness of the reference sequence and the
order and orientation of sequence scaffolds into chromosome arm assemblies.
Representation of the Y chromosome and other heterochromatic regions
is particularly improved. The new 143.9-Mb reference sequence, designated Release 6,
effectively exhausts clone-based technologies for mapping and sequencing. Highly
repeat-rich regions, including large satellite blocks and functional elements such as
the ribosomal RNA genes and the centromeres, are largely inaccessible to current
sequencing and assembly methods and remain poorly represented. Further significant
improvements will require sequencing technologies that do not depend on molecular
cloning and that produce very long reads.
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Affiliation(s)
- Roger A Hoskins
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA;
| | - Joseph W Carlson
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Kenneth H Wan
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Soo Park
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Ivonne Mendez
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Samuel E Galle
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Benjamin W Booth
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Barret D Pfeiffer
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA
| | - Reed A George
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA
| | - Robert Svirskas
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA
| | - Martin Krzywinski
- Genome Sciences Centre, BC Cancer Agency, Vancouver, BC, V5Z 4S6, Canada
| | - Jacqueline Schein
- Genome Sciences Centre, BC Cancer Agency, Vancouver, BC, V5Z 4S6, Canada
| | - Maria Carmela Accardo
- Dipartimento di Biologia e Biotecnologie "Charles Darwin" and Istituto Pasteur Fondazione Cenci-Bolognetti, Sapienza Università di Roma, 00185 Roma, Italy
| | - Elisabetta Damia
- Dipartimento di Biologia e Biotecnologie "Charles Darwin" and Istituto Pasteur Fondazione Cenci-Bolognetti, Sapienza Università di Roma, 00185 Roma, Italy
| | - Giovanni Messina
- Dipartimento di Biologia e Biotecnologie "Charles Darwin" and Istituto Pasteur Fondazione Cenci-Bolognetti, Sapienza Università di Roma, 00185 Roma, Italy
| | - María Méndez-Lago
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Beatriz de Pablos
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Olga V Demakova
- Institute of Molecular and Cellular Biology, Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Evgeniya N Andreyeva
- Institute of Molecular and Cellular Biology, Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Lidiya V Boldyreva
- Institute of Molecular and Cellular Biology, Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Marco Marra
- Genome Sciences Centre, BC Cancer Agency, Vancouver, BC, V5Z 4S6, Canada
| | - A Bernardo Carvalho
- Departamento de Genética, Universidade Federal do Rio de Janeiro, CEP 21944-970, Rio de Janeiro, Brazil
| | - Patrizio Dimitri
- Dipartimento di Biologia e Biotecnologie "Charles Darwin" and Istituto Pasteur Fondazione Cenci-Bolognetti, Sapienza Università di Roma, 00185 Roma, Italy
| | - Alfredo Villasante
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Igor F Zhimulev
- Institute of Molecular and Cellular Biology, Russian Academy of Sciences, Novosibirsk, 630090, Russia; Novosibirsk State University, Novosibirsk, 630090, Russia
| | - Gerald M Rubin
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA
| | - Gary H Karpen
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
| | - Susan E Celniker
- Department of Genome Dynamics, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA;
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20
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Garavís M, González C, Villasante A. On the origin of the eukaryotic chromosome: the role of noncanonical DNA structures in telomere evolution. Genome Biol Evol 2013; 5:1142-50. [PMID: 23699225 PMCID: PMC3698924 DOI: 10.1093/gbe/evt079] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The transition of an ancestral circular genome to multiple linear chromosomes was crucial for eukaryogenesis because it allowed rapid adaptive evolution through aneuploidy. Here, we propose that the ends of nascent linear chromosomes should have had a dual function in chromosome end protection (capping) and chromosome segregation to give rise to the “proto-telomeres.” Later on, proper centromeres evolved at subtelomeric regions. We also propose that both noncanonical structures based on guanine–guanine interactions and the end-protection proteins recruited by the emergent telomeric heterochromatin have been required for telomere maintenance through evolution. We further suggest that the origin of Drosophila telomeres may be reminiscent of how the first telomeres arose.
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Affiliation(s)
- Miguel Garavís
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid, Spain
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21
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Satellite DNA-like elements associated with genes within euchromatin of the beetle Tribolium castaneum. G3-GENES GENOMES GENETICS 2012; 2:931-41. [PMID: 22908042 PMCID: PMC3411249 DOI: 10.1534/g3.112.003467] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 06/18/2012] [Indexed: 01/30/2023]
Abstract
In the red flour beetle Tribolium castaneum the major TCAST satellite DNA accounts for 35% of the genome and encompasses the pericentromeric regions of all chromosomes. Because of the presence of transcriptional regulatory elements and transcriptional activity in these sequences, TCAST satellite DNAs also have been proposed to be modulators of gene expression within euchromatin. Here, we analyze the distribution of TCAST homologous repeats in T. castaneum euchromatin and study their association with genes as well as their potential gene regulatory role. We identified 68 arrays composed of TCAST-like elements distributed on all chromosomes. Based on sequence characteristics the arrays were composed of two types of TCAST-like elements. The first type consists of TCAST satellite-like elements in the form of partial monomers or tandemly arranged monomers, up to tetramers, whereas the second type consists of TCAST-like elements embedded with a complex unit that resembles a DNA transposon. TCAST-like elements were also found in the 5′ untranslated region (UTR) of the CR1-3_TCa retrotransposon, and therefore retrotransposition may have contributed to their dispersion throughout the genome. No significant difference in the homogenization of dispersed TCAST-like elements was found either at the level of local arrays or chromosomes nor among different chromosomes. Of 68 TCAST-like elements, 29 were located within introns, with the remaining elements flanked by genes within a 262 to 404,270 nt range. TCAST-like elements are statistically overrepresented near genes with immunoglobulin-like domains attesting to their nonrandom distribution and a possible gene regulatory role.
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22
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Piñeyro D, López-Panadès E, Lucena-Pérez M, Casacuberta E. Transcriptional analysis of the HeT-A retrotransposon in mutant and wild type stocks reveals high sequence variability at Drosophila telomeres and other unusual features. BMC Genomics 2011; 12:573. [PMID: 22111838 PMCID: PMC3235214 DOI: 10.1186/1471-2164-12-573] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 11/23/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Telomere replication in Drosophila depends on the transposition of a domesticated retroelement, the HeT-A retrotransposon. The sequence of the HeT-A retrotransposon changes rapidly resulting in differentiated subfamilies. This pattern of sequence change contrasts with the essential function with which the HeT-A is entrusted and brings about questions concerning the extent of sequence variability, the telomere contribution of different subfamilies, and whether wild type and mutant Drosophila stocks show different HeT-A scenarios. RESULTS A detailed study on the variability of HeT-A reveals that both the level of variability and the number of subfamilies are higher than previously reported. Comparisons between GIII, a strain with longer telomeres, and its parental strain Oregon-R indicate that both strains have the same set of HeT-A subfamilies. Finally, the presence of a highly conserved splicing pattern only in its antisense transcripts indicates a putative regulatory, functional or structural role for the HeT-A RNA. Interestingly, our results also suggest that most HeT-A copies are actively expressed regardless of which telomere and where in the telomere they are located. CONCLUSIONS Our study demonstrates how the HeT-A sequence changes much faster than previously reported resulting in at least nine different subfamilies most of which could actively contribute to telomere extension in Drosophila. Interestingly, the only significant difference observed between Oregon-R and GIII resides in the nature and proportion of the antisense transcripts, suggesting a possible mechanism that would in part explain the longer telomeres of the GIII stock.
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Affiliation(s)
- David Piñeyro
- Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003, Barcelona, Spain
| | - Elisenda López-Panadès
- Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003, Barcelona, Spain
| | - María Lucena-Pérez
- Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003, Barcelona, Spain
| | - Elena Casacuberta
- Institute of Evolutionary Biology (CSIC-UPF), Passeig Marítim de la Barceloneta 37-49, 08003, Barcelona, Spain
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23
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Abstract
Reverse transcriptases have shaped genomes in many ways. A remarkable example of this shaping is found on telomeres of the genus Drosophila, where retrotransposons have a vital role in chromosome structure. Drosophila lacks telomerase; instead, three telomere-specific retrotransposons maintain chromosome ends. Repeated transpositions to chromosome ends produce long head to tail arrays of these elements. In both form and function, these arrays are analogous to the arrays of repeats added by telomerase to chromosomes in other organisms. Distantly related Drosophila exhibit this variant mechanism of telomere maintenance, which was established before the separation of extant Drosophila species. Nevertheless, the telomere-specific elements still have the hallmarks that characterize non-long terminal repeat (non-LTR) retrotransposons; they have also acquired characteristics associated with their roles at telomeres. These telomeric retrotransposons have shaped the Drosophila genome, but they have also been shaped by the genome. Here, we discuss ways in which these three telomere-specific retrotransposons have been modified for their roles in Drosophila chromosomes.
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24
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Abstract
Repeated DNA in heterochromatin presents enormous difficulties for whole-genome sequencing; hence, sequence organization in a significant portion of the genomes of multicellular organisms is relatively unknown. Two sequenced BACs now allow us to compare telomeric retrotransposon arrays from Drosophila melanogaster telomeres with an array of telomeric retrotransposons that transposed into the centromeric region of the Y chromosome >13 MYA, providing a unique opportunity to compare the structural evolution of this retrotransposon in two contexts. We find that these retrotransposon arrays, both heterochromatic, are maintained quite differently, resulting in sequence organizations that apparently reflect different roles in the two chromosomal environments. The telomere array has grown only by transposition of new elements to the chromosome end; the centromeric array instead has grown by repeated amplifications of segments of the original telomere array. Many elements in the telomere have been variably 5'-truncated apparently by gradual erosion and irregular deletions of the chromosome end; however, a significant fraction (4 and possibly 5 or 6 of 15 elements examined) remain complete and capable of further retrotransposition. In contrast, each element in the centromere region has lost ≥ 40% of its sequence by internal, rather than terminal, deletions, and no element retains a significant part of the original coding region. Thus the centromeric array has been restructured to resemble the highly repetitive satellite sequences typical of centromeres in multicellular organisms, whereas, over a similar or longer time period, the telomere array has maintained its ability to provide retrotransposons competent to extend telomere ends.
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25
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Méndez-Lago M, Wild J, Whitehead SL, Tracey A, de Pablos B, Rogers J, Szybalski W, Villasante A. Novel sequencing strategy for repetitive DNA in a Drosophila BAC clone reveals that the centromeric region of the Y chromosome evolved from a telomere. Nucleic Acids Res 2009; 37:2264-73. [PMID: 19237394 PMCID: PMC2673431 DOI: 10.1093/nar/gkp085] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The centromeric and telomeric heterochromatin of eukaryotic chromosomes is mainly composed of middle-repetitive elements, such as transposable elements and tandemly repeated DNA sequences. Because of this repetitive nature, Whole Genome Shotgun Projects have failed in sequencing these regions. We describe a novel kind of transposon-based approach for sequencing highly repetitive DNA sequences in BAC clones. The key to this strategy relies on physical mapping the precise position of the transposon insertion, which enables the correct assembly of the repeated DNA. We have applied this strategy to a clone from the centromeric region of the Y chromosome of Drosophila melanogaster. The analysis of the complete sequence of this clone has allowed us to prove that this centromeric region evolved from a telomere, possibly after a pericentric inversion of an ancestral telocentric chromosome. Our results confirm that the use of transposon-mediated sequencing, including positional mapping information, improves current finishing strategies. The strategy we describe could be a universal approach to resolving the heterochromatic regions of eukaryotic genomes.
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26
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Villasante A, Abad JP, Planelló R, Méndez-Lago M, Celniker SE, de Pablos B. Drosophila telomeric retrotransposons derived from an ancestral element that was recruited to replace telomerase. Genome Res 2007; 17:1909-18. [PMID: 17989257 DOI: 10.1101/gr.6365107] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Drosophila telomeres do not have arrays of simple telomerase-generated G-rich repeats. Instead, Drosophila maintains its telomeres by occasional transposition of specific non-long terminal repeat (non-LTR) retrotransposons to chromosome ends. The genus Drosophila provides a superb model system for comparative telomere analysis. Here we present an evolutionary study of Drosophila telomeric elements to ascertain the significance of telomeric retrotransposons (TRs) in the maintenance of Drosophila telomeres. PCR and in silico surveys in the sibling species of Drosophila melanogaster and in more distantly related species show that multiple TRs maintain telomeres in Drosophila. In addition to TRs with two open reading frames (ORFs) capable of autonomous transposition, there are deleted telomeric retrotransposons that have lost their ORF2, which we refer to as half telomeric-retrotransposons (HTRs). The phylogenetic relationship among these telomeric elements is congruent with the phylogeny of the species, suggesting that they have been vertically inherited from a common ancestor. Our results suggest that an existing non-LTR retrotransposon was recruited to perform the cellular function of telomere maintenance.
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Affiliation(s)
- Alfredo Villasante
- Centro de Biología Molecular Severo Ochoa, Cantoblanco, 28049 Madrid, Spain.
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27
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Andreyeva EN, Kolesnikova TD, Demakova OV, Mendez-Lago M, Pokholkova GV, Belyaeva ES, Rossi F, Dimitri P, Villasante A, Zhimulev IF. High-resolution analysis of Drosophila heterochromatin organization using SuUR Su(var)3-9 double mutants. Proc Natl Acad Sci U S A 2007; 104:12819-24. [PMID: 17640911 PMCID: PMC1937550 DOI: 10.1073/pnas.0704690104] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The structural and functional analyses of heterochromatin are essential to understanding how heterochromatic genes are regulated and how centromeric chromatin is formed. Because the repetitive nature of heterochromatin hampers its genome analysis, new approaches need to be developed. Here, we describe how, in double mutants for Su(var)3-9 and SuUR genes encoding two structural proteins of heterochromatin, new banded heterochromatic segments appear in all polytene chromosomes due to the strong suppression of under-replication in pericentric regions. FISH on salivary gland polytene chromosomes from these double mutant larvae allows high resolution of heterochromatin mapping. In addition, immunostaining experiments with a set of antibodies against euchromatic and heterochromatic proteins reveal their unusual combinations in the newly appeared segments: binding patterns for HP1 and HP2 are coincident, but both are distinct from H3diMetK9 and H4triMetK20. In several regions, partial overlapping staining is observed for the proteins characteristic of active chromatin RNA Pol II, H3triMetK4, Z4, and JIL1, the boundary protein BEAF, and the heterochromatin-enriched proteins HP1, HP2, and SU(VAR)3-7. The exact cytological position of the centromere of chromosome 3 was visualized on salivary gland polytene chromosomes by using the centromeric dodeca satellite and the centromeric protein CID. This region is enriched in H3diMetK9 and H4triMetK20 but is devoid of other proteins analyzed.
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Affiliation(s)
- Eugenia N. Andreyeva
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Tatyana D. Kolesnikova
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Olga V. Demakova
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Maria Mendez-Lago
- Centro de Biología Molecular “Severo Ochoa,” Universidad Autonóma de Madrid, Cantoblanco, 28049 Madrid, Spain; and
| | - Galina V. Pokholkova
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Elena S. Belyaeva
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Fabrizio Rossi
- Istituto Pasteur–Fondazione Cenci Bolognetti and Dipartimento di Genetica e Biologia Molecolare, Università “La Sapienza,” Via dei Sardi, 70, 00185 Rome, Italy
| | - Patrizio Dimitri
- Istituto Pasteur–Fondazione Cenci Bolognetti and Dipartimento di Genetica e Biologia Molecolare, Università “La Sapienza,” Via dei Sardi, 70, 00185 Rome, Italy
| | - Alfredo Villasante
- Centro de Biología Molecular “Severo Ochoa,” Universidad Autonóma de Madrid, Cantoblanco, 28049 Madrid, Spain; and
| | - Igor F. Zhimulev
- *Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia
- To whom correspondence should be addressed at:
Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Lavrentyev Avenue 10, Novosibirsk 630090, Russia. E-mail:
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28
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Villasante A, Abad JP, Méndez-Lago M. Centromeres were derived from telomeres during the evolution of the eukaryotic chromosome. Proc Natl Acad Sci U S A 2007; 104:10542-7. [PMID: 17557836 PMCID: PMC1965549 DOI: 10.1073/pnas.0703808104] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Indexed: 12/24/2022] Open
Abstract
The centromere is the DNA region of the eukaryotic chromosome that determines kinetochore formation and sister chromatid cohesion. Centromeres interact with spindle microtubules to ensure the segregation of chromatids during mitosis and of homologous chromosomes in meiosis. The origin of centromeres, therefore, is inseparable from the evolution of cytoskeletal components that distribute chromosomes to offspring cells. Although the origin of the nucleus has been debated, no explanation for the evolutionary appearance of centromeres is available. We propose an evolutionary scenario: The centromeres originated from telomeres. The breakage of the ancestral circular genophore activated the transposition of retroelements at DNA ends that allowed the formation of telomeres by a recombination-dependent replication mechanism. Afterward, the modification of the tubulin-based cytoskeleton that allowed specific subtelomeric repeats to be recognized as new cargo gave rise to the first centromere. This switch from actin-based genophore partition to a tubulin-based mechanism generated a transition period during which both types of cytoskeleton contributed to fidelity of chromosome segregation. During the transition, pseudodicentric chromosomes increased the tendency toward chromosomal breakage and instability. This instability generated multiple telocentric chromosomes that eventually evolved into metacentric or holocentric chromosomes.
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Affiliation(s)
- Alfredo Villasante
- Centro de Biología Molecular Severo Ochoa, Universidad Autonóma de Madrid, Cantoblanco, 28049 Madrid, Spain.
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Usakin L, Abad J, Vagin VV, de Pablos B, Villasante A, Gvozdev VA. Transcription of the 1.688 satellite DNA family is under the control of RNA interference machinery in Drosophila melanogaster ovaries. Genetics 2007; 176:1343-9. [PMID: 17409066 PMCID: PMC1894595 DOI: 10.1534/genetics.107.071720] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Here we show that RNA interference (RNAi) machinery operates in Drosophila melanogaster 1.688 satellite transcription. Mutation in the spn-E gene, known to be involved in RNAi in the oocytes, causes an increase of satellite transcript abundance. Transcripts of both strands of 1.688 satellite repeats in germinal tissues were detected. The strength of the effects of the spn-E mutation differs for 1.688 satellite DNA subfamilies and is more pronounced for autosomal pericentromeric satellites compared to the X-linked centromeric ones. The spn-E(1) mutation causes an increase of the H3-AcK9 mark and TAF1 (a component of the polymerase II transcriptional complex) occupancy in the chromatin of autosomal pericentromeric repeats. Thus, we revealed that RNAi operates in ovaries to maintain the silenced state of centromeric and pericentromeric 1.688 repeats.
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Affiliation(s)
- Lev Usakin
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - José Abad
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Vasily V. Vagin
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Beatriz de Pablos
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Alfredo Villasante
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Vladimir A. Gvozdev
- Department of Animal Molecular Genetics, Institute of Molecular Genetics, Moscow 123182, Russia, Department of Molecular Biology, Moscow State University, Moscow 119992, Russia and Centro de Biología Molecular “Severo Ochoa,” Universidad Autonoma de Madrid, Cantoblanco, Madrid 28049, Spain
- Corresponding author: Department of Animal Molecular Genetics, Institute of Molecular Genetics, Kurchatov sq. 2, Moscow 123182, Russia. E-mail:
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Osoegawa K, Vessere GM, Li Shu C, Hoskins RA, Abad JP, de Pablos B, Villasante A, de Jong PJ. BAC clones generated from sheared DNA. Genomics 2006; 89:291-9. [PMID: 17098394 PMCID: PMC1909752 DOI: 10.1016/j.ygeno.2006.10.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Revised: 09/15/2006] [Accepted: 10/06/2006] [Indexed: 01/31/2023]
Abstract
BAC libraries generated from restriction-digested genomic DNA display representational bias and lack some sequences. To facilitate completion of genome projects, procedures have been developed to create BACs from DNA physically sheared to create fragments extending up to 200 kb. The DNA fragments were repaired to create blunt ends and ligated to a new BAC vector. This approach has been tested by generating BAC libraries from Drosophila DNA with insert lengths between 50 and 150 kb. The libraries lack chimeric clone problems as determined by mapping paired BAC-end sequences to the assembled fly genome sequence. The utility of "sheared" libraries was demonstrated by closure of a previous clone gap and by isolation of clones from telomeric regions, which were notably absent from previous Drosophila BAC libraries.
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Affiliation(s)
- Kazutoyo Osoegawa
- Children's Hospital and Research Center at Oakland, 747 52nd Street, Oakland, CA 94609, USA.
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31
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Berloco M, Fanti L, Sheen F, Levis RW, Pimpinelli S. Heterochromatic distribution of HeT-A- and TART-like sequences in several Drosophila species. Cytogenet Genome Res 2005; 110:124-33. [PMID: 16093664 DOI: 10.1159/000084944] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Accepted: 05/18/2004] [Indexed: 11/19/2022] Open
Abstract
Drosophila melanogaster telomeres contain arrays of two non-LTR retrotransposons called HeT-A and TART. Previous studies have shown that HeT-A- and TART-like sequences are also located at non-telomeric sites in the Y chromosome heterochromatin. By in situ hybridization experiments, we mapped TART sequences in the h16 region of the long arm close to the centromere of the Y chromosome of D. melanogaster. HeT-A sequences were localized in two different regions on the Y chromosome, one very close to the centromere in the short arm (h18-h19) and the other in the long arm (h13-h14). To assess a possible heterochromatic location of TART and HeT-A elements in other Drosophila species, we performed in situ hybridization experiments, using both TART and HeT-A probes, on mitotic and polytene chromosomes of D. simulans, D. sechellia, D. mauritiana, D. yakuba and D. teissieri. We found that TART and HeT-A probes hybridize at specific heterochromatic regions of the Y chromosome in all Drosophila species that we analyzed.
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Affiliation(s)
- M Berloco
- Dipartimento di Anatomia Patologica e di Genetica (DAPEG), Università degli Studi di Bari, Bari, Italy
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32
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Bi X, Srikanta D, Fanti L, Pimpinelli S, Badugu R, Kellum R, Rong YS. Drosophila ATM and ATR checkpoint kinases control partially redundant pathways for telomere maintenance. Proc Natl Acad Sci U S A 2005; 102:15167-72. [PMID: 16203987 PMCID: PMC1257705 DOI: 10.1073/pnas.0504981102] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Accepted: 09/02/2005] [Indexed: 01/05/2023] Open
Abstract
In higher eukaryotes, the ataxia telangiectasia mutated (ATM) and ATM and Rad3-related (ATR) checkpoint kinases play distinct, but partially overlapping, roles in DNA damage response. Yet their interrelated function has not been defined for telomere maintenance. We discover in Drosophila that the two proteins control partially redundant pathways for telomere protection: the loss of ATM leads to the fusion of some telomeres, whereas the loss of both ATM and ATR renders all telomeres susceptible to fusion. The ATM-controlled pathway includes the Mre11 and Nijmegen breakage syndrome complex but not the Chk2 kinase, whereas the ATR-regulated pathway includes its partner ATR-interacting protein but not the Chk1 kinase. This finding suggests that ATM and ATR regulate different molecular events at the telomeres compared with the sites of DNA damage. This compensatory relationship between ATM and ATR is remarkably similar to that observed in yeast despite the fact that the biochemistry of telomere elongation is completely different in the two model systems. We provide evidence suggesting that both the loading of telomere capping proteins and normal telomeric silencing requires ATM and ATR in Drosophila and propose that ATM and ATR protect telomere integrity by safeguarding chromatin architecture that favors the loading of telomere-elongating, capping, and silencing proteins.
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Affiliation(s)
- Xiaolin Bi
- Laboratory of Molecular Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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33
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Biessmann H, Prasad S, Semeshin VF, Andreyeva EN, Nguyen Q, Walter MF, Mason JM. Two distinct domains in Drosophila melanogaster telomeres. Genetics 2005; 171:1767-77. [PMID: 16143601 PMCID: PMC1382029 DOI: 10.1534/genetics.105.048827] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Telomeres are generally considered heterochromatic. On the basis of DNA composition, the telomeric region of Drosophila melanogaster contains two distinct subdomains: a subtelomeric region of repetitive DNA, termed TAS, and a terminal array of retrotransposons, which perform the elongation function instead of telomerase. We have identified several P-element insertions into this retrotransposon array and compared expression levels of transgenes with similar integrations into TAS and euchromatic regions. In contrast to insertions in TAS, which are silenced, reporter genes in the terminal HeT-A, TAHRE, or TART retroelements did not exhibit repressed expression in comparison with the same transgene construct in euchromatin. These data, in combination with cytological studies, provide evidence that the subtelomeric TAS region exhibits features resembling heterochromatin, while the terminal retrotransposon array exhibits euchromatic characteristics.
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Affiliation(s)
- Harald Biessmann
- Department of Biological Chemistry, University of California-Irvine, Irvine, CA 92697, USA
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34
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Abad JP, de Pablos B, Agudo M, Molina I, Giovinazzo G, Martín-Gallardo A, Villasante A. Genomic and cytological analysis of the Y chromosome of Drosophila melanogaster: telomere-derived sequences at internal regions. Chromosoma 2004; 113:295-304. [PMID: 15616866 DOI: 10.1007/s00412-004-0318-0] [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] [Received: 07/07/2004] [Revised: 09/20/2004] [Accepted: 09/21/2004] [Indexed: 10/26/2022]
Abstract
The genomic analysis of heterochromatin is essential for studying chromosome behavior as well as for understanding chromosome evolution. The Y chromosome of Drosophila melanogaster is entirely heterochromatic and the under-representation of this chromosome in genomic libraries together with the difficulty of assembling its sequence has made its study very difficult. Here, we present the construction of bacterial artificial chromosome (BAC) contigs from regions h14, h16 and the centromeric region h18. The analysis of these contigs shows that telomere-derived sequences are present at internal regions. In addition, immunostaining of prometaphase chromosomes with an antibody to the kinetochore-specific protein BubR1 has revealed the presence of this protein in some Y chromosome regions rich in telomere-related sequences. Collectively, our data provide further evidence for the hypothesis that the Drosophila Y chromosomes might have evolved from supernumerary chromosomes.
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Affiliation(s)
- José P Abad
- Centro de Biología Molecular Severo Ochoa,CSIC-UAM, Cantoblanco, 28049, Madrid Spain
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35
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Perrini B, Piacentini L, Fanti L, Altieri F, Chichiarelli S, Berloco M, Turano C, Ferraro A, Pimpinelli S. HP1 controls telomere capping, telomere elongation, and telomere silencing by two different mechanisms in Drosophila. Mol Cell 2004; 15:467-76. [PMID: 15304225 DOI: 10.1016/j.molcel.2004.06.036] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 05/28/2004] [Accepted: 06/02/2004] [Indexed: 11/24/2022]
Abstract
HP1 is a conserved chromosomal protein, first discovered in Drosophila, which is predominantly associated with the heterochromatin of many organisms. Recently, it has been shown that HP1 is required for telomere capping, telomere elongation, and transcriptional repression of telomeric sequences. Several studies have suggested a model for heterochromatin formation and epigenetic gene silencing in different species that is based on interactions among histone methyltransferases (HMTases), histone H3 methylated at lysine 9 (H3-MeK9), and the HP1 chromodomain. This model has been extended to HP1 telomeric localization by data showing that H3-MeK9 is present at all of the telomeres. Here, we tested this model, and we found that the capping function of HP1 is due to its direct binding to telomeric DNA, while the silencing of telomeric sequences and telomere elongation is due to its interaction with H3-MeK9.
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Affiliation(s)
- Barbara Perrini
- Fondazione Cenci Bolognetti and Dipartimento, di Genetica e Biologia Molecolare, Università "La Sapienza", 00185 Roma, Italy
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36
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Tek AL, Jiang J. The centromeric regions of potato chromosomes contain megabase-sized tandem arrays of telomere-similar sequence. Chromosoma 2004; 113:77-83. [PMID: 15258808 DOI: 10.1007/s00412-004-0297-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 05/07/2004] [Accepted: 05/19/2004] [Indexed: 11/24/2022]
Abstract
Telomere-similar sequences have been found in non-telomeric regions in various eukaryotic species. Centromeric regions often harbor such interstitial telomeric repeats (ITRs). We isolated a 2.8 kb ITR, pSbTC1, in a diploid potato species Solanum bulbocastanum. DNA sequences related to the pSbTC1 family are widely distributed in different Solanum species. The pSbTC1-related sequences are organized into tandem arrays and located mainly in the centromeric regions of potato chromosomes. Most notably, the pSbTC1-related sequences have undergone extensive amplification and a single array can span up to multiple megabases. These results suggest that the pSbTC1-related sequences are not simple relics of ancient events in karyotype evolution, such as chromosomal fusions. We also demonstrated that the pSbTC1-related sequences are heavily methylated and are associated with highly condensed centromeric heterochromatin.
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Affiliation(s)
- Ahmet L Tek
- Department of Horticulture, University of Wisconsin-Madison, Madison, WI 53706, USA
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37
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Abad JP, De Pablos B, Osoegawa K, De Jong PJ, Martín-Gallardo A, Villasante A. TAHRE, a novel telomeric retrotransposon from Drosophila melanogaster, reveals the origin of Drosophila telomeres. Mol Biol Evol 2004; 21:1620-4. [PMID: 15175413 DOI: 10.1093/molbev/msh180] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Drosophila telomeres do not have typical telomerase repeats. Instead, two families of non-LTR retrotransposons, HeT-A and TART, maintain telomere length by occasional transposition to the chromosome ends. Despite the work on Drosophila telomeres, its evolutionary origin remains controversial. Herein we describe a novel telomere-specific retroelement that we name TAHRE (Telomere-Associated and HeT-A-Related Element). The structure of the three telomere-specific elements indicates a common ancestor. These results suggest that preexisting transposable elements were recruited to perform the cellular function of telomere maintenance. A recruitment similar to that of a retrotransposal reverse transcriptase has been suggested as the common origin of telomerases.
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38
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Abad JP, De Pablos B, Osoegawa K, De Jong PJ, Martín-Gallardo A, Villasante A. Genomic analysis of Drosophila melanogaster telomeres: full-length copies of HeT-A and TART elements at telomeres. Mol Biol Evol 2004; 21:1613-9. [PMID: 15163766 DOI: 10.1093/molbev/msh174] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The repetitive nature of heterochromatin hampers its analysis in general genome-sequencing projects. Specific studies are needed to extend the sequence into telomeric and centromeric heterochromatin. Drosophila telomeres lack the telomerase-generated repeats that are characteristic of other eukaryotic chromosomes. Instead, they consist of tandem arrays of HeT-A and TART elements. Herein, we present the genomic organization of the telomeres in the isogenic strain (y; cn bw sp) that was used for the Drosophila melanogaster sequencing project. The data indicate that the canonical features of telomere organization are widely conserved in evolution. In addition, we have identified full-length elements, likely competent elements, for HeT-A and TART.
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Maggert KA, Golic KG. The Y chromosome of Drosophila melanogaster exhibits chromosome-wide imprinting. Genetics 2002; 162:1245-58. [PMID: 12454070 PMCID: PMC1462351 DOI: 10.1093/genetics/162.3.1245] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Genomic imprinting is well known as a regulatory property of a few specific chromosomal regions and leads to differential behavior of maternally and paternally inherited alleles. We surveyed the activity of two reporter genes in 23 independent P-element insertions on the heterochromatic Y chromosome of Drosophila melanogaster and found that all but one location showed differential expression of one or both genes according to the parental source of the chromosome. In contrast, genes inserted in autosomal heterochromatin generally did not show imprint-regulated expression. The imprints were established on Y-linked transgenes inserted into many different sequences and locations. We conclude that genomic imprinting affecting gene expression is a general property of the Drosophila Y chromosome and distinguishes the Y from the autosomal complement.
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Affiliation(s)
- Keith A Maggert
- The Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA.
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40
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Abstract
As in other eukaryotes, telomeres in Drosophila melanogaster are composed of long arrays of repeated DNA sequences. Remarkably, in D. melanogaster these repeats are produced, not by telomerase, but by successive transpositions of two telomere-specific retrotransposons, HeT-A and TART. These are the only transposable elements known to be completely dedicated to a role in chromosomes, a finding that provides an opportunity for investigating questions about the evolution of telomeres, telomerase, and the transposable elements themselves. Recent studies of D. yakuba revealed the presence of HeT-A elements with precisely the same unusual characteristics as HeT-A(mel) although they had only 55% nucleotide sequence identity. We now report that the second element, TART, is also a telomere component in D. yakuba; thus, these two elements have been evolving together since before the separation of the melanogaster and yakuba species complexes. Like HeT-A(yak), TART(yak) is undergoing concerted sequence evolution, yet they retain the unusual features TART(mel) shares with HeT-A(mel). There are at least two subfamilies of TART(yak) with significantly different sequence and expression. Surprisingly, one subfamily of TART(yak) has >95% sequence identity with a subfamily of TART(mel) and shows similar transcription patterns. As in D. melanogaster, other retrotransposons are excluded from the D. yakuba terminal arrays studied to date.
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Affiliation(s)
- Elena Casacuberta
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Losada A, Abad JP, Agudo M, Villasante A. Long-range analysis of the centromeric region of Drosophila melanogaster chromosome 3. Chromosome Res 2001; 8:651-3. [PMID: 11117362 DOI: 10.1023/a:1009250411192] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- A Losada
- Centro de Biologia Molecular Severo Ochoa (CSIC-UAM), Madrid, Spain
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Miller WJ, Nagel A, Bachmann J, Bachmann L. Evolutionary dynamics of the SGM transposon family in the Drosophila obscura species group. Mol Biol Evol 2000; 17:1597-609. [PMID: 11070048 DOI: 10.1093/oxfordjournals.molbev.a026259] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
SGM (Drosophila subobscura, Drosophila guanche, and Drosophila madeirensis) transposons are a family of transposable elements (TEs) in Drosophila with some functional and structural similarities to miniature inverted-repeat transposable elements (MITEs). These elements were recently active in D. subobscura and D. madeirensis (1-2 MYA), but in D. guanche (3-4 MYA), they gave rise to a species-specifically amplified satellite DNA making up approximately 10% of its genome. SGM elements were already active in the common ancestor of all three species, giving rise to the A-type specific promoter section of the P:-related neogene cluster. SGM sequences are similar to elements found in other obscura group species, such as the ISY elements in D. miranda and the ISamb elements in Drosophila ambigua. SGM elements are composed of different sequence modules, and some of them, i.e., LS and LS-core, are found throughout the Drosophila and Sophophora radiation with similarity to more distantly related TEs. The LS-core module is highly enriched in the noncoding sections of the Drosophila melanogaster genome, suggesting potential regulatory host gene functions. The SGM elements can be considered as a model system elucidating the evolutionary dynamics of mobile elements in their arms race with host-directed silencing mechanisms and their evolutionary impact on the structure and composition of their respective host genomes.
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Affiliation(s)
- W J Miller
- Institute of Medical Biology, General Genetics, University of Vienna, Austria.
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43
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Zhao X, Haqqi T, Yadav SP. Sequencing telomeric DNA template with short tandem repeats using dye terminator cycle sequencing. J Biomol Tech 2000; 11:111-121. [PMID: 19499047 PMCID: PMC2291630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The standard DNA sequencing methods for use in conjunction with commercially available sequencing kits are effective in sequencing a majority of templates. However, templates rich in dinucleotide and tetranucleotide repeats and a telomeric DNA containing tandem repeats are difficult to sequence adequately using these methods. Base compression artifacts due to formation of secondary structure on the nascent strands and slippage of the DNA polymerase accompanied by premature chain termination in homopolymer and short tandem repeat regions of DNA are commonly encountered problems in sequencing core laboratories. In an attempt to sequence such repeat regions of telomeric DNA templates using dye terminator chemistry, we investigated the effect of increasing the annealing time and temperature in combination with the use of denaturing conditions. Specifically, we compared the commonly used ABI PRISM BigDye, dGTP BigDye, and DYEnamic ET terminator chemistries for sequencing telomeric DNA templates rich in CA- and AACCCC-type repeats and for sequencing a template rich in dinucleotide (GT and CT) and tetranucleotide repeats. The routine reaction protocol was modified by adding either 1 M 1-carboxy-N,N,N-trimethylmethanaminium inner salt (betaine) or 5% dimethyl sulfoxide (DMSO) as denaturants in the reaction mixture. In addition, the annealing and denaturation times were increased to allow successful primer extension for linear growth of sequencing reaction product. Many of the artifacts in sequencing are known to be due to reduced stability of the hybrid formed between the template and the nascent strand. The effects of using denaturants to break secondary structures in the nascent chain and of increasing the denaturation and annealing times are discussed.We were able to sequence DNA templates with tandem repeats that failed to sequence under routine reaction conditions.
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Affiliation(s)
- X Zhao
- Molecular Biotechnology Core, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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44
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Rosén M, Edström J. DNA structures common for chironomid telomeres terminating with complex repeats. INSECT MOLECULAR BIOLOGY 2000; 9:341-347. [PMID: 10886419 DOI: 10.1046/j.1365-2583.2000.00193.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Tandem repeats, 340 bp long, have been shown to terminate the chromosomes in Chironomus pallidivittatus and similar DNA may be used for this purpose by related insects. In view of the importance of Chironomus in telomere studies, representing in principle a third system after short repeats and Drosophila telomeric retrotransposons, we have investigated the related Chironomus dilutus, to learn what DNA structures are conserved at the chromosome ends. Interspersed subrepeats in the telomeric repeats, which contain a long palindrome, and a zone of about 100 bp of relatively constant subtelomeric DNA towards the junction to the telomeric DNA, are characteristic for C. dilutus as for previously investigated species. C. dilutus has similar subtelomeric DNA at all chromosome ends, but typical telomeric repeats in only seven of the pairs since the eighth telocentric pair contains centromere-specific repeats.
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Affiliation(s)
- M Rosén
- Department of Genetics, Lund University, Lund, Sweden
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