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Bolzán AD. Considerations on the scoring of telomere aberrations in vertebrate cells detected by telomere or telomere plus centromere PNA-FISH. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2024; 794:108507. [PMID: 38802042 DOI: 10.1016/j.mrrev.2024.108507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 05/20/2024] [Accepted: 05/21/2024] [Indexed: 05/29/2024]
Abstract
Given that telomeres play a fundamental role in maintaining genomic stability, the study of the chromosomal aberrations involving telomeric sequences is a topic of considerable research interest. In recent years, the scoring of these types of aberrations has been used in vertebrate cells, particularly human cells, to evaluate the effects of genotoxic agents on telomeres and the involvement of telomeric sequences on chromosomal aberrations. Currently, chromosomal aberrations involving telomeric sequences are evaluated in peripheral blood lymphocytes or immortalized cell lines, using telomere or telomere plus centromere fluorescence in situ hybridization (FISH) with Peptide Nucleic Acid (PNA) probes (PNA-FISH). The telomere PNA probe is more efficient in the detection of telomeric sequences than conventional FISH with a telomere DNA probe. In addition, the intensity of the telomeric PNA-FISH probe signal is directly correlated with the number of telomeric repeats. Therefore, use of this type of probe can identify chromosomal aberrations involving telomeres as well as determine the telomere length of the sample. There are several mistakes and inconsistencies in the literature regarding the identification of telomere aberrations, which prevent accurate scoring and data comparison between different publications concerning these types of aberrations. The aim of this review is to clarify these issues, and provide proper terminology and criteria for the identification, scoring, and analysis of telomere aberrations.
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Affiliation(s)
- Alejandro D Bolzán
- Laboratorio de Citogenética y Mutagénesis, Instituto Multidisciplinario de Biología Celular (IMBICE, CONICET-UNLP-CICPBA), calle 526 y Camino General Belgrano, La Plata, Buenos Aires B1906APO, Argentina; Universidad Nacional de La Plata, Facultad de Ciencias Naturales y Museo, calle 60 y 122, La Plata, Buenos Aires, Argentina.
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2
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Maliar NL, Talbot EJ, Edwards AR, Khoronenkova SV. Microglial inflammation in genome instability: A neurodegenerative perspective. DNA Repair (Amst) 2024; 135:103634. [PMID: 38290197 DOI: 10.1016/j.dnarep.2024.103634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/08/2024] [Accepted: 01/21/2024] [Indexed: 02/01/2024]
Abstract
The maintenance of genome stability is crucial for cell homeostasis and tissue integrity. Numerous human neuropathologies display chronic inflammation in the central nervous system, set against a backdrop of genome instability, implying a close interplay between the DNA damage and immune responses in the context of neurological disease. Dissecting the molecular mechanisms of this crosstalk is essential for holistic understanding of neuroinflammatory pathways in genome instability disorders. Non-neuronal cell types, specifically microglia, are major drivers of neuroinflammation in the central nervous system with neuro-protective and -toxic capabilities. Here, we discuss how persistent DNA damage affects microglial homeostasis, zooming in on the cytosolic DNA sensing cGAS-STING pathway and the downstream inflammatory response, which can drive neurotoxic outcomes in the context of genome instability.
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Affiliation(s)
- Nina L Maliar
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Emily J Talbot
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Abigail R Edwards
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, UK
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3
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Pennarun G, Picotto J, Bertrand P. Close Ties between the Nuclear Envelope and Mammalian Telomeres: Give Me Shelter. Genes (Basel) 2023; 14:genes14040775. [PMID: 37107534 PMCID: PMC10137478 DOI: 10.3390/genes14040775] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/18/2023] [Accepted: 03/20/2023] [Indexed: 04/29/2023] Open
Abstract
The nuclear envelope (NE) in eukaryotic cells is essential to provide a protective compartment for the genome. Beside its role in connecting the nucleus with the cytoplasm, the NE has numerous important functions including chromatin organization, DNA replication and repair. NE alterations have been linked to different human diseases, such as laminopathies, and are a hallmark of cancer cells. Telomeres, the ends of eukaryotic chromosomes, are crucial for preserving genome stability. Their maintenance involves specific telomeric proteins, repair proteins and several additional factors, including NE proteins. Links between telomere maintenance and the NE have been well established in yeast, in which telomere tethering to the NE is critical for their preservation and beyond. For a long time, in mammalian cells, except during meiosis, telomeres were thought to be randomly localized throughout the nucleus, but recent advances have uncovered close ties between mammalian telomeres and the NE that play important roles for maintaining genome integrity. In this review, we will summarize these connections, with a special focus on telomere dynamics and the nuclear lamina, one of the main NE components, and discuss the evolutionary conservation of these mechanisms.
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Affiliation(s)
- Gaëlle Pennarun
- Université Paris Cité, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
- Université Paris-Saclay, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
| | - Julien Picotto
- Université Paris Cité, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
- Université Paris-Saclay, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
| | - Pascale Bertrand
- Université Paris Cité, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
- Université Paris-Saclay, INSERM, CEA, Stabilité Génétique Cellules Souches et Radiations, LREV/iRCM/IBFJ, F-92260 Fontenay-aux-Roses, France
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4
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Dutta B, Osato M. The RUNX Family, a Novel Multifaceted Guardian of the Genome. Cells 2023; 12:255. [PMID: 36672189 PMCID: PMC9856552 DOI: 10.3390/cells12020255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 12/24/2022] [Accepted: 12/30/2022] [Indexed: 01/11/2023] Open
Abstract
The DNA repair machinery exists to protect cells from daily genetic insults by orchestrating multiple intrinsic and extrinsic factors. One such factor recently identified is the Runt-related transcription factor (RUNX) family, a group of proteins that act as a master transcriptional regulator for multiple biological functions such as embryonic development, stem cell behaviors, and oncogenesis. A significant number of studies in the past decades have delineated the involvement of RUNX proteins in DNA repair. Alterations in RUNX genes cause organ failure and predisposition to cancers, as seen in patients carrying mutations in the other well-established DNA repair genes. Herein, we review the currently existing findings and provide new insights into transcriptional and non-transcriptional multifaceted regulation of DNA repair by RUNX family proteins.
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Affiliation(s)
- Bibek Dutta
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore
- Cancer Science Institute of Singapore, National University of Singapore, Singapore 117599, Singapore
| | - Motomi Osato
- Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117599, Singapore
- Cancer Science Institute of Singapore, National University of Singapore, Singapore 117599, Singapore
- International Research Center for Medical Sciences, Kumamoto University, Kumamoto 860-0811, Japan
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5
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Srikanth P, Chowdhury AR, Low GKM, Saraswathy R, Fujimori A, Banerjee B, Martinez-Lopez W, Hande MP. Oxidative Damage Induced Telomere Mediated Genomic Instability in Cells from Ataxia Telangiectasia Patients. Genome Integr 2022; 13:2. [PMID: 38021281 PMCID: PMC10557037 DOI: 10.14293/genint.13.1.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023] Open
Abstract
Our cellular genome is susceptible to cytotoxic lesions which include single strand breaks and double strand breaks among other lesions. Ataxia telangiectasia mutated (ATM) protein was one of the first DNA damage sensor proteins to be discovered as being involved in DNA repair and as well as in telomere maintenance. Telomeres help maintain the stability of our chromosomes by protecting the ends from degradation. Cells from ataxia telangiectasia (AT) patients lack ATM and accumulate chromosomal alterations. AT patients display heightened susceptibility to cancer. In this study, cells from AT patients (called as AT -/- and AT +/- cells) were characterized for genome stability status and it was observed that AT -/- cells show considerable telomere attrition. Furthermore, DNA damage and genomic instability were compared between normal (AT +/+ cells) and AT -/- cells exhibiting increased frequencies of spontaneous DNA damage and genomic instability markers. Both AT -/- and AT +/- cells were sensitive to sodium arsenite (1.5 and 3.0 μg/ml) and ionizing radiation-induced (2 Gy, gamma rays) oxidative stress. Interestingly, telomeric fragments were detected in the comet tails as revealed by comet-fluorescence in situ hybridization analysis, suggestive of telomeric instability in AT -/- cells upon exposure to sodium arsenite or radiation. Besides, there was an increase in the number of chromosome alterations in AT -/- cells following arsenite treatment or irradiation. In addition, complex chromosome aberrations were detected by multicolor fluorescence in situ hybridization in AT -/- cells in comparison to AT +/- and normal cells. Telomere attrition and chromosome alterations were detected even at lower doses of sodium arsenite. Peptide nucleic acid - FISH analysis revealed defective chromosome segregation in cells lacking ATM proteins. The data obtained in this study substantiates the role of ATM in telomere stability under oxidative stress.
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Affiliation(s)
- Prarthana Srikanth
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Biomedical Sciences, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, India
| | - Amit Roy Chowdhury
- inDNA Center for Research and Innovation in Molecular Diagnostics, inDNA Life Sciences Private Limited, Bhubaneswar, India
| | - Grace Kah Mun Low
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Radha Saraswathy
- Department of Biomedical Sciences, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, India
| | - Akira Fujimori
- Molecular and Cellular Radiation Biology Group, Department of Charged Particle Therapy Research Institute for Quantum Medical Science Chiba, Japan
| | - Birendranath Banerjee
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- inDNA Center for Research and Innovation in Molecular Diagnostics, inDNA Life Sciences Private Limited, Bhubaneswar, India
| | - Wilner Martinez-Lopez
- Department of Biomedical Sciences, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, India
- Genetics Department and Biodosimetry Services, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
- Associate Unit on Genomic Stability, Faculty of Medicine, University of the Republic (UdelaR), Montevideo, Uruguay
| | - M. Prakash Hande
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Biomedical Sciences, School of Biosciences and Technology, Vellore Institute of Technology, Vellore, India
- Department of Applied Zoology, Mangalore University, Mangalore, India
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6
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Low GKM, Ting APL, Fok EDZ, Gopalakrishnan K, Zeegers D, Khaw AK, Jayapal M, Martinez-Lopez W, Hande MP. Role of Xeroderma pigmentosum D (XPD) protein in genome maintenance in human cells under oxidative stress. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2022; 876-877:503444. [PMID: 35483790 DOI: 10.1016/j.mrgentox.2022.503444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/29/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
Xeroderma pigmentosum D (XPD) protein plays a pivotal role in the nucleotide excision repair pathway. XPD unwinds the local area of the damaged DNA by virtue of constituting transcription factor II H (TFIIH) and is important not only for repair but also for basal transcription. Although cells deficient in XPD have shown to be defective in oxidative base-lesion repair, the effects of the oxidative assault on primary fibroblasts from patients suffering from Xeroderma Pigmentosum D have not been fully explored. Therefore, we sought to investigate the role of XPD in oxidative DNA damage-repair by treating primary fibroblasts derived from a patient suffering from Xeroderma Pigmentosum D, with hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with minimal effect on cytotoxicity with H2O2 in XPD deficient cells compared to control cells. XPD deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. XPD deficient fibroblasts exhibited increased telomeric loss after H2O2 treatment. In addition, we demonstrated that chronic oxidative stress induced accelerated premature senescence characteristics. Gene expression profiling revealed alterations in genes involved in transcription and nucleotide metabolisms, as well as in cellular and cell cycle processes in a more significant way than in other pathways. This study highlights the role of XPD in the repair of oxidative stress and telomere maintenance. Lack of functional XPD seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum D patients.
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Affiliation(s)
- Grace Kah Mun Low
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Aloysius Poh Leong Ting
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Edwin Dan Zhihao Fok
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Kalpana Gopalakrishnan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Dimphy Zeegers
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Aik Kia Khaw
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Manikandan Jayapal
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Wilner Martinez-Lopez
- Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay; Associate Unit on Genomic Stability, Faculty of Medicine, University of the Republic (UdelaR), Montevideo, Uruguay; Vellore Institute of Technology, Vellore, India
| | - M Prakash Hande
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; Vellore Institute of Technology, Vellore, India; Mangalore University, India.
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7
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Levi H, Bar E, Cohen-Adiv S, Sweitat S, Kanner S, Galron R, Mitiagin Y, Barzilai A. Dysfunction of cerebellar microglia in Ataxia-telangiectasia. Glia 2021; 70:536-557. [PMID: 34854502 DOI: 10.1002/glia.24122] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 11/09/2021] [Accepted: 11/12/2021] [Indexed: 12/13/2022]
Abstract
Ataxia-telangiectasia (A-T) is a multisystem autosomal recessive disease caused by mutations in the ATM gene and characterized by cerebellar atrophy, progressive ataxia, immunodeficiency, male and female sterility, radiosensitivity, cancer predisposition, growth retardation, insulin-resistant diabetes, and premature aging. ATM phosphorylates more than 1500 target proteins, which are involved in cell cycle control, DNA repair, apoptosis, modulation of chromatin structure, and other cytoplasmic as well as mitochondrial processes. In our quest to better understand the mechanisms by which ATM deficiency causes cerebellar degeneration, we hypothesized that specific vulnerabilities of cerebellar microglia underlie the etiology of A-T. Our hypothesis is based on the recent finding that dysfunction of glial cells affect a variety of process leading to impaired neuronal functionality (Song et al., 2019). Whereas astrocytes and neurons descend from the neural tube, microglia originate from the hematopoietic system, invade the brain at early embryonic stage, and become the innate immune cells of the central nervous system and important participants in development of synaptic plasticity. Here we demonstrate that microglia derived from Atm-/- mouse cerebellum display accelerated cell migration and are severely impaired in phagocytosis, secretion of neurotrophic factors, and mitochondrial activity, suggestive of apoptotic processes. Interestingly, no microglial impairment was detected in Atm-deficient cerebral cortex, and Atm deficiency had less impact on astroglia than microglia. Collectively, our findings validate the roles of glial cells in cerebellar attrition in A-T.
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Affiliation(s)
- Hadar Levi
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ela Bar
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Stav Cohen-Adiv
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Suzan Sweitat
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Sivan Kanner
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ronit Galron
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Yulia Mitiagin
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ari Barzilai
- Department of Neurobiology, George S. Wise, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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8
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DNA Repair Inhibition Leads to Active Export of Repetitive Sequences to the Cytoplasm Triggering an Inflammatory Response. J Neurosci 2021; 41:9286-9307. [PMID: 34593604 DOI: 10.1523/jneurosci.0845-21.2021] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 07/25/2021] [Accepted: 09/01/2021] [Indexed: 01/02/2023] Open
Abstract
Adult-onset neurodegenerative diseases are often accompanied by evidence of a chronic inflammation that includes activation of microglial cells and altered levels of brain cytokines. Aspects of this response are likely secondary reactions to neurodegeneration, but for many illnesses the inflammation may itself be an early and even causative disease event. In such cases, the inflammation is referred to as "sterile" as it occurs in the absence of an actual bacterial or viral pathogen. A potent trigger of sterile inflammation in CNS microglia has been shown to be the presence of DNA in the cytoplasm (cytoDNA) induced either by direct DNA damage or by inhibited DNA repair. We have shown that cytoDNA comes from the cell nucleus as a result of insufficient DNA damage repair. Using wild-type and Atm -/- mouse microglia, we extend these observations here by showing that its genomic origins are not random, but rather are heavily biased toward transcriptionally inactive, intergenic regions, in particular repetitive elements and AT-rich sequences. Once released from the genome, in both males and females, we show that cytoDNA is actively exported to the cytoplasm by a CRM1-dependent mechanism. In the cytoplasm, it is degraded either by a cytosolic exonuclease, Trex1, or an autophagy pathway that ends with degradation in the lysosome. Blocking the accumulation of cytoDNA prevents the emergence of the sterile inflammation reaction. These findings offer new insights into the emergence of sterile inflammation and offer novel approaches that may be of use in combatting a wide range of neurodegenerative conditions.SIGNIFICANCE STATEMENT Sterile inflammation describes a state where the defenses of the immune system are activated in the absence of a true pathogen. A potent trigger of this unorthodox response is the presence of DNA in the cytoplasm, which immune cells interpret as an invading virus or pathogen. We show that when DNA damage increases, fragments of the cell's own genome are actively exported to the cytoplasm where they are normally degraded. If this degradation is incomplete an immune reaction is triggered. Both age and stress increase DNA damage, and as age-related neurodegenerative diseases are frequently accompanied by a chronic low-level inflammation, strategies that reduce the induction of cytoplasmic DNA or speed its clearance become attractive therapeutic targets.
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9
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Silva GLA, Tosi LRO, McCulloch R, Black JA. Unpicking the Roles of DNA Damage Protein Kinases in Trypanosomatids. Front Cell Dev Biol 2021; 9:636615. [PMID: 34422791 PMCID: PMC8377203 DOI: 10.3389/fcell.2021.636615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 07/13/2021] [Indexed: 12/31/2022] Open
Abstract
To preserve genome integrity when faced with DNA lesions, cells activate and coordinate a multitude of DNA repair pathways to ensure timely error correction or tolerance, collectively called the DNA damage response (DDR). These interconnecting damage response pathways are molecular signal relays, with protein kinases (PKs) at the pinnacle. Focused efforts in model eukaryotes have revealed intricate aspects of DNA repair PK function, including how they direct DDR pathways and how repair reactions connect to wider cellular processes, including DNA replication and transcription. The Kinetoplastidae, including many parasites like Trypanosoma spp. and Leishmania spp. (causative agents of debilitating, neglected tropical infections), exhibit peculiarities in several core biological processes, including the predominance of multigenic transcription and the streamlining or repurposing of DNA repair pathways, such as the loss of non-homologous end joining and novel operation of nucleotide excision repair (NER). Very recent studies have implicated ATR and ATM kinases in the DDR of kinetoplastid parasites, whereas DNA-dependent protein kinase (DNA-PKcs) displays uncertain conservation, questioning what functions it fulfills. The wide range of genetic manipulation approaches in these organisms presents an opportunity to investigate DNA repair kinase roles in kinetoplastids and to ask if further kinases are involved. Furthermore, the availability of kinase inhibitory compounds, targeting numerous eukaryotic PKs, could allow us to test the suitability of DNA repair PKs as novel chemotherapeutic targets. Here, we will review recent advances in the study of trypanosomatid DNA repair kinases.
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Affiliation(s)
- Gabriel L A Silva
- The Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom.,Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Luiz R O Tosi
- Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Richard McCulloch
- The Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Jennifer Ann Black
- The Wellcome Centre for Integrative Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom.,Department of Cell and Molecular Biology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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10
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Yang B, Dan X, Hou Y, Lee J, Wechter N, Krishnamurthy S, Kimura R, Babbar M, Demarest T, McDevitt R, Zhang S, Zhang Y, Mattson MP, Croteau DL, Bohr VA. NAD + supplementation prevents STING-induced senescence in ataxia telangiectasia by improving mitophagy. Aging Cell 2021; 20:e13329. [PMID: 33734555 PMCID: PMC8045911 DOI: 10.1111/acel.13329] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 01/10/2021] [Accepted: 02/04/2021] [Indexed: 12/14/2022] Open
Abstract
Senescence phenotypes and mitochondrial dysfunction are implicated in aging and in premature aging diseases, including ataxia telangiectasia (A‐T). Loss of mitochondrial function can drive age‐related decline in the brain, but little is known about whether improving mitochondrial homeostasis alleviates senescence phenotypes. We demonstrate here that mitochondrial dysfunction and cellular senescence with a senescence‐associated secretory phenotype (SASP) occur in A‐T patient fibroblasts, and in ATM‐deficient cells and mice. Senescence is mediated by stimulator of interferon genes (STING) and involves ectopic cytoplasmic DNA. We further show that boosting intracellular NAD+ levels with nicotinamide riboside (NR) prevents senescence and SASP by promoting mitophagy in a PINK1‐dependent manner. NR treatment also prevents neurodegeneration, suppresses senescence and neuroinflammation, and improves motor function in Atm−/− mice. Our findings suggest a central role for mitochondrial dysfunction‐induced senescence in A‐T pathogenesis, and that enhancing mitophagy as a potential therapeutic intervention.
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Affiliation(s)
- Beimeng Yang
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Xiuli Dan
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Yujun Hou
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Jong‐Hyuk Lee
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Noah Wechter
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | | | - Risako Kimura
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Mansi Babbar
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Tyler Demarest
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Ross McDevitt
- Mouse Phenotyping Unit National Institute on Aging NIH Baltimore MD USA
| | - Shiliang Zhang
- Electron Microscopy Core National Institute on Drug Abuse Intramural Research Program NIH Baltimore MD USA
| | - Yongqing Zhang
- Laboratory of Genetics and Genomics National Institute on Aging National Institutes of Health Baltimore MD USA
| | - Mark P. Mattson
- Department of Neuroscience Johns Hopkins University School of Medicine Baltimore MD USA
| | - Deborah L. Croteau
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
| | - Vilhelm A. Bohr
- Laboratory of Molecular Gerontology National Institute on Aging NIH Baltimore MD USA
- Danish Center for Healthy Aging University of Copenhagen Copenhagen Denmark
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11
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Potential roles of telomeres and telomerase in neurodegenerative diseases. Int J Biol Macromol 2020; 163:1060-1078. [DOI: 10.1016/j.ijbiomac.2020.07.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/23/2020] [Accepted: 07/06/2020] [Indexed: 12/16/2022]
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12
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Bajaj S, Kumar MS, Peters GJ, Mayur YC. Targeting telomerase for its advent in cancer therapeutics. Med Res Rev 2020; 40:1871-1919. [PMID: 32391613 DOI: 10.1002/med.21674] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 04/19/2020] [Accepted: 04/21/2020] [Indexed: 12/24/2022]
Abstract
Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.
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Affiliation(s)
| | | | - G J Peters
- Department of Medical Oncology, VU University Medical Centre, Amsterdam, The Netherlands
| | - Y C Mayur
- SPPSPTM, SVKM's NMIMS, Mumbai, India
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13
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Ain Q, Schmeer C, Wengerodt D, Witte OW, Kretz A. Extrachromosomal Circular DNA: Current Knowledge and Implications for CNS Aging and Neurodegeneration. Int J Mol Sci 2020; 21:ijms21072477. [PMID: 32252492 PMCID: PMC7177960 DOI: 10.3390/ijms21072477] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 03/26/2020] [Accepted: 03/30/2020] [Indexed: 12/13/2022] Open
Abstract
Still unresolved is the question of how a lifetime accumulation of somatic gene copy number alterations impact organ functionality and aging and age-related pathologies. Such an issue appears particularly relevant in the broadly post-mitotic central nervous system (CNS), where non-replicative neurons are restricted in DNA-repair choices and are prone to accumulate DNA damage, as they remain unreplaced over a lifetime. Both DNA injuries and consecutive DNA-repair strategies are processes that can evoke extrachromosomal circular DNA species, apparently from either part of the genome. Due to their capacity to amplify gene copies and related transcripts, the individual cellular load of extrachromosomal circular DNAs will contribute to a dynamic pool of additional coding and regulatory chromatin elements. Analogous to tumor tissues, where the mosaicism of circular DNAs plays a well-characterized role in oncogene plasticity and drug resistance, we suggest involvement of the "circulome" also in the CNS. Accordingly, we summarize current knowledge on the molecular biogenesis, homeostasis and gene regulatory impacts of circular extrachromosomal DNA and propose, in light of recent discoveries, a critical role in CNS aging and neurodegeneration. Future studies will elucidate the influence of individual extrachromosomal DNA species according to their sequence complexity and regional distribution or cell-type-specific abundance.
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Affiliation(s)
- Quratul Ain
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
| | - Christian Schmeer
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
| | - Diane Wengerodt
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
| | - Otto W. Witte
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
| | - Alexandra Kretz
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
- Correspondence:
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14
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Renault AL, Mebirouk N, Cavaciuti E, Le Gal D, Lecarpentier J, d'Enghien CD, Laugé A, Dondon MG, Labbé M, Lesca G, Leroux D, Gladieff L, Adenis C, Faivre L, Gilbert-Dussardier B, Lortholary A, Fricker JP, Dahan K, Bay JO, Longy M, Buecher B, Janin N, Zattara H, Berthet P, Combès A, Coupier I, Hall J, Stoppa-Lyonnet D, Andrieu N, Lesueur F. Telomere length, ATM mutation status and cancer risk in Ataxia-Telangiectasia families. Carcinogenesis 2017; 38:994-1003. [PMID: 28981872 PMCID: PMC5862273 DOI: 10.1093/carcin/bgx074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 07/08/2017] [Indexed: 11/12/2022] Open
Abstract
Recent studies have linked constitutive telomere length (TL) to aging-related diseases including cancer at different sites. ATM participates in the signaling of telomere erosion, and inherited mutations in ATM have been associated with increased risk of cancer, particularly breast cancer. The goal of this study was to investigate whether carriage of an ATM mutation and TL interplay to modify cancer risk in ataxia-telangiectasia (A-T) families.The study population consisted of 284 heterozygous ATM mutation carriers (HetAT) and 174 non-carriers (non-HetAT) from 103 A-T families. Forty-eight HetAT and 14 non-HetAT individuals had cancer, among them 25 HetAT and 6 non-HetAT were diagnosed after blood sample collection. We measured mean TL using a quantitative PCR assay and genotyped seven single-nucleotide polymorphisms (SNPs) recurrently associated with TL in large population-based studies.HetAT individuals were at increased risk of cancer (OR = 2.3, 95%CI = 1.2-4.4, P = 0.01), and particularly of breast cancer for women (OR = 2.9, 95%CI = 1.2-7.1, P = 0.02), in comparison to their non-HetAT relatives. HetAT individuals had longer telomeres than non-HetAT individuals (P = 0.0008) but TL was not associated with cancer risk, and no significant interaction was observed between ATM mutation status and TL. Furthermore, rs9257445 (ZNF311) was associated with TL in HetAT subjects and rs6060627 (BCL2L1) modified cancer risk in HetAT and non-HetAT women.Our findings suggest that carriage of an ATM mutation impacts on the age-related TL shortening and that TL per se is not related to cancer risk in ATM carriers. TL measurement alone is not a good marker for predicting cancer risk in A-T families.
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Affiliation(s)
- Anne-Laure Renault
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Noura Mebirouk
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Eve Cavaciuti
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Dorothée Le Gal
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Julie Lecarpentier
- Centre for Cancer Genetic Epidemiology, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | | | | | - Marie-Gabrielle Dondon
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Martine Labbé
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Gaetan Lesca
- CHU de Lyon, Groupement Hospitalier Est, Service de Génétique Médicale, Lyon, France
| | - Dominique Leroux
- CHU de Grenoble, Hôpital Couple-Enfant, Département de Génétique, Grenoble, France
| | - Laurence Gladieff
- Institut Claudius Regaud-IUCT-Oncopole, Service d'Oncologie Médicale, Toulouse, France
| | | | - Laurence Faivre
- Hôpital d'Enfants, Service de Génétique Médicale, Dijon, France
| | | | - Alain Lortholary
- Centre Catherine de Sienne, Service d'Oncologie Médicale, Nantes, France
| | | | - Karin Dahan
- Clinique Universitaire Saint-Luc, Génétique, Bruxelles, Belgium
| | | | | | | | - Nicolas Janin
- Clinique Universitaire Saint-Luc, Génétique, Bruxelles, Belgium
| | | | - Pascaline Berthet
- Centre François Baclesse, Unité de Pathologie Gynécologique, Caen, France
| | - Audrey Combès
- Centre Hospitalier Universitaire de Nîmes, Unité de Génétique Médicale et Cytogénétique, Nîmes, France
| | - Isabelle Coupier
- Hôpital Arnaud de Villeneuve, CHU Montpellier, Service de Génétique Médicale et Oncogénétique, Montpellier, France.,ICM Val d'Aurel, Unité d'Oncogénétique, Montpellier, France
| | | | - Janet Hall
- Centre de Recherche en Cancérologie de Lyon, Lyon, France.,UMR INSERM 1052, Lyon, France.,CNRS 5286, Lyon, France
| | - Dominique Stoppa-Lyonnet
- Service de Génétique, Institut Curie, Paris, France.,INSERM, U830, Paris, France.,Université Paris Descartes, Paris, France
| | - Nadine Andrieu
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
| | - Fabienne Lesueur
- INSERM, U900, Paris, France.,PSL Research University, Paris, France.,Institut Curie, Paris, France.,Mines Paris Tech, Fontainebleau, France
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15
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Abstract
Bacteria and viruses possess circular DNA, whereas eukaryotes with typically very large DNA molecules have had to evolve into linear chromosomes to circumvent the problem of supercoiling circular DNA of that size. Consequently, such organisms possess telomeres to cap chromosome ends. Telomeres are essentially tandem repeats of any DNA sequence that are present at the ends of chromosomes. Their biology has been an enigmatic one, involving various molecules interacting dynamically in an evolutionarily well-trimmed fashion. Telomeres range from canonical hexameric repeats in most eukaryotes to unimaginably random retrotransposons, which attach to chromosome ends and reverse-transcribe to DNA in some plants and insects. Telomeres invariably associate with specialised protein complexes that envelop it, also regulating access of the ends to legitimate enzymes involved in telomere metabolism. They also transcribe into repetitive RNA which also seems to be playing significant roles in telomere maintenance. Telomeres thus form the intersection of DNA, protein, and RNA molecules acting in concert to maintain chromosome integrity. Telomere biology is emerging to appear ever more complex than previously envisaged, with the continual discovery of more molecules and interplays at the telomeres. This review also includes a section dedicated to the history of telomere biology, and intends to target the scientific audience new to the field by rendering an understanding of the phenomenon of chromosome end protection at large, with more emphasis on the biology of human telomeres. The review provides an update on the field and mentions the questions that need to be addressed.
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Affiliation(s)
- Shriram Venkatesan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore, Singapore.
| | - Aik Kia Khaw
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore, Singapore.
- Clinical Research Unit, Khoo Teck Puat Hospital, 768828 Singapore, Singapore.
| | - Manoor Prakash Hande
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597 Singapore, Singapore.
- Tembusu College, National University of Singapore, 138598 Singapore, Singapore.
- VIT University, Vellore 632014, India.
- Mangalore University, Mangalore 574199, India.
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16
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Berardinelli F, Coluzzi E, Sgura A, Antoccia A. Targeting telomerase and telomeres to enhance ionizing radiation effects in in vitro and in vivo cancer models. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2017; 773:204-219. [PMID: 28927529 DOI: 10.1016/j.mrrev.2017.02.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/13/2017] [Accepted: 02/14/2017] [Indexed: 01/05/2023]
Abstract
One of the hallmarks of cancer consists in the ability of tumor cells to divide indefinitely, and to maintain stable telomere lengths throughout the activation of specific telomere maintenance mechanisms (TMM). Therefore in the last fifteen years, researchers proposed to target telomerase or telomeric structure in order to block limitless replicative potential of cancer cells providing a fascinating strategy for a broad-spectrum cancer therapy. In the present review, we report in vitro and in vivo evidence regarding the use of chemical agents targeting both telomerase or telomere structure and showing promising antitumor effects when used in combination with ionizing radiation (IR). RNA interference, antisense oligonucleotides (e.g., GRN163L), non-nucleoside inhibitors (e.g., BIBR1532) and nucleoside analogs (e.g., AZT) represent some of the most potent strategies to inhibit telomerase activity used in combination with IR. Furthermore, radiosensitizing effects were demonstrated also for agents acting directly on the telomeric structure such as G4-ligands (e.g., RHPS4 and Telomestatin) or telomeric-oligos (T-oligos). To date, some of these compounds are under clinical evaluation (e.g., GRN163L and KML001). Advantages of Telomere/Telomerase Targeting Compounds (T/TTCs) coupled with radiotherapy may be relevant in the treatment of radioresistant tumors and in the development of new optimized treatment plans with reduced dose adsorbed by patients and consequent attenuation of short- end long-term side effects. Pros and cons of possible future applications in cancer therapy based on the combination of T/TCCs and radiation treatment are discussed.
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Affiliation(s)
- F Berardinelli
- Dipartimento di Scienze, Università Roma Tre, Rome Italy; Istituto Nazionale di Fisica Nucleare, INFN, Sezione di Roma Tre, Rome, Italy.
| | - E Coluzzi
- Dipartimento di Scienze, Università Roma Tre, Rome Italy
| | - A Sgura
- Dipartimento di Scienze, Università Roma Tre, Rome Italy; Istituto Nazionale di Fisica Nucleare, INFN, Sezione di Roma Tre, Rome, Italy
| | - A Antoccia
- Dipartimento di Scienze, Università Roma Tre, Rome Italy; Istituto Nazionale di Fisica Nucleare, INFN, Sezione di Roma Tre, Rome, Italy
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17
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Kim JY, An YM, Park JH. Role of GLTSCR2 in the regulation of telomerase activity and chromosome stability. Mol Med Rep 2016; 14:1697-703. [PMID: 27357325 DOI: 10.3892/mmr.2016.5427] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 01/11/2016] [Indexed: 11/05/2022] Open
Abstract
Telomerase is essential for regulating telomeres, and its activation is a critical step in cellular immortalization and tumorigenesis. The transcriptional activation of human telomerase reverse transcriptase (hTERT) is critical for telomerase expression. Although several transcriptional activators have been identified, factors responsible for enhancing the hTERT promoter remain to be fully elucidated. In the present study, the role of glioma tumor-suppressor candidate region gene 2 (GLTSCR2) in telomerase regulation was analyzed. A doxycyclin-inducible green fluorescent protein (GFP)-tagged GLTSCR2-expressing adenovirus (Ad‑GLT/GFP) was used for the transduction of SK‑Hep‑1 and T98G cancer cells, and normal human umbilical vein endothelial cells. Changes in telomerase activity using telomere repeat amplification protocol assay were assessed, and the gene expression levels of hTERT were then examined. To investigate chromosome instability and senescence, Giemsa and β-galactosidase staining was performed. The results revealed that overexpression of GLTSCR2 significantly increased telomerase activity in the cancer and normal cell lines. This increase was consistent with increases in the protein and mRNA expression levels of hTERT. In luciferase assays, the hTERT promoter was activated by GLTSCR2. Knockdown of GLTSCR2 led to the downregulation of telomerase activity, abnormal nuclear morphology as a marker of chromosome instability, significant suppression of growth rate, alterations in cellular morphology and, eventually, cellular senescence. Taken together, the results of the present study suggested that GLTSCR2 is crucially involved in the positive regulation of telomerase and chromosome stability.
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Affiliation(s)
- Jee-Youn Kim
- Department of Pathology, School of Medicine, Kyung Hee University, Seoul 130‑701, Republic of Korea
| | - Yong-Min An
- Department of Pathology, School of Medicine, Kyung Hee University, Seoul 130‑701, Republic of Korea
| | - Jae-Hoon Park
- Department of Pathology, School of Medicine, Kyung Hee University, Seoul 130‑701, Republic of Korea
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18
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Lee SS, Bohrson C, Pike AM, Wheelan SJ, Greider CW. ATM Kinase Is Required for Telomere Elongation in Mouse and Human Cells. Cell Rep 2015; 13:1623-32. [PMID: 26586427 PMCID: PMC4663052 DOI: 10.1016/j.celrep.2015.10.035] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 09/11/2015] [Accepted: 10/11/2015] [Indexed: 12/26/2022] Open
Abstract
Short telomeres induce a DNA damage response, senescence, and apoptosis, thus maintaining telomere length equilibrium is essential for cell viability. Telomerase addition of telomere repeats is tightly regulated in cells. To probe pathways that regulate telomere addition, we developed the ADDIT assay to measure new telomere addition at a single telomere in vivo. Sequence analysis showed telomerase-specific addition of repeats onto a new telomere occurred in just 48 hr. Using the ADDIT assay, we found that ATM is required for addition of new repeats onto telomeres in mouse cells. Evaluation of bulk telomeres, in both human and mouse cells, showed that blocking ATM inhibited telomere elongation. Finally, the activation of ATM through the inhibition of PARP1 resulted in increased telomere elongation, supporting the central role of the ATM pathway in regulating telomere addition. Understanding this role of ATM may yield new areas for possible therapeutic intervention in telomere-mediated disease.
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Affiliation(s)
- Stella Suyong Lee
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Predoctoral Training Program in Human Genetics and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Craig Bohrson
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alexandra Mims Pike
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Sarah Jo Wheelan
- Predoctoral Training Program in Human Genetics and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Carol Widney Greider
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Predoctoral Training Program in Human Genetics and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
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19
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Venkatesan S, Natarajan AT, Hande MP. Chromosomal instability--mechanisms and consequences. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2015; 793:176-84. [PMID: 26520388 DOI: 10.1016/j.mrgentox.2015.08.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 08/21/2015] [Indexed: 01/08/2023]
Abstract
Chromosomal instability is defined as a state of numerical and/or structural chromosomal anomalies in cells. Numerous studies have documented the incidence of chromosomal instability, which acutely or chronically may lead to accelerated ageing (tissue-wide or even organismal), cancer or other genetic disorders. Potential mechanisms leading to the generation of chromosome-genome instability include erroneous/inefficient DNA repair, chromosome segregation defects, spindle assembly defects, DNA replication stress, telomere shortening/dysfunction - to name a few. Understanding the cellular and molecular mechanisms for chromosomal instability in various human cells and tissues will be useful in elucidating the cause for many age associated diseases including cancer. This approach holds a great promise for the cytogenetic assays not only for prognosis but also for diagnostic purposes in clinical settings. In this review, a multi-dimensional approach has been attempted to portray the complexity behind the incidence of chromosome-genome instability including evolutionary implications at the species level for some of the mechanisms of chromosomal instability.
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Affiliation(s)
- Shriram Venkatesan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597
| | - Adayapalam T Natarajan
- Department of Ecological and Biological Sciences, University of Tuscia, Viterbo 01100, Italy
| | - M Prakash Hande
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597; Tembusu College, National University of Singapore, Singapore, 138597.
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20
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Osterwald S, Deeg KI, Chung I, Parisotto D, Wörz S, Rohr K, Erfle H, Rippe K. PML induces compaction, TRF2 depletion and DNA damage signaling at telomeres and promotes their alternative lengthening. J Cell Sci 2015; 128:1887-1900. [DOI: 10.1242/jcs.148296] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
Abstract
ABSTRACT
The alternative lengthening of telomeres (ALT) mechanism allows cancer cells to escape senescence and apoptosis in the absence of active telomerase. A characteristic feature of this pathway is the assembly of ALT-associated promyelocytic leukemia (PML) nuclear bodies (APBs) at telomeres. Here, we dissected the role of APBs in a human ALT cell line by performing an RNA interference screen using an automated 3D fluorescence microscopy platform and advanced 3D image analysis. We identified 29 proteins that affected APB formation, which included proteins involved in telomere and chromatin organization, protein sumoylation and DNA repair. By integrating and extending these findings, we found that APB formation induced clustering of telomere repeats, telomere compaction and concomitant depletion of the shelterin protein TRF2 (also known as TERF2). These APB-dependent changes correlated with the induction of a DNA damage response at telomeres in APBs as evident by a strong enrichment of the phosphorylated form of the ataxia telangiectasia mutated (ATM) kinase. Accordingly, we propose that APBs promote telomere maintenance by inducing a DNA damage response in ALT-positive tumor cells through changing the telomeric chromatin state to trigger ATM phosphorylation.
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Affiliation(s)
- Sarah Osterwald
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Katharina I. Deeg
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Inn Chung
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Daniel Parisotto
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
| | - Stefan Wörz
- Department of Bioinformatics and Functional Genomics, Biomedical Computer Vision Group, University of Heidelberg & DKFZ, BioQuant, IPMB, 69120 Heidelberg, Germany
| | - Karl Rohr
- Department of Bioinformatics and Functional Genomics, Biomedical Computer Vision Group, University of Heidelberg & DKFZ, BioQuant, IPMB, 69120 Heidelberg, Germany
| | - Holger Erfle
- ViroQuant-CellNetworks RNAi Screening Facility, University of Heidelberg & BioQuant, 69120 Heidelberg, Germany
| | - Karsten Rippe
- Research Group Genome Organization & Function, Deutsches Krebsforschungszentrum (DKFZ) & BioQuant, 69120 Heidelberg, Germany
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21
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Changes in the expression of DNA double strand break repair genes in primordial follicles from immature and aged rats. Reprod Biomed Online 2015; 30:303-10. [DOI: 10.1016/j.rbmo.2014.11.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/14/2014] [Accepted: 11/18/2014] [Indexed: 11/19/2022]
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22
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Komosa M, Root H, Meyn MS. Visualization and quantitative analysis of extrachromosomal telomere-repeat DNA in individual human cells by Halo-FISH. Nucleic Acids Res 2015; 43:2152-63. [PMID: 25662602 PMCID: PMC4344523 DOI: 10.1093/nar/gkv091] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Current methods for characterizing extrachromosomal nuclear DNA in mammalian cells do not permit single-cell analysis, are often semi-quantitative and frequently biased toward the detection of circular species. To overcome these limitations, we developed Halo-FISH to visualize and quantitatively analyze extrachromosomal DNA in single cells. We demonstrate Halo-FISH by using it to analyze extrachromosomal telomere-repeat (ECTR) in human cells that use the Alternative Lengthening of Telomeres (ALT) pathway(s) to maintain telomere lengths. We find that GM847 and VA13 ALT cells average ∼80 detectable G/C-strand ECTR DNA molecules/nucleus, while U2OS ALT cells average ∼18 molecules/nucleus. In comparison, human primary and telomerase-positive cells contain <5 ECTR DNA molecules/nucleus. ECTR DNA in ALT cells exhibit striking cell-to-cell variations in number (<20 to >300), range widely in length (<1 to >200 kb) and are composed of primarily G- or C-strand telomere-repeat DNA. Halo-FISH enables, for the first time, the simultaneous analysis of ECTR DNA and chromosomal telomeres in a single cell. We find that ECTR DNA comprises ∼15% of telomere-repeat DNA in GM847 and VA13 cells, but <4% in U2OS cells. In addition to its use in ALT cell analysis, Halo-FISH can facilitate the study of a wide variety of extrachromosomal DNA in mammalian cells.
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Affiliation(s)
- Martin Komosa
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada
| | - Heather Root
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada
| | - M Stephen Meyn
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, M5G 0A4, Canada Division of Clinical and Metabolic Genetics, The Hospital for Sick Children, Toronto, Ontario, M5G 1X8, Canada Department of Paediatrics, University of Toronto, Toronto, Ontario, M5S 1A8, Canada Department of Molecular Genetics, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
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23
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Harland JL, Chang YT, Moser BA, Nakamura TM. Tpz1-Ccq1 and Tpz1-Poz1 interactions within fission yeast shelterin modulate Ccq1 Thr93 phosphorylation and telomerase recruitment. PLoS Genet 2014; 10:e1004708. [PMID: 25330395 PMCID: PMC4199508 DOI: 10.1371/journal.pgen.1004708] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 08/26/2014] [Indexed: 11/22/2022] Open
Abstract
In both fission yeast and humans, the shelterin complex plays central roles in regulation of telomerase recruitment, protection of telomeres against DNA damage response factors, and formation of heterochromatin at telomeres. While shelterin is essential for limiting activation of the DNA damage checkpoint kinases ATR and ATM at telomeres, these kinases are required for stable maintenance of telomeres. In fission yeast, Rad3ATR and Tel1ATM kinases are redundantly required for telomerase recruitment, since Rad3ATR/Tel1ATM-dependent phosphorylation of the shelterin subunit Ccq1 at Thr93 promotes interaction between Ccq1 and the telomerase subunit Est1. However, it remained unclear how protein-protein interactions within the shelterin complex (consisting of Taz1, Rap1, Poz1, Tpz1, Pot1 and Ccq1) contribute to the regulation of Ccq1 Thr93 phosphorylation and telomerase recruitment. In this study, we identify domains and amino acid residues that are critical for mediating Tpz1-Ccq1 and Tpz1-Poz1 interaction within the fission yeast shelterin complex. Using separation of function Tpz1 mutants that maintain Tpz1-Pot1 interaction but specifically disrupt either Tpz1-Ccq1 or Tpz1-Poz1 interaction, we then establish that Tpz1-Ccq1 interaction promotes Ccq1 Thr93 phosphorylation, telomerase recruitment, checkpoint inhibition and telomeric heterochromatin formation. Furthermore, we demonstrate that Tpz1-Poz1 interaction promotes telomere association of Poz1, and loss of Poz1 from telomeres leads to increases in Ccq1 Thr93 phosphorylation and telomerase recruitment, and telomeric heterochromatin formation defect. In addition, our studies establish that Tpz1-Poz1 and Tpz1-Ccq1 interactions redundantly fulfill the essential telomere protection function of the shelterin complex, since simultaneous loss of both interactions caused immediate loss of cell viability for the majority of cells and generation of survivors with circular chromosomes. Based on these findings, we suggest that the negative regulatory function of Tpz1-Poz1 interaction works upstream of Rad3ATR kinase, while Tpz1-Ccq1 interaction works downstream of Rad3ATR kinase to facilitate Ccq1 Thr93 phosphorylation and telomerase recruitment. Proper maintenance of telomeres is essential for maintaining genomic stability, and genomic instability caused by dysfunctional telomeres could lead to accumulation of mutations that may drive tumor formation. Telomere dysfunction has also been linked to premature aging caused by depletion of stem cells. Therefore, it is important to understand how cells ensure proper maintenance of telomeres. Mammalian cells and fission yeast cells utilize an evolutionarily conserved multi-subunit telomere protection complex called shelterin to ensure protection against telomere fusions by DNA repair factors and cell cycle arrest by DNA damage checkpoint kinases. However, previous studies have not yet fully established how protein-protein interactions within the shelterin complex contribute to the regulation of DNA damage checkpoint signaling and telomerase recruitment. By utilizing separation of function mutations that specifically disrupt either Tpz1-Ccq1 or Tpz1-Poz1 interaction within the fission yeast shelterin, we establish that Tpz1-Ccq1 interaction is essential for phosphorylation of Ccq1 by the DNA damage checkpoint kinases Rad3ATR and Tel1ATM that is needed for telomerase recruitment to telomeres, while Tpz1-Poz1 interaction prevents Ccq1 phosphorylation by promoting Poz1 association with telomeres. These findings thus establish for the first time how protein-protein interactions within the shelterin complex modulate checkpoint kinase-dependent phosphorylation essential for telomerase recruitment.
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Affiliation(s)
- Jennifer L. Harland
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Ya-Ting Chang
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Bettina A. Moser
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Toru M. Nakamura
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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Lan YY, Londoño D, Bouley R, Rooney MS, Hacohen N. Dnase2a deficiency uncovers lysosomal clearance of damaged nuclear DNA via autophagy. Cell Rep 2014; 9:180-192. [PMID: 25284779 DOI: 10.1016/j.celrep.2014.08.074] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 07/30/2014] [Accepted: 08/28/2014] [Indexed: 12/22/2022] Open
Abstract
Deficiencies in DNA-degrading nucleases lead to accumulation of self DNA and induction of autoimmunity in mice and in monogenic and polygenic human diseases. However, the sources of DNA and the mechanisms that trigger immunity remain unclear. We analyzed mice deficient for the lysosomal nuclease Dnase2a and observed elevated levels of undegraded DNA in both phagocytic and nonphagocytic cells. In nonphagocytic cells, the excess DNA originated from damaged DNA in the nucleus based on colocalization studies, live-cell imaging, and exacerbation by DNA-damaging agents. Removal of damaged DNA by Dnase2a required nuclear export and autophagy-mediated delivery of the DNA to lysosomes. Finally, DNA was found to accumulate in Dnase2a(-/-) or autophagy-deficient cells and induce inflammation via the Sting cytosolic DNA-sensing pathway. Our results reveal a cell-autonomous process for removal of damaged nuclear DNA with implications for conditions with elevated DNA damage, such as inflammation, cancer, and chemotherapy.
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Affiliation(s)
- Yuk Yuen Lan
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, 149 13(th) Street, Charlestown, MA 02129, USA; Broad Institute, 415 Main Street, Cambridge, MA 02142, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA
| | - Diana Londoño
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, 149 13(th) Street, Charlestown, MA 02129, USA
| | - Richard Bouley
- Center for Systems Biology, Program in Membrane Biology and Nephrology Division, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA
| | - Michael S Rooney
- Broad Institute, 415 Main Street, Cambridge, MA 02142, USA; Harvard/MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA
| | - Nir Hacohen
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, 149 13(th) Street, Charlestown, MA 02129, USA; Broad Institute, 415 Main Street, Cambridge, MA 02142, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
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25
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Schneider JS, Cheng X, Zhao Q, Underbayev C, Gonzalez JP, Raveche ES, Fraidenraich D, Ivessa AS. Reversible mitochondrial DNA accumulation in nuclei of pluripotent stem cells. Stem Cells Dev 2014; 23:2712-9. [PMID: 24964274 DOI: 10.1089/scd.2013.0630] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
According to the endosymbiotic hypothesis, the precursor of mitochondria invaded the precursor of eukaryotic cells, a process that began roughly 2 billion years ago. Since then, the majority of the genetic material translocated from the mitochondria to the nucleus, where now almost all mitochondrial proteins are expressed. Only a tiny amount of DNA remained in the mitochondria, known as mitochondrial DNA (mtDNA). In this study, we report that the transfer of mtDNA fragments to the nucleus of pluripotent stem cells is still ongoing. We show by in situ hybridization and agarose DNA two-dimensional gel technique that induced pluripotent stem (iPS) cells contain high levels of mtDNA in the nucleus. We found that a large proportion of the accumulated mtDNA sequences appear to be extrachromosomal. Accumulation of mtDNA in the nucleus is present not only in the iPS cells, but also in embryonic stem (ES) cells. However upon differentiation, the level of mtDNA in the nuclei of iPS and ES cells is substantially reduced. This reversible accumulation of mtDNA in the nucleus supports the notion that the nuclear copy number of mtDNA sequences may provide a novel mechanism by which chromosomal DNA is dynamically regulated in pluripotent stem cells.
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Affiliation(s)
- Joel S Schneider
- 1 Department of Cell Biology and Molecular Medicine, Rutgers Biomedical and Health Sciences , Newark, New Jersey
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26
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Accelerated aging during chronic oxidative stress: a role for PARP-1. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:680414. [PMID: 24319532 PMCID: PMC3844163 DOI: 10.1155/2013/680414] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/20/2013] [Accepted: 09/23/2013] [Indexed: 12/15/2022]
Abstract
Oxidative stress plays a major role in the pathophysiology of chronic inflammatory disease and it has also been linked to accelerated telomere shortening. Telomeres are specialized structures at the ends of linear chromosomes that protect these ends from degradation and fusion. Telomeres shorten with each cell division eventually leading to cellular senescence. Research has shown that poly(ADP-ribose) polymerase-1 (PARP-1) and subtelomeric methylation play a role in telomere stability. We hypothesized that PARP-1 plays a role in accelerated aging in chronic inflammatory diseases due to its role as coactivator of NF-κb and AP-1. Therefore we evaluated the effect of chronic PARP-1 inhibition (by fisetin and minocycline) in human fibroblasts (HF) cultured under normal conditions and under conditions of chronic oxidative stress, induced by tert-butyl hydroperoxide (t-BHP). Results showed that PARP-1 inhibition under normal culturing conditions accelerated the rate of telomere shortening. However, under conditions of chronic oxidative stress, PARP-1 inhibition did not show accelerated telomere shortening. We also observed a strong correlation between telomere length and subtelomeric methylation status of HF cells. We conclude that chronic PARP-1 inhibition appears to be beneficial in conditions of chronic oxidative stress but may be detrimental under relatively normal conditions.
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Walker JR, Zhu XD. Post-translational modifications of TRF1 and TRF2 and their roles in telomere maintenance. Mech Ageing Dev 2012; 133:421-34. [PMID: 22634377 DOI: 10.1016/j.mad.2012.05.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 04/27/2012] [Accepted: 05/04/2012] [Indexed: 11/29/2022]
Abstract
Telomeres, heterochromatic structures, found at the ends of linear eukaryotic chromosomes, function to protect natural chromosome ends from nucleolytic attack. Human telomeric DNA is bound by a telomere-specific six-subunit protein complex, termed shelterin/telosome. The shelterin subunits TRF1 and TRF2 bind in a sequence-specific manner to double-stranded telomeric DNA, providing a vital platform for recruitment of additional shelterin proteins as well as non-shelterin factors crucial for the maintenance of telomere length and structure. Both TRF1 and TRF2 are engaged in multiple roles at telomeres including telomere protection, telomere replication, sister telomere resolution and telomere length maintenance. Regulation of TRF1 and TRF2 in these various processes is controlled by post-translational modifications, at times in a cell-cycle-dependent manner, affecting key functions such as DNA binding, dimerization, localization, degradation and interactions with other proteins. Here we review the post-translational modifications of TRF1 and TRF2 and discuss the mechanisms by which these modifications contribute to the function of these two proteins.
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Affiliation(s)
- John R Walker
- Department of Biology, LSB438, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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28
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Pickett HA, Reddel RR. The role of telomere trimming in normal telomere length dynamics. Cell Cycle 2012; 11:1309-15. [PMID: 22421147 DOI: 10.4161/cc.19632] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Telomeres consist of repetitive DNA and associated proteins that protect chromosome ends from illicit DNA repair. It is well known that telomeric DNA is progressively eroded during cell division, until telomeres become too short and the cell stops dividing. There is a second mode of telomere shortening, however, which is a regulated form of telomere rapid deletion (TRD) termed telomere trimming that is reviewed here. Telomere trimming appears to involve resolution of recombination intermediate structures, which shortens the telomere by release of extrachromosomal telomeric DNA. This has been detected in human and in mouse cells and occurs both in somatic and germline cells, where it sets an upper limit on telomere length and contributes to a length equilibrium set-point in cells that have a telomere elongation mechanism. Telomere trimming thus represents an additional mechanism of telomere length control that contributes to normal telomere dynamics and cell proliferative potential.
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Affiliation(s)
- Hilda A Pickett
- Children's Medical Research Institute and Sydney Medical School, University of Sydney, New South Wales, Australia
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McKerlie M, Lin S, Zhu XD. ATM regulates proteasome-dependent subnuclear localization of TRF1, which is important for telomere maintenance. Nucleic Acids Res 2012; 40:3975-89. [PMID: 22266654 PMCID: PMC3351164 DOI: 10.1093/nar/gks035] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ataxia telangiectasia mutated (ATM), a PI-3 kinase essential for maintaining genomic stability, has been shown to regulate TRF1, a negative mediator of telomerase-dependent telomere extension. However, little is known about ATM-mediated TRF1 phosphorylation site(s) in vivo. Here, we report that ATM phosphorylates S367 of TRF1 and that this phosphorylation renders TRF1 free of chromatin. We show that phosphorylated (pS367)TRF1 forms distinct non-telomeric subnuclear foci and that these foci occur predominantly in S and G2 phases, implying that their formation is cell cycle regulated. We show that phosphorylated (pS367)TRF1-containing foci are sensitive to proteasome inhibition. We find that a phosphomimic mutation of S367D abrogates TRF1 binding to telomeric DNA and renders TRF1 susceptible to protein degradation. In addition, we demonstrate that overexpressed TRF1-S367D accumulates in the subnuclear domains containing phosphorylated (pS367)TRF1 and that these subnuclear domains overlap with nuclear proteasome centers. Taken together, these results suggest that phosphorylated (pS367)TRF1-containing foci may represent nuclear sites for TRF1 proteolysis. Furthermore, we show that TRF1 carrying the S367D mutation is unable to inhibit telomerase-dependent telomere lengthening or to suppress the formation of telomere doublets and telomere loss in TRF1-depleted cells, suggesting that S367 phosphorylation by ATM is important for the regulation of telomere length and stability.
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Affiliation(s)
- Megan McKerlie
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON L8S4K1, Canada
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30
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Sapir E, Gozaly-Chianea Y, Al-Wahiby S, Ravindran S, Yasaei H, Slijepcevic P. Effects of BRCA2 deficiency on telomere recombination in non-ALT and ALT cells. Genome Integr 2011; 2:9. [PMID: 22152194 PMCID: PMC3264516 DOI: 10.1186/2041-9414-2-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 12/09/2011] [Indexed: 12/29/2022] Open
Abstract
Background Recent studies suggest that BRCA2 affects telomere maintenance. Interestingly, anti cancer treatments that involve BRCA2 and telomerase individually are currently being explored. In the light of the above recent studies their combinatorial targeting may be justified in the development of future treatments. In order to investigate effects of BRCA2 that can be explored for this combinatorial targeting we focused on the analysis of recombination rates at telomeres by monitoring T-SCEs (Telomere Sister Chromatid Exchanges). Results We observed a significant increase in T-SCE frequencies in four BRCA2 defective human cell lines thus suggesting that BRCA2 suppresses recombination at telomeres. To test this hypothesis further we analyzed T-SCE frequencies in a set of Chinese hamster cell lines with or without functional BRCA2. Our results indicate that introduction of functional BRCA2 normalizes frequencies of T-SCEs thus supporting the notion that BRCA2 suppresses recombination at telomeres. Given that ALT (Alternative Lengthening of Telomeres) positive cells maintain telomeres by recombination we investigated the effect of BRCA2 depletion in these cells. Our results show that this depletion causes a dramatic reduction in T-SCE frequencies in ALT positive cells, but not in non-ALT cells. Conclusion BRCA2 suppresses recombination at telomeres in cells that maintain them by conventional mechanisms. Furthermore, BRCA2 depletion in ALT positive cells reduces high levels of T-SCEs normally found in these cells. Our results could be potentially important for refining telomerase-based anti-cancer therapies.
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Affiliation(s)
- Ester Sapir
- Brunel Institute of Cancer Genetics and Pharmacogenomics, Division of Biosciences, School of Health Sciences & Social Care, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK.
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Characterization of TTAGG telomeric repeats, their interstitial occurrence and constitutively active telomerase in the mealybug Planococcus lilacinus (Homoptera; Coccoidea). Chromosoma 2010; 120:165-75. [PMID: 21088846 DOI: 10.1007/s00412-010-0299-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 10/12/2010] [Accepted: 11/02/2010] [Indexed: 10/18/2022]
Abstract
We confirmed the occurrence of the insect TTAGG telomeric repeats in the mealybug Planococcus lilacinus, a radiation-resistant coccid, by single primer polymerase chain reaction (PCR) and Southern hybridization. Analysis of Bal31 nuclease-digested DNA by Southern hybridization and chromosomes by FISH suggests that these repeats occur mainly at the ends of the chromosomes. However, sequence analysis of the PCR products of TTAGG-associated sequences from genomic DNA showed their interstitial occurrence and association with certain unrelated low-copy repeats. Because of their shorter length, the interstitial TTAGG sequences were detectable by primed in situ hybridizations but not by FISH. Analysis of chromosomes recovered after irradiation by fluorescent in situ hybridization suggested acquisition of TTAGG repeats at a majority of the healed ends. We also observed mild telomerase activity in unirradiated insects which was further enhanced after irradiation. Taken together, these results suggest that the mealybug has an efficient mechanism of formation of TTAGG repeats at radiation-induced chromosome ends and constitutively active telomerase may be a feature associated with rapid recovery of chromosome ends damaged by ionizing radiation.
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32
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Benson EK, Lee SW, Aaronson SA. Role of progerin-induced telomere dysfunction in HGPS premature cellular senescence. J Cell Sci 2010; 123:2605-12. [PMID: 20605919 PMCID: PMC2908049 DOI: 10.1242/jcs.067306] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2010] [Indexed: 12/27/2022] Open
Abstract
Hutchinson-Gilford Progeria Syndrome (HGPS) is a premature-aging syndrome caused by a dominant mutation in the gene encoding lamin A, which leads to an aberrantly spliced and processed protein termed progerin. Previous studies have shown that progerin induces early senescence associated with increased DNA-damage signaling and that telomerase extends HGPS cellular lifespan. We demonstrate that telomerase extends HGPS cellular lifespan by decreasing progerin-induced DNA-damage signaling and activation of p53 and Rb pathways that otherwise mediate the onset of premature senescence. We show further that progerin-induced DNA-damage signaling is localized to telomeres and is associated with telomere aggregates and chromosomal aberrations. Telomerase amelioration of DNA-damage signaling is relatively rapid, requires both its catalytic and DNA-binding functions, and correlates in time with the acquisition by HGPS cells of the ability to proliferate. All of these findings establish that HGPS premature cellular senescence results from progerin-induced telomere dysfunction.
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Affiliation(s)
- Erica K. Benson
- Department of Oncological Sciences, Mount Sinai School of Medicine, Box 1130, One Gustave L. Levy Place, NY 10012, USA
| | - Sam W. Lee
- Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charleston, MA 02129, USA
| | - Stuart A. Aaronson
- Department of Oncological Sciences, Mount Sinai School of Medicine, Box 1130, One Gustave L. Levy Place, NY 10012, USA
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Abstract
Background Repair of DNA double strand breaks by non-homologous end joining (NHEJ) requires several proteins including Ku, DNA-PKcs, Artemis, XRCC4, Ligase IV and XLF. Two of these proteins, namely Ku and DNA-PKcs, are also involved in maintenance of telomeres, chromosome end-structures. In contrast, cells defective in Ligase IV and XRCC4 do not show changes in telomere length or function suggesting that these proteins are not involved in telomere maintenance. Since a mouse study indicated that defective Artemis may cause telomere dysfunction we investigated the effects of defective Artemis on telomere maintenance in human cells. Results We observed significantly elevated frequencies of telomeric fusions in two primary fibroblast cell lines established from Artemis defective patients relative to the control cell line. The frequencies of telomeric fusions increased after exposure of Artemis defective cells to ionizing radiation. Furthermore, we observed increased incidence of DNA damage at telomeres in Artemis defective cells that underwent more than 32 population doublings using the TIF (Telomere dysfunction Induced Foci) assay. We have also inhibited the expression levels of DNA-PKcs in Artemis defective cell lines by either using synthetic inhibitor (IC86621) or RNAi and observed their greater sensitivity to telomere dysfunction relative to control cells. Conclusion These results suggest that defective Artemis causes a mild telomere dysfunction phenotype in human cell lines.
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Telomere dysfunction-induced foci arise with the onset of telomeric deletions and complex chromosomal aberrations in resistant chronic lymphocytic leukemia cells. Blood 2010; 116:239-49. [PMID: 20424183 DOI: 10.1182/blood-2009-12-257618] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In somatic cells, eroded telomeres can induce DNA double-strand break signaling, leading to a form of replicative senescence or apoptosis, both of which are barriers to tumorigenesis. However, cancer cells might display telomere dysfunctions which in conjunction with defects in DNA repair and apoptosis, enables them to circumvent these pathways. Chronic lymphocytic leukemia (CLL) cells exhibit telomere dysfunction, and a subset of these cells are resistant to DNA damage-induced apoptosis and display short telomeres. We show here that these cells exhibit significant resection of their protective telomeric 3' single-stranded overhangs and an increased number of telomere-induced foci containing gammaH2AX and 53BP1. Chromatin immunoprecipitation and immunofluorescence experiments demonstrated increased levels of telomeric Ku70 and phospho-S2056-DNA-PKcs, 2 essential components of the mammalian nonhomologous end-joining DNA repair system. Notably, these CLL cells display deletions of telomeric signals on one or 2 chromatids in parallel with 11q22 deletions, or with 13q14 deletions associated with another chromosomal aberration or with a complex karyotype. Taken together, our results indicate that a subset of CLL cells from patients with an unfavorable clinical outcome harbor a novel type of chromosomal aberration resulting from telomere dysfunction.
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35
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McNees CJ, Tejera AM, Martínez P, Murga M, Mulero F, Fernandez-Capetillo O, Blasco MA. ATR suppresses telomere fragility and recombination but is dispensable for elongation of short telomeres by telomerase. ACTA ACUST UNITED AC 2010; 188:639-52. [PMID: 20212315 PMCID: PMC2835929 DOI: 10.1083/jcb.200908136] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Telomere shortening caused by incomplete DNA replication is balanced by telomerase-mediated telomere extension, with evidence indicating that the shortest telomeres are preferred substrates in primary cells. Critically short telomeres are detected by the cellular DNA damage response (DDR) system. In budding yeast, the important DDR kinase Tel1 (homologue of ATM [ataxia telangiectasia mutated]) is vital for telomerase recruitment to short telomeres, but mammalian ATM is dispensable for this function. We asked whether closely related ATR (ATM and Rad3 related) kinase, which is important for preventing replicative stress and chromosomal breakage at common fragile sites, might instead fulfill this role. The newly created ATR-deficient Seckel mouse strain was used to examine the function of ATR in telomerase recruitment and telomere function. Telomeres were recently found to resemble fragile sites, and we show in this study that ATR has an important role in the suppression of telomere fragility and recombination. We also find that wild-type ATR levels are important to protect short telomeres from chromosomal fusions but do not appear essential for telomerase recruitment to short telomeres in primary mouse embryonic fibroblasts from the ATR-deficient Seckel mouse model. These results reveal a previously unnoticed role for mammalian ATR in telomere protection and stability.
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Affiliation(s)
- Carolyn J McNees
- Telomeres and Telomerase Group, Spanish National Cancer Centre, Madrid 28029, Spain
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36
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DNA damage-induced phosphorylation of TRF2 is required for the fast pathway of DNA double-strand break repair. Mol Cell Biol 2009; 29:3597-604. [PMID: 19398584 DOI: 10.1128/mcb.00944-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protein kinases of the phosphatidylinositol 3-kinase-like kinase family, originally known to act in maintaining genomic integrity via DNA repair pathways, have been shown to also function in telomere maintenance. Here we focus on the functional role of DNA damage-induced phosphorylation of the essential mammalian telomeric DNA binding protein TRF2, which coordinates the assembly of the proteinaceous cap to disguise the chromosome end from being recognized as a double-stand break (DSB). Previous results suggested a link between the transient induction of human TRF2 phosphorylation at threonine 188 (T188) by the ataxia telangiectasia mutated protein kinase (ATM) and the DNA damage response. Here, we report evidence that X-ray-induced phosphorylation of TRF2 at T188 plays a role in the fast pathway of DNA DSB repair. These results connect the highly transient induction of human TRF2 phosphorylation to the DNA damage response machinery. Thus, we find that a protein known to function in telomere maintenance, TRF2, also plays a functional role in DNA DSB repair.
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Misri S, Pandita S, Kumar R, Pandita TK. Telomeres, histone code, and DNA damage response. Cytogenet Genome Res 2009; 122:297-307. [PMID: 19188699 DOI: 10.1159/000167816] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2008] [Indexed: 12/30/2022] Open
Abstract
Genomic stability is maintained by telomeres, the end terminal structures that protect chromosomes from fusion or degradation. Shortening or loss of telomeric repeats or altered telomere chromatin structure is correlated with telomere dysfunction such as chromosome end-to-end associations that could lead to genomic instability and gene amplification. The structure at the end of telomeres is such that its DNA differs from DNA double strand breaks (DSBs) to avoid nonhomologous end-joining (NHEJ), which is accomplished by forming a unique higher order nucleoprotein structure. Telomeres are attached to the nuclear matrix and have a unique chromatin structure. Whether this special structure is maintained by specific chromatin changes is yet to be thoroughly investigated. Chromatin modifications implicated in transcriptional regulation are thought to be the result of a code on the histone proteins (histone code). This code, involving phosphorylation, acetylation, methylation, ubiquitylation, and sumoylation of histones, is believed to regulate chromatin accessibility either by disrupting chromatin contacts or by recruiting non-histone proteins to chromatin. The histone code in which distinct histone tail-protein interactions promote engagement may be the deciding factor for choosing specific DSB repair pathways. Recent evidence suggests that such mechanisms are involved in DNA damage detection and repair. Altered telomere chromatin structure has been linked to defective DNA damage response (DDR), and eukaryotic cells have evolved DDR mechanisms utilizing proficient DNA repair and cell cycle checkpoints in order to maintain genomic stability. Recent studies suggest that chromatin modifying factors play a critical role in the maintenance of genomic stability. This review will summarize the role of DNA damage repair proteins specifically ataxia-telangiectasia mutated (ATM) and its effectors and the telomere complex in maintaining genome stability.
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Affiliation(s)
- S Misri
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63108, USA
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Raynaud CM, Sabatier L, Philipot O, Olaussen KA, Soria JC. Telomere length, telomeric proteins and genomic instability during the multistep carcinogenic process. Crit Rev Oncol Hematol 2008; 66:99-117. [PMID: 18243729 DOI: 10.1016/j.critrevonc.2007.11.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 11/08/2007] [Accepted: 11/30/2007] [Indexed: 12/29/2022] Open
Abstract
Telomeres form specialized structures at the ends of eukaryotic chromosomes, preventing them from being wrongly recognized as DNA damage. The human telomere DNA sequence is a tandem repetition of the sequence TTAGGG. In normal cells, the DNA replication machinery is unable to completely duplicate the telomeric DNA; thus, telomeres are shortened after every cell division. Having reached a critical length, telomeres may be recognized as double strand break DNA lesions, and cells eventually enter senescence. Carcinogenesis is a multistep process involving multiple mutations and chromosomal aberrations. One of the most prevalent aberrations in pre-cancerous lesions is telomere shortening and telomerase activation. We discuss the role and homeostasis of telomeres in normal cells and their implication in the early steps of carcinogenesis. We also discuss various techniques used, and their limitations, in the study of telomeres and genome instability and their role in carcinogenesis and related genomic modifications.
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Pennarun G, Granotier C, Hoffschir F, Mandine E, Biard D, Gauthier LR, Boussin FD. Role of ATM in the telomere response to the G-quadruplex ligand 360A. Nucleic Acids Res 2008; 36:1741-54. [PMID: 18263609 PMCID: PMC2275132 DOI: 10.1093/nar/gkn026] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Telomeres are known to prevent chromosome ends from being recognized as DNA double-strand breaks. Conversely, many DNA damage response proteins, including ATM, are thought to participate to telomere maintenance. However, the precise roles of ATM at telomeres remain unclear due to its multiple functions in cell checkpoints and apoptosis. To gain more insights into the role of ATM in telomere maintenance, we determined the effects of the G-quadruplex ligand 360A in various cell lines lacking functional ATM. We showed, by using Fluorescence in situ hybridization (FISH) and Chromosome Orientation-FISH using telomere PNA probes, that 360A induced specific telomere aberrations occurring during or after replication, mainly consisting in sister telomere fusions and also recombinations that involved preferentially the lagging strand telomeres. We demonstrate that ATM reduced telomere instability independently of apoptosis induction. Our results suggest thus that ATM has a direct role in preventing inappropriate DNA repair at telomeres, which could be related to its possible participation to the formation of protected structures at telomeres.
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Affiliation(s)
- Gaëlle Pennarun
- CEA, DSV, iRCM, Laboratoire de Radiopathologie-IPSC, 92265 Fontenay-aux-Roses, France
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Slijepcevic P. DNA damage response, telomere maintenance and ageing in light of the integrative model. Mech Ageing Dev 2008; 129:11-6. [DOI: 10.1016/j.mad.2007.10.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Revised: 10/19/2007] [Accepted: 10/26/2007] [Indexed: 11/28/2022]
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Ju Z, Rudolph L. Telomere dysfunction and stem cell ageing. Biochimie 2008; 90:24-32. [DOI: 10.1016/j.biochi.2007.09.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2007] [Accepted: 09/10/2007] [Indexed: 02/08/2023]
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ATM regulates the length of individual telomere tracts in Arabidopsis. Proc Natl Acad Sci U S A 2007; 104:18145-50. [PMID: 17989233 DOI: 10.1073/pnas.0704466104] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Telomeres have the paradoxical ability of protecting linear chromosome ends from DNA damage sensors by using these same proteins as essential components of their maintenance machinery. We have previously shown that the absence of ataxia telangiectasia mutated (ATM), a central regulator of the DNA damage response, accelerates the onset of genome instability in telomerase-deficient Arabidopsis, without increasing the rate of bulk telomere shortening. Here, we examine individual telomere tracts through successive plant generations using both fluorescence situ in hybridization (FISH) and primer extension telomere repeat amplification (PETRA). Unexpectedly, we found that the onset of profound developmental defects and abundant end-to-end chromosome fusions in fifth generation (G(5)) atm tert mutants required the presence of only one critically shortened telomere. Parent progeny analysis revealed that the short telomere arose as a consequence of an unusually large telomere rapid deletion (TRD) event. The most dramatic TRD was detected in atm tert mutants that had undergone meiosis. Notably, in contrast to TRD, alternative lengthening of telomeres (ALT) was suppressed in the absence of ATM. Finally, we show that size differences between telomeres on homologous chromosome ends are greater for atm tert than tert plants. Altogether, these findings suggest a dual role for ATM in regulating telomere size by promoting elongation of short telomeres and by preventing the accumulation of cells that harbor large telomere deletions.
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Khaw AK, Silasudjana M, Banerjee B, Suzuki M, Baskar R, Hande MP. Inhibition of telomerase activity and human telomerase reverse transcriptase gene expression by histone deacetylase inhibitor in human brain cancer cells. Mutat Res 2007; 625:134-44. [PMID: 17669439 DOI: 10.1016/j.mrfmmm.2007.06.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2007] [Revised: 06/07/2007] [Accepted: 06/13/2007] [Indexed: 10/23/2022]
Abstract
The aim of the present study is to investigate the effect of histone deacetylase inhibitor, trichostatin A (TSA) on the cell growth, apoptosis, genomic DNA damage and the expression of telomerase and associated factors in human normal and brain cancer cells. Here, human normal un-transformed fibroblasts (MRC-5), human normal hTERT-immortalised fibroblasts (hTERT-BJ1) and human brain cancer cell lines (glioblastoma cell line, A-172 and medulloblastoma cell line, ONS-76) were treated with 0.5-3.0microM TSA for 24h. Exposure to TSA resulted in apoptosis in a dose-dependent manner in the brain cancer cells. Glioblastoma cell line (A-172) displayed higher sensitivity to TSA-induced cell killing effect and apoptosis than the medulloblastoma cell line (ONS-76). The brain cancer cell lines and hTERT-BJ1 cell line displayed significant inhibition in telomerase activity and hTERT mRNA level after 2microM TSA treatment. Elevated expressions of p53 and p21 with a decrease in cyclin-D level supported the observation on cell cycle arrest following TSA treatment. Upregulation of Bax and cytochrome c correlated with the apoptotic events in TSA-treated cells. This study suggests that telomerase and hTERT might be the primary targets of TSA which may have the potential to be used as a telomerase inhibitor in cancer therapy.
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Affiliation(s)
- Aik Kia Khaw
- Genome Stability Laboratory, Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Republic of Singapore
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Ariyoshi K, Suzuki K, Goto M, Watanabe M, Kodama S. Increased chromosome instability and accumulation of DNA double-strand breaks in Werner syndrome cells. JOURNAL OF RADIATION RESEARCH 2007; 48:219-31. [PMID: 17449919 DOI: 10.1269/jrr.07017] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Werner syndrome (WS) is a premature aging syndrome caused by mutations of the WRN gene. Here, we demonstrate that a strain of WS fibroblast cells shows abnormal karyotypes characterized by several complex translocations and 50-fold more frequency of abnormal metaphases including dicentric chromosomes without fragments than normal cells when examined at a similar culture stage. Further, telomere fluorescence in situ hybridization indicates that the abnormal signals, extra telomere signal and loss of telomere signal, emerge two- to three-fold more frequently in WS cells than in normal cells. Taken together, these results indicate that chromosome instability including dysfunction of telomere maintenance is more prominent in WS cells than in normal cells. In addition, the accumulation of DNA double-strand breaks (DSBs) at the G(1) phase, including those at telomeres, detected by phosphorylated ATM (ataxia telangiectasia mutated) foci is accelerated in WS cells even at a low senescence level. The increased accumulation of DSBs in WS cells is reduced in the presence of anti-oxidative agents, suggesting that enhanced oxidative stress in WS cells is involved in accelerated accumulation of DSBs. These results indicate that WS cells are prone to accumulate DSBs spontaneously due to a defect of WRN, which leads to increased chromosome instability that could activate checkpoints, resulting in accelerated senescence.
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Affiliation(s)
- Kentaro Ariyoshi
- Laboratory of Radiation Biology, Research Reactor Institute, Kyoto University
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Banerjee B, Sharma S, Hegde S, Hande MP. Analysis of telomere damage by fluorescence in situ hybridisation on micronuclei in lymphocytes of breast carcinoma patients after radiotherapy. Breast Cancer Res Treat 2007; 107:25-31. [PMID: 17333339 DOI: 10.1007/s10549-007-9530-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Accepted: 01/24/2007] [Indexed: 11/29/2022]
Abstract
Radiotherapy has become an indispensable tool in the effective management of most of the cancers. There have been efforts earlier to study the differential radio-sensitivity patterns in patients undergoing radiation treatment to correlate with treatment induced complications such as tissue injury, cell death, and chromosomal aberration frequencies etc. The present study is an attempt to correlate the radiation-induced damage in the peripheral blood lymphocytes (PBLs) of breast cancer patients with the frequency of telomere mediated chromosomal damage. Blood samples from 55 patients with (Gr-II and Gr-III) CA-breast were obtained pre- and post-radiotherapy. The patients were treated with external beam radiotherapy of 50.4 Gy over a period of 6 weeks. Chromosome damage was measured by analysing micronucleus (MN) frequency in PBLs. The MN-frequency of the irradiated patients increased significantly compared to the patients being self-controls. The micronuclei were hybridized with telomere probes to study the extent of telomere damage. The fluorescence signals of the telomere regions in the first generation of the binucleated cells were significantly higher in the post-radiotherapy patients. There was also significant correlation observed in the patients with higher-grade tumours. Inter-individual variability was observed in the radiation-induced MN frequency in lymphocytes of patients after six weeks of radiotherapy. There was a significant correlation between functionally intact telomeres and the cellular response to ionising radiation. Our findings suggest that fluorescence in situ hybridisation on micronuclei could be effectively used as routine clinical application to determine the individual sensitivity to ionising radiation with respect to telomere damage.
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Francia S, Weiss RS, d'Adda di Fagagna F. Need telomere maintenance? Call 911. Cell Div 2007; 2:3. [PMID: 17229321 PMCID: PMC1784088 DOI: 10.1186/1747-1028-2-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Accepted: 01/17/2007] [Indexed: 01/23/2023] Open
Abstract
"Natura non facit saltum" (nature makes no leap) the Latins used to say, meaning that nature does not like discontinuities. Cells make no exception and indeed any discontinuity in the DNA double helix is promptly detected, triggering an alteration of cell proliferation and an attempt to repair. Yet, linear chromosomes bear DNA ends that are compatible with normal cell proliferation and they escape, under normal conditions, any repair. How telomeres, the chromosomes tips, achieve that is not fully understood. We recently observed that the Rad9/Hus1/Rad1 (911) complex, previously known for its functions in DNA metabolism and DNA damage responses, is constitutively associated with telomeres and plays an important role in their maintenance. Here, we summarize the available data and discuss the potential mechanisms of 911 action at telomeres.
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Affiliation(s)
- Sofia Francia
- IFOM Foundation – FIRC Institute of Molecular Oncology Foundation, Milan, Italy
| | - Robert S Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, New York, USA
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Newman JPA, Banerjee B, Fang W, Poonepalli A, Balakrishnan L, Low GKM, Bhattacharjee RN, Akira S, Jayapal M, Melendez AJ, Baskar R, Lee HW, Hande MP. Short dysfunctional telomeres impair the repair of arsenite-induced oxidative damage in mouse cells. J Cell Physiol 2007; 214:796-809. [PMID: 17849448 DOI: 10.1002/jcp.21276] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Telomeres and telomerase appear to participate in the repair of broken DNA ends produced by oxidative damage. Arsenite is an environmental contaminant and a potent human carcinogen, which induces oxidative stress on cells via the generation of reactive oxygen species affecting cell viability and chromosome stability. It promotes telomere attrition and reduces cell survival by apoptosis. In this study, we used mouse embryonic fibroblasts (MEFs) from mice lacking telomerase RNA component (mTERC(-/-) mice) with long (early passage or EP) and short (late passage or LP) telomeres to investigate the extent of oxidative damage by comparing the differences in DNA damage, chromosome instability, and cell survival at 24 and 48 h of exposure to sodium arsenite (As3+; NaAsO2). There was significantly high level of DNA damage in mTERC(-/-) cells with short telomeres as determined by alkaline comet assay. Consistent with elevated DNA damage, increased micronuclei (MN) induction reflecting gross genomic instability was also observed. Fluorescence in situ hybridization (FISH) analysis revealed that increasing doses of arsenite augmented the chromosome aberrations, which contributes to genomic instability leading to possibly apoptotic cell death and cell cycle arrest. Microarray analysis has revealed that As3+ treatment altered the expression of 456 genes of which 20% of them have known functions in cell cycle and DNA damage signaling and response, cell growth, and/or maintenance. Results from our studies imply that short dysfunctional telomeres impair the repair of oxidative damage caused by arsenite. The results will have implications in risk estimation as well as cancer chemotherapy.
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Affiliation(s)
- Jennifer P A Newman
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Slijepcevic P. The role of DNA damage response proteins at telomeres—an “integrative” model. DNA Repair (Amst) 2006; 5:1299-306. [PMID: 16798109 DOI: 10.1016/j.dnarep.2006.05.038] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 05/19/2006] [Accepted: 05/22/2006] [Indexed: 12/22/2022]
Abstract
Telomeres are specialized structures at chromosome ends which play the key role in chromosomal end protection. There is increasing evidence that many DNA damage response proteins are involved in telomere maintenance. For example, cells defective in DNA double strand break repair proteins including Ku, DNA-PKcs, RAD51D and the MRN (MRE11/RAD51/NBS1) complex show loss of telomere capping function. Similarly, mouse and human cells defective in ataxia telangiectasia mutated (ATM) have defective telomeres. A total of 14 mammalian DNA damage response proteins have, so far, been implicated in telomere maintenance. Recent studies indicate that three more proteins, namely BRCA1, hRad9 and PARP1 are involved in telomere maintenance. The involvement of a wide range of DNA damage response proteins at telomeres raises an important question: do telomere maintenance mechanisms constitute an integral part of DNA damage response machinery? A model termed the "integrative" model is proposed here to argue in favour of telomere maintenance being an integral part of DNA damage response. The "integrative" model is supported by the observation that a telomeric protein, TRF2, is not confined to its local telomeric environment but it migrates to the sites of DNA breakage following exposure of cells to ionizing radiation. Furthermore, even if telomeres are maintained in a non-canonical way, as in the case of Drosophila, DNA damage response proteins are still involved in telomere maintenance suggesting integration of telomere maintenance mechanisms into the DNA damage response network.
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Affiliation(s)
- Predrag Slijepcevic
- Brunel Institute of Cancer Genetics and Pharmacogenomics, Division of Biosceinces, School of Health Sciences and Social Care, Brunel University, Kingston Lane, Uxbridge, Middlesex, UB8 3PH, United Kingdom.
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Kuttler F, Mai S. Formation of non-random extrachromosomal elements during development, differentiation and oncogenesis. Semin Cancer Biol 2006; 17:56-64. [PMID: 17116402 DOI: 10.1016/j.semcancer.2006.10.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 10/17/2006] [Indexed: 11/25/2022]
Abstract
Extrachromosomal elements (EEs) were first discovered as minute chromatin bodies [Cox et al. Minute chromatin bodies in malignant tumors of childhood. Lancet 1965;62:55-8], and subsequently characterized as small circular DNA molecules physically separated from chromosomes. They include episomes, minichromosomes, small polydispersed DNAs or double minutes. This review focuses on eukaryotic EEs generated by genome rearrangements under physiological or pathological conditions. Some of those rearrangements occur randomly, but others are strictly non-random, highly regulated, and involve specific chromosomal locations (V(D)J-recombination, telomere maintenance mechanisms, c-myc deregulation). The multiple mechanisms of EEs formation are strongly interconnected and frequently linked to gene amplification. Identification of genes located on EEs will undoubtedly allow a better understanding of genome dynamics and oncogenic pathways.
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Affiliation(s)
- Fabien Kuttler
- Manitoba Institute of Cell Biology, CancerCare Manitoba, University of Manitoba, 675 McDermot Avenue, Winnipeg, Man. R3E 0V9, Canada.
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van Overbeek M, de Lange T. Apollo, an Artemis-related nuclease, interacts with TRF2 and protects human telomeres in S phase. Curr Biol 2006; 16:1295-302. [PMID: 16730176 DOI: 10.1016/j.cub.2006.05.022] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 05/07/2006] [Accepted: 05/10/2006] [Indexed: 01/03/2023]
Abstract
Human chromosome ends are protected by shelterin, an abundant six-subunit protein complex that binds specifically to the telomeric-repeat sequences, regulates telomere length, and ensures that chromosome ends do not elicit a DNA-damage response (reviewed in). Using mass spectrometry of proteins associated with the shelterin component Rap1, we identified an SMN1/PSO2 nuclease family member that is closely related to Artemis. We refer to this protein as Apollo and report that Apollo has the ability to localize to telomeres through an interaction with the shelterin component TRF2. Although its low abundance at telomeres indicates that Apollo is not a core component of shelterin, Apollo knockdown with RNAi resulted in senescence and the activation of a DNA-damage signal at telomeres as evidenced by telomere-dysfunction-induced foci (TIFs). The TIFs occurred primarily in S phase, suggesting that Apollo contributes to a processing step associated with the replication of chromosome ends. Furthermore, some of the metaphase chromosomes showed two telomeric signals at single-chromatid ends, suggesting an aberrant telomere structure. We propose that the Artemis-like nuclease Apollo is a shelterin accessory factor required for the protection of telomeres during or after their replication.
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Affiliation(s)
- Megan van Overbeek
- Laboratory for Cell Biology and Genetics, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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