1
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Wang H, Yang S, Chen L, Li Y, He P, Wang G, Dong H, Ma P, Ding G. Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer. Bioact Mater 2024; 33:174-222. [PMID: 38034499 PMCID: PMC10684566 DOI: 10.1016/j.bioactmat.2023.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 09/15/2023] [Accepted: 10/05/2023] [Indexed: 12/02/2023] Open
Abstract
Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.
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Affiliation(s)
- Hang Wang
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Siwei Yang
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Liangfeng Chen
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Yongqiang Li
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Peng He
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Gang Wang
- Department of Microelectronic Science and Engineering, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, PR China
| | - Hui Dong
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- CAS Center for Excellence in Superconducting Electronics (CENSE), Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
| | - Peixiang Ma
- Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, PR China
| | - Guqiao Ding
- National Key Laboratory of Materials for Integrated Circuit, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, PR China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences (UCAS), Beijing, 100049, PR China
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2
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Li B. Unwrap RAP1's Mystery at Kinetoplastid Telomeres. Biomolecules 2024; 14:67. [PMID: 38254667 PMCID: PMC10813129 DOI: 10.3390/biom14010067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 12/27/2023] [Accepted: 12/27/2023] [Indexed: 01/24/2024] Open
Abstract
Although located at the chromosome end, telomeres are an essential chromosome component that helps maintain genome integrity and chromosome stability from protozoa to mammals. The role of telomere proteins in chromosome end protection is conserved, where they suppress various DNA damage response machineries and block nucleolytic degradation of the natural chromosome ends, although the detailed underlying mechanisms are not identical. In addition, the specialized telomere structure exerts a repressive epigenetic effect on expression of genes located at subtelomeres in a number of eukaryotic organisms. This so-called telomeric silencing also affects virulence of a number of microbial pathogens that undergo antigenic variation/phenotypic switching. Telomere proteins, particularly the RAP1 homologs, have been shown to be a key player for telomeric silencing. RAP1 homologs also suppress the expression of Telomere Repeat-containing RNA (TERRA), which is linked to their roles in telomere stability maintenance. The functions of RAP1s in suppressing telomere recombination are largely conserved from kinetoplastids to mammals. However, the underlying mechanisms of RAP1-mediated telomeric silencing have many species-specific features. In this review, I will focus on Trypanosoma brucei RAP1's functions in suppressing telomeric/subtelomeric DNA recombination and in the regulation of monoallelic expression of subtelomere-located major surface antigen genes. Common and unique mechanisms will be compared among RAP1 homologs, and their implications will be discussed.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Arts and Sciences, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA;
- Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
- Center for RNA Science and Therapeutics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
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3
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Nassar R, Thompson L, Fouquerel E. Molecular mechanisms protecting centromeres from self-sabotage and implications for cancer therapy. NAR Cancer 2023; 5:zcad019. [PMID: 37180029 PMCID: PMC10167631 DOI: 10.1093/narcan/zcad019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 03/27/2023] [Accepted: 04/20/2023] [Indexed: 05/15/2023] Open
Abstract
Centromeres play a crucial role in DNA segregation by mediating the cohesion and separation of sister chromatids during cell division. Centromere dysfunction, breakage or compromised centromeric integrity can generate aneuploidies and chromosomal instability, which are cellular features associated with cancer initiation and progression. Maintaining centromere integrity is thus essential for genome stability. However, the centromere itself is prone to DNA breaks, likely due to its intrinsically fragile nature. Centromeres are complex genomic loci that are composed of highly repetitive DNA sequences and secondary structures and require the recruitment and homeostasis of a centromere-associated protein network. The molecular mechanisms engaged to preserve centromere inherent structure and respond to centromeric damage are not fully understood and remain a subject of ongoing research. In this article, we provide a review of the currently known factors that contribute to centromeric dysfunction and the molecular mechanisms that mitigate the impact of centromere damage on genome stability. Finally, we discuss the potential therapeutic strategies that could arise from a deeper understanding of the mechanisms preserving centromere integrity.
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Affiliation(s)
- Rim Nassar
- UPMC Hillman Cancer Center, Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA
| | - Lily Thompson
- UPMC Hillman Cancer Center, Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Elise Fouquerel
- UPMC Hillman Cancer Center, Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232, USA
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4
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Soman A, Korolev N, Nordenskiöld L. Telomeric chromatin structure. Curr Opin Struct Biol 2022; 77:102492. [PMID: 36335846 DOI: 10.1016/j.sbi.2022.102492] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 09/19/2022] [Accepted: 09/23/2022] [Indexed: 11/06/2022]
Abstract
Eukaryotic DNA is packaged into nucleosomes, which further condenses into chromosomes. The telomeres, which form the protective end-capping of chromosomes, play a pivotal role in ageing and cancer. Recently, significant advances have been made in understanding the nucleosomal and telomeric chromatin structure at the molecular level. In addition, recent studies shed light on the nucleosomal organisation at telomeres revealing its ultrastructural organisation, the atomic structure at the nucleosome level, its dynamic properties, and higher-order packaging of telomeric chromatin. Considerable advances have furthermore been made in understanding the structure, function and organisation of shelterin, telomerase and CST complexes. Here we discuss these recent advances in the organisation of telomeric nucleosomes and chromatin and highlight progress in the structural understanding of shelterin, telomerase and CST complexes.
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Affiliation(s)
- Aghil Soman
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Nikolay Korolev
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Lars Nordenskiöld
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore; NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore.
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5
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Hübner B, von Otter E, Ahsan B, Wee ML, Henriksson S, Ludwig A, Sandin S. Ultrastructure and nuclear architecture of telomeric chromatin revealed by correlative light and electron microscopy. Nucleic Acids Res 2022; 50:5047-5063. [PMID: 35489064 PMCID: PMC9122609 DOI: 10.1093/nar/gkac309] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 04/07/2022] [Accepted: 04/19/2022] [Indexed: 11/25/2022] Open
Abstract
Telomeres, the ends of linear chromosomes, are composed of repetitive DNA sequences, histones and a protein complex called shelterin. How DNA is packaged at telomeres is an outstanding question in the field with significant implications for human health and disease. Here, we studied the architecture of telomeres and their spatial association with other chromatin domains in different cell types using correlative light and electron microscopy. To this end, the shelterin protein TRF1 or TRF2 was fused in tandem to eGFP and the peroxidase APEX2, which provided a selective and electron-dense label to interrogate telomere organization by transmission electron microscopy, electron tomography and scanning electron microscopy. Together, our work reveals, for the first time, ultrastructural insight into telomere architecture. We show that telomeres are composed of a dense and highly compacted mesh of chromatin fibres. In addition, we identify marked differences in telomere size, shape and chromatin compaction between cancer and non-cancer cells and show that telomeres are in direct contact with other heterochromatin regions. Our work resolves the internal architecture of telomeres with unprecedented resolution and advances our understanding of how telomeres are organized in situ.
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Affiliation(s)
- Barbara Hübner
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Eric von Otter
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Bilal Ahsan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Mei Ling Wee
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Sara Henriksson
- Umeå Centre for Electron Microscopy, Umeå University, Chemical Biological Centre (KBC) Building, Linnaeus väg 6, SE-90736 Umeå, Sweden
| | - Alexander Ludwig
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
| | - Sara Sandin
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore
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6
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Li B, Zhao Y. Regulation of Antigenic Variation by Trypanosoma brucei Telomere Proteins Depends on Their Unique DNA Binding Activities. Pathogens 2021; 10:pathogens10080967. [PMID: 34451431 PMCID: PMC8402208 DOI: 10.3390/pathogens10080967] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 07/22/2021] [Accepted: 07/27/2021] [Indexed: 01/17/2023] Open
Abstract
Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, Variant Surface Glycoprotein (VSG), to evade the host immune response. Such antigenic variation is a key pathogenesis mechanism that enables T. brucei to establish long-term infections. VSG is expressed exclusively from subtelomere loci in a strictly monoallelic manner, and DNA recombination is an important VSG switching pathway. The integrity of telomere and subtelomere structure, maintained by multiple telomere proteins, is essential for T. brucei viability and for regulating the monoallelic VSG expression and VSG switching. Here we will focus on T. brucei TRF and RAP1, two telomere proteins with unique nucleic acid binding activities, and summarize their functions in telomere integrity and stability, VSG switching, and monoallelic VSG expression. Targeting the unique features of TbTRF and TbRAP1′s nucleic acid binding activities to perturb the integrity of telomere structure and disrupt VSG monoallelic expression may serve as potential therapeutic strategy against T. brucei.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
- Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
- Center for RNA Science and Therapeutics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
- Correspondence: (B.L.); (Y.Z.)
| | - Yanxiang Zhao
- Shenzhen Research Institute, The Hong Kong Polytechnic University, Shenzhen, China
- State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
- Correspondence: (B.L.); (Y.Z.)
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7
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Li B. Keeping Balance Between Genetic Stability and Plasticity at the Telomere and Subtelomere of Trypanosoma brucei. Front Cell Dev Biol 2021; 9:699639. [PMID: 34291053 PMCID: PMC8287324 DOI: 10.3389/fcell.2021.699639] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/08/2021] [Indexed: 12/13/2022] Open
Abstract
Telomeres, the nucleoprotein complexes at chromosome ends, are well-known for their essential roles in genome integrity and chromosome stability. Yet, telomeres and subtelomeres are frequently less stable than chromosome internal regions. Many subtelomeric genes are important for responding to environmental cues, and subtelomeric instability can facilitate organismal adaptation to extracellular changes, which is a common theme in a number of microbial pathogens. In this review, I will focus on the delicate and important balance between stability and plasticity at telomeres and subtelomeres of a kinetoplastid parasite, Trypanosoma brucei, which causes human African trypanosomiasis and undergoes antigenic variation to evade the host immune response. I will summarize the current understanding about T. brucei telomere protein complex, the telomeric transcript, and telomeric R-loops, focusing on their roles in maintaining telomere and subtelomere stability and integrity. The similarities and differences in functions and underlying mechanisms of T. brucei telomere factors will be compared with those in human and yeast cells.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, Cleveland, OH, United States.,Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, United States.,Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.,Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, OH, United States
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8
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Abstract
Decades of study on cell cycle regulation have provided great insight into human cellular life span barriers, as well as their dysregulation during tumorigenesis. Telomeres, the extremities of linear chromosomes, perform an essential role in implementing these proliferative boundaries and preventing the propagation of potentially cancerous cells. The tumor-suppressive function of telomeres relies on their ability to initiate DNA damage signaling pathways and downstream cellular events, ranging from cell cycle perturbation to inflammation and cell death. While the tumor-suppressor role of telomeres is undoubtable, recent advances have pointed to telomeres as a major source of many of the genomic aberrations found in both early- and late-stage cancers, including the most recently discovered mutational phenomenon of chromothripsis. Telomere shortening appears as a double-edged sword that can function in opposing directions in carcinogenesis. This review focuses on the current knowledge of the dual role of telomeres in cancer and suggests a new perspective to reconcile the paradox of telomeres and their implications in cancer etiology.
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Affiliation(s)
- Joe Nassour
- Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Tobias T Schmidt
- Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
| | - Jan Karlseder
- Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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9
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Lim CJ, Cech TR. Shaping human telomeres: from shelterin and CST complexes to telomeric chromatin organization. Nat Rev Mol Cell Biol 2021; 22:283-298. [PMID: 33564154 DOI: 10.1038/s41580-021-00328-y] [Citation(s) in RCA: 103] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2021] [Indexed: 01/14/2023]
Abstract
The regulation of telomere length in mammals is crucial for chromosome end-capping and thus for maintaining genome stability and cellular lifespan. This process requires coordination between telomeric protein complexes and the ribonucleoprotein telomerase, which extends the telomeric DNA. Telomeric proteins modulate telomere architecture, recruit telomerase to accessible telomeres and orchestrate the conversion of the newly synthesized telomeric single-stranded DNA tail into double-stranded DNA. Dysfunctional telomere maintenance leads to telomere shortening, which causes human diseases including bone marrow failure, premature ageing and cancer. Recent studies provide new insights into telomerase-related interactions (the 'telomere replisome') and reveal new challenges for future telomere structural biology endeavours owing to the dynamic nature of telomere architecture and the great number of structures that telomeres form. In this Review, we discuss recently determined structures of the shelterin and CTC1-STN1-TEN1 (CST) complexes, how they may participate in the regulation of telomere replication and chromosome end-capping, and how disease-causing mutations in their encoding genes may affect specific functions. Major outstanding questions in the field include how all of the telomere components assemble relative to each other and how the switching between different telomere structures is achieved.
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Affiliation(s)
- Ci Ji Lim
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA. .,Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA. .,BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA.
| | - Thomas R Cech
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA. .,BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA. .,Howard Hughes Medical Institute, University of Colorado Boulder, Boulder, CO, USA.
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10
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Kulbay M, Bernier-Parker N, Bernier J. The role of the DFF40/CAD endonuclease in genomic stability. Apoptosis 2021; 26:9-23. [PMID: 33387146 DOI: 10.1007/s10495-020-01649-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2020] [Indexed: 12/18/2022]
Abstract
Maintenance of genomic stability in cells is primordial for cellular integrity and protection against tumor progression. Many factors such as ultraviolet light, oxidative stress, exposure to chemical reagents, particularly mutagens and radiation, can alter the integrity of the genome. Thus, human cells are equipped with many mechanisms that prevent these irreversible lesions in the genome, as DNA repair pathways, cell cycle checkpoints, and telomeric function. These mechanisms activate cellular apoptosis to maintain DNA stability. Emerging studies have proposed a new protein in the maintenance of genomic stability: the DNA fragmentation factor (DFF). The DFF40 is an endonuclease responsible of the oligonucleosomal fragmentation of the DNA during apoptosis. The lack of DFF in renal carcinoma cells induces apoptosis without oligonucleosomal fragmentation, which poses a threat to genetic information transfer between cancerous and healthy cells. In this review, we expose the link between the DFF and genomic instability as the source of disease development.
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Affiliation(s)
- Merve Kulbay
- INRS - Centre Armand-Frappier-Santé-Biotechnologie, 531 Boul. des Prairies, Laval, QC, H7V 1B7, Canada.,Department of Medicine, Université de Montréal, 2900 Blvd. Edouard Montpetit, Montreal, QC, Canada
| | - Nathan Bernier-Parker
- Toronto Animal Health Partners Emergency and Specialty Hospital, 1 Scarsdale Road, North York, ON, M3B 2R2, Canada
| | - Jacques Bernier
- INRS - Centre Armand-Frappier-Santé-Biotechnologie, 531 Boul. des Prairies, Laval, QC, H7V 1B7, Canada.
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11
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Mazzucco G, Huda A, Galli M, Piccini D, Giannattasio M, Pessina F, Doksani Y. Telomere damage induces internal loops that generate telomeric circles. Nat Commun 2020; 11:5297. [PMID: 33082350 PMCID: PMC7576219 DOI: 10.1038/s41467-020-19139-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 09/28/2020] [Indexed: 12/21/2022] Open
Abstract
Extrachromosomal telomeric circles are commonly invoked as important players in telomere maintenance, but their origin has remained elusive. Using electron microscopy analysis on purified telomeres we show that, apart from known structures, telomeric repeats accumulate internal loops (i-loops) that occur in the proximity of nicks and single-stranded DNA gaps. I-loops are induced by single-stranded damage at normal telomeres and represent the majority of telomeric structures detected in ALT (Alternative Lengthening of Telomeres) tumor cells. Our data indicate that i-loops form as a consequence of the exposure of single-stranded DNA at telomeric repeats. Finally, we show that these damage-induced i-loops can be excised to generate extrachromosomal telomeric circles resulting in loss of telomeric repeats. Our results identify damage-induced i-loops as a new intermediate in telomere metabolism and reveal a simple mechanism that links telomere damage to the accumulation of extrachromosomal telomeric circles and to telomere erosion.
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Affiliation(s)
- Giulia Mazzucco
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Armela Huda
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Martina Galli
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Daniele Piccini
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Michele Giannattasio
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy.,Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Via Festa del Perdono 7, Milan, 20122, Italy
| | - Fabio Pessina
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Ylli Doksani
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy.
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12
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Bryan TM. G-Quadruplexes at Telomeres: Friend or Foe? Molecules 2020; 25:molecules25163686. [PMID: 32823549 PMCID: PMC7464828 DOI: 10.3390/molecules25163686] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/09/2020] [Accepted: 08/10/2020] [Indexed: 12/28/2022] Open
Abstract
Telomeres are DNA-protein complexes that cap and protect the ends of linear chromosomes. In almost all species, telomeric DNA has a G/C strand bias, and the short tandem repeats of the G-rich strand have the capacity to form into secondary structures in vitro, such as four-stranded G-quadruplexes. This has long prompted speculation that G-quadruplexes play a positive role in telomere biology, resulting in selection for G-rich tandem telomere repeats during evolution. There is some evidence that G-quadruplexes at telomeres may play a protective capping role, at least in yeast, and that they may positively affect telomere maintenance by either the enzyme telomerase or by recombination-based mechanisms. On the other hand, G-quadruplex formation in telomeric DNA, as elsewhere in the genome, can form an impediment to DNA replication and a source of genome instability. This review summarizes recent evidence for the in vivo existence of G-quadruplexes at telomeres, with a focus on human telomeres, and highlights some of the many unanswered questions regarding the location, form, and functions of these structures.
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Affiliation(s)
- Tracy M Bryan
- Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
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13
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Tomáška Ľ, Cesare AJ, AlTurki TM, Griffith JD. Twenty years of t-loops: A case study for the importance of collaboration in molecular biology. DNA Repair (Amst) 2020; 94:102901. [PMID: 32620538 DOI: 10.1016/j.dnarep.2020.102901] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 06/22/2020] [Indexed: 12/12/2022]
Abstract
Collaborative studies open doors to breakthroughs otherwise unattainable by any one laboratory alone. Here we describe the initial collaboration between the Griffith and de Lange laboratories that led to thinking about the telomere as a DNA template for homologous recombination, the proposal of telomere looping, and the first electron micrographs of t-loops. This was followed by collaborations that revealed t-loops across eukaryotic phyla. The Griffith and Tomáška/Nosek collaboration revealed circular telomeric DNA (t-circles) derived from the linear mitochondrial chromosomes of nonconventional yeast, which spurred discovery of t-circles in ALT-positive human cells. Collaborative work between the Griffith and McEachern labs demonstrated t-loops and t-circles in a series of yeast species. The de Lange and Zhuang laboratories then applied super-resolution light microscopy to demonstrate a genetic role for TRF2 in loop formation. Recent work from the Griffith laboratory linked telomere transcription with t-loop formation, providing a new model of the t-loop junction. A recent collaboration between the Cesare and Gaus laboratories utilized super-resolution light microscopy to provide details about t-loops as protective elements, followed by the Boulton and Cesare laboratories showing how cell cycle regulation of TRF2 and RTEL enables t-loop opening and reformation to promote telomere replication. Twenty years after the discovery of t-loops, we reflect on the collective history of their research as a case study in collaborative molecular biology.
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Affiliation(s)
- Ľubomír Tomáška
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 84215, Bratislava, Slovakia
| | - Anthony J Cesare
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, 2145, Australia
| | - Taghreed M AlTurki
- Lineberger Comprehensive Cancer Center and Departments of Microbiology and Immunology, and Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center and Departments of Microbiology and Immunology, and Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
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14
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Amato R, Valenzuela M, Berardinelli F, Salvati E, Maresca C, Leone S, Antoccia A, Sgura A. G-quadruplex Stabilization Fuels the ALT Pathway in ALT-positive Osteosarcoma Cells. Genes (Basel) 2020; 11:genes11030304. [PMID: 32183119 PMCID: PMC7140816 DOI: 10.3390/genes11030304] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/20/2020] [Accepted: 03/09/2020] [Indexed: 12/20/2022] Open
Abstract
Most human tumors maintain telomere lengths by telomerase, whereas a portion of them (10–15%) uses a mechanism named alternative lengthening of telomeres (ALT). The telomeric G-quadruplex (G4) ligand RHPS4 is known for its potent antiproliferative effect, as shown in telomerase-positive cancer models. Moreover, RHPS4 is also able to reduce cell proliferation in ALT cells, although the influence of G4 stabilization on the ALT mechanism has so far been poorly investigated. Here we show that sensitivity to RHPS4 is comparable in ALT-positive (U2OS; SAOS-2) and telomerase-positive (HOS) osteosarcoma cell lines, unlinking the telomere maintenance mechanism and RHPS4 responsiveness. To investigate the impact of G4 stabilization on ALT, the cardinal ALT hallmarks were analyzed. A significant induction of telomeric doublets, telomeric clusterized DNA damage, ALT-associated Promyelocytic Leukaemia-bodies (APBs), telomere sister chromatid exchanges (T-SCE) and c-circles was found exclusively in RHPS4-treated ALT cells. We surmise that RHPS4 affects ALT mechanisms through the induction of replicative stress that in turn is converted in DNA damage at telomeres, fueling recombination. In conclusion, our work indicates that RHPS4-induced telomeric DNA damage promotes overactivation of telomeric recombination in ALT cells, opening new questions on the therapeutic employment of G4 ligands in the treatment of ALT positive tumors.
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Affiliation(s)
- Roberta Amato
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
| | - Martina Valenzuela
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
| | - Francesco Berardinelli
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
- Correspondence: ; Tel.: +39-0657-33-6330
| | - Erica Salvati
- BPM-CNR Institute of Molecular Biology and Pathology, National Research Council, 00185 Rome, Italy;
- Oncogenomic and Epigenetic Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy;
| | - Carmen Maresca
- Oncogenomic and Epigenetic Unit, IRCCS Regina Elena National Cancer Institute, 00144 Rome, Italy;
| | - Stefano Leone
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
| | - Antonio Antoccia
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
| | - Antonella Sgura
- Department of Science, Roma Tre University, I-00146 Rome, Italy; (R.A.); (M.V.); (S.L.); (A.A.); (A.S.)
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15
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Wang ZN, Su RN, Yang BY, Yang KX, Yang LF, Yan Y, Chen ZG. Potential Role of Cellular Senescence in Asthma. Front Cell Dev Biol 2020; 8:59. [PMID: 32117985 PMCID: PMC7026390 DOI: 10.3389/fcell.2020.00059] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/22/2020] [Indexed: 12/18/2022] Open
Abstract
Cellular senescence is a complicated process featured by irreversible cell cycle arrest and senescence-associated secreted phenotype (SASP), resulting in accumulation of senescent cells, and low-grade inflammation. Cellular senescence not only occurs during the natural aging of normal cells, but also can be accelerated by various pathological factors. Cumulative studies have shown the role of cellular senescence in the pathogenesis of chronic lung diseases including chronic obstructive pulmonary diseases (COPD) and idiopathic pulmonary fibrosis (IPF) by promoting airway inflammation and airway remodeling. Recently, great interest has been raised in the involvement of cellular senescence in asthma. Limited but valuable data has indicated accelerating cellular senescence in asthma. This review will compile current findings regarding the underlying relationship between cellular senescence and asthma, mainly through discussing the potential mechanisms of cellular senescence in asthma, the impact of senescent cells on the pathobiology of asthma, and the efficiency and feasibility of using anti-aging therapies in asthmatic patients.
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Affiliation(s)
- Zhao-Ni Wang
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,Guangzhou Institute of Respiratory Diseases, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, China
| | - Ruo-Nan Su
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Bi-Yuan Yang
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Ke-Xin Yang
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Li-Fen Yang
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Yan Yan
- Guangdong Provincial Key Laboratory of Biomedical Imaging, Guangdong Provincial Engineering Research Center of Molecular Imaging, The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, China.,Center for Interventional Medicine, The Fifth Affiliated Hospital, Sun Yat-sen University, Zhuhai, China
| | - Zhuang-Gui Chen
- Department of Pediatrics, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
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16
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X-rays Activate Telomeric Homologous Recombination Mediated Repair in Primary Cells. Cells 2019; 8:cells8070708. [PMID: 31336873 PMCID: PMC6678842 DOI: 10.3390/cells8070708] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 06/27/2019] [Accepted: 07/06/2019] [Indexed: 12/31/2022] Open
Abstract
Cancer cells need to acquire telomere maintenance mechanisms in order to counteract progressive telomere shortening due to multiple rounds of replication. Most human tumors maintain their telomeres expressing telomerase whereas the remaining 15%–20% utilize the alternative lengthening of telomeres (ALT) pathway. Previous studies have demonstrated that ionizing radiations (IR) are able to modulate telomere lengths and to transiently induce some of the ALT-pathway hallmarks in normal primary fibroblasts. In the present study, we investigated the telomere length modulation kinetics, telomeric DNA damage induction, and the principal hallmarks of ALT over a period of 13 days in X-ray-exposed primary cells. Our results show that X-ray-treated cells primarily display telomere shortening and telomeric damage caused by persistent IR-induced oxidative stress. After initial telomere erosion, we observed a telomere elongation that was associated to the transient activation of a homologous recombination (HR) based mechanism, sharing several features with the ALT pathway observed in cancer cells. Data indicate that telomeric damage activates telomeric HR-mediated repair in primary cells. The characterization of HR-mediated telomere repair in normal cells may contribute to the understanding of the ALT pathway and to the identification of novel strategies in the treatment of ALT-positive cancers.
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17
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Doksani Y. The Response to DNA Damage at Telomeric Repeats and Its Consequences for Telomere Function. Genes (Basel) 2019; 10:genes10040318. [PMID: 31022960 PMCID: PMC6523756 DOI: 10.3390/genes10040318] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/13/2019] [Accepted: 04/18/2019] [Indexed: 01/17/2023] Open
Abstract
Telomeric repeats, coated by the shelterin complex, prevent inappropriate activation of the DNA damage response at the ends of linear chromosomes. Shelterin has evolved distinct solutions to protect telomeres from different aspects of the DNA damage response. These solutions include formation of t-loops, which can sequester the chromosome terminus from DNA-end sensors and inhibition of key steps in the DNA damage response. While blocking the DNA damage response at chromosome ends, telomeres make wide use of many of its players to deal with exogenous damage and replication stress. This review focuses on the interplay between the end-protection functions and the response to DNA damage occurring inside the telomeric repeats, as well as on the consequences that telomere damage has on telomere structure and function.
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Affiliation(s)
- Ylli Doksani
- IFOM, The FIRC Institute of Molecular Oncology, via Adamello 16, 20139 Milan, Italy.
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18
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Zhang Z, Zhang T, Ge Y, Tang M, Ma W, Zhang Q, Gong S, Wright WE, Shay J, Liu H, Zhao Y. 2D gel electrophoresis reveals dynamics of t-loop formation during the cell cycle and t-loop in maintenance regulated by heterochromatin state. J Biol Chem 2019; 294:6645-6656. [PMID: 30819801 DOI: 10.1074/jbc.ra119.007677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 02/20/2019] [Indexed: 12/15/2022] Open
Abstract
Linear chromosome ends are capped by telomeres that have been previously reported to adopt a t-loop structure. The lack of simple methods for detecting t-loops has hindered progress in understanding the dynamics of t-loop formation and its function in protecting chromosome ends. Here, we employed a classical two-dimensional agarose gel method (2D gel method) to innovatively apply to t-loop detection. Briefly, restriction fragments of genomic DNA were separated in a 2D gel, and the telomere sequence was detected by in-gel hybridization with telomeric probe. Using this method, we found that t-loops are present throughout the cell cycle, and t-loop formation tightly couples to telomere replication. We also observed that t-loop abundance positively correlates with chromatin condensation, i.e. cells with less compact telomeric chromatin (ALT cells and trichostatin A (TSA)-treated HeLa cells) exhibited fewer t-loops. Moreover, we observed that telomere dysfunction-induced foci, ALT-associated promyelocytic leukemia bodies, and telomere sister chromatid exchanges are activated upon TSA-induced loss of t-loops. These findings confirm the importance of the t-loop in protecting linear chromosomes from damage or illegitimate recombination.
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Affiliation(s)
- Zepeng Zhang
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Tianpeng Zhang
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yuanlong Ge
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Mengfan Tang
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Wenbin Ma
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Qinfen Zhang
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Shengzhao Gong
- Department of Chemical Engineering, Guangdong Industry Technical College, Guangzhou 510006, China
| | - Woodring E Wright
- the Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Jerry Shay
- the Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Haiying Liu
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China,
| | - Yong Zhao
- From the MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China,
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19
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Flamand L. Chromosomal Integration by Human Herpesviruses 6A and 6B. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1045:209-226. [PMID: 29896669 DOI: 10.1007/978-981-10-7230-7_10] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Upon infection and depending on the infected cell type, human herpesvirus 6A (HHV-6A) and 6B (HHV-6B) can replicate or enter a state of latency. HHV-6A and HHV-6B can integrate their genomes into host chromosomes as one way to establish latency. Viral integration takes place near the subtelomeric/telomeric junction of chromosomes. When HHV-6 infection and integration occur in gametes, the virus can be genetically transmitted. Inherited chromosomally integrated HHV-6 (iciHHV-6)-positive individuals carry one integrated HHV-6 copy per somatic cell. The prevalence of iciHHV-6+ individuals varies between 0.6% and 2%, depending on the geographical region sampled. In this chapter, the mechanisms leading to viral integration and reactivation from latency, as well as some of the biological and medical consequences associated with iciHHV-6, were discussed.
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Affiliation(s)
- Louis Flamand
- Division of Infectious and Immune Diseases, CHU de Québec Research Center, QC, Quebec, Canada. .,Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, Université Laval, QC, Quebec, Canada.
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20
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Greenwood J, Patel H, Cech TR, Cooper JP. Fission yeast telosomes: non-canonical histone-containing chromatin structures dependent on shelterin and RNA. Nucleic Acids Res 2018; 46:8865-8875. [PMID: 29992245 PMCID: PMC6158490 DOI: 10.1093/nar/gky605] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 05/25/2018] [Accepted: 06/25/2018] [Indexed: 12/16/2022] Open
Abstract
Despite the prime importance of telomeres in chromosome stability, significant mysteries surround the architecture of telomeric chromatin. Through micrococcal nuclease mapping, we show that fission yeast chromosome ends are assembled into distinct protected structures ('telosomes') encompassing the telomeric DNA repeats and over half a kilobase of subtelomeric DNA. Telosome formation depends on the conserved telomeric proteins Taz1 and Rap1, and surprisingly, RNA. Although yeast telomeres have long been thought to be free of histones, we show that this is not the case; telomere repeats contain histones. While telomeric histone H3 bears the heterochromatic lys9-methyl mark, we show that this mark is dispensable for telosome formation. Therefore, telomeric chromatin is organized at an architectural level, in which telomere-binding proteins and RNAs impose a unique nucleosome arrangement, and a second level, in which histone modifications are superimposed upon the higher order architecture.
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Affiliation(s)
- Jessica Greenwood
- Telomere Biology Laboratory, Cancer Research UK, London Research Institute, London, WC2A 3LY, UK
- Cell Cycle Lab, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Harshil Patel
- Bioinformatics and Biostatistics, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Thomas R Cech
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado, Boulder, CO 80309, USA
| | - Julia Promisel Cooper
- Telomere Biology Laboratory, Cancer Research UK, London Research Institute, London, WC2A 3LY, UK
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, BioFrontiers Institute, University of Colorado, Boulder, CO 80309, USA
- Telomere Biology Section, Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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21
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Van Ly D, Low RRJ, Frölich S, Bartolec TK, Kafer GR, Pickett HA, Gaus K, Cesare AJ. Telomere Loop Dynamics in Chromosome End Protection. Mol Cell 2018; 71:510-525.e6. [PMID: 30033372 DOI: 10.1016/j.molcel.2018.06.025] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/28/2018] [Accepted: 06/15/2018] [Indexed: 01/07/2023]
Abstract
Telomeres regulate DNA damage response (DDR) and DNA repair activity at chromosome ends. How telomere macromolecular structure contributes to ATM regulation and its potential dissociation from control over non-homologous end joining (NHEJ)-dependent telomere fusion is of central importance to telomere-dependent cell aging and tumor suppression. Using super-resolution microscopy, we identify that ATM activation at mammalian telomeres with reduced TRF2 or at human telomeres during mitotic arrest occurs specifically with a structural change from telomere loops (t-loops) to linearized telomeres. Additionally, we find the TRFH domain of TRF2 regulates t-loop formation while suppressing ATM activity. Notably, we demonstrate that ATM activation and telomere linearity occur separately from telomere fusion via NHEJ and that linear DDR-positive telomeres can remain resistant to fusion, even during an extended G1 arrest, when NHEJ is most active. Collectively, these results suggest t-loops act as conformational switches that specifically regulate ATM activation independent of telomere mechanisms to inhibit NHEJ.
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Affiliation(s)
- David Van Ly
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia; School of Medicine, The University of Notre Dame Australia, Sydney, NSW 2010, Australia
| | - Ronnie Ren Jie Low
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Sonja Frölich
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Tara K Bartolec
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Georgia R Kafer
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia; ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, NSW 2052, Australia
| | - Anthony J Cesare
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia.
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22
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Smith ED, Garza-Gongora AG, MacQuarrie KL, Kosak ST. Interstitial telomeric loops and implications of the interaction between TRF2 and lamin A/C. Differentiation 2018; 102:19-26. [PMID: 29979997 DOI: 10.1016/j.diff.2018.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 11/19/2022]
Abstract
The protein-DNA complexes that compose the end of mammalian chromosomes-telomeres-serve to stabilize linear genomic DNA and are involved in cellular and organismal aging. One mechanism that protects telomeres from premature degradation is the formation of structures called t-loops, in which the single-stranded 3' overhang present at the terminal end of telomeres loops back and invades medial double-stranded telomeric DNA. We identified looped structures formed between terminal chromosome ends and interstitial telomeric sequences (ITSs), which are found throughout the human genome, that we have termed interstitial telomeric loops (ITLs). While they form in a TRF2-dependent manner similar to t-loops, ITLs further require the physical interaction of TRF2 with the nuclear intermediate filament protein lamin A/C. Our findings suggest that interactions between telomeres and the nucleoskeleton broadly impact genomic integrity, including telomere stability, chromosome structure, and chromosome fragility. Here, we review the roles of TRF2 and lamin A/C in telomere biology and consider how their interaction may relate telomere homeostasis to cellular and organismal aging.
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Affiliation(s)
- Erica D Smith
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Arturo G Garza-Gongora
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Kyle L MacQuarrie
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA; Division of Hematology, Oncology and Stem Cell Transplantation, Ann & Robert H. Lurie Children's Hospital of Chicago, USA
| | - Steven T Kosak
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
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23
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Aljarbou F, Almousa N, Bazzi M, Aldaihan S, Alanazi M, Alharbi O, Almadi M, Aljebreen AM, Azzam NA, Arafa M, Aldbass A, Shaik J, Alasirri S, Warsy A, Alamri A, Parine NR, Alamro G. The expression of telomere-related proteins and DNA damage response and their association with telomere length in colorectal cancer in Saudi patients. PLoS One 2018; 13:e0197154. [PMID: 29870526 PMCID: PMC5988329 DOI: 10.1371/journal.pone.0197154] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 04/27/2018] [Indexed: 01/04/2023] Open
Abstract
Background Colorectal cancer is the leading cause of cancer-related deaths in Saudi Arabia. Cancer has a multifactorial nature and can be described as a disease of altered gene expression. The profiling of gene expression has been used to identify cancer subtypes and to predict patients’ responsiveness. Telomere-associated proteins that regulate telomere biology are essential molecules in cancer development. Thus, the present study examined their contributions to colorectal cancer progression in Saudi patients. Methods The expression of hTERT, TRF1, TRF2, POT1, ATR, ATM, Chk1 and Chk2 were measured via real-time PCR in matched cancerous and adjacent tissues of CRC patients. The protein level of hTERT, TRF1, TRF2, ATR, ATM, Chk1 and Chk2 were measured using immunohistochemistry. A region of hTERT core promoter was sequenced via Sanger sequencing. Methylation of CTCF binding site was examined via methylation-specific PCR. Finally, the length of telomere was estimated using q-PCR. Results Our results showed that POT1, ATR, Chk1 and Chk2 show increased expression in CRC relative to the adjacent mucosa. The expression levels of each gene were associated with clinicopathological characteristics of patients with CRC. There was a positive correlation between the age of the patients and hTERT expression. Regarding tumor site, telomere length, ATR, ATM and Chk1 were shown to be altered. No somatic mutation was detected in hTERT core promoter, and no differences in methylation patterns at CTCF binding site in the promoter between normal and cancer tissues. Conclusion Analysis of targeted genes expression in colorectal cancer based on the clinical variables revealed that tumor location and age could have a role in gene expression and telomere length variations and this could be taken under consideration during CRC diagnosis and therapy. Other epigenetic mechanisms could influence hTERT expression in cancers. Our findings warrant further validation through experiments involving a larger number of patients.
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Affiliation(s)
- Ftoon Aljarbou
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
- * E-mail:
| | - Nourah Almousa
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Bazzi
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Sooad Aldaihan
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Mohammed Alanazi
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Othman Alharbi
- Division of Gastroenterology, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - Majid Almadi
- Division of Gastroenterology, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - Abdulrahman M. Aljebreen
- Division of Gastroenterology, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - Nahla Ali Azzam
- Division of Gastroenterology, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
| | - Maha Arafa
- Department of Histopathology, King Saud University, King Khalid University Hospital, Riyadh, Saudi Arabia
| | - Abeer Aldbass
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Jilani Shaik
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Shaheerah Alasirri
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Arjumand Warsy
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Abdullah Alamri
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Narasimha Reddy Parine
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Ghadah Alamro
- Genome Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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24
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Lorenzi M, Bonassi S, Lorenzi T, Giovannini S, Bernabei R, Onder G. A review of telomere length in sarcopenia and frailty. Biogerontology 2018; 19:209-221. [PMID: 29549539 DOI: 10.1007/s10522-018-9749-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 02/23/2018] [Indexed: 12/16/2022]
Abstract
Sarcopenia and frailty are associated with several important health-related adverse events, including disability, loss of independence, institutionalization and mortality. Sarcopenia can be considered a biological substrate of frailty, and the prevalence of both these conditions progressively increases with age. Telomeres are nucleoprotein structures located at the end of linear chromosomes and implicated in cellular ageing, shorten with age, and are associated with various age-related diseases. In addition, telomere length (TL) is widely considered a molecular/cellular hallmark of the ageing process. This narrative review summarizes the knowledge about telomeres and analyzes for the first time a possible association of TL with sarcopenia and frailty. The overview provided by the present review suggests that leukocyte TL as single measurement, calculated by quantitative real-time polymerase chain reaction (qRT-PCR), cannot be considered a meaningful biological marker for complex, multidimensional age-related conditions, such as sarcopenia and frailty. Panels of biomarkers, including TL, may provide more accurate assessment and prediction of outcomes in these geriatric syndromes in elderly people.
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Affiliation(s)
- Maria Lorenzi
- Laboratory of Biogerontology, Department of Geriatrics, Neurosciences and Orthopedics, A. Gemelli Foundation, Catholic University of the Sacred Heart, School of Medicine, L.go F. Vito 1, 00168, Rome, Italy.
| | - Stefano Bonassi
- Unit of Clinical and Molecular Epidemiology, IRCCS San Raffaele Pisana, Via di Val Cannuta 247, 00166, Rome, Italy
| | - Teresa Lorenzi
- Department of Experimental and Clinical Medicine, Section of Neuroscience and Cell Biology, School of Medicine, Università Politecnica delle Marche, Via Tronto 10/A, 60020, Ancona, Italy
| | - Silvia Giovannini
- Laboratory of Biogerontology, Department of Geriatrics, Neurosciences and Orthopedics, A. Gemelli Foundation, Catholic University of the Sacred Heart, School of Medicine, L.go F. Vito 1, 00168, Rome, Italy
| | - Roberto Bernabei
- Department of Geriatrics, Neurosciences and Orthopedics, A. Gemelli Foundation, Catholic University of the Sacred Heart, School of Medicine, L.go F. Vito 1, 00168, Rome, Italy
| | - Graziano Onder
- Department of Geriatrics, Neurosciences and Orthopedics, A. Gemelli Foundation, Catholic University of the Sacred Heart, School of Medicine, L.go F. Vito 1, 00168, Rome, Italy
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25
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Telomerase activity is required for the telomere G-overhang structure in Trypanosoma brucei. Sci Rep 2017; 7:15983. [PMID: 29167542 PMCID: PMC5700094 DOI: 10.1038/s41598-017-16182-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 11/08/2017] [Indexed: 01/24/2023] Open
Abstract
Trypanosoma brucei causes fatal human African trypanosomiasis and evades the host immune response by regularly switching its major surface antigen, VSG, which is expressed exclusively from subtelomeric loci. Telomere length and telomere proteins play important roles in regulating VSG silencing and switching. T. brucei telomerase plays a key role in maintaining telomere length, and T. brucei telomeres terminate in a single-stranded 3′ G-rich overhang. Understanding the detailed structure of the telomere G-overhang and its maintenance will contribute greatly to better understanding telomere maintenance mechanisms. Using an optimized adaptor ligation assay, we found that most T. brucei telomere G-overhangs end in 5′ TTAGGG 3′, while a small portion of G-overhangs end in 5′ TAGGGT 3′. Additionally, the protein and the RNA components of the telomerase (TbTERT and TbTR) and TbKu are required for telomere G-overhangs that end in 5′ TTAGGG 3′ but do not significantly affect the 5′ TAGGGT 3′-ending overhangs, indicating that telomerase-mediated telomere synthesis is important for the telomere G-overhang structure. Furthermore, using telomere oligo ligation-mediated PCR, we showed for the first time that the T. brucei telomere 5′ end sequence – an important feature of the telomere terminal structure – is not random but preferentially 5′ CCTAAC 3′.
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Apte MS, Cooper JP. Life and cancer without telomerase: ALT and other strategies for making sure ends (don't) meet. Crit Rev Biochem Mol Biol 2016; 52:57-73. [PMID: 27892716 DOI: 10.1080/10409238.2016.1260090] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
While most cancer cells rely on telomerase expression/re-activation for linear chromosome maintenance and sustained proliferation, a significant population of cancers (10-15%) employs telomerase-independent strategies, collectively dubbed Alternative Lengthening of Telomeres (ALT). Most ALT cells relax the usual role of telomeres as inhibitors of local homologous recombination while maintaining the ability of telomeres to prohibit local non-homologous end joining reactions. Here we review current concepts surrounding how ALT telomeres achieve this new balance via alterations in chromatin landscape, DNA damage repair processes and handling of telomeric transcription. We also discuss telomerase independent end maintenance strategies utilized by other organisms, including fruitflies and yeasts, to draw parallels and contrasts and highlight additional modes, beyond ALT, that may be available to telomerase-minus cancers. We conclude by commenting on promises and challenges in the development of effective anti-ALT cancer therapies.
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Affiliation(s)
- Manasi S Apte
- a Laboratory of Biochemistry and Molecular Biology , Center for Cancer Research, National Cancer Institute, NIH , Bethesda , MD , USA
| | - Julia Promisel Cooper
- a Laboratory of Biochemistry and Molecular Biology , Center for Cancer Research, National Cancer Institute, NIH , Bethesda , MD , USA
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Konishi A, Izumi T, Shimizu S. TRF2 Protein Interacts with Core Histones to Stabilize Chromosome Ends. J Biol Chem 2016; 291:20798-810. [PMID: 27514743 PMCID: PMC5034068 DOI: 10.1074/jbc.m116.719021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 12/03/2022] Open
Abstract
Mammalian chromosome ends are protected by a specialized nucleoprotein complex called telomeres. Both shelterin, a telomere-specific multi-protein complex, and higher order telomeric chromatin structures combine to stabilize the chromosome ends. Here, we showed that TRF2, a component of shelterin, binds to core histones to protect chromosome ends from inappropriate DNA damage response and loss of telomeric DNA. The N-terminal Gly/Arg-rich domain (GAR domain) of TRF2 directly binds to the globular domain of core histones. The conserved arginine residues in the GAR domain of TRF2 are required for this interaction. A TRF2 mutant with these arginine residues substituted by alanine lost the ability to protect telomeres and induced rapid telomere shortening caused by the cleavage of a loop structure of the telomeric chromatin. These findings showed a previously unnoticed interaction between the shelterin complex and nucleosomal histones to stabilize the chromosome ends.
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Affiliation(s)
- Akimitsu Konishi
- From the Department of Pathological Cell Biology and Medical Top Track Program, Medical Research Institute, Tokyo Medical and Dental University, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan, the Department of Biochemistry, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan, and the Laboratory of Cell Biology and Genetics, The Rockefeller University, New York, New York 10065
| | - Takashi Izumi
- the Department of Biochemistry, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma 371-8511, Japan, and
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Hadj Salem I, Dubé J, Boulet LP, Chakir J. Telomere shortening correlates with accelerated replicative senescence of bronchial fibroblasts in asthma. Clin Exp Allergy 2016; 45:1713-5. [PMID: 26252159 DOI: 10.1111/cea.12611] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- I Hadj Salem
- Centre de recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - J Dubé
- CRC-CHUS et Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Québec, Canada
| | - L-P Boulet
- Centre de recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
| | - J Chakir
- Centre de recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada
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Wood AM, Laster K, Rice EL, Kosak ST. A beginning of the end: new insights into the functional organization of telomeres. Nucleus 2016; 6:172-8. [PMID: 25961132 PMCID: PMC4615733 DOI: 10.1080/19491034.2015.1048407] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ever since the first demonstration of their repetitive sequence and unique replication pathway, telomeres have beguiled researchers with how they function in protecting chromosome ends. Of course much has been learned over the years, and we now appreciate that telomeres are comprised of the multimeric protein/DNA shelterin complex and that the formation of t-loops provides protection from DNA damage machinery. Deriving their name from D-loops, t-loops are generated by the insertion of the 3′ overhang into telomeric repeats facilitated by the binding of TRF2. Recent studies have uncovered novel forms of chromosome end-structure that may implicate telomere organization in cellular processes beyond its essential role in telomere protection and homeostasis. In particular, we have recently described that t-loops form in a TRF2-dependent manner at interstitial telomere repeat sequences, which we termed interstitial telomere loops (ITLs). These structures are also dependent on association of lamin A/C, a canonical component of the nucleoskeleton that is mutated in myriad human diseases, including human segmental progeroid syndromes. Since ITLs are associated with telomere stability and require functional lamin A/C, our study suggests a mechanistic link between cellular aging (replicative senescence induced by telomere shortening) and organismal aging (modeled by Hutchinson Gilford Progeria Syndrome). Here we speculate on other potential ramifications of ITL formation, from gene expression to genome stability to chromosome structure.
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Affiliation(s)
- Ashley M Wood
- a Department of Cell and Molecular Biology; Feinberg School of Medicine; Northwestern University ; Chicago , IL , USA
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TRF2-RAP1 is required to protect telomeres from engaging in homologous recombination-mediated deletions and fusions. Nat Commun 2016; 7:10881. [PMID: 26941064 PMCID: PMC4785230 DOI: 10.1038/ncomms10881] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 01/29/2016] [Indexed: 12/27/2022] Open
Abstract
Repressor/activator protein 1 (RAP1) is a highly conserved telomere-interacting protein. Yeast Rap1 protects telomeres from non-homologous end joining (NHEJ), plays important roles in telomere length control and is involved in transcriptional gene regulation. However, a role for mammalian RAP1 in telomere end protection remains controversial. Here we present evidence that mammalian RAP1 is essential to protect telomere from homology directed repair (HDR) of telomeres. RAP1 cooperates with the basic domain of TRF2 (TRF2B) to repress PARP1 and SLX4 localization to telomeres. Without RAP1 and TRF2B, PARP1 and SLX4 HR factors promote rapid telomere resection, resulting in catastrophic telomere loss and the generation of telomere-free chromosome fusions in both mouse and human cells. The RAP1 Myb domain is required to repress both telomere loss and formation of telomere-free fusions. Our results highlight the importance of the RAP1-TRF2 heterodimer in protecting telomeres from inappropriate processing by the HDR pathway. While yeast Rap1 regulates telomere length and protects telomeres from non-homologous end joining, its role in higher eukaryotes is controversial. Here the authors present evidence that in mammals, RAP1 cooperates with TRF2 to prevent homologous recombination-mediated repair of telomeres.
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Zhou Z, Irudayaraj J. A native chromatin extraction method based on salicylic acid coated magnetic nanoparticles and characterization of chromatin. Analyst 2015; 140:938-44. [PMID: 25475154 DOI: 10.1039/c4an01897d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Native chromatin contains valuable genetic, epigenetic and structural information. Though DNA and nucleosome structures are well defined, less is known about the higher-order chromatin structure. Traditional chromatin extraction methods involve fixation, fragmentation and centrifugation, which might distort the higher-order structural information of native chromatin. We present a simple approach to isolate native chromatin from cultured mammalian cells using salicylic acid coated magnetic nanoparticles (SAMNPs). Chromatin is magnetically separated from cell lysates without any filtration or high-speed centrifugation. The purified chromatin is suitable for the examination of histone modifications and other chromatin associated proteins as confirmed by western blotting analysis. The structure of chromatin was determined by confocal fluorescence microscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM). High-resolution AFM and TEM images clearly show a classical bead-on-a-string structure. The higher-order chromatin structure is also determined via electron microscopy. Our method provides a simple, inexpensive and an environmentally friendly means to extract native chromatin not possible before, suitable for both biochemical and structural analysis.
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Affiliation(s)
- Zhongwu Zhou
- Bindley Bioscience Center and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA.
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Meyer JM, Rödelsperger C, Eichholz K, Tillmann U, Cembella A, McGaughran A, John U. Transcriptomic characterisation and genomic glimps into the toxigenic dinoflagellate Azadinium spinosum, with emphasis on polykeitde synthase genes. BMC Genomics 2015; 16:27. [PMID: 25612855 PMCID: PMC4316588 DOI: 10.1186/s12864-014-1205-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 12/24/2014] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Unicellular dinoflagellates are an important group of primary producers within the marine plankton community. Many of these species are capable of forming harmful algae blooms (HABs) and of producing potent phycotoxins, thereby causing deleterious impacts on their environment and posing a threat to human health. The recently discovered toxigenic dinoflagellate Azadinium spinosum is known to produce azaspiracid toxins. These toxins are most likely produced by polyketide synthases (PKS). Recently, PKS I-like transcripts have been identified in a number of dinoflagellate species. Despite the global distribution of A. spinosum, little is known about molecular features. In this study, we investigate the genomic and transcriptomic features of A. spinosum with a focus on polyketide synthesis and PKS evolution. RESULTS We identify orphan and homologous genes by comparing the transcriptome data of A. spinosum with a diverse set of 18 other dinoflagellates, five further species out of the Rhizaria Alveolate Stramelopile (RAS)-group, and one representative from the Plantae. The number of orphan genes in the analysed dinoflagellate species averaged 27%. In contrast, within the A. spinosum transcriptome, we discovered 12,661 orphan transcripts (18%). The dinoflagellates toxins known as azaspiracids (AZAs) are structurally polyethers; we therefore analyse the transcriptome of A. spinosum with respect to polyketide synthases (PKSs), the primary biosynthetic enzymes in polyketide synthesis. We find all the genes thought to be potentially essential for polyketide toxin synthesis to be expressed in A. spinosum, whose PKS transcripts fall into the dinoflagellate sub-clade in PKS evolution. CONCLUSIONS Overall, we demonstrate that the number of orphan genes in the A. spinosum genome is relatively small compared to other dinoflagellate species. In addition, all PKS domains needed to produce the azaspiracid carbon backbone are present in A. spinosum. Our study underscores the extraordinary evolution of such gene clusters and, in particular, supports the proposed structural and functional paradigm for PKS Type I genes in dinoflagellates.
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Affiliation(s)
- Jan M Meyer
- Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany. .,Evolutionary biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
| | - Christian Rödelsperger
- Evolutionary biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
| | - Karsten Eichholz
- Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany. .,Adenoviridae: Receptors, Trafficking and Vectorology, Institut de Génétique Moléculaire de Montpellier, Montpellier, France.
| | - Urban Tillmann
- Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
| | - Allan Cembella
- Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
| | - Angela McGaughran
- Evolutionary biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
| | - Uwe John
- Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
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Wood AM, Danielsen JMR, Lucas CA, Rice EL, Scalzo D, Shimi T, Goldman RD, Smith ED, Le Beau MM, Kosak ST. TRF2 and lamin A/C interact to facilitate the functional organization of chromosome ends. Nat Commun 2014; 5:5467. [PMID: 25399868 PMCID: PMC4235626 DOI: 10.1038/ncomms6467] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 10/03/2014] [Indexed: 12/28/2022] Open
Abstract
Telomeres protect the ends of linear genomes, and the gradual loss of telomeres is associated with cellular ageing. Telomere protection involves the insertion of the 3' overhang facilitated by telomere repeat-binding factor 2 (TRF2) into telomeric DNA, forming t-loops. We present evidence suggesting that t-loops can also form at interstitial telomeric sequences in a TRF2-dependent manner, forming an interstitial t-loop (ITL). We demonstrate that TRF2 association with interstitial telomeric sequences is stabilized by co-localization with A-type lamins (lamin A/C). We also find that lamin A/C interacts with TRF2 and that reduction in levels of lamin A/C or mutations in LMNA that cause an autosomal dominant premature ageing disorder--Hutchinson Gilford Progeria Syndrome (HGPS)-lead to reduced ITL formation and telomere loss. We propose that cellular and organismal ageing are intertwined through the effects of the interaction between TRF2 and lamin A/C on chromosome structure.
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Affiliation(s)
- Ashley M. Wood
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | | | - Catherine A. Lucas
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Ellen L. Rice
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - David Scalzo
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Takeshi Shimi
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Robert D. Goldman
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Erica D. Smith
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
| | - Michelle M. Le Beau
- Section of Hematology/Oncology, Department of Medicine and Comprehensive Cancer Center, The University of Chicago, Chicago, Illinois 60637, USA
| | - Steven T. Kosak
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA
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Kaufer BB, Flamand L. Chromosomally integrated HHV-6: impact on virus, cell and organismal biology. Curr Opin Virol 2014; 9:111-8. [PMID: 25462442 DOI: 10.1016/j.coviro.2014.09.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/24/2014] [Accepted: 09/25/2014] [Indexed: 11/16/2022]
Abstract
HHV-6 integrates its genome into telomeres of human chromosomes. Integration can occur in somatic cells or gametes, the latter leading to individuals harboring the HHV-6 genome in every cell. This condition is transmitted to descendants and referred to as inherited chromosomally integrated human herpesvirus 6 (iciHHV-6). Although integration can occur in different chromosomes, it invariably takes place in the telomere region. This integration mechanism represents a way to maintain the virus genome during latency, which is so far unique amongst human herpesviruses. Recent work provides evidence that the integrated HHV-6 genome can be mobilized from the host chromosome, resulting in the onset of disease. Details on required structural determinants, putative integration mechanisms and biological and medical consequences of iciHHV-6 are discussed.
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Affiliation(s)
| | - Louis Flamand
- Division of Infectious and Immune Diseases, CHU de Quebec, Research Center and Department of Microbiology-Infectious Diseases and Immunology, Université Laval, Quebec, Canada.
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35
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Fojtová M, Fajkus J. Epigenetic Regulation of Telomere Maintenance. Cytogenet Genome Res 2014; 143:125-35. [DOI: 10.1159/000360775] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Anton T, Bultmann S, Leonhardt H, Markaki Y. Visualization of specific DNA sequences in living mouse embryonic stem cells with a programmable fluorescent CRISPR/Cas system. Nucleus 2014; 5:163-72. [PMID: 24637835 PMCID: PMC4049922 DOI: 10.4161/nucl.28488] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Labeling and tracing of specific sequences in living cells has been a major challenge in studying the spatiotemporal dynamics of native chromatin. Here we repurposed the prokaryotic CRISPR/Cas adaptive immunity system to specifically detect endogenous genomic loci in mouse embryonic stem cells. We constructed a catalytically inactive version of the Cas9 endonuclease, fused it with eGFP (dCas9-eGFP) and co-expressed small guide RNAs (gRNAs) to target pericentric, centric, and telomeric repeats, which are enriched in distinct nuclear structures. With major satellite specific gRNAs we obtained a characteristic chromocenter (CC) pattern, while gRNAs targeting minor satellites and telomeres highlighted smaller foci coinciding with centromere protein B (CENP-B) and telomeric repeat-binding factor 2 (TRF2), respectively. DNA sequence specific labeling by gRNA/dCas9-eGFP complexes was directly shown with 3D-fluorescent in situ hybridization (3D-FISH). Structured illumination microscopy (3D-SIM) of gRNA/dCas9-eGFP expressing cells revealed chromatin ultrastructures and demonstrated the potential of this approach for chromatin conformation studies by super resolution microscopy. This programmable dCas9 labeling system opens new perspectives to study functional nuclear architecture.
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Affiliation(s)
- Tobias Anton
- Department of Biology II; Center for Integrated Protein Science Munich (CIPSM); Ludwig Maximilians University Munich; Planegg-Martinsried, Germany
| | - Sebastian Bultmann
- Department of Biology II; Center for Integrated Protein Science Munich (CIPSM); Ludwig Maximilians University Munich; Planegg-Martinsried, Germany
| | - Heinrich Leonhardt
- Department of Biology II; Center for Integrated Protein Science Munich (CIPSM); Ludwig Maximilians University Munich; Planegg-Martinsried, Germany
| | - Yolanda Markaki
- Department of Biology II; Center for Integrated Protein Science Munich (CIPSM); Ludwig Maximilians University Munich; Planegg-Martinsried, Germany
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Fulcher N, Derboven E, Valuchova S, Riha K. If the cap fits, wear it: an overview of telomeric structures over evolution. Cell Mol Life Sci 2014; 71:847-65. [PMID: 24042202 PMCID: PMC11113737 DOI: 10.1007/s00018-013-1469-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/16/2013] [Accepted: 08/30/2013] [Indexed: 10/26/2022]
Abstract
Genome organization into linear chromosomes likely represents an important evolutionary innovation that has permitted the development of the sexual life cycle; this process has consequently advanced nuclear expansion and increased complexity of eukaryotic genomes. Chromosome linearity, however, poses a major challenge to the internal cellular machinery. The need to efficiently recognize and repair DNA double-strand breaks that occur as a consequence of DNA damage presents a constant threat to native chromosome ends known as telomeres. In this review, we present a comparative survey of various solutions to the end protection problem, maintaining an emphasis on DNA structure. This begins with telomeric structures derived from a subset of prokaryotes, mitochondria, and viruses, and will progress into the typical telomere structure exhibited by higher organisms containing TTAGG-like tandem sequences. We next examine non-canonical telomeres from Drosophila melanogaster, which comprise arrays of retrotransposons. Finally, we discuss telomeric structures in evolution and possible switches between canonical and non-canonical solutions to chromosome end protection.
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Affiliation(s)
- Nick Fulcher
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Elisa Derboven
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Sona Valuchova
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
| | - Karel Riha
- Gregor Mendel Institute, Austrian Academy of Sciences, Dr. Bohrgasse 3, 1030 Vienna, Austria
- Central European Institute of Technology, Kamenice 753/5, Brno, Czech Republic
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Super-resolution fluorescence imaging of telomeres reveals TRF2-dependent T-loop formation. Cell 2013; 155:345-356. [PMID: 24120135 DOI: 10.1016/j.cell.2013.09.048] [Citation(s) in RCA: 329] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 08/27/2013] [Accepted: 09/03/2013] [Indexed: 01/13/2023]
Abstract
We have applied a super-resolution fluorescence imaging method, stochastic optical reconstruction microscopy (STORM), to visualize the structure of functional telomeres and telomeres rendered dysfunctional through removal of shelterin proteins. The STORM images showed that functional telomeres frequently exhibit a t-loop configuration. Conditional deletion of individual components of shelterin showed that TRF2 was required for the formation and/or maintenance of t-loops, whereas deletion of TRF1, Rap1, or the POT1 proteins (POT1a and POT1b) had no effect on the frequency of t-loop occurrence. Within the shelterin complex, TRF2 uniquely serves to protect telomeres from two pathways that are initiated on free DNA ends: classical nonhomologous end-joining (NHEJ) and ATM-dependent DNA damage signaling. The TRF2-dependent remodeling of telomeres into t-loop structures, which sequester the ends of chromosomes, can explain why NHEJ and the ATM signaling pathway are repressed when TRF2 is present.
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Abstract
In the 1960s, I developed methods for directly visualizing DNA and DNA-protein complexes using an electron microscope. This made it possible to examine the shape of DNA and to visualize proteins as they fold and loop DNA. Early applications included the first visualization of true nucleosomes and linkers and the demonstration that repeating tracts of adenines can cause a curvature in DNA. The binding of DNA repair proteins, including p53 and BRCA2, has been visualized at three- and four-way junctions in DNA. The trombone model of DNA replication was directly verified, and the looping of DNA at telomeres was discovered.
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Affiliation(s)
- Jack D Griffith
- From the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295
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40
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Affiliation(s)
- Agnel Sfeir
- The Helen L and Martin S Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA.
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Giraud-Panis MJ, Pisano S, Benarroch-Popivker D, Pei B, Le Du MH, Gilson E. One identity or more for telomeres? Front Oncol 2013; 3:48. [PMID: 23509004 PMCID: PMC3598436 DOI: 10.3389/fonc.2013.00048] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 02/23/2013] [Indexed: 12/19/2022] Open
Abstract
A major issue in telomere research is to understand how the integrity of chromosome ends is controlled. The fact that different types of nucleoprotein complexes have been described at the telomeres of different organisms raises the question of whether they have in common a structural identity that explains their role in chromosome protection. We will review here how telomeric nucleoprotein complexes are structured, comparing different organisms and trying to link these structures to telomere biology. It emerges that telomeres are formed by a complex and specific network of interactions between DNA, RNA, and proteins. The fact that these interactions and associated activities are reinforcing each other might help to guarantee the robustness of telomeric functions across the cell cycle and in the event of cellular perturbations. We will also discuss the recent notion that telomeres have evolved specific systems to overcome the DNA topological stress generated during their replication and transcription. This will lead to revisit the way we envisage the functioning of telomeric complexes since the regulation of topology is central to DNA stability, replication, recombination, and transcription as well as to chromosome higher-order organization.
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Affiliation(s)
- Marie-Josèphe Giraud-Panis
- Faculté de Médecine de Nice, Université de Nice-Sophia Antipolis, Institute for Research on Cancer and Aging Nice, UMR 7284 CNRS, U1081 INSERM Nice, France
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Galati A, Micheli E, Cacchione S. Chromatin structure in telomere dynamics. Front Oncol 2013; 3:46. [PMID: 23471416 PMCID: PMC3590461 DOI: 10.3389/fonc.2013.00046] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Accepted: 02/21/2013] [Indexed: 11/13/2022] Open
Abstract
The establishment of a specific nucleoprotein structure, the telomere, is required to ensure the protection of chromosome ends from being recognized as DNA damage sites. Telomere shortening below a critical length triggers a DNA damage response that leads to replicative senescence. In normal human somatic cells, characterized by telomere shortening with each cell division, telomere uncapping is a regulated process associated with cell turnover. Nevertheless, telomere dysfunction has also been associated with genomic instability, cell transformation, and cancer. Despite the essential role telomeres play in chromosome protection and in tumorigenesis, our knowledge of the chromatin structure involved in telomere maintenance is still limited. Here we review the recent findings on chromatin modifications associated with the dynamic changes of telomeres from protected to deprotected state and their role in telomere functions.
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Affiliation(s)
- Alessandra Galati
- Dipartimento di Biologia e Biotecnologie, Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza Università di Roma Rome, Italy
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Luke-Glaser S, Poschke H, Luke B. Getting in (and out of) the loop: regulating higher order telomere structures. Front Oncol 2012; 2:180. [PMID: 23226680 PMCID: PMC3510458 DOI: 10.3389/fonc.2012.00180] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 11/09/2012] [Indexed: 11/26/2022] Open
Abstract
The DNA at the ends of linear chromosomes (the telomere) folds back onto itself and forms an intramolecular lariat-like structure. Although the telomere loop has been implicated in the protection of chromosome ends from nuclease-mediated resection and unscheduled DNA repair activities, it potentially poses an obstacle to the DNA replication machinery during S-phase. Therefore, the coordinated regulation of telomere loop formation, maintenance, and resolution is required in order to establish a balance between protecting the chromosome ends and promoting their duplication prior to cell division. Until recently, the only factor known to influence telomere looping in human cells was TRF2, a component of the shelterin complex. Recent work in yeast and mouse cells has uncovered additional regulatory factors that affect the loop structure at telomeres. In the following “perspective” we outline what is known about telomere looping and highlight the latest results regarding the regulation of this chromosome end structure. We speculate about how the manipulation of the telomere loop may have therapeutic implications in terms of diseases associated with telomere dysfunction and uncontrolled proliferation.
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Affiliation(s)
- Sarah Luke-Glaser
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Allianz Heidelberg, Germany
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Xu L, Li S, Stohr BA. The role of telomere biology in cancer. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2012; 8:49-78. [PMID: 22934675 DOI: 10.1146/annurev-pathol-020712-164030] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Telomere biology plays a critical and complex role in the initiation and progression of cancer. Although telomere dysfunction resulting from replicative attrition constrains tumor growth by engaging DNA-damage signaling pathways, it can also promote tumorigenesis by causing oncogenic chromosomal rearrangements. Expression of the telomerase enzyme enables telomere-length homeostasis and allows tumor cells to escape the antiproliferative barrier posed by short telomeres. Telomeres and telomerase also function independently of one another. Recent work has suggested that telomerase promotes cell growth through pathways unrelated to telomere maintenance, and a subset of tumors elongate telomeres through telomerase-independent mechanisms. In an effort to exploit the integral link between telomere biology and cancer growth, investigators have developed several telomerase-based therapeutic strategies, which are currently in clinical trials. Here, we broadly review the state of the field with a particular focus on recent developments of interest.
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Affiliation(s)
- Lifeng Xu
- Department of Microbiology, University of California-Davis, CA 95616, USA
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Choi YH, Lim JK, Jeong MW, Kim KT. HnRNP A1 phosphorylated by VRK1 stimulates telomerase and its binding to telomeric DNA sequence. Nucleic Acids Res 2012; 40:8499-518. [PMID: 22740652 PMCID: PMC3458570 DOI: 10.1093/nar/gks634] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The telomere integrity is maintained via replication machinery, telomere associated proteins and telomerase. Many telomere associated proteins are regulated in a cell cycle-dependent manner. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), a single-stranded oligonucleotide binding protein, is thought to play a pivotal role in telomere maintenance. Here, we identified hnRNP A1 as a novel substrate for vaccinia-related kinase 1 (VRK1), a cell cycle regulating kinase. Phosphorylation by VRK1 potentiates the binding of hnRNP A1 to telomeric ssDNA and telomerase RNA in vitro and enhances its function for telomerase reaction. VRK1 deficiency induces a shortening of telomeres with an abnormal telomere arrangement and activation of DNA-damage signaling in mouse male germ cells. Together, our data suggest that VRK1 is required for telomere maintenance via phosphorylation of hnRNP A1, which regulates proteins associated with the telomere and telomerase RNA.
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Affiliation(s)
- Yoon Ha Choi
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology (POSTECH), San-31, Hyoja-Dong, Pohang 790-784, Republic of Korea
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Galati A, Magdinier F, Colasanti V, Bauwens S, Pinte S, Ricordy R, Giraud-Panis MJ, Pusch MC, Savino M, Cacchione S, Gilson E. TRF2 controls telomeric nucleosome organization in a cell cycle phase-dependent manner. PLoS One 2012; 7:e34386. [PMID: 22536324 PMCID: PMC3335031 DOI: 10.1371/journal.pone.0034386] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 02/27/2012] [Indexed: 01/12/2023] Open
Abstract
Mammalian telomeres stabilize chromosome ends as a result of their assembly into a peculiar form of chromatin comprising a complex of non-histone proteins named shelterin. TRF2, one of the shelterin components, binds to the duplex part of telomeric DNA and is essential to fold the telomeric chromatin into a protective cap. Although most of the human telomeric DNA is organized into tightly spaced nucleosomes, their role in telomere protection and how they interplay with telomere-specific factors in telomere organization is still unclear. In this study we investigated whether TRF2 can regulate nucleosome assembly at telomeres. By means of chromatin immunoprecipitation (ChIP) and Micrococcal Nuclease (MNase) mapping assay, we found that the density of telomeric nucleosomes in human cells was inversely proportional to the dosage of TRF2 at telomeres. This effect was not observed in the G1 phase of the cell cycle but appeared coincident of late or post-replicative events. Moreover, we showed that TRF2 overexpression altered nucleosome spacing at telomeres increasing internucleosomal distance. By means of an in vitro nucleosome assembly system containing purified histones and remodeling factors, we reproduced the short nucleosome spacing found in telomeric chromatin. Importantly, when in vitro assembly was performed in the presence of purified TRF2, nucleosome spacing on a telomeric DNA template increased, in agreement with in vivo MNase mapping. Our results demonstrate that TRF2 negatively regulates the number of nucleosomes at human telomeres by a cell cycle-dependent mechanism that alters internucleosomal distance. These findings raise the intriguing possibility that telomere protection is mediated, at least in part, by the TRF2-dependent regulation of nucleosome organization.
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Affiliation(s)
- Alessandra Galati
- Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Roma, Italy
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Frédérique Magdinier
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Valentina Colasanti
- Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Roma, Italy
| | - Serge Bauwens
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Sébastien Pinte
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
| | - Ruggero Ricordy
- Istituto di Biologia e Patologia Molecolari del CNR, Roma, Italy
| | - Marie-Josèphe Giraud-Panis
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
- Institute for Research on Cancer and Aging in Nice (IRCAN), UMR 7284 CNRS U1081 INSERM 28 Faculté de Médecine, University of Nice, Nice, France
| | - Miriam Caroline Pusch
- Adolf-Butenandt-Institut, Molekularbiologie, Ludwig-Maximilians-Universität, München, Germany
| | - Maria Savino
- Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Roma, Italy
- Istituto di Biologia e Patologia Molecolari del CNR, Roma, Italy
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Roma, Italy
| | - Stefano Cacchione
- Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Roma, Italy
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Roma, Italy
- * E-mail: (SC); (EG)
| | - Eric Gilson
- Laboratoire de Biologie Moléculaire de la cellule, Université de Lyon, CNRS UMR5239, Ecole Normale Supérieure de Lyon, Lyon, France
- Institute for Research on Cancer and Aging in Nice (IRCAN), UMR 7284 CNRS U1081 INSERM 28 Faculté de Médecine, University of Nice, Nice, France
- Department of Medical Genetics, Archet 2 Hospital, CHU of Nice, Nice, France
- * E-mail: (SC); (EG)
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Telomeres and the nucleus. Semin Cancer Biol 2012; 23:116-24. [PMID: 22330096 DOI: 10.1016/j.semcancer.2012.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 02/01/2012] [Accepted: 02/02/2012] [Indexed: 01/08/2023]
Abstract
Telomeres are crucial for the maintenance of genome stability through "capping" of chromosome ends to prevent their recognition as double-strand breaks, thus avoiding end-to-end fusions or illegitimate recombination [1-3]. Similar to other genomic regions, telomeres participate to the nuclear architecture while being highly mobile. The interaction of telomeres with nuclear domains or compartments greatly differs not only between organisms but also between cells within the same organism. It is also expected that biological processes like replication, repair or telomere elongation impact the distribution of chromosome extremities within the nucleus, as they probably do with other regions of the genome. Pathological processes such as cancer induce profound changes in the nuclear architecture, which also affects telomere dynamics and spatial organization. Here we will expose our present knowledge on the relationship between telomeres and nuclear architecture and on how this relationship is affected by normal or abnormal telomere metabolisms.
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Abstract
Telomeres, the nucleoprotein "caps" protecting the ends of linear chromosomes, are maintained by telomerase. Telomeres have important roles in maintaining genomic stability and preventing senescence or oncogenesis. Chicken is a classical model animal for genetic and developmental studies. With further development of chicken genomics, great progress has been made in research of chicken telomere and telomerase. This review describes recent advances and future research directions in chicken telomere biology.
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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] [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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D'Souza Y, Lauzon C, Chu TW, Autexier C. Regulation of telomere length and homeostasis by telomerase enzyme processivity. J Cell Sci 2012. [PMID: 23178942 DOI: 10.1242/jcs.119297] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Telomerase is a ribonucleoprotein consisting of a catalytic subunit, the telomerase reverse transcriptase, TERT, and an integrally associated RNA, TR, which contains a template for the synthesis of short repetitive G-rich DNA sequences at the ends of telomeres. Telomerase can repetitively reverse transcribe its short RNA template, acting processively to add multiple telomeric repeats onto the same DNA substrate. The contribution of enzyme processivity to telomere length regulation in human cells is not well characterized. In cancer cells, under homeostatic telomere length-maintenance conditions, telomerase acts processively, while under nonequilibrium conditions, telomerase acts distributively on the shortest telomeres. To investigate the role of increased telomerase processivity on telomere length regulation in human cells with limited lifespan that are dependent on human TERT (hTERT) for lifespan extension and immortalization, we mutated the leucine at position 866 in the reverse transcriptase C motif of hTERT to a tyrosine (L866Y), which is the amino acid found at a similar position in HIV-1 reverse transcriptase. We report that, similar to the previously reported ‘gain of function’ Tetrahymena telomerase mutant (L813Y), the human telomerase variant displays increased processivity. hTERT-L866Y, like wild-type hTERT can immortalize and extend the lifespan of limited lifespan cells. Moreover, hTERT-L866Y expressing cells display heterogenous telomere lengths, telomere elongation, multiple telomeric signals indicative of fragile sites and replicative stress, and an increase in short telomeres, which is accompanied by telomere trimming events. Our results suggest that telomere length and homeostasis in human cells may be regulated by telomerase enzyme processivity.
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Affiliation(s)
- Yasmin D'Souza
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montréal, Québec H3A 2B2, Canada
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