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Abstract
Telomeres form protective caps at the ends of linear chromosomes to prevent nucleolytic degradation, end-to-end fusion, irregular recombination, and chromosomal instability. Telomeres are composed of repetitive DNA sequences (TTAGGG)n in humans, that are bound by specialized telomere binding proteins. Telomeres lose capping function in response to telomere shortening, which occurs during each division of cells that lack telomerase activity-the enzyme that can synthesize telomeres de novo. Telomeres have a dual role in cancer: telomere shortening can lead to induction of chromosomal instability and to the initiation of tumors, however, initiated tumors need to reactivate telomerase in order to stabilize chromosomes and to gain immortal growth capacity. In this review, we summarize current knowledge on the role of telomeres in the maintenance of chromosomal stability and carcinogenesis.
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Turner KJ, Vasu V, Greenall J, Griffin DK. Telomere length analysis and preterm infant health: the importance of assay design in the search for novel biomarkers. Biomark Med 2014; 8:485-98. [PMID: 24796612 DOI: 10.2217/bmm.14.13] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Preterm infants develop an 'aged' phenotype in comparison with term-born infants, one component of which is adverse metabolic health and, therefore, long-term health follow-up is warranted to identify morbidity. In light of this, the identification and use of biomarkers to aid with prognosis would be a welcome development. Telomeres are repeat sequences at the ends of each chromosome arm known to shorten as a consequence of cellular aging, and in relation to several disease conditions. The hypothesis that expreterm infants manifest alterations in telomere attrition rate is, therefore, one of interest. Analysis of telomere length maybe a plausible technique to predict prognosis in relation to preterm birth, and early life environmental and nutritional exposures. In this article, we review the literature on telomere length analysis in the preterm infant population and examine the tools available to measure telomere length.
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Affiliation(s)
- Kara J Turner
- University of Kent, School of Biosciences, Giles Lane, Canterbury, Kent, CT2 7NJ, UK
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Alternative lengthening of telomeres is enriched in, and impacts survival of TP53 mutant pediatric malignant brain tumors. Acta Neuropathol 2014; 128:853-62. [PMID: 25315281 DOI: 10.1007/s00401-014-1348-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/23/2014] [Accepted: 09/26/2014] [Indexed: 12/18/2022]
Abstract
Although telomeres are maintained in most cancers by telomerase activation, a subset of tumors utilize alternative lengthening of telomeres (ALT) to sustain self-renewal capacity. In order to study the prevalence and significance of ALT in childhood brain tumors we screened 517 pediatric brain tumors using the novel C-circle assay. We examined the association of ALT with alterations in genes found to segregate with specific histological phenotypes and with clinical outcome. ALT was detected almost exclusively in malignant tumors (p = 0.001). ALT was highly enriched in primitive neuroectodermal tumors (12 %), choroid plexus carcinomas (23 %) and high-grade gliomas (22 %). Furthermore, in contrast to adult gliomas, pediatric low grade gliomas which progressed to high-grade tumors did not exhibit the ALT phenotype. Somatic but not germline TP53 mutations were highly associated with ALT (p = 1.01 × 10(-8)). Of the other alterations examined, only ATRX point mutations and reduced expression were associated with the ALT phenotype (p = 0.0005). Interestingly, ALT attenuated the poor outcome conferred by TP53 mutations in specific pediatric brain tumors. Due to very poor prognosis, one year overall survival was quantified in malignant gliomas, while in children with choroid plexus carcinoma, five year overall survival was investigated. For children with TP53 mutant malignant gliomas, one year overall survival was 63 ± 12 and 23 ± 10 % for ALT positive and negative tumors, respectively (p = 0.03), while for children with TP53 mutant choroid plexus carcinomas, 5 years overall survival was 67 ± 19 and 27 ± 13 % for ALT positive and negative tumors, respectively (p = 0.07). These observations suggest that the presence of ALT is limited to a specific group of childhood brain cancers which harbor somatic TP53 mutations and may influence the outcome of these patients. Analysis of ALT may contribute to risk stratification and targeted therapies to improve outcome for these children.
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Gutierrez-Rodrigues F, Santana-Lemos BA, Scheucher PS, Alves-Paiva RM, Calado RT. Direct comparison of flow-FISH and qPCR as diagnostic tests for telomere length measurement in humans. PLoS One 2014; 9:e113747. [PMID: 25409313 PMCID: PMC4237503 DOI: 10.1371/journal.pone.0113747] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 10/28/2014] [Indexed: 01/11/2023] Open
Abstract
Telomere length measurement is an essential test for the diagnosis of telomeropathies, which are caused by excessive telomere erosion. Commonly used methods are terminal restriction fragment (TRF) analysis by Southern blot, fluorescence in situ hybridization coupled with flow cytometry (flow-FISH), and quantitative PCR (qPCR). Although these methods have been used in the clinic, they have not been comprehensively compared. Here, we directly compared the performance of flow-FISH and qPCR to measure leukocytes' telomere length of healthy individuals and patients evaluated for telomeropathies, using TRF as standard. TRF and flow-FISH showed good agreement and correlation in the analysis of healthy subjects (R2 = 0.60; p<0.0001) and patients (R2 = 0.51; p<0.0001). In contrast, the comparison between TRF and qPCR yielded modest correlation for the analysis of samples of healthy individuals (R2 = 0.35; p<0.0001) and low correlation for patients (R2 = 0.20; p = 0.001); Bland-Altman analysis showed poor agreement between the two methods for both patients and controls. Quantitative PCR and flow-FISH modestly correlated in the analysis of healthy individuals (R2 = 0.33; p<0.0001) and did not correlate in the comparison of patients' samples (R2 = 0.1, p = 0.08). Intra-assay coefficient of variation (CV) was similar for flow-FISH (10.8±7.1%) and qPCR (9.5±7.4%; p = 0.35), but the inter-assay CV was lower for flow-FISH (9.6±7.6% vs. 16±19.5%; p = 0.02). Bland-Altman analysis indicated that flow-FISH was more precise and reproducible than qPCR. Flow-FISH and qPCR were sensitive (both 100%) and specific (93% and 89%, respectively) to distinguish very short telomeres. However, qPCR sensitivity (40%) and specificity (63%) to detect telomeres below the tenth percentile were lower compared to flow-FISH (80% sensitivity and 85% specificity). In the clinical setting, flow-FISH was more accurate, reproducible, sensitive, and specific in the measurement of human leukocyte's telomere length in comparison to qPCR. In conclusion, flow-FISH appears to be a more appropriate method for diagnostic purposes.
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Affiliation(s)
- Fernanda Gutierrez-Rodrigues
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
- Center for Cell-based Therapy, São Paulo Research Foundation (FAPESP), Ribeirão Preto, São Paulo, Brazil
| | - Bárbara A. Santana-Lemos
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
- Center for Cell-based Therapy, São Paulo Research Foundation (FAPESP), Ribeirão Preto, São Paulo, Brazil
| | - Priscila S. Scheucher
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
- Center for Cell-based Therapy, São Paulo Research Foundation (FAPESP), Ribeirão Preto, São Paulo, Brazil
| | - Raquel M. Alves-Paiva
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
- Center for Cell-based Therapy, São Paulo Research Foundation (FAPESP), Ribeirão Preto, São Paulo, Brazil
| | - Rodrigo T. Calado
- Department of Internal Medicine, University of São Paulo at Ribeirão Preto School of Medicine, Ribeirão Preto, São Paulo, Brazil
- Center for Cell-based Therapy, São Paulo Research Foundation (FAPESP), Ribeirão Preto, São Paulo, Brazil
- * E-mail:
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Absolute qPCR for Measuring Telomere Length in Bone Marrow Samples of Plasma Cell Disorders. Mol Biotechnol 2014; 57:155-9. [DOI: 10.1007/s12033-014-9811-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Abstract
BACKGROUND The exciting discovery that telomere shortening is associated with many health conditions and that telomere lengths can be altered in response to social and environmental exposures has underscored the need for methods to accurately and consistently quantify telomere length. OBJECTIVES The purpose of this article is to provide a comprehensive summary that compares and contrasts the current technologies used to assess telomere length. DISCUSSION Multiple methods have been developed for the study of telomeres. These techniques include quantification of telomere length by terminal restriction fragmentation-which was one of the earliest tools used for length assessment-making it the gold standard in telomere biology. Quantitative polymerase chain reaction provides the advantage of being able to use smaller amounts of DNA, thereby making it amenable to epidemiology studies involving large numbers of people. An alternative method uses fluorescent probes to quantify not only mean telomere lengths but also chromosome-specific telomere lengths; however, the downside of this approach is that it can only be used on mitotically active cells. Additional methods that permit assessment of the length of a subset of chromosome-specific telomeres or the subset of telomeres that demonstrate shortening are also reviewed. CONCLUSION Given the increased utility for telomere assessments as a biomarker in physiological, psychological, and biobehavioral research, it is important that investigators become familiar with the methodological nuances of the various procedures used for measuring telomere length. This will ensure that they are empowered to select an optimal assessment approach to meet the needs of their study designs. Gaining a better understanding of the benefits and drawbacks of various measurement techniques is important not only in individual studies, but also to further establish the science of telomere associations with biobehavioral phenomena.
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Parrotta L, Ortuso F, Moraca F, Rocca R, Costa G, Alcaro S, Artese A. Targeting unimolecular G-quadruplex nucleic acids: a new paradigm for the drug discovery? Expert Opin Drug Discov 2014; 9:1167-87. [PMID: 25109710 DOI: 10.1517/17460441.2014.941353] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
INTRODUCTION G-quadruplexes (G4s) are targets of great interest because of their roles in crucial biological processes, such as aging and cancer. G4s are based on the formation of G-quartets, stabilised by Hoogsteen-type hydrogen bonds and by interaction with cations between the tetrads. These biologically relevant conformations were first discovered in eukaryotic chromosomal telomeric DNA, but have also been found in the proximal location of promoters in a number of human genes. Therefore, the extensive analysis of an intriguing target could move towards the rational drug design of new selective anticancer agents. AREAS COVERED The authors review G4 structural characterisation, with detailed insight related to the polymorphism issue. The authors describe the topologically distinct G4 structural forms and the factors involved in their interconversion mechanisms, such as the sequence of the oligonucleotides, the strand stoichiometry and orientation, the syn-anti conformation of the guanine glycosidic bonds and the G4 loop types and the environmental factors. Furthermore, the authors report several studies related to folding and unfolding kinetic profiles in order to understand the conformational view of monomolecular G4 formations. EXPERT OPINION G4 unimolecular nucleic acids can be considered as valid targets for the rational drug development of novel anticancer agents. Structural biology represents an essential link between the biology and medicinal chemistry knowledge in this field. In silico methods have already been demonstrated to be useful, especially if well integrated with biophysical tests. If this proves successful, the G4-targeting paradigm could also be extended to drug discovery beyond neoplastic pathologies.
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Affiliation(s)
- Lucia Parrotta
- Università degli Studi "Magna Græcia", Dipartimento di Scienze della Salute , Campus "S. Venuta", Viale Europa, Germaneto, 88100, Catanzaro , Italy
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Acharya S, Kaul Z, Gocha AS, Martinez AR, Harris J, Parvin JD, Groden J. Association of BLM and BRCA1 during Telomere Maintenance in ALT Cells. PLoS One 2014; 9:e103819. [PMID: 25084169 PMCID: PMC4118958 DOI: 10.1371/journal.pone.0103819] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 07/07/2014] [Indexed: 11/18/2022] Open
Abstract
Fifteen percent of tumors utilize recombination-based alternative lengthening of telomeres (ALT) to maintain telomeres. The mechanisms underlying ALT are unclear but involve several proteins involved in homologous recombination including the BLM helicase, mutated in Bloom's syndrome, and the BRCA1 tumor suppressor. Cells deficient in either BLM or BRCA1 have phenotypes consistent with telomere dysfunction. Although BLM associates with numerous DNA damage repair proteins including BRCA1 during DNA repair, the functional consequences of BLM-BRCA1 association in telomere maintenance are not completely understood. Our earlier work showed the involvement of BRCA1 in different mechanisms of ALT, and telomere shortening upon loss of BLM in ALT cells. In order to delineate their roles in telomere maintenance, we studied their association in telomere metabolism in cells using ALT. This work shows that BLM and BRCA1 co-localize with RAD50 at telomeres during S- and G2-phases of the cell cycle in immortalized human cells using ALT but not in cells using telomerase to maintain telomeres. Co-immunoprecipitation of BRCA1 and BLM is enhanced in ALT cells at G2. Furthermore, BRCA1 and BLM interact with RAD50 predominantly in S- and G2-phases, respectively. Biochemical assays demonstrate that full-length BRCA1 increases the unwinding rate of BLM three-fold in assays using a DNA substrate that models a forked structure composed of telomeric repeats. Our results suggest that BRCA1 participates in ALT through its interactions with RAD50 and BLM.
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Affiliation(s)
- Samir Acharya
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Zeenia Kaul
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - April Sandy Gocha
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Alaina R. Martinez
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Julia Harris
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Jeffrey D. Parvin
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
| | - Joanna Groden
- Department of Molecular Virology, Immunology and Medical Genetics, College of Medicine, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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Kozlowski MR. The ARPE-19 cell line: mortality status and utility in macular degeneration research. Curr Eye Res 2014; 40:501-9. [PMID: 24977298 DOI: 10.3109/02713683.2014.935440] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE The present report examines several subcultures of a single sample of ARPE-19 cells to determine their status with respect to cell mortality. If a transformation from mortal to immortal has occurred in these cells, it may impact their characteristics and, thereby, their utility for modeling natural retinal pigment epithelial (RPE) cells. METHODS Five separate subcultures of ARPE-19 cells were grown as recommended by the supplier. During the course of culture, they were periodically monitored for signs of mortality including erosion of telomeres, increased senescence-associated beta-galactosidase (SABG) staining, altered morphology and reduced viability with an increased population doubling level (PDL). There were also observed for signs of immortality including continuous growth to very high population doubling levels and maintenance of short telomere lengths. RESULTS Each of the subcultures showed both mortal and immortal characteristics. Telomere erosion, increased SABG staining, changes in cell morphology and a modest drop in cell viability took place within a range of population doublings (59-77) in which cell senescence would be expected to occur. The cultures, however, continued to proliferate even after signs of senescence had appeared, with one subculture propagating to 257 population doublings. In addition, little further telomere erosion occurred at high PDL. CONCLUSION These results suggest that the ARPE-19 subcultures contained both mortal and immortal cells. Since no transformation event was witnessed during the study, it appears likely that both types of cells were present in the original sample. Based on the proportion of cells demonstrating senescence-related changes, the mortal cells were estimated to comprise approximately 27% of the total culture. Because of the differences that can exist between normal and immortalized cells, and given the large proportion of ARPE-19 cells that are immortalized, discretion should be exercised when using ARPE-19 cells to model native RPE cells for the study of retinal diseases such as AMD.
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Radan L, Hughes CS, Teichroeb JH, Vieira Zamora FM, Jewer M, Postovit LM, Betts DH. Microenvironmental regulation of telomerase isoforms in human embryonic stem cells. Stem Cells Dev 2014; 23:2046-66. [PMID: 24749509 DOI: 10.1089/scd.2013.0373] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Recent evidence points to extra-telomeric, noncanonical roles for telomerase in regulating stem cell function. In this study, human embryonic stem cells (hESCs) were cultured in 20% or 2% O2 microenvironments for up to 5 days and evaluated for telomerase reverse transcriptase (TERT) expression and telomerase activity. Results showed increased cell survival and maintenance of the undifferentiated state with elevated levels of nuclear TERT in 2% O2-cultured hESCs despite no significant difference in telomerase activity compared with their high-O2-cultured counterparts. Pharmacological inhibition of telomerase activity using a synthetic tea catechin resulted in spontaneous hESC differentiation, while telomerase inhibition with a phosphorothioate oligonucleotide telomere mimic did not. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed variations in transcript levels of full-length and alternate splice variants of TERT in hESCs cultured under varying O2 atmospheres. Steric-blocking of Δα and Δβ hTERT splicing using morpholino oligonucleotides altered the hTERT splicing pattern and rapidly induced spontaneous hESC differentiation that appeared biased toward endomesodermal and neuroectodermal cell fates, respectively. Together, these results suggest that post-transcriptional regulation of TERT under varying O2 microenvironments may help regulate hESC survival, self-renewal, and differentiation capabilities through expression of extra-telomeric telomerase isoforms.
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Affiliation(s)
- Lida Radan
- 1 Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario , London, Ontario, Canada
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No association between mean telomere length and life stress observed in a 30 year birth cohort. PLoS One 2014; 9:e97102. [PMID: 24816913 PMCID: PMC4016252 DOI: 10.1371/journal.pone.0097102] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 04/14/2014] [Indexed: 11/22/2022] Open
Abstract
Telomeres are specialised structures that cap the ends of chromosomes. They shorten with each cell division and have been proposed as a marker of cellular aging. Previous studies suggest that early life stressors increase the rate of telomere shortening with potential impact on disease states and mortality later in life. This study examined the associations between telomere length and exposure to a number of stressors that arise during development from the antenatal/perinatal period through to young adulthood. Participants were from the Christchurch Health and Development Study (CHDS), a New Zealand longitudinal birth cohort which has followed participants from birth until age 30. Telomere length was obtained on DNA from peripheral blood samples collected from consenting participants (n = 677) at age 28–30, using a quantitative PCR assay. These data were assessed for associations with 26 measures of life course adversity or stress which occurred prior to 25 years of age. No associations were found between telomere length measured at age 28–30 years and life course adversity or stress for specific measures and for the summary risk scores for each developmental domain. The correlations were very small ranging from −0.06 to 0.06 with a median of 0.01, and none were statistically significant. Our results in this well-studied birth cohort do not support prior reports of such associations, and underscore the need for more extensive replication of proposed links between stress and telomere biology in larger cohorts with appropriate phenotypic data.
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Petkova R, Chicheva Z, Chakarov S. Measuring Telomere Length—From Ends to Means. BIOTECHNOL BIOTEC EQ 2014. [DOI: 10.5504/bbeq.2011.0103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Abstract
Telomerase reverse transcriptase (TERT) is the protein component of telomerase and combined with an RNA molecule, telomerase RNA component, forms the telomerase enzyme responsible for telomere elongation. Telomerase is essential for maintaining telomere length from replicative attrition and thus contributes to the preservation of genome integrity. Although diverse mouse models have been developed and studied to prove the physiological roles of telomerase as a telomere- elongating enzyme, recent studies have revealed non-canonical TERT activities beyond telomeres. To gain insights into the physiological impact of extra-telomeric roles, this review revisits the strategies and phenotypes of telomerase mouse models in terms of the extra-telomeric functions of telomerase.
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Affiliation(s)
- Young Hoon Sung
- Department of Biochemistry, College of Life Science and Biotechnology, Laboratory Animal Research Center, Yonsei University, Seoul, Korea
| | - Muhammad Ali
- Department of Biochemistry, College of Life Science and Biotechnology, Laboratory Animal Research Center, Yonsei University, Seoul, Korea
| | - Han-Woong Lee
- Department of Biochemistry, College of Life Science and Biotechnology, Laboratory Animal Research Center, Yonsei University, Seoul, Korea
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Sattin G, Artese A, Nadai M, Costa G, Parrotta L, Alcaro S, Palumbo M, Richter SN. Conformation and stability of intramolecular telomeric G-quadruplexes: sequence effects in the loops. PLoS One 2013; 8:e84113. [PMID: 24367632 PMCID: PMC3867476 DOI: 10.1371/journal.pone.0084113] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 11/12/2013] [Indexed: 01/15/2023] Open
Abstract
Telomeres are guanine-rich sequences that protect the ends of chromosomes. These regions can fold into G-quadruplex structures and their stabilization by G-quadruplex ligands has been employed as an anticancer strategy. Genetic analysis in human telomeres revealed extensive allelic variation restricted to loop bases, indicating that the variant telomeric sequences maintain the ability to fold into G-quadruplex. To assess the effect of mutations in loop bases on G-quadruplex folding and stability, we performed a comprehensive analysis of mutant telomeric sequences by spectroscopic techniques, molecular dynamics simulations and gel electrophoresis. We found that when the first position in the loop was mutated from T to C or A the resulting structure adopted a less stable antiparallel topology; when the second position was mutated to C or A, lower thermal stability and no evident conformational change were observed; in contrast, substitution of the third position from A to C induced a more stable and original hybrid conformation, while mutation to T did not significantly affect G-quadruplex topology and stability. Our results indicate that allelic variations generate G-quadruplex telomeric structures with variable conformation and stability. This aspect needs to be taken into account when designing new potential anticancer molecules.
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Affiliation(s)
- Giovanna Sattin
- Department of Molecular Medicine, University of Padua, Padua, Italy
| | - Anna Artese
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Matteo Nadai
- Department of Molecular Medicine, University of Padua, Padua, Italy
| | - Giosuè Costa
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Lucia Parrotta
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Stefano Alcaro
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Manlio Palumbo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
| | - Sara N. Richter
- Department of Molecular Medicine, University of Padua, Padua, Italy
- * E-mail:
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Lee M, Hills M, Conomos D, Stutz MD, Dagg RA, Lau LMS, Reddel RR, Pickett HA. Telomere extension by telomerase and ALT generates variant repeats by mechanistically distinct processes. Nucleic Acids Res 2013; 42:1733-46. [PMID: 24225324 PMCID: PMC3919612 DOI: 10.1093/nar/gkt1117] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Telomeres are terminal repetitive DNA sequences on chromosomes, and are considered to comprise almost exclusively hexameric TTAGGG repeats. We have evaluated telomere sequence content in human cells using whole-genome sequencing followed by telomere read extraction in a panel of mortal cell strains and immortal cell lines. We identified a wide range of telomere variant repeats in human cells, and found evidence that variant repeats are generated by mechanistically distinct processes during telomerase- and ALT-mediated telomere lengthening. Telomerase-mediated telomere extension resulted in biased repeat synthesis of variant repeats that differed from the canonical sequence at positions 1 and 3, but not at positions 2, 4, 5 or 6. This indicates that telomerase is most likely an error-prone reverse transcriptase that misincorporates nucleotides at specific positions on the telomerase RNA template. In contrast, cell lines that use the ALT pathway contained a large range of variant repeats that varied greatly between lines. This is consistent with variant repeats spreading from proximal telomeric regions throughout telomeres in a stochastic manner by recombination-mediated templating of DNA synthesis. The presence of unexpectedly large numbers of variant repeats in cells utilizing either telomere maintenance mechanism suggests a conserved role for variant sequences at human telomeres.
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Affiliation(s)
- Michael Lee
- Telomere Length Regulation Group, Children's Medical Research Institute, Westmead NSW 2145, Australia, Cancer Research Unit, Children's Medical Research Institute, Westmead NSW 2145, Australia, Terry Fox Laboratory, BC Cancer Agency, Vancouver V5Z 1L3, Canada, Sydney Medical School, University of Sydney, Sydney NSW 2006, Australia and Children's Cancer Research Unit, The Children's Hospital at Westmead, Westmead NSW 2145, Australia
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Artese A, Costa G, Ortuso F, Parrotta L, Alcaro S. Identification of new natural DNA G-quadruplex binders selected by a structure-based virtual screening approach. Molecules 2013; 18:12051-70. [PMID: 24084014 PMCID: PMC6270229 DOI: 10.3390/molecules181012051] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 09/18/2013] [Accepted: 09/22/2013] [Indexed: 02/06/2023] Open
Abstract
The G-quadruplex DNA structures are mainly present at the terminal portion of telomeres and can be stabilized by ligands able to recognize them in a specific manner. The recognition process is usually related to the inhibition of the enzyme telomerase indirectly involved and over-expressed in a high percentage of human tumors. There are several ligands, characterized by different chemical structures, already reported in the literature for their ability to bind and stabilize the G-quadruplex structures. Using the structural and biological information available on these structures; we performed a high throughput in silico screening of commercially natural compounds databases by means of a structure-based approach followed by docking experiments against the human telomeric sequence d[AG₃(T₂AG₃)₃]. We identified 12 best hits characterized by different chemical scaffolds and conformational and physicochemical properties. All of them were associated to an improved theoretical binding affinity with respect to that of known selective G-binders. Among these hits there is a chalcone derivative; structurally very similar to the polyphenol butein; known to remarkably inhibit the telomerase activity.
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Affiliation(s)
- Anna Artese
- Dipartimento di Scienze della Salute, Università degli Studi "Magna Græcia", Campus "S. Venuta", Viale Europa, Germaneto, Catanzaro 88100, Italy.
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Huang Y, Hidalgo-Bravo A, Zhang E, Cotton VE, Mendez-Bermudez A, Wig G, Medina-Calzada Z, Neumann R, Jeffreys AJ, Winney B, Wilson JF, Clark DA, Dyer MJ, Royle NJ. Human telomeres that carry an integrated copy of human herpesvirus 6 are often short and unstable, facilitating release of the viral genome from the chromosome. Nucleic Acids Res 2013; 42:315-27. [PMID: 24057213 PMCID: PMC3874159 DOI: 10.1093/nar/gkt840] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Linear chromosomes are stabilized by telomeres, but the presence of short dysfunctional telomeres triggers cellular senescence in human somatic tissues, thus contributing to ageing. Approximately 1% of the population inherits a chromosomally integrated copy of human herpesvirus 6 (CI-HHV-6), but the consequences of integration for the virus and for the telomere with the insertion are unknown. Here we show that the telomere on the distal end of the integrated virus is frequently the shortest measured in somatic cells but not the germline. The telomere carrying the CI-HHV-6 is also prone to truncations that result in the formation of a short telomere at a novel location within the viral genome. We detected extra-chromosomal circular HHV-6 molecules, some surprisingly comprising the entire viral genome with a single fully reconstituted direct repeat region (DR) with both terminal cleavage and packaging elements (PAC1 and PAC2). Truncated CI-HHV-6 and extra-chromosomal circular molecules are likely reciprocal products that arise through excision of a telomere-loop (t-loop) formed within the CI-HHV-6 genome. In summary, we show that the CI-HHV-6 genome disrupts stability of the associated telomere and this facilitates the release of viral sequences as circular molecules, some of which have the potential to become fully functioning viruses.
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Affiliation(s)
- Yan Huang
- Department of Genetics, University of Leicester, University Road, Leicester, LE1 7RH, UK, Department of Oncology, ORCRB, University of Oxford, Old Road Campus, Headington, Oxford, OX3 7DQ, UK, Centre for Population Health Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Teviot Place, Edinburgh, EH8 9AG, Scotland, Department of Virology, Barts Health NHS Trust, Pathology and Pharmacy Building, 80 Newark St, London E1 2ES, UK and Department of Cancer Studies and Molecular Medicine, University of Leicester, University Road, Leicester, LE1 7RH, UK
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68
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Lim KW, Ng VCM, Martín-Pintado N, Heddi B, Phan AT. Structure of the human telomere in Na+ solution: an antiparallel (2+2) G-quadruplex scaffold reveals additional diversity. Nucleic Acids Res 2013; 41:10556-62. [PMID: 23999095 PMCID: PMC3905899 DOI: 10.1093/nar/gkt771] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Single-stranded DNA overhangs at the ends of human telomeric repeats are capable of adopting four-stranded G-quadruplex structures, which could serve as potential anticancer targets. Out of the five reported intramolecular human telomeric G-quadruplex structures, four were formed in the presence of K+ ions and only one in the presence of Na+ ions, leading often to a perception that this structural polymorphism occurs exclusively in the presence of K+ but not Na+. Here we present the structure of a new antiparallel (2+2) G-quadruplex formed by a derivative of a 27-nt human telomeric sequence in Na+ solution, which comprises a novel core arrangement distinct from the known topologies. This structure complements the previously elucidated basket-type human telomeric G-quadruplex to serve as reference structures in Na+-containing environment. These structures, together with the coexistence of other conformations in Na+ solution as observed by nuclear magnetic resonance spectroscopy, establish the polymorphic nature of human telomeric repeats beyond the influence of K+ ions.
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Affiliation(s)
- Kah Wai Lim
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore, School of Biological Sciences, Nanyang Technological University, 637551 Singapore and Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain
| | - Veronica Chinn Min Ng
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore, School of Biological Sciences, Nanyang Technological University, 637551 Singapore and Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain
| | - Nerea Martín-Pintado
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore, School of Biological Sciences, Nanyang Technological University, 637551 Singapore and Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain
| | - Brahim Heddi
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore, School of Biological Sciences, Nanyang Technological University, 637551 Singapore and Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain
| | - Anh Tuân Phan
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore, School of Biological Sciences, Nanyang Technological University, 637551 Singapore and Instituto de Química Física Rocasolano, CSIC, 28006 Madrid, Spain
- *To whom correspondence should be addressed. Tel: +65 6514 1915; Fax: +65 6795 7981;
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69
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Artese A, Costa G, Distinto S, Moraca F, Ortuso F, Parrotta L, Alcaro S. Toward the design of new DNA G-quadruplex ligands through rational analysis of polymorphism and binding data. Eur J Med Chem 2013; 68:139-49. [PMID: 23974014 DOI: 10.1016/j.ejmech.2013.07.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 07/15/2013] [Accepted: 07/17/2013] [Indexed: 12/21/2022]
Abstract
Human telomeres play a key role in protecting chromosomal ends from fusion events; they are composed of d(TTAGGG) repeats, ranging in size from 3 to 15 kb. They form G-quadruplex DNA structures, stabilized by G-quartets in the presence of cations, and are involved in several biological processes. In particular, a telomere maintenance mechanism is provided by a specialized enzyme called telomerase, a reverse transcriptase able to add multiple copies of the 5'-GGTTAG-3' motif to the end of the G-strand of the telomere and which is over-expressed in the majority of cancer cells. The central cation has a crucial role in maintaining the stability of the structure. Based on its nature, it can be associated with different topological telomeric quadruplexes, which depend also on the orientation of the DNA strands and the syn/anti conformation of the guanines. Such a polymorphism, confirmed by the different structures deposited in the Protein Data Bank (PDB), prompted us to apply a computational protocol in order to investigate the conformational properties of a set of known G-quadruplex ligands and their molecular recognition against six different experimental models of the human telomeric sequence d[AG3(T2AG3)3]. The average AutoDock correlation between theoretical and experimental data yielded an r2 value equal to 0.882 among all the studied models. Such a result was always improved with respect to those of the single folds, with the exception of the parallel structure (r2 equal to 0.886), thus suggesting a key role of this G4 conformation in the stacking interaction network. Among the studied binders, a trisubstituted acridine and a dibenzophenanthroline derivative were well recognized by the parallel and the mixed G-quadruplex structures, allowing the identification of specific key contacts with DNA and the further design of more potent or target specific G-quadruplex ligands.
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Affiliation(s)
- Anna Artese
- Dipartimento di Scienze della Salute, Università degli Studi "Magna Græcia", Campus "S. Venuta", Viale Europa, Germaneto, 88100 Catanzaro, Italy.
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70
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Novo CL, Polese C, Matheus N, Decottignies A, Londono-Vallejo A, Castronovo V, Mottet D. A new role for histone deacetylase 5 in the maintenance of long telomeres. FASEB J 2013; 27:3632-42. [PMID: 23729589 DOI: 10.1096/fj.12-224204] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Telomeres are major regulators of genome stability and cell proliferation. A detailed understanding of the mechanisms involved in their maintenance is of foremost importance. Of those, telomere chromatin remodeling is probably the least studied; thus, we intended to explore the role of a specific histone deacetylase on telomere maintenance. We uncovered a new role for histone deacetylase 5 (HDAC5) in telomere biology. We report that HDAC5 is recruited to the long telomeres of osteosarcoma- and fibrosarcoma-derived cell lines, where it ensures proper maintenance of these repetitive regions. Indeed, depletion of HDAC5 by RNAi resulted in the shortening of longer telomeres and homogenization of telomere length in cells that use either telomerase or an alternative mechanism of telomere maintenance. Furthermore, we present evidence for the activation of telomere recombination on depletion of HDAC5 in fibrosarcoma telomerase-positive cancer cells. Of potential importance, we also found that depletion of HDAC5 sensitizes cancer cells with long telomeres to chemotherapeutic drugs. Cells with shorter telomeres were used to control the specificity of HDAC5 role in the maintenance of long telomeres. HDAC5 is essential for the length maintenance of long telomeres and its depletion is required for sensitization of cancer cells with long telomeres to chemotherapy.
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Affiliation(s)
- Clara Lopes Novo
- University of Liege Sart-Tilman, Groupe Interdisciplinaire de Génoprotéomique Appliquée (GIGA)-Cancer, Metastasis Research Laboratory, Pathology Institute B23, Liege, Belgium
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71
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Abstract
Measurement of telomere length currently requires a large population of cells, which masks telomere length heterogeneity in single cells, or requires FISH in metaphase arrested cells, posing technical challenges. A practical method for measuring telomere length in single cells has been lacking. We established a simple and robust approach for single-cell telomere length measurement (SCT-pqPCR). We first optimized a multiplex preamplification specific for telomeres and reference genes from individual cells, such that the amplicon provides a consistent ratio (T/R) of telomeres (T) to the reference genes (R) by quantitative PCR (qPCR). The average T/R ratio of multiple single cells corresponded closely to that of a given cell population measured by regular qPCR, and correlated with those of telomere restriction fragments (TRF) and quantitative FISH measurements. Furthermore, SCT-pqPCR detected the telomere length for quiescent cells that are inaccessible by quantitative FISH. The reliability of SCT-pqPCR also was confirmed using sister cells from two cell embryos. Telomere length heterogeneity was identified by SCT-pqPCR among cells of various human and mouse cell types. We found that the T/R values of human fibroblasts at later passages and from old donors were lower and more heterogeneous than those of early passages and from young donors, that cancer cell lines show heterogeneous telomere lengths, that human oocytes and polar bodies have nearly identical telomere lengths, and that the telomere lengths progressively increase from the zygote, two-cell to four-cell embryo. This method will facilitate understanding of telomere heterogeneity and its role in tumorigenesis, aging, and associated diseases.
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72
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Shalev I, Moffitt TE, Sugden K, Williams B, Houts RM, Danese A, Mill J, Arseneault L, Caspi A. Exposure to violence during childhood is associated with telomere erosion from 5 to 10 years of age: a longitudinal study. Mol Psychiatry 2013; 18:576-81. [PMID: 22525489 PMCID: PMC3616159 DOI: 10.1038/mp.2012.32] [Citation(s) in RCA: 312] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 02/02/2012] [Accepted: 03/05/2012] [Indexed: 12/23/2022]
Abstract
There is increasing interest in discovering mechanisms that mediate the effects of childhood stress on late-life disease morbidity and mortality. Previous studies have suggested one potential mechanism linking stress to cellular aging, disease and mortality in humans: telomere erosion. We examined telomere erosion in relation to children's exposure to violence, a salient early-life stressor, which has known long-term consequences for well-being and is a major public-health and social-welfare problem. In the first prospective-longitudinal study with repeated telomere measurements in children while they experienced stress, we tested the hypothesis that childhood violence exposure would accelerate telomere erosion from age 5 to age 10 years. Violence was assessed as exposure to maternal domestic violence, frequent bullying victimization and physical maltreatment by an adult. Participants were 236 children (49% females; 42% with one or more violence exposures) recruited from the Environmental-Risk Longitudinal Twin Study, a nationally representative 1994-1995 birth cohort. Each child's mean relative telomere length was measured simultaneously in baseline and follow-up DNA samples, using the quantitative PCR method for T/S ratio (the ratio of telomere repeat copy numbers to single-copy gene numbers). Compared with their counterparts, the children who experienced two or more kinds of violence exposure showed significantly more telomere erosion between age-5 baseline and age-10 follow-up measurements, even after adjusting for sex, socioeconomic status and body mass index (B=-0.052, s.e.=0.021, P=0.015). This finding provides support for a mechanism linking cumulative childhood stress to telomere maintenance, observed already at a young age, with potential impact for life-long health.
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Affiliation(s)
- I Shalev
- Department of Psychology and Neuroscience, Duke University, Suite 201 Grey House, 2020 West Main Street, Box 104410, Durham, NC 27708, USA.
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73
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Karasawa K, Sano Y, Arakawa H. Development of a novel telomerase assay using the PPDK-luciferin-luciferase detection system. LUMINESCENCE 2013; 29:52-7. [PMID: 23554164 DOI: 10.1002/bio.2501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 12/15/2012] [Accepted: 01/26/2013] [Indexed: 11/06/2022]
Abstract
Telomerase participates in malignant transformation or immortalization of cells, and has attracted attention as an anticancer drug screening and diagnostic tumor marker. We developed a novel telomerase assay called the PPDK-luciferin-luciferase system bioluminescence assay (PLLBA) using pyruvate phosphate dikinase (PPDK). In this assay, pyrophosphate produced by the telomerase reaction and polymerase chain reaction (PCR) is converted to ATP by PPDK, and ATP is detected by the firefly luciferin-luciferase reaction. In this work, telomerase substrate was obtained in accordance with the telomeric repeat amplification protocol (TRAP). Telomerase-positive (500 cells/assay), -inactive (heated for 10 min at 85 °C) and -negative (only Chaps lysis buffer) samples were used. As a result, the findings clearly showed that the signal-to-noise (S/N) ratio of the positive cells was 39.5. After the telomerase reaction and PCR, PLLBA was completed ~ 120 s later. A high level of reproducibility was obtained with - coefficient of variation (CV) of 4.1% (positive cells). The detection limit for cells using telomerase was one cell per assay. This assay for telomerase activity was also shown to be adaptable to human cancer-derived cell lines.
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Affiliation(s)
- K Karasawa
- Department of Analytical Biochemistry, School of Pharmacy, Showa University, Tokyo, Japan
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74
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Conomos D, Pickett HA, Reddel RR. Alternative lengthening of telomeres: remodeling the telomere architecture. Front Oncol 2013; 3:27. [PMID: 23429284 PMCID: PMC3576624 DOI: 10.3389/fonc.2013.00027] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 02/02/2013] [Indexed: 01/16/2023] Open
Abstract
To escape from the normal limits on proliferative potential, cancer cells must employ a means to counteract the gradual telomere attrition that accompanies semi-conservative DNA replication. While the majority of human cancers do this by up-regulating telomerase enzyme activity, most of the remainder use a homologous recombination-mediated mechanism of telomere elongation known as alternative lengthening of telomeres (ALT). Many molecular details of the ALT pathway are unknown, and even less is known regarding the mechanisms by which this pathway is activated. Here, we review current findings about telomere structure in ALT cells, including DNA sequence, shelterin content, and heterochromatic state. We speculate that remodeling of the telomere architecture may contribute to the emergence and maintenance of the ALT phenotype.
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Affiliation(s)
- Dimitri Conomos
- Cancer Research Unit, Children's Medical Research Institute Westmead, NSW, Australia ; Sydney Medical School, University of Sydney NSW, Australia
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75
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Conomos D, Stutz MD, Hills M, Neumann AA, Bryan TM, Reddel RR, Pickett HA. Variant repeats are interspersed throughout the telomeres and recruit nuclear receptors in ALT cells. ACTA ACUST UNITED AC 2013; 199:893-906. [PMID: 23229897 PMCID: PMC3518223 DOI: 10.1083/jcb.201207189] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Variant repeats interspersed throughout ALT telomeres recruit nuclear receptors, leading to the destabilized telomere architecture and enhanced telomeric recombination. Telomeres in cells that use the recombination-mediated alternative lengthening of telomeres (ALT) pathway elicit a DNA damage response that is partly independent of telomere length. We therefore investigated whether ALT telomeres contain structural abnormalities that contribute to ALT activity. Here we used next generation sequencing to analyze the DNA content of ALT telomeres. We discovered that variant repeats were interspersed throughout the telomeres of ALT cells. We found that the C-type (TCAGGG) variant repeat predominated and created a high-affinity binding site for the nuclear receptors COUP-TF2 and TR4. Nuclear receptors were directly recruited to telomeres and ALT-associated characteristics were induced after incorporation of the C-type variant repeat by a mutant telomerase. We propose that the presence of variant repeats throughout ALT telomeres results from recombination-mediated telomere replication and spreading of variant repeats from the proximal regions of the telomeres and that the consequent binding of nuclear receptors alters the architecture of telomeres to facilitate further recombination.
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Affiliation(s)
- Dimitri Conomos
- Cancer Research Unit, Children's Medical Research Institute, Westmead NSW 2145, Australia
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Abstract
The length of telomeres, and in particular the abundance of short telomeres, has been proposed as a biomarker of aging and of general health status. A wide variety of studies show the association of short telomeres with age related pathologies and cancer, as well as with lifespan and mortality. These facts highlight the importance of measuring telomere length in human populations and by using reliable methods to uncover the association between telomere length and human disease. This review discusses the advantages and drawbacks of current telomere length measurement methods. Most of these methods provide mean telomere length values per cell or per sample and very few of them are able to measure the abundance of short telomeres, which are the ones indicative of telomere dysfunction. The information provided by each method and their suitability for different studies is discussed here.
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Affiliation(s)
- Elsa Vera
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid, E-28029, Spain
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77
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Zeng S, Liu L, Sun Y, Xie P, Hu L, Yuan D, Chen D, Ouyang Q, Lin G, Lu G. Telomerase-mediated telomere elongation from human blastocysts to embryonic stem cells. J Cell Sci 2013; 127:752-62. [DOI: 10.1242/jcs.131433] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
High telomerase activity is a characteristic of human embryonic stem cells (hESCs), however the regulation and maintenance of correct telomere length in hESCs is unclear. In this study we investigated telomere elongation in hESCs in vitro and found that telomeres lengthened from derivation in blastocysts through early expansion, but telomere length stabilized at later passages. We report that the core unit of telomerase, hTERT, was highly expressed in hESCs in blastocysts and throughout long-term culture; furthermore, this was regulated in a Wnt–β-catenin signaling dependent manner. Our observations that the alternative lengthening of telomeres (ALT) pathway was suppressed in hESCs and that hTERT knockdown partially inhibited telomere elongation, demonstrated that high telomerase activity was required for telomere elongation. We observed that chromatin modification through trimethylation of H3K9 and H4K20 at telomeric regions decreased during early culture. This was concurrent with telomere elongation, suggesting that epigenetic regulation of telomeric chromatin may influence telomerase function. By measuring telomere length in 96 hESC lines, we were able to establish that telomere length remained relatively stable at 12.02±1.01 kb during later passages (15–95). In contrast, hESCs with genomic instability and hESC-derived teratomas displayed variations in telomere length. In summary, we propose that correct, stable telomere length may serve as a potential biomarker for genetically stable hESCs.
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78
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Artese A, Parrotta L, Alcaro S, Ortuso F, Costa G, Sissi C. Molecular Recognition of Human Telomeric DNA by Phenanthroline-Based G-Quadruplex Ligands. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/ojmc.2013.32006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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79
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Kalmbach KH, Fontes Antunes DM, Dracxler RC, Knier TW, Seth-Smith ML, Wang F, Liu L, Keefe DL. Telomeres and human reproduction. Fertil Steril 2013; 99:23-29. [PMID: 23273986 PMCID: PMC3857638 DOI: 10.1016/j.fertnstert.2012.11.039] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 11/20/2012] [Accepted: 11/20/2012] [Indexed: 12/31/2022]
Abstract
Telomeres mediate biologic aging in organisms as diverse as plants, yeast, and mammals. We propose a telomere theory of reproductive aging that posits telomere shortening in the female germ line as the primary driver of reproductive aging in women. Experimental shortening of telomeres in mice, which normally do not exhibit appreciable oocyte aging, and which have exceptionally long telomeres, recapitulates the aging phenotype of human oocytes. Telomere shortening in mice reduces synapsis and chiasmata, increases embryo fragmentation, cell cycle arrest, apoptosis, spindle dysmorphologies, and chromosome abnormalities. Telomeres are shorter in the oocytes from women undergoing in vitro fertilization, who then produce fragmented, aneuploid embryos that fail to implant. In contrast, the testes are replete with spermatogonia that can rejuvenate telomere reserves throughout the life of the man by expressing telomerase. Differences in telomere dynamics across the life span of men and women may have evolved because of the difference in the inherent risks of aging on reproduction between men and women. Additionally, growing evidence links altered telomere biology to endometriosis and gynecologic cancers, thus future studies should examine the role of telomeres in pathologies of the reproductive tract.
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Affiliation(s)
- Keri Horan Kalmbach
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York
| | - Danielle Mota Fontes Antunes
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York; Graduate Program in Pathology, Fluminense Federal University, Rio de Janeiro, and CAPES Foundation, Ministry of Education of Brazil, Brasilia, Brazil
| | - Roberta Caetano Dracxler
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York; São Paulo University, São Paulo, Brazil
| | - Taylor Warner Knier
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York
| | - Michelle Louise Seth-Smith
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York
| | - Fang Wang
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York
| | - Lin Liu
- College of Life Sciences, Nankai University, Tianjin, People's Republic of China
| | - David Lawrence Keefe
- Department of Obstetrics and Gynecology, New York University, Langone Medical Center, New York City, New York.
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80
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Rezazadeh S. On BLM helicase in recombination-mediated telomere maintenance. Mol Biol Rep 2012; 40:3049-64. [DOI: 10.1007/s11033-012-2379-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 12/17/2012] [Indexed: 11/29/2022]
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81
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Structure-based design, synthesis and evaluation of novel anthra[1,2-d]imidazole-6,11-dione derivatives as telomerase inhibitors and potential for cancer polypharmacology. Eur J Med Chem 2012; 60:29-41. [PMID: 23279865 DOI: 10.1016/j.ejmech.2012.11.032] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 11/12/2012] [Accepted: 11/22/2012] [Indexed: 12/22/2022]
Abstract
A series of anthra[1,2-d]imidazole-6,11-dione derivatives were synthesized and evaluated for telomerase inhibition, hTERT expression and suppression of cancer cell growth in vitro. All of the compounds tested, except for compounds 4, 7, 16, 24, 27 and 28 were selected by the NCI screening system. Among them, compounds 16, 39, and 40 repressed hTERT expression without greatly affecting cell growth, suggesting for the selectivity toward hTERT expression. Taken together, our findings indicated that the analysis of cytotoxicity and telomerase inhibition might provide information applicable for further developing potential telomerase and polypharmacological targeting strategy.
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82
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Xu J, McEachern MJ. Long telomeres produced by telomerase-resistant recombination are established from a single source and are subject to extreme sequence scrambling. PLoS Genet 2012; 8:e1003017. [PMID: 23133400 PMCID: PMC3486848 DOI: 10.1371/journal.pgen.1003017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 07/30/2012] [Indexed: 11/18/2022] Open
Abstract
Considerable evidence now supports the idea that the moderate telomere lengthening produced by recombinational telomere elongation (RTE) in a Kluyveromyces lactis telomerase deletion mutant occurs through a roll-and-spread mechanism. However, it is unclear whether this mechanism can account for other forms of RTE that produce much longer telomeres such as are seen in human alternative lengthening of telomere (ALT) cells or in the telomerase-resistant type IIR “runaway” RTE such as occurs in the K. lactis stn1-M1 mutant. In this study we have used mutationally tagged telomeres to examine the mechanism of RTE in an stn1-M1 mutant both with and without telomerase. Our results suggest that the establishment stage of the mutant state in newly generated stn1-M1 ter1-Δ mutants surprisingly involves a first stage of sudden telomere shortening. Our data also show that, as predicted by the roll-and-spread mechanism, all lengthened telomeres in a newly established mutant cell commonly emerge from a single telomere source. However, in sharp contrast to the RTE of telomerase deletion survivors, we show that the RTE of stn1-M1 ter1-Δ cells produces telomeres whose sequences undergo continuous intense scrambling via recombination. While telomerase was not necessary for the long telomeres in stn1-M1 cells, its presence during their establishment was seen to interfere with the amplification of repeats via recombination, a result consistent with telomerase retaining its ability to add repeats during active RTE. Finally, we observed that the presence of active mismatch repair or telomerase had important influences on telomeric amplification and/or instability. Indefinite growth of tumor cells requires a mechanism to maintain telomeres. While most cancers use telomerase for this, some maintain long and heterogeneous telomeres using a recombination-dependent mechanism termed alternative lengthening of telomeres (ALT). What causes ALT and how their long and heterogeneous telomeres form and are maintained are not well understood. In this study, we use mutationally tagged telomeric repeats to probe the mechanisms by which highly elongated telomeres are generated by recombination in an ALT–like yeast mutant. Our data show that most or all lengthened telomeres in a newly established mutant cell are commonly generated by amplifying sequence from a single telomere source. This is consistent with the roll-and-spread model, which proposes that a single circle of telomeric DNA can be the ultimate source of all newly amplified telomeres. Other evidence showed that the telomeres of the mutant are exceptionally dynamic. Rapid terminal deletions preceded telomere elongation at the establishment of the mutant state. Also, patterns of telomeric repeats present in long telomeres became rapidly scrambled. These findings may have implications for the establishment and maintenance of long telomeres in human ALT cells.
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Affiliation(s)
| | - Michael J. McEachern
- Department of Genetics, Fred Davision Life Science Complex, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
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83
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Shalev I. Early life stress and telomere length: investigating the connection and possible mechanisms: a critical survey of the evidence base, research methodology and basic biology. Bioessays 2012; 34:943-52. [PMID: 22991129 PMCID: PMC3557830 DOI: 10.1002/bies.201200084] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
How can adverse experiences in early life, such as maltreatment, exert such powerful negative effects on health decades later? The answer may lie in changes to DNA. New research suggests that exposure to stress can accelerate the erosion of DNA segments called telomeres. Shorter telomere length correlates with chronological age and also disease morbidity and mortality. Thus, telomere erosion is a potential mechanism linking childhood stress to health problems later in life. However, an array of mechanistic, methodological, and basic biological questions must be addressed in order to translate telomere discoveries into clinical applications for monitoring health and predicting disease risk. This paper covers the current state of the science and lays out new research directions.
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Affiliation(s)
- Idan Shalev
- Department of Psychology and Neuroscience, Duke University, Durham, NC, USA.
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84
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Harbo M, Koelvraa S, Serakinci N, Bendix L. Telomere dynamics in human mesenchymal stem cells after exposure to acute oxidative stress. DNA Repair (Amst) 2012; 11:774-9. [DOI: 10.1016/j.dnarep.2012.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 06/14/2012] [Accepted: 06/14/2012] [Indexed: 12/30/2022]
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85
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Exploring the utility of genetic markers for predicting biological age. Leg Med (Tokyo) 2012; 14:279-85. [PMID: 22770678 DOI: 10.1016/j.legalmed.2012.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 05/31/2012] [Indexed: 12/28/2022]
Abstract
DNA evidence can be analyzed for genetic markers to determine phenotypes such as hair and eye color, ancestry, and even age estimation. Currently, telomere length is the only genetic biomarker that has been correlated to cell replication and replicative cell senescence--both strong indicators of tissue aging in humans. Unfortunately, while many studies have found a strong correlation between telomere length and age, many data sets show extreme variability, technical assay malfunction, inadequate evaluation of other variables that can impact telomere, altogether conflicting results, or insignificant correlations due to low sample size. Other, non-telomere based methods are problematic, as they often have only the ability to identify newborns or are only viable for specific tissue or cell types, and for most, the effects of outside variables have not been fully evaluated. Thus, telomeres remain the most promising biomarker for age estimation; mechanisms for telomere repeat attrition over time have been well documented. Unfortunately, assays currently used determine mean telomere length of a sample, are not precise or reproducible. New techniques should be robust enough to determine age across a broad spectrum of age ranges, and the effect of other variables (gender, race, disease, etc.), must be explored.
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86
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Multiplex time-reducing quantitative polymerase chain reaction assay for determination of telomere length in blood and tissue DNA. Anal Bioanal Chem 2012; 403:157-66. [PMID: 22327932 DOI: 10.1007/s00216-012-5783-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Revised: 01/18/2012] [Accepted: 01/23/2012] [Indexed: 10/14/2022]
Abstract
In this paper we describe a multiplex time-reducing quantitative polymerase chain reaction (qPCR) method for determination of telomere length. This multiplex qPCR assay enables two pairs of primers to simultaneously amplify telomere and single copy gene (albumin) templates, thus reducing analysis time and labor compared with the previously established singleplex assay. The chemical composition of the master mix and primers for the telomere and albumin were systematically optimized. The thermal cycling program was designed to ensure complete separation of the melting processes of the telomere and albumin. Semi-log standard curves of DNA concentration versus cycle threshold (C (t)) were established, with a linear relationship over an 81-fold DNA concentration range. The well-performed intra-assay (RSD range 2.4-4.7%) and inter-assay (RSD range: 3.1-5.0%) reproducibility were demonstrated to ensure measurement stability. Using wild-type, Lewis lung carcinoma and H22 liver carcinoma C57BL/6 mouse models, significantly different telomere lengths among different DNA samples were not observed in wild-type mice. However, the relative telomere lengths of the tumor DNA in the two strains of tumor-bearing mice were significantly shorter than the lengths in the surrounding non-tumor DNA of tumor-bearing mice and the tissue DNA of wild-type mice. These results suggest that the shortening of telomere lengths may be regarded as an important indicator for cancer control and prevention. Quantification of telomere lengths was further confirmed by the traditional Southern blotting method. This method could be successfully used to reduce the time needed for rapid, precise measurement of telomere lengths in biological samples.
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87
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Telomeres and the nucleus. Semin Cancer Biol 2012; 23:116-24. [PMID: 22330096 DOI: 10.1016/j.semcancer.2012.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 02/01/2012] [Accepted: 02/02/2012] [Indexed: 01/08/2023]
Abstract
Telomeres are crucial for the maintenance of genome stability through "capping" of chromosome ends to prevent their recognition as double-strand breaks, thus avoiding end-to-end fusions or illegitimate recombination [1-3]. Similar to other genomic regions, telomeres participate to the nuclear architecture while being highly mobile. The interaction of telomeres with nuclear domains or compartments greatly differs not only between organisms but also between cells within the same organism. It is also expected that biological processes like replication, repair or telomere elongation impact the distribution of chromosome extremities within the nucleus, as they probably do with other regions of the genome. Pathological processes such as cancer induce profound changes in the nuclear architecture, which also affects telomere dynamics and spatial organization. Here we will expose our present knowledge on the relationship between telomeres and nuclear architecture and on how this relationship is affected by normal or abnormal telomere metabolisms.
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88
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Hou L, Zhang X, Gawron AJ, Liu J. Surrogate tissue telomere length and cancer risk: shorter or longer? Cancer Lett 2012; 319:130-135. [PMID: 22269209 DOI: 10.1016/j.canlet.2012.01.028] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 01/13/2012] [Accepted: 01/16/2012] [Indexed: 12/24/2022]
Abstract
Telomeres play a critical role in chromosome stability. Telomere length (TL) shortening is a risk factor for cancers. Measuring TL in surrogate tissues that can be easily collected may provide a potential tool for early detection of cancers. A number of studies on surrogate tissue TL and cancer risks have been conducted and results are inconsistent, including positive, negative, or null associations. In this article, we reviewed the published data on surrogate tissue TL in relation to cancer risks, discussed the possible reasons for the differences in the results and future directions and challenges for this line of research.
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Affiliation(s)
- Lifang Hou
- Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, 680 N. Lake Shore Drive, Chicago, IL 60611, United States; The Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, 303 E. Superior Street, Chicago, IL 60611, United States.
| | - Xiao Zhang
- Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, 680 N. Lake Shore Drive, Chicago, IL 60611, United States
| | - Andrew J Gawron
- Division of Gastroenterology and Hepatology, Department of Medicine, Feinberg School of Medicine, Northwestern University, 676 N. St. Clair, Chicago, IL 60611, United States
| | - Jie Liu
- Department of Digestive Diseases of Huashan Hospital, Fudan University, 12 Middle Wulumuqi Road, Shanghai 200040, PR China.
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89
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Dewar JM, Lydall D. Similarities and differences between "uncapped" telomeres and DNA double-strand breaks. Chromosoma 2011; 121:117-30. [PMID: 22203190 DOI: 10.1007/s00412-011-0357-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 12/08/2011] [Indexed: 11/25/2022]
Abstract
Telomeric DNA is present at the ends of eukaryotic chromosomes and is bound by telomere "capping" proteins, which are the (Cdc13-Stn1-Ten1) CST complex, Ku (Yku70-Yku80), and Rap1-Rif1-Rif2 in budding yeast. Inactivation of any of these complexes causes telomere "uncapping," stimulating a DNA damage response (DDR) that frequently involves resection of telomeric DNA and stimulates cell cycle arrest. This is presumed to occur because telomeres resemble one half of a DNA double-strand break (DSB). In this review, we outline the DDR that occurs at DSBs and compare it to the DDR occurring at uncapped telomeres, in both budding yeast and metazoans. We give particular attention to the resection of DSBs in budding yeast by Mre11-Xrs2-Rad50 (MRX), Sgs1/Dna2, and Exo1 and compare their roles at DSBs and uncapped telomeres. We also discuss how resection uncapped telomeres in budding yeast is promoted by the by 9-1-1 complex (Rad17-Mec3-Ddc1), to illustrate how analysis of uncapped telomeres can serve as a model for the DDR elsewhere in the genome. Finally, we discuss the role of the helicase Pif1 and its requirement for resection of uncapped telomeres, but not DSBs. Pif1 has roles in DNA replication and mammalian and plant CST complexes have been identified and have roles in global genome replication. Based on these observations, we suggest that while the DDR at uncapped telomeres is partially due to their resemblance to a DSB, it may also be partially due to defective DNA replication. Specifically, we propose that the budding yeast CST complex has dual roles to inhibit a DSB-like DDR initiated by Exo1 and a replication-associated DDR initiated by Pif1. If true, this would suggest that the mammalian CST complex inhibits a Pif1-dependent DDR.
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Affiliation(s)
- James M Dewar
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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90
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Qu K, Zhao C, Ren J, Qu X. Human telomeric G-quadruplex formation and highly selective fluorescence detection of toxic strontium ions. MOLECULAR BIOSYSTEMS 2011; 8:779-82. [PMID: 22183243 DOI: 10.1039/c2mb05446a] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Strontium ions play important roles in biological systems. The inhalation of strontium can cause severe respiratory difficulties, anaphylactic reaction and extreme tachycardia. Strontium can replace calcium in organisms, inhibit normal calcium absorption and induce strontium "rickets" in childhood. Thus, the development of sensitive and selective methods for the determination of trace amounts of Sr(2+) in aqueous media is of considerable importance for environmental and human health protection. A number of methodologies, such as X-ray energy dispersive spectrometry, inductively coupled argon plasma atomic emission spectroscopy (ICP-AES), atomic absorption spectrometry (AAS) and instrumental thermal neutron activation analysis, have been reported. However, these methods are somewhat complex, costly, time consuming and, especially, need special instruments. Thus, the design of convenient and inexpensive approaches for the sensitive and selective detection of Sr(2+) with rapid, easy manipulation is in ever-increasing demand. To the best of our knowledge, using DNA conformational change to detect Sr(2+) has not yet been reported. Herein we utilized thiazole orange (TO) as a signal reporter to devise a simple Sr(2+) detection assay based on Sr(2+) induced human telomeric DNA conformational change in the presence of SWNTs. The limit of detection is 10 nM Sr(2+) (0.87 μg L(-1)), far below 4 mg L(-1), the U.S. Federal threshold in drinking water defined by the U.S. EPA.
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Affiliation(s)
- Konggang Qu
- Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, China
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91
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Targeting different types of human meningioma and glioma cells using a novel adenoviral vector expressing GFP-TRAIL fusion protein from hTERT promoter. Cancer Cell Int 2011; 11:35. [PMID: 22035360 PMCID: PMC3283457 DOI: 10.1186/1475-2867-11-35] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 10/28/2011] [Indexed: 01/23/2023] Open
Abstract
Objective The objective of this study was to evaluate the anti-tumor effects of Ad/gTRAIL (an adenoviral vector in which expression of GFP and TRAIL is driven by a human telomerase reverse transcriptase promoter, hTERT) on malignant meningiomas and gliomas. Background Gliomas and meningiomas are the two most common types of human brain tumors. Currently there is no effective cure for recurrent malignant meningiomas or for gliomas. Ad/gTRAIL has been shown to be effective in killing selected lung, colon and breast cancer cells, but there have been no studies reporting its antitumor effects on malignant meningiomas. Therefore, we tested the antitumor effect of Ad/gTRAIL for the first time in human malignant meningioma and glioma cell lines, and in intracranial M6 and U87 xenografts. Methods Materials and Methods: Human malignant meningioma and glioma cells were infected with adenoviruses, Ad/gTRAIL and Ad/CMV-GFP. Cell viability was determined by proliferation assay. FACS analysis and quantification of TRAIL were used to measure apoptosis in these cells. We injected Ad/gTRAIL viruses in intracranial M6 and U87 xenografts, and measured the brain tumor volume, quantified apoptosis by TUNEL assay in the brain tumor tissue. Results Our studies demonstrate that in vitro/in vivo treatment with Ad/gTRAIL virus resulted in significant increase of TRAIL activity, and elicited a greater tumor cell apoptosis in malignant brain tumor cells as compared to treatment with the control, Ad/CMV-GFP virus without TRAIL activity. Conclusions We showed for the first time that adenovirus Ad/gTRAIL had significant antitumor effects against high grade malignant meningiomas as well as gliomas. Although more work needs to be done, our data suggests that Ad/gTRAIL has the potential to be useful as a tool against malignant brain tumors.
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92
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Telomere length is associated with types of chromosome 21 nondisjunction: a new insight into the maternal age effect on Down syndrome birth. Hum Genet 2011; 127:403-9. [PMID: 20063167 DOI: 10.1007/s00439-009-0785-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 12/30/2009] [Indexed: 12/11/2022]
Abstract
Advanced maternal age is a well-documented risk factor of chromosome 21 nondisjunction in humans, but understanding of this association at the genetic level is still limited. In particular, the state of maternal genetic age is unclear. In the present study, we estimated maternal genetic age by measuring telomere length of peripheral blood lymphocytes among age-matched mothers of children with Down syndrome (cases: N = 75) and mothers of euploid children (controls: N = 75) in an age range of 18-42 years. All blood samples were taken within 1 week of the birth of the child in both cases and controls. The telomere length estimation was performed by restriction digestion--Southern blot hybridization method. We stratified the cases on the basis of centromeric STR genotyping into maternal meiosis I (N = 48) and maternal meiosis II (N = 27) nondisjunction groups and used linear regression to compare telomere length as a function of age in the euploid, meiosis I and meiosis II groups. Our results show that all three groups have similar telomere length on average for younger mothers. As age increases, all groups show telomere loss, but that loss is largest in the meiosis II mother group and smallest in the euploid mother group with the meiosis I mother group in the middle. The regression lines for all three were statistically significantly different from each other (p < 0.001). Our results do not support the theory that younger women who have babies with Down syndrome do so because are 'genetically older' than their chronological age, but we provide the first evidence that older mothers who have babies with Down syndrome are 'genetically older' than controls, who have euploid babies at the same age. We also show for the first time that telomere length attrition may be associated in some way with meiosis I and meiosis II nondisjunction of chromosome 21 and subsequent Down syndrome births at advanced maternal age.
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93
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TCAGG, an alternative telomeric sequence in insects. Chromosoma 2011; 120:367-76. [PMID: 21499744 DOI: 10.1007/s00412-011-0317-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 03/06/2011] [Accepted: 03/06/2011] [Indexed: 10/18/2022]
Abstract
The TTAGG repeat, the only determined telomerase-dependent sequence in the Insecta, is generally reputed to be the canonical telomeric motif within the class. By studying the distribution of telomeric DNAs in 30 coleopteran beetles using Southern hybridization, BAL 31 DNA end-degradation assay and fluorescence in situ hybridization, we showed that arrays built of a TCAGG repeat substitute for (TTAGG)n sequences in all tested species within the superfamily Tenebrionoidea. We also provided the experimental evidence that (TCAGG)n repeats represent the terminal sequences on all chromosomes of the model species Tribolium castaneum. (TCAGG)n repeats are therefore promoted as the first sequence-motif alternative to TTAGG-type chromosome ends in insects. Detection of species negative for both TTAGG and TCAGG reveals that, although widespread, these motifs are not ubiquitous telomeric sequences within the order Coleoptera. In addition, Timarcha balearica proved to be a species that harbors (TTAGG)n repeats, but not at telomeric positions, thus further increasing the complexity of telomeric DNAs. Our experiments discarded CTAGG, CTGGG, TTGGG, and TTAGGG variants as potential replacements in TTAGG/TCAGG-negative species, indicating that chromosome termini of these beetles comprise other form(s) of telomeric sequences and telomere maintenance mechanisms.
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94
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Kojima K, Hiyama E, Otani K, Ohtaki M, Fukuba I, Fukuda E, Sueda T, Hiyama K. Telomerase activation without shortening of telomeric 3'-overhang is a poor prognostic factor in human colorectal cancer. Cancer Sci 2011; 102:330-5. [PMID: 21108695 DOI: 10.1111/j.1349-7006.2010.01786.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our previous report demonstrated a good correlation between high telomerase activity of cancer tissues and a poor prognosis of patients with colorectal cancers, except for several cases. To elucidate the additional factors that contribute to patient prognosis, the correlation among the expression levels of telomere binding proteins (TBP), the lengths of telomeres, the lengths of telomere 3'-overhang (3'-OH) and telomerase activity in 106 paired colorectal cancer and corresponding noncancerous mucosa (NCM) specimens were examined. The expression levels of eight TBP genes (TRF1, TRF2, TIN2, TANK1, TANK2, POT1, RAP1 and TPP1) were analyzed. Among the 106 cases, 35 cases had shortened telomeres (<7 kb), 15 had shortened 3'-OH (3'-OH length ratio of cancer/NCM <0.5) and 88 were classified as telomerase-activated cancers (activity ratio of cancer/NCM >2). Comparison between NCM and cancer in each case showed that all TBP except for POT1 were downregulated in cancers. A survival analysis using a Cox proportional hazard model showed that the survival rate of the telomerase-activated cases with shortened 3'-OH and that of telomerase-inactivated cases were significantly better than that of telomerase-activated cases without 3'-OH shortening, that is, restored or maintained 3'-OH (P = 0.018). In the telomerase-activated cancers, the length of 3'-OH was significantly correlated with the expression levels of POT1. Elongation of telomeric overhang by telomerase, which might be regulated by POT1, may contribute to the increase of malignant potential in colorectal cancers.
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Affiliation(s)
- Kensaku Kojima
- Department of Surgery, Graduate School of Biomedical Sciences, Hiroshima University Hospital, Hiroshima University, Hiroshima, Japan
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95
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Wojtyla A, Gladych M, Rubis B. Human telomerase activity regulation. Mol Biol Rep 2010; 38:3339-49. [PMID: 21086176 PMCID: PMC3085100 DOI: 10.1007/s11033-010-0439-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 11/08/2010] [Indexed: 01/27/2023]
Abstract
Telomerase has been recognized as a relevant factor distinguishing cancer cells from normal cells. Thus, it has become a very promising target for anticancer therapy. The cell proliferative potential can be limited by replication end problem, due to telomeres shortening, which is overcome in cancer cells by telomerase activity or by alternative telomeres lengthening (ALT) mechanism. However, this multisubunit enzymatic complex can be regulated at various levels, including expression control but also other factors contributing to the enzyme phosphorylation status, assembling or complex subunits transport. Thus, we show that the telomerase expression targeting cannot be the only possibility to shorten telomeres and induce cell apoptosis. It is important especially since the transcription expression is not always correlated with the enzyme activity which might result in transcription modulation failure or a possibility for the gene therapy to be overcome. This review summarizes the current state of knowledge of numerous telomerase regulation mechanisms that take place after telomerase subunits coding genes transcription. Thus we show the possible mechanisms of telomerase activity regulation which might become attractive anticancer therapy targets.
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Affiliation(s)
- Aneta Wojtyla
- Department of Clinical Chemistry and Molecular Diagnostics, Poznan University of Medical Sciences, Przybyszewskiego 49 St, 60-355 Poznan, Poland
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96
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Telomere dysfunction and fusion during the progression of chronic lymphocytic leukemia: evidence for a telomere crisis. Blood 2010; 116:1899-907. [PMID: 20538793 DOI: 10.1182/blood-2010-02-272104] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We performed single-molecule telomere length and telomere fusion analysis in patients at different stages of chronic lymphocytic leukemia (CLL). Our work identified the shortest telomeres ever recorded in primary human tissue, reinforcing the concept that there is significant cell division in CLL. Furthermore, we provide direct evidence that critical telomere shortening, dysfunction, and fusion contribute to disease progression. The frequency of short telomeres and fusion events increased with advanced disease, but importantly these were also found in a subset of early-stage patient samples, indicating that these events can precede disease progression. Sequence analysis of fusion events isolated from persons with the shortest telomeres revealed limited numbers of repeats at the breakpoint, subtelomeric deletion, and microhomology. Array-comparative genome hybridization analysis of persons displaying evidence of telomere dysfunction revealed large-scale genomic rearrangements that were concentrated in the telomeric regions; this was not observed in samples with longer telomeres. The telomere dynamics observed in CLL B cells were indistinguishable from that observed in cells undergoing crisis in culture after abrogation of the p53 pathway. Taken together, our data support the concept that telomere erosion and subsequent telomere fusion are critical in the progression of CLL and that this paradigm may extend to other malignancies.
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97
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Bendix L, Horn PB, Jensen UB, Rubelj I, Kolvraa S. The load of short telomeres, estimated by a new method, Universal STELA, correlates with number of senescent cells. Aging Cell 2010; 9:383-97. [PMID: 20331440 DOI: 10.1111/j.1474-9726.2010.00568.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Short telomeres are thought to trigger senescence, most likely through a single - or a group of few - critically shortened telomeres. Such short telomeres are thought to result from a combination of gradual linear shortening resulting from the end replication problem, reflecting the division history of the cell, superimposed by a more stochastic mechanism, suddenly causing a significant shortening of a single telomere. Previously, studies that have tried to explore the role of critically shortened telomeres have been hampered by methodological problems. With the method presented here, Universal STELA, we have a tool that can directly investigate the relationship between senescence and the load of short telomeres. The method is a variant of the chromosome-specific STELA method but has the advantage that it can demonstrate short telomeres regardless of chromosome. With Universal STELA, we find a strong correlation between the load of short telomeres and cellular senescence. Further we show that the load of short telomeres is higher in senescent cells compared to proliferating cells at the same passage, offering an explanation of premature cell senescence. This new method, Universal STELA, offers some advantages compared to existing methods and can be used to explore many of the unanswered questions in telomere biology including the role that telomeres play in cancer and aging.
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Affiliation(s)
- Laila Bendix
- Danish Aging Research Center, University of Southern Denmark, Odense, Denmark.
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98
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Hu L, Lim KW, Bouaziz S, Phan AT. Giardia telomeric sequence d(TAGGG)4 forms two intramolecular G-quadruplexes in K+ solution: effect of loop length and sequence on the folding topology. J Am Chem Soc 2010; 131:16824-31. [PMID: 19874015 DOI: 10.1021/ja905611c] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recently, it has been shown that in K(+) solution the human telomeric sequence d[TAGGG(TTAGGG)(3)] forms a (3 + 1) intramolecular G-quadruplex, while the Bombyx mori telomeric sequence d[TAGG(TTAGG)(3)], which differs from the human counterpart only by one G deletion in each repeat, forms a chair-type intramolecular G-quadruplex, indicating an effect of G-tract length on the folding topology of G-quadruplexes. To explore the effect of loop length and sequence on the folding topology of G-quadruplexes, here we examine the structure of the four-repeat Giardia telomeric sequence d[TAGGG(TAGGG)(3)], which differs from the human counterpart only by one T deletion within the non-G linker in each repeat. We show by NMR that this sequence forms two different intramolecular G-quadruplexes in K(+) solution. The first one is a novel basket-type antiparallel-stranded G-quadruplex containing two G-tetrads, a G x (A-G) triad, and two A x T base pairs; the three loops are consecutively edgewise-diagonal-edgewise. The second one is a propeller-type parallel-stranded G-quadruplex involving three G-tetrads; the three loops are all double-chain-reversal. Recurrence of several structural elements in the observed structures suggests a "cut and paste" principle for the design and prediction of G-quadruplex topologies, for which different elements could be extracted from one G-quadruplex and inserted into another.
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Affiliation(s)
- Lanying Hu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
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99
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Zhang Z, Dai J, Veliath E, Jones RA, Yang D. Structure of a two-G-tetrad intramolecular G-quadruplex formed by a variant human telomeric sequence in K+ solution: insights into the interconversion of human telomeric G-quadruplex structures. Nucleic Acids Res 2010; 38:1009-21. [PMID: 19946019 PMCID: PMC2817458 DOI: 10.1093/nar/gkp1029] [Citation(s) in RCA: 133] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2009] [Revised: 10/19/2009] [Accepted: 10/20/2009] [Indexed: 12/21/2022] Open
Abstract
Human telomeric DNA G-quadruplex has been considered as an attractive target for cancer therapeutic intervention. The telomeric sequence shows intrinsic structure polymorphism. Here we report a novel intramolecular G-quadruplex structure formed by a variant human telomeric sequence in K(+) solution. This sequence forms a basket-type intramolecular G-quadruplex with only two G-tetrads but multiple-layer capping structures formed by loop residues. While it is shown that this structure can only be detected in the specifically truncated telomeric sequences without any 5'-flanking residues, our results suggest that this two-G-tetrad conformation is likely to be an intermediate form of the interconversion of different telomeric G-quadruplex conformations.
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Affiliation(s)
- Zhenjiang Zhang
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721, USA, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724, BIO5 Institute, The University of Arizona, 1140 E. South Campus Dr, Tucson, AZ 85721 and Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
| | - Jixun Dai
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721, USA, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724, BIO5 Institute, The University of Arizona, 1140 E. South Campus Dr, Tucson, AZ 85721 and Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
| | - Elizabeth Veliath
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721, USA, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724, BIO5 Institute, The University of Arizona, 1140 E. South Campus Dr, Tucson, AZ 85721 and Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
| | - Roger A. Jones
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721, USA, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724, BIO5 Institute, The University of Arizona, 1140 E. South Campus Dr, Tucson, AZ 85721 and Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
| | - Danzhou Yang
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721, USA, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China, Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ 85724, BIO5 Institute, The University of Arizona, 1140 E. South Campus Dr, Tucson, AZ 85721 and Department of Chemistry, The University of Arizona, Tucson, AZ 85721, USA
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Bhattacharyya S, Sandy A, Groden J. Unwinding protein complexes in ALTernative telomere maintenance. J Cell Biochem 2010; 109:7-15. [PMID: 19911388 PMCID: PMC2892175 DOI: 10.1002/jcb.22388] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Telomeres are composed of specialized chromatin that includes DNA repair/recombination proteins, telomere DNA-binding proteins and a number of three dimensional nucleic acid structures including G-quartets and D-loops. A number of studies suggest that the BLM and WRN recQ-like helicases play important roles in recombination-mediated mechanisms of telomere elongation or Alternative Lengthening of Telomeres (ALT), processes that maintain/elongate telomeres in the absence of telomerase. BLM and WRN localize within ALT-associated nuclear bodies in telomerase-negative immortalized cell lines and interact with the telomere-specific proteins POT1, TRF1 and TRF2. Helicase activity is modulated by these interactions. BLM functions in DNA double-strand break repair processes such as non-homologous end joining, homologous recombination-mediated repair, resolution of stalled replication forks and synthesis-dependent strand annealing, although its precise functions at the telomeres are speculative. WRN also functions in DNA replication, recombination and repair, and in addition to its helicase domain, includes an exonuclease domain not found in other recQ-like helicases. The biochemical properties of BLM and WRN are, therefore, important in biological processes other than DNA replication, recombination and repair. In this review, we discuss some previous and recent findings of human rec-Q-like helicases and their role in telomere elongation during ALT processes.
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Affiliation(s)
- Saumitri Bhattacharyya
- Department of Molecular Virology, Immunology & Medical Genetics, The Ohio State University College of Medicine, 460 W 12th Avenue, 986 Biomedical Research Tower, Columbus, Ohio 43210-2207
| | - April Sandy
- Department of Molecular Virology, Immunology & Medical Genetics, The Ohio State University College of Medicine, 460 W 12th Avenue, 986 Biomedical Research Tower, Columbus, Ohio 43210-2207
| | - Joanna Groden
- Department of Molecular Virology, Immunology & Medical Genetics, The Ohio State University College of Medicine, 460 W 12th Avenue, 986 Biomedical Research Tower, Columbus, Ohio 43210-2207
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