1
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Alanazi AFR, Parkinson GN, Haider S. Structural Motifs at the Telomeres and Their Role in Regulatory Pathways. Biochemistry 2024; 63:827-842. [PMID: 38481135 PMCID: PMC10993422 DOI: 10.1021/acs.biochem.4c00023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Telomeres are specialized structures, found at the ends of linear chromosomes in eukaryotic cells, that play a crucial role in maintaining the stability and integrity of genomes. They are composed of repetitive DNA sequences, ssDNA overhangs, and several associated proteins. The length of telomeres is linked to cellular aging in humans, and deficiencies in their maintenance are associated with various diseases. Key structural motifs at the telomeres serve to protect vulnerable chromosomal ends. Telomeric DNA also has the ability to form diverse complex DNA higher-order structures, including T-loops, D-loops, R-loops, G-loops, G-quadruplexes, and i-motifs, in the complementary C-rich strand. While many essential proteins at telomeres have been identified, the intricacies of their interactions and structural details are still not fully understood. This Perspective highlights recent advancements in comprehending the structures associated with human telomeres. It emphasizes the significance of telomeres, explores various telomeric structural motifs, and delves into the structural biology surrounding telomeres and telomerase. Furthermore, telomeric loops, their topologies, and the associated proteins that contribute to the safeguarding of telomeres are discussed.
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Affiliation(s)
- Abeer F R Alanazi
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Gary N Parkinson
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - Shozeb Haider
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
- UCL Centre for Advanced Research Computing, University College London, London WC1H 9RN, United Kingdom
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2
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Wang Y, Zhu W, Jang Y, Sommers JA, Yi G, Puligilla C, Croteau DL, Yang Y, Kai M, Liu Y. The RNA-binding motif protein 14 regulates telomere integrity at the interface of TERRA and telomeric R-loops. Nucleic Acids Res 2023; 51:12242-12260. [PMID: 37930826 PMCID: PMC10711441 DOI: 10.1093/nar/gkad967] [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: 02/09/2023] [Accepted: 10/13/2023] [Indexed: 11/08/2023] Open
Abstract
Telomeric repeat-containing RNA (TERRA) and its formation of RNA:DNA hybrids (or TERRA R-loops), influence telomere maintenance, particularly in human cancer cells that use homologous recombination-mediated alternative lengthening of telomeres. Here, we report that the RNA-binding motif protein 14 (RBM14) is associated with telomeres in human cancer cells. RBM14 negatively regulates TERRA expression. It also binds to TERRA and inhibits it from forming TERRA R-loops at telomeres. RBM14 depletion has several effects, including elevated TERRA levels, telomeric R-loops, telomere dysfunction-induced DNA damage foci formation, particularly in the presence of DNA replication stress, pRPA32 accumulation at telomeres and telomere signal-free ends. Thus, RBM14 protects telomere integrity via modulating TERRA levels and its R-loop formation at telomeres.
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Affiliation(s)
- Yajun Wang
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Wei Zhu
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
| | - Yumi Jang
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Joshua A Sommers
- Translational Gerontology Branch, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
| | - Gong Yi
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
| | - Chandrakala Puligilla
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
| | - Deborah L Croteau
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
| | - Yibin Yang
- Blood Cell Development and Function Program, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Mihoko Kai
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Yie Liu
- Laboratory of Genetics and Genomics, 251 Bayview Blvd, National Institute on Aging/National Institutes of Health, Baltimore, MD 21224, USA
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3
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Loe TK, Lazzerini Denchi E, Tricola GM, Azeroglu B. ALTercations at telomeres: stress, recombination and extrachromosomal affairs. Biochem Soc Trans 2023; 51:1935-1946. [PMID: 37767563 DOI: 10.1042/bst20230265] [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: 08/11/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 09/29/2023]
Abstract
Approximately 15% of human cancers depend on the alternative lengthening of telomeres (ALT) pathway to maintain telomeres and proliferate. Telomeres that are elongated using ALT display unique features raising the exciting prospect of tailored cancer therapies. ALT-mediated telomere elongation shares several features with recombination-based DNA repair. Strikingly, cells that use the ALT pathway display abnormal levels of replication stress at telomeres and accumulate abundant extrachromosomal telomeric DNA. In this review, we examine recent findings that shed light on the ALT mechanisms and the strategies currently available to suppress this telomere elongation mechanism.
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Affiliation(s)
- Taylor K Loe
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, U.S.A
| | - Eros Lazzerini Denchi
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
| | - Gianna M Tricola
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
| | - Benura Azeroglu
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
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4
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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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5
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Alghoul E, Basbous J, Constantinou A. Compartmentalization of the DNA damage response: Mechanisms and functions. DNA Repair (Amst) 2023; 128:103524. [PMID: 37320957 DOI: 10.1016/j.dnarep.2023.103524] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 05/31/2023] [Accepted: 06/02/2023] [Indexed: 06/17/2023]
Abstract
Cells have evolved an arsenal of molecular mechanisms to respond to continuous alterations in the primary structure of DNA. At the cellular level, DNA damage response proteins accumulate at sites of DNA damage and organize into nuclear foci. As recounted by Errol Friedberg, pioneering work on DNA repair in the 1930 s was stimulated by collaborations between physicists and geneticists. In recent years, the introduction of ideas from physics on self-organizing compartments has taken the field of cell biology by storm. Percolation and phase separation theories are increasingly used to model the self-assembly of compartments, called biomolecular condensates, that selectively concentrate molecules without a surrounding membrane. In this review, we discuss these concepts in the context of the DNA damage response. We discuss how studies of DNA repair foci as condensates can link molecular mechanisms with cell physiological functions, provide new insights into regulatory mechanisms, and open new perspectives for targeting DNA damage responses for therapeutic purposes.
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Affiliation(s)
- Emile Alghoul
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France
| | - Jihane Basbous
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France
| | - Angelos Constantinou
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France.
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6
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Alghoul E, Paloni M, Takedachi A, Urbach S, Barducci A, Gaillard PH, Basbous J, Constantinou A. Compartmentalization of the SUMO/RNF4 pathway by SLX4 drives DNA repair. Mol Cell 2023; 83:1640-1658.e9. [PMID: 37059091 DOI: 10.1016/j.molcel.2023.03.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 02/06/2023] [Accepted: 03/21/2023] [Indexed: 04/16/2023]
Abstract
SLX4, disabled in the Fanconi anemia group P, is a scaffolding protein that coordinates the action of structure-specific endonucleases and other proteins involved in the replication-coupled repair of DNA interstrand cross-links. Here, we show that SLX4 dimerization and SUMO-SIM interactions drive the assembly of SLX4 membraneless compartments in the nucleus called condensates. Super-resolution microscopy reveals that SLX4 forms chromatin-bound clusters of nanocondensates. We report that SLX4 compartmentalizes the SUMO-RNF4 signaling pathway. SENP6 and RNF4 regulate the assembly and disassembly of SLX4 condensates, respectively. SLX4 condensation per se triggers the selective modification of proteins by SUMO and ubiquitin. Specifically, SLX4 condensation induces ubiquitylation and chromatin extraction of topoisomerase 1 DNA-protein cross-links. SLX4 condensation also induces the nucleolytic degradation of newly replicated DNA. We propose that the compartmentalization of proteins by SLX4 through site-specific interactions ensures the spatiotemporal control of protein modifications and nucleolytic reactions during DNA repair.
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Affiliation(s)
- Emile Alghoul
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France
| | - Matteo Paloni
- Centre de Biologie Structurale (CBS), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Arato Takedachi
- Aix Marseille Univ, CNRS, INSERM, Institut Paoli-Calmettes, CRCM, Marseille, France
| | - Serge Urbach
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; Montpellier RIO Imaging, Montpellier, France
| | - Alessandro Barducci
- Centre de Biologie Structurale (CBS), Université de Montpellier, CNRS, INSERM, Montpellier, France
| | | | - Jihane Basbous
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France.
| | - Angelos Constantinou
- Institut de Génétique Humaine, Université de Montpellier, CNRS, Montpellier, France.
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Hou K, Yu Y, Li D, Zhang Y, Zhang K, Tong J, Yang K, Jia S. Alternative Lengthening of Telomeres and Mediated Telomere Synthesis. Cancers (Basel) 2022; 14:cancers14092194. [PMID: 35565323 PMCID: PMC9105334 DOI: 10.3390/cancers14092194] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/24/2022] [Accepted: 04/25/2022] [Indexed: 12/01/2022] Open
Abstract
Simple Summary Alternative lengthing of telomere (ALT) is an important mechanism for maintaining telomere length and cell proliferation in telomerase-negative tumor cells. However, the molecular mechanism of ALT is still poorly understood. ALT occurs in a wide range of tumor types and usually associated with a worse clinical consequence. Here, we review the recent findings of ALT mechanisms, which promise ALT could be a valuable drug target for clinical telomerase-negative tumor treatment. Abstract Telomeres are DNA–protein complexes that protect eukaryotic chromosome ends from being erroneously repaired by the DNA damage repair system, and the length of telomeres indicates the replicative potential of the cell. Telomeres shorten during each division of the cell, resulting in telomeric damage and replicative senescence. Tumor cells tend to ensure cell proliferation potential and genomic stability by activating telomere maintenance mechanisms (TMMs) for telomere lengthening. The alternative lengthening of telomeres (ALT) pathway is the most frequently activated TMM in tumors of mesenchymal and neuroepithelial origin, and ALT also frequently occurs during experimental cellular immortalization of mesenchymal cells. ALT is a process that relies on homologous recombination (HR) to elongate telomeres. However, some processes in the ALT mechanism remain poorly understood. Here, we review the most recent understanding of ALT mechanisms and processes, which may help us to better understand how the ALT pathway is activated in cancer cells and determine the potential therapeutic targets in ALT pathway-stabilized tumors.
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Affiliation(s)
- Kailong Hou
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China;
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
- First People’s Hospital of Yunnan Province, 157 Jinbi Road, Kunming 650032, China
| | - Yuyang Yu
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Duda Li
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Yanduo Zhang
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Ke Zhang
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Jinkai Tong
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Kunxian Yang
- First People’s Hospital of Yunnan Province, 157 Jinbi Road, Kunming 650032, China
- Correspondence: (K.Y.); (S.J.)
| | - Shuting Jia
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
- Correspondence: (K.Y.); (S.J.)
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8
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Sakellariou D, Bak ST, Isik E, Barroso SI, Porro A, Aguilera A, Bartek J, Janscak P, Peña-Diaz J. MutSβ regulates G4-associated telomeric R-loops to maintain telomere integrity in ALT cancer cells. Cell Rep 2022; 39:110602. [PMID: 35385755 DOI: 10.1016/j.celrep.2022.110602] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/17/2021] [Accepted: 03/10/2022] [Indexed: 12/24/2022] Open
Abstract
Up to 15% of human cancers maintain their telomeres through a telomerase-independent mechanism, termed "alternative lengthening of telomeres" (ALT) that relies on homologous recombination between telomeric sequences. Emerging evidence suggests that the recombinogenic nature of ALT telomeres results from the formation of RNA:DNA hybrids (R-loops) between telomeric DNA and the long-noncoding telomeric repeat-containing RNA (TERRA). Here, we show that the mismatch repair protein MutSβ, a heterodimer of MSH2 and MSH3 subunits, is enriched at telomeres in ALT cancer cells, where it prevents the accumulation of telomeric G-quadruplex (G4) structures and R-loops. Cells depleted of MSH3 display increased incidence of R-loop-dependent telomere fragility and accumulation of telomeric C-circles. We also demonstrate that purified MutSβ recognizes and destabilizes G4 structures in vitro. These data suggest that MutSβ destabilizes G4 structures in ALT telomeres to regulate TERRA R-loops, which is a prerequisite for maintenance of telomere integrity during ALT.
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Affiliation(s)
- Despoina Sakellariou
- Center for Healthy Aging, Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark; Danish Cancer Society Research Center, 2100 Copenhagen, Denmark
| | - Sara Thornby Bak
- Center for Healthy Aging, Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Esin Isik
- Institute of Molecular Cancer Research, University of Zurich, 8057 Zürich, Switzerland
| | - Sonia I Barroso
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, University of Seville-CSIC-UPO, Seville, Spain
| | - Antonio Porro
- Institute of Molecular Cancer Research, University of Zurich, 8057 Zürich, Switzerland
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, University of Seville-CSIC-UPO, Seville, Spain
| | - Jiri Bartek
- Danish Cancer Society Research Center, 2100 Copenhagen, Denmark; Division of Genome Biology, Department of Medical Biochemistry and Biophysics, Science for Life Laboratory, Karolinska Institute, 17177 Stockholm, Sweden; Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 14300 Prague, Czech Republic
| | - Pavel Janscak
- Institute of Molecular Cancer Research, University of Zurich, 8057 Zürich, Switzerland; Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 14300 Prague, Czech Republic.
| | - Javier Peña-Diaz
- Center for Healthy Aging, Department of Neuroscience and Pharmacology, University of Copenhagen, 2200 Copenhagen, Denmark.
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9
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Badra Fajardo N, Taraviras S, Lygerou Z. Fanconi anemia proteins and genome fragility: unraveling replication defects for cancer therapy. Trends Cancer 2022; 8:467-481. [DOI: 10.1016/j.trecan.2022.01.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 01/25/2022] [Indexed: 10/19/2022]
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10
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Barroso-González J, García-Expósito L, Galaviz P, Lynskey ML, Allen JAM, Hoang S, Watkins SC, Pickett HA, O'Sullivan RJ. Anti-recombination function of MutSα restricts telomere extension by ALT-associated homology-directed repair. Cell Rep 2021; 37:110088. [PMID: 34879271 PMCID: PMC8724847 DOI: 10.1016/j.celrep.2021.110088] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/13/2021] [Accepted: 11/10/2021] [Indexed: 01/02/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere-elongation mechanism observed in ~15% of cancer subtypes. Current models indicate that ALT is mediated by homology-directed repair mechanisms. By disrupting MSH6 gene expression, we show that the deficiency of MutSα (MSH2/MSH6) DNA mismatch repair complex causes striking telomere hyperextension. Mechanistically, we show MutSα is specifically recruited to telomeres in ALT cells by associating with the proliferating-cell nuclear antigen (PCNA) subunit of the ALT telomere replisome. We also provide evidence that MutSα counteracts Bloom (BLM) helicase, which adopts a crucial role in stabilizing hyper-extended telomeres and maintaining the survival of MutSα-deficient ALT cancer cells. Lastly, we propose a model in which MutSα deficiency impairs heteroduplex rejection, leading to premature initiation of telomere DNA synthesis that coincides with an accumulation of telomere variant repeats (TVRs). These findings provide evidence that the MutSα DNA mismatch repair complex acts to restrain unwarranted ALT. Barroso-Gonzalez et al. show that the mismatch repair complex MutSα restricts the alternative lengthening of telomeres (ALT) pathway in cancer cells. MutSα has an anti-recombination function and limits recombination between heteroduplex sequences at telomeres, in part by counteracting the Bloom helicase (BLM).
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Affiliation(s)
- Jonathan Barroso-González
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Laura García-Expósito
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Pablo Galaviz
- Bioinformatics Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Michelle Lee Lynskey
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Joshua A M Allen
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - SongMy Hoang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Department of Cell Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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11
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Payliss BJ, Patel A, Sheppard AC, Wyatt HDM. Exploring the Structures and Functions of Macromolecular SLX4-Nuclease Complexes in Genome Stability. Front Genet 2021; 12:784167. [PMID: 34804132 PMCID: PMC8599992 DOI: 10.3389/fgene.2021.784167] [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: 09/27/2021] [Accepted: 10/21/2021] [Indexed: 12/15/2022] Open
Abstract
All organisms depend on the ability of cells to accurately duplicate and segregate DNA into progeny. However, DNA is frequently damaged by factors in the environment and from within cells. One of the most dangerous lesions is a DNA double-strand break. Unrepaired breaks are a major driving force for genome instability. Cells contain sophisticated DNA repair networks to counteract the harmful effects of genotoxic agents, thus safeguarding genome integrity. Homologous recombination is a high-fidelity, template-dependent DNA repair pathway essential for the accurate repair of DNA nicks, gaps and double-strand breaks. Accurate homologous recombination depends on the ability of cells to remove branched DNA structures that form during repair, which is achieved through the opposing actions of helicases and structure-selective endonucleases. This review focuses on a structure-selective endonuclease called SLX1-SLX4 and the macromolecular endonuclease complexes that assemble on the SLX4 scaffold. First, we discuss recent developments that illuminate the structure and biochemical properties of this somewhat atypical structure-selective endonuclease. We then summarize the multifaceted roles that are fulfilled by human SLX1-SLX4 and its associated endonucleases in homologous recombination and genome stability. Finally, we discuss recent work on SLX4-binding proteins that may represent integral components of these macromolecular nuclease complexes, emphasizing the structure and function of a protein called SLX4IP.
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Affiliation(s)
- Brandon J Payliss
- Department of Biochemistry, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Ayushi Patel
- Department of Biochemistry, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Anneka C Sheppard
- Department of Biochemistry, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Haley D M Wyatt
- Department of Biochemistry, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada.,Canada Research Chairs Program, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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12
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Glousker G, Lingner J. Challenging endings: How telomeres prevent fragility. Bioessays 2021; 43:e2100157. [PMID: 34436787 DOI: 10.1002/bies.202100157] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 12/23/2022]
Abstract
It has become apparent that difficulties to replicate telomeres concern not only the very ends of eukaryotic chromosomes. The challenges already start when the replication fork enters the telomeric repeats. The obstacles encountered consist mainly of noncanonical nucleic acid structures that interfere with replication if not resolved. Replication stress at telomeres promotes the formation of so-called fragile telomeres displaying an abnormal appearance in metaphase chromosomes though their exact molecular nature remains to be elucidated. A substantial number of factors is required to counteract fragility. In this review we promote the hypothesis that telomere fragility is not caused directly by an initial insult during replication but it results as a secondary consequence of DNA repair of damaged replication forks by the homologous DNA recombination machinery. Incomplete DNA synthesis at repair sites or partial chromatin condensation may become apparent as telomere fragility. Fragility and DNA repair during telomere replication emerges as a common phenomenon which exacerbates in multiple disease conditions.
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Affiliation(s)
- Galina Glousker
- 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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13
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Xu X, Wang M, Sun J, Yu Z, Li G, Yang N, Xu RM. Structure specific DNA recognition by the SLX1-SLX4 endonuclease complex. Nucleic Acids Res 2021; 49:7740-7752. [PMID: 34181713 PMCID: PMC8287910 DOI: 10.1093/nar/gkab542] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Revised: 06/04/2021] [Accepted: 06/11/2021] [Indexed: 11/13/2022] Open
Abstract
The SLX1–SLX4 structure-specific endonuclease complex is involved in processing diverse DNA damage intermediates, including resolution of Holliday junctions, collapse of stalled replication forks and removal of DNA flaps. The nuclease subunit SLX1 is inactive on its own, but become activated upon binding to SLX4 via its conserved C-terminal domain (CCD). Yet, how the SLX1–SLX4 complex recognizes specific DNA structure and chooses cleavage sites remains unknown. Here we show, through a combination of structural, biochemical and computational analyses, that the SAP domain of SLX4 is critical for efficient and accurate processing of 5′-flap DNA. It binds the minor groove of DNA about one turn away from the flap junction, and the 5′-flap is implicated in binding the core domain of SLX1. This binding mode accounts for specific recognition of 5′-flap DNA and specification of cleavage site by the SLX1–SLX4 complex.
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Affiliation(s)
- Xiang Xu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Key Laboratory of Medical Data Analysis and Statistical Research of Tianjin, Nankai University, Tianjin 300353, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Mingzhu Wang
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, Anhui, China
| | - Jixue Sun
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Key Laboratory of Medical Data Analysis and Statistical Research of Tianjin, Nankai University, Tianjin 300353, China
| | - Zhenyu Yu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Guohong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,School of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Na Yang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Key Laboratory of Medical Data Analysis and Statistical Research of Tianjin, Nankai University, Tianjin 300353, China
| | - Rui-Ming Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,School of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
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14
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Wang T, Zhang H, Zhou Y, Shi J. Extrachromosomal circular DNA: a new potential role in cancer progression. J Transl Med 2021; 19:257. [PMID: 34112178 PMCID: PMC8194206 DOI: 10.1186/s12967-021-02927-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 06/04/2021] [Indexed: 12/15/2022] Open
Abstract
Extrachromosomal circular DNA (eccDNA) is considered a circular DNA molecule that exists widely in nature and is independent of conventional chromosomes. eccDNA can be divided into small polydispersed circular DNA (spcDNA), telomeric circles (t-circles), microDNA, and extrachromosomal DNA (ecDNA) according to its size and sequence. Multiple studies have shown that eccDNA is the product of genomic instability, has rich and important biological functions, and is involved in the occurrence of many diseases, including cancer. In this review, we focus on the discovery history, formation process, characteristics, and physiological functions of eccDNAs; the potential functions of various eccDNAs in human cancer; and the research methods employed to study eccDNA.
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Affiliation(s)
- Tianyi Wang
- Nantong Key Laboratory of Translational Medicine in Cardiothoracic Diseases, and Research Institution of Translational Medicine in Cardiothoracic Diseases, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China.,Department of Thoracic Surgery, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Haijian Zhang
- Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Youlang Zhou
- Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Jiahai Shi
- Nantong Key Laboratory of Translational Medicine in Cardiothoracic Diseases, and Research Institution of Translational Medicine in Cardiothoracic Diseases, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China. .,Department of Thoracic Surgery, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China.
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15
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Sadhukhan R, Ghosh U. PARP1 modulates telomere sister chromatid exchange and telomere length homeostasis by regulating telomere localization of SLX4 in U2OS cells. Life Sci 2021; 277:119556. [PMID: 33945829 DOI: 10.1016/j.lfs.2021.119556] [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: 01/23/2021] [Revised: 04/12/2021] [Accepted: 04/20/2021] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Poly(ADP-ribose) polymerase1 (PARP1) interacts and poly(ADP-ribosyl)ates telomere repeat binding factor 2 (TRF2), which acts as a platform to recruit a large number of proteins at the telomere. Since the discovery of TRF2-SLX4 interaction, SLX4 is becoming the key player in telomere length (TL) maintenance and repair by telomere sister chromatid exchange (T-SCE). Defective TL maintenance pathway results in a spectrum of diseases called telomeropathies like dyskeratosis congenita, aplastic anemia, fanconi anemia, cancer. We aimed to study the role of SLX4 and PARP1 on each other's telomere localization, T-SCE, and TL maintenance in human telomerase-negative osteosarcoma U2OS cells to understand some of the molecular mechanisms of telomere homeostasis. MATERIALS AND METHODS We checked the role of SLX4 and PARP1 on each other's telomere localization by telomere immunofluorescence. We have cloned full-length wild-type and catalytically inactive mutant PARP1 to understand the role of poly(ADP-ribosyl)ation reaction by PARP1 in telomere length homeostasis. TL of U2OS cells was measured by Q-FISH. T-SCE was measured by Telomere-FISH. KEY FINDINGS We observed that SLX4 has no role in the telomere localization of PARP1. However, reduced localization of SLX4 at undamaged and damaged telomere upon PARP1 depletion was reversed by overexpression of exogenous wild-type PARP1 but not by overexpression of catalytically inactive mutant PARP1. PARP1 depletion synergized SLX4 depletion-mediated reduction of T-SCE. Furthermore, SLX4 depletion elongated TL, and combined insufficiency of SLX4 with PARP1 further elongated TL. CONCLUSION So, PARP1 controls SLX4 recruitment at telomere by poly(ADP-ribosyl)ation reaction, thereby regulating SLX4-mediated T-SCE and TL homeostasis.
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Affiliation(s)
- Ratan Sadhukhan
- Department of Biochemistry & Biophysics, University of Kalyani, Kalyani 741235, India
| | - Utpal Ghosh
- Department of Biochemistry & Biophysics, University of Kalyani, Kalyani 741235, India.
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16
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Young SJ, West SC. Coordinated roles of SLX4 and MutSβ in DNA repair and the maintenance of genome stability. Crit Rev Biochem Mol Biol 2021; 56:157-177. [PMID: 33596761 PMCID: PMC7610648 DOI: 10.1080/10409238.2021.1881433] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 01/06/2021] [Accepted: 01/22/2021] [Indexed: 12/14/2022]
Abstract
SLX4 provides a molecular scaffold for the assembly of multiple protein complexes required for the maintenance of genome stability. It is involved in the repair of DNA crosslinks, the resolution of recombination intermediates, the response to replication stress and the maintenance of telomere length. To carry out these diverse functions, SLX4 interacts with three structure-selective endonucleases, MUS81-EME1, SLX1 and XPF-ERCC1, as well as the telomere binding proteins TRF2, RTEL1 and SLX4IP. Recently, SLX4 was shown to interact with MutSβ, a heterodimeric protein involved in DNA mismatch repair, trinucleotide repeat instability, crosslink repair and recombination. Importantly, MutSβ promotes the pathogenic expansion of CAG/CTG trinucleotide repeats, which is causative of myotonic dystrophy and Huntington's disease. The colocalization and specific interaction of MutSβ with SLX4, together with their apparently overlapping functions, are suggestive of a common role in reactions that promote DNA maintenance and genome stability. This review will focus on the role of SLX4 in DNA repair, the interplay between MutSβ and SLX4, and detail how they cooperate to promote recombinational repair and DNA crosslink repair. Furthermore, we speculate that MutSβ and SLX4 may provide an alternative cellular mechanism that modulates trinucleotide instability.
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Affiliation(s)
- Sarah J Young
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London, UK
| | - Stephen C West
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London, UK
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17
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Codd V, Wang Q, Allara E, Musicha C, Kaptoge S, Stoma S, Jiang T, Hamby SE, Braund PS, Bountziouka V, Budgeon CA, Denniff M, Swinfield C, Papakonstantinou M, Sheth S, Nanus DE, Warner SC, Wang M, Khera AV, Eales J, Ouwehand WH, Thompson JR, Di Angelantonio E, Wood AM, Butterworth AS, Danesh JN, Nelson CP, Samani NJ. Polygenic basis and biomedical consequences of telomere length variation. Nat Genet 2021; 53:1425-1433. [PMID: 34611362 PMCID: PMC8492471 DOI: 10.1038/s41588-021-00944-6] [Citation(s) in RCA: 139] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 08/18/2021] [Indexed: 02/08/2023]
Abstract
Telomeres, the end fragments of chromosomes, play key roles in cellular proliferation and senescence. Here we characterize the genetic architecture of naturally occurring variation in leukocyte telomere length (LTL) and identify causal links between LTL and biomedical phenotypes in 472,174 well-characterized UK Biobank participants. We identified 197 independent sentinel variants associated with LTL at 138 genomic loci (108 new). Genetically determined differences in LTL were associated with multiple biological traits, ranging from height to bone marrow function, as well as several diseases spanning neoplastic, vascular and inflammatory pathologies. Finally, we estimated that, at the age of 40 years, people with an LTL >1 s.d. shorter than the population mean had a 2.5-year-lower life expectancy compared with the group with ≥1 s.d. longer LDL. Overall, we furnish new insights into the genetic regulation of LTL, reveal wide-ranging influences of LTL on physiological traits, diseases and longevity, and provide a powerful resource available to the global research community.
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Affiliation(s)
- Veryan Codd
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Qingning Wang
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Elias Allara
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK
| | - Crispin Musicha
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Stephen Kaptoge
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK
| | - Svetlana Stoma
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Tao Jiang
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
| | - Stephen E. Hamby
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Peter S. Braund
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Vasiliki Bountziouka
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Charley A. Budgeon
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK ,grid.1012.20000 0004 1936 7910School of Population and Global Health, University of Western Australia, Perth, Western Australia Australia
| | - Matthew Denniff
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Chloe Swinfield
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Manolo Papakonstantinou
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Shilpi Sheth
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Dominika E. Nanus
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Sophie C. Warner
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
| | - Minxian Wang
- grid.66859.34Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA USA ,grid.32224.350000 0004 0386 9924Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA USA
| | - Amit V. Khera
- grid.66859.34Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA USA ,grid.32224.350000 0004 0386 9924Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA USA ,grid.38142.3c000000041936754XDepartment of Medicine, Harvard Medical School, Boston, MA USA ,grid.32224.350000 0004 0386 9924Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston, MA USA
| | - James Eales
- grid.5379.80000000121662407Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Willem H. Ouwehand
- grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934Department of Haematology, University of Cambridge, Cambridge, UK ,grid.436365.10000 0000 8685 6563NHS Blood and Transplant, Cambridge, UK ,grid.52996.310000 0000 8937 2257University College London Hospitals NHS Foundation Trust, London, UK
| | - John R. Thompson
- grid.9918.90000 0004 1936 8411Department of Health Sciences, University of Leicester, Leicester, UK
| | - Emanuele Di Angelantonio
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK ,grid.10306.340000 0004 0606 5382Health Data Research UK Cambridge, Wellcome Sanger Institute, EMBL-European Bioinformatics Institute and University of Cambridge, Cambridge, UK
| | - Angela M. Wood
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK ,grid.10306.340000 0004 0606 5382Health Data Research UK Cambridge, Wellcome Sanger Institute, EMBL-European Bioinformatics Institute and University of Cambridge, Cambridge, UK ,grid.499548.d0000 0004 5903 3632The Alan Turing Institute, London, UK
| | - Adam S. Butterworth
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK ,grid.10306.340000 0004 0606 5382Health Data Research UK Cambridge, Wellcome Sanger Institute, EMBL-European Bioinformatics Institute and University of Cambridge, Cambridge, UK
| | - John N. Danesh
- grid.5335.00000000121885934British Heart Foundation Cardiovascular Epidemiology Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics, University of Cambridge, Cambridge, UK ,grid.5335.00000000121885934British Heart Foundation Centre of Research Excellence, University of Cambridge, Cambridge, UK ,grid.10306.340000 0004 0606 5382Health Data Research UK Cambridge, Wellcome Sanger Institute, EMBL-European Bioinformatics Institute and University of Cambridge, Cambridge, UK ,grid.10306.340000 0004 0606 5382Department of Human Genetics, Wellcome Sanger Institute, Hinxton, UK
| | - Christopher P. Nelson
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
| | - Nilesh J. Samani
- grid.9918.90000 0004 1936 8411Department of Cardiovascular Sciences, University of Leicester, Leicester, UK ,grid.412925.90000 0004 0400 6581NIHR Leicester Biomedical Research Centre, Glenfield Hospital, Leicester, UK
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18
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Young SJ, Sebald M, Shah Punatar R, Larin M, Masino L, Rodrigo-Brenni MC, Liang CC, West SC. MutSβ Stimulates Holliday Junction Resolution by the SMX Complex. Cell Rep 2020; 33:108289. [PMID: 33086055 DOI: 10.1016/j.celrep.2020.108289] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 09/02/2020] [Accepted: 09/29/2020] [Indexed: 12/20/2022] Open
Abstract
MutSα and MutSβ play important roles in DNA mismatch repair and are linked to inheritable cancers and degenerative disorders. Here, we show that MSH2 and MSH3, the two components of MutSβ, bind SLX4 protein, a scaffold for the assembly of the SLX1-SLX4-MUS81-EME1-XPF-ERCC1 (SMX) trinuclease complex. SMX promotes the resolution of Holliday junctions (HJs), which are intermediates in homologous recombinational repair. We find that MutSβ binds HJs and stimulates their resolution by SLX1-SLX4 or SMX in reactions dependent upon direct interactions between MutSβ and SLX4. In contrast, MutSα does not stimulate HJ resolution. MSH3-depleted cells exhibit reduced sister chromatid exchanges and elevated levels of homologous recombination ultrafine bridges (HR-UFBs) at mitosis, consistent with defects in the processing of recombination intermediates. These results demonstrate a role for MutSβ in addition to its established role in the pathogenic expansion of CAG/CTG trinucleotide repeats, which is causative of myotonic dystrophy and Huntington's disease.
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Affiliation(s)
- Sarah J Young
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Marie Sebald
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Meghan Larin
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Laura Masino
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Chih-Chao Liang
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Stephen C West
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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19
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Tomáška Ľ, Cesare AJ, AlTurki TM, Griffith JD. Twenty years of t-loops: A case study for the importance of collaboration in molecular biology. DNA Repair (Amst) 2020; 94:102901. [PMID: 32620538 DOI: 10.1016/j.dnarep.2020.102901] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 06/22/2020] [Indexed: 12/12/2022]
Abstract
Collaborative studies open doors to breakthroughs otherwise unattainable by any one laboratory alone. Here we describe the initial collaboration between the Griffith and de Lange laboratories that led to thinking about the telomere as a DNA template for homologous recombination, the proposal of telomere looping, and the first electron micrographs of t-loops. This was followed by collaborations that revealed t-loops across eukaryotic phyla. The Griffith and Tomáška/Nosek collaboration revealed circular telomeric DNA (t-circles) derived from the linear mitochondrial chromosomes of nonconventional yeast, which spurred discovery of t-circles in ALT-positive human cells. Collaborative work between the Griffith and McEachern labs demonstrated t-loops and t-circles in a series of yeast species. The de Lange and Zhuang laboratories then applied super-resolution light microscopy to demonstrate a genetic role for TRF2 in loop formation. Recent work from the Griffith laboratory linked telomere transcription with t-loop formation, providing a new model of the t-loop junction. A recent collaboration between the Cesare and Gaus laboratories utilized super-resolution light microscopy to provide details about t-loops as protective elements, followed by the Boulton and Cesare laboratories showing how cell cycle regulation of TRF2 and RTEL enables t-loop opening and reformation to promote telomere replication. Twenty years after the discovery of t-loops, we reflect on the collective history of their research as a case study in collaborative molecular biology.
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Affiliation(s)
- Ľubomír Tomáška
- Department of Genetics, Comenius University in Bratislava, Faculty of Natural Sciences, Ilkovicova 6, 84215, Bratislava, Slovakia
| | - Anthony J Cesare
- Genome Integrity Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, 2145, Australia
| | - Taghreed M AlTurki
- Lineberger Comprehensive Cancer Center and Departments of Microbiology and Immunology, and Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Jack D Griffith
- Lineberger Comprehensive Cancer Center and Departments of Microbiology and Immunology, and Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
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20
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Saccharomyces cerevisiae Mus81-Mms4 prevents accelerated senescence in telomerase-deficient cells. PLoS Genet 2020; 16:e1008816. [PMID: 32469862 PMCID: PMC7286520 DOI: 10.1371/journal.pgen.1008816] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 06/10/2020] [Accepted: 04/30/2020] [Indexed: 01/31/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) in human cells is a conserved process that is often activated in telomerase-deficient human cancers. This process exploits components of the recombination machinery to extend telomere ends, thus allowing for increased proliferative potential. Human MUS81 (Mus81 in Saccharomyces cerevisiae) is the catalytic subunit of structure-selective endonucleases involved in recombination and has been implicated in the ALT mechanism. However, it is unclear whether MUS81 activity at the telomere is specific to ALT cells or if it is required for more general aspects of telomere stability. In this study, we use S. cerevisiae to evaluate the contribution of the conserved Mus81-Mms4 endonuclease in telomerase-deficient yeast cells that maintain their telomeres by mechanisms akin to human ALT. Similar to human cells, we find that yeast Mus81 readily localizes to telomeres and its activity is important for viability after initial loss of telomerase. Interestingly, our analysis reveals that yeast Mus81 is not required for the survival of cells undergoing recombination-mediated telomere lengthening, i.e. for ALT itself. Rather we infer from genetic analysis that Mus81-Mms4 facilitates telomere replication during times of telomere instability. Furthermore, combining mus81 mutants with mutants of a yeast telomere replication factor, Rrm3, reveals that the two proteins function in parallel to promote normal growth during times of telomere stress. Combined with previous reports, our data can be interpreted in a consistent model in which both yeast and human MUS81-dependent nucleases participate in the recovery of stalled replication forks within telomeric DNA. Furthermore, this process becomes crucial under conditions of additional replication stress, such as telomere replication in telomerase-deficient cells. Cancer cell divisions require active chromosome lengthening through extension of their highly repetitive ends, called telomeres. This process is accomplished through two main mechanisms: the activity of an RNA-protein complex, telomerase, or through a telomerase-independent process termed alternative lengthening of telomeres (ALT). Human MUS81, the catalytic subunit of a set of structure-selective endonucleases, was found to be essential in human cells undergoing ALT and proposed to be directly involved in telomere lengthening. Using telomerase-deficient Saccharomyces cerevisiae cells as a model for ALT, we tested the hypothesis that Mus81-Mms4, the budding yeast homolog of human MUS81-dependent nucleases, is essential for telomere lengthening as proposed for human cells. Using genetic and molecular assays we confirm that Mus81-Mms4 is involved in telomere metabolism in yeast. However, to our surprise, we find that Mus81-Mms4 is not directly involved in recombination-based mechanisms of telomere lengthening. Rather it appears that Mus81-Mms4 is involved in resolving replication stress at telomeres, which is augmented in cells undergoing telomere instability. This model is consistent with observations in mammalian cells and suggest that cells undergoing telomere shortening experience replication stress at telomeres.
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21
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Cherdyntseva V, Gagos S. Chromosome extremities under the microscopy lens: molecular cytogenetics in telomere research. Curr Opin Genet Dev 2020; 60:69-76. [PMID: 32193147 DOI: 10.1016/j.gde.2020.02.011] [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: 12/15/2019] [Revised: 02/03/2020] [Accepted: 02/06/2020] [Indexed: 02/07/2023]
Abstract
At the crossroads of DNA damage repair and genomic instability, telomere research significantly expands our knowledge on fundamental mechanisms involved in cancer initiation and progression, pledging novel tools for targeted and universal onco-therapies. Molecular cytogenetics through the application of a battery of fluorescent hybridization technologies plays an important role toward understanding telomere homeostasis. Herein, we review distinct molecular cytogenetic phenotypes associated with telomere repair, functionality, and elongation. We discuss the underlying mechanisms responsible for their formation or repair, focusing on Break-induced-Replication (BIR)-mediated conservative telomeric neo-synthesis, recently shown to drive the enigmatic Alternative Lengthening of Telomeres in neoplasia.
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Affiliation(s)
- Veronica Cherdyntseva
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, 11527, Greece
| | - Sarantis Gagos
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research, Biomedical Research Foundation of the Academy of Athens, Athens, 11527, Greece.
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22
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Robinson NJ, Morrison-Smith CD, Gooding AJ, Schiemann BJ, Jackson MW, Taylor DJ, Schiemann WP. SLX4IP and telomere dynamics dictate breast cancer metastasis and therapeutic responsiveness. Life Sci Alliance 2020; 3:3/4/e201900427. [PMID: 32071280 PMCID: PMC7032570 DOI: 10.26508/lsa.201900427] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 02/10/2020] [Accepted: 02/11/2020] [Indexed: 02/06/2023] Open
Abstract
An unbiased genetic screen established SLX4IP as an essential driver of telomere maintenance mechanism identity, metastatic progression, and therapeutic response of breast cancers. Metastasis is the leading cause of breast cancer-related death and poses a substantial clinical burden owing to a paucity of targeted treatment options. The clinical manifestations of metastasis occur years-to-decades after initial diagnosis and treatment because disseminated tumor cells readily evade detection and resist therapy, ultimately giving rise to recurrent disease. Using an unbiased genetic screen, we identified SLX4-interacting protein (SLX4IP) as a regulator of metastatic recurrence and established its relationship in governing telomere maintenance mechanisms (TMMs). Inactivation of SLX4IP suppressed alternative lengthening of telomeres (ALT), coinciding with activation of telomerase. Importantly, TMM selection dramatically influenced metastatic progression and survival of patients with genetically distinct breast cancer subtypes. Notably, pharmacologic and genetic modulation of TMMs elicited telomere-dependent cell death and prevented disease recurrence by disseminated tumor cells. This study illuminates SLX4IP as a potential predictive biomarker for breast cancer progression and metastatic relapse. SLX4IP expression correlates with TMM identity, which also carries prognostic value and informs treatment selection, thereby revealing new inroads into combating metastatic breast cancers.
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Affiliation(s)
- Nathaniel J Robinson
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | | | - Alex J Gooding
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Barbara J Schiemann
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, USA
| | - Mark W Jackson
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Derek J Taylor
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - William P Schiemann
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, USA
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23
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Alternative Lengthening of Telomeres: Building Bridges To Connect Chromosome Ends. Trends Cancer 2020; 6:247-260. [PMID: 32101727 DOI: 10.1016/j.trecan.2019.12.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/16/2019] [Accepted: 12/19/2019] [Indexed: 12/15/2022]
Abstract
Alternative lengthening of telomeres (ALT) is a mechanism of telomere maintenance that is observed in many of the most recalcitrant cancer subtypes. Telomeres in ALT cancer cells exhibit a distinctive nucleoprotein architecture shaped by the mismanagement of chromatin that fosters cycles of DNA damage and replicative stress that activate homology-directed repair (HDR). Mutations in specific chromatin-remodeling factors appear to be key determinants of the emergence and survival of ALT cancer cells. However, these may represent vulnerabilities for the targeted elimination of ALT cancer cells that infiltrate tissues and organs to become devastating tumors. In this review we examine recent findings that provide new insights into the factors and mechanisms that mediate telomere length maintenance and survival of ALT cancer cells.
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24
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Zhang H, Chen Z, Ye Y, Ye Z, Cao D, Xiong Y, Srivastava M, Feng X, Tang M, Wang C, Tainer JA, Chen J. SLX4IP acts with SLX4 and XPF-ERCC1 to promote interstrand crosslink repair. Nucleic Acids Res 2019; 47:10181-10201. [PMID: 31495888 PMCID: PMC6821277 DOI: 10.1093/nar/gkz769] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 08/03/2019] [Accepted: 09/05/2019] [Indexed: 12/13/2022] Open
Abstract
Interstrand crosslinks (ICLs) are highly toxic DNA lesions that are repaired via a complex process requiring the coordination of several DNA repair pathways. Defects in ICL repair result in Fanconi anemia, which is characterized by bone marrow failure, developmental abnormalities, and a high incidence of malignancies. SLX4, also known as FANCP, acts as a scaffold protein and coordinates multiple endonucleases that unhook ICLs, resolve homologous recombination intermediates, and perhaps remove unhooked ICLs. In this study, we explored the role of SLX4IP, a constitutive factor in the SLX4 complex, in ICL repair. We found that SLX4IP is a novel regulatory factor; its depletion sensitized cells to treatment with ICL-inducing agents and led to accumulation of cells in the G2/M phase. We further discovered that SLX4IP binds to SLX4 and XPF-ERCC1 simultaneously and that disruption of one interaction also disrupts the other. The binding of SLX4IP to both SLX4 and XPF-ERCC1 not only is vital for maintaining the stability of SLX4IP protein, but also promotes the interaction between SLX4 and XPF-ERCC1, especially after DNA damage. Collectively, these results demonstrate a new regulatory role for SLX4IP in maintaining an efficient SLX4-XPF-ERCC1 complex in ICL repair.
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Affiliation(s)
- Huimin Zhang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zhen Chen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Yin Ye
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Zu Ye
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Dan Cao
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Yun Xiong
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Mrinal Srivastava
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Xu Feng
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Mengfan Tang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Chao Wang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Junjie Chen
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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25
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Panier S, Maric M, Hewitt G, Mason-Osann E, Gali H, Dai A, Labadorf A, Guervilly JH, Ruis P, Segura-Bayona S, Belan O, Marzec P, Gaillard PHL, Flynn RL, Boulton SJ. SLX4IP Antagonizes Promiscuous BLM Activity during ALT Maintenance. Mol Cell 2019; 76:27-43.e11. [PMID: 31447390 PMCID: PMC6863466 DOI: 10.1016/j.molcel.2019.07.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 06/03/2019] [Accepted: 07/08/2019] [Indexed: 12/18/2022]
Abstract
Cancer cells acquire unlimited proliferative capacity by either re-expressing telomerase or inducing alternative lengthening of telomeres (ALT), which relies on telomere recombination. Here, we show that ALT recombination requires coordinate regulation of the SMX and BTR complexes to ensure the appropriate balance of resolution and dissolution activities at recombining telomeres. Critical to this control is SLX4IP, which accumulates at ALT telomeres and interacts with SLX4, XPF, and BLM. Loss of SLX4IP increases ALT-related phenotypes, which is incompatible with cell growth following concomitant loss of SLX4. Inactivation of BLM is sufficient to rescue telomere aggregation and the synthetic growth defect in this context, suggesting that SLX4IP favors SMX-dependent resolution by antagonizing promiscuous BLM activity during ALT recombination. Finally, we show that SLX4IP is inactivated in a subset of ALT-positive osteosarcomas. Collectively, our findings uncover an SLX4IP-dependent regulatory mechanism critical for telomere maintenance in ALT cancer cells.
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Affiliation(s)
| | - Marija Maric
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Graeme Hewitt
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Emily Mason-Osann
- Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA
| | - Himabindu Gali
- Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA
| | - Anqi Dai
- Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA
| | - Adam Labadorf
- Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA
| | - Jean-Hugues Guervilly
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
| | - Philip Ruis
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | | | - Ondrej Belan
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Paulina Marzec
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Pierre-Henri L Gaillard
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
| | - Rachel L Flynn
- Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA
| | - Simon J Boulton
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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26
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Arias-Salgado EG, Galvez E, Planas-Cerezales L, Pintado-Berninches L, Vallespin E, Martinez P, Carrillo J, Iarriccio L, Ruiz-Llobet A, Catalá A, Badell-Serra I, Gonzalez-Granado LI, Martín-Nalda A, Martínez-Gallo M, Galera-Miñarro A, Rodríguez-Vigil C, Bastos-Oreiro M, Perez de Nanclares G, Leiro-Fernández V, Uria ML, Diaz-Heredia C, Valenzuela C, Martín S, López-Muñiz B, Lapunzina P, Sevilla J, Molina-Molina M, Perona R, Sastre L. Genetic analyses of aplastic anemia and idiopathic pulmonary fibrosis patients with short telomeres, possible implication of DNA-repair genes. Orphanet J Rare Dis 2019; 14:82. [PMID: 30995915 PMCID: PMC6471801 DOI: 10.1186/s13023-019-1046-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/12/2019] [Indexed: 01/19/2023] Open
Abstract
Background Telomeres are nucleoprotein structures present at the terminal region of the chromosomes. Mutations in genes coding for proteins involved in telomere maintenance are causative of a number of disorders known as telomeropathies. The genetic origin of these diseases is heterogeneous and has not been determined for a significant proportion of patients. Methods This article describes the genetic characterization of a cohort of patients. Telomere length was determined by Southern blot and quantitative PCR. Nucleotide variants were analyzed either by high-resolution melting analysis and Sanger sequencing of selected exons or by massive sequencing of a panel of genes. Results Forty-seven patients with telomere length below the 10% of normal population, affected with three telomeropathies: dyskeratosis congenita (4), aplastic anemia (22) or pulmonary fibrosis (21) were analyzed. Eighteen of these patients presented known pathogenic or novel possibly pathogenic variants in the telomere-related genes TERT, TERC, RTEL1, CTC1 and ACD. In addition, the analyses of a panel of 188 genes related to haematological disorders indicated that a relevant proportion of the patients (up to 35%) presented rare variants in genes related to DNA repair or in genes coding for proteins involved in the resolution of complex DNA structures, that participate in telomere replication. Mutations in some of these genes are causative of several syndromes previously associated to telomere shortening. Conclusion Novel variants in telomere, DNA repair and replication genes are described that might indicate the contribution of variants in these genes to the development of telomeropathies. Patients carrying variants in telomere-related genes presented worse evolution after diagnosis than the rest of patients analyzed. Electronic supplementary material The online version of this article (10.1186/s13023-019-1046-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elena G Arias-Salgado
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain.,Advanced Medical Projects, Madrid, Spain
| | - Eva Galvez
- Hospital Niño Jesús, Hematología y Hemoterapia, Madrid, Spain
| | - Lurdes Planas-Cerezales
- ILD Unit Pneumology Department, University Hospital of Bellvitge, IDIBELL, University of Barcelona, Barcelona, Spain
| | - Laura Pintado-Berninches
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain.,Advanced Medical Projects, Madrid, Spain
| | - Elena Vallespin
- Institute of Medical and Molecular Genetics (INGEMM), Hospital Universitario La Paz, Madrid, Spain
| | - Pilar Martinez
- Institute of Medical and Molecular Genetics (INGEMM), Hospital Universitario La Paz, Madrid, Spain
| | - Jaime Carrillo
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain
| | - Laura Iarriccio
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain.,Advanced Medical Projects, Madrid, Spain
| | - Anna Ruiz-Llobet
- Pediatric Hematology and Oncology Department, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain.,Institut de Recerca Pediàtrica Hospital Sant Joan de Déu (IRP-HSJD), Esplugues de Llobregat, Barcelona, Spain
| | - Albert Catalá
- Pediatric Hematology and Oncology Department, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain.,Institut de Recerca Pediàtrica Hospital Sant Joan de Déu (IRP-HSJD), Esplugues de Llobregat, Barcelona, Spain
| | | | | | - Andrea Martín-Nalda
- Immunology Division, Pediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron (HUVH), Vall d'Hebron Research Institute (VHIR), Department of Cell Biology, Physiology and Immunology, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | - Mónica Martínez-Gallo
- Immunology Division, Pediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron (HUVH), Vall d'Hebron Research Institute (VHIR), Department of Cell Biology, Physiology and Immunology, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | | | | | | | - Guiomar Perez de Nanclares
- Molecular (Epi)Genetics Laboratory, BioAraba National Health Institute, OSI Araba University Hospital, Vitoria-Gasteiz, Spain
| | - Virginia Leiro-Fernández
- Pneumology Department, Hospital Álvaro Cunqueiro, Complexo Hospitalario Universitario de Vigo, NeumoVigoI+i Research Group, Vigo Biomedical Research Institute (IBIV), Barcelona, Spain
| | - Maria-Luz Uria
- Immunology Division, Pediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron (HUVH), Vall d'Hebron Research Institute (VHIR), Department of Cell Biology, Physiology and Immunology, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | - Cristina Diaz-Heredia
- Immunology Division, Pediatric Infectious Diseases and Immunodeficiencies Unit, Hospital Universitari Vall d'Hebron (HUVH), Vall d'Hebron Research Institute (VHIR), Department of Cell Biology, Physiology and Immunology, Autonomous University of Barcelona (UAB), Barcelona, Spain
| | | | - Sara Martín
- ILD Unit Pneumology Department, University Hospital of Bellvitge, IDIBELL, University of Barcelona, Barcelona, Spain
| | | | - Pablo Lapunzina
- Institute of Medical and Molecular Genetics (INGEMM), Hospital Universitario La Paz, Madrid, Spain.,CIBER de enfermedades raras (CIBERER), Madrid, Spain
| | - Julian Sevilla
- Hospital Niño Jesús, Hematología y Hemoterapia, Madrid, Spain.,CIBER de enfermedades raras (CIBERER), Madrid, Spain
| | - María Molina-Molina
- ILD Unit Pneumology Department, University Hospital of Bellvitge, IDIBELL, University of Barcelona, Barcelona, Spain.,CIBER of Respiratory diseases (CIBERES), Barcelona, Spain
| | - Rosario Perona
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain.,CIBER de enfermedades raras (CIBERER), Madrid, Spain
| | - Leandro Sastre
- Instituto de Investigaciones Biomedicas CSIC/UAM, IDIPaz, Arturo Duperier, 4, 28029, Madrid, Spain. .,CIBER de enfermedades raras (CIBERER), Madrid, Spain.
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27
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Sommers JA, Kulikowicz T, Croteau DL, Dexheimer T, Dorjsuren D, Jadhav A, Maloney DJ, Simeonov A, Bohr VA, Brosh RM. A high-throughput screen to identify novel small molecule inhibitors of the Werner Syndrome Helicase-Nuclease (WRN). PLoS One 2019; 14:e0210525. [PMID: 30625228 PMCID: PMC6326523 DOI: 10.1371/journal.pone.0210525] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 12/26/2018] [Indexed: 01/26/2023] Open
Abstract
Werner syndrome (WS), an autosomal recessive genetic disorder, displays accelerated clinical symptoms of aging leading to a mean lifespan less than 50 years. The WS helicase-nuclease (WRN) is involved in many important pathways including DNA replication, recombination and repair. Replicating cells are dependent on helicase activity, leading to the pursuit of human helicases as potential therapeutic targets for cancer treatment. Small molecule inhibitors of DNA helicases can be used to induce synthetic lethality, which attempts to target helicase-dependent compensatory DNA repair pathways in tumor cells that are already genetically deficient in a specific pathway of DNA repair. Alternatively, helicase inhibitors may be useful as tools to study the specialized roles of helicases in replication and DNA repair. In this study, approximately 350,000 small molecules were screened based on their ability to inhibit duplex DNA unwinding by a catalytically active WRN helicase domain fragment in a high-throughput fluorometric assay to discover new non-covalent small molecule inhibitors of the WRN helicase. Select compounds were screened to exclude ones that inhibited DNA unwinding by other helicases in the screen, bound non-specifically to DNA, acted as irreversible inhibitors, or possessed unfavorable chemical properties. Several compounds were tested for their ability to impair proliferation of cultured tumor cells. We observed that two of the newly identified WRN helicase inhibitors inhibited proliferation of cancer cells in a lineage-dependent manner. These studies represent the first high-throughput screen for WRN helicase inhibitors and the results have implications for anti-cancer strategies targeting WRN in different cancer cells and genetic backgrounds.
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Affiliation(s)
- Joshua A. Sommers
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Tomasz Kulikowicz
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Deborah L. Croteau
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Thomas Dexheimer
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Dorjbal Dorjsuren
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Ajit Jadhav
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - David J. Maloney
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, United States of America
| | - Vilhelm A. Bohr
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Robert M. Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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28
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Kim SM, Forsburg SL. Regulation of Structure-Specific Endonucleases in Replication Stress. Genes (Basel) 2018; 9:genes9120634. [PMID: 30558228 PMCID: PMC6316474 DOI: 10.3390/genes9120634] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 12/11/2018] [Accepted: 12/12/2018] [Indexed: 12/16/2022] Open
Abstract
Replication stress results in various forms of aberrant replication intermediates that need to be resolved for faithful chromosome segregation. Structure-specific endonucleases (SSEs) recognize DNA secondary structures rather than primary sequences and play key roles during DNA repair and replication stress. Holliday junction resolvase MUS81 (methyl methane sulfonate (MMS), and UV-sensitive protein 81) and XPF (xeroderma pigmentosum group F-complementing protein) are a subset of SSEs that resolve aberrant replication structures. To ensure genome stability and prevent unnecessary DNA breakage, these SSEs are tightly regulated by the cell cycle and replication checkpoints. We discuss the regulatory network that control activities of MUS81 and XPF and briefly mention other SSEs involved in the resolution of replication intermediates.
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Affiliation(s)
- Seong Min Kim
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
| | - Susan L Forsburg
- Program in Molecular & Computational Biology, University of Southern California, Los Angeles, CA 90089, USA.
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29
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Abstract
The SLX4/FANCP tumor suppressor has emerged as a key player in the maintenance of genome stability, making pivotal contributions to the repair of interstrand cross-links, homologous recombination, and in response to replication stress genome-wide as well as at specific loci such as common fragile sites and telomeres. SLX4 does so in part by acting as a scaffold that controls and coordinates the XPF-ERCC1, MUS81-EME1, and SLX1 structure-specific endonucleases in different DNA repair and recombination mechanisms. It also interacts with other important DNA repair and cell cycle control factors including MSH2, PLK1, TRF2, and TOPBP1 as well as with ubiquitin and SUMO. This review aims at providing an up-to-date and comprehensive view on the key functions that SLX4 fulfills to maintain genome stability as well as to highlight and discuss areas of uncertainty and emerging concepts.
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Affiliation(s)
- Jean-Hugues Guervilly
- a CRCM, CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes , Marseille , France
| | - Pierre Henri Gaillard
- a CRCM, CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes , Marseille , France
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30
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Abstract
For more than a decade, it has been known that mammalian cells use shelterin to protect chromosome ends. Much progress has been made on the mechanism by which shelterin prevents telomeres from inadvertently activating DNA damage signaling and double-strand break (DSB) repair pathways. Shelterin averts activation of three DNA damage response enzymes [the ataxia-telangiectasia-mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) kinases and poly(ADP-ribose) polymerase 1 (PARP1)], blocks three DSB repair pathways [classical nonhomologous end joining (c-NHEJ), alternative (alt)-NHEJ, and homology-directed repair (HDR)], and prevents hyper-resection at telomeres. For several of these functions, mechanistic insights have emerged. In addition, much has been learned about how shelterin maintains the telomeric 3' overhang, forms and protects the t-loop structure, and promotes replication through telomeres. These studies revealed that shelterin is compartmentalized, with individual subunits dedicated to distinct aspects of the end-protection problem. This review focuses on the current knowledge of shelterin-mediated telomere protection, highlights differences between human and mouse shelterin, and discusses some of the questions that remain.
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Affiliation(s)
- Titia de Lange
- Laboratory of Cell Biology and Genetics, Rockefeller University, New York, NY 10065, USA;
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31
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Dagg RA, Pickett HA, Neumann AA, Napier CE, Henson JD, Teber ET, Arthur JW, Reynolds CP, Murray J, Haber M, Sobinoff AP, Lau LMS, Reddel RR. Extensive Proliferation of Human Cancer Cells with Ever-Shorter Telomeres. Cell Rep 2018. [PMID: 28636942 DOI: 10.1016/j.celrep.2017.05.087] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Acquisition of replicative immortality is currently regarded as essential for malignant transformation. This is achieved by activating a telomere lengthening mechanism (TLM), either telomerase or alternative lengthening of telomeres, to counter normal telomere attrition. However, a substantial proportion of some cancer types, including glioblastomas, liposarcomas, retinoblastomas, and osteosarcomas, are reportedly TLM-negative. As serial samples of human tumors cannot usually be obtained to monitor telomere length changes, it has previously been impossible to determine whether tumors are truly TLM-deficient, there is a previously unrecognized TLM, or the assay results are false-negative. Here, we show that a subset of high-risk neuroblastomas (with ∼50% 5-year mortality) lacked significant TLM activity. Cancer cells derived from these highly aggressive tumors initially had long telomeres and proliferated for >200 population doublings with ever-shorter telomeres. This indicates that prevention of telomere shortening is not always required for oncogenesis, which has implications for inhibiting TLMs for cancer therapy.
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Affiliation(s)
- Rebecca A Dagg
- Children's Cancer Research Unit, The Children's Hospital at Westmead, University of Sydney, Westmead, NSW 2145, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Axel A Neumann
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Christine E Napier
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Jeremy D Henson
- Cancer Cell Immortality Group, Adult Cancer Program, Prince of Wales Clinical School, University of New South Wales, Randwick, NSW 2052, Australia
| | - Erdahl T Teber
- Bioinformatics Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Jonathan W Arthur
- Bioinformatics Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - C Patrick Reynolds
- Cancer Center, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Department of Cell Biology and Biochemistry, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Department of Internal Medicine, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Department of Pediatrics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Jayne Murray
- Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales Australia, Randwick, NSW 2031, Australia
| | - Michelle Haber
- Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales Australia, Randwick, NSW 2031, Australia
| | - Alexander P Sobinoff
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Loretta M S Lau
- Children's Cancer Research Unit, The Children's Hospital at Westmead, University of Sydney, Westmead, NSW 2145, Australia; Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW 2145, Australia.
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Kalathiya U, Padariya M, Baginski M. The structurally similar TRFH domain of TRF1 and TRF2 dimers shows distinct behaviour towards TIN2. Arch Biochem Biophys 2018; 642:52-62. [PMID: 29428209 DOI: 10.1016/j.abb.2018.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 02/06/2018] [Accepted: 02/07/2018] [Indexed: 01/25/2023]
Abstract
The telomere repeat binding-factor 1 and 2 (TRF1 and TRF2) proteins of the shelterin complex bind to duplex telomeric DNA as homodimers, and the homodimerization is mediated by their TRFH (TRF-homology) domains. We performed molecular dynamic (MD) simulations of the dimer forms of TRF1TRFH and TRF2TRFH in the presence/absence of the TIN2TBM (TIN2, TRF-interacting nuclear protein 2, TBM, TRF-binding motif) peptide. The MD results suggest that TIN2TBM is necessary to ensure the stability of TRF1TRFH homodimer but not the TRF2TRFH homodimer. In TRF1-TIN2-TRF2 complex, the peptide enhances the protein-protein interactions to yield a stable heterodimer. Both monomers in TRF1TRFH homodimer interact almost equally with the peptide, whereas in TRF2TRFH homodimer, monomer TRF2TRFH(M1) exhibits more dominant interactions than the TRF2TRFH(M2). The common residues of TRF1/2TRFH(M1) that form interactions with TIN2TBM in all peptide-bound systems originate from the H3 (helix) and L3 (loop) regions. Additionally, in the homodimer systems, residues of TRF1/2TRFH(M2) also interact with the peptide. The residue pair E71-K213 is responsible for different conformations of TRF1TRFH homodimers; specifically, this residue pair enhances the protein-peptide/protein interactions in peptide-bound/unbound systems, respectively. TRF1TRFH and TRF2TRFH proteins have a conserved but different interface responsible for the protein-protein/peptide interactions that exist in the corresponding dimers.
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Affiliation(s)
- Umesh Kalathiya
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Narutowicza St 11/12, 80-233 Gdansk, Poland.
| | - Monikaben Padariya
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Narutowicza St 11/12, 80-233 Gdansk, Poland
| | - Maciej Baginski
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Narutowicza St 11/12, 80-233 Gdansk, Poland
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Necasová I, Janoušková E, Klumpler T, Hofr C. Basic domain of telomere guardian TRF2 reduces D-loop unwinding whereas Rap1 restores it. Nucleic Acids Res 2017; 45:12170-12180. [PMID: 28981702 PMCID: PMC5716094 DOI: 10.1093/nar/gkx812] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 09/09/2017] [Indexed: 01/06/2023] Open
Abstract
Telomeric repeat binding factor 2 (TRF2) folds human telomeres into loops to prevent unwanted DNA repair and chromosome end-joining. The N-terminal basic domain of TRF2 (B-domain) protects the telomeric displacement loop (D-loop) from cleavage by endonucleases. Repressor activator protein 1 (Rap1) binds TRF2 and improves telomeric DNA recognition. We found that the B-domain of TRF2 stabilized the D-loop and thus reduced unwinding by BLM and RPA, whereas the formation of the Rap1–TRF2 complex restored DNA unwinding. To understand how the B-domain of TRF2 affects DNA binding and D-loop processing, we analyzed DNA binding of full-length TRF2 and a truncated TRF2 construct lacking the B-domain. We quantified how the B-domain improves TRF2’s interaction with DNA via enhanced long-range electrostatic interactions. We developed a structural envelope model of the B-domain bound on DNA. The model revealed that the B-domain is flexible in solution but becomes rigid upon binding to telomeric DNA. We proposed a mechanism for how the B-domain stabilizes the D-loop.
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Affiliation(s)
- Ivona Necasová
- LifeB, Chromatin Molecular Complexes, CEITEC and Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno CZ-62500, Czech Republic
| | - Eliška Janoušková
- LifeB, Chromatin Molecular Complexes, CEITEC and Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno CZ-62500, Czech Republic
| | - Tomáš Klumpler
- Structural Biology of Gene Regulation, CEITEC, Masaryk University, Brno CZ-62500, Czech Republic
| | - Ctirad Hofr
- LifeB, Chromatin Molecular Complexes, CEITEC and Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno CZ-62500, Czech Republic
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Sobinoff AP, Pickett HA. Alternative Lengthening of Telomeres: DNA Repair Pathways Converge. Trends Genet 2017; 33:921-932. [DOI: 10.1016/j.tig.2017.09.003] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Revised: 08/30/2017] [Accepted: 09/08/2017] [Indexed: 02/08/2023]
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Garcia-Exposito L, Bournique E, Bergoglio V, Bose A, Barroso-Gonzalez J, Zhang S, Roncaioli JL, Lee M, Wallace CT, Watkins SC, Opresko PL, Hoffmann JS, O'Sullivan RJ. Proteomic Profiling Reveals a Specific Role for Translesion DNA Polymerase η in the Alternative Lengthening of Telomeres. Cell Rep 2017; 17:1858-1871. [PMID: 27829156 PMCID: PMC5406014 DOI: 10.1016/j.celrep.2016.10.048] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Revised: 09/18/2016] [Accepted: 10/14/2016] [Indexed: 11/22/2022] Open
Abstract
Cancer cells rely on the activation of telomerase or the alternative lengthening of telomeres (ALT) pathways for telomere maintenance and survival. ALT involves homologous recombination (HR)-dependent exchange and/or HR-associated synthesis of telomeric DNA. Utilizing proximity-dependent biotinylation (BioID), we sought to determine the proteome of telomeres in cancer cells that employ these distinct telomere elongation mechanisms. Our analysis reveals that multiple DNA repair networks converge at ALT telomeres. These include the specialized translesion DNA synthesis (TLS) proteins FANCJ-RAD18-PCNA and, most notably, DNA polymerase eta (Polη). We observe that the depletion of Polη leads to increased ALT activity and late DNA polymerase δ (Polδ)-dependent synthesis of telomeric DNA in mitosis. We propose that Polη fulfills an important role in managing replicative stress at ALT telomeres, maintaining telomere recombination at tolerable levels and stimulating DNA synthesis by Polδ.
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Affiliation(s)
- Laura Garcia-Exposito
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Elodie Bournique
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Valérie Bergoglio
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Arindam Bose
- Department of Environmental and Occupational Health, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jonathan Barroso-Gonzalez
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Sufang Zhang
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
| | - Justin L Roncaioli
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Marietta Lee
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
| | - Callen T Wallace
- Department of Cell Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Simon C Watkins
- Department of Cell Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jean-Sébastien Hoffmann
- CRCT, Université de Toulouse, Inserm, CNRS, UPS Equipe Labellisée Ligue Contre le Cancer, Laboratoire d'Excellence Toulouse Cancer, 2 Avenue Hubert Curien, 31037 Toulouse, France
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, University of Pittsburgh Cancer Institute, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Expression of Telomere-Associated Proteins is Interdependent to Stabilize Native Telomere Structure and Telomere Dysfunction by G-Quadruplex Ligand Causes TERRA Upregulation. Cell Biochem Biophys 2017; 76:311-319. [DOI: 10.1007/s12013-017-0835-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 09/18/2017] [Indexed: 11/26/2022]
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37
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Sobinoff AP, Allen JA, Neumann AA, Yang SF, Walsh ME, Henson JD, Reddel RR, Pickett HA. BLM and SLX4 play opposing roles in recombination-dependent replication at human telomeres. EMBO J 2017; 36:2907-2919. [PMID: 28877996 DOI: 10.15252/embj.201796889] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 08/03/2017] [Accepted: 08/09/2017] [Indexed: 11/09/2022] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere lengthening pathway that predominates in aggressive tumors of mesenchymal origin; however, the underlying mechanism of telomere synthesis is not fully understood. Here, we show that the BLM-TOP3A-RMI (BTR) dissolvase complex is required for ALT-mediated telomere synthesis. We propose that recombination intermediates formed during strand invasion are processed by the BTR complex, initiating rapid and extensive POLD3-dependent telomere synthesis followed by dissolution, with no overall exchange of telomeric DNA. This process is counteracted by the SLX4-SLX1-ERCC4 complex, which promotes resolution of the recombination intermediate, resulting in telomere exchange in the absence of telomere extension. Our data are consistent with ALT being a conservative DNA replication process, analogous to break-induced replication, which is dependent on BTR and counteracted by SLX4 complex-mediated resolution events.
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Affiliation(s)
- Alexander P Sobinoff
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Joshua Am Allen
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Axel A Neumann
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Sile F Yang
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Monica E Walsh
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Jeremy D Henson
- Cancer Cell Immortality Group, Prince of Wales Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, University of Sydney, Westmead, NSW, Australia
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Structural insights into POT1-TPP1 interaction and POT1 C-terminal mutations in human cancer. Nat Commun 2017; 8:14929. [PMID: 28393832 PMCID: PMC5394241 DOI: 10.1038/ncomms14929] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 02/14/2017] [Indexed: 01/01/2023] Open
Abstract
Mammalian shelterin proteins POT1 and TPP1 form a stable heterodimer that protects chromosome ends and regulates telomerase-mediated telomere extension. However, how POT1 interacts with TPP1 remains unknown. Here we present the crystal structure of the C-terminal portion of human POT1 (POT1C) complexed with the POT1-binding motif of TPP1. The structure shows that POT1C contains two domains, a third OB fold and a Holliday junction resolvase-like domain. Both domains are essential for binding to TPP1. Notably, unlike the heart-shaped structure of ciliated protozoan Oxytricha nova TEBPα–β complex, POT1–TPP1 adopts an elongated V-shaped conformation. In addition, we identify several missense mutations in human cancers that disrupt the POT1C–TPP1 interaction, resulting in POT1 instability. POT1C mutants that bind TPP1 localize to telomeres but fail to repress a DNA damage response and inappropriate repair by A-NHEJ. Our results reveal that POT1 C terminus is essential to prevent initiation of genome instability permissive for tumorigenesis. Human telomeres are protected by a specialized shelterin complex composed of six proteins. Here the authors structurally characterize the interaction between the POT1-TPP1 shelterin component and identify mutations associated with genome instability and cancer that disrupt the POT1-TPP1 interaction.
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39
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DNA Replication Origins and Fork Progression at Mammalian Telomeres. Genes (Basel) 2017; 8:genes8040112. [PMID: 28350373 PMCID: PMC5406859 DOI: 10.3390/genes8040112] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 12/20/2022] Open
Abstract
Telomeres are essential chromosomal regions that prevent critical shortening of linear chromosomes and genomic instability in eukaryotic cells. The bulk of telomeric DNA is replicated by semi-conservative DNA replication in the same way as the rest of the genome. However, recent findings revealed that replication of telomeric repeats is a potential cause of chromosomal instability, because DNA replication through telomeres is challenged by the repetitive telomeric sequences and specific structures that hamper the replication fork. In this review, we summarize current understanding of the mechanisms by which telomeres are faithfully and safely replicated in mammalian cells. Various telomere-associated proteins ensure efficient telomere replication at different steps, such as licensing of replication origins, passage of replication forks, proper fork restart after replication stress, and dissolution of post-replicative structures. In particular, shelterin proteins have central roles in the control of telomere replication. Through physical interactions, accessory proteins are recruited to maintain telomere integrity during DNA replication. Dormant replication origins and/or homology-directed repair may rescue inappropriate fork stalling or collapse that can cause defects in telomere structure and functions.
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40
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Dehé PM, Gaillard PHL. Control of structure-specific endonucleases to maintain genome stability. Nat Rev Mol Cell Biol 2017; 18:315-330. [PMID: 28327556 DOI: 10.1038/nrm.2016.177] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Structure-specific endonucleases (SSEs) have key roles in DNA replication, recombination and repair, and emerging roles in transcription. These enzymes have specificity for DNA secondary structure rather than for sequence, and therefore their activity must be precisely controlled to ensure genome stability. In this Review, we discuss how SSEs are controlled as part of genome maintenance pathways in eukaryotes, with an emphasis on the elaborate mechanisms that regulate the members of the major SSE families - including the xeroderma pigmentosum group F-complementing protein (XPF) and MMS and UV-sensitive protein 81 (MUS81)-dependent nucleases, and the flap endonuclease 1 (FEN1), XPG and XPG-like endonuclease 1 (GEN1) enzymes - during processes such as DNA adduct repair, Holliday junction processing and replication stress. We also discuss newly characterized connections between SSEs and other classes of DNA-remodelling enzymes and cell cycle control machineries, which reveal the importance of SSE scaffolds such as the synthetic lethal of unknown function 4 (SLX4) tumour suppressor for the maintenance of genome stability.
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Affiliation(s)
- Pierre-Marie Dehé
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
| | - Pierre-Henri L Gaillard
- Centre de Recherche en Cancérologie de Marseille, CRCM, CNRS, Aix Marseille Université, INSERM, Institut Paoli-Calmettes, 27 Boulevard Leï Roure, 13009 Marseille, France
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41
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Brosh RM, Bellani M, Liu Y, Seidman MM. Fanconi Anemia: A DNA repair disorder characterized by accelerated decline of the hematopoietic stem cell compartment and other features of aging. Ageing Res Rev 2017; 33:67-75. [PMID: 27223997 DOI: 10.1016/j.arr.2016.05.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/06/2016] [Accepted: 05/13/2016] [Indexed: 01/05/2023]
Abstract
Fanconi Anemia (FA) is a rare autosomal genetic disorder characterized by progressive bone marrow failure (BMF), endocrine dysfunction, cancer, and other clinical features commonly associated with normal aging. The anemia stems directly from an accelerated decline of the hematopoietic stem cell compartment. Although FA is a complex heterogeneous disease linked to mutations in 19 currently identified genes, there has been much progress in understanding the molecular pathology involved. FA is broadly considered a DNA repair disorder and the FA gene products, together with other DNA repair factors, have been implicated in interstrand cross-link (ICL) repair. However, in addition to the defective DNA damage response, altered epigenetic regulation, and telomere defects, FA is also marked by elevated levels of inflammatory mediators in circulation, a hallmark of faster decline in not only other hereditary aging disorders but also normal aging. In this review, we offer a perspective of FA as a monogenic accelerated aging disorder, citing the latest evidence for its multi-factorial deficiencies underlying its unique clinical and cellular features.
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42
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Distinct functions of human RecQ helicases during DNA replication. Biophys Chem 2016; 225:20-26. [PMID: 27876204 DOI: 10.1016/j.bpc.2016.11.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/13/2016] [Accepted: 11/13/2016] [Indexed: 12/31/2022]
Abstract
DNA replication is the most vulnerable process of DNA metabolism in proliferating cells and therefore it is tightly controlled and coordinated with processes that maintain genomic stability. Human RecQ helicases are among the most important factors involved in the maintenance of replication fork integrity, especially under conditions of replication stress. RecQ helicases promote recovery of replication forks being stalled due to different replication roadblocks of either exogenous or endogenous source. They prevent generation of aberrant replication fork structures and replication fork collapse, and are involved in proper checkpoint signaling. The essential role of human RecQ helicases in the genome maintenance during DNA replication is underlined by association of defects in their function with cancer predisposition.
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43
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Rendeková J, Ward TA, Šimoničová L, Thomas PH, Nosek J, Tomáška Ľ, McHugh PJ, Chovanec M. Mgm101: A double-duty Rad52-like protein. Cell Cycle 2016; 15:3169-3176. [PMID: 27636878 PMCID: PMC5176325 DOI: 10.1080/15384101.2016.1231288] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mgm101 has well-characterized activity for the repair and replication of the mitochondrial genome. Recent work has demonstrated a further role for Mgm101 in nuclear DNA metabolism, contributing to an S-phase specific DNA interstrand cross-link repair pathway that acts redundantly with a pathway controlled by Pso2 exonuclease. Due to involvement of FANCM, FANCJ and FANCP homologues (Mph1, Chl1 and Slx4), this pathway has been described as a Fanconi anemia-like pathway. In this pathway, Mgm101 physically interacts with the DNA helicase Mph1 and the MutSα (Msh2/Msh6) heterodimer, but its precise role is yet to be elucidated. Data presented here suggests that Mgm101 functionally overlaps with Rad52, supporting previous suggestions that, based on protein structure and biochemical properties, Mgm101 and Rad52 belong to a family of proteins with similar function. In addition, our data shows that this overlap extends to the function of both proteins at telomeres, where Mgm101 is required for telomere elongation during chromosome replication in rad52 defective cells. We hypothesize that Mgm101 could, in Rad52-like manner, preferentially bind single-stranded DNAs (such as at stalled replication forks, broken chromosomes and natural chromosome ends), stabilize them and mediate single-strand annealing-like homologous recombination event to prevent them from converting into toxic structures.
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Affiliation(s)
- Jana Rendeková
- a Department of Genetics , Cancer Research Institute, Biomedical Research Center, Slovak Academy of Science , Bratislava , Slovak Republic
| | - Thomas A Ward
- b Department of Oncology , Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital , Oxford , UK
| | - Lucia Šimoničová
- c Department of Genetics , Faculty of Natural Sciences, Comenius University , Bratislava , Slovakia
| | - Peter H Thomas
- b Department of Oncology , Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital , Oxford , UK
| | - Jozef Nosek
- d Department of Biochemistry , Faculty of Natural Sciences, Comenius University , Bratislava , Slovakia
| | - Ľubomír Tomáška
- c Department of Genetics , Faculty of Natural Sciences, Comenius University , Bratislava , Slovakia
| | - Peter J McHugh
- b Department of Oncology , Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital , Oxford , UK
| | - Miroslav Chovanec
- a Department of Genetics , Cancer Research Institute, Biomedical Research Center, Slovak Academy of Science , Bratislava , Slovak Republic
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Abstract
Telomeres at chromosome ends are nucleoprotein structures consisting of tandem TTAGGG repeats and a complex of proteins termed shelterin. DNA damage and repair at telomeres is uniquely influenced by the ability of telomeric DNA to form alternate structures including loops and G-quadruplexes, coupled with the ability of shelterin proteins to interact with and regulate enzymes in every known DNA repair pathway. The role of shelterin proteins in preventing telomeric ends from being falsely recognized and processed as DNA double strand breaks is well established. Here we focus instead on recent developments in understanding the roles of shelterin proteins and telomeric DNA sequence and structure in processing genuine damage at telomeres induced by endogenous and exogenous DNA damage agents. We will highlight advances in double strand break repair, base excision repair and nucleotide excision repair at telomeres, and will discuss important questions remaining in the field.
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Affiliation(s)
- Elise Fouquerel
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, University of Pittsburgh Cancer Institute Research Pavilion, 5117 Centre Avenue, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Dhvani Parikh
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, University of Pittsburgh Cancer Institute Research Pavilion, 5117 Centre Avenue, University of Pittsburgh, Pittsburgh, PA 15213, United States
| | - Patricia Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, University of Pittsburgh Cancer Institute Research Pavilion, 5117 Centre Avenue, University of Pittsburgh, Pittsburgh, PA 15213, United States.
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45
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Yin J, Wan B, Sarkar J, Horvath K, Wu J, Chen Y, Cheng G, Wan K, Chin P, Lei M, Liu Y. Dimerization of SLX4 contributes to functioning of the SLX4-nuclease complex. Nucleic Acids Res 2016; 44:4871-80. [PMID: 27131364 PMCID: PMC4889959 DOI: 10.1093/nar/gkw354] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/05/2016] [Accepted: 04/21/2016] [Indexed: 11/16/2022] Open
Abstract
The Fanconi anemia protein SLX4 assembles a genome and telomere maintenance toolkit, consisting of the nucleases SLX1, MUS81 and XPF. Although it is known that SLX4 acts as a scaffold for building this complex, the molecular basis underlying this function of SLX4 remains unclear. Here, we report that functioning of SLX4 is dependent on its dimerization via an oligomerization motif called the BTB domain. We solved the crystal structure of the SLX4BTB dimer, identifying key contacts (F681 and F708) that mediate dimerization. Disruption of BTB dimerization abrogates nuclear foci formation and telomeric localization of not only SLX4 but also of its associated nucleases. Furthermore, dimerization-deficient SLX4 mutants cause defective cellular response to DNA interstrand crosslinking agent and telomere maintenance, underscoring the contribution of BTB domain-mediated dimerization of SLX4 in genome and telomere maintenance.
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Affiliation(s)
- Jinhu Yin
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
| | - Bingbing Wan
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 333 Haike Road, Shanghai 200031, China Shanghai Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Jaya Sarkar
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
| | - Kent Horvath
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
| | - Jian Wu
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 333 Haike Road, Shanghai 200031, China
| | - Yong Chen
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 333 Haike Road, Shanghai 200031, China
| | - Guangjuan Cheng
- Shanghai Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Ke Wan
- Shanghai Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Peiju Chin
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
| | - Ming Lei
- National Center for Protein Science Shanghai, State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 333 Haike Road, Shanghai 200031, China Department of Biological Chemistry, University of Michigan Medical School, 1150 W. Medical Center Drive, Ann Arbor, MI 48109, USA Shanghai Research Center, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yie Liu
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
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46
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Sarkar J, Liu Y. Fanconi anemia proteins in telomere maintenance. DNA Repair (Amst) 2016; 43:107-12. [PMID: 27118469 DOI: 10.1016/j.dnarep.2016.02.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 02/03/2016] [Indexed: 11/15/2022]
Abstract
Mammalian chromosome ends are protected by nucleoprotein structures called telomeres. Telomeres ensure genome stability by preventing chromosome termini from being recognized as DNA damage. Telomere length homeostasis is inevitable for telomere maintenance because critical shortening or over-lengthening of telomeres may lead to DNA damage response or delay in DNA replication, and hence genome instability. Due to their repetitive DNA sequence, unique architecture, bound shelterin proteins, and high propensity to form alternate/secondary DNA structures, telomeres are like common fragile sites and pose an inherent challenge to the progression of DNA replication, repair, and recombination apparatus. It is conceivable that longer the telomeres are, greater is the severity of such challenges. Recent studies have linked excessively long telomeres with increased tumorigenesis. Here we discuss telomere abnormalities in a rare recessive chromosomal instability disorder called Fanconi Anemia and the role of the Fanconi Anemia pathway in telomere biology. Reports suggest that Fanconi Anemia proteins play a role in maintaining long telomeres, including processing telomeric joint molecule intermediates. We speculate that ablation of the Fanconi Anemia pathway would lead to inadequate aberrant structural barrier resolution at excessively long telomeres, thereby causing replicative burden on the cell.
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Affiliation(s)
- Jaya Sarkar
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA
| | - Yie Liu
- Laboratory of Molecular Gerontology, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21044, USA.
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47
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Complex interactions between the DNA-damage response and mammalian telomeres. Nat Struct Mol Biol 2016; 22:859-66. [PMID: 26581520 DOI: 10.1038/nsmb.3092] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/23/2015] [Indexed: 12/28/2022]
Abstract
Natural chromosome ends resemble double-stranded DNA breaks, but they do not activate a damage response in healthy cells. Telomeres therefore have evolved to solve the 'end-protection problem' by inhibiting multiple DNA damage-response pathways. During the past decade, the view of telomeres has progressed from simple caps that hide chromosome ends to complex machineries that have an active role in organizing the genome. Here we focus on mammalian telomeres and summarize and interpret recent discoveries in detail, focusing on how repair pathways are inhibited, how resection and replication are controlled and how these mechanisms govern cell fate during senescence, crisis and transformation.
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Cox KE, Maréchal A, Flynn RL. SMARCAL1 Resolves Replication Stress at ALT Telomeres. Cell Rep 2016; 14:1032-1040. [PMID: 26832416 PMCID: PMC5051350 DOI: 10.1016/j.celrep.2016.01.011] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/25/2015] [Accepted: 12/29/2015] [Indexed: 11/20/2022] Open
Abstract
Cancer cells overcome replicative senescence by exploiting mechanisms of telomere elongation, a process often accomplished by reactivation of the enzyme telomerase. However, a subset of cancer cells lack telomerase activity and rely on the alternative lengthening of telomeres (ALT) pathway, a recombination-based mechanism of telomere elongation. Although the mechanisms regulating ALT are not fully defined, chronic replication stress at telomeres might prime these fragile regions for recombination. Here, we demonstrate that the replication stress response protein SMARCAL1 is a critical regulator of ALT activity. SMARCAL1 associates with ALT telomeres to resolve replication stress and ensure telomere stability. In the absence of SMARCAL1, persistently stalled replication forks at ALT telomeres deteriorate into DNA double-strand breaks promoting the formation of chromosome fusions. Our studies not only define a role for SMARCAL1 in ALT telomere maintenance, but also demonstrate that resolution of replication stress is a crucial step in the ALT mechanism.
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Affiliation(s)
- Kelli E Cox
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; Department of Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA
| | - Alexandre Maréchal
- Department of Biology, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada
| | - Rachel Litman Flynn
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; Department of Medicine, Cancer Center, Boston University School of Medicine, Boston, MA 02118, USA.
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49
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Pickett HA, Reddel RR. Molecular mechanisms of activity and derepression of alternative lengthening of telomeres. Nat Struct Mol Biol 2015; 22:875-80. [PMID: 26581522 DOI: 10.1038/nsmb.3106] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 09/01/2015] [Indexed: 02/08/2023]
Abstract
Alternative lengthening of telomeres (ALT) involves homology-directed telomere synthesis. This multistep process is facilitated by loss of the ATRX or DAXX chromatin-remodeling factors and by abnormalities of the telomere nucleoprotein architecture, including altered DNA sequence and decreased TRF2 saturation. Induction of telomere-specific DNA damage triggers homology-directed searches, and NuRD-ZNF827 protein-protein interactions provide a platform for the telomeric recruitment of homologous recombination (HR) proteins. Telomere lengthening proceeds by strand exchange and template-driven DNA synthesis, which culminates in dissolution of HR intermediates.
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Affiliation(s)
- Hilda A Pickett
- Telomere Length Regulation Group, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
| | - Roger R Reddel
- Cancer Research Unit, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
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