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] [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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Boldyreva LV, Andreyeva EN, Pindyurin AV. Position Effect Variegation: Role of the Local Chromatin Context in Gene Expression Regulation. Mol Biol 2022. [DOI: 10.1134/s0026893322030049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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DeBose-Scarlett EM, Sullivan BA. Genomic and Epigenetic Foundations of Neocentromere Formation. Annu Rev Genet 2021; 55:331-348. [PMID: 34496611 DOI: 10.1146/annurev-genet-071719-020924] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Centromeres are essential to genome inheritance, serving as the site of kinetochore assembly and coordinating chromosome segregation during cell division. Abnormal centromere function is associated with birth defects, infertility, and cancer. Normally, centromeres are assembled and maintained at the same chromosomal location. However, ectopic centromeres form spontaneously at new genomic locations and contribute to genome instability and developmental defects as well as to acquired and congenital human disease. Studies in model organisms have suggested that certain regions of the genome, including pericentromeres, heterochromatin, and regions of open chromatin or active transcription, support neocentromere activation. However, there is no universal mechanism that explains neocentromere formation. This review focuses on recent technological and intellectual advances in neocentromere research and proposes future areas of study. Understanding neocentromere biology will provide a better perspective on chromosome and genome organization and functional context for information generated from the Human Genome Project, ENCODE, and other large genomic consortia. Expected final online publication date for the Annual Review of Genetics, Volume 55 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Evon M DeBose-Scarlett
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710, USA;
| | - Beth A Sullivan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina 27710, USA;
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4
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Spradling AC. Polytene Chromosome Structure and Somatic Genome Instability. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2017; 82:293-304. [PMID: 29167281 DOI: 10.1101/sqb.2017.82.033670] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Polytene chromosomes have for 80 years provided the highest resolution view of interphase genome structure in an animal cell nucleus. These chromosomes represent the normal genomic state of nearly all Drosophila larval and many adult cells, and a better understanding of their striking banded structure has been sought for decades. A more recently appreciated characteristic of Drosophila polytene cells is somatic genome instability caused by unfinished replication (UR). Repair of stalled forks generates enough deletions in polytene salivary gland cells to alter 10%-90% of the DNA strands within more than 100 UR regions comprising 20% of the euchromatic genome. We accurately map UR regions and show that most approximate large polytene bands, indicating that replication forks frequently stall near band boundaries in late S phase. Chromosome conformation capture has recently identified dense topologically associated domains (TADs) in many genomes and most UR bands are similar or slightly smaller than a cognate Drosophila TAD. We argue that bands serve the evolutionarily ancient function of coordinating genome replication with local gene activity. We also discuss the relatively recent evolution of polyteny and somatic instability in Diptera and propose that these processes helped propel the amazing success of two-winged flies in becoming the most ecologically diverse insect group, with 200 times the number of species as mammals.
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Affiliation(s)
- Allan C Spradling
- Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution for Science, Baltimore, Maryland 21218
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5
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Sullivan LL, Maloney KA, Towers AJ, Gregory SG, Sullivan BA. Human centromere repositioning within euchromatin after partial chromosome deletion. Chromosome Res 2016; 24:451-466. [PMID: 27581771 DOI: 10.1007/s10577-016-9536-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/18/2016] [Accepted: 08/22/2016] [Indexed: 10/21/2022]
Abstract
Centromeres are defined by a specialized chromatin organization that includes nucleosomes that contain the centromeric histone variant centromere protein A (CENP-A) instead of canonical histone H3. Studies in various organisms have shown that centromeric chromatin (i.e., CENP-A chromatin or centrochromatin) exhibits plasticity, in that it can assemble on different types of DNA sequences. However, once established on a chromosome, the centromere is maintained at the same position. In humans, this location is the highly homogeneous repetitive DNA alpha satellite. Mislocalization of centromeric chromatin to atypical locations can lead to genome instability, indicating that restriction of centromeres to a distinct genomic position is important for cell and organism viability. Here, we describe a rearrangement of Homo sapiens chromosome 17 (HSA17) that has placed alpha satellite DNA next to euchromatin. We show that on this mutant chromosome, CENP-A chromatin has spread from the alpha satellite into the short arm of HSA17, establishing a ∼700 kb hybrid centromeric domain that spans both repetitive and unique sequences and changes the expression of at least one gene over which it spreads. Our results illustrate the plasticity of human centromeric chromatin and suggest that heterochromatin normally constrains CENP-A chromatin onto alpha satellite DNA. This work highlights that chromosome rearrangements, particularly those that remove the pericentromere, create opportunities for centromeric nucleosomes to move into non-traditional genomic locations, potentially changing the surrounding chromatin environment and altering gene expression.
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Affiliation(s)
- Lori L Sullivan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA
| | - Kristin A Maloney
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA.,Department of Medicine, Division of Endocrinology, Diabetes, and Nutrition, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Aaron J Towers
- University Program in Genetics and Genomics, Duke University School of Medicine, Durham, NC, 27710, USA.,Quintiles, 4820 Emperor Blvd., Durham, NC, 27703, USA
| | - Simon G Gregory
- Department of Medicine, Duke Molecular Physiology Institute, 300 N. Duke Street, Durham, NC, 27701, USA.,Division of Human Genetics, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Beth A Sullivan
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3054, Durham, NC, 27710, USA. .,Quintiles, 4820 Emperor Blvd., Durham, NC, 27703, USA.
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6
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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: 50] [Impact Index Per Article: 5.6] [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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7
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Yarosh W, Spradling AC. Incomplete replication generates somatic DNA alterations within Drosophila polytene salivary gland cells. Genes Dev 2014; 28:1840-55. [PMID: 25128500 PMCID: PMC4197960 DOI: 10.1101/gad.245811.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
DNA replication remains unfinished in many Drosophila polyploid cells, which harbor disproportionately fewer copies of late-replicating chromosomal regions. Using NextGen sequencing of DNA from giant polytene cells of the larval salivary gland, Yarosh and Spradling show that sporadic, incomplete replication during the endocycle S phase alters the Drosophila genome at thousands of sites that differ in every cell; similar events occur in the ovary. The authors propose that the extensive somatic DNA instability described here underlies position effect variegation and molds the structure of polytene chromosomes. DNA replication remains unfinished in many Drosophila polyploid cells, which harbor disproportionately fewer copies of late-replicating chromosomal regions. By analyzing paired-end high-throughput sequence data from polytene larval salivary gland cells, we define 112 underreplicated (UR) euchromatic regions 60–480 kb in size. To determine the effects of underreplication on genome integrity, we analyzed anomalous read pairs and breakpoint reads throughout the euchromatic genome. Each UR euchromatic region contains many different deletions 10–500 kb in size, while very few deletions are present in fully replicated chromosome regions or UR zones from embryo DNA. Thus, during endocycles, stalled forks within UR regions break and undergo local repair instead of remaining stable and generating nested forks. As a result, each salivary gland cell contains hundreds of unique deletions that account for their copy number reductions. Similar UR regions and deletions were observed in ovarian DNA, suggesting that incomplete replication, fork breakage, and repair occur widely in polytene cells. UR regions are enriched in genes encoding immunoglobulin superfamily proteins and contain many neurally expressed and homeotic genes. We suggest that the extensive somatic DNA instability described here underlies position effect variegation, molds the structure of polytene chromosomes, and should be investigated for possible functions.
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Affiliation(s)
- Will Yarosh
- Howard Hughes Medical Institute, Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
| | - Allan C Spradling
- Howard Hughes Medical Institute, Department of Embryology, Carnegie Institution for Science, Baltimore, Maryland 21218, USA
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8
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9
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Elgin SCR, Reuter G. Position-effect variegation, heterochromatin formation, and gene silencing in Drosophila. Cold Spring Harb Perspect Biol 2013; 5:a017780. [PMID: 23906716 DOI: 10.1101/cshperspect.a017780] [Citation(s) in RCA: 309] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Position-effect variegation (PEV) results when a gene normally in euchromatin is juxtaposed with heterochromatin by rearrangement or transposition. When heterochromatin packaging spreads across the heterochromatin/euchromatin border, it causes transcriptional silencing in a stochastic pattern. PEV is intensely studied in Drosophila using the white gene. Screens for dominant mutations that suppress or enhance white variegation have identified many conserved epigenetic factors, including the histone H3 lysine 9 methyltransferase SU(VAR)3-9. Heterochromatin protein HP1a binds H3K9me2/3 and interacts with SU(VAR)3-9, creating a core memory system. Genetic, molecular, and biochemical analysis of PEV in Drosophila has contributed many key findings concerning establishment and maintenance of heterochromatin with concomitant gene silencing.
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Affiliation(s)
- Sarah C R Elgin
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
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10
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Kolesnikova TD, Demakov SA, Ivankin AV, Zhimulev IF. Molecular combing in studies of the genome organization and DNA replication. RUSS J GENET+ 2010. [DOI: 10.1134/s102279541010025x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Karpen GH. Preparation of high-molecular-weight DNA from Drosophila embryos. Cold Spring Harb Protoc 2010; 2009:pdb.prot5254. [PMID: 20147219 DOI: 10.1101/pdb.prot5254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Standard methods for extracting DNA from cells or organisms (e.g., phenol extraction and ethanol precipitation) produce fragments with an average size of 50-200 kb under optimal conditions. The shearing forces that are applied to DNA in solution during mechanical vortexing or mixing and pipetting produce frequent double-stranded breaks. To prepare high-molecular-weight (HMW) DNA, it is necessary to guard against such damaging forces by performing all extractions and manipulations on DNA that is embedded within a protective matrix. Preparation of HMW DNA from Drosophila embryos is described in detail here because, in our hands, it is the simplest and most reliable protocol and can be used for large- or small-scale preparations. The overall strategy is to purify nuclei, gently embed them in molten agarose, and then extract proteins and perform other enzymatic reactions by transferring the solidified agarose block into the appropriate solutions. Salts, soaps, and enzymes act on the DNA by diffusing through the agarose matrix, while the matrix protects the DNA from shearing forces.
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12
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Kolesnikova TD, Demakov SA, Ivankin AV, Andreenkova NG, Zhimulev IF. The mutation of the Suppressor of Underreplication gene does not affect the replication fork rate in the Drosophila melanogaster salivary gland polytene chromosomes. DOKL BIOCHEM BIOPHYS 2009; 427:175-8. [PMID: 19817130 DOI: 10.1134/s1607672909040024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- T D Kolesnikova
- Institute of Cytology and Genetics, Siberian Branch, Russian Academy ofSciences, pr Akademika Lavrent'eva 10, Novosibirsk 630090, Russia
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13
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Andreyenkova NG, Kokoza EB, Semeshin VF, Belyaeva ES, Demakov SA, Pindyurin AV, Andreyeva EN, Volkova EI, Zhimulev IF. Localization and characteristics of DNA underreplication zone in the 75C region of intercalary heterochromatin in Drosophila melanogaster polytene chromosomes. Chromosoma 2009; 118:747-61. [PMID: 19685068 DOI: 10.1007/s00412-009-0232-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2009] [Revised: 07/16/2009] [Accepted: 07/22/2009] [Indexed: 10/20/2022]
Abstract
In Drosophila polytene chromosomes, regions of intercalary heterochromatin are scattered throughout the euchromatic arms. Here, we present data on the first fine analysis of the individual intercalary heterochromatin region, 75C1-2, located in the 3L chromosome. By using electron microscopy, we demonstrated that this region appears as three closely adjacent condensed bands. Mapping of the region on the physical map by means of the chromosomal rearrangements with known breakpoints showed that the length of the region is about 445 kb. Although it seems that the SUUR protein binds to the whole 75C1-2 region, the proximal part of the region is fully polytenized, so the DNA underreplication zone is asymmetric and located in the distal half of the region. Finally, we speculate that intercalary heterochromatin regions of Drosophila polytene chromosomes are organized into three different types with respect to the localization of the underreplication zone.
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Affiliation(s)
- Natalya G Andreyenkova
- Department of Molecular and Cellular Biology, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of Russian Academy of Sciences, Novosibirsk, Russia
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14
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Mehrotra S, Maqbool SB, Kolpakas A, Murnen K, Calvi BR. Endocycling cells do not apoptose in response to DNA rereplication genotoxic stress. Genes Dev 2009; 22:3158-71. [PMID: 19056894 DOI: 10.1101/gad.1710208] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Initiation of DNA replication at origins more than once per cell cycle results in rereplication and has been implicated in cancer. Here we use Drosophila to examine the checkpoint responses to rereplication in a developmental context. We find that increased Double-parked (Dup), the Drosophila ortholog of Cdt1, results in rereplication and DNA damage. In most cells, this rereplication triggers caspase activation and apoptotic cell death mediated by both p53-dependent and -independent pathways. Elevated Dup also caused DNA damage in endocycling cells, which switch to a G/S cycle during normal development, indicating that rereplication and the endocycling DNA reduplication program are distinct processes. Unexpectedly, however, endocycling cells do not apoptose regardless of tissue type. Our combined evidence suggests that endocycling apoptosis is repressed in part because proapoptotic gene promoters are silenced. Normal endocycling cells had DNA lesions near heterochromatin, which increased after rereplication, explaining why endocycling cells must constantly repress the genotoxic apoptotic response. Our results reveal a novel regulation of apoptosis in development and new insights into the little-understood endocycle. Similar mechanisms may operate during vertebrate development, with implications for cancer predisposition in certain tissues.
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Affiliation(s)
- Sonam Mehrotra
- Department of Biology, Syracuse University, Syracuse, New York 13244, USA
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15
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Panchenko T, Black BE. The epigenetic basis for centromere identity. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2009; 48:1-32. [PMID: 19521810 DOI: 10.1007/978-3-642-00182-6_1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The centromere serves as the control locus for chromosome segregation at mitosis and meiosis. In most eukaryotes, including mammals, the location of the centromere is epigenetically defined. The contribution of both genetic and epigenetic determinants to centromere function is the subject of current investigation in diverse eukaryotes. Here we highlight key findings from several organisms that have shaped the current view of centromeres, with special attention to experiments that have elucidated the epigenetic nature of their specification. Recent insights into the histone H3 variant, CENP-A, which assembles into centromeric nucleosomes that serve as the epigenetic mark to perpetuate centromere identity, have added important mechanistic understanding of how centromere identity is initially established and subsequently maintained in every cell cycle.
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Affiliation(s)
- Tanya Panchenko
- Department of Biochemistry, University of Pennsylvania, Philadelphia, PA 19104-6059, USA
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16
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Anaka M, Lynn A, McGinn P, Lloyd VK. Genomic Imprinting in Drosophila has properties of both mammalian and insect imprinting. Dev Genes Evol 2008; 219:59-66. [DOI: 10.1007/s00427-008-0267-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Accepted: 10/29/2008] [Indexed: 11/30/2022]
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17
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Gvozdev VA, Abramov YA, Kogan GL, Lavrov SA. Distorted heterochromatin replication in Drosophila melanogaster polytene chromosomes as a result of euchromatin-heterochromatin rearrangements. RUSS J GENET+ 2007. [DOI: 10.1134/s1022795407010024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Demakova OV, Pokholkova GV, Kolesnikova TD, Demakov SA, Andreyeva EN, Belyaeva ES, Zhimulev IF. The SU(VAR)3-9/HP1 complex differentially regulates the compaction state and degree of underreplication of X chromosome pericentric heterochromatin in Drosophila melanogaster. Genetics 2006; 175:609-20. [PMID: 17151257 PMCID: PMC1800617 DOI: 10.1534/genetics.106.062133] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In polytene chromosomes of Drosophila melanogaster, regions of pericentric heterochromatin coalesce to form a compact chromocenter and are highly underreplicated. Focusing on study of X chromosome heterochromatin, we demonstrate that loss of either SU(VAR)3-9 histone methyltransferase activity or HP1 protein differentially affects the compaction of different pericentric regions. Using a set of inversions breaking X chromosome heterochromatin in the background of the Su(var)3-9 mutations, we show that distal heterochromatin (blocks h26-h29) is the only one within the chromocenter to form a big "puff"-like structure. The "puffed" heterochromatin has not only unique morphology but also very special protein composition as well: (i) it does not bind proteins specific for active chromatin and should therefore be referred to as a pseudopuff and (ii) it strongly associates with heterochromatin-specific proteins SU(VAR)3-7 and SUUR, despite the fact that HP1 and HP2 are depleted particularly from this polytene structure. The pseudopuff completes replication earlier than when it is compacted as heterochromatin, and underreplication of some DNA sequences within the pseudopuff is strongly suppressed. So, we show that pericentric heterochromatin is heterogeneous in its requirement for SU(VAR)3-9 with respect to the establishment of the condensed state, time of replication, and DNA polytenization.
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Affiliation(s)
- Olga V Demakova
- Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk 630090, Russia
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19
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Belyaeva ES, Demakov SA, Pokholkova GV, Alekseyenko AA, Kolesnikova TD, Zhimulev IF. DNA underreplication in intercalary heterochromatin regions in polytene chromosomes of Drosophila melanogaster correlates with the formation of partial chromosomal aberrations and ectopic pairing. Chromosoma 2006; 115:355-66. [PMID: 16583218 DOI: 10.1007/s00412-006-0063-7] [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: 01/19/2006] [Revised: 02/26/2006] [Accepted: 03/06/2006] [Indexed: 11/25/2022]
Abstract
We studied the influence of the Suppressor of Underreplication (SuUR) gene expression on the intercalary heterochromatin (IH) regions of Drosophila melanogaster polytene chromosomes. We observed a strong positive correlation between increased SuUR expression, underreplication extent, amount of DNA truncation, and formation of ectopic contacts in IH regions. SuUR overexpression from heat shock-driven transgene results in the formation of partial chromosomal aberrations whose breakpoints map exclusively to the regions of intercalary and pericentric heterochromatin. It is important to note that all these effects are seen only if SuUR overexpression is induced during early stages of chromosome polytenization. Therefore, we developed the idea that ectopic pairing results from the joining of free DNA ends, which are formed as a consequence of underreplication.
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Affiliation(s)
- Elena S Belyaeva
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk, 630090, Russia
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20
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Goday C, Pimpinelli S. The occurrence, role and evolution of chromatin diminution in nematodes. ACTA ACUST UNITED AC 2005; 9:319-22. [PMID: 15463793 DOI: 10.1016/0169-4758(93)90229-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Chromatin diminution takes place in presomatic cells of some parasitic nematodes during early development. This phenomenon may play an important role in somatic cell differentiation, since the somatic cells of these species undergo an extensive genome reorganization during development via chromatin diminution and polyploidization, as explained here by Clara Goday and Sergio Pimpinelli.
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Affiliation(s)
- C Goday
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Cientificas, Veĺazquez 188, 28006 Madrid, Spain
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21
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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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22
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DePamphili ML. How transcription factors regulate origins of DNA replication in eukaryotic cells. Trends Cell Biol 2004; 3:161-7. [PMID: 14731611 DOI: 10.1016/0962-8924(93)90137-p] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Eukaryotic chromosomes contain a few thousand origins of DNA replication, which are activated in a temporal and spatial order during S phase. One parameter that is strongly implicated in determining the order of replication is transcription. This review focuses on the role of transcription factors in activating origins of replication in eukaryotic cells. Studies of viral and mitochondrial replication origins have revealed several mechanisms by which transcription factors activate origins, but it remains to be seen whether any of these are used to regulate cellular chromosome replication.
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Affiliation(s)
- M L DePamphili
- Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110, USA
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23
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Konev AY, Yan CM, Acevedo D, Kennedy C, Ward E, Lim A, Tickoo S, Karpen GH. Genetics of P-Element Transposition Into Drosophila melanogaster Centric Heterochromatin. Genetics 2003; 165:2039-53. [PMID: 14704184 PMCID: PMC1462875 DOI: 10.1093/genetics/165.4.2039] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Heterochromatin is a major component of higher eukaryotic genomes, but progress in understanding the molecular structure and composition of heterochromatin has lagged behind the production of relatively complete euchromatic genome sequences. The introduction of single-copy molecular-genetic entry points can greatly facilitate structure and sequence analysis of heterochromatic regions that are rich in repeated DNA. In this study, we report the isolation of 502 new P-element insertions into Drosophila melanogaster centric heterochromatin, generated in nine different genetic screens that relied on mosaic silencing (position-effect variegation, or PEV) of the yellow gene present in the transposon. The highest frequencies of recovery of variegating insertions were observed when centric insertions were used as the source for mobilization. We propose that the increased recovery of variegating insertions from heterochromatic starting sites may result from the physical proximity of different heterochromatic regions in germline nuclei or from the association of mobilizing elements with heterochromatin proteins. High frequencies of variegating insertions were also recovered when a potent suppressor of PEV (an extra Y chromosome) was present in both the mobilization and selection generations, presumably due to the effects of chromatin structure on P-element mobilization, insertion, and phenotypic selection. Finally, fewer variegating insertions were recovered after mobilization in females, in comparison to males, which may reflect differences in heterochromatin structure in the female and male germlines. FISH localization of a subset of the insertions confirmed that 98% of the variegating lines contain heterochromatic insertions and that these schemes produce a broader distribution of insertion sites. The results of these schemes have identified the most efficient methods for generating centric heterochromatin P insertions. In addition, the large collection of insertions produced by these screens provides molecular-genetic entry points for mapping, sequencing, and functional analysis of Drosophila heterochromatin.
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Affiliation(s)
- Alexander Y Konev
- Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, San Diego, CA 92037, USA
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24
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Belyaeva ES, Boldyreva LV, Volkova EI, Nanayev RA, Alekseyenko AA, Zhimulev IF. Effect of the Suppressor of Underreplication (SuUR) Gene on Position-Effect Variegation Silencing in Drosophila melanogaster. Genetics 2003; 165:1209-20. [PMID: 14668376 PMCID: PMC1462842 DOI: 10.1093/genetics/165.3.1209] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
It has been previously shown that the SuUR gene encodes a protein located in intercalary and pericentromeric heterochromatin in Drosophila melanogaster polytene chromosomes. The SuUR mutation suppresses the formation of ectopic contacts and DNA underreplication in polytene chromosomes; SuUR+ in extra doses enhances the expression of these characters. This study demonstrates that heterochromatin-dependent PEV silencing is also influenced by SuUR. The SuUR protein localizes to chromosome regions compacted as a result of PEV; the SuUR mutation suppresses DNA underreplication arising in regions of polytene chromosomes undergoing PEV. The SuUR mutation also suppresses variegation of both adult morphological characters and chromatin compaction observed in rearranged chromosomes. In contrast, SuUR+ in extra doses and its overexpression enhance variegation. Thus, SuUR affects PEV silencing in a dose-dependent manner. However, its effect is expressed weaker than that of the strong modifier Su(var)2-5.
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Affiliation(s)
- E S Belyaeva
- Institute of Cytology and Genetics, Siberian Division of Russian Academy of Sciences, Novosibirsk 630090, Russia
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25
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Abstract
Centromeres are the site for kinetochore formation and spindle attachment and are embedded in heterochromatin in most eukaryotes. The repeat-rich nature of heterochromatin has hindered obtaining a detailed understanding of the composition and organization of heterochromatic and centromeric DNA sequences. Here, we report the results of extensive sequence analysis of a fully functional centromere present in the Drosophila Dp1187 minichromosome. Approximately 8.4% (31 kb) of the highly repeated satellite DNA (AATAT and TTCTC) was sequenced, representing the largest data set of Drosophila satellite DNA sequence to date. Sequence analysis revealed that the orientation of the arrays is uniform and that individual repeats within the arrays mostly differ by rare, single-base polymorphisms. The entire complex DNA component of this centromere (69.7 kb) was sequenced and assembled. The 39-kb "complex island" Maupiti contains long stretches of a complex A+T rich repeat interspersed with transposon fragments, and most of these elements are organized as direct repeats. Surprisingly, five single, intact transposons are directly inserted at different locations in the AATAT satellite arrays. We find no evidence for centromere-specific sequences within this centromere, providing further evidence for sequence-independent, epigenetic determination of centromere identity and function in higher eukaryotes. Our results also demonstrate that the sequence composition and organization of large regions of centric heterochromatin can be determined, despite the presence of repeated DNA.
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Affiliation(s)
- Xiaoping Sun
- Molecular and Cell Biology Laboratory, The Salk Institute, La Jolla, CA 92037, USA
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26
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Eissenberg JC, Wallrath LL. Heterochromatin, Position Effects, and the Genetic Dissection of Chromatin. ACTA ACUST UNITED AC 2003; 74:275-99. [PMID: 14510079 DOI: 10.1016/s0079-6603(03)01016-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
Affiliation(s)
- Joel C Eissenberg
- Department of Biochemistry and Molecular Biology, St. Louis School of Medicine, St. Louis, Missouri 63104, USA
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27
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Yan CM, Dobie KW, Le HD, Konev AY, Karpen GH. Efficient recovery of centric heterochromatin P-element insertions in Drosophila melanogaster. Genetics 2002; 161:217-29. [PMID: 12019236 PMCID: PMC1462106 DOI: 10.1093/genetics/161.1.217] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Approximately one-third of the human and Drosophila melanogaster genomes are heterochromatic, yet we know very little about the structure and function of this enigmatic component of eukaryotic genomes. To facilitate molecular and cytological analysis of heterochromatin we introduced a yellow(+) (y(+))-marked P element into centric heterochromatin by screening for variegated phenotypes, that is, mosaic gene inactivation. We recovered >110 P insertions with variegated yellow expression from approximately 3500 total mobilization events. FISH analysis of 71 of these insertions showed that 69 (97%) were in the centric heterochromatin, rather than telomeres or euchromatin. High-resolution banding analysis showed a wide but nonuniform distribution of insertions within centric heterochromatin; variegated insertions were predominantly recovered near regions of satellite DNA. We successfully used inverse PCR to clone and sequence the flanking DNA for approximately 63% of the insertions. BLAST analysis of the flanks demonstrated that either most of the variegated insertions could not be placed on the genomic scaffold, and thus may be inserted within novel DNA sequence, or that the flanking DNA hit multiple sites on the scaffold, due to insertions within different transposons. Taken together these data suggest that screening for yellow variegation is a very efficient method for recovering centric insertions and that a large-scale screen for variegated yellow P insertions will provide important tools for detailed analysis of centric heterochromatin structure and function.
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Affiliation(s)
- Christopher M Yan
- Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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28
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Morcillo P, MacIntyre RJ. Genetic and molecular characterization of a variegating hsp70-acZ fusion gene in the euchromatic 31 B region of Drosophila melanogaster. Genome 2001; 44:698-707. [PMID: 11550907 DOI: 10.1139/g01-038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A hsp70-lacZ fusion gene introduced into Drosophila melanogaster at the euchromatic 31B region by Pelement transformation displayed a variegated expression with respect to the lacZ fusion protein in the salivary gland cells under heat-shock conditions. The variegation is also reflected by the chromosome puffing pattern. Subsequent transposition of the 31B P element to other euchromatic positions restored wild-type activity, that is, a nonvariegated phenotype. A lower developmental temperature reduced the amount of expression under heat-shock conditions, similar to genes undergoing position-effect variegation (PEV). However, other modifiers of PEV did not affect the expression pattern of the gene. These results show a novel euchromatic tissue-specific variegation that is not associated with classical heterochromatic PEV.
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Affiliation(s)
- P Morcillo
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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29
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Maggert KA, Karpen GH. The activation of a neocentromere in Drosophila requires proximity to an endogenous centromere. Genetics 2001; 158:1615-28. [PMID: 11514450 PMCID: PMC1461751 DOI: 10.1093/genetics/158.4.1615] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The centromere is essential for proper segregation and inheritance of genetic information. Centromeres are generally regulated to occur exactly once per chromosome; failure to do so leads to chromosome loss or damage and loss of linked genetic material. The mechanism for faithful regulation of centromere activity and number is unknown. The presence of ectopic centromeres (neocentromeres) has allowed us to probe the requirements and characteristics of centromere activation, maintenance, and structure. We utilized chromosome derivatives that placed a 290-kilobase "test segment" in three different contexts within the Drosophila melanogaster genome--immediately adjacent to (1) centromeric chromatin, (2) centric heterochromatin, or (3) euchromatin. Using irradiation mutagenesis, we freed this test segment from the source chromosome and genetically assayed whether the liberated "test fragment" exhibited centromere activity. We observed that this test fragment behaved differently with respect to centromere activity when liberated from different chromosomal contexts, despite an apparent sequence identity. Test segments juxtaposed to an active centromere produced fragments with neocentromere activity, whereas test segments far from centromeres did not. Once established, neocentromere activity was stable. The imposition of neocentromere activity on juxtaposed DNA supports the hypothesis that centromere activity and identity is capable of spreading and is regulated epigenetically.
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Affiliation(s)
- K A Maggert
- Stower's Institute for Medical Research, Kansas City, Missouri 64110, USA
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30
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Leach TJ, Chotkowski HL, Wotring MG, Dilwith RL, Glaser RL. Replication of heterochromatin and structure of polytene chromosomes. Mol Cell Biol 2000; 20:6308-16. [PMID: 10938107 PMCID: PMC86105 DOI: 10.1128/mcb.20.17.6308-6316.2000] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Heterochromatin is characteristically the last portion of the genome to be replicated. In polytene cells, heterochromatic sequences are underreplicated because S phase ends before replication of heterochromatin is completed. Truncated heterochromatic DNAs have been identified in polytene cells of Drosophila and may be the discontinuous molecules that form between fully replicated euchromatic and underreplicated heterochromatic regions of the chromosome. In this report, we characterize the temporal pattern of heterochromatic DNA truncation during development of polytene cells. Underreplication occurred during the first polytene S phase, yet DNA truncation, which was found within heterochromatic sequences of all four Drosophila chromosomes, did not occur until the second polytene S phase. DNA truncation was correlated with underreplication, since increasing the replication of satellite sequences with the cycE(1672) mutation caused decreased production of truncated DNAs. Finally, truncation of heterochromatic DNAs was neither quantitatively nor qualitatively affected by modifiers of position effect variegation including the Y chromosome, Su(var)205(2), parental origin, or temperature. We propose that heterochromatic satellite sequences present a barrier to DNA replication and that replication forks that transiently stall at such barriers in late S phase of diploid cells are left unresolved in the shortened S phase of polytene cells. DNA truncation then occurs in the second polytene S phase, when new replication forks extend to the position of forks left unresolved in the first polytene S phase.
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Affiliation(s)
- T J Leach
- Laboratory of Developmental Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201, USA
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31
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Alleman M, Doctor J. Genomic imprinting in plants: observations and evolutionary implications. PLANT MOLECULAR BIOLOGY 2000; 43:147-161. [PMID: 10999401 DOI: 10.1023/a:1006419025155] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The epigenetic phenomenon of genomic imprinting occurs among both plants and animals. In species where imprinting is observed, there are parent-of-origin effects on the expression of imprinted genes in offspring. This review focuses on imprinting in plants with examples from maize, where gene imprinting was first described, and Arabidopsis. Our current understanding of imprinting in plants is presented in the context of cytosine methylation and imprinting in mammals, where developmentally essential genes are imprinted. Important considerations include the structure and organization of imprinted genes and the role of regional, differential methylation. Imprinting in plants may be related to other epigenetic phenomena including paramutation and transgene silencing. Finally, we discuss the role of gene structure and evolutionary implications of imprinting in plants.
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Affiliation(s)
- M Alleman
- Department of Biological Sciences, Duquesne University, Pittsburgh, PA 15282, USA.
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32
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Haller BS, Woodruff RC. Varied expression of a Y-linked P[w+] insert due to imprinting in Drosophila melanogaster. Genome 2000; 43:285-92. [PMID: 10791816 DOI: 10.1139/g99-125] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During gametogenesis, a gene can become imprinted affecting its expression in progeny. We have used the expression of a Y-linked P[w+]YAL transposable DNA element as a reporter system to investigate the effect of parental origination on the expression of the w+ insert. Expression of w+ was greater in male progeny when the Y chromosome, harboring the insert, was inherited from the parental male rather than from the parental female. Imprinting was not due to a genetic background influence in the males, since the only difference among the males was the parental origin of the Y chromosome. It was also observed that the genetic background can affect imprinting, since w+ expression was also higher in males when the Y was derived from C(1)DX attached-X parental females rather than from C(1)RM attached-X parental females. Though the heterochromatic imprinting mechanism is unknown, a mutated Heterochromatin Protein 1 (HP1) gene, which is associated with suppression of position-effect variegation, increases expression of the w+ locus in the P[w+]YAL insert, indicating that HP1 may play a role in Y chromosome packaging.
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Affiliation(s)
- B S Haller
- Department of Biological Sciences, Bowling Green State University, OH 43403, USA
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33
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Agudo M, Losada A, Abad JP, Pimpinelli S, Ripoll P, Villasante A. Centromeres from telomeres? The centromeric region of the Y chromosome of Drosophila melanogaster contains a tandem array of telomeric HeT-A- and TART-related sequences. Nucleic Acids Res 1999; 27:3318-24. [PMID: 10454639 PMCID: PMC148565 DOI: 10.1093/nar/27.16.3318] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cytological and cytogenetic studies have previously defined the region needed for centromeric function in the Y chromosome of Drosophila melanogaster. We have identified a YAC clone that originated from this region. Molecular analysis of the YAC and genomic DNAs has allowed the description of a satellite DNA made of telomeric HeT-A- and TART-derived sequences and the construction of a long-range physical map of the heterochromatic region h18. Sequences within the YAC clone are conserved in the centromeric region of the sibling species Drosophila simulans. That telomere-derived DNA now forms part of the centromeric region of the Y chromosome could indicate a telomeric origin of this centromere. The existence of common determinants for the function of both centromeres and telomeres is discussed.
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Affiliation(s)
- M Agudo
- Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM), 28049 Madrid, Spain
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34
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Affiliation(s)
- I F Zhimulev
- Institute of Cytology and Genetics, Siberian Division of Russian Academy of Sciences, Novosibirsk, Russia
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35
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Lloyd VK, Sinclair DA, Grigliatti TA. Genomic imprinting and position-effect variegation in Drosophila melanogaster. Genetics 1999; 151:1503-16. [PMID: 10101173 PMCID: PMC1460573 DOI: 10.1093/genetics/151.4.1503] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Genomic imprinting is a phenomenon in which the expression of a gene or chromosomal region depends on the sex of the individual transmitting it. The term imprinting was first coined to describe parent-specific chromosome behavior in the dipteran insect Sciara and has since been described in many organisms, including other insects, plants, fish, and mammals. In this article we describe a mini-X chromosome in Drosophila melanogaster that shows genomic imprinting of at least three closely linked genes. The imprinting of these genes is observed as mosaic silencing when the genes are transmitted by the male parent, in contrast to essentially wild-type expression when the same genes are maternally transmitted. We show that the imprint is due to the sex of the parent rather than to a conventional maternal effect, differential mitotic instability of the mini-X chromosome, or an allele-specific effect. Finally, we have examined the effects of classical modifiers of position-effect variegation on the maintenance and the establishment of the imprint. Factors that modify position-effect variegation alter the somatic expression but not the establishment of the imprint. This suggests that chromatin structure is important in maintenance of the imprint, but a separate mechanism may be responsible for its initiation.
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Affiliation(s)
- V K Lloyd
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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36
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Bhadra U, Bhadra MP, Birchler JA. Interactions among dosage-dependent trans-acting modifiers of gene expression and position-effect variegation in Drosophila. Genetics 1998; 150:251-63. [PMID: 9725844 PMCID: PMC1460319 DOI: 10.1093/genetics/150.1.251] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have investigated the effect of dosage-dependent trans-acting regulators of the white eye color gene in combinations to understand their interaction properties. The consequences of the interactions will aid in an understanding of aneuploid syndromes, position-effect variegation (PEV), quantitative traits, and dosage compensation, all of which are affected by dosage-dependent modifiers. Various combinations modulate two functionally related transcripts, white and scarlet, differently. The overall trend is that multiple modifiers are noncumulative or epistatic to each other. In some combinations, developmental transitions from larvae to pupae to adults act as a switch for whether the effect is positive or negative. With position-effect variegation, similar responses were found as with gene expression. The highly multigenic nature of dosage-sensitive modulation of both gene expression and PEV suggests that dosage effects can be progressively transduced through a series of steps in a hierarchical manner.
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Affiliation(s)
- U Bhadra
- Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA
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37
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Clegg NJ, Honda BM, Whitehead IP, Grigliatti TA, Wakimoto B, Brock HW, Lloyd VK, Sinclair DAR. Suppressors of position-effect variegation in Drosophila melanogaster affect expression of the heterochromatic gene light in the absence of a chromosome rearrangement. Genome 1998. [DOI: 10.1139/g98-041] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Suppressors of position-effect variegation (Su(var)s) in Drosophila melanogaster are usually studied in the presence of chromosomal rearrangements, which exhibit variegated expression of euchromatic genes moved near to, or heterochromatic genes moved away from, centromeric heterochromatin. However, the effects of Su(var) mutations on heterochromatic gene expression in the absence of a variegating re-arrangement have not yet been defined. Here we present a number of results which suggest that Su(var) gene products can interact to affect the expression of the light gene in its normal heterochromatic location. We initially observed that eye pigment was reduced in several Su(var) double mutants; the phenotype resembled that of light mutations and was more severe when only one copy of the light gene was present. This reduced pigmentation could be alleviated by a duplication for the light gene or by a reduction in the amount of cellular heterochromatin. In addition, the viability of most Su(var) double mutant combinations tested was greatly reduced in a genetic background of reduced light gene dosage, when extra heterochromatin is present. We conclude that Su(var) gene products can affect expression of the heterochromatic light gene in the absence of any chromosomal rearrangements. However, it is noteworthy that mutations in any single Su(var) gene have little effect on light expression; we observe instead that different pairings of Su(var) mutations are required to show an effect on light expression. Interestingly, we have obtained evidence that at least two of the second chromosome Su(var) mutations are gain-of-function lesions, which also suggests that there may be different modes of interaction among these genes. It may therefore be possible to use this more sensitive assay of Su(var) effects on heterochromatic genes to infer functional relationships among the products of the 50 or more known Su(var) loci.Key words: heterochromatin, chromatin, gene interactions.
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38
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Roche SE, Rio DC. Trans-silencing by P elements inserted in subtelomeric heterochromatin involves the Drosophila Polycomb group gene, Enhancer of zeste. Genetics 1998; 149:1839-55. [PMID: 9691041 PMCID: PMC1460262 DOI: 10.1093/genetics/149.4.1839] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Drosophila P-element transposition is regulated by a maternally inherited state known as P cytotype. An important aspect of P cytotype is transcriptional repression of the P-element promoter. P cytotype can also repress non-P-element promoters within P-element ends, suggesting that P cytotype repression might involve chromatin-based transcriptional silencing. To learn more about the role of chromatin in P cytotype repression, we have been studying the P strain Lk-P(1A). This strain contains two full-length P elements inserted in the heterochromatic telomere-associated sequences (TAS elements) at cytological location 1A. Mutations in the Polycomb group gene (Pc-G gene), Enhancer of zeste (E(z)), whose protein product binds at 1A, resulted in a loss of Lk-P(1A) cytotype control. E(z) mutations also affected the trans-silencing of heterologous promoters between P-element termini by P-element transgenes inserted in the TAS repeats. These data suggest that pairing interactions between P elements, resulting in exchange of chromatin structures, may be a mechanism for controlling the expression and activity of P elements.
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Affiliation(s)
- S E Roche
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3204, USA
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39
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Belyaeva ES, Zhimulev IF, Volkova EI, Alekseyenko AA, Moshkin YM, Koryakov DE. Su(UR)ES: a gene suppressing DNA underreplication in intercalary and pericentric heterochromatin of Drosophila melanogaster polytene chromosomes. Proc Natl Acad Sci U S A 1998; 95:7532-7. [PMID: 9636184 PMCID: PMC22673 DOI: 10.1073/pnas.95.13.7532] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A genetic locus suppressing DNA underreplication in intercalary heterochromatin (IH) and pericentric heterochromatin (PH) of the polytene chromosomes of Drosophila melanogaster salivary glands, has been described. Found in the In(1)scV2 strain, the mutation, designated as Su(UR)ES, was located on chromosome 3L at position 34. 8 and cytologically mapped to region 68A3-B4. A cytological phenotype was observed in the salivary gland chromosomes of larvae homozygous and hemizygous for Su(UR)ES: (i) in the IH regions, that normally are incompletely polytenized and so they often break to form "weak points," underreplication is suppressed, breaks and ectopic contacts disappear; (ii) the degree of polytenization in PH grows higher. That is why the regions in chromosome arm basements, normally beta-heterochromatic, acquire a distinct banding pattern, i. e., become euchromatic by morphological criteria; (iii) an additional bulk of polytenized material arises between the arms of chromosome 3 to form a fragment with a typical banding pattern. Chromosome 2 PH reveals additional alpha-heterochromatin. Su(UR)ES does not affect the viability, fertility, or morphological characters of the imago, and has semidominant expression in the heterozygote and distinct maternal effect. The results obtained provide evidence that the processes leading to DNA underreplication in IH and PH are affected by the same genetic mechanism.
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Affiliation(s)
- E S Belyaeva
- Laboratory of Molecular Cytogenetics, Institute of Cytology and Genetics, Russian Academy of Sciences, 10 Lavrentiev Avenue, Novosibirsk, 630090, Russia
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40
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Lu BY, Ma J, Eissenberg JC. Developmental regulation of heterochromatin-mediated gene silencing in Drosophila. Development 1998; 125:2223-34. [PMID: 9584122 DOI: 10.1242/dev.125.12.2223] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The roles of differentiation, mitotic activity and intrinsic promoter strength in the maintenance of heterochromatic silencing were investigated during development using an inducible lacZ gene as an in vivo probe. Heterochromatic silencing is initiated at the onset of gastrulation, approximately 1 hour after heterochromatin is first visible cytologically. A high degree of silencing is maintained in the mitotically active imaginal cells from mid-embryogenesis until early third instar larval stage, and extensive relaxation of silencing is tightly associated with the onset of differentiation. Relaxation of silencing can be triggered in vitro by ecdysone. In contrast, timing and extent of silencing at both the initiation and relaxation stages are insensitive to changes in cell cycle activity, and intrinsic promoter strength also does not influence the extent of silencing by heterochromatin. These data suggest that the silencing activity of heterochromatin is developmentally programmed.
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Affiliation(s)
- B Y Lu
- Cell and Molecular Biology Program and Edward A. Doisy Department of Biochemistry and Molecular Biology, St Louis University Health Sciences Center, St Louis, MO 63104, USA
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41
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Sekelsky JJ, Burtis KC, Hawley RS. Damage control: the pleiotropy of DNA repair genes in Drosophila melanogaster. Genetics 1998; 148:1587-98. [PMID: 9560378 PMCID: PMC1460071 DOI: 10.1093/genetics/148.4.1587] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- J J Sekelsky
- Department of Genetics, Section of Molecular and Cellular Biology, University of California, Davis 95616, USA
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42
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Williams BC, Murphy TD, Goldberg ML, Karpen GH. Neocentromere activity of structurally acentric mini-chromosomes in Drosophila. Nat Genet 1998; 18:30-7. [PMID: 9425896 DOI: 10.1038/ng0198-30] [Citation(s) in RCA: 142] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Chromosome fragments that lack centromeric DNA (structurally acentric chromosomes) are usually not inherited in mitosis and meiosis. We previously described the isolation, after irradiation of a Drosophila melanogaster mini-chromosome, of structurally acentric mini-chromosomes that display efficient mitotic and meiotic transmission despite their small size (under 300 kb) and lack of centromeric DNA. Here we report that these acentric mini-chromosomes bind the centromere-specific protein ZW10 and associate with the spindle poles in anaphase. The sequences in these acentric mini-chromosomes were derived from the tip of the X chromosome, which does not display centromere activity or localize ZW10, even when separated from the rest of the X. We conclude that the normally non-centromeric DNAs present in these acentric mini-chromosomes have acquired centromere function, and suggest that this example of 'neocentromere' formation involves appropriation of a self-propagating centromeric chromatin structure. The potential relevance of these observations to the identity, propagation and function of normal centromeres is discussed.
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Affiliation(s)
- B C Williams
- Section of Genetics and Development, Cornell University, Ithaca, New York 14853, USA
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43
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Abstract
Centromeres play a critical role in chromosome inheritance but are among the most difficult genomic components to analyze in multicellular eukaryotes. Here, we present a highly detailed molecular structure of a functional centromere in a multicellular organism. The centromere of the Drosophila minichromosome Dp1187 is contained within a 420 kb region of centric heterochromatin. We have used a new approach to characterize the detailed structure of this centromere and found that it is primarily composed of satellites and single, complete transposable elements. In the rest of the Drosophila genome, these satellites and transposable elements are neither unique to the centromeres nor present at all centromeres. We discuss the impact of these results on our understanding of heterochromatin structure and on the determinants of centromere identity and function.
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Affiliation(s)
- X Sun
- Molecular Biology and Virology Laboratory, The Salk Institute, La Jolla, California 92037, USA
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44
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Zhimulev IF. Polytene chromosomes, heterochromatin, and position effect variegation. ADVANCES IN GENETICS 1997; 37:1-566. [PMID: 9352629 DOI: 10.1016/s0065-2660(08)60341-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- I F Zhimulev
- Institute of Cytology and Genetics, Siberian Division of the Russian Academy of Sciences, Novosibirsk, Russia
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45
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PERONDINI AL, RIBEIRO AF. Chromosome elimination in germ cells ofSciaraembryos: involvement of the nuclear envelope. INVERTEBR REPROD DEV 1997. [DOI: 10.1080/07924259.1997.9672614] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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46
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Cléard F, Delattre M, Spierer P. SU(VAR)3-7, a Drosophila heterochromatin-associated protein and companion of HP1 in the genomic silencing of position-effect variegation. EMBO J 1997; 16:5280-8. [PMID: 9311988 PMCID: PMC1170160 DOI: 10.1093/emboj/16.17.5280] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
An increase in the dose of the Su(var)3-7 locus of Drosophila melanogaster enhances the genomic silencing of position-effect variegation caused by centromeric heterochromatin. Here we show that the product of Su(var)3-7 is a nuclear protein which associates with pericentromeric heterochromatin at interphase, whether on diploid chromosomes from embryonic nuclei or on polytene chromosomes from larval salivary glands. The protein also associates with the partially heterochromatic chromosome 4. As these phenotypes and localizations resemble those described by others for the Su(var)2-5 locus and its heterochromatin-associated protein HP1, the presumed co-operation of the two proteins was tested further. The effect of the dose of Su(var)3-7 on silencing of a number of variegating rearrangements and insertions is strikingly similar to the effect of the dose of Su(var)2-5 reported by others. In addition, the two loci interact genetically, and the two proteins co-immunoprecipitate from nuclear extracts. The results suggest that SU(VAR)3-7 and HP1 co-operate in building the genomic silencing associated with heterochromatin.
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Affiliation(s)
- F Cléard
- Department of Zoology and Animal Biology, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland
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47
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Bhadra U, Pal-Bhadra M, Birchler JA. A sex-influenced modifier in Drosophila that affects a broad spectrum of target loci including the histone repeats. Genetics 1997; 146:903-17. [PMID: 9215896 PMCID: PMC1208060 DOI: 10.1093/genetics/146.3.903] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A second chromosomal trans-acting modifier, Lightener of white (Low), modulates the phenotypic expression of various alleles of the white eye color gene. This modifier has an unusually broad spectrum of affected genes including white, brown, scarlet and the eye developmental genes, Bar and Lobe. In addition, Low weakly suppresses position effect variegation. Northern blot hybridization with different X and autosomal probes reveals that Low modulates genes of independent expression patterns. Interestingly, many of the modulations of gene expression are developmentally restricted and differ in intensity between the sexes. Low also elevates the expression of the histone tandem repeats in three distinct developmental stages. A deficiency encompassing the histone cluster reduces their transcript levels and significantly alters the expression of some of the tested genes. Thus, Low is a modifier that plays a role in modulating the expression of genes governing various processes including pigment deposition, eye development, chromosomal proteins and position effect variegation.
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Affiliation(s)
- U Bhadra
- Division of Biological Sciences, University of Missouri-Columbia 65211, USA
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48
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Glaser RL, Leach TJ, Ostrowski SE. The structure of heterochromatic DNA is altered in polyploid cells of Drosophila melanogaster. Mol Cell Biol 1997; 17:1254-63. [PMID: 9032252 PMCID: PMC231850 DOI: 10.1128/mcb.17.3.1254] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
DNA sequences within heterochromatin are often selectively underrepresented during development of polyploid chromosomes, and DNA molecules of altered structure are predicted to form as a consequence of the underrepresentation process. We have identified heterochromatic DNAs of altered structure within sequences that are underrepresented in polyploid cells of Drosophila melanogaster. Specifically, restriction fragments that extend into centric heterochromatin of the minichromosome Dp(1;f)1187 are shortened in polyploid cells of both the ovary and salivary gland but not in the predominantly diploid cells of the embryo or larval imaginal discs and brains. Shortened DNA molecules were also identified within heterochromatic sequences of chromosome III. These results suggest that the structure of heterochromatic DNA is altered as a general consequence of polyploid chromosome formation and that the shortened molecules identified form as a consequence of heterochromatic underrepresentation. Finally, alteration of heterochromatic DNA structure on Dp(1;f)1187 was not correlated with changes in the variegated expression of the yellow gene located on the minichromosome.
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Affiliation(s)
- R L Glaser
- Laboratory of Developmental Genetics, Wadsworth Center, New York State Department of Health, Albany, New York 12201-2002, USA.
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49
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Cook KR, Murphy TD, Nguyen TC, Karpen GH. Identification of trans-acting genes necessary for centromere function in Drosophila melanogaster using centromere-defective minichromosomes. Genetics 1997; 145:737-47. [PMID: 9055083 PMCID: PMC1207858 DOI: 10.1093/genetics/145.3.737] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Deletions in the Drosophila minichromosome Dp1187 were used to investigate the genetic interactions of trans-acting genes with the centromere. Mutations in several genes known to have a role in chromosome inheritance were shown to have dominant effects on the stability of minichromosomes with partially defective centromeres. Heterozygous mutations in the ncd and klp3A kinesin-like protein genes strongly reduced the transmission of minichromosomes missing portions of the genetically defined centromere but had little effect on the transmission of minichromosomes with intact centromeres. Using this approach, ncd and klp3A were shown to require only the centromeric region of the chromosome for their roles in chromosome segregation. Increased gene dosage also affected minichromosome transmission and was used to demonstrate that the nod kinesin-like protein gene interacts genetically with the centro mere, in addition to interacting with extracentromeric regions as demonstrated previously. The results presented in this study strongly suggest that dominant genetic interactions between mutations and centromere-defective minichromosomes could be used effectively to identify novel genes necessary for centromere function.
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Affiliation(s)
- K R Cook
- Molecular Biology and Virology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037, USA
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50
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Henchoz S, De Rubertis F, Pauli D, Spierer P. The dose of a putative ubiquitin-specific protease affects position-effect variegation in Drosophila melanogaster. Mol Cell Biol 1996; 16:5717-25. [PMID: 8816485 PMCID: PMC231572 DOI: 10.1128/mcb.16.10.5717] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A dominant insertional P-element mutation enhances position-effect variegation in Drosophila melanogaster. The mutation is homozygous, viable, and fertile and maps at 64E on the third chromosome. The corresponding gene was cloned by transposon tagging. Insertion of the transposon upstream of the open reading frame correlates with a strong reduction of transcript level. A transgene was constructed with the cDNA and found to have the effect opposite from that of the mutation, namely, to suppress variegation. Sequencing of the cDNA reveals a large open reading frame encoding a putative ubiquitin-specific protease (Ubp). Ubiquitin marks various proteins, frequently for proteasome-dependent degradation. Ubps can cleave the ubiquitin part from these proteins. We discuss the link established here between a deubiquitinating enzyme and epigenetic silencing processes.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Genetically Modified
- Base Sequence
- Chromosome Mapping
- Crosses, Genetic
- Drosophila melanogaster/enzymology
- Drosophila melanogaster/genetics
- Embryo, Nonmammalian
- Endopeptidases/genetics
- Endopeptidases/metabolism
- Female
- Gene Expression Regulation, Developmental
- Gene Expression Regulation, Enzymologic
- Genes, Homeobox
- Genes, Insect
- Homozygote
- Male
- Molecular Sequence Data
- Mutagenesis, Insertional
- Open Reading Frames
- Pigmentation
- Recombination, Genetic
- Restriction Mapping
- Sequence Homology, Amino Acid
- Transcription, Genetic
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Affiliation(s)
- S Henchoz
- Department of Zoology and Animal Biology, University of Geneva, Switzerland
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