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Lickwar CR, Mueller F, Hanlon SE, McNally JG, Lieb JD. Genome-wide protein-DNA binding dynamics suggest a molecular clutch for transcription factor function. Nature 2012; 484:251-5. [PMID: 22498630 PMCID: PMC3341663 DOI: 10.1038/nature10985] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Accepted: 02/23/2012] [Indexed: 12/26/2022]
Abstract
Dynamic access to genetic information is central to organismal development and environmental response. Consequently, genomic processes must be regulated by mechanisms that alter genome function relatively rapidly. Conventional chromatin immunoprecipitation (ChIP) experiments measure transcription factor occupancy, but give no indication of kinetics and are poor predictors of transcription factor function at a given locus. To measure transcription-factor-binding dynamics across the genome, we performed competition ChIP (refs 6, 7) with a sequence-specific Saccharomyces cerevisiae transcription factor, Rap1 (ref. 8). Rap1-binding dynamics and Rap1 occupancy were only weakly correlated (R(2) = 0.14), but binding dynamics were more strongly linked to function than occupancy. Long Rap1 residence was coupled to transcriptional activation, whereas fast binding turnover, which we refer to as 'treadmilling', was linked to low transcriptional output. Thus, DNA-binding events that seem identical by conventional ChIP may have different underlying modes of interaction that lead to opposing functional outcomes. We propose that transcription factor binding turnover is a major point of regulation in determining the functional consequences of transcription factor binding, and is mediated mainly by control of competition between transcription factors and nucleosomes. Our model predicts a clutch-like mechanism that rapidly engages a treadmilling transcription factor into a stable binding state, or vice versa, to modulate transcription factor function.
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Affiliation(s)
- Colin R. Lickwar
- Department of Biology, Carolina Center for the Genome Sciences, Curriculum in Genetics and Molecular Biology, and Lineberger Comprehensive Cancer Center CB #3280, 408 Fordham Hall University of North Carolina at Chapel Hill Chapel Hill, NC 27599-3280
| | - Florian Mueller
- LRBGE-National Cancer Institute The National Institutes of Health 41 Library Drive Bethesda, MD 20892
- Institut Pasteur Groupe Imagerie et Modélisation Centre National de la Recherche Scientifique, Unité de Recherche Associée 2582 25-28 rue du Docteur Roux, 75015 Paris, France
| | - Sean E. Hanlon
- Department of Biology, Carolina Center for the Genome Sciences, Curriculum in Genetics and Molecular Biology, and Lineberger Comprehensive Cancer Center CB #3280, 408 Fordham Hall University of North Carolina at Chapel Hill Chapel Hill, NC 27599-3280
| | - James G McNally
- LRBGE-National Cancer Institute The National Institutes of Health 41 Library Drive Bethesda, MD 20892
| | - Jason D. Lieb
- Department of Biology, Carolina Center for the Genome Sciences, Curriculum in Genetics and Molecular Biology, and Lineberger Comprehensive Cancer Center CB #3280, 408 Fordham Hall University of North Carolina at Chapel Hill Chapel Hill, NC 27599-3280
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152
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Matot B, Le Bihan YV, Lescasse R, Pérez J, Miron S, David G, Castaing B, Weber P, Raynal B, Zinn-Justin S, Gasparini S, Le Du MH. The orientation of the C-terminal domain of the Saccharomyces cerevisiae Rap1 protein is determined by its binding to DNA. Nucleic Acids Res 2012; 40:3197-207. [PMID: 22139930 PMCID: PMC3326314 DOI: 10.1093/nar/gkr1166] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 11/10/2011] [Accepted: 11/11/2011] [Indexed: 11/22/2022] Open
Abstract
Rap1 is an essential DNA-binding factor from the yeast Saccharomyces cerevisiae involved in transcription and telomere maintenance. Its binding to DNA targets Rap1 at particular loci, and may optimize its ability to form functional macromolecular assemblies. It is a modular protein, rich in large potentially unfolded regions, and comprising BRCT, Myb and RCT well-structured domains. Here, we present the architectures of Rap1 and a Rap1/DNA complex, built through a step-by-step integration of small angle X-ray scattering, X-ray crystallography and nuclear magnetic resonance data. Our results reveal Rap1 structural adjustment upon DNA binding that involves a specific orientation of the C-terminal (RCT) domain with regard to the DNA binding domain (DBD). Crystal structure of DBD in complex with a long DNA identifies an essential wrapping loop, which constrains the orientation of the RCT and affects Rap1 affinity to DNA. Based on our structural information, we propose a model for Rap1 assembly at telomere.
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Affiliation(s)
- Béatrice Matot
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Yann-Vaï Le Bihan
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Rachel Lescasse
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Javier Pérez
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Simona Miron
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Gabriel David
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Bertrand Castaing
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Patrick Weber
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Bertrand Raynal
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Sophie Zinn-Justin
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Sylvaine Gasparini
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
| | - Marie-Hélène Le Du
- Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Biologie et Technologie de Saclay, Laboratoire de Biologie Structurale et Radiobiologie, CNRS-URA2096, 91191 Gif-sur-Yvette, France, Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut de Radiobiologie Cellulaire et Moléculaire, Service Instabilité Génétique Réparation et Recombinaison, Laboratoire Télomère et Réparation du Chromosome, 92260 Fontenay-aux-roses, SOLEIL Synchrotron, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, Centre de Biophysique Moléculaire, UPR4301, CNRS, rue Charles Sadron, 45071 Orléans cedex 02, Institut Pasteur, CNRS-URA2185, Plate-forme 6, Cristallogenèse et Diffraction des Rayons X, 25 Rue Dr. Roux, 75724 Paris and Institut Pasteur, Plateforme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, F-75015 Paris, France
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153
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Cantara S, Capuano S, Capezzone M, Benigni M, Pisu M, Marchisotta S, Pacini F. Lack of mutations of the telomerase RNA component in familial papillary thyroid cancer with short telomeres. Thyroid 2012; 22:363-8. [PMID: 22304389 DOI: 10.1089/thy.2011.0109] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND The occurrence of familial papillary thyroid cancer (FPTC) is well established but no susceptibility genes for this disease have been discovered. Our group has recently demonstrated that patients with FPTC have shorter telomeres, not associated with mutations in telomerase reverse transcriptase, gene than patients with sporadic papillary thyroid cancer (SPTC), healthy subjects (HS), and unaffected family members (UFMs). Several diseases, however, have short telomeres associated with mutations in the telomerase RNA component (TERC) gene or in the shelterin complex (POT1, RAP1, TIN2, TPP1, TRF1, and TRF2) genes. The objective of the present study was to verify whether short telomeres observed in FPTC patients were related to mutations in TERC or shelterin genes. METHODS Sixty-six patients with FPTC, 46 UFMs, 111 patients with SPTC, and 153 HS were analyzed by polymerase chain reaction followed by denaturing high performance liquid chromatography analysis and direct sequencing for the presence of TERC or shelterin gene mutations. When present, single-nucleotide polymorphisms were tested by χ(2) analysis at the genotypic, allelic, and haplotypic levels. RESULTS The entire sequence of the TERC gene was analyzed with particular attention to known mutations known to be associated with short telomeres. All samples appeared to be homozygous wild type for A-771G, C-99G, G305A, G322A, C323T, C408G, G450A, T467C, G508A, A514G, G623A, and C727G substitutions and for the 378Δ→3' deletion in the TERC gene. In addition, upon analysis of all samples for shelterin proteins, we observed a significant decrease in POT1 and RAP1 protein expression in the blood of FPTC patients compared with SPTC subjects. However, no mutations or polymorphisms were found when in the coding sequences of both genes. CONCLUSIONS To our knowledge this is the first study of TERC mutations or alterations in the shelterin complex in relation to FPTC. Shorter telomeres observed in FPTC are not linked to mutations or polymorphisms in TERC, POT1, or RAP1 genes.
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Affiliation(s)
- Silvia Cantara
- Section of Endocrinology & Metabolism, Department of Internal Medicine, Endocrinology & Metabolism, and Biochemistry, University of Siena, Siena, Italy.
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154
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Miller AS, Balakrishnan L, Buncher NA, Opresko PL, Bambara RA. Telomere proteins POT1, TRF1 and TRF2 augment long-patch base excision repair in vitro. Cell Cycle 2012; 11:998-1007. [PMID: 22336916 PMCID: PMC3323798 DOI: 10.4161/cc.11.5.19483] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 01/24/2012] [Accepted: 01/25/2012] [Indexed: 12/13/2022] Open
Abstract
Human telomeres consist of multiple tandem hexameric repeats, each containing a guanine triplet. Guanosine-rich clusters are highly susceptible to oxidative base damage, necessitating base excision repair (BER). Previous demonstration of enhanced strand displacement synthesis by the BER component DNA polymerase β in the presence of telomere protein TRF2 suggests that telomeres employ long-patch (LP) BER. Earlier analyses in vitro showed that efficiency of BER reactions is reduced in the DNA-histone environment of chromatin. Evidence presented here indicates that BER is promoted at telomeres. We found that the three proteins that contact telomere DNA, POT1, TRF1 and TRF2, enhance the rate of individual steps of LP-BER and stimulate the complete reconstituted LP-BER pathway. Thought to protect telomere DNA from degradation, these proteins still apparently evolved to allow selective access of repair proteins.
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Affiliation(s)
- Adam S Miller
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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155
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Stewart JA, Chaiken MF, Wang F, Price CM. Maintaining the end: roles of telomere proteins in end-protection, telomere replication and length regulation. Mutat Res 2012; 730:12-9. [PMID: 21945241 PMCID: PMC3256267 DOI: 10.1016/j.mrfmmm.2011.08.011] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 08/15/2011] [Accepted: 08/17/2011] [Indexed: 11/16/2022]
Abstract
Chromosome end protection is essential to protect genome integrity. Telomeres, tracts of repetitive DNA sequence and associated proteins located at the chromosomal terminus, serve to safeguard the ends from degradation and unwanted double strand break repair. Due to the essential nature of telomeres in protecting the genome, a number of unique proteins have evolved to ensure that telomere length and structure are preserved. The inability to properly maintain telomeres can lead to diseases such as dyskeratosis congenita, pulmonary fibrosis and cancer. In this review, we will discuss the known functions of mammalian telomere-associated proteins, their role in telomere replication and length regulation and how these processes relate to genome instability and human disease.
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Affiliation(s)
- Jason A. Stewart
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Mary F. Chaiken
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Feng Wang
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Carolyn M. Price
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
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156
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Hayano M, Kanoh Y, Matsumoto S, Renard-Guillet C, Shirahige K, Masai H. Rif1 is a global regulator of timing of replication origin firing in fission yeast. Genes Dev 2012; 26:137-50. [PMID: 22279046 PMCID: PMC3273838 DOI: 10.1101/gad.178491.111] [Citation(s) in RCA: 182] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 12/14/2011] [Indexed: 11/24/2022]
Abstract
One of the long-standing questions in eukaryotic DNA replication is the mechanisms that determine where and when a particular segment of the genome is replicated. Cdc7/Hsk1 is a conserved kinase required for initiation of DNA replication and may affect the site selection and timing of origin firing. We identified rif1Δ, a null mutant of rif1(+), a conserved telomere-binding factor, as an efficient bypass mutant of fission yeast hsk1. Extensive deregulation of dormant origins over a wide range of the chromosomes occurs in rif1Δ in the presence or absence of hydroxyurea (HU). At the same time, many early-firing, efficient origins are suppressed or delayed in firing timing in rif1Δ. Rif1 binds not only to telomeres, but also to many specific locations on the arm segments that only partially overlap with the prereplicative complex assembly sites, although Rif1 tends to bind in the vicinity of the late/dormant origins activated in rif1Δ. The binding to the arm segments occurs through M to G1 phase in a manner independent of Taz1 and appears to be essential for the replication timing program during the normal cell cycle. Our data demonstrate that Rif1 is a critical determinant of the origin activation program on the fission yeast chromosomes.
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Affiliation(s)
- Motoshi Hayano
- Genome Dynamics, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8613, Japan
| | - Yutaka Kanoh
- Genome Dynamics, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8613, Japan
| | - Seiji Matsumoto
- Genome Dynamics, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8613, Japan
| | - Claire Renard-Guillet
- Laboratory of Genome Structure and Function, Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Katsuhiko Shirahige
- Laboratory of Genome Structure and Function, Research Center for Epigenetic Disease, Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Hisao Masai
- Genome Dynamics, Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8613, Japan
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157
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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158
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Abstract
It is well known that sulphonylureas (SUs), commonly used in the treatment of type 2 diabetes mellitus, stimulate insulin secretion by closing ATP-sensitive K(+) (K(ATP) ) channels in pancreatic β-cells by binding to the SU receptor SUR1. SUs are now known also to activate cAMP sensor Epac2 (cAMP-GEFII) to Rap1 signalling, which promotes insulin granule exocytosis. For SUs to exert their full effects in insulin secretion, they are required to activate Epac2 as well as to inhibit the β-cell K(ATP) channels. As Epac2 is also necessary for potentiation of glucose-induced insulin secretion by cAMP-increasing agents, such as incretin, Epac2 is a target of both cAMP and SUs. The distinct effects of various SUs appear to be because of their different actions on Epac2/Rap1 signalling as well as K(ATP) channels. Differently from other SUs, gliclazide is unique in that it is specific for β-cell K(ATP) channel and does not activate Epac2.
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Affiliation(s)
- S Seino
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Japan.
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159
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Affiliation(s)
- Yaniv Harari
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Linda Rubinstein
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
| | - Martin Kupiec
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv, Israel
- * E-mail:
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160
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Abstract
Cells accumulate single-stranded DNA (ssDNA) when telomere capping, DNA replication, or DNA repair is impeded. This accumulation leads to cell cycle arrest through activating the DNA–damage checkpoints involved in cancer protection. Hence, ssDNA accumulation could be an anti-cancer mechanism. However, ssDNA has to accumulate above a certain threshold to activate checkpoints. What determines this checkpoint-activation threshold is an important, yet unanswered question. Here we identify Rif1 (Rap1-Interacting Factor 1) as a threshold-setter. Following telomere uncapping, we show that budding yeast Rif1 has unprecedented effects for a protein, inhibiting the recruitment of checkpoint proteins and RPA (Replication Protein A) to damaged chromosome regions, without significantly affecting the accumulation of ssDNA at those regions. Using chromatin immuno-precipitation, we provide evidence that Rif1 acts as a molecular “band-aid” for ssDNA lesions, associating with DNA damage independently of Rap1. In consequence, small or incipient lesions are protected from RPA and checkpoint proteins. When longer stretches of ssDNA are generated, they extend beyond the junction-proximal Rif1-protected regions. In consequence, the damage is detected and checkpoint signals are fired, resulting in cell cycle arrest. However, increased Rif1 expression raises the checkpoint-activation threshold to the point it simulates a checkpoint knockout and can also terminate a checkpoint arrest, despite persistent telomere deficiency. Our work has important implications for understanding the checkpoint and RPA–dependent DNA–damage responses in eukaryotic cells. Here we identified arguably the first anti-checkpoint protein in Rif1. The term anti-checkpoint was proposed by Ted Weinert, one of the parents of the checkpoint concept, to describe a factor that stops checkpoint proteins from responding to DNA damage by other means than repair, reduced amounts of ssDNA, or adaptation [1]. No such factor has been clearly identified; potential candidates (for example, shelterin or CST complexes at chromosome ends) may reduce the amount of damage, therefore exerting an indirect “anti-checkpoint” function. Interestingly, mammalian Rif1 was once thought to be a checkpoint protein [2]. Our study indicates that Rif1 out-competes checkpoint proteins for their substrate and sets a threshold for checkpoint activation in budding yeast. Rif1 can tune down the checkpoint responses, thus permitting cells to proliferate with DNA damage, a pre-requisite for chromosomal instability, the hallmark of cancer cells. Rif1 is an important link in understanding how eukaryotic cells balance the need to proliferate with the need to preserve their genetic heritage. Finding an anti-checkpoint is not of pure theoretical interest. In the future, Rif1 inhibitors could limit proliferation of chromosomally unstable cells. Conversely, Rif1 enhancers could tune down the over-blown checkpoint responses that lead to massive cell death following different insults.
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Affiliation(s)
- Yuan Xue
- Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Michael D. Rushton
- Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Laura Maringele
- Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, United Kingdom
- * E-mail:
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161
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Yang D, He Q, Kim H, Ma W, Songyang Z. TIN2 protein dyskeratosis congenita missense mutants are defective in association with telomerase. J Biol Chem 2011; 286:23022-30. [PMID: 21536674 PMCID: PMC3123070 DOI: 10.1074/jbc.m111.225870] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 04/29/2011] [Indexed: 12/18/2022] Open
Abstract
Dyskeratosis congenita (DC) is a progressive and heterogeneous congenital disorder that affects multiple systems and is characterized by bone marrow failure and a triad of abnormal skin pigmentation, nail dystrophy, and oral leukoplakia. One common feature for all DC patients is abnormally short telomeres and defects in telomere biology. Most of the known DC mutations have been found to affect core components of the telomerase holoenzyme. Recently, multiple mutations in the gene encoding the telomeric protein TIN2 have been identified in DC patients with intact telomerase genes, but the molecular mechanisms underlying TIN2 mutation-mediated DC remain unknown. Here, we demonstrate that ectopic expression of TIN2 with DC missense mutations in human cells led to accelerated telomere shortening, similar to the telomere phenotypes found in DC patients. However, this telomere shortening was not accompanied by changes in total telomerase activity, localization of TIN2, or telomere end protection status. Interestingly, we found TIN2 to participate in the TPP1-dependent recruitment of telomerase activity. Furthermore, DC mutations in TIN2 led to its decreased ability to associate with TERC and telomerase activity. Taken together, our data suggest that TIN2 mutations in DC may compromise the telomere recruitment of telomerase, leading to telomere shortening and the associated pathogenesis.
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Affiliation(s)
- Dong Yang
- the Verna and Mars McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Quanyuan He
- the Verna and Mars McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Hyeung Kim
- the Verna and Mars McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Wenbin Ma
- From the State Key Laboratory for Biocontrol, Sun Yat-Sen University, Guangzhou 510275, China and
- the Verna and Mars McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Zhou Songyang
- From the State Key Laboratory for Biocontrol, Sun Yat-Sen University, Guangzhou 510275, China and
- the Verna and Mars McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
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162
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Abstract
Telomeres are nucleoprotein complexes which protect the ends of linear chromosomes from detection as DNA damage and provide a sequence buffer against replication-associated shortening. In mammals, telomeres consist of repetitive DNA sequence (TTAGGG) and associated proteins. The telomeric core complex is called shelterin and is comprised of the proteins TRF1, TRF2, POT1, TIN2, TPP1 and RAP1. Excessive telomere shortening or de-protection of telomeres through the loss of shelterin subunits allows the detection of telomeres as DNA damage, which can be visualized as DNA damage protein foci at chromosome ends called TIF (Telomere Dysfunction-Induced Foci). We sought to exploit the TIF phenotype as marker for telomere dysfunction to identify novel genes involved in telomere protection by siRNA-mediated knock-down of a set of 386 candidates. Here we report the establishment, specificity and feasibility of such a screen and the results of the genes tested. Only one of the candidate genes showed a unique TIF phenotype comparable to the suppression of the main shelterin components TRF2 or TRF1 and that gene was identified as a TRF1-like pseudogene. We also identified a weak TIF phenotype for SKIIP (SNW1), a splicing factor and transcriptional co-activator. However, the knock-down of SKIIP also induced a general, not telomere-specific DNA damage response, which complicates conclusions about a telomeric role. In summary, this report is a technical demonstration of the feasibility of a cell-based screen for telomere deprotection with the potential of scaling it to a high-throughput approach.
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Affiliation(s)
- Daniel H. Lackner
- Molecular and Cellular Biology Department, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Daniel Durocher
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Jan Karlseder
- Molecular and Cellular Biology Department, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- * E-mail:
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163
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Chen J, Zhang B, Wong N, Lo AWI, To KF, Chan AWH, Ng MHL, Ho CYS, Cheng SH, Lai PBS, Yu J, Ng HK, Ling MT, Huang AL, Cai XF, Ko BCB. Sirtuin 1 is upregulated in a subset of hepatocellular carcinomas where it is essential for telomere maintenance and tumor cell growth. Cancer Res 2011; 71:4138-49. [PMID: 21527554 DOI: 10.1158/0008-5472.can-10-4274] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hepatocellular carcinoma (HCC) is a highly malignant tumor with a poor prognosis. Treatment of HCC is complicated by the fact that the disease is often diagnosed at an advanced stage when it is no longer amenable to curative surgery, and current systemic chemotherapeutics are mostly inefficacious. Sirtuin 1 (SIRT1) is a class III histone deacetylase that is implicated in gene regulations and stress resistance. In this study, we found that SIRT1 is essential for the tumorigenesis of HCC. We showed that although SIRT1 was expressed at very low levels in normal livers, it was overexpressed in HCC cell lines and in a subset of HCC. Tissue microarray analysis of HCC and adjacent nontumoral liver tissues revealed a positive correlation between the expression levels of SIRT1 and advancement in tumor grades. Downregulation of SIRT1 consistently suppressed the proliferation of HCC cells via the induction of cellular senescence or apoptosis. SIRT1 silencing also caused telomere dysfunction-induced foci and nuclear abnormality that were clearly associated with reduced expressions of telomerase reverse transcriptase (TERT), and PTOP, which is a member of the shelter in complex. Ectopic expression of either TERT or PTOP in SIRT1-depleted cells significantly restored cell proliferation. There was also a positive correlation between the level of induction of SIRT1 and TERT [corrected] in human HCC. Finally, SIRT1-silencing sensitized HCC cells to doxorubicin treatment. Together, our findings reveal a novel function for SIRT1 in telomere maintenance of HCC, and they rationalize the clinical exploration of SIRT1 inhibitors for HCC therapy.
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Affiliation(s)
- Juan Chen
- The State Key Laboratory in Oncology in South China, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong, Hong Kong, China
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164
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Abstract
The processes regulating telomere function have major impacts on fundamental issues in human cancer biology. First, active telomere maintenance is almost always required for full oncogenic transformation of human cells, through cellular immortalization by endowment of an infinite replicative potential. Second, the attrition that telomeres undergo upon replication is responsible for the finite replicative life span of cells in culture, a process called senescence, which is of paramount importance for tumor suppression in vivo. The process of telomere-based senescence is intimately coupled to the induction of a DNA damage response emanating from telomeres, which can be elicited by both the ATM and ATR dependent pathways. At telomeres, the shelterin complex is constituted by a group of six proteins which assembles quantitatively along the telomere tract, and imparts both telomere maintenance and telomere protection. Shelterin is known to regulate the action of telomerase, and to prevent inappropriate DNA damage responses at chromosome ends, mostly through inhibition of ATM and ATR. The roles of shelterin have increasingly been associated with transient interactions with downstream factors that are not associated quantitatively or stably with telomeres. Here, some of the important known interactions between shelterin and these associated factors and their interplay to mediate telomere functions are reviewed.
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Affiliation(s)
- Raffaella Diotti
- Department of Biological Sciences, Hunter College, New York, NY, USA
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165
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Xie Y, Yang D, He Q, Songyang Z. Zebrafish as a model system to study the physiological function of telomeric protein TPP1. PLoS One 2011; 6:e16440. [PMID: 21311760 PMCID: PMC3032778 DOI: 10.1371/journal.pone.0016440] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 12/16/2010] [Indexed: 01/08/2023] Open
Abstract
Telomeres are specialized chromatin structures at the end of chromosomes. Telomere dysfunction can lead to chromosomal abnormalities, DNA damage responses, and even cancer. In mammalian cells, a six-protein complex (telosome/shelterin) is assembled on the telomeres through the interactions between various domain structures of the six telomere proteins (POT1, TPP1, TIN2, TRF1, TRF2 and RAP1), and functions in telomere maintenance and protection. Within the telosome, TPP1 interacts directly with POT1 and TIN2 and help to mediate telosome assembly. Mechanisms of telomere regulation have been extensively studied in a variety of model organisms. For example, the physiological roles of telomere-targeted proteins have been assessed in mice through homozygous inactivation. In these cases, early embryonic lethality has prevented further studies of these proteins in embryogenesis and development. As a model system, zebrafish offers unique advantages such as genetic similarities with human, rapid developmental cycles, and ease of manipulation of its embryos. In this report, we detailed the identification of zebrafish homologues of TPP1, POT1, and TIN2, and showed that the domain structures and interactions of these telosome components appeared intact in zebrafish. Importantly, knocking down TPP1 led to multiple abnormalities in zebrafish embryogenesis, including neural death, heart malformation, and caudal defect. And these embryos displayed extensive apoptosis. These results underline the importance of TPP1 in zebrafish embryogenesis, and highlight the feasibility and advantages of investigating the signaling pathways and physiological function of telomere proteins in zebrafish.
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Affiliation(s)
- Yiying Xie
- Verna and Marrs McLean Department of Biochemistry and Molecular biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Dong Yang
- Verna and Marrs McLean Department of Biochemistry and Molecular biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Quanyuan He
- Verna and Marrs McLean Department of Biochemistry and Molecular biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Zhou Songyang
- State Key laboratory for Biocontrol, Sun Yat-Sen University, Guangzhou, People's Republic of China
- * E-mail:
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166
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Kojima K, Hiyama E, Otani K, Ohtaki M, Fukuba I, Fukuda E, Sueda T, Hiyama K. Telomerase activation without shortening of telomeric 3'-overhang is a poor prognostic factor in human colorectal cancer. Cancer Sci 2011; 102:330-5. [PMID: 21108695 DOI: 10.1111/j.1349-7006.2010.01786.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our previous report demonstrated a good correlation between high telomerase activity of cancer tissues and a poor prognosis of patients with colorectal cancers, except for several cases. To elucidate the additional factors that contribute to patient prognosis, the correlation among the expression levels of telomere binding proteins (TBP), the lengths of telomeres, the lengths of telomere 3'-overhang (3'-OH) and telomerase activity in 106 paired colorectal cancer and corresponding noncancerous mucosa (NCM) specimens were examined. The expression levels of eight TBP genes (TRF1, TRF2, TIN2, TANK1, TANK2, POT1, RAP1 and TPP1) were analyzed. Among the 106 cases, 35 cases had shortened telomeres (<7 kb), 15 had shortened 3'-OH (3'-OH length ratio of cancer/NCM <0.5) and 88 were classified as telomerase-activated cancers (activity ratio of cancer/NCM >2). Comparison between NCM and cancer in each case showed that all TBP except for POT1 were downregulated in cancers. A survival analysis using a Cox proportional hazard model showed that the survival rate of the telomerase-activated cases with shortened 3'-OH and that of telomerase-inactivated cases were significantly better than that of telomerase-activated cases without 3'-OH shortening, that is, restored or maintained 3'-OH (P = 0.018). In the telomerase-activated cancers, the length of 3'-OH was significantly correlated with the expression levels of POT1. Elongation of telomeric overhang by telomerase, which might be regulated by POT1, may contribute to the increase of malignant potential in colorectal cancers.
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Affiliation(s)
- Kensaku Kojima
- Department of Surgery, Graduate School of Biomedical Sciences, Hiroshima University Hospital, Hiroshima University, Hiroshima, Japan
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167
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Abstract
Unlimitedly proliferating cells need to acquire the telomere DNA maintenance mechanism, to counteract possible shortening through multiple rounds of replication and segregation of linear chromosomes. Most human cancer cells express telomerase whereas the other cells utilize the alternative lengthening of telomeres (ALT) pathway to elongate telomere DNA. It is suggested that ALT depends on the recombination between telomere repetitive DNAs. However, the molecular details remain unknown. Recent studies have provided evidence of special structures of telomere DNA and genes essential for the phenotypes of ALT cells. The molecular models of the ALT pathway should be validated to elucidate recombination-mediated telomere maintenance and promote the applications to anti-cancer therapy.
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Affiliation(s)
- Akira Nabetani
- Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University,Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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168
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Cha I, Lee SH, Jeon TJ. Chemoattractant-mediated Rap1 activation requires GPCR/G proteins. Mol Cells 2010; 30:563-7. [PMID: 21103944 DOI: 10.1007/s10059-010-0153-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/08/2010] [Accepted: 09/10/2010] [Indexed: 10/18/2022] Open
Abstract
Rap1 is rapidly activated upon chemoattractant stimulation and plays an important role in cell adhesion and cytoskeletal reorganization during chemotaxis. Here, we demonstrate that G-protein coupled receptors and G-proteins are essential for chemoattractant-mediated Rap1 activation in Dictyostelium. The rapid Rap1 activation upon cAMP chemoattractant stimulation was absent in cells lacking chemoattractant cAMP receptors cAR1/cAR3 or a subunit of the heterotrimeric G-protein complex Gα2. Loss of guanylyl cyclases GCA/SGC or a cGMP-binding protein GbpC exhibited no effect on Rap1 activation kinetics. These results suggest that Rap1, a key regulator for the regulation of cytoskeletal reorganization during cell movement, is activated through the G-protein coupled receptors cAR1/cAR3 and Gα2 proteins in a way independent of the cGMP signaling pathway.
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Affiliation(s)
- Injun Cha
- Department of Biology, College of Natural Sciences, Chosun University, Gwangju 501-759, Korea
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169
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Abstract
Dyskeratosis congenita (DC) was originally defined as a rare inherited bone marrow failure (BMF) syndrome associated with distinct mucocutaneous features. Today DC is defined by its pathogenetic mechanism and mutations in components of the telomere maintenance machinery resulting in excessively short telomeres in highly proliferating tissues. With this new definition the disease spectrum has broadened and ranges from intrauterine growth retardation, cerebellar hypoplasia, and death in early childhood to asymptomatic mutation carriers whose descendants are predisposed to malignancy, BMF, or pulmonary disease. The degree of telomere dysfunction is the major determinant of disease onset and manifestations.
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Affiliation(s)
- Monica Bessler
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St Louis, MO 63110, USA.
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170
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Martinez P, Thanasoula M, Carlos AR, Gómez-López G, Tejera AM, Schoeftner S, Dominguez O, Pisano DG, Tarsounas M, Blasco MA. Mammalian Rap1 controls telomere function and gene expression through binding to telomeric and extratelomeric sites. Nat Cell Biol 2010; 12:768-80. [PMID: 20622869 PMCID: PMC3792482 DOI: 10.1038/ncb2081] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 06/01/2010] [Indexed: 12/12/2022]
Abstract
Rap1 is a component of the shelterin complex at mammalian telomeres, but its in vivo role in telomere biology has remained largely unknown to date. Here we show that Rap1 deficiency is dispensable for telomere capping but leads to increased telomere recombination and fragility. We generated cells and mice deleted for Rap1; mice with Rap1 deletion in stratified epithelia were viable but had shorter telomeres and developed skin hyperpigmentation in adulthood. By performing chromatin immunoprecipitation coupled with ultrahigh-throughput sequencing, we found that Rap1 binds to both telomeres and to extratelomeric sites through the (TTAGGG)(2) consensus motif. Extratelomeric Rap1-binding sites were enriched at subtelomeric regions, in agreement with preferential deregulation of subtelomeric genes in Rap1-deficient cells. More than 70% of extratelomeric Rap1-binding sites were in the vicinity of genes, and 31% of the genes deregulated in Rap1-null cells contained Rap1-binding sites, suggesting a role for Rap1 in transcriptional control. These findings place a telomere protein at the interface between telomere function and transcriptional regulation.
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Affiliation(s)
- Paula Martinez
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, Madrid, E-28029, Spain
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171
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Uhlírová R, Horáková AH, Galiová G, Legartová S, Matula P, Fojtová M, Varecha M, Amrichová J, Vondrácek J, Kozubek S, Bártová E. SUV39h- and A-type lamin-dependent telomere nuclear rearrangement. J Cell Biochem 2010; 109:915-26. [PMID: 20069564 DOI: 10.1002/jcb.22466] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Telomeres are specialized chromatin structures that are situated at the end of linear chromosomes and play an important role in cell senescence and immortalization. Here, we investigated whether changes in histone signature influence the nuclear arrangement and positioning of telomeres. Analysis of mouse embryonic fibroblasts revealed that telomeres were organized into specific clusters that partially associated with centromeric clusters. This nuclear arrangement was influenced by deficiency of the histone methyltransferase SUV39h, LMNA deficiency, and the histone deacetylase inhibitor Trichostatin A (TSA). Similarly, nuclear radial distributions of telomeric clusters were preferentially influenced by TSA, which caused relocation of telomeres closer to the nuclear center. Telomeres also co-localized with promyelocytic leukemia bodies (PML). This association was increased by SUV39h deficiency and decreased by LMNA deficiency. These differences could be explained by differing levels of the telomerase subunit, TERT, in SUV39h- and LMNA-deficient fibroblasts. Taken together, our data show that SUV39h and A-type lamins likely play a key role in telomere maintenance and telomere nuclear architecture.
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Affiliation(s)
- Radka Uhlírová
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Královopolská 135, CZ-612 65 Brno, Czech Republic
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172
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Abstract
Proteins that specifically bind the single-stranded overhang at the ends of telomeres have been identified in a wide range of eukaryotes and play pivotal roles in chromosome end protection and telomere length regulation. Here we summarize recent findings regarding the functions of POT1 proteins in vertebrates and discuss the functional evolution of POT1 proteins following gene duplication in protozoa, plants, nematodes and mice.
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Affiliation(s)
- Peter Baumann
- Howard Hughes Medical Institute, Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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173
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Shen J, Gammon MD, Wu HC, Terry MB, Wang Q, Bradshaw PT, Teitelbaum SL, Neugut AI, Santella RM. Multiple genetic variants in telomere pathway genes and breast cancer risk. Cancer Epidemiol Biomarkers Prev 2010; 19:219-28. [PMID: 20056641 DOI: 10.1158/1055-9965.epi-09-0771] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
PURPOSE To explore the etiologic role of genetic variants in telomere pathway genes and breast cancer risk. METHODS A population-based case-control study, the Long Island Breast Cancer Study Project, was conducted, and 1,067 cases and 1,110 controls were included in the present study. Fifty-two genetic variants of nine telomere-related genes were genotyped. RESULTS Seven single nucleotide polymorphisms (SNP) showed significant case-control differences at the level of P < 0.05. The top three statistically significant SNPs under a dominant model were TERT-07 (rs2736109), TERT-54 (rs3816659), and POT1-03 (rs33964002). The odds ratios (OR) were 1.56 [95% confidence interval (95% CI), 1.22-1.99] for the TERT-07 G-allele, 1.27 (95% CI, 1.05-1.52) for the TERT-54 T-allele, and 0.79 (95% CI, 0.67-0.95) for the POT1-03 A-allele. TERT-67 (rs2853669) was statistically significant under a recessive model; the OR of the CC genotype was 0.69 (95% CI, 0.69-0.93) compared with the T-allele. However, none of the SNPs retained significance after Bonferroni adjustment for multiple testing at the level of P < 0.001 (0.05/52) except for TERT-07. When restricted to Caucasians (94% of the study subjects), a stronger association for the TERT-07 G-allele was observed with an OR of 1.60 (95% CI, 1.24-2.05; P = 0.0002). No effect modifications were found for variant alleles and menopausal status, telomere length, cigarette smoking, body mass index status, and family history of breast cancer risk. CONCLUSIONS Four SNPs in the TERT and POT1 genes were significantly related with overall breast cancer risk. This initial analysis provides valuable clues for further exploration of the biological role of telomere pathway genes in breast cancer.
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Affiliation(s)
- Jing Shen
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 630 West 168th Street, P&S 19-418, New York, NY 10032, USA.
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174
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Wang H, Linghu H, Wang J, Che YL, Xiang TX, Tang WX, Yao ZW. The role of Crk/Dock180/Rac1 pathway in the malignant behavior of human ovarian cancer cell SKOV3. Tumour Biol 2009; 31:59-67. [PMID: 20237902 DOI: 10.1007/s13277-009-0009-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 11/04/2009] [Indexed: 11/25/2022] Open
Abstract
Small GTPases, particularly the Rho family, are key regulators of cell motility and migration. Dock180 was well known for the main target of signal adaptor protein Crk and acted as a guanine-nucleotide exchange factor for small GTPase Rac1. In the present study, Dock180 was found to combine primarily with CrkI other than CrkII, and its association with Elmo1 was also demonstrated in ovarian cancer cell SKOV3. To evaluate the role of Dock180 in human ovarian cancer cell, we performed RNAi-mediated knockdown of Dock180 in SKOV3 cells using small interfering RNA expression vector. In Dock180 knockdown cells, we found that Elmo1 expression and Rac1 activity were decreased simultaneously. By contrast, the expressions of both another Crk-combining molecule C3G and Rap1 activity were observed to increase obviously. Accordingly, all Dock180 knockdown cells present with evident change in cell morphology, reduced cell proliferation, and attenuated cell migration. Taken together, these results suggest that signal transfer of Crk/Dock180/Rac1 is implicated in actin cytoskeleton reorganization and thus in the cell proliferation, motility, invasion, and of human ovarian cancer cell line SKOV3.
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Affiliation(s)
- Hui Wang
- Department of Obstetrics and Gynecology, The First Affiliated Hospital, Chongqing Medical University, Chongqing, 400016, China
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175
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Koerber RT, Rhee HS, Jiang C, Pugh BF. Interaction of transcriptional regulators with specific nucleosomes across the Saccharomyces genome. Mol Cell 2009; 35:889-902. [PMID: 19782036 DOI: 10.1016/j.molcel.2009.09.011] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 08/17/2009] [Accepted: 09/09/2009] [Indexed: 01/03/2023]
Abstract
A canonical nucleosome architecture around promoters establishes the context in which proteins regulate gene expression. Whether gene regulatory proteins that interact with nucleosomes are selective for individual nucleosome positions across the genome is not known. Here, we examine on a genomic scale several protein-nucleosome interactions, including those that (1) bind histones (Bdf1/SWR1 and Srm1), (2) bind specific DNA sequences (Rap1 and Reb1), and (3) potentially collide with nucleosomes during transcription (RNA polymerase II). We find that the Bdf1/SWR1 complex forms a dinucleosome complex that is selective for the +1 and +2 nucleosomes of active genes. Rap1 selectively binds to its cognate site on the rotationally exposed first and second helical turn of nucleosomal DNA. We find that a transcribing RNA polymerase creates a delocalized state of resident nucleosomes. These findings suggest that nucleosomes around promoter regions have position-specific functions and that some gene regulators have position-specific nucleosomal interactions.
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Affiliation(s)
- R Thomas Koerber
- Center for Eukaryotic Gene Regulation, Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
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176
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Atanassov BS, Evrard YA, Multani AS, Zhang Z, Tora L, Devys D, Chang S, Dent SYR. Gcn5 and SAGA regulate shelterin protein turnover and telomere maintenance. Mol Cell 2009; 35:352-64. [PMID: 19683498 DOI: 10.1016/j.molcel.2009.06.015] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Revised: 05/02/2009] [Accepted: 06/10/2009] [Indexed: 12/17/2022]
Abstract
Histone acetyltransferases (HATs) play important roles in gene regulation and DNA repair by influencing the accessibility of chromatin to transcription factors and repair proteins. Here, we show that deletion of Gcn5 leads to telomere dysfunction in mouse and human cells. Biochemical studies reveal that depletion of Gcn5 or ubiquitin-specific protease 22 (Usp22), which is another bona fide component of the Gcn5-containing SAGA complex, increases ubiquitination and turnover of TRF1, a primary component of the telomeric shelterin complex. Inhibition of the proteasome or overexpression of USP22 opposes this effect. The USP22 deubiquitinating module requires association with SAGA complexes for activity, and we find that depletion of Gcn5 compromises this association in mammalian cells. Thus, our results indicate that Gcn5 regulates TRF1 levels through effects on Usp22 activity and SAGA integrity.
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Affiliation(s)
- Boyko S Atanassov
- Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, 77030, USA
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177
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Hu J, Sun L, Wang LM, Jiang SJ. Analysis of the nuclear localization signal of TRF1 in non-small cell lung cancer. Biol Res 2009; 42:217-222. [PMID: 19746267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Abstract
Several studies revealed a similar down-regulation of telomeric repeat binding factor 1 (TRF1) in tumors. We have previously reported the TRFl expression levels were down-regulation in non-small cell lung cancer (NSCLC). The regulation of TRFl localization is proposed to be important for the function and expression. The nuclear localization signal (NLS) and nuclear export signal (NES) are often important clues to localization of protein. The objective of the present study was to investigate the NLS and NES of TRFl in NSCLC patients. Thirty (30) patients with NSCLCs had undergone radical operations in The First Affiliated Hospital, College of Medicine, Zhejiang University. DNA sequences of NLSs and NESs were amplified by PCR. The PCR products were analyzed by DNA sequencing. There were four NLSs of the TRFl protein, including two monopartite and two bipartite NLSs. The NLSs sequences were included in 337KKERRVGTPQSTKKKKESRR356. The exon 8 and exon 9 of TRFl DNA were covered the NLS sequences. The sequences of predicted NESs were 11WMLDFLCLSL86 and 174NLLKLQALAV183, respectively. The exon 1, exon 3 and exon 4 of TRFl were covered the NES sequences. In NSCLCs, there was no a mutation, deletion, or substitution in NLS and NES of TRFl. We conclude that the NLS and NES sequences in NSCLCs patients did not have mutations. Down-expression of TRFl does not indicate gene mutation of NLS and NES in NSCLCs.
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Affiliation(s)
- Jian Hu
- Department of Thoracic and Cardiovascular Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, China.
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178
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Enyeart JA, Enyeart JJ. Metabolites of an Epac-selective cAMP analog induce cortisol synthesis by adrenocortical cells through a cAMP-independent pathway. PLoS One 2009; 4:e6088. [PMID: 19564912 PMCID: PMC2698983 DOI: 10.1371/journal.pone.0006088] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Accepted: 05/28/2009] [Indexed: 11/18/2022] Open
Abstract
Adrenal zona fasciculata (AZF) cells express a cAMP-activated guanine nucleotide exchange protein (Epac2) that may function in ACTH-stimulated cortisol synthesis. Experiments were done to determine whether cAMP analogs that selectively activate Epacs could induce cortisol synthesis and the expression of genes coding for steroidogenic proteins in bovine AZF cells. Treatment of AZF cells with the Epac-selective cAMP analog (ESCA) 8CPT-2'-OMe-cAMP induced large (>100 fold), concentration-dependent, delayed increases in cortisol synthesis and the expression of mRNAs coding for the steroid hydroxylases CYP11a1, CYP17, CYP21, and the steroid acute regulatory protein (StAR). However, a non-hydrolyzable analog of this ESCA, Sp-8CPT-2'-OMe-cAMP, failed to stimulate cortisol production even at concentrations that activated Rap1, a downstream effector of Epac2. Accordingly, putative metabolites of 8CPT-2'-OMe-cAMP, including 8CPT-2'-OMe-5'AMP, 8CPT-2'-OMe-adenosine, and 8CPT-adenine all induced cortisol synthesis and steroid hydroxylase mRNA expression with a temporal pattern, potency, and effectiveness similar to the parent compound. At concentrations that markedly stimulated cortisol production, none of these metabolites significantly activated cAMP-dependent protein kinase (PKA). These results show that one or more metabolites of the ESCA 8CPT-2'-OMe-cAMP induce cortico-steroidogenesis by activating a panel of genes that code for steroidogenic proteins. The remarkable increases in cortisol synthesis observed in this study appear to be mediated by a novel cAMP-, Epac- and PKA-independent signaling pathway.
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Affiliation(s)
- Judith A. Enyeart
- Department of Neuroscience, The Ohio State University, College of Medicine and Public Health, Columbus, Ohio, United States of America
| | - John J. Enyeart
- Department of Neuroscience, The Ohio State University, College of Medicine and Public Health, Columbus, Ohio, United States of America
- * E-mail:
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179
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Borland G, Bird RJ, Palmer TM, Yarwood SJ. Activation of protein kinase Calpha by EPAC1 is required for the ERK- and CCAAT/enhancer-binding protein beta-dependent induction of the SOCS-3 gene by cyclic AMP in COS1 cells. J Biol Chem 2009; 284:17391-403. [PMID: 19423709 PMCID: PMC2719379 DOI: 10.1074/jbc.m109.015370] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Revised: 04/30/2009] [Indexed: 01/09/2023] Open
Abstract
We recently found that induction of the anti-inflammatory SOCS-3 gene by cyclic AMP occurs through novel cyclic AMP-dependent protein kinase-independent mechanisms involving activation of CCAAT/enhancer-binding protein (C/EBP) transcription factors, notably C/EBPbeta, by the cyclic AMP GEF EPAC1 and the Rap1 GTPase. In this study we show that down-regulation of phospholipase (PL) Cepsilon with small interfering RNA or blockade of PLC activity with chemical inhibitors ablates exchange protein directly activated by cyclic AMP (EPAC)-dependent induction of SOCS-3 in COS1 cells. Consistent with this, stimulation of cells with 1-oleoyl-2-acetyl-sn-glycerol and phorbol 12-myristate 13-acetate, both cell-permeable analogues of the PLC product diacylglycerol, are sufficient to induce SOCS-3 expression in a Ca2+-dependent manner. Moreover, the diacylglycerol- and Ca2+-dependent protein kinase C (PKC) isoform PKCalpha becomes activated following cyclic AMP elevation or EPAC stimulation. Conversely, down-regulation of PKC activity with chemical inhibitors or small interfering RNA-mediated depletion of PKCalpha or -delta blocks EPAC-dependent SOCS-3 induction. Using the MEK inhibitor U0126, we found that activation of ERK MAPKs is essential for SOCS-3 induction by either cyclic AMP or PKC. C/EBPbeta is known to be phosphorylated and activated by ERK. Accordingly, we found ERK activation to be essential for cyclic AMP-dependent C/EBP activation and C/EBPbeta-dependent SOCS-3 induction by cyclic AMP and PKC. Moreover, overexpression of a mutant form of C/EBPbeta (T235A), which lacks the ERK phosphorylation site, blocks SOCS-3 induction by cyclic AMP and PKC in a dominant-negative manner. Together, these results indicate that EPAC mediates novel regulatory cross-talk between the cyclic AMP and PKC signaling pathways leading to ERK- and C/EBPbeta-dependent induction of the SOCS-3 gene.
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Affiliation(s)
- Gillian Borland
- From the Division of Molecular and Cellular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Rebecca J. Bird
- From the Division of Molecular and Cellular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Timothy M. Palmer
- From the Division of Molecular and Cellular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | - Stephen J. Yarwood
- From the Division of Molecular and Cellular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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180
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Li B, Reddy S, Comai L. Sequence-specific processing of telomeric 3' overhangs by the Werner syndrome protein exonuclease activity. Aging (Albany NY) 2009; 1:289-302. [PMID: 20157518 PMCID: PMC2806009 DOI: 10.18632/aging.100032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 03/13/2009] [Indexed: 04/23/2023]
Abstract
Werner syndrome is a premature aging disease caused by loss of function mutations in the Werner syndrome protein (WRN) gene. WRN is a RecQ helicase that in contrast to every other member of this family of proteins possesses an exonuclease activity. The findings that cells lacking WRN activity display accelerated telomere shortening and WRN can be detected at chromosome ends suggest that this protein participates in some aspects of telomere metabolism. In this study we examined the impact of WRN on telomeric substrates with a 3' single-stranded overhang in vitro and show that WRN has sequence-specific exonuclease activity that removes several nucleotides inward with a periodical pattern from the 3' end of the telomeric overhang. This activity is strictly dependent on the presence of telomeric sequences in both the duplex DNA and 3' overhang DNA segment and is strongly inhibited by the telomeric factor POT1 but not TRF2. These data demonstrate that WRN processes telomeric DNA substrates with a 3' single-stranded overhang with high specificity and suggest that this protein could influence the configuration of telomere ends prior to the formation of a protective t-loop structure.
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Affiliation(s)
- Baomin Li
- Department of Molecular Microbiology and Immunology, Institute for Genetic Medicine, University of Southern California, Los Angeles, CA 90033, USA
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181
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Ahn B, Lee JW, Jung H, Beck G, Bohr VA. Mechanism of Werner DNA helicase: POT1 and RPA stimulates WRN to unwind beyond gaps in the translocating strand. PLoS One 2009; 4:e4673. [PMID: 19262689 PMCID: PMC2650403 DOI: 10.1371/journal.pone.0004673] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 01/28/2009] [Indexed: 01/05/2023] Open
Abstract
WRN belongs to the RecQ family of DNA helicases and it plays a role in recombination, replication, telomere maintenance and long-patch base excision repair. Here, we demonstrate that WRN efficiently unwinds DNA substrates containing a 1-nucleotide gap in the translocating DNA strand, but when the gap size is increased to 3-nucleotides unwinding activity significantly declines. In contrast, E. coli UvrD (3′→5′ helicase), which recognizes nicks in DNA to initiate unwinding, does not unwind past a 1-nucleotide gap. This unique ability of WRN to bypass gaps supports its involvement in DNA replication and LP-BER where such gaps can be produced by glycosylases and the apurinic/apyrimidinic endonuclease 1 (APE1). Furthermore, we tested telomere repeat binding factor 2 (TRF2), both variants 1 and 2 of protector of telomeres 1 (POT1v1 and POT1v2) and RPA on telomeric DNA substrates containing much bigger gaps than 3-nucleotides in order to determine whether unwinding could be facilitated through WRN-protein interaction. Interestingly, POT1v1 and RPA are capable of stimulating WRN helicase on gapped DNA and 5′-overhang substrates, respectively.
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Affiliation(s)
- Byungchan Ahn
- Department of Life Sciences, University of Ulsan, Ulsan, Korea
| | - Jae Wan Lee
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Hana Jung
- Department of Life Sciences, University of Ulsan, Ulsan, Korea
| | - Gad Beck
- Department of Life Sciences, University of Ulsan, Ulsan, Korea
| | - Vilhelm A. Bohr
- Laboratory of Molecular Gerontology, Biomedical Research Center, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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182
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Nellore A, Paziana K, Ma C, Tsygankova OM, Wang Y, Puttaswamy K, Iqbal AU, Franks SR, Lv Y, Troxel AB, Feldman MD, Meinkoth JL, Brose MS. Loss of Rap1GAP in papillary thyroid cancer. J Clin Endocrinol Metab 2009; 94:1026-32. [PMID: 19066305 PMCID: PMC2681278 DOI: 10.1210/jc.2008-1042] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
CONTEXT Rap1 GTPase-activating protein (GAP) regulates the activity of Rap1, a putative oncogene. We previously reported Rap1GAP was highly expressed in normal human thyroid cells and decreased in five papillary thyroid carcinomas (PTCs). OBJECTIVES To confirm the significance of these findings, we analyzed Rap1GAP expression in a larger set of benign tumors (adenomas and hyperplastic nodules) and PTCs. We determined whether the presence of the BRAF(V600E) mutation or allelic loss of Rap1GAP related to changes in Rap1GAP protein expression. To determine the consequences of Rap1GAP loss, we targeted Rap1GAP in culture using small interfering RNA. DESIGN, PATIENTS, AND METHODS A highly specific Rap1GAP antibody was applied to sections of 55 human thyroid tissues. Genomic DNA was analyzed for the presence of the BRAF(V600E) mutation, and loss of Rap1GAP. Rap1GAP expression in rat thyroid cells was abolished using small interfering RNA. RESULTS We observed that down-regulation of Rap1GAP in benign lesions and PTCs was common. Rap1GAP expression was more severely decreased in PTCs. Loss of Rap1GAP expression was observed in multiple histological variants of PTCs. Approximately 20% of PTCs and adenomas exhibited allelic loss of Rap1GAP. Loss of Rap1GAP was not associated with the presence of the BRAF(V600E) mutation. In vitro, loss of Rap1GAP was sufficient to increase Rap1 activity in thyroid cells. CONCLUSIONS These data indicate that loss of Rap1GAP is a frequent event in PTC. The more frequent and greater down-regulation of Rap1GAP in PTCs compared with adenomas suggests a role for Rap1GAP depletion in the progression of human thyroid tumors, possibly through unrestrained Rap activity.
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Affiliation(s)
- Anoma Nellore
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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183
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Kanoh J. [Regulation of telomere DNA by telomere-specific chromatin structure]. Tanpakushitsu Kakusan Koso 2009; 54:514-520. [PMID: 21089501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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184
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Chebel A, Bauwens S, Gerland LM, Belleville A, Urbanowicz I, de Climens AR, Tourneur Y, Chien WW, Catallo R, Salles G, Gilson E, Ffrench M. Telomere uncapping during in vitro T-lymphocyte senescence. Aging Cell 2009; 8:52-64. [PMID: 19077045 DOI: 10.1111/j.1474-9726.2008.00448.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Normal lymphocytes represent examples of somatic cells that are able to induce telomerase activity when stimulated. As previously reported, we showed that, during lymphocyte long-term culture and repeated stimulations, the appearance of senescent cells is associated with telomere shortening and a progressive drop in telomerase activity. We further showed that this shortening preferentially occured at long telomeres and was interrupted at each stimulation by a transitory increase in telomere length. In agreement with the fact that telomere uncapping triggers lymphocyte senescence, we observed an increase in gamma-H2AX and 53BP1 foci as well as in the percentage of cells exhibiting DNA damage foci in telomeres. Such a DNA damage response may be related to the continuous increase of p16(ink4a) upon cell stimulation and cell aging. Remarkably, at each stimulation, the expression of shelterin genes, such as hTRF1, hTANK1, hTIN2, hPOT1 and hRAP1, was decreased. We propose that telomere dysfunction during lymphocyte senescence caused by iterative stimulations does not only result from an excessive telomere shortening, but also from a decrease in shelterin content. These observations may be relevant for T-cell biology and aging.
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Affiliation(s)
- Amel Chebel
- Université Claude Bernard Lyon, CNRS UMR ENS - HCL, Oullins, France
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185
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McGlynn LM, Stevenson K, Lamb K, Zino S, Brown M, Prina A, Kingsmore D, Shiels PG. Cellular senescence in pretransplant renal biopsies predicts postoperative organ function. Aging Cell 2009; 8:45-51. [PMID: 19067655 DOI: 10.1111/j.1474-9726.2008.00447.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Older and marginal donors have been used to meet the shortfall in available organs for renal transplantation. Post-transplant renal function and outcome from these donors are often poorer than chronologically younger donors. Some organs, however, function adequately for many years. We have hypothesized that such organs are biologically younger than poorer performing counterparts. We have tested this hypothesis in a cohort of preimplantation human renal allograft biopsies ( n = 75) that have been assayed by real-time polymerase chain reaction for the expression of known markers of cellular damage and biological aging, including CDKN2A, CDKN1A, SIRT2 and POT1. These have been investigated for any associations with traditional factors affecting transplant outcome (donor age, cold ischaemic time) and organ function posttransplant (serum creatinine levels). Linear regression analyses indicated a strong association for serum creatinine with pre-transplant CDKN2A levels ( p = 0.001) and donor age ( p = 0.004) at 6 months post-transplant. Both these markers correlated significantly with urinary protein to creatinine ratios ( p = 0.002 and p = 0.005 respectively), an informative marker for subsequent graft dysfunction. POT1 expression also showed a significant association with this parameter ( p = 0.05). Multiple linear regression analyses for CDKN2A and donor age accounted for 24.6% ( p = 0.001) of observed variability in serum creatinine levels at 6 months and 23.7% ( p = 0.001) at 1 year posttransplant. Thus, these data indicate that allograft biological age is an important novel prognostic determinant for renal transplant outcome.
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186
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Lissitzky JC, Parriaux D, Ristorcelli E, Vérine A, Lombardo D, Verrando P. Cyclic AMP signaling as a mediator of vasculogenic mimicry in aggressive human melanoma cells in vitro. Cancer Res 2009; 69:802-9. [PMID: 19176384 DOI: 10.1158/0008-5472.can-08-2391] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aggressive melanoma cells can engage in a process termed vasculogenic mimicry (VM) that reflects the ability of tumor cells to express a multipotent, stem cell-like phenotype. Melanoma cell plasticity contributes to the lack of efficient therapeutic strategies targeting metastatic tumors. This study reveals cyclic AMP as a mediator of VM in vitro. In uveal and cutaneous metastatic aggressive human melanoma cells, an increase in cyclic AMP by forskolin, dibutyryl cyclic AMP, or G protein-coupled receptor (GPCR) ligands such as adrenaline and vasoactive intestinal peptide inhibited VM to different extents. Although chemical modulators of protein kinase A (PKA) had no effect, a specific pharmacologic activator of Exchange protein directly activated by cyclic AMP (Epac) impaired VM. Ras-associated protein-1 (Rap1) activation assays revealed that cyclic AMP-elevating agents induce a PKA-independent activation of Epac/Rap1. Pharmacologic inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) activity abolished VM. Phosphorylation of ERK1/2 was PKA-independently inhibited by forskolin but not inhibited by Epac/Rap1 signaling, PKA modulation, or GPCR ligands. Furthermore, the forskolin also inhibited phosphatidyl inositol-3-kinase (PI3K)-mediated activation of protein kinase Akt, as monitored by Ser473 phosphorylation. The pharmacologic activation of Epac and GPCR ligands slightly stimulated Akt, a likely concomitant process of VM modulation. Collectively, these data show that forskolin strongly inhibits VM through PKA-independent activation of Epac/Rap1, PKA-, and Epac-independent inactivation of ERK1/2 and inhibition of PI3K/Akt. The data also show that VM inhibition by GPCR ligands involves mainly the Epac/Rap1-activated signal. Thus cyclic AMP inhibits VM through multiple signaling pathways.
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Affiliation(s)
- Jean-Claude Lissitzky
- Institut National de la Sante et de la Recherche Medicale UMR911, Centre de Recherche en Oncologie Biologique et Onco-pharmacologie, Aix-Marseille University, School of Medicine Timone, Marseille, France
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187
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Yamamoto Y, Sakisaka T. [Vesicle transport-dependent axon formation]. Tanpakushitsu Kakusan Koso 2008; 53:2207-2213. [PMID: 21038610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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188
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Miyoshi T, Ishikawa F. [Conserved telomeric-end structures among fission yeast and humans]. Tanpakushitsu Kakusan Koso 2008; 53:1850-1857. [PMID: 19044021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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189
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Wanat JJ, Kim KP, Koszul R, Zanders S, Weiner B, Kleckner N, Alani E. Csm4, in collaboration with Ndj1, mediates telomere-led chromosome dynamics and recombination during yeast meiosis. PLoS Genet 2008; 4:e1000188. [PMID: 18818741 PMCID: PMC2533701 DOI: 10.1371/journal.pgen.1000188] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Accepted: 08/04/2008] [Indexed: 11/18/2022] Open
Abstract
Chromosome movements are a general feature of mid-prophase of meiosis. In budding yeast, meiotic chromosomes exhibit dynamic movements, led by nuclear envelope (NE)-associated telomeres, throughout the zygotene and pachytene stages. Zygotene motion underlies the global tendency for colocalization of NE-associated chromosome ends in a "bouquet." In this study, we identify Csm4 as a new molecular participant in these processes and show that, unlike the two previously identified components, Ndj1 and Mps3, Csm4 is not required for meiosis-specific telomere/NE association. Instead, it acts to couple telomere/NE ensembles to a force generation mechanism. Mutants lacking Csm4 and/or Ndj1 display the following closely related phenotypes: (i) elevated crossover (CO) frequencies and decreased CO interference without abrogation of normal pathways; (ii) delayed progression of recombination, and recombination-coupled chromosome morphogenesis, with resulting delays in the MI division; and (iii) nondisjunction of homologs at the MI division for some reason other than absence of (the obligatory) CO(s). The recombination effects are discussed in the context of a model where the underlying defect is chromosome movement, the absence of which results in persistence of inappropriate chromosome relationships that, in turn, results in the observed mutant phenotypes.
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Affiliation(s)
- Jennifer J. Wanat
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Keun P. Kim
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Romain Koszul
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Sarah Zanders
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Beth Weiner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Nancy Kleckner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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190
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McCord A. Elite controllers may show way to a cure. Proj Inf Perspect 2008:23-24. [PMID: 19048679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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191
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Chi YK, Shen Q, Wang JC, Zheng XZ, Hou L, Zhang B. [Correlation of telomere length and the expression of its regulating proteins in mesenchymal sarcomas]. Beijing Da Xue Xue Bao Yi Xue Ban 2008; 40:363-368. [PMID: 18677381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
OBJECTIVE To explore the significance in the change of telomere length in mesenchymal sarcomas, through analyzing telomere length and expression of its associated proteins, including TRF1, POT1, hTERT, P53 and c-myc. METHODS The telomere length in 20 cases of osteosarcomas, 25 of chondrosarcomas, 19 of rhabdomyosarcomas, 26 of liposarcomas was measured by telomere fluorescence in situ hybridization (Telo-FISH), and the expression of TRF1, POT1, hTERT, p53 or c-myc was analyzed by immunohistochemistry, respectively. RESULTS The telomere length in osteosarcomas was significantly shorter than that of either chondrosarcomas or liposarcomas (P<0.05). Similarly, the telomere length of rhabdomyosarcoma was shorter than that of chondrosarcoma (P<0.05). Meanwhile, telomere shortening was positively correlated with down expression of telomere binding proteins TRF1 and POT1 (P<0.05), but trends were detected more frequently in positive expression of hTERT (P<0.05) and in nuclear accumulation of P53 or expression of c-myc. With advancing in histological grading, telomere length was shortened markedly in chondrosarcomas, especially in liposarcomas (P<0.05). CONCLUSION The shortening of telomere could prevail in mesenchymal sarcoma and reflect the malignant potential. Telomere attrition usually correlated with down expression of POT1, TRF1 and with increased levels of hTERT, P53 and c-myc.
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Affiliation(s)
- Ying-kai Chi
- Department of Pathology, Peking University School of Basic Medical Sciences, Beijing, China
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192
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Ning XY, Fang DC. [Telomeres and Shelterin complex: an update]. Zhonghua Bing Li Xue Za Zhi 2008; 37:410-412. [PMID: 19031724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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193
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Fujii K, Sasahira T, Moriwaka Y, Oue N, Yasui W, Kuniyasu H. Protection of telomeres 1 protein levels are associated with telomere length in gastric cancer. Int J Mol Med 2008; 21:599-604. [PMID: 18425352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023] Open
Abstract
Protection of telomeres 1 (Pot1) is a telomere-associated protein, which binds to the single-stranded DNA extensions of telomeres and regulates telomere length. Pot1 production was examined and compared with telomere length in gastric cancer. Pot1 production and telomere lengths were assessed in 5 human gastric cancer cell lines by immunoblotting and Southern blotting, respectively. Pot1 intracellular localization was examined with protein fractionation. Pot1 index and telomere volume were examined in human gastric mucosa and cancer by immunohistochemistry and in situ hybridization. Pot1 protein levels, which were lower than those in the lymphocytes of healthy persons, were significantly correlated with telomere length in gastric cancer cells (P=0.0167). Pot1 protein was mainly detected in the nuclear fraction and increased by G2/M blocking with nocodazole in MKN28 cells. Pot1 indexes were correlated with telomere volumes in gastric cancers (P<0.0001). Pot1 index was decreased in gastric epithelia distant from cancer (84+/-14%), in peritumoral epithelia (72+/-24%), and in stage I-II (39+/-14%) and stage III-IV (23+/-14%) gastric cancers (P<0.0001). Pot1 index was lower in stage III-IV than in stage I-II gastric cancers (P<0.05). Pot1-low cases showed advanced cancer invasion (P<0.05). Thus, Pot1 production was closely associated with telomere length in gastric mucosa and cancers. Pot1 might be a good in situ marker for the examination of cell-specific telomere length.
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Affiliation(s)
- Kiyomu Fujii
- Department of Molecular Pathology, Nara Medical University School of Medicine, Kashihara, Nara, Japan
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194
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Abstract
In this issue of Molecular Cell, Hogues et al. (2008) demonstrate a wholesale shift in the key regulatory protein involved in ribosomal protein (RP) synthesis during the evolution of S. cerevisiae and, en passant, raise interesting questions about the relationship between RP genes and telomeres.
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Affiliation(s)
- Arpita Bhattacharya
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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195
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Abstract
Elucidating oncogenic pathways in prostate cancer is an arduous task. In this issue of Cancer Cell, Yu and colleagues show that repression of Adrenergic Receptor Beta-2 gene expression by Enhancer of Zeste 2 results in acquisition of transforming activities. It is interesting that these activities point to a role for GTPases as important regulators of transformation in prostate cancer cells. They further implicate epithelial-mesenchymal transition as a biologic end point in this process. Overall, on the basis of their findings, the authors nominate a novel oncogenic pathway for prostate cancer that deserves critical thought and attention.
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Affiliation(s)
- Timothy C Thompson
- Department of Genitourinary Medical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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196
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Rossignol P, Collier S, Bush M, Shaw P, Doonan JH. Arabidopsis POT1A interacts with TERT-V(I8), an N-terminal splicing variant of telomerase. J Cell Sci 2007; 120:3678-87. [PMID: 17911168 DOI: 10.1242/jcs.004119] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chromosome integrity is maintained via the actions of ribonucleoprotein complexes that can add telomeric repeats or can protect the chromosome end from being degraded. POT1 (protection of telomeres 1), a class of single-stranded-DNA-binding proteins, is a regulator of telomeric length. The Arabidopsis genome contains three POT1 homologues: POT1A, POT1B and POT1C. Using yeast two-hybrid assays to identify components of a potential POT1A complex, we retrieved three interactors: the N-terminus of the telomerase, a protein kinase and a plant-specific protein. Further analysis of the interaction of POT1 proteins with telomerase showed that this interaction is specific to POT1A, suggesting a specific role for this paralogue. The interaction is specific to the N-terminal region of the telomerase, which can be encoded by splicing variants. This interaction indicates possible mechanisms for telomerase regulation by alternative splicing and by POT1 proteins.
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Affiliation(s)
- Pascale Rossignol
- Department of Cellular and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, UK
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197
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Abstract
BACKGROUND Progression of prostate cancer to a fatal androgen-independent disease is associated with activation of MAP kinase, consistent with chronic stimulation of the Ras-signaling pathway. We have previously shown that Ras activation is sufficient to induce androgen-independent growth of prostate cancer cells. One mechanism of MAP kinase regulation is modulation of Ras signaling by other Ras family members, the Rap gene paralogs Rap1a/b and Rap2a/b. Here we ask if Rap proteins play a role in determining androgen sensitivity of human prostate cancer cells either alone or in the context of an activated Ras. METHODS To evaluate the role of Rap proteins in androgen responsiveness we use Rap over-expression with or without mutated Ras co-transfection and Rap siRNA knockdown to evaluate androgen-dependent prostate-specific antigen (PSA) promoter reporter expression and cell growth in androgen-dependent LNCaP and independent C4-2 human prostate cancer cells. RESULTS Rap1 is equally expressed between LNCaP and C4-2 cells and thus we focused on Rap2 which is minimally expressed in C4-2. Rap2a affects androgen-dependent PSA reporter expression in a dose-dependent manner in LNCaP and C4-2 cells. Low levels of Rap2a enhance PSA reporter expression, whereas higher concentrations inhibit expression. We show that Rap2a antagonizes the enhanced PSA reporter expression conferred by an active RasV12 gene in prostate cancer cells. siRNA knockdown data indicate that Rap2 has a greater effect on androgen-stimulated growth in LNCaP than in C4-2 cells. CONCLUSIONS We show that Rap2 is involved in androgen-mediated transcriptional and growth responses of human prostate cancer cells.
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Affiliation(s)
- Dora Bigler
- Department of Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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198
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Kirmizis A, Santos-Rosa H, Penkett CJ, Singer MA, Vermeulen M, Mann M, Bähler J, Green RD, Kouzarides T. Arginine methylation at histone H3R2 controls deposition of H3K4 trimethylation. Nature 2007; 449:928-32. [PMID: 17898715 PMCID: PMC3350864 DOI: 10.1038/nature06160] [Citation(s) in RCA: 280] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 08/09/2007] [Indexed: 11/08/2022]
Abstract
Modifications on histones control important biological processes through their effects on chromatin structure. Methylation at lysine 4 on histone H3 (H3K4) is found at the 5' end of active genes and contributes to transcriptional activation by recruiting chromatin-remodelling enzymes. An adjacent arginine residue (H3R2) is also known to be asymmetrically dimethylated (H3R2me2a) in mammalian cells, but its location within genes and its function in transcription are unknown. Here we show that H3R2 is also methylated in budding yeast (Saccharomyces cerevisiae), and by using an antibody specific for H3R2me2a in a chromatin immunoprecipitation-on-chip analysis we determine the distribution of this modification on the entire yeast genome. We find that H3R2me2a is enriched throughout all heterochromatic loci and inactive euchromatic genes and is present at the 3' end of moderately transcribed genes. In all cases the pattern of H3R2 methylation is mutually exclusive with the trimethyl form of H3K4 (H3K4me3). We show that methylation at H3R2 abrogates the trimethylation of H3K4 by the Set1 methyltransferase. The specific effect on H3K4me3 results from the occlusion of Spp1, a Set1 methyltransferase subunit necessary for trimethylation. Thus, the inability of Spp1 to recognize H3 methylated at R2 prevents Set1 from trimethylating H3K4. These results provide the first mechanistic insight into the function of arginine methylation on chromatin.
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Affiliation(s)
- Antonis Kirmizis
- Gurdon Institute and Department of Pathology, Tennis Court Road, Cambridge CB2 1QN, UK
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199
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200
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Abstract
Telomeres are specialized chromatin structures that protect chromosome ends. Critical among telomere proteins are those that bind the telomeric single-strand DNA (ssDNA) overhangs. These proteins are thought to differ among eukaryotes. Three interacting proteins (Cdc13, Stn1, and Ten1) associate with the telomeric overhang in budding yeast, a single protein known as Pot1 (protection of telomeres-1) performs this function in fission yeast, and a two-subunit complex consisting of POT1 and TPP1 associates with telomeric ssDNA in humans. Cdc13 and Pot1 have related oligonucleotide/oligosaccharide-binding fold (OB-fold) domains that bind the telomeric ssDNA overhang. Here we show that Schizosaccharomyces pombe has Stn1- and Ten1-like proteins that are essential for chromosome end protection. Stn1 orthologs exist in all species that have Pot1, whereas Ten1-like proteins can be found in all fungi. Fission yeast Stn1 and Ten1 localize at telomeres in a manner that correlates with the length of the ssDNA overhang, suggesting that they specifically associate with the telomeric ssDNA. Unlike in budding yeast, in which Cdc13, Stn1, and Ten1 all interact, fission yeast Stn1 and Ten1 associate with each other, but not with Pot1. Our findings suggest that two separate protein complexes are required for chromosome end protection in fission yeast. Structural profiling studies detect OB-fold domains in Stn1 and Ten1 orthologs, indicating that protection of telomeres by multiple proteins with OB-fold domains is conserved in eukaryotic evolution.
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Affiliation(s)
| | - Li-Lin Du
- Departments of *Molecular Biology and
| | | | - Paul Russell
- Departments of *Molecular Biology and
- Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
- To whom correspondence should be addressed. E-mail:
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