1
|
Jahan J, Joshi S, Oca IMD, Toelle A, Lopez-Yang C, Chacon CV, Beyer AM, Garcia CA, Jarajapu YP. The role of telomerase reverse transcriptase in the mitochondrial protective functions of Angiotensin-(1-7) in diabetic CD34 + cells. Biochem Pharmacol 2024; 222:116109. [PMID: 38458330 PMCID: PMC11007670 DOI: 10.1016/j.bcp.2024.116109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 01/08/2024] [Accepted: 03/05/2024] [Indexed: 03/10/2024]
Abstract
Angiotensin (Ang)-(1-7) stimulates vasoprotective functions of diabetic (DB) CD34+ hematopoietic stem/progenitor cells partly by decreasing reactive oxygen species (ROS), increasing nitric oxide (NO) levels and decreasing TGFβ1 secretion. Telomerase reverse transcriptase (TERT) translocates to mitochondria and regulates ROS generation. Alternative splicing of TERT results in variants α-, β- and α-β-TERT, which may oppose functions of full-length (FL) TERT. This study tested if the protective functions of Ang-(1-7) or TGFβ1-silencing are mediated by mitoTERT and that diabetes decreases FL-TERT expression by inducing splicing. CD34+ cells were isolated from the peripheral blood mononuclear cells of nondiabetic (ND, n = 68) or DB (n = 74) subjects. NO and mitoROS levels were evaluated by flow cytometry. TERT splice variants and mitoDNA-lesions were characterized by qPCR. TRAP assay was used for telomerase activity. Decoy peptide was used to block mitochondrial translocation (mitoXTERT). TERT inhibitor or mitoXTERT prevented the effects of Ang-(1-7) on NO or mitoROS levels in DB-CD34+ cells. FL-TERT expression and telomerase activity were lower and mitoDNA-lesions were higher in DB cells compared to ND and were reversed by Ang-(1-7) or TGFβ1-silencing. The prevalence of TERT splice variants, with predominant β-TERT expression, was higher and the expression of FL-TERT was lower in DB cells (n = 25) compared to ND (n = 30). Ang-(1-7) or TGFβ1-silencing decreased TERT-splicing and increased FL-TERT. Blocking of β-splicing increased FL-TERT and protected mitoDNA in DB-cells. The findings suggest that diabetes induces TERT-splicing in CD34+ cells and that β-TERT splice variant largely contributes to the mitoDNA oxidative damage.
Collapse
Affiliation(s)
- Jesmin Jahan
- Department of Pharmaceutical Sciences, College of Health Professions, North Dakota State University, Fargo, ND, USA
| | - Shrinidh Joshi
- Department of Pharmaceutical Sciences, College of Health Professions, North Dakota State University, Fargo, ND, USA
| | | | - Andrew Toelle
- Department of Pharmaceutical Sciences, College of Health Professions, North Dakota State University, Fargo, ND, USA
| | | | | | - Andreas M Beyer
- Department of Medicine and Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Yagna Pr Jarajapu
- Department of Pharmaceutical Sciences, College of Health Professions, North Dakota State University, Fargo, ND, USA.
| |
Collapse
|
2
|
Kim JJ, Ahn A, Ying J, Hickman E, Ludlow AT. Exercise as a Therapy to Maintain Telomere Function and Prevent Cellular Senescence. Exerc Sport Sci Rev 2023; 51:150-160. [PMID: 37288975 PMCID: PMC10526708 DOI: 10.1249/jes.0000000000000324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Exercise transiently impacts the expression, regulation, and activity of TERT/telomerase to maintain telomeres and protect the genome from insults. By protecting the telomeres (chromosome ends) and the genome, telomerase promotes cellular survival and prevents cellular senescence. By increasing cellular resiliency, via the actions of telomerase and TERT, exercise promotes healthy aging.
Collapse
Affiliation(s)
- Jeongjin J Kim
- School of Kinesiology, University of Michigan, Ann Arbor, MI
| | | | | | | | | |
Collapse
|
3
|
Ali JH, Walter M. Combining old and new concepts in targeting telomerase for cancer therapy: transient, immediate, complete and combinatory attack (TICCA). Cancer Cell Int 2023; 23:197. [PMID: 37679807 PMCID: PMC10483736 DOI: 10.1186/s12935-023-03041-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 08/25/2023] [Indexed: 09/09/2023] Open
Abstract
Telomerase can overcome replicative senescence by elongation of telomeres but is also a specific element in most cancer cells. It is expressed more vastly than any other tumor marker. Telomerase as a tumor target inducing replicative immortality can be overcome by only one other mechanism: alternative lengthening of telomeres (ALT). This limits the probability to develop resistance to treatments. Moreover, telomerase inhibition offers some degree of specificity with a low risk of toxicity in normal cells. Nevertheless, only one telomerase antagonist reached late preclinical studies. The underlying causes, the pitfalls of telomerase-based therapies, and future chances based on recent technical advancements are summarized in this review. Based on new findings and approaches, we propose a concept how long-term survival in telomerase-based cancer therapies can be significantly improved: the TICCA (Transient Immediate Complete and Combinatory Attack) strategy.
Collapse
Affiliation(s)
- Jaber Haj Ali
- Institute of Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Institute of Clinical Chemistry and Laboratory Medicine, Universitätsmedizin Rostock, Ernst-Heydemann-Straße 6, 18057, Rostock, Germany
| | - Michael Walter
- Institute of Clinical Chemistry and Laboratory Medicine, Universitätsmedizin Rostock, Ernst-Heydemann-Straße 6, 18057, Rostock, Germany.
| |
Collapse
|
4
|
Yang R, Han Y, Guan X, Hong Y, Meng J, Ding S, Long Q, Yi W. Regulation and clinical potential of telomerase reverse transcriptase (TERT/hTERT) in breast cancer. Cell Commun Signal 2023; 21:218. [PMID: 37612721 PMCID: PMC10463831 DOI: 10.1186/s12964-023-01244-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 07/23/2023] [Indexed: 08/25/2023] Open
Abstract
Telomerase reverse transcriptase (TERT/hTERT) serves as the pivotal catalytic subunit of telomerase, a crucial enzyme responsible for telomere maintenance and human genome stability. The high activation of hTERT, observed in over 90% of tumors, plays a significant role in tumor initiation and progression. An in-depth exploration of hTERT activation mechanisms in cancer holds promise for advancing our understanding of the disease and developing more effective treatment strategies. In breast cancer, the expression of hTERT is regulated by epigenetic, transcriptional, post-translational modification mechanisms and DNA variation. Besides its canonical function in telomere maintenance, hTERT exerts non-canonical roles that contribute to disease progression through telomerase-independent mechanisms. This comprehensive review summarizes the regulatory mechanisms governing hTERT in breast cancer and elucidates the functional implications of its activation. Given the overexpression of hTERT in most breast cancer cells, the detection of hTERT and its associated molecules are potential for enhancing early screening and prognostic evaluation of breast cancer. Although still in its early stages, therapeutic approaches targeting hTERT and its regulatory molecules show promise as viable strategies for breast cancer treatment. These methods are also discussed in this paper. Video Abstract.
Collapse
Affiliation(s)
- Ruozhu Yang
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China
| | - Yi Han
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China
| | - Xinyu Guan
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China
| | - Yue Hong
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China
| | - Jiahao Meng
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China
| | - Shirong Ding
- Department of Oncology, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China.
| | - Qian Long
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China.
| | - Wenjun Yi
- Department of General Surgery, the Second Xiangya Hospital of Central South University, 139 Middle Renmin Road, Changsha, 410011, China.
| |
Collapse
|
5
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [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.
Collapse
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
| |
Collapse
|
6
|
Ropio J, Prochazkova-Carlotti M, Batista R, Pestana A, Chebly A, Ferrer J, Idrissi Y, Cappellen D, Durães C, Boaventura P, Vinagre J, Azzi-Martin L, Poglio S, Cabeçadas J, Campos MA, Beylot-Barry M, Sobrinho-Simões M, Merlio JP, Soares P, Chevret E. Spotlight on hTERT Complex Regulation in Cutaneous T-Cell Lymphomas. Genes (Basel) 2023; 14:439. [PMID: 36833366 PMCID: PMC9956048 DOI: 10.3390/genes14020439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/05/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
As a major cancer hallmark, there is a sustained interest in understanding the telomerase contribution to carcinogenesis in order to therapeutically target this enzyme. This is particularly relevant in primary cutaneous T-cell lymphomas (CTCL), a malignancy showing telomerase dysregulation with few investigative data available. In CTCL, we examined the mechanisms involved in telomerase transcriptional activation and activity regulation. We analyzed 94 CTCL patients from a Franco-Portuguese cohort, as well as 8 cell lines, in comparison to 101 healthy controls. Our results showed that not only polymorphisms (SNPs) located at the promoter of human telomerase reverse transcriptase (hTERT) gene (rs2735940 and rs2853672) but also an SNP located within the coding region (rs2853676) could influence CTCL occurrence. Furthermore, our results sustained that the post-transcriptional regulation of hTERT contributes to CTCL lymphomagenesis. Indeed, CTCL cells present a different pattern of hTERT spliced transcripts distribution from the controls, mostly marked by an increase in the hTERT β+ variants proportion. This increase seems to be associated with CTCL development and progression. Through hTERT splicing transcriptome modulation with shRNAs, we observed that the decrease in the α-β+ transcript induced a decrease in the cell proliferation and tumorigenic capacities of T-MF cells in vitro. Taken together, our data highlight the major role of post-transcriptional mechanisms regulating telomerase non canonical functions in CTCL and suggest a new potential role for the α-β+ hTERT transcript variant.
Collapse
Affiliation(s)
- Joana Ropio
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- Institute of Biomedical Sciences of Abel Salazar, Porto University, 4050-313 Porto, Portugal
- Faculty of Veterinary Medicine, Lusófona University, 1749-024 Lisbon, Portugal
| | | | - Rui Batista
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
- Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
| | - Ana Pestana
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
- Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
| | - Alain Chebly
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- Medical Genetics Unit, Faculty of Medicine, Saint Joseph University, Beirut 1104 2020, Lebanon
- Higher Institute of Public Health, Saint Joseph University, Beirut 1104 2020, Lebanon
| | - Jacky Ferrer
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
| | - Yamina Idrissi
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
| | - David Cappellen
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- Tumor Bank and Tumor Biology Laboratory, Bordeaux University Hospital, 33075 Bordeaux, France
| | - Cecília Durães
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
| | - Paula Boaventura
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
| | - João Vinagre
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
| | - Lamia Azzi-Martin
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- UFR des Sciences Médicales, Bordeaux University, 33076 Bordeaux, France
| | - Sandrine Poglio
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
| | - José Cabeçadas
- Dermatology Departement, Instituto Português de Oncologia de Lisboa (IPO-L), 1099-023 Lisbon, Portugal
| | - Manuel António Campos
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
- Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
- Centro Hospitalar Vila Nova de Gaia/Espinho, E.P.E., Dermatology Departement, 4434-502 Vila Nova de Gaia, Portugal
| | - Marie Beylot-Barry
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- Dermatology Department, Bordeaux University Hospital, 33075 Bordeaux, France
| | - Manuel Sobrinho-Simões
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
- Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
- Department of Pathology, Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
| | - Jean-Philippe Merlio
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
- Tumor Bank and Tumor Biology Laboratory, Bordeaux University Hospital, 33075 Bordeaux, France
| | - Paula Soares
- Institute for Research and Innovation in Health (I3S), Porto University, 4200-135 Porto, Portugal
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Cancer Biology Group, Porto University, 4200-465 Porto, Portugal
- Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
- Department of Pathology, Faculty of Medicine, Porto University, 4200-319 Porto, Portugal
| | - Edith Chevret
- BRIC (BoRdeaux Institute of onCology), UMR1312, INSERM, University of Bordeaux, 33000 Bordeaux, France
| |
Collapse
|
7
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
|
8
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
9
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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.
| |
Collapse
|
10
|
Robinson NJ, Schiemann WP. Telomerase in Cancer: Function, Regulation, and Clinical Translation. Cancers (Basel) 2022; 14:808. [PMID: 35159075 DOI: 10.3390/cancers14030808] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/29/2022] [Accepted: 02/02/2022] [Indexed: 02/04/2023] Open
Abstract
Simple Summary Cells undergoing malignant transformation must circumvent replicative senescence and eventual cell death associated with progressive telomere shortening that occurs through successive cell division. To do so, malignant cells reactivate telomerase to extend their telomeres and achieve cellular immortality, which is a “Hallmark of Cancer”. Here we review the telomere-dependent and -independent functions of telomerase in cancer, as well as its potential as a biomarker and therapeutic target to diagnose and treat cancer patients. Abstract During the process of malignant transformation, cells undergo a series of genetic, epigenetic, and phenotypic alterations, including the acquisition and propagation of genomic aberrations that impart survival and proliferative advantages. These changes are mediated in part by the induction of replicative immortality that is accompanied by active telomere elongation. Indeed, telomeres undergo dynamic changes to their lengths and higher-order structures throughout tumor formation and progression, processes overseen in most cancers by telomerase. Telomerase is a multimeric enzyme whose function is exquisitely regulated through diverse transcriptional, post-transcriptional, and post-translational mechanisms to facilitate telomere extension. In turn, telomerase function depends not only on its core components, but also on a suite of binding partners, transcription factors, and intra- and extracellular signaling effectors. Additionally, telomerase exhibits telomere-independent regulation of cancer cell growth by participating directly in cellular metabolism, signal transduction, and the regulation of gene expression in ways that are critical for tumorigenesis. In this review, we summarize the complex mechanisms underlying telomere maintenance, with a particular focus on both the telomeric and extratelomeric functions of telomerase. We also explore the clinical utility of telomeres and telomerase in the diagnosis, prognosis, and development of targeted therapies for primary, metastatic, and recurrent cancers.
Collapse
|
11
|
Kosebent EG, Ozturk S. Telomere associated gene expression as well as TERT protein level and telomerase activity are altered in the ovarian follicles of aged mice. Sci Rep 2021; 11:15569. [PMID: 34330985 DOI: 10.1038/s41598-021-95239-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 07/05/2021] [Indexed: 01/23/2023] Open
Abstract
Telomeres cap the ends of eukaryotic chromosomes to maintain genomic stability and integrity during an organism’s lifespan. The length of telomeres inevitably shortens due to DNA replication, genotoxic agents, and biological aging. A limited number of cell types, e.g., stem cells, germline cells, and early embryos can elongate shortened telomeres via the enzymatic action of telomerase, which is composed of telomerase reverse transcriptase (TERT) and telomerase RNA component (Terc). Additionally, telomere-associated proteins including telomeric repeat binding factor 1 (TRF1) and 2 (TRF2), as well as protection of telomeres 1a (POT1a), bind to telomeres to maintain their structural integrity and length. During ovarian aging in mammals, telomeres progressively shorten, accompanied by fertility loss; however, the molecular mechanism underlying this attrition during follicle development remains unclear. In this study, the primary, secondary, preantral, and antral follicles were obtained either from 6-week-old adult (n = 19) or 52-week-old aged (n = 12) mice. We revealed that the Tert, Terc, Trf1, Trf2, and Pot1a gene expression (P < 0.001) and TERT protein (P < 0.01) levels significantly decreased in certain ovarian follicles of the aged group when compared to those of the adult group. Also, telomerase activity exhibited remarkable changes in the follicles of both groups. Consequently, altered telomere-associated gene expression and reduced TERT protein levels in the follicles of aged mice may be a determinant of telomere shortening during ovarian aging, and infertility appearing in the later decades of reproductive lifespan. Further investigations are required to determine the molecular mechanisms underlying these alterations in the follicles during ovarian aging.
Collapse
|
12
|
Dlamini Z, Hull R, Mbatha SZ, Alaouna M, Qiao YL, Yu H, Chatziioannou A. Prognostic Alternative Splicing Signatures in Esophageal Carcinoma. Cancer Manag Res 2021; 13:4509-4527. [PMID: 34113176 PMCID: PMC8186946 DOI: 10.2147/cmar.s305464] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 04/06/2021] [Indexed: 01/10/2023] Open
Abstract
Alternative splicing (AS) is a method of increasing the number of proteins that the genome is capable of coding for, by altering the pre-mRNA during its maturation. This process provides the ability of a broad range of proteins to arise from a single gene. AS events are known to occur in up to 94% of human genes. Cumulative data have shown that aberrant AS functionality is a major factor in human diseases. This review focuses on the contribution made by aberrant AS functionality in the development and progression of esophageal cancer. The changes in the pattern of expression of alternately spliced isoforms in esophageal cancer can be used as diagnostic or prognostic biomarkers. Additionally, these can be used as targets for the development of new treatments for esophageal cancer.
Collapse
Affiliation(s)
- Zodwa Dlamini
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa
| | - Rodney Hull
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa
| | - Sikhumbuzo Z Mbatha
- Department of Surgery, Steve Biko Academic Hospital, University of Pretoria, Pretoria, South Africa
| | - Mohammed Alaouna
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa.,Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - You-Lin Qiao
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa.,Cancer Institute/Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, People's Republic of China
| | - Herbert Yu
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa.,University of Hawaii Cancer Center, Honolulu, HI, USA
| | - Aristotelis Chatziioannou
- SAMRC Precision Prevention & Novel Drug Targets for HIV-Associated Cancers Extramural Unit, Pan African Cancer Research Institute, University of Pretoria, Pretoria, South Africa.,Center of Systems Biology, Biomedical Research Foundation Academy of Athens, Athens, Greece.,e-NIOS Applications PC, Kallithea, Athens, 17676, Greece
| |
Collapse
|
13
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
| | - Dmitry D. Zhdanov
- Institute of Biomedical Chemistry, Pogodinskaya st 10/8, 119121 Moscow, Russia;
| |
Collapse
|
14
|
Abstract
Simple Summary Maintenance of telomeres is a fundamental step in human carcinogenesis and is primarily regulated by telomerase and the human telomerase reverse transcriptase gene (TERT). Improved understanding of the transcriptional control of this gene may provide potential therapeutic targets. Epigenetic modifications are a prominent mechanism to control telomerase activity and regulation of the TERT gene. TERT-targeting miRNAs have been widely studied and their function explained through pre-clinical in vivo model-based validation studies. Further, histone deacetylase inhibitors are now in pre and early clinical trials with significant clinical success. Importantly, TERT downregulation through epigenetic modifications including TERT promoter methylation, histone deacetylase inhibitors, and miRNA activity might contribute to clinical study design. This review provides an overview of the epigenetic mechanisms involved in the regulation of TERT expression and telomerase activity. Abstract Telomerase was first described by Greider and Blackburn in 1984, a discovery ultimately recognized by the Nobel Prize committee in 2009. The three decades following on from its discovery have been accompanied by an increased understanding of the fundamental mechanisms of telomerase activity, and its role in telomere biology. Telomerase has a clearly defined role in telomere length maintenance and an established influence on DNA replication, differentiation, survival, development, apoptosis, tumorigenesis, and a further role in therapeutic resistance in human stem and cancer cells including those of breast and cervical origin. TERT encodes the catalytic subunit and rate-limiting factor for telomerase enzyme activity. The mechanisms of activation or silencing of TERT remain open to debate across somatic, cancer, and stem cells. Promoter mutations upstream of TERT may promote dysregulated telomerase activation in tumour cells but additional factors including epigenetic, transcriptional and posttranscriptional modifications also have a role to play. Previous systematic analysis indicated methylation and mutation of the TERT promoter in 53% and 31%, respectively, of TERT expressing cancer cell lines supporting the concept of a key role for epigenetic alteration associated with TERT dysregulation and cellular transformation. Epigenetic regulators including DNA methylation, histone modification, and non-coding RNAs are now emerging as drivers in the regulation of telomeres and telomerase activity. Epigenetic regulation may be responsible for reversible silencing of TERT in several biological processes including development and differentiation, and increased TERT expression in cancers. Understanding the epigenetic mechanisms behind telomerase regulation holds important prospects for cancer treatment, diagnosis and prognosis. This review will focus on the role of epigenetics in telomerase regulation.
Collapse
Affiliation(s)
- Fatma Dogan
- The Guy Hilton Research Laboratories, School of Pharmacy and Bioengineering, Faculty of Medicine and Health Sciences, Keele University, Stoke on Trent ST4 7QB, UK;
| | - Nicholas R. Forsyth
- The Guy Hilton Research Laboratories, School of Pharmacy and Bioengineering, Faculty of Medicine and Health Sciences, Keele University, Stoke on Trent ST4 7QB, UK;
- School of Medicine, Tongji University, Shanghai 200092, China
- Correspondence:
| |
Collapse
|
15
|
Salimi-Jeda A, Badrzadeh F, Esghaei M, Abdoli A. The role of telomerase and viruses interaction in cancer development, and telomerase-dependent therapeutic approaches. Cancer Treat Res Commun 2021; 27:100323. [PMID: 33530025 DOI: 10.1016/j.ctarc.2021.100323] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/19/2021] [Accepted: 01/21/2021] [Indexed: 12/21/2022]
Abstract
Human telomerase reverse transcriptase (hTERT) is an enzyme that is critically involved in elongating and maintaining telomeres length to control cell life span and replicative potential. Telomerase activity is continuously expressed in human germ-line cells and most cancer cells, whereas it is suppressed in most somatic cells. In normal cells, by reducing telomerase activity and progressively shortening the telomeres, the cells progress to the senescence or apoptosis process. However, in cancer cells, telomere lengths remain constant due to telomerase's reactivation, and cells continue to proliferate and inhibit apoptosis, and ultimately lead to cancer development and human death due to metastasis. Studies demonstrated that several DNA and RNA oncoviruses could interact with telomerase by integrating their genome sequence within the host cell telomeres specifically. Through the activation of the hTERT promoter and lengthening the telomere, these cells contributes to cancer development. Since oncoviruses can activate telomerase and increase hTERT expression, there are several therapeutic strategies based on targeting the telomerase of cancer cells like telomerase-targeted peptide vaccines, hTERT-targeting dendritic cells (DCs), hTERT-targeting gene therapy, and hTERT-targeting CRISPR/Cas9 system that can overcome tumor-mediated toleration mechanisms and specifically apoptosis in cancer cells. This study reviews available data on the molecular structure of telomerase and the role of oncoviruses and telomerase interaction in cancer development and telomerase-dependent therapeutic approaches to conquest the cancer cells.
Collapse
Affiliation(s)
- Ali Salimi-Jeda
- Department of Virology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
| | - Fariba Badrzadeh
- Faculti of Medicine, Golestan University of Medical sciences, Golestan, Iran.
| | - Maryam Esghaei
- Department of Virology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran.
| | - Asghar Abdoli
- Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran, Iran.
| |
Collapse
|
16
|
Xiao W, Chen X, Li X, Deng K, Liu H, Ma J, Wang Z, Hu Y, Hou J. RBM10 regulates human TERT gene splicing and inhibits pancreatic cancer progression. Am J Cancer Res 2021; 11:157-170. [PMID: 33520366 PMCID: PMC7840715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 10/14/2020] [Indexed: 06/12/2023] Open
Abstract
Dysregulation of alternative splicing of hTERT gene to generate full-length Htert (hTERT-FL) that reactivate telomerase has been recognized as a major pathological alteration in pancreatic cancer (PrCa). Mechanism about the factors that regulate hTERT-FL splicing is lacking. Through bioinformatics approach, we focus on a candidate splicing factor RBM10, which leads to a switch in hTERT transcripts to generate a function-less isoform hTERT-s in PrCa, suppressed both telomerase activity and subsequent telomere shortening. RBM10 expression is negatively associated with PrCa progression. Gain or loss of RBM10 also significantly changed PrCa cell proliferation in vitro and in xenografts. RNA-IP and RNA pull-down assays reveal that RBM10 promotes the exclusion of exons7 and 8 which results in the production of TERT-s transcripts. This study may increase knowledge about potentially targetable cancer associated splicing factors and provide novel insights into therapeutic approach in PrCa.
Collapse
Affiliation(s)
- Wenjing Xiao
- School of Materials Science and Engineering, Southwest Jiaotong UniversityChengdu 611756, China
- Department of Pharmacy, The General Hospital of Western Theater Command of PLAChengdu 610083, China
| | - Xin Chen
- Department of Laboratory Medicine, The Third People’s Hospital of Chengdu/Affiliated Hospital of Southwest Jiaotong UniversityChengdu 610015, China
| | - Xia Li
- Department of Ultrasound Diagnosis, Women and Children’s Health Care Hospital of LinyiLinyi 276000, China
| | - Kaiwen Deng
- Department of Pharmacy, The General Hospital of Western Theater Command of PLAChengdu 610083, China
| | - Huawei Liu
- Department of Laboratory Medicine, The Third People’s Hospital of Chengdu/Affiliated Hospital of Southwest Jiaotong UniversityChengdu 610015, China
| | - Jie Ma
- Department of Pharmacy, The General Hospital of Western Theater Command of PLAChengdu 610083, China
| | - Zhanhao Wang
- Department of Laboratory Medicine, The Third People’s Hospital of Chengdu/Affiliated Hospital of Southwest Jiaotong UniversityChengdu 610015, China
| | - Yonghe Hu
- School of Materials Science and Engineering, Southwest Jiaotong UniversityChengdu 611756, China
- Department of Pharmacy, The General Hospital of Western Theater Command of PLAChengdu 610083, China
| | - Jun Hou
- Department of Pharmacy, The General Hospital of Western Theater Command of PLAChengdu 610083, China
| |
Collapse
|
17
|
Kamal S, Junaid M, Ejaz A, Bibi I, Akash MSH, Rehman K. The secrets of telomerase: Retrospective analysis and future prospects. Life Sci 2020; 257:118115. [PMID: 32698073 DOI: 10.1016/j.lfs.2020.118115] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 07/06/2020] [Accepted: 07/13/2020] [Indexed: 12/12/2022]
Abstract
Telomerase plays a significant role to maintain and regulate the telomere length, cellular immortality and senescence by the addition of guanine-rich repetitive sequences. Chronic inflammation or oxidative stress-induced infection downregulates TERT gene modifying telomerase activity thus contributing to the early steps of gastric carcinogenesis process. Furthermore, telomere-telomerase system performs fundamental role in the pathogenesis and progression of diabetes mellitus as well as in its vascular intricacy. The cessation of cell proliferation in cultured cells by inhibiting the telomerase activity of transformed cells renders the rationale for culling of telomerase as a target therapy for the treatment of metabolic disorders and various types of cancers. In this article, we have briefly described the role of immune system and malignant cells in the expression of telomerase with critical analysis on the gaps and potential for future studies. The key findings regarding the secrets of the telomerase summarized in this article will help in future treatment modalities for the prevention of various types of cancers and metabolic disorders notably diabetes mellitus.
Collapse
Affiliation(s)
- Shagufta Kamal
- Department of Biochemistry, Government College University Faisalabad, Pakistan
| | - Muhammad Junaid
- Department of Biochemistry, Government College University Faisalabad, Pakistan
| | - Arslan Ejaz
- Department of Biochemistry, Government College University Faisalabad, Pakistan
| | - Ismat Bibi
- Department of Chemistry, Islamia University, Bahawalpur, Pakistan
| | | | - Kanwal Rehman
- Department of Pharmacy, University of Agriculture, Faisalabad, Pakistan.
| |
Collapse
|
18
|
Fernandes SG, Dsouza R, Pandya G, Kirtonia A, Tergaonkar V, Lee SY, Garg M, Khattar E. Role of Telomeres and Telomeric Proteins in Human Malignancies and Their Therapeutic Potential. Cancers (Basel) 2020; 12:E1901. [PMID: 32674474 PMCID: PMC7409176 DOI: 10.3390/cancers12071901] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/10/2020] [Accepted: 07/13/2020] [Indexed: 12/19/2022] Open
Abstract
Telomeres are the ends of linear chromosomes comprised of repetitive nucleotide sequences in humans. Telomeres preserve chromosomal stability and genomic integrity. Telomere length shortens with every cell division in somatic cells, eventually resulting in replicative senescence once telomere length becomes critically short. Telomere shortening can be overcome by telomerase enzyme activity that is undetectable in somatic cells, while being active in germline cells, stem cells, and immune cells. Telomeres are bound by a shelterin complex that regulates telomere lengthening as well as protects them from being identified as DNA damage sites. Telomeres are transcribed by RNA polymerase II, and generate a long noncoding RNA called telomeric repeat-containing RNA (TERRA), which plays a key role in regulating subtelomeric gene expression. Replicative immortality and genome instability are hallmarks of cancer and to attain them cancer cells exploit telomere maintenance and telomere protection mechanisms. Thus, understanding the role of telomeres and their associated proteins in cancer initiation, progression and treatment is very important. The present review highlights the critical role of various telomeric components with recently established functions in cancer. Further, current strategies to target various telomeric components including human telomerase reverse transcriptase (hTERT) as a therapeutic approach in human malignancies are discussed.
Collapse
Affiliation(s)
- Stina George Fernandes
- Sunandan Divatia School of Science, SVKM’s NMIMS (Deemed to be University), Vile Parle West, Mumbai 400056, India; (S.G.F.); (R.D.)
| | - Rebecca Dsouza
- Sunandan Divatia School of Science, SVKM’s NMIMS (Deemed to be University), Vile Parle West, Mumbai 400056, India; (S.G.F.); (R.D.)
| | - Gouri Pandya
- Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Uttar Pradesh, Noida 201313, India; (G.P.); (A.K.)
| | - Anuradha Kirtonia
- Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Uttar Pradesh, Noida 201313, India; (G.P.); (A.K.)
| | - Vinay Tergaonkar
- Laboratory of NF-κB Signaling, Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; (V.T.); (S.Y.L.)
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore
- Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore
| | - Sook Y. Lee
- Laboratory of NF-κB Signaling, Institute of Molecular and Cell Biology (IMCB), 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; (V.T.); (S.Y.L.)
| | - Manoj Garg
- Amity Institute of Molecular Medicine and Stem Cell Research (AIMMSCR), Amity University Uttar Pradesh, Noida 201313, India; (G.P.); (A.K.)
| | - Ekta Khattar
- Sunandan Divatia School of Science, SVKM’s NMIMS (Deemed to be University), Vile Parle West, Mumbai 400056, India; (S.G.F.); (R.D.)
| |
Collapse
|
19
|
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: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
| | | | - Andrew T. Ludlow
- School of Kinesiology, University of Michigan, Ann Arbor, MI 48109, USA; (A.L.S.); (J.J.K.)
| |
Collapse
|
20
|
Thompson CA, Wong JM. Non-canonical Functions of Telomerase Reverse Transcriptase: Emerging Roles and Biological Relevance. Curr Top Med Chem 2020; 20:498-507. [DOI: 10.2174/1568026620666200131125110] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 01/10/2020] [Accepted: 01/21/2020] [Indexed: 12/11/2022]
Abstract
Increasing evidence from research on telomerase suggests that in addition to its catalytic telomere
repeat synthesis activity, telomerase may have other biologically important functions. The canonical
roles of telomerase are at the telomere ends where they elongate telomeres and maintain genomic
stability and cellular lifespan. The catalytic protein component Telomerase Reverse Transcriptase
(TERT) is preferentially expressed at high levels in cancer cells despite the existence of an alternative
mechanism for telomere maintenance (alternative lengthening of telomeres or ALT). TERT is also expressed
at higher levels than necessary for maintaining functional telomere length, suggesting other possible
adaptive functions. Emerging non-canonical roles of TERT include regulation of non-telomeric
DNA damage responses, promotion of cell growth and proliferation, acceleration of cell cycle kinetics,
and control of mitochondrial integrity following oxidative stress. Non-canonical activities of TERT primarily
show cellular protective effects, and nuclear TERT has been shown to protect against cell death
following double-stranded DNA damage, independent of its role in telomere length maintenance. TERT
has been suggested to act as a chromatin modulator and participate in the transcriptional regulation of
gene expression. TERT has also been reported to regulate transcript levels through an RNA-dependent
RNA Polymerase (RdRP) activity and produce siRNAs in a Dicer-dependent manner. At the mitochondria,
TERT is suggested to protect against oxidative stress-induced mtDNA damage and promote mitochondrial
integrity. These extra-telomeric functions of TERT may be advantageous in the context of increased
proliferation and metabolic stress often found in rapidly-dividing cancer cells. Understanding
the spectrum of non-canonical functions of telomerase may have important implications for the rational
design of anti-cancer chemotherapeutic drugs.
Collapse
Affiliation(s)
- Connor A.H. Thompson
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, V6T 1Z3, Canada
| | - Judy M.Y. Wong
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, V6T 1Z3, Canada
| |
Collapse
|
21
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
22
|
Patrick M, Weng NP. Expression and regulation of telomerase in human T cell differentiation, activation, aging and diseases. Cell Immunol 2019; 345:103989. [PMID: 31558266 DOI: 10.1016/j.cellimm.2019.103989] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 09/18/2019] [Accepted: 09/18/2019] [Indexed: 12/15/2022]
Abstract
Telomeres are essential for chromosomal integrity. Telomere shortening during cell division restricts cellular proliferative capacity and leads to cellular senescence when critically shortened telomere lengths are reached. Similar to hematopoietic stem cells, T cells can upregulate telomerase activity to compensate for telomere loss incurred during proliferation in response to engagement of the T cell antigen receptor (TCR) or exposure to homeostatic cytokines. However, this compensation for telomere loss by telomerase in T cells is imperfect or limited, as shortening of T cell telomeres is observed in human aging and during in vitro longterm culture. In this review, we summarize the current state of knowledge regarding the expression and regulation of telomerase in human T cells and changes of telomerase expression during development, activation, differentiation, aging and disease conditions. In conclusion, we discuss how controlled enhancement of telomerase activity could be a potential strategy to improve T cell function in the elderly and in immunotherapy.
Collapse
Affiliation(s)
- Michael Patrick
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Nan-Ping Weng
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
| |
Collapse
|
23
|
Patrick MS, Cheng NL, Kim J, An J, Dong F, Yang Q, Zou I, Weng NP. Human T Cell Differentiation Negatively Regulates Telomerase Expression Resulting in Reduced Activation-Induced Proliferation and Survival. Front Immunol 2019; 10:1993. [PMID: 31497023 PMCID: PMC6712505 DOI: 10.3389/fimmu.2019.01993] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 08/07/2019] [Indexed: 01/10/2023] Open
Abstract
Maintenance of telomeres is essential for preserving T cell proliferative responses yet the precise role of telomerase in human T cell differentiation, function, and aging is not fully understood. Here we analyzed human telomerase reverse transcriptase (hTERT) expression and telomerase activity in six T cell subsets from 111 human adults and found that levels of hTERT mRNA and telomerase activity had an ordered decrease from naïve (TN) to central memory (TCM) to effector memory (TEM) cells and were higher in CD4+ than their corresponding CD8+ subsets. This differentiation-related reduction of hTERT mRNA and telomerase activity was preserved after activation. Furthermore, the levels of hTERT mRNA and telomerase activity were positively correlated with the degree of activation-induced proliferation and survival of T cells in vitro. Partial knockdown of hTERT by an anti-sense oligo in naïve CD4+ cells led to a modest but significant reduction of cell proliferation. Finally, we found that activation-induced levels of telomerase activity in CD4+ TN and TCM cells were significantly lower in old than in young subjects. These findings reveal that hTERT/telomerase expression progressively declines during T cell differentiation and age-associated reduction of activation-induced expression of hTERT/telomerase mainly affects naïve CD4+ T cells and suggest that enhancing telomerase activity could be a strategy to improve T cell function in the elderly.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Nan-ping Weng
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD, United States
| |
Collapse
|
24
|
Mazzolini R, Gonzàlez N, Garcia-Garijo A, Millanes-Romero A, Peiró S, Smith S, García de Herreros A, Canudas S. Snail1 transcription factor controls telomere transcription and integrity. Nucleic Acids Res 2019; 46:146-158. [PMID: 29059385 PMCID: PMC5758914 DOI: 10.1093/nar/gkx958] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 10/16/2017] [Indexed: 02/06/2023] Open
Abstract
Besides controlling epithelial-to-mesenchymal transition (EMT) and cell invasion, the Snail1 transcriptional factor also provides cells with cancer stem cell features. Since telomere maintenance is essential for stemness, we have examined the control of telomere integrity by Snail1. Fluorescence in situ hybridization (FISH) analysis indicates that Snail1-depleted mouse mesenchymal stem cells (MSC) have both a dramatic increase of telomere alterations and shorter telomeres. Remarkably, Snail1-deficient MSC present higher levels of both telomerase activity and the long non-coding RNA called telomeric repeat-containing RNA (TERRA), an RNA that controls telomere integrity. Accordingly, Snail1 expression downregulates expression of the telomerase gene (TERT) as well as of TERRA 2q, 11q and 18q. TERRA and TERT are transiently downregulated during TGFβ-induced EMT in NMuMG cells, correlating with Snail1 expression. Global transcriptome analysis indicates that ectopic expression of TERRA affects the transcription of some genes induced during EMT, such as fibronectin, whereas that of TERT does not modify those genes. We propose that Snail1 repression of TERRA is required not only for telomere maintenance but also for the expression of a subset of mesenchymal genes.
Collapse
Affiliation(s)
- Rocco Mazzolini
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain
| | - Núria Gonzàlez
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain
| | - Andrea Garcia-Garijo
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain
| | - Alba Millanes-Romero
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain
| | - Sandra Peiró
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain
| | - Susan Smith
- Kimmel Center for Biology and Medicine at the Skirball Institute, Department of Pathology, New York University School of Medicine, New York University, USA
| | - Antonio García de Herreros
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain.,Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Sílvia Canudas
- Programa de Recerca en Càncer, Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Spain.,Unitat de Nutrició Humana, Facultat de Medicina i Ciències de la Salut, Institut d'Investigació Sanitaria Pere Virgili (IISPV), Reus, Spain.,CIBER Fisiología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| |
Collapse
|
25
|
Jie MM, Chang X, Zeng S, Liu C, Liao GB, Wu YR, Liu CH, Hu CJ, Yang SM, Li XZ. Diverse regulatory manners of human telomerase reverse transcriptase. Cell Commun Signal 2019; 17:63. [PMID: 31186051 PMCID: PMC6560729 DOI: 10.1186/s12964-019-0372-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 05/17/2019] [Indexed: 12/22/2022] Open
Abstract
Human telomerase reverse transcriptase (hTERT) is the core subunit of human telomerase and plays important roles in human cancers. Aberrant expression of hTERT is closely associated with tumorigenesis, cancer cell stemness maintaining, cell proliferation, apoptosis inhibition, senescence evasion and metastasis. The molecular basis of hTERT regulation is highly complicated and consists of various layers. A deep and full-scale comprehension of the regulatory mechanisms of hTERT is pivotal in understanding the pathogenesis and searching for therapeutic approaches. In this review, we summarize the recent advances regarding the diverse regulatory mechanisms of hTERT, including the transcriptional (promoter mutation, promoter region methylation and histone acetylation), post-transcriptional (mRNA alternative splicing and non-coding RNAs) and post-translational levels (phosphorylation and ubiquitination), which may provide novel perspectives for further translational diagnosis or therapeutic strategies targeting hTERT.
Collapse
Affiliation(s)
- Meng-Meng Jie
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Xing Chang
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Shuo Zeng
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Cheng Liu
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Guo-Bin Liao
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Ya-Ran Wu
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Chun-Hua Liu
- Teaching evaluation center of Third Military Medical University (Army Medical University), Chongqing, 400038, China
| | - Chang-Jiang Hu
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China
| | - Shi-Ming Yang
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China.
| | - Xin-Zhe Li
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University (Army Medical University), Chongqing, 400037, China.
| |
Collapse
|
26
|
Abstract
Telomeres are specialised structures at the end of linear chromosomes. They consist of tandem repeats of the hexanucleotide sequence TTAGGG, as well as a protein complex called shelterin. Together, they form a protective loop structure against chromosome fusion and degradation. Shortening or damage to telomeres and opening of the loop induce an uncapped state that triggers a DNA damage response resulting in senescence or apoptosis.Average telomere length, usually measured in human blood lymphocytes, was thought to be a biomarker for ageing, survival and mortality. However, it becomes obvious that regulation of telomere length is very complex and involves multiple processes. For example, the "end replication problem" during DNA replication as well as oxidative stress are responsible for the shortening of telomeres. In contrast, telomerase activity can potentially counteract telomere shortening when it is able to access and interact with telomeres. However, while highly active during development and in cancer cells, the enzyme is down-regulated in most human somatic cells with a few exceptions such as human lymphocytes. In addition, telomeres can be transcribed, and the transcription products called TERRA are involved in telomere length regulation.Thus, telomere length and their integrity are regulated at many different levels, and we only start to understand this process under conditions of increased oxidative stress, inflammation and during diseases as well as the ageing process.This chapter aims to describe our current state of knowledge on telomeres and telomerase and their regulation in order to better understand their role for the ageing process.
Collapse
|
27
|
Ludlow AT, Slusher AL, Sayed ME. Insights into Telomerase/hTERT Alternative Splicing Regulation Using Bioinformatics and Network Analysis in Cancer. Cancers (Basel) 2019; 11:E666. [PMID: 31091669 DOI: 10.3390/cancers11050666] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 05/10/2019] [Accepted: 05/13/2019] [Indexed: 01/08/2023] Open
Abstract
The reactivation of telomerase in cancer cells remains incompletely understood. The catalytic component of telomerase, hTERT, is thought to be the limiting component in cancer cells for the formation of active enzymes. hTERT gene expression is regulated at several levels including chromatin, DNA methylation, transcription factors, and RNA processing events. Of these regulatory events, RNA processing has received little attention until recently. RNA processing and alternative splicing regulation have been explored to understand how hTERT is regulated in cancer cells. The cis- and trans-acting factors that regulate the alternative splicing choice of hTERT in the reverse transcriptase domain have been investigated. Further, it was discovered that the splicing factors that promote the production of full-length hTERT were also involved in cancer cell growth and survival. The goals are to review telomerase regulation via alternative splicing and the function of hTERT splicing variants and to point out how bioinformatics approaches are leading the way in elucidating the networks that regulate hTERT splicing choice and ultimately cancer growth.
Collapse
|
28
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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.
| |
Collapse
|
29
|
Sayed ME, Yuan L, Robin JD, Tedone E, Batten K, Dahlson N, Wright WE, Shay JW, Ludlow AT. NOVA1 directs PTBP1 to hTERT pre-mRNA and promotes telomerase activity in cancer cells. Oncogene 2019; 38:2937-52. [PMID: 30568224 DOI: 10.1038/s41388-018-0639-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/24/2018] [Accepted: 12/04/2018] [Indexed: 11/09/2022]
Abstract
Alternative splicing is dysregulated in cancer cells, driving the production of isoforms that allow tumor cells to survive and continuously proliferate. Part of the reactivation of telomerase involves the splicing of hTERT transcripts to produce full-length (FL) TERT. Very few splicing factors to date have been described to interact with hTERT and promote the production of FL TERT. We recently described one such splicing factor, NOVA1, that acts as an enhancer of FL hTERT splicing, increases telomerase activity, and promotes telomere maintenance in cancer cells. NOVA1 is expressed primarily in neurons and is involved in neurogenesis. In the present studies, we describe that polypyrimidine-tract binding proteins (PTBPs), which are also typically involved in neurogenesis, are also participating in the splicing of hTERT to FL in cancer. Knockdown experiments of PTBP1 in cancer cells indicate that PTBP1 reduces hTERT FL splicing and telomerase activity. Stable knockdown of PTBP1 results in progressively shortened telomere length in H1299 and H920 lung cancer cells. RNA pulldown experiments reveal that PTBP1 interacts with hTERT pre-mRNA in a NOVA1 dependent fashion. Knockdown of PTBP1 increases the expression of PTBP2 which also interacts with NOVA1, potentially preventing the association of NOVA1 with hTERT pre-mRNA. These new data highlight that splicing in cancer cells is regulated by competition for splice sites and that combinations of splicing factors interact at cis regulatory sites on pre-mRNA transcripts. By employing hTERT as a model gene, we show the coordination of the splicing factors NOVA1 and PTBP1 in cancer by regulating telomerase that is expressed in the vast majority of cancer cell types.
Collapse
|
30
|
Kazemi Noureini S, Fatemi L, Wink M. Telomere shortening in breast cancer cells (MCF7) under treatment with low doses of the benzylisoquinoline alkaloid chelidonine. PLoS One 2018; 13:e0204901. [PMID: 30281650 PMCID: PMC6169906 DOI: 10.1371/journal.pone.0204901] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 09/17/2018] [Indexed: 01/23/2023] Open
Abstract
Telomeres, the specialized dynamic structures at chromosome ends, regularly shrink with every replication. Thus, they function as an internal molecular clock counting down the number of cell divisions. However, most cancer cells escape this limitation by activating telomerase, which can maintain telomere length. Previous studies showed that the benzylisoquinoline alkaloid chelidonine stimulates multiple modes of cell death and strongly down-regulates telomerase. It is still unknown if down-regulation of telomerase by chelidonine boosts substantial telomere shortening. The breast cancer cell line MCF7 was sequentially treated with very low concentrations of chelidonine over several cell passages. Telomere length and telomerase activity were measured by a monochrome multiplex quantitative PCR and a q-TRAP assay, respectively. Changes in population size and doubling time correlated well with telomerase inhibition and telomere shortening. MCF7 cell growth was arrested completely after three sequential treatments with 0.1 μM chelidonine, each ending after 48 h, while telomere length was reduced to almost 10% of the untreated control. However, treatment with 0.01 μM chelidonine did not have any apparent consequence. In addition to dose and time dependent telomerase inhibition, chelidonine changed the splicing pattern of hTERT towards non-enzyme coding isoforms of the transcript. In conclusion, telomere length and telomere stability are strongly affected by chelidonine in addition to microtubule formation.
Collapse
Affiliation(s)
- Sakineh Kazemi Noureini
- Department of Biology, Faculty of Basic Sciences, Hakim Sabzevari University, Sabzevar, Iran
- * E-mail:
| | - Leili Fatemi
- Department of Biology, Faculty of Basic Sciences, Hakim Sabzevari University, Sabzevar, Iran
| | - Michael Wink
- Department of Biology, Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany
| |
Collapse
|
31
|
Ludlow AT, Wong MS, Robin JD, Batten K, Yuan L, Lai TP, Dahlson N, Zhang L, Mender I, Tedone E, Sayed ME, Wright WE, Shay JW. NOVA1 regulates hTERT splicing and cell growth in non-small cell lung cancer. Nat Commun 2018; 9:3112. [PMID: 30082712 PMCID: PMC6079032 DOI: 10.1038/s41467-018-05582-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/12/2018] [Indexed: 12/12/2022] Open
Abstract
Alternative splicing is dysregulated in cancer and the reactivation of telomerase involves the splicing of TERT transcripts to produce full-length (FL) TERT. Knowledge about the splicing factors that enhance or silence FL hTERT is lacking. We identified splicing factors that reduced telomerase activity and shortened telomeres using a siRNA minigene reporter screen and a lung cancer cell bioinformatics approach. A lead candidate, NOVA1, when knocked down resulted in a shift in hTERT splicing to non-catalytic isoforms, reduced telomerase activity, and progressive telomere shortening. NOVA1 knockdown also significantly altered cancer cell growth in vitro and in xenografts. Genome engineering experiments reveal that NOVA1 promotes the inclusion of exons in the reverse transcriptase domain of hTERT resulting in the production of FL hTERT transcripts. Utilizing hTERT splicing as a model splicing event in cancer may provide new insights into potentially targetable dysregulated splicing factors in cancer.
Collapse
Affiliation(s)
- Andrew T Ludlow
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA.
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, 48109, USA.
| | - Mandy Sze Wong
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
- Cold Spring Harbor Laboratories, One Bungtown Road, Cold Spring Harbor, New York, NY, 11724, USA
| | - Jerome D Robin
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
- Aix-Marseille University, Marseille Medical Genetics (MMG), UMR125, Marseille, 13385, France
| | - Kimberly Batten
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Laura Yuan
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Tsung-Po Lai
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Nicole Dahlson
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Lu Zhang
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Ilgen Mender
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Enzo Tedone
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Mohammed E Sayed
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
- School of Kinesiology, University of Michigan, 401 Washtenaw Ave., Ann Arbor, MI, 48109, USA
| | - Woodring E Wright
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| | - Jerry W Shay
- Department of Cell Biology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390, USA
| |
Collapse
|
32
|
Dong W, Wu L, Sun H, Ren X, Epling-Burnette PK, Yang L. MDS shows a higher expression of hTERT and alternative splice variants in unactivated T-cells. Oncotarget 2018; 7:71904-71914. [PMID: 27655690 PMCID: PMC5342131 DOI: 10.18632/oncotarget.12115] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/10/2016] [Indexed: 12/19/2022] Open
Abstract
Telomere instability and telomerase reactivation are believed to play an important role in the development of myelodysplastic syndromes (MDS). Abnormal enzymatic activity of human telomerase reverse transcriptase (hTERT), and its alternative splice variants have been reported to account for deregulated telomerase function in many cancers. In this study, we aim to compare the differences in expression of hTERT and hTERT splice variants, as well as telomere length and telomerase activity in unstimulated T-cells between MDS subgroups and healthy controls. Telomere length in MDS cases was significantly shorter than controls (n = 20, p<0.001) and observed across all subtypes of MDS using World Health Organization classification (WHO subgroups versus control: RARS, p= 0.009; RCMD, p=0.0002; RAEB1/2, p=0.004, respectively) and the International Prognostic Scoring System (IPSS subgroups: Low+Int-1, p<0.001; Int-2+High, p=0.004). However, unstimulated T-cells from MDS patients (n=20) had significantly higher telomerase activity (p=0.002), higher total hTERT mRNA levels (p=0.001) and hTERT α+β- splice variant expression (p<0.001) compared to controls. Other hTERT splice variants were lower in expression and not significantly different among cases and controls. Telomerase activity was positively correlated with total hTERT levels in MDS (r=0.58, p=0.007). This data is in sharp contrast to data published previously by our group showing a reduction in telomerase and hTERT mRNA in MDS T-cells after activation. In conclusion, this study provides additional insight into hTERT transcript patterns and activity in peripheral T-cells of MDS patients. Additional studies are necessary to better understand the role of this pathway in MDS development and progression.
Collapse
Affiliation(s)
- Wen Dong
- Department of Orthopaedic Surgery, Tianjin Hongqiao Hospital, Tianjin, P.R. China
| | - Lei Wu
- Department of Immunology, Tianjin Cancer Institute and Hospital, Tianjin Medical University, P.R. China.,National Clinical Research Center of Cancer, P.R. China.,Key Laboratory of Cancer Immunology and Biotherapy, Tianjin, P.R. China
| | - Houfang Sun
- Department of Immunology, Tianjin Cancer Institute and Hospital, Tianjin Medical University, P.R. China.,National Clinical Research Center of Cancer, P.R. China.,Key Laboratory of Cancer Immunology and Biotherapy, Tianjin, P.R. China
| | - Xiubao Ren
- Department of Immunology, Tianjin Cancer Institute and Hospital, Tianjin Medical University, P.R. China.,National Clinical Research Center of Cancer, P.R. China.,Key Laboratory of Cancer Immunology and Biotherapy, Tianjin, P.R. China
| | | | - Lili Yang
- Department of Immunology, Tianjin Cancer Institute and Hospital, Tianjin Medical University, P.R. China.,National Clinical Research Center of Cancer, P.R. China.,Key Laboratory of Cancer Immunology and Biotherapy, Tianjin, P.R. China
| |
Collapse
|
33
|
Zhdanov DD, Pokrovsky VS, Orlova EV, Orlova VS, Pokrovskaya MV, Aleksandrova SS, Sokolov NN. Intracellular Localization of Apoptotic Endonuclease EndoG and Splice-Variants of Telomerase Catalytic Subunit hTERT. Biochemistry (Mosc) 2017; 82:894-905. [PMID: 28941457 DOI: 10.1134/s0006297917080041] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The activity of telomerase catalytic subunit hTERT (human telomerase reverse transcriptase) can be regulated by alternative splicing of its mRNA. The mechanism of hTERT splicing is not understood in detail. Apoptotic endonuclease EndoG is known to participate in this process. In the present work, the intracellular colocalization and mRNA levels of EndoG and hTERT splice-variants in normal and apoptotic cancer cells were studied. We found that the development of apoptosis increased the expression of EndoG and changed the ratio of hTERT splice-variants, which decreased the telomerase activity in the cells. The development of apoptosis was accompanied by changes in the amount of mRNA and in the localization of EndoG and hTERT splice-variants in the cytoplasm, nuclei, and mitochondria of the cells. The suppression of EndoG expression using RNA interference prevented induction of the α+β- splice-variant of hTERT and inhibition of the telomerase activity. A high degree of the intracellular colocalization of EndoG and hTERT was shown. The changes in the expression and localization of EndoG corresponded with changes in the amount and localization of hTERT splice-variants. These data confirm the participation of EndoG in the alternative splicing of mRNA of the telomerase catalytic subunit and in regulation of the telomerase activity.
Collapse
Affiliation(s)
- D D Zhdanov
- Orekhovich Institute of Biomedical Chemistry, Moscow, 119121, Russia.
| | | | | | | | | | | | | |
Collapse
|
34
|
Zhdanov DD, Vasina DA, Orlova EV, Orlova VS, Pokrovskaya MV, Aleksandrova SS, Sokolov NN. Apoptotic endonuclease EndoG regulates alternative splicing of human telomerase catalytic subunit hTERT. Biochem Moscow Suppl Ser B 2017. [DOI: 10.1134/s1990750817020135] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
35
|
Zhdanov DD, Vasina DA, Orlova EV, Orlova VS, Pokrovskaya MV, Aleksandrova SS, Sokolov NN. [Apoptotic endonuclease EndoG regulates alternative splicing of human telomerase catalytic subunit hTERT]. Biomed Khim 2017; 62:544-554. [PMID: 27797329 DOI: 10.18097/pbmc20166205544] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Human telomerase catalytic subunit hTERT is subjected to alternative splicing results in loss of its function and leads to decrease of telomerase activity. However, very little is known about the mechanism of hTERT pre-mRNA alternative splicing. Apoptotic endonuclease EndoG is known to participate this process. The aim of this study was to determine the role of EndoG in regulation of hTERT alternative splicing. Increased expression of b-deletion splice variant was determined during EndoG over-expression in CaCo-2 cell line, after EndoG treatment of cell cytoplasm and nuclei and after nuclei incubation with EndoG digested cell RNA. hTERT alternative splicing was induced by 47-mer RNA oligonucleotide in naked nuclei and in cells after transfection. Identified long non-coding RNA, that is the precursor of 47-mer RNA oligonucleotide. Its size is 1754 nucleotides. Based on the results the following mechanism was proposed. hTERT pre-mRNA is transcribed from coding DNA strand while long non-coding RNA is transcribed from template strand of hTERT gene. EndoG digests long non-coding RNA and produces 47-mer RNA oligonucleotide complementary to hTERT pre-mRNA exon 8 and intron 8 junction place. Interaction of 47-mer RNA oligonucleotide and hTERT pre-mRNA causes alternative splicing.
Collapse
Affiliation(s)
- D D Zhdanov
- Institute of Biomedical Chemistry, Moscow, Russia; Ecological faculty, Peoples Friendship University of Russia, Moscow, Russia
| | - D A Vasina
- Ecological faculty, Peoples Friendship University of Russia, Moscow, Russia
| | - E V Orlova
- Institute of Theoretical and Experimental Biophysics, Pushchino, Russia
| | - V S Orlova
- Ecological faculty, Peoples Friendship University of Russia, Moscow, Russia
| | | | | | - N N Sokolov
- Institute of Biomedical Chemistry, Moscow, Russia
| |
Collapse
|
36
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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.
| |
Collapse
|
37
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
38
|
Abstract
Activation of telomerase is a critical step in the development of about 85 % of human cancers. Levels of Tert, which encodes the reverse transcriptase subunit of telomerase, are limiting in normal somatic cells. Tert is subjected to transcriptional, post-transcriptional and epigenetic regulation, but the precise mechanism of how telomerase is re-activated in cancer cells is poorly understood. Reactivation of the Tert promoter involves multiple changes which evolve during cancer progression including mutations and chromosomal re-arrangements. Newly described non-coding mutations in the Tert promoter region of many cancer cells (19 %) in two key positions, C250T and C228T, have added another layer of complexity to telomerase reactivation. These mutations create novel consensus sequences for transcription factors which can enhance Tert expression. In this review, we will discuss gene structure and function of Tert and provide insights into the mechanisms of Tert reactivation in cancers, highlighting the contribution of recently identified Tert promoter mutations.
Collapse
Affiliation(s)
- Semih Can Akincilar
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), Proteos, 61, Biopolis Drive, Singapore, 138673, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore, 117597, Singapore
| | - Bilal Unal
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), Proteos, 61, Biopolis Drive, Singapore, 138673, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore, 117597, Singapore
| | - Vinay Tergaonkar
- Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), Proteos, 61, Biopolis Drive, Singapore, 138673, Singapore.
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore, 117597, Singapore.
- Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, Australia.
| |
Collapse
|
39
|
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.
Collapse
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
| |
Collapse
|
40
|
Mohammadi M, Hedayati M, Zarghami N, Ghaemmaghami S. RESISTIN EFFECT ON TELOMERASE GENE EXPRESSION IN GASTRIC CANCER CELL LINE AGS. Acta Endocrinol (Buchar) 2016; 12:145-149. [PMID: 31149079 DOI: 10.4183/aeb.2016.145] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Background Resistin, as an adipokine, has been shown to be increased in serum plasma of gastric cancer patients and suggested to be a major factor in gastric carcinogenesis. However, it is still not clear how Resistin influences gastric cancer progression. The aim of this study was to evaluate Resistin effect on cell proliferation and expression of telomerase gene in gastric cancer cell line (AGS). Methods In this study, the proliferating activity of AGS cells stimulated with Resistin was also evaluated by using 2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT) assay and trypan blue staining method. To investigate telomerase gene expression affected by Resistin, total RNA was extracted, cDNA was synthesized and expression of hTERT mRNA was carried out by real-time reverse transcription polymerase chain reaction. Results Exogenous Resistin has induced gastric cancer cells proliferation in a dose-dependent manner and could improve cell viability. Also the expression of Human Telomerase Reverse Transcriptase (hTERT) was upregulated in 24 hours, after Resistin treatment. Conclusions This study has shown Resistin induces exogenously gastric cancer cell proliferation and increases hTERT gene expression. These findings may clarify the role of Resistin in gastric carcinogenesis. Therefore blocking Resistin signaling and limiting its secretion may be valuable for the treatment of gastric cancer.
Collapse
Affiliation(s)
- M Mohammadi
- Shahid Beheshti University of Medical Sciences, Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Tehran, Islamic Republic of Iran
| | - M Hedayati
- Shahid Beheshti University of Medical Sciences, Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Tehran, Islamic Republic of Iran
| | - N Zarghami
- Tabriz University of Medical Sciences, Division of Molecular Medicine, Department of Clinical Biochemistry, Tabriz, Islamic Republic of Iran
| | - S Ghaemmaghami
- Tabriz University of Medical Sciences, Division of Molecular Medicine, Department of Clinical Biochemistry, Tabriz, Islamic Republic of Iran
| |
Collapse
|
41
|
Cui W, Qian Y, Zhou X, Lin Y, Jiang J, Chen J, Zhao Z, Shen B. Discovery and characterization of long intergenic non-coding RNAs (lincRNA) module biomarkers in prostate cancer: an integrative analysis of RNA-Seq data. BMC Genomics 2015; 16 Suppl 7:S3. [PMID: 26100580 PMCID: PMC4474418 DOI: 10.1186/1471-2164-16-s7-s3] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background Prostate cancer (PCa) is a leading cause of cancer-related death of men worldwide. There is an urgent need to develop novel biomarkers for PCa prognosis and diagnosis in the post prostate-specific antigen era. Long intergenic noncoding RNAs (lincRNAs) play essential roles in many physiological processes and can serve as alternative biomarkers for prostate cancer, but there has been no systematic investigation of lincRNAs in PCa yet. Results Nine lincRNA co-expression modules were identified from PCa RNA-Seq data. The association between the principle component of each module and the PCa phenotype was examined by calculating the Pearson's correlation coefficients. Three modules (M1, M3, and M5) were found associated with PCa. Two modules (M3 and M5) were significantly enriched with lincRNAs, and one of them, M3, may be used as a lincRNA module-biomarker for PCa diagnosis. This module includes seven essential lincRNAs: TCONS_l2_00001418, TCONS_l2_00008237, TCONS_l2_00011130, TCONS_l2_00013175, TCONS_l2_00022611, TCONS_l2_00022670 and linc-PXN-1. The clustering analysis and microRNA enrichment analysis further confirmed our findings. Conclusion The correlation between lincRNAs and protein-coding genes is helpful for further exploration of functional mechanisms of lincRNAs in PCa. This study provides some important insights into the roles of lincRNAs in PCa and suggests a few lincRNAs as candidate biomarkers for PCa diagnosis and prognosis.
Collapse
|
42
|
Fleisig HB, Hukezalie KR, Thompson CAH, Au-Yeung TTT, Ludlow AT, Zhao CR, Wong JMY. Telomerase reverse transcriptase expression protects transformed human cells against DNA-damaging agents, and increases tolerance to chromosomal instability. Oncogene 2015; 35:218-27. [PMID: 25893297 DOI: 10.1038/onc.2015.75] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 01/28/2015] [Accepted: 02/06/2015] [Indexed: 12/12/2022]
Abstract
Reactivation of telomerase reverse transcriptase (TERT) expression is found in more than 85% of human cancers. The remaining cancers rely on the alternative lengthening of telomeres (ALT), a recombination-based mechanism for telomere-length maintenance. Prevalence of TERT reactivation over the ALT mechanism was linked to secondary TERT function unrelated to telomere length maintenance. To characterize this non-canonical function, we created a panel of ALT cells with recombinant expression of TERT and TERT variants: TERT-positive ALT cells showed higher tolerance to genotoxic insults compared with their TERT-negative counterparts. We identified telomere synthesis-defective TERT variants that bestowed similar genotoxic stress tolerance, indicating that telomere synthesis activity is dispensable for this survival phenotype. TERT expression improved the kinetics of double-strand chromosome break repair and reduced DNA damage-related nuclear division abnormalities, a phenotype associated with ALT tumors. Despite this reduction in cytological abnormalities, surviving TERT-positive ALT cells were found to have gross chromosomal instabilities. We sorted TERT-positive cells with cytogenetic changes and followed their growth. We found that the chromosome-number changes persisted, and TERT-positive ALT cells surviving genotoxic events propagated through subsequent generations with new chromosome numbers. Our data confirm that telomerase expression protects against double-strand DNA (dsDNA)-damaging events, and show that this protective function is uncoupled from its role in telomere synthesis. TERT expression promotes oncogene-transformed cell growth by reducing the inhibitory effects of cell-intrinsic (telomere attrition) and cell-extrinsic (chemical- or metabolism-induced genotoxic stress) challenges. These data provide the impetus to develop new therapeutic interventions for telomerase-positive cancers through simultaneous targeting of multiple telomerase activities.
Collapse
Affiliation(s)
- H B Fleisig
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - K R Hukezalie
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - C A H Thompson
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - T T T Au-Yeung
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - A T Ludlow
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - C R Zhao
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - J M Y Wong
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
43
|
Augustine TA, Baig M, Sood A, Budagov T, Atzmon G, Mariadason JM, Aparo S, Maitra R, Goel S. Telomere length is a novel predictive biomarker of sensitivity to anti-EGFR therapy in metastatic colorectal cancer. Br J Cancer 2015; 112:313-8. [PMID: 25412235 DOI: 10.1038/bjc.2014.561] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 09/26/2014] [Accepted: 10/02/2014] [Indexed: 01/05/2023] Open
Abstract
Background: Telomeres are TTAGGG tandem repeats capping chromosomal ends and partially controlled by the telomerase enzyme. The EGFR pathway putatively regulates telomerase function, prompting an investigation of telomere length (TL) and its association with anti-epidermal growth factor receptor (EGFR) therapy in metastatic colorectal cancer (mCRC). Methods: Colorectal cancer cell lines were treated with multiple drugs and sensitivity determined. Clinical information was gathered from 75 patients who had received anti-EGFR drugs. Telomere length was measured using a validated qRT–PCR technique. Results: In CRC cell lines, TL independently predicted cetuximab sensitivity. Cells with shorter TL had growth inhibition of 18.6±3.41% as compared with 41.39±8.58% in longer TL (P=0.02). These in vitro findings were validated clinically, in a robust multivariate model. Among patients with KRas WT tumours, those with longer TL had a superior median progression-free survival (PFS) of 24.9 weeks than those with shorter TL; median 11.1 weeks, HR 0.31; P=0.048. Conclusion: Telomere length could be a potential unique biomarker predictive of clinical benefit (PFS) of mCRC patients treated with anti-EGFR therapy. This is the novel demonstration of a complex hitherto undescribed interaction, placing anti-EGFR therapy, EGFR pathway, and the telomerase complex within a clinical context.
Collapse
|
44
|
Wong MS, Wright WE, Shay JW. Alternative splicing regulation of telomerase: a new paradigm? Trends Genet 2014; 30:430-8. [PMID: 25172021 DOI: 10.1016/j.tig.2014.07.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 01/01/2023]
Abstract
Alternative splicing affects approximately 95% of eukaryotic genes, greatly expanding the coding capacity of complex genomes. Although our understanding of alternative splicing has increased rapidly, current knowledge of splicing regulation has largely been derived from studies of highly expressed mRNAs. Telomerase is a key example of a protein that is alternatively spliced, but it is expressed at very low levels and although it is known that misregulation of telomerase splicing is a hallmark of nearly all cancers, the details of this process are unclear. Here we review work showing that hTERT expression is in part regulated by atypical alternative splicing, perhaps due to its exceptionally low expression level. We propose that these differential regulatory mechanisms may be widely applicable to other genes and may provide new opportunities for the development of cancer therapeutics.
Collapse
Affiliation(s)
- Mandy S Wong
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390-9039, USA
| | - Woodring E Wright
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390-9039, USA
| | - Jerry W Shay
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390-9039, USA; Center for Excellence in Genomics Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia.
| |
Collapse
|
45
|
Abstract
Atherosclerosis (AS) is a complex inflammatory process and is categorized as a multifactorial disease involving the interplay of genetic and environmental factors. There are many factors which play role in predisposition and development of AS. In this review we have tried to address the basic pathophysiology of AS lesions and the role played by two important factors - telomeres and estrogens in the development of this disease.
Collapse
Affiliation(s)
- Aga Syed Sameer
- Department of Biochemistry, Sher-I-Kashmir Institute of Medical Sciences Associated Medical College, Bemina, Srinagar, Kashmir 190018, India
| | - Saniya Nissar
- Department of Biochemistry, Kashmir University, Hazratbal, Srinagar, Kashmir 190006, India
| | - Ruqaya Aziz
- Department of Biochemistry, Sher-I-Kashmir Institute of Medical Sciences Associated Medical College, Bemina, Srinagar, Kashmir 190018, India
| |
Collapse
|
46
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Lida Radan
- 1 Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, University of Western Ontario , London, Ontario, Canada
| | | | | | | | | | | | | |
Collapse
|
47
|
Zhu S, Rousseau P, Lauzon C, Gandin V, Topisirovic I, Autexier C. Inactive C-terminal telomerase reverse transcriptase insertion splicing variants are dominant-negative inhibitors of telomerase. Biochimie 2014; 101:93-103. [DOI: 10.1016/j.biochi.2013.12.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 12/30/2013] [Indexed: 12/12/2022]
|
48
|
|
49
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 07/29/2013] [Indexed: 12/22/2022]
|
50
|
Abstract
Telomerase is responsible for maintaining the length of telomeres at the ends of chromosomes. Although most somatic cells do not exhibit telomerase activity, it is reactivated in approximately 85% of cancers. This simple and attractive phenomenon steers the development of anticancer drugs targeting telomeres and telomerase. Recent studies have been revealing extratelomeric roles of telomerase in normal tissues, affecting processes that are critical for survival and aging of organisms. In this review, we will discuss the current therapeutic strategies targeting telomeres and telomerase and evaluate their potential advantages and risks with respect to nontelomeric functions.
Collapse
Affiliation(s)
- Jae-Il Roh
- Mouse Molecular Genetics Laboratory, Department of Biochemistry, Yonsei Laboratory Animal Research Center, Yonsei University, Seoul, Korea
| | | | | |
Collapse
|