1
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Vaquero-Sedas MI, Vega-Palas MA. A Nested PCR Telomere Fusion Assay Highlights the Widespread End-Capping Protection of Arabidopsis CTC1. Int J Mol Sci 2024; 25:672. [PMID: 38203842 PMCID: PMC10779545 DOI: 10.3390/ijms25010672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/15/2023] [Accepted: 11/18/2023] [Indexed: 01/12/2024] Open
Abstract
Telomeres protect the ends of linear eukaryotic chromosomes from being recognized as DNA double-strand breaks. Two major protein complexes are involved in the protection of telomeres: shelterin and CST. The dysfunction of these complexes can challenge the function of telomeres and lead to telomere fusions, breakage-fusion-bridge cycles, and cell death. Therefore, monitoring telomere fusions helps to understand telomeres biology. Telomere fusions are often analyzed by Fluorescent In Situ Hybridization (FISH) or PCR. Usually, both methods involve hybridization with a telomeric probe, which allows the detection of fusions containing telomeric sequences, but not of those lacking them. With the aim of detecting both types of fusion events, we have developed a nested PCR method to analyze telomere fusions in Arabidopsis thaliana. This method is simple, accurate, and does not require hybridization. We have used it to analyze telomere fusions in wild-type and mutant plants altered in CTC1, one of the three components of the Arabidopsis CST telomere capping complex. Our results show that null ctc1-2 mutant plants display fusions between all telomeric regions present in Arabidopsis chromosomes 1, 3 and 5, thus highlighting the widespread end-capping protection achieved by CTC1.
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Affiliation(s)
| | - Miguel A. Vega-Palas
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, IBVF (CSIC-US), E41092 Seville, Spain;
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2
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Wu G, Cao A, Wen Y, Bao W, She F, Wu W, Zheng S, Yang N. Characteristics and Functions of MYB (v-Myb avivan myoblastsis virus oncogene homolog)-Related Genes in Arabidopsis thaliana. Genes (Basel) 2023; 14:2026. [PMID: 38002969 PMCID: PMC10671209 DOI: 10.3390/genes14112026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/19/2023] [Accepted: 10/26/2023] [Indexed: 11/26/2023] Open
Abstract
The MYB (v-Myb avivan myoblastsis virus oncogene homolog) transcription factor family is one of the largest families of plant transcription factors which plays a vital role in many aspects of plant growth and development. MYB-related is a subclass of the MYB family. Fifty-nine Arabidopsis thaliana MYB-related (AtMYB-related) genes have been identified. In order to understand the functions of these genes, in this review, the promoters of AtMYB-related genes were analyzed by means of bioinformatics, and the progress of research into the functions of these genes has been described. The main functions of these AtMYB-related genes are light response and circadian rhythm regulation, root hair and trichome development, telomere DNA binding, and hormone response. From an analysis of cis-acting elements, it was found that the promoters of these genes contained light-responsive elements and plant hormone response elements. Most genes contained elements related to drought, low temperature, and defense and stress responses. These analyses suggest that AtMYB-related genes may be involved in A. thaliana growth and development, and environmental adaptation through plant hormone pathways. However, the functions of many genes do not occur independently but instead interact with each other through different pathways. In the future, the study of the role of the gene in different pathways will be conducive to a comprehensive understanding of the function of the gene. Therefore, gene cloning and protein functional analyses can be subsequently used to understand the regulatory mechanisms of AtMYB-related genes in the interaction of multiple signal pathways. This review provides theoretical guidance for the follow-up study of plant MYB-related genes.
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Affiliation(s)
- Guofan Wu
- College of Life Sciences, Northwest Normal University, Lanzhou 730070, China; (A.C.); (Y.W.); (W.B.); (F.S.); (W.W.); (S.Z.); (N.Y.)
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3
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Valeeva LR, Abdulkina LR, Agabekian IA, Shakirov EV. Telomere biology and ribosome biogenesis: structural and functional interconnections. Biochem Cell Biol 2023; 101:394-409. [PMID: 36989538 DOI: 10.1139/bcb-2022-0383] [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] [Indexed: 03/31/2023] Open
Abstract
Telomeres are nucleoprotein structures that play a pivotal role in the protection and maintenance of eukaryotic chromosomes. Telomeres and the enzyme telomerase, which replenishes telomeric DNA lost during replication, are important factors necessary to ensure continued cell proliferation. Cell proliferation is also dependent on proper and efficient protein synthesis, which is carried out by ribosomes. Mutations in genes involved in either ribosome biogenesis or telomere biology result in cellular abnormalities and can cause human genetic diseases, defined as ribosomopathies and telomeropathies, respectively. Interestingly, recent discoveries indicate that many of the ribosome assembly and rRNA maturation factors have additional noncanonical functions in telomere biology. Similarly, several key proteins and enzymes involved in telomere biology, including telomerase, have unexpected roles in rRNA transcription and maturation. These observations point to an intriguing cross-talk mechanism potentially explaining the multiple pleiotropic symptoms of mutations in many causal genes identified in various telomeropathy and ribosomopathy diseases. In this review, we provide a brief summary of eukaryotic telomere and rDNA loci structures, highlight several universal features of rRNA and telomerase biogenesis, evaluate intriguing interconnections between telomere biology and ribosome assembly, and conclude with an assessment of overlapping features of human diseases of telomeropathies and ribosomopathies.
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Affiliation(s)
- Liia R Valeeva
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
- Department of Biological Sciences, College of Science, Marshall University, Huntington, WV 25701, USA
| | - Liliia R Abdulkina
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
| | - Inna A Agabekian
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan 420008, Republic of Tatarstan, Russia
| | - Eugene V Shakirov
- Department of Biological Sciences, College of Science, Marshall University, Huntington, WV 25701, USA
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25755, USA
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4
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Kusová A, Steinbachová L, Přerovská T, Drábková LZ, Paleček J, Khan A, Rigóová G, Gadiou Z, Jourdain C, Stricker T, Schubert D, Honys D, Schrumpfová PP. Completing the TRB family: newly characterized members show ancient evolutionary origins and distinct localization, yet similar interactions. PLANT MOLECULAR BIOLOGY 2023; 112:61-83. [PMID: 37118559 PMCID: PMC10167121 DOI: 10.1007/s11103-023-01348-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/02/2023] [Indexed: 05/09/2023]
Abstract
Telomere repeat binding proteins (TRBs) belong to a family of proteins possessing a Myb-like domain which binds to telomeric repeats. Three members of this family (TRB1, TRB2, TRB3) from Arabidopsis thaliana have already been described as associated with terminal telomeric repeats (telomeres) or short interstitial telomeric repeats in gene promoters (telo-boxes). They are also known to interact with several protein complexes: telomerase, Polycomb repressive complex 2 (PRC2) E(z) subunits and the PEAT complex (PWOs-EPCRs-ARIDs-TRBs). Here we characterize two novel members of the TRB family (TRB4 and TRB5). Our wide phylogenetic analyses have shown that TRB proteins evolved in the plant kingdom after the transition to a terrestrial habitat in Streptophyta, and consequently TRBs diversified in seed plants. TRB4-5 share common TRB motifs while differing in several others and seem to have an earlier phylogenetic origin than TRB1-3. Their common Myb-like domains bind long arrays of telomeric repeats in vitro, and we have determined the minimal recognition motif of all TRBs as one telo-box. Our data indicate that despite the distinct localization patterns of TRB1-3 and TRB4-5 in situ, all members of TRB family mutually interact and also bind to telomerase/PRC2/PEAT complexes. Additionally, we have detected novel interactions between TRB4-5 and EMF2 and VRN2, which are Su(z)12 subunits of PRC2.
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Affiliation(s)
- Alžbeta Kusová
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Lenka Steinbachová
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czech Republic
| | - Tereza Přerovská
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Lenka Záveská Drábková
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Paleček
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Ahamed Khan
- Institute of Plant Molecular Biology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic
| | - Gabriela Rigóová
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Zuzana Gadiou
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czech Republic
| | - Claire Jourdain
- Institute of Biology, Freie Universität Berlin, 14195, Berlin, Germany
| | - Tino Stricker
- Institute of Biology, Freie Universität Berlin, 14195, Berlin, Germany
| | - Daniel Schubert
- Institute of Biology, Freie Universität Berlin, 14195, Berlin, Germany
| | - David Honys
- Laboratory of Pollen Biology, Institute of Experimental Botany of the Czech Academy of Sciences, Prague, Czech Republic
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague, Czech Republic
| | - Petra Procházková Schrumpfová
- Laboratory of Functional Genomics and Proteomics, Faculty of Science, National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic.
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czech Republic.
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5
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Shakirov EV, Chen JJL, Shippen DE. Plant telomere biology: The green solution to the end-replication problem. THE PLANT CELL 2022; 34:2492-2504. [PMID: 35511166 PMCID: PMC9252485 DOI: 10.1093/plcell/koac122] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 04/14/2022] [Indexed: 05/04/2023]
Abstract
Telomere maintenance is a fundamental cellular process conserved across all eukaryotic lineages. Although plants and animals diverged over 1.5 billion years ago, lessons learned from plants continue to push the boundaries of science, revealing detailed molecular mechanisms in telomere biology with broad implications for human health, aging biology, and stress responses. Recent studies of plant telomeres have unveiled unexpected divergence in telomere sequence and architecture, and the proteins that engage telomeric DNA and telomerase. The discovery of telomerase RNA components in the plant kingdom and some algae groups revealed new insight into the divergent evolution and the universal core of telomerase across major eukaryotic kingdoms. In addition, resources cataloging the abundant natural variation in Arabidopsis thaliana, maize (Zea mays), and other plants are providing unparalleled opportunities to understand the genetic networks that govern telomere length polymorphism and, as a result, are uncovering unanticipated crosstalk between telomeres, environmental factors, organismal fitness, and plant physiology. Here we recap current advances in plant telomere biology and put this field in perspective relative to telomere and telomerase research in other eukaryotic lineages.
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Affiliation(s)
- Eugene V Shakirov
- Department of Biological Sciences, College of Science, Marshall University, Huntington, West Virginia 25701, USA
| | - Julian J -L Chen
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, USA
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6
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Zeng Q, Liu H, Chu X, Niu Y, Wang C, Markov GV, Teng L. Independent Evolution of the MYB Family in Brown Algae. Front Genet 2022; 12:811993. [PMID: 35186015 PMCID: PMC8854648 DOI: 10.3389/fgene.2021.811993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
Myeloblastosis (MYB) proteins represent one of the largest families of eukaryotic transcription factors and regulate important processes in growth and development. Studies on MYBs have mainly focused on animals and plants; however, comprehensive analysis across other supergroups such as SAR (stramenopiles, alveolates, and rhizarians) is lacking. This study characterized the structure, evolution, and expression of MYBs in four brown algae, which comprise the biggest multicellular lineage of SAR. Subfamily 1R-MYB comprised heterogeneous proteins, with fewer conserved motifs found outside the MYB domain. Unlike the SHAQKY subgroup of plant 1R-MYB, THAQKY comprised the largest subgroup of brown algal 1R-MYBs. Unlike the expansion of 2R-MYBs in plants, brown algae harbored more 3R-MYBs than 2R-MYBs. At least ten 2R-MYBs, fifteen 3R-MYBs, and one 6R-MYB orthologs existed in the common ancestor of brown algae. Phylogenetic analysis showed that brown algal MYBs had ancient origins and a diverged evolution. They showed strong affinity with stramenopile species, while not with red algae, green algae, or animals, suggesting that brown algal MYBs did not come from the secondary endosymbiosis of red and green plastids. Sequence comparison among all repeats of the three types of MYB subfamilies revealed that the repeat of 1R-MYBs showed higher sequence identity with the R3 of 2R-MYBs and 3R-MYBs, which supports the idea that 1R-MYB was derived from loss of the first and second repeats of the ancestor MYB. Compared with other species of SAR, brown algal MYB proteins exhibited a higher proportion of intrinsic disordered regions, which might contribute to multicellular evolution. Expression analysis showed that many MYB genes are responsive to different stress conditions and developmental stages. The evolution and expression analyses provided a comprehensive analysis of the phylogeny and functions of MYBs in brown algae.
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Affiliation(s)
| | - Hanyu Liu
- College of Life Sciences, Dezhou University, Dezhou, China
| | - Xiaonan Chu
- College of Life Sciences, Dezhou University, Dezhou, China
| | - Yonggang Niu
- College of Life Sciences, Dezhou University, Dezhou, China
| | - Caili Wang
- College of Life Sciences, Dezhou University, Dezhou, China
| | - Gabriel V. Markov
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Linhong Teng
- College of Life Sciences, Dezhou University, Dezhou, China
- *Correspondence: Linhong Teng,
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7
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Farrell C, Vaquero-Sedas MI, Cubiles MD, Thompson M, Vega-Vaquero A, Pellegrini M, Vega-Palas MA. A complex network of interactions governs DNA methylation at telomeric regions. Nucleic Acids Res 2022; 50:1449-1464. [PMID: 35061900 PMCID: PMC8860613 DOI: 10.1093/nar/gkac012] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/10/2022] [Indexed: 12/13/2022] Open
Abstract
DNA methylation modulates telomere function. In Arabidopsis thaliana, telomeric regions have a bimodal chromatin organization with unmethylated telomeres and methylated subtelomeres. To gain insight into this organization we have generated TAIR10-Tel, a modified version of the Arabidopsis reference genome with additional sequences at most chromosome ends. TAIR10-Tel has allowed us to analyse DNA methylation at nucleotide resolution level in telomeric regions. We have analysed the wild-type strain and mutants that encode inactive versions of all currently known relevant methyltransferases involved in cytosine methylation. These analyses have revealed that subtelomeric DNA methylation extends 1 to 2 kbp from Interstitial Telomeric Sequences (ITSs) that abut or are very near to telomeres. However, DNA methylation drops at the telomeric side of the telomere-subtelomere boundaries and disappears at the inner part of telomeres. We present a comprehensive and integrative model for subtelomeric DNA methylation that should help to decipher the mechanisms that govern the epigenetic regulation of telomeres. This model involves a complex network of interactions between methyltransferases and subtelomeric DNA sequences.
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Affiliation(s)
- Colin Farrell
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA90095, USA
| | - María I Vaquero-Sedas
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, IBVF (CSIC-US), Seville, E41092, Spain
| | - María D Cubiles
- Departamento de Estadística e Investigación Operativa, Facultad de Matemáticas, Universidad de Sevilla, Seville, E41012, Spain
| | - Michael Thompson
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA90095, USA
| | - Alejandro Vega-Vaquero
- Escuela Técnica Superior de Ingeniería Informática, Universidad de Sevilla, Seville, E41012, Spain
| | - Matteo Pellegrini
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA90095, USA.,Institute of Genomics and Proteomics, Los Angeles, CA90095, USA
| | - Miguel A Vega-Palas
- Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla, IBVF (CSIC-US), Seville, E41092, Spain
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8
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Yang J, Zhang S, Li H, Wang L, Liu Y, Niu L, Yang Q, Meng D, Fu Y. Genome-wide analysis and characterization of R2R3-MYB family in pigeon pea (Cajanus cajan) and their functional identification in phenylpropanoids biosynthesis. PLANTA 2021; 254:64. [PMID: 34487243 DOI: 10.1007/s00425-021-03713-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Accepted: 08/28/2021] [Indexed: 06/13/2023]
Abstract
Thirty CcMYB were identified to involve in flavonoid and lignin biosynthesis in pigeon pea genome. A comprehensive analysis of gene structure, phylogenetic relationships, distribution on chromosomes, gene duplication, and expression patterns was performed. MYB transcription factor is one of the largest gene families in plants and plays critical roles in plant growth and development, as well as resistance to biotic and abiotic stress. However, the function of MYB genes in pigeon pea (Cajanus cajan) remains largely unknown. Here, 30 R2R3-MYB which involved flavonoid and lignin biosynthesis were identified in the pigeon pea genome and were classified into five groups based on phylogenetic analysis. Simultaneously, another 122 key enzyme genes from biosynthetic pathways of flavonoid and lignin were identified and all of them were mapped on 11 chromosomes with the co-linearity relationship. Among these genes, the intron/exon organization and motif compositions were conserved and they have undergone a strong purifying selection and tandem duplications during evolution. Expression profile analysis demonstrated most of these genes were expressed in different tissues and responded significantly to MeJA, RNA-seq analysis revealed clear details of genes varied with time of induction. Ten key genes from the phenylpropanoid pathway were selected to further verify whether they responded to induction under different abiotic stress conditions (UV-B, cold, heat, salt, drought, and GA3). This study elaborates on potential regulatory relationships between R2R3-MYB genes and some key genes involved in flavonoid and lignin biosynthesis under MeJA treatment, as well as adding to the understanding of improving abiotic stress tolerance and regulating the secondary metabolism in woody crops. A simplified discussion model for the different regulation networks involved with flavonoid and lignin biosynthesis in pigeon pea is proposed.
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Affiliation(s)
- Jie Yang
- College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040, China
| | - Su Zhang
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China
- College of Forestry, Beijing Forestry University, Beijing, 100083, China
| | - Hongquan Li
- College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040, China
| | - Litao Wang
- College of Forestry, Beijing Forestry University, Beijing, 100083, China
| | - Ying Liu
- College of Chemistry, Chemical Engineering and Resource Utilization, Northeast Forestry University, Harbin, 150040, China
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040, China
| | - Lili Niu
- College of Forestry, Beijing Forestry University, Beijing, 100083, China
| | - Qing Yang
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China
- College of Forestry, Beijing Forestry University, Beijing, 100083, China
| | - Dong Meng
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China
- College of Forestry, Beijing Forestry University, Beijing, 100083, China
| | - Yujie Fu
- Key Laboratory of Forest Plant Ecology, Ministry of Education, Northeast Forestry University, Harbin, 150040, China.
- Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China.
- College of Forestry, Beijing Forestry University, Beijing, 100083, China.
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9
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Bonnot T, Nagel DH. Time of the day prioritizes the pool of translating mRNAs in response to heat stress. THE PLANT CELL 2021; 33:2164-2182. [PMID: 33871647 PMCID: PMC8364243 DOI: 10.1093/plcell/koab113] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 04/07/2021] [Indexed: 05/24/2023]
Abstract
The circadian clock helps organisms to anticipate and coordinate gene regulatory responses to changes in environmental stimuli. Under growth limiting temperatures, the time of the day modulates the accumulation of polyadenylated mRNAs. In response to heat stress, plants will conserve energy and selectively translate mRNAs. How the clock and/or the time of the day regulates polyadenylated mRNAs bound by ribosomes in response to heat stress is unknown. In-depth analysis of Arabidopsis thaliana translating mRNAs found that the time of the day gates the response of approximately one-third of the circadian-regulated heat-responsive translatome. Specifically, the time of the day and heat stress interact to prioritize the pool of mRNAs in cue to be translated. For a subset of mRNAs, we observed a stronger gated response during the day, and preferentially before the peak of expression. We propose previously overlooked transcription factors (TFs) as regulatory nodes and show that the clock plays a role in the temperature response for select TFs. When the stress was removed, the redefined priorities for translation recovered within 1 h, though slower recovery was observed for abiotic stress regulators. Through hierarchical network connections between clock genes and prioritized TFs, our work provides a framework to target key nodes underlying heat stress tolerance throughout the day.
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Affiliation(s)
- Titouan Bonnot
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA, USA
| | - Dawn H. Nagel
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA, USA
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10
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Kobayashi CR, Castillo-González C, Survotseva Y, Canal E, Nelson ADL, Shippen DE. Recent emergence and extinction of the protection of telomeres 1c gene in Arabidopsis thaliana. PLANT CELL REPORTS 2019; 38:1081-1097. [PMID: 31134349 PMCID: PMC6708462 DOI: 10.1007/s00299-019-02427-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 03/27/2019] [Indexed: 05/20/2023]
Abstract
Duplicate POT1 genes must rapidly diverge or be inactivated. Protection of telomeres 1 (POT1) encodes a conserved telomere binding protein implicated in both chromosome end protection and telomere length maintenance. Most organisms harbor a single POT1 gene, but in the few lineages where the POT1 family has expanded, the duplicate genes have diversified. Arabidopsis thaliana bears three POT1-like loci, POT1a, POT1b and POT1c. POT1a retains the ancestral function of telomerase regulation, while POT1b is implicated in chromosome end protection. Here we examine the function and evolution of the third POT1 paralog, POT1c. POT1c is a new gene, unique to A. thaliana, and was derived from a duplication event involving the POT1a locus and a neighboring gene encoding ribosomal protein S17. The duplicate S17 locus (dS17) is highly conserved across A. thaliana accessions, while POT1c is highly divergent, harboring multiple deletions within the gene body and two transposable elements within the promoter. The POT1c locus is transcribed at very low to non-detectable levels under standard growth conditions. In addition, no discernable molecular or developmental defects are associated with plants bearing a CRISPR mutation in the POT1c locus. However, forced expression of POT1c leads to decreased telomerase enzyme activity and shortened telomeres. Evolutionary reconstruction indicates that transposons invaded the POT1c promoter soon after the locus was formed, permanently silencing the gene. Altogether, these findings argue that POT1 dosage is critically important for viability and duplicate gene copies are retained only upon functional divergence.
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Affiliation(s)
- Callie R Kobayashi
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | | | - Yulia Survotseva
- Yale Center for Molecular Discovery, Yale University, New Haven, Connecticut, USA
| | - Elijah Canal
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Andrew D L Nelson
- The School of Plant Sciences, University of Arizona, Tucson, Arizona, USA
| | - Dorothy E Shippen
- Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA.
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11
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Telomeres in Plants and Humans: Not So Different, Not So Similar. Cells 2019; 8:cells8010058. [PMID: 30654521 PMCID: PMC6356271 DOI: 10.3390/cells8010058] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/07/2019] [Accepted: 01/07/2019] [Indexed: 01/01/2023] Open
Abstract
Parallel research on multiple model organisms shows that while some principles of telomere biology are conserved among all eukaryotic kingdoms, we also find some deviations that reflect different evolutionary paths and life strategies, which may have diversified after the establishment of telomerase as a primary mechanism for telomere maintenance. Much more than animals, plants have to cope with environmental stressors, including genotoxic factors, due to their sessile lifestyle. This is, in principle, made possible by an increased capacity and efficiency of the molecular systems ensuring maintenance of genome stability, as well as a higher tolerance to genome instability. Furthermore, plant ontogenesis differs from that of animals in which tissue differentiation and telomerase silencing occur during early embryonic development, and the “telomere clock” in somatic cells may act as a preventive measure against carcinogenesis. This does not happen in plants, where growth and ontogenesis occur through the serial division of apical meristems consisting of a small group of stem cells that generate a linear series of cells, which differentiate into an array of cell types that make a shoot and root. Flowers, as generative plant organs, initiate from the shoot apical meristem in mature plants which is incompatible with the human-like developmental telomere shortening. In this review, we discuss differences between human and plant telomere biology and the implications for aging, genome stability, and cell and organism survival. In particular, we provide a comprehensive comparative overview of telomere proteins acting in humans and in Arabidopsis thaliana model plant, and discuss distinct epigenetic features of telomeric chromatin in these species.
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12
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Byun MY, Cui LH, Lee H, Kim WT. Telomere association of Oryza sativa telomere repeat-binding factor like 1 and its roles in telomere maintenance and development in rice, Oryza sativa L. BMB Rep 2018. [PMID: 29936933 PMCID: PMC6283022 DOI: 10.5483/bmbrep.2018.51.11.122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Telomeres are specialized nucleoprotein complexes that function to protect eukaryotic chromosomes from recombination and erosion. Several telomere binding proteins (TBPs) have been characterized in higher plants, but their detailed in vivo functions at the plant level are largely unknown. In this study, we identified and characterized OsTRFL1 (Oryza sativa Telomere Repeat-binding Factor Like 1) in rice, a monocot model crop. Although OsTRFL1 did not directly bind to telomere repeats (TTTAGGG)4in vitro, it was associated with telomeric sequences in planta. OsTRFL1 interacted with rice TBPs, such as OsTRBF1 and RTBP1, in yeast and plant cells as well as in vitro. Thus, it seems likely that the association of OsTRFL1 with other TBPs enables OsTRFL1 to bind to telomeres indirectly. T-DNA inserted OsTRFL1 knock-out mutant rice plants displayed significantly longer telomeres (6–25 kb) than those (5–12 kb) in wild-type plants, indicating that OsTRFL1 is a negative factor for telomere lengthening. The reduced levels of OsTRFL1 caused serious developmental defects in both vegetative and reproductive organs of rice plants. These results suggest that OsTRFL1 is an essential factor for the proper maintenance of telomeres and normal development of rice.
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Affiliation(s)
- Mi Young Byun
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, Korea
| | - Li Hua Cui
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea
| | - Hyoungseok Lee
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, Korea
| | - Woo Taek Kim
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea
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13
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Jørgensen MM, Ekundayo B, Zaratiegui M, Skriver K, Thon G, Schalch T. Structure of the replication regulator Sap1 reveals functionally important interfaces. Sci Rep 2018; 8:10930. [PMID: 30026545 PMCID: PMC6053445 DOI: 10.1038/s41598-018-29198-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/04/2018] [Indexed: 01/05/2023] Open
Abstract
The mechanism by which specific protein-DNA complexes induce programmed replication fork stalling in the eukaryotic genome remains poorly understood. In order to shed light on this process we carried out structural investigations on the essential fission yeast protein Sap1. Sap1 was identified as a protein involved in mating-type switching in Schizosaccharomyces pombe, and has been shown to be involved in programmed replication fork stalling. Interestingly, Sap1 assumes two different DNA binding modes. At the mating-type locus dimers of Sap1 bind the SAS1 sequence in a head-to-head arrangement, while they bind to replication fork blocking sites at rDNA and Tf2 transposons in a head-to-tail mode. In this study, we have solved the crystal structure of the Sap1 DNA binding domain and we observe that Sap1 molecules interact in the crystal using a head-to-tail arrangement that is compatible with DNA binding. We find that Sap1 mutations which alleviate replication-fork blockage at Tf2 transposons in CENP-B mutants map to the head-to-tail interface. Furthermore, several other mutations introduced in this interface are found to be lethal. Our data suggests that essential functions of Sap1 depend on its head-to-tail oligomerization.
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Affiliation(s)
- Maria M Jørgensen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Babatunde Ekundayo
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, CH-1211, Geneva 4, Switzerland
| | - Mikel Zaratiegui
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, USA
| | - Karen Skriver
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Geneviève Thon
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Thomas Schalch
- Department of Molecular Biology, Science III, Institute of Genetics and Genomics of Geneva (iGE3), University of Geneva, CH-1211, Geneva 4, Switzerland. .,Leicester Institute for Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Leicester, LE1 9HN, UK.
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14
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Dokládal L, Benková E, Honys D, Dupľáková N, Lee LY, Gelvin SB, Sýkorová E. An armadillo-domain protein participates in a telomerase interaction network. PLANT MOLECULAR BIOLOGY 2018; 97:407-420. [PMID: 29948659 DOI: 10.1007/s11103-018-0747-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/04/2018] [Indexed: 06/08/2023]
Abstract
Arabidopsis and human ARM protein interact with telomerase. Deregulated mRNA levels of DNA repair and ribosomal protein genes in an Arabidopsis arm mutant suggest non-telomeric ARM function. The human homolog ARMC6 interacts with hTRF2. Telomerase maintains telomeres and has proposed non-telomeric functions. We previously identified interaction of the C-terminal domain of Arabidopsis telomerase reverse transcriptase (AtTERT) with an armadillo/β-catenin-like repeat (ARM) containing protein. Here we explore protein-protein interactions of the ARM protein, AtTERT domains, POT1a, TRF-like family and SMH family proteins, and the chromatin remodeling protein CHR19 using bimolecular fluorescence complementation (BiFC), yeast two-hybrid (Y2H) analysis, and co-immunoprecipitation. The ARM protein interacts with both the N- and C-terminal domains of AtTERT in different cellular compartments. ARM interacts with CHR19 and TRF-like I family proteins that also bind AtTERT directly or through interaction with POT1a. The putative human ARM homolog co-precipitates telomerase activity and interacts with hTRF2 protein in vitro. Analysis of Arabidopsis arm mutants shows no obvious changes in telomere length or telomerase activity, suggesting that ARM is not essential for telomere maintenance. The observed interactions with telomerase and Myb-like domain proteins (TRF-like family I) may therefore reflect possible non-telomeric functions. Transcript levels of several DNA repair and ribosomal genes are affected in arm mutants, and ARM, likely in association with other proteins, suppressed expression of XRCC3 and RPSAA promoter constructs in luciferase reporter assays. In conclusion, ARM can participate in non-telomeric functions of telomerase, and can also perform its own telomerase-independent functions.
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Affiliation(s)
- Ladislav Dokládal
- Institute of Biophysics, The Czech Academy of Sciences, Královopolská 135, 61265, Brno, Czech Republic
- Laboratory of Functional Genomics and Proteomics, NCBR, Faculty of Science, Masaryk University, Brno, Czech Republic
- Department of Biology, Faculty of Science and Medicine, University of Fribourg, Fribourg, Switzerland
| | - Eva Benková
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - David Honys
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojova 263, 16502, Prague, Czech Republic
| | - Nikoleta Dupľáková
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojova 263, 16502, Prague, Czech Republic
| | - Lan-Ying Lee
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907-1392, USA
| | - Stanton B Gelvin
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907-1392, USA
| | - Eva Sýkorová
- Institute of Biophysics, The Czech Academy of Sciences, Královopolská 135, 61265, Brno, Czech Republic.
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15
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Majerská J, Schrumpfová PP, Dokládal L, Schořová Š, Stejskal K, Obořil M, Honys D, Kozáková L, Polanská PS, Sýkorová E. Tandem affinity purification of AtTERT reveals putative interaction partners of plant telomerase in vivo. PROTOPLASMA 2017; 254:1547-1562. [PMID: 27853871 DOI: 10.1007/s00709-016-1042-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 11/04/2016] [Indexed: 05/15/2023]
Abstract
The life cycle of telomerase involves dynamic and complex interactions between proteins within multiple macromolecular networks. Elucidation of these associations is a key to understanding the regulation of telomerase under diverse physiological and pathological conditions from telomerase biogenesis, through telomere recruitment and elongation, to its non-canonical activities outside of telomeres. We used tandem affinity purification coupled to mass spectrometry to build an interactome of the telomerase catalytic subunit AtTERT, using Arabidopsis thaliana suspension cultures. We then examined interactions occurring at the AtTERT N-terminus, which is thought to fold into a discrete domain connected to the rest of the molecule via a flexible linker. Bioinformatic analyses revealed that interaction partners of AtTERT have a range of molecular functions, a subset of which is specific to the network around its N-terminus. A significant number of proteins co-purifying with the N-terminal constructs have been implicated in cell cycle and developmental processes, as would be expected of bona fide regulatory interactions and we have confirmed experimentally the direct nature of selected interactions. To examine AtTERT protein-protein interactions from another perspective, we also analysed AtTERT interdomain contacts to test potential dimerization of AtTERT. In total, our results provide an insight into the composition and architecture of the plant telomerase complex and this will aid in delineating molecular mechanisms of telomerase functions.
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Affiliation(s)
- Jana Majerská
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 135, CZ-61265, Brno, Czech Republic
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Petra Procházková Schrumpfová
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Ladislav Dokládal
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 135, CZ-61265, Brno, Czech Republic
| | - Šárka Schořová
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
| | - Karel Stejskal
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
| | - Michal Obořil
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
| | - David Honys
- Institute of Experimental Biology, Academy of Sciences of the Czech Republic, v.v.i., Rozvojová 263, CZ-165 02, Prague, Czech Republic
| | - Lucie Kozáková
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
| | - Pavla Sováková Polanská
- Central European Institute of Technology and Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137, Brno, Czech Republic
| | - Eva Sýkorová
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 135, CZ-61265, Brno, Czech Republic.
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16
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Fulcher N, Riha K. Using Centromere Mediated Genome Elimination to Elucidate the Functional Redundancy of Candidate Telomere Binding Proteins in Arabidopsis thaliana. Front Genet 2016; 6:349. [PMID: 26779251 PMCID: PMC4700174 DOI: 10.3389/fgene.2015.00349] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 11/29/2015] [Indexed: 12/23/2022] Open
Abstract
Proteins that bind to telomeric DNA form the key structural and functional constituents of telomeres. While telomere binding proteins have been described in the majority of organisms, their identity in plants remains unknown. Several protein families containing a telomere binding motif known as the telobox have been previously described in Arabidopsis thaliana. Nonetheless, functional evidence for their involvement at telomeres has not been obtained, likely due to functional redundancy. Here we performed genetic analysis on the TRF-like family consisting of six proteins (TRB1, TRP1, TRFL1, TRFL2, TRFL4, and TRF9) which have previously shown to bind telomeric DNA in vitro. We used haploid genetics to create multiple knock-out plants deficient for all six proteins of this gene family. These plants did not exhibit changes in telomere length, or phenotypes associated with telomere dysfunction. This data demonstrates that this telobox protein family is not involved in telomere maintenance in Arabidopsis. Phylogenetic analysis in major plant lineages revealed early diversification of telobox proteins families indicating that telomere function may be associated with other telobox proteins.
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Affiliation(s)
- Nick Fulcher
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Austria
| | - Karel Riha
- Central European Institute of Technology, Masaryk University, Brno Czech Republic
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17
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Procházková Schrumpfová P, Schořová Š, Fajkus J. Telomere- and Telomerase-Associated Proteins and Their Functions in the Plant Cell. FRONTIERS IN PLANT SCIENCE 2016; 7:851. [PMID: 27446102 PMCID: PMC4924339 DOI: 10.3389/fpls.2016.00851] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 05/31/2016] [Indexed: 05/20/2023]
Abstract
Telomeres, as physical ends of linear chromosomes, are targets of a number of specific proteins, including primarily telomerase reverse transcriptase. Access of proteins to the telomere may be affected by a number of diverse factors, e.g., protein interaction partners, local DNA or chromatin structures, subcellular localization/trafficking, or simply protein modification. Knowledge of composition of the functional nucleoprotein complex of plant telomeres is only fragmentary. Moreover, the plant telomeric repeat binding proteins that were characterized recently appear to also be involved in non-telomeric processes, e.g., ribosome biogenesis. This interesting finding was not totally unexpected since non-telomeric functions of yeast or animal telomeric proteins, as well as of telomerase subunits, have been reported for almost a decade. Here we summarize known facts about the architecture of plant telomeres and compare them with the well-described composition of telomeres in other organisms.
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Affiliation(s)
- Petra Procházková Schrumpfová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityBrno, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityBrno, Czech Republic
- *Correspondence: Petra Procházková Schrumpfová,
| | - Šárka Schořová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityBrno, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityBrno, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityBrno, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i.Brno, Czech Republic
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18
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Nelson ADL, Shippen DE. Evolution of TERT-interacting lncRNAs: expanding the regulatory landscape of telomerase. Front Genet 2015; 6:277. [PMID: 26442096 PMCID: PMC4564757 DOI: 10.3389/fgene.2015.00277] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 08/17/2015] [Indexed: 12/17/2022] Open
Abstract
Long non-coding RNAs (lncRNAs) evolve rapidly and are functionally diverse. The emergence of new lncRNAs is driven by genome disturbance events, including whole genome duplication, and transposition. One of the few lncRNAs with a conserved role throughout eukaryotes is the telomerase RNA, TER. TER works in concert with the telomerase reverse transcriptase (TERT) to maintain telomeres. Here we discuss recent findings from Arabidopsis thaliana and its relatives illustrating the remarkable evolutionary flexibility within TER and the potential for non-canonical TERT-lncRNA interactions. We highlight the two TERs in A. thaliana. One is a conventional telomerase template. The other lncRNA negatively regulates telomerase activity in response to DNA damage, a function mediated by co-option of a transposable element. In addition, we discuss evidence for multiple independent TER loci throughout the plant family Brassicaceae, and how these loci not only reflect rapid convergent evolution, but also the flexibility of having a lncRNA at the core of telomerase. Lastly, we discuss the propensity for TERT to bind a suite of non-templating lncRNAs, and how such RNAs may facilitate telomerase regulation and off-telomere functions.
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Affiliation(s)
| | - Dorothy E Shippen
- Department of Biochemistry and Biophysics, Texas A&M University , College Station, TX, USA
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19
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Identification and Characterization of 40 Isolated Rehmannia glutinosa MYB Family Genes and Their Expression Profiles in Response to Shading and Continuous Cropping. Int J Mol Sci 2015; 16:15009-30. [PMID: 26147429 PMCID: PMC4519885 DOI: 10.3390/ijms160715009] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/18/2015] [Accepted: 06/23/2015] [Indexed: 12/15/2022] Open
Abstract
The v-myb avian myeloblastosis viral oncogene homolog (MYB) superfamily constitutes one of the most abundant groups of transcription factors (TFs) described in plants. To date, little is known about the MYB genes in Rehmannia glutinosa. Forty unique MYB genes with full-length cDNA sequences were isolated. These 40 genes were grouped into five categories, one R1R2R3-MYB, four TRFL MYBs, four SMH MYBs, 25 R2R3-MYBs, and six MYB-related members. The MYB DNA-binding domain (DBD) sequence composition was conserved among proteins of the same subgroup. As expected, most of the closely related members in the phylogenetic tree exhibited common motifs. Additionally, the gene structure and motifs of the R. glutinosa MYB genes were analyzed. MYB gene expression was analyzed in the leaf and the tuberous root under two abiotic stress conditions. Expression profiles showed that most R. glutinosa MYB genes were expressed in the leaf and the tuberous root, suggesting that MYB genes are involved in various physiological and developmental processes in R. glutinosa. Seven MYB genes were up-regulated in response to shading in at least one tissue. Two MYB genes showed increased expression and 13 MYB genes showed decreased expression in the tuberous root under continuous cropping. This investigation is the first comprehensive study of the MYB gene family in R. glutinosa.
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20
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Beilstein MA, Renfrew KB, Song X, Shakirov EV, Zanis MJ, Shippen DE. Evolution of the Telomere-Associated Protein POT1a in Arabidopsis thaliana Is Characterized by Positive Selection to Reinforce Protein-Protein Interaction. Mol Biol Evol 2015; 32:1329-41. [PMID: 25697340 DOI: 10.1093/molbev/msv025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Gene duplication is a major driving force in genome evolution. Here, we explore the nature and origin of the POT1 gene duplication in Arabidopsis thaliana. Protection of Telomeres (POT1) is a conserved multifunctional protein that modulates telomerase activity and its engagement with telomeres. Arabidopsis thaliana encodes two divergent POT1 paralogs termed AtPOT1a and AtPOT1b. AtPOT1a positively regulates telomerase activity, whereas AtPOT1b is proposed to negatively regulate telomerase and promote chromosome end protection. Phylogenetic analysis uncovered two independent POT1 duplication events in the plant kingdom, including one at the base of Brassicaceae. Tests for positive selection implemented in PAML revealed that the Brassicaceae POT1a lineage experienced positive selection postduplication and identified three amino acid residues with signatures of positive selection. A sensitive and quantitative genetic complementation assay was developed to assess POT1a function in A. thaliana. The assay showed that AtPOT1a is functionally distinct from single-copy POT1 genes in other plants. Moreover, for two of the sites with a strong signature of positive selection, substitutions that swap the amino acids in AtPOT1a for residues found in AtPOT1b dramatically compromised AtPOT1a function in vivo. In vitro-binding studies demonstrated that all three sites under positive selection specifically enhance the AtPOT1a interaction with CTC1, a core component of the highly conserved CST (CTC1/STN1/TEN1) telomere protein complex. Our results reveal a molecular mechanism for the role of these positively selected sites in AtPOT1a. The data also provide an important empirical example to refine theories of duplicate gene retention, as the outcome of positive selection here appears to be reinforcement of an ancestral function, rather than neofunctionalization. We propose that this outcome may not be unusual when the duplicated protein is a component of a multisubunit complex whose function is in part specified by other members.
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Affiliation(s)
- Mark A Beilstein
- School of Plant Sciences, University of Arizona Department of Biochemistry and Biophysics, Texas A&M University
| | - Kyle B Renfrew
- Department of Biochemistry and Biophysics, Texas A&M University
| | - Xiangyu Song
- Department of Biochemistry and Biophysics, Texas A&M University
| | - Eugene V Shakirov
- Department of Integrative Biology, University of Texas at Austin Institute of Fundamental Medicine and Biology, Kazan (Volga Region) Federal University, Kazan, Republic of Tatarstan, Russia
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21
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Nelson ADL, Forsythe ES, Gan X, Tsiantis M, Beilstein MA. Extending the model of Arabidopsis telomere length and composition across Brassicaceae. Chromosome Res 2015; 22:153-66. [PMID: 24846723 DOI: 10.1007/s10577-014-9423-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Telomeres are repetitive TG-rich DNA elements essential for maintaining the stability of genomes and replicative capacity of cells in almost all eukaryotes. Most of what is known about telomeres in plants comes from the angiosperm Arabidopsis thaliana, which has become an important comparative model for telomere biology. Arabidopsis tolerates numerous insults to its genome, many of which are catastrophic or lethal in other eukaryotic systems such as yeast and vertebrates. Despite the importance of Arabidopsis in establishing a model for the structure and regulation of plant telomeres, only a handful of studies have used this information to assay components of telomeres from across land plants, or even among the closest relatives of Arabidopsis in the plant family Brassicaceae. Here, we determined how well Arabidopsis represents Brassicaceae by comparing multiple aspects of telomere biology in species that represent major clades in the family tree. Specifically, we determined the telomeric repeat sequence, measured bulk telomere length, and analyzed variation in telomere length on syntenic chromosome arms. In addition, we used a phylogenetic approach to infer the evolutionary history of putative telomere-binding proteins, CTC1, STN1, TEN1 (CST), telomere repeat-binding factor like (TRFL), and single Myb histone (SMH). Our analyses revealed conservation of the telomeric DNA repeat sequence, but considerable variation in telomere length among the sampled species, even in comparisons of syntenic chromosome arms. We also found that the single-stranded and double-stranded telomeric DNA-binding complexes CST and TRFL, respectively, differ in their pattern of gene duplication and loss. The TRFL and SMH gene families have undergone numerous duplication events, and these duplicate copies are often retained in the genome. In contrast, CST components occur as single-copy genes in all sampled genomes, even in species that experienced recent whole genome duplication events. Taken together, our results place the Arabidopsis model in the context of other species in Brassicaceae, making the family the best characterized plant group in regard to telomere architecture.
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Affiliation(s)
- Andrew D L Nelson
- School of Plant Sciences, University of Arizona, Tucson, AZ, 85721, USA
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22
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Sutoh K, Washio K, Imai R, Wada M, Nakai T, Yamauchi D. An N-terminal region of a Myb-like protein is involved in its intracellular localization and activation of a gibberellin-inducible proteinase gene in germinated rice seeds. Biosci Biotechnol Biochem 2015; 79:747-59. [PMID: 25559339 DOI: 10.1080/09168451.2014.998620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The expression of the gene for a proteinase (Rep1) is upregulated by gibberellins. The CAACTC regulatory element (CARE) of the Rep1 promoter is involved in the gibberellin response. We isolated a cDNA for a CARE-binding protein containing a Myb domain in its carboxyl-terminal region and designated the gene Carboxyl-terminal Myb1 (CTMyb1). This gene encodes two polypeptides of two distinctive lengths, CTMyb1L and CTMyb1S, which include or exclude 213 N-terminal amino acid residues, respectively. CTMyb1S transactivated the Rep1 promoter in the presence of OsGAMyb, but not CTMyb1L. We observed an interaction between CTMyb1S and the rice prolamin box-binding factor (RPBF). A bimolecular fluorescence complex analysis detected the CTMyb1S and RPBF complex in the nucleus, but not the CTMyb1L and RPBF complex. The results suggest that the arrangement of the transfactors is involved in gibberellin-inducible expression of Rep1.
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Affiliation(s)
- Keita Sutoh
- a R&D Planning Admin Dept , Life Science Institute Co. Ltd , Tokyo , Japan
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23
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Amiard S, Olivier M, Allain E, Choi K, Smith-Unna R, Henderson IR, White CI, Gallego ME. Telomere stability and development of ctc1 mutants are rescued by inhibition of EJ recombination pathways in a telomerase-dependent manner. Nucleic Acids Res 2014; 42:11979-91. [PMID: 25274733 PMCID: PMC4231758 DOI: 10.1093/nar/gku897] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 09/16/2014] [Accepted: 09/18/2014] [Indexed: 12/11/2022] Open
Abstract
The telomeres of linear eukaryotic chromosomes are protected by caps consisting of evolutionarily conserved nucleoprotein complexes. Telomere dysfunction leads to recombination of chromosome ends and this can result in fusions which initiate chromosomal breakage-fusion-bridge cycles, causing genomic instability and potentially cell death or cancer. We hypothesize that in the absence of the recombination pathways implicated in these fusions, deprotected chromosome ends will instead be eroded by nucleases, also leading to the loss of genes and cell death. In this work, we set out to specifically test this hypothesis in the plant, Arabidopsis. Telomere protection in Arabidopsis implicates KU and CST and their absence leads to chromosome fusions, severe genomic instability and dramatic developmental defects. We have analysed the involvement of end-joining recombination pathways in telomere fusions and the consequences of this on genomic instability and growth. Strikingly, the absence of the multiple end-joining pathways eliminates chromosome fusion and restores normal growth and development to cst ku80 mutant plants. It is thus the chromosomal fusions, per se, which are the underlying cause of the severe developmental defects. This rescue is mediated by telomerase-dependent telomere extension, revealing a competition between telomerase and end-joining recombination proteins for access to deprotected telomeres.
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Affiliation(s)
- Simon Amiard
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France
| | - Margaux Olivier
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France
| | - Elisabeth Allain
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Kyuha Choi
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | | | - Ian R Henderson
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Charles I White
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France
| | - Maria Eugenia Gallego
- Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France
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Renfrew KB, Song X, Lee JR, Arora A, Shippen DE. POT1a and components of CST engage telomerase and regulate its activity in Arabidopsis. PLoS Genet 2014; 10:e1004738. [PMID: 25329641 PMCID: PMC4199523 DOI: 10.1371/journal.pgen.1004738] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 09/06/2014] [Indexed: 11/18/2022] Open
Abstract
Protection of Telomeres 1 (POT1) is a conserved nucleic acid binding protein implicated in both telomere replication and chromosome end protection. We previously showed that Arabidopsis thaliana POT1a associates with the TER1 telomerase RNP, and is required for telomere length maintenance in vivo. Here we further dissect the function of POT1a and explore its interplay with the CST (CTC1/STN1/TEN1) telomere complex. Analysis of pot1a null mutants revealed that POT1a is not required for telomerase recruitment to telomeres, but is required for telomerase to maintain telomere tracts. We show that POT1a stimulates the synthesis of long telomere repeat arrays by telomerase, likely by enhancing repeat addition processivity. We demonstrate that POT1a binds STN1 and CTC1 in vitro, and further STN1 and CTC1, like POT1a, associate with enzymatically active telomerase in vivo. Unexpectedly, the in vitro interaction of STN1 with TEN1 and POT1a was mutually exclusive, indicating that POT1a and TEN1 may compete for the same binding site on STN1 in vivo. Finally, unlike CTC1 and STN1, TEN1 was not associated with active telomerase in vivo, consistent with our previous data showing that TEN1 negatively regulates telomerase enzyme activity. Altogether, our data support a two-state model in which POT1a promotes an extendable telomere state via contacts with the telomerase RNP as well as STN1 and CTC1, while TEN1 opposes these functions.
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Affiliation(s)
- Kyle B. Renfrew
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Xiangyu Song
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Jung Ro Lee
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Amit Arora
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Dorothy E. Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Procházková Schrumpfová P, Vychodilová I, Dvořáčková M, Majerská J, Dokládal L, Schořová Š, Fajkus J. Telomere repeat binding proteins are functional components of Arabidopsis telomeres and interact with telomerase. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 77:770-81. [PMID: 24397874 PMCID: PMC4282523 DOI: 10.1111/tpj.12428] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/06/2013] [Accepted: 12/23/2013] [Indexed: 05/19/2023]
Abstract
Although telomere-binding proteins constitute an essential part of telomeres, in vivo data indicating the existence of a structure similar to mammalian shelterin complex in plants are limited. Partial characterization of a number of candidate proteins has not identified true components of plant shelterin or elucidated their functional mechanisms. Telomere repeat binding (TRB) proteins from Arabidopsis thaliana bind plant telomeric repeats through a Myb domain of the telobox type in vitro, and have been shown to interact with POT1b (Protection of telomeres 1). Here we demonstrate co-localization of TRB1 protein with telomeres in situ using fluorescence microscopy, as well as in vivo interaction using chromatin immunoprecipitation. Classification of the TRB1 protein as a component of plant telomeres is further confirmed by the observation of shortening of telomeres in knockout mutants of the trb1 gene. Moreover, TRB proteins physically interact with plant telomerase catalytic subunits. These findings integrate TRB proteins into the telomeric interactome of A. thaliana.
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Affiliation(s)
- Petra Procházková Schrumpfová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Functional Genomics and Proteomics, CEITEC National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- *For correspondence (e-mails or )
| | - Ivona Vychodilová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Functional Genomics and Proteomics, CEITEC National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
| | - Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republicv.v.i, Královopolská 135, Brno, CZ, 61265, Czech Republic
| | - Jana Majerská
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- †Swiss Institute for Experimental Cancer Research, Ecole Polytechnique Fédérale de LausanneStation 19, 1015, Lausanne, Switzerland
| | - Ladislav Dokládal
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republicv.v.i, Královopolská 135, Brno, CZ, 61265, Czech Republic
| | - Šárka Schořová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Functional Genomics and Proteomics, CEITEC National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Functional Genomics and Proteomics, CEITEC National Centre for Biomolecular Research, Faculty of Science, Masaryk UniversityKamenice 5, Brno, CZ, 62500, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republicv.v.i, Královopolská 135, Brno, CZ, 61265, Czech Republic
- *For correspondence (e-mails or )
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Boltz KA, Jasti M, Townley JM, Shippen DE. Analysis of poly(ADP-Ribose) polymerases in Arabidopsis telomere biology. PLoS One 2014; 9:e88872. [PMID: 24551184 PMCID: PMC3923816 DOI: 10.1371/journal.pone.0088872] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Accepted: 01/17/2014] [Indexed: 11/22/2022] Open
Abstract
Maintaining the length of the telomere tract at chromosome ends is a complex process vital to normal cell division. Telomere length is controlled through the action of telomerase as well as a cadre of telomere-associated proteins that facilitate replication of the chromosome end and protect it from eliciting a DNA damage response. In vertebrates, multiple poly(ADP-ribose) polymerases (PARPs) have been implicated in the regulation of telomere length, telomerase activity and chromosome end protection. Here we investigate the role of PARPs in plant telomere biology. We analyzed Arabidopsis thaliana mutants null for PARP1 and PARP2 as well as plants treated with the PARP competitive inhibitor 3-AB. Plants deficient in PARP were hypersensitive to genotoxic stress, and expression of PARP1 and PARP2 mRNA was elevated in response to MMS or zeocin treatment or by the loss of telomerase. Additionally, PARP1 mRNA was induced in parp2 mutants, and conversely, PARP2 mRNA was induced in parp1 mutants. PARP3 mRNA, by contrast, was elevated in both parp1 and parp2 mutants, but not in seedlings treated with 3-AB or zeocin. PARP mutants and 3-AB treated plants displayed robust telomerase activity, no significant changes in telomere length, and no end-to-end chromosome fusions. Although there remains a possibility that PARPs play a role in Arabidopsis telomere biology, these findings argue that the contribution is a minor one.
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Affiliation(s)
- Kara A. Boltz
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Madhu Jasti
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Jennifer M. Townley
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
| | - Dorothy E. Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Leehy KA, Lee JR, Song X, Renfrew KB, Shippen DE. MERISTEM DISORGANIZATION1 encodes TEN1, an essential telomere protein that modulates telomerase processivity in Arabidopsis. THE PLANT CELL 2013; 25:1343-54. [PMID: 23572541 PMCID: PMC3663272 DOI: 10.1105/tpc.112.107425] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Telomeres protect chromosome ends from being recognized as DNA damage, and they facilitate the complete replication of linear chromosomes. CST [for CTC1(Cdc13)/STN1/TEN1] is a trimeric chromosome end binding complex implicated in both aspects of telomere function. Here, we characterize TEN1 in the flowering plant Arabidopsis thaliana. We report that TEN1 (for telomeric pathways in association with Stn1, which stands for suppressor of cdc thirteen) is encoded by a previously characterized gene, MERISTEM DISORGANIZATION1 (MDO1). A point mutation in MDO1, mdo1-1/ten1-3 (G77E), triggers stem cell differentiation and death as well as a constitutive DNA damage response. We provide biochemical and genetic evidence that ten1-3 is likely to be a null mutation. As with ctc1 and stn1 null mutants, telomere tracts in ten1-3 are shorter and more heterogeneous than the wild type. Mutants also exhibit frequent telomere fusions, increased single-strand telomeric DNA, and telomeric circles. However, unlike stn1 or ctc1 mutants, telomerase enzyme activity is elevated in ten1-3 mutants due to an increase in repeat addition processivity. In addition, TEN1 is detected at a significantly smaller fraction of telomeres than CTC1. These data indicate that TEN1 is critical for telomere stability and also plays an unexpected role in modulating telomerase enzyme activity.
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Giraud-Panis MJ, Pisano S, Benarroch-Popivker D, Pei B, Le Du MH, Gilson E. One identity or more for telomeres? Front Oncol 2013; 3:48. [PMID: 23509004 PMCID: PMC3598436 DOI: 10.3389/fonc.2013.00048] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 02/23/2013] [Indexed: 12/19/2022] Open
Abstract
A major issue in telomere research is to understand how the integrity of chromosome ends is controlled. The fact that different types of nucleoprotein complexes have been described at the telomeres of different organisms raises the question of whether they have in common a structural identity that explains their role in chromosome protection. We will review here how telomeric nucleoprotein complexes are structured, comparing different organisms and trying to link these structures to telomere biology. It emerges that telomeres are formed by a complex and specific network of interactions between DNA, RNA, and proteins. The fact that these interactions and associated activities are reinforcing each other might help to guarantee the robustness of telomeric functions across the cell cycle and in the event of cellular perturbations. We will also discuss the recent notion that telomeres have evolved specific systems to overcome the DNA topological stress generated during their replication and transcription. This will lead to revisit the way we envisage the functioning of telomeric complexes since the regulation of topology is central to DNA stability, replication, recombination, and transcription as well as to chromosome higher-order organization.
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Affiliation(s)
- Marie-Josèphe Giraud-Panis
- Faculté de Médecine de Nice, Université de Nice-Sophia Antipolis, Institute for Research on Cancer and Aging Nice, UMR 7284 CNRS, U1081 INSERM Nice, France
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Nelson ADL, Shippen DE. Surprises from the chromosome front: lessons from Arabidopsis on telomeres and telomerase. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2013; 77:7-15. [PMID: 23460576 DOI: 10.1101/sqb.2013.77.017053] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Telomeres serve two vital functions: They act as a buffer against the end-replication problem, and they prevent chromosome ends from being recognized as double-strand DNA (dsDNA) breaks. These functions are orchestrated by the telomerase reverse transcriptase and a variety of telomere protein complexes. Here, we discuss our recent studies with Arabidopsis thaliana that uncovered a new and highly conserved telomere complex called CST (Cdc13/CTC1, STN1, TEN1). Formerly believed to be yeast specific, CST has now been identified as a key component of both plant and vertebrate telomeres, which is essential for genome integrity and stem cell viability. We also describe the unexpected discovery of alternative telomerase ribonucleoprotein complexes in Arabidopsis. Fueled by duplication and diversification of the telomerase RNA subunit and telomerase accessory proteins, these telomerase complexes act in concert to maintain genome stability. In addition to the canonical telomerase enzyme, one of two alternative telomerase ribonucleoprotein (RNP) complexes functions as a novel negative regulator of enzyme activity in response to genotoxic stress. These contributions highlight the immense potential of Arabidopsis in probing the depths of the chromosome end.
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Affiliation(s)
- A D L Nelson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, USA
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30
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An alternative telomerase RNA in Arabidopsis modulates enzyme activity in response to DNA damage. Genes Dev 2012; 26:2512-23. [PMID: 23109676 DOI: 10.1101/gad.202960.112] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Telomerase replenishes telomere tracts by reiteratively copying its RNA template, TER. Unlike other model organisms, Arabidopsis thaliana harbors two divergent TER genes. However, only TER1 is required for telomere maintenance. Here we examine the function of TER2. We show that TER2 is spliced and its 3' end is truncated in vivo to generate a third TER isoform, TER2(S). TERT preferentially associates with TER2 > TER1 > TER2(S). Moreover, TER2 and TER2(S) assemble with Ku and POT1b (protection of telomeres), forming RNP (ribonucleoprotein) complexes distinct from TER1 RNP. Plants null for TER2 display increased telomerase enzyme activity, while TER2 overexpression inhibits telomere synthesis from TER1 and leads to telomere shortening. These findings argue that TER2 negatively regulates telomerase by sequestering TERT in a nonproductive RNP complex. Introduction of DNA double-strand breaks by zeocin leads to an immediate and specific spike in TER2 and a concomitant decrease in telomerase enzyme activity. This response is not triggered by replication stress or telomere dysfunction and is abrogated in ter2 mutants. We conclude that Arabidopsis telomerase is modulated by TER2, a novel DNA damage-induced noncoding RNA that works in concert with the canonical TER to promote genome integrity.
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Nelson ADL, Shippen DE. Blunt-ended telomeres: an alternative ending to the replication and end protection stories. Genes Dev 2012; 26:1648-52. [PMID: 22855827 DOI: 10.1101/gad.199059.112] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Telomeres ensure the complete replication of genetic material while simultaneously distinguishing the chromosome terminus from a double-strand break. A prevailing theme in telomere biology is that the two chromosome ends are symmetrical. Both terminate in a single-strand 3' extension, and the 3' extension is crucial for telomere end protection. In this issue of Genes & Development, Kazda and colleagues (pp. 1703-1713) challenge this paradigm using a series of elegant biochemical and genetic assays to demonstrate that half of the chromosomes in flowering plants are blunt-ended. This discovery reveals unanticipated complexity in telomeric DNA processing and a novel mode of chromosome end protection.
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Affiliation(s)
- Andrew D L Nelson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, 77843, USA
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32
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Katiyar A, Smita S, Lenka SK, Rajwanshi R, Chinnusamy V, Bansal KC. Genome-wide classification and expression analysis of MYB transcription factor families in rice and Arabidopsis. BMC Genomics 2012. [PMID: 23050870 DOI: 10.1186/1471-2164-13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023] Open
Abstract
BACKGROUND The MYB gene family comprises one of the richest groups of transcription factors in plants. Plant MYB proteins are characterized by a highly conserved MYB DNA-binding domain. MYB proteins are classified into four major groups namely, 1R-MYB, 2R-MYB, 3R-MYB and 4R-MYB based on the number and position of MYB repeats. MYB transcription factors are involved in plant development, secondary metabolism, hormone signal transduction, disease resistance and abiotic stress tolerance. A comparative analysis of MYB family genes in rice and Arabidopsis will help reveal the evolution and function of MYB genes in plants. RESULTS A genome-wide analysis identified at least 155 and 197 MYB genes in rice and Arabidopsis, respectively. Gene structure analysis revealed that MYB family genes possess relatively more number of introns in the middle as compared with C- and N-terminal regions of the predicted genes. Intronless MYB-genes are highly conserved both in rice and Arabidopsis. MYB genes encoding R2R3 repeat MYB proteins retained conserved gene structure with three exons and two introns, whereas genes encoding R1R2R3 repeat containing proteins consist of six exons and five introns. The splicing pattern is similar among R1R2R3 MYB genes in Arabidopsis. In contrast, variation in splicing pattern was observed among R1R2R3 MYB members of rice. Consensus motif analysis of 1kb upstream region (5' to translation initiation codon) of MYB gene ORFs led to the identification of conserved and over-represented cis-motifs in both rice and Arabidopsis. Real-time quantitative RT-PCR analysis showed that several members of MYBs are up-regulated by various abiotic stresses both in rice and Arabidopsis. CONCLUSION A comprehensive genome-wide analysis of chromosomal distribution, tandem repeats and phylogenetic relationship of MYB family genes in rice and Arabidopsis suggested their evolution via duplication. Genome-wide comparative analysis of MYB genes and their expression analysis identified several MYBs with potential role in development and stress response of plants.
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Affiliation(s)
- Amit Katiyar
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
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Katiyar A, Smita S, Lenka SK, Rajwanshi R, Chinnusamy V, Bansal KC. Genome-wide classification and expression analysis of MYB transcription factor families in rice and Arabidopsis. BMC Genomics 2012; 13:544. [PMID: 23050870 PMCID: PMC3542171 DOI: 10.1186/1471-2164-13-544] [Citation(s) in RCA: 322] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 10/01/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The MYB gene family comprises one of the richest groups of transcription factors in plants. Plant MYB proteins are characterized by a highly conserved MYB DNA-binding domain. MYB proteins are classified into four major groups namely, 1R-MYB, 2R-MYB, 3R-MYB and 4R-MYB based on the number and position of MYB repeats. MYB transcription factors are involved in plant development, secondary metabolism, hormone signal transduction, disease resistance and abiotic stress tolerance. A comparative analysis of MYB family genes in rice and Arabidopsis will help reveal the evolution and function of MYB genes in plants. RESULTS A genome-wide analysis identified at least 155 and 197 MYB genes in rice and Arabidopsis, respectively. Gene structure analysis revealed that MYB family genes possess relatively more number of introns in the middle as compared with C- and N-terminal regions of the predicted genes. Intronless MYB-genes are highly conserved both in rice and Arabidopsis. MYB genes encoding R2R3 repeat MYB proteins retained conserved gene structure with three exons and two introns, whereas genes encoding R1R2R3 repeat containing proteins consist of six exons and five introns. The splicing pattern is similar among R1R2R3 MYB genes in Arabidopsis. In contrast, variation in splicing pattern was observed among R1R2R3 MYB members of rice. Consensus motif analysis of 1kb upstream region (5' to translation initiation codon) of MYB gene ORFs led to the identification of conserved and over-represented cis-motifs in both rice and Arabidopsis. Real-time quantitative RT-PCR analysis showed that several members of MYBs are up-regulated by various abiotic stresses both in rice and Arabidopsis. CONCLUSION A comprehensive genome-wide analysis of chromosomal distribution, tandem repeats and phylogenetic relationship of MYB family genes in rice and Arabidopsis suggested their evolution via duplication. Genome-wide comparative analysis of MYB genes and their expression analysis identified several MYBs with potential role in development and stress response of plants.
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Affiliation(s)
- Amit Katiyar
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
- National Bureau of Plant Genetic Resources, Indian Agricultural Research Institute Campus, New Delhi, 110012, India
| | - Shuchi Smita
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
- National Bureau of Plant Genetic Resources, Indian Agricultural Research Institute Campus, New Delhi, 110012, India
| | - Sangram Keshari Lenka
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
- Department of Biology, University of Massachusetts, Amherst, MA, 01003, USA
| | - Ravi Rajwanshi
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
- Department of Biotechnology, Assam University, Silchar, Assam, 788011, India
| | - Viswanathan Chinnusamy
- Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi, 110012, India
| | - Kailash Chander Bansal
- National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute, New Delhi, 110012, India
- National Bureau of Plant Genetic Resources, Indian Agricultural Research Institute Campus, New Delhi, 110012, India
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Visacka K, Hofr C, Willcox S, Necasova I, Pavlouskova J, Sepsiova R, Wimmerova M, Simonicova L, Nosek J, Fajkus J, Griffith JD, Tomaska L. Synergism of the two Myb domains of Tay1 protein results in high affinity binding to telomeres. J Biol Chem 2012; 287:32206-15. [PMID: 22815473 DOI: 10.1074/jbc.m112.385591] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Double-stranded regions of the telomeres are recognized by proteins containing Myb-like domains conferring specificity toward telomeric repeats. Although biochemical and structural studies revealed basic molecular principles involved in DNA binding, relatively little is known about evolutionary pathways leading to various types of Myb domain-containing proteins in divergent species of eukaryotes. Recently we identified a novel type of telomere-binding protein YlTay1p from the yeast Yarrowia lipolytica containing two Myb domains (Myb1, Myb2) very similar to the Myb domain of mammalian TRF1 and TRF2. In this study we prepared mutant versions of YlTay1p lacking Myb1, Myb2, or both Myb domains and found that YlTay1p carrying either Myb domain exhibits preferential affinity to both Y. lipolytica (GGGTTAGTCA)(n) and human (TTAGGG)(n) telomeric sequences. Quantitative measurements of the protein binding to telomeric DNA revealed that the presence of both Myb domains is required for a high affinity of YlTay1p to either telomeric repeat. Additionally, we performed detailed thermodynamic analysis of the YlTay1p interaction with its cognate telomeric DNA, which is to our knowledge the first energetic description of a full-length telomeric-protein binding to DNA. Interestingly, when compared with human TRF1 and TRF2 proteins, YlTay1p exhibited higher affinity not only for Y. lipolytica telomeres but also for human telomeric sequences. The duplication of the Myb domain region in YlTay1p thus produces a synergistic effect on its affinity toward the cognate telomeric sequence, alleviating the need for homodimerization observed in TRF-like proteins possessing a single Myb domain.
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Affiliation(s)
- Katarina Visacka
- Department of Genetics and Biochemistry, Comenius University, Faculty of Natural Sciences, Mlynska dolina, 842 15 Bratislava, Slovakia
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Amiard S, Depeiges A, Allain E, White CI, Gallego ME. Arabidopsis ATM and ATR kinases prevent propagation of genome damage caused by telomere dysfunction. THE PLANT CELL 2011; 23:4254-65. [PMID: 22158468 PMCID: PMC3269864 DOI: 10.1105/tpc.111.092387] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 11/22/2011] [Accepted: 11/30/2011] [Indexed: 05/18/2023]
Abstract
The ends of linear eukaryotic chromosomes are hidden in nucleoprotein structures called telomeres, and loss of the telomere structure causes inappropriate repair, leading to severe karyotypic and genomic instability. Although it has been shown that DNA damaging agents activate a DNA damage response (DDR), little is known about the signaling of dysfunctional plant telomeres. We show that absence of telomerase in Arabidopsis thaliana elicits an ATAXIA-TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR)-dependent DDR at telomeres, principally through ATM. By contrast, telomere dysfunction induces an ATR-dependent response in telomeric Conserved telomere maintenance component1 (Ctc1)-Suppressor of cdc thirteen (Stn1)-Telomeric pathways in association with Stn1 (CST)-complex mutants. These results uncover a new role for the CST complex in repressing the ATR-dependent DDR pathway in plant cells and show that plant cells use two different DNA damage surveillance pathways to signal telomere dysfunction. The absence of either ATM or ATR in ctc1 and stn1 mutants significantly enhances developmental and genome instability while reducing stem cell death. These data thus give a clear illustration of the action of ATM/ATR-dependent programmed cell death in maintaining genomic integrity through elimination of genetically unstable cells.
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Wei SY, Lou YC, Tsai JY, Ho MR, Chou CC, Rajasekaran M, Hsu HM, Tai JH, Hsiao CD, Chen C. Structure of the Trichomonas vaginalis Myb3 DNA-binding domain bound to a promoter sequence reveals a unique C-terminal β-hairpin conformation. Nucleic Acids Res 2011; 40:449-60. [PMID: 21908401 PMCID: PMC3245928 DOI: 10.1093/nar/gkr707] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Trichomonas vaginalis Myb3 transcription factor (tvMyb3) recognizes the MRE-1 promoter sequence and regulates ap65-1 gene, which encodes a hydrogenosomal malic enzyme that may play a role in the cytoadherence of the parasite. Here, we identified tvMyb353–180 as the essential fragment for DNA recognition and report the crystal structure of tvMyb353–180 bound to MRE-1 DNA. The N-terminal fragment adopts the classical conformation of an Myb DNA-binding domain, with the third helices of R2 and R3 motifs intercalating in the major groove of DNA. The C-terminal extension forms a β-hairpin followed by a flexible tail, which is stabilized by several interactions with the R3 motif and is not observed in other Myb proteins. Interestingly, this unique C-terminal fragment does not stably connect with DNA in the complex structure but is involved in DNA binding, as demonstrated by NMR chemical shift perturbation, 1H-15N heteronuclear-nuclear Overhauser effect and intermolecular paramagnetic relaxation enhancement. Site-directed mutagenesis also revealed that this C-terminal fragment is crucial for DNA binding, especially the residue Arg153 and the fragment K170KRK173. We provide a structural basis for MRE-1 DNA recognition and suggest a possible post-translational regulation of tvMyb3 protein.
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Affiliation(s)
- Shu-Yi Wei
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, ROC
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Lee YW, Kim WT. Roles of NtGTBP1 in telomere stability. PLANT SIGNALING & BEHAVIOR 2011; 6:523-5. [PMID: 21474994 PMCID: PMC3142381 DOI: 10.4161/psb.6.4.14749] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 01/07/2011] [Indexed: 05/25/2023]
Abstract
Telomeres are protective nucleoprotein structures at the ends of linear eukaryotic chromosomes. In contrast to double-stranded-specific telomere-binding proteins, the cellular roles of single-stranded-specific telomeric proteins are not well understood in higher plants. Three highly conserved tobacco G-strand-specific telomere-binding protein paralogs (NtGTBP1, NtGTBP2, and NtGTBP3) were identified and characterized. All three NtGTBPs were able to bind specifically to the plant single-stranded telomeric repeat elements in vitro with similar affinities. Suppression of NtGTBP1 by means of the RNAi-mediated gene knock-down method resulted in developmental defects in transgenic tobacco plants accompanied by lengthened telomeres, extra-chromosomal telomeric circles, and abnormal anaphase bridges. These results suggest that the down-regulation of NtGTBP1 results in genome instability. NtGTBP1 prevented in vitro strand invasion, a prerequisite process for inter-chromosomal telomeric recombination. Therefore, tobacco NtGTBP1 is one of the essential factors for telomere stability. Because abnormal telomeric elongation and recombination due to the suppression of NtGTBP1 are reminiscent of the recombinational telomere lengthening mechanism that purportedly operates in telomerase negative cancer cells, it is of interest to investigate whether telomeric recombination is associated with cell death in animal systems.
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Affiliation(s)
- Yong Woo Lee
- Yonsei University, Department of Systems Biology, Seoul, South Korea
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38
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Abstract
Telomerase is a ribonucleoprotein (RNP) reverse transcriptase whose essential RNA subunit (TER) functions as a template for telomere repeat synthesis. Here we report the identification of two divergent TER moieties in the flowering plant Arabidopsis thaliana. Although both TER1 and TER2 copurify with telomerase activity and serve as templates for telomerase in vitro, depletion of TER1, but not TER2, leads to decreased telomerase activity and progressive telomere shortening in vivo. Moreover, mutation of the templating domain in TER1 results in the incorporation of mutant telomere repeats on chromosome ends. Thus, TER1 provides the major template for telomerase in vivo. We also show that POT1a binds TER1 with a Kd of 2 × 10(-7) M and the two components assemble into an enzymatically active RNP in vivo. In contrast, TER1-POT1b and TER2-POT1a associations were not observed. In other organisms POT1 proteins bind telomeric DNA and provide chromosome end protection. We propose that duplication of TER and POT1 in Arabidopsis fueled the evolution of novel protein-nucleic acid interactions and the migration of POT1 from the telomere to the telomerase RNP.
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Dubruille R, Orsi GA, Delabaere L, Cortier E, Couble P, Marais GAB, Loppin B. Specialization of a Drosophila capping protein essential for the protection of sperm telomeres. Curr Biol 2010; 20:2090-9. [PMID: 21093267 DOI: 10.1016/j.cub.2010.11.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 10/28/2010] [Accepted: 11/02/2010] [Indexed: 11/26/2022]
Abstract
BACKGROUND A critical function of telomeres is to prevent fusion of chromosome ends by the DNA repair machinery. In Drosophila somatic cells, assembly of the protecting capping complex at telomeres notably involves the recruitment of HOAP, HP1, and their recently identified partner, HipHop. We previously showed that the hiphop gene was duplicated before the radiation of the melanogaster subgroup of species, giving birth to K81, a unique paternal effect gene specifically expressed in the male germline. RESULTS Here we show that K81 specifically associates with telomeres during spermiogenesis, along with HOAP and HP1, and is retained on paternal chromosomes until zygote formation. In K81 mutant testes, capping proteins are not maintained at telomeres in differentiating spermatids, resulting in the transmission of uncapped paternal chromosomes that fail to properly divide during the first zygotic mitosis. Despite the apparent similar capping roles of K81 and HipHop in their respective domain of expression, we demonstrate by in vivo reciprocal complementation analyses that they are not interchangeable. Strikingly, HipHop appeared to be unable to maintain capping proteins at telomeres during the global chromatin remodeling of spermatid nuclei. CONCLUSIONS Our data demonstrate that K81 is essential for the maintenance of capping proteins at telomeres in postmeiotic male germ cells. In species of the melanogaster subgroup, HipHop and K81 have not only acquired complementary expression domains, they have also functionally diverged following the gene duplication event. We propose that K81 specialized in the maintenance of telomere protection in the highly peculiar chromatin environment of differentiating male gametes.
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Price CM, Boltz KA, Chaiken MF, Stewart JA, Beilstein MA, Shippen DE. Evolution of CST function in telomere maintenance. Cell Cycle 2010; 9:3157-65. [PMID: 20697207 DOI: 10.4161/cc.9.16.12547] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Telomeres consist of an elaborate, higher-order DNA architecture, and a suite of proteins that provide protection for the chromosome terminus by blocking inappropriate recombination and nucleolytic attack. In addition, telomeres facilitate telomeric DNA replication by physical interactions with telomerase and the lagging strand replication machinery. The prevailing view has been that two distinct telomere capping complexes evolved, shelterin in vertebrates and a trimeric complex comprised of Cdc13, Stn1 and Ten1 (CST) in yeast. The recent discovery of a CST-like complex in plants and humans raises new questions about the composition of telomeres and their regulatory mechanisms in multicellular eukaryotes. In this review we discuss the evolving functions and interactions of CST components and their contributions to chromosome end protection and DNA replication.
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Affiliation(s)
- Carolyn M Price
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, OH, USA.
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Watson JM, Riha K. Comparative biology of telomeres: where plants stand. FEBS Lett 2010; 584:3752-9. [PMID: 20580356 PMCID: PMC3767043 DOI: 10.1016/j.febslet.2010.06.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/11/2010] [Accepted: 06/14/2010] [Indexed: 01/02/2023]
Abstract
Telomeres are essential structures at the ends of eukaryotic chromosomes. Work on their structure and function began almost 70 years ago in plants and flies, continued through the Nobel Prize winning work on yeast and ciliates, and goes on today in many model and non-model organisms. The basic molecular mechanisms of telomeres are highly conserved throughout evolution, and our current understanding of how telomeres function is a conglomeration of insights gained from many different species. This review will compare the current knowledge of telomeres in plants with other organisms, with special focus on the functional length of telomeric DNA, the search for TRF homologs, the family of POT1 proteins, and the recent discovery of members of the CST complex.
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Affiliation(s)
- J Matthew Watson
- Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria
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42
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Shakirov EV, Perroud PF, Nelson AD, Cannell ME, Quatrano RS, Shippen DE. Protection of Telomeres 1 is required for telomere integrity in the moss Physcomitrella patens. THE PLANT CELL 2010; 22:1838-48. [PMID: 20515974 PMCID: PMC2910979 DOI: 10.1105/tpc.110.075846] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
In vertebrates, the single-stranded telomeric DNA binding protein Protection of Telomeres 1 (POT1) shields chromosome ends and prevents them from eliciting a DNA damage response. By contrast, Arabidopsis thaliana encodes two divergent full-length POT1 paralogs that do not exhibit telomeric DNA binding in vitro and have evolved to mediate telomerase regulation instead of chromosome end protection. To further investigate the role of POT1 in plants, we established the moss Physcomitrella patens as a new model for telomere biology and a counterpoint to Arabidopsis. The sequence and architecture of the telomere tract is similar in P. patens and Arabidopsis, but P. patens harbors only a single-copy POT1 gene. Unlike At POT1 proteins, Pp POT1 efficiently bound single-stranded telomeric DNA in vitro. Deletion of the P. patens POT1 gene resulted in the rapid onset of severe developmental defects and sterility. Although telomerase activity levels were unperturbed, telomeres were substantially shortened, harbored extended G-overhangs, and engaged in end-to-end fusions. We conclude that the telomere capping function of POT1 is conserved in early diverging land plants but is subsequently lost in Arabidopsis.
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Affiliation(s)
- Eugene V. Shakirov
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
| | | | - Andrew D. Nelson
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
| | - Maren E. Cannell
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
| | - Ralph S. Quatrano
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Dorothy E. Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
- Address correspondence to
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Dvorácková M, Rossignol P, Shaw PJ, Koroleva OA, Doonan JH, Fajkus J. AtTRB1, a telomeric DNA-binding protein from Arabidopsis, is concentrated in the nucleolus and shows highly dynamic association with chromatin. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:637-49. [PMID: 19947985 DOI: 10.1111/j.1365-313x.2009.04094.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
AtTRB1, 2 and 3 are members of the SMH (single Myb histone) protein family, which comprises double-stranded DNA-binding proteins that are specific to higher plants. They are structurally conserved, containing a Myb domain at the N-terminus, a central H1/H5-like domain and a C-terminally located coiled-coil domain. AtTRB1, 2 and 3 interact through their Myb domain specifically with telomeric double-stranded DNA in vitro, while the central H1/H5-like domain interacts non-specifically with DNA sequences and mediates protein-protein interactions. Here we show that AtTRB1, 2 and 3 preferentially localize to the nucleus and nucleolus during interphase. Both the central H1/H5-like domain and the Myb domain from AtTRB1 can direct a GFP fusion protein to the nucleus and nucleolus. AtTRB1-GFP localization is cell cycle-regulated, as the level of nuclear-associated GFP diminishes during mitotic entry and GFP progressively re-associates with chromatin during anaphase/telophase. Using fluorescence recovery after photobleaching and fluorescence loss in photobleaching, we determined the dynamics of AtTRB1 interactions in vivo. The results reveal that AtTRB1 interaction with chromatin is regulated at two levels at least, one of which is coupled with cell-cycle progression, with the other involving rapid exchange.
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Affiliation(s)
- Martina Dvorácková
- Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
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44
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Xiang Q, Judelson HS. Myb transcription factors in the oomycete Phytophthora with novel diversified DNA-binding domains and developmental stage-specific expression. Gene 2010; 453:1-8. [PMID: 20060444 DOI: 10.1016/j.gene.2009.12.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 12/14/2009] [Accepted: 12/15/2009] [Indexed: 10/20/2022]
Abstract
Transcription factors containing two or three imperfect tandem repeats of the Myb DNA-binding domain (named R2R3 and R1R2R3, respectively) regulate important processes in growth and development. This study characterizes the structure, evolution, and expression of these proteins in the potato pathogen Phytophthora infestans and other oomycetes. P. infestans was found to encode five R2R3 and nine R1R2R3 transcription factor-like proteins, plus several with additional configurations of Myb domains. Sets of R2R3 and R1R2R3 orthologs are well-conserved in three Phytophthora species. Analyses of sites that bind DNA in canonical Myb transcription factors, such as mammalian c-Myb, revealed unusual diversification in the DNA recognition helices of the oomycete proteins. While oomycete R2R3 proteins contain c-Myb-like helices, R1R2R3 proteins exhibit either c-Myb-like or novel sequences. This suggests divergence in their DNA-binding specificities, which was confirmed by electrophoretic mobility shift assays. Eight of the P. infestans R2R3 and R1R2R3 genes are up-regulated during sporulation and three during zoospore release, which suggests their involvement in spore development. This is supported by the observation that an oomycete that does not form zoospores, Hyaloperonospora arabidopsidis, contains one-third fewer of these genes than Phytophthora.
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Affiliation(s)
- Qijun Xiang
- Department of Plant Pathology and Microbiology, University of California, Riverside, 92521, USA
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45
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Hong JP, Byun MY, An K, Yang SJ, An G, Kim WT. OsKu70 is associated with developmental growth and genome stability in rice. PLANT PHYSIOLOGY 2010; 152:374-87. [PMID: 19923234 PMCID: PMC2799371 DOI: 10.1104/pp.109.150391] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The cellular functions of Ku70 in repair of DNA double-stranded breaks and telomere regulation have been described in a wide range of organisms. In this study, we identified the rice (Oryza sativa) Ku70 homolog (OsKu70) from the rice genome database. OsKu70 transcript was detected constitutively in every tissue and developmental stage examined and also in undifferentiated callus cells in rice. Yeast two-hybrid and in vitro pull-down experiments revealed that OsKu70 physically interacts with OsKu80. We obtained loss-of-function osku70 T-DNA knockout mutant lines and constructed transgenic rice plants that overexpress the OsKu70 gene in the sense (35S:OsKu70) or antisense (35S:anti-OsKu70) orientation. The homozygous G2 osku70 mutant lines were more sensitive than wild-type plants to a DNA-damaging agent (0.01%-0.05% methyl-methane sulfonate), consistent with the notion that OsKu70 participates in the DNA repair mechanism. Terminal restriction fragment analysis revealed that telomeres in homozygous G2 osku70 mutants were markedly longer (10-20 kb) than those in wild-type plants (5-10 kb), whereas telomere length in heterozygous G2 osku70 mutant and T2 OsKu70-overexpressing transgenic (35S:OsKu70) rice resembled that of the wild-type plant. In contrast to what was observed in Arabidopsis (Arabidopsis thaliana) atku70 mutants, homozygous G2 osku70 rice plants displayed severe developmental defects in both vegetative and reproductive organs under normal growth conditions, resulting in sterile flowers. Analysis of meiotic progression in pollen mother cells demonstrated that up to 11.1% (seven of 63) of G2 mutant anaphase cells displayed one or more chromosomal fusions. These results suggest that OsKu70 is required for the maintenance of chromosome stability and normal developmental growth in rice plants.
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46
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Linger BR, Price CM. Conservation of telomere protein complexes: shuffling through evolution. Crit Rev Biochem Mol Biol 2009; 44:434-46. [PMID: 19839711 DOI: 10.3109/10409230903307329] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The rapid evolution of telomere proteins has hindered identification of orthologs from diverse species and created the impression that certain groups of eukaryotes have largely non-overlapping sets of telomere proteins. However, the recent identification of additional telomere proteins from various model organisms has dispelled this notion by expanding our understanding of the composition, architecture and range of telomere protein complexes present in individual species. It is now apparent that versions of the budding yeast CST complex and mammalian shelterin are present in multiple phyla. While the precise subunit composition and architecture of these complexes vary between species, the general function is often conserved. Despite the overall conservation of telomere protein complexes, there is still considerable species-specific variation, with some organisms having lost a particular subunit or even an entire complex. In some cases, complex components appear to have migrated between the telomere and the telomerase RNP. Finally, gene duplication has created telomere protein paralogs with novel functions. While one paralog may be part of a conserved telomere protein complex and have the expected function, the other paralog may serve in a completely different aspect of telomere biology.
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Affiliation(s)
- Benjamin R Linger
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, OH 45267-0521, USA
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47
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Shakirov EV, McKnight TD, Shippen DE. POT1-independent single-strand telomeric DNA binding activities in Brassicaceae. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 58:1004-15. [PMID: 19228335 PMCID: PMC5880214 DOI: 10.1111/j.1365-313x.2009.03837.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Telomeres define the ends of linear eukaryotic chromosomes and are required for genome maintenance and continued cell proliferation. The extreme ends of telomeres terminate in a single-strand protrusion, termed the G-overhang, which, in vertebrates and fission yeast, is bound by evolutionarily conserved members of the POT1 (protection of telomeres) protein family. Unlike most other model organisms, the flowering plant Arabidopsis thaliana encodes two divergent POT1-like proteins. Here we show that the single-strand telomeric DNA binding activity present in A. thaliana nuclear extracts is not dependent on POT1a or POT1b proteins. Furthermore, in contrast to POT1 proteins from yeast and vertebrates, recombinant POT1a and POT1b proteins from A. thaliana, and from two additional Brassicaceae species, Arabidopsis lyrata and Brassica oleracea (cauliflower), fail to bind single-strand telomeric DNA in vitro under the conditions tested. Finally, although we detected four single-strand telomeric DNA binding activities in nuclear extracts from B. oleracea, partial purification and DNA cross-linking analysis of these complexes identified proteins that are smaller than the predicted sizes of BoPOT1a or BoPOT1b. Taken together, these data suggest that POT1 proteins are not the major single-strand telomeric DNA binding activities in A. thaliana and its close relatives, underscoring the remarkable functional divergence of POT1 proteins from plants and other eukaryotes.
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Affiliation(s)
- Eugene V. Shakirov
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, USA
| | - Thomas D. McKnight
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, Texas 77843-3258, USA
| | - Dorothy E. Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, Texas 77843-2128, USA
- For correspondence (fax +1 979 845 9274; )
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48
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Ko S, Yu EY, Shin J, Yoo HH, Tanaka T, Kim WT, Cho HS, Lee W, Chung IK. Solution Structure of the DNA Binding Domain of Rice Telomere Binding Protein RTBP1,. Biochemistry 2009; 48:827-38. [DOI: 10.1021/bi801270g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sunggeon Ko
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Eun Young Yu
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Joon Shin
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Hyun Hee Yoo
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Toshiyuki Tanaka
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Woo Taek Kim
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Hyun-Soo Cho
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Weontae Lee
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - In Kwon Chung
- Departments of Biochemistry and Biology, Protein Network Research Center, Yonsei University, Seoul 120-749, Korea, and Institute of Applied Biochemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
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Abstract
Telomeres shield the natural ends of chromosomes from nucleolytic attack, recognition as double-strand breaks, and inappropriate processing by DNA repair machinery. The trimeric Stn1/Ten1/Cdc13 complex is critical for chromosome end protection in Saccharomyces cerevisiae, while vertebrate telomeres are protected by shelterin, a complex of six proteins that does not include STN1 or TEN1. Recent studies demonstrate that Stn1 and Ten1 orthologs in Schizosaccharomyces pombe contribute to telomere integrity in a complex that is distinct from the shelterin components, Pot1 and Tpp1. Thus, chromosome-end protection may be mediated by distinct subcomplexes of telomere proteins. Here we report the identification of a STN1 gene in Arabidopsis that is essential for chromosome-end protection. AtSTN1 encodes an 18-kDa protein bearing a single oligonucleotide/oligosaccharide binding fold with significant sequence similarity to the yeast Stn1 proteins. Plants null for AtSTN1 display an immediate onset of growth and developmental defects and reduced fertility. These outward phenotypes are accompanied by catastrophic loss of telomeric and subtelomeric DNA, high levels of end-to-end chromosome fusions, increased G-overhang signals, and elevated telomere recombination. Thus, AtSTN1 is a crucial component of the protective telomere cap in Arabidopsis, and likely in other multicellular eukaryotes.
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50
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Shakirov EV, Salzberg SL, Alam M, Shippen DE. Analysis of Carica papaya Telomeres and Telomere-Associated Proteins: Insights into the Evolution of Telomere Maintenance in Brassicales. TROPICAL PLANT BIOLOGY 2008; 1:202-215. [PMID: 20664721 PMCID: PMC2909770 DOI: 10.1007/s12042-008-9018-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Telomeres are terminal regions of linear eukaryotic chromosomes that are critical for genome stability and continued cell proliferation. The draft assembly of the papaya genome provides an opportunity to analyze and compare the evolution of telomeric DNA sequence composition and telomere maintenance machinery in this and other organisms of the Brassicales Order, which includes Arabidopsis. Here we investigate telomere size and sequence variation at papaya chromosome ends. As with most other plant species, papaya telomeres consist of TTTAGGG repeats. However, in contrast to members of the closely related Brassicaceae family, telomeres in papaya are ~10-fold longer. Sequence analysis reveals that many centromereproximal telomere repeats in papaya harbor nucleotide substitutions and insertions of Gs and Ts. In contrast, we found very few N-to-C substitutions, and even fewer instances of nucleotide deletion, suggesting that a six-nucleotide telomere repeat is not well tolerated. The papaya genome encodes single-copy sequence homologues of several genes involved in telomere maintenance and chromosome end protection, including the Telomerase Reverse Transcriptase (TERT) and Protection Of Telomeres (POT1). Notably, unlike Arabidopsis, which encodes six Telomere Repeat binding Factor-like (TRFL) proteins that bind double-stranded telomere DNA, papaya appears to encode only two such proteins. Thus, the more streamlined genome of papaya will provide an excellent resource for comparative and functional analysis of telomeres in plants.
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Affiliation(s)
- E. V. Shakirov
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA
| | - S. L. Salzberg
- Center for Bioinformatics and Computational Biology, and Department of Computer Science, University of Maryland, 3125 Biomolecular Sciences Bldg, College Park, MD 20742, USA
| | - M. Alam
- Advanced Studies in Genomics, Proteomics and Bioinformatics, and Department of Microbiology, University of Hawaii, Honolulu, HI 96822, USA
| | - D. E. Shippen
- Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA,
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