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Shawi M, Chu TW, Martinez-Marignac V, Yu Y, Gryaznov SM, Johnston JB, Lees-Miller SP, Assouline SE, Autexier C, Aloyz R. Telomerase contributes to fludarabine resistance in primary human leukemic lymphocytes. PLoS One 2013; 8:e70428. [PMID: 23922990 PMCID: PMC3726637 DOI: 10.1371/journal.pone.0070428] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 06/17/2013] [Indexed: 12/17/2022] Open
Abstract
We report that Imetelstat, a telomerase inhibitor that binds to the RNA component of telomerase (hTR), can sensitize primary CLL lymphocytes to fludarabine in vitro. This effect was observed in lymphocytes from clinically resistant cases and with cytogenetic abnormalities associated with bad prognosis. Imetelstat mediated-sensitization to fludarabine was not associated with telomerase activity, but with the basal expression of Ku80. Since both Imetelstat and Ku80 bind hTR, we assessed 1) if Ku80 and Imetelstat alter each other's binding to hTR in vitro and 2) the effect of an oligonucleotide complementary to the Ku binding site in hTR (Ku oligo) on the survival of primary CLL lymphocytes exposed to fludarabine. We show that Imetelstat interferes with the binding of Ku70/80 (Ku) to hTR and that the Ku oligo can sensitize CLL lymphocytes to FLU. Our results suggest that Ku binding to hTR may contribute to fludarabine resistance in CLL lmphocytes. This is the first report highlighting the potentially broad effectiveness of Imetelstat in CLL, and the potential biological and clinical implications of a functional interaction between Ku and hTR in primary human cancer cells.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Antineoplastic Agents/pharmacology
- Antineoplastic Agents/therapeutic use
- Catalytic Domain/drug effects
- Chromosome Deletion
- Chromosomes, Human, Pair 11
- Chromosomes, Human, Pair 17
- DNA Helicases/genetics
- DNA Helicases/metabolism
- Drug Resistance, Neoplasm/genetics
- Enzyme Activation
- Gene Expression Regulation, Leukemic/drug effects
- Histones/metabolism
- Humans
- Indoles/pharmacology
- Ku Autoantigen
- Leukemia, Lymphoid/drug therapy
- Leukemia, Lymphoid/genetics
- Leukemia, Lymphoid/metabolism
- Middle Aged
- Niacinamide/analogs & derivatives
- Niacinamide/pharmacology
- Oligonucleotides
- Phosphorylation
- Protein Binding/drug effects
- Telomerase/chemistry
- Telomerase/genetics
- Telomerase/metabolism
- Vidarabine/analogs & derivatives
- Vidarabine/pharmacology
- Vidarabine/therapeutic use
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Affiliation(s)
- May Shawi
- Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
- Bloomfield Centre for Research in Ageing, Jewish General Hospital, Montreal, Quebec, Canada
| | - Tsz Wai Chu
- Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Bloomfield Centre for Research in Ageing, Jewish General Hospital, Montreal, Quebec, Canada
| | - Veronica Martinez-Marignac
- Lady Davis Institute for Medical Research & Cancer Segal Center, Jewish General Hospital, Montreal, Quebec, Canada
| | - Y. Yu
- University of Calgary, Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Research Institute, Calgary, Alberta, Canada
| | | | - James B. Johnston
- Manitoba Institute of Cell Biology, Cancer Care Manitoba, Winnipeg, Manitoba, Canada
| | - Susan P. Lees-Miller
- University of Calgary, Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Research Institute, Calgary, Alberta, Canada
| | - Sarit E. Assouline
- Oncology Department, McGill University, Montreal, Quebec, Canada
- Lady Davis Institute for Medical Research & Cancer Segal Center, Jewish General Hospital, Montreal, Quebec, Canada
| | - Chantal Autexier
- Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
- Bloomfield Centre for Research in Ageing, Jewish General Hospital, Montreal, Quebec, Canada
| | - Raquel Aloyz
- Department of Medicine, Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Oncology Department, McGill University, Montreal, Quebec, Canada
- Lady Davis Institute for Medical Research & Cancer Segal Center, Jewish General Hospital, Montreal, Quebec, Canada
- * E-mail:
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2
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Abstract
This chapter describes the preparation of NMR quantities of RNA purified to single-nucleotide resolution for protein-RNA interaction studies. The protocol is easily modified to make nucleotide-specific isotopically labeled RNAs or uniformly labeled RNA fragments for ligation to generate segmentally labeled RNAs.
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Affiliation(s)
- Carla A Theimer
- Department of Chemistry, University at Albany SUNY, Albany, NY, USA.
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3
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Lin J, Ly H, Hussain A, Abraham M, Pearl S, Tzfati Y, Parslow TG, Blackburn EH. A universal telomerase RNA core structure includes structured motifs required for binding the telomerase reverse transcriptase protein. Proc Natl Acad Sci U S A 2004; 101:14713-8. [PMID: 15371596 PMCID: PMC522012 DOI: 10.1073/pnas.0405879101] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Telomerase synthesizes telomeric DNA by copying a short template sequence within its telomerase RNA component. We delineated nucleotides and base-pairings within a previously mapped central domain of the Saccharomyces cerevisiae telomerase RNA (TLC1) that are important for telomerase function and for binding to the telomerase catalytic protein Est2p. Phylogenetic comparison of telomerase RNA sequences from several budding yeasts revealed a core structure common to Saccharomyces and Kluyveromyces yeast species. We show that in this structure three conserved sequences interact to provide a binding site for Est2p positioned near the template. These results, combined with previous studies on telomerase RNAs from other budding yeasts, vertebrates, and ciliates, define a minimal universal core for telomerase RNAs.
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Affiliation(s)
- Jue Lin
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA
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4
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Abstract
Arthur Kornberg "never met a dull enzyme" (For the Love of Enzymes: The Odyssey of a Biochemist, Harvard University Press, 1989) and telomerase is no exception. Telomerase is a remarkable polymerase that uses an internal RNA template to reverse-transcribe telomere DNA, one nucleotide at a time, onto telomeric, G-rich single-stranded DNA. In the 17 years since its discovery, the characterization of telomerase enzyme components has uncovered a highly conserved family of telomerase reverse transcriptases that, together with the telomerase RNA, appear to comprise the enzymatic core of telomerase. While not as comprehensively understood as yet, some telomerase-associated proteins also serve crucial roles in telomerase function in vivo, such as telomerase ribonudeoprotein (RNP) assembly, recruitment to the telomere, and the coordination of DNA replication at the telomere. A selected overview of the biochemical properties of this unique enzyme, in vitro and in vivo, will be presented.
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5
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Gavory G, Farrow M, Balasubramanian S. Minimum length requirement of the alignment domain of human telomerase RNA to sustain catalytic activity in vitro. Nucleic Acids Res 2002; 30:4470-80. [PMID: 12384594 PMCID: PMC137139 DOI: 10.1093/nar/gkf575] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Telomeres are essential for genomic stability and cell viability. Telomerase, the enzyme responsible for telomere maintenance, is composed of a reverse transcriptase protein subunit and an integral RNA component which contains the templating domain. In human telomerase, the template region consists of 11 nt (3'-rCAAUCCCAAUC-5') and comprises an alignment domain (italicised) plus a template sequence encoding the telomeric repeat d(GGT TAG). In this study, the alignment domain of human telomerase was systematically reduced from the 3' end and the resultant recombinant enzyme activity was evaluated in vitro. Deletion or substitution of one or two residues from the 3' end of the alignment domain caused only a slight reduction in overall catalytic activity and did not alter the processivity of the enzyme. Deletion or substitution of three or more residues from the 3' end of the alignment domain resulted in total loss of catalytic activity. These results suggest that the two most 3' terminal RNA residues are relevant but not essential for overall activity and that the minimal length requirement of the alignment domain is 3 nt. Furthermore, base pairing between the 3' end of the primer substrate and the first two residues of the alignment domain is also not an absolute requirement for processive synthesis.
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Affiliation(s)
- Gérald Gavory
- University Chemical Laboratory, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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6
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Ye AJ, Romero DP. A unique pause pattern during telomere addition by the error-prone telomerase from the ciliate Paramecium tetraurelia. Gene 2002; 294:205-13. [PMID: 12234682 DOI: 10.1016/s0378-1119(02)00790-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Telomeric DNA - the short, tandemly repeated sequences at the ends of chromosomes - is synthesized by telomerase, a ribonucleoprotein enzyme that copies a specific template sequence within its integral RNA moiety. The error-prone telomerase from the ciliate Paramecium tetraurelia stereotypically misincorporates TTP at telomerase RNA templating nucleotide C52, accounting for the 30% TTTGGG repeats randomly distributed in wild-type telomeres. Paramecium tetraurelia telomerase has been isolated from macronuclear extracts and characterized with respect to the extension of telomeric primers in vitro. Unlike telomerase activities from other species, the predominant pause during telomeric repeat synthesis by P. tetraurelia telomerase does not occur at the 5' end of the templating domain (templating nucleotide C49). Instead, the pause by P. tetraurelia telomerase is at templating nucleotide C53, immediately prior to incorporation of dGTP (or TTP) at C52. The configuration of the catalytic site at this template position during telomere synthesis is most likely responsible for the high incidence of misincorporation of TTP at C52. The gene for the P. tetraurelia telomerase catalytic subunit, telomerase reverse transcriptase (TERT), has been cloned and sequenced. A comparative analysis of the P. tetraurelia TERT with homologs from other species, including that from another Paramecium species that does not make a high percentage of misincorporation errors, has been initiated. This study may delineate those TERT structural elements that contribute to telomerase fidelity.
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Affiliation(s)
- Amanda J Ye
- Department of Pharmacology, Medical School, University of Minnesota, 6-120 Jackson Hall, 321 Church Street S.E., Minneapolis, MN 55455, USA
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7
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Abstract
Telomere length is maintained in most eukaryotic cells by telomerase. The core components of this ribonucleoprotein (RNP) enzyme include a protein catalytic subunit, composed of motifs conserved among reverse transcriptases (RT), and an RNA subunit that contains a short template sequence essential for the synthesis of telomeric repeats. We developed an electrophoretic mobility shift assay using active telomerase partially purified from 293 cells and radiolabeled, in vitro-transcribed human telomerase RNA (hTR) to investigate the molecular interactions of the human telomerase RT (hTERT) and telomerase-associated proteins with hTR. A specific hTR-protein complex was identified and shown to contain hTERT and human Staufen by antibody supershift assays. Variants of hTR altered in distinct structural elements were analyzed for their ability to competitively inhibit complex formation. Human telomerase RNAs lacking the CR4-CR5 domain were poor inhibitors of hTR-protein complex formation, suggesting that the CR4-CR5 domain of hTR is a potential protein-binding site. Furthermore, alterations in the telomerase RNA pseudoknot's P3 helix, the CR7 domain, or the H/ACA box efficiently inhibited formation of the complex, indicating that these domains are dispensable for the assembly of a telomerase RNP in vitro. Potential telomerase-associated proteins that bind hTR were also identified using a UV cross-linking assay.
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Affiliation(s)
- F Bachand
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 2B2, Canada
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8
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Bachand F, Autexier C. Functional regions of human telomerase reverse transcriptase and human telomerase RNA required for telomerase activity and RNA-protein interactions. Mol Cell Biol 2001; 21:1888-97. [PMID: 11238925 PMCID: PMC86762 DOI: 10.1128/mcb.21.5.1888-1897.2001] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Telomerase is a specialized reverse transcriptase (RT) that is minimally composed of a protein catalytic subunit and an RNA component. The RNA subunit contains a short template sequence that directs the synthesis of DNA repeats at the ends of chromosomes. Human telomerase activity can be reconstituted in vitro by the expression of the human telomerase protein catalytic subunit (hTERT) in the presence of recombinant human telomerase RNA (hTR) in a rabbit reticulocyte lysate (RRL) system. We analyzed telomerase activity and binding of hTR to hTERT in RRL by expressing different hTERT and hTR variants. hTRs containing nucleotide substitutions that are predicted to disrupt base pairing in the P3 helix of the pseudoknot weakly reconstituted human telomerase activity yet retained their ability to bind hTERT. Our results also identified two distinct regions of hTR that can independently bind hTERT in vitro. Furthermore, sequences or structures between nucleotides 208 and 330 of hTR (which include the conserved CR4-CR5 domain) were found to be important for hTERT-hTR interactions and for telomerase activity reconstitution. Human TERT carboxy-terminal amino acid deletions extending to motif E or the deletion of the first 280 amino acids abolished human telomerase activity without affecting the ability of hTERT to associate with hTR, suggesting that the RT and RNA binding functions of hTERT are separable. These results indicate that the reconstitution of human telomerase activity in vitro requires regions of hTERT that (i) are distinct from the conserved RT motifs and (ii) bind nucleotides distal to the hTR template sequence.
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Affiliation(s)
- F Bachand
- Department of Anatomy & Cell Biology, McGill University, Montréal, Québec, Canada H3A 2B2
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9
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Beattie TL, Zhou W, Robinson MO, Harrington L. Polymerization defects within human telomerase are distinct from telomerase RNA and TEP1 binding. Mol Biol Cell 2000; 11:3329-40. [PMID: 11029039 PMCID: PMC14995 DOI: 10.1091/mbc.11.10.3329] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The minimal, active core of human telomerase is postulated to contain two components, the telomerase RNA hTER and the telomerase reverse transcriptase hTERT. The reconstitution of human telomerase activity in vitro has facilitated the identification of sequences within the telomerase RNA and the RT motifs of hTERT that are essential for telomerase activity. However, the precise role of residues outside the RT domain of hTERT is unknown. Here we have delineated several regions within hTERT that are important for telomerase catalysis, primer use, and interaction with the telomerase RNA and the telomerase-associated protein TEP1. In particular, certain deletions of the amino and carboxy terminus of hTERT that retained an interaction with telomerase RNA and TEP1 were nonetheless completely inactive in vitro and in vivo. Furthermore, hTERT truncations lacking the amino terminus that were competent to bind the telomerase RNA were severely compromised for the ability to elongate telomeric and nontelomeric primers. These results suggest that the interaction of telomerase RNA with hTERT can be functionally uncoupled from polymerization, and that there are regions outside the RT domain of hTERT that are critical for telomerase activity and primer use. These results establish that the human telomerase RT possesses unique polymerization determinants that distinguish it from other RTs.
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Affiliation(s)
- T L Beattie
- Ontario Cancer Institute/Amgen Institute, Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2C1 Canada
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