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Bettin N, Querido E, Gialdini I, Grupelli GP, Goretti E, Cantarelli M, Andolfato M, Soror E, Sontacchi A, Jurikova K, Chartrand P, Cusanelli E. TERRA transcripts localize at long telomeres to regulate telomerase access to chromosome ends. SCIENCE ADVANCES 2024; 10:eadk4387. [PMID: 38865460 PMCID: PMC11168465 DOI: 10.1126/sciadv.adk4387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 05/08/2024] [Indexed: 06/14/2024]
Abstract
The function of TERRA in the regulation of telomerase in human cells is still debated. While TERRA interacts with telomerase, how it regulates telomerase function remains unknown. Here, we show that TERRA colocalizes with the telomerase RNA subunit hTR in the nucleoplasm and at telomeres during different phases of the cell cycle. We report that TERRA transcripts relocate away from chromosome ends during telomere lengthening, leading to a reduced number of telomeric TERRA-hTR molecules and consequent increase in "TERRA-free" telomerase molecules at telomeres. Using live-cell imaging and super-resolution microscopy, we show that upon transcription, TERRA relocates from its telomere of origin to long chromosome ends. Furthermore, TERRA depletion by antisense oligonucleotides promoted hTR localization to telomeres, leading to increased residence time and extended half-life of hTR molecules at telomeres. Overall, our findings indicate that telomeric TERRA transcripts inhibit telomere elongation by telomerase acting in trans, impairing telomerase access to telomeres that are different from their chromosome end of origin.
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Affiliation(s)
- Nicole Bettin
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Emmanuelle Querido
- Department of Biochemistry and Molecular Medicine, University of Montreal, 2900 boul. Edouard Montpetit, H3T1J4 Montreal, Canada
| | - Irene Gialdini
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Glenda Paola Grupelli
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Elena Goretti
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Marta Cantarelli
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Marta Andolfato
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Eslam Soror
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
| | - Alessandra Sontacchi
- 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
| | - Pascal Chartrand
- Department of Biochemistry and Molecular Medicine, University of Montreal, 2900 boul. Edouard Montpetit, H3T1J4 Montreal, Canada
| | - Emilio Cusanelli
- Laboratory of Cell Biology and Molecular Genetics, Department CIBIO, University of Trento, via Sommarive 9, 38123 Trento, Italy
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2
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Lee J, Lee J, Sohn EJ, Taglialatela A, O’Sullivan RJ, Ciccia A, Min J. Extrachromosomal telomere DNA derived from excessive strand displacements. Proc Natl Acad Sci U S A 2024; 121:e2318438121. [PMID: 38696464 PMCID: PMC11087782 DOI: 10.1073/pnas.2318438121] [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: 10/22/2023] [Accepted: 04/03/2024] [Indexed: 05/04/2024] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism mediated by break-induced replication, evident in approximately 15% of human cancers. A characteristic feature of ALT cancers is the presence of C-circles, circular single-stranded telomeric DNAs composed of C-rich sequences. Despite the fact that extrachromosomal C-rich single-stranded DNAs (ssDNAs), including C-circles, are unique to ALT cells, their generation process remains undefined. Here, we introduce a method to detect single-stranded telomeric DNA, called 4SET (Strand-Specific Southern-blot for Single-stranded Extrachromosomal Telomeres) assay. Utilizing 4SET, we are able to capture C-rich single-stranded DNAs that are near 200 to 1500 nucleotides in size. Both linear C-rich ssDNAs and C-circles are abundant in the fractions of cytoplasm and nucleoplasm, which supports the idea that linear and circular C-rich ssDNAs are generated concurrently. We also found that C-rich ssDNAs originate during Okazaki fragment processing during lagging strand DNA synthesis. The generation of C-rich ssDNA requires CST-PP (CTC1/STN1/TEN1-PRIMASE-Polymerase alpha) complex-mediated priming of the C-strand DNA synthesis and subsequent excessive strand displacement of the C-rich strand mediated by the DNA Polymerase delta and the BLM helicase. Our work proposes a model for the generation of C-rich ssDNAs and C-circles during ALT-mediated telomere elongation.
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Affiliation(s)
- Junyeop Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Jina Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Eric J. Sohn
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Angelo Taglialatela
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Roderick J. O’Sullivan
- Department of Pharmacology and Chemical Biology, Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA15213
| | - Alberto Ciccia
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
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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: 0] [Impact Index Per Article: 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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Xu M, Senanayaka D, Zhao R, Chigumira T, Tripathi A, Tones J, Lackner RM, Wondisford AR, Moneysmith LN, Hirschi A, Craig S, Alishiri S, O'Sullivan RJ, Chenoweth DM, Reiter NJ, Zhang H. TERRA-LSD1 phase separation promotes R-loop formation for telomere maintenance in ALT cancer cells. Nat Commun 2024; 15:2165. [PMID: 38461301 PMCID: PMC10925046 DOI: 10.1038/s41467-024-46509-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 02/28/2024] [Indexed: 03/11/2024] Open
Abstract
The telomere repeat-containing RNA (TERRA) forms R-loops to promote homology-directed DNA synthesis in the alternative lengthening of telomere (ALT) pathway. Here we report that TERRA contributes to ALT via interacting with the lysine-specific demethylase 1A (LSD1 or KDM1A). We show that LSD1 localizes to ALT telomeres in a TERRA dependent manner and LSD1 function in ALT is largely independent of its demethylase activity. Instead, LSD1 promotes TERRA recruitment to ALT telomeres via RNA binding. In addition, LSD1 and TERRA undergo phase separation, driven by interactions between the RNA binding properties of LSD1 and the G-quadruplex structure of TERRA. Importantly, the formation of TERRA-LSD1 condensates enriches the R-loop stimulating protein Rad51AP1 and increases TERRA-containing R-loops at telomeres. Our findings suggest that LSD1-TERRA phase separation enhances the function of R-loop regulatory molecules for ALT telomere maintenance, providing a mechanism for how the biophysical properties of histone modification enzyme-RNA interactions impact chromatin function.
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Affiliation(s)
- Meng Xu
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Dulmi Senanayaka
- Klingler College of Arts and Sciences, Department of Chemistry, Marquette University, Milwaukee, WI, 53233, USA
| | - Rongwei Zhao
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Tafadzwa Chigumira
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Astha Tripathi
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Jason Tones
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Rachel M Lackner
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19014, USA
| | - Anne R Wondisford
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - Laurel N Moneysmith
- Klingler College of Arts and Sciences, Department of Chemistry, Marquette University, Milwaukee, WI, 53233, USA
| | - Alexander Hirschi
- Cepheid Diagnostics, 904 E. Caribbean Dr., Sunnyvale, California, 94089, USA
| | - Sara Craig
- Klingler College of Arts and Sciences, Department of Chemistry, Marquette University, Milwaukee, WI, 53233, USA
| | - Sahar Alishiri
- Klingler College of Arts and Sciences, Department of Chemistry, Marquette University, Milwaukee, WI, 53233, USA
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, 15213, USA
| | - David M Chenoweth
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19014, USA
| | - Nicholas J Reiter
- Klingler College of Arts and Sciences, Department of Chemistry, Marquette University, Milwaukee, WI, 53233, USA
| | - Huaiying Zhang
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
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5
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Azzalin CM. TERRA and the alternative lengthening of telomeres: a dangerous affair. FEBS Lett 2024. [PMID: 38445359 DOI: 10.1002/1873-3468.14844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 02/14/2024] [Accepted: 02/20/2024] [Indexed: 03/07/2024]
Abstract
Eukaryotic telomeres are transcribed into the long noncoding RNA TERRA. A fraction of TERRA remains associated with telomeres by forming RNA:DNA hybrids dubbed telR-loops. TERRA and telR-loops are essential to promote telomere elongation in human cancer cells that maintain telomeres through a homology-directed repair pathway known as alternative lengthening of telomeres or ALT. However, TERRA and telR-loops compromise telomere integrity and cell viability if their levels are not finely tuned. The study of telomere transcription in ALT cells will enormously expand our understanding of the ALT mechanism and of how genome integrity is maintained. Moreover, telomere transcription, TERRA and telR-loops are likely to become exceptionally suited targets for the development of novel anti-cancer therapies.
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Affiliation(s)
- Claus M Azzalin
- Instituto de Medicina Molecular João Lobo Antunes (iMM), Faculdade de Medicina da Universidade de Lisboa, Portugal
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Chen L, Gai X, Yu X. Pre-rRNA facilitates the recruitment of RAD51AP1 to DNA double-strand breaks. J Biol Chem 2024; 300:107115. [PMID: 38403248 PMCID: PMC10959706 DOI: 10.1016/j.jbc.2024.107115] [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: 01/04/2024] [Revised: 02/02/2024] [Accepted: 02/13/2024] [Indexed: 02/27/2024] Open
Abstract
RAD51-associated protein 1 (RAD51AP1) is known to promote homologous recombination (HR) repair. However, the precise mechanism of RAD51AP1 in HR repair is unclear. Here, we identify that RAD51AP1 associates with pre-rRNA. Both the N terminus and C terminus of RAD51AP1 recognize pre-rRNA. Pre-rRNA not only colocalizes with RAD51AP1 at double-strand breaks (DSBs) but also facilitates the recruitment of RAD51AP1 to DSBs. Consistently, transient inhibition of pre-rRNA synthesis by RNA polymerase I inhibitor suppresses the recruitment of RAD51AP1 as well as HR repair. Moreover, RAD51AP1 forms liquid-liquid phase separation in the presence of pre-rRNA in vitro, which may be the molecular mechanism of RAD51AP1 foci formation. Taken together, our results demonstrate that pre-rRNA mediates the relocation of RAD51AP1 to DSBs for HR repair.
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Affiliation(s)
- Linlin Chen
- School of Life Sciences, Fudan University, Shanghai, China; School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China
| | - Xiaochen Gai
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang Province, China
| | - Xiaochun Yu
- School of Life Sciences, Westlake University, Hangzhou, Zhejiang, China; Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, Zhejiang, China; Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, Zhejiang Province, China.
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7
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Zhang J, Chen F, Tang M, Xu W, Tian Y, Liu Z, Shu Y, Yang H, Zhu Q, Lu X, Peng B, Liu X, Xu X, Gullerova M, Zhu WG. The ARID1A-METTL3-m6A axis ensures effective RNase H1-mediated resolution of R-loops and genome stability. Cell Rep 2024; 43:113779. [PMID: 38358891 DOI: 10.1016/j.celrep.2024.113779] [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: 07/12/2023] [Revised: 12/02/2023] [Accepted: 01/26/2024] [Indexed: 02/17/2024] Open
Abstract
R-loops are three-stranded structures that can pose threats to genome stability. RNase H1 precisely recognizes R-loops to drive their resolution within the genome, but the underlying mechanism is unclear. Here, we report that ARID1A recognizes R-loops with high affinity in an ATM-dependent manner. ARID1A recruits METTL3 and METTL14 to the R-loop, leading to the m6A methylation of R-loop RNA. This m6A modification facilitates the recruitment of RNase H1 to the R-loop, driving its resolution and promoting DNA end resection at DSBs, thereby ensuring genome stability. Depletion of ARID1A, METTL3, or METTL14 leads to R-loop accumulation and reduced cell survival upon exposure to cytotoxic agents. Therefore, ARID1A, METTL3, and METTL14 function in a coordinated, temporal order at DSB sites to recruit RNase H1 and to ensure efficient R-loop resolution. Given the association of high ARID1A levels with resistance to genotoxic therapies in patients, these findings open avenues for exploring potential therapeutic strategies for cancers with ARID1A abnormalities.
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Affiliation(s)
- Jun Zhang
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Feng Chen
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Ming Tang
- Shanghai Key Laboratory of Maternal Fetal Medicine, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai 200092, China
| | - Wenchao Xu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Yuan Tian
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Zhichao Liu
- Sir William Dunn School of Pathology, South Parks Road, Oxford OX1 3RE, UK
| | - Yuxin Shu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Hui Yang
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Qian Zhu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Xiaopeng Lu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Bin Peng
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Cell Biology and Medical Genetics, Shenzhen University Medical School, Shenzhen 518055, China
| | - Xiangyu Liu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China
| | - Xingzhi Xu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Cell Biology and Medical Genetics, Shenzhen University Medical School, Shenzhen 518055, China
| | - Monika Gullerova
- Sir William Dunn School of Pathology, South Parks Road, Oxford OX1 3RE, UK
| | - Wei-Guo Zhu
- International Cancer Center, Guangdong Key Laboratory of Genome Instability and Human Disease Prevention, Department of Biochemistry and Molecular Biology, Shenzhen University Medical School, Shenzhen 518055, China; Marshall Laboratory of Biomedical Engineering, Shenzhen University Medical School, Shenzhen 518055, China; School of Basic Medical Sciences, Wannan Medical College, Wuhu, Anhui 241002, China; Department of Biochemistry and Molecular Biology, Peking University Health Science Centre, Beijing 100191, China.
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8
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Rai R, Sodeinde T, Boston A, Chang S. Telomeres cooperate with the nuclear envelope to maintain genome stability. Bioessays 2024; 46:e2300184. [PMID: 38047499 DOI: 10.1002/bies.202300184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 11/12/2023] [Accepted: 11/14/2023] [Indexed: 12/05/2023]
Abstract
Mammalian telomeres have evolved safeguards to prevent their recognition as DNA double-stranded breaks by suppressing the activation of various DNA sensing and repair proteins. We have shown that the telomere-binding proteins TRF2 and RAP1 cooperate to prevent telomeres from undergoing aberrant homology-directed recombination by mediating t-loop protection. Our recent findings also suggest that mammalian telomere-binding proteins interact with the nuclear envelope to maintain chromosome stability. RAP1 interacts with nuclear lamins through KU70/KU80, and disruption of RAP1 and TRF2 function result in nuclear envelope rupture, promoting telomere-telomere recombination to form structures termed ultrabright telomeres. In this review, we discuss the importance of the interactions between shelterin components and the nuclear envelope to maintain telomere homeostasis and genome stability.
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Affiliation(s)
- Rekha Rai
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Tori Sodeinde
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Molecular, Cellular and Developmental Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Ava Boston
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Molecular, Cellular and Developmental Biology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Sandy Chang
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Pathology, Yale University School of Medicine, New Haven, Connecticut, USA
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut, USA
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9
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Spegg V, Altmeyer M. Genome maintenance meets mechanobiology. Chromosoma 2024; 133:15-36. [PMID: 37581649 PMCID: PMC10904543 DOI: 10.1007/s00412-023-00807-5] [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: 04/04/2023] [Revised: 06/20/2023] [Accepted: 07/26/2023] [Indexed: 08/16/2023]
Abstract
Genome stability is key for healthy cells in healthy organisms, and deregulated maintenance of genome integrity is a hallmark of aging and of age-associated diseases including cancer and neurodegeneration. To maintain a stable genome, genome surveillance and repair pathways are closely intertwined with cell cycle regulation and with DNA transactions that occur during transcription and DNA replication. Coordination of these processes across different time and length scales involves dynamic changes of chromatin topology, clustering of fragile genomic regions and repair factors into nuclear repair centers, mobilization of the nuclear cytoskeleton, and activation of cell cycle checkpoints. Here, we provide a general overview of cell cycle regulation and of the processes involved in genome duplication in human cells, followed by an introduction to replication stress and to the cellular responses elicited by perturbed DNA synthesis. We discuss fragile genomic regions that experience high levels of replication stress, with a particular focus on telomere fragility caused by replication stress at the ends of linear chromosomes. Using alternative lengthening of telomeres (ALT) in cancer cells and ALT-associated PML bodies (APBs) as examples of replication stress-associated clustered DNA damage, we discuss compartmentalization of DNA repair reactions and the role of protein properties implicated in phase separation. Finally, we highlight emerging connections between DNA repair and mechanobiology and discuss how biomolecular condensates, components of the nuclear cytoskeleton, and interfaces between membrane-bound organelles and membraneless macromolecular condensates may cooperate to coordinate genome maintenance in space and time.
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Affiliation(s)
- Vincent Spegg
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Matthias Altmeyer
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland.
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10
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Gómez-González B, Aguilera A. Break-induced RNA-DNA hybrids (BIRDHs) in homologous recombination: friend or foe? EMBO Rep 2023; 24:e57801. [PMID: 37818834 DOI: 10.15252/embr.202357801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 08/29/2023] [Accepted: 09/26/2023] [Indexed: 10/13/2023] Open
Abstract
Double-strand breaks (DSBs) are the most harmful DNA lesions, with a strong impact on cell proliferation and genome integrity. Depending on cell cycle stage, DSBs are preferentially repaired by non-homologous end joining or homologous recombination (HR). In recent years, numerous reports have revealed that DSBs enhance DNA-RNA hybrid formation around the break site. We call these hybrids "break-induced RNA-DNA hybrids" (BIRDHs) to differentiate them from sporadic R-loops consisting of DNA-RNA hybrids and a displaced single-strand DNA occurring co-transcriptionally in intact DNA. Here, we review and discuss the most relevant data about BIRDHs, with a focus on two main questions raised: (i) whether BIRDHs form by de novo transcription after a DSB or by a pre-existing nascent RNA in DNA regions undergoing transcription and (ii) whether they have a positive role in HR or are just obstacles to HR accidentally generated as an intrinsic risk of transcription. We aim to provide a comprehensive view of the exciting and yet unresolved questions about the source and impact of BIRDHs in the cell.
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Affiliation(s)
- Belén Gómez-González
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC, Seville, Spain
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC, Seville, Spain
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11
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Rosso I, Jones-Weinert C, Rossiello F, Cabrini M, Brambillasca S, Munoz-Sagredo L, Lavagnino Z, Martini E, Tedone E, Garre' M, Aguado J, Parazzoli D, Mione M, Shay JW, Mercurio C, d'Adda di Fagagna F. Alternative lengthening of telomeres (ALT) cells viability is dependent on C-rich telomeric RNAs. Nat Commun 2023; 14:7086. [PMID: 37925537 PMCID: PMC10625592 DOI: 10.1038/s41467-023-42831-0] [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: 03/24/2022] [Accepted: 10/23/2023] [Indexed: 11/06/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism activated in ~10-15% of cancers, characterized by telomeric damage. Telomeric damage-induced long non-coding RNAs (dilncRNAs) are transcribed at dysfunctional telomeres and contribute to telomeric DNA damage response (DDR) activation and repair. Here we observed that telomeric dilncRNAs are preferentially elevated in ALT cells. Inhibition of C-rich (teloC) dilncRNAs with antisense oligonucleotides leads to DNA replication stress responses, increased genomic instability, and apoptosis induction selectively in ALT cells. Cell death is dependent on DNA replication and is increased by DNA replication stress. Mechanistically, teloC dilncRNA inhibition reduces RAD51 and 53BP1 recruitment to telomeres, boosts the engagement of BIR machinery, and increases C-circles and telomeric sister chromatid exchanges, without increasing telomeric non-S phase synthesis. These results indicate that teloC dilncRNA is necessary for a coordinated recruitment of DDR factors to ALT telomeres and it is essential for ALT cancer cells survival.
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Affiliation(s)
- Ilaria Rosso
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Corey Jones-Weinert
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- The Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Matteo Cabrini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Silvia Brambillasca
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Leonel Munoz-Sagredo
- Institute of Biological and Chemical Systems - Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- School of Medicine, Universidad de Valparaiso, Valparaiso, Chile
| | - Zeno Lavagnino
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Emanuele Martini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Milan, Italy
| | - Enzo Tedone
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Massimiliano Garre'
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- RCSI, Royal College of Surgeons in Ireland, Department of Chemistry, Dublin, Ireland
| | - Julio Aguado
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Dario Parazzoli
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Marina Mione
- Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ciro Mercurio
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Fabrizio d'Adda di Fagagna
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy.
- Institute of Molecular Genetics IGM-CNR "Luigi Luca Cavalli-Sforza", Pavia, Italy.
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12
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Gambelli A, Ferrando A, Boncristiani C, Schoeftner S. Regulation and function of R-loops at repetitive elements. Biochimie 2023; 214:141-155. [PMID: 37619810 DOI: 10.1016/j.biochi.2023.08.013] [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: 05/05/2023] [Revised: 08/13/2023] [Accepted: 08/19/2023] [Indexed: 08/26/2023]
Abstract
R-loops are atypical, three-stranded nucleic acid structures that contain a stretch of RNA:DNA hybrids and an unpaired, single stranded DNA loop. R-loops are physiological relevant and can act as regulators of gene expression, chromatin structure, DNA damage repair and DNA replication. However, unscheduled and persistent R-loops are mutagenic and can mediate replication-transcription conflicts, leading to DNA damage and genome instability if left unchecked. Detailed transcriptome analysis unveiled that 85% of the human genome, including repetitive regions, hold transcriptional activity. This anticipates that R-loops management plays a central role for the regulation and integrity of genomes. This function is expected to have a particular relevance for repetitive sequences that make up to 75% of the human genome. Here, we review the impact of R-loops on the function and stability of repetitive regions such as centromeres, telomeres, rDNA arrays, transposable elements and triplet repeat expansions and discuss their relevance for associated pathological conditions.
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Affiliation(s)
- Alice Gambelli
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Alessandro Ferrando
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Chiara Boncristiani
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy
| | - Stefan Schoeftner
- Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Via E. Weiss 2, 34127, Trieste, Italy.
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13
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Lee J, Lee J, Sohn EJ, Taglialatela A, O’Sullivan RJ, Ciccia A, Min J. Extrachromosomal Telomeres Derived from Excessive Strand Displacements. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.31.551186. [PMID: 37577643 PMCID: PMC10418088 DOI: 10.1101/2023.07.31.551186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Alternative Lengthening of Telomeres (ALT) is a telomere maintenance mechanism mediated by break-induced replication (BIR), evident in approximately 15% of human cancers. A characteristic feature of ALT cancers is the presence of C-circles, circular single-stranded telomeric DNAs composed of C-rich sequences. Despite the fact that extrachromosomal C-rich single-stranded DNAs (ssDNAs), unique to ALT cells, are considered potential precursors of C-circles, their generation process remains undefined. Here, we introduce a highly sensitive method to detect single stranded telomeric DNA, called 4SET (Strand-Specific Southern-blot for Single-stranded Extrachromosomal Telomeres) assay. Utilizing 4SET, we are able to capture C-rich single stranded DNAs that are near 200 to 1500 nucleotides in size. Both linear C-rich ssDNAs and C-circles are abundant in the fractions of cytoplasm and nucleoplasm, which supports the idea that linear C-rich ssDNA accumulation may indeed precede C-circle formation. We also found that C-rich ssDNAs originate during Okazaki fragment processing during lagging strand DNA synthesis. The generation of C-rich ssDNA requires CST-PP (CTC1/STN1/TEN1-PRIMASE-Polymerase alpha) complex-mediated priming of the C-strand DNA synthesis and subsequent excessive strand displacement of the C-rich strand mediated by the DNA Polymerase delta and the BLM helicase. Our work proposes a new model for the generation of C-rich ssDNAs and C-circles during ALT-mediated telomere elongation.
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Affiliation(s)
- Junyeop Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Jina Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Eric J. Sohn
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Roderick J. O’Sullivan
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alberto Ciccia
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
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14
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LIU R, LI M, HU Z, SONG Z, CHEN J. [Research Advances of RAD51AP1 in Tumor Progression and Drug Resistance]. ZHONGGUO FEI AI ZA ZHI = CHINESE JOURNAL OF LUNG CANCER 2023; 26:701-708. [PMID: 37985156 PMCID: PMC10600754 DOI: 10.3779/j.issn.1009-3419.2023.102.34] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Indexed: 11/22/2023]
Abstract
The genomic instability may lead to an initiation of cancer in many organisms. Homologous recombination repair (HRR) is vital in maintaining cellular genomic stability. RAD51 associated protein 1 (RAD51AP1), which plays a crucial role in HRR and primarily participates in forming D-loop, was reported as an essential protein for maintaining cellular genomic stability. However, recent studies showed that RAD51AP1 was significantly overexpressed in various cancer types and correlated with poor prognosis. These results suggested that RAD51AP1 may play a significant pro-cancer effect in multiple cancers. The underlying mechanism is still unclear. Cancer stemness-maintaining effects of RAD51AP1 might be considered as the most reliable mechanism. Meanwhile, RAD51AP1 also promoted resistance to radiation therapy and chemotherapy in many cancers. Thus, researches focused on RAD51AP1, and its regulatory molecules may provide new targets for overcoming cancer progression and treatment resistance. Here, we reviewed the latest research on RAD51AP1 in cancers and summarized its differential expression and prognostic implications. In this review, we also outlined the potential mechanisms of its pro-cancer and drug resistance-promoting effects to provide several potential directions for further research.
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15
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Pizzul P, Rinaldi C, Bonetti D. The multistep path to replicative senescence onset: zooming on triggering and inhibitory events at telomeric DNA. Front Cell Dev Biol 2023; 11:1250264. [PMID: 37771378 PMCID: PMC10524272 DOI: 10.3389/fcell.2023.1250264] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 08/29/2023] [Indexed: 09/30/2023] Open
Abstract
Replicative senescence is an essential cellular process playing important physiological functions, but it is better known for its implications in aging, cancer, and other pathologies. One of the main triggers of replicative senescence is telomere shortening and/or its dysfunction and, therefore, a deep understanding of the molecular determinants is crucial. However, replicative senescence is a heterogeneous and hard to study process, especially in mammalian cells, and some important questions still need an answer. These questions concern i) the exact molecular causes triggering replicative senescence, ii) the role of DNA repair mechanisms and iii) the importance of R-loops at telomeres in regulating senescence onset, and iv) the mechanisms underlying the bypass of replicative senescence. In this review, we will report and discuss recent findings about these mechanisms both in mammalian cells and in the model organism Saccharomyces cerevisiae.
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Affiliation(s)
| | | | - Diego Bonetti
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milan, Italy
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16
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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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17
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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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18
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Göder A, Quinlan A, Rainey MD, Bennett D, Shamavu D, Corso J, Santocanale C. PTBP1 enforces ATR-CHK1 signaling determining the potency of CDC7 inhibitors. iScience 2023; 26:106951. [PMID: 37378325 PMCID: PMC10291475 DOI: 10.1016/j.isci.2023.106951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/27/2023] [Accepted: 05/22/2023] [Indexed: 06/29/2023] Open
Abstract
CDC7 kinase is crucial for DNA replication initiation and fork processing. CDC7 inhibition mildly activates the ATR pathway, which further limits origin firing; however, to date the relationship between CDC7 and ATR remains controversial. We show that CDC7 and ATR inhibitors are either synergistic or antagonistic depending on the degree of inhibition of each individual kinase. We find that Polypyrimidine Tract Binding Protein 1 (PTBP1) is important for ATR activity in response to CDC7 inhibition and genotoxic agents. Compromised PTBP1 expression makes cells defective in RPA recruitment, genomically unstable, and resistant to CDC7 inhibitors. PTBP1 deficiency affects the expression and splicing of many genes indicating a multifactorial impact on drug response. We find that an exon skipping event in RAD51AP1 contributes to checkpoint deficiency in PTBP1-deficient cells. These results identify PTBP1 as a key factor in replication stress response and define how ATR activity modulates the activity of CDC7 inhibitors.
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Affiliation(s)
- Anja Göder
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
| | - Aisling Quinlan
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
| | - Michael D. Rainey
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
| | - Declan Bennett
- School of Mathematical & Statistical Sciences, University of Galway, Galway H91TK33, Ireland
| | - Daniel Shamavu
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
| | - Jacqueline Corso
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
| | - Corrado Santocanale
- Centre for Chromosome Biology, School of Biological and Chemical Sciences, University of Galway, Galway H91W2TY, Ireland
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19
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Broderick R, Cherdyntseva V, Nieminuszczy J, Dragona E, Kyriakaki M, Evmorfopoulou T, Gagos S, Niedzwiedz W. Pathway choice in the alternative telomere lengthening in neoplasia is dictated by replication fork processing mediated by EXD2's nuclease activity. Nat Commun 2023; 14:2428. [PMID: 37105990 PMCID: PMC10140042 DOI: 10.1038/s41467-023-38029-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
Telomerase-independent cancer proliferation via the alternative lengthening of telomeres (ALT) relies upon two distinct, largely uncharacterized, break-induced-replication (BIR) processes. How cancer cells initiate and regulate these terminal repair mechanisms is unknown. Here, we establish that the EXD2 nuclease is recruited to ALT telomeres to direct their maintenance. We demonstrate that EXD2 loss leads to telomere shortening, elevated telomeric sister chromatid exchanges, C-circle formation as well as BIR-mediated telomeric replication. We discover that EXD2 fork-processing activity triggers a switch between RAD52-dependent and -independent ALT-associated BIR. The latter is suppressed by EXD2 but depends specifically on the fork remodeler SMARCAL1 and the MUS81 nuclease. Thus, our findings suggest that processing of stalled replication forks orchestrates elongation pathway choice at ALT telomeres. Finally, we show that co-depletion of EXD2 with BLM, DNA2 or POLD3 confers synthetic lethality in ALT cells, identifying EXD2 as a potential druggable target for ALT-reliant cancers.
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Affiliation(s)
| | - Veronica Cherdyntseva
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | | | - Eleni Dragona
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Maria Kyriakaki
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Theodora Evmorfopoulou
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Sarantis Gagos
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece.
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20
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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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21
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Clatterbuck Soper SF, Meltzer PS. ATRX/DAXX: Guarding the Genome against the Hazards of ALT. Genes (Basel) 2023; 14:genes14040790. [PMID: 37107548 PMCID: PMC10137841 DOI: 10.3390/genes14040790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 03/21/2023] [Accepted: 03/22/2023] [Indexed: 03/29/2023] Open
Abstract
Proliferating cells must enact a telomere maintenance mechanism to ensure genomic stability. In a subset of tumors, telomeres are maintained not by telomerase, but through a homologous recombination-based mechanism termed Alternative Lengthening of Telomeres or ALT. The ALT process is linked to mutations in the ATRX/DAXX/H3.3 histone chaperone complex. This complex is responsible for depositing non-replicative histone variant H3.3 at pericentric and telomeric heterochromatin but has also been found to have roles in ameliorating replication in repeat sequences and in promoting DNA repair. In this review, we will discuss ways in which ATRX/DAXX helps to protect the genome, and how loss of this complex allows ALT to take hold.
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22
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Yadav T, Zhang JM, Ouyang J, Leung W, Simoneau A, Zou L. TERRA and RAD51AP1 promote alternative lengthening of telomeres through an R- to D-loop switch. Mol Cell 2022; 82:3985-4000.e4. [PMID: 36265486 PMCID: PMC9637728 DOI: 10.1016/j.molcel.2022.09.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/08/2022] [Accepted: 09/23/2022] [Indexed: 11/05/2022]
Abstract
Alternative lengthening of telomeres (ALT), a telomerase-independent process maintaining telomeres, is mediated by break-induced replication (BIR). RAD52 promotes ALT by facilitating D-loop formation, but ALT also occurs through a RAD52-independent BIR pathway. Here, we show that the telomere non-coding RNA TERRA forms dynamic telomeric R-loops and contributes to ALT activity in RAD52 knockout cells. TERRA forms R-loops in vitro and at telomeres in a RAD51AP1-dependent manner. The formation of R-loops by TERRA increases G-quadruplexes (G4s) at telomeres. G4 stabilization enhances ALT even when TERRA is depleted, suggesting that G4s act downstream of R-loops to promote BIR. In vitro, the telomeric R-loops assembled by TERRA and RAD51AP1 generate G4s, which persist after R-loop resolution and allow formation of telomeric D-loops without RAD52. Thus, the dynamic telomeric R-loops formed by TERRA and RAD51AP1 enable the RAD52-independent ALT pathway, and G4s orchestrate an R- to D-loop switch at telomeres to stimulate BIR.
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Affiliation(s)
- Tribhuwan Yadav
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jian Ouyang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Wendy Leung
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Antoine Simoneau
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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23
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TERRA and RAD51AP1 at the R&D-loop department of ALT telomeres. Mol Cell 2022; 82:3963-3965. [DOI: 10.1016/j.molcel.2022.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 10/05/2022] [Accepted: 10/05/2022] [Indexed: 11/05/2022]
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