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Unraveling the DNA Methylation in the rDNA Foci in Mutagen-Induced Brachypodium distachyon Micronuclei. Int J Mol Sci 2022; 23:ijms23126797. [PMID: 35743241 PMCID: PMC9224279 DOI: 10.3390/ijms23126797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/15/2022] [Accepted: 06/17/2022] [Indexed: 02/01/2023] Open
Abstract
Many years have passed since micronuclei were first observed then accepted as an indicator of the effect of mutagens. However, the possible mechanisms of their formation and elimination from the cell are still not fully understood. Various stresses, including mutagens, can alter gene expression through changes in DNA methylation in plants. In this study we demonstrate for the first time DNA methylation in the foci of 5S and 35S rDNA sequences in individual Brachypodium distachyon micronuclei that are induced by mutagenic treatment with maleic acid hydrazide (MH). The impact of MH on global epigenetic modifications in nuclei and micronuclei has been studied in plants before; however, no in situ analyses of DNA methylation in specific DNA sequence sites are known. To address this problem, we used sequential immunodetection of 5-methylcytosine and fluorescence in situ hybridization (FISH) with 5S and 25S rDNA probes on the non-dividing cells of B. distachyon. Such investigations into the presence or absence of DNA methylation within specific DNA sequences are extremely important in plant mutagenesis in the light of altering gene expression.
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2
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Hummel G, Liu C. Organization and epigenomic control of RNA polymerase III-transcribed genes in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 67:102199. [PMID: 35364484 DOI: 10.1016/j.pbi.2022.102199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 01/24/2022] [Accepted: 02/14/2022] [Indexed: 06/14/2023]
Abstract
The genetic information linearly scripted in chromosomes is wrapped in a ribonucleoprotein complex called chromatin. The adaptation of its compaction level and spatiotemporal organization refines gene expression in response to developmental and environmental cues. RNA polymerase III (RNAPIII) is responsible for the biogenesis of elementary non-coding RNAs. Their genes are subjected to high duplication and mutational rates, and invade nuclear genomes. Their insertion into different epigenomic environments raises the question of how chromatin packing affects their individual transcription. In this review, we provide a unique perspective to this issue in plants. In addition, we discuss how the genomic organization of RNAPIII-transcribed loci, combined with epigenetic differences, might participate to plant trait variations.
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Affiliation(s)
- Guillaume Hummel
- Institute of Biology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
| | - Chang Liu
- Institute of Biology, University of Hohenheim, Garbenstraße 30, 70599, Stuttgart, Germany.
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3
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Hummel G, Berr A, Graindorge S, Cognat V, Ubrig E, Pflieger D, Molinier J, Drouard L. Epigenetic silencing of clustered tRNA genes in Arabidopsis. Nucleic Acids Res 2020; 48:10297-10312. [PMID: 32941623 PMCID: PMC7544208 DOI: 10.1093/nar/gkaa766] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 07/21/2020] [Accepted: 09/03/2020] [Indexed: 12/12/2022] Open
Abstract
Beyond their key role in translation, cytosolic transfer RNAs (tRNAs) are involved in a wide range of other biological processes. Nuclear tRNA genes (tDNAs) are transcribed by the RNA polymerase III (RNAP III) and cis-elements, trans-factors as well as genomic features are known to influence their expression. In Arabidopsis, besides a predominant population of dispersed tDNAs spread along the 5 chromosomes, some clustered tDNAs have been identified. Here, we demonstrate that these tDNA clusters are transcriptionally silent and that pathways involved in the maintenance of DNA methylation play a predominant role in their repression. Moreover, we show that clustered tDNAs exhibit repressive chromatin features whilst their dispersed counterparts contain permissive euchromatic marks. This work demonstrates that both genomic and epigenomic contexts are key players in the regulation of tDNAs transcription. The conservation of most of these regulatory processes suggests that this pioneering work in Arabidopsis can provide new insights into the regulation of RNA Pol III transcription in other organisms, including vertebrates.
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Affiliation(s)
- Guillaume Hummel
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Alexandre Berr
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Stéfanie Graindorge
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Valérie Cognat
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Elodie Ubrig
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - David Pflieger
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Jean Molinier
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
| | - Laurence Drouard
- Institut de biologie moléculaire des plantes-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, F-67084 Strasbourg, France
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4
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Simon L, Rabanal FA, Dubos T, Oliver C, Lauber D, Poulet A, Vogt A, Mandlbauer A, Le Goff S, Sommer A, Duborjal H, Tatout C, Probst AV. Genetic and epigenetic variation in 5S ribosomal RNA genes reveals genome dynamics in Arabidopsis thaliana. Nucleic Acids Res 2019. [PMID: 29518237 PMCID: PMC5887818 DOI: 10.1093/nar/gky163] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Organized in tandem repeat arrays in most eukaryotes and transcribed by RNA polymerase III, expression of 5S rRNA genes is under epigenetic control. To unveil mechanisms of transcriptional regulation, we obtained here in depth sequence information on 5S rRNA genes from the Arabidopsis thaliana genome and identified differential enrichment in epigenetic marks between the three 5S rDNA loci situated on chromosomes 3, 4 and 5. We reveal the chromosome 5 locus as the major source of an atypical, long 5S rRNA transcript characteristic of an open chromatin structure. 5S rRNA genes from this locus translocated in the Landsberg erecta ecotype as shown by linkage mapping and chromosome-specific FISH analysis. These variations in 5S rDNA locus organization cause changes in the spatial arrangement of chromosomes in the nucleus. Furthermore, 5S rRNA gene arrangements are highly dynamic with alterations in chromosomal positions through translocations in certain mutants of the RNA-directed DNA methylation pathway and important copy number variations among ecotypes. Finally, variations in 5S rRNA gene sequence, chromatin organization and transcripts indicate differential usage of 5S rDNA loci in distinct ecotypes. We suggest that both the usage of existing and new 5S rDNA loci resulting from translocations may impact neighboring chromatin organization.
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Affiliation(s)
- Lauriane Simon
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Fernando A Rabanal
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Tristan Dubos
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Cecilia Oliver
- Departamento de Genética, Facultad de Biología, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Damien Lauber
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Axel Poulet
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Alexander Vogt
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Ariane Mandlbauer
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Samuel Le Goff
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Andreas Sommer
- Vienna Biocenter Core Facilities GmbH (VBCF), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Hervé Duborjal
- Plant Engineering Platform, BIOGEMMA, Route d'Ennezat Centre de Recherche de Chappes, 63720 Chappes, France
| | - Christophe Tatout
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
| | - Aline V Probst
- GReD, Université Clermont Auvergne, CNRS, INSERM, BP 38, 63001 Clermont-Ferrand, France
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Tamayo-Ordóñez YJ, Narváez-Zapata JA, Tamayo-Ordóñez MC, Sánchez-Teyer LF. Retroelements and DNA Methylation Could Contribute to Diversity of 5S rDNA in Agave L. J Mol Evol 2018; 86:404-423. [DOI: 10.1007/s00239-018-9856-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 07/03/2018] [Indexed: 01/21/2023]
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6
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Systematic application of DNA fiber-FISH technique in cotton. PLoS One 2013; 8:e75674. [PMID: 24086609 PMCID: PMC3785504 DOI: 10.1371/journal.pone.0075674] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 08/09/2013] [Indexed: 01/16/2023] Open
Abstract
Fluorescence in situ hybridization on extended DNA (fiber-FISH) is a powerful tool in high-resolution physical mapping. To introduce this technique into cotton, we developed the technique and tested it by deliberately mapping of telomere and 5S rDNA. Results showed that telomere-length ranged from 0.80 kb to 37.86 kb in three species, G. hirsutum, G. herbaceum and G. arboreum. However, most of the telomeres (>91.0%) were below 10 kb. The length of 5S rDNA was revealed as 964 kb in G. herbaceum whereas, in G. arboreum, it was approximately three times longer (3.1 Mb). A fiber-FISH based immunofluorescence method was also described to assay the DNA methylation. Using this technique, we revealed that both telomere and 5S rDNA were methylated at different levels. In addition, we developed a BAC molecule-based fiber-FISH technique. Using this technique, we can precisely map BAC clones on each other and evaluated the size and location of overlapped regions. The development and application of fiber-FISH technique will facilitate high-resolution physical mapping and further directed sequencing projects for cotton.
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Lafon-Placette C, Faivre-Rampant P, Delaunay A, Street N, Brignolas F, Maury S. Methylome of DNase I sensitive chromatin in Populus trichocarpa shoot apical meristematic cells: a simplified approach revealing characteristics of gene-body DNA methylation in open chromatin state. THE NEW PHYTOLOGIST 2013; 197:416-430. [PMID: 23253333 DOI: 10.1111/nph.12026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 10/02/2012] [Indexed: 05/17/2023]
Abstract
DNA methylation is involved in the control of plant development and adaptation to the environment through modifications of chromatin compaction and gene expression. In poplar (Populus trichocarpa), a perennial plant, variations in DNA methylation have been reported between genotypes and tissues or in response to drought. Nevertheless, the relationships between gene-body DNA methylation, gene expression and chromatin compaction still need clarification. Here, DNA methylation was mapped in the noncondensed chromatin fraction from P. trichocarpa shoot apical meristematic cells, the center of plant morphogenesis, where DNA methylation variations could influence the developmental trajectory. DNase I was used to isolate the noncondensed chromatin fraction. Methylated sequences were immunoprecipitated, sequenced using Illumina/Solexa technology and mapped on the v2.0 poplar genome. Bisulfite sequencing of candidate sequences was used to confirm mapping data and to assess cytosine contexts and methylation levels. While the methylated DNase I hypersensitive site fraction covered 1.9% of the poplar genome, it contained sequences corresponding to 74% of poplar gene models, mostly exons. The level and cytosine context of gene-body DNA methylation varied with the structural characteristics of the genes. Taken together, our data show that DNA methylation is widespread and variable among genes in open chromatin of meristematic cells, in agreement with a role in their developmental trajectory.
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Affiliation(s)
- Clément Lafon-Placette
- Université d'Orléans, Faculté des Sciences, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA 1207, Orléans, 45067, France
- INRA, USC1328 Arbres et Réponses aux Contraintes Hydriques et Environnementales (ARCHE), Orléans, 45067, France
| | - Patricia Faivre-Rampant
- INRA, UMR1165, UMR INRA / Université d'Evry, Unité de Recherche en Génomique Végétale, Centre de Recherche de Versailles-Grignon, Evry, 91057, France
| | - Alain Delaunay
- Université d'Orléans, Faculté des Sciences, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA 1207, Orléans, 45067, France
- INRA, USC1328 Arbres et Réponses aux Contraintes Hydriques et Environnementales (ARCHE), Orléans, 45067, France
| | - Nathaniel Street
- Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, Umeå, 901 87, Sweden
| | - Franck Brignolas
- Université d'Orléans, Faculté des Sciences, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA 1207, Orléans, 45067, France
- INRA, USC1328 Arbres et Réponses aux Contraintes Hydriques et Environnementales (ARCHE), Orléans, 45067, France
| | - Stéphane Maury
- Université d'Orléans, Faculté des Sciences, Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), UPRES EA 1207, Orléans, 45067, France
- INRA, USC1328 Arbres et Réponses aux Contraintes Hydriques et Environnementales (ARCHE), Orléans, 45067, France
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8
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Garcia S, Crhák Khaitová L, Kovařík A. Expression of 5 S rRNA genes linked to 35 S rDNA in plants, their epigenetic modification and regulatory element divergence. BMC PLANT BIOLOGY 2012; 12:95. [PMID: 22716941 PMCID: PMC3409069 DOI: 10.1186/1471-2229-12-95] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/20/2012] [Indexed: 05/09/2023]
Abstract
BACKGROUND In plants, the 5 S rRNA genes usually occur as separate tandems (S-type arrangement) or, less commonly, linked to 35 S rDNA units (L-type). The activity of linked genes remains unknown so far. We studied the homogeneity and expression of 5 S genes in several species from family Asteraceae known to contain linked 35 S-5 S units. Additionally, their methylation status was determined using bisulfite sequencing. Fluorescence in situ hybridization was applied to reveal the sub-nuclear positions of rDNA arrays. RESULTS We found that homogenization of L-type units went to completion in most (4/6) but not all species. Two species contained major L-type and minor S-type units (termed L(s)-type). The linked genes dominate 5 S rDNA expression while the separate tandems do not seem to be expressed. Members of tribe Anthemideae evolved functional variants of the polymerase III promoter in which a residing C-box element differs from the canonical angiosperm motif by as much as 30%. On this basis, a more relaxed consensus sequence of a plant C-box: (5'-RGSWTGGGTG-3') is proposed. The 5 S paralogs display heavy DNA methylation similarly as to their unlinked counterparts. FISH revealed the close association of 35 S-5 S arrays with nucleolar periphery indicating that transcription of 5 S genes may occur in this territory. CONCLUSIONS We show that the unusual linked arrangement of 5 S genes, occurring in several plant species, is fully compatible with their expression and functionality. This extraordinary 5 S gene dynamics is manifested at different levels, such as variation in intrachromosomal positions, unit structure, epigenetic modification and considerable divergence of regulatory motifs.
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MESH Headings
- Animals
- Asteraceae/chemistry
- Asteraceae/genetics
- Asteraceae/metabolism
- Base Sequence
- Consensus Sequence
- DNA Methylation
- DNA, Plant/chemistry
- DNA, Plant/genetics
- DNA, Plant/metabolism
- Epigenesis, Genetic
- Evolution, Molecular
- Gene Expression Regulation, Plant
- Molecular Sequence Data
- Promoter Regions, Genetic
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- Regulatory Sequences, Nucleic Acid
- Response Elements
- Sequence Alignment
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Affiliation(s)
- Sònia Garcia
- Laboratori de Botànica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s. n., Barcelona, Catalonia, 08028, Spain
| | - Lucie Crhák Khaitová
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, CZ-6125, Czech Republic
| | - Aleš Kovařík
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, Brno, CZ-6125, Czech Republic
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9
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Blevins T, Pontes O, Pikaard CS, Meins F. Heterochromatic siRNAs and DDM1 independently silence aberrant 5S rDNA transcripts in Arabidopsis. PLoS One 2009; 4:e5932. [PMID: 19529764 PMCID: PMC2691480 DOI: 10.1371/journal.pone.0005932] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 05/11/2009] [Indexed: 12/22/2022] Open
Abstract
5S ribosomal RNA gene repeats are arranged in heterochromatic arrays (5S rDNA) situated near the centromeres of Arabidopsis chromosomes. The chromatin remodeling factor DDM1 is known to maintain 5S rDNA methylation patterns while silencing transcription through 5S rDNA intergenic spacers (IGS). We mapped small-interfering RNAs (siRNA) to a composite 5S rDNA repeat, revealing a high density of siRNAs matching silenced IGS transcripts. IGS transcript repression requires proteins of the heterochromatic siRNA pathway, including RNA polymerase IV (Pol IV), RNA-DEPENDENT RNA POLYMERASE 2 (RDR2) and DICER-LIKE 3 (DCL3). Using molecular and cytogenetic approaches, we show that the DDM1 and siRNA-dependent silencing effects are genetically independent. DDM1 suppresses production of the siRNAs, however, thereby limiting RNA-directed DNA methylation at 5S rDNA repeats. We conclude that DDM1 and siRNA-dependent silencing are overlapping processes that both repress aberrant 5S rDNA transcription and contribute to the heterochromatic state of 5S rDNA arrays.
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MESH Headings
- Arabidopsis/metabolism
- Arabidopsis Proteins/metabolism
- Chromatin/chemistry
- Computational Biology/methods
- Crosses, Genetic
- DNA, Intergenic
- DNA, Ribosomal/metabolism
- DNA-Binding Proteins/metabolism
- Gene Silencing
- Genes, Plant
- In Situ Hybridization, Fluorescence
- Models, Biological
- RNA, Ribosomal, 5S/metabolism
- RNA, Small Interfering/metabolism
- Transcription Factors/metabolism
- Transcription, Genetic
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Affiliation(s)
- Todd Blevins
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Olga Pontes
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Craig S. Pikaard
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Frederick Meins
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- * E-mail:
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10
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Baubec T, Pecinka A, Rozhon W, Mittelsten Scheid O. Effective, homogeneous and transient interference with cytosine methylation in plant genomic DNA by zebularine. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 57:542-54. [PMID: 18826433 PMCID: PMC2667684 DOI: 10.1111/j.1365-313x.2008.03699.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 09/09/2008] [Accepted: 09/18/2008] [Indexed: 05/21/2023]
Abstract
Covalent modification by methylation of cytosine residues represents an important epigenetic hallmark. While sequence analysis after bisulphite conversion allows correlative analyses with single-base resolution, functional analysis by interference with DNA methylation is less precise, due to the complexity of methylation enzymes and their targets. A cytidine analogue, 5-azacytidine, is frequently used as an inhibitor of DNA methyltransferases, but its rapid degradation in aqueous solution is problematic for culture periods of longer than a few hours. Application of zebularine, a more stable cytidine analogue with a similar mode of action that is successfully used as a methylation inhibitor in Neurospora and mammalian tumour cell lines, can significantly reduce DNA methylation in plants in a dose-dependent and transient manner independent of sequence context. Demethylation is connected with transcriptional reactivation and partial decondensation of heterochromatin. Zebularine represents a promising new and versatile tool for investigating the role of DNA methylation in plants with regard to transcriptional control, maintenance and formation of (hetero-) chromatin.
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11
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Li CF, Henderson IR, Song L, Fedoroff N, Lagrange T, Jacobsen SE. Dynamic regulation of ARGONAUTE4 within multiple nuclear bodies in Arabidopsis thaliana. PLoS Genet 2008; 4:e27. [PMID: 18266474 PMCID: PMC2233678 DOI: 10.1371/journal.pgen.0040027] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Accepted: 12/17/2007] [Indexed: 12/22/2022] Open
Abstract
DNA methylation directed by 24-nucleotide small RNAs involves the small RNA-binding protein ARGONAUTE4 (AGO4), and it was previously shown that AGO4 localizes to nucleolus-adjacent Cajal bodies, sites of snRNP complex maturation. Here we demonstrate that AGO4 also localizes to a second class of nuclear bodies, called AB-bodies, which are found immediately adjacent to condensed 45S ribosomal DNA (rDNA) sequences. AB-bodies also contain other proteins involved in RNA-directed DNA methylation including NRPD1b (a subunit of the RNA Polymerase IV complex, RNA PolIV), NRPD2 (a second subunit of this complex), and the DNA methyltransferase DRM2. These two classes of AGO4 bodies are structurally independent—disruption of one class does not affect the other—suggesting a dynamic regulation of AGO4 within two distinct nuclear compartments in Arabidopsis. Abolishing Cajal body formation in a coilin mutant reduced overall AGO4 protein levels, and coilin dicer-like3 double mutants showed a small decrease in DNA methylation beyond that seen in dicer-like3 single mutants, suggesting that Cajal bodies are required for a fully functioning DNA methylation system in Arabidopsis. Argonautes are components of the RNA interference (RNAi) pathway that bind small interfering RNAs (siRNAs) of 21–24 nucleotide length. In the flowering plant Arabidopsis thaliana, ARGONAUTE4 (AGO4) is involved in gene silencing at the transcriptional level in a process called RNA-directed DNA methylation (RdDM), during which siRNAs cause transcriptional gene repression at complementary sequences. Previously, we found that AGO4 localized to nucleolus-adjacent Cajal bodies, sites of snRNP complex assembly. In this study, we show the existence of a second class of AGO4 nuclear foci, which we call the “AB-bodies,” that is distinct from the Cajal body and is immediately adjacent to the condensed 45S ribosomal DNA (rDNA) loci. In addition to AGO4, AB-bodies also contained NRPD1b and NRPD2 (subunits of the plant-specific RNA polymerase IV complex) and the DNA methyltransferase DRM2. The two different classes of AGO4 nuclear foci are structurally distinct, since the loss of one class did not affect the other. Losing Cajal bodies resulted in the enhancement of the DNA methylation defects seen in the RNA silencing mutant dicer-like3, suggesting Cajal bodies are required for a fully functioning RdDM pathway leading to gene silencing.
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Affiliation(s)
- Carey F Li
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Ian R Henderson
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
| | - Liang Song
- Biology Department and Huck Institute of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Nina Fedoroff
- Biology Department and Huck Institute of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Thierry Lagrange
- Laboratoire Génome et Développement de Plantes (LGDP), UMR 5096, Université de Perpignan, Perpignan Cedex, France
| | - Steven E Jacobsen
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Department of Molecular, Cell and Developmental Biology, University of California Los Angeles, Los Angeles, California, United States of America
- Howard Hughes Medical Institute, University of California, Los Angeles, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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12
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Vaillant I, Tutois S, Jasencakova Z, Douet J, Schubert I, Tourmente S. Hypomethylation and hypermethylation of the tandem repetitive 5S rRNA genes in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 54:299-309. [PMID: 18208523 DOI: 10.1111/j.1365-313x.2008.03413.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
5S ribosomal DNA (5S rDNA) is organized in tandem repeats on chromosomes 3, 4 and 5 in Arabidopsis thaliana. One part of the 5S rDNA is located within the heterochromatic chromocenters, and the other fraction forms loops with euchromatic features that emanate from the chromocenters. We investigated whether the A. thaliana heterochromatin, and particularly the 5S rDNA, is modified when changing the culture conditions (cultivation in growth chamber versus greenhouse). Nuclei from challenged tissues displayed larger total, as well as 5S rDNA, heterochromatic fractions, and the DNA methyltransferase mutants met1 and cmt3 had different impacts in Arabidopsis. The enlarged fraction of heterochromatic 5S rDNA was observed, together with the reversal of the silencing of some 5S rRNA genes known as minor genes. We observed hypermethylation at CATG sites, and a concomitant DNA hypomethylation at CG/CXG sites in 5S rDNA. Our results show that the asymmetrical hypermethylation is correlated with the ageing of the plants, whereas hypomethylation results from the growth chamber/culture conditions. In spite of severely reduced DNA methylation, the met1 mutant revealed no increase in minor 5S rRNA transcripts in these conditions. The increasing proportion of cytosines in asymmetrical contexts during transition from the euchromatic to the heterochromatic state in the 5S rDNA array suggests that 5S rDNA units are differently affected by the (hypo and hyper)methylation patterns along the 5S rDNA locus. This might explain the different behaviour of 5S rDNA subpopulations inside a 5S array in terms of chromatin compaction and expression, i.e. some 5S rRNA genes would become derepressed, whereas others would join the heterochromatic fraction.
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Affiliation(s)
- Isabelle Vaillant
- Unité Mixte de Recherche CNRS 6247 GReD, INSERM, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France
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Fulnecek J, Kovarik A. Low abundant spacer 5S rRNA transcripts are frequently polyadenylated in Nicotiana. Mol Genet Genomics 2007; 278:565-73. [PMID: 17671796 DOI: 10.1007/s00438-007-0273-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 06/22/2007] [Accepted: 06/27/2007] [Indexed: 10/23/2022]
Abstract
In plants, 5S rRNA genes (5S rDNA) encoding 120-nt structural RNA molecules of ribosomes are organized in tandem arrays comprising thousands of units. Failure to correctly terminate transcription would generate longer inaccurately processed transcripts interfering with ribosome biogenesis. Hence multiple termination signals occur immediately after the 5S rRNA coding sequence. To obtain information about the efficiency of termination of 5S rDNA transcription in plants we analyzed 5S rRNA pools in three Nicotiana species, N. sylvestris, N. tomentosiformis and N. tabacum. In addition to highly abundant 120-nt 5S rRNA transcripts, we also detected RNA species composed of a genic region and variable lengths of intergenic sequences. These genic-intergenic RNA molecules occur at a frequency severalfold lower than the mature 120-nt transcripts, and are posttranscriptionally modified by polyadenylation at their 3' end in contrast to 120-nt transcripts. An absence of 5S small RNAs (smRNA) argue against a dominant role for the smRNA biosynthesis pathway in the degradation of aberrant 5S rRNA in Nicotiana. This work is the first description of polyadenylated 5S rRNA species in higher eukaryotes originating from a read-through transcription into the intergenic spacer. We propose that polyadenylation may function in a "quality control" pathway ensuring that only correctly processed molecules enter the ribosome biogenesis.
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Affiliation(s)
- Jaroslav Fulnecek
- Institute of Biophysics, Academy of Sciences of the Czech Republic v.v.i, Kralovopolska 135, 612 65, Brno, Czech Republic.
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14
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Hetzl J, Foerster AM, Raidl G, Mittelsten Scheid O. CyMATE: a new tool for methylation analysis of plant genomic DNA after bisulphite sequencing. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 51:526-36. [PMID: 17559516 DOI: 10.1111/j.1365-313x.2007.03152.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Cytosine methylation is a hallmark of epigenetic information in the DNA of many fungi, vertebrates and plants. The technique of bisulphite genomic sequencing reveals the methylation state of every individual cytosine in a sequence, and thereby provides high-resolution data on epigenetic diversity; however, the manual evaluation and documentation of large amounts of data is laborious and error-prone. While some software is available for facilitating the analysis of mammalian DNA methylation, which is found nearly exclusively at CG sites, there is no software optimally suited for data from DNA with significant non-CG methylation. We describe CyMATE (Cytosine Methylation Analysis Tool for Everyone) for in silico analysis of DNA sequences after bisulphite conversion of plant DNA, in which methylation is more divergent with respect to sequence context and biological relevance. From aligned sequences, CyMATE includes and distinguishes methylation at CG, CHG and CHH (where H = A, C or T), and can extract both quantitative and qualitative data regarding general and pattern-specific methylation per sequence and per position, i.e. data for individual sites in a sequence and the epigenetic divergence within a sample. In addition, it can provide graphical output from alignments in either an overview or a 'zoom-in' view as pdf files. Detailed information, including a quality control of the sequencing data, is provided in text format. We applied CyMATE to the analysis of DNA methylation at transcriptionally silenced promoters in diploid and polyploid Arabidopsis and found significant hypermethylation, high stability of the methylated state independent of chromosome number, and non-redundant patterns of mC distribution. CyMATE is freely available for non-commercial use at http://www.gmi.oeaw.ac.at/CyMATE.
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Affiliation(s)
- Jennifer Hetzl
- Institute for Computer Graphics and Algorithms, Vienna University of Technology, Favoritenstrasse 9-11, A-1040 Vienna, Austria
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15
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Douet J, Tourmente S. Transcription of the 5S rRNA heterochromatic genes is epigenetically controlled in Arabidopsis thaliana and Xenopus laevis. Heredity (Edinb) 2007; 99:5-13. [PMID: 17487217 DOI: 10.1038/sj.hdy.6800964] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
5S ribosomal DNA is a highly conserved tandemly repeated multigenic family. As suggested for a long time, we have shown that only a fraction of the 5S rRNA genes are expressed in Arabidopsis thaliana. In Xenopus laevis, there is a developmental control of the expression of the 5S rRNA genes with only one of the two 5S rDNA families expressed during oogenesis. For both Arabidopsis and Xenopus, the strongest transcription of 5S rRNA, respectively in the seed and during oogenesis is correlated with heterogeneity in the transcribed 5S rRNAs. Epigenetic mechanisms such as modification of the chromatin structure are involved in the transcriptional regulation of the 5S rRNA genes in both organisms. In Arabidopsis, two silencing pathways, methylation-dependent (RNAi) and methylation-independent (MOM pathway), are involved in the silencing of a 5S rDNA fraction.
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Affiliation(s)
- J Douet
- Unité Mixte de Recherche CNRS 6547 BIOMOVE, Université Blaise Pascal, Aubière Cedex, France
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16
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Vaillant I, Tutois S, Cuvillier C, Schubert I, Tourmente S. Regulation of Arabidopsis thaliana 5S rRNA Genes. PLANT & CELL PHYSIOLOGY 2007; 48:745-52. [PMID: 17412735 DOI: 10.1093/pcp/pcm043] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The Arabidopsis thaliana genome comprises around 1,000 copies of 5S rRNA genes encoding both major and minor 5S rRNAs. In mature wild-type leaves, the minor 5S rRNA genes are silent. Using different mutants of DNA methyltransferases (met1, cmt3 and met1 cmt3), components of the RNAi pathway (ago4) or post-translational histone modifier (hda6/sil1), we show that the corresponding proteins are needed to maintain proper methylation patterns at heterochromatic 5S rDNA repeats. Using reverse transcription-PCR and cytological analyses, we report that a decrease of 5S rDNA methylation at CG or CNG sites in these mutants leads to the release of 5S rRNA gene silencing which occurred without detectable changes of the 5S rDNA chromatin structure. In spite of severely reduced DNA methylation, the met1 cmt3 double mutant revealed no increase in minor 5S rRNA transcripts. Furthermore, the release of silencing of minor 5S rDNAs can be achieved without increased formation of euchromatic loops by 5S rDNA, and is independent from the global heterochromatin content. Additionally, fluorescence in situ hybridization with centromeric 180 bp repeats confirmed that these highly repetitive sequences, in spite of their elevated transcriptional activity in the DNA methyltransferase mutants (met1, cmt3 and met1 cmt3), remain within chromocenters of the mutant nuclei.
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Affiliation(s)
- Isabelle Vaillant
- Unité Mixte de Recherche CNRS 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, F-63177 Aubière Cedex, France
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17
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Fulnecek J, Matyasek R, Kovarik A. Plant 5S rDNA has multiple alternative nucleosome positions. Genome 2006; 49:840-50. [PMID: 16936792 DOI: 10.1139/g06-039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In plants, 5S ribosomal DNA (5S rDNA) is typically found in hundreds of copies of tandemly arranged units. Nucleotide database searches revealed that the majority of 5S genes (>90%) have repeat lengths that are not simple multiples of a plant nucleosomal unit, ranging in plants from 175-185 bp. To get insight into the chromatin structure, we have determined positions of nucleosomes in the Nicotiana sylvestris and Nicotiana tomentosiformis 5S rDNA units with repeat lengths of about 430 and 645 bp, respectively. Mapping experiments carried out on isolated nucleo somal DNA revealed many (>50) micrococcal nuclease cleavage sites in each class of repeats. Permutation analysis and theoretical computer prediction showed multiple DNA bend sites, mostly located in the nontranscribed spacer region. The distance between bend sites, however, did not correspond to the average spacing of nucleosomes in 5S chromatin (approximately 180 bp). These data indicate that 5S rDNA does not have fixed nucleosomal positioning sites and that units can be wrapped in a number of alternative nucleosome frames. Consequently, accessibility of transcription factors to cognate motifs might vary across the tandem array, potentially influencing gene expression.
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Affiliation(s)
- Jaroslav Fulnecek
- Institute of Biophysics, Academy of Scences of Czech Republic, Kralovopolska, Czech Republic
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18
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Abstract
DNA in plants is highly methylated, containing 5-methylcytosine (m5C) and N6-methyladenine (m6A); m5C is located mainly in symmetrical CG and CNG sequences but it may occur also in other non-symmetrical contexts. m6A but not m5C was found in plant mitochondrial DNA. DNA methylation in plants is species-, tissue-, organelle- and age-specific. It is controlled by phytohormones and changes on seed germination, flowering and under the influence of various pathogens (viral, bacterial, fungal). DNA methylation controls plant growth and development, with particular involvement in regulation of gene expression and DNA replication. DNA replication is accompanied by the appearance of under-methylated, newly formed DNA strands including Okazaki fragments; asymmetry of strand DNA methylation disappears until the end of the cell cycle. A model for regulation of DNA replication by methylation is suggested. Cytosine DNA methylation in plants is more rich and diverse compared with animals. It is carried out by the families of specific enzymes that belong to at least three classes of DNA methyltransferases. Open reading frames (ORF) for adenine DNA methyltransferases are found in plant and animal genomes, and a first eukaryotic (plant) adenine DNA methyltransferase (wadmtase) is described; the enzyme seems to be involved in regulation of the mitochondria replication. Like in animals, DNA methylation in plants is closely associated with histone modifications and it affects binding of specific proteins to DNA and formation of respective transcription complexes in chromatin. The same gene (DRM2) in Arabidopsis thaliana is methylated both at cytosine and adenine residues; thus, at least two different, and probably interdependent, systems of DNA modification are present in plants. Plants seem to have a restriction-modification (R-M) system. RNA-directed DNA methylation has been observed in plants; it involves de novo methylation of almost all cytosine residues in a region of siRNA-DNA sequence identity; therefore, it is mainly associated with CNG and non-symmetrical methylations (rare in animals) in coding and promoter regions of silenced genes. Cytoplasmic viral RNA can affect methylation of homologous nuclear sequences and it maybe one of the feedback mechanisms between the cytoplasm and the nucleus to control gene expression.
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Affiliation(s)
- B F Vanyushin
- Belozersky Institute of Physical and Chemical Biology, Lomonosov Moscow State University, Russia.
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Lund G, Lauria M, Guldberg P, Zaina S. Duplication-Dependent CG Suppression of the Seed Storage Protein Genes of Maize. Genetics 2003; 165:835-48. [PMID: 14573492 PMCID: PMC1462805 DOI: 10.1093/genetics/165.2.835] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
This study investigates the prevalence of CG and CNG suppression in single- vs. multicopy DNA regions of the maize genome. The analysis includes the single- and multicopy seed storage proteins (zeins), the miniature inverted-repeat transposable elements (MITEs), and long terminal repeat (LTR) retrotransposons. Zein genes are clustered on specific chromosomal regions, whereas MITEs and LTRs are dispersed in the genome. The multicopy zein genes are CG suppressed and exhibit large variations in CG suppression. The variation observed correlates with the extent of duplication each zein gene has undergone, indicating that gene duplication results in an increased turnover of cytosine residues. Alignment of individual zein genes confirms this observation and demonstrates that CG depletion results primarily from polarized C:T and G:A transition mutations from a less to a more extensively duplicated gene. In addition, transition mutations occur primarily in a CG or CNG context suggesting that CG suppression may result from deamination of methylated cytosine residues. Duplication-dependent CG depletion is likely to occur at other loci as duplicated MITEs and LTR elements, or elements inserted into duplicated gene regions, also exhibit CG depletion.
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Affiliation(s)
- Gertrud Lund
- Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural University, DK-1871 Frederiksberg C, Denmark.
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Cloix C, Yukawa Y, Tutois S, Sugiura M, Tourmente S. In vitro analysis of the sequences required for transcription of the Arabidopsis thaliana 5S rRNA genes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:251-261. [PMID: 12848829 DOI: 10.1046/j.1365-313x.2003.01793.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In vivo, we have already shown that only two of the 5S rDNA array blocks of the Arabidopsis thaliana genome produce the mature 5S rRNAs. Deletions and point mutations were introduced in an Arabidopsis 5S rDNA-transcribed region and its 5'- and 3'-flanks in order to analyse their effects on transcription activity. In vitro transcription revealed different transcription control regions. One control region essential for transcription initiation was identified in the 5'-flanking sequence. The major sequence determinants were a TATA-like motif (-28 to -23), a GC dinucleotide (-12 to -11), a 3-bp AT-rich region (-4 to -2) and a C residue at -1. They are important for both accurate transcription initiation and transcription efficiency. Transcription level was regulated by polymerase III (Pol III) re-initiation rate as in tRNA genes in which TATA-like motif is involved. Active 5S rDNA transcription additionally required an intragenic promoter composed of an A-box, an Intermediate Element (IE) and a C-box. Double-stranded oligonucleotides corresponding to different fragments of the transcribed region, used as competitors, revealed the main importance of internal promoter elements. A stretch of four T is sufficient for transcription termination. Transcription of Arabidopsis 5S rDNA requires 30 bp of 5'-flanking region, a promoter internal to the transcribed region, and a stretch of T for transcription termination.
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Affiliation(s)
- Catherine Cloix
- U. M. R. 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France
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21
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Mathieu O, Picard G, Tourmente S. Methylation of a euchromatin-heterochromatin transition region in Arabidopsis thaliana chromosome 5 left arm. Chromosome Res 2003; 10:455-66. [PMID: 12489828 DOI: 10.1023/a:1020936229771] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cytosine methylation was studied at the level of the euchromatin/heterochromatin transition genomic region of the Arabidopsis chromosome 5 left arm. It has been shown using a monoclonal antibody against 5-methylcytosines that the density of DNA methylation increases from the euchromatin towards the heterochromatin. YACs mapped along this region were characterized for their repeated sequences content. Some of them, corresponding to euchromatin, euchromatin/heterochromatin border and heterochromatin regions, were used as probes for a Southern blot analysis of methylation. This revealed that the degree of mCmCGG and GATmC methylation increases significantly from the euchromatin towards the heterochromatin. Moreover, an analysis of cytosine methylation levels (% of 5-methylcytosine) of different DNA fragments, inside the same genomic region, was performed using PCR and/or Southern blot approaches. There is a gradual increase of methylation along the genomic region analyzed: CpG methylation in the euchromatic fraction, CpG and CpNpG methylation at the euchromatin/heterochromatin transition and an additional asymmetrical methylation in the repeated-heterochromatic fraction. The most methylated repeated family at CpG, CpNpG and asymmetrical sites is the 5S ribosomal DNA, highly methylated even though it is transcribed.
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MESH Headings
- 5-Methylcytosine
- Arabidopsis/genetics
- Blotting, Southern
- Chromosomes/genetics
- Chromosomes, Artificial, Yeast/genetics
- CpG Islands
- Cytosine/analogs & derivatives
- Cytosine/metabolism
- DNA Methylation
- DNA, Plant/metabolism
- DNA, Ribosomal/genetics
- DNA, Ribosomal/metabolism
- Euchromatin/metabolism
- Gene Expression Regulation, Plant
- Genome, Plant
- Heterochromatin/metabolism
- In Situ Hybridization, Fluorescence
- Mutation
- Polymerase Chain Reaction
- Repetitive Sequences, Nucleic Acid
- Saccharomyces cerevisiae
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Affiliation(s)
- Olivier Mathieu
- U.M.R. CNRS 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France
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22
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Mathieu O, Yukawa Y, Prieto JL, Vaillant I, Sugiura M, Tourmente S. Identification and characterization of transcription factor IIIA and ribosomal protein L5 from Arabidopsis thaliana. Nucleic Acids Res 2003; 31:2424-33. [PMID: 12711688 PMCID: PMC154221 DOI: 10.1093/nar/gkg335] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Thus far, no transcription factor IIIA (TFIIIA) from higher plants has been cloned and characterized. We have cloned and characterized TFIIIA and ribosomal protein L5 from Arabidopsis thaliana. Primary sequence comparison revealed a high divergence of AtTFIIIA and a relatively high conservation of AtL5 when compared with other organisms. The AtTFIIIA cDNA encodes a protein with nine Cys(2)-His(2)-type zinc fingers, a 23 amino acid spacer between fingers 1 and 2, a 66 amino acid spacer between fingers 4 and 5, and a 50 amino acid non-finger C-terminal tail. Aside from the amino acids required for proper zinc finger folding, AtTFIIIA is highly divergent from other known TFIIIAs. AtTFIIIA can bind 5S rDNA, as well as 5S rRNA, and efficiently stimulates the transcription of an Arabidopsis 5S rRNA gene in vitro. AtL5 identity was confirmed by demonstrating that this protein binds to 5S rRNA but not to 5S rDNA. Protoplast transient expression assays with green fluorescent protein fusion proteins revealed that AtTFIIIA is absent from the cytoplasm and concentrated at several nuclear foci including the nucleolus. AtL5 protein accumulates in the nucleus, especially in the nucleolus, and is also present in the cytoplasm.
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Affiliation(s)
- Olivier Mathieu
- UMR CNRS 6547 BIOMOVE, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France
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