1
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Gu L, Liu M, Zhang Y, Zhou H, Wang Y, Xu ZX. Telomere-related DNA damage response pathways in cancer therapy: prospective targets. Front Pharmacol 2024; 15:1379166. [PMID: 38910895 PMCID: PMC11190371 DOI: 10.3389/fphar.2024.1379166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Accepted: 05/23/2024] [Indexed: 06/25/2024] Open
Abstract
Maintaining the structural integrity of genomic chromosomal DNA is an essential role of cellular life and requires two important biological mechanisms: the DNA damage response (DDR) mechanism and telomere protection mechanism at chromosome ends. Because abnormalities in telomeres and cellular DDR regulation are strongly associated with human aging and cancer, there is a reciprocal regulation of telomeres and cellular DDR. Moreover, several drug treatments for DDR are currently available. This paper reviews the progress in research on the interaction between telomeres and cellular DNA damage repair pathways. The research on the crosstalk between telomere damage and DDR is important for improving the efficacy of tumor treatment. However, further studies are required to confirm this hypothesis.
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Affiliation(s)
- Liting Gu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, Jilin, China
| | - Mingdi Liu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, Jilin, China
| | - Yuning Zhang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, Jilin, China
| | - Honglan Zhou
- Department of Urology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Yishu Wang
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, Jilin, China
| | - Zhi-Xiang Xu
- Key Laboratory of Pathobiology, Ministry of Education, Jilin University, Changchun, Jilin, China
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2
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Waitkus MS, Erman EN, Reitman ZJ, Ashley DM. Mechanisms of telomere maintenance and associated therapeutic vulnerabilities in malignant gliomas. Neuro Oncol 2024; 26:1012-1024. [PMID: 38285162 PMCID: PMC11145458 DOI: 10.1093/neuonc/noae016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Indexed: 01/30/2024] Open
Abstract
A majority of cancers (~85%) activate the enzyme telomerase to maintain telomere length over multiple rounds of cellular division. Telomerase-negative cancers activate a distinct, telomerase-independent mechanism of telomere maintenance termed alternative lengthening of telomeres (ALT). ALT uses homologous recombination to maintain telomere length and exhibits features of break-induced DNA replication. In malignant gliomas, the activation of either telomerase or ALT is nearly ubiquitous in pediatric and adult tumors, and the frequency with which these distinct telomere maintenance mechanisms (TMMs) is activated varies according to genetically defined glioma subtypes. In this review, we summarize the current state of the field of TMMs and their relevance to glioma biology and therapy. We review the genetic alterations and molecular mechanisms leading to telomerase activation or ALT induction in pediatric and adult gliomas. With this background, we review emerging evidence on strategies for targeting TMMs for glioma therapy. Finally, we comment on critical gaps and issues for moving the field forward to translate our improved understanding of glioma telomere maintenance into better therapeutic strategies for patients.
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Affiliation(s)
- Matthew S Waitkus
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Elise N Erman
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Zachary J Reitman
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA
| | - David M Ashley
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
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3
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Jiang H, Zhang T, Kaur H, Shi T, Krishnan A, Kwon Y, Sung P, Greenberg RA. BLM helicase unwinds lagging strand substrates to assemble the ALT telomere damage response. Mol Cell 2024; 84:1684-1698.e9. [PMID: 38593805 PMCID: PMC11069441 DOI: 10.1016/j.molcel.2024.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 02/12/2024] [Accepted: 03/14/2024] [Indexed: 04/11/2024]
Abstract
The Bloom syndrome (BLM) helicase is critical for alternative lengthening of telomeres (ALT), a homology-directed repair (HDR)-mediated telomere maintenance mechanism that is prevalent in cancers of mesenchymal origin. The DNA substrates that BLM engages to direct telomere recombination during ALT remain unknown. Here, we determine that BLM helicase acts on lagging strand telomere intermediates that occur specifically in ALT-positive cells to assemble a replication-associated DNA damage response. Loss of ATRX was permissive for BLM localization to ALT telomeres in S and G2, commensurate with the appearance of telomere C-strand-specific single-stranded DNA (ssDNA). DNA2 nuclease deficiency increased 5'-flap formation in a BLM-dependent manner, while telomere C-strand, but not G-strand, nicks promoted ALT. These findings define the seminal events in the ALT DNA damage response, linking aberrant telomeric lagging strand DNA replication with a BLM-directed HDR mechanism that sustains telomere length in a subset of human cancers.
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Affiliation(s)
- Haoyang Jiang
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Tianpeng Zhang
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Hardeep Kaur
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Tao Shi
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Aravind Krishnan
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Roger A Greenberg
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6160, USA.
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4
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Liang CC, Greenhough LA, Masino L, Maslen S, Bajrami I, Tuppi M, Skehel M, Taylor IA, West SC. Mechanism of single-stranded DNA annealing by RAD52-RPA complex. Nature 2024; 629:697-703. [PMID: 38658755 PMCID: PMC11096129 DOI: 10.1038/s41586-024-07347-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 03/22/2024] [Indexed: 04/26/2024]
Abstract
RAD52 is important for the repair of DNA double-stranded breaks1,2, mitotic DNA synthesis3-5 and alternative telomere length maintenance6,7. Central to these functions, RAD52 promotes the annealing of complementary single-stranded DNA (ssDNA)8,9 and provides an alternative to BRCA2/RAD51-dependent homologous recombination repair10. Inactivation of RAD52 in homologous-recombination-deficient BRCA1- or BRCA2-defective cells is synthetically lethal11,12, and aberrant expression of RAD52 is associated with poor cancer prognosis13,14. As a consequence, RAD52 is an attractive therapeutic target against homologous-recombination-deficient breast, ovarian and prostate cancers15-17. Here we describe the structure of RAD52 and define the mechanism of annealing. As reported previously18-20, RAD52 forms undecameric (11-subunit) ring structures, but these rings do not represent the active form of the enzyme. Instead, cryo-electron microscopy and biochemical analyses revealed that ssDNA annealing is driven by RAD52 open rings in association with replication protein-A (RPA). Atomic models of the RAD52-ssDNA complex show that ssDNA sits in a positively charged channel around the ring. Annealing is driven by the RAD52 N-terminal domains, whereas the C-terminal regions modulate the open-ring conformation and RPA interaction. RPA associates with RAD52 at the site of ring opening with critical interactions occurring between the RPA-interacting domain of RAD52 and the winged helix domain of RPA2. Our studies provide structural snapshots throughout the annealing process and define the molecular mechanism of ssDNA annealing by the RAD52-RPA complex.
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Affiliation(s)
| | | | | | | | | | - Marcel Tuppi
- The Francis Crick Institute, London, UK
- Abcam, Cambridge Biomedical Campus, Cambridge, UK
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5
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Muoio D, Laspata N, Dannenberg RL, Curry C, Darkoa-Larbi S, Hedglin M, Uttam S, Fouquerel E. PARP2 promotes Break Induced Replication-mediated telomere fragility in response to replication stress. Nat Commun 2024; 15:2857. [PMID: 38565848 PMCID: PMC10987537 DOI: 10.1038/s41467-024-47222-7] [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: 05/30/2023] [Accepted: 03/22/2024] [Indexed: 04/04/2024] Open
Abstract
PARP2 is a DNA-dependent ADP-ribosyl transferase (ARTs) enzyme with Poly(ADP-ribosyl)ation activity that is triggered by DNA breaks. It plays a role in the Base Excision Repair pathway, where it has overlapping functions with PARP1. However, additional roles for PARP2 have emerged in the response of cells to replication stress. In this study, we demonstrate that PARP2 promotes replication stress-induced telomere fragility and prevents telomere loss following chronic induction of oxidative DNA lesions and BLM helicase depletion. Telomere fragility results from the activity of the break-induced replication pathway (BIR). During this process, PARP2 promotes DNA end resection, strand invasion and BIR-dependent mitotic DNA synthesis by orchestrating POLD3 recruitment and activity. Our study has identified a role for PARP2 in the response to replication stress. This finding may lead to the development of therapeutic approaches that target DNA-dependent ART enzymes, particularly in cancer cells with high levels of replication stress.
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Affiliation(s)
- Daniela Muoio
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA, 15213, USA
| | - Natalie Laspata
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA, 15213, USA
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233S. 10th street, Philadelphia, PA, 19107, USA
| | - Rachel L Dannenberg
- Department of Chemistry, The Pennsylvania State University, University park, State College, PA, 16802, USA
| | - Caroline Curry
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233S. 10th street, Philadelphia, PA, 19107, USA
| | - Simone Darkoa-Larbi
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233S. 10th street, Philadelphia, PA, 19107, USA
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University park, State College, PA, 16802, USA
| | - Shikhar Uttam
- Department of Computational and Systems Biology, UPMC Hillman Cancer Center, University of Pittsburgh, 5117 Centre Avenue, Pittsburgh, PA, 15213, USA
| | - Elise Fouquerel
- UPMC Hillman Cancer Center, University of Pittsburgh Cancer Institute, Department of Pharmacology and Chemical Biology, Pittsburgh, PA, 15213, USA.
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6
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Ngoi NYL, Pilié PG, McGrail DJ, Zimmermann M, Schlacher K, Yap TA. Targeting ATR in patients with cancer. Nat Rev Clin Oncol 2024; 21:278-293. [PMID: 38378898 DOI: 10.1038/s41571-024-00863-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2024] [Indexed: 02/22/2024]
Abstract
Pharmacological inhibition of the ataxia telangiectasia and Rad3-related protein serine/threonine kinase (ATR; also known as FRAP-related protein (FRP1)) has emerged as a promising strategy for cancer treatment that exploits synthetic lethal interactions with proteins involved in DNA damage repair, overcomes resistance to other therapies and enhances antitumour immunity. Multiple novel, potent ATR inhibitors are being tested in clinical trials using biomarker-directed approaches and involving patients across a broad range of solid cancer types; some of these inhibitors have now entered phase III trials. Further insight into the complex interactions of ATR with other DNA replication stress response pathway components and with the immune system is necessary in order to optimally harness the potential of ATR inhibitors in the clinic and achieve hypomorphic targeting of the various ATR functions. Furthermore, a deeper understanding of the diverse range of predictive biomarkers of response to ATR inhibitors and of the intraclass differences between these agents could help to refine trial design and patient selection strategies. Key challenges that remain in the clinical development of ATR inhibitors include the optimization of their therapeutic index and the development of rational combinations with these agents. In this Review, we detail the molecular mechanisms regulated by ATR and their clinical relevance, and discuss the challenges that must be addressed to extend the benefit of ATR inhibitors to a broad population of patients with cancer.
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Affiliation(s)
- Natalie Y L Ngoi
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Haematology-Oncology, National University Cancer Institute, Singapore, Singapore
- Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Patrick G Pilié
- Department of Genitourinary Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Daniel J McGrail
- Center for Immunotherapy and Precision Immuno-Oncology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | | | - Katharina Schlacher
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
| | - Timothy A Yap
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Therapeutics Discovery Division, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Khalifa Institute for Personalized Cancer Therapy, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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7
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Azzalin CM. TERRA and the alternative lengthening of telomeres: a dangerous affair. FEBS Lett 2024. [PMID: 38445359 DOI: 10.1002/1873-3468.14844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 02/14/2024] [Accepted: 02/20/2024] [Indexed: 03/07/2024]
Abstract
Eukaryotic telomeres are transcribed into the long noncoding RNA TERRA. A fraction of TERRA remains associated with telomeres by forming RNA:DNA hybrids dubbed telR-loops. TERRA and telR-loops are essential to promote telomere elongation in human cancer cells that maintain telomeres through a homology-directed repair pathway known as alternative lengthening of telomeres or ALT. However, TERRA and telR-loops compromise telomere integrity and cell viability if their levels are not finely tuned. The study of telomere transcription in ALT cells will enormously expand our understanding of the ALT mechanism and of how genome integrity is maintained. Moreover, telomere transcription, TERRA and telR-loops are likely to become exceptionally suited targets for the development of novel anti-cancer therapies.
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Affiliation(s)
- Claus M Azzalin
- Instituto de Medicina Molecular João Lobo Antunes (iMM), Faculdade de Medicina da Universidade de Lisboa, Portugal
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8
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Zhao R, Xu M, Wondisford AR, Lackner RM, Salsman J, Dellaire G, Chenoweth DM, O’Sullivan RJ, Zhao X, Zhang H. SUMO Promotes DNA Repair Protein Collaboration to Support Alterative Telomere Lengthening in the Absence of PML. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.29.582813. [PMID: 38463993 PMCID: PMC10925274 DOI: 10.1101/2024.02.29.582813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
Alternative lengthening of telomeres (ALT) pathway maintains telomeres in a significant fraction of cancers associated with poor clinical outcomes. A better understanding of ALT mechanisms can provide a basis for developing new treatment strategies for ALT cancers. SUMO modification of telomere proteins plays a critical role in the formation of ALT telomere-associated PML bodies (APBs), where telomeres are clustered and DNA repair proteins are enriched to promote homology-directed telomere DNA synthesis in ALT. However, whether and how SUMO contributes to ALT beyond APB formation remains elusive. Here, we report that SUMO promotes collaboration among DNA repair proteins to achieve APB-independent telomere maintenance. By using ALT cancer cells with PML protein knocked out and thus devoid of APBs, we show that sumoylation is required for manifesting ALT features, including telomere clustering and telomeric DNA synthesis, independent of PML and APBs. Further, small molecule-induced telomere targeting of SUMO produces signatures of phase separation and ALT features in PML null cells in a manner depending on both sumoylation and SUMO interaction with SUMO interaction motifs (SIMs). Mechanistically, SUMO-induced effects are linked to the enrichment of DNA repair proteins, including Rad52, Rad51AP1, and BLM, to the SUMO-containing telomere foci. Finally, we find that Rad52 can undergo phase separation, enrich SUMO on telomeres, and promote telomere DNA synthesis in collaboration with the BLM helicase in a SUMO-dependent manner. Collectively, our findings suggest that, in addition to forming APBs, SUMO also promotes collaboration among DNA repair proteins to support telomere maintenance in ALT cells. Given the promising effects of sumoylation inhibitors in cancer treatment, our findings suggest their potential use in perturbing telomere maintenance in ALT cancer cells.
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Affiliation(s)
- Rongwei Zhao
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Meng Xu
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Anne R. Wondisford
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Rachel M. Lackner
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19014 , USA
| | - Jayme Salsman
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Graham Dellaire
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - David M. Chenoweth
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19014 , USA
| | - Roderick J. O’Sullivan
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Huaiying Zhang
- Department of Biology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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9
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Thosar SA, Barnes RP, Detwiler A, Bhargava R, Wondisford A, O'Sullivan RJ, Opresko PL. Oxidative guanine base damage plays a dual role in regulating productive ALT-associated homology-directed repair. Cell Rep 2024; 43:113656. [PMID: 38194346 PMCID: PMC10851105 DOI: 10.1016/j.celrep.2023.113656] [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: 07/28/2023] [Revised: 11/06/2023] [Accepted: 12/20/2023] [Indexed: 01/10/2024] Open
Abstract
Cancer cells maintain telomeres by upregulating telomerase or alternative lengthening of telomeres (ALT) via homology-directed repair at telomeric DNA breaks. 8-Oxoguanine (8oxoG) is a highly prevalent endogenous DNA lesion in telomeric sequences, altering telomere structure and telomerase activity, but its impact on ALT is unclear. Here, we demonstrate that targeted 8oxoG formation at telomeres stimulates ALT activity and homologous recombination specifically in ALT cancer cells. Mechanistically, an acute 8oxoG induction increases replication stress, as evidenced by increased telomere fragility and ATR kinase activation at ALT telomeres. Furthermore, ALT cells are more sensitive to chronic telomeric 8oxoG damage than telomerase-positive cancer cells, consistent with increased 8oxoG-induced replication stress. However, telomeric 8oxoG production in G2 phase, when ALT telomere elongation occurs, impairs telomeric DNA synthesis. Our study demonstrates that a common oxidative base lesion has a dual role in regulating ALT depending on when the damage arises in the cell cycle.
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Affiliation(s)
- Sanjana A Thosar
- Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA; UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Ryan P Barnes
- Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA; UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Ariana Detwiler
- Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA; UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Ragini Bhargava
- UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Anne Wondisford
- UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Roderick J O'Sullivan
- UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh School of Public Health, Pittsburgh, PA, USA; UPMC Hillman Cancer Center, Pittsburgh, PA, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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10
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Lu R, Nelson CB, Rogers S, Cesare AJ, Sobinoff AP, Pickett HA. Distinct modes of telomere synthesis and extension contribute to Alternative Lengthening of Telomeres. iScience 2024; 27:108655. [PMID: 38213617 PMCID: PMC10783591 DOI: 10.1016/j.isci.2023.108655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/13/2023] [Accepted: 12/04/2023] [Indexed: 01/13/2024] Open
Abstract
Alternative lengthening of telomeres (ALT) is a homology-directed repair mechanism that becomes activated in a subset of cancers to maintain telomere length. One of the defining features of ALT cells is the prevalence of extrachromosomal telomeric repeat (ECTR) DNA. Here, we identify that ALT cells engage in two modes of telomere synthesis. Non-productive telomere synthesis occurs during the G2 phase of the cell cycle and is characterized by newly synthesized internal telomeric regions that are not retained in the subsequent G1, coinciding with an induction of ECTR DNA. Productive telomere synthesis occurs specifically during the transition from G2 to mitosis and is defined as the extension of the telomere termini. While many proteins associated with break-induced telomere synthesis function in both non-productive and productive telomere synthesis, POLH specifically promotes productive telomere lengthening and suppresses non-productive telomere synthesis. These findings delineate the mechanism and cell cycle regulation of ALT-mediated telomere synthesis and extension.
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Affiliation(s)
- Robert Lu
- Telomere Length Regulation Unit, Children’s Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Christopher B. Nelson
- Telomere Length Regulation Unit, Children’s Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Samuel Rogers
- Genome Integrity Unit, Children’s Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Anthony J. Cesare
- Genome Integrity Unit, Children’s Medical Research Institute, University of Sydney, Westmead, NSW, Australia
| | - Alexander P. Sobinoff
- Telomere Length Regulation 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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11
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Mori JO, Keegan J, Flynn RL, Heaphy CM. Alternative lengthening of telomeres: mechanism and the pathogenesis of cancer. J Clin Pathol 2024; 77:82-86. [PMID: 37890990 DOI: 10.1136/jcp-2023-209005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/12/2023] [Indexed: 10/29/2023]
Abstract
Telomere maintenance and elongation allows cells to gain replicative immortality and evade cellular senescence during cancer development. While most cancers use telomerase to maintain telomere lengths, a subset of cancers engage the alternative lengthening of telomeres (ALT) pathway for telomere maintenance. ALT is present in 5%-10% of all cancers, although the prevalence is dramatically higher in certain cancer types, including complex karyotype sarcomas, isocitrate dehydrogenase-mutant astrocytoma (WHO grade II-IV), pancreatic neuroendocrine tumours, neuroblastoma and chromophobe hepatocellular carcinomas. ALT is maintained through a homology-directed DNA repair mechanism. Resembling break-induced replication, this aberrant process results in dramatic cell-to-cell telomere length heterogeneity, widespread chromosomal instability and chronic replication stress. Additionally, ALT-positive cancers frequently harbour inactivating mutations in either chromatin remodelling proteins (ATRX, DAXX and H3F3A) or DNA damage repair factors (SMARCAL1 and SLX4IP). ALT can readily be detected in tissue by assessing the presence of unique molecular characteristics, such as large ultrabright nuclear telomeric foci or partially single-stranded telomeric DNA circles (C-circles). Importantly, ALT has been validated as a robust diagnostic and prognostic biomarker for certain cancer types and may even be exploited as a therapeutic target via small molecular inhibitors and/or synthetic lethality approaches.
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Affiliation(s)
- Joakin O Mori
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Joshua Keegan
- Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Rachel L Flynn
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
- Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Christopher M Heaphy
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
- Pathology and Laboratory Medicine, Boston Medical Center, Boston, Massachusetts, USA
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12
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Spegg V, Altmeyer M. Genome maintenance meets mechanobiology. Chromosoma 2024; 133:15-36. [PMID: 37581649 PMCID: PMC10904543 DOI: 10.1007/s00412-023-00807-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/20/2023] [Accepted: 07/26/2023] [Indexed: 08/16/2023]
Abstract
Genome stability is key for healthy cells in healthy organisms, and deregulated maintenance of genome integrity is a hallmark of aging and of age-associated diseases including cancer and neurodegeneration. To maintain a stable genome, genome surveillance and repair pathways are closely intertwined with cell cycle regulation and with DNA transactions that occur during transcription and DNA replication. Coordination of these processes across different time and length scales involves dynamic changes of chromatin topology, clustering of fragile genomic regions and repair factors into nuclear repair centers, mobilization of the nuclear cytoskeleton, and activation of cell cycle checkpoints. Here, we provide a general overview of cell cycle regulation and of the processes involved in genome duplication in human cells, followed by an introduction to replication stress and to the cellular responses elicited by perturbed DNA synthesis. We discuss fragile genomic regions that experience high levels of replication stress, with a particular focus on telomere fragility caused by replication stress at the ends of linear chromosomes. Using alternative lengthening of telomeres (ALT) in cancer cells and ALT-associated PML bodies (APBs) as examples of replication stress-associated clustered DNA damage, we discuss compartmentalization of DNA repair reactions and the role of protein properties implicated in phase separation. Finally, we highlight emerging connections between DNA repair and mechanobiology and discuss how biomolecular condensates, components of the nuclear cytoskeleton, and interfaces between membrane-bound organelles and membraneless macromolecular condensates may cooperate to coordinate genome maintenance in space and time.
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Affiliation(s)
- Vincent Spegg
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Matthias Altmeyer
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland.
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13
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Zhang Y, Hou K, Tong J, Zhang H, Xiong M, Liu J, Jia S. The Altered Functions of Shelterin Components in ALT Cells. Int J Mol Sci 2023; 24:16830. [PMID: 38069153 PMCID: PMC10706665 DOI: 10.3390/ijms242316830] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
Telomeres are nucleoprotein complexes that cap the ends of eukaryotic linear chromosomes. Telomeric DNA is bound by shelterin protein complex to prevent telomeric chromosome ends from being recognized as damaged sites for abnormal repair. To overcome the end replication problem, cancer cells mostly preserve their telomeres by reactivating telomerase, but a minority (10-15%) of cancer cells use a homologous recombination-based pathway called alternative lengthening of telomeres (ALT). Recent studies have found that shelterin components play an important role in the ALT mechanism. The binding of TRF1, TRF2, and RAP1 to telomeres attenuates ALT activation, while the maintenance of ALT telomere requires TRF1 and TRF2. POT1 and TPP1 can also influence the occurrence of ALT. The elucidation of how shelterin regulates the initiation of ALT remains elusive. This review presents a comprehensive overview of the current findings on the regulation of ALT by shelterin components, aiming to enhance the insight into the altered functions of shelterin components in ALT cells and to identify potential targets for the treatment of ALT tumor cells.
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Affiliation(s)
| | | | | | | | | | - Jing Liu
- 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.Z.); (K.H.); (J.T.); (H.Z.); (M.X.)
| | - 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.Z.); (K.H.); (J.T.); (H.Z.); (M.X.)
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14
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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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15
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Osia B, Merkell A, Lopezcolorado FW, Ping X, Stark JM. RAD52 and ERCC6L/PICH have a compensatory relationship for genome stability in mitosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.23.554522. [PMID: 37662271 PMCID: PMC10473716 DOI: 10.1101/2023.08.23.554522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
The mammalian RAD52 protein is a DNA repair factor that has both strand annealing and recombination mediator activities, yet is dispensable for cell viability. To characterize genetic contexts that reveal dependence on RAD52 to sustain cell viability (i.e., synthetic lethal relationships), we performed genome-wide CRISPR knock-out screens. Subsequent secondary screening found that depletion of ERCC6L in RAD52-deficient cells causes reduced viability and elevated genome instability, measured as accumulation of 53BP1 into nuclear foci. Furthermore, loss of RAD52 causes elevated levels of anaphase ultrafine bridges marked by ERCC6L, and conversely depletion of ERCC6L causes elevated RAD52 foci both in prometaphase and interphase cells. These effects were enhanced with combination treatments using hydroxyurea and the topoisomerase IIα inhibitor ICRF-193, and the timing of these treatments are consistent with defects in addressing such stress in mitosis. Thus, loss of RAD52 appears to cause an increased reliance on ERCC6L in mitosis, and vice versa. Consistent with this notion, combined depletion of ERCC6L and disrupting G2/M progression via CDK1 inhibition causes a marked loss of viability in RAD52-deficient cells. We suggest that RAD52 and ERCC6L play compensatory roles in protecting genome stability in mitosis.
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16
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Richards F, Llorca-Cardenosa MJ, Langton J, Buch-Larsen SC, Shamkhi NF, Sharma AB, Nielsen ML, Lakin ND. Regulation of Rad52-dependent replication fork recovery through serine ADP-ribosylation of PolD3. Nat Commun 2023; 14:4310. [PMID: 37463936 DOI: 10.1038/s41467-023-40071-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 07/06/2023] [Indexed: 07/20/2023] Open
Abstract
Although Poly(ADP-ribose)-polymerases (PARPs) are key regulators of genome stability, how site-specific ADP-ribosylation regulates DNA repair is unclear. Here, we describe a novel role for PARP1 and PARP2 in regulating Rad52-dependent replication fork repair to maintain cell viability when homologous recombination is dysfunctional, suppress replication-associated DNA damage, and maintain genome stability. Mechanistically, Mre11 and ATM are required for induction of PARP activity in response to replication stress that in turn promotes break-induced replication (BIR) through assembly of Rad52 at stalled/damaged replication forks. Further, by mapping ADP-ribosylation sites induced upon replication stress, we identify that PolD3 is a target for PARP1/PARP2 and that its site-specific ADP-ribosylation is required for BIR activity, replication fork recovery and genome stability. Overall, these data identify a critical role for Mre11-dependent PARP activation and site-specific ADP-ribosylation in regulating BIR to maintain genome integrity during DNA synthesis.
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Affiliation(s)
- Frederick Richards
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK
| | | | - Jamie Langton
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK
| | - Sara C Buch-Larsen
- Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Noor F Shamkhi
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK
| | | | - Michael L Nielsen
- Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200, Copenhagen, Denmark
| | - Nicholas D Lakin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK.
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17
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Zhang T, Rawal Y, Jiang H, Kwon Y, Sung P, Greenberg RA. Break-induced replication orchestrates resection-dependent template switching. Nature 2023; 619:201-208. [PMID: 37316655 PMCID: PMC10937050 DOI: 10.1038/s41586-023-06177-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 05/05/2023] [Indexed: 06/16/2023]
Abstract
Break-induced telomere synthesis (BITS) is a RAD51-independent form of break-induced replication that contributes to alternative lengthening of telomeres1,2. This homology-directed repair mechanism utilizes a minimal replisome comprising proliferating cell nuclear antigen (PCNA) and DNA polymerase-δ to execute conservative DNA repair synthesis over many kilobases. How this long-tract homologous recombination repair synthesis responds to complex secondary DNA structures that elicit replication stress remains unclear3-5. Moreover, whether the break-induced replisome orchestrates additional DNA repair events to ensure processivity is also unclear. Here we combine synchronous double-strand break induction with proteomics of isolated chromatin segments (PICh) to capture the telomeric DNA damage response proteome during BITS1,6. This approach revealed a replication stress-dominated response, highlighted by repair synthesis-driven DNA damage tolerance signalling through RAD18-dependent PCNA ubiquitination. Furthermore, the SNM1A nuclease was identified as the major effector of ubiquitinated PCNA-dependent DNA damage tolerance. SNM1A recognizes the ubiquitin-modified break-induced replisome at damaged telomeres, and this directs its nuclease activity to promote resection. These findings show that break-induced replication orchestrates resection-dependent lesion bypass, with SNM1A nuclease activity serving as a critical effector of ubiquitinated PCNA-directed recombination in mammalian cells.
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Affiliation(s)
- Tianpeng Zhang
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Yashpal Rawal
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Haoyang Jiang
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology and Greehey Children's Cancer Research Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Roger A Greenberg
- Department of Cancer Biology, Penn Center for Genome Integrity, Basser Center for BRCA, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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18
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Carson LM, Flynn RL. Highlighting vulnerabilities in the alternative lengthening of telomeres pathway. Curr Opin Pharmacol 2023; 70:102380. [PMID: 37149932 PMCID: PMC10247456 DOI: 10.1016/j.coph.2023.102380] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 02/03/2023] [Accepted: 03/28/2023] [Indexed: 05/09/2023]
Abstract
The alternative lengthening of telomeres (ALT) pathway is a telomere elongation mechanism found in a small but often aggressive subset of cancers. Dependent on break-induced replication, telomere extension in ALT-positive cells relies on a baseline level of DNA replication stress to initiate elongation events. This results in an elevated level of DNA damage and presents a possible vulnerability to be exploited in the development of ALT-targeted cancer therapies. Currently, there are no treatment options that target the ALT mechanism or that are specific for ALT-positive tumors. Here, we review recent developments and promising directions in the development of ALT-targeted therapeutics, many of which involve tipping the balance towards inhibition or exacerbation of ALT activity to selectively target these cells.
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Affiliation(s)
- Lisa M Carson
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA, 02118, USA
| | - Rachel L Flynn
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA, 02118, USA.
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19
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Broderick R, Cherdyntseva V, Nieminuszczy J, Dragona E, Kyriakaki M, Evmorfopoulou T, Gagos S, Niedzwiedz W. Pathway choice in the alternative telomere lengthening in neoplasia is dictated by replication fork processing mediated by EXD2's nuclease activity. Nat Commun 2023; 14:2428. [PMID: 37105990 PMCID: PMC10140042 DOI: 10.1038/s41467-023-38029-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
Telomerase-independent cancer proliferation via the alternative lengthening of telomeres (ALT) relies upon two distinct, largely uncharacterized, break-induced-replication (BIR) processes. How cancer cells initiate and regulate these terminal repair mechanisms is unknown. Here, we establish that the EXD2 nuclease is recruited to ALT telomeres to direct their maintenance. We demonstrate that EXD2 loss leads to telomere shortening, elevated telomeric sister chromatid exchanges, C-circle formation as well as BIR-mediated telomeric replication. We discover that EXD2 fork-processing activity triggers a switch between RAD52-dependent and -independent ALT-associated BIR. The latter is suppressed by EXD2 but depends specifically on the fork remodeler SMARCAL1 and the MUS81 nuclease. Thus, our findings suggest that processing of stalled replication forks orchestrates elongation pathway choice at ALT telomeres. Finally, we show that co-depletion of EXD2 with BLM, DNA2 or POLD3 confers synthetic lethality in ALT cells, identifying EXD2 as a potential druggable target for ALT-reliant cancers.
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Affiliation(s)
| | - Veronica Cherdyntseva
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | | | - Eleni Dragona
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Maria Kyriakaki
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Theodora Evmorfopoulou
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Sarantis Gagos
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece.
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20
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Rai R, Biju K, Sun W, Sodeinde T, Al-Hiyasat A, Morgan J, Ye X, Li X, Chen Y, Chang S. Homology directed telomere clustering, ultrabright telomere formation and nuclear envelope rupture in cells lacking TRF2 B and RAP1. Nat Commun 2023; 14:2144. [PMID: 37059728 PMCID: PMC10104862 DOI: 10.1038/s41467-023-37761-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 03/30/2023] [Indexed: 04/16/2023] Open
Abstract
Double-strand breaks (DSBs) due to genotoxic stress represent potential threats to genome stability. Dysfunctional telomeres are recognized as DSBs and are repaired by distinct DNA repair mechanisms. RAP1 and TRF2 are telomere binding proteins essential to protect telomeres from engaging in homology directed repair (HDR), but how this occurs remains unclear. In this study, we examined how the basic domain of TRF2 (TRF2B) and RAP1 cooperate to repress HDR at telomeres. Telomeres lacking TRF2B and RAP1 cluster into structures termed ultrabright telomeres (UTs). HDR factors localize to UTs, and UT formation is abolished by RNaseH1, DDX21 and ADAR1p110, suggesting that they contain DNA-RNA hybrids. Interaction between the BRCT domain of RAP1 and KU70/KU80 is also required to repress UT formation. Expressing TRF2∆B in Rap1-/- cells resulted in aberrant lamin A localization in the nuclear envelope and dramatically increased UT formation. Expressing lamin A phosphomimetic mutants induced nuclear envelope rupturing and aberrant HDR-mediated UT formation. Our results highlight the importance of shelterin and proteins in the nuclear envelope in repressing aberrant telomere-telomere recombination to maintain telomere homeostasis.
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Affiliation(s)
- Rekha Rai
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA.
| | - Kevin Biju
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
- Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Wenqi Sun
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Tori Sodeinde
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Amer Al-Hiyasat
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Jaida Morgan
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Xianwen Ye
- University of Chinese Academy of Sciences, 100049, Beijing, China
- School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai, 201210, China
| | - Xueqing Li
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Yong Chen
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
- School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai, 201210, China
| | - Sandy Chang
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA.
- Department of Pathology, Yale University School of Medicine, 330 Cedar Street, New Haven, CT, 06520, USA.
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 330 Cedar Street, New Haven, CT, 06520, USA.
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21
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Li F, Wang Y, Hwang I, Jang JY, Xu L, Deng Z, Yu EY, Cai Y, Wu C, Han Z, Huang YH, Huang X, Zhang L, Yao J, Lue NF, Lieberman PM, Ying H, Paik J, Zheng H. Histone demethylase KDM2A is a selective vulnerability of cancers relying on alternative telomere maintenance. Nat Commun 2023; 14:1756. [PMID: 36991019 PMCID: PMC10060224 DOI: 10.1038/s41467-023-37480-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Accepted: 03/17/2023] [Indexed: 03/31/2023] Open
Abstract
Telomere length maintenance is essential for cellular immortalization and tumorigenesis. 5% - 10% of human cancers rely on a recombination-based mechanism termed alternative lengthening of telomeres (ALT) to sustain their replicative immortality, yet there are currently no targeted therapies. Through CRISPR/Cas9-based genetic screens in an ALT-immortalized isogenic cellular model, here we identify histone lysine demethylase KDM2A as a molecular vulnerability selectively for cells contingent on ALT-dependent telomere maintenance. Mechanistically, we demonstrate that KDM2A is required for dissolution of the ALT-specific telomere clusters following recombination-directed telomere DNA synthesis. We show that KDM2A promotes de-clustering of ALT multitelomeres through facilitating isopeptidase SENP6-mediated SUMO deconjugation at telomeres. Inactivation of KDM2A or SENP6 impairs post-recombination telomere de-SUMOylation and thus dissolution of ALT telomere clusters, leading to gross chromosome missegregation and mitotic cell death. These findings together establish KDM2A as a selective molecular vulnerability and a promising drug target for ALT-dependent cancers.
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Affiliation(s)
- Fei Li
- Department of Neurosurgery, Southwest Hospital, Chongqing, 400038, China
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Yizhe Wang
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Inah Hwang
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA
- Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul, 03760, Republic of Korea
| | - Ja-Young Jang
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Libo Xu
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
- Key Laboratory of Pathobiology, Ministry of Education, and Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin, China
| | - Zhong Deng
- The Wistar Institute, Philadelphia, PA, 19104, USA
| | - Eun Young Yu
- Department of Microbiology and Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Yiming Cai
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77030, USA
| | - Caizhi Wu
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Zhenbo Han
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77030, USA
| | - Yu-Han Huang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Xiangao Huang
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Ling Zhang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
- Key Laboratory of Pathobiology, Ministry of Education, and Department of Pathophysiology, College of Basic Medical Sciences, Jilin University, Changchun, Jilin, China
| | - Jun Yao
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77030, USA
| | - Neal F Lue
- Department of Microbiology and Immunology, W. R. Hearst Microbiology Research Center, Weill Cornell Medicine, New York, NY, 10065, USA
| | | | - Haoqiang Ying
- Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX, 77030, USA
| | - Jihye Paik
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA.
| | - Hongwu Zheng
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, 10065, USA.
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22
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Ramakrishnan N, Malachowski T, Verma P. A high-content flow cytometry and dual CRISPR-Cas9 based platform to quantify genetic interactions. Methods Cell Biol 2023; 182:299-312. [PMID: 38359984 DOI: 10.1016/bs.mcb.2023.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Probing epistasis between two genes can be a critical first step in identifying the molecular players in a cellular pathway. The advent of CRISPR-Cas mediated genetic screen has enabled studying of these genetic interactions at a genomic scale. However, when combining depletion of two genes using CRISPR Cas9, reduced targeting efficiencies due to competition for Cas loading and recombination in the cloning step have emerged as key challenges. Moreover, given conventional CRISPR screens typically involve comparison between the initial and final time point, it is difficult to parse the time kinetics with which a perturbed genetic interaction impacts viability, and it also becomes challenging to assess epistasis with essential genes. Here, we discuss a high-throughput flow-based approach to study genetic interactions. By utilizing two different Cas9 orthologs and monitoring viability at multiple time points, this approach helps to effectively mitigate the limitations of Cas9 competition and enables assessment of genetic interactions with both essential and non-essential genes at a high temporal resolution.
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Affiliation(s)
- Natasha Ramakrishnan
- Division of Oncology, Department of Medicine, Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, United States
| | - Taylor Malachowski
- Division of Oncology, Department of Medicine, Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, United States
| | - Priyanka Verma
- Division of Oncology, Department of Medicine, Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, United States.
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23
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Clatterbuck Soper SF, Meltzer PS. ATRX/DAXX: Guarding the Genome against the Hazards of ALT. Genes (Basel) 2023; 14:genes14040790. [PMID: 37107548 PMCID: PMC10137841 DOI: 10.3390/genes14040790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 03/21/2023] [Accepted: 03/22/2023] [Indexed: 03/29/2023] Open
Abstract
Proliferating cells must enact a telomere maintenance mechanism to ensure genomic stability. In a subset of tumors, telomeres are maintained not by telomerase, but through a homologous recombination-based mechanism termed Alternative Lengthening of Telomeres or ALT. The ALT process is linked to mutations in the ATRX/DAXX/H3.3 histone chaperone complex. This complex is responsible for depositing non-replicative histone variant H3.3 at pericentric and telomeric heterochromatin but has also been found to have roles in ameliorating replication in repeat sequences and in promoting DNA repair. In this review, we will discuss ways in which ATRX/DAXX helps to protect the genome, and how loss of this complex allows ALT to take hold.
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24
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Kinoshita C, Takizawa Y, Saotome M, Ogino S, Kurumizaka H, Kagawa W. The cryo-EM structure of full-length RAD52 protein contains an undecameric ring. FEBS Open Bio 2023; 13:408-418. [PMID: 36707939 PMCID: PMC9989933 DOI: 10.1002/2211-5463.13565] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 12/29/2022] [Accepted: 01/26/2023] [Indexed: 01/29/2023] Open
Abstract
The human RAD52 protein, which forms an oligomeric ring structure, is involved in DNA double-strand break repair. The N-terminal half of RAD52 is primarily responsible for self-oligomerisation and DNA binding. Crystallographic studies have revealed the detailed structure of the N-terminal half. However, only low-resolution structures have been reported for the full-length protein, and thus the structural role of the C-terminal half in self-oligomerisation has remained elusive. In this study, we determined the solution structure of the human RAD52 protein by cryo-electron microscopy (cryo-EM), at an average resolution of 3.5 Å. The structure revealed an undecameric ring that is nearly identical to the crystal structures of the N-terminal half. The cryo-EM map for the C-terminal half was poorly defined, indicating that the region is intrinsically disordered. The present cryo-EM structure provides important insights into the mechanistic roles played by the N-terminal and C-terminal halves of RAD52 during DNA double-strand break repair.
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Affiliation(s)
- Chiaki Kinoshita
- Department of Chemistry, Graduate School of Science and Engineering, Meisei University, Tokyo, Japan
| | - Yoshimasa Takizawa
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, Japan
| | - Mika Saotome
- Department of Chemistry, Graduate School of Science and Engineering, Meisei University, Tokyo, Japan
| | - Shun Ogino
- Department of Chemistry, Graduate School of Science and Engineering, Meisei University, Tokyo, Japan
| | - Hitoshi Kurumizaka
- Laboratory of Chromatin Structure and Function, Institute for Quantitative Biosciences, The University of Tokyo, Japan
| | - Wataru Kagawa
- Department of Chemistry, Graduate School of Science and Engineering, Meisei University, Tokyo, Japan
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25
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A non-genetic switch triggers alternative telomere lengthening and cellular immortalization in ATRX deficient cells. Nat Commun 2023; 14:939. [PMID: 36805596 PMCID: PMC9941109 DOI: 10.1038/s41467-023-36294-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 01/25/2023] [Indexed: 02/22/2023] Open
Abstract
Alternative Lengthening of Telomeres (ALT) is an aberrant DNA recombination pathway which grants replicative immortality to approximately 10% of all cancers. Despite this high prevalence of ALT in cancer, the mechanism and genetics by which cells activate this pathway remain incompletely understood. A major challenge in dissecting the events that initiate ALT is the extremely low frequency of ALT induction in human cell systems. Guided by the genetic lesions that have been associated with ALT from cancer sequencing studies, we genetically engineered primary human pluripotent stem cells to deterministically induce ALT upon differentiation. Using this genetically defined system, we demonstrate that disruption of the p53 and Rb pathways in combination with ATRX loss-of-function is sufficient to induce all hallmarks of ALT and results in functional immortalization in a cell type-specific manner. We further demonstrate that ALT can be induced in the presence of telomerase, is neither dependent on telomere shortening nor crisis, but is rather driven by continuous telomere instability triggered by the induction of differentiation in ATRX-deficient stem cells.
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Histone demethylase KDM2A is a selective vulnerability of cancers relying on alternative telomere maintenance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.10.528023. [PMID: 36798426 PMCID: PMC9934630 DOI: 10.1101/2023.02.10.528023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Telomere length maintenance is essential for cellular immortalization and tumorigenesis. 5% - 10% of human cancers rely on a recombination-based mechanism termed alternative lengthening of telomeres (ALT) to sustain their replicative immortality, yet there are currently no targeted therapies. Through CRISPR/Cas9-based genetic screens in an ALT-immortalized isogenic cellular model, here we identify histone lysine demethylase KDM2A as a molecular vulnerability selectively for cells contingent on ALT-dependent telomere maintenance. Mechanistically, we demonstrate that KDM2A is required for dissolution of the ALT-specific telomere clusters following homology-directed telomere DNA synthesis. We show that KDM2A promotes de-clustering of ALT multitelomeres through facilitating isopeptidase SENP6-mediated SUMO deconjugation at telomeres. Inactivation of KDM2A or SENP6 impairs post-recombination telomere de-SUMOylation and thus dissolution of ALT telomere clusters, leading to gross chromosome missegregation and mitotic cell death. These findings together establish KDM2A as a selective molecular vulnerability and a promising drug target for ALT-dependent cancers.
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27
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Barnes RP, Thosar SA, Opresko PL. Telomere Fragility and MiDAS: Managing the Gaps at the End of the Road. Genes (Basel) 2023; 14:genes14020348. [PMID: 36833275 PMCID: PMC9956152 DOI: 10.3390/genes14020348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/20/2023] [Accepted: 01/24/2023] [Indexed: 01/31/2023] Open
Abstract
Telomeres present inherent difficulties to the DNA replication machinery due to their repetitive sequence content, formation of non-B DNA secondary structures, and the presence of the nucleo-protein t-loop. Especially in cancer cells, telomeres are hot spots for replication stress, which can result in a visible phenotype in metaphase cells termed "telomere fragility". A mechanism cells employ to mitigate replication stress, including at telomeres, is DNA synthesis in mitosis (MiDAS). While these phenomena are both observed in mitotic cells, the relationship between them is poorly understood; however, a common link is DNA replication stress. In this review, we will summarize what is known to regulate telomere fragility and telomere MiDAS, paying special attention to the proteins which play a role in these telomere phenotypes.
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Affiliation(s)
- Ryan P. Barnes
- Department of Environmental and Occupational Health, School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
- UPMC Hillman Cancer Center, University of Pittsburgh, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
- Correspondence: (R.P.B.); (P.L.O.)
| | - Sanjana A. Thosar
- Department of Environmental and Occupational Health, School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
- UPMC Hillman Cancer Center, University of Pittsburgh, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
| | - Patricia L. Opresko
- Department of Environmental and Occupational Health, School of Public Health, University of Pittsburgh, Pittsburgh, PA 15261, USA
- UPMC Hillman Cancer Center, University of Pittsburgh, 5117 Centre Avenue, Pittsburgh, PA 15213, USA
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Correspondence: (R.P.B.); (P.L.O.)
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de Bardet JC, Cardentey CR, González BL, Patrone D, Mulet IL, Siniscalco D, Robinson-Agramonte MDLA. Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention. BIOTECH 2023; 12:biotech12010014. [PMID: 36810441 PMCID: PMC9944833 DOI: 10.3390/biotech12010014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/25/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.
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Affiliation(s)
- Javier Curi de Bardet
- Department of Neurobiology, International Center for Neurological Restoration, Havana 11300, Cuba
| | | | - Belkis López González
- Department of Allergy, Calixto Garcia General University Hospital, Havana 10400, Cuba
| | - Deanira Patrone
- Department of Experimental Medicine, Division of Molecular Biology, Biotechnology and Histology, University of Campania, 80138 Naples, Italy
| | | | - Dario Siniscalco
- Department of Experimental Medicine, Division of Molecular Biology, Biotechnology and Histology, University of Campania, 80138 Naples, Italy
- Correspondence:
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DNA repair protein RAD52 is required for protecting G-quadruplexes in mammalian cells. J Biol Chem 2022; 299:102770. [PMID: 36470428 PMCID: PMC9807996 DOI: 10.1016/j.jbc.2022.102770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 12/09/2022] Open
Abstract
G-quadruplex (G4)-forming DNA sequences are abundant in the human genome, and they are hot spots for inducing DNA double-strand breaks (DSBs) and genome instability. The mechanisms involved in protecting G4s and maintaining genome stability have not been fully elucidated. Here, we demonstrated that RAD52 plays an important role in suppressing DSB accumulation at G4s, and RAD52-deficient cells are sensitive to G4-stabilizing compounds. Mechanistically, we showed that RAD52 is required for efficient homologous recombination repair at G4s, likely due to its function in recruiting structure-specific endonuclease XPF to remove G4 structures at DSB ends. We also demonstrated that upon G4 stabilization, endonuclease MUS81 mediates cleavage of stalled replication forks at G4s. The resulting DSBs recruit RAD52 and XPF to G4s for processing DSB ends to facilitate homologous recombination repair. Loss of RAD52 along with G4-resolving helicase FANCJ leads to a significant increase of DSB accumulation before and after treatment with the G4-stabilizing compound pyridostatin, and RAD52 exhibits a synthetic lethal interaction with FANCJ. Collectively, our findings reveal a new role of RAD52 in protecting G4 integrity and provide insights for new cancer treatment strategies.
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30
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Li T, Tang L, Kou H, Wang F. PRIMPOL competes with RAD51 to resolve G-quadruplex-induced replication stress via its interaction with RPA. Acta Biochim Biophys Sin (Shanghai) 2022; 55:498-507. [PMID: 36647718 PMCID: PMC10160237 DOI: 10.3724/abbs.2022165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
<p indent="0mm">PRIMPOL (primase-polymerase) is a recently discovered DNA primase-polymerase involved in DNA damage tolerance and replication stress response in eukaryotic cells. However, the detailed mechanism of the PRIMPOL response to replication stress remains elusive. Here, we demonstrate that replication-related factors, including replication protein A (RPA), regulate the accumulation of PRIMPOL in subnuclear foci in response to replication stress induced by replication inhibitors. Moreover, PRIMPOL works at G-quadruplexes (G4s) in human cells to resolve the replication stress induced by G4s. The formation of PRIMPOL foci persists throughout the cell cycle. We further demonstrate that PRIMPOL competes with RAD51 to resolve G4-induced replication stress. In conclusion, our results provide novel insight into the mechanism of PRIMPOL in G4s to resolve replication stress and competition between PRIMPOL (repriming)- and RAD51 (fork reversal)-mediated pathways, which indicates a new strategy to improve the tumor response to DNA-damaging chemotherapy by targeting the PRIMPOL pathway.</p>.
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Affiliation(s)
- Tingfang Li
- Department of Genetics, School of Basic Medical Sciences, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical, General Hospital, Tianjin Medical University, Tianjin 300070, China
| | - Lu Tang
- Department of Stomatology, Shengjing Hospital, China Medical University, Shenyang 110004, China
| | - Haomeng Kou
- Department of Genetics, School of Basic Medical Sciences, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical, General Hospital, Tianjin Medical University, Tianjin 300070, China
| | - Feng Wang
- Department of Genetics, School of Basic Medical Sciences, The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical, General Hospital, Tianjin Medical University, Tianjin 300070, China.,School and Hospital of Stomatology, Tianjin Medical University, Tianjin 300070, China
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31
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Yadav T, Zhang JM, Ouyang J, Leung W, Simoneau A, Zou L. TERRA and RAD51AP1 promote alternative lengthening of telomeres through an R- to D-loop switch. Mol Cell 2022; 82:3985-4000.e4. [PMID: 36265486 PMCID: PMC9637728 DOI: 10.1016/j.molcel.2022.09.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/08/2022] [Accepted: 09/23/2022] [Indexed: 11/05/2022]
Abstract
Alternative lengthening of telomeres (ALT), a telomerase-independent process maintaining telomeres, is mediated by break-induced replication (BIR). RAD52 promotes ALT by facilitating D-loop formation, but ALT also occurs through a RAD52-independent BIR pathway. Here, we show that the telomere non-coding RNA TERRA forms dynamic telomeric R-loops and contributes to ALT activity in RAD52 knockout cells. TERRA forms R-loops in vitro and at telomeres in a RAD51AP1-dependent manner. The formation of R-loops by TERRA increases G-quadruplexes (G4s) at telomeres. G4 stabilization enhances ALT even when TERRA is depleted, suggesting that G4s act downstream of R-loops to promote BIR. In vitro, the telomeric R-loops assembled by TERRA and RAD51AP1 generate G4s, which persist after R-loop resolution and allow formation of telomeric D-loops without RAD52. Thus, the dynamic telomeric R-loops formed by TERRA and RAD51AP1 enable the RAD52-independent ALT pathway, and G4s orchestrate an R- to D-loop switch at telomeres to stimulate BIR.
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Affiliation(s)
- Tribhuwan Yadav
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jian Ouyang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Wendy Leung
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Antoine Simoneau
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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Kaminski N, Wondisford AR, Kwon Y, Lynskey ML, Bhargava R, Barroso-González J, García-Expósito L, He B, Xu M, Mellacheruvu D, Watkins SC, Modesti M, Miller KM, Nesvizhskii AI, Zhang H, Sung P, O'Sullivan RJ. RAD51AP1 regulates ALT-HDR through chromatin-directed homeostasis of TERRA. Mol Cell 2022; 82:4001-4017.e7. [PMID: 36265488 PMCID: PMC9713952 DOI: 10.1016/j.molcel.2022.09.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/10/2022] [Accepted: 09/23/2022] [Indexed: 11/05/2022]
Abstract
Alternative lengthening of telomeres (ALT) is a homology-directed repair (HDR) mechanism of telomere elongation that controls proliferation in subsets of aggressive cancer. Recent studies have revealed that telomere repeat-containing RNA (TERRA) promotes ALT-associated HDR (ALT-HDR). Here, we report that RAD51AP1, a crucial ALT factor, interacts with TERRA and utilizes it to generate D- and R-loop HR intermediates. We also show that RAD51AP1 binds to and might stabilize TERRA-containing R-loops as RAD51AP1 depletion reduces R-loop formation at telomere DNA breaks. Proteomic analyses uncover a role for RAD51AP1-mediated TERRA R-loop homeostasis in a mechanism of chromatin-directed suppression of TERRA and prevention of transcription-replication collisions (TRCs) during ALT-HDR. Intriguingly, we find that both TERRA binding and this non-canonical function of RAD51AP1 require its intrinsic SUMO-SIM regulatory axis. These findings provide insights into the multi-contextual functions of RAD51AP1 within the ALT mechanism and regulation of TERRA.
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Affiliation(s)
- Nicole Kaminski
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Anne R Wondisford
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Youngho Kwon
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Michelle Lee Lynskey
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ragini Bhargava
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jonathan Barroso-González
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Laura García-Expósito
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Boxue He
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA; Department of Thoracic Surgery, Second Xiangya Hospital, Central South University, Changsha 410011, China
| | - Meng Xu
- Department of Biological Sciences, Mellon College of Science, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Dattatreya Mellacheruvu
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Simon C Watkins
- Department of Cell Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mauro Modesti
- Cancer Research Center of Marseille, CNRS UMR7258, Inserm UMR1068, Aix Marseille Université U105, Institut Paoli Calmettes, 27 Boulevard Lei Roure CS30059, 13273 Marseille Cedex 09, France
| | - Kyle M Miller
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2506 Speedway, Austin, TX 78712, USA
| | - Alexey I Nesvizhskii
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Computational Medicine and Bioinformatics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Huaiying Zhang
- Department of Biological Sciences, Mellon College of Science, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Patrick Sung
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA.
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33
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Gao J, Pickett HA. Targeting telomeres: advances in telomere maintenance mechanism-specific cancer therapies. Nat Rev Cancer 2022; 22:515-532. [PMID: 35790854 DOI: 10.1038/s41568-022-00490-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/25/2022] [Indexed: 12/31/2022]
Abstract
Cancer cells establish replicative immortality by activating a telomere-maintenance mechanism (TMM), be it telomerase or the alternative lengthening of telomeres (ALT) pathway. Targeting telomere maintenance represents an intriguing opportunity to treat the vast majority of all cancer types. Whilst telomerase inhibitors have historically been heralded as promising anticancer agents, the reality has been more challenging, and there are currently no therapeutic options for cancer types that use ALT despite their aggressive nature and poor prognosis. In this Review, we discuss the mechanistic differences between telomere maintenance by telomerase and ALT, the current methods used to detect each mechanism, the utility of these tests for clinical diagnosis, and recent developments in the therapeutic strategies being employed to target both telomerase and ALT. We present notable developments in repurposing established therapeutic agents and new avenues that are emerging to target cancer types according to which TMM they employ. These opportunities extend beyond inhibition of telomere maintenance, by finding and exploiting inherent weaknesses in the telomeres themselves to trigger rapid cellular effects that lead to cell death.
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Affiliation(s)
- Jixuan Gao
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia.
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de Nonneville A, Salas S, Bertucci F, Sobinoff AP, Adélaïde J, Guille A, Finetti P, Noble JR, Churikov D, Chaffanet M, Lavit E, Pickett HA, Bouvier C, Birnbaum D, Reddel RR, Géli V. TOP3A amplification and ATRX inactivation are mutually exclusive events in pediatric osteosarcomas using ALT. EMBO Mol Med 2022; 14:e15859. [PMID: 35920001 PMCID: PMC9549729 DOI: 10.15252/emmm.202215859] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 07/13/2022] [Accepted: 07/14/2022] [Indexed: 02/05/2023] Open
Abstract
In some types of cancer, telomere length is maintained by the alternative lengthening of telomeres (ALT) mechanism. In many ALT cancers, the α-thalassemia/mental retardation syndrome X-linked (ATRX) gene is mutated leading to the conclusion that the ATRX complex represses ALT. Here, we report that most high-grade pediatric osteosarcomas maintain their telomeres by ALT, and that the majority of these ALT tumors are ATRX wild-type (wt) and instead carry an amplified 17p11.2 chromosomal region containing TOP3A. We found that TOP3A was overexpressed in the ALT-positive ATRX-wt tumors consistent with its amplification. We demonstrated the functional significance of these results by showing that TOP3A overexpression in ALT cancer cells countered ATRX-mediated ALT inhibition and that TOP3A knockdown disrupted the ALT phenotype in ATRX-wt cells. Moreover, we report that TOP3A is required for proper BLM localization and promotes ALT DNA synthesis in ALT cell lines. Collectively, our results identify TOP3A as a major ALT player and potential therapeutic target.
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Affiliation(s)
- Alexandre de Nonneville
- Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐Calmettes, Team « Telomere and Chromatin ». Equipe labellisée Ligue Nationale Contre Le CancerAix‐Marseille UnivMarseilleFrance,Cancer Research Unit, Faculty of Medicine and Health, Children's Medical Research InstituteUniversity of SydneyWestmeadNSWAustralia,Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance,Department of Medical Oncology, CRCM, CNRS, INSERM, Institut Paoli‐CalmettesAix‐Marseille UnivMarseilleFrance
| | - Sébastien Salas
- Department of Medical OncologyAssistance Publique Hôpitaux de Marseille ‐ Timone HospitalMarseilleFrance
| | - François Bertucci
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance,Department of Medical Oncology, CRCM, CNRS, INSERM, Institut Paoli‐CalmettesAix‐Marseille UnivMarseilleFrance
| | - Alexander P Sobinoff
- Telomere Length Regulation Unit, Faculty of Medicine and Health, Children's Medical Research InstituteUniversity of SydneyWestmeadNSWAustralia
| | - José Adélaïde
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance
| | - Arnaud Guille
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance
| | - Pascal Finetti
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance
| | - Jane R Noble
- Cancer Research Unit, Faculty of Medicine and Health, Children's Medical Research InstituteUniversity of SydneyWestmeadNSWAustralia
| | - Dimitri Churikov
- Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐Calmettes, Team « Telomere and Chromatin ». Equipe labellisée Ligue Nationale Contre Le CancerAix‐Marseille UnivMarseilleFrance
| | - Max Chaffanet
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance
| | - Elise Lavit
- Department of Medical OncologyAssistance Publique Hôpitaux de Marseille ‐ Timone HospitalMarseilleFrance
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Faculty of Medicine and Health, Children's Medical Research InstituteUniversity of SydneyWestmeadNSWAustralia
| | - Corinne Bouvier
- Department of PathologyAssistance Publique Hôpitaux de Marseille ‐ Timone HospitalMarseilleFrance
| | - Daniel Birnbaum
- Predictive Oncology Laboratory, Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐CalmettesAix‐Marseille UniversityMarseilleFrance
| | - Roger R Reddel
- Cancer Research Unit, Faculty of Medicine and Health, Children's Medical Research InstituteUniversity of SydneyWestmeadNSWAustralia
| | - Vincent Géli
- Marseille Cancer Research Centre (CRCM), Inserm U1068, CNRS UMR7258, Institut Paoli‐Calmettes, Team « Telomere and Chromatin ». Equipe labellisée Ligue Nationale Contre Le CancerAix‐Marseille UnivMarseilleFrance
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Zimmermann M, Bernier C, Kaiser B, Fournier S, Li L, Desjardins J, Skeldon A, Rimkunas V, Veloso A, Young JTF, Roulston A, Zinda M. Guiding ATR and PARP inhibitor combinationswith chemogenomic screens. Cell Rep 2022; 40:111081. [PMID: 35830811 DOI: 10.1016/j.celrep.2022.111081] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 04/27/2022] [Accepted: 06/21/2022] [Indexed: 11/03/2022] Open
Abstract
Combinations of ataxia telangiectasia- and Rad3-related kinase inhibitors (ATRis) and poly(ADP-ribose) polymerase inhibitors (PARPis) synergistically kill tumor cells through modulation of complementary DNA repair pathways, but their tolerability is limited by hematological toxicities. To address this, we performed a genome-wide CRISPR-Cas9 screen to identify genetic alterations that hypersensitize cells to a combination of the ATRi RP-3500 with PARPi, including deficiency in RNase H2, RAD51 paralog mutations, or the "alternative lengthening of telomeres" telomere maintenance mechanism. We show that RP-3500 and PARPi combinations kill cells carrying these genetic alterations at doses sub-therapeutic as single agents. We also demonstrate the mechanism of combination hypersensitivity in RNase H2-deficient cells, where we observe an irreversible replication catastrophe, allowing us to design a highly efficacious and tolerable in vivo dosing schedule. We present a comprehensive dataset to inform development of ATRi and PARPi combinations and an experimental framework applicable to other drug combination strategies.
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Affiliation(s)
- Michal Zimmermann
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada.
| | - Cynthia Bernier
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Beatrice Kaiser
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Sara Fournier
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Li Li
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Jessica Desjardins
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Alexander Skeldon
- Ventus Therapeutics, 7150 Rue Frederick-Banting, St-Laurent, QC H4S 2A1, Canada
| | - Victoria Rimkunas
- Repare Therapeutics, 101 Main Street, Suite 1650, Cambridge, MA 02142, USA
| | - Artur Veloso
- Repare Therapeutics, 101 Main Street, Suite 1650, Cambridge, MA 02142, USA
| | - Jordan T F Young
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Anne Roulston
- Repare Therapeutics, 7171 Rue Frederick-Banting, St-Laurent, QC H4S 1Z9, Canada
| | - Michael Zinda
- Repare Therapeutics, 101 Main Street, Suite 1650, Cambridge, MA 02142, USA
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Betlej G, Ząbek T, Lewińska A, Błoniarz D, Rzeszutek I, Wnuk M. RNA 5-methylcytosine status is associated with DNMT2/TRDMT1 nuclear localization in osteosarcoma cell lines. J Bone Oncol 2022; 36:100448. [PMID: 35942470 PMCID: PMC9356272 DOI: 10.1016/j.jbo.2022.100448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 11/25/2022] Open
Abstract
Selected phenotypic features of three osteosarcoma (OS) cell lines were evaluated. Redox disequilibrium promoted sustained AKT and ERK1/2 activation. Redox imbalance modulated cell death pathways in OS cells. Nuclear levels of TRDMT1 methyltransferase were associated with RNA methylation. A novel marker for predicting therapy response in OS patients is proposed.
Osteosarcoma (OS) is a pediatric malignant bone tumor with unsatisfying improvements in survival rates due to limited understanding of OS biology and potentially druggable targets. The present study aims to better characterize osteosarcoma U-2 OS, SaOS-2, and MG-63 cell lines that are commonly used as in vitro models of OS. We focused on evaluating the differences in cell death pathways, redox equilibrium, the activity of proliferation-related signaling pathways, DNA damage response, telomere maintenance, DNMT2/TRDMT1-based responses and RNA 5-methylcytosine status. SaOS-2 cells were characterized by higher levels of superoxide and nitric oxide that promoted AKT and ERK1/2 activation thus modulating cell death pathways. OS cell lines also differed in the levels and localization of DNA repair regulator DNMT2/TRDMT1. SaOS-2 cells possessed the lowest levels of total, cytoplasmic and nuclear DNMT2/TRDMT1, whereas in MG-63 cells, the highest levels of nuclear DNMT2/TRDMT1 were associated with the most pronounced status of RNA 5-methylcytosine. In silico analysis revealed potential phosphorylation sites at DNMT2/TRDMT1 that may be related to the regulation of DNMT2/TRDMT1 localization. We postulate that redox homeostasis, proliferation-related pathways and DNMT2/TRDMT1-based effects can be modulated as a part of anti-osteosarcoma strategy reflecting diverse phenotypic features of OS cells.
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Affiliation(s)
- Gabriela Betlej
- Institute of Physical Culture Studies, College of Medical Sciences, University of Rzeszow, Rzeszow 35-310, Poland
| | - Tomasz Ząbek
- Laboratory of Genomics, National Research Institute of Animal Production, Krakowska 1, Balice 32-083, Poland
| | - Anna Lewińska
- Department of Biotechnology, Institute of Biology and Biotechnology, College of Nature Sciences, University of Rzeszow, Pigonia 1, Rzeszow 35-310, Poland
| | - Dominika Błoniarz
- Department of Biotechnology, Institute of Biology and Biotechnology, College of Nature Sciences, University of Rzeszow, Pigonia 1, Rzeszow 35-310, Poland
| | - Iwona Rzeszutek
- Department of Biotechnology, Institute of Biology and Biotechnology, College of Nature Sciences, University of Rzeszow, Pigonia 1, Rzeszow 35-310, Poland
- Corresponding authors.
| | - Maciej Wnuk
- Department of Biotechnology, Institute of Biology and Biotechnology, College of Nature Sciences, University of Rzeszow, Pigonia 1, Rzeszow 35-310, Poland
- Corresponding authors.
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Brenner KA, Nandakumar J. Consequences of telomere replication failure: the other end-replication problem. Trends Biochem Sci 2022; 47:506-517. [PMID: 35440402 PMCID: PMC9106919 DOI: 10.1016/j.tibs.2022.03.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 02/28/2022] [Accepted: 03/17/2022] [Indexed: 01/14/2023]
Abstract
Telomeres are chromosome-capping structures that protect ends of the linear genome from DNA damage sensors. However, these structures present obstacles during DNA replication. Incomplete telomere replication accelerates telomere shortening and limits replicative lifespan. Therefore, continued proliferation under conditions of replication stress requires a means of telomere repair, particularly in the absence of telomerase. It was recently revealed that replication stress triggers break-induced replication (BIR) and mitotic DNA synthesis (MiDAS) at mammalian telomeres; however, these mechanisms are error prone and primarily utilized in tumorigenic contexts. In this review article, we discuss the consequences of replication stress at telomeres and how use of available repair pathways contributes to genomic instability. Current research suggests that fragile telomeres are ultimately tumor-suppressive and thus may be better left unrepaired.
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Affiliation(s)
- Kirsten A Brenner
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Jayakrishnan Nandakumar
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
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Bhargava R, Lynskey ML, O’Sullivan RJ. New twists to the ALTernative endings at telomeres. DNA Repair (Amst) 2022; 115:103342. [DOI: 10.1016/j.dnarep.2022.103342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/02/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022]
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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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Lu R, Pickett HA. Telomeric replication stress: the beginning and the end for alternative lengthening of telomeres cancers. Open Biol 2022; 12:220011. [PMID: 35259951 PMCID: PMC8905155 DOI: 10.1098/rsob.220011] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Telomeres are nucleoprotein structures that cap the ends of linear chromosomes. Telomeric DNA comprises terminal tracts of G-rich tandem repeats, which are inherently difficult for the replication machinery to navigate. Structural aberrations that promote activation of the alternative lengthening of telomeres (ALT) pathway of telomere maintenance exacerbate replication stress at ALT telomeres, driving fork stalling and fork collapse. This form of telomeric DNA damage perpetuates recombination-mediated repair pathways and break-induced telomere synthesis. The relationship between replication stress and DNA repair is tightly coordinated for the purpose of regulating telomere length in ALT cells, but has been shown to be experimentally manipulatable. This raises the intriguing possibility that induction of replication stress can be used as a means to cause toxic levels of DNA damage at ALT telomeres, thereby selectively disrupting the viability of ALT cancers.
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Affiliation(s)
- Robert Lu
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Hilda A. Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
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41
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Li D, Hou K, Zhang K, Jia S. Regulation of Replication Stress in Alternative Lengthening of Telomeres by Fanconi Anaemia Protein. Genes (Basel) 2022; 13:genes13020180. [PMID: 35205225 PMCID: PMC8872277 DOI: 10.3390/genes13020180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/17/2022] [Accepted: 01/19/2022] [Indexed: 02/04/2023] Open
Abstract
Fanconi anaemia (FA)-related proteins function in interstrand crosslink (ICL) repair pathways and multiple damage repair pathways. Recent studies have found that FA proteins are involved in the regulation of replication stress (RS) in alternative lengthening of telomeres (ALT). Since ALT cells often exhibit high-frequency ATRX mutations and high levels of telomeric secondary structure, high levels of DNA damage and replicative stress exist in ALT cells. Persistent replication stress is required to maintain the activity of ALT mechanistically, while excessive replication stress causes ALT cell death. FA proteins such as FANCD2 and FANCM are involved in the regulation of this balance by resolving or inhibiting the formation of telomere secondary structures to stabilize stalled replication forks and promote break-induced repair (BIR) to maintain the survival of ALT tumour cells. Therefore, we review the role of FA proteins in replication stress in ALT cells, providing a rationale and direction for the targeted treatment of ALT tumours.
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42
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Epum EA, Haber JE. DNA replication: the recombination connection. Trends Cell Biol 2022; 32:45-57. [PMID: 34384659 PMCID: PMC8688190 DOI: 10.1016/j.tcb.2021.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 01/03/2023]
Abstract
Failure to complete DNA replication is one of the major sources of genome instability leading to aneuploidy, chromosome breakage, and chromosome rearrangements that are associated with human cancer. One of the surprising revelations of the past decade is that the completion of replication at so-called common fragile sites (CFS) occurs very late in the cell cycle - at mitosis - through a process termed MiDAS (mitotic DNA synthesis). MiDAS is strongly related to another cancer-promoting phenomenon: the activation of alternative lengthening of telomeres (ALT). Our understanding of the mechanisms of ALT and MiDAS in mammalian cells has drawn heavily from recent advances in the study of break-induced replication (BIR), especially in budding yeast. We provide new insights into the BIR, MiDAS, and ALT pathways and their shared similarities.
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43
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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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44
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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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45
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Rossi MJ, DiDomenico SF, Patel M, Mazin AV. RAD52: Paradigm of Synthetic Lethality and New Developments. Front Genet 2021; 12:780293. [PMID: 34887904 PMCID: PMC8650160 DOI: 10.3389/fgene.2021.780293] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/05/2021] [Indexed: 12/31/2022] Open
Abstract
DNA double-strand breaks and inter-strand cross-links are the most harmful types of DNA damage that cause genomic instability that lead to cancer development. The highest fidelity pathway for repairing damaged double-stranded DNA is termed Homologous recombination (HR). Rad52 is one of the key HR proteins in eukaryotes. Although it is critical for most DNA repair and recombination events in yeast, knockouts of mammalian RAD52 lack any discernable phenotypes. As a consequence, mammalian RAD52 has been long overlooked. That is changing now, as recent work has shown RAD52 to be critical for backup DNA repair pathways in HR-deficient cancer cells. Novel findings have shed light on RAD52's biochemical activities. RAD52 promotes DNA pairing (D-loop formation), single-strand DNA and DNA:RNA annealing, and inverse strand exchange. These activities contribute to its multiple roles in DNA damage repair including HR, single-strand annealing, break-induced replication, and RNA-mediated repair of DNA. The contributions of RAD52 that are essential to the viability of HR-deficient cancer cells are currently under investigation. These new findings make RAD52 an attractive target for the development of anti-cancer therapies against BRCA-deficient cancers.
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46
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Kent T, Clynes D. Alternative Lengthening of Telomeres: Lessons to Be Learned from Telomeric DNA Double-Strand Break Repair. Genes (Basel) 2021; 12:1734. [PMID: 34828344 PMCID: PMC8619803 DOI: 10.3390/genes12111734] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 10/22/2021] [Accepted: 10/28/2021] [Indexed: 12/25/2022] Open
Abstract
The study of the molecular pathways underlying cancer has given us important insights into how breaks in our DNA are repaired and the dire consequences that can occur when these processes are perturbed. Extensive research over the past 20 years has shown that the key molecular event underpinning a subset of cancers involves the deregulated repair of DNA double-strand breaks (DSBs) at telomeres, which in turn leads to telomere lengthening and the potential for replicative immortality. Here we discuss, in-depth, recent major breakthroughs in our understanding of the mechanisms underpinning this pathway known as the alternative lengthening of telomeres (ALT). We explore how this gives us important insights into how DSB repair at telomeres is regulated, with relevance to the cell-cycle-dependent regulation of repair, repair of stalled replication forks and the spatial regulation of DSB repair.
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Affiliation(s)
- Thomas Kent
- Molecular Haematology Unit, Radcliffe Department of Medicine, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK;
| | - David Clynes
- Department of Oncology, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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47
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Wu X, Malkova A. Break-induced replication mechanisms in yeast and mammals. Curr Opin Genet Dev 2021; 71:163-170. [PMID: 34481360 DOI: 10.1016/j.gde.2021.08.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/17/2021] [Accepted: 08/05/2021] [Indexed: 11/26/2022]
Abstract
Break-induced replication (BIR) is a pathway specialized in repair of double-strand DNA breaks with only one end capable of invading homologous template that can arise following replication collapse, telomere erosion or DNA cutting by site-specific endonucleases. For a long time, yeast remained the only model system to study BIR. Studies in yeast demonstrated that BIR represents an unusual mode of DNA synthesis that is driven by a migrating bubble and leads to conservative inheritance of newly synthesized DNA. This unusual type of DNA synthesis leads to high levels of mutations and chromosome rearrangements. Recently, multiple examples of BIR were uncovered in mammalian cells that allowed the comparison of BIR between organisms. It appeared initially that BIR in mammalian cells is predominantly independent of RAD51, and therefore different from BIR that is predominantly Rad51-dependent in yeast. However, a series of systematic studies utilizing site-specific DNA breaks for BIR initiation in mammalian reporters led to the discovery of highly efficient RAD51-dependent BIR, allowing side-by side comparison with BIR in yeast which is the focus of this review.
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Affiliation(s)
- Xiaohua Wu
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, United States.
| | - Anna Malkova
- Department of Biology, University of Iowa, Iowa City, IA 52242, United States.
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48
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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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49
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Homology length dictates the requirement for Rad51 and Rad52 in gene targeting in the Basidiomycota yeast Naganishia liquefaciens. Curr Genet 2021; 67:919-936. [PMID: 34296348 DOI: 10.1007/s00294-021-01201-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 07/05/2021] [Accepted: 07/05/2021] [Indexed: 10/20/2022]
Abstract
Here, we report the development of methodologies that enable genetic modification of a Basidiomycota yeast, Naganishia liquifaciens. The gene targeting method employs electroporation with PCR products flanked by an 80 bp sequence homologous to the target. The method, combined with a newly devised CRISPR-Cas9 system, routinely achieves 80% gene targeting efficiency. We further explored the genetic requirement for this homologous recombination (HR)-mediated gene targeting. The absence of Ku70, a major component of the non-homologous end joining (NHEJ) pathway of DNA double-strand break repair, almost completely eliminated inaccurate integration of the marker. Gene targeting with short homology (80 bp) was almost exclusively dependent on Rad52, an essential component of HR in the Ascomycota yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. By contrast, the RecA homolog Rad51, which performs homology search and strand exchange in HR, plays a relatively minor role in gene targeting, regardless of the homology length (80 bp or 1 kb). The absence of both Rad51 and Rad52, however, completely eliminated gene targeting. Unlike Ascomycota yeasts, the absence of Rad52 in N. liquefaciens conferred only mild sensitivity to ionizing radiation. These traits associated with the absence of Rad52 are reminiscent of findings in mice.
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50
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Robinson NJ, Miyagi M, Scarborough JA, Scott JG, Taylor DJ, Schiemann WP. SLX4IP promotes RAP1 SUMOylation by PIAS1 to coordinate telomere maintenance through NF-κB and Notch signaling. Sci Signal 2021; 14:eabe9613. [PMID: 34187905 PMCID: PMC8353884 DOI: 10.1126/scisignal.abe9613] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The maintenance of telomere length supports repetitive cell division and therefore plays a central role in cancer development and progression. Telomeres are extended by either the enzyme telomerase or the alternative lengthening of telomeres (ALT) pathway. Here, we found that the telomere-associated protein SLX4IP dictates telomere proteome composition by recruiting and activating the E3 SUMO ligase PIAS1 to the SLX4 complex. PIAS1 SUMOylated the telomere-binding protein RAP1, which disrupted its interaction with the telomere-binding protein TRF2 and facilitated its nucleocytoplasmic shuttling. In the cytosol, RAP1 bound to IκB kinase (IKK), resulting in activation of the transcription factor NF-κB and its induction of Jagged-1 expression, which promoted Notch signaling and the institution of ALT. This axis could be targeted therapeutically in ALT-driven cancers and in tumor cells that develop resistance to antitelomerase therapies. Our results illuminate the mechanisms underlying SLX4IP-dependent telomere plasticity and demonstrate the role of telomere proteins in directly coordinating intracellular signaling and telomere maintenance dynamics.
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Affiliation(s)
- Nathaniel J Robinson
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Masaru Miyagi
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Jessica A Scarborough
- Department of Translational Hematology and Oncology Research, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Jacob G Scott
- Department of Translational Hematology and Oncology Research, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Derek J Taylor
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - William P Schiemann
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA.
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