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Hinchie AM, Sanford SL, Loughridge KE, Sutton RM, Parikh AH, Gil Silva AA, Sullivan DI, Chun-On P, Morrell MR, McDyer JF, Opresko PL, Alder JK. A persistent variant telomere sequence in a human pedigree. Nat Commun 2024; 15:4681. [PMID: 38824190 PMCID: PMC11144197 DOI: 10.1038/s41467-024-49072-9] [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: 01/20/2024] [Accepted: 05/22/2024] [Indexed: 06/03/2024] Open
Abstract
The telomere sequence, TTAGGG, is conserved across all vertebrates and plays an essential role in suppressing the DNA damage response by binding a set of proteins termed shelterin. Changes in the telomere sequence impair shelterin binding, initiate a DNA damage response, and are toxic to cells. Here we identify a family with a variant in the telomere template sequence of telomerase, the enzyme responsible for telomere elongation, that led to a non-canonical telomere sequence. The variant is inherited across at least one generation and one family member reports no significant medical concerns despite ~9% of their telomeres converting to the novel sequence. The variant template disrupts telomerase repeat addition processivity and decreased the binding of the telomere-binding protein POT1. Despite these disruptions, the sequence is readily incorporated into cellular chromosomes. Incorporation of a variant sequence prevents POT1-mediated inhibition of telomerase suggesting that incorporation of a variant sequence may influence telomere addition. These findings demonstrate that telomeres can tolerate substantial degeneracy while remaining functional and provide insights as to how incorporation of a non-canonical telomere sequence might alter telomere length dynamics.
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Affiliation(s)
- Angela M Hinchie
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Samantha L Sanford
- Environmental and Occupational Health Department, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
- University of Pittsburgh Medical Center, Hillman Cancer Center, Pittsburgh, PA, USA
| | - Kelly E Loughridge
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Rachel M Sutton
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Anishka H Parikh
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Agustin A Gil Silva
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Daniel I Sullivan
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Pattra Chun-On
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Matthew R Morrell
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - John F McDyer
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Patricia L Opresko
- Environmental and Occupational Health Department, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
- University of Pittsburgh Medical Center, Hillman Cancer Center, Pittsburgh, PA, USA
- Pharmacology and Chemical Biology Department, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jonathan K Alder
- Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease, University of Pittsburgh, Pittsburgh, PA, USA.
- Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
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2
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Liu Y, Betori RC, Pagacz J, Frost GB, Efimova EV, Wu D, Wolfgeher DJ, Bryan TM, Cohen SB, Scheidt KA, Kron SJ. Targeting telomerase reverse transcriptase with the covalent inhibitor NU-1 confers immunogenic radiation sensitization. Cell Chem Biol 2022; 29:1517-1531.e7. [PMID: 36206753 PMCID: PMC9588800 DOI: 10.1016/j.chembiol.2022.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 07/29/2022] [Accepted: 09/15/2022] [Indexed: 11/03/2022]
Abstract
Beyond synthesizing telomere repeats, the telomerase reverse transcriptase (TERT) also serves multiple other roles supporting cancer growth. Blocking telomerase to drive telomere erosion appears impractical, but TERT's non-canonical activities have yet to be fully explored as cancer targets. Here, we used an irreversible TERT inhibitor, NU-1, to examine impacts on resistance to conventional cancer therapies. In vitro, inhibiting TERT sensitized cells to chemotherapy and radiation. NU-1 delayed repair of double-strand breaks, resulting in persistent DNA damage signaling and cellular senescence. Although NU-1 alone did not impact growth of syngeneic CT26 tumors in BALB/c mice, it dramatically enhanced the effects of radiation, leading to immune-dependent tumor elimination. Tumors displayed persistent DNA damage, suppressed proliferation, and increased activated immune infiltrate. Our studies confirm TERT's role in limiting genotoxic effects of conventional therapy but also implicate TERT as a determinant of immune evasion and therapy resistance.
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Affiliation(s)
- Yue Liu
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Rick C Betori
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Joanna Pagacz
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Grant B Frost
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Elena V Efimova
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Ding Wu
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Donald J Wolfgeher
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Tracy M Bryan
- Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Scott B Cohen
- Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Karl A Scheidt
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
| | - Stephen J Kron
- Ludwig Center for Metastasis Research and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
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3
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Vanderwaeren L, Dok R, Voordeckers K, Nuyts S, Verstrepen KJ. Saccharomyces cerevisiae as a Model System for Eukaryotic Cell Biology, from Cell Cycle Control to DNA Damage Response. Int J Mol Sci 2022; 23:11665. [PMID: 36232965 PMCID: PMC9570374 DOI: 10.3390/ijms231911665] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/26/2022] [Accepted: 09/28/2022] [Indexed: 11/08/2022] Open
Abstract
The yeast Saccharomyces cerevisiae has been used for bread making and beer brewing for thousands of years. In addition, its ease of manipulation, well-annotated genome, expansive molecular toolbox, and its strong conservation of basic eukaryotic biology also make it a prime model for eukaryotic cell biology and genetics. In this review, we discuss the characteristics that made yeast such an extensively used model organism and specifically focus on the DNA damage response pathway as a prime example of how research in S. cerevisiae helped elucidate a highly conserved biological process. In addition, we also highlight differences in the DNA damage response of S. cerevisiae and humans and discuss the challenges of using S. cerevisiae as a model system.
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Affiliation(s)
- Laura Vanderwaeren
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
| | - Rüveyda Dok
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Karin Voordeckers
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
| | - Sandra Nuyts
- Laboratory of Experimental Radiotherapy, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
- Department of Radiation Oncology, Leuven Cancer Institute, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Kevin J. Verstrepen
- Laboratory of Genetics and Genomics, Centre for Microbial and Plant Genetics, Department M2S, KU Leuven, 3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB-KU Leuven Center for Microbiology, 3001 Leuven, Belgium
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4
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Sharaf R, Frampton GM, Albacker LA. Mutations in the TERC template sequence can be incorporated into the telomeres of human tumors. PLoS One 2022; 17:e0272707. [PMID: 36006930 PMCID: PMC9409504 DOI: 10.1371/journal.pone.0272707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 07/25/2022] [Indexed: 11/29/2022] Open
Abstract
Telomerase-mediated lengthening is a mechanism by which some cancer cells avoid senescence-mediated cell cycle arrest due to shortened telomeres. By reverse transcribing an RNA template, encoded by TERC, the enzyme telomerase synthesizes the elongation of telomeric DNA using the 3’ end of the chromosome as a primer. TERC harbors a highly conserved template region consisting of 11 nucleotides spanning hg19 coordinates chr3:169482793–169482803. In human cell lines, when TERC was mutated to alter its template region, telomerase generated the predicted mutant telomeric repeats. However, it is unknown if this can occur in human clinical samples. Here, we report on the rare occurrence of two tumor samples where TERC template mutations were reflected in telomeric repeats.
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Affiliation(s)
- Radwa Sharaf
- Foundation Medicine Inc., Cambridge, MA, United States of America
| | | | - Lee A. Albacker
- Foundation Medicine Inc., Cambridge, MA, United States of America
- * E-mail:
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5
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6
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Xu C, Xie N, Su Y, Sun Z, Liang Y, Zhang N, Liu D, Jia S, Xing X, Han L, Li G, Tong T, Chen J. HnRNP F/H associate with hTERC and telomerase holoenzyme to modulate telomerase function and promote cell proliferation. Cell Death Differ 2019; 27:1998-2013. [PMID: 31863069 PMCID: PMC7244589 DOI: 10.1038/s41418-019-0483-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 12/09/2019] [Accepted: 12/10/2019] [Indexed: 12/16/2022] Open
Abstract
Human telomerase RNA component hTERC comprises multiple motifs that contribute to hTERC biogenesis, holoenzyme activity, and enzyme recruitment to telomeres. hTERC contains several guanine tracts (G-tracts) at its 5′-end, but its associated proteins and potential roles in telomerase function are still poorly understood. The heterogeneous nuclear ribonucleoproteins F, H1, and H2 (hnRNP F/H) are splicing factors that preferentially bind to poly(G)-rich sequences RNA. Here, we demonstrate that hnRNP F/H associate with both hTERC and telomerase holoenzyme to regulate telomerase activity. We reveal hnRNP F/H bind to the 5′-end region of hTERC in vitro and in vivo, and identify the first three G-tracts of hTERC and qRRM1 domain of hnRNP F/H are required for their interaction. Furthermore, hnRNP F/H also directly interact with telomerase holoenzyme. Functionally, we show that hnRNP F/H plays important roles in modulating telomerase activity and telomere length. Moreover, hnRNP F/H deletion greatly impair cancer and stem cell proliferation, and induce stem cell senescence, while hnRNP F/H overexpression delay stem cell senescence. Collectively, our findings unveil a novel role of hnRNP F/H as the binding partners of hTERC and telomerase holoenzyme to regulate telomerase function.
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Affiliation(s)
- Chenzhong Xu
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Nan Xie
- Department of Physiology and Pathophysiology, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Yuanyuan Su
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Zhaomeng Sun
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Yao Liang
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Na Zhang
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Doudou Liu
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Shuqin Jia
- Department of Molecular Diagnostics, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Cancer Hospital & Institute, Beijing, 100142, China
| | - Xiaofang Xing
- Department of Molecular Diagnostics, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Cancer Hospital & Institute, Beijing, 100142, China
| | - Limin Han
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Guodong Li
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Tanjun Tong
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China
| | - Jun Chen
- Peking University Research Center on Aging, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, Department of Biochemistry and Molecular Biology, Department of Integration of Chinese and Western Medicine, School of Basic Medical Science, Peking University, Beijing, 100191, China.
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7
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Alexiou A, Chatzichronis S, Perveen A, Hafeez A, Ashraf GM. Algorithmic and Stochastic Representations of Gene Regulatory Networks and Protein-Protein Interactions. Curr Top Med Chem 2019; 19:413-425. [PMID: 30854971 DOI: 10.2174/1568026619666190311125256] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/15/2018] [Accepted: 12/26/2018] [Indexed: 02/06/2023]
Abstract
BACKGROUND Latest studies reveal the importance of Protein-Protein interactions on physiologic functions and biological structures. Several stochastic and algorithmic methods have been published until now, for the modeling of the complex nature of the biological systems. OBJECTIVE Biological Networks computational modeling is still a challenging task. The formulation of the complex cellular interactions is a research field of great interest. In this review paper, several computational methods for the modeling of GRN and PPI are presented analytically. METHODS Several well-known GRN and PPI models are presented and discussed in this review study such as: Graphs representation, Boolean Networks, Generalized Logical Networks, Bayesian Networks, Relevance Networks, Graphical Gaussian models, Weight Matrices, Reverse Engineering Approach, Evolutionary Algorithms, Forward Modeling Approach, Deterministic models, Static models, Hybrid models, Stochastic models, Petri Nets, BioAmbients calculus and Differential Equations. RESULTS GRN and PPI methods have been already applied in various clinical processes with potential positive results, establishing promising diagnostic tools. CONCLUSION In literature many stochastic algorithms are focused in the simulation, analysis and visualization of the various biological networks and their dynamics interactions, which are referred and described in depth in this review paper.
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Affiliation(s)
| | | | - Asma Perveen
- Glocal School of Life Sciences, Glocal University, Mirzapur Pole, Saharanpur, Uttar Pradesh, India
| | - Abdul Hafeez
- Glocal School of Pharmacy, Glocal University, Mirzapur Pole, Saharanpur, Uttar Pradesh, India
| | - Ghulam Md. Ashraf
- King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia
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8
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Srivastava P, Hira SK, Sharma A, Kashif M, Srivastava P, Srivastava DN, Singh RA, Manna PP. Telomerase Responsive Delivery of Doxorubicin from Mesoporous Silica Nanoparticles in Multiple Malignancies: Therapeutic Efficacies against Experimental Aggressive Murine Lymphoma. Bioconjug Chem 2018; 29:2107-2119. [DOI: 10.1021/acs.bioconjchem.8b00342] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Sumit Kumar Hira
- Department of Zoology, The University of Burdwan, Purba Bardhhaman-713104, India
| | - Amod Sharma
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal-462 066, India
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9
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Wu Q, Liu Z, Su L, Han G, Liu R, Zhao J, Zhao T, Jiang C, Zhang Z. Sticky-flares for in situ monitoring of human telomerase RNA in living cells. NANOSCALE 2018; 10:9386-9392. [PMID: 29740658 DOI: 10.1039/c8nr01260a] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Human telomerase RNA (hTR), a template of telomerase for telomeric repeat synthesis, was used to reflect the telomerase activity and act as a potential target of antitumor therapy. Here, we report a novel DNA-conjugated AuNP probe termed sticky-flares for the in situ detection of intracellular human telomerase RNA. The sticky-flares probe is capable of entering living cells directly without any auxiliary and recognizing the binding domain of human telomerase RNA. On recognition, the fluorophore-modified recognition flares can specifically bind to the target, separate from the sticky-flares and act as a fluorescent reporter to quantify and dynamically profile human telomerase RNA in living cells. We envision that the sticky-flares probe would be a valuable platform to investigate the function and regulation of hTR in antitumor therapy and hTR-related drug invention.
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Affiliation(s)
- Qilong Wu
- Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
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10
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Telomeres: Implications for Cancer Development. Int J Mol Sci 2018; 19:ijms19010294. [PMID: 29351238 PMCID: PMC5796239 DOI: 10.3390/ijms19010294] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/12/2018] [Accepted: 01/16/2018] [Indexed: 12/31/2022] Open
Abstract
Telomeres facilitate the protection of natural ends of chromosomes from constitutive exposure to the DNA damage response (DDR). This is most likely achieved by a lariat structure that hides the linear telomeric DNA through protein-protein and protein-DNA interactions. The telomere shortening associated with DNA replication in the absence of a compensatory mechanism culminates in unmasked telomeres. Then, the subsequent activation of the DDR will define the fate of cells according to the functionality of cell cycle checkpoints. Dysfunctional telomeres can suppress cancer development by engaging replicative senescence or apoptotic pathways, but they can also promote tumour initiation. Studies in telomere dynamics and karyotype analysis underpin telomere crisis as a key event driving genomic instability. Significant attainment of telomerase or alternative lengthening of telomeres (ALT)-pathway to maintain telomere length may be permissive and required for clonal evolution of genomically-unstable cells during progression to malignancy. We summarise current knowledge of the role of telomeres in the maintenance of chromosomal stability and carcinogenesis.
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11
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Mild Telomere Dysfunction as a Force for Altering the Adaptive Potential of Subtelomeric Genes. Genetics 2017; 208:537-548. [PMID: 29242289 DOI: 10.1534/genetics.117.300607] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/08/2017] [Indexed: 11/18/2022] Open
Abstract
Subtelomeric regions have several unusual characteristics, including complex repetitive structures, increased rates of evolution, and enrichment for genes involved in niche adaptation. The adaptive telomere failure hypothesis suggests that certain environmental stresses can induce a low level of telomere failure, potentially leading to elevated subtelomeric recombination that could result in adaptive mutational changes within subtelomeric genes. Here, we tested a key prediction of the adaptive telomere failure hypothesis-that telomere dysfunction mild enough to have little or no overall effect on cell fitness could still lead to substantial increases in the mutation rates of subtelomeric genes. Our results show that a mutant of Kluyveromyces lactis with stably short telomeres produced a large increase in the frequency of mutations affecting the native subtelomeric β-galactosidase (LAC4) gene. All lac4 mutants examined from strains with severe telomere dysfunction underwent terminal deletion/duplication events consistent with being due to break-induced replication. In contrast, although cells with mild telomere dysfunction also exhibited similar terminal deletion and duplication events, up to 50% of lac4 mutants from this background unexpectedly contained base changes within the LAC4 coding region. This mutational bias for producing base changes demonstrates that mild telomere dysfunction can be well suited as a force for altering the adaptive potential of subtelomeric genes.
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12
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Telomeres and Telomerase: Role in Marek's Disease Virus Pathogenesis, Integration and Tumorigenesis. Viruses 2017; 9:v9070173. [PMID: 28677643 PMCID: PMC5537665 DOI: 10.3390/v9070173] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 06/15/2017] [Accepted: 06/26/2017] [Indexed: 12/21/2022] Open
Abstract
Telomeres protect the ends of vertebrate chromosomes from deterioration and consist of tandem nucleotide repeats (TTAGGG)n that are associated with a number of proteins. Shortening of the telomeres occurs during genome replication, thereby limiting the replication potential of somatic cells. To counteract this shortening, vertebrates encode the telomerase complex that maintains telomere length in certain cell types via de novo addition of telomeric repeats. Several herpesviruses, including the highly oncogenic alphaherpesvirus Marek's disease virus (MDV), harbor telomeric repeats (TMR) identical to the host telomere sequences at the ends of their linear genomes. These TMR facilitate the integration of the MDV genome into host telomeres during latency, allowing the virus to persist in the host for life. Integration into host telomeres is critical for disease and tumor induction by MDV, but also enables efficient reactivation of the integrated virus genome. In addition to the TMR, MDV also encodes a telomerase RNA subunit (vTR) that shares 88% sequence identity with the telomerase RNA in chicken (chTR). vTR is highly expressed during all stages of the virus lifecycle, enhances telomerase activity and plays an important role in MDV-induced tumor formation. This review will focus on the recent advances in understanding the role of viral TMR and vTR in MDV pathogenesis, integration and tumorigenesis.
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13
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Martin WJ, Reiter NJ. Structural Roles of Noncoding RNAs in the Heart of Enzymatic Complexes. Biochemistry 2016; 56:3-13. [PMID: 27935277 DOI: 10.1021/acs.biochem.6b01106] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Over billions of years of evolution, nature has embraced proteins as the major workhorse molecules of the cell. However, nearly every aspect of metabolism is dependent upon how structured RNAs interact with proteins, ligands, and other nucleic acids. Key processes, including telomere maintenance, RNA processing, and protein synthesis, require large RNAs that assemble into elaborate three-dimensional shapes. These RNAs can (i) act as flexible scaffolds for protein subunits, (ii) participate directly in substrate recognition, and (iii) serve as catalytic components. Here, we juxtapose the near atomic level interactions of three ribonucleoprotein complexes: ribonuclease P (involved in 5' pre-tRNA processing), the spliceosome (responsible for pre-mRNA splicing), and telomerase (an RNA-directed DNA polymerase that extends the ends of chromosomes). The focus of this perspective is profiling the structural and dynamic roles of RNAs at the core of these enzymes, highlighting how large RNAs contribute to molecular recognition and catalysis.
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Affiliation(s)
- William J Martin
- Department of Biochemistry, Vanderbilt University , Nashville, Tennessee 37232, United States
| | - Nicholas J Reiter
- Department of Biochemistry, Vanderbilt University , Nashville, Tennessee 37232, United States
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14
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Bilsland AE, Pugliese A, Liu Y, Revie J, Burns S, McCormick C, Cairney CJ, Bower J, Drysdale M, Narita M, Sadaie M, Keith WN. Identification of a Selective G1-Phase Benzimidazolone Inhibitor by a Senescence-Targeted Virtual Screen Using Artificial Neural Networks. Neoplasia 2015; 17:704-715. [PMID: 26476078 PMCID: PMC4611071 DOI: 10.1016/j.neo.2015.08.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 08/28/2015] [Accepted: 08/31/2015] [Indexed: 12/29/2022]
Abstract
Cellular senescence is a barrier to tumorigenesis in normal cells, and tumor cells undergo senescence responses to genotoxic stimuli, which is a potential target phenotype for cancer therapy. However, in this setting, mixed-mode responses are common with apoptosis the dominant effect. Hence, more selective senescence inducers are required. Here we report a machine learning-based in silico screen to identify potential senescence agonists. We built profiles of differentially affected biological process networks from expression data obtained under induced telomere dysfunction conditions in colorectal cancer cells and matched these to a panel of 17 protein targets with confirmatory screening data in PubChem. We trained a neural network using 3517 compounds identified as active or inactive against these targets. The resulting classification model was used to screen a virtual library of ~2M lead-like compounds. One hundred and forty-seven virtual hits were acquired for validation in growth inhibition and senescence-associated β-galactosidase assays. Among the found hits, a benzimidazolone compound, CB-20903630, had low micromolar IC50 for growth inhibition of HCT116 cells and selectively induced senescence-associated β-galactosidase activity in the entire treated cell population without cytotoxicity or apoptosis induction. Growth suppression was mediated by G1 blockade involving increased p21 expression and suppressed cyclin B1, CDK1, and CDC25C. In addition, the compound inhibited growth of multicellular spheroids and caused severe retardation of population kinetics in long-term treatments. Preliminary structure-activity and structure clustering analyses are reported, and expression analysis of CB-20903630 against other cell cycle suppressor compounds suggested a PI3K/AKT-inhibitor-like profile in normal cells, with different pathways affected in cancer cells.
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Affiliation(s)
- Alan E Bilsland
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Angelo Pugliese
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Yu Liu
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - John Revie
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Sharon Burns
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Carol McCormick
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Claire J Cairney
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK
| | - Justin Bower
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Martin Drysdale
- Cancer Research UK Beatson Institute, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
| | - Masashi Narita
- University of Cambridge, Cancer Research UK Cambridge Institute, Li Ka Shing Centre Robinson Way, Cambridge, CB2 0RE, UK
| | - Mahito Sadaie
- Kyoto University, Graduate School of Biostudies, Yoshidakonoe-cho, Sakyo-ku Kyoto 606-8501 Japan
| | - W Nicol Keith
- Institute of Cancer Sciences, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1QH, UK.
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15
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A novel telomerase substrate precursor rapidly induces telomere dysfunction in telomerase positive cancer cells but not telomerase silent normal cells. Oncoscience 2015; 2:693-5. [PMID: 26425659 PMCID: PMC4580061 DOI: 10.18632/oncoscience.213] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 08/17/2015] [Indexed: 12/22/2022] Open
Abstract
Although telomerase is an almost universal target for cancer therapy, there has been no effective telomerase targeted inhibitor that has progressed to late stage human clinical trials. Recently, we reported that a telomerase-mediated telomere-disrupting compound, 6-thio-2′-deoxyguanosine (6-thio-dG), was very effective at targeting telomerase positive cancer cells while sparing telomerase silent normal cells. 6-thio-dG, a nucleoside analogue of the already-approved drug 6-thioguanine, is incorporated into telomeres by telomerase, resulting in disruption of the telomere-protecting shelterin complex. This disruption leads to Telomere dysfunction-Induced Foci (TIFs) formation and rapid cell death for the vast majority of cancer cells. Since most chemotherapies eventually fail due to drug acquired resistance, novel drugs such as 6-thio-dG, as a single first line agent or in the maintenance setting, may represent an effective new treatment for cancer patients.
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16
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Mar FA, Debnath J, Stohr BA. Autophagy-independent senescence and genome instability driven by targeted telomere dysfunction. Autophagy 2015; 11:527-37. [PMID: 25751002 PMCID: PMC4502814 DOI: 10.1080/15548627.2015.1017189] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 01/14/2015] [Accepted: 01/21/2015] [Indexed: 02/08/2023] Open
Abstract
Telomere dysfunction plays a complex role in tumorigenesis. While dysfunctional telomeres can block the proliferation of incipient cancer clones by inducing replicative senescence, fusion of dysfunctional telomeres can drive genome instability and oncogenic genomic rearrangements. Therefore, it is important to define the regulatory pathways that guide these opposing effects. Recent work has shown that the autophagy pathway regulates both senescence and genome instability in various contexts. Here, we apply models of acute telomere dysfunction to determine whether autophagy modulates the resulting genome instability and senescence responses. While telomere dysfunction rapidly induces autophagic flux in human fibroblast cell lines, inhibition of the autophagy pathway does not have a significant impact upon the transition to senescence, in contrast to what has previously been reported for oncogene-induced senescence. Our results suggest that this difference may be explained by disparities in the development of the senescence-associated secretory phenotype. We also show that chromosome fusions induced by telomere dysfunction are comparable in autophagy-proficient and autophagy-deficient cells. Altogether, our results highlight the complexity of the senescence-autophagy interface and indicate that autophagy induction is unlikely to play a significant role in telomere dysfunction-driven senescence and chromosome fusions.
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Key Words
- ACD/Tpp1, adrenocortical dysplasia homolog (mouse)
- ATG5, autophagy-related 5, ATG7, autophagy-related 7
- B2M, β-2-microglobulin
- HBSS, Hank's buffered salt solution
- HMECs, human mammary epithelial cells
- MEFs, mouse embryonic fibroblasts
- MT-HsTER, mutant template-Homo sapiens template-containing RNA
- MT-MmTER, mutant template-Mus musculus template-containing RNA
- OIS, oncogene-induced senescence
- RBBP8/CtIP, retinoblastoma binding protein 8
- SA-β-Gal, senescence-associated β-galactosidase
- SASP
- SASP, senescence associated secretory phenotype
- TDIS, telomere dysfunction-induced senescence
- TERT, telomerase reverse transcriptase
- TIFs, telomere dysfunction-induced foci
- autophagy
- chromosome fusions
- genome instability
- senescence
- telomerase
- telomeres
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Affiliation(s)
- Florie A Mar
- Biomedical Sciences Graduate Program; University of California San Francisco; San Francisco, CA USA
- Department of Pathology; University of California San Francisco; San Francisco, CA USA
| | - Jayanta Debnath
- Department of Pathology; University of California San Francisco; San Francisco, CA USA
- Helen Diller Family Comprehensive Cancer Center; University of California San Francisco; San Francisco, CA USA
| | - Bradley A Stohr
- Department of Pathology; University of California San Francisco; San Francisco, CA USA
- Helen Diller Family Comprehensive Cancer Center; University of California San Francisco; San Francisco, CA USA
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17
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Abstract
The budding yeast Saccharomyces cerevisiae is a powerful model organism for studying fundamental aspects of eukaryotic cell biology. This Primer article presents a brief historical perspective on the emergence of this organism as a premier experimental system over the course of the past century. An overview of the central features of the S. cerevisiae genome, including the nature of its genetic elements and general organization, is also provided. Some of the most common experimental tools and resources available to yeast geneticists are presented in a way designed to engage and challenge undergraduate and graduate students eager to learn more about the experimental amenability of budding yeast. Finally, a discussion of several major discoveries derived from yeast studies highlights the far-reaching impact that the yeast system has had and will continue to have on our understanding of a variety of cellular processes relevant to all eukaryotes, including humans.
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18
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Li C, Yang L, Lin C. Long noncoding RNAs in prostate cancer: mechanisms and applications. Mol Cell Oncol 2014; 1:e963469. [PMID: 27308347 DOI: 10.4161/23723548.2014.963469] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/04/2014] [Accepted: 08/12/2014] [Indexed: 12/26/2022]
Abstract
A large proportion of the control of gene expression in humans is mediated by noncoding elements in the genome. Long noncoding RNAs (lncRNAs) have emerged as a new class of pivotal regulatory components, orchestrating extensive cellular processes and connections. LncRNAs play various roles from chromatin modification to alternative splicing and post-transcriptional processing and are involved in almost all aspects of eukaryotic regulation. LncRNA-based mechanisms modulate cell fates during development, and their dysregulation underscores many human disorders, especially cancer, through chromosomal translocation, deletion, and nucleotide expansions. Recent studies demonstrate that multiple prostate cancer risk loci are associated with lncRNAs and that ectopic expression of these transcripts triggers a cascade of cellular events driving tumor initiation and progression. The recent increased rate of discovery of lncRNAs has been leveraged for application in clinical strategies such as novel biomarkers and therapeutic targets. Despite this potential, many issues remain to be addressed in this fast-growing field.
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Affiliation(s)
- Chunlai Li
- Department of Molecular and Cellular Oncology; The University of Texas MD Anderson Cancer Center ; Houston, TX, 77030, USA
| | - Liuqing Yang
- Department of Molecular and Cellular Oncology; The University of Texas MD Anderson Cancer Center; Houston, TX, 77030, USA; Program in Cancer Biology; The University of Texas Graduate School of Biomedical Sciences at Houston; Houston, TX, 77030, USA
| | - Chunru Lin
- Department of Molecular and Cellular Oncology; The University of Texas MD Anderson Cancer Center; Houston, TX, 77030, USA; Program in Cancer Biology; The University of Texas Graduate School of Biomedical Sciences at Houston; Houston, TX, 77030, USA
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19
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Lee M, Hills M, Conomos D, Stutz MD, Dagg RA, Lau LMS, Reddel RR, Pickett HA. Telomere extension by telomerase and ALT generates variant repeats by mechanistically distinct processes. Nucleic Acids Res 2013; 42:1733-46. [PMID: 24225324 PMCID: PMC3919612 DOI: 10.1093/nar/gkt1117] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Telomeres are terminal repetitive DNA sequences on chromosomes, and are considered to comprise almost exclusively hexameric TTAGGG repeats. We have evaluated telomere sequence content in human cells using whole-genome sequencing followed by telomere read extraction in a panel of mortal cell strains and immortal cell lines. We identified a wide range of telomere variant repeats in human cells, and found evidence that variant repeats are generated by mechanistically distinct processes during telomerase- and ALT-mediated telomere lengthening. Telomerase-mediated telomere extension resulted in biased repeat synthesis of variant repeats that differed from the canonical sequence at positions 1 and 3, but not at positions 2, 4, 5 or 6. This indicates that telomerase is most likely an error-prone reverse transcriptase that misincorporates nucleotides at specific positions on the telomerase RNA template. In contrast, cell lines that use the ALT pathway contained a large range of variant repeats that varied greatly between lines. This is consistent with variant repeats spreading from proximal telomeric regions throughout telomeres in a stochastic manner by recombination-mediated templating of DNA synthesis. The presence of unexpectedly large numbers of variant repeats in cells utilizing either telomere maintenance mechanism suggests a conserved role for variant sequences at human telomeres.
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Affiliation(s)
- Michael Lee
- Telomere Length Regulation Group, Children's Medical Research Institute, Westmead NSW 2145, Australia, Cancer Research Unit, Children's Medical Research Institute, Westmead NSW 2145, Australia, Terry Fox Laboratory, BC Cancer Agency, Vancouver V5Z 1L3, Canada, Sydney Medical School, University of Sydney, Sydney NSW 2006, Australia and Children's Cancer Research Unit, The Children's Hospital at Westmead, Westmead NSW 2145, Australia
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20
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Smekalova EM, Shubernetskaya OS, Zvereva MI, Gromenko EV, Rubtsova MP, Dontsova OA. Telomerase RNA biosynthesis and processing. BIOCHEMISTRY (MOSCOW) 2013; 77:1120-8. [PMID: 23157292 DOI: 10.1134/s0006297912100045] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Telomerase synthesizes repetitive G-rich sequences (telomeric repeats) at the ends of eukaryotic chromosomes. This mechanism maintains the integrity of the genome, as telomere shortening leads to degradation and fusion of chromosomes. The core components of telomerase are the telomerase catalytic subunit and telomerase RNA, which possesses a small template region serving for the synthesis of a telomeric repeat. Mutations in the telomerase RNA are associated with some cases of aplastic anemia and also cause dyskeratosis congenita, myelodysplasia, and pulmonary fibrosis. Telomerase is active in 85% of cancers, and telomerase activation is one of the first steps in cell transformation. The study of telomerase and pathways where this enzyme is involved will help to understand the mechanism of the mentioned diseases and to develop new approaches for their treatment. In this review we describe the modern conception of telomerase RNA biosynthesis, processing, and functioning in the three most studied systems - yeast, vertebrates, and ciliates.
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Affiliation(s)
- E M Smekalova
- Chemical Faculty, Lomonosov Moscow State University, 119991 Moscow, Russia
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21
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A trans-spliced telomerase RNA dictates telomere synthesis in Trypanosoma brucei. Cell Res 2013; 23:537-51. [PMID: 23478302 DOI: 10.1038/cr.2013.35] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Telomerase is a ribonucleoprotein enzyme typically required for sustained cell proliferation. Although both telomerase activity and the telomerase catalytic protein component, TbTERT, have been identified in the eukaryotic pathogen Trypanosoma brucei, the RNA molecule that dictates telomere synthesis remains unknown. Here, we identify the RNA component of Trypanosoma brucei telomerase, TbTR, and provide phylogenetic and in vivo evidence for TbTR's native folding and activity. We show that TbTR is processed through trans-splicing, and is a capped transcript that interacts and copurifies with TbTERT in vivo. Deletion of TbTR caused progressive shortening of telomeres at a rate of 3-5 bp/population doubling (PD), which can be rescued by ectopic expression of a wild-type allele of TbTR in an apparent dose-dependent manner. Remarkably, introduction of mutations in the TbTR template domain resulted in corresponding mutant telomere sequences, demonstrating that telomere synthesis in T. brucei is dependent on TbTR. We also propose a secondary structure model for TbTR based on phylogenetic analysis and chemical probing experiments, thus defining TbTR domains that may have important functional implications in telomere synthesis. Identification and characterization of TbTR not only provide important insights into T. brucei telomere functions, which have been shown to play important roles in T. brucei pathogenesis, but also offer T. brucei as an attractive model system for studying telomerase biology in pathogenic protozoa and for comparative analysis of telomerase function with higher eukaryotes.
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22
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Conomos D, Stutz MD, Hills M, Neumann AA, Bryan TM, Reddel RR, Pickett HA. Variant repeats are interspersed throughout the telomeres and recruit nuclear receptors in ALT cells. ACTA ACUST UNITED AC 2013; 199:893-906. [PMID: 23229897 PMCID: PMC3518223 DOI: 10.1083/jcb.201207189] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Variant repeats interspersed throughout ALT telomeres recruit nuclear receptors, leading to the destabilized telomere architecture and enhanced telomeric recombination. Telomeres in cells that use the recombination-mediated alternative lengthening of telomeres (ALT) pathway elicit a DNA damage response that is partly independent of telomere length. We therefore investigated whether ALT telomeres contain structural abnormalities that contribute to ALT activity. Here we used next generation sequencing to analyze the DNA content of ALT telomeres. We discovered that variant repeats were interspersed throughout the telomeres of ALT cells. We found that the C-type (TCAGGG) variant repeat predominated and created a high-affinity binding site for the nuclear receptors COUP-TF2 and TR4. Nuclear receptors were directly recruited to telomeres and ALT-associated characteristics were induced after incorporation of the C-type variant repeat by a mutant telomerase. We propose that the presence of variant repeats throughout ALT telomeres results from recombination-mediated telomere replication and spreading of variant repeats from the proximal regions of the telomeres and that the consequent binding of nuclear receptors alters the architecture of telomeres to facilitate further recombination.
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Affiliation(s)
- Dimitri Conomos
- Cancer Research Unit, Children's Medical Research Institute, Westmead NSW 2145, Australia
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23
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Cole DI, Legassie JD, Bonifacio LN, Sekaran VG, Ding F, Dokholyan NV, Jarstfer MB. New models of Tetrahymena telomerase RNA from experimentally derived constraints and modeling. J Am Chem Soc 2012; 134:20070-80. [PMID: 23163801 DOI: 10.1021/ja305636u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The telomerase ribonucleoprotein complex ensures complete replication of eukaryotic chromosomes. Telomerase RNA (TER) provides the template for replicating the G-rich strand of telomeric DNA, provides an anchor site for telomerase-associated proteins, and participates in catalysis through several incompletely characterized mechanisms. A major impediment toward understanding its nontemplating roles is the absence of high content structural information for TER within the telomerase complex. Here, we used selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) to examine the structure of Tetrahymena TER free in solution and bound to tTERT in the minimal telomerase RNP. We discovered a striking difference in the two conformations and established direct evidence for base triples in the tTER pseudoknot. We then used SHAPE data, previously published FRET data, and biochemical inference to model the structure of tTER using discrete molecular dynamics simulations. The resulting tTER structure was docked with a homology model of the Tetrahymena telomerase reverse transcriptase (tTERT) to characterize the conformational changes of tTER telomerase assembly. Free in solution, tTER appears to contain four pairing regions: stems I, II, and IV, which are present in the commonly accepted structure, and stem III, a large paired region that encompasses the template and pseudoknot domains. Our interpretation of the data and subsequent modeling affords a molecular model for telomerase assemblage in which a large stem III of tTER unwinds to allow proper association of the template with the tTERT active site and formation of the pseudoknot. Additionally, analysis of our SHAPE data and previous enzymatic footprinting allow us to propose a model for stem-loop IV function in which tTERT is activated by binding stem IV in the major groove of the helix-capping loop.
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Affiliation(s)
- Daud I Cole
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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24
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Lamm N, Bsoul S, Kabaha MM, Tzfati Y. "Poisoning" yeast telomeres distinguishes between redundant telomere capping pathways. Chromosoma 2012; 121:613-27. [PMID: 23052336 DOI: 10.1007/s00412-012-0385-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 09/18/2012] [Accepted: 09/18/2012] [Indexed: 01/24/2023]
Abstract
In most eukaryotes, telomeres are composed of tandem arrays of species-specific DNA repeats ending with a G-rich 3' overhang. In budding yeast, Cdc13 binds this overhang and recruits Ten1-Stn1 and the telomerase protein Est1 to protect (cap) and elongate the telomeres, respectively. To dissect and study the various pathways employed to cap and maintain the telomere end, we engineered telomerase to incorporate Tetrahymena telomeric repeats (G₄T₂) onto the telomeres of the budding yeast Kluyveromyces lactis. These heterologous repeats caused telomere-telomere fusions, cell cycle arrest at G2/M, and severely reduced viability--the hallmarks of telomere uncapping. Fusing Cdc13 or Est1 to universal minicircle sequence binding protein (UMSBP), a small protein that binds the single-stranded G₄T₂ repeats, rescued the cell viability and restored telomere capping, but not telomerase-mediated telomere maintenance. Surprisingly, Cdc13-UMSBP-mediated telomere capping was dependent on the homologous recombination factor Rad52, while Est1-UMSBP was not. Thus, our results distinguish between two, redundant, telomere capping pathways.
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Affiliation(s)
- Noa Lamm
- Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel
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25
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Altschuler SE, Croy JE, Wuttke DS. A small molecule inhibitor of Pot1 binding to telomeric DNA. Biochemistry 2012; 51:7833-45. [PMID: 22978652 DOI: 10.1021/bi300365k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Chromosome ends are complex structures, consisting of repetitive DNA sequence terminating in an ssDNA overhang with many associated proteins. Because alteration of the regulation of these ends is a hallmark of cancer, telomeres and telomere maintenance have been prime drug targets. The universally conserved ssDNA overhang is sequence-specifically bound and regulated by Pot1 (protection of telomeres 1), and perturbation of Pot1 function has deleterious effects for proliferating cells. The specificity of the Pot1/ssDNA interaction and the key involvement of this protein in telomere maintenance have suggested directed inhibition of Pot1/ssDNA binding as an efficient means of disrupting telomere function. To explore this idea, we developed a high-throughput time-resolved fluorescence resonance energy transfer (TR-FRET) screen for inhibitors of Pot1/ssDNA interaction. We conducted this screen with the DNA-binding subdomain of Schizosaccharomyces pombe Pot1 (Pot1pN), which confers the vast majority of Pot1 sequence-specificity and is highly similar to the first domain of human Pot1 (hPOT1). Screening a library of ∼20 000 compounds yielded a single inhibitor, which we found interacted tightly with sub-micromolar affinity. Furthermore, this compound, subsequently identified as the bis-azo dye Congo red (CR), was able to competitively inhibit hPOT1 binding to telomeric DNA. Isothermal titration calorimetry and NMR chemical shift analysis suggest that CR interacts specifically with the ssDNA-binding cleft of Pot1, and that alteration of this surface disrupts CR binding. The identification of a specific inhibitor of ssDNA interaction establishes a new pathway for targeted telomere disruption.
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Affiliation(s)
- Sarah E Altschuler
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
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26
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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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27
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Bilsland AE, Cairney CJ, Keith WN. Targeting the telomere and shelterin complex for cancer therapy: current views and future perspectives. J Cell Mol Med 2012; 15:179-86. [PMID: 21199331 PMCID: PMC3822786 DOI: 10.1111/j.1582-4934.2010.01253.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Aberrant telomere homeostasis is essential for cell immortality, enabling cells to evade telomere dependent senescence. Disruption of telomere structure and function in cancer cells is highly toxic as shown by detailed pre-clinical evaluation of telomerase inhibitors. Under telomerase inhibition, cells must divide sufficiently frequently to allow one or more telomeres to shorten to an unprotected length. Functioning telomeres are disguised from the DNA damage machinery by DNA remodelling and other activities of the telomere binding complex shelterin. Direct interference with shelterin has been shown to result in cell killing and small molecules directly targeting telomere DNA also have anti-tumour effects partially dependent on shelterin disruption. However, shelterin components have not generally been regarded as therapeutic targets in their own right. In this review, we explore the possibilities for therapeutic targeting of the shelterin complex.
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Affiliation(s)
- Alan E Bilsland
- University of Glasgow, Institute of Cancer Sciences, Beatson Laboratories, Bearsden, Glasgow, UK
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28
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Booy EP, Meier M, Okun N, Novakowski SK, Xiong S, Stetefeld J, McKenna SA. The RNA helicase RHAU (DHX36) unwinds a G4-quadruplex in human telomerase RNA and promotes the formation of the P1 helix template boundary. Nucleic Acids Res 2012; 40:4110-24. [PMID: 22238380 PMCID: PMC3351167 DOI: 10.1093/nar/gkr1306] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Human telomerase RNA (hTR) contains several guanine tracts at its 5′-end that can form a G4-quadruplex structure. Previous evidence suggests that a G4-quadruplex within this region disrupts the formation of an important structure within hTR known as the P1 helix, a critical element in defining the template boundary for reverse transcription. RNA associated with AU-rich element (RHAU) is an RNA helicase that has specificity for DNA and RNA G4-quadruplexes. Two recent studies identify a specific interaction between hTR and RHAU. Herein, we confirm this interaction and identify the minimally interacting RNA fragments. We demonstrate the existence of multiple quadruplex structures within the 5′ region of hTR and find that these regions parallel the minimal sequences capable of RHAU interaction. We confirm the importance of the RHAU-specific motif in the interaction with hTR and demonstrate that the helicase activity of RHAU is sufficient to unwind the quadruplex and promote an interaction with 25 internal nucleotides to form a stable P1 helix. Furthermore, we have found that a 5′-terminal quadruplex persists following P1 helix formation that retains affinity for RHAU. Finally, we have investigated the functional implications of this interaction and demonstrated a reduction in average telomere length following RHAU knockdown by small interfering RNA (siRNA).
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Affiliation(s)
- E P Booy
- Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada
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29
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Fujimori J, Matsuo T, Shimose S, Kubo T, Ishikawa M, Yasunaga Y, Ochi M. Antitumor effects of telomerase inhibitor TMPyP4 in osteosarcoma cell lines. J Orthop Res 2011; 29:1707-11. [PMID: 21590716 DOI: 10.1002/jor.21451] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 04/20/2011] [Indexed: 02/04/2023]
Abstract
Telomere studies in carcinomas have been extensively reported for prognostic utility and effective methods for targeting telomerase therapy has been described, but efficacy of telomerase inhibitor remained unknown in sarcoma cells. In this study, we investigated the effects of telomerase inhibitor cationic porphyrin TMPyP4 on telomerase activity, telomere length, cell growth, and apoptosis in osteosarcoma cell lines. TMPyP4 significantly inhibited telomerase activity in telomerase positive HOS and Saos-2, but not in MG-63. TMPyP4 significantly induced telomere shortening, and inhibition of the cell growth in HOS and Saos-2 with over 17% apoptosis rates. In terms of MG-63, TMPyP4 did not induce inhibition of both telomerase activity and cell growth, although it induced significant telomere shortening. Telomere length after treatment was 5.60 kb in HOS, 4.00 kb in Saos-2, and 9.89 kb in MG-63. These results may suggest that both telomerase activity loss and sufficient telomere shortening are necessary to inhibit cell growth in telomerase positive osteosarcoma cells. TMPyP4 did not induced telomere shortening but significantly inhibited the growth with 22.6% apoptosis rate in telomerase negative with extremely longer telomere-U2OS, may indicating the antitumor effect of TMPyP4 may be related to DNA damage including telomere dysfunction through G-quadruplex stabilization, independent on telomere length.
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Affiliation(s)
- Jun Fujimori
- Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.
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30
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Kaufer BB, Arndt S, Trapp S, Osterrieder N, Jarosinski KW. Herpesvirus telomerase RNA (vTR) with a mutated template sequence abrogates herpesvirus-induced lymphomagenesis. PLoS Pathog 2011; 7:e1002333. [PMID: 22046133 PMCID: PMC3203187 DOI: 10.1371/journal.ppat.1002333] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 09/08/2011] [Indexed: 02/03/2023] Open
Abstract
Telomerase reverse transcriptase (TERT) and telomerase RNA (TR) represent the enzymatically active components of telomerase. In the complex, TR provides the template for the addition of telomeric repeats to telomeres, a protective structure at the end of linear chromosomes. Human TR with a mutation in the template region has been previously shown to inhibit proliferation of cancer cells in vitro. In this report, we examined the effects of a mutation in the template of a virus encoded TR (vTR) on herpesvirus-induced tumorigenesis in vivo. For this purpose, we used the oncogenic avian herpesvirus Marek's disease virus (MDV) as a natural virus-host model for lymphomagenesis. We generated recombinant MDV in which the vTR template sequence was mutated from AATCCCAATC to ATATATATAT (vAU5) by two-step Red-mediated mutagenesis. Recombinant viruses harboring the template mutation replicated with kinetics comparable to parental and revertant viruses in vitro. However, mutation of the vTR template sequence completely abrogated virus-induced tumor formation in vivo, although the virus was able to undergo low-level lytic replication. To confirm that the absence of tumors was dependent on the presence of mutant vTR in the telomerase complex, a second mutation was introduced in vAU5 that targeted the P6.1 stem loop, a conserved region essential for vTR-TERT interaction. Absence of vTR-AU5 from the telomerase complex restored virus-induced lymphoma formation. To test if the attenuated vAU5 could be used as an effective vaccine against MDV, we performed vaccination-challenge studies and determined that vaccination with vAU5 completely protected chickens from lethal challenge with highly virulent MDV. Taken together, our results demonstrate 1) that mutation of the vTR template sequence can completely abrogate virus-induced tumorigenesis, likely by the inhibition of cancer cell proliferation, and 2) that this strategy could be used to generate novel vaccine candidates against virus-induced lymphoma.
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MESH Headings
- Animals
- Cell Proliferation
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Chickens
- Gene Expression Regulation, Leukemic
- Gene Expression Regulation, Viral
- Herpesvirus 2, Gallid/enzymology
- Herpesvirus 2, Gallid/genetics
- Herpesvirus 2, Gallid/pathogenicity
- Host-Pathogen Interactions
- Lymphoma, T-Cell/genetics
- Lymphoma, T-Cell/veterinary
- Lymphoma, T-Cell/virology
- Marek Disease/genetics
- Marek Disease/virology
- Mutation
- RNA/genetics
- RNA, Viral/analysis
- Telomerase/genetics
- Templates, Genetic
- Vaccination/veterinary
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Affiliation(s)
- Benedikt B. Kaufer
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- Institut für Virologie, Freie Universität Berlin, Berlin, Germany
| | - Sina Arndt
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Sascha Trapp
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Nikolaus Osterrieder
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- Institut für Virologie, Freie Universität Berlin, Berlin, Germany
| | - Keith W. Jarosinski
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
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Mahalingam D, Tay LL, Tan WH, Chai JH, Wang X. Mutant telomerase RNAs induce DNA damage and apoptosis via the TRF2-ATM pathway in telomerase-overexpressing primary fibroblasts. FEBS J 2011; 278:3724-38. [PMID: 21824286 DOI: 10.1111/j.1742-4658.2011.08290.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Mutant template human telomerase RNAs (MT-hTers) have been shown to induce apoptosis in various cancer cells with high telomerase activity. However, the mechanism by which MT-hTers inhibit the growth of cancer cells and their effects on normal cells remain unknown. To determine the effects of MT-hTers on normal cells, MT-hTer-47A and -AU5 were introduced into IMR90 lung fibroblasts, which have low telomerase levels. Growth of IMR90 cells after MT-hTers infection was not significantly impaired; however, similar treatments in telomerase-overexpressing IMR90 [IMR90 wild-type (WT)hTERT] cells inhibited cell proliferation and induced apoptosis. Confocal microscopy showed that MT-hTers induced DNA damage foci (i.e. 53BP1 and γ-H2AX) in IMR90 WThTERT cells. Microarray analysis revealed that GADD45γ was significantly elevated in MT-hTer-treated IMR90 WThTERT cells. MT-hTers also induced ATM phosphorylation at Ser1981 in IMR90 WThTERT cells, and western blot analysis revealed high levels of phosphorylated p53 after the down-regulation of cellular TRF2 expression in MT-hTer-treated IMR90 WThTERT cells. Taken together, we have shown that MT-hTers induce double-stranded DNA break-like damages in telomerase positive IMR90 WThTERT cells after phosphorylation of ATM and p53 via suppression of TRF2, which may eventually lead to apoptosis via elevation of GADD45γ.
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Affiliation(s)
- Dashayini Mahalingam
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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32
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Lacroix L, Séosse A, Mergny JL. Fluorescence-based duplex-quadruplex competition test to screen for telomerase RNA quadruplex ligands. Nucleic Acids Res 2011; 39:e21. [PMID: 21106496 PMCID: PMC3045579 DOI: 10.1093/nar/gkq1199] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/12/2010] [Accepted: 11/05/2010] [Indexed: 11/25/2022] Open
Abstract
RNA and DNA guanine-rich sequences can adopt unusual structures called Guanine quadruplexes (G4). A quadruplex-prone RNA sequence is present at the 5'-end of the 451-nt-long RNA component of telomerase, hTERC. As this quadruplex may interfere with P1 helix formation, a key structural element for this RNA, we are seeking molecules that would alter this RNA duplex-quadruplex equilibrium. In this work, we present a fluorescence-based test designed to identify G4 ligands specific for the hTERC G-rich motif and that can prevent P1 helix formation. From an initial panel of 169 different molecules, 11 were found to be excellent P1 duplex inhibitors. Interestingly, some of the compounds not only exhibit a strong selectivity for quadruplexes over duplexes, but also demonstrated a preference for G4-RNA over all other quadruplexes. This test may easily be adapted to almost any quadruplex-forming sequence and converted into HTS format.
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Affiliation(s)
- Laurent Lacroix
- INSERM U565, CNRS-Muséum National d'Histoire Naturelle UMR 7196, 43 rue Cuvier, Paris, France.
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33
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Folini M, Venturini L, Cimino-Reale G, Zaffaroni N. Telomeres as targets for anticancer therapies. Expert Opin Ther Targets 2011; 15:579-93. [DOI: 10.1517/14728222.2011.556621] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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34
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Xu Y. Chemistry in human telomere biology: structure, function and targeting of telomere DNA/RNA. Chem Soc Rev 2011; 40:2719-40. [DOI: 10.1039/c0cs00134a] [Citation(s) in RCA: 249] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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35
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Abstract
Telomeric recombination has been observed in telomerase-negative alternative lengthening of telomeres in human cancer cells and following telomerase inhibition or gene deletion. This study shows that telomeric recombination mechanisms can also be activated by dysfunctional telomeres without telomerase inhibition in telomerase-positive cells. Telomere maintenance is essential for cellular immortality, and most cancer cells maintain their telomeres through the enzyme telomerase. Telomeres and telomerase represent promising anticancer targets. However, 15% of cancer cells maintain their telomeres through alternative recombination-based mechanisms, and previous analyses showed that recombination-based telomere maintenance can be activated after telomerase inhibition. We determined whether telomeric recombination can also be promoted by telomere dysfunction. We report for the first time that telomeric recombination can be induced in human telomerase-positive cancer cells with dysfunctional telomeres.
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Affiliation(s)
- Marie Eve Brault
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2
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36
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Stohr BA, Xu L, Blackburn EH. The terminal telomeric DNA sequence determines the mechanism of dysfunctional telomere fusion. Mol Cell 2010; 39:307-14. [PMID: 20670897 DOI: 10.1016/j.molcel.2010.06.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Revised: 02/19/2010] [Accepted: 05/07/2010] [Indexed: 12/27/2022]
Abstract
Mammalian telomeres consist of tandem DNA repeats that bind protective protein factors collectively termed shelterins. Telomere disruption typically results in genome instability induced by telomere fusions. The mechanism of telomere fusion varies depending on the means of telomere disruption. Here, we investigate telomere fusions caused by overexpression of mutant telomerases that add mutated telomeric repeats, thereby compromising shelterin binding to telomeric termini. While all mutant telomeric sequences tested induced heterodicentric chromosome fusions in ATM-competent cells, only those mutant repeat sequences with significant self complementarity induced ATM-independent sister chromatid and isodicentric chromosome fusions. Thus, once a telomere becomes dysfunctional, the terminal telomeric sequence itself determines the fate of that telomere. These results suggest that annealing of self-complementary DNA sequence engages an alternative telomere fusion pathway in human cells, and provide one explanation for the conspicuous lack of self complementarity in the majority of known naturally occurring eukaryotic telomeric sequences.
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Affiliation(s)
- Bradley A Stohr
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94143, USA
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37
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Xu T, Xu Y, Liao CP, Lau R, Goldkorn A. Reprogramming murine telomerase rapidly inhibits the growth of mouse cancer cells in vitro and in vivo. Mol Cancer Ther 2010; 9:438-49. [PMID: 20124445 DOI: 10.1158/1535-7163.mct-09-0682] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Telomerase plays a critical role in cancer, prompting the pursuit of various telomerase-based therapeutic strategies. One such strategy, telomerase interference, exploits the high telomerase activity in cancer cells and reprograms telomerase to encode "toxic" telomeres. To date, telomerase interference has been tested in human cancer cells xenografted into mice, an approach that does not recapitulate spontaneous malignancy and offers few insights about host toxicities, because human telomerase is targeted in a mouse host. To address these limitations, we designed and validated two new gene constructs specifically targeting mouse telomerase: mutant template mouse telomerase RNA (MT-mTer) and small interfering RNA against wild-type mouse telomerase RNA (α-mTer-siRNA). Using lentiviral delivery in mouse prostate cancer cells, we achieved α-mTer-siRNA-mediated knockdown of wild-type mTer (80% depletion) and concurrent overexpression of MT-mTer (50-fold). We showed that the two constructs effectively synergize to reprogram murine telomerase to add mutant instead of wild-type telomeric repeats, resulting in rapid telomeric uncapping (5-fold increase in DNA damage foci). This, in turn, led to rapid and significant apoptosis (>90% of cells) and growth inhibition in vitro (90% reduction in viable cell mass) and in vivo (75% reduction in tumor allograft wet weight). In summary, we have shown that mouse cancer cells are vulnerable to direct telomerase interference using novel murine telomerase-targeting constructs; this approach can now be used to study the true therapeutic potential of telomerase interference in mouse spontaneous cancer models.
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Affiliation(s)
- Tong Xu
- Division of Medical Oncology, Department of Internal Medicine, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
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38
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Telomere and telomerase as targets for cancer therapy. Appl Biochem Biotechnol 2009; 160:1460-72. [PMID: 19412578 DOI: 10.1007/s12010-009-8633-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Accepted: 03/31/2009] [Indexed: 02/08/2023]
Abstract
Telomere maintenance and telomerase reactivation is essential for the transformation of most human cancer cells. Telomere shortening to the threshold length, mutations of the telomere-associated proteins, and/or telomerase RNA lead to telomeric dysfunction and therefore genomic instability. Telomerase up-regulation in 85% of human cancer cells has become a hallmark of cancers, hence a promising target for anticancer therapy. In this review, we discuss the mechanism of cancer due to telomere dysfunction and the resulting biological effects, the control of telomerase activity, and the new developments in cancer therapies targeting telomere and telomerase.
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39
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Yu HQ, Zhang DH, Gu XB, Miyoshi D, Sugimoto N. Regulation of telomerase activity by the thermodynamic stability of a DNA x RNA hybrid. Angew Chem Int Ed Engl 2008; 47:9034-8. [PMID: 18850626 DOI: 10.1002/anie.200803577] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Hai-Qing Yu
- Frontier Institute for Biomolecular Engineering Research, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe 658-8501, Japan
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40
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Marie-Egyptienne DT, Brault ME, Nimmo GAM, Londoño-Vallejo JA, Autexier C. Growth defects in mouse telomerase RNA-deficient cells expressing a template-mutated mouse telomerase RNA. Cancer Lett 2008; 275:266-76. [PMID: 19056167 DOI: 10.1016/j.canlet.2008.10.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Revised: 10/15/2008] [Accepted: 10/17/2008] [Indexed: 01/03/2023]
Abstract
Cellular viability requires telomere maintenance, which, in mammals, is mainly mediated by the reverse transcriptase telomerase. Telomerase core components are a catalytic subunit TERT and an RNA subunit TR (hTR in humans, mTR in mouse) that carries the template to generate telomeres de novo. Telomere dysfunction can lead to senescence or apoptosis and impairs the continued growth of immortal cancerous cell lines. The introduction of a template-mutated hTR in telomerase-positive and telomerase-negative human cell lines results in dramatic growth defects. No study has addressed the consequences of expressing a template-mutated mTR in mouse immortal cell lines. Therefore, we analyzed the effects of long-term expression of a template-mutated mTR in the telomerase-positive and telomerase-negative murine cell lines CB17 and DKO301, respectively. Whereas the CB17 clones expressing the template-mutated mTR did not demonstrate any growth impairment, many of the DKO301 clones expressing the template-mutated mTR underwent growth and cell cycle defects and eventual cell death. These results suggest that in the absence of wild-type telomerase, the expression of the template-mutated mTR likely perturbs telomere function, leading to decreased cellular viability. Furthermore, whereas the expression of template-mutated hTR in telomerase-negative human cell lines leads to immediate cellular toxicity, the expression of the template-mutated mTR in the telomerase-negative mouse cell line did not.
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41
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Yu HQ, Zhang DH, Gu XB, Miyoshi D, Sugimoto N. Regulation of Telomerase Activity by the Thermodynamic Stability of a DNA⋅RNA Hybrid. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200803577] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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42
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Stohr BA, Blackburn EH. ATM mediates cytotoxicity of a mutant telomerase RNA in human cancer cells. Cancer Res 2008; 68:5309-17. [PMID: 18593932 DOI: 10.1158/0008-5472.can-08-0504] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Telomeres are elongated by the enzyme telomerase, which contains a template-bearing RNA (TER or TERC) and a protein reverse transcriptase. Overexpression of a particular mutant human TER with a mutated template sequence (MT-hTer-47A) in telomerase-positive cancer cells causes incorporation of mutant telomeric sequences, telomere uncapping, and initiation of a DNA damage response, ultimately resulting in cell growth inhibition and apoptosis. The DNA damage pathways underlying these cellular effects are not well understood. Here, we show that the ataxia-telangiectasia mutated (ATM) protein is activated and forms telomeric foci in response to MT-hTer-47A expression. Depletion of ATM from two cancer cell lines, including the p53-mutant UM-UC-3 bladder cancer line, rendered the cells largely unresponsive to MT-hTer-47A. Relative to ATM-competent controls, ATM-depleted cells showed increased proliferation and clonogenic survival and reduced cell death following MT-hTer-47A treatment. In contrast, ATM depletion sensitized the cancer cells to treatment with camptothecin, a topoisomerase inhibitor that induces DNA double-strand breaks. We show that the effects of ATM depletion on the MT-hTer-47A response were not due to decreased expression of MT-hTer-47A or reduced activity of telomerase at the telomere. Instead, ATM depletion allowed robust cancer cell growth despite the continued presence of dysfunctional telomeres containing mutant sequence. Notably, the number of end-to-end telomere fusions induced by MT-hTer-47A treatment was markedly reduced in ATM-depleted cells. Our results identify ATM as a key mediator of the MT-hTer-47A dysfunctional telomere response, even in cells lacking wild-type p53, and provide evidence that telomere fusions contribute to MT-hTer-47A cytotoxicity.
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Affiliation(s)
- Bradley A Stohr
- Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143-2200, USA
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43
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Ueda N, Shiraha H, Fujikawa T, Takaoka N, Nakanishi Y, Suzuki M, Matsuo N, Tanaka S, Nishina SI, Uemura M, Takaki A, Shiratori Y, Yamamoto K. Exon 2 deletion splice variant of gamma-glutamyl carboxylase causes des-gamma-carboxy prothrombin production in hepatocellular carcinoma cell lines. Mol Oncol 2008; 2:241-9. [PMID: 19383345 DOI: 10.1016/j.molonc.2008.06.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2008] [Revised: 06/11/2008] [Accepted: 06/15/2008] [Indexed: 01/02/2023] Open
Abstract
Using GGCX gene-specific real-time PCR, exon 2 deletion splice variant of vitamin K-dependent gamma-glutamyl carboxylase (GGCX) mRNA was identified in HCC cell lines. Expressions of wild type and exon 2 deletion variant of GGCX were analyzed with relevance to DCP production in HCC cell lines. Hep3B, HepG2, HuH1, HuH7, and PLC/PRF/5 produced DCP, while SK-Hep-1, HLE, HLF, and JHH1 produced no detectable level of DCP. DCP-producing cells expressed exon 2 deletion variant of GGCX mRNA and protein, while DCP-negative cells expressed no detectable level of exon 2 deletion variant of GGCX. These results suggest that exon 2 deletion splice variant of GGCX causes dysfunction of GGCX enzyme activity resulting in DCP production in HCC cell lines.
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Affiliation(s)
- Naoki Ueda
- Department of Gastroenterology and Hepatology, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama 700-8558, Japan
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44
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Kelland L. Targeting the Limitless Replicative Potential of Cancer: The Telomerase/Telomere Pathway: Fig. 1. Clin Cancer Res 2007; 13:4960-3. [PMID: 17785545 DOI: 10.1158/1078-0432.ccr-07-0422] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The maintenance of telomeric DNA underlies the ability of tumors to possess unlimited replicative potential, one of the hallmarks of cancer. Telomere length and structure are maintained by the reverse transcriptase telomerase and a multiprotein telomere complex termed shelterin. Telomerase activity is elevated in the vast majority of tumors, and telomeres are critically shortened in tumors versus normal tissues, thus providing a compelling rationale to target the telomerase/telomere pathway for broad-spectrum cancer therapy. This strategy is supported by a variety of genetic-based target validation studies. Both telomerase inhibitors and telomere interactive molecules have shown stand-alone antitumor activity at nontoxic doses against a variety of human tumor xenografts in mice. These translational advances have resulted in the first antitelomerase agent, the oligonucleotide-based GRN163L targeting the telomerase RNA template, entering clinical evaluation. Additional translational approaches, such as targeting telomeres using G-quadruplex ligands, should result in antitelomere agents, such as RHPS4, entering the clinic in the near future. These prototype trials will be extremely informative in determining the role of the telomerase/telomere pathway in clinical oncology and, moreover, whether drugs targeting the unlimited replicative potential of cancer will find a place in cancer chemotherapy.
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Affiliation(s)
- Lloyd Kelland
- Cancer Research Technology Development Laboratory, Wolfson Institute for Biomedical Research, University College London, London, United Kingdom.
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45
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Li S, Blackburn EH. Expression and suppression of human telomerase RNA. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 71:211-5. [PMID: 17381299 DOI: 10.1101/sqb.2006.71.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Telomeres are maintained by the ribonucleoprotein (RNP) enzyme telomerase, which replenishes telomeres through its unique mechanism of internal RNA-templated addition of telomeric DNA. Telomerase is active in most human cancers, typically because its core protein subunit, TERT, is up-regulated. Although the major known function of telomerase in cancer is to replenish telomeric DNA and maintain cell immortality, the regulation of the RNA component of telomerase is not well understood. In the course of investigations that have implicated telomerase RNA in key aspects of cancer progression, including metastasis, we explored some of the cis-acting elements affecting telomerase RNA expression and knockdown. The expression efficiency and subsequent RNA processing to produce the mature hTER differed considerably among various promoters. Together with other results, these findings establish that the crucial elements of the hTER gene affecting RNA-processing efficiency to produce the mature hTER RNA are the promoter and internal telomerase RNA-coding sequences.
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Affiliation(s)
- S Li
- Department of Biochemistry and Biophysics, University of California, San Fransisco, California 94158-2517, USA
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46
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Westin ER, Chavez E, Lee KM, Gourronc FA, Riley S, Lansdorp PM, Goldman FD, Klingelhutz AJ. Telomere restoration and extension of proliferative lifespan in dyskeratosis congenita fibroblasts. Aging Cell 2007; 6:383-94. [PMID: 17381549 PMCID: PMC2225626 DOI: 10.1111/j.1474-9726.2007.00288.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Dyskeratosis congenita (DC), an inherited bone marrow failure syndrome, is caused by defects in telomerase. Somatic cells from DC patients have shortened telomeres and clinical symptoms are most pronounced in organs with a high cell turnover, including those involved in hematopoiesis and skin function. We previously identified an autosomal dominant (AD) form of DC that is caused by mutations in the telomerase RNA component (TER). In this study, we evaluated whether retroviral expression of TER and/or telomerase reverse transcriptase (TERT), the catalytic component of telomerase, could extend telomere length and rescue AD DC cells from a phenotype characteristic of early senescence. Exogenous TER expression, without TERT, could not activate telomerase in AD DC skin fibroblasts. Transduction of TERT alone, however, provided AD DC cells with sufficient telomerase activity to extend average telomere length and proliferative capacity. Interestingly, we found that expression of TER and TERT together resulted in extension of lifespan and higher levels of telomerase and longer telomeres than expression of TERT alone in both AD DC and normal cells. Our results provide evidence that AD DC cells can be rescued from defects in telomere maintenance and proliferation, and that coexpression of TERT and TER together provides a more efficient means to elongate telomeres than expression of TERT alone. Similar strategies may be useful for ameliorating the detrimental effects of telomere shortening in AD DC and other diseases associated with telomerase or telomere defects.
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Affiliation(s)
- Erik R. Westin
- Interdisciplinary Program in Genetics, University of Iowa, Iowa City, IA, USA
| | - Elizabeth Chavez
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
| | - Kimberly M. Lee
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
| | | | - Soraya Riley
- Program in Molecular and Cellular Biology, University of Iowa, Iowa City, IA, USA
| | - Peter M. Lansdorp
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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47
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Paranjape JM, Xu D, Kushner DM, Okicki J, Lindner DJ, Cramer H, Silverman RH, Leaman DW. Human telomerase RNA degradation by 2'-5'-linked oligoadenylate antisense chimeras in a cell-free system, cultured tumor cells, and murine xenograft models. Oligonucleotides 2006; 16:225-38. [PMID: 16978086 DOI: 10.1089/oli.2006.16.225] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ribonuclease L (RNase L) is a latent single-stranded RNA-directed endoribonuclease that is activated on binding to short 2'-5'-linked oligoadenylates (2-5A), a feature that has led to its use in antisense therapeutic strategies. By attaching a 2-5A moiety to the 5' terminus of standard antisense oligonucleotides, it is possible to activate RNase L and guide it to specific RNAs for degradation. These 2-5A antisense chimeras have been used successfully to target a variety of cellular and viral RNAs. Telomerase is a nuclear ribonucleoprotein complex that elongates telomeric DNA and contributes to cellular immortalization. Telomerase is composed of a protein catalytic subunit and an RNA (hTR or TERC) component, both of which are critical for holoenzyme activity. We describe the characterization of 2-5A antisense chimeras targeting the hTR component of telomerase (2-5A antihTR). Newly designed 2-5A anti-hTR molecules were assayed for their abilities to selectively degrade hTR in a cell-free system. Of the five chimeras tested, one (RBI011) degraded hTR by 97%, and two others (RBI013 and RBI009) were also found to be highly active (73-76% degradation). The ability of transfected RBI011, and its homolog RBI254, to degrade hTR in cultured tumor cells was assessed by real-time RT-PCR. In these studies, RBI011 and RBI254 effectively degraded hTR in a variety of hTR-positive tumor cell lines. The hTR degradation studies were extended to growth assays to determine whether hTR ablation affected tumor cell viability or proliferation. RBI254 treatment resulted in reduced tumor cell viability over the course of 4-day growth assays, effects that were augmented by cotreatment with interferon-beta. To extend these results to an in vivo system, nude mice were implanted subcutaneously or orthotopically with hTR-positive prostate tumors and treated with RBI254. RBI254-treated mice exhibited enhanced tumor cell apoptosis and reduced tumor volume as compared with controls. These findings demonstrated the effectiveness of highly active forms of 2-5A antisense against hTR, and also highlight the usefulness of the cell-free system in predicting chimera efficacy before to inception of cell-based and in vivo studies.
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Affiliation(s)
- Jayashree M Paranjape
- Department of Cancer Biology and Immunology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH, USA
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Canales BK, Li Y, Thompson MG, Gleason JM, Chen Z, Malaeb B, Corey DR, Herbert BS, Shay JW, Koeneman KS. Small molecule, oligonucleotide-based telomerase template inhibition in combination with cytolytic therapy in an in vitro androgen-independent prostate cancer model. Urol Oncol 2006; 24:141-51. [PMID: 16520278 DOI: 10.1016/j.urolonc.2005.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
PURPOSE Determine the efficacy and timing of small molecule oligonucleotide-based inhibitors to the enzyme telomerase in an in vitro model of androgen-independent, osseous prostate cancer. MATERIALS AND METHODS Telomerase was inhibited in prostate cancer cell lines C4-2/C4-2B and in controls by using small molecule antisense oligonucleotide-based inhibitors alone or in various combinations of small-dose Taxotere (sanofi-aventis, Bridgewater, NJ) and/or conditionally replication competent adenovirus (AD-BSP-E1a). After transfection and proliferation, telomerase telomeric repeat amplification protocol and telomere restriction fragment assays were performed, with specific times for evaluating telomere length. Specimens were stained for analysis with hematoxylin and eosin (H&E), terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL), and prostate-specific antigen (PSA). RESULTS C4-2/C4-2B cell lines had the shortest initial mean telomere length (approximately 2.5 kilobase [kb]) compared to PC-3 (approximately 5.5 kb). Dose-dependent inhibition of telomerase activity was seen using match oligonucleotide-based inhibitors to telomerase (50% inhibitory concentration 3-5 nm), whereas mismatch compound showed no telomerase inhibition. Significant growth delay and apoptosis in cell lines occurred after > 50 days of treatment. Cells treated with combination "triple therapy" (i.e., telomerase inhibitors, adenovirus, and Taxotere) had the highest amount of apoptosis. Compared to controls, all combination treatment groups had statistically significant reductions in prostate-specific antigen in the conditioned media. CONCLUSIONS Combining cytotoxic regimens with small molecule inhibitors to telomerase with oligonucleotide-based agents could be beneficial in controlling osseous hormone refractory prostate cancer, as evidenced by these in vitro, preclinical investigations. Telomerase inhibition needs to move into in vivo models and human studies.
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Affiliation(s)
- Benjamin K Canales
- Department of Urology, University of Minnesota, Minneapolis, MN 55455, USA
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Ji XM, Xie CH, Fang MH, Zhou FX, Zhang WJ, Zhang MS, Zhou YF. Efficient inhibition of human telomerase activity by antisense oligonucleotides sensitizes cancer cells to radiotherapy. Acta Pharmacol Sin 2006; 27:1185-91. [PMID: 16923339 DOI: 10.1111/j.1745-7254.2006.00417.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
AIM To investigate the effect of the antisense oligonucleotides (ASODN) specific for human telomerase RNA (hTR) on radio sensitization and proliferation inhibition in human neurogliocytoma cells (U251). METHODS U251 cells were transfected with hTR ASODN or nonspecific oligonucleotides (NSODN). Before and after irradiation of (60)Co- gamma ray, telomerase activity was assayed by telomeric repeat amplification protocol ( TRAP-PCR-ELISA), and DNA damage and repair were examined by the comet assay. The classical colony assay was used to plot the cell-survival curve, to detect the D(0 )value. RESULTS hTR antisense oligonucleotides could downregulate the telomerase activity, increase radiation induced DNA damage and reduce the subsequent repair. Furthermore, it could inhibit the proliferation and decrease the D(0 ) value which demonstrates rising radiosensitivity. However, telomere length was unchanged over a short period of time. CONCLUSION These findings suggest that an ASODN-based strategy may be used to develop telomerase inhibitors, which can efficiently sensitize radiotherapy.
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Affiliation(s)
- Xue-mei Ji
- Department of Chemotherapy and Radiation Oncology, Zhongnan Hospital, Wuhan University, Wuhan 430071, China
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Goldkorn A, Blackburn EH. Assembly of mutant-template telomerase RNA into catalytically active telomerase ribonucleoprotein that can act on telomeres is required for apoptosis and cell cycle arrest in human cancer cells. Cancer Res 2006; 66:5763-71. [PMID: 16740715 DOI: 10.1158/0008-5472.can-05-3782] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The telomerase ribonucleoprotein is a promising target for cancer therapy, as it is highly active in many human malignancies. A novel telomerase targeting approach combines short interfering RNA (siRNA) knockdown of endogenous human telomerase RNA (hTer) with expression of a mutant-template hTer (MT-hTer). Such combination MT-hTer/siRNA constructs induce a rapid DNA damage response, telomere uncapping, and inhibition of cell proliferation in a variety of human cancer cell lines. We tested which functional aspects of the protein catalytic component of telomerase [human telomerase reverse transcriptase (hTERT)] are required for these effects using human LOX melanoma cells overexpressing various hTERTs of known properties. Within 3 days of MT-hTer/siRNA introduction, both growth inhibition and DNA damage responses were significantly higher in the setting of wild-type hTERT versus catalytically dead hTERT or mutant hTERT that is catalytically competent but unable to act on telomeres. These effects were not attenuated by siRNA-induced knockdown of the telomeric protein human Rap1 and were additive with knockdown of the telomere-binding protein TRF2. Hence, the effects of MT-hTer/siRNA require a telomerase that is both catalytically competent to polymerize DNA and able to act on telomeres in cells.
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Affiliation(s)
- Amir Goldkorn
- Department of Internal Medicine, Division of Hematology and Oncology, University of California at San Francisco, San Francisco, California, USA
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