1
|
Mizuno T, Hirabayashi K, Miyazawa S, Kobayashi Y, Shoji K, Kobayashi M, Hanaoka F, Imamoto N, Torigoe H. The intrinsically disordered N-terminal region of mouse DNA polymerase alpha mediates its interaction with POT1a/b at telomeres. Genes Cells 2021; 26:360-380. [PMID: 33711210 DOI: 10.1111/gtc.12845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 03/09/2021] [Accepted: 03/09/2021] [Indexed: 01/12/2023]
Abstract
Mouse telomerase and the DNA polymerase alpha-primase complex elongate the leading and lagging strands of telomeres, respectively. To elucidate the molecular mechanism of lagging strand synthesis, we investigated the interaction between DNA polymerase alpha and two paralogs of the mouse POT1 telomere-binding protein (POT1a and POT1b). Yeast two-hybrid analysis and a glutathione S-transferase pull-down assay indicated that the C-terminal region of POT1a/b binds to the intrinsically disordered N-terminal region of p180, the catalytic subunit of mouse DNA polymerase alpha. Subcellular distribution analyses showed that although POT1a, POT1b, and TPP1 were localized to the cytoplasm, POT1a-TPP1 and POT1b-TPP1 coexpressed with TIN2 localized to the nucleus in a TIN2 dose-dependent manner. Coimmunoprecipitation and cell cycle synchronization experiments indicated that POT1b-TPP1-TIN2 was more strongly associated with p180 than POT1a-TPP1-TIN2, and this complex accumulated during the S phase. Fluorescence in situ hybridization and proximity ligation assays showed that POT1a and POT1b interacted with p180 and TIN2 on telomeric chromatin. Based on the present study and a previous study, we propose a model in which POT1a/b-TPP1-TIN2 translocates into the nucleus in a TIN2 dose-dependent manner to target the telomere, where POT1a/b interacts with DNA polymerase alpha for recruitment at the telomere for lagging strand synthesis.
Collapse
Affiliation(s)
| | - Kei Hirabayashi
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| | - Sae Miyazawa
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| | - Yurika Kobayashi
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| | - Kenta Shoji
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| | - Masakazu Kobayashi
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| | | | - Naoko Imamoto
- Cellular Dynamics Laboratory, CPR, RIKEN, Wako, Japan
| | - Hidetaka Torigoe
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
| |
Collapse
|
2
|
Schrumpfová PP, Fajkus J. Composition and Function of Telomerase-A Polymerase Associated with the Origin of Eukaryotes. Biomolecules 2020; 10:biom10101425. [PMID: 33050064 PMCID: PMC7658794 DOI: 10.3390/biom10101425] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 09/29/2020] [Accepted: 10/01/2020] [Indexed: 12/19/2022] Open
Abstract
The canonical DNA polymerases involved in the replication of the genome are unable to fully replicate the physical ends of linear chromosomes, called telomeres. Chromosomal termini thus become shortened in each cell cycle. The maintenance of telomeres requires telomerase—a specific RNA-dependent DNA polymerase enzyme complex that carries its own RNA template and adds telomeric repeats to the ends of chromosomes using a reverse transcription mechanism. Both core subunits of telomerase—its catalytic telomerase reverse transcriptase (TERT) subunit and telomerase RNA (TR) component—were identified in quick succession in Tetrahymena more than 30 years ago. Since then, both telomerase subunits have been described in various organisms including yeasts, mammals, birds, reptiles and fish. Despite the fact that telomerase activity in plants was described 25 years ago and the TERT subunit four years later, a genuine plant TR has only recently been identified by our group. In this review, we focus on the structure, composition and function of telomerases. In addition, we discuss the origin and phylogenetic divergence of this unique RNA-dependent DNA polymerase as a witness of early eukaryotic evolution. Specifically, we discuss the latest information regarding the recently discovered TR component in plants, its conservation and its structural features.
Collapse
Affiliation(s)
- Petra Procházková Schrumpfová
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic;
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500 Brno, Czech Republic
- Correspondence:
| | - Jiří Fajkus
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic;
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, CZ-62500 Brno, Czech Republic
- The Czech Academy of Sciences, Institute of Biophysics, Královopolská 135, 612 65 Brno, Czech Republic
| |
Collapse
|
3
|
Pike AM, Strong MA, Ouyang JPT, Greider CW. TIN2 Functions with TPP1/POT1 To Stimulate Telomerase Processivity. Mol Cell Biol 2019; 39:e00593-18. [PMID: 31383750 PMCID: PMC6791651 DOI: 10.1128/mcb.00593-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2018] [Revised: 02/10/2019] [Accepted: 07/30/2019] [Indexed: 12/20/2022] Open
Abstract
TIN2 is an important regulator of telomere length, and mutations in TINF2, the gene encoding TIN2, cause short-telomere syndromes. While the genetics underscore the importance of TIN2, the mechanism through which TIN2 regulates telomere length remains unclear. Here, we tested the effects of human TIN2 on telomerase activity. We identified a new isoform in human cells, TIN2M, that is expressed at levels similar to those of previously studied TIN2 isoforms. All three TIN2 isoforms localized to and maintained telomere integrity in vivo, and localization was not disrupted by telomere syndrome mutations. Using direct telomerase activity assays, we discovered that TIN2 stimulated telomerase processivity in vitro All of the TIN2 isoforms stimulated telomerase to similar extents. Mutations in the TPP1 TEL patch abrogated this stimulation, suggesting that TIN2 functions with TPP1/POT1 to stimulate telomerase processivity. We conclude from our data and previously published work that TIN2/TPP1/POT1 is a functional shelterin subcomplex.
Collapse
Affiliation(s)
- Alexandra M Pike
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Margaret A Strong
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - John Paul T Ouyang
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Biochemistry Cell and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Carol W Greider
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Cellular and Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Graduate Program in Biochemistry Cell and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| |
Collapse
|
4
|
Treating Cancer by Targeting Telomeres and Telomerase. Antioxidants (Basel) 2017; 6:antiox6010015. [PMID: 28218725 PMCID: PMC5384178 DOI: 10.3390/antiox6010015] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 12/22/2022] Open
Abstract
Telomerase is expressed in more than 85% of cancer cells. Tumor cells with metastatic potential may have a high telomerase activity, allowing cells to escape from the inhibition of cell proliferation due to shortened telomeres. Human telomerase primarily consists of two main components: hTERT, a catalytic subunit, and hTR, an RNA template whose sequence is complimentary to the telomeric 5′-dTTAGGG-3′ repeat. In humans, telomerase activity is typically restricted to renewing tissues, such as germ cells and stem cells, and is generally absent in normal cells. While hTR is constitutively expressed in most tissue types, hTERT expression levels are low enough that telomere length cannot be maintained, which sets a proliferative lifespan on normal cells. However, in the majority of cancers, telomerase maintains stable telomere length, thereby conferring cell immortality. Levels of hTERT mRNA are directly related to telomerase activity, thereby making it a more suitable therapeutic target than hTR. Recent data suggests that stabilization of telomeric G-quadruplexes may act to indirectly inhibit telomerase action by blocking hTR binding. Telomeric DNA has the propensity to spontaneously form intramolecular G-quadruplexes, four-stranded DNA secondary structures that are stabilized by the stacking of guanine residues in a planar arrangement. The functional roles of telomeric G-quadruplexes are not completely understood, but recent evidence suggests that they can stall the replication fork during DNA synthesis and inhibit telomere replication by preventing telomerase and related proteins from binding to the telomere. Long-term treatment with G-quadruplex stabilizers induces a gradual reduction in the length of the G-rich 3’ end of the telomere without a reduction of the total telomere length, suggesting that telomerase activity is inhibited. However, inhibition of telomerase, either directly or indirectly, has shown only moderate success in cancer patients. Another promising approach of targeting the telomere is the use of guanine-rich oligonucleotides (GROs) homologous to the 3’ telomere overhang sequence (T-oligos). T-oligos, particularly a specific 11-base oligonucleotide (5’-dGTTAGGGTTAG-3’) called T11, have been shown to induce DNA damage responses (DDRs) such as senescence, apoptosis, and cell cycle arrest in numerous cancer cell types with minimal or no cytostatic effects in normal, non-transformed cells. As a result, T-oligos and other GROs are being investigated as prospective anticancer therapeutics. Interestingly, the DDRs induced by T-oligos in cancer cells are similar to the effects seen after progressive telomere degradation in normal cells. The loss of telomeres is an important tumor suppressor mechanism that is commonly absent in transformed malignant cells, and hence, T-oligos have garnered significant interest as a novel strategy to combat cancer. However, little is known about their mechanism of action. In this review, we discuss the current understanding of how T-oligos exert their antiproliferative effects in cancer cells and their role in inhibition of telomerase. We also discuss the current understanding of telomerase in cancer and various therapeutic targets related to the telomeres and telomerase.
Collapse
|
5
|
Lobetti-Bodoni C, Bernocco E, Genuardi E, Boccadoro M, Ladetto M. Telomeres and telomerase in normal and malignant B-cells. Hematol Oncol 2011; 28:157-67. [PMID: 20213664 DOI: 10.1002/hon.937] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The telomeric checkpoint is emerging as a critical sensor of cellular damage, playing a major role in human aging and cancer development. In the meantime, telomere biology is rapidly evolving from a basic discipline to a translational branch, capable of providing major hints for biomarker development, risk assessment and targeted treatment of cancer. These advances have a number of implications in the biology of lymphoid tumours. Moreover, there is considerable interest in the potential role of telomeric dysfunction in the wide array of immunological abnormalities, grouped under the definition of 'immunosenescence'. This review will summarize the impact of recent advances in telomere biology on the physiology and pathology of the B lymphocyte, with special interest in immunosenescence and lymphomagenesis.
Collapse
Affiliation(s)
- Chiara Lobetti-Bodoni
- Department of Experimental Oncology, Division of Hematology, University of Torino, Italy
| | | | | | | | | |
Collapse
|
6
|
O'Hare TH, Delany ME. Genetic variation exists for telomeric array organization within and among the genomes of normal, immortalized, and transformed chicken systems. Chromosome Res 2009; 17:947-64. [PMID: 19890728 PMCID: PMC2793383 DOI: 10.1007/s10577-009-9082-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 09/03/2009] [Accepted: 09/28/2009] [Indexed: 11/30/2022]
Abstract
This study investigated telomeric array organization of diverse chicken genotypes utilizing in vivo and in vitro cells having phenotypes with different proliferation potencies. Our experimental objective was to characterize the extent and nature of array variation present to explore the hypothesis that mega-telomeres are a universal and fixed feature of chicken genotypes. Four different genotypes were studied including normal (UCD 001, USDA-ADOL Line 0), immortalized (DF-1), and transformed (DT40) cells. Both cytogenetic and molecular approaches were utilized to develop an integrated view of telomeric array organization. It was determined that significant variation exists within and among chicken genotypes for chromosome-specific telomeric array organization and total genomic-telomeric sequence content. Although there was variation for mega-telomere number and distribution, two mega-telomere loci were in common among chicken genetic lines (GGA 9 and GGA W). The DF-1 cell line was discovered to maintain a complex derivative karyotype involving chromosome fusions in the homozygous and heterozygous condition. Also, the DF-1 cell line was found to contain the greatest amount of telomeric sequence per genome (17%) as compared to UCD 001 (5%) and DT40 (1.2%). The chicken is an excellent model for studying unique and universal features of vertebrate telomere biology, and characterization of the telomere length variation among genotypes will be useful in the exploration of mechanisms controlling telomere length maintenance in different cell types having unique phenotypes.
Collapse
Affiliation(s)
- Thomas H O'Hare
- Department of Animal Science, University of California, Davis, Davis, CA 95616, USA.
| | | |
Collapse
|
7
|
Kaminker PG, Kim SH, Desprez PY, Campisi J. A novel form of the telomere-associated protein TIN2 localizes to the nuclear matrix. Cell Cycle 2009; 8:931-9. [PMID: 19229133 PMCID: PMC2751576 DOI: 10.4161/cc.8.6.7941] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Telomeres are specialized heterochromatin at the ends of linear chromosomes. Telomeres are crucial for maintaining genome stability and play important roles in cellular senescence and tumor biology. Six core proteins-TRF1, TRF2, TIN2, POT1, TPP1 and Rap1 (termed the telosome or shelterin complex)-regulate telomere structure and function. One of these proteins, TIN2, regulates telomere length and structure indirectly by interacting with TRF1, TRF2 and TPP1, but no direct function has been attributed to TIN2. Here we present evidence for a TIN2 isoform (TIN2L) that differs from the originally described TIN2 isoform (TIN2S) in two ways: TIN2L contains an additional 97 amino acids, and TIN2L associates strongly with the nuclear matrix. Stringent salt and detergent conditions failed to extract TIN2L from the nuclear matrix, despite removing other telomere components, including TIN2S. In human mammary epithelial cells, each isoform showed a distinct nuclear distribution both as a function of cell cycle position and telomere length. Our results suggest a dual role for TIN2 in mediating the function of the shelterin complex and tethering telomeres to the nuclear matrix.
Collapse
Affiliation(s)
- Patrick G. Kaminker
- Buck Institute for Age Research; Novato, California USA
- Life Sciences Division; Lawrence Berkeley National Laboratory; Berkeley, California USA
| | - Sahn-Ho Kim
- Life Sciences Division; Lawrence Berkeley National Laboratory; Berkeley, California USA
| | - Pierre-Yves Desprez
- Buck Institute for Age Research; Novato, California USA
- California Pacific Medical Center; Cancer Research Institute; San Francisco, California USA
| | - Judith Campisi
- Buck Institute for Age Research; Novato, California USA
- Life Sciences Division; Lawrence Berkeley National Laboratory; Berkeley, California USA
| |
Collapse
|
8
|
Horikawa I, Chiang YJ, Patterson T, Feigenbaum L, Leem SH, Michishita E, Larionov V, Hodes RJ, Barrett JC. Differential cis-regulation of human versus mouse TERT gene expression in vivo: identification of a human-specific repressive element. Proc Natl Acad Sci U S A 2005; 102:18437-42. [PMID: 16344462 PMCID: PMC1317953 DOI: 10.1073/pnas.0508964102] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In vivo expression of human telomerase is significantly different from that of mouse telomerase. To assess the basis for this difference, a bacterial artificial chromosome clone containing the entire hTERT (human telomerase reverse transcriptase) gene was introduced in mice. In these transgenic mice, expression of the hTERT transgene was similar to that of endogenous hTERT in humans, rather than endogenous mTERT (mouse telomerase reverse transcriptase). In tissues and cells showing a striking difference in expression levels between hTERT in humans and mTERT in mice (i.e., liver, kidney, lung, uterus, and fibroblasts), expression of the hTERT transgene in transgenic mice was repressed, mimicking hTERT in humans. The transcriptional activity of the hTERT promoter was much lower than that of the mTERT promoter in mouse embryonic fibroblasts or human fibroblasts. Mutational analysis of the hTERT and mTERT promoters revealed that a nonconserved GC-box within the hTERT promoter was responsible for the human-specific repression. These results reveal that a difference in cis-regulation of transcription, rather than transacting transcription factors, is critical to species differences in tissue-specific TERT expression. Our data also suggest that the GC-box-mediated, human-specific mechanism for TERT repression is impaired in human cancers. This study represents a detailed characterization of the functional difference in a gene promoter of mice versus humans and provides not only important insight into species-specific regulation of telomerase and telomeres but also an experimental basis for generating mice humanized for telomerase enzyme and its pattern of expression.
Collapse
Affiliation(s)
- Izumi Horikawa
- Laboratory of Biosystems and Cancer, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Hartmann N, Scherthan H. Characterization of the telomere complex, TERF1 and TERF2 genes in muntjac species with fusion karyotypes. Exp Cell Res 2005; 306:64-74. [PMID: 15878333 DOI: 10.1016/j.yexcr.2005.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 01/28/2005] [Accepted: 02/01/2005] [Indexed: 11/18/2022]
Abstract
The telomere binding proteins TRF1 and TRF2 maintain and protect chromosome ends and confer karyotypic stability. Chromosome evolution in the genus Muntiacus is characterized by numerous tandem (end-to-end) fusions. To study TRF1 and TRF2 telomere binding proteins in Muntiacus species, we isolated and characterized the TERF1 and -2 genes from Indian muntjac (Muntiacus muntjak vaginalis; 2n = 6 female) and from Chinese muntjac (Muntiacus reveesi; 2n = 46). Expression analysis revealed that both genes are ubiquitously expressed and sequence analysis identified several transcript variants of both TERF genes. Control experiments disclosed a novel testis-specific splice variant of TERF1 in human testes. Amino acid sequence comparisons demonstrate that Muntiacus TRF1 and in particular TRF2 are highly conserved between muntjac and human. In vivo TRF2-GFP and immuno-staining studies in muntjac cell lines revealed telomeric TRF2 localization, while deletion of the DNA binding domain abrogated this localization, suggesting muntjac TRF2 represents a functional telomere protein. Finally, expression analysis of a set of telomere-related genes revealed their presence in muntjac fibroblasts and testis tissue, which suggests the presence of a conserved telomere complex in muntjacs. However, a deviation from the common theme was noted for the TERT gene, encoding the catalytic subunit of telomerase; TERT expression could not be detected in Indian or Chinese muntjac cDNA or genomic DNA using a series of conserved primers, while TRAP assay revealed functional telomerase in Chinese muntjac testis tissues. This suggests muntjacs may harbor a diverged telomerase sequence.
Collapse
Affiliation(s)
- Nils Hartmann
- Max Planck Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany
| | | |
Collapse
|
10
|
Kaminker P, Plachot C, Kim SH, Chung P, Crippen D, Petersen OW, Bissell MJ, Campisi J, Lelièvre SA. Higher-order nuclear organization in growth arrest of human mammary epithelial cells: a novel role for telomere-associated protein TIN2. J Cell Sci 2005; 118:1321-30. [PMID: 15741234 PMCID: PMC2933191 DOI: 10.1242/jcs.01709] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nuclear organization, such as the formation of specific nuclear subdomains, is generally thought to be involved in the control of cellular phenotype; however, there are relatively few specific examples of how mammalian nuclei organize during radical changes in phenotype, such as those occurring during differentiation and growth arrest. Using human mammary epithelial cells in which growth arrest is essential for morphological differentiation, we show that the arrest of cell proliferation is accompanied by a reorganization of the telomere-associated protein, TIN2, into one to three large nuclear subdomains. The large TIN2 domains do not contain telomeres and occur concomitant with the continued presence of TIN2 at telomeres. The TIN2 domains were sensitive to DNase, but not RNase, occurred frequently, but not exclusively near nucleoli, and overlapped often with dense domains containing heterochromatin protein 1gamma. Expression of truncated forms of TIN2 simultaneously prevented the formation of TIN2 domains and relaxed the stringent morphogenesis-induced growth arrest in human mammary epithelial cells. Here we show that a novel extra-telomeric organization of TIN2 is associated with the control of cell proliferation and identify TIN2 as an important regulator of mammary epithelial differentiation.
Collapse
Affiliation(s)
- Patrick Kaminker
- Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, California 94945, USA
| | - Cedric Plachot
- Department of Basic Medical Sciences and Cancer Center, Purdue University, 625 Harrison Street, West Lafayette, Indiana 47907-2026, USA
| | - Sahn-Ho Kim
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720, USA
| | - Peter Chung
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720, USA
| | - Danielle Crippen
- Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, California 94945, USA
| | - Ole W. Petersen
- Structural Cell Biology Unit, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200, Copenhagen, Denmark
| | - Mina J. Bissell
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720, USA
| | - Judith Campisi
- Buck Institute for Age Research, 8001 Redwood Boulevard, Novato, California 94945, USA
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720, USA
| | - Sophie A. Lelièvre
- Department of Basic Medical Sciences and Cancer Center, Purdue University, 625 Harrison Street, West Lafayette, Indiana 47907-2026, USA
- Author for correspondence ()
| |
Collapse
|
11
|
Lages CS, Etienne O, Comte J, Gauthier LR, Granotier C, Pennarun G, Boussin FD. Identification of alternative transcripts of theTRF1/Pin2 gene. J Cell Biochem 2004; 93:968-79. [PMID: 15389875 DOI: 10.1002/jcb.20235] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
TRF1 and Pin2 play an essential role in telomere homeostasis, by regulating telomere maintenance. They are generated from the same gene, TRF1/Pin2, by alternative splicing but no functional differences between these proteins have been demonstrated. We report here the detection of new alternative transcripts of the TRF1/Pin2 gene in peripheral blood lymphocytes resulting from a 76 nt insertion. Real-time RT-PCR showed that these transcripts were also produced in various normal human cells and tissues and in immortalized cell lines, but at levels lower (by a factor of 8-111) than those for the TRF1 and Pin2 transcripts. These new transcripts are predicted to encode polypeptides identical to TRF1/Pin2 at the C-terminal end but entirely lacking the acid domain and the amino-terminal part of the homodimerization domain of TRF1/Pin2. These proteins, fused at their N-terminal ends to enhanced green fluorescent protein (EGFP), were found to be located at telomeres and to induce apoptosis in cell lines with short telomeres, thereby displaying similar activity to TRF1/Pin2. However, these putative proteins lack regions important for interactions with other proteins and for homodimerization. Unlike TRF1/Pin2, they were unable to interact with tankyrase 1, suggesting that these proteins may play a role in telomere homeostasis different from those of TRF1/Pin2. The production of these alternative transcripts was down-regulated in peripheral blood lymphocytes following PHA-p activation, suggesting a possible role in resting lymphocytes.
Collapse
Affiliation(s)
- Céline Silva Lages
- Laboratoire de RadioPathologie, DRR/DSV, CEA, IPSC, Fontenay-aux-Roses, France
| | | | | | | | | | | | | |
Collapse
|
12
|
Heist EK, Huq F, Hajjar R. Telomerase and the aging heart. SCIENCE OF AGING KNOWLEDGE ENVIRONMENT : SAGE KE 2003; 2003:PE11. [PMID: 12844532 DOI: 10.1126/sageke.2003.19.pe11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Telomeres are highly conserved structures that cap and protect the ends of linear chromosomes. The telomerase enzyme is present in germline cells as well as in many rapidly dividing tissues and serves to maintain chromosome length and integrity during cell division. Telomerase activity is typically reduced as an organism ages, and this phenomenon has been implicated in the aging process. In this Perspective, we focus on the effects of both gene knockout and gene replacement of telomerase in the heart and discuss the implications of these findings for potential cardiovascular therapeutics.
Collapse
Affiliation(s)
- E Kevin Heist
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA 02129, USA
| | | | | |
Collapse
|