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Banerjee P, Gaddam N, Pandita TK, Chakraborty S. Cellular Senescence as a Brake or Accelerator for Oncogenic Transformation and Role in Lymphatic Metastasis. Int J Mol Sci 2023; 24:ijms24032877. [PMID: 36769195 PMCID: PMC9917379 DOI: 10.3390/ijms24032877] [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: 11/29/2022] [Revised: 01/29/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
Cellular senescence-the irreversible cell cycle arrest driven by a variety of mechanisms and, more specifically, the senescence-associated secretory phenotype (SASP)-is an important area of research in the context of different age-related diseases, such as cardiovascular disease and cancer. SASP factors play both beneficial and detrimental roles in age-related disease progression depending on the source of the SASPs, the target cells, and the microenvironment. The impact of senescence and the SASP on different cell types, the immune system, and the vascular system has been widely discussed. However, the impact of replicative or stress-induced senescence on lymphatic biology and pathological lymphangiogenesis remains underexplored. The lymphatic system plays a crucial role in the maintenance of body fluid homeostasis and immune surveillance. The perturbation of lymphatic function can hamper normal physiological function. Natural aging or stress-induced premature aging influences the lymphatic vessel structure and function, which significantly affect the role of lymphatics in tumor dissemination and metastasis. In this review, we focus on the role of senescence on lymphatic pathobiology, its impact on cancer, and potential therapeutic interventions to manipulate the aged or senescent lymphatic system for disease management.
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Affiliation(s)
- Priyanka Banerjee
- Department of Medical Physiology, Texas A&M Health Science Center, Bryan, TX 77807, USA
| | - Niyanshi Gaddam
- Department of Medical Physiology, Texas A&M Health Science Center, Bryan, TX 77807, USA
| | - Tej K. Pandita
- Center for Genomics and Precision Medicine, Texas A&M College of Medicine, Houston, TX 77030, USA
| | - Sanjukta Chakraborty
- Department of Medical Physiology, Texas A&M Health Science Center, Bryan, TX 77807, USA
- Correspondence: ; Tel.: +1-979-436-0697
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2
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Establishment of a fetal cow (Bos Borus) skin fibroblasts cell line with immortalized characterization through human telomerase reverse transcriptase (hTERT) ectopic expression. J Virol Methods 2022; 309:114605. [PMID: 35961484 DOI: 10.1016/j.jviromet.2022.114605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 08/07/2022] [Accepted: 08/08/2022] [Indexed: 12/24/2022]
Abstract
The ectopic introduction of the human telomerase reverse transcriptase (hTERT) is an effective way to establish an immortalized cell line. Here, hTERT was obtained by RT-PCR, and the eukaryotic expression plasmid and lentivirus shuttle plasmid of hTERT was successfully constructed by the homologous recombination method. The stable expression of hTERT in fetal cow skin fibroblasts (CSF) was established using the lentivirus package system. The hTERT-CSF proliferate and have immortalized characteristics. Meanwhile, the chromosome analysis identified that the number and structure of the hTERT-CSF genome maintain stable. The indirect immunofluorescence, western blot, and flow cytometry showed that the hTERT gene had been successfully integrated into the primary genome of bovine skin and stably expressed. The viral infection experiment first identifies the hTERT-CSF as a vulnerable cell model responding to the Lumpy skin disease virus (LSDV). Establishing hTERT-CSF provides an important cell model for basic and applied research, clinical application, and vaccine development. It provides an essential reference for the future's rapid establishment of other immortalized cell lines.
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3
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Aguado J, Gómez-Inclán C, Leeson HC, Lavin MF, Shiloh Y, Wolvetang EJ. The hallmarks of aging in Ataxia-Telangiectasia. Ageing Res Rev 2022; 79:101653. [PMID: 35644374 DOI: 10.1016/j.arr.2022.101653] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/28/2022] [Accepted: 05/24/2022] [Indexed: 01/10/2023]
Abstract
Ataxia-telangiectasia (A-T) is caused by absence of the catalytic activity of ATM, a protein kinase that plays a central role in the DNA damage response, many branches of cellular metabolism, redox and mitochondrial homeostasis, and cell cycle regulation. A-T is a complex disorder characterized mainly by progressive cerebellar degeneration, immunodeficiency, radiation sensitivity, genome instability, and predisposition to cancer. It is increasingly recognized that the premature aging component of A-T is an important driver of this disease, and A-T is therefore an attractive model to study the aging process. This review outlines the current state of knowledge pertaining to the molecular and cellular signatures of aging in A-T and proposes how these new insights can guide novel therapeutic approaches for A-T.
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Affiliation(s)
- Julio Aguado
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Queensland 4072, Australia.
| | - Cecilia Gómez-Inclán
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Queensland 4072, Australia
| | - Hannah C Leeson
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Queensland 4072, Australia
| | - Martin F Lavin
- University of Queensland Centre for Clinical Research, The University of Queensland, Herston, Brisbane, Australia
| | - Yosef Shiloh
- The David and Inez Myers Laboratory of Cancer Genetics, Department of Human Molecular Genetics and Biochemistry, Tel Aviv University School of Medicine, Tel Aviv, Israel
| | - Ernst J Wolvetang
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Queensland 4072, Australia.
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Stagni V, Ferri A, Cirotti C, Barilà D. ATM Kinase-Dependent Regulation of Autophagy: A Key Player in Senescence? Front Cell Dev Biol 2021; 8:599048. [PMID: 33490066 PMCID: PMC7817534 DOI: 10.3389/fcell.2020.599048] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/24/2020] [Indexed: 01/02/2023] Open
Abstract
Increasing evidence suggests a strong interplay between autophagy and genomic stability. Recently, several papers have demonstrated a molecular connection between the DNA Damage Response (DDR) and autophagy and have explored how this link influences cell fate and the choice between apoptosis and senescence in response to different stimuli. The aberrant deregulation of this interplay is linked to the development of pathologies, including cancer and neurodegeneration. Ataxia-telangiectasia mutated kinase (ATM) is the product of a gene that is lost in Ataxia-Telangiectasia (A-T), a rare genetic disorder characterized by ataxia and cerebellar neurodegeneration, defects in the immune response, higher incidence of lymphoma development, and premature aging. Importantly, ATM kinase plays a central role in the DDR, and it can finely tune the balance between senescence and apoptosis: activated ATM promotes autophagy and in particular sustains the lysosomal-mitochondrial axis, which in turn promotes senescence and inhibits apoptosis. Therefore, ATM is the key factor that enables cells to escape apoptosis by entering senescence through modulation of autophagy. Importantly, unlike apoptotic cells, senescent cells are viable and have the ability to secrete proinflammatory and mitogenic factors, thus influencing the cellular environment. In this review we aim to summarize recent advances in the understanding of molecular mechanisms linking DDR and autophagy to senescence, pointing out the role of ATM kinase in these cellular responses. The significance of this regulation in the pathogenesis of Ataxia-Telangiectasia will be discussed.
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Affiliation(s)
- Venturina Stagni
- Institute of Molecular Biology and Pathology, National Research Council (CNR), Rome, Italy
- Laboratory of Cell Signaling, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Fondazione Santa Lucia, Rome, Italy
| | - Alessandra Ferri
- Laboratory of Cell Signaling, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Fondazione Santa Lucia, Rome, Italy
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Claudia Cirotti
- Laboratory of Cell Signaling, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Fondazione Santa Lucia, Rome, Italy
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Daniela Barilà
- Laboratory of Cell Signaling, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Fondazione Santa Lucia, Rome, Italy
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
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5
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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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Sunderland P, Augustyniak J, Lenart J, Bużańska L, Carlessi L, Delia D, Sikora E. ATM-deficient neural precursors develop senescence phenotype with disturbances in autophagy. Mech Ageing Dev 2020; 190:111296. [PMID: 32621937 DOI: 10.1016/j.mad.2020.111296] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/29/2020] [Accepted: 06/22/2020] [Indexed: 01/09/2023]
Abstract
ATM is a kinase involved in DNA damage response (DDR), regulation of response to oxidative stress, autophagy and mitophagy. Mutations in the ATM gene in humans result in ataxi A-Telangiectasia disease (A-T) characterized by a variety of symptoms with neurodegeneration and premature ageing among them. Since brain is one of the most affected organs in A-T, we have focused on senescence of neural progenitor cells (NPCs) derived from A-T reprogrammed fibroblasts. Accordingly, A-T NPCs obtained through neural differentiation of iPSCs in 5% oxygen possessed some features of senescence including increased activity of SA-β-gal and secretion of IL6 and IL8 in comparison to control NPCs. This phenotype of A-T NPC was accompanied by elevated oxidative stress. A-T NPCs exhibited symptoms of impaired autophagy and mitophagy with lack of response to chloroquine treatment. Additional sources of oxidative stress like increased oxygen concentration (20 %) and H2O2 respectively aggravated the phenotype of senescence and additionally disturbed the process of mitophagy. In both cases only A-T NPCs reacted to the treatment. We conclude that oxidative stress may be responsible for the phenotype of senescence and impairment of autophagy in A-T NPCs. Our results point to senescent A-T cells as a potential therapeutic target in this disease.
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Affiliation(s)
- Piotr Sunderland
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
| | - Justyna Augustyniak
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Jacek Lenart
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Leonora Bużańska
- Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Luigi Carlessi
- Department of Research, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy
| | - Domenico Delia
- Department of Research, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy; IFOM, FIRC Institute of Molecular Oncology, Milano, Italy
| | - Ewa Sikora
- Nencki Institute of Experimental Biology, Polish Academy of Sciences, Warsaw, Poland.
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7
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Abstract
Many recent advances have emerged in the telomere and telomerase fields. This Timeline article highlights the key advances that have expanded our views on the mechanistic underpinnings of telomeres and telomerase and their roles in ageing and disease. Three decades ago, the classic view was that telomeres protected the natural ends of linear chromosomes and that telomerase was a specific telomere-terminal transferase necessary for the replication of chromosome ends in single-celled organisms. While this concept is still correct, many diverse fields associated with telomeres and telomerase have substantially matured. These areas include the discovery of most of the key molecular components of telomerase, implications for limits to cellular replication, identification and characterization of human genetic disorders that result in premature telomere shortening, the concept that inhibiting telomerase might be a successful therapeutic strategy and roles for telomeres in regulating gene expression. We discuss progress in these areas and conclude with challenges and unanswered questions in the field.
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Affiliation(s)
- Jerry W Shay
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA.
| | - Woodring E Wright
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX, USA
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8
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The Role for the DSB Response Pathway in Regulating Chromosome Translocations. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1044:65-87. [PMID: 29956292 DOI: 10.1007/978-981-13-0593-1_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In response to DNA double strand breaks (DSB), mammalian cells activate the DNA Damage Response (DDR), a network of factors that coordinate their detection, signaling and repair. Central to this network is the ATM kinase and its substrates at chromatin surrounding DSBs H2AX, MDC1 and 53BP1. In humans, germline inactivation of ATM causes Ataxia Telangiectasia (A-T), an autosomal recessive syndrome of increased proneness to hematological malignancies driven by clonal chromosomal translocations. Studies of cancers arising in A-T patients and in genetically engineered mouse models (GEMM) deficient for ATM and its substrates have revealed complex, multilayered roles for ATM in translocation suppression and identified functional redundancies between ATM and its substrates in this context. "Programmed" DSBs at antigen receptor loci in developing lymphocytes employ ubiquitous DDR factors for signaling and repair and have been particularly useful for mechanistic studies because they are region-specific and can be monitored in vitro and in vivo. In this context, murine thymocytes deficient for ATM recapitulate the molecular events that lead to transformation in T cells from A-T patients and provide a widely used model to study the mechanisms that suppress RAG recombinase-dependent translocations. Similarly, analyses of the fate of Activation induced Cytidine Deaminase (AID)-dependent DSBs during mature B cell Class Switch Recombination (CSR) have defined the genetic requirements for end-joining and translocation suppression in this setting. Moreover, a unique role for 53BP1 in the promotion of synapsis of distant DSBs has emerged from these studies.
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Carranza D, Torres-Rusillo S, Ceballos-Pérez G, Blanco-Jimenez E, Muñoz-López M, García-Pérez JL, Molina IJ. Reconstitution of the Ataxia-Telangiectasia Cellular Phenotype With Lentiviral Vectors. Front Immunol 2018; 9:2703. [PMID: 30515174 PMCID: PMC6255946 DOI: 10.3389/fimmu.2018.02703] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/01/2018] [Indexed: 11/13/2022] Open
Abstract
Ataxia-telangiectasia (A-T) is a complex disease arising from mutations in the ATM gene (Ataxia-Telangiectasia Mutated), which plays crucial roles in repairing double-strand DNA breaks (DSBs). Heterogeneous immunodeficiency, extreme radiosensitivity, frequent appearance of tumors and neurological degeneration are hallmarks of the disease, which carries high morbidity and mortality because only palliative treatments are currently available. Gene therapy was effective in animal models of the disease, but the large size of the ATM cDNA required the use of HSV-1 or HSV/AAV hybrid amplicon vectors, whose characteristics make them unlikely tools for treating A-T patients. Due to recent advances in vector packaging, production and biosafety, we developed a lentiviral vector containing the ATM cDNA and tested whether or not it could rescue cellular defects of A-T human mutant fibroblasts. Although the cargo capacity of lentiviral vectors is an inherent limitation in their use, and despite the large size of the transgene, we successfully transduced around 20% of ATM-mutant cells. ATM expression and phosphorylation assays indicated that the neoprotein was functional in transduced cells, further reinforced by their restored capacity to phosphorylate direct ATM substrates such as p53 and their capability to repair radiation-induced DSBs. In addition, transduced cells also restored cellular radiosensitivity and cell cycle abnormalities. Our results demonstrate that lentiviral vectors can be used to rescue the intrinsic cellular defects of ATM-mutant cells, which represent, in spite of their limitations, a proof-of-concept for A-T gene therapy.
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Affiliation(s)
- Diana Carranza
- Institute of Biopathology and Regenerative Medicine, Center for Biomedical Research, University of Granada, Granada, Spain
| | - Sara Torres-Rusillo
- Institute of Biopathology and Regenerative Medicine, Center for Biomedical Research, University of Granada, Granada, Spain
| | - Gloria Ceballos-Pérez
- Institute of Biopathology and Regenerative Medicine, Center for Biomedical Research, University of Granada, Granada, Spain
| | - Eva Blanco-Jimenez
- Genomic Medicine Department, Centro Pfizer-Universidad de Granada-Junta de Andalucía de Genómica e Investigación Oncológica (GENYO), Granada, Spain
| | - Martin Muñoz-López
- Genomic Medicine Department, Centro Pfizer-Universidad de Granada-Junta de Andalucía de Genómica e Investigación Oncológica (GENYO), Granada, Spain
| | - José L García-Pérez
- Genomic Medicine Department, Centro Pfizer-Universidad de Granada-Junta de Andalucía de Genómica e Investigación Oncológica (GENYO), Granada, Spain.,Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, University of Edinburgh, Edinburgh, United Kingdom
| | - Ignacio J Molina
- Institute of Biopathology and Regenerative Medicine, Center for Biomedical Research, University of Granada, Granada, Spain.,Instituto de Investigación Biosanitaria ibs.GRANADA, Granada University Hospitals, University of Granada, Granada, Spain
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10
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Hung CLK, Maiuri T, Bowie LE, Gotesman R, Son S, Falcone M, Giordano JV, Gillis T, Mattis V, Lau T, Kwan V, Wheeler V, Schertzer J, Singh K, Truant R. A patient-derived cellular model for Huntington's disease reveals phenotypes at clinically relevant CAG lengths. Mol Biol Cell 2018; 29:2809-2820. [PMID: 30256717 PMCID: PMC6249865 DOI: 10.1091/mbc.e18-09-0590] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The huntingtin protein participates in several cellular processes that are disrupted when the polyglutamine tract is expanded beyond a threshold of 37 CAG DNA repeats in Huntington’s disease (HD). Cellular biology approaches to understand these functional disruptions in HD have primarily focused on cell lines with synthetically long CAG length alleles that clinically represent outliers in this disease and a more severe form of HD that lacks age onset. Patient-derived fibroblasts are limited to a finite number of passages before succumbing to cellular senescence. We used human telomerase reverse transcriptase (hTERT) to immortalize fibroblasts taken from individuals of varying age, sex, disease onset, and CAG repeat length, which we have termed TruHD cells. TruHD cells display classic HD phenotypes of altered morphology, size and growth rate, increased sensitivity to oxidative stress, aberrant adenosine diphosphate/adenosine triphosphate (ADP/ATP) ratios, and hypophosphorylated huntingtin protein. We additionally observed dysregulated reactive oxygen species (ROS)-dependent huntingtin localization to nuclear speckles in HD cells. We report the generation and characterization of a human, clinically relevant cellular model for investigating disease mechanisms in HD at the single-cell level, which, unlike transformed cell lines, maintains functions critical for huntingtin transcriptional regulation and genomic integrity.
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Affiliation(s)
- Claudia Lin-Kar Hung
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Tamara Maiuri
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Laura Erin Bowie
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Ryan Gotesman
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Susie Son
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Mina Falcone
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - James Victor Giordano
- Center for Genomic Medicine, Harvard Medical School, Boston, MA 02114.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Tammy Gillis
- Center for Genomic Medicine, Harvard Medical School, Boston, MA 02114.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Virginia Mattis
- Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048
| | - Trevor Lau
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Vickie Kwan
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada.,Stem Cell and Cancer Research Institute, Faculty of Health Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Vanessa Wheeler
- Center for Genomic Medicine, Harvard Medical School, Boston, MA 02114.,Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Jonathan Schertzer
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Karun Singh
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Ray Truant
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada
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Zaki-Dizaji M, Akrami SM, Azizi G, Abolhassani H, Aghamohammadi A. Inflammation, a significant player of Ataxia-Telangiectasia pathogenesis? Inflamm Res 2018; 67:559-570. [PMID: 29582093 DOI: 10.1007/s00011-018-1142-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 02/03/2018] [Accepted: 03/21/2018] [Indexed: 12/21/2022] Open
Abstract
INTRODUCTION Ataxia-Telangiectasia (A-T) syndrome is an autosomal recessive neurodegenerative disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, chromosome instability, radiosensitivity, and predisposition to malignancy. There is growing evidence that A-T patients suffer from pathologic inflammation that is responsible for many symptoms of this syndrome, including neurodegeneration, autoimmunity, cardiovascular disease, accelerated aging, and insulin resistance. In addition, epidemiological studies have shown A-T heterozygotes, somewhat like deficient patients, are susceptible to ionizing irradiation and have a higher risk of cancers and metabolic disorders. AREA COVERED This review summarizes clinical and molecular findings of inflammation in A-T syndrome. CONCLUSION Ataxia-Telangiectasia Mutated (ATM), a master regulator of the DNA damage response is the protein known to be associated with A-T and has a complex nuclear and cytoplasmic role. Loss of ATM function may induce immune deregulation and systemic inflammation.
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Affiliation(s)
- Majid Zaki-Dizaji
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.,Research Center for Immunodeficiencies, Children's Medical Center Hospital, Tehran University of Medical Science, 62 Qarib St., Keshavarz Blvd., Tehran, 14194, Iran
| | - Seyed Mohammad Akrami
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Gholamreza Azizi
- Non-Communicable Diseases Research Center, Alborz University of Medical Sciences, Karaj, Iran.,Department of Laboratory Medicine, Imam Hassan Mojtaba Hospital, Alborz University of Medical Sciences, Karaj, Iran
| | - Hassan Abolhassani
- Research Center for Immunodeficiencies, Children's Medical Center Hospital, Tehran University of Medical Science, 62 Qarib St., Keshavarz Blvd., Tehran, 14194, Iran.,Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska Institute at Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Asghar Aghamohammadi
- Research Center for Immunodeficiencies, Children's Medical Center Hospital, Tehran University of Medical Science, 62 Qarib St., Keshavarz Blvd., Tehran, 14194, Iran.
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12
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Maiuri T, Mocle AJ, Hung CL, Xia J, van Roon-Mom WMC, Truant R. Huntingtin is a scaffolding protein in the ATM oxidative DNA damage response complex. Hum Mol Genet 2017; 26:395-406. [PMID: 28017939 DOI: 10.1093/hmg/ddw395] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/11/2016] [Indexed: 11/15/2022] Open
Abstract
Huntington's disease (HD) is an age-dependent neurodegenerative disease. DNA repair pathways have recently been implicated as the most predominant modifiers of age of onset in HD patients. We report that endogenous huntingtin protein directly participates in oxidative DNA damage repair. Using novel chromobodies to detect endogenous human huntingtin in live cells, we show that localization of huntingtin to DNA damage sites is dependent on the kinase activity of ataxia telangiectasia mutated (ATM) protein. Super-resolution microscopy and biochemical assays revealed that huntingtin co-localizes with and scaffolds proteins of the DNA damage response pathway in response to oxidative stress. In HD patient fibroblasts bearing typical clinical HD allele lengths, we demonstrate that there is deficient oxidative DNA damage repair. We propose that DNA damage in HD is caused by dysfunction of the mutant huntingtin protein in DNA repair, and accumulation of DNA oxidative lesions due to elevated reactive oxygen species may contribute to the onset of HD.
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Affiliation(s)
- Tamara Maiuri
- Department of Biochemistry and Biomedical Research, McMaster University, HSC 4N54, 1200 Main Street West, Hamilton, Canada L8N3Z5
| | - Andrew J Mocle
- Department of Biochemistry and Biomedical Research, McMaster University, HSC 4N54, 1200 Main Street West, Hamilton, Canada L8N3Z5
| | - Claudia L Hung
- Department of Biochemistry and Biomedical Research, McMaster University, HSC 4N54, 1200 Main Street West, Hamilton, Canada L8N3Z5
| | - Jianrun Xia
- Department of Biochemistry and Biomedical Research, McMaster University, HSC 4N54, 1200 Main Street West, Hamilton, Canada L8N3Z5
| | - Willeke M C van Roon-Mom
- Center for Human and Clinical Genetics, Leiden University Medical Center, Postzone S4-0P, P.O. Box 9600 2300RC Leiden, The Netherlands
| | - Ray Truant
- Department of Biochemistry and Biomedical Research, McMaster University, HSC 4N54, 1200 Main Street West, Hamilton, Canada L8N3Z5
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13
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Telomere-associated aging disorders. Ageing Res Rev 2017; 33:52-66. [PMID: 27215853 PMCID: PMC9926533 DOI: 10.1016/j.arr.2016.05.009] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/17/2016] [Accepted: 05/19/2016] [Indexed: 01/25/2023]
Abstract
Telomeres are dynamic nucleoprotein-DNA structures that cap and protect linear chromosome ends. Several monogenic inherited diseases that display features of human premature aging correlate with shortened telomeres, and are referred to collectively as telomeropathies. These disorders have overlapping symptoms and a common underlying mechanism of telomere dysfunction, but also exhibit variable symptoms and age of onset, suggesting they fall along a spectrum of disorders. Primary telomeropathies are caused by defects in the telomere maintenance machinery, whereas secondary telomeropathies have some overlapping symptoms with primary telomeropathies, but are generally caused by mutations in DNA repair proteins that contribute to telomere preservation. Here we review both the primary and secondary telomeropathies, discuss potential mechanisms for tissue specificity and age of onset, and highlight outstanding questions in the field and future directions toward elucidating disease etiology and developing therapeutic strategies.
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14
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Shiloh Y, Lederman HM. Ataxia-telangiectasia (A-T): An emerging dimension of premature ageing. Ageing Res Rev 2017; 33:76-88. [PMID: 27181190 DOI: 10.1016/j.arr.2016.05.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/02/2016] [Accepted: 05/10/2016] [Indexed: 12/28/2022]
Abstract
A-T is a prototype genome instability syndrome and a multifaceted disease. A-T leads to neurodegeneration - primarily cerebellar atrophy, immunodeficiency, oculocutaneous telangiectasia (dilated blood vessels), vestigial thymus and gonads, endocrine abnormalities, cancer predisposition and varying sensitivity to DNA damaging agents, particularly those that induce DNA double-strand breaks. With the recent increase in life expectancy of A-T patients, the premature ageing component of this disease is gaining greater awareness. The complex A-T phenotype reflects the ever growing number of functions assigned to the protein encoded by the responsible gene - the homeostatic protein kinase, ATM. The quest to thoroughly understand the complex A-T phenotype may reveal yet elusive ATM functions.
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Abstract
Loss of function or mutation of the ataxia-telangiectasia mutated gene product (ATM) results in inherited genetic disorders characterized by neurodegeneration, immunodeficiency, and cancer. Ataxia-telangiectasia mutated (ATM) gene product belongs to the PI3K-like protein kinase (PIKKs) family and is functionally implicated in mitogenic signal transduction, chromosome condensation, meiotic recombination, cell-cycle control, and telomere maintenance. The ATM protein kinase is primarily activated in response to DNA double strand breaks (DSBs), the most deleterious form of DNA damage produced by ionizing radiation (IR) or radiomimetic drugs. It is detected at DNA damage sites, where ATM autophosphorylation causes dissociation of the inactive homodimeric form to the activated monomeric form. Interestingly, heat shock can activate ATM independent of the presence of DNA strand breaks. ATM is an integral part of the sensory machinery that detects DSBs during meiosis, mitosis, or DNA breaks mediated by free radicals. These DNA lesions can trigger higher order chromatin reorganization fuelled by posttranslational modifications of histones and histone binding proteins. Our group, and others, have shown that ATM activation is tightly regulated by chromatin modifications. This review summarizes the multiple approaches used to discern the role of ATM and other associated proteins in chromatin modification in response to DNA damage.
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Infection of a Single Cell Line with Distinct Strains of Human Cytomegalovirus Can Result in Large Variations in Virion Production and Facilitate Efficient Screening of Virus Protein Function. J Virol 2015; 90:2523-35. [PMID: 26676783 DOI: 10.1128/jvi.01762-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 12/11/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Previously, we reported that the absence of the ataxia telangiectasia mutated (ATM) kinase, a critical DNA damage response (DDR) signaling component for double-strand breaks, caused no change in HCMV Towne virion production. Later, others reported decreased AD169 viral titers in the absence of ATM. To address this discrepancy, human foreskin fibroblasts (HFF) and three ATM(-) lines (GM02530, GM05823, and GM03395) were infected with both Towne and AD169. Two additional ATM(-) lines (GM02052 and GM03487) were infected with Towne. Remarkably, both previous studies' results were confirmed. However, the increased number of cell lines and infections with both lab-adapted strains confirmed that ATM was not necessary to produce wild-type-level titers in fibroblasts. Instead, interactions between individual virus strains and the cellular microenvironment of the individual ATM(-) line determined efficiency of virion production. Surprisingly, these two commonly used lab-adapted strains produced drastically different titers in one ATM(-) cell line, GM05823. The differences in titer suggested a rapid method for identifying genes involved in differential virion production. In silico comparison of the Towne and AD169 genomes determined a list of 28 probable candidates responsible for the difference. Using serial iterations of an experiment involving virion entry and input genome nuclear trafficking with a panel of related strains, we reduced this list to four (UL129, UL145, UL147, and UL148). As a proof of principle, reintroduction of UL148 largely rescued genome trafficking. Therefore, use of a battery of related strains offers an efficient method to narrow lists of candidate genes affecting various virus life cycle checkpoints. IMPORTANCE Human cytomegalovirus (HCMV) infection of multiple cell lines lacking ataxia telangiectasia mutated (ATM) protein produced wild-type levels of infectious virus. Interactions between virus strains and the microenvironment of individual ATM(-) lines determined the efficiency of virion production. Infection of one ATM(-) cell line, GM05823, produced large titer differentials dependent on the strain used, Towne or AD169. This discrepancy resolved a disagreement in the literature of a requirement for ATM expression and HCMV reproduction. The titer differentials in GM08523 cells were due, in part, to a decreased capacity of AD169 virions to enter the cell and traffic genomes to the nucleus. In silico comparison of the Towne, AD169, and related variant strains' genomes was coupled with serial iterations of a virus entry experiment, narrowing 28 candidate proteins responsible for the phenotype down to 4. Reintroduction of UL148 significantly rescued genome trafficking. Differential behavior of virus strains can be exploited to elucidate gene function.
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Pandita RK, Chow TT, Udayakumar D, Bain AL, Cubeddu L, Hunt CR, Shi W, Horikoshi N, Zhao Y, Wright WE, Khanna KK, Shay JW, Pandita TK. Single-strand DNA-binding protein SSB1 facilitates TERT recruitment to telomeres and maintains telomere G-overhangs. Cancer Res 2015; 75:858-69. [PMID: 25589350 DOI: 10.1158/0008-5472.can-14-2289] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Proliferating mammalian stem and cancer cells express telomerase [telomerase reverse transcriptase (TERT)] in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA-binding protein SSB1, which has a critical role in DNA double-strand break (DSB) repair. Here, we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacts with the TERT catalytic subunit and regulates its interaction with telomeres. Deletion of SSB1 reduces TERT interaction with telomeres and leads to G-overhang loss. Although SSB1 is recruited to DSB sites, we found no corresponding change in TERT levels at these sites, implying that SSB1-TERT interaction relies upon a specific chromatin structure or context. Our findings offer an explanation for how telomerase is recruited to telomeres to facilitate G-strand DNA extension, a critical step in maintaining telomere ends and cell viability in all cancer cells. Cancer Res; 75(5); 858-69. ©2015 AACR.
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Affiliation(s)
- Raj K Pandita
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas. Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas
| | - Tracy T Chow
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Durga Udayakumar
- Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Amanda L Bain
- QIMR Berghofer Medical Research Institute, Herston, Brisbane, Australia
| | - Liza Cubeddu
- School of Science and Health, University of Western Sydney, Sydney, Australia
| | - Clayton R Hunt
- Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Wei Shi
- QIMR Berghofer Medical Research Institute, Herston, Brisbane, Australia
| | - Nobuo Horikoshi
- Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Yong Zhao
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Woodring E Wright
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Kum Kum Khanna
- QIMR Berghofer Medical Research Institute, Herston, Brisbane, Australia
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas. Center for Excellence in Genomics Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia.
| | - Tej K Pandita
- Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, Texas. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas.
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Zheng YL, Zhang F, Sun B, Du J, Sun C, Yuan J, Wang Y, Tao L, Kota K, Liu X, Schlegel R, Yang Q. Telomerase enzymatic component hTERT shortens long telomeres in human cells. Cell Cycle 2014; 13:1765-76. [PMID: 24721976 DOI: 10.4161/cc.28705] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Telomere lengths are tightly regulated within a narrow range in normal human cells. Previous studies have extensively focused on how short telomeres are extended and have demonstrated that telomerase plays a central role in elongating short telomeres. However, much about the molecular mechanisms of regulating excessively long telomeres is unknown. In this report, we demonstrated that the telomerase enzymatic component, hTERT, plays a dual role in the regulation of telomere length. It shortens excessively long telomeres and elongates short telomeres simultaneously in one cell, maintaining the optimal telomere length at each chromosomal end for efficient protection. This novel hTERT-mediated telomere-shortening mechanism not only exists in cancer cells, but also in primary human cells. The hTERT-mediated telomere shortening requires hTERT's enzymatic activity, but the telomerase RNA component, hTR, is not involved in that process. We found that expression of hTERT increases telomeric circular DNA formation, suggesting that telomere homologous recombination is involved in the telomere-shortening process. We further demonstrated that shelterin protein TPP1 interacts with hTERT and recruits hTERT onto the telomeres, suggesting that TPP1 might be involved in regulation of telomere shortening. This study reveals a novel function of hTERT in telomere length regulation and adds a new element to the current molecular model of telomere length maintenance.
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Affiliation(s)
- Yun-Ling Zheng
- Cancer Prevention and Control; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Fan Zhang
- Cancer Biology Division; Washington University School of Medicine; Saint Louis, MO USA
| | - Bing Sun
- Cancer Prevention and Control; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Juan Du
- Cancer Biology Division; Washington University School of Medicine; Saint Louis, MO USA
| | - Chongkui Sun
- Cancer Biology Division; Washington University School of Medicine; Saint Louis, MO USA
| | - Jie Yuan
- Medical College; Jinan University; Guangzhou, China
| | - Ying Wang
- Cancer Prevention and Control; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Lian Tao
- Cancer Prevention and Control; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Krishna Kota
- Cancer Prevention and Control; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Xuefeng Liu
- Molecular Oncology Programs; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Richard Schlegel
- Molecular Oncology Programs; Lombardi Comprehensive Cancer Center; Georgetown University Medical Center; Washington, DC USA
| | - Qin Yang
- Cancer Biology Division; Washington University School of Medicine; Saint Louis, MO USA
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19
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Kong CM, Lee XW, Wang X. Telomere shortening in human diseases. FEBS J 2013; 280:3180-93. [PMID: 23647631 DOI: 10.1111/febs.12326] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 04/12/2013] [Accepted: 04/30/2013] [Indexed: 01/22/2023]
Abstract
The discovery of telomeres dates back to the early 20th century. In humans, telomeres are heterochromatic structures with tandem DNA repeats of 5'-TTAGGG-3' at the chromosomal ends. Telomere length varies greatly among species and ranges from 10 to 15 kb in humans. With each cell division, telomeres shorten progressively because of the 'end-replication problem'. Short or dysfunctional telomeres are often recognized as DNA DSBs, triggering cell-cycle arrest and result in cellular senescence or apoptotic cell death. Therefore, telomere shortening serves as an important tumor-suppressive mechanism by limiting cellular proliferative capacity by regulating senescence checkpoint activation. Although telomeres serve as a mitotic clock to cells, they also confer capping on chromosomes, with help from telomere-associated proteins. Over the past decades, many studies of telomere biology have demonstrated that telomeres and telomere-associated proteins are implicated in human genetic diseases. In addition, it has become more apparent that accelerated telomere erosion is associated with a myriad of metabolic and inflammatory diseases. Moreover, critically short or unprotected telomeres are likely to form telomeric fusions, leading to genomic instability, the cornerstone for carcinogenesis. In light of these, this minireview summarizes studies on telomeres and telomere-associated proteins in human diseases. Elucidating the roles of telomeres involved in the mechanisms underlying pathogenesis of these diseases may open up new possibilities for novel molecular targets as well as provide important diagnostic and therapeutic implications.
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Affiliation(s)
- Chiou Mee Kong
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Tivey HSE, Brook AJC, Rokicki MJ, Kipling D, Davis T. p38 (MAPK) stress signalling in replicative senescence in fibroblasts from progeroid and genomic instability syndromes. Biogerontology 2012; 14:47-62. [PMID: 23112078 PMCID: PMC3627027 DOI: 10.1007/s10522-012-9407-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 10/17/2012] [Indexed: 12/26/2022]
Abstract
Werner Syndrome (WS) is a human segmental progeria resulting from mutations in a DNA helicase. WS fibroblasts have a shortened replicative capacity, an aged appearance, and activated p38 MAPK, features that can be modulated by inhibition of the p38 pathway. Loss of the WRNp RecQ helicase has been shown to result in replicative stress, suggesting that a link between faulty DNA repair and stress-induced premature cellular senescence may lead to premature ageing in WS. Other progeroid syndromes that share overlapping pathophysiological features with WS also show defects in DNA processing, raising the possibility that faulty DNA repair, leading to replicative stress and premature cellular senescence, might be a more widespread feature of premature ageing syndromes. We therefore analysed replicative capacity, cellular morphology and p38 activation, and the effects of p38 inhibition, in fibroblasts from a range of progeroid syndromes. In general, populations of young fibroblasts from non-WS progeroid syndromes do not have a high level of cells with an enlarged morphology and F-actin stress fibres, unlike young WS cells, although this varies between strains. p38 activation and phosphorylated HSP27 levels generally correlate well with cellular morphology, and treatment with the p38 inhibitor SB203580 effects cellular morphology only in strains with enlarged cells and phosphorylated HSP27. For some syndromes fibroblast replicative capacity was within the normal range, whereas for others it was significantly shorter (e.g. HGPS and DKC). However, although in most cases SB203580 extended replicative capacity, with the exception of WS and DKC the magnitude of the effect was not significantly different from normal dermal fibroblasts. This suggests that stress-induced premature cellular senescence via p38 activation is restricted to a small subset of progeroid syndromes.
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Affiliation(s)
- Hannah S E Tivey
- Institute of Cancer and Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK
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21
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Shin JS, Foot T, Hong A, Zhang M, Lum T, Solomon MJ, Soon Lee C. Telomerase expression as a predictive marker of radiotherapy response in rectal cancer: in vitro and in vivo study. Pathology 2012; 44:209-15. [DOI: 10.1097/pat.0b013e3283511cd5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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22
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Kozlov SV, Graham ME, Jakob B, Tobias F, Kijas AW, Tanuji M, Chen P, Robinson PJ, Taucher-Scholz G, Suzuki K, So S, Chen D, Lavin MF. Autophosphorylation and ATM activation: additional sites add to the complexity. J Biol Chem 2011; 286:9107-19. [PMID: 21149446 PMCID: PMC3059052 DOI: 10.1074/jbc.m110.204065] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Indexed: 12/18/2022] Open
Abstract
The recognition and signaling of DNA double strand breaks involves the participation of multiple proteins, including the protein kinase ATM (mutated in ataxia-telangiectasia). ATM kinase is activated in the vicinity of the break and is recruited to the break site by the Mre11-Rad50-Nbs1 complex, where it is fully activated. In human cells, the activation process involves autophosphorylation on three sites (Ser(367), Ser(1893), and Ser(1981)) and acetylation on Lys(3016). We now describe the identification of a new ATM phosphorylation site, Thr(P)(1885) and an additional autophosphorylation site, Ser(P)(2996), that is highly DNA damage-inducible. We also confirm that human and murine ATM share five identical phosphorylation sites. We targeted the ATM phosphorylation sites, Ser(367) and Ser(2996), for further study by generating phosphospecific antibodies against these sites and demonstrated that phosphorylation of both was rapidly induced by radiation. These phosphorylations were abolished by a specific inhibitor of ATM and were dependent on ATM and the Mre11-Rad50-Nbs1 complex. As found for Ser(P)(1981), ATM phosphorylated at Ser(367) and Ser(2996) localized to sites of DNA damage induced by radiation, but ATM recruitment was not dependent on phosphorylation at these sites. Phosphorylation at Ser(367) and Ser(2996) was functionally important because mutant forms of ATM were defective in correcting the S phase checkpoint defect and restoring radioresistance in ataxia-telangiectasia cells. These data provide further support for the importance of autophosphorylation in the activation and function of ATM in vivo.
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Affiliation(s)
- Sergei V. Kozlov
- From Radiation Biology and Oncology, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
| | - Mark E. Graham
- the Children's Medical Research Institute, University of Sydney, Westmead, New South Wales 2145, Australia
| | - Burkhard Jakob
- GSI Helmholtzzentrum für Schwerionenforschung GmbH, Biophysik, Planckstrasse 1, D-64291 Darmstadt, Germany
| | - Frank Tobias
- GSI Helmholtzzentrum für Schwerionenforschung GmbH, Biophysik, Planckstrasse 1, D-64291 Darmstadt, Germany
| | - Amanda W. Kijas
- From Radiation Biology and Oncology, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
| | - Marcel Tanuji
- From Radiation Biology and Oncology, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
| | - Philip Chen
- From Radiation Biology and Oncology, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
| | - Phillip J. Robinson
- the Children's Medical Research Institute, University of Sydney, Westmead, New South Wales 2145, Australia
| | - Gisela Taucher-Scholz
- GSI Helmholtzzentrum für Schwerionenforschung GmbH, Biophysik, Planckstrasse 1, D-64291 Darmstadt, Germany
| | - Keiji Suzuki
- the Department of Molecular Medicine, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan
| | - Sairai So
- the University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - David Chen
- the University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Martin F. Lavin
- From Radiation Biology and Oncology, Queensland Institute of Medical Research, Brisbane, Queensland 4029, Australia
- the University of Queensland Centre for Clinical Research, Brisbane, Queensland 4029, Australia
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23
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Phosphatidylserine increases IKBKAP levels in familial dysautonomia cells. PLoS One 2010; 5:e15884. [PMID: 21209961 PMCID: PMC3012102 DOI: 10.1371/journal.pone.0015884] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2010] [Accepted: 11/26/2010] [Indexed: 11/19/2022] Open
Abstract
Familial Dysautonomia (FD) is an autosomal recessive congenital neuropathy that results from abnormal development and progressive degeneration of the sensory and autonomic nervous system. The mutation observed in almost all FD patients is a point mutation at position 6 of intron 20 of the IKBKAP gene; this gene encodes the IκB kinase complex-associated protein (IKAP). The mutation results in a tissue-specific splicing defect: Exon 20 is skipped, leading to reduced IKAP protein expression. Here we show that phosphatidylserine (PS), an FDA-approved food supplement, increased IKAP mRNA levels in cells derived from FD patients. Long-term treatment with PS led to a significant increase in IKAP protein levels in these cells. A conjugate of PS and an omega-3 fatty acid also increased IKAP mRNA levels. Furthermore, PS treatment released FD cells from cell cycle arrest and up-regulated a significant number of genes involved in cell cycle regulation. Our results suggest that PS has potential for use as a therapeutic agent for FD. Understanding its mechanism of action may reveal the mechanism underlying the FD disease.
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24
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Benson EK, Zhao B, Sassoon DA, Lee SW, Aaronson SA. Effects of p21 deletion in mouse models of premature aging. Cell Cycle 2009; 8:2002-4. [PMID: 19535900 DOI: 10.4161/cc.8.13.8997] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
An approach to investigate the role of cellular senescence in organismal aging has been to abrogate signaling pathways known to induce cellular senescence and to assess the effects in mouse models of premature aging. Recently, we reported the effect of loss of function of p21, a gene implicated in p53-induced cellular senescence, in the background of the Ku80(-/-) premature aging mouse (Zhao et al., EMBO Rep 2009). Here, we provide an overview of the effects of p21 deletion in different models of premature aging.
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Affiliation(s)
- Erica K Benson
- Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA
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25
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Wu YH, Cheng ML, Ho HY, Chiu DTY, Wang TCV. Telomerase prevents accelerated senescence in glucose-6-phosphate dehydrogenase (G6PD)-deficient human fibroblasts. J Biomed Sci 2009; 16:18. [PMID: 19272180 PMCID: PMC2653519 DOI: 10.1186/1423-0127-16-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Accepted: 02/05/2009] [Indexed: 12/23/2022] Open
Abstract
Fibroblasts derived from glucose-6-phosphate dehydrogenase (G6PD)-deficient patients display retarded growth and accelerated cellular senescence that is attributable to increased accumulation of oxidative DNA damage and increased sensitivity to oxidant-induced senescence, but not to accelerated telomere attrition. Here, we show that ectopic expression of hTERT stimulates telomerase activity and prevents accelerated senescence in G6PD-deficient cells. Stable clones derived from hTERT-expressing normal and G6PD-deficient fibroblasts have normal karyotypes, and display no sign of senescence beyond 145 and 105 passages, respectively. Activation of telomerase, however, does not prevent telomere attrition in earlier-passage cells, but does stabilize telomere lengths at later passages. In addition, we provide evidence that ectopic expression of hTERT attenuates the increased sensitivity of G6PD-deficient fibroblasts to oxidant-induced senescence. These results suggest that ectopic expression of hTERT, in addition to acting in telomere length maintenance by activating telomerase, also functions in regulating senescence induction.
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Affiliation(s)
- Yi-Hsuan Wu
- Graduate Institute of Basic Medical Sciences, Chang Gung University, Kwei-San, Tao-Yuan 333, Taiwan.
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26
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Misri S, Pandita S, Pandita TK. Detecting ATM-dependent chromatin modification in DNA damage and heat shock response. Methods Mol Biol 2009; 523:395-410. [PMID: 19381924 DOI: 10.1007/978-1-59745-190-1_26] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The ataxia telangiectasia-mutated gene product (ATM), whose loss of function is responsible for ataxia telangiectasia (A-T), is a protein kinase that interacts with several substrates and is implicated in mitogenic signal transduction, chromosome condensation, meiotic recombination, cell-cycle control and telomere maintenance (Pandita, Expert Reviews in Molecular Medicine 5:1-21, 2003; Pandita, Oncogene 21:611-618, 2002; Matsuoka et al., Science 316:1160-1166, 2007). The ATM protein kinase is primarily activated in response to DNA double-strand breaks (DSBs) caused by ionizing radiation (IR) or radiomimetic drugs (Pandita et al., Oncogene 19:1386-1391, 2000). ATM is also activated by heat shock, which occurs independent of DNA damage (Hunt et al., Can Res 69:3010-3017, 2007). ATM is observed at the sites of DNA damage, where it is autophosphorylated and is dissociated from its non-active dimeric form to the active monomeric form (Bakkenist and Kastan, Nature 421:499-506, 2003). The ATM protein appears to be a part of the sensory machinery that detects DSBs during meiosis or mitosis, or breaks consequent to the damage by free radicals. Recent studies support the argument that ATM activation is regulated by chromatin modifications (Gupta, Mol Cell Biol 25:5292-5305, 2005). This review summarizes the multiple approaches used to discern the role of ATM in chromatin modification in response to DNA damage as well as heat shock.
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Affiliation(s)
- Sandeep Misri
- Washington University School of Medicine, St Louis, MO, USA
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Rainey MD, Charlton ME, Stanton RV, Kastan MB. Transient inhibition of ATM kinase is sufficient to enhance cellular sensitivity to ionizing radiation. Cancer Res 2008; 68:7466-74. [PMID: 18794134 DOI: 10.1158/0008-5472.can-08-0763] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In response to DNA damage, the ATM protein kinase activates signal transduction pathways essential for coordinating cell cycle progression with DNA repair. In the human disease ataxia-telangiectasia, mutation of the ATM gene results in multiple cellular defects, including enhanced sensitivity to ionizing radiation (IR). This phenotype highlights ATM as a potential target for novel inhibitors that could be used to enhance tumor cell sensitivity to radiotherapy. A targeted compound library was screened for potential inhibitors of the ATM kinase, and CP466722 was identified. The compound is nontoxic and does not inhibit phosphatidylinositol 3-kinase (PI3K) or PI3K-like protein kinase family members in cells. CP466722 inhibited cellular ATM-dependent phosphorylation events and disruption of ATM function resulted in characteristic cell cycle checkpoint defects. Inhibition of cellular ATM kinase activity was rapidly and completely reversed by removing CP466722. Interestingly, clonogenic survival assays showed that transient inhibition of ATM is sufficient to sensitize cells to IR and suggests that therapeutic radiosensitization may only require ATM inhibition for short periods of time. The ability of CP466722 to rapidly and reversibly regulate ATM activity provides a new tool to ask questions about ATM function that could not easily be addressed using genetic models or RNA interference technologies.
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Affiliation(s)
- Michael D Rainey
- Department of Oncology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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Role for proteasome activator PA200 and postglutamyl proteasome activity in genomic stability. Proc Natl Acad Sci U S A 2008; 105:16165-70. [PMID: 18845680 DOI: 10.1073/pnas.0803145105] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Proteasome activator PA200 enhances proteasome-mediated cleavage after acidic residues in vitro; however, its role within cells is not known. Here, we show that, in response to ionizing radiation, PA200 forms hybrid proteasomes with 19S caps and 20S core proteasomes that accumulate on chromatin, leading to an increase in proteolytic activity. Unlike many other proteins that respond to DNA damage, the response of PA200 appears to be independent of Ataxia Telangiectasia Mutated and p53, but dependent on DNA-dependent protein kinase activity. Nonetheless, PA200 is critical because PA200-knockdown cells show genomic instability and reduced survival after exposure to ionizing radiation. This phenotype is reproduced by specific inhibition of postglutamyl activity of proteasomes, but combined treatment with PA200 siRNA and postglutamyl inhibitor does not show additive effects on survival. Together, these data suggest a unique role for PA200 in genomic stability that is likely mediated through its ability to enhance postglutamyl cleavage by proteasomes.
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Davis T, Kipling D. Assessing the role of stress signalling via p38 MAP kinase in the premature senescence of ataxia telangiectasia and Werner syndrome fibroblasts. Biogerontology 2008; 10:253-66. [PMID: 18830681 DOI: 10.1007/s10522-008-9179-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 09/18/2008] [Indexed: 10/21/2022]
Abstract
The premature ageing ataxia telangiectasia (AT) and Werner syndromes (WS) are associated with accelerated cellular ageing. Young WS fibroblasts have an aged appearance and activated p38 MAP kinase, and treatment with the p38 inhibitor SB230580 extends their lifespan to within the normal range. SB203580 also extends the replicative lifespan of normal adult dermal fibroblasts, however, the effect is much reduced when compared to WS cells, suggesting that WS fibroblasts undergo a form of stress-induced premature senescence (SIPS). A small lifespan extension is seen in AT cells, which is not significant compared to normal fibroblasts, and the majority of young AT cells do not have an aged appearance and lack p38 activation, suggesting that the premature ageing does not result from SIPS. The lack of p38 activation is supported by the clinical manifestation, since AT is not associated with inflammatory disease, whereas WS individuals are predisposed to atherosclerosis, type II diabetes and osteoporosis, conditions known to be associated with p38 activation.
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Affiliation(s)
- Terence Davis
- Department of Pathology, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK.
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Glaviano A, Mothersill C, Case CP, Rubio MA, Newson R, Lyng F. Effects of hTERT on genomic instability caused by either metal or radiation or combined exposure. Mutagenesis 2008; 24:25-33. [PMID: 18776173 DOI: 10.1093/mutage/gen048] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Genomic instability is considered to be an important component in carcinogenesis. It can be caused by low-dose exposure to agents, which appear to act through induction of stress-response pathways related to oxidative stress. These agents have been studied mostly in the radiation field but evidence is accumulating that chemicals, especially heavy metals such as Cr (VI), can also act in the same manner. Previous work showed that metal ions could initiate long-term genomic instability in human primary fibroblasts and this phenomenon was regulated by telomerase. The aim of this study was to examine the difference in clonogenic survival and cytogenetic damage after exposure to Cr (VI) and radiation both singly and in combination in normal human fibroblasts (hTERT- cells) and engineered human fibroblasts, infected with a retrovirus carrying a cDNA encoding hTERT, which rendered these cells telomerase positive and replicatively immortal (hTERT+ cells). Cr (VI) induced genomic instability in hTERT- cells but not in hTERT+ cells, whereas radiation induced genomic instability in hTERT+ cells and to a lesser extent in hTERT- cells. Combined exposure caused genomic instability in both types of cells. However, this genomic instability was more pronounced in hTERT- cells after radiation followed by Cr (VI) and more pronounced in hTERT+ cells after Cr (VI) followed by radiation. Moreover, the biological effects provoked by combined exposure of Cr (VI) and radiation also led to a synergistic action in both types of cells, compared to either Cr (VI) treatment only or radiation exposure only. This study suggests that telomerase can prevent genomic instability caused by Cr (VI), but not by radiation. Furthermore, genomic instability may be prevented by telomerase when cells are exposed to radiation and then Cr (VI) but not after exposure to Cr (VI) and then radiation.
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Affiliation(s)
- A Glaviano
- Radiation and Environmental Science Centre, Focas Institute, Dublin Institute of Technology, Dublin, Ireland.
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31
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Agarwal M, Pandita S, Hunt CR, Gupta A, Yue X, Khan S, Pandita RK, Pratt D, Shay JW, Taylor JSA, Pandita TK. Inhibition of telomerase activity enhances hyperthermia-mediated radiosensitization. Cancer Res 2008; 68:3370-8. [PMID: 18451164 DOI: 10.1158/0008-5472.can-07-5831] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hyperthermia is a potent sensitizer of cell killing by ionizing radiation (IR); however, hyperthermia also induces heat shock protein 70 (HSP70) synthesis and HSP70 expression is associated with radioresistance. Because HSP70 interacts with the telomerase complex and expression of the telomerase catalytic unit (hTERT) extends the life span of the human cells, we determined if heat shock influences telomerase activity and whether telomerase inhibition enhances heat-mediated IR-induced cell killing. In the present study, we show that moderate hyperthermia (43 degrees C) enhances telomerase activity. Inhibition of telomerase activity with human telomerase RNA-targeted antisense agents, and in particular GRN163L, results in enhanced hyperthermia-mediated IR-induced cell killing, and ectopic expression of catalytic unit of telomerase (TERT) decreased hyperthermia-mediated IR-induced cell killing. The increased cell killing by heat and IR exposure in telomerase-inhibited cells correlates with delayed appearance and disappearance of gamma-H2AX foci as well as decreased chromosome repair. These results suggest that inactivation of telomerase before combined hyperthermia and radiotherapy could improve tumor killing.
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Affiliation(s)
- Manjula Agarwal
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63108, USA
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32
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Nakamura H. hTERT-immortalized cells useful for analyzing effects of low-dose-rate radiation on human cells. JOURNAL OF RADIATION RESEARCH 2008; 49:9-15. [PMID: 18160772 DOI: 10.1269/jrr.07088] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
To establish immortal human cells, we introduced the cDNA of the human telomere reverse transcriptase (hTERT) gene into skin fibroblast cells obtained from normal and ataxia telangiectasia (AT) individuals of Japanese origin. hTERT-immortalized cells retained their original characteristics and radiosensitivity except for immortalization, suggesting that these cells might be useful for analyzing the effects of radiation on human cells.hTERT-immortalized cells from a normal individual showed a greater resistance after low-dose-rate irradiation than after high-dose-rate irradiation. In contrast, cells from AT patients irradiated at a low-dose rate showed virtually the same survival as those irradiated at a high-dose rate. In hTERT-immortalized normal cells, the genetic effects of low-dose-rate radiation were quantitatively and qualitatively less severe than those of high-dose-rate radiation. In hTERT-immortalized AT cells, some fraction of DNA damage such as DNA double-strand breaks might not be repaired, and AT cells were severely affected by low-dose-rate radiation. The activation of ataxia telangiectasia mutated (ATM) protein was confirmed during low-dose-rate radiation, and may play an important role in repair of DNA damage induced by low-dose-rate radiation. This paper reviews briefly the current research at our laboratory. The hTERT-immortalized cells may be useful in determining the effects of low-dose and low-dose-rate radiation on human cells.
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Affiliation(s)
- Hideaki Nakamura
- Central Laboratory and Radiation Biology, Aichi Cancer Center Research Institute, Nagoya, Japan.
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Alterman N, Fattal-Valevski A, Moyal L, Crawford TO, Lederman HM, Ziv Y, Shiloh Y. Ataxia-telangiectasia: mild neurological presentation despite null ATM mutation and severe cellular phenotype. Am J Med Genet A 2007; 143A:1827-34. [PMID: 17632790 DOI: 10.1002/ajmg.a.31853] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by progressive neurodegeneration, immunodeficiency, susceptibility to cancer, genomic instability, and sensitivity to ionizing radiation. A-T is caused by mutations that eliminate or inactivate the nuclear protein kinase ATM, the chief activator of the cellular response to double strand breaks (DSBs) in the DNA. Mild A-T is usually caused by ATM mutations that leave residual amounts of active ATM. We studied two siblings with mild A-T, as defined by clinical examination and a quantitative A-T neurological index. Surprisingly, no ATM was detected in the patients' cells, and sequence analysis revealed that they were homozygous for a truncating ATM mutation (5653delA) that is expected to lead to the classical, severe neurological presentation. Moreover, the cellular phenotype of these patients was indistinguishable from that of classical A-T: all the tested parameters of the DSB response were severely defective as in typical A-T. This analysis shows that the severity of the neurological component of A-T is determined not only by ATM mutations but also by other influences yet to be found.
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Affiliation(s)
- Neora Alterman
- The David and Inez Myers Laboratory for Genetic Research, Department of Human Molecular Genetics and Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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Infante RE, Abi-Mosleh L, Radhakrishnan A, Dale JD, Brown MS, Goldstein JL. Purified NPC1 protein. I. Binding of cholesterol and oxysterols to a 1278-amino acid membrane protein. J Biol Chem 2007; 283:1052-63. [PMID: 17989073 DOI: 10.1074/jbc.m707943200] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Niemann-Pick, Type C1 protein (NPC1) is required for the transport of lipoprotein-derived cholesterol from lysosomes to endoplasmic reticulum. The 1278-amino acid, polytopic membrane protein has not been purified, and its mechanism of action is unknown. Unexpectedly, we encountered NPC1 in a search for a membrane protein that binds 25-hydroxycholesterol (25-HC) and other oxysterols. A 25-HC-binding protein was purified more than 14,000-fold from rabbit liver membranes and identified as NPC1 by mass spectroscopy. We prepared recombinant human NPC1 and confirmed its ability to bind oxysterols, including those with a hydroxyl group on the 24, 25, or 27 positions. Hydroxyl groups on the 7, 19, or 20 positions failed to confer binding. Recombinant human NPC1 also bound [(3)H]cholesterol in a reaction inhibited by Nonidet P-40 above its critical micellar concentration. Low concentrations of unlabeled 25-HC abolished binding of [(3)H]cholesterol, but the converse was not true, i.e. unlabeled cholesterol, even at high concentrations, did not abolish binding of [(3)H]25-HC. NPC1 is not required for the known regulatory actions of oxysterols. Thus, in NPC1-deficient fibroblasts 25-HC blocked the processing of sterol regulatory element-binding proteins and activated acyl-CoA:cholesterol acyltransferase in a normal fashion. The availability of assays to measure NPC1 binding in vitro may further the understanding of ways in which oxysterols regulate intracellular lipid transport.
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Affiliation(s)
- Rodney E Infante
- Department of Molecular Genetics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
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35
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The mammalian ortholog of Drosophila MOF that acetylates histone H4 lysine 16 is essential for embryogenesis and oncogenesis. Mol Cell Biol 2007; 28:397-409. [PMID: 17967868 DOI: 10.1128/mcb.01045-07] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The mammalian ortholog of the Drosophila MOF (males absent on the first) gene product is a histone H4 lysine 16-specific acetyltransferase. Recent studies have shown that depletion of human MOF (hMOF) in human cell lines leads to genomic instability, spontaneous chromosomal aberrations, cell cycle defects, altered nuclear morphology, reduced transcription of certain genes, and defective DNA damage response to ionizing radiation (IR). Here we show that MOF plays an essential role in mammals during embryogenesis and oncogenesis. Ablation of the mouse Mof gene (mMof) by gene targeting resulted in early embryonic lethality and cell death. Lethality correlated with the loss of H4 lysine 16 acetylation (H4K16ac) and could not be rescued by concomitant inactivation of ATM or p53. In comparison to primary cells or normal tissue, all immortalized human normal and tumor cell lines and primary tumors demonstrated similar or elevated hMOF and H4K16ac levels. Accordingly, MOF overexpression correlated with increased cellular proliferation, oncogenic transformation, and tumor growth. Thus, these data reveal that the acetylation of histone H4 at K16 by MOF is an epigenetic signature of cellular proliferation common to both embryogenesis and oncogenesis and that MOF is an essential factor for embryogenesis and oncogenesis.
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36
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Satra M, Tsougos I, Papanikolaou V, Theodorou K, Kappas C, Tsezou A. Correlation between radiation-induced telomerase activity and human telomerase reverse transcriptase mRNA expression in HeLa cells. Int J Radiat Biol 2006; 82:401-9. [PMID: 16846975 DOI: 10.1080/09553000600800090] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE To quantify and correlate human telomerase reverse transcriptase (hTERT) mRNA expression with telomerase activity (TA) after ionizing irradiation of HeLa cells. MATERIALS AND METHODS TA and hTERT mRNA expression were evaluated, at 24-h intervals, in HeLa cells cultured for up to 144 h, before and after treatment with increasing doses of 6 MV photon ionizing radiation (5 - 20 Gy), using the telomeric repeat amplification protocol (TRAP) assay and real-time reverse transcriptase polymerase chain reaction (RT-PCR), respectively. Cell viability was determined using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. A prototype phantom was constructed for accurate irradiation of HeLa cells. RESULTS Treated cells showed a decrease in viability with increasing radiation dose, and a correlation was observed with post-treatment period. TA and hTERT mRNA expression of HeLa cells increased for the first 24 h after irradiation. The maximal increases were approximately two times the un-irradiated cell levels at 24 h post-irradiation, followed by a decrease and a return to the control levels 72 h post-irradiation. The time-course of telomerase activation after 24 h, differed among radiation doses. A dose-dependent G2/M arrest was observed 24 h post-irradiation, along with an increase in polyploidy 48 h post-irradiation and afterwards. CONCLUSION A correlation between TA and hTERT mRNA expression and a radiation induced cell cycle dependent modification of hTERT mRNA expression was established for the first 24 h post-irradiation.
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Affiliation(s)
- Maria Satra
- Department of Biology, University of Thessaly, Medical School, Larissa, Greece
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37
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Park I, Avraham HK. Cell cycle-dependent DNA damage signaling induced by ICRF-193 involves ATM, ATR, CHK2, and BRCA1. Exp Cell Res 2006; 312:1996-2008. [PMID: 16630610 DOI: 10.1016/j.yexcr.2006.02.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Revised: 02/11/2006] [Accepted: 02/28/2006] [Indexed: 01/13/2023]
Abstract
Topoisomerase II is essential for cell proliferation and survival and has been a target of various anticancer drugs. ICRF-193 has long been used as a catalytic inhibitor to study the function of topoisomerase II. Here, we show that ICRF-193 treatment induces DNA damage signaling. Treatment with ICRF-193 induced G2 arrest and DNA damage signaling involving gamma-H2AX foci formation and CHK2 phosphorylation. DNA damage by ICRF-193 was further demonstrated by formation of the nuclear foci of 53BP1, NBS1, BRCA1, MDC1, and FANCD2 and increased comet tail moment. The DNA damage signaling induced by ICRF-193 was mediated by ATM and ATR and was restricted to cells in specific cell cycle stages such as S, G2, and mitosis including late and early G1 phases. Downstream signaling of ATM and ATR involved the phosphorylation of CHK2 and BRCA1. Altogether, our results demonstrate that ICRF-193 induces DNA damage signaling in a cell cycle-dependent manner and suggest that topoisomerase II might be essential for the progression of the cell cycle at several stages including DNA decondensation.
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Affiliation(s)
- Iha Park
- Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, 4 Blackfan Circle, 3rd Floor, Boston, MA 02115, USA
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38
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Nakamura H, Yasui Y, Saito N, Tachibana A, Komatsu K, Ishizaki K. DNA repair defect in AT cells and their hypersensitivity to low-dose-rate radiation. Radiat Res 2006; 165:277-82. [PMID: 16494515 DOI: 10.1667/rr3519.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Ataxia telangiectasia (AT) and normal cells immortalized with the human telomerase gene were irradiated in non-proliferative conditions with high- (2 Gy/min) or low-dose-rate (0.3 mGy/min) radiation. While normal cells showed a higher resistance after irradiation at a low dose rate than a high dose rate, AT cells showed virtually the same survival after low- and high-dose-rate irradiation. Although the frequency of micronuclei induced by low-dose-rate radiation was greatly reduced in normal cells, it was not reduced significantly in AT cells. The number of gamma-H2AX foci increased in proportion to the dose in both AT and normal cells after high-dose-rate irradiation. Although few gamma-H2AX foci were observed after low-dose-rate irradiation in normal cells, significant and dose-dependent numbers of gamma-H2AX foci were observed in AT cells even after low-dose-rate irradiation, indicating that DNA damage was not completely repaired during low-dose-rate irradiation. Significant phosphorylation of ATM proteins was detected in normal cells after low-dose-rate irradiation, suggesting that the activation of ATM plays an important role in the repair of DNA damage during low-dose-rate irradiation. In conclusion, AT cells may not be able to repair some fraction of DNA damage and are severely affected by low-dose-rate radiation.
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Affiliation(s)
- Hideaki Nakamura
- Central Laboratory and Radiation Biology, Aichi Cancer Center Research Institute, Nagoya 464-8681, Japan.
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39
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Lewis CM, Herbert BS, Bu D, Halloway S, Beck A, Shadeo A, Zhang C, Ashfaq R, Shay JW, Euhus DM. Telomerase immortalization of human mammary epithelial cells derived from a BRCA2 mutation carrier. Breast Cancer Res Treat 2006; 99:103-15. [PMID: 16541310 DOI: 10.1007/s10549-006-9189-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Accepted: 02/05/2006] [Indexed: 12/13/2022]
Abstract
A novel human mammary epithelial cell line, HME348, was established from benign breast tissue from a 44-year-old germ-line BRCA2 mutation carrier with a history of stage 1 breast cancer. Mutation analysis showed that the patient had a known 6872del4 BRCA2 heterozygous mutation. The human mammary epithelial cells passaged in culture exhibited cellular replicative aging as evidenced by telomere shortening, lack of telomerase activity, and senescence. Ectopic expression of telomerase (hTERT) reconstituted telomerase activity in these cells and led to the immortalization of the cells. When grown on glass, the majority of immortalized HME348 cells expressed ESA and p63 with a small population also expressing EMA. In three-dimensional Matrigel culture, HME348 cells formed complex branching acini structures that expressed luminal (EMA, CK18) and myoepithelial (p63, CALLA, CK14) markers. Three clones derived from this culture were also p63(+)/ESA(+)/EMA(+/-) on glass but formed similar acinar structures with both luminal and myoepithelial cell differentiation in Matrigel confirming the mammary progenitor nature of these cells. Additionally, the experimentally immortalized HME348 cells formed acini in cleared mammary fat pads in vivo. As this is the first report establishing and characterizing a benign human mammary epithelial cell line derived from a BRCA2 patient without the use of viral oncogenes, these cells may be useful for the study of BRCA2 function in breast morphogenesis and carcinogenesis.
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Affiliation(s)
- Cheryl M Lewis
- Hamon Center for Therapeutic Oncology Research and Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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40
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Glaviano A, Nayak V, Cabuy E, Baird DM, Yin Z, Newson R, Ladon D, Rubio MA, Slijepcevic P, Lyng F, Mothersill C, Case CP. Effects of hTERT on metal ion-induced genomic instability. Oncogene 2006; 25:3424-35. [PMID: 16449970 DOI: 10.1038/sj.onc.1209399] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
There is currently a great interest in delayed chromosomal and other damaging effects of low-dose exposure to a variety of pollutants which appear collectively to act through induction of stress-response pathways related to oxidative stress and ageing. These have been studied mostly in the radiation field but evidence is accumulating that the mechanisms can also be triggered by chemicals, especially heavy metals. Humans are exposed to metals, including chromium (Cr) (VI) and vanadium (V) (V), from the environment, industry and surgical implants. Thus, the impact of low-dose stress responses may be larger than expected from individual toxicity projections. In this study, a short (24 h) exposure of human fibroblasts to low doses of Cr (VI) and V (V) caused both acute chromosome damage and genomic instability in the progeny of exposed cells for at least 30 days after exposure. Acutely, Cr (VI) caused chromatid breaks without aneuploidy while V (V) caused aneuploidy without chromatid breaks. The longer-term genomic instability was similar but depended on hTERT positivity. In telomerase-negative hTERT- cells, Cr (VI) and V (V) caused a long lasting and transmissible induction of dicentric chromosomes, nucleoplasmic bridges, micronuclei and aneuploidy. There was also a long term and transmissible reduction of clonogenic survival, with an increased beta-galactosidase staining and apoptosis. This instability was not present in telomerase-positive hTERT+ cells. In contrast, in hTERT+ cells the metals caused a persistent induction of tetraploidy, which was not noted in hTERT- cells. The growth and survival of both metal-exposed hTERT+ and hTERT- cells differed if they were cultured at subconfluent levels or plated out as colonies. Genomic instability is considered to be a driving force towards cancer. This study suggests that the type of genomic instability in human cells may depend critically on whether they are telomerase-positive or -negative and that their sensitivities to metals could depend on whether they are clustered or diffuse.
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Affiliation(s)
- A Glaviano
- Bristol Implant Research Centre, University of Bristol, Bristol, UK
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41
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Gupta A, Sharma GG, Young CSH, Agarwal M, Smith ER, Paull TT, Lucchesi JC, Khanna KK, Ludwig T, Pandita TK. Involvement of human MOF in ATM function. Mol Cell Biol 2005; 25:5292-305. [PMID: 15923642 PMCID: PMC1140595 DOI: 10.1128/mcb.25.12.5292-5305.2005] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have determined that hMOF, the human ortholog of the Drosophila MOF gene (males absent on the first), encoding a protein with histone acetyltransferase activity, interacts with the ATM (ataxia-telangiectasia-mutated) protein. Cellular exposure to ionizing radiation (IR) enhances hMOF-dependent acetylation of its target substrate, lysine 16 (K16) of histone H4 independently of ATM function. Blocking the IR-induced increase in acetylation of histone H4 at K16, either by the expression of a dominant negative mutant DeltahMOF or by RNA interference-mediated hMOF knockdown, resulted in decreased ATM autophosphorylation, ATM kinase activity, and the phosphorylation of downstream effectors of ATM and DNA repair while increasing cell killing. In addition, decreased hMOF activity was associated with loss of the cell cycle checkpoint response to DNA double-strand breaks. The overexpression of wild-type hMOF yielded the opposite results, i.e., a modest increase in cell survival and enhanced DNA repair after IR exposure. These results suggest that hMOF influences the function of ATM.
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Affiliation(s)
- Arun Gupta
- Department of Radiation Oncology, Washington University School of Medicine, 4511 Forest Park, St. Louis, MO 63108, USA
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42
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Hofer AC, Tran RT, Aziz OZ, Wright W, Novelli G, Shay J, Lewis M. Shared phenotypes among segmental progeroid syndromes suggest underlying pathways of aging. J Gerontol A Biol Sci Med Sci 2005; 60:10-20. [PMID: 15741277 DOI: 10.1093/gerona/60.1.10] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Segmental progeroid syndromes are those whose phenotypes resemble accelerated aging. Here we analyze those phenotypes and hypothesize that short telomeres produce the same group of symptoms in a variety of otherwise unrelated progeroid syndromes. Specific findings are the following: (a) short telomeres in some progeroid syndromes cause an alopecia/osteoporosis/fingernail-atrophy group of symptoms; (b) fingernail atrophy in progeroid syndromes resembles the natural slowing of nail growth that occurs in normal aging and nail growth velocity, and may be a marker of replicative aging in keratinocyte stem cells; (c) alopecia and reduced hair diameter parallel the nail results; (d) osteoporosis in Dyskeratosis Congenita resembles age-related osteoporosis, but the same is not true of other progerias; and (e) gray hair is associated with short telomeres, but may also involve reactive oxygen species. On the basis of these results, we make several predictions and discuss how the segmental quality of progeroid syndromes may provide insight into normative aging.
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Affiliation(s)
- Anne C Hofer
- Department of Psychology, The University of Texas at Austin, Austin, Texas 78703, USA
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43
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Shahrabani-Gargir L, Pandita TK, Werner H. Ataxia-telangiectasia mutated gene controls insulin-like growth factor I receptor gene expression in a deoxyribonucleic acid damage response pathway via mechanisms involving zinc-finger transcription factors Sp1 and WT1. Endocrinology 2004; 145:5679-87. [PMID: 15345673 DOI: 10.1210/en.2004-0613] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The IGF-I receptor (IGF-IR) has a central role in cell cycle progression as well as in the establishment of the transformed phenotype. Increased expression of the IGF-IR gene, in addition, is correlated with acquisition of radioresistance for cell killing. The ataxia-telangiectasia mutated (ATM) gene product has a pivotal role in coordinating the cellular response to DNA damage. The present study was aimed at testing the hypothesis that the ability of ATM to coordinate the DNA damage response that will lead to cell survival or, alternatively, to apoptosis depends, to a significant extent, on its capacity to control IGF-IR gene expression. The potential involvement of ATM in regulation of IGF-IR expression and function was investigated in isogenic cells with and without ATM function [AT22IJE-T/pEBS7 (ATM -/-) and ATM-corrected AT22IJE-T/YZ5 (ATM +/+) cells and 293 human embryonic kidney cells transfected with small interfering RNAs targeted to ATM]. In addition, the effect of ATM on IGF-IR expression was assessed in nonisogenic cells with ATM function (HFF + human telomerase reverse transcriptase) and without ATM function (GM5823 + human telomerase reverse transcriptase). Results obtained showed that IGF-IR gene expression and IGF-IR promoter activity were largely reduced in ATM -/- cells. Addition of the radiomimetic agent neocarzinostatin for 4 h, however, induced a significant increase in IGF-IR levels in cells without ATM function. In addition, IGF-I-induced IGF-IR and insulin receptor substrate-1 phosphorylation were greatly impaired in ATM-deficient cells. Furthermore, we identified zinc-finger transcription factors Sp1 and WT1 as potential mediators of the effect of ATM on IGF-IR gene expression. The present data suggests that the IGF-IR gene is a novel downstream target in an ATM-mediated DNA damage response pathway. Deregulated expression of the IGF-IR gene after ionizing radiation may be linked to genomic instability and enhanced transforming capacity.
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Affiliation(s)
- Limor Shahrabani-Gargir
- Department of Clinical Biochemistry, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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44
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Maser RS, DePinho RA. Telomeres and the DNA damage response: why the fox is guarding the henhouse. DNA Repair (Amst) 2004; 3:979-88. [PMID: 15279784 DOI: 10.1016/j.dnarep.2004.05.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DNA double strand breaks (DSBs) are repaired by an extensive network of proteins that recognize damaged DNA and catalyze its repair. By virtue of their similarity, the normal ends of linear chromosomes and internal DNA DSBs are both potential substrates for DSB repair enzymes. Thus, telomeres, specialized nucleo-protein complexes that cap chromosomal ends, serve a critical function to differentiate themselves from internal DNA strand breaks, and as a result prevent genomic instability that can result from their inappropriate involvement in repair reactions. Telomeres that become critically short due to failure of telomere maintenance mechanisms, or which become dysfunctional by loss of telomere binding proteins, elicit extensive checkpoint responses that in normal cells blocks proliferation. In this situation, the DNA DSB repair machinery plays a major role in responding to these "damaged" telomeres - creating chromosome fusions or capturing telomeres from other chromosomes in an effort to rid the cell of the perceived damage. However, a surprising aspect of telomere maintenance is that many of the same proteins that facilitate this repair of damaged telomeres are also necessary for their proper integrity. Here, we review recent work defining the roles for DSB repair machinery in telomere maintenance and in response to telomere dysfunction.
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Affiliation(s)
- Richard S Maser
- Department of Medical Oncology, Dana-Farber Cancer Institute, Departments of Medicine and Genetics, Harvard Medical School, Boston, MA 02115, USA.
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45
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Herbig U, Jobling WA, Chen BPC, Chen DJ, Sedivy JM. Telomere shortening triggers senescence of human cells through a pathway involving ATM, p53, and p21(CIP1), but not p16(INK4a). Mol Cell 2004; 14:501-13. [PMID: 15149599 DOI: 10.1016/s1097-2765(04)00256-4] [Citation(s) in RCA: 913] [Impact Index Per Article: 45.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 03/29/2004] [Accepted: 03/30/2004] [Indexed: 11/16/2022]
Abstract
Cellular senescence can be triggered by telomere shortening as well as a variety of stresses and signaling imbalances. We used multiparameter single-cell detection methods to investigate upstream signaling pathways and ensuing cell cycle checkpoint responses in human fibroblasts. Telomeric foci containing multiple DNA damage response factors were assembled in a subset of senescent cells and signaled through ATM to p53, upregulating p21 and causing G1 phase arrest. Inhibition of ATM expression or activity resulted in cell cycle reentry, indicating that stable arrest requires continuous signaling. ATR kinase appears to play a minor role in normal cells but in the absence of ATM elicited a delayed G2 phase arrest. These pathways do not affect expression of p16, which was upregulated in a telomere- and DNA damage-independent manner in a subset of cells. Distinct senescence programs can thus progress in parallel, resulting in mosaic cultures as well as individual cells responding to multiple signals.
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Affiliation(s)
- Utz Herbig
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
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Baross A, Schertzer M, Zuyderduyn SD, Jones SJM, Marra MA, Lansdorp PM. Effect of TERT and ATM on gene expression profiles in human fibroblasts. Genes Chromosomes Cancer 2004; 39:298-310. [PMID: 14978791 DOI: 10.1002/gcc.20006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Telomeres protect chromosomes from degradation, end-to-end fusion, and illegitimate recombination. Loss of telomeres may lead to cell death or senescence or may cause genomic instability, leading to tumor formation. Expression of human telomerase reverse transcriptase (TERT) in human fibroblast cells elongates their telomeres and extends their lifespan. Ataxia telangiectasia mutated (ATM) deficiency in A-T human fibroblasts results in accelerated telomere shortening, abnormal cell-cycle response to DNA damage, and early senescence. Gene expression profiling was performed by serial analysis of gene expression (SAGE) on BJ normal human skin fibroblasts, A-T cells, and BJ and A-T cells transduced with TERT cDNA and expressing telomerase activity. In the four SAGE libraries, 36,921 unique SAGE tags were detected. Pairwise comparisons between the libraries showed differential expression levels of 1%-8% of the tags. Transcripts affected by both TERT and ATM were identified according to expression patterns, making them good candidates for further studies of pathways affected by both TERT and ATM. These include MT2A, P4HB, LGALS1, CFL1, LDHA, S100A10, EIF3S8, RANBP9, and SEC63. These genes are involved in apoptosis or processes related to cell growth, and most have been found to be deregulated in cancer. Our results have provided further insight into the roles of TERT and ATM by identifying genes likely to be involved in their function. Supplementary material for this article can be found on the Genes, Chromosomes and Cancer website at http://www.interscience.wiley.com/jpages/1045-2257/suppmat/index.html.
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Affiliation(s)
- Agnes Baross
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
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Ianari A, Gallo R, Palma M, Alesse E, Gulino A. Specific role for p300/CREB-binding protein-associated factor activity in E2F1 stabilization in response to DNA damage. J Biol Chem 2004; 279:30830-5. [PMID: 15123636 DOI: 10.1074/jbc.m402403200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
E2F1, a member of the E2F family of transcription factors, plays a pivotal role in controlling both physiological cell-cycle progression and apoptotic cell death in response to DNA damage and oncogene activation. In response to genotoxic stresses, E2F1 is stabilized by signals that include ATM-dependent phosphorylation. We recently demonstrated that DNA damage induces also E2F1 acetylation, which is required for its recruitment onto apoptotic gene promoters. Here we show that E2F1 is stabilized in response to doxorubicin and cisplatin treatments even in the absence of either ATM-dependent phosphorylation or p53 and cAbl, two major transducers of DNA damage signaling. We found that acetylation of E2F1 is, instead, required to stabilize the protein in response to doxorubicin. Finally, we report that the formation of E2F1-p300/CREB-binding protein-associated factor (P/CAF) complexes is preferentially induced in doxorubicin-treated cells, and that P/CAF acetyltransferase (HAT), but not p300 HAT activity, is required for a significant E2F1 stabilization and accumulation. Our results unveil a differential role of P/CAF and p300 in acetylation-induced stabilization of E2F1, thus supporting a specific role for P/CAF HAT activity in E2F1-dependent apoptosis in response to DNA damage.
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Affiliation(s)
- Alessandra Ianari
- Department of Experimental Medicine and Pathology, University of Rome La Sapienza, 00161 Rome, Italy
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Walter M, Forsyth NR, Wright WE, Shay JW, Roth MG. The establishment of telomerase-immortalized Tangier disease cell lines indicates the existence of an apolipoprotein A-I-inducible but ABCA1-independent cholesterol efflux pathway. J Biol Chem 2004; 279:20866-73. [PMID: 15001567 DOI: 10.1074/jbc.m401714200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tangier disease (TD) is a human genetic disorder associated with defective apolipoprotein-I-induced lipid efflux and increased atherosclerotic susceptibility. It has been linked to mutations in the ATP-binding cassette protein A1 (ABCA1). Here we describe the establishment of permanent Tangier cell lines using telomerase. Ectopic expression of the catalytic subunit of human telomerase extended the life span of control and TD skin fibroblasts, and (in contrast to immortalization procedures using viral oncogenes) did not impair apolipoprotein A-I-induced lipid efflux. The key characteristics of TD fibroblasts (reduced cholesterol and phospholipid efflux) were observed both in primary and telomerase-immortalized fibroblasts from two unrelated homozygous patients. Surprisingly, the apolipoprotein-inducible cholesterol efflux in TD cells was significantly improved after immortalization (up to 40% of normal values). In contrast to ABCA1-dependent cholesterol efflux, this efflux was not inhibited by brefeldin A, glybenclamide, or intracellular ATP depletion but was inhibited in the presence of cytochalasin D. Apolipoprotein A-I-dependent cholesterol efflux was inversely correlated with the population doubling number in cell culture and was inhibited up to 40% in near-senescent normal diploid fibroblasts. This inhibition was completely reversed by telomerase. Thus ectopic expression of telomerase is a way to circumvent the lack of critical experimental material and represents a major improvement for studying cholesterol efflux pathways in lipid disorders. Our findings indicate the existence of an ABCA1-independent but cytoskeleton-dependent cholesterol removal pathway that may help to prevent early atherosclerosis in Tangier disease but may also be sensitive to aging phenomena ex vivo and possibly in vivo.
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Affiliation(s)
- Michael Walter
- Department of Biochemistry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9038, USA
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Hunt CR, Dix DJ, Sharma GG, Pandita RK, Gupta A, Funk M, Pandita TK. Genomic instability and enhanced radiosensitivity in Hsp70.1- and Hsp70.3-deficient mice. Mol Cell Biol 2004; 24:899-911. [PMID: 14701760 PMCID: PMC343815 DOI: 10.1128/mcb.24.2.899-911.2004] [Citation(s) in RCA: 191] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Heat shock proteins (HSPs) are highly conserved among all organisms from prokaryotes to eukaryotes. In mice, the HSP genes Hsp70.1 and Hsp70.3 are induced by both endogenous and exogenous stressors, such as heat and toxicants. In order to determine whether such proteins specifically influence genomic instability, mice deficient for Hsp70.1 and Hsp70.3 (Hsp70.1/3(-/-) mice) were generated by gene targeting. Mouse embryonic fibroblasts (MEFs) prepared from Hsp70.1/3(-/-) mice did not synthesize Hsp70.1 or Hsp70.3 after heat-induced stress. While the Hsp70.1/3(-/-) mutant mice were fertile, their cells displayed genomic instability that was enhanced by heat treatment. Cells from Hsp70.1/3(-/-) mice also display a higher frequency of chromosome end-to-end associations than do control Hsp70.1/3(+/+) cells. To determine whether observed genomic instability was related to defective chromosome repair, Hsp70.1/3(-/-) and Hsp70.1/3(+/+) fibroblasts were treated with ionizing radiation (IR) alone or heat and IR. Exposure to IR led to more residual chromosome aberrations, radioresistant DNA synthesis (a hallmark of genomic instability), increased cell killing, and enhanced IR-induced oncogenic transformation in Hsp70.1/3(-/-) cells. Heat treatment prior to IR exposure enhanced cell killing, S-phase-specific chromosome damage, and the frequency of transformants in Hsp70.1/3(-/-) cells in comparison to Hsp70.1/3(+/+) cells. Both in vivo and in vitro studies demonstrate for the first time that Hsp70.1 and Hsp70.3 have an essential role in maintaining genomic stability under stress conditions.
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Affiliation(s)
- Clayton R Hunt
- Department of Oncology, Radiation, Washington University School of Medicine, 4511 Forest Park, St. Louis, MO 63108, USA
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Uziel T, Lerenthal Y, Moyal L, Andegeko Y, Mittelman L, Shiloh Y. Requirement of the MRN complex for ATM activation by DNA damage. EMBO J 2004; 22:5612-21. [PMID: 14532133 PMCID: PMC213795 DOI: 10.1093/emboj/cdg541] [Citation(s) in RCA: 844] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The ATM protein kinase is a primary activator of the cellular response to DNA double-strand breaks (DSBs). In response to DSBs, ATM is activated and phosphorylates key players in various branches of the DNA damage response network. ATM deficiency causes the genetic disorder ataxia-telangiectasia (A-T), characterized by cerebellar degeneration, immunodeficiency, radiation sensitivity, chromosomal instability and cancer predisposition. The MRN complex, whose core contains the Mre11, Rad50 and Nbs1 proteins, is involved in the initial processing of DSBs. Hypomorphic mutations in the NBS1 and MRE11 genes lead to two other genomic instability disorders: the Nijmegen breakage syndrome (NBS) and A-T like disease (A-TLD), respectively. The order in which ATM and MRN act in the early phase of the DSB response is unclear. Here we show that functional MRN is required for ATM activation, and consequently for timely activation of ATM-mediated pathways. Collectively, these and previous results assign to components of the MRN complex roles upstream and downstream of ATM in the DNA damage response pathway and explain the clinical resemblance between A-T and A-TLD.
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Affiliation(s)
- Tamar Uziel
- The David and Inez Myers Laboratory for Genetic Research, Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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