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Bozděchová L, Havlová K, Fajkus P, Fajkus J. Analysis of Telomerase RNA Structure in Physcomitrium patens Indicates Functionally Relevant Transitions Between OPEN and CLOSED Conformations. J Mol Biol 2024; 436:168417. [PMID: 38143018 DOI: 10.1016/j.jmb.2023.168417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
Telomerase RNA (TR) conformation determines its function as a template for telomere synthesis and as a scaffold for the assembly of the telomerase nucleoprotein complex. Experimental analyses of TR secondary structure using DMS-Map Seq and SHAPE-Map Seq techniques show its CLOSED conformation as the consensus structure where the template region cannot perform its function. Our data show that the apparent discrepancy between experimental results and predicted TR functional conformation, mostly ignored in published studies, can be explained using data analysis based on single-molecule structure prediction from individual sequencing reads by the recently established DaVinci method. This method results in several clusters of secondary structures reflecting the structural dynamics of TR, possibly related to its multiple functional states. Interestingly, the presumed active (OPEN) conformation of TR corresponds to a minor fraction of TR under in vivo conditions. Therefore, structural polymorphism and dynamic TR transitions between CLOSED and OPEN conformations may be involved in telomerase activity regulation as a switch that functions independently of total TR transcript levels.
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Affiliation(s)
- Lucie Bozděchová
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Kateřina Havlová
- National Center for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Petr Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic; Institute of Biophysics, Czech Acad Sci, Královopolská 135, 61200 Brno, Czech Republic
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic; National Center for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic; Institute of Biophysics, Czech Acad Sci, Královopolská 135, 61200 Brno, Czech Republic.
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2
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Liu M, Zhang Y, Jian Y, Gu L, Zhang D, Zhou H, Wang Y, Xu ZX. The regulations of telomerase reverse transcriptase (TERT) in cancer. Cell Death Dis 2024; 15:90. [PMID: 38278800 PMCID: PMC10817947 DOI: 10.1038/s41419-024-06454-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 01/04/2024] [Accepted: 01/08/2024] [Indexed: 01/28/2024]
Abstract
Abnormal activation of telomerase occurs in most cancer types, which facilitates escaping from cell senescence. As the key component of telomerase, telomerase reverse transcriptase (TERT) is regulated by various regulation pathways. TERT gene changing in its promoter and phosphorylation respectively leads to TERT ectopic expression at the transcription and protein levels. The co-interacting factors play an important role in the regulation of TERT in different cancer types. In this review, we focus on the regulators of TERT and these downstream functions in cancer regulation. Determining the specific regulatory mechanism will help to facilitate the development of a cancer treatment strategy that targets telomerase and cancer cell senescence. As the most important catalytic subunit component of telomerase, TERT is rapidly regulated by transcriptional factors and PTM-related activation. These changes directly influence TERT-related telomere maintenance by regulating telomerase activity in telomerase-positive cancer cells, telomerase assembly with telomere-binding proteins, and recruiting telomerase to the telomere. Besides, there are also non-canonical functions that are influenced by TERT, including the basic biological functions of cancer cells, such as proliferation, apoptosis, cell cycle regulation, initiating cell formation, EMT, and cell invasion. Other downstream effects are the results of the influence of transcriptional factors by TERT. Currently, some small molecular inhibitors of TERT and TERT vaccine are under research as a clinical therapeutic target. Purposeful work is in progress.
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Affiliation(s)
- Mingdi Liu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Yuning Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Yongping Jian
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Liting Gu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Dan Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China
| | - Honglan Zhou
- Department of Urology, The First Hospital of Jilin University, Changchun, 130021, Jilin, China.
| | - Yishu Wang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China.
| | - Zhi-Xiang Xu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, 130021, Jilin, China.
- Department of Urology, The First Hospital of Jilin University, Changchun, 130021, Jilin, China.
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3
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Liao X, Zhu W, Zhou J, Li H, Xu X, Zhang B, Gao X. Repetitive DNA sequence detection and its role in the human genome. Commun Biol 2023; 6:954. [PMID: 37726397 PMCID: PMC10509279 DOI: 10.1038/s42003-023-05322-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 09/04/2023] [Indexed: 09/21/2023] Open
Abstract
Repetitive DNA sequences playing critical roles in driving evolution, inducing variation, and regulating gene expression. In this review, we summarized the definition, arrangement, and structural characteristics of repeats. Besides, we introduced diverse biological functions of repeats and reviewed existing methods for automatic repeat detection, classification, and masking. Finally, we analyzed the type, structure, and regulation of repeats in the human genome and their role in the induction of complex diseases. We believe that this review will facilitate a comprehensive understanding of repeats and provide guidance for repeat annotation and in-depth exploration of its association with human diseases.
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Affiliation(s)
- Xingyu Liao
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Wufei Zhu
- Department of Endocrinology, Yichang Central People's Hospital, The First College of Clinical Medical Science, China Three Gorges University, 443000, Yichang, P.R. China
| | - Juexiao Zhou
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Haoyang Li
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Xiaopeng Xu
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Bin Zhang
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia
| | - Xin Gao
- Computational Bioscience Research Center (CBRC), Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.
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4
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Lue NF, Autexier C. Orchestrating nucleic acid-protein interactions at chromosome ends: telomerase mechanisms come into focus. Nat Struct Mol Biol 2023; 30:878-890. [PMID: 37400652 PMCID: PMC10539978 DOI: 10.1038/s41594-023-01022-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 05/16/2023] [Indexed: 07/05/2023]
Abstract
Telomerase is a special reverse transcriptase ribonucleoprotein dedicated to the synthesis of telomere repeats that protect chromosome ends. Among reverse transcriptases, telomerase is unique in using a stably associated RNA with an embedded template to synthesize a specified sequence. Moreover, it is capable of iteratively copying the same template region (repeat addition processivity) through multiple rounds of RNA-DNA unpairing and reannealing, that is, the translocation reaction. Biochemical analyses of telomerase over the past 3 decades in protozoa, fungi and mammals have identified structural elements that underpin telomerase mechanisms and have led to models that account for the special attributes of telomerase. Notably, these findings and models can now be interpreted and adjudicated through recent cryo-EM structures of Tetrahymena and human telomerase holoenzyme complexes in association with substrates and regulatory proteins. Collectively, these structures reveal the intricate protein-nucleic acid interactions that potentiate telomerase's unique translocation reaction and clarify how this enzyme reconfigures the basic reverse transcriptase scaffold to craft a polymerase dedicated to the synthesis of telomere DNA. Among the many new insights is the resolution of the telomerase 'anchor site' proposed more than 3 decades ago. The structures also highlight the nearly universal conservation of a protein-protein interface between an oligonucleotide/oligosaccharide-binding (OB)-fold regulatory protein and the telomerase catalytic subunit, which enables spatial and temporal regulation of telomerase function in vivo. In this Review, we discuss key features of the structures in combination with relevant functional analyses. We also examine conserved and divergent aspects of telomerase mechanisms as gleaned from studies in different model organisms.
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Affiliation(s)
- Neal F Lue
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, NY, USA.
| | - Chantal Autexier
- Lady Davis Institute for Medical Research, Jewish General Hospital and Department of Anatomy and Cell Biology and Department of Medicine, McGill University, Montreal, Quebec, Canada.
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5
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Padmanaban S, Tesmer VM, Nandakumar J. Interaction hub critical for telomerase recruitment and primer-template handling for catalysis. Life Sci Alliance 2023; 6:e202201727. [PMID: 36963832 PMCID: PMC10055720 DOI: 10.26508/lsa.202201727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 03/26/2023] Open
Abstract
Telomerase processively adds telomeric DNA repeats to chromosome ends using catalytic protein subunit TERT and a template on its RNA subunit TR. Mammalian telomerase is recruited to telomeres by the TEL patch and NOB regions of shelterin component TPP1. Recent cryo-EM structures of human telomerase reveal that a composite TERT TEN-(IFD-TRAP) domain interacts with TPP1. Here, we generate TERT mutants to demonstrate that a three-way TEN-(IFD-TRAP)-TPP1 interaction is critical for telomerase recruitment to telomeres and processive telomere repeat addition. Single mutations of IFD-TRAP at its interface with TR or the DNA primer impair telomerase catalysis. We further reveal the importance of TERT motif 3N and TEN domain loop 99FGF101 in telomerase action. Finally, we demonstrate that TPP1 TEL patch loop residue F172, which undergoes a structural rearrangement to bind telomerase, contributes to the human-mouse species specificity of the telomerase-TPP1 interaction. Our study provides insights into the multiple functions of TERT IFD-TRAP, reveals novel TERT and TPP1 elements critical for function, and helps explain how TPP1 binding licenses robust telomerase action at natural chromosome ends.
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Affiliation(s)
- Shilpa Padmanaban
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Valerie M Tesmer
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Jayakrishnan Nandakumar
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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6
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Welfer GA, Freudenthal BD. Recent advancements in the structural biology of human telomerase and their implications for improved design of cancer therapeutics. NAR Cancer 2023; 5:zcad010. [PMID: 36879683 PMCID: PMC9984990 DOI: 10.1093/narcan/zcad010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/31/2023] [Accepted: 02/27/2023] [Indexed: 03/06/2023] Open
Abstract
Telomerase is a specialized reverse transcriptase that synthesizes telomeric repeats at the ends of linear chromosomes. Telomerase is transiently expressed in germ and stem cells, but nearly all somatic cells silence it after differentiating. However, the vast majority of cancer cells reactivate and constitutively express telomerase to maintain replicative immortality. Because of this, telomerase has remained a promising broad-spectrum chemotherapeutic target for over 30 years. However, various challenges associated with obtaining high-resolution structural data for telomerase have limited the development of rationally designed structure-based therapeutics. Various techniques and model systems have been utilized to advance our understanding of the structural biology of telomerase. In particular, multiple high-resolution cryogenic electron microscopy (cryo-EM) structures published within the past few years have revealed new components of the telomerase complex with near atomic resolution structural models. Additionally, these structures have provided details for how telomerase is recruited to telomeres and its mechanism of telomere synthesis. With these new pieces of evidence, and the promising outlook for future refinements to our current models, the possibility of telomerase specific chemotherapeutics is becoming more tangible than ever. This review summarizes these recent advancements and outlines outstanding questions in the field.
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Affiliation(s)
- Griffin A Welfer
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- University of Kansas Cancer Center, Kansas City, KS 66160, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
- University of Kansas Cancer Center, Kansas City, KS 66160, USA
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7
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Welfer GA, Borin VA, Cortez LM, Opresko PL, Agarwal PK, Freudenthal BD. Altered Nucleotide Insertion Mechanisms of Disease-Associated TERT Variants. Genes (Basel) 2023; 14:281. [PMID: 36833208 PMCID: PMC9957172 DOI: 10.3390/genes14020281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/15/2023] [Accepted: 01/17/2023] [Indexed: 01/26/2023] Open
Abstract
Telomere biology disorders (TBDs) are a spectrum of diseases that arise from mutations in genes responsible for maintaining telomere integrity. Human telomerase reverse transcriptase (hTERT) adds nucleotides to chromosome ends and is frequently mutated in individuals with TBDs. Previous studies have provided insight into how relative changes in hTERT activity can lead to pathological outcomes. However, the underlying mechanisms describing how disease-associated variants alter the physicochemical steps of nucleotide insertion remain poorly understood. To address this, we applied single-turnover kinetics and computer simulations to the Tribolium castaneum TERT (tcTERT) model system and characterized the nucleotide insertion mechanisms of six disease-associated variants. Each variant had distinct consequences on tcTERT's nucleotide insertion mechanism, including changes in nucleotide binding affinity, rates of catalysis, or ribonucleotide selectivity. Our computer simulations provide insight into how each variant disrupts active site organization, such as suboptimal positioning of active site residues, destabilization of the DNA 3' terminus, or changes in nucleotide sugar pucker. Collectively, this work provides a holistic characterization of the nucleotide insertion mechanisms for multiple disease-associated TERT variants and identifies additional functions of key active site residues during nucleotide insertion.
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Affiliation(s)
- Griffin A. Welfer
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66103, USA
- University of Kansas Cancer Center, Kansas City, KS 66103, USA
| | - Veniamin A. Borin
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State University, Stillwater, OK 74077, USA
| | - Luis M. Cortez
- University of Kansas Cancer Center, Kansas City, KS 66103, USA
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66103, USA
| | - Patricia L. Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, and UPMC Hillman Cancer Center, Pittsburgh, PA 15232, USA
| | - Pratul K. Agarwal
- Department of Physiological Sciences and High-Performance Computing Center, Oklahoma State University, Stillwater, OK 74077, USA
| | - Bret D. Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS 66103, USA
- University of Kansas Cancer Center, Kansas City, KS 66103, USA
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66103, USA
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8
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He Y, Feigon J. Telomerase structural biology comes of age. Curr Opin Struct Biol 2022; 76:102446. [PMID: 36081246 PMCID: PMC9884118 DOI: 10.1016/j.sbi.2022.102446] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 07/22/2022] [Accepted: 07/26/2022] [Indexed: 01/31/2023]
Abstract
Telomerase is an RNA-protein complex comprising telomerase reverse transcriptase, a non-coding telomerase RNA, and proteins involved in biogenesis, assembly, localization, or recruitment. Telomerase synthesizes the telomeric DNA at the 3'-ends of linear chromosomes. During the past decade, structural studies have defined the architecture of Tetrahymena and human telomerase as well as protein and RNA domain structures, but high-resolution details of interactions remained largely elusive. In the past two years, several sub-4 Å cryo-electron microscopy structures of telomerase were published, including Tetrahymena telomerase at different steps of telomere repeat addition and human telomerase with telomere shelterin proteins that recruit telomerase to telomeres. These and other recent structural studies have expanded our understanding of telomerase assembly, mechanism, recruitment, and mutations leading to disease.
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Affiliation(s)
- Yao He
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095-1569, USA; Department of Microbiology, Immunology, and Molecular Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Juli Feigon
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095-1569, USA.
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9
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Gao J, Pickett HA. Targeting telomeres: advances in telomere maintenance mechanism-specific cancer therapies. Nat Rev Cancer 2022; 22:515-532. [PMID: 35790854 DOI: 10.1038/s41568-022-00490-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/25/2022] [Indexed: 12/31/2022]
Abstract
Cancer cells establish replicative immortality by activating a telomere-maintenance mechanism (TMM), be it telomerase or the alternative lengthening of telomeres (ALT) pathway. Targeting telomere maintenance represents an intriguing opportunity to treat the vast majority of all cancer types. Whilst telomerase inhibitors have historically been heralded as promising anticancer agents, the reality has been more challenging, and there are currently no therapeutic options for cancer types that use ALT despite their aggressive nature and poor prognosis. In this Review, we discuss the mechanistic differences between telomere maintenance by telomerase and ALT, the current methods used to detect each mechanism, the utility of these tests for clinical diagnosis, and recent developments in the therapeutic strategies being employed to target both telomerase and ALT. We present notable developments in repurposing established therapeutic agents and new avenues that are emerging to target cancer types according to which TMM they employ. These opportunities extend beyond inhibition of telomere maintenance, by finding and exploiting inherent weaknesses in the telomeres themselves to trigger rapid cellular effects that lead to cell death.
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Affiliation(s)
- Jixuan Gao
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia.
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10
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Structure of Tetrahymena telomerase-bound CST with polymerase α-primase. Nature 2022; 608:813-818. [PMID: 35831498 PMCID: PMC9728385 DOI: 10.1038/s41586-022-04931-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 06/06/2022] [Indexed: 02/03/2023]
Abstract
Telomeres are the physical ends of linear chromosomes. They are composed of short repeating sequences (such as TTGGGG in the G-strand for Tetrahymena thermophila) of double-stranded DNA with a single-strand 3' overhang of the G-strand and, in humans, the six shelterin proteins: TPP1, POT1, TRF1, TRF2, RAP1 and TIN21,2. TPP1 and POT1 associate with the 3' overhang, with POT1 binding the G-strand3 and TPP1 (in complex with TIN24) recruiting telomerase via interaction with telomerase reverse transcriptase5 (TERT). The telomere DNA ends are replicated and maintained by telomerase6, for the G-strand, and subsequently DNA polymerase α-primase7,8 (PolαPrim), for the C-strand9. PolαPrim activity is stimulated by the heterotrimeric complex CTC1-STN1-TEN110-12 (CST), but the structural basis of the recruitment of PolαPrim and CST to telomere ends remains unknown. Here we report cryo-electron microscopy (cryo-EM) structures of Tetrahymena CST in the context of the telomerase holoenzyme, in both the absence and the presence of PolαPrim, and of PolαPrim alone. Tetrahymena Ctc1 binds telomerase subunit p50, a TPP1 orthologue, on a flexible Ctc1 binding motif revealed by cryo-EM and NMR spectroscopy. The PolαPrim polymerase subunit POLA1 binds Ctc1 and Stn1, and its interface with Ctc1 forms an entry port for G-strand DNA to the POLA1 active site. We thus provide a snapshot of four key components that are required for telomeric DNA synthesis in a single active complex-telomerase-core ribonucleoprotein, p50, CST and PolαPrim-that provides insights into the recruitment of CST and PolαPrim and the handoff between G-strand and C-strand synthesis.
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11
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Structure of active human telomerase with telomere shelterin protein TPP1. Nature 2022; 604:578-583. [PMID: 35418675 PMCID: PMC9912816 DOI: 10.1038/s41586-022-04582-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/23/2022] [Indexed: 12/13/2022]
Abstract
Human telomerase is a RNA-protein complex that extends the 3' end of linear chromosomes by synthesizing multiple copies of the telomeric repeat TTAGGG1. Its activity is a determinant of cancer progression, stem cell renewal and cellular aging2-5. Telomerase is recruited to telomeres and activated for telomere repeat synthesis by the telomere shelterin protein TPP16,7. Human telomerase has a bilobal structure with a catalytic core ribonuclear protein and a H and ACA box ribonuclear protein8,9. Here we report cryo-electron microscopy structures of human telomerase catalytic core of telomerase reverse transcriptase (TERT) and telomerase RNA (TER (also known as hTR)), and of telomerase with the shelterin protein TPP1. TPP1 forms a structured interface with the TERT-unique telomerase essential N-terminal domain (TEN) and the telomerase RAP motif (TRAP) that are unique to TERT, and conformational dynamics of TEN-TRAP are damped upon TPP1 binding, defining the requirements for recruitment and activation. The structures further reveal that the elements of TERT and TER that are involved in template and telomeric DNA handling-including the TEN domain and the TRAP-thumb helix channel-are largely structurally homologous to those in Tetrahymena telomerase10, and provide unique insights into the mechanism of telomerase activity. The binding site of the telomerase inhibitor BIBR153211,12 overlaps a critical interaction between the TER pseudoknot and the TERT thumb domain. Numerous mutations leading to telomeropathies13,14 are located at the TERT-TER and TEN-TRAP-TPP1 interfaces, highlighting the importance of TER-TERT and TPP1 interactions for telomerase activity, recruitment and as drug targets.
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12
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Single-Run Catalysis and Kinetic Control of Human Telomerase Holoenzyme. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1371:109-129. [PMID: 34962637 DOI: 10.1007/5584_2021_676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Genome stability in eukaryotic cells relies on proper maintenance of telomeres at the termini of linear chromosomes. Human telomerase holoenzyme is required for maintaining telomere stability in a majority of proliferative human cells, making it essential for control of cell division and aging, stem cell maintenance, and development and survival of tumor or cancer. A dividing human cell usually contains a limited number of active telomerase holoenzymes. Recently, we discovered that a human telomerase catalytic site undergoes catalysis-dependent shut-off and an inactive site can be reactivated by cellular fractions containing human intracellular telomerase-activating factors (hiTAFs). Such ON-OFF control of human telomerase activity suggests a dynamic switch between inactive and active pools of the holoenzymes. In this review, we will link the ON-OFF control to the thermodynamic and kinetic properties of human telomerase holoenzymes, and discuss its potential contributions to the maintenance of telomere length equilibrium. This treatment suggests probabilistic fluctuations in the number of active telomerase holoenzymes as well as the number of telomeres that are extended in a limited number of cell cycles, and may be an important component of a fully quantitative model for the dynamic control of telomerase activities and telomere lengths in different types of eukaryotic cells.
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13
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Fajkus P, Kilar A, Nelson ADL, Holá M, Peška V, Goffová I, Fojtová M, Zachová D, Fulnečková J, Fajkus J. Evolution of plant telomerase RNAs: farther to the past, deeper to the roots. Nucleic Acids Res 2021; 49:7680-7694. [PMID: 34181710 PMCID: PMC8287931 DOI: 10.1093/nar/gkab545] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/01/2021] [Accepted: 06/10/2021] [Indexed: 01/10/2023] Open
Abstract
The enormous sequence heterogeneity of telomerase RNA (TR) subunits has thus far complicated their characterization in a wider phylogenetic range. Our recent finding that land plant TRs are, similarly to known ciliate TRs, transcribed by RNA polymerase III and under the control of the type-3 promoter, allowed us to design a novel strategy to characterize TRs in early diverging Viridiplantae taxa, as well as in ciliates and other Diaphoretickes lineages. Starting with the characterization of the upstream sequence element of the type 3 promoter that is conserved in a number of small nuclear RNAs, and the expected minimum TR template region as search features, we identified candidate TRs in selected Diaphoretickes genomes. Homologous TRs were then used to build covariance models to identify TRs in more distant species. Transcripts of the identified TRs were confirmed by transcriptomic data, RT-PCR and Northern hybridization. A templating role for one of our candidates was validated in Physcomitrium patens. Analysis of secondary structure demonstrated a deep conservation of motifs (pseudoknot and template boundary element) observed in all published TRs. These results elucidate the evolution of the earliest eukaryotic TRs, linking the common origin of TRs across Diaphoretickes, and underlying evolutionary transitions in telomere repeats.
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Affiliation(s)
- Petr Fajkus
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, Brno CZ-61265, Czech Republic.,Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic
| | - Agata Kilar
- Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic.,Laboratory of Functional Genomics and Proteomics, NCBR, Faculty of Science, Masaryk University, Brno CZ-61137, Czech Republic
| | | | - Marcela Holá
- Institute of Experimental Botany of the Czech Academy of Sciences, Prague CZ-16000, Czech Republic
| | - Vratislav Peška
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, Brno CZ-61265, Czech Republic
| | - Ivana Goffová
- Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic.,Laboratory of Functional Genomics and Proteomics, NCBR, Faculty of Science, Masaryk University, Brno CZ-61137, Czech Republic
| | - Miloslava Fojtová
- Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic.,Laboratory of Functional Genomics and Proteomics, NCBR, Faculty of Science, Masaryk University, Brno CZ-61137, Czech Republic
| | - Dagmar Zachová
- Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic
| | - Jana Fulnečková
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, Brno CZ-61265, Czech Republic
| | - Jiří Fajkus
- Department of Cell Biology and Radiobiology, Institute of Biophysics of the Czech Academy of Sciences, Brno CZ-61265, Czech Republic.,Mendel Centre for Plant Genomics and Proteomics, CEITEC Masaryk University, Brno CZ-62500, Czech Republic.,Laboratory of Functional Genomics and Proteomics, NCBR, Faculty of Science, Masaryk University, Brno CZ-61137, Czech Republic
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14
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How DNA damage and non-canonical nucleotides alter the telomerase catalytic cycle. DNA Repair (Amst) 2021; 107:103198. [PMID: 34371388 DOI: 10.1016/j.dnarep.2021.103198] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 01/01/2023]
Abstract
Telomeres at the ends of linear chromosomes are essential for genome maintenance and sustained cellular proliferation, but shorten with each cell division. Telomerase, a specialized reverse transcriptase with its own integral RNA template, compensates for this by lengthening the telomeric 3' single strand overhang. Mammalian telomerase has the unique ability to processively synthesize multiple GGTTAG repeats, by translocating along its product and reiteratively copying the RNA template, termed repeat addition processivity (RAP). This unusual form of processivity is distinct from the nucleotide addition processivity (NAP) shared by all other DNA polymerases. In this review, we focus on the minimally active human telomerase catalytic core consisting of the telomerase reverse transcriptase (TERT) and the integral RNA (TR), which catalyzes DNA synthesis. We review the mechanisms by which oxidatively damaged nucleotides, and anti-viral and anti-cancer nucleotide drugs affect the telomerase catalytic cycle. Finally, we offer perspective on how we can leverage telomerase's unique properties, and advancements in understanding of telomerase catalytic mechanism, to selectively manipulate telomerase activity with therapeutics, particularly in cancer treatment.
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15
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Structures of telomerase at several steps of telomere repeat synthesis. Nature 2021; 593:454-459. [PMID: 33981033 DOI: 10.1038/s41586-021-03529-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 04/09/2021] [Indexed: 12/14/2022]
Abstract
Telomerase is unique among the reverse transcriptases in containing a noncoding RNA (known as telomerase RNA (TER)) that includes a short template that is used for the processive synthesis of G-rich telomeric DNA repeats at the 3' ends of most eukaryotic chromosomes1. Telomerase maintains genomic integrity, and its activity or dysregulation are critical determinants of human longevity, stem cell renewal and cancer progression2,3. Previous cryo-electron microscopy structures have established the general architecture, protein components and stoichiometries of Tetrahymena and human telomerase, but our understandings of the details of DNA-protein and RNA-protein interactions and of the mechanisms and recruitment involved remain limited4-6. Here we report cryo-electron microscopy structures of active Tetrahymena telomerase with telomeric DNA at different steps of nucleotide addition. Interactions between telomerase reverse transcriptase (TERT), TER and DNA reveal the structural basis of the determination of the 5' and 3' template boundaries, handling of the template-DNA duplex and separation of the product strand during nucleotide addition. The structure and binding interface between TERT and telomerase protein p50 (a homologue of human TPP17,8) define conserved interactions that are required for telomerase activation and recruitment to telomeres. Telomerase La-related protein p65 remodels several regions of TER, bridging the 5' and 3' ends and the conserved pseudoknot to facilitate assembly of the TERT-TER catalytic core.
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