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Zhang M, Wang H, Han J, Wang H, Jia Y, Hong W, Tang F, Li Z. Specific recognition and sensitive quantification of mRNA splice variants via one-pot ligation-dependent loop-mediated isothermal amplification. Analyst 2023; 148:5605-5611. [PMID: 37818948 DOI: 10.1039/d3an01382k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Specific recognition and sensitive quantification of mRNA alternative splice variants have been a necessity for exploring the regulatory mechanism of RNA splicing and revealing the association between pre-mRNA splicing and transcriptome function, as well as disease diagnosis. However, their wide abundance range and high sequence homology pose enormous challenges for high sensitivity and selectivity quantification of splice variants. Herein, taking advantage of the excellent specificity of ligation and the powerful nucleic acid replication feature of loop-mediated isothermal amplification (LAMP), we developed a one-pot method (termed one-pot ligation-LAMP) for specific recognition and sensitive quantification of mRNA splicing variants based on two splicing junction-specific stem-loop DNA probe ligation and the subsequently initiating LAMP. The one-pot ligation-LAMP can specifically detect as low as 100 aM mRNA splice variants without any nonspecific signals and quantify them with a wide dynamics range spanning at least six orders of magnitude. We have demonstrated that the one-pot ligation-LAMP is a versatile and practical strategy for accurately quantifying different splicing variants in complex biological samples with high sensitivity all in one tube within 90 min, thereby providing an attractive tool for mRNA splice variant-related studies.
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Affiliation(s)
- Mai Zhang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
| | - Hui Wang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
| | - Jun Han
- National Textile and Leather Product Quality Inspection and Testing Centre, 15 Xili-Balizhuang, Chaoyang District, Beijing 100025, China
| | - Honghong Wang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
| | - Yuting Jia
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
| | - Weixiang Hong
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
| | - Fu Tang
- School of Materials Science and Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China
| | - Zhengping Li
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biological Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China.
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Kim JJ, Sayed ME, Ahn A, Slusher AL, Ying JY, Ludlow AT. Dynamics of TERT regulation via alternative splicing in stem cells and cancer cells. PLoS One 2023; 18:e0289327. [PMID: 37531400 PMCID: PMC10395990 DOI: 10.1371/journal.pone.0289327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 07/17/2023] [Indexed: 08/04/2023] Open
Abstract
Part of the regulation of telomerase activity includes the alternative splicing (AS) of the catalytic subunit telomerase reverse transcriptase (TERT). Although a therapeutic window for telomerase/TERT inhibition exists between cancer cells and somatic cells, stem cells express TERT and rely on telomerase activity for physiological replacement of cells. Therefore, identifying differences in TERT regulation between stem cells and cancer cells is essential for developing telomerase inhibition-based cancer therapies that reduce damage to stem cells. In this study, we measured TERT splice variant expression and telomerase activity in induced pluripotent stem cells (iPSCs), neural progenitor cells (NPCs), and non-small cell lung cancer cells (NSCLC, Calu-6 cells). We observed that a NOVA1-PTBP1-PTBP2 axis regulates TERT alternative splicing (AS) in iPSCs and their differentiation into NPCs. We also found that splice-switching of TERT, which regulates telomerase activity, is induced by different cell densities in stem cells but not cancer cells. Lastly, we identified cell type-specific splicing factors that regulate TERT AS. Overall, our findings represent an important step forward in understanding the regulation of TERT AS in stem cells and cancer cells.
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Affiliation(s)
- Jeongjin J. Kim
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Mohammed E. Sayed
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Alexander Ahn
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Aaron L. Slusher
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Jeffrey Y. Ying
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Andrew T. Ludlow
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
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Udroiu I, Marinaccio J, Sgura A. Many Functions of Telomerase Components: Certainties, Doubts, and Inconsistencies. Int J Mol Sci 2022; 23:ijms232315189. [PMID: 36499514 PMCID: PMC9736166 DOI: 10.3390/ijms232315189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 11/23/2022] [Accepted: 11/29/2022] [Indexed: 12/12/2022] Open
Abstract
A growing number of studies have evidenced non-telomeric functions of "telomerase". Almost all of them, however, investigated the non-canonical effects of the catalytic subunit TERT, and not the telomerase ribonucleoprotein holoenzyme. These functions mainly comprise signal transduction, gene regulation and the increase of anti-oxidative systems. Although less studied, TERC (the RNA component of telomerase) has also been shown to be involved in gene regulation, as well as other functions. All this has led to the publication of many reviews on the subject, which, however, are often disseminating personal interpretations of experimental studies of other researchers as original proofs. Indeed, while some functions such as gene regulation seem ascertained, especially because mechanistic findings have been provided, other ones remain dubious and/or are contradicted by other direct or indirect evidence (e.g., telomerase activity at double-strand break site, RNA polymerase activity of TERT, translation of TERC, mitochondrion-processed TERC). In a critical study of the primary evidence so far obtained, we show those functions for which there is consensus, those showing contradictory results and those needing confirmation. The resulting picture, together with some usually neglected aspects, seems to indicate a link between TERT and TERC functions and cellular stemness and gives possible directions for future research.
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Slusher AL, Kim JJJ, Ribick M, Pollens-Voigt J, Bankhead A, Palmbos PL, Ludlow AT. Intronic Cis-Element DR8 in hTERT Is Bound by Splicing Factor SF3B4 and Regulates hTERT Splicing in Non-Small Cell Lung Cancer. Mol Cancer Res 2022; 20:1574-1588. [PMID: 35852380 PMCID: PMC9532359 DOI: 10.1158/1541-7786.mcr-21-0058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 11/14/2021] [Accepted: 06/14/2022] [Indexed: 11/16/2022]
Abstract
Splicing of the hTERT gene to produce the full-length (FL) transcript is necessary for telomerase enzyme activity and telomere-dependent cellular immortality in the majority of human tumors, including non-small cell lung cancer (NSCLC) cells. The molecular machinery to splice hTERT to the FL isoform remains mostly unknown. Previously, we reported that an intron 8 cis-element termed "direct repeat 8" (DR8) promotes FL hTERT splicing, telomerase, and telomere length maintenance when bound by NOVA1 and PTBP1 in NSCLC cells. However, some NSCLC cells and patient tumor samples lack NOVA1 expression. This leaves a gap in knowledge about the splicing factors and cis-elements that promote telomerase in the NOVA1-negative context. We report that DR8 regulates FL hTERT splicing in the NOVA1-negative and -positive lung cancer contexts. We identified splicing factor 3b subunit 4 (SF3B4) as an RNA trans-factor whose expression is increased in lung adenocarcinoma (LUAD) tumors compared with adjacent normal tissue and predicts poor LUAD patient survival. In contrast to normal lung epithelial cells, which continued to grow with partial reductions of SF3B4 protein, SF3B4 knockdown reduced hTERT splicing, telomerase activity, telomere length, and cell growth in lung cancer cells. SF3B4 was also demonstrated to bind the DR8 region of hTERT pre-mRNA in both NOVA1-negative and -positive NSCLC cells. These findings provide evidence that DR8 is a critical binding hub for trans-factors to regulate FL hTERT splicing in NSCLC cells. These studies help define mechanisms of gene regulation important to the generation of telomerase activity during carcinogenesis. IMPLICATIONS Manipulation of a core spliceosome protein reduces telomerase/hTERT splicing in lung cancer cells and results in slowed cancer cell growth and cell death, revealing a potential therapeutic strategy.
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Affiliation(s)
- Aaron L. Slusher
- School of Kinesiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Jeongjin JJ Kim
- School of Kinesiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Mark Ribick
- School of Kinesiology, University of Michigan, Ann Arbor, MI, 48109, USA
| | | | - Armand Bankhead
- Biostatistics Department and School of Public Health, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Phillip L. Palmbos
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, MI, 48109, USA
| | - Andrew T. Ludlow
- School of Kinesiology, University of Michigan, Ann Arbor, MI, 48109, USA
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5
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Taheri M, Ghafouri-Fard S, Najafi S, Kallenbach J, Keramatfar E, Atri Roozbahani G, Heidari Horestani M, Hussen BM, Baniahmad A. Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer. Cancer Cell Int 2022; 22:258. [PMID: 35974340 PMCID: PMC9380309 DOI: 10.1186/s12935-022-02678-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 08/05/2022] [Indexed: 11/10/2022] Open
Abstract
Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.
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Affiliation(s)
- Mohammad Taheri
- Urology and Nephrology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Najafi
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Julia Kallenbach
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | - Elmira Keramatfar
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | | | | | - Bashdar Mahmud Hussen
- Department of Pharmacognosy, College of Pharmacy, Hawler Medical University, Kurdistan Region, Erbil, Iraq.,Center of Research and Strategic Studies, Lebanese French University, Erbil, Kurdistan Region, Iraq
| | - Aria Baniahmad
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany.
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Ebata H, Loo TM, Takahashi A. Telomere Maintenance and the cGAS-STING Pathway in Cancer. Cells 2022; 11:1958. [PMID: 35741087 PMCID: PMC9221635 DOI: 10.3390/cells11121958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 06/15/2022] [Accepted: 06/16/2022] [Indexed: 11/17/2022] Open
Abstract
Cancer cells exhibit the unique characteristics of high proliferation and aberrant DNA damage response, which prevents cancer therapy from effectively eliminating them. The machinery required for telomere maintenance, such as telomerase and the alternative lengthening of telomeres (ALT), enables cancer cells to proliferate indefinitely. In addition, the molecules in this system are involved in noncanonical pro-tumorigenic functions. Of these, the function of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, which contains telomere-related molecules, is a well-known contributor to the tumor microenvironment (TME). This review summarizes the current knowledge of the role of telomerase and ALT in cancer regulation, with emphasis on their noncanonical roles beyond telomere maintenance. The components of the cGAS-STING pathway are summarized with respect to intercell communication in the TME. Elucidating the underlying functional connection between telomere-related molecules and TME regulation is important for the development of cancer therapeutics that target cancer-specific pathways in different contexts. Finally, strategies for designing new cancer therapies that target cancer cells and the TME are discussed.
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Affiliation(s)
- Hiroshi Ebata
- Department of Biological Sciences, Faculty of Science, The University of Tokyo, Tokyo 113-0033, Japan;
- Project for Cellular Senescence, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan;
| | - Tze Mun Loo
- Project for Cellular Senescence, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan;
| | - Akiko Takahashi
- Project for Cellular Senescence, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan;
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Jia Y, Han J, Wang H, Hong W, Wang H, Zhang M, Li Z. Ultrasensitive quantification of multiplexed mRNA variants via splice-junction anchored DNA probes and SplintR ligase-initiated PCR. Chem Commun (Camb) 2021; 57:10011-10014. [PMID: 34498616 DOI: 10.1039/d1cc03033g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A method based on mRNA-templated ligation of splice-junction anchored DNA probes followed by PCR amplification of the ligated product has been developed for multiplexed detection of mRNA splice variants with high sensitivity and specificity. The proposed assay can detect as low as 10 aM mRNA splicing variants and has been successfully applied to detect real samples.
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Affiliation(s)
- Yuting Jia
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Jun Han
- National Textile and Leather Product Quality Supervision Testing Center, Beijing 100025, China
| | - Hui Wang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Weixiang Hong
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Honghong Wang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Mai Zhang
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Zhengping Li
- Beijing Key Laboratory for Bioengineering and Sensing Technology, School of Chemistry and Biology Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
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Plyasova AA, Zhdanov DD. Alternative Splicing of Human Telomerase Reverse Transcriptase (hTERT) and Its Implications in Physiological and Pathological Processes. Biomedicines 2021; 9:526. [PMID: 34065134 PMCID: PMC8150890 DOI: 10.3390/biomedicines9050526] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 12/24/2022] Open
Abstract
Alternative splicing (AS) of human telomerase catalytic subunit (hTERT, human telomerase reverse transcriptase) pre-mRNA strongly regulates telomerase activity. Several proteins can regulate AS in a cell type-specific manner and determine the functions of cells. In addition to being involved in telomerase activity regulation, AS provides cells with different splice variants that may have alternative biological activities. The modulation of telomerase activity through the induction of hTERT AS is involved in the development of different cancer types and embryos, and the differentiation of stem cells. Regulatory T cells may suppress the proliferation of target human and murine T and B lymphocytes and NK cells in a contact-independent manner involving activation of TERT AS. This review focuses on the mechanism of regulation of hTERT pre-mRNA AS and the involvement of splice variants in physiological and pathological processes.
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Affiliation(s)
| | - Dmitry D. Zhdanov
- Institute of Biomedical Chemistry, Pogodinskaya st 10/8, 119121 Moscow, Russia;
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Dratwa M, Wysoczańska B, Łacina P, Kubik T, Bogunia-Kubik K. TERT-Regulation and Roles in Cancer Formation. Front Immunol 2020; 11:589929. [PMID: 33329574 PMCID: PMC7717964 DOI: 10.3389/fimmu.2020.589929] [Citation(s) in RCA: 117] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 10/16/2020] [Indexed: 12/16/2022] Open
Abstract
Telomerase reverse transcriptase (TERT) is a catalytic subunit of telomerase. Telomerase complex plays a key role in cancer formation by telomere dependent or independent mechanisms. Telomere maintenance mechanisms include complex TERT changes such as gene amplifications, TERT structural variants, TERT promoter germline and somatic mutations, TERT epigenetic changes, and alternative lengthening of telomere. All of them are cancer specific at tissue histotype and at single cell level. TERT expression is regulated in tumors via multiple genetic and epigenetic alterations which affect telomerase activity. Telomerase activity via TERT expression has an impact on telomere length and can be a useful marker in diagnosis and prognosis of various cancers and a new therapy approach. In this review we want to highlight the main roles of TERT in different mechanisms of cancer development and regulation.
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Affiliation(s)
- Marta Dratwa
- Laboratory of Clinical Immunogenetics and Pharmacogenetics, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - Barbara Wysoczańska
- Laboratory of Clinical Immunogenetics and Pharmacogenetics, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - Piotr Łacina
- Laboratory of Clinical Immunogenetics and Pharmacogenetics, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
| | - Tomasz Kubik
- Department of Computer Engineering, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland
| | - Katarzyna Bogunia-Kubik
- Laboratory of Clinical Immunogenetics and Pharmacogenetics, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland
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Slusher AL, Kim JJJ, Ludlow AT. The Role of Alternative RNA Splicing in the Regulation of hTERT, Telomerase, and Telomeres: Implications for Cancer Therapeutics. Cancers (Basel) 2020; 12:E1514. [PMID: 32531916 PMCID: PMC7352778 DOI: 10.3390/cancers12061514] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/01/2020] [Accepted: 06/08/2020] [Indexed: 12/13/2022] Open
Abstract
Alternative RNA splicing impacts the majority (>90%) of eukaryotic multi-exon genes, expanding the coding capacity and regulating the abundance of gene isoforms. Telomerase (hTERT) is a key example of a gene that is alternatively spliced during human fetal development and becomes dysregulated in nearly all cancers. Approximately 90% of human tumors use telomerase to synthesize de novo telomere repeats and obtain telomere-dependent cellular immortality. Paradigm shifting data indicates that hTERT alternative splicing, in addition to transcription, plays an important role in the regulation of active telomerase in cells. Our group and others are pursuing the basic science studies to progress this emerging area of telomerase biology. Recent evidence demonstrates that switching splicing of hTERT from the telomerase activity producing full-length hTERT isoform to alternatively spliced, non-coding isoforms may be a novel telomerase inhibition strategy to prevent cancer growth and survival. Thus, the goals of this review are to detail the general roles of telomerase in cancer development, explore the emerging regulatory mechanisms of alternative RNA splicing of the hTERT gene in various somatic and cancer cell types, define the known and potential roles of hTERT splice isoforms in cancer cell biology, and provide insight into new treatment strategies targeting hTERT in telomerase-positive cancers.
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Affiliation(s)
| | | | - Andrew T. Ludlow
- School of Kinesiology, University of Michigan, Ann Arbor, MI 48109, USA; (A.L.S.); (J.J.K.)
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11
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Nemirovich-Danchenko NM, Khodanovich MY. Telomerase Gene Editing in the Neural Stem Cells in vivo as a Possible New Approach against Brain Aging. RUSS J GENET+ 2020. [DOI: 10.1134/s1022795420040092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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12
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Ségal-Bendirdjian E, Geli V. Non-canonical Roles of Telomerase: Unraveling the Imbroglio. Front Cell Dev Biol 2019; 7:332. [PMID: 31911897 PMCID: PMC6914764 DOI: 10.3389/fcell.2019.00332] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 11/27/2019] [Indexed: 12/11/2022] Open
Abstract
Telomerase plays a critical role in stem cell function and tissue regeneration that depends on its ability to elongate telomeres. For nearly two decades, it turned out that TERT regulates a broad spectrum of functions including signal transduction, gene expression regulation, and protection against oxidative damage that are independent of its telomere elongation activity. These conclusions that were mainly obtained in cell lines overexpressing telomerase were further strengthened by in vivo models of ectopic expression of telomerase or models of G1 TERT knockout mice without detectable telomere dysfunction. However, the later models were questioned due to the presence of aberrantly shortened telomere in the germline of the parents TERT+/- that were used to create the G1 TERT -/- mice. The physiological relevance of the functions associated with overexpressed telomerase raised also some concerns due to artifactual situations and localizations and complications to quantify the level of TERT. Another concern with non-canonical functions of TERT was the difficulty to separate a direct TERT-related function from secondary effects. Despite these concerns, more and more evidence accumulates for non-canonical roles of telomerase that are non-obligatory extra-telomeric. Here, we review these non-canonical roles of the TERT subunit of telomerase. Also, we emphasize recent results that link TERT to mitochondria and protection to reactive oxygen species suggesting a protective role of TERT in neurons. Throughout this review, we dissect some controversies regarding the non-canonical functions of telomerase and provide some insights to explain these discrepancies. Finally, we discuss the importance of understanding these alternative functions of telomerase for the development of anticancer strategies.
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Affiliation(s)
- Evelyne Ségal-Bendirdjian
- INSERM UMR-S 1124, Team: Cellular Homeostasis, Cancer and Therapies, INSERM US36, CNRS UMS 2009, BioMedTech Facilities, Université de Paris, Paris, France
| | - Vincent Geli
- Marseille Cancer Research Center, U1068 INSERM, UMR 7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Equipe labellisée Ligue, Marseille, France
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13
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Wang F, Cheng Y, Zhang C, Chang G, Geng X. A novel antisense oligonucleotide anchored on the intronic splicing enhancer of hTERT pre-mRNA inhibits telomerase activity and induces apoptosis in glioma cells. J Neurooncol 2019; 143:57-68. [PMID: 30887243 DOI: 10.1007/s11060-019-03150-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Accepted: 03/11/2019] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Alternative splicing of hTERT pre-mRNA is an important step in the regulation of telomerase activity, but the regulation mechanisms and functions remain unclear. METHODS RT-PCR analysis was used to detect hTERT splicing in glioma cell lines and brain tissues. TRAP assay was used to detect the telomerase activity. Then, we designed and synthesized 2'-O-methyl-RNA phosphorothioate AONs and transfected them into glioma cells to detect the changes in telomerase activity. MTT assay, plate colony formation assay, western blotting and Annexin V/PI assay were used to detect cell proliferation and apoptosis. At last, bioinformatics analyses were used to predict the expression and function of splicing protein SRSF2 in gliomas. RESULTS hTERT splicing occurs both in glioma cell lines and glioma patients' tissues. The telomerase activity was related to the expression level of the full-length hTERT, rather than the total hTERT transcript level. AON-Ex726 was complementary to the sequence of the intronic splicing enhancer (ISE) in intron six, and significantly altered the splicing pattern of hTERT pre-mRNA, reducing the expression level of the full-length hTERT mRNA and increasing the expression level of the -β hTERT mRNA. After transfection with AON-Ex726, the level of apoptosis was increased, while telomerase activity and cell proliferation were significantly decreased. By bioinformatic predictions, we found the AON-Ex726 anchoring sequence in ISE overlaps the binding site of SRSF2 protein, which is up-regulated during the development of gliomas. CONCLUSIONS Our findings provided new targets and important clues for the gene therapy of gliomas by regulating the alternative splicing pattern of hTERT pre-mRNA.
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Affiliation(s)
- Fei Wang
- Department of Neurology, General Hospital, Tianjin Medical University, Tianjin, 300052, China
| | - Yajing Cheng
- Department of Neurology, General Hospital, Tianjin Medical University, Tianjin, 300052, China
| | - Chi Zhang
- Department of Neurology, General Hospital, Tianjin Medical University, Tianjin, 300052, China
| | - Guangming Chang
- Department of Clinical Laboratory, General Hospital, Tianjin Medical University, Tianjin, 300052, China
| | - Xin Geng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Key Laboratory of Immune Microenvironment and Disease, Ministry of Education, Tianjin Medical University, 22nd Qixiangtai Road, Tianjin, 300070, China.
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Alsiary R, Brownhill SC, Brüning-Richardson A, Hutson R, Griffin N, Morrison EE, Bond J, Burchill SA, Bell SM. Expression analysis of the MCPH1/BRIT1 and BRCA1 tumor suppressor genes and telomerase splice variants in epithelial ovarian cancer. Gene 2018; 672:34-44. [PMID: 29860064 DOI: 10.1016/j.gene.2018.05.113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/27/2018] [Accepted: 05/30/2018] [Indexed: 10/14/2022]
Abstract
AIMS The aim of this study was to explore the correlation of hTERT splice variant expression with MCPH1/BRIT1 and BRCA1 expression in epithelial ovarian cancer (EOC) samples. BACKGROUND Telomerase activation can contribute to the progression of tumors and the development of cancer. However, the regulation of telomerase activity remains unclear. MCPH1 (also known as BRIT1, BRCT-repeat inhibitor of hTERT expression) and BRCA1 are tumor suppressor genes that have been linked to telomerase expression. METHODS qPCR was used to investigate telomerase splice variants, MCPH1/BRIT1 and BRCA1 expression in EOC tissue and primary cultures. RESULTS The wild type α+/β+ hTERT variant was the most common splice variant in the EOC samples, followed by α+/β- hTERT, a dominant negative regulator of telomerase activity. EOC samples expressing high total hTERT demonstrated significantly lower MCPH1/BRIT1 expression in both tissue (p = 0.05) and primary cultures (p = 0.03). We identified a negative correlation between MCPH1/BRIT1 and α+/β+ hTERT (p = 0.04), and a strong positive association between MCPH1/BRIT1 and both α-/β+ hTERT and α-/β- hTERT (both p = 0.02). A positive association was observed between BRCA1 and α-/β+ hTERT and α-/β- hTERT expression (p = 0.003 and p = 0.04, respectively). CONCLUSIONS These findings support a regulatory effect of MCPH1/BRIT1 and BRCA1 on telomerase activity, particularly the negative association between MCPH1/BRIT1 and the functional form of hTERT (α+/β+).
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Affiliation(s)
- Rawiah Alsiary
- Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Samantha C Brownhill
- Leeds Institute of Cancer and Pathology, University of Leeds, St. James's University Hospital Leeds, LS9 7TF, UK
| | - Anke Brüning-Richardson
- Leeds Institute of Cancer and Pathology, University of Leeds, St. James's University Hospital Leeds, LS9 7TF, UK
| | - Richard Hutson
- Institute of Oncology, Leeds Teaching Hospitals NHS Trust, Leeds LS9 7TF, UK
| | - Nicholas Griffin
- Department of Histopathology, Leeds Teaching Hospitals NHS Trust, Leeds LS9 7TF, UK
| | - Ewan E Morrison
- Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Jacquelyn Bond
- Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, UK
| | - Susan A Burchill
- Leeds Institute of Cancer and Pathology, University of Leeds, St. James's University Hospital Leeds, LS9 7TF, UK
| | - Sandra M Bell
- Leeds Institute of Biomedical and Clinical Sciences, University of Leeds, St. James's University Hospital, Leeds LS9 7TF, UK.
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Li G, Shen J, Cao J, Zhou G, Lei T, Sun Y, Gao H, Ding Y, Xu W, Zhan Z, Chen Y, Huang H. Alternative splicing of human telomerase reverse transcriptase in gliomas and its modulation mediated by CX-5461. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2018; 37:78. [PMID: 29631594 PMCID: PMC5891986 DOI: 10.1186/s13046-018-0749-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 04/02/2018] [Indexed: 02/08/2023]
Abstract
Background Glioma is a heterogeneous, invasive primary brain tumor with a wide range of patient survival and a lack of reliable prognostic biomarkers. Human telomerase reverse transcriptase (hTERT) has been reported in the presence of multiple transcripts in various tumor systems. The biological function and precise regulatory mechanisms of hTERT transcripts remain uncertain. Methods Alternative splicing of hTERT and telomerase activity were examined in 96 glioma specimens, including 38 glioblastomas (GBMs), 23 oligodendrogliomas (ODMs), and 35 oligoastrocytomas (OAMs). The correlation between telomerase activity or hTERT transcripts and patient clinical characteristics was investigated. We examined the regulation of alternative splicing of hTERT and telomerase activity by G-quadruplex stabilizer CX-5461 in GBM cells. The biological effects of CX-5461 on GBM cell lines, including inhibition of cell proliferation, effects on cell cycle/apoptosis, and telomere DNA damage were further explored. Results The β splicing was verified in human gliomas and hTERT+β was significantly correlated with higher telomerase activity, higher KPS, larger tumor size, and higher tumor grades. Meanwhile, glioma patients lacking hTERT+β expression or telomerase activity showed a significant survival benefit. Notably, CX-5461 altered hTERT splicing patterns, leading to an increase of hTERT-β transcript and a decrease of hTERT+β transcript expression, which inhibits telomerase activity. In addition, CX-5461 had cytotoxic effects on GBM cells and caused telomere DNA damage response, induced G2/M arrest and apoptosis. Conclusions The hTERT+β is verified to be correlated with clinical parameters in gliomas, and could serve as a prognostic marker or possibly therapeutic target for gliomas. CX-5461 can regulate the splicing pattern of hTERT, inhibit telomerase activity, and kill GBM cells.
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Affiliation(s)
- Guihong Li
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China.,Department of Neurosurgery, First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450000, China
| | - Jing Shen
- Department of Cardiology, Shengze Hospital of Jiangsu Province, Suzhou, 215200, China
| | - Junguo Cao
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Guangtong Zhou
- Department of Neurosurgery, First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450000, China
| | - Ting Lei
- Department of Neurovascular Research Laboratory and Neuroscience, Universitat Autonoma de Barcelona, 08035, Barcelona, Spain
| | - Yuxue Sun
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Haijun Gao
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Yaonan Ding
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Weidong Xu
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Zhixin Zhan
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China
| | - Yong Chen
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China.
| | - Haiyan Huang
- Department of Neurosurgery, First Hospital of Jilin University, Changchun, 130021, China.
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16
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Liu X, Wang Y, Chang G, Wang F, Wang F, Geng X. Alternative Splicing of hTERT Pre-mRNA: A Potential Strategy for the Regulation of Telomerase Activity. Int J Mol Sci 2017; 18:ijms18030567. [PMID: 28272339 PMCID: PMC5372583 DOI: 10.3390/ijms18030567] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 02/14/2017] [Accepted: 03/02/2017] [Indexed: 12/11/2022] Open
Abstract
The activation of telomerase is one of the key events in the malignant transition of cells, and the expression of human telomerase reverse transcriptase (hTERT) is indispensable in the process of activating telomerase. The pre-mRNA alternative splicing of hTERT at the post-transcriptional level is one of the mechanisms for the regulation of telomerase activity. Shifts in splicing patterns occur in the development, tumorigenesis, and response to diverse stimuli in a tissue-specific and cell type–specific manner. Despite the regulation of telomerase activity, the alternative splicing of hTERT pre-mRNA may play a role in other cellular functions. Modulating the mode of hTERT pre-mRNA splicing is providing a new precept of therapy for cancer and aging-related diseases. This review focuses on the patterns of hTERT pre-mRNA alternative splicing and their biological functions, describes the potential association between the alternative splicing of hTERT pre-mRNA and telomerase activity, and discusses the possible significance of the alternative splicing of the hTERT pre-mRNA in the diagnosis, therapy, and prognosis of cancer and aging-related diseases.
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Affiliation(s)
- Xuewen Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China.
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Tianjin Medical University, Tianjin 300070, China.
| | - Yuchuan Wang
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300070, China.
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070, China.
| | - Guangming Chang
- Department of Clinical Laboratory, General Hospital, Tianjin Medical University, Tianjin 300070, China.
| | - Feng Wang
- Department of Genetics, Tianjin Medical University, Tianjin 300070, China.
| | - Fei Wang
- Department of Neurology, General Hospital, Tianjin Medical University, Tianjin 300052, China.
| | - Xin Geng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China.
- Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Tianjin Medical University, Tianjin 300070, China.
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Pestana A, Vinagre J, Sobrinho-Simões M, Soares P. TERT biology and function in cancer: beyond immortalisation. J Mol Endocrinol 2017; 58:R129-R146. [PMID: 28057768 DOI: 10.1530/jme-16-0195] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 01/05/2017] [Indexed: 12/23/2022]
Abstract
Evasion of replicative senescence and proliferation without restriction, sometimes designated as immortalisation, is one of the hallmarks of cancer that may be attained through reactivation of telomerase in somatic cells. In contrast to most normal cells in which there is lack of telomerase activity, upregulation of TERT transcription/activity is detected in 80-90% of malignant tumours. In several types of cancer, there is a relationship between the presence of TERT promoter mutations, TERT mRNA expression and clinicopathological features, but the biological bridge between the occurrence of TERT promoter mutations and the aggressive/invasive features displayed by the tumours remains unidentified. We and others have associated the presence of TERT promoter mutations with metastisation/survival in several types of cancer. In follicular cell-derived thyroid cancer, such mutations are associated with worse prognostic features (age of patients, tumour size and tumour stage) as well as with distant metastases, worse response to treatment and poorer survival. In this review, we analyse the data reported in several studies that imply TERT transcription reactivation/activity with cell proliferation, tumour invasion and metastisation. A particular attention is given to the putative connections between TERT transcriptional reactivation and signalling pathways frequently altered in cancer, such as c-MYC, NF-κB and B-Catenin.
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Affiliation(s)
- Ana Pestana
- Institute of Molecular Pathology and ImmunologyUniversity of Porto (IPATIMUP), Porto, Portugal
- Institute for Research and Innovation in Health (I3S)University of Porto, Porto, Portugal
| | - João Vinagre
- Institute of Molecular Pathology and ImmunologyUniversity of Porto (IPATIMUP), Porto, Portugal
- Institute for Research and Innovation in Health (I3S)University of Porto, Porto, Portugal
| | - Manuel Sobrinho-Simões
- Institute of Molecular Pathology and ImmunologyUniversity of Porto (IPATIMUP), Porto, Portugal
- Institute for Research and Innovation in Health (I3S)University of Porto, Porto, Portugal
- Medical FacultyUniversity of Porto, Porto, Portugal
- Department of PathologyCentro Hospitalar S. João, Porto, Portugal
- Department of PathologyMedical Faculty, University of Porto, Porto, Portugal
| | - Paula Soares
- Institute of Molecular Pathology and ImmunologyUniversity of Porto (IPATIMUP), Porto, Portugal
- Institute for Research and Innovation in Health (I3S)University of Porto, Porto, Portugal
- Medical FacultyUniversity of Porto, Porto, Portugal
- Department of PathologyMedical Faculty, University of Porto, Porto, Portugal
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18
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Rousseau P, Khondaker S, Zhu S, Lauzon C, Mai S, Autexier C. An intact putative mouse telomerase essential N-terminal domain is necessary for proper telomere maintenance. Biol Cell 2016; 108:96-112. [PMID: 26787169 DOI: 10.1111/boc.201500089] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 01/14/2016] [Indexed: 12/15/2022]
Abstract
BACKGROUND INFORMATION Naturally occurring telomerase reverse transcriptase (TERT) isoforms may regulate telomerase activity, and possibly function independently of telomeres to modulate embryonic stem (ES) cell self-renewal and differentiation. RESULTS We report the characterisation of two novel mouse TERT (mTERT) splice variants, Ins-i1[1-102] (Insi1 for short) and Del-e12[1-40] (Dele12 for short) that have not been previously described. Insi1 represents an in-frame insertion of nucleotides 1-102 from intron 1, encoding a 34 amino acid insertion at amino acid 73. Based on known functions of this region in human and Tetrahymena TERTs, the insertion interrupts the RNA interaction domain 1 implicated in low-affinity RNA binding and the telomerase essential N-terminal domain implicated in DNA substrate interactions. Dele12 contains a 40 nucleotide deletion of exon 12 which generates a premature stop codon, and possible protein lacking the C-terminus. We found Insi1 expressed in adult mouse brain and kidney and Dele12 expressed in adult mouse ovary. Dele12 was inactive in vitro and in mTERT(-/-) ES cells and Insi1 retained 26-48% of telomerase activity reconstituted by wild-type mTERT in vitro and in mTERT(-/-) ES cells. The Insi1 variant exhibited reduced DNA substrate binding in vitro and both variants exhibited a reduction in binding the telomerase RNA, mTR, when expressed in mTERT(-/-) ES cells. Stable expression of Dele12 in the mouse fibroblast CB17 cell line inhibited telomerase activity and slowed cell growth, suggesting a potential dominant-negative effect. Levels of signal-free ends, representing short telomeres, and end-to-end fusions were higher in mTERT(-/-) ES cells expressing mTERT-Insi1 and mTERT-Dele12, compared with levels observed in mTERT(-/-) ES cells expressing wild-type mTERT. In addition, in mTERT(-/-) cells expressing mTERT-Insi1, we observed chromosomes that were products of repeated breakage-bridge-fusion cycles and other telomere dysfunction-related aberrations. CONCLUSION AND SIGNIFICANCE An intact mTERT N-terminus which contributes to mTR binding, DNA binding and telomerase activity is necessary for elongation of short telomeres and the maintenance of functional telomeres. It is reasonable to speculate that relative levels of mTERT-Insi1 may regulate telomere function in specific tissues.
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Affiliation(s)
- Philippe Rousseau
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada
| | - Shanjadia Khondaker
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Division of Experimental Medicine, McGill University, Montréal, Québec, Canada
| | - Shusen Zhu
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada
| | - Catherine Lauzon
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada
| | - Sabine Mai
- Manitoba Institute of Cell Biology, University of Manitoba, Manitoba, R3E 0V9, Canada
| | - Chantal Autexier
- Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital, Montréal, Québec, H3T 1E2, Canada.,Division of Experimental Medicine, McGill University, Montréal, Québec, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada
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19
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Teichroeb JH, Kim J, Betts DH. The role of telomeres and telomerase reverse transcriptase isoforms in pluripotency induction and maintenance. RNA Biol 2016; 13:707-19. [PMID: 26786236 DOI: 10.1080/15476286.2015.1134413] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Telomeres are linear guanine-rich DNA structures at the ends of chromosomes. The length of telomeric DNA is actively regulated by a number of mechanisms in highly proliferative cells such as germ cells, cancer cells, and pluripotent stem cells. Telomeric DNA is synthesized by way of the ribonucleoprotein called telomerase containing a reverse transcriptase (TERT) subunit and RNA component (TERC). TERT is highly conserved across species and ubiquitously present in their respective pluripotent cells. Recent studies have uncovered intricate associations between telomeres and the self-renewal and differentiation properties of pluripotent stem cells. Interestingly, the past decade's work indicates that the TERT subunit also has the capacity to modulate mitochondrial function, to remodel chromatin structure, and to participate in key signaling pathways such as the Wnt/β-catenin pathway. Many of these non-canonical functions do not require TERT's catalytic activity, which hints at possible functions for the extensive number of alternatively spliced TERT isoforms that are highly expressed in pluripotent stem cells. In this review, some of the established and potential routes of pluripotency induction and maintenance are highlighted from the perspectives of telomere maintenance, known TERT isoform functions and their complex regulation.
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Affiliation(s)
- Jonathan H Teichroeb
- a Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry , The University of Western Ontario , London , Ontario , Canada
| | - Joohwan Kim
- a Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry , The University of Western Ontario , London , Ontario , Canada
| | - Dean H Betts
- a Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry , The University of Western Ontario , London , Ontario , Canada.,b Children's Health Research Institute, Lawson Health Research Institute , London , Ontario , Canada
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20
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Safari F, Tamaddon AM, Zarghami N, Abolmali S, Akbarzadeh A. Polyelectrolyte complexes of hTERT siRNA and polyethyleneimine: Effect of degree of PEG grafting on biological and cellular activity. ARTIFICIAL CELLS NANOMEDICINE AND BIOTECHNOLOGY 2015; 44:1561-8. [DOI: 10.3109/21691401.2015.1064936] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Fatemeh Safari
- Medical Biotechnology Department, Tabriz Advanced Medical Science Faculty, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Ali M. Tamaddon
- Center for Pharmaceutical Nanotechnology and Biomaterials, Shiraz Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Nosratollah Zarghami
- Medical Biotechnology Department, Tabriz Advanced Medical Science Faculty, Tabriz University of Medical Sciences, Tabriz, Iran
| | - S. Abolmali
- Center for Pharmaceutical Nanotechnology and Biomaterials, Shiraz Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Abolfazl Akbarzadeh
- Medical Biotechnology Department, Tabriz Advanced Medical Science Faculty, Tabriz University of Medical Sciences, Tabriz, Iran
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21
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Oncogenic fusion protein EWS-FLI1 is a network hub that regulates alternative splicing. Proc Natl Acad Sci U S A 2015; 112:E1307-16. [PMID: 25737553 DOI: 10.1073/pnas.1500536112] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The synthesis and processing of mRNA, from transcription to translation initiation, often requires splicing of intragenic material. The final mRNA composition varies based on proteins that modulate splice site selection. EWS-FLI1 is an Ewing sarcoma (ES) oncoprotein with an interactome that we demonstrate to have multiple partners in spliceosomal complexes. We evaluate the effect of EWS-FLI1 on posttranscriptional gene regulation using both exon array and RNA-seq. Genes that potentially regulate oncogenesis, including CLK1, CASP3, PPFIBP1, and TERT, validate as alternatively spliced by EWS-FLI1. In a CLIP-seq experiment, we find that EWS-FLI1 RNA-binding motifs most frequently occur adjacent to intron-exon boundaries. EWS-FLI1 also alters splicing by directly binding to known splicing factors including DDX5, hnRNP K, and PRPF6. Reduction of EWS-FLI1 produces an isoform of γ-TERT that has increased telomerase activity compared with wild-type (WT) TERT. The small molecule YK-4-279 is an inhibitor of EWS-FLI1 oncogenic function that disrupts specific protein interactions, including helicases DDX5 and RNA helicase A (RHA) that alters RNA-splicing ratios. As such, YK-4-279 validates the splicing mechanism of EWS-FLI1, showing alternatively spliced gene patterns that significantly overlap with EWS-FLI1 reduction and WT human mesenchymal stem cells (hMSC). Exon array analysis of 75 ES patient samples shows similar isoform expression patterns to cell line models expressing EWS-FLI1, supporting the clinical relevance of our findings. These experiments establish systemic alternative splicing as an oncogenic process modulated by EWS-FLI1. EWS-FLI1 modulation of mRNA splicing may provide insight into the contribution of splicing toward oncogenesis, and, reciprocally, EWS-FLI1 interactions with splicing proteins may inform the splicing code.
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22
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Khosravi- Maharlooei M, Jaberipour M, Hosseini Tashnizi A, Attar A, Amirmoezi F, Habibagahi M. Expression Pattern of Alternative Splicing Variants of Human Telomerase Reverse Transcriptase (hTERT) in Cancer Cell Lines Was not Associated with the Origin of the Cells. INTERNATIONAL JOURNAL OF MOLECULAR AND CELLULAR MEDICINE 2015; 4:109-19. [PMID: 26261800 PMCID: PMC4499573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/14/2015] [Accepted: 03/24/2015] [Indexed: 11/03/2022]
Abstract
Telomerase and systems controlling their activity have been of great attention. There are controversies regarding the role of the alternative splicing forms of the human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. Therefore, the correlation between telomerase enzyme activity, the abundance of alternatively spliced variants of hTERT and doubling time of a series of cancer cell lines originated from hematopoietic, breast, colorectal, neural, ovarian, lung, kidney, bladder, prostate and head and neck cancers were investigated. Expression levels of four different variants of hTERT (the full length, α-deletion, β-deletion and α/β-deletion) were quantitatively measured by real time PCR. Telomerase activity was determined by the telomerase repeat amplification protocol (TRAP) while doubling time of the cells measured by plotting growth curves. Results showed high diversity in the relative proportions of hTERT transcripts while the majority of the cells expressed the full length variant as the main transcript. Telomerase activity could not be detected in all cells. Relative assessment of hTERT expression showed greater expression of the α-deleted variant in the telomerase negative cells (P= 0.04). Those cells possessed the α/β-deleted variant to a smaller extent when compared to the cells with telomerase activity. Greater association between full length spliced variant and β-variant expression was observed in cells presenting telomerase activity (P= 0.0007, r= 0.74). High degrees of variation among the studied cells regarding the pattern of hTERT expression were present. In spite that, the regulatory roles of hTERT on telomerase activity is still a potential to be utilized as targets for cancer therapies.
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Affiliation(s)
- Mohsen Khosravi- Maharlooei
- Student Research Committee, Cell and Molecular Medicine Research Group, Shiraz University of Medical Sciences, Shiraz, Iran.
| | - Mansooreh Jaberipour
- Shiraz Institute for Cancer Research, Shiraz University of Medical Sciences, Shiraz, Iran.
| | | | - Armin Attar
- Student Research Committee, Cell and Molecular Medicine Research Group, Shiraz University of Medical Sciences, Shiraz, Iran.
| | - Fatemeh Amirmoezi
- Student Research Committee, Cell and Molecular Medicine Research Group, Shiraz University of Medical Sciences, Shiraz, Iran.
| | - Mojtaba Habibagahi
- Immunotherapy Laboratory, Department of Immunology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Corresponding author: Department of Immunology, School of Medicine, Shiraz University of Medical Sciences, Zand Blvd, Shiraz, Iran. Email,
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23
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Wang N, Xu D, Sofiadis A, Höög A, Vukojević V, Bäckdahl M, Zedenius J, Larsson C. Telomerase-dependent and independent telomere maintenance and its clinical implications in medullary thyroid carcinoma. J Clin Endocrinol Metab 2014; 99:E1571-9. [PMID: 24758186 PMCID: PMC4207931 DOI: 10.1210/jc.2014-1158] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
CONTEXT Telomere maintenance via telomerase activation and the alternative lengthening of telomeres (ALT) mechanism was assessed in medullary thyroid carcinoma. SETTING AND DESIGN In total, 42 medullary thyroid carcinomas (MTC) were studied including 24 rearranged during transfection (RET)- mutated cases. Relative telomerase reverse transcriptase (TERT) expression, splice forms, and telomere length were determined by PCR-based methods, and telomerase activity by ELISA. The ALT mechanism was detected by Southern blot analysis and immunofluorescence. RESULTS TERT expression and telomerase activity were detected in 21/42 tumors (50%), and was independent of the common somatic M918T RET mutation. Mean telomere length was shorter in MTCs compared with thyroids. Telomerase activation was associated with large tumor size (P = .027), advanced clinical stage (P = .0001), and short survival (P = .0001). Full-length TERT and the α(-) and β(-)-deletion forms were revealed, and the full-length form was associated with short survival (P = .04). A subset of cases without telomerase activation showed involvement of the ALT mechanism, which was associated with a low MIB-1 proliferation index (P = .024). CONCLUSIONS Stabilization of telomeres by telomerase activation occurs in half of the MTCs and by the ALT mechanism in a subset of cases. Telomerase activation may be used as an additional prognostic marker in medullary thyroid carcinoma.
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Affiliation(s)
- Na Wang
- Department of Oncology-Pathology (N.W., A.S., A.H., C.L.), Department of Medicine, Division of Hematology (D.X.), Department of Clinical Neuroscience, Center for Molecular Medicine (V.V.), Department of Molecular Medicine and Surgery (M.B., J.Z.), Karolinska Institutet, SE-171 76 Stockholm, Sweden; Cancer Center Karolinska (N.W., A.S., A.H., C.L.), Department of Pathology-Cytology (A.H.), Department of Breast and Endocrine Surgery (M.B., J.Z.), Karolinska University Hospital, SE-171 76 Stockholm, Sweden
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24
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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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Bollmann FM. Physiological and pathological significance of human telomerase reverse transcriptase splice variants. Biochimie 2013; 95:1965-70. [DOI: 10.1016/j.biochi.2013.07.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/29/2013] [Indexed: 12/22/2022]
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Liu S, Cheng C. Alternative RNA splicing and cancer. WILEY INTERDISCIPLINARY REVIEWS. RNA 2013; 4:547-66. [PMID: 23765697 PMCID: PMC4426271 DOI: 10.1002/wrna.1178] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/10/2013] [Accepted: 05/11/2013] [Indexed: 01/04/2023]
Abstract
Alternative splicing of pre-messenger RNA (mRNA) is a fundamental mechanism by which a gene can give rise to multiple distinct mRNA transcripts, yielding protein isoforms with different, even opposing, functions. With the recognition that alternative splicing occurs in nearly all human genes, its relationship with cancer-associated pathways has emerged as a rapidly growing field. In this review, we summarize recent findings that have implicated the critical role of alternative splicing in cancer and discuss current understandings of the mechanisms underlying dysregulated alternative splicing in cancer cells.
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Affiliation(s)
- Sali Liu
- Department of Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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Alternatively spliced telomerase reverse transcriptase variants lacking telomerase activity stimulate cell proliferation. Mol Cell Biol 2012; 32:4283-96. [PMID: 22907755 DOI: 10.1128/mcb.00550-12] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Eight human and six chicken novel alternatively spliced (AS) variants of telomerase reverse transcriptase (TERT) were identified, including a human variant (Δ4-13) containing an in-frame deletion which removed exons 4 through 13, encoding the catalytic domain of telomerase. This variant was expressed in telomerase-negative normal cells and tissues as well as in transformed telomerase-positive cell lines and cells which employ an alternative method to maintain telomere length. The overexpression of the Δ4-13 variant significantly elevated the proliferation rates of several cell types without enhancing telomerase activity, while decreasing the endogenous expression of this variant by use of small interfering RNA (siRNA) technology reduced cell proliferation. The expression of the Δ4-13 variant stimulated Wnt signaling. In chicken cells, AS TERT variants containing internal deletions or insertions that eliminated or reduced telomerase activity also enhanced cell proliferation. This is the first report that naturally occurring AS TERT variants which lack telomerase activity stimulate cell proliferation.
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Liu Y, Wu BQ, Zhong HH, Tian XX, Fang WG. Quantification of alternative splicing variants of human telomerase reverse transcriptase and correlations with telomerase activity in lung cancer. PLoS One 2012; 7:e38868. [PMID: 22723897 PMCID: PMC3377688 DOI: 10.1371/journal.pone.0038868] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Accepted: 05/15/2012] [Indexed: 01/24/2023] Open
Abstract
Telomerase plays important roles in the development and progression of malignant tumors, and its activity is primarily determined by transcriptional regulation of human telomerase reverse transcriptase (hTERT). Several mRNA alternative splicing variants (ASVs) for hTERT have been identified, but it remains unclear whether telomerase activity is directly associated with hTERT splicing transcripts. In this study, we developed novel real-time PCR protocols using molecular beacons and applied to lung carcinoma cell lines and cancerous tissues for quantification of telomerase activity and three essential hTERT deletion transcripts respectively. The results showed that lung carcinoma cell lines consistently demonstrated telomerase activity (14.22–31.43 TPG units per 100 cells) and various hTERT alternative splicing transcripts. For 165 lung cancer cases, telomerase activity showed significant correlation with tumor differentiation (poorly->moderately->well-differentiated, P<0.01) and with histotypes (combined small cell and squamous cell carcinoma>squamous cell carcinoma>adenosquamous carcinoma>adenocarcinoma, P<0.05). Although the overall hTERT transcripts were detected in all the samples, they were not associated with telomerase activity (r = 0.092, P = 0.24). Telomerase activity was significantly correlated with the transcriptional constituent ratio of α-deletion (r = -0.267, P = 0.026), β-deletion (r = -0.693, P = 0.0001) and γ-deletion (r = –0.614, P = 0.001). The positive rate and average constituent ratio of β-deletion transcripts (92.12%, 0.23) were higher than those of α-deletion (41.82%, 0.12) or γ-deletion (16.36%, 0.18) transcripts. The combined small-cell and squamous cell carcinomas expressed less deletion transcripts, especially β-deletion, than other histotypes, which might explain their higher telomerase activity. In conclusion, the molecular beacon-based real-time PCR protocols are rapid, sensitive and specific methods to quantify telomerase activity and hTERT ASVs. Telomerase activity may serve as a reliable and effective molecular marker to assist the evaluation of histological subtype and differentiation of lung carcinomas. Further studies on hTERT deletion splicing transcripts, rather than the overall hTERT transcripts, may improve our understanding of telomerase regulation.
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Affiliation(s)
- Yan Liu
- Department of Pathology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Bing-quan Wu
- Department of Pathology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Hao-hao Zhong
- Department of Pathology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Xin-xia Tian
- Department of Pathology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
- * E-mail: (W-gF); (X-xT)
| | - Wei-gang Fang
- Department of Pathology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
- * E-mail: (W-gF); (X-xT)
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Hrdličková R, Nehyba J, Lim SL, Grützner F, Bose HR. Insights into the evolution of mammalian telomerase: platypus TERT shares similarities with genes of birds and other reptiles and localizes on sex chromosomes. BMC Genomics 2012; 13:216. [PMID: 22655747 PMCID: PMC3546421 DOI: 10.1186/1471-2164-13-216] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 05/04/2012] [Indexed: 01/05/2023] Open
Abstract
Background The TERT gene encodes the catalytic subunit of the telomerase complex and is responsible for maintaining telomere length. Vertebrate telomerase has been studied in eutherian mammals, fish, and the chicken, but less attention has been paid to other vertebrates. The platypus occupies an important evolutionary position, providing unique insight into the evolution of mammalian genes. We report the cloning of a platypus TERT (OanTERT) ortholog, and provide a comparison with genes of other vertebrates. Results The OanTERT encodes a protein with a high sequence similarity to marsupial TERT and avian TERT. Like the TERT of sauropsids and marsupials, as well as that of sharks and echinoderms, OanTERT contains extended variable linkers in the N-terminal region suggesting that they were present already in basal vertebrates and lost independently in ray-finned fish and eutherian mammals. Several alternatively spliced OanTERT variants structurally similar to avian TERT variants were identified. Telomerase activity is expressed in all platypus tissues like that of cold-blooded animals and murine rodents. OanTERT was localized on pseudoautosomal regions of sex chromosomes X3/Y2, expanding the homology between human chromosome 5 and platypus sex chromosomes. Synteny analysis suggests that TERT co-localized with sex-linked genes in the last common mammalian ancestor. Interestingly, female platypuses express higher levels of telomerase in heart and liver tissues than do males. Conclusions OanTERT shares many features with TERT of the reptilian outgroup, suggesting that OanTERT represents the ancestral mammalian TERT. Features specific to TERT of eutherian mammals have, therefore, evolved more recently after the divergence of monotremes.
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Affiliation(s)
- Radmila Hrdličková
- Section of Molecular Genetics and Microbiology, School of Biological Science, University of Texas at Austin, 78712-1095, USA
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Rubtsova M, Vasilkova D, Malyavko A, Naraikina Y, Zvereva M, Dontsova O. Telomere lengthening and other functions of telomerase. Acta Naturae 2012; 4:44-61. [PMID: 22872811 PMCID: PMC3408703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Telomerase is an enzyme that maintains the length of the telomere. The telomere length specifies the number of divisions a cell can undergo before it finally dies (i.e. the proliferative potential of cells). For example, telomerase is activated in embryonic cell lines and the telomere length is maintained at a constant level; therefore, these cells have an unlimited fission potential. Stem cells are characterized by a lower telomerase activity, which enables only partial compensation for the shortening of telomeres. Somatic cells are usually characterized by the absence of telomerase activity. Telomere shortening leads to the attainment of the Hayflick limit, the transition of cells to a state of senescence. The cells subsequently enter a state of crisis, accompanied by massive cell death. The surviving cells become cancer cells, which are capable both of dividing indefinitely and maintaining telomere length (usually with the aid of telomerase). Telomerase is a reverse transcriptase. It consists of two major components: telomerase RNA (TER) and reverse transcriptase (TERT). TER is a non-coding RNA, and it contains the region which serves as a template for telomere synthesis. An increasing number of articles focussing on the alternative functions of telomerase components have recently started appearing. The present review summarizes data on the structure, biogenesis, and functions of telomerase.
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Affiliation(s)
- M.P. Rubtsova
- Lomonosov Moscow State University, Chemistry Department
- Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State
University
| | | | - A.N. Malyavko
- Lomonosov Moscow State University, Chemistry Department
| | - Yu.V. Naraikina
- Lomonosov Moscow State University, Faculty of Bioengineering and
Bioinformatics
| | - M.I. Zvereva
- Lomonosov Moscow State University, Chemistry Department
- Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State
University
| | - O.A. Dontsova
- Lomonosov Moscow State University, Chemistry Department
- Belozersky Institute of Physicochemical Biology, Lomonosov Moscow State
University
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Wang Y, Meeker AK, Kowalski J, Tsai HL, Somervell H, Heaphy C, Sangenario LE, Prasad N, Westra WH, Zeiger MA, Umbricht CB. Telomere length is related to alternative splice patterns of telomerase in thyroid tumors. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 179:1415-24. [PMID: 21763260 DOI: 10.1016/j.ajpath.2011.05.056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 04/19/2011] [Accepted: 05/11/2011] [Indexed: 01/02/2023]
Abstract
Telomere dysfunction and aberrant telomerase expression play important roles in tumorigenesis. In thyroid tumors, three possibly inhibitory splice variants of the active full-length isoform of human telomerase reverse transcriptase (hTERT) may be expressed. These variants might regulate telomerase activity and telomere length because it is the fraction of the full-length isoform, rather than the total transcript level, that correlates with enzymatic activity. Telomerase reactivation may be critical in the early stages of tumorigenesis, when progressive telomere shortening may be limiting cell viability. The aim of this study was to investigate the relationship between telomere length and hTERT splice variant expression patterns in benign and well-differentiated malignant thyroid tumors. Telomere lengths of 61 thyroid tumors were examined by fluorescence in situ hybridization, comparing tumors with adjacent normal thyroid tissue on the same slide. Expression patterns of hTERT splice variants were evaluated by quantitative and nested RT-PCR. Telomere length was inversely correlated with percentage of full-length hTERT expression rather than with total hTERT expression levels. Short telomeres and high fractions of full-length hTERT transcripts were associated with follicular and papillary thyroid carcinomas, whereas long telomeres and low levels of full-length hTERT were associated with benign thyroid nodules. Intermediate levels of full-length hTERT and telomere length were found in follicular variant of papillary thyroid carcinomas and follicular adenomas.
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Affiliation(s)
- Yongchun Wang
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
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33
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Petrenko A, Korolenkova L, Skvortsov D, Fedorova M, Skoblov M, Baranova A, Zvereva M, Rubtsova M, Kisseljov F. Cervical intraepithelial neoplasia: Telomerase activity and splice pattern of hTERT mRNA. Biochimie 2010; 92:1827-31. [DOI: 10.1016/j.biochi.2010.07.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Accepted: 07/27/2010] [Indexed: 11/26/2022]
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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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35
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Strati A, Papoutsi Z, Lianidou E, Moutsatsou P. Effect of ellagic acid on the expression of human telomerase reverse transcriptase (hTERT) alpha+beta+ transcript in estrogen receptor-positive MCF-7 breast cancer cells. Clin Biochem 2009; 42:1358-62. [PMID: 19501078 DOI: 10.1016/j.clinbiochem.2009.05.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 05/25/2009] [Accepted: 05/29/2009] [Indexed: 11/24/2022]
Abstract
OBJECTIVES To evaluate the potential of ellagic acid to inhibit the expression of human telomerase reverse transcriptase (hTERT) alpha+beta+ splice variant in MCF-7 breast cancer cells. DESIGN AND METHODS MCF-7 cells were incubated with ellagic acid (10(-)(9) M-10(-5) M) in the absence and in the presence of 17beta-estradiol (10(-8) M), a known inducer of hTERT transcription, and hTERT alpha+beta+ mRNA expression was quantified by real-time RT-PCR. 17beta-estradiol and ICI182780, a known estrogen antagonist, served as positive and negative controls respectively. RESULTS Ellagic acid, when alone, increased hTERT alpha+beta+ mRNA while its coexistence with 17beta-estradiol reduced significantly the 17beta-estradiol-induced increase in hTERT alpha+beta+ mRNA, implicating thus both its estrogenic and anti-estrogenic effects in breast cancer cells. CONCLUSIONS The potential of ellagic acid to down-regulate the 17beta-estradiol-induced hTERT alpha+beta+ mRNA expression may be a mechanism via which ellagic acid exerts, at least in part, its chemopreventive effects in breast cancer.
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Affiliation(s)
- Areti Strati
- Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, 15771, Greece
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Skvortzov DA, Rubzova MP, Zvereva ME, Kiselev FL, Donzova OA. The regulation of telomerase in oncogenesis. Acta Naturae 2009; 1:51-67. [PMID: 22649586 PMCID: PMC3347505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The influence that the expression of the human (glial-derived neurotrophic factor (GDNF)) neurotrophic factor has on the morphology and proliferative activity of embryonic stem cells (SC) of a mouse with R1 lineage, as well as their ability to form embroid bodies (EB), has been studied. Before that, using a PCR (polymerase chain reaction) coupled with reverse transcription, it was shown that, in this very lineage of the embryonic SC, the expression of the receptors' genes is being fulfilled for the neurotropfic RET and GFRα1 glia factor. The mouse's embryonic SC lineage has been obtained, transfected by the human GDNF gene, and has been fused with the "green" fluorescent protein (GFP) gene. The presence of the expression of the human GDNF gene in the cells was shown by northern hybridization and the synthesis of its albuminous product by immunocitochemical coloration with the use of specific antibodies. The reliable slowing-down of the embriod-body formation by the embryonic SC transfected by the GDNF gene has been shown. No significant influence of the expression of the GDNF gene on the morphology and the proliferative activity of the transfected embryonic SCs has been found when compared with the control ones.
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Affiliation(s)
- D A Skvortzov
- Department of Chemistry, Moscow State University, 119992 Moscow
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37
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Deville L, Hillion J, Ségal-Bendirdjian E. Telomerase regulation in hematological cancers: a matter of stemness? Biochim Biophys Acta Mol Basis Dis 2009; 1792:229-39. [PMID: 19419697 DOI: 10.1016/j.bbadis.2009.01.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 01/30/2009] [Accepted: 01/30/2009] [Indexed: 01/02/2023]
Abstract
Human telomerase is a nuclear ribonucleoprotein enzyme complex that catalyzes the synthesis and extension of telomeric DNA. This enzyme is highly expressed and active in most malignant tumors while it is usually not or transiently detectable in normal somatic cells, suggesting that it plays an important role in cellular immortalization and tumorigenesis. As most leukemic cells are generally telomerase-positive and have often shortened telomeres, our understanding of how telomerase is deregulated in these diseases could help to define novel therapies targeting the telomere/telomerase complex. Nonetheless, considering that normal hematopoietic stem cells and some of their progeny do express a functional telomerase, it is tempting to consider such an activity in leukemias as a sustained stemness feature and important to understand how telomere length and telomerase activity are regulated in the various forms of leukemias.
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Affiliation(s)
- Laure Deville
- INSERM UMR-S 685, Institut d'Hématologie, Hôpital Saint-Louis, 75475 Paris cedex 10, France
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Prognostic relevance of hTERT mRNA expression in ductal adenocarcinoma of the pancreas. Neoplasia 2009; 10:973-6. [PMID: 18714398 DOI: 10.1593/neo.08578] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 06/17/2008] [Accepted: 06/20/2008] [Indexed: 12/18/2022] Open
Abstract
Telomerase is thought to play an essential role in tumorigenesis and progression. Its activity is directly correlated with the expression of its catalytic subunit, human telomerase reverse transcriptase (hTERT). A correlation of transcript expression with a poor prognosis has been detected in different human malignancies. However, data on hTERT in pancreatic ductal adenocarcinoma (PDAC) are purely descriptive so far. Therefore, we evaluated the impact of hTERT expression on patients' prognosis. Human telomerase reverse transcriptase mRNA isolates from 56 human microdissected PDAC tissues were analyzed by quantitative reverse transcription-polymerase chain reaction and multivariate Cox regression hazard test. Elevated hTERT transcript levels were measured in 23 of 56 PDAC tissues, 33 patients showed no detectable transcripts. Unexpectedly, a low expression of hTERT mRNA levels was associated with a worse prognosis for overall survival (relative risk = 5.33; P = .013) when compared to high levels, whereas undetectable expression showed an intermediate risk of tumor-related death. These data challenge previous findings outlining hTERT's negative impact on overall survival. The risk pattern obtained in PDAC suggests a more complex regulation of hTERT.
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Quantification of hTERT splice variants in melanoma by SYBR green real-time polymerase chain reaction indicates a negative regulatory role for the beta deletion variant. Neoplasia 2008; 10:1131-7. [PMID: 18813352 DOI: 10.1593/neo.08644] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 07/18/2008] [Accepted: 07/18/2008] [Indexed: 11/18/2022] Open
Abstract
Telomerase activity is primarily determined by transcriptional regulation of the catalytic subunit, human telomerase reverse transcriptase (hTERT). Several mRNA splice variants for hTERT have been identified, but it is not clear if telomerase activity is determined by the absolute or relative levels of full-length (functional) and variant hTERT transcripts. We have developed an SYBR green-based reverse transcription-quantitative polymerase chain reaction assay for the enumeration of the four common hTERT mRNA variants and correlated these with telomerase activity and telomere length in 24 human melanoma cell lines. All except five of the lines expressed four hTERT transcripts, with an overall significant level of co-occurrence between absolute mRNA levels of full-length alpha+/beta+ hTERT and the three splice variants alpha-/beta+, alpha+/beta-, and alpha-/beta-. On average, alpha+/beta+ made up the majority (48.1%) of transcripts, followed by alpha+/beta- (44.6%), alpha-/beta- (4.4%), and alpha-/beta+ (2.9%). Telomerase activity ranged from 1 to 247 relative telomerase activity and correlated most strongly with the absolute amount of alpha+/beta+ (R = 0.791, P = .000004) and the relative amount of alpha+/beta- (R = -0.465, P = .022). This study shows that telomerase activity in melanoma cells is best determined by the absolute expression of full-length hTERT mRNA and indicates a role for the hTERT beta deletion variant in the negative regulation of enzyme activity.
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40
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Canis familiaris telomerase reverse transcriptase undergoes alternative splicing. Mamm Genome 2008; 19:647-53. [PMID: 18836773 DOI: 10.1007/s00335-008-9144-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Accepted: 09/05/2008] [Indexed: 10/21/2022]
Abstract
The enzyme telomerase is essential for cell proliferation and tumorigenesis. Telomerase reverse transcriptase (TERT) represents the catalytic subunit of the enzyme. In humans, TERT expression is regulated by several different mechanisms, including alternative splicing. Canis familiaris TERT (dogTERT) has been shown to have a high level of sequence similarity with human TERT, indicating that the dog may represent a suitable animal model for telomerase studies. In the present report we sought to investigate whether dogTERT undergoes alternative splicing. During the analysis of canine mammary tissues (both tumor and paired adjacent to the tumor normal tissues) for dogTERT expression by RT-PCR, we identified eight samples-one tumor and seven adjacent normal-which gave PCR products of unexpected sizes. DNA sequencing revealed two insertions (175 and 28 bp long) and two deletions (17 and 32 bp long), which were encountered in different combinations and gave rise to five different transcripts. The generation of all variants could be explained by the employment of alternative splicing sites within dogTERT genomic sequences. The 175-bp and 28-bp insertions, identified between exons 7 and 8 and between 8 and 9, respectively, constituted unspliced sequences of introns 7 and 8, respectively. Both deletions originated from exon 8 sequence removals due to alternative splicing. All five variants encoded truncated proteins, which lacked essential motifs for reverse transcription and might have thus lost their ability to compose active telomerase enzymes. This is the first identification of alternative splicing events within dogTERT. The results presented here may provide the basis for more thorough studies on the regulation of telomerase activity in canine normal and cancer cells.
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Wang Y, Kowalski J, Tsai HL, Marik R, Prasad N, Somervell H, Lo PK, Sangenario LE, Dyrskjot L, Orntoft TF, Westra WH, Meeker AK, Eshleman JR, Umbricht CB, Zeiger MA. Differentiating alternative splice variant patterns of human telomerase reverse transcriptase in thyroid neoplasms. Thyroid 2008; 18:1055-63. [PMID: 18816183 PMCID: PMC2857449 DOI: 10.1089/thy.2008.0101] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Although fine-needle aspiration (FNA) biopsy of thyroid nodules is very sensitive in detecting thyroid malignancy, it remains ambiguous in 20-30% of cases. Current biomarkers for thyroid cancer lack either the sensitivity or specificity to substantially address this clinical problem. The aim of this study was to investigate the gene expression patterns of human telomerase reverse transcriptase (hTERT) alternative splice variants in benign and malignant thyroid tumors in an attempt to find a more reliable biomarker in the differential diagnosis of thyroid nodules. METHODS One hundred and thirty-three thyroid tumors from eight histopathological tumor types were collected from patients undergoing thyroid surgery at Johns Hopkins Hospital. Gene expression patterns of hTERT alternative splice variants were investigated in the tumors by nested reverse transcriptase-PCR. Telomerase enzyme activity was evaluated in a subset of 16 samples associated with the different hTERT patterns. Association of c-myc expression and hTERT patterns was also examined. RESULTS Malignant thyroid tumors exhibited a greater proportion of the active full-length hTERT transcript (0.57 +/- 0.15) than inactive splice variants, alpha(-) (0.13 +/- 0.02), or beta(-)/alpha(-)beta(-) deletion transcripts (0.30 +/- 0.11; p < 0.001). The opposite was observed in benign tumors, which exhibited greater proportions of beta(-)/alpha(-)beta(-) deletion transcripts (0.64 +/- 0.08) than either the full-length (0.19 +/- 0.06) or alpha(-) deletion transcripts (0.17 +/- 0.02; p < 0.001). Similar results were observed among a diagnostically challenging subset of 50 thyroid tumors that were suspicious for malignancy on FNA. Further, increased telomerase enzymatic activity was only associated with expression of the full-length hTERT isoform. In contrast, c-myc expression, which has been implicated in hTERT regulation, correlated with overall hTERT transcription without specificity for expression of the full-length isoform. CONCLUSIONS These differences in gene expression patterns of hTERT alternative splice variants may provide a useful adjunct to FNA diagnosis of suspicious thyroid tumors.
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Affiliation(s)
- Yongchun Wang
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Jeanne Kowalski
- Division of Oncology Biostatistics, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Hua-Ling Tsai
- Division of Oncology Biostatistics, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Radharani Marik
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Nijaguna Prasad
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Helina Somervell
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Pang-Kuo Lo
- Department of Oncology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Lauren E. Sangenario
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Lars Dyrskjot
- Molecular Diagnostic Laboratory, Department of Clinical Biochemistry, Aarhus University Hospital, Skejby, Denmark
| | - Torben F. Orntoft
- Molecular Diagnostic Laboratory, Department of Clinical Biochemistry, Aarhus University Hospital, Skejby, Denmark
| | - William H. Westra
- Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Alan K. Meeker
- Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - James R. Eshleman
- Department of Oncology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Christopher B. Umbricht
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Oncology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
| | - Martha A. Zeiger
- Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
- Department of Oncology, The Johns Hopkins Medical Institutions, Baltimore, Maryland
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Katyal S, Gao Z, Liu RZ, Godbout R. Evolutionary conservation of alternative splicing in chicken. Cytogenet Genome Res 2007; 117:146-57. [PMID: 17675855 PMCID: PMC3726401 DOI: 10.1159/000103175] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 09/13/2006] [Indexed: 12/21/2022] Open
Abstract
Alternative splicing represents a source of great diversity for regulating protein expression and function. It has been estimated that one-third to two-thirds of mammalian genes are alternatively spliced. With the sequencing of the chicken genome and analysis of transcripts expressed in chicken tissues, we are now in a position to address evolutionary conservation of alternative splicing events in chicken and mammals. Here, we compare chicken and mammalian transcript sequences of 41 alternatively-spliced genes and 50 frequently accessed genes. Our results support a high frequency of splicing events in chicken, similar to that observed in mammals.
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Affiliation(s)
- S Katyal
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada
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43
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Hrdlicková R, Nehyba J, Liss AS, Bose HR. Mechanism of telomerase activation by v-Rel and its contribution to transformation. J Virol 2007; 80:281-95. [PMID: 16352553 PMCID: PMC1317554 DOI: 10.1128/jvi.80.1.281-295.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Telomerase is activated during the transformation of lymphoid cells and fibroblasts by v-Rel, the oncogenic member of the Rel/NF-kappaB family of transcription factors. v-Rel-transformed cell lines have longer telomeres than untransformed chicken lymphoid cells and have high levels of telomerase activity. v-Rel-mediated activation of telomerase is achieved by multiple mechanisms. The expression of the gene encoding the catalytic subunit of telomerase (TERT) was directly upregulated by v-Rel. Moreover, the expression of v-Rel altered the ratio of alternatively spliced and full-length TERT transcripts in favor of the full-length forms. The activation of telomerase by v-Rel in lymphocytes was also accompanied by inactivation of nuclear inhibitors. The inhibition of telomerase activity in v-Rel-transformed cell lines led to apoptosis within 24 h. The expression of v-Rel in a macrophage cell line resulted in elevated levels of reactive oxygen species (ROS), increased telomerase activity, and increased sensitivity to telomerase inhibitors. In contrast, the ectopic expression of TERT decreased the extent of apoptosis induced by ROS. The activation of telomerase by v-Rel may, therefore, partially protect the transformed cells from apoptosis induced by ROS.
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Affiliation(s)
- Radmila Hrdlicková
- Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX 78712-1095, USA
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44
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Mavrogiannou E, Strati A, Stathopoulou A, Tsaroucha EG, Kaklamanis L, Lianidou ES. Real-Time RT-PCR Quantification of Human Telomerase Reverse Transcriptase Splice Variants in Tumor Cell Lines and Non–Small Cell Lung Cancer. Clin Chem 2007; 53:53-61. [PMID: 17130181 DOI: 10.1373/clinchem.2006.073015] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractBackground: We developed and validated a real-time reverse transcription (RT)–PCR for the quantification of 4 individual human telomerase reverse transcriptase (TERT) splice variants (α+β+, α−β+, α+β−, α−β−) in tumor cell lines and non–small cell lung cancer (NSCLC).Methods: We used in silico designed primers and a common TaqMan probe for highly specific amplification of each TERT splice variant, PCR transcript–specific DNA external standards as calibrators, and the MCF-7 cell line for the development and validation of the method. We then quantified TERT splice variants in 6 tumor cell lines and telomerase activity and TERT splice variant expression in cancerous and paired noncancerous tissue samples from 28 NSCLC patients.Results: In most tumor cell lines, we observed little variation in the proportion of TERT splice variants. The α+β− splice variant showed the highest expression and α−β+ and α−β− the lowest. Quantification of the 4 TERT splice variants in NSCLC and surrounding nonneoplastic tissues showed the highest expression percentage for the α+β− variant in both NSCLC and adjacent nonneoplastic tissue samples, followed by α+β+, with the α−β+ and α−β− splice variants having the lowest expression. In the NSCLC tumors, the α+β+ variant had higher expression than other splice variants, and its expression correlated with telomerase activity, overall survival, and disease-free survival.Conclusions: Real-time RT-PCR quantification is a specific, sensitive, and rapid method that can elucidate the biological role of TERT splice variants in tumor development and progression. Our results suggest that the expression of the TERT α+β+ splice variant may be an independent negative prognostic factor for NSCLC patients.
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Affiliation(s)
- Eleni Mavrogiannou
- Laboratory of Analytical Chemistry, University of Athens, Athens, Greece
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45
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Kotoula V, Bobos M, Kostopoulos I, Kaloutsi V, Koletsa T, Karayannopoulou G, Papadimitriou CS. In situ detection of hTERT variants in anaplastic large cell lymphoma. Leuk Lymphoma 2006; 47:1639-50. [PMID: 16966278 DOI: 10.1080/10428190600653317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The expression of hTERT and its isoforms is difficult to assess in lymphoma tissues with the commonly used reverse transcription-polymerase chain reaction (RT-PCR) methods, because non-neoplastic lymphocytes expressing hTERT are always present in the lymphomatous infiltrates. The present study aimed to investigate hTERT mRNA variants in anaplastic large cell lymphoma (ALCL) (n = 38) with in situ hybridization (ISH), along with the immunodetection of hTERT protein. Probes for the identification of mRNAs containing (Bplus) and lacking (Bdel) exons 7 and 8 of the hTERT mRNA were used. Normal lymphocyte populations equally expressed both Bplus and Bdel mRNAs. Although all ALCL examined were found positive for hTERT expression with RT-PCR, hTERT mRNAs were identified in 68% of these tumors with ISH, with a higher incidence in the group bearing ALK translocations (10 out of 11; 90.9%) compared to the ALK negative group (17 out of 27; 59.3%) (PPearson's = 0.002). The same results were obtained with immunohistochemistry for hTERT. In approximately 50% of cases, only Bplus positive cells were identified, again with a higher incidence in the ALK positive compared to the ALK negative group (PPearson's = 0.016). In conclusion, ISH for hTERT mRNAs appears to be a valuable tool for the investigation of hTERT expression in lymphomas. Aberrations in hTERT variant profiles and a decline in the expression of the B deleted isoform may be associated with the pathogenesis of ALCL, especially with respect to ALK positive tumors.
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Affiliation(s)
- Vassiliki Kotoula
- Department of Pathology, School of Medicine, Aristotle University, Thessaloniki, Greece
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46
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Abstract
Telomeres are terminal, repeated deoxyribonucleic acid (DNA) sequences that stabilize and protect the ends of the chromosomes. Mounting evidence indicates that by initiating chromosomal instability, short dysfunctional telomeres may be involved in prostate carcinogenesis. Although the exact cause of the telomere shortening observed in prostate cancer remains a mystery, telomere loss is known to occur during cell division and oxidative DNA damage, 2 byproducts of chronic inflammation, which is a common histologic finding in the prostate. In addition to prostate cancer causation, telomeres may also play a role in disease progression, and there are indications that tumor telomere content may prove useful as a prognostic marker. Once established, prostate cancer cells almost invariably activate the telomeric DNA polymerase enzyme telomerase, the detection of which may prove useful for diagnostic purposes. Interestingly, telomerase activity is suppressed in prostate cancer cells after androgen withdrawal, raising the possibility that androgen ablative therapies may re-instigate telomere loss, and consequent genetic instability, in surviving cancer cells, thus contributing to the emergence of an androgen-independent, lethal phenotype. A more thorough understanding of telomere biology as it relates to prostate cancer should provide new opportunities for disease prevention, diagnosis, prognostication, and treatment.
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Affiliation(s)
- Alan K Meeker
- Department of Pathology, Division of Genitourinary Pathology, The Johns Hopkins Medical Institutions, Baltimore, MD 21231-1000, USA.
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47
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Sæbøe-Larssen S, Fossberg E, Gaudernack G. Characterization of novel alternative splicing sites in human telomerase reverse transcriptase (hTERT): analysis of expression and mutual correlation in mRNA isoforms from normal and tumour tissues. BMC Mol Biol 2006; 7:26. [PMID: 16939641 PMCID: PMC1560392 DOI: 10.1186/1471-2199-7-26] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 08/29/2006] [Indexed: 11/30/2022] Open
Abstract
Background Human telomerase reverse transcriptase (hTERT) is a key component for synthesis and maintenance of telomeres on chromosome ends and is required for the continued proliferation of cells. Estimation of hTERT expression therefore has broad relevance in oncology and stem cell research. Several splicing variants of hTERT have been described whose regulated expression contributes to the control of telomerase activity. Knowledge of the different hTERT mRNA isoforms and the ability to distinguish between them is an important issue when evaluating telomerase expression. Results By establishing cDNA-clone panels from lung and colon tissues, we could map hTERT clones individually for differences in DNA sequence. This made possible the identification of novel alternatively spliced sites as well as analysis of their frequency and mutual correlation in mRNA isoforms. Ten different alternatively spliced sites were detected, of which six were novel sites resulting from alternative splicing of intron 2 or 14. The majority of hTERT cDNA clones from normal and tumour lung and colon tissues encoded truncated proteins ending close after exon 2 or 6. Conclusion The increased complexity in telomerase expression revealed here has implications for our understanding of telomerase regulation and for the choice of suitable methods for addressing hTERT expression.
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Affiliation(s)
- Stein Sæbøe-Larssen
- Section for Immunotherapy, Department of Immunology, The Norwegian Radium Hospital, Cancer Research Institute, University of Oslo, N-0310 Oslo, Norway
| | - Ellen Fossberg
- Section for Immunotherapy, Department of Immunology, The Norwegian Radium Hospital, Cancer Research Institute, University of Oslo, N-0310 Oslo, Norway
| | - Gustav Gaudernack
- Section for Immunotherapy, Department of Immunology, The Norwegian Radium Hospital, Cancer Research Institute, University of Oslo, N-0310 Oslo, Norway
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Chang H, Delany ME. Complicated RNA splicing of chicken telomerase reverse transcriptase revealed by profiling cells both positive and negative for telomerase activity. Gene 2006; 379:33-9. [PMID: 16806743 DOI: 10.1016/j.gene.2006.04.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 04/10/2006] [Accepted: 04/12/2006] [Indexed: 11/17/2022]
Abstract
Telomerase reverse transcriptase (TERT) is an essential component of the telomerase ribonucleoprotein complex which maintains telomeres. The objective of this study was to investigate chicken TERT (cTERT) alternative RNA splicing profiles of samples varying for telomerase activity and immortalization parameters. These included systems both in vivo (gastrula embryo, embryo and adult liver) and in vitro (chicken embryo fibroblasts (CEFs) and DT40 cells). Nineteen cTERT variants were discovered, which were generated through exon skipping, intron retention, and alternative usage of splice donor and acceptor sites. Three variants were predicted to introduce in-frame mutations, whereas the others were predicted to have premature termination codons. The number of cTERT variants detected ranged from 10 in adult liver to 13 in CEFs. One variant (V4) was found in all samples and was predicted to generate a truncated protein lacking telomerase catalytic activity. Interestingly, the standard TERT expected from the full-length transcript was expressed not only in telomerase-positive, but also in telomerase-negative samples. The complicated expression profiles of cTERT in various cell systems suggest that sophisticated regulatory pathways are involved in cTERT pre-mRNA editing. Further, these results support the body of increasing evidence that alternative splicing of TERT, both in human and chicken, contributes to telomerase activity regulation.
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Affiliation(s)
- Hong Chang
- Department of Animal Science, University of California, Davis, Davis, CA 95616, USA
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Rehemtulla A, Ross BD. A review of the past, present, and future directions of neoplasia. Neoplasia 2006; 7:1039-46. [PMID: 16354585 PMCID: PMC1501177 DOI: 10.1593/neo.05793] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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50
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Dome JS, Bockhold CA, Li SM, Baker SD, Green DM, Perlman EJ, Hill DA, Breslow NE. High Telomerase RNA Expression Level Is an Adverse Prognostic Factor for Favorable-Histology Wilms' Tumor. J Clin Oncol 2005; 23:9138-45. [PMID: 16172460 DOI: 10.1200/jco.2005.00.562] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Purpose A primary objective of the fifth National Wilms Tumor Study (NWTS-5) was to identify prognostic indicators for patients with favorable-histology Wilms' tumor. The prognostic significance of telomerase expression level in primary tumor samples was assessed. Patients and Methods A case-cohort study was conducted involving 291 NWTS-5 registrants. Telomerase activity was measured using the telomeric repeat amplification protocol (TRAP). Expression levels of TERT mRNA (encoding the telomerase catalytic component) and TERC/hTR (the telomerase RNA template) were measured using quantitative real-time polymerase chain reaction. Results After excluding samples because of lack of viable tumor, RNA degradation, or insufficient clinical information, 244 patients remained for the final analysis (96 with relapse and 148 without relapse). Univariate analysis revealed a positive correlation between relative risk (RR) of relapse and levels of TERT mRNA and TERC expression. For each doubling in TERT mRNA and TERC level, the RR increased by a factor of 1.16 (95% CI, 1.04 to 1.29; P = .01) and 1.35 (95% CI, 1.11 to 1.64; P = .003), respectively. The one third of patients whose tumors had the highest TERC expression level had an RR of 2.06 (95% CI, 1.14 to 3.70; P = .02) compared with patients with the lowest level. TERC expression level remained a significant prognostic indicator in a multivariate analysis adjusting for TERT mRNA, tumor stage, and patient age. TRAP level did not correlate with RR of relapse. Telomerase expression levels were not predictive of overall survival. Conclusion Telomerase RNA expression level may provide a clinically useful adjunct to the current risk classification schema for favorable-histology Wilms' tumor.
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Affiliation(s)
- Jeffrey S Dome
- Department of Hematology/Oncology, St Jude Children's Research Hospital, Memphis, TN 38105, USA.
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