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Wilson C, Murnane JP. High-throughput screen to identify compounds that prevent or target telomere loss in human cancer cells. NAR Cancer 2022; 4:zcac029. [PMID: 36196242 PMCID: PMC9527662 DOI: 10.1093/narcan/zcac029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 09/09/2022] [Accepted: 09/29/2022] [Indexed: 11/14/2022] Open
Abstract
Chromosome instability (CIN) is an early step in carcinogenesis that promotes tumor cell progression and resistance to therapy. Using plasmids integrated adjacent to telomeres, we have previously demonstrated that the sensitivity of subtelomeric regions to DNA double-strand breaks (DSBs) contributes to telomere loss and CIN in cancer. A high-throughput screen was created to identify compounds that affect telomere loss due to subtelomeric DSBs introduced by I-SceI endonuclease, as detected by cells expressing green fluorescent protein (GFP). A screen of a library of 1832 biologically-active compounds identified a variety of compounds that increase or decrease the number of GFP-positive cells following activation of I-SceI. A curated screen done in triplicate at various concentrations found that inhibition of classical nonhomologous end joining (C-NHEJ) increased DSB-induced telomere loss, demonstrating that C-NHEJ is functional in subtelomeric regions. Compounds that decreased DSB-induced telomere loss included inhibitors of mTOR, p38 and tankyrase, consistent with our earlier hypothesis that the sensitivity of subtelomeric regions to DSBs is a result of inappropriate resection during repair. Although this assay was also designed to identify compounds that selectively target cells experiencing telomere loss and/or chromosome instability, no compounds of this type were identified in the current screen.
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Affiliation(s)
- Chris Wilson
- Department of Pharmaceutical Chemistry, Small Molecule Discovery Center, University of California, San Francisco, CA 94143, USA
| | - John P Murnane
- To whom correspondence should be addressed. Tel: +1 415 680 4434;
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2
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Nieri D, Berardinelli F, Sgura A, Cherubini R, De Nadal V, Gerardi S, Tanzarella C, Antoccia A. Cyogenetics effects in AG01522 human primary fibroblasts exposed to low doses of radiations with different quality. Int J Radiat Biol 2013; 89:698-707. [DOI: 10.3109/09553002.2013.797126] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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3
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Muraki K, Nyhan K, Han L, Murnane JP. Mechanisms of telomere loss and their consequences for chromosome instability. Front Oncol 2012; 2:135. [PMID: 23061048 PMCID: PMC3463808 DOI: 10.3389/fonc.2012.00135] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 09/19/2012] [Indexed: 12/17/2022] Open
Abstract
The ends of chromosomes in mammals, called telomeres, are composed of a 6-bp repeat sequence, TTAGGG, which is added on by the enzyme telomerase. In combination with a protein complex called shelterin, these telomeric repeat sequences form a cap that protects the ends of chromosomes. Due to insufficient telomerase expression, telomeres shorten gradually with each cell division in human somatic cells, which limits the number of times they can divide. The extensive cell division involved in cancer cell progression therefore requires that cancer cells must acquire the ability to maintain telomeres, either through expression of telomerase, or through an alternative mechanism involving recombination. It is commonly thought that the source of many chromosome rearrangements in cancer cells is a result of the extensive telomere shortening that occurs prior to the expression of telomerase. However, despite the expression of telomerase, tumor cells can continue to show chromosome instability due to telomere loss. Dysfunctional telomeres in cancer cells can result from oncogene-induced replication stress, which results in double-strand breaks (DSBs) at fragile sites, including telomeres. DSBs near telomeres are especially prone to chromosome rearrangements, because telomeric regions are deficient in DSB repair. The deficiency in DSB repair near telomeres is also an important mechanism for ionizing radiation-induced replicative senescence in normal human cells. In addition, DSBs near telomeres can result in chromosome instability in mouse embryonic stem cells, suggesting that telomere loss can contribute to heritable chromosome rearrangements. Consistent with this possibility, telomeric regions in humans are highly heterogeneous, and chromosome rearrangements near telomeres are commonly involved in human genetic disease. Understanding the mechanisms of telomere loss will therefore provide important insights into both human cancer and genetic disease.
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Affiliation(s)
- Keiko Muraki
- Department of Radiation Oncology, University of California at San Francisco San Francisco, CA, USA
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Bell DW, Sikdar N, Lee KY, Price JC, Chatterjee R, Park HD, Fox J, Ishiai M, Rudd ML, Pollock LM, Fogoros SK, Mohamed H, Hanigan CL, Zhang S, Cruz P, Renaud G, Hansen NF, Cherukuri PF, Borate B, McManus KJ, Stoepel J, Sipahimalani P, Godwin AK, Sgroi DC, Merino MJ, Elliot G, Elkahloun A, Vinson C, Takata M, Mullikin JC, Wolfsberg TG, Hieter P, Lim DS, Myung K. Predisposition to cancer caused by genetic and functional defects of mammalian Atad5. PLoS Genet 2011; 7:e1002245. [PMID: 21901109 PMCID: PMC3161924 DOI: 10.1371/journal.pgen.1002245] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 06/28/2011] [Indexed: 11/19/2022] Open
Abstract
ATAD5, the human ortholog of yeast Elg1, plays a role in PCNA deubiquitination. Since PCNA modification is important to regulate DNA damage bypass, ATAD5 may be important for suppression of genomic instability in mammals in vivo. To test this hypothesis, we generated heterozygous (Atad5+/m) mice that were haploinsuffficient for Atad5. Atad5+/m mice displayed high levels of genomic instability in vivo, and Atad5+/m mouse embryonic fibroblasts (MEFs) exhibited molecular defects in PCNA deubiquitination in response to DNA damage, as well as DNA damage hypersensitivity and high levels of genomic instability, apoptosis, and aneuploidy. Importantly, 90% of haploinsufficient Atad5+/m mice developed tumors, including sarcomas, carcinomas, and adenocarcinomas, between 11 and 20 months of age. High levels of genomic alterations were evident in tumors that arose in the Atad5+/m mice. Consistent with a role for Atad5 in suppressing tumorigenesis, we also identified somatic mutations of ATAD5 in 4.6% of sporadic human endometrial tumors, including two nonsense mutations that resulted in loss of proper ATAD5 function. Taken together, our findings indicate that loss-of-function mutations in mammalian Atad5 are sufficient to cause genomic instability and tumorigenesis. Genomic instability is a hallmark of tumorigenesis, suggesting that mutations in genes suppressing genomic instability contribute to this phenotype. In this study, we demonstrate for the first time that haploinsufficiency for Atad5, a protein that is important in stabilizing stalled DNA replication forks by regulating PCNA ubiquitination during DNA damage bypass, predisposes >90% of mice to tumorigenesis in multiple organs. In heterozygous Atad5 mice, both somatic cells and the spontaneous tumors showed high levels of genomic instability. In a subset of sporadic human endometrial tumors, we identified heterozygous loss-of-function somatic mutations in the ATAD5 gene, consistent with the role of mouse Atad5 in suppressing tumorigenesis. Collectively, our findings suggest that ATAD5 may be a novel tumor suppressor gene.
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Affiliation(s)
- Daphne W. Bell
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (DWB); (KM)
| | - Nilabja Sikdar
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Kyoo-young Lee
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jessica C. Price
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Raghunath Chatterjee
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hee-Dong Park
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- National Research Laboratory for Genomic Stability, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Jennifer Fox
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Masamichi Ishiai
- Laboratory of DNA Damage Signaling, Department of Late Effect Studies, Radiation Biology Center, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto, Japan
| | - Meghan L. Rudd
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Lana M. Pollock
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sarah K. Fogoros
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hassan Mohamed
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Christin L. Hanigan
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | | | - Suiyuan Zhang
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Pedro Cruz
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Gabriel Renaud
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Nancy F. Hansen
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Praveen F. Cherukuri
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Bhavesh Borate
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Kirk J. McManus
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Jan Stoepel
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Payal Sipahimalani
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Andrew K. Godwin
- Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Dennis C. Sgroi
- Molecular Pathology Unit and Center for Cancer Research, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America
| | - Maria J. Merino
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Gene Elliot
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Abdel Elkahloun
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Charles Vinson
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effect Studies, Radiation Biology Center, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto, Japan
| | - James C. Mullikin
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Tyra G. Wolfsberg
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Philip Hieter
- Michael Smith Laboratories, University of British Columbia, Vancouver, Canada
| | - Dae-Sik Lim
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- National Research Laboratory for Genomic Stability, Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Kyungjae Myung
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (DWB); (KM)
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Endt H, Sprung CN, Keller U, Gaipl U, Fietkau R, Distel LV. Detailed analysis of DNA repair and senescence marker kinetics over the life span of a human fibroblast cell line. J Gerontol A Biol Sci Med Sci 2010; 66:367-75. [PMID: 21081476 DOI: 10.1093/gerona/glq197] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We examined phosphorylation of H2AX, a marker for DNA double-strand breaks over the life of a human fibroblast cell line. This marker was compared with a number of other cellular senescence and DNA repair endpoints. An increase in γH2AX foci number was observed after 24 hours of repair time following DNA damage over the course of fibroblast passaging. Progressive and relatively constant changes in growth retardation, doubling time, and telomere length were also observed. The fraction of cells expressing β-gal, a marker of cellular senescence, increased considerably around the 40th passage as did some other cell morphology endpoints. The detectable γH2AX foci at 24 hours after ionizing radiation were far fewer than the number detected at 1 hour across all passage numbers. We conclude that although residual DNA damage level increases with passage number, it is unlikely to be the result of less efficient DNA repair in the aged fibroblast since most DNA damage is repaired, even at late passages.
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Affiliation(s)
- Heidrun Endt
- Department of Radiation Oncology, Friedrich-Alexander-University Erlangen-Nuremberg, Universitätsstraße 27, D-91054 Erlangen, Germany
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Zschenker O, Kulkarni A, Miller D, Reynolds GE, Granger-Locatelli M, Pottier G, Sabatier L, Murnane JP. Increased sensitivity of subtelomeric regions to DNA double-strand breaks in a human cancer cell line. DNA Repair (Amst) 2009; 8:886-900. [PMID: 19540174 PMCID: PMC2901176 DOI: 10.1016/j.dnarep.2009.05.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 05/05/2009] [Accepted: 05/08/2009] [Indexed: 12/25/2022]
Abstract
We previously reported that a single DNA double-strand break (DSB) near a telomere in mouse embryonic stem cells can result in chromosome instability. We have observed this same type of instability as a result of spontaneous telomere loss in human tumor cell lines, suggesting that a deficiency in the repair of DSBs near telomeres has a role in chromosome instability in human cancer. We have now investigated the frequency of the chromosome instability resulting from DSBs near telomeres in the EJ-30 human bladder carcinoma cell line to determine whether subtelomeric regions are sensitive to DSBs, as previously reported in yeast. These studies involved determining the frequency of large deletions, chromosome rearrangements, and chromosome instability resulting from I-SceI endonuclease-induced DSBs at interstitial and telomeric sites. As an internal control, we also analyzed the frequency of small deletions, which have been shown to be the most common type of mutation resulting from I-SceI-induced DSBs at interstitial sites. The results demonstrate that although the frequency of small deletions is similar at interstitial and telomeric DSBs, the frequency of large deletions and chromosome rearrangements is much greater at telomeric DSBs. DSB-induced chromosome rearrangements at telomeric sites also resulted in prolonged periods of chromosome instability. Telomeric regions in mammalian cells are therefore highly sensitive to DSBs, suggesting that spontaneous or ionizing radiation-induced DSBs at these locations may be responsible for many of the chromosome rearrangements that are associated with human cancer.
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Affiliation(s)
- Oliver Zschenker
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, United States
| | - Avanti Kulkarni
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, United States
| | - Douglas Miller
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, United States
| | - Gloria. E. Reynolds
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, United States
| | - Marine Granger-Locatelli
- Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux Roses, France
| | - Géraldine Pottier
- Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux Roses, France
| | - Laure Sabatier
- Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux Roses, France
| | - John. P. Murnane
- Department of Radiation Oncology, University of California, San Francisco, CA 94103, United States
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Škrobot Vidaček N, Çukušić A, Ferenac Kiš M, Ivanković M, Jevtov I, Mrsić S, Rubelj I. Telomere dynamics and genome stability in the human pancreatic tumor cell line MIAPaCa-2. Cytogenet Genome Res 2007; 119:60-7. [DOI: 10.1159/000109620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 05/23/2007] [Indexed: 12/19/2022] Open
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Gilley D, Herbert BS, Huda N, Tanaka H, Reed T. Factors impacting human telomere homeostasis and age-related disease. Mech Ageing Dev 2007; 129:27-34. [PMID: 18054990 DOI: 10.1016/j.mad.2007.10.010] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 10/03/2007] [Accepted: 10/23/2007] [Indexed: 11/25/2022]
Abstract
Loss of telomere length homeostasis has been linked to age-related disease especially cancer. In this review, we discuss two major causes of telomere dysfunction that potentially lead to tumorigenesis: replicative aging and environmental assaults. Aging has long been recognized as a source for telomere dysfunction through increasing numbers of cell divisions in the absence of sufficient telomerase activity. However, environmental assaults that cause telomere dysfunction are only beginning to be identified and recognized. Environmental stressors that influence telomere length may be physical or induced by psychological situations like stress. Knowledge of all factors, including genetic and environmental forces, that moderate telomere length will be critical for understanding basic mechanisms of human telomere maintenance during development and aging as well as for disease prevention and treatment strategies.
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Affiliation(s)
- David Gilley
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202, United States.
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9
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Endings in the middle: current knowledge of interstitial telomeric sequences. Mutat Res 2007; 658:95-110. [PMID: 17921045 DOI: 10.1016/j.mrrev.2007.08.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/28/2007] [Accepted: 08/30/2007] [Indexed: 01/24/2023]
Abstract
Interstitial telomeric sequences (ITSs) consist of tandem repeats of the canonical telomeric repeat and are common in mammals. They are localized at intrachromosomal sites, including those repeats located close to the centromeres and those found at interstitial sites, i.e., between the centromeres and the telomeres. ITSs might originate from ancestral intrachromosomal rearrangements (inversions and fusions), from differential crossing-over or from the repair of double-strand break during evolution. Three classes of ITSs have been described in the human genome, namely, short ITSs, long subtelomeric ITSs and fusion ITSs. The fourth class of ITSs, pericentromeric ITSs, has been found in other species. The function of ITSs can be inferred from the association of heritable diseases with ITS polymorphic variants, both in copy number and sequence. This is one of the most attractive aspects of ITS studies because it leads to new and useful markers for genetic linkage studies, forensic applications, and detection of genetic instability in tumors. Some ITSs also might be hotspots of chromosome breakage, rearrangement and amplification sites, based on the type of clastogens and the nature of ITSs. This study will contribute new knowledge with respect to ITSs' biology and mechanism, prevalence of diseases, risk evaluation and prevention of related diseases, thus facilitates the design of early detection markers for diseases caused by genomic instability.
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Snow BE, Mateyak M, Paderova J, Wakeham A, Iorio C, Zakian V, Squire J, Harrington L. Murine Pif1 interacts with telomerase and is dispensable for telomere function in vivo. Mol Cell Biol 2006; 27:1017-26. [PMID: 17130244 PMCID: PMC1800700 DOI: 10.1128/mcb.01866-06] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Pif1 is a 5'-to-3' DNA helicase critical to DNA replication and telomere length maintenance in the budding yeast Saccharomyces cerevisiae. ScPif1 is a negative regulator of telomeric repeat synthesis by telomerase, and recombinant ScPif1 promotes the dissociation of the telomerase RNA template from telomeric DNA in vitro. In order to dissect the role of mPif1 in mammals, we cloned and disrupted the mPif1 gene. In wild-type animals, mPif1 expression was detected only in embryonic and hematopoietic lineages. mPif1(-/-) mice were viable at expected frequencies, displayed no visible abnormalities, and showed no reproducible alteration in telomere length in two different null backgrounds, even after several generations. Spectral karyotyping of mPif1(-/-) fibroblasts and splenocytes revealed no significant change in chromosomal rearrangements. Furthermore, induction of apoptosis or DNA damage revealed no differences in cell viability compared to what was found for wild-type fibroblasts and splenocytes. Despite a novel association of mPif1 with telomerase, mPif1 did not affect the elongation activity of telomerase in vitro. Thus, in contrast to what occurs with ScPif1, murine telomere homeostasis or genetic stability does not depend on mPif1, perhaps due to fundamental differences in the regulation of telomerase and/or telomere length between mice and yeast or due to genetic redundancy with other DNA helicases.
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Affiliation(s)
- Bryan E Snow
- Ontario Cancer Institute, Campbell Family Institute for Breast Cancer Research, 620 University Avenue, Room 706, Toronto M5G 2C1, Canada
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Abstract
Genomic instability has been proposed to play an important role in cancer by accelerating the accumulation of genetic changes responsible for cancer cell evolution. One mechanism for chromosome instability is through the loss of telomeres, which are DNA-protein complexes that protect the ends of chromosomes and prevent chromosome fusion. Telomere loss can occur as a result of exogenous DNA damage, or spontaneously in cancer cells that commonly have a high rate of telomere loss. Mouse embryonic stem cells and human tumor cell lines that contain a selectable marker gene located immediately adjacent to a telomere have been used to investigate the consequences of telomere loss. In both cell types, telomere loss is followed by either the addition of a new telomere on to the end of the broken chromosome, or sister chromatid fusion and prolonged breakage/fusion/bridge (B/F/B) cycles that result in DNA amplification and large terminal deletions. The regions amplified by B/F/B cycles can then be transferred to other chromosomes, either through the formation of double-minute chromosomes that reintegrate at other sites, or through end-to-end fusions between chromosomes. B/F/B cycles eventually end when a chromosome acquires a new telomere by one of several mechanisms, the most common of which is translocation, which can involve either nonreciprocal transfer or duplication of all or part of an arm of another chromosome. Telomere acquisition involving nonreciprocal translocations results in the loss of a telomere on the donor chromosome, which subsequently becomes unstable. In contrast, translocations involving duplications do not destabilize the donor chromosome, although they result in allelic imbalances. Thus, the loss of a single telomere can generate a wide variety of chromosome alterations commonly associated with human cancer, not only on the chromosome that originally lost its telomere, but other chromosomes as well. Factors promoting spontaneous telomere loss and the resulting B/F/B cycles are therefore likely to be important in generating the karyotypic changes associated with human cancer.
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Affiliation(s)
- John P Murnane
- Department of Radiation Oncology, University of California, San Francisco, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA.
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12
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Abstract
Telomeres are composed of repetitive G-rich sequence and an abundance of associated proteins that together form a dynamic cap that protects chromosome ends and allows them to be distinguished from deleterious DSBs. Telomere-associated proteins also function to regulate telomerase, the ribonucleoprtotein responsible for addition of the species-specific terminal repeat sequence. Loss of telomere function is an important mechanism for the chromosome instability commonly found in cancer. Dysfunctional telomeres can result either from alterations in the telomere-associated proteins required for end-capping function, or from alterations that promote the gradual or sudden loss of sufficient repeat sequence necessary to maintain proper telomere structure. Regardless of the mechanism, loss of telomere function can result in sister chromatid fusion and prolonged breakage/fusion/bridge (B/F/B) cycles, leading to extensive DNA amplification and large terminal deletions. B/F/B cycles terminate primarily when the unstable chromosome acquires a new telomere, most often by translocation of the ends of other chromosomes, thereby providing a mechanism for transfer of instability from one chromosome to another. Thus, the loss of a single telomere can result in on-going instability, affect multiple chromosomes, and generate many of the types of rearrangements commonly associated with human cancer.
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Affiliation(s)
- Susan M Bailey
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA.
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Tanaka H, Mendonca MS, Bradshaw PS, Hoelz DJ, Malkas LH, Meyn MS, Gilley D. DNA damage-induced phosphorylation of the human telomere-associated protein TRF2. Proc Natl Acad Sci U S A 2005; 102:15539-44. [PMID: 16223874 PMCID: PMC1266153 DOI: 10.1073/pnas.0507915102] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Several protein kinases from diverse eukaryotes known to perform important roles in DNA repair have also been shown to play critical roles in telomere maintenance. Here, we report that the human telomere-associated protein TRF2 is rapidly phosphorylated in response to DNA damage. We find that the phosphorylated form of TRF2 is not bound to telomeric DNA, as is the ground form of TRF2, and is rapidly localized to damage sites. Our results suggest that the ataxia-telangiectasia-mutated (ATM) protein kinase signal-transduction pathway is primarily responsible for the DNA damage-induced phosphorylation of TRF2. Unlike DNA damage-induced phosphorylation of other ATM targets, the phosphorylated form of TRF2 is transient, being detected rapidly at DNA damage sites postirradiation, but largely dissipated by 2 hours. In addition, we report that the phosphorylated form of TRF2 is present at telomeres in cell types undergoing telomere-based crisis and a recombination-driven, telomerase-independent, alternative lengthening of telomeres (ALT) pathway, likely as a consequence of a telomere-based DNA damage response. Our results link the induction of TRF2 phosphorylation to the DNA damage-response system, providing an example of direct cross-talk via a signaling pathway between these two major cellular processes essential for genomic stability, telomere maintenance, and DNA repair.
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Affiliation(s)
- Hiromi Tanaka
- Departments of Medical and Molecular Genetics, Radiation Oncology, and Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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14
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Gilley D, Tanaka H, Herbert BS. Telomere dysfunction in aging and cancer. Int J Biochem Cell Biol 2005; 37:1000-13. [PMID: 15743674 DOI: 10.1016/j.biocel.2004.09.003] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 08/20/2004] [Accepted: 09/02/2004] [Indexed: 11/26/2022]
Abstract
Telomeres are unique DNA-protein structures that contain noncoding TTAGGG repeats and telomere-associated proteins. These specialized structures are essential for maintaining genomic integrity. Alterations that lead to the disruption of telomere maintenance result in chromosome end-to-end fusions and/or ends being recognized as double-strand breaks. A large body of evidence suggests that the cell responds to dysfunctional telomeres by undergoing senescence, apoptosis, or genomic instability. In conjunction with other predisposing mechanisms, the genomic instability encountered in preimmortal cells due to dysfunctional or uncapped telomeres might lead to cancer. Furthermore, telomere dysfunction has been proposed to play critical roles in aging as well as cancer progression. Conversely, recent evidence has shown that targeting telomere maintenance mechanisms and inducing telomere dysfunction in cancer cells by inhibiting telomerase can lead to catastrophic events including rapid cell death and increased sensitivity to other cancer therapeutics. Thus, given the major role telomeres play during development, it is important to continue our understanding telomere structure, function and maintenance. Herein, we provide an overview of the emerging knowledge of telomere dysfunction and how it relates to possible links between aging and cancer.
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Affiliation(s)
- David Gilley
- Department of Medical and Molecular Genetics, The Indiana University Cancer Center, Indiana University School of Medicine, 975 West Walnut St, IB 242, Indianapolis, IN 46202-5251, USA
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Abstract
Telomeres are essential for genome stability in all eukaryotes. Changes in telomere functions and the associated chromosomal abnormalities have been implicated in human aging and cancer. Telomeres are composed of repetitive sequences that can be maintained by telomerase, a complex containing a reverse transcriptase (hTERT in humans and Est2 in budding yeast), a template RNA (hTERC in humans and Tlc1 in yeast), and accessory factors (the Est1 proteins and dyskerin in humans and Est1, Est3, and Sm proteins in budding yeast). Telomerase is regulated in cis by proteins that bind to telomeric DNA. This regulation can take place at the telomere terminus, involving single-stranded DNA-binding proteins (POT1 in humans and Cdc13 in budding yeast), which have been proposed to contribute to the recruitment of telomerase and may also regulate the extent or frequency of elongation. In addition, proteins that bind along the length of the telomere (TRF1/TIN2/tankyrase in humans and Rap1/Rif1/Rif2 in budding yeast) are part of a negative feedback loop that regulates telomere length. Here we discuss the details of telomerase and its regulation by the telomere.
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Londoño-Vallejo JA. Telomere length heterogeneity and chromosome instability. Cancer Lett 2004; 212:135-44. [PMID: 15341022 DOI: 10.1016/j.canlet.2004.05.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2004] [Accepted: 05/12/2004] [Indexed: 01/04/2023]
Abstract
Chromosome aberrations are the hallmark of cancer cells. Although a few specific chromosome aberrations are frequently detected in some types of cancer, the majority of karyotypic abnormalities tend to differ between different histological types and between individuals with the same type of cancer. Recent work indicates that telomeres may be directly involved in shaping the karyotypes of tumor cells. In particular, the heterogeneity of telomere lengths within cells may have direct influence on the frequency with which chromosomes engage in telomeric fusions and in subsequent breakage-fusion-bridge cycles. Since telomere length distribution among chromosome arms is a polymorphic trait, difference in distributions between individuals may account, at least in part, for the karyotypic differences found among tumors of the same type. Conversely, if single telomere lengths happen to be inherited, the segregation of particularly short telomeres in families may increase the incidence of specific chromosome aberrations during tumor evolution, and perhaps contribute, along with other factors, to cancer pre-disposition.
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Smith S, Hwang JY, Banerjee S, Majeed A, Gupta A, Myung K. Mutator genes for suppression of gross chromosomal rearrangements identified by a genome-wide screening in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2004; 101:9039-44. [PMID: 15184655 PMCID: PMC428469 DOI: 10.1073/pnas.0403093101] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Different types of gross chromosomal rearrangements (GCRs), including translocations, interstitial deletions, terminal deletions with de novo telomere additions, and chromosome fusions, are observed in many cancers. Multiple pathways, such as S-phase checkpoints, DNA replication, recombination, chromatin remodeling, and telomere maintenance that suppress GCRs have been identified. To experimentally expand our knowledge of other pathway(s) that suppress GCRs, we developed a generally applicable genome-wide screening method. In this screen, we identified 10 genes (ALO1, CDC50, CSM2, ELG1, ESC1, MMS4, RAD5, RAD18, TSA1, and UFO1) that encode proteins functioning in the suppression of GCRs. Moreover, the breakpoint junctions of GCRs from these GCR mutator mutants were determined with modified breakpoint-mapping methods. We also identified nine genes (AKR1, BFR1, HTZ1, IES6, NPL6, RPL13B, RPL27A, RPL35A, and SHU2) whose mutations generated growth defects with the pif1Delta mutation. In addition, we found that some of these mutations changed the telomere size.
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Affiliation(s)
- Stephanie Smith
- Genome Instability Section, Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, 49 Convent Drive, Bethesda, MD 20892, USA
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Murnane JP, Sabatier L. Chromosome rearrangements resulting from telomere dysfunction and their role in cancer. Bioessays 2004; 26:1164-74. [PMID: 15499579 DOI: 10.1002/bies.20125] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Telomeres play a vital role in protecting the ends of chromosomes and preventing chromosome fusion. The failure of cancer cells to properly maintain telomeres can be an important source of the chromosome instability involved in cancer cell progression. Telomere loss results in sister chromatid fusion and prolonged breakage/fusion/bridge (B/F/B) cycles, leading to extensive DNA amplification and large deletions. These B/F/B cycles end primarily when the unstable chromosome acquires a new telomere by translocation of the ends of other chromosomes. Many of these translocations are nonreciprocal, resulting in the loss of the telomere from the donor chromosome, providing a mechanism for transfer of instability from one chromosome to another until a chromosome acquires a telomere by a mechanism other than nonreciprocal translocation. B/F/B cycles can also result in other forms of chromosome rearrangements, including double-minute chromosomes and large duplications. Thus, the loss of a single telomere can result in instability in multiple chromosomes, and generate many of the types of rearrangements commonly associated with human cancer.
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Affiliation(s)
- John P Murnane
- Radiation Oncology Research Laboratory, University of California, San Francisco, CA 94103, USA.
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Lo AWI, Sabatier L, Fouladi B, Pottier G, Ricoul M, Murnane JP. DNA amplification by breakage/fusion/bridge cycles initiated by spontaneous telomere loss in a human cancer cell line. Neoplasia 2002; 4:531-8. [PMID: 12407447 PMCID: PMC1503667 DOI: 10.1038/sj.neo.7900267] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Accepted: 07/24/2002] [Indexed: 11/09/2022]
Abstract
The development of genomic instability is an important step in generating the multiple genetic changes required for cancer. One consequence of genomic instability is the overexpression of oncogenes due to gene amplification. One mechanism for gene amplification is the breakage/fusion/bridge (B/F/B) cycle that involves the repeated fusion and breakage of chromosomes following the loss of a telomere. B/F/B cycles have been associated with low-copy gene amplification in human cancer cells, and have been proposed to be an initiating event in high-copy gene amplification. We have found that spontaneous telomere loss on a marker chromosome 16 in a human tumor cell line results in sister chromatid fusion and prolonged periods of chromosome instability. The high rate of anaphase bridges involving chromosome 16 demonstrates that this instability results from B/F/B cycles. The amplification of subtelomeric DNA on the marker chromosome provides conclusive evidence that B/F/B cycles initiated by spontaneous telomere loss are a mechanism for gene amplification in human cancer cells.
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Affiliation(s)
- Anthony W I Lo
- Radiation Oncology Research Laboratory, University of California, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA
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20
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Dafotakis M, Vehoff J, Korr H, Schmitz C. Prenatal Programming of Depression and Schizophrenia? Neuroembryology Aging 2002. [DOI: 10.1159/000063531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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21
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Lo AWI, Sprung CN, Fouladi B, Pedram M, Sabatier L, Ricoul M, Reynolds GE, Murnane JP. Chromosome instability as a result of double-strand breaks near telomeres in mouse embryonic stem cells. Mol Cell Biol 2002; 22:4836-50. [PMID: 12052890 PMCID: PMC133890 DOI: 10.1128/mcb.22.13.4836-4850.2002] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Telomeres are essential for protecting the ends of chromosomes and preventing chromosome fusion. Telomere loss has been proposed to play an important role in the chromosomal rearrangements associated with tumorigenesis. To determine the relationship between telomere loss and chromosome instability in mammalian cells, we investigated the events resulting from the introduction of a double-strand break near a telomere with I-SceI endonuclease in mouse embryonic stem cells. The inactivation of a selectable marker gene adjacent to a telomere as a result of the I-SceI-induced double-strand break involved either the addition of a telomere at the site of the break or the formation of inverted repeats and large tandem duplications on the end of the chromosome. Nucleotide sequence analysis demonstrated large deletions and little or no complementarity at the recombination sites involved in the formation of the inverted repeats. The formation of inverted repeats was followed by a period of chromosome instability, characterized by amplification of the subtelomeric region, translocation of chromosomal fragments onto the end of the chromosome, and the formation of dicentric chromosomes. Despite this heterogeneity, the rearranged chromosomes eventually acquired telomeres and were stable in most of the cells in the population at the time of analysis. Our observations are consistent with a model in which broken chromosomes that do not regain a telomere undergo sister chromatid fusion involving nonhomologous end joining. Sister chromatid fusion is followed by chromosome instability resulting from breakage-fusion-bridge cycles involving the sister chromatids and rearrangements with other chromosomes. This process results in highly rearranged chromosomes that eventually become stable through the addition of a telomere onto the broken end. We have observed similar events after spontaneous telomere loss in a human tumor cell line, suggesting that chromosome instability resulting from telomere loss plays a role in chromosomal rearrangements associated with tumor cell progression.
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Affiliation(s)
- Anthony W. I. Lo
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Carl N. Sprung
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Bijan Fouladi
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Mehrdad Pedram
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Laure Sabatier
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Michelle Ricoul
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Gloria E. Reynolds
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - John P. Murnane
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
- Corresponding author. Mailing address: Department of Radiation Oncology, University of California, 1855 Folsom St., MCB 200, San Francisco, CA 94103. Phone: (415) 476-9083. Fax: (415) 476-9069. E-mail:
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22
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Pendergrass WR, Penn PE, Li J, Wolf NS. Age-related telomere shortening occurs in lens epithelium from old rats and is slowed by caloric restriction. Exp Eye Res 2001; 73:221-8. [PMID: 11446772 DOI: 10.1006/exer.2001.1033] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated whether the average relative telomere length of lens epithelial cells (LECs) from brown Norway rats decreases with the age of the donor animal, and whether chronic caloric restriction (CR) of the rats delays the telomere shortening. Our previous studies have demonstrated that clonal proliferative potential of rodent LECs as well as the in vivo rate of DNA synthesis decreases with age and that this decrease is slowed by chronic lifelong caloric restriction (CR). In order to determine if telomeric shortening might be involved in this loss of proliferative potential, we examined relative telomeric lengths in young, old ad lib fed (AL), and old calorically restricted (CR) brown Norway rats. We used fluorescence in situ hybridization with a peptide nucleic acid probe (PNA) complementary to the telomeric repeat sequence to quantitate relative telomere lengths in LECs in lens sections (TELO-FISH). Control experiments demonstrated that the PNA probe binding was restricted almost entirely to the terminal portions of the rat chromosomes with less than 5% bound at interstitial sites in typical metaphase spreads. The relative telomere lengths of interphase human fibroblast standards, as determined by TELO-FISH, were in good agreement with terminal restriction fragment analyses of the same standards and with literature values for rat cells. The average telomere lengths of interphase nuclei in the old AL rat LECs were found to be 21% shorter than paired young AL controls (P < 0.01 by Wilcoxian signed rank test). The calorically restricted old rats had less telomere erosion (12%) than the old AL group (P < 0.05). Although it is not clear whether such moderate telomeric erosion can limit cell division in rodent LECs, the telomeric shortening correlated well with previous studies demonstrating reduced clonal, replicative potential, and reduced rates of in vivo DNA replication in LECs from old rodents and a delay in this attenuation in animals on chronic CR.
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Affiliation(s)
- W R Pendergrass
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
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23
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Nagele RG, Velasco AQ, Anderson WJ, McMahon DJ, Thomson Z, Fazekas J, Wind K, Lee H. Telomere associations in interphase nuclei: possible role in maintenance of interphase chromosome topology. J Cell Sci 2001; 114:377-88. [PMID: 11148139 DOI: 10.1242/jcs.114.2.377] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The relative sizes of individual telomeres in cultured human cells under conditions of cell cycling, replicative quiescence, cell transformation and immortalization were determined using quantitative fluorescence in situ hybridization (Q-FISH) with a telomere-specific peptide nucleic acid (PNA) probe. Results obtained from analysis of telomere length profiles (TLPs), which display the distribution of relative telomere lengths for individual cells, confirmed telomere length heterogeneity at the single cell level and proportional shortening of telomere length during replicative aging of virus-transformed cells. TLPs also revealed that some telomeric ends of chromosomes are so closely juxtaposed within interphase nuclei that their fluorescent signals appear as a single spot. These telomeric associations (TAs) were far more prevalent in interphase nuclei of noncycling normal and virus-transformed cells than in their cycling counterparts. The number of interphase TAs per nucleus observed in late-passage E6/E7-transformed cells did not increase during progression to crisis, suggesting that telomere shortening does not increase the frequency of interphase TAs. Furthermore, interphase TAs were rarely observed in rapidly cycling, telomerase-positive, immortalized cells that exhibit somewhat shortened, but stabilized, telomere length through the activity of telomerase. Our overall results suggest that the number of interphase TAs is dependent more on whether or not cells are cycling than on telomere length, with TAs being most prominent in the nuclei of replicatively quiescent cells in which nonrandom (even preferred) chromosome spatial arrangements have been observed. We propose that interphase TAs may play a role in the generation and/or maintenance of nuclear architecture and chromosome positional stability in interphase nuclei, especially in cells with a prolonged G(1)/G(0) phase and possibly in terminally differentiated cells.
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Affiliation(s)
- R G Nagele
- Department of Molecular Biology, University of Medicine and Dentistry of New Jersey - School of Osteopathic Medicine, Stratford, New Jersey 08084, USA.
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Fouladi B, Sabatier L, Miller D, Pottier G, Murnane JP. The relationship between spontaneous telomere loss and chromosome instability in a human tumor cell line. Neoplasia 2000; 2:540-54. [PMID: 11228547 PMCID: PMC1508089 DOI: 10.1038/sj.neo.7900107] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2000] [Accepted: 08/19/2000] [Indexed: 11/08/2022]
Abstract
Chromosome instability plays an important role in cancer by promoting the alterations in the genome required for tumor cell progression. The loss of telomeres that protect the ends of chromosomes and prevent chromosome fusion has been proposed as one mechanism for chromosome instability in cancer cells, however, there is little direct evidence to support this hypothesis. To investigate the relationship between spontaneous telomere loss and chromosome instability in human cancer cells, clones of the EJ-30 tumor cell line were isolated in which a herpes simplex virus thymidine kinase (HSV-tk) gene was integrated immediately adjacent to a telomere. Selection for HSV-tk-deficient cells with ganciclovir demonstrated a high rate of loss of the end these "marked" chromosomes (10-4 events/cell per generation). DNA sequence and cytogenetic analysis suggests that the loss of function of the HSV-tk gene most often involves telomere loss, sister chromatid fusion, and prolonged periods of chromosome instability. In some HSV-tk-deficient cells, telomeric repeat sequences were added on to the end of the truncated HSV-tk gene at a new location, whereas in others, no telomere was detected on the end of the marked chromosome. These results suggest that spontaneous telomere loss is a mechanism for chromosome instability in human cancer cells.
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Affiliation(s)
- B Fouladi
- Radiation Oncology Research Laboratory, University of California, San Francisco, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA
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25
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Bromidge T, Lowe C, Prentice A, Johnson S. p53 intronic point mutation, aberrant splicing and telomeric associations in a case of B-chronic lymphocytic leukaemia. Br J Haematol 2000. [DOI: 10.1111/j.1365-2141.2000.02335.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Bromidge T, Lowe C, Prentice A, Johnson S. p53 intronic point mutation, aberrant splicing and telomeric associations in a case of B-chronic lymphocytic leukaemia. Br J Haematol 2000; 111:223-9. [PMID: 11091205 DOI: 10.1046/j.1365-2141.2000.02335.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We report a case of chronic lymphocytic leukaemia (CLL) with telomeric associations and a p53 intronic point mutation. Karyotypic analysis revealed clonal and non-clonal telomeric associations, accompanied by clonal cytogenetic abnormalities and also in isolation. The p53 mutation, which occurred at the invariant base pair -2 of the splice acceptor site in intron 7 resulted in the abolition of correct splicing of exon 7 to exon 8. Multiple aberrant splice products were characterized, all of which differed from wildtype in the DNA binding domain. Fluorescence in situ hybridization demonstrated that the clone retained two copies of the p53 gene and wild-type p53 transcript was detected on cloning of reverse transcriptase polymerase chain reaction (RT-PCR) product, indicating that one wild-type allele remained. However, a plasmid clone with correct splicing at the exon 7/8 boundary, but with a 21 bp deletion in exon 8, was also found at low frequency. This finding indicates clonal evolution, resulting in complete loss of wild-type p53. The intronic point mutation was not present in DNA extracted from cervical tissue indicating that it was a leukaemic phenomenon. This is the first case of an intronic point mutation to be reported in CLL. This mutation led to chaotic p53 expression and, interestingly, occurred in a case showing telomeric associations, a rare phenomenon in B-CLL.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Carcinoma, Squamous Cell/complications
- Carcinoma, Squamous Cell/genetics
- Chromosomes, Human, Pair 12
- Chromosomes, Human, Pair 2
- Chromosomes, Human, Pair 9
- Female
- Genes, p53
- Humans
- Introns
- Karyotyping
- Leukemia, Lymphocytic, Chronic, B-Cell/complications
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Lip Neoplasms/complications
- Lip Neoplasms/genetics
- Middle Aged
- Molecular Sequence Data
- Neoplasms, Multiple Primary/genetics
- Point Mutation
- RNA Splice Sites
- Reverse Transcriptase Polymerase Chain Reaction
- Telomere
- Trisomy
- Uterine Cervical Neoplasms/complications
- Uterine Cervical Neoplasms/genetics
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Affiliation(s)
- T Bromidge
- Leukaemia Research Unit, Taunton and Somerset Hospital, UK.
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