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Zhai LT, Rety S, Chen WF, Song ZY, Auguin D, Sun B, Dou SX, Xi XG. Crystal structures of N-terminally truncated telomerase reverse transcriptase from fungi‡. Nucleic Acids Res 2021; 49:4768-4781. [PMID: 33856462 PMCID: PMC8096264 DOI: 10.1093/nar/gkab261] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 03/28/2021] [Accepted: 04/05/2021] [Indexed: 12/12/2022] Open
Abstract
Telomerase plays critical roles in cellular aging, in the emergence and/or development of cancer, and in the capacity for stem-cell renewal, consists of a catalytic telomerase reverse transcriptase (TERT) and a template-encoding RNA (TER). TERs from diverse organisms contain two conserved structural elements: the template-pseudoknot (T-PK) and a helical three-way junction (TWJ). Species-specific features of the structure and function of telomerase make obtaining a more in-depth understanding of the molecular mechanism of telomerase particularly important. Here, we report the first structural studies of N-terminally truncated TERTs from Candida albicans and Candida tropicalis in apo form and complexed with their respective TWJs in several conformations. We found that Candida TERT proteins perform only one round of telomere addition in the presence or absence of PK/TWJ and display standard reverse transcriptase activity. The C-terminal domain adopts at least two extreme conformations and undergoes conformational interconversion, which regulates the catalytic activity. Most importantly, we identified a conserved tertiary structural motif, called the U-motif, which interacts with the reverse transcriptase domain and is crucial for catalytic activity. Together these results shed new light on the structure and mechanics of fungal TERTs, which show common TERT characteristics, but also display species-specific features.
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Affiliation(s)
- Liu-Tao Zhai
- State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Stephane Rety
- University Lyon, ENS de Lyon, University Claude Bernard, CNRS UMR 5239, INSERM U1210, LBMC, 46 Allée d’Italie Site Jacques Monod, F-69007 Lyon, France
| | - Wei-Fei Chen
- State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Ze-Yu Song
- State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Daniel Auguin
- Laboratoire de Biologie des Ligneux et des Grandes Cultures (LBLGC), Université d’Orléans, INRA, USC1328, 45067 Orléans; Structural Motility, Institut Curie, CNRS, UMR 144 Paris, France
| | - Bo Sun
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Shuo-Xing Dou
- Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xu-Guang Xi
- State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China
- Laboratoire de Biologie et de Pharmacologie Appliquée (LBPA), UMR 8113 CNRS, Institut D’Alembert, École Normale Supérieure Paris-Saclay, Université Paris-Saclay, 4, Avenue des Sciences, 91190 Gif sur Yvette, France
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2
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Wu ZJ, Liu JC, Man X, Gu X, Li TY, Cai C, He MH, Shao Y, Lu N, Xue X, Qin Z, Zhou JQ. Cdc13 is predominant over Stn1 and Ten1 in preventing chromosome end fusions. eLife 2020; 9:53144. [PMID: 32755541 PMCID: PMC7406354 DOI: 10.7554/elife.53144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 06/12/2020] [Indexed: 12/16/2022] Open
Abstract
Telomeres define the natural ends of eukaryotic chromosomes and are crucial for chromosomal stability. The budding yeast Cdc13, Stn1 and Ten1 proteins form a heterotrimeric complex, and the inactivation of any of its subunits leads to a uniformly lethal phenotype due to telomere deprotection. Although Cdc13, Stn1 and Ten1 seem to belong to an epistasis group, it remains unclear whether they function differently in telomere protection. Here, we employed the single-linear-chromosome yeast SY14, and surprisingly found that the deletion of CDC13 leads to telomere erosion and intrachromosome end-to-end fusion, which depends on Rad52 but not Yku. Interestingly, the emergence frequency of survivors in the SY14 cdc13Δ mutant was ~29 fold higher than that in either the stn1Δ or ten1Δ mutant, demonstrating a predominant role of Cdc13 in inhibiting telomere fusion. Chromosomal fusion readily occurred in the telomerase-null SY14 strain, further verifying the default role of intact telomeres in inhibiting chromosome fusion.
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Affiliation(s)
- Zhi-Jing Wu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Jia-Cheng Liu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xin Man
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xin Gu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Ting-Yi Li
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Chen Cai
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Ming-Hong He
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Yangyang Shao
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Ning Lu
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Xiaoli Xue
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Zhongjun Qin
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences; University of Chinese Academy of Sciences, Shanghai, China.,School of Life Science and Technology, ShanghaiTech University, Shanghai, China
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3
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Chen YF, Lu CY, Lin YC, Yu TY, Chang CP, Li JR, Li HW, Lin JJ. Modulation of yeast telomerase activity by Cdc13 and Est1 in vitro. Sci Rep 2016; 6:34104. [PMID: 27659693 PMCID: PMC5034320 DOI: 10.1038/srep34104] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 09/08/2016] [Indexed: 01/08/2023] Open
Abstract
Telomerase is the enzyme involved in extending telomeric DNA. Control of telomerase activity by modulating its access to chromosome ends is one of the most important fundamental mechanisms. This study established an in vitro yeast telomerase reconstitution system that resembles telomere replication in vivo. In this system, a tailed-duplex DNA formed by telomeric DNA was employed to mimic the structure of telomeres. The core catalytic components of telomerase Est2/Tlc1 RNA were used as the telomeric DNA extension machinery. Using the reconstituted systems, this study found that binding of Cdc13 to telomeric DNA inhibited the access of telomerase to its substrate. The result was further confirmed by a single-molecule approach using the tethered-particle motion (TPM)-based telomerase assay. The findings also showed that the inhibitory effect can be relieved by telomerase-associated protein Est1, consistent with the role of Cdc13 and Est1 in regulating telomere extension in vivo. Significantly, this study found that the DNA binding property of Cdc13 was altered by Est1, providing the first mechanistic evidence of Est1 regulating the access of telomerase to its substrate. Thus, the roles of Cdc13 and Est1 in modulating telomerase activity were clearly defined using the in vitro reconstituted system.
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Affiliation(s)
- Yu-Fan Chen
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei 112, Taiwan
| | - Chia-Ying Lu
- Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, Taipei 100, Taiwan
| | - Yi-Chien Lin
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei 112, Taiwan
| | - Tai-Yuan Yu
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei 112, Taiwan
| | - Chun-Ping Chang
- Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, Taipei 100, Taiwan
| | - Jing-Ru Li
- Department of Chemistry, National Taiwan University, Taipei 100, Taiwan
| | - Hung-Wen Li
- Department of Chemistry, National Taiwan University, Taipei 100, Taiwan
| | - Jing-Jer Lin
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei 112, Taiwan.,Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, Taipei 100, Taiwan
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4
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Peltier G, Aro EM, Shikanai T. NDH-1 and NDH-2 Plastoquinone Reductases in Oxygenic Photosynthesis. ANNUAL REVIEW OF PLANT BIOLOGY 2016; 67:55-80. [PMID: 26735062 DOI: 10.1146/annurev-arplant-043014-114752] [Citation(s) in RCA: 169] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Oxygenic photosynthesis converts solar energy into chemical energy in the chloroplasts of plants and microalgae as well as in prokaryotic cyanobacteria using a complex machinery composed of two photosystems and both membrane-bound and soluble electron carriers. In addition to the major photosynthetic complexes photosystem II (PSII), cytochrome b6f, and photosystem I (PSI), chloroplasts also contain minor components, including a well-conserved type I NADH dehydrogenase (NDH-1) complex that functions in close relationship with photosynthesis and likewise originated from the endosymbiotic cyanobacterial ancestor. Some plants and many microalgal species have lost plastidial ndh genes and a functional NDH-1 complex during evolution, and studies have suggested that a plastidial type II NADH dehydrogenase (NDH-2) complex substitutes for the electron transport activity of NDH-1. However, although NDH-1 was initially thought to use NAD(P)H as an electron donor, recent research has demonstrated that both chloroplast and cyanobacterial NDH-1s oxidize reduced ferredoxin. We discuss more recent findings related to the biochemical composition and activity of NDH-1 and NDH-2 in relation to the physiology and regulation of photosynthesis, particularly focusing on their roles in cyclic electron flow around PSI, chlororespiration, and acclimation to changing environments.
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Affiliation(s)
- Gilles Peltier
- Institute of Environmental Biology and Biotechnology, CEA, CNRS, Aix-Marseille University, CEA Cadarache, 13018 Saint-Paul-lès-Durance, France;
| | - Eva-Mari Aro
- Department of Biochemistry, University of Turku, 20014 Turku, Finland;
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Advani VM, Belew AT, Dinman JD. Yeast telomere maintenance is globally controlled by programmed ribosomal frameshifting and the nonsense-mediated mRNA decay pathway. ACTA ACUST UNITED AC 2014; 1:e24418. [PMID: 24563826 PMCID: PMC3908577 DOI: 10.4161/trla.24418] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 11/26/2022]
Abstract
We have previously shown that ~10% of all eukaryotic mRNAs contain potential programmed -1 ribosomal frameshifting (-1 PRF) signals and that some function as mRNA destabilizing elements through the Nonsense-Mediated mRNA Decay (NMD) pathway by directing translating ribosomes to premature termination codons. Here, the connection between -1 PRF, NMD and telomere end maintenance are explored. Functional -1 PRF signals were identified in the mRNAs encoding two components of yeast telomerase, EST1 and EST2, and in mRNAs encoding proteins involved in recruiting telomerase to chromosome ends, STN1 and CDC13. All of these elements responded to mutants and drugs previously known to stimulate or inhibit -1 PRF, further supporting the hypothesis that they promote -1 PRF through the canonical mechanism. All affected the steady-state abundance of a reporter mRNA and the wide range of -1 PRF efficiencies promoted by these elements enabled the determination of an inverse logarithmic relationship between -1 PRF efficiency and mRNA accumulation. Steady-state abundances of the endogenous EST1, EST2, STN1 and CDC13 mRNAs were similarly inversely proportional to changes in -1 PRF efficiency promoted by mutants and drugs, supporting the hypothesis that expression of these genes is post-transcriptionally controlled by -1 PRF under native conditions. Overexpression of EST2 by ablation of -1 PRF signals or inhibition of NMD promoted formation of shorter telomeres and accumulation of large budded cells at the G2/M boundary. A model is presented describing how limitation and maintenance of correct stoichiometries of telomerase components by -1 PRF is used to maintain yeast telomere length.
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Affiliation(s)
- Vivek M Advani
- Department of Cell Biology and Molecular Genetics; University of Maryland; College Park MD, USA
| | - Ashton T Belew
- Department of Cell Biology and Molecular Genetics; University of Maryland; College Park MD, USA
| | - Jonathan D Dinman
- Department of Cell Biology and Molecular Genetics; University of Maryland; College Park MD, USA
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6
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Fukuzawa H, Ogawa T, Kaplan A. The Uptake of CO2 by Cyanobacteria and Microalgae. PHOTOSYNTHESIS 2012. [DOI: 10.1007/978-94-007-1579-0_25] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Peng J, Zhou JQ. The tail-module of yeast Mediator complex is required for telomere heterochromatin maintenance. Nucleic Acids Res 2012; 40:581-93. [PMID: 21930512 PMCID: PMC3258146 DOI: 10.1093/nar/gkr757] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Revised: 08/15/2011] [Accepted: 08/30/2011] [Indexed: 11/23/2022] Open
Abstract
Eukaryotic chromosome ends have a DNA-protein complex structure termed telomere. Integrity of telomeres is essential for cell proliferation. Genome-wide screenings for telomere length maintenance genes identified several components of the transcriptional regulator, the Mediator complex. Our work provides evidence that Mediator is involved in telomere length regulation and telomere heterochromatin maintenance. Tail module of Mediator is required for telomere silencing by promoting or stabilizing Sir protein binding and spreading on telomeres. Mediator binds on telomere and may be a component of telomeric chromatin. Our study reveals a specific role of Mediator complex at the heterochromatic telomere and this function is specific to telomeres as it has no effect on the HMR locus.
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Affiliation(s)
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Graduate School of the Chinese Academy of Sciences, Shanghai, China
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8
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Belew AT, Advani VM, Dinman JD. Endogenous ribosomal frameshift signals operate as mRNA destabilizing elements through at least two molecular pathways in yeast. Nucleic Acids Res 2010; 39:2799-808. [PMID: 21109528 PMCID: PMC3074144 DOI: 10.1093/nar/gkq1220] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Although first discovered in viruses, previous studies have identified operational −1 ribosomal frameshifting (−1 RF) signals in eukaryotic genomic sequences, and suggested a role in mRNA stability. Here, four yeast −1 RF signals are shown to promote significant mRNA destabilization through the nonsense mediated mRNA decay pathway (NMD), and genetic evidence is presented suggesting that they may also operate through the no-go decay pathway (NGD) as well. Yeast EST2 mRNA is highly unstable and contains up to five −1 RF signals. Ablation of the −1 RF signals or of NMD stabilizes this mRNA, and changes in −1 RF efficiency have opposing effects on the steady-state abundance of the EST2 mRNA. These results demonstrate that endogenous −1 RF signals function as mRNA destabilizing elements through at least two molecular pathways in yeast. Consistent with current evolutionary theory, phylogenetic analyses suggest that −1 RF signals are rapidly evolving cis-acting regulatory elements. Identification of high confidence −1 RF signals in ∼10% of genes in all eukaryotic genomes surveyed suggests that −1 RF is a broadly used post-transcriptional regulator of gene expression.
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Affiliation(s)
- Ashton T Belew
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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9
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Yeast telomerase subunit Est1p has guanine quadruplex-promoting activity that is required for telomere elongation. Nat Struct Mol Biol 2010; 17:202-9. [PMID: 20098422 DOI: 10.1038/nsmb.1760] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 11/04/2009] [Indexed: 11/08/2022]
Abstract
Telomeres are eukaryotic protein-DNA complexes found at the ends of linear chromosomes that are essential for maintaining genome integrity and are implicated in cellular aging and cancer. The guanine (G)-rich strand of telomeric DNA, usually elongated by the telomerase reverse transcriptase, can form a higher-order structure known as a G-quadruplex in vitro and in vivo. Several factors that promote or resolve G-quadruplexes have been identified, but the functional importance of these structures for telomere maintenance is not well understood. Here we show that the yeast telomerase subunit Est1p, known to be involved in telomerase recruitment to telomeres, can convert single-stranded telomeric G-rich DNA into a G-quadruplex structure in vitro in a Mg(2+)-dependent manner. Cells carrying Est1p mutants deficient in G-quadruplex formation in vitro showed gradual telomere shortening and cellular senescence, indicating a positive regulatory role for G-quadruplex in the maintenance of telomere length.
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Shukla RK, Tripathi V, Jain D, Yadav RK, Chattopadhyay D. CAP2 enhances germination of transgenic tobacco seeds at high temperature and promotes heat stress tolerance in yeast. FEBS J 2009; 276:5252-62. [PMID: 19674105 DOI: 10.1111/j.1742-4658.2009.07219.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We reported earlier that ectopic expression of CAP2, a single AP2 domain containing transcription activator from chickpea (Cicer arietinum) in tobacco improves growth and development, and tolerance to dehydration and salt stress, of the transgenic plants. Here, we report that, in addition, the CAP2-transgenic tobacco seeds also exhibit higher germination efficiency at high temperature and show higher expression levels of genes for tobacco heat shock proteins and a heat shock factor. CAP2 was able to activate the 5'-upstream activating sequence of tobacco heat shock factor. Surprisingly, expression of CAP2 cDNA in Saccharomyces cerevisiae also enhanced heat tolerance, with increased expression of the gene for yeast heat shock factor 1 (Hsf1) and its target, the gene for yeast heat shock protein 104 (Hsp104). Sequence analysis of the Hsf1 promoter revealed the presence of a dehydration-responsive element/C-repeat-like element (DRE/CRE). Recombinant CAP2 protein bound to the DRE/CRE in the Hsf1 promoter in a gel shift assay and transactivated the Hsf1 promoter-His reporter construct. The full-length CAP2 protein was required to provide thermotolerance in yeast. If these findings are taken together, our results suggest that CAP2 is involved in the heat stress response and provides an example of functioning of a plant transcription factor in yeast, highlighting the strong evolutionary conservation of the stress response mechanism.
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Affiliation(s)
- Rakesh Kumar Shukla
- National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, India
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11
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Qian W, Wang J, Jin NN, Fu XH, Lin YC, Lin JJ, Zhou JQ. Ten1p promotes the telomeric DNA-binding activity of Cdc13p: implication for its function in telomere length regulation. Cell Res 2009; 19:849-63. [DOI: 10.1038/cr.2009.67] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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12
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Sua5p a single-stranded telomeric DNA-binding protein facilitates telomere replication. EMBO J 2009; 28:1466-78. [PMID: 19369944 DOI: 10.1038/emboj.2009.92] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Accepted: 03/17/2009] [Indexed: 11/08/2022] Open
Abstract
In budding yeast Saccharomyces cerevisiae, telomere length maintenance involves a complicated network as more than 280 telomere maintenance genes have been identified in the nonessential gene deletion mutant set. As a supplement, we identified additional 29 telomere maintenance genes, which were previously taken as essential genes. In this study, we report a novel function of Sua5p in telomere replication. Epistasis analysis and telomere sequencing show that sua5Delta cells display progressively shortened telomeres at early passages, and Sua5 functions downstream telomerase recruitment. Further, biochemical, structural and genetic studies show that Sua5p specifically binds single-stranded telomeric (ssTG) DNA in vitro through a distinct DNA-binding region on its surface, and the DNA-binding ability is essential for its telomere function. Thus, Sua5p represents a novel ssTG DNA-binding protein and positively regulates the telomere length in vivo.
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Battchikova N, Aro EM. Cyanobacterial NDH-1 complexes: multiplicity in function and subunit composition. PHYSIOLOGIA PLANTARUM 2007; 131:22-32. [PMID: 18251921 DOI: 10.1111/j.1399-3054.2007.00929.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In cyanobacteria, the NAD(P)H:quinone oxidoreductase (NDH-1) is involved in a variety of functions like respiration, cyclic electron flow around PSI and CO(2) uptake. Several types of NDH-1 complexes, which differ in structure and are responsible for these functions, exist in cyanobacterial membranes. This minireview is based on data obtained by reverse genetics and proteomics studies and focuses on the structural and functional differences of the two types of cyanobacterial NDH-1 complexes: NDH-1L, important for respiration and PSI cyclic electron flow, and NDH-1MS, the low-CO(2) inducible complex participating in CO(2) uptake. The NDH-1 complexes in cyanobacteria share a common NDH-1M 'core' complex and differ in the composition of the distal membrane domain composed of specific NdhD and NdhF proteins, which in complexes involved in CO(2) uptake is further associated with the hydrophilic carbon uptake (CUP) domain. At present, however, very important questions concerning the nature of catalytically active subunits that constitute the electron input device (like NADH dehydrogenase module of the eubacterial 'model' NDH-1 analogs), the substrate specificity and reaction mechanisms of cyanobacterial complexes remain unanswered and are shortly discussed here.
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Affiliation(s)
- Natalia Battchikova
- Plant Physiology and Molecular Biology, Department of Biology, University of Turku, FI-20520 Turku, Finland.
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14
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Ogawa T, Mi H. Cyanobacterial NADPH dehydrogenase complexes. PHOTOSYNTHESIS RESEARCH 2007; 93:69-77. [PMID: 17279442 DOI: 10.1007/s11120-006-9128-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Accepted: 12/18/2006] [Indexed: 05/08/2023]
Abstract
Cyanobacteria possess functionally distinct multiple NADPH dehydrogenase (NDH-1) complexes that are essential to CO(2) uptake, photosystem-1 cyclic electron transport and respiration. The unique nature of cyanobacterial NDH-1 complexes is the presence of subunits involved in CO(2) uptake. Other than CO(2) uptake, chloroplastic NDH-1 complex has a similar role as cyanobacterial NDH-1 complexes in photosystem-1 cyclic electron transport and respiration (chlororespiration). In this mini-review we focus on the structure and function of cyanobacterial NDH-1 complexes and their phylogeny. The function of chloroplastic NDH-1 complex and characteristics of plants defective in NDH-1 are also described for comparison.
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Affiliation(s)
- Teruo Ogawa
- National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
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15
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Abstract
The light reactions in photosynthesis convert light energy into chemical energy in the form of ATP and drive the production of NADPH from NADP+. The reactions involve two types of electron flow in the chloroplast. While linear electron transport generates both ATP and NADPH, photosystem I cyclic electron transport is exclusively involved in ATP synthesis. The physiological significance of photosystem I cyclic electron transport has been underestimated, and our knowledge of the machineries involved remains very limited. However, recent genetic approaches using Arabidopsis thaliana have clarified the essential functions of this electron flow in both photoprotection and photosynthesis. Based on several lines of evidence presented here, it is necessary to reconsider the fundamental mechanisms of chloroplast energetics.
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Affiliation(s)
- Toshiharu Shikanai
- Graduate School of Agriculture, Kyushu University, Fukuoka, Japan 812-8581.
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16
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Theimer CA, Feigon J. Structure and function of telomerase RNA. Curr Opin Struct Biol 2006; 16:307-18. [PMID: 16713250 DOI: 10.1016/j.sbi.2006.05.005] [Citation(s) in RCA: 155] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 04/25/2006] [Accepted: 05/08/2006] [Indexed: 12/21/2022]
Abstract
Maintenance of telomeres by the enzyme telomerase is essential for genomic stability and cell viability in ciliates, vertebrates and yeast. The minimal components of telomerase required for catalytic activity are the telomerase reverse transcriptase (TERT) protein and the template-containing telomerase RNA (TER). Recent studies have afforded significant advances in the biophysical characterization of telomerase RNAs from various species. The first TER structures have been reported, for regions of the catalytically essential pseudoknot and CR4/CR5 domains of human TER, and provide a structural basis for interpretation of mutational and biochemical data. The domains and interactions of the Tetrahymena thermophila telomerase holoenzyme RNA and protein components have been further characterized biochemically, and structures of the TER template boundary element and the N-terminal domain of T. thermophila TERT have been determined. Phylogenetic and biochemical analyses of yeast TERs have revealed core structural elements in common with ciliates and vertebrates, and the minimal domains required for function in vivo.
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Affiliation(s)
- Carla A Theimer
- Department of Chemistry and Biochemistry, and Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA
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17
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Current awareness on yeast. Yeast 2006. [DOI: 10.1002/yea.1285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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18
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Yang CP, Chen YB, Meng FL, Zhou JQ. Saccharomyces cerevisiae Est3p dimerizes in vitro and dimerization contributes to efficient telomere replication in vivo. Nucleic Acids Res 2006; 34:407-16. [PMID: 16418502 PMCID: PMC1331985 DOI: 10.1093/nar/gkj445] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In Saccharomyces cerevisiae at least five genes, EST1, EST2, EST3, TLC1 and CDC13, are required for telomerase activity in vivo. The telomerase catalytic subunit Est2p and telomerase RNA subunit Tlc1 constitute the telomerase core enzyme. Est1p and Est3p are the other subunits of telomerase holoenzyme. In order to dissect the function of Est3p in telomere replication, we over-expressed and purified recombinant wild-type and mutant Est3 proteins. The wild-type protein, as well as the K71A, E104A and T115A mutants were able to dimerize in vitro, while the Est3p-D49A, -K68A or -D166A mutant showed reduced ability to dimerize. Mutations in Est3p that decreased dimerization also appeared to cause telomere shortening in vivo. Double point mutation of Est3p-D49A-K68A and single point mutation of Est3p-K68A showed similar telomere shortening, suggesting that the K68 residue might be more important for telomerase activity. The ectopic co-expression of K71A or T115A mutant with wild-type Est3p using centromere plasmids caused telomere shortening, while co-expression of the D49A, K68A, D86A or F103A mutants with wild-type Est3p had no effect on telomere length regulation. These data suggested that dimerization is important for Est3p function in vivo.
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Affiliation(s)
| | | | | | - Jin-Qiu Zhou
- To whom correspondence should be addressed. Tel: 011 86 21 54921078; Fax: 011 86 21 54921076;
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