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Kannan A, Gangadharan Leela S, Branzei D, Gangwani L. Role of senataxin in R-loop-mediated neurodegeneration. Brain Commun 2024; 6:fcae239. [PMID: 39070547 PMCID: PMC11277865 DOI: 10.1093/braincomms/fcae239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 06/14/2024] [Accepted: 07/13/2024] [Indexed: 07/30/2024] Open
Abstract
Senataxin is an RNA:DNA helicase that plays an important role in the resolution of RNA:DNA hybrids (R-loops) formed during transcription. R-loops are involved in the regulation of biological processes such as immunoglobulin class switching, gene expression and DNA repair. Excessive accumulation of R-loops results in DNA damage and loss of genomic integrity. Senataxin is critical for maintaining optimal levels of R-loops to prevent DNA damage and acts as a genome guardian. Within the nucleus, senataxin interacts with various RNA processing factors and DNA damage response and repair proteins. Senataxin interactors include survival motor neuron and zinc finger protein 1, with whom it co-localizes in sub-nuclear bodies. Despite its ubiquitous expression, mutations in senataxin specifically affect neurons and result in distinct neurodegenerative diseases such as amyotrophic lateral sclerosis type 4 and ataxia with oculomotor apraxia type 2, which are attributed to the gain-of-function and the loss-of-function mutations in senataxin, respectively. In addition, low levels of senataxin (loss-of-function) in spinal muscular atrophy result in the accumulation of R-loops causing DNA damage and motor neuron degeneration. Senataxin may play multiple functions in diverse cellular processes; however, its emerging role in R-loop resolution and maintenance of genomic integrity is gaining attention in the field of neurodegenerative diseases. In this review, we highlight the role of senataxin in R-loop resolution and its potential as a therapeutic target to treat neurodegenerative diseases.
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Affiliation(s)
| | - Shyni Gangadharan Leela
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
| | - Dana Branzei
- The AIRC Institute of Molecular Oncology Foundation, IFOM ETS, Milan 20139, Italy
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Pavia 27100, Italy
| | - Laxman Gangwani
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO 65211, USA
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Xu Y, Jiao Y, Liu C, Miao R, Liu C, Wang Y, Ma C, Liu J. R-loop and diseases: the cell cycle matters. Mol Cancer 2024; 23:84. [PMID: 38678239 PMCID: PMC11055327 DOI: 10.1186/s12943-024-02000-3] [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: 02/11/2024] [Accepted: 04/13/2024] [Indexed: 04/29/2024] Open
Abstract
The cell cycle is a crucial biological process that is involved in cell growth, development, and reproduction. It can be divided into G1, S, G2, and M phases, and each period is closely regulated to ensure the production of two similar daughter cells with the same genetic material. However, many obstacles influence the cell cycle, including the R-loop that is formed throughout this process. R-loop is a triple-stranded structure, composed of an RNA: DNA hybrid and a single DNA strand, which is ubiquitous in organisms from bacteria to mammals. The existence of the R-loop has important significance for the regulation of various physiological processes. However, aberrant accumulation of R-loop due to its limited resolving ability will be detrimental for cells. For example, DNA damage and genomic instability, caused by the R-loop, can activate checkpoints in the cell cycle, which in turn induce cell cycle arrest and cell death. At present, a growing number of factors have been proven to prevent or eliminate the accumulation of R-loop thereby avoiding DNA damage and mutations. Therefore, we need to gain detailed insight into the R-loop resolution factors at different stages of the cell cycle. In this review, we review the current knowledge of factors that play a role in resolving the R-loop at different stages of the cell cycle, as well as how mutations of these factors lead to the onset and progression of diseases.
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Affiliation(s)
- Yuqin Xu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yue Jiao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chengbin Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Rui Miao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunyan Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yilong Wang
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunming Ma
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Jiao Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China.
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3
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Rivosecchi J, Jurikova K, Cusanelli E. Telomere-specific regulation of TERRA and its impact on telomere stability. Semin Cell Dev Biol 2024; 157:3-23. [PMID: 38088000 DOI: 10.1016/j.semcdb.2023.11.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 11/02/2023] [Indexed: 01/08/2024]
Abstract
TERRA is a class of telomeric repeat-containing RNAs that are expressed from telomeres in multiple organisms. TERRA transcripts play key roles in telomere maintenance and their physiological levels are essential to maintain the integrity of telomeric DNA. Indeed, deregulated TERRA expression or its altered localization can impact telomere stability by multiple mechanisms including fueling transcription-replication conflicts, promoting resection of chromosome ends, altering the telomeric chromatin, and supporting homologous recombination. Therefore, a fine-tuned control of TERRA is important to maintain the integrity of the genome. Several studies have reported that different cell lines express substantially different levels of TERRA. Most importantly, TERRA levels markedly vary among telomeres of a given cell type, indicating the existence of telomere-specific regulatory mechanisms which may help coordinate TERRA functions. TERRA molecules contain distinct subtelomeric sequences, depending on their telomere of origin, which may instruct specific post-transcriptional modifications or mediate distinct functions. In addition, all TERRA transcripts share a repetitive G-rich sequence at their 3' end which can form DNA:RNA hybrids and fold into G-quadruplex structures. Both structures are involved in TERRA functions and can critically affect telomere stability. In this review, we examine the mechanisms controlling TERRA levels and the impact of their telomere-specific regulation on telomere stability. We compare evidence obtained in different model organisms, discussing recent advances as well as controversies in the field. Furthermore, we discuss the importance of DNA:RNA hybrids and G-quadruplex structures in the context of TERRA biology and telomere maintenance.
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Affiliation(s)
- Julieta Rivosecchi
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Katarina Jurikova
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy; Department of Genetics, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina, 84215 Bratislava, Slovakia
| | - Emilio Cusanelli
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy.
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4
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Hidmi O, Oster S, Monin J, Aqeilan RI. TOP1 and R-loops facilitate transcriptional DSBs at hypertranscribed cancer driver genes. iScience 2024; 27:109082. [PMID: 38375218 PMCID: PMC10875566 DOI: 10.1016/j.isci.2024.109082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/26/2023] [Accepted: 01/28/2024] [Indexed: 02/21/2024] Open
Abstract
DNA double-stranded breaks (DSBs) pose a significant threat to genomic integrity, and their generation during essential cellular processes like transcription remains poorly understood. In this study, we employ several techniques to map DSBs, R-loops, and topoisomerase 1 cleavage complex (TOP1cc) to comprehensively investigate the interplay between transcription, DSBs, topoisomerase 1 (TOP1), and R-loops. Our findings reveal the presence of DSBs at highly expressed genes enriched with TOP1 and R-loops. Remarkably, transcription-associated DSBs at these loci are significantly reduced upon depletion of R-loops and TOP1, uncovering the pivotal roles of TOP1 and R-loops in transcriptional DSB formation. By elucidating the intricate interplay between TOP1cc trapping, R-loops, and DSBs, our study provides insights into the mechanisms underlying transcription-associated genomic instability. Moreover, we establish a link between transcriptional DSBs and early molecular changes driving cancer development, highlighting the distinct etiology and molecular characteristics of driver mutations compared to passenger mutations.
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Affiliation(s)
- Osama Hidmi
- The Concern Foundation Laboratories, The Lautenberg Center for Immunology and Cancer Research, Department of Immunology and Cancer Research-IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Sara Oster
- The Concern Foundation Laboratories, The Lautenberg Center for Immunology and Cancer Research, Department of Immunology and Cancer Research-IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Jonathan Monin
- The Concern Foundation Laboratories, The Lautenberg Center for Immunology and Cancer Research, Department of Immunology and Cancer Research-IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Rami I. Aqeilan
- The Concern Foundation Laboratories, The Lautenberg Center for Immunology and Cancer Research, Department of Immunology and Cancer Research-IMRIC, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
- Cyprus Cancer Research Institute (CCRI), Nicosia, Cyprus
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5
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Hourvitz N, Awad A, Tzfati Y. The many faces of the helicase RTEL1 at telomeres and beyond. Trends Cell Biol 2024; 34:109-121. [PMID: 37532653 DOI: 10.1016/j.tcb.2023.07.002] [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: 04/13/2023] [Revised: 07/01/2023] [Accepted: 07/05/2023] [Indexed: 08/04/2023]
Abstract
Regulator of telomere elongation 1 (RTEL1) is known as a DNA helicase that is important for telomeres and genome integrity. However, the diverse phenotypes of RTEL1 dysfunction, the wide spectrum of symptoms caused by germline RTEL1 mutations, and the association of RTEL1 mutations with cancers suggest that RTEL1 is a complex machine that interacts with DNA, RNA, and proteins, and functions in diverse cellular pathways. We summarize the proposed functions of RTEL1 and discuss their implications for telomere maintenance. Studying RTEL1 is crucial for understanding the complex interplay between telomere maintenance and other nuclear pathways, and how compromising these pathways causes telomere biology diseases, various aging-associated pathologies, and cancer.
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Affiliation(s)
- Noa Hourvitz
- Department of Genetics, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Safra Campus, Jerusalem 91904, Israel
| | - Aya Awad
- Department of Genetics, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Safra Campus, Jerusalem 91904, Israel
| | - Yehuda Tzfati
- Department of Genetics, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Safra Campus, Jerusalem 91904, Israel.
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Sze S, Bhardwaj A, Fnu P, Azarm K, Mund R, Ring K, Smith S. TERRA R-loops connect and protect sister telomeres in mitosis. Cell Rep 2023; 42:113235. [PMID: 37843976 PMCID: PMC10873023 DOI: 10.1016/j.celrep.2023.113235] [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: 04/27/2023] [Revised: 08/08/2023] [Accepted: 09/22/2023] [Indexed: 10/18/2023] Open
Abstract
Resolution of cohesion between sister telomeres in human cells depends on TRF1-mediated recruitment of the polyADP-ribosyltransferase tankyrase to telomeres. In human aged cells, due to insufficient recruitment of TRF1/tankyrase to shortened telomeres, sisters remain cohered in mitosis. This persistent cohesion plays a protective role, but the mechanism by which sisters remain cohered is not well understood. Here we show that telomere repeat-containing RNA (TERRA) holds sister telomeres together through RNA-DNA hybrid (R-loop) structures. We show that a tankyrase-interacting partner, the RNA-binding protein C19orf43, is required for repression of TERRA R-loops. Persistent telomere cohesion in C19orf43-depleted cells is counteracted by RNaseH1, confirming that RNA-DNA hybrids hold sisters together. Consistent with a protective role for persistent telomere cohesion, depletion of C19orf43 in aged cells reduces DNA damage and delays replicative senescence. We propose that the inherent inability of shortened telomeres to recruit R-loop-repressing machinery permits a controlled onset of senescence.
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Affiliation(s)
- Samantha Sze
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| | | | - Priyanka Fnu
- University of Rochester Medical Center, Rochester, NY 14642, USA
| | | | - Rachel Mund
- New York Medical College, Valhalla, NY 10595, USA
| | - Katherine Ring
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| | - Susan Smith
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA.
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Quttina M, Waiters KD, Khan AF, Karami S, Peidl AS, Babajide MF, Pennington J, Merchant FA, Bawa-Khalfe T. Exosc9 Initiates SUMO-Dependent lncRNA TERRA Degradation to Impact Telomeric Integrity in Endocrine Therapy Insensitive Hormone Receptor-Positive Breast Cancer. Cells 2023; 12:2495. [PMID: 37887339 PMCID: PMC10605189 DOI: 10.3390/cells12202495] [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: 08/16/2023] [Revised: 10/11/2023] [Accepted: 10/14/2023] [Indexed: 10/28/2023] Open
Abstract
Long, noncoding RNAs (lncRNAs) are indispensable for normal cell physiology and, consequently, are tightly regulated in human cells. Yet, unlike mRNA, substantially less is known about the mechanisms for lncRNA degradation. It is important to delineate the regulatory control of lncRNA degradation, particularly for lncRNA telomeric repeat-containing RNA (TERRA), as the TERRA-telomere R-loops dictate cell cycle progression and genomic stability. We now report that the exosome complex component Exosc9 degrades lncRNA TERRA in human mammary epithelial cells. Heterochromatin protein 1 alpha (HP1α) recruits Exosc9 to the telomeres; specifically, the SUMO-modified form of HP1α supports interaction with Exosc9 and, as previously reported, lncRNA TERRA. The telomeric enrichment of Exosc9 is cell cycle-dependent and consistent with the loss of telomeric TERRA in the S/G2 phase. Elevated Exosc9 is frequently observed and drives the growth of endocrine therapy-resistant (ET-R) HR+ breast cancer (BCa) cells. Specifically, the knockdown of Exosc9 inversely impacts telomeric R-loops and the integrity of the chromosome ends of ET-R cells. Consistently, Exosc9 levels dictate DNA damage and the sensitivity of ET-R BCa cells to PARP inhibitors. In this regard, Exosc9 may serve as a promising biomarker for predicting the response to PARP inhibitors as a targeted monotherapy for ET-R HR+ BCa.
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Affiliation(s)
- Maram Quttina
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
- Engineering Technology College of Technology, University of Houston at Sugarland, 13850 University Blvd, SAB1 Bldg, Rm 348, Sugarland, TX 77479, USA
| | - Kacie D. Waiters
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Ashfia Fatima Khan
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Samaneh Karami
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Anthony S. Peidl
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Mariam Funmi Babajide
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Justus Pennington
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
| | - Fatima A. Merchant
- Engineering Technology College of Technology, University of Houston at Sugarland, 13850 University Blvd, SAB1 Bldg, Rm 348, Sugarland, TX 77479, USA
| | - Tasneem Bawa-Khalfe
- Center for Nuclear Receptors & Cell Signaling, Department of Biology & Biochemistry, University of Houston, 3517 Cullen Blvd, SERC Bldg, Rm 3010, Houston, TX 77204-5056, USA (A.F.K.)
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Stylianakis E, Chan JPK, Law PP, Jiang Y, Khadayate S, Karimi MM, Festenstein R, Vannier JB. Mouse HP1γ regulates TRF1 expression and telomere stability. Life Sci 2023; 331:122030. [PMID: 37598977 DOI: 10.1016/j.lfs.2023.122030] [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: 11/29/2022] [Revised: 08/16/2023] [Accepted: 08/17/2023] [Indexed: 08/22/2023]
Abstract
AIMS Telomeric repeat-containing RNAs are long non-coding RNAs generated from the telomeres. TERRAs are essential for the establishment of heterochromatin marks at telomeres, which serve for the binding of members of the heterochromatin protein 1 (HP1) protein family of epigenetic modifiers involved with chromatin compaction and gene silencing. While HP1γ is enriched on gene bodies of actively transcribed human and mouse genes, it is unclear if its transcriptional role is important for HP1γ function in telomere cohesion and telomere maintenance. We aimed to study the effect of mouse HP1γ on the transcription of telomere factors and molecules that can affect telomere maintenance. MAIN METHODS We investigated the telomere function of HP1γ by using HP1γ deficient mouse embryonic fibroblasts (MEFs). We used gene expression analysis of HP1γ deficient MEFs and validated the molecular and mechanistic consequences of HP1γ loss by telomere FISH, immunofluorescence, RT-qPCR and DNA-RNA immunoprecipitation (DRIP). KEY FINDINGS Loss of HP1γ in primary MEFs led to a downregulation of various telomere and telomere-accessory transcripts, including the shelterin protein TRF1. Its downregulation is associated with increased telomere replication stress and DNA damage (γH2AX), effects more profound in females. We suggest that the source for the impaired telomere maintenance is a consequence of increased telomeric DNA-RNA hybrids and TERRAs arising at and from mouse chromosomes 18 and X. SIGNIFICANCE Our results suggest an important transcriptional control by mouse HP1γ of various telomere factors including TRF1 protein and TERRAs that has profound consequences on telomere stability, with a potential sexually dimorphic nature.
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Affiliation(s)
- Emmanouil Stylianakis
- Telomere Replication & Stability group, Medical Research Council London Institute of Medical Sciences, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom; Gene Control Mechanisms and Disease Group, Faculty of Medicine, Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Jackson Ping Kei Chan
- Gene Control Mechanisms and Disease Group, Faculty of Medicine, Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Pui Pik Law
- Gene Control Mechanisms and Disease Group, Faculty of Medicine, Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Yi Jiang
- Gene Control Mechanisms and Disease Group, Faculty of Medicine, Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Sanjay Khadayate
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Mohammad Mahdi Karimi
- Comprehensive Cancer Centre, School of Cancer & Pharmaceutical Sciences, Faculty of Life Sciences & Medicine, King's College London, London, United Kingdom
| | - Richard Festenstein
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom; Gene Control Mechanisms and Disease Group, Faculty of Medicine, Department of Brain Sciences, Imperial College London, London, United Kingdom
| | - Jean-Baptiste Vannier
- Telomere Replication & Stability group, Medical Research Council London Institute of Medical Sciences, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom.
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Liu J, Zheng T, Chen D, Huang J, Zhao Y, Ma W, Liu H. RBMX involves in telomere stability maintenance by regulating TERRA expression. PLoS Genet 2023; 19:e1010937. [PMID: 37756323 PMCID: PMC10529574 DOI: 10.1371/journal.pgen.1010937] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 08/23/2023] [Indexed: 09/29/2023] Open
Abstract
Telomeric repeat-containing RNA (TERRA) is a class of long noncoding RNAs (lncRNAs) that are transcribed from subtelomeric to telomeric region of chromosome ends. TERRA is prone to form R-loop structures at telomeres by invading into telomeric DNA. Excessive telomere R-loops result in telomere instability, so the TERRA level needs to be delicately modulated. However, the molecular mechanisms and factors controlling TERRA level are still largely unknown. In this study, we report that the RNA binding protein RBMX is a novel regulator of TERRA level and telomere integrity. The expression level of TERRA is significantly elevated in RBMX depleted cells, leading to enhanced telomere R-loop formation, replication stress, and telomere instability. We also found that RBMX binds to TERRA and the nuclear exosome targeting protein ZCCHC8 simultaneously, and that TERRA degradation slows down upon RBMX depletion, implying that RBMX promotes TERRA degradation by regulating its transportation to the nuclear exosome, which decays nuclear RNAs. Altogether, these findings uncover a new role of RBMX in TERRA expression regulation and telomere integrity maintenance, and raising RBMX as a potential target of cancer therapy.
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Affiliation(s)
- Jingfan Liu
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
| | - Tian Zheng
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
- NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People’s Republic of China
| | - Dandan Chen
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
| | - Junjiu Huang
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
| | - Yong Zhao
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
| | - Wenbin Ma
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
| | - Haiying Liu
- MOE Key Laboratory of Gene Function and Regulation, School of Life Sciences, Sun Yat-sen University, Guangzhou, People’s Republic of China
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Rivosecchi J, Cusanelli E. TERRA beyond cancer: the biology of telomeric repeat-containing RNAs in somatic and germ cells. FRONTIERS IN AGING 2023; 4:1224225. [PMID: 37636218 PMCID: PMC10448526 DOI: 10.3389/fragi.2023.1224225] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 07/31/2023] [Indexed: 08/29/2023]
Abstract
The telomeric noncoding RNA TERRA is a key component of telomeres and it is widely expressed in normal as well as cancer cells. In the last 15 years, several publications have shed light on the role of TERRA in telomere homeostasis and cell survival in cancer cells. However, only few studies have investigated the regulation or the functions of TERRA in normal tissues. A better understanding of the biology of TERRA in non-cancer cells may provide unexpected insights into how these lncRNAs are transcribed and operate in cells, and their potential role in physiological processes, such as aging, age-related pathologies, inflammatory processes and human genetic diseases. In this review we aim to discuss the findings that have advanced our understanding of the biology of TERRA using non-cancer mammalian cells as a model system.
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Affiliation(s)
- Julieta Rivosecchi
- Laboratory of Cell Biology and Molecular Genetics, Department of Cellular, Computational and Integrative Biology—CIBIO, University of Trento, Trento, Italy
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11
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Kuan XY, Fauzi NSA, Ng KY, Bakhtiar A. Exploring the Causal Relationship Between Telomere Biology and Alzheimer's Disease. Mol Neurobiol 2023; 60:4169-4183. [PMID: 37046137 PMCID: PMC10293431 DOI: 10.1007/s12035-023-03337-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 04/03/2023] [Indexed: 04/14/2023]
Abstract
Telomeres, also known as the "protective caps" of our chromosomes, shorten with each cell cycle due to the end replication problem. This process, termed telomere attrition, is associated with many age-related disorders, such as Alzheimer's disease (AD). Despite the numerous studies conducted in this field, the role of telomere attrition in the onset of the disease remains unclear. To investigate the causal relationship between short telomeres and AD, this review aims to highlight the primary factors that regulate telomere length and maintain its integrity, with an additional outlook on the role of oxidative stress, which is commonly associated with aging and molecular damage. Although some findings thus far might be contradictory, telomere attrition likely plays a crucial role in the progression of AD due to its close association with oxidative stress. The currently available treatments for AD are only symptomatic without affecting the progression of the disease. The components of telomere biology discussed in this paper have previously been studied as an alternative treatment option for several diseases and have exhibited promising in vitro and in vivo results. Hence, this should provide a basis for future research to develop a potential therapeutic strategy for AD. (Created with BioRender.com).
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Affiliation(s)
- Xi-Yuen Kuan
- School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia
| | - Nurul Syahira Ahmad Fauzi
- School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia
| | - Khuen Yen Ng
- School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia
| | - Athirah Bakhtiar
- School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia.
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Fernandes RV, Lingner J. The THO complex counteracts TERRA R-loop-mediated telomere fragility in telomerase+ cells and telomeric recombination in ALT+ cells. Nucleic Acids Res 2023; 51:6702-6722. [PMID: 37246640 PMCID: PMC10359610 DOI: 10.1093/nar/gkad448] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 04/26/2023] [Accepted: 05/14/2023] [Indexed: 05/30/2023] Open
Abstract
Telomeres are the nucleoprotein structures at the ends of linear chromosomes. Telomeres are transcribed into long non-coding Telomeric Repeat-Containing RNA (TERRA), whose functions rely on its ability to associate with telomeric chromatin. The conserved THO complex (THOC) was previously identified at human telomeres. It links transcription with RNA processing, decreasing the accumulation of co-transcriptional DNA:RNA hybrids throughout the genome. Here, we explore the role of THOC at human telomeres, as a regulator of TERRA localization to chromosome ends. We show that THOC counteracts TERRA association with telomeres via R-loops formed co-transcriptionally and also post-transcriptionally, in trans. We demonstrate that THOC binds nucleoplasmic TERRA, and that RNaseH1 loss, which increases telomeric R-loops, promotes THOC occupancy at telomeres. Additionally, we show that THOC counteracts lagging and mainly leading strand telomere fragility, suggesting that TERRA R-loops can interfere with replication fork progression. Finally, we observed that THOC suppresses telomeric sister-chromatid exchange and C-circle accumulation in ALT cancer cells, which maintain telomeres by recombination. Altogether, our findings reveal crucial roles of THOC in telomeric homeostasis through the co- and post-transcriptional regulation of TERRA R-loops.
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Affiliation(s)
- Rita Valador Fernandes
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Joachim Lingner
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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13
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Gong Y, Liu Y. R-Loops at Chromosome Ends: From Formation, Regulation, and Cellular Consequence. Cancers (Basel) 2023; 15:cancers15072178. [PMID: 37046839 PMCID: PMC10093737 DOI: 10.3390/cancers15072178] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 04/03/2023] [Accepted: 04/04/2023] [Indexed: 04/14/2023] Open
Abstract
Telomeric repeat containing RNA (TERRA) is transcribed from subtelomeric regions to telomeres. TERRA RNA can invade telomeric dsDNA and form telomeric R-loop structures. A growing body of evidence suggests that TERRA-mediated R-loops are critical players in telomere length homeostasis. Here, we will review current knowledge on the regulation of R-loop levels at telomeres. In particular, we will discuss how the central player TERRA and its binding proteins modulate R-loop levels through various mechanisms. We will further provide an overview of the consequences of TERRA-mediated persistent or unscheduled R-loops at telomeres in human ALT cancers and other organisms, with a focus on telomere length regulation after replication interference-induced damage and DNA homologous recombination-mediated repair.
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Affiliation(s)
- Yi Gong
- Laboratory of Genetics and Genomics, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21224, USA
| | - Yie Liu
- Laboratory of Genetics and Genomics, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21224, USA
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14
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Laspata N, Kaur P, Mersaoui S, Muoio D, Liu Z, Bannister MH, Nguyen H, Curry C, Pascal J, Poirier G, Wang H, Masson JY, Fouquerel E. PARP1 associates with R-loops to promote their resolution and genome stability. Nucleic Acids Res 2023; 51:2215-2237. [PMID: 36794853 PMCID: PMC10018367 DOI: 10.1093/nar/gkad066] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 01/19/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023] Open
Abstract
PARP1 is a DNA-dependent ADP-Ribose transferase with ADP-ribosylation activity that is triggered by DNA breaks and non-B DNA structures to mediate their resolution. PARP1 was also recently identified as a component of the R-loop-associated protein-protein interaction network, suggesting a potential role for PARP1 in resolving this structure. R-loops are three-stranded nucleic acid structures that consist of a RNA-DNA hybrid and a displaced non-template DNA strand. R-loops are involved in crucial physiological processes but can also be a source of genome instability if persistently unresolved. In this study, we demonstrate that PARP1 binds R-loops in vitro and associates with R-loop formation sites in cells which activates its ADP-ribosylation activity. Conversely, PARP1 inhibition or genetic depletion causes an accumulation of unresolved R-loops which promotes genomic instability. Our study reveals that PARP1 is a novel sensor for R-loops and highlights that PARP1 is a suppressor of R-loop-associated genomic instability.
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Affiliation(s)
- Natalie Laspata
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Parminder Kaur
- Physics Department, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, Raleigh, NC 27695, USA
| | - Sofiane Yacine Mersaoui
- CHU de Québec Research Centre, HDQ Pavilion, Oncology Division, Laval University Cancer Research Center, McMahon, Québec City, Québec G1R 3S3, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
| | - Daniela Muoio
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
| | - Zhiyan Silvia Liu
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Maxwell Henry Bannister
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Hai Dang Nguyen
- Department of Pharmacology, The Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Caroline Curry
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - John M Pascal
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Montréal, Québec H3C 3J7, Canada
| | - Guy G Poirier
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
- CHU de Québec Research Centre, CHUL Pavilion, Oncology Division, Quebec, Canada
| | - Hong Wang
- Physics Department, Raleigh, NC 27695, USA
- Center for Human Health and the Environment, Raleigh, NC 27695, USA
- Toxicology Program, North Carolina State University, Raleigh, NC, USA
| | - Jean-Yves Masson
- CHU de Québec Research Centre, HDQ Pavilion, Oncology Division, Laval University Cancer Research Center, McMahon, Québec City, Québec G1R 3S3, Canada
- Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Quebec, Canada
| | - Elise Fouquerel
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA 15213, USA
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15
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Telomere Transcription in MLL-Rearranged Leukemia Cell Lines: Increased Levels of TERRA Associate with Lymphoid Lineage and Are Independent of Telomere Length and Ploidy. Biomedicines 2023; 11:biomedicines11030925. [PMID: 36979904 PMCID: PMC10046226 DOI: 10.3390/biomedicines11030925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/25/2023] [Accepted: 03/02/2023] [Indexed: 03/19/2023] Open
Abstract
Telomere transcription into telomeric repeat-containing RNA (TERRA) is an integral component of all aspects of chromosome end protection consisting of telomerase- or recombination-dependent telomere elongation, telomere capping, and the preservation of the (sub)telomeric heterochromatin structure. The chromatin modifier and transcriptional regulator MLL binds to telomeres and regulates TERRA transcription in telomere length homeostasis and response to telomere dysfunction. MLL fusion proteins (MLL-FPs), the product of MLL rearrangements in leukemia, also bind to telomeric chromatin. However, an effect on telomere transcription in MLL-rearranged (MLL-r) leukemia has not yet been evaluated. Here, we show increased UUAGGG repeat-containing RNA levels in MLL-r acute lymphoblastic leukemia (ALL) when compared to non-MLL-r ALL and myeloid leukemia. MLL rearrangements do not affect telomere length and UUAGGG repeat-containing RNA levels correlate with mean telomere length and reflect increased levels of TERRA. Furthermore, high levels of TERRA in MLL-r ALL occur in the presence of telomerase activity and are independent of ploidy, an underestimated source of variation on the overall transcriptome size in a cell. This MLL rearrangement-dependent and lymphoid lineage-associated increase in levels of TERRA supports a sustained telomere transcription by MLL-FPs that correlates with marked genomic stability previously reported in pediatric MLL-r ALL.
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16
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Al-Turki TM, Griffith JD. Mammalian telomeric RNA (TERRA) can be translated to produce valine-arginine and glycine-leucine dipeptide repeat proteins. Proc Natl Acad Sci U S A 2023; 120:e2221529120. [PMID: 36812212 PMCID: PMC9992779 DOI: 10.1073/pnas.2221529120] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 01/25/2023] [Indexed: 02/24/2023] Open
Abstract
Mammalian telomeres consist of (TTAGGG)n repeats. Transcription of the C-rich strand generates a G-rich RNA, termed TERRA, containing G-quadruplex structures. Recent discoveries in several human nucleotide expansion diseases revealed that RNA transcripts containing long runs of 3 or 6 nt repeats which can form strong secondary structures can be translated in multiple frames to generate homopeptide or dipeptide repeat proteins, and multiple studies have shown them to be toxic in cells. We noted that the translation of TERRA would generate two dipeptide repeat proteins: highly charged repeating valine-arginine (VR)n and hydrophobic repeating glycine-leucine (GL)n. Here, we synthesized these two dipeptide proteins and raised polyclonal antibodies to VR. The VR dipeptide repeat protein binds nucleic acids and localizes strongly to replication forks in DNA. Both VR and GL form long 8-nm filaments with amyloid properties. Using labeled antibodies to VR and laser scanning confocal microscopy, threefold to fourfold more VR was observed in the nuclei of cell lines containing elevated TERRA as contrasted to a primary fibroblast line. Induction of telomere dysfunction via knockdown of TRF2 led to higher amounts of VR, and alteration of TERRA levels using a locked nucleic acid (LNA) GapmeR led to large nuclear VR aggregates. These observations suggest that telomeres, in particular in cells undergoing telomere dysfunction, may express two dipeptide repeat proteins with potentially strong biological properties.
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Affiliation(s)
- Taghreed M. Al-Turki
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC27599-7295
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC27599-7295
| | - Jack D. Griffith
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC27599-7295
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC27599-7295
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17
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Mohapatra S, Winkle M, Ton AN, Nguyen D, Calin GA. The Role of Non-Coding RNAs in Chromosomal Instability in Cancer. J Pharmacol Exp Ther 2023; 384:10-19. [PMID: 36167417 PMCID: PMC9827503 DOI: 10.1124/jpet.122.001357] [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: 06/15/2022] [Revised: 07/22/2022] [Accepted: 08/17/2022] [Indexed: 01/12/2023] Open
Abstract
Chromosomal instability (CIN) is characterized by an increased frequency of changes in chromosome structure or number and is regarded as a hallmark of cancer. CIN plays a prevalent role in tumorigenesis and cancer progression by assisting the cancer cells' phenotypic adaptation to stress, which have been tightly linked to therapy resistance and metastasis. Both CIN-inducing and CIN-repressing agents are being clinically tested for the treatment of cancer to increase CIN levels to unsustainable levels leading to cell death or to decrease CIN levels to limit the development of drug resistance, respectively. Non-coding RNAs (ncRNAs) including microRNAs and long ncRNAs (lncRNAs) have been fundamentally implicated in CIN. The miR-22, miR-26a, miR-28, and miR-186 target important checkpoint proteins involved in mediating chromosomal stability and their expression modulation has been directly related to CIN occurrence. lncRNAs derived from telomeric, centrosomal, and enhancer regions play an important role in mediating genome stability, while specific lncRNA transcripts including genomic instability inducing RNA called Ginir, P53-responsive lncRNA termed as GUARDIN, colon cancer-associated transcript 2, PCAT2, and ncRNA activated by DNA damage called NORAD have been shown to act within CIN-associated pathways. In this review, we discuss how these ncRNAs either maintain or disrupt the stability of chromosomes and how these mechanisms could be exploited for novel therapeutic approaches targeting CIN in cancer patients. SIGNIFICANCE STATEMENT: Chromosomal instability increases tumor heterogeneity and thereby assists the phenotypic adaptation of cancer cells, causing therapy resistance and metastasis. Several microRNAs and long non-coding RNAs that have been causally linked to chromosomal instability could represent novel therapeutic targets. Understanding the role of non-coding RNAs in regulating different genes involved in driving chromosomal instability will give insights into how non-coding RNAs can be utilized toward modifying chemotherapeutic regimens in different cancers.
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Affiliation(s)
- Swati Mohapatra
- Department of Translational Molecular Pathology (S.M., M.W., A.N.T., G.A.C.), UT Health Graduate School of Biomedical Sciences (S.M.), Program in Molecular Genetic Technology, School of Health Professions (A.N.T.), and Center for RNA Interference and Non-Coding RNAs (G.A.C.), The University of Texas MD Anderson Cancer Center, Houston, Texas; and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (D.N.)
| | - Melanie Winkle
- Department of Translational Molecular Pathology (S.M., M.W., A.N.T., G.A.C.), UT Health Graduate School of Biomedical Sciences (S.M.), Program in Molecular Genetic Technology, School of Health Professions (A.N.T.), and Center for RNA Interference and Non-Coding RNAs (G.A.C.), The University of Texas MD Anderson Cancer Center, Houston, Texas; and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (D.N.)
| | - Anh N Ton
- Department of Translational Molecular Pathology (S.M., M.W., A.N.T., G.A.C.), UT Health Graduate School of Biomedical Sciences (S.M.), Program in Molecular Genetic Technology, School of Health Professions (A.N.T.), and Center for RNA Interference and Non-Coding RNAs (G.A.C.), The University of Texas MD Anderson Cancer Center, Houston, Texas; and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (D.N.)
| | - Dien Nguyen
- Department of Translational Molecular Pathology (S.M., M.W., A.N.T., G.A.C.), UT Health Graduate School of Biomedical Sciences (S.M.), Program in Molecular Genetic Technology, School of Health Professions (A.N.T.), and Center for RNA Interference and Non-Coding RNAs (G.A.C.), The University of Texas MD Anderson Cancer Center, Houston, Texas; and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (D.N.)
| | - George A Calin
- Department of Translational Molecular Pathology (S.M., M.W., A.N.T., G.A.C.), UT Health Graduate School of Biomedical Sciences (S.M.), Program in Molecular Genetic Technology, School of Health Professions (A.N.T.), and Center for RNA Interference and Non-Coding RNAs (G.A.C.), The University of Texas MD Anderson Cancer Center, Houston, Texas; and Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (D.N.)
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18
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Khan ES, Danckwardt S. Pathophysiological Role and Diagnostic Potential of R-Loops in Cancer and Beyond. Genes (Basel) 2022; 13:genes13122181. [PMID: 36553448 PMCID: PMC9777984 DOI: 10.3390/genes13122181] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/07/2022] [Accepted: 11/14/2022] [Indexed: 11/24/2022] Open
Abstract
R-loops are DNA-RNA hybrids that play multifunctional roles in gene regulation, including replication, transcription, transcription-replication collision, epigenetics, and preserving the integrity of the genome. The aberrant formation and accumulation of unscheduled R-loops can disrupt gene expression and damage DNA, thereby causing genome instability. Recent links between unscheduled R-loop accumulation and the abundance of proteins that modulate R-loop biogenesis have been associated with numerous human diseases, including various cancers. Although R-loops are not necessarily causative for all disease entities described to date, they can perpetuate and even exacerbate the initially disease-eliciting pathophysiology, making them structures of interest for molecular diagnostics. In this review, we discuss the (patho) physiological role of R-loops in health and disease, their surprising diagnostic potential, and state-of-the-art techniques for their detection.
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Affiliation(s)
- Essak S. Khan
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Consortium for Translational Cancer Research (DKTK), DKFZ Frankfurt-Mainz, 60590 Frankfurt am Main, Germany
| | - Sven Danckwardt
- Posttranscriptional Gene Regulation, Cancer Research and Experimental Hemostasis, University Medical Center Mainz, 55131 Mainz, Germany
- Institute for Clinical Chemistry and Laboratory Medicine, University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- Center for Thrombosis and Hemostasis (CTH), University Medical Center of the Johannes Gutenberg University, 55131 Mainz, Germany
- German Center for Cardiovascular Research (DZHK), Rhine-Main, 55131 Mainz, Germany
- Correspondence:
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19
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Chen L, Zhang C, Ma W, Huang J, Zhao Y, Liu H. METTL3-mediated m6A modification stabilizes TERRA and maintains telomere stability. Nucleic Acids Res 2022; 50:11619-11634. [PMID: 36399511 PMCID: PMC9723618 DOI: 10.1093/nar/gkac1027] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 09/23/2022] [Accepted: 10/21/2022] [Indexed: 11/19/2022] Open
Abstract
Telomeric repeat-containing RNA (TERRA) is a type of long non-coding RNA transcribed from telomeres, and it forms R-loops by invasion into telomeric DNA. Since either an excessive or inadequate number of R-loops leads to telomere instability, the TERRA levels need to be delicately modulated. In this study, we found that m6A modification presents on the subtelomeric regions of TERRA and stabilizes it, and the loss of METTL3 impacts telomere stability. Mechanically, the m6A modification on TERRA is catalyzed by METTL3, recognized and stabilized by the m6A reader YTHDC1. Knockdown of either METTL3 or YTHDC1 enhances TERRA degradation. The m6A-modified TERRA forms R-loops and promotes homologous recombination which is essential for the alternative lengthening of telomeres (ALT) pathway in cancer cells. METTL3 depletion leads to R-loop reduction, telomere shortening and instability. Altogether, these findings reveal that METTL3 protects telomeres by catalyzing m6A modification on TERRA, indicating that inhibition or deletion of METTL3 is potentially a new avenue for ALT cancer therapy.
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Affiliation(s)
| | | | - Wenbin Ma
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Junjiu Huang
- MOE Key Laboratory of Gene Function and Regulation, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
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20
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Misic J, Milenkovic D, Al-Behadili A, Xie X, Jiang M, Jiang S, Filograna R, Koolmeister C, Siira S, Jenninger L, Filipovska A, Clausen A, Caporali L, Valentino M, La Morgia C, Carelli V, Nicholls T, Wredenberg A, Falkenberg M, Larsson NG. Mammalian RNase H1 directs RNA primer formation for mtDNA replication initiation and is also necessary for mtDNA replication completion. Nucleic Acids Res 2022; 50:8749-8766. [PMID: 35947649 PMCID: PMC9410905 DOI: 10.1093/nar/gkac661] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 07/08/2022] [Accepted: 08/04/2022] [Indexed: 12/24/2022] Open
Abstract
The in vivo role for RNase H1 in mammalian mitochondria has been much debated. Loss of RNase H1 is embryonic lethal and to further study its role in mtDNA expression we characterized a conditional knockout of Rnaseh1 in mouse heart. We report that RNase H1 is essential for processing of RNA primers to allow site-specific initiation of mtDNA replication. Without RNase H1, the RNA:DNA hybrids at the replication origins are not processed and mtDNA replication is initiated at non-canonical sites and becomes impaired. Importantly, RNase H1 is also needed for replication completion and in its absence linear deleted mtDNA molecules extending between the two origins of mtDNA replication are formed accompanied by mtDNA depletion. The steady-state levels of mitochondrial transcripts follow the levels of mtDNA, and RNA processing is not altered in the absence of RNase H1. Finally, we report the first patient with a homozygous pathogenic mutation in the hybrid-binding domain of RNase H1 causing impaired mtDNA replication. In contrast to catalytically inactive variants of RNase H1, this mutant version has enhanced enzyme activity but shows impaired primer formation. This finding shows that the RNase H1 activity must be strictly controlled to allow proper regulation of mtDNA replication.
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Affiliation(s)
- Jelena Misic
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | | | - Ali Al-Behadili
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Xie Xie
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Min Jiang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, Zhejiang 310024, China
| | - Shan Jiang
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Roberta Filograna
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Camilla Koolmeister
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden
| | - Stefan J Siira
- Harry Perkins Institute of Medical Research and ARC Centre of Excellence in Synthetic Biology, Nedlands, WA 6009, Australia
| | - Louise Jenninger
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Aleksandra Filipovska
- Harry Perkins Institute of Medical Research and ARC Centre of Excellence in Synthetic Biology, Nedlands, WA 6009, Australia,Telethon Kids Institute, Northern Entrance, Perth Children's Hospital, 15 Hospital Avenue, Nedlands, WA, Australia
| | - Anders R Clausen
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
| | - Leonardo Caporali
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Maria Lucia Valentino
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy,Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Chiara La Morgia
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy
| | - Valerio Carelli
- IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, Bologna, Italy,Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy
| | - Thomas J Nicholls
- Wellcome Centre for Mitochondrial Research, Biosciences Institute, Newcastle University, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Anna Wredenberg
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 17177, Sweden,Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Maria Falkenberg
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, PO Box 440, Gothenburg 405 30, Sweden
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21
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Shih HT, Chen WY, Wang HY, Chao T, Huang HD, Chou CH, Chang ZF. DNMT3b protects centromere integrity by restricting R-loop-mediated DNA damage. Cell Death Dis 2022; 13:546. [PMID: 35688824 PMCID: PMC9187704 DOI: 10.1038/s41419-022-04989-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 05/26/2022] [Accepted: 05/30/2022] [Indexed: 01/21/2023]
Abstract
This study used DNA methyltransferase 3b (DNMT3b) knockout cells and the functional loss of DNMT3b mutation in immunodeficiency-centromeric instability-facial anomalies syndrome (ICF) cells to understand how DNMT3b dysfunction causes genome instability. We demonstrated that R-loops contribute to DNA damages in DNMT3b knockout and ICF cells. More prominent DNA damage signal in DNMT3b knockout cells was due to the loss of DNMT3b expression and the acquirement of p53 mutation. Genome-wide ChIP-sequencing mapped DNA damage sites at satellite repetitive DNA sequences including (peri-)centromere regions. However, the steady-state levels of (peri-)centromeric R-loops were reduced in DNMT3b knockout and ICF cells. Our analysis indicates that XPG and XPF endonucleases-mediated cleavages remove (peri-)centromeric R-loops to generate DNA beaks, causing chromosome instability. DNMT3b dysfunctions clearly increase R-loops susceptibility to the cleavage process. Finally, we showed that DNA double-strand breaks (DSBs) in centromere are probably repaired by error-prone end-joining pathway in ICF cells. Thus, DNMT3 dysfunctions undermine the integrity of centromere by R-loop-mediated DNA damages and repair.
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Affiliation(s)
- Hsueh-Tzu Shih
- Institute of Molecular Medicine, National Taiwan University, Taipei, 10051, Taiwan
- Center of Precision Medicine, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan
| | - Wei-Yi Chen
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
- Cancer Progression Research Center, National Yang Ming Chiao Tung University, Taipei, 11221, Taiwan
| | - Hsin-Yen Wang
- Institute of Molecular Medicine, National Taiwan University, Taipei, 10051, Taiwan
| | - Tung Chao
- Institute of Molecular Medicine, National Taiwan University, Taipei, 10051, Taiwan
| | - Hsien-Da Huang
- Warshel Institute for Computational Biology, The Chinese University of Hong Kong, Longgang District, 518172, Shenzhen, China
- School of Life and Health Sciences, The Chinese University of Hong Kong, Longgang District, 518172, Shenzhen, China
- School of Medicine, The Chinese University of Hong Kong, Longgang District, 518172, Shenzhen, China
| | - Chih-Hung Chou
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
| | - Zee-Fen Chang
- Institute of Molecular Medicine, National Taiwan University, Taipei, 10051, Taiwan.
- Center of Precision Medicine, College of Medicine, National Taiwan University, Taipei, 10051, Taiwan.
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22
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Stanek TJ, Cao W, Mehra RM, Ellison CE. Sex-specific variation in R-loop formation in Drosophila melanogaster. PLoS Genet 2022; 18:e1010268. [PMID: 35687614 PMCID: PMC9223372 DOI: 10.1371/journal.pgen.1010268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 06/23/2022] [Accepted: 05/22/2022] [Indexed: 11/18/2022] Open
Abstract
R-loops are three-stranded nucleotide structures consisting of a DNA:RNA hybrid and a displaced ssDNA non-template strand. Previous work suggests that R-loop formation is primarily determined by the thermodynamics of DNA:RNA binding, which are governed by base composition (e.g., GC skew) and transcription-induced DNA superhelicity. However, R-loops have been described at genomic locations that lack these properties, suggesting that they may serve other context-specific roles. To better understand the genetic determinants of R-loop formation, we have characterized the Drosophila melanogaster R-loop landscape across strains and between sexes using DNA:RNA immunoprecipitation followed by high-throughput sequencing (DRIP-seq). We find that R-loops are associated with sequence motifs that are G-rich or exhibit G/C skew, as well as highly expressed genes, tRNAs, and small nuclear RNAs, consistent with a role for DNA sequence and torsion in R-loop specification. However, we also find motifs associated with R-loops that are A/T-rich and lack G/C skew as well as a subset of R-loops that are enriched in polycomb-repressed chromatin. Differential enrichment analysis reveals a small number of sex-biased R-loops: while non-differentially enriched and male-enriched R-loops form at similar genetic features and chromatin states and contain similar sequence motifs, female-enriched R-loops form at unique genetic features, chromatin states, and sequence motifs and are associated with genes that show ovary-biased expression. Male-enriched R-loops are most abundant on the dosage-compensated X chromosome, where R-loops appear stronger compared to autosomal R-loops. R-loop-containing genes on the X chromosome are dosage-compensated yet show lower MOF binding and reduced H4K16ac compared to R-loop-absent genes, suggesting that H4K16ac or MOF may attenuate R-loop formation. Collectively, these results suggest that R-loop formation in vivo is not fully explained by DNA sequence and topology and raise the possibility that a distinct subset of these hybrid structures plays an important role in the establishment and maintenance of epigenetic differences between sexes.
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Affiliation(s)
- Timothy J. Stanek
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- Department of Pathology, Robert Wood Johnson Medical School, Piscataway, New Jersey, United States of America
| | - Weihuan Cao
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Rohan M Mehra
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Christopher E. Ellison
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- * E-mail:
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23
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Zahid S, Aloe S, Sutherland JH, Holloman WK, Lue NF. Ustilago maydis telomere protein Pot1 harbors an extra N-terminal OB fold and regulates homology-directed DNA repair factors in a dichotomous and context-dependent manner. PLoS Genet 2022; 18:e1010182. [PMID: 35587917 PMCID: PMC9119445 DOI: 10.1371/journal.pgen.1010182] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 04/02/2022] [Indexed: 01/11/2023] Open
Abstract
The telomere G-strand binding protein Pot1 plays multifaceted roles in telomere maintenance and protection. We examined the structure and activities of Pot1 in Ustilago maydis, a fungal model that recapitulates key features of mammalian telomere regulation. Compared to the well-characterized primate and fission yeast Pot1 orthologs, UmPot1 harbors an extra N-terminal OB-fold domain (OB-N), which was recently shown to be present in most metazoans. UmPot1 binds directly to Rad51 and regulates the latter's strand exchange activity. Deleting the OB-N domain, which is implicated in Rad51-binding, caused telomere shortening, suggesting that Pot1-Rad51 interaction facilitates telomere maintenance. Depleting Pot1 through transcriptional repression triggered growth arrest as well as rampant recombination, leading to multiple telomere aberrations. In addition, telomere repeat RNAs transcribed from both the G- and C-strand were dramatically up-regulated, and this was accompanied by elevated levels of telomere RNA-DNA hybrids. Telomere abnormalities of pot1-deficient cells were suppressed, and cell viability was restored by the deletion of genes encoding Rad51 or Brh2 (the BRCA2 ortholog), indicating that homology-directed repair (HDR) proteins are key mediators of telomere aberrations and cellular toxicity. Together, these observations underscore the complex physical and functional interactions between Pot1 and DNA repair factors, leading to context-dependent and dichotomous effects of HDR proteins on telomere maintenance and protection.
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Affiliation(s)
- Syed Zahid
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, New York, United States of America
| | - Sarah Aloe
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, New York, United States of America
| | - Jeanette H. Sutherland
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, New York, United States of America
| | - William K. Holloman
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, New York, United States of America
| | - Neal F. Lue
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, New York, United States of America
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medicine, New York, New York, United States of America
- * E-mail:
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24
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Brickner JR, Garzon JL, Cimprich KA. Walking a tightrope: The complex balancing act of R-loops in genome stability. Mol Cell 2022; 82:2267-2297. [PMID: 35508167 DOI: 10.1016/j.molcel.2022.04.014] [Citation(s) in RCA: 81] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 03/28/2022] [Accepted: 04/10/2022] [Indexed: 12/14/2022]
Abstract
Although transcription is an essential cellular process, it is paradoxically also a well-recognized cause of genomic instability. R-loops, non-B DNA structures formed when nascent RNA hybridizes to DNA to displace the non-template strand as single-stranded DNA (ssDNA), are partially responsible for this instability. Yet, recent work has begun to elucidate regulatory roles for R-loops in maintaining the genome. In this review, we discuss the cellular contexts in which R-loops contribute to genomic instability, particularly during DNA replication and double-strand break (DSB) repair. We also summarize the evidence that R-loops participate as an intermediate during repair and may influence pathway choice to preserve genomic integrity. Finally, we discuss the immunogenic potential of R-loops and highlight their links to disease should they become pathogenic.
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Affiliation(s)
- Joshua R Brickner
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jada L Garzon
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Karlene A Cimprich
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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25
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Mehmetbeyoglu E, Kianmehr L, Borlu M, Yilmaz Z, Basar Kılıc S, Rajabi-Maham H, Taheri S, Rassoulzadegan M. Decrease in RNase HII and Accumulation of lncRNAs/DNA Hybrids: A Causal Implication in Psoriasis? Biomolecules 2022; 12:biom12030368. [PMID: 35327560 PMCID: PMC8945458 DOI: 10.3390/biom12030368] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/14/2022] [Accepted: 02/21/2022] [Indexed: 02/05/2023] Open
Abstract
Functional long non-coding RNAs (lncRNAs) have been in the limelight in aging research because short telomeres are associated with higher levels of TERRA (Telomeric Repeat containing RNA). The genomic instability, which leads to short telomeres, is a mechanism observed in cell aging and in a class of cancer cells. Psoriasis, a skin disease, is a disorder of epidermal keratinocytes, with altered telomerase activity. Research on the fraction of nascent RNAs in hybrid with DNA offers avenues for new strategies. Skin and blood samples from patients were fractionated to obtain the RNA associated with DNA as a R-loop structure. The higher amount of TERRA levels attached with each chromosome end was found with psoriasis patients in blood and skin. In addition to telomeric TERRA, we evidenced accumulation of others non-coding RNA, such as non-telomeric TERRA and centromeric transcripts. Increased levels of non-coding RNAs attached to DNA correlates with a decreased in Ribonuclease HII (RNase-HII) transcript which means that overall unresolved DNA–RNA hybrids can ultimately weaken DNA and cause skin lesions. Since the genome is actively transcribed, cellular RNase-HII is essential for removing RNA from the DNA–RNA hybrid in controls of genome stability and epigenome shaping and can be used as a causal prognostic marker in patients with psoriasis.
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Affiliation(s)
- Ecmel Mehmetbeyoglu
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
| | - Leila Kianmehr
- Animal Sciences and Marine Biology Department, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran 1983963411, Iran; (H.R.-M.); (L.K.)
| | - Murat Borlu
- Dermatology and Venereology Department, Medical School, Erciyes University, 38280 Kayseri, Turkey;
| | - Zeynep Yilmaz
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
| | - Seyma Basar Kılıc
- Dermatology and Venereology Department, Training and Research Hospital, Aksaray University, 68000 Aksaray, Turkey;
| | - Hassan Rajabi-Maham
- Animal Sciences and Marine Biology Department, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran 1983963411, Iran; (H.R.-M.); (L.K.)
| | - Serpil Taheri
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- Department of Medical Biology, Medical Faculty, Erciyes University, 38280 Kayseri, Turkey
- Correspondence: (S.T.); (M.R.)
| | - Minoo Rassoulzadegan
- Betul Ziya Eren Genome and Stem Cell Center, Erciyes University, 38280 Kayseri, Turkey; (E.M.); (Z.Y.)
- INSERM-CNRS, Université de Nice, 06000 Nice, France
- Correspondence: (S.T.); (M.R.)
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26
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Abstract
RNase H1 has become an essential tool to uncover the physiological and pathological roles of R-loops, three-stranded structures consisting of and RNA-DNA hybrid opposite to a single DNA strand (ssDNA). RNase H1 degrades the RNA portion of the R-loops returning the two DNA strands to double-stranded form (dsDNA). Overexpression of RNase H1 in different systems has helped to address the questions of where R-loops are located, their abundance, and mechanisms of formation, stability, and degradation. In this chapter we review multiple studies that used RNase H1 as an instrument to investigate R-loops multiple functions and their relevance in health and diseases.
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Affiliation(s)
- Susana M Cerritelli
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Kiran Sakhuja
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Robert J Crouch
- Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA.
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27
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Abstract
Telomeres protect chromosome ends from nucleolytic degradation, uncontrolled recombination by DNA repair enzymes and checkpoint signaling, and they provide mechanisms for their maintenance by semiconservative DNA replication, telomerase and homologous recombination. The telomeric long noncoding RNA TERRA is transcribed from a large number of chromosome ends. TERRA has been implicated in modulating telomeric chromatin structure and checkpoint signaling, and in telomere maintenance by homology directed repair, and telomerase – when telomeres are damaged or very short. Recent work indicates that TERRA association with telomeres involves the formation of DNA:RNA hybrid structures that can be formed post transcription by the RAD51 DNA recombinase, which in turn may trigger homologous recombination between telomeric repeats and telomere elongation. In this review, we describe the mechanisms of TERRA recruitment to telomeres, R-loop formation and its regulation by shelterin proteins. We discuss the consequences of R-loop formation, with regard to telomere maintenance by DNA recombination and how this may impinge on telomere replication while counteracting telomere shortening in normal cells and in ALT cancer cells, which maintain telomeres in the absence of telomerase.
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Affiliation(s)
- Rita Valador Fernandes
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Institute for Experimental Cancer Research (ISREC), Lausanne, Switzerland
| | - Marianna Feretzaki
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Institute for Experimental Cancer Research (ISREC), Lausanne, Switzerland
| | - Joachim Lingner
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Institute for Experimental Cancer Research (ISREC), Lausanne, Switzerland
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28
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Endurance training alleviates MCP-1 and TERRA accumulation at old age in human skeletal muscle. Exp Gerontol 2021; 153:111510. [PMID: 34371098 DOI: 10.1016/j.exger.2021.111510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 07/15/2021] [Accepted: 07/31/2021] [Indexed: 11/22/2022]
Abstract
Both oxidative stress and telomere transcription are up-regulated by acute endurance exercise in human skeletal muscle. Whether and how life-long exercise training influences the antioxidant system response at transcriptional level and TERRA expression is unknown, especially during aging. Response to acute endurance exercise was investigated in muscle biopsies of 3 male subjects after 45 min of cycling. MCP-1 and SOD1 mRNA levels increased up to, 15-fold and 63%, respectively, after the cycling session while the mRNA levels of SOD2 were downregulated by 25%. The effects of chronic endurance exercise and aging were tested in the blood and muscle of 34 male subjects divided into four groups: young (YU) or old (OU) untrained, young (YT) or old (OT) trained cyclists. Long-term endurance training limited the age-dependent elevation in SOD1 (OT vs OU, -26%, P = 0.03) and the decline in SOD2 mRNA levels (OU vs YU, -41%, P = 0.04). A high endurance training status alleviated the age-related increase in the aging biological marker MCP-1 in plasma (OU vs YU, +48%, P = 0.005). Similar results were observed for telomeric transcription as the age-associated increase in 16p TERRA levels (OU vs YU, +39%, P = 0.001) was counteracted by a high endurance training status (OT vs OU, -63%, P = 0.0005). In conclusion, as MCP-1, we propose that the age-related TERRA accumulation might represent a novel biological marker of aging. Those aging-related increase expression might be alleviated by a high endurance training status. Whether those biological markers of aging are linked to an elevation of oxidative stress is still an open question. Therefore, whether the positive adaptations provided by endurance training indeed reduce oxidative stress, including at telomeres, and whether TERRA plays any role in this, need to be further investigated.
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29
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Role of Melatonin in Angiotensin and Aging. Molecules 2021; 26:molecules26154666. [PMID: 34361818 PMCID: PMC8347812 DOI: 10.3390/molecules26154666] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/27/2021] [Accepted: 07/29/2021] [Indexed: 12/19/2022] Open
Abstract
The cellular utilization of oxygen leads to the generation of free radicals in organisms. The accumulation of these free radicals contributes significantly to aging and several age-related diseases. Angiotensin II can contribute to DNA damage through oxidative stress by activating the NAD(P)H oxidase pathway, which in turn results in the production of reactive oxygen species. This radical oxygen-containing molecule has been linked to aging and several age-related disorders, including renal damage. Considering the role of angiotensin in aging, melatonin might relieve angiotensin-II-induced stress by enhancing the mitochondrial calcium uptake 1 pathway, which is crucial in preventing the mitochondrial calcium overload that may trigger increased production of reactive oxygen species and oxidative stress. This review highlights the role and importance of melatonin together with angiotensin in aging and age-related diseases.
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30
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Li B. Keeping Balance Between Genetic Stability and Plasticity at the Telomere and Subtelomere of Trypanosoma brucei. Front Cell Dev Biol 2021; 9:699639. [PMID: 34291053 PMCID: PMC8287324 DOI: 10.3389/fcell.2021.699639] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/08/2021] [Indexed: 12/13/2022] Open
Abstract
Telomeres, the nucleoprotein complexes at chromosome ends, are well-known for their essential roles in genome integrity and chromosome stability. Yet, telomeres and subtelomeres are frequently less stable than chromosome internal regions. Many subtelomeric genes are important for responding to environmental cues, and subtelomeric instability can facilitate organismal adaptation to extracellular changes, which is a common theme in a number of microbial pathogens. In this review, I will focus on the delicate and important balance between stability and plasticity at telomeres and subtelomeres of a kinetoplastid parasite, Trypanosoma brucei, which causes human African trypanosomiasis and undergoes antigenic variation to evade the host immune response. I will summarize the current understanding about T. brucei telomere protein complex, the telomeric transcript, and telomeric R-loops, focusing on their roles in maintaining telomere and subtelomere stability and integrity. The similarities and differences in functions and underlying mechanisms of T. brucei telomere factors will be compared with those in human and yeast cells.
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Affiliation(s)
- Bibo Li
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological, and Environmental Sciences, College of Sciences and Health Professions, Cleveland State University, Cleveland, OH, United States.,Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, United States.,Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.,Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, OH, United States
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31
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DNA-RNA Hybrid (R-Loop): From a Unified Picture of the Mammalian Telomere to the Genome-Wide Profile. Cells 2021; 10:cells10061556. [PMID: 34205454 PMCID: PMC8233970 DOI: 10.3390/cells10061556] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/11/2021] [Accepted: 06/16/2021] [Indexed: 01/16/2023] Open
Abstract
Local three-stranded DNA/RNA hybrid regions of genomes (R-loops) have been detected either by binding of a monoclonal antibody (DRIP assay) or by enzymatic recognition by RNaseH. Such a structure has been postulated for mouse and human telomeres, clearly suggested by the identification of the complementary RNA Telomeric repeat-containing RNA “TERRA”. However, the tremendous disparity in the information obtained with antibody-based technology drove us to investigate a new strategy. Based on the observation that DNA/RNA hybrids in a triplex complex genome co-purify with the double-stranded chromosomal DNA fraction, we developed a direct preparative approach from total protein-free cellular extract without antibody that allows their physical isolation and determination of their RNA nucleotide sequence. We then define in the normal mouse and human sperm genomes the notion of stable DNA associated RNA terminal R-loop complexes, including TERRA molecules synthesized from local promoters of every chromosome. Furthermore, the first strong evidence of all telomeric structures, applied additionally to the whole murine sperm genome compared to the testes, showed reproducible R-loop complexes of the whole genome and suggesting a defined profile in the sperm genome for the next generation.
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32
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TERRA transcription destabilizes telomere integrity to initiate break-induced replication in human ALT cells. Nat Commun 2021; 12:3760. [PMID: 34145295 PMCID: PMC8213692 DOI: 10.1038/s41467-021-24097-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 05/31/2021] [Indexed: 01/22/2023] Open
Abstract
Alternative Lengthening of Telomeres (ALT) is a Break-Induced Replication (BIR)-based mechanism elongating telomeres in a subset of human cancer cells. While the notion that spontaneous DNA damage at telomeres is required to initiate ALT, the molecular triggers of this physiological telomere instability are largely unknown. We previously proposed that the telomeric long noncoding RNA TERRA may represent one such trigger; however, given the lack of tools to suppress TERRA transcription in cells, our hypothesis remained speculative. We have developed Transcription Activator-Like Effectors able to rapidly inhibit TERRA transcription from multiple chromosome ends in an ALT cell line. TERRA transcription inhibition decreases marks of DNA replication stress and DNA damage at telomeres and impairs ALT activity and telomere length maintenance. We conclude that TERRA transcription actively destabilizes telomere integrity in ALT cells, thereby triggering BIR and promoting telomere elongation. Our data point to TERRA transcription manipulation as a potentially useful target for therapy. TERRA RNA has previously been linked to Alternative lengthening of telomeres (ALT). Here the authors developed a tool to rapidly inhibit TERRA transcription from different chromosome ends in an ALT cell line to show that TERRA transcription actively promotes break induced replication (BIR) and destabilizes telomere integrity in ALT cells.
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33
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Vohhodina J, Goehring LJ, Liu B, Kong Q, Botchkarev VV, Huynh M, Liu Z, Abderazzaq FO, Clark AP, Ficarro SB, Marto JA, Hatchi E, Livingston DM. BRCA1 binds TERRA RNA and suppresses R-Loop-based telomeric DNA damage. Nat Commun 2021; 12:3542. [PMID: 34112789 PMCID: PMC8192922 DOI: 10.1038/s41467-021-23716-6] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 05/11/2021] [Indexed: 12/13/2022] Open
Abstract
R-loop structures act as modulators of physiological processes such as transcription termination, gene regulation, and DNA repair. However, they can cause transcription-replication conflicts and give rise to genomic instability, particularly at telomeres, which are prone to forming DNA secondary structures. Here, we demonstrate that BRCA1 binds TERRA RNA, directly and physically via its N-terminal nuclear localization sequence, as well as telomere-specific shelterin proteins in an R-loop-, and a cell cycle-dependent manner. R-loop-driven BRCA1 binding to CpG-rich TERRA promoters represses TERRA transcription, prevents TERRA R-loop-associated damage, and promotes its repair, likely in association with SETX and XRN2. BRCA1 depletion upregulates TERRA expression, leading to overly abundant TERRA R-loops, telomeric replication stress, and signs of telomeric aberrancy. Moreover, BRCA1 mutations within the TERRA-binding region lead to an excess of TERRA-associated R-loops and telomeric abnormalities. Thus, normal BRCA1/TERRA binding suppresses telomere-centered genome instability. BRCA1-mediated resolution of R-loops has previously been described. Here the authors reveal a functional association of BRCA1 with TERRA RNA at telomeres, which develops in an R-loop-, and a cell cycle-dependent manner.
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Affiliation(s)
- Jekaterina Vohhodina
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA. .,Department of Genetics, Harvard Medical School, Boston, MA, USA.
| | - Liana J Goehring
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Ben Liu
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Qing Kong
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Vladimir V Botchkarev
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Mai Huynh
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Zhiqi Liu
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Fieda O Abderazzaq
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Allison P Clark
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Scott B Ficarro
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Oncologic Pathology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Jarrod A Marto
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Blais Proteomics Center, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Oncologic Pathology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Elodie Hatchi
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.,Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - David M Livingston
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA. .,Department of Genetics, Harvard Medical School, Boston, MA, USA.
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34
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RTEL1 influences the abundance and localization of TERRA RNA. Nat Commun 2021; 12:3016. [PMID: 34021146 PMCID: PMC8140157 DOI: 10.1038/s41467-021-23299-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 04/22/2021] [Indexed: 12/13/2022] Open
Abstract
Telomere repeat containing RNAs (TERRAs) are a family of long non-coding RNAs transcribed from the subtelomeric regions of eukaryotic chromosomes. TERRA transcripts can form R-loops at chromosome ends; however the importance of these structures or the regulation of TERRA expression and retention in telomeric R-loops remain unclear. Here, we show that the RTEL1 (Regulator of Telomere Length 1) helicase influences the abundance and localization of TERRA in human cells. Depletion of RTEL1 leads to increased levels of TERRA RNA while reducing TERRA-containing R loops at telomeres. In vitro, RTEL1 shows a strong preference for binding G-quadruplex structures which form in TERRA. This binding is mediated by the C-terminal region of RTEL1, and is independent of the RTEL1 helicase domain. RTEL1 binding to TERRA appears to be essential for cell viability, underscoring the importance of this function. Degradation of TERRA-containing R-loops by overexpression of RNAse H1 partially recapitulates the increased TERRA levels and telomeric instability associated with RTEL1 deficiency. Collectively, these data suggest that regulation of TERRA is a key function of the RTEL1 helicase, and that loss of that function may contribute to the disease phenotypes of patients with RTEL1 mutations. Long non coding RNA TERRA transcripts can form R-loops at chromosome ends. Here, the authors reveal a role for the helicase RTEL in affecting TERRA levels and localization.
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35
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Unoki M. Chromatin remodeling in replication-uncoupled maintenance DNA methylation and chromosome stability: Insights from ICF syndrome studies. Genes Cells 2021; 26:349-359. [PMID: 33960584 PMCID: PMC9292322 DOI: 10.1111/gtc.12850] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/06/2021] [Accepted: 04/06/2021] [Indexed: 12/19/2022]
Abstract
Immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is characterized by frequent appearance of multiradial chromosomes, which are distinctive chromosome fusions that occur at hypomethylated pericentromeric regions comprising repetitive sequences, in activated lymphocytes. The syndrome is caused by mutations in DNMT3B, ZBTB24, CDCA7, or HELLS. De novo DNA methylation is likely defective in patients with ICF syndrome harboring mutations in DNMT3B, whereas accumulating evidence suggests that replication‐uncoupled maintenance DNA methylation of late‐replicating regions is impaired in patients with ICF syndrome harboring mutations in ZBTB24, CDCA7, or HELLS. ZBTB24 is a transcriptional activator of CDCA7, and CDCA7 and HELLS compose a chromatin remodeling complex and are involved in the maintenance DNA methylation through an interaction with UHRF1 in a feed‐forward manner. Furthermore, our recent studies possibly provided the missing link between DNA hypomethylation and the formation of the abnormal chromosomes; it could occur via aberrant transcription from the hypomethylated regions, followed by pathological R‐loop formation. The homologous‐recombination dominant condition caused by a defect in nonhomologous end joining observed in several types of ICF syndrome could facilitate the formation of multiradial chromosomes. Here, the latest knowledge regarding maintenance DNA methylation and chromosome stability provided by those studies is reviewed.
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Affiliation(s)
- Motoko Unoki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
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Toubiana S, Tzur-Gilat A, Selig S. Epigenetic Characteristics of Human Subtelomeres Vary in Cells Utilizing the Alternative Lengthening of Telomeres (ALT) Pathway. Life (Basel) 2021; 11:life11040278. [PMID: 33810393 PMCID: PMC8065733 DOI: 10.3390/life11040278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/22/2021] [Accepted: 03/23/2021] [Indexed: 12/26/2022] Open
Abstract
Most human cancers circumvent senescence by activating a telomere length maintenance mechanism, most commonly involving telomerase activation. A minority of cancers utilize the recombination-based alternative lengthening of telomeres (ALT) pathway. The exact requirements for unleashing normally repressed recombination at telomeres are yet unclear. Epigenetic modifications at telomeric regions were suggested to be pivotal for activating ALT; however, conflicting data exist regarding their exact nature and necessity. To uncover common ALT-positive epigenetic characteristics, we performed a comprehensive analysis of subtelomeric DNA methylation, histone modifications, and TERRA expression in several ALT-positive and ALT-negative cell lines. We found that subtelomeric DNA methylation does not differentiate between the ALT-positive and ALT-negative groups, and most of the analyzed subtelomeres within each group do not share common DNA methylation patterns. Additionally, similar TERRA levels were measured in the ALT-positive and ALT-negative groups, and TERRA levels varied significantly among the members of the ALT-positive group. Subtelomeric H3K4 and H3K9 trimethylation also differed significantly between samples in the ALT-positive group. Our findings do not support a common route by which epigenetic modifications activate telomeric recombination in ALT-positive cells, and thus, different therapeutic approaches will be necessary to overcome ALT-dependent cellular immortalization.
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Affiliation(s)
- Shir Toubiana
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel; (S.T.); (A.T.-G.)
| | - Aya Tzur-Gilat
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel; (S.T.); (A.T.-G.)
| | - Sara Selig
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel; (S.T.); (A.T.-G.)
- Laboratory of Molecular Medicine, Rambam Health Care Campus, Haifa 31096, Israel
- Correspondence:
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Morea EGO, Vasconcelos EJR, Alves CDS, Giorgio S, Myler PJ, Langoni H, Azzalin CM, Cano MIN. Exploring TERRA during Leishmania major developmental cycle and continuous in vitro passages. Int J Biol Macromol 2021; 174:573-586. [PMID: 33548324 DOI: 10.1016/j.ijbiomac.2021.01.192] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 01/25/2021] [Accepted: 01/28/2021] [Indexed: 12/22/2022]
Abstract
Telomeres from different eukaryotes, including trypanosomatids, are transcribed into TERRA noncoding RNAs, crucial in regulating chromatin deposition and telomere length. TERRA is transcribed from the C-rich subtelomeric strand towards the 3'-ends of the telomeric array. Using bioinformatics, we confirmed the presence of subtelomeric splice acceptor sites at all L. major chromosome ends. Splice leader sequences positioned 5' upstream of L. major chromosomes subtelomeres were then mapped using SL-RNA-Seq libraries constructed from three independent parasite life stages and helped confirm TERRA expression from several chromosomes ends. Northern blots and RT-qPCR validated the results showing that L. major TERRA is processed by trans-splicing and polyadenylation coupled reactions. The number of transcripts varied with the parasite's life stage and continuous passages, being more abundant in the infective forms. However, no putative subtelomeric promoters involved in TERRA's transcriptional regulation were detected. In contrast, the observed changes in parasite's telomere length during development, suggest that differences in telomeric base J levels may control TERRA transcription in L. major. Also, TERRA-R loops' detection, mainly in the infective forms, was suggestive of TERRA's involvement in telomere protection. Therefore, Leishmania TERRA shares conserved features with other eukaryotes and advances new telomere specific functions in a Public Health-impacting parasite.
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Affiliation(s)
- Edna Gicela Ortiz Morea
- Department of Chemical and Biological Sciences, Biosciences Institute, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil
| | | | - Cristiane de Santis Alves
- Department of Chemical and Biological Sciences, Biosciences Institute, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil
| | - Selma Giorgio
- Department of Animal Biology, Biology Institute, State University of Campinas, UNICAMP, Brazil
| | - Peter J Myler
- Department of Global Health and Department of Biomedical Informatics & Medical Education, University of Washington, Seattle, WA, United States of America
| | - Helio Langoni
- Department of Public Health, Veterinary Medical School, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil
| | | | - Maria Isabel Nogueira Cano
- Department of Chemical and Biological Sciences, Biosciences Institute, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil.
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Viceconte N, Loriot A, Lona Abreu P, Scheibe M, Fradera Sola A, Butter F, De Smet C, Azzalin CM, Arnoult N, Decottignies A. PAR-TERRA is the main contributor to telomeric repeat-containing RNA transcripts in normal and cancer mouse cells. RNA (NEW YORK, N.Y.) 2021; 27:106-121. [PMID: 33127860 PMCID: PMC7749631 DOI: 10.1261/rna.076281.120] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 10/28/2020] [Indexed: 05/12/2023]
Abstract
Telomeric repeat-containing RNA (TERRA) molecules play important roles at telomeres, from heterochromatin regulation to telomerase activity control. In human cells, TERRA is transcribed from subtelomeric promoters located on most chromosome ends and associates with telomeres. The origin of mouse TERRA molecules is, however, unclear, as transcription from the pseudoautosomal PAR locus was recently suggested to account for the vast majority of TERRA in embryonic stem cells (ESC). Here, we confirm the production of TERRA from both the chromosome 18q telomere and the PAR locus in mouse embryonic fibroblasts, ESC, and various mouse cancer and immortalized cell lines, and we identify two novel sources of TERRA on mouse chromosome 2 and X. Using various approaches, we show that PAR-TERRA molecules account for the majority of TERRA transcripts, displaying an increase of two to four orders of magnitude compared to the telomeric 18q transcript. Finally, we present a SILAC-based pull-down screen revealing a large overlap between TERRA-interacting proteins in human and mouse cells, including PRC2 complex subunits, chromatin remodeling factors, DNA replication proteins, Aurora kinases, shelterin complex subunits, Bloom helicase, Coilin, and paraspeckle proteins. Hence, despite originating from distinct genomic regions, mouse and human TERRA are likely to play similar functions in cells.
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Affiliation(s)
- Nikenza Viceconte
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Université catholique de Louvain (UCLouvain), 1200 Brussels, Belgium
| | - Axelle Loriot
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Université catholique de Louvain (UCLouvain), 1200 Brussels, Belgium
| | - Patrícia Lona Abreu
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Marion Scheibe
- Quantitative Proteomics, Institute of Molecular Biology (IMB), 55128 Mainz, Germany
| | - Albert Fradera Sola
- Quantitative Proteomics, Institute of Molecular Biology (IMB), 55128 Mainz, Germany
| | - Falk Butter
- Quantitative Proteomics, Institute of Molecular Biology (IMB), 55128 Mainz, Germany
| | - Charles De Smet
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Université catholique de Louvain (UCLouvain), 1200 Brussels, Belgium
| | - Claus M Azzalin
- Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, 1649-028 Lisboa, Portugal
| | - Nausica Arnoult
- MCBD-University of Colorado Boulder, Boulder, Colorado 80309-0347, USA
| | - Anabelle Decottignies
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Université catholique de Louvain (UCLouvain), 1200 Brussels, Belgium
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Grill S, Nandakumar J. Molecular mechanisms of telomere biology disorders. J Biol Chem 2021; 296:100064. [PMID: 33482595 PMCID: PMC7948428 DOI: 10.1074/jbc.rev120.014017] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 11/11/2020] [Accepted: 11/12/2020] [Indexed: 12/20/2022] Open
Abstract
Genetic mutations that affect telomerase function or telomere maintenance result in a variety of diseases collectively called telomeropathies. This wide spectrum of disorders, which include dyskeratosis congenita, pulmonary fibrosis, and aplastic anemia, is characterized by severely short telomeres, often resulting in hematopoietic stem cell failure in the most severe cases. Recent work has focused on understanding the molecular basis of these diseases. Mutations in the catalytic TERT and TR subunits of telomerase compromise activity, while others, such as those found in the telomeric protein TPP1, reduce the recruitment of telomerase to the telomere. Mutant telomerase-associated proteins TCAB1 and dyskerin and the telomerase RNA maturation component poly(A)-specific ribonuclease affect the maturation and stability of telomerase. In contrast, disease-associated mutations in either CTC1 or RTEL1 are more broadly associated with telomere replication defects. Yet even with the recent surge in studies decoding the mechanisms underlying these diseases, a significant proportion of dyskeratosis congenita mutations remain uncharacterized or poorly understood. Here we review the current understanding of the molecular basis of telomeropathies and highlight experimental data that illustrate how genetic mutations drive telomere shortening and dysfunction in these patients. This review connects insights from both clinical and molecular studies to create a comprehensive view of the underlying mechanisms that drive these diseases. Through this, we emphasize recent advances in therapeutics and pinpoint disease-associated variants that remain poorly defined in their mechanism of action. Finally, we suggest future avenues of research that will deepen our understanding of telomere biology and telomere-related disease.
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Affiliation(s)
- Sherilyn Grill
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jayakrishnan Nandakumar
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA.
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Detection of Telomeric DNA:RNA Hybrids Using TeloDRIP-qPCR. Int J Mol Sci 2020; 21:ijms21249774. [PMID: 33371452 PMCID: PMC7767442 DOI: 10.3390/ijms21249774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 12/17/2020] [Indexed: 11/17/2022] Open
Abstract
Because of their intrinsic characteristics, telomeres are genomic loci that pose significant problems during the replication of the genome. In particular, it has been observed that telomeres that are maintained in cancer cells by the alternative mechanism of the lengthening of telomeres (ALT) harbor higher levels of replicative stress compared with telomerase-positive cancer cells. R-loops are three-stranded structures formed by a DNA:RNA hybrid and a displaced ssDNA. Emerging evidence suggests that controlling the levels of R-loops at ALT telomeres is critical for telomere maintenance. In fact, on the one hand, they favor telomere recombination, but on the other, they are a source of detrimental replicative stress. DRIP (DNA:RNA immunoprecipitation) is the main technique used for the detection of R-loops, and it is based on the use of the S9.6 antibody, which recognizes preferentially DNA:RNA hybrids in a sequence-independent manner. The detection of DNA:RNA hybrids in repetitive sequences such as telomeres requires some additional precautions as a result of their repetitive nature. Here, we share an optimized protocol for the detection of telomeric DNA:RNA hybrids, and we demonstrate its application in an ALT and in a telomerase-positive cell line. We demonstrate that ALT telomeres bear higher levels of DNA:RNA hybrids, and we propose this method as a reliable way to detect them in telomeres.
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Toubiana S, Larom G, Smoom R, Duszynski RJ, Godley LA, Francastel C, Velasco G, Selig S. Regulation of telomeric function by DNA methylation differs between humans and mice. Hum Mol Genet 2020; 29:3197-3210. [PMID: 32916696 DOI: 10.1093/hmg/ddaa206] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/02/2020] [Accepted: 09/04/2020] [Indexed: 11/13/2022] Open
Abstract
The most distal 2 kb region in the majority of human subtelomeres contains CpG-rich promoters for TERRA, a long non-coding RNA. When the function of the de novo DNA methyltransferase DNMT3B is disrupted, as in ICF1 syndrome, subtelomeres are abnormally hypomethylated, subtelomeric heterochromatin acquires open chromatin characteristics, TERRA is highly expressed, and telomeres shorten rapidly. In this study, we explored whether the regulation of subtelomeric epigenetic characteristics by DNMT3B is conserved between humans and mice. Studying the DNA sequence of the distal 30 kb of the majority of murine q-arm subtelomeres indicated that these regions are relatively CpG-poor and do not contain TERRA promoters similar to those present in humans. Despite the lack of human-like TERRA promoters, we clearly detected TERRA expression originating from at least seven q-arm subtelomeres, and at higher levels in mouse pluripotent stem cells in comparison with mouse embryonic fibroblasts (MEFs). However, these differences in TERRA expression could not be explained by differential methylation of CpG islands present in the TERRA-expressing murine subtelomeres. To determine whether Dnmt3b regulates the expression of TERRA in mice, we characterized subtelomeric methylation and associated telomeric functions in cells derived from ICF1 model mice. Littermate-derived WT and ICF1 MEFs demonstrated no significant differences in subtelomeric DNA methylation, chromatin modifications, TERRA expression levels, telomere sister chromatid exchange or telomere length. We conclude that the epigenetic characteristics of murine subtelomeres differ substantially from their human counterparts and that TERRA transcription in mice is regulated by factors others than Dnmt3b.
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Affiliation(s)
- Shir Toubiana
- Department of Genetics, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel
| | - Gal Larom
- Department of Genetics, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel
| | - Riham Smoom
- Department of Genetics, The Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Robert J Duszynski
- Department of Medicine, Section of Hematology Oncology, The University of Chicago, Chicago 60637, USA
| | - Lucy A Godley
- Department of Medicine, Section of Hematology Oncology, The University of Chicago, Chicago 60637, USA
| | - Claire Francastel
- Université de Paris, Epigénétique et Destin Cellulaire, CNRS, Paris 75013, France
| | - Guillaume Velasco
- Université de Paris, Epigénétique et Destin Cellulaire, CNRS, Paris 75013, France
| | - Sara Selig
- Department of Genetics, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel
- Laboratory of Molecular Medicine, Rambam Health Care Campus, Haifa 31096, Israel
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Unoki M, Sharif J, Saito Y, Velasco G, Francastel C, Koseki H, Sasaki H. CDCA7 and HELLS suppress DNA:RNA hybrid-associated DNA damage at pericentromeric repeats. Sci Rep 2020; 10:17865. [PMID: 33082427 PMCID: PMC7576824 DOI: 10.1038/s41598-020-74636-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/30/2020] [Indexed: 12/18/2022] Open
Abstract
Immunodeficiency, centromeric instability, facial anomalies (ICF) syndrome is a rare autosomal recessive disorder that is caused by mutations in either DNMT3B, ZBTB24, CDCA7, HELLS, or yet unidentified gene(s). Previously, we reported that the CDCA7/HELLS chromatin remodeling complex facilitates non-homologous end-joining. Here, we show that the same complex is required for the accumulation of proteins on nascent DNA, including the DNMT1/UHRF1 maintenance DNA methylation complex as well as proteins involved in the resolution or prevention of R-loops composed of DNA:RNA hybrids and ssDNA. Consistent with the hypomethylation state of pericentromeric repeats, the transcription and formation of aberrant DNA:RNA hybrids at the repeats were increased in ICF mutant cells. Furthermore, the ectopic expression of RNASEH1 reduced the accumulation of DNA damage at a broad range of genomic regions including pericentromeric repeats in these cells. Hence, we propose that hypomethylation due to inefficient DNMT1/UHRF1 recruitment at pericentromeric repeats by defects in the CDCA7/HELLS complex could induce pericentromeric instability, which may explain a part of the molecular pathogenesis of ICF syndrome.
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Affiliation(s)
- Motoko Unoki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka-shi, Fukuoka, 812-8582, Japan.
| | - Jafar Sharif
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Kanagawa, 230-0045, Japan
| | - Yuichiro Saito
- Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Shizuoka, 411-8540, Japan
| | - Guillaume Velasco
- CNRS UMR7216, Epigenetics and Cell Fate, Université Paris Diderot, Sorbonne Paris Cité, 75205, Paris, France
| | - Claire Francastel
- CNRS UMR7216, Epigenetics and Cell Fate, Université Paris Diderot, Sorbonne Paris Cité, 75205, Paris, France
| | - Haruhiko Koseki
- Laboratory for Developmental Genetics, RIKEN Center for Integrative Medical Sciences, Kanagawa, 230-0045, Japan
| | - Hiroyuki Sasaki
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka-shi, Fukuoka, 812-8582, Japan
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Feretzaki M, Pospisilova M, Valador Fernandes R, Lunardi T, Krejci L, Lingner J. RAD51-dependent recruitment of TERRA lncRNA to telomeres through R-loops. Nature 2020; 587:303-308. [PMID: 33057192 PMCID: PMC7116795 DOI: 10.1038/s41586-020-2815-6] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 07/16/2020] [Indexed: 12/12/2022]
Abstract
Telomeres which are present at the ends of eukaryotic chromosomes mediate genome stability and determine cellular lifespan1. Telomeric repeat containing RNAs (TERRA) are long noncoding RNAs transcribed from chromosome ends2,3, which regulate telomeric chromatin structure and telomere maintenance via telomerase and homology directed repair (HDR)4,5. The mechanisms by which TERRA is recruited to chromosome ends remain poorly defined. Here we develop a reporter system to dissect the underlying mechanisms and demonstrate that the UUAGGG-repeats of TERRA are both necessary and sufficient to target TERRA to chromosome ends. TERRA preferentially associates with short telomeres through the formation of telomeric DNA:RNA hybrid (R-loop) structures that can form in trans. Telomere association and R-loop formation triggers telomere fragility and is promoted by the RAD51 recombinase and its interacting partner BRCA2 but counteracted by RNA surveillance factors, RNaseH1 and TRF1. RAD51 physically interacts with TERRA and catalyzes R-loop formation with TERRA in vitro supporting a direct involvement of this DNA recombinase in TERRA recruitment by strand invasion. Together, our findings reveal a RAD51-dependent pathway that governs TERRA mediated R-loop formation post transcription providing a mechanism of how lncRNAs can be recruited to new loci in trans.
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Affiliation(s)
- Marianna Feretzaki
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Michaela Pospisilova
- Department of Biology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - Rita Valador Fernandes
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Thomas Lunardi
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Lumir Krejci
- Department of Biology and National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic. .,International Clinical Research Center, St Anne's University Hospital, Brno, Czech Republic.
| | - Joachim Lingner
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
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Aguado J, d’Adda di Fagagna F, Wolvetang E. Telomere transcription in ageing. Ageing Res Rev 2020; 62:101115. [PMID: 32565330 DOI: 10.1016/j.arr.2020.101115] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/05/2020] [Accepted: 06/11/2020] [Indexed: 02/08/2023]
Abstract
Telomeres, the ends of eukaryotic chromosomes, play a central role in the control of cellular senescence and organismal ageing and need to be protected in order to avoid being recognised as damaged DNA and activate DNA damage response pathways. Dysfunctional telomeres arise from critically short telomeres or altered telomere structures, which ultimately lead to replicative cellular senescence and chromosome instability: both hallmarks of ageing. The observation that telomeres are transcribed led to the discovery that telomeric transcripts play important roles in chromosome end protection and genome stability maintenance. Recent evidence indicates that particular long non-coding (nc)RNAs transcribed at telomeres, namely TElomeric Repeat-containing RNA (TERRA) and telomeric damage-induced long ncRNAs (tdilncRNA), play key roles in age-related pathways by actively orchestrating the mechanisms known to regulate telomere length, chromosome end protection and DNA damage signalling. Here, we provide a comprehensive overview of the telomere transcriptome, outlining how it functions as a regulatory platform with essential functions in safeguarding telomere integrity and stability. We next review emerging antisense oligonucleotides therapeutic strategies that target telomeric ncRNAs and discuss their potential for ameliorating ageing and age-related diseases. Altogether, this review provides insights on the biological relevance of telomere transcription mechanisms in human ageing physiology and pathology.
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Abid HZ, McCaffrey J, Raseley K, Young E, Lassahn K, Varapula D, Riethman H, Xiao M. Single-molecule analysis of subtelomeres and telomeres in Alternative Lengthening of Telomeres (ALT) cells. BMC Genomics 2020; 21:485. [PMID: 32669102 PMCID: PMC7364475 DOI: 10.1186/s12864-020-06901-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 07/08/2020] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Telomeric DNA is typically comprised of G-rich tandem repeat motifs and maintained by telomerase (Greider CW, Blackburn EH; Cell 51:887-898; 1987). In eukaryotes lacking telomerase, a variety of DNA repair and DNA recombination based pathways for telomere maintenance have evolved in organisms normally dependent upon telomerase for telomere elongation (Webb CJ, Wu Y, Zakian VA; Cold Spring Harb Perspect Biol 5:a012666; 2013); collectively called Alternative Lengthening of Telomeres (ALT) pathways. By measuring (TTAGGG) n tract lengths from the same large DNA molecules that were optically mapped, we simultaneously analyzed telomere length dynamics and subtelomere-linked structural changes at a large number of specific subtelomeric loci in the ALT-positive cell lines U2OS, SK-MEL-2 and Saos-2. RESULTS Our results revealed loci-specific ALT telomere features. For example, while each subtelomere included examples of single molecules with terminal (TTAGGG) n tracts as well as examples of recombinant telomeric single molecules, the ratio of these molecules was subtelomere-specific, ranging from 33:1 (19p) to 1:25 (19q) in U2OS. The Saos-2 cell line shows a similar percentage of recombinant telomeres. The frequency of recombinant subtelomeres of SK-MEL-2 (11%) is about half that of U2OS and Saos-2 (24 and 19% respectively). Terminal (TTAGGG) n tract lengths and heterogeneity levels, the frequencies of telomere signal-free ends, and the frequency and size of retained internal telomere-like sequences (ITSs) at recombinant telomere fusion junctions all varied according to the specific subtelomere involved in a particular cell line. Very large linear extrachromosomal telomere repeat (ECTR) DNA molecules were found in all three cell lines; these are in principle capable of templating synthesis of new long telomere tracts via break-induced repair (BIR) long-tract DNA synthesis mechanisms and contributing to the very long telomere tract length and heterogeneity characteristic of ALT cells. Many of longest telomere tracts (both end-telomeres and linear ECTRs) displayed punctate CRISPR/Cas9-dependent (TTAGGG) n labeling patterns indicative of interspersion of stretches of non-canonical telomere repeats. CONCLUSION Identifying individual subtelomeres and characterizing linked telomere (TTAGGG) n tract lengths and structural changes using our new single-molecule methodologies reveals the structural consequences of telomere damage, repair and recombination mechanisms in human ALT cells in unprecedented molecular detail and significant differences in different ALT-positive cell lines.
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Affiliation(s)
- Heba Z Abid
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Jennifer McCaffrey
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Kaitlin Raseley
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Eleanor Young
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Katy Lassahn
- School of Medical Diagnostic and Transnational Sciences, Old Dominion University, Norfolk, VA, USA
| | - Dharma Varapula
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Harold Riethman
- School of Medical Diagnostic and Transnational Sciences, Old Dominion University, Norfolk, VA, USA.
| | - Ming Xiao
- School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, PA, USA. .,Institute of Molecular Medicine and Infectious Disease, School of Medicine, Drexel University, Philadelphia, PA, USA.
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Barral A, Déjardin J. Telomeric Chromatin and TERRA. J Mol Biol 2020; 432:4244-4256. [DOI: 10.1016/j.jmb.2020.03.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 03/03/2020] [Accepted: 03/03/2020] [Indexed: 01/01/2023]
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Criqui M, Qamra A, Chu TW, Sharma M, Tsao J, Henry DA, Barsyte-Lovejoy D, Arrowsmith CH, Winegarden N, Lupien M, Harrington L. Telomere dysfunction cooperates with epigenetic alterations to impair murine embryonic stem cell fate commitment. eLife 2020; 9:47333. [PMID: 32297856 PMCID: PMC7192583 DOI: 10.7554/elife.47333] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 04/06/2020] [Indexed: 12/11/2022] Open
Abstract
The precise relationship between epigenetic alterations and telomere dysfunction is still an extant question. Previously, we showed that eroded telomeres lead to differentiation instability in murine embryonic stem cells (mESCs) via DNA hypomethylation at pluripotency-factor promoters. Here, we uncovered that telomerase reverse transcriptase null (Tert-/-) mESCs exhibit genome-wide alterations in chromatin accessibility and gene expression during differentiation. These changes were accompanied by an increase of H3K27me3 globally, an altered chromatin landscape at the Pou5f1/Oct4 promoter, and a refractory response to differentiation cues. Inhibition of the Polycomb Repressive Complex 2 (PRC2), an H3K27 tri-methyltransferase, exacerbated the impairment in differentiation and pluripotency gene repression in Tert-/-mESCs but not wild-type mESCs, whereas inhibition of H3K27me3 demethylation led to a partial rescue of the Tert-/- phenotype. These data reveal a new interdependent relationship between H3K27me3 and telomere integrity in stem cell lineage commitment that may have implications in aging and cancer.
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Affiliation(s)
- Mélanie Criqui
- Institut de Recherche en Immunologie et Cancérologie (IRIC), Département de biologie moléculaire, Faculté de Médecine, Université de Montréal, Montréal, Canada
| | - Aditi Qamra
- Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Tsz Wai Chu
- Institut de Recherche en Immunologie et Cancérologie (IRIC), Département de biologie moléculaire, Faculté de Médecine, Université de Montréal, Montréal, Canada
| | - Monika Sharma
- Princess Margaret Genomics Centre, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Julissa Tsao
- Princess Margaret Genomics Centre, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Danielle A Henry
- Institut de Recherche en Immunologie et Cancérologie (IRIC), Département de biologie moléculaire, Faculté de Médecine, Université de Montréal, Montréal, Canada
| | - Dalia Barsyte-Lovejoy
- Structural Genomics Consortium, Princess Margaret Cancer Centre, University of Toronto, Department of Medical Biophysics, Toronto, Canada
| | - Cheryl H Arrowsmith
- Structural Genomics Consortium, Princess Margaret Cancer Centre, University of Toronto, Department of Medical Biophysics, Toronto, Canada
| | - Neil Winegarden
- Princess Margaret Genomics Centre, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Mathieu Lupien
- Princess Margaret Cancer Centre, University Health Network, Toronto, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Canada
| | - Lea Harrington
- Institut de Recherche en Immunologie et Cancérologie (IRIC), Département de biologie moléculaire, Faculté de Médecine, Université de Montréal, Montréal, Canada
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Human subtelomeric DNA methylation: regulation and roles in telomere function. Curr Opin Genet Dev 2020; 60:9-16. [PMID: 32109830 DOI: 10.1016/j.gde.2020.02.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/21/2020] [Accepted: 02/02/2020] [Indexed: 12/26/2022]
Abstract
Subtelomeres are the regions at chromosome ends, immediately adjacent to the terminal telomeric repeats. The majority of human subtelomeres are CpG-rich in their distal two kilobases, and are methylated during early embryonic development by the de novo DNA methyltransferase DNMT3B. The biological relevance of subtelomeric DNA methylation is highlighted by the presence of promoters for the long non-coding TERRA transcripts in these CpG-rich regions. Indeed, deviant subtelomeric methylation has been linked with abnormal telomeric phenotypes, as most strikingly found in ICF syndrome. Here we review recent studies that explore new aspects of subtelomeric methylation regulation and demonstrate the significance of maintaining proper DNA methylation at the extreme distal human subtelomeric regions.
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Lalonde M, Chartrand P. TERRA, a Multifaceted Regulator of Telomerase Activity at Telomeres. J Mol Biol 2020; 432:4232-4243. [PMID: 32084415 DOI: 10.1016/j.jmb.2020.02.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/06/2020] [Accepted: 02/10/2020] [Indexed: 02/07/2023]
Abstract
In eukaryotes, telomeres are repetitive sequences at the end of chromosomes, which are maintained in a constitutive heterochromatin state. It is now known that telomeres can be actively transcribed, leading to the production of a telomeric repeat-containing noncoding RNA called TERRA. Due to its sequence complementarity to the telomerase template, it was suggested early on that TERRA could be an inhibitor of telomerase. Since then, TERRA has been shown to be involved in heterochromatin formation at telomeres, to invade telomeric dsDNA and form R-loops, and even to promote telomerase recruitment at short telomeres. All these functions depend on the diverse capacities of this lncRNA to bind various cofactors, act as a scaffold, and promote higher-order complexes in cells. In this review, it will be highlighted as to how these properties of TERRA work together to regulate telomerase activity at telomeres.
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Affiliation(s)
- Maxime Lalonde
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Quebec, Canada
| | - Pascal Chartrand
- Department of Biochemistry and Molecular Medicine, Université de Montréal, Quebec, Canada.
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