1
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Kim S, Park SH, Kang N, Ra JS, Myung K, Lee KY. Polyubiquitinated PCNA triggers SLX4-mediated break-induced replication in alternative lengthening of telomeres (ALT) cancer cells. Nucleic Acids Res 2024:gkae785. [PMID: 39291733 DOI: 10.1093/nar/gkae785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 08/23/2024] [Accepted: 08/29/2024] [Indexed: 09/19/2024] Open
Abstract
Replication stresses are the major source of break-induced replication (BIR). Here, we show that in alternative lengthening of telomeres (ALT) cells, replication stress-induced polyubiquitinated proliferating cell nuclear antigen (PCNA) (polyUb-PCNA) triggers BIR at telomeres and the common fragile site (CFS). Consistently, depleting RAD18, a PCNA ubiquitinating enzyme, reduces the occurrence of ALT-associated promyelocytic leukemia (PML) bodies (APBs) and mitotic DNA synthesis at telomeres and CFS, both of which are mediated by BIR. In contrast, inhibiting ubiquitin-specific protease 1 (USP1), an Ub-PCNA deubiquitinating enzyme, results in an increase in the above phenotypes in a RAD18- and UBE2N (the PCNA polyubiquitinating enzyme)-dependent manner. Furthermore, deficiency of ATAD5, which facilitates USP1 activity and unloads PCNAs, augments recombination-associated phenotypes. Mechanistically, telomeric polyUb-PCNA accumulates SLX4, a nuclease scaffold, at telomeres through its ubiquitin-binding domain and increases telomere damage. Consistently, APB increase induced by Ub-PCNA depends on SLX4 and structure-specific endonucleases. Taken together, our results identified the polyUb-PCNA-SLX4 axis as a trigger for directing BIR.
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Affiliation(s)
- Sangin Kim
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
- Department of Biological Sciences, College of Information-Bio Convergence Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Su Hyung Park
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
- Department of Biomedical Engineering, College of Information-Bio Convergence Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Nalae Kang
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
| | - Jae Sun Ra
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
| | - Kyungjae Myung
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
- Department of Biomedical Engineering, College of Information-Bio Convergence Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Kyoo-Young Lee
- Center for Genomic Integrity, Institute for Basic Science, Ulsan 44919, Korea
- Department of Biochemistry, College of Medicine, Hallym University, Chuncheon 24252, Gangwon-do, Republic of Korea
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2
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Panda S, Roychowdhury T, Dutta A, Chakraborty S, Das T, Chatterjee S. ALTering Cancer by Triggering Telomere Replication Stress through the Stabilization of Promoter G-Quadruplex in SMARCAL1. ACS Chem Biol 2024; 19:1433-1439. [PMID: 38959478 DOI: 10.1021/acschembio.4c00285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
Most of the human cancers are dependent on telomerase to extend the telomeres. But ∼10% of all cancers use a telomerase-independent, homologous recombination mediated pathway called alternative lengthening of telomeres (ALT). Due to the poor prognosis, ALT status is not being considered yet in the diagnosis of cancer. No such specific treatment is available to date for ALT positive cancers. ALT positive cancers are dependent on replication stress to deploy DNA repair pathways to the telomeres to execute homologous recombination mediated telomere extension. SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent regulator of chromatin, subfamily A-like 1) is associated with the ALT telomeres to resolve replication stress thus providing telomere stability. Thus, the dependency on replication stress regulatory factors like SMARCAL1 made it a suitable therapeutic target for the treatment of ALT positive cancers. In this study, we found a significant downregulation of SMARCAL1 expression by stabilizing the G-quadruplex (G4) motif found in the promoter of SMARCAL1 by potent G4 stabilizers, like TMPyP4 and BRACO-19. SMARCAL1 downregulation led toward the increased localization of PML (promyelocytic leukemia) bodies in ALT telomeres and triggered the formation of APBs (ALT-associated promyelocytic leukemia bodies) in ALT positive cell lines, increasing telomere replication stress and DNA damage at a genomic level. Induction of replication stress and hyper-recombinogenic phenotype in ALT positive cells mediated by G4 stabilizing molecules already highlighted their possible application as a new therapeutic window to target ALT positive tumors. In accordance with this, our study will also provide a valuable insight toward the development of G4-based ALT therapeutics targeting SMARCAL1.
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Affiliation(s)
- Suman Panda
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
| | - Tanaya Roychowdhury
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, New York 10065, United States of America
| | - Anindya Dutta
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
| | - Sourio Chakraborty
- Division of Molecular Medicine, Centenary Campus, Bose Institute, P-1/12 C.I.T. Scheme VII-M, Kolkata 700054, India
| | - Tanya Das
- Division of Molecular Medicine, Centenary Campus, Bose Institute, P-1/12 C.I.T. Scheme VII-M, Kolkata 700054, India
| | - Subhrangsu Chatterjee
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
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3
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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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4
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Machitani M, Nomura A, Yamashita T, Yasukawa M, Ueki S, Fujita KI, Ueno T, Yamashita A, Tanzawa Y, Watanabe M, Taniguchi T, Saitoh N, Kaneko S, Kato Y, Mano H, Masutomi K. Maintenance of R-loop structures by phosphorylated hTERT preserves genome integrity. Nat Cell Biol 2024; 26:932-945. [PMID: 38806647 DOI: 10.1038/s41556-024-01427-6] [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: 07/18/2023] [Accepted: 04/23/2024] [Indexed: 05/30/2024]
Abstract
As aberrant accumulation of RNA-DNA hybrids (R-loops) causes DNA damage and genome instability, cells express regulators of R-loop structures. Here we report that RNA-dependent RNA polymerase (RdRP) activity of human telomerase reverse transcriptase (hTERT) regulates R-loop formation. We found that the phosphorylated form of hTERT (p-hTERT) exhibits RdRP activity in nuclear speckles both in telomerase-positive cells and telomerase-negative cells with alternative lengthening of telomeres (ALT) activity. The p-hTERT did not associate with telomerase RNA component in nuclear speckles but, instead, with TERRA RNAs to resolve R-loops. Targeting of the TERT gene in ALT cells ablated RdRP activity and impaired tumour growth. Using a genome-scale CRISPR loss-of-function screen, we identified Fanconi anaemia/BRCA genes as synthetic lethal partners of hTERT RdRP. Inactivation of RdRP and Fanconi anaemia/BRCA genes caused accumulation of R-loop structures and DNA damage. These findings indicate that RdRP activity of p-hTERT guards against genome instability by removing R-loop structures.
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Affiliation(s)
- Mitsuhiro Machitani
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan
| | - Akira Nomura
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan
- Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Isehara, Japan
| | - Taro Yamashita
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan
| | - Mami Yasukawa
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan
| | - Saori Ueki
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan
| | - Ken-Ichi Fujita
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan
| | - Toshihide Ueno
- Division of Cellular Signaling, National Cancer Center Research Institute, Tokyo, Japan
| | - Akio Yamashita
- Department of Investigative Medicine, University of the Ryukyus Graduate School of Medicine, Nakagami, Japan
| | - Yoshikazu Tanzawa
- Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Isehara, Japan
| | - Masahiko Watanabe
- Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, Isehara, Japan
| | - Toshiyasu Taniguchi
- Department of Molecular Life Science, Tokai University School of Medicine, Isehara, Japan
| | - Noriko Saitoh
- Division of Cancer Biology, The Cancer Institute of JFCR, Tokyo, Japan
| | - Shuichi Kaneko
- Department of Gastroenterology, Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan
| | - Yukinari Kato
- Department of Antibody Drug Development, Tohoku University Graduate School of Medicine, Sendai, Japan
- Department of Molecular Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Hiroyuki Mano
- Division of Cellular Signaling, National Cancer Center Research Institute, Tokyo, Japan
| | - Kenkichi Masutomi
- Division of Cancer Stem Cell, National Cancer Center Research Institute, Tokyo, Japan.
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5
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Lee J, Lee J, Sohn EJ, Taglialatela A, O’Sullivan RJ, Ciccia A, Min J. Extrachromosomal telomere DNA derived from excessive strand displacements. Proc Natl Acad Sci U S A 2024; 121:e2318438121. [PMID: 38696464 PMCID: PMC11087782 DOI: 10.1073/pnas.2318438121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 04/03/2024] [Indexed: 05/04/2024] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism mediated by break-induced replication, evident in approximately 15% of human cancers. A characteristic feature of ALT cancers is the presence of C-circles, circular single-stranded telomeric DNAs composed of C-rich sequences. Despite the fact that extrachromosomal C-rich single-stranded DNAs (ssDNAs), including C-circles, are unique to ALT cells, their generation process remains undefined. Here, we introduce a method to detect single-stranded telomeric DNA, called 4SET (Strand-Specific Southern-blot for Single-stranded Extrachromosomal Telomeres) assay. Utilizing 4SET, we are able to capture C-rich single-stranded DNAs that are near 200 to 1500 nucleotides in size. Both linear C-rich ssDNAs and C-circles are abundant in the fractions of cytoplasm and nucleoplasm, which supports the idea that linear and circular C-rich ssDNAs are generated concurrently. We also found that C-rich ssDNAs originate during Okazaki fragment processing during lagging strand DNA synthesis. The generation of C-rich ssDNA requires CST-PP (CTC1/STN1/TEN1-PRIMASE-Polymerase alpha) complex-mediated priming of the C-strand DNA synthesis and subsequent excessive strand displacement of the C-rich strand mediated by the DNA Polymerase delta and the BLM helicase. Our work proposes a model for the generation of C-rich ssDNAs and C-circles during ALT-mediated telomere elongation.
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Affiliation(s)
- Junyeop Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Jina Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Eric J. Sohn
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Angelo Taglialatela
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Roderick J. O’Sullivan
- Department of Pharmacology and Chemical Biology, Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA15213
| | - Alberto Ciccia
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY10032
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6
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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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7
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Olson CL, Wuttke DS. Guardians of the Genome: How the Single-Stranded DNA-Binding Proteins RPA and CST Facilitate Telomere Replication. Biomolecules 2024; 14:263. [PMID: 38540683 PMCID: PMC10968030 DOI: 10.3390/biom14030263] [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: 12/21/2023] [Revised: 02/02/2024] [Accepted: 02/20/2024] [Indexed: 04/26/2024] Open
Abstract
Telomeres act as the protective caps of eukaryotic linear chromosomes; thus, proper telomere maintenance is crucial for genome stability. Successful telomere replication is a cornerstone of telomere length regulation, but this process can be fraught due to the many intrinsic challenges telomeres pose to the replication machinery. In addition to the famous "end replication" problem due to the discontinuous nature of lagging strand synthesis, telomeres require various telomere-specific steps for maintaining the proper 3' overhang length. Bulk telomere replication also encounters its own difficulties as telomeres are prone to various forms of replication roadblocks. These roadblocks can result in an increase in replication stress that can cause replication forks to slow, stall, or become reversed. Ultimately, this leads to excess single-stranded DNA (ssDNA) that needs to be managed and protected for replication to continue and to prevent DNA damage and genome instability. RPA and CST are single-stranded DNA-binding protein complexes that play key roles in performing this task and help stabilize stalled forks for continued replication. The interplay between RPA and CST, their functions at telomeres during replication, and their specialized features for helping overcome replication stress at telomeres are the focus of this review.
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Affiliation(s)
- Conner L. Olson
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Deborah S. Wuttke
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA
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8
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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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9
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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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10
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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: 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: 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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11
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Nickoloff JA, Jaiswal AS, Sharma N, Williamson EA, Tran MT, Arris D, Yang M, Hromas R. Cellular Responses to Widespread DNA Replication Stress. Int J Mol Sci 2023; 24:16903. [PMID: 38069223 PMCID: PMC10707325 DOI: 10.3390/ijms242316903] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 11/22/2023] [Accepted: 11/27/2023] [Indexed: 12/18/2023] Open
Abstract
Replicative DNA polymerases are blocked by nearly all types of DNA damage. The resulting DNA replication stress threatens genome stability. DNA replication stress is also caused by depletion of nucleotide pools, DNA polymerase inhibitors, and DNA sequences or structures that are difficult to replicate. Replication stress triggers complex cellular responses that include cell cycle arrest, replication fork collapse to one-ended DNA double-strand breaks, induction of DNA repair, and programmed cell death after excessive damage. Replication stress caused by specific structures (e.g., G-rich sequences that form G-quadruplexes) is localized but occurs during the S phase of every cell division. This review focuses on cellular responses to widespread stress such as that caused by random DNA damage, DNA polymerase inhibition/nucleotide pool depletion, and R-loops. Another form of global replication stress is seen in cancer cells and is termed oncogenic stress, reflecting dysregulated replication origin firing and/or replication fork progression. Replication stress responses are often dysregulated in cancer cells, and this too contributes to ongoing genome instability that can drive cancer progression. Nucleases play critical roles in replication stress responses, including MUS81, EEPD1, Metnase, CtIP, MRE11, EXO1, DNA2-BLM, SLX1-SLX4, XPF-ERCC1-SLX4, Artemis, XPG, FEN1, and TATDN2. Several of these nucleases cleave branched DNA structures at stressed replication forks to promote repair and restart of these forks. We recently defined roles for EEPD1 in restarting stressed replication forks after oxidative DNA damage, and for TATDN2 in mitigating replication stress caused by R-loop accumulation in BRCA1-defective cells. We also discuss how insights into biological responses to genome-wide replication stress can inform novel cancer treatment strategies that exploit synthetic lethal relationships among replication stress response factors.
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Affiliation(s)
- Jac A. Nickoloff
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Aruna S. Jaiswal
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
| | - Neelam Sharma
- Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, CO 80523, USA
| | - Elizabeth A. Williamson
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
| | - Manh T. Tran
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
| | - Dominic Arris
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
| | - Ming Yang
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
| | - Robert Hromas
- Department of Medicine and the Mays Cancer Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA; (A.S.J.); (M.T.T.); (R.H.)
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12
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Rosso I, Jones-Weinert C, Rossiello F, Cabrini M, Brambillasca S, Munoz-Sagredo L, Lavagnino Z, Martini E, Tedone E, Garre' M, Aguado J, Parazzoli D, Mione M, Shay JW, Mercurio C, d'Adda di Fagagna F. Alternative lengthening of telomeres (ALT) cells viability is dependent on C-rich telomeric RNAs. Nat Commun 2023; 14:7086. [PMID: 37925537 PMCID: PMC10625592 DOI: 10.1038/s41467-023-42831-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 10/23/2023] [Indexed: 11/06/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism activated in ~10-15% of cancers, characterized by telomeric damage. Telomeric damage-induced long non-coding RNAs (dilncRNAs) are transcribed at dysfunctional telomeres and contribute to telomeric DNA damage response (DDR) activation and repair. Here we observed that telomeric dilncRNAs are preferentially elevated in ALT cells. Inhibition of C-rich (teloC) dilncRNAs with antisense oligonucleotides leads to DNA replication stress responses, increased genomic instability, and apoptosis induction selectively in ALT cells. Cell death is dependent on DNA replication and is increased by DNA replication stress. Mechanistically, teloC dilncRNA inhibition reduces RAD51 and 53BP1 recruitment to telomeres, boosts the engagement of BIR machinery, and increases C-circles and telomeric sister chromatid exchanges, without increasing telomeric non-S phase synthesis. These results indicate that teloC dilncRNA is necessary for a coordinated recruitment of DDR factors to ALT telomeres and it is essential for ALT cancer cells survival.
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Affiliation(s)
- Ilaria Rosso
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Corey Jones-Weinert
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- The Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Matteo Cabrini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Silvia Brambillasca
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Leonel Munoz-Sagredo
- Institute of Biological and Chemical Systems - Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- School of Medicine, Universidad de Valparaiso, Valparaiso, Chile
| | - Zeno Lavagnino
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Emanuele Martini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Milan, Italy
| | - Enzo Tedone
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Massimiliano Garre'
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- RCSI, Royal College of Surgeons in Ireland, Department of Chemistry, Dublin, Ireland
| | - Julio Aguado
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Dario Parazzoli
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Marina Mione
- Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ciro Mercurio
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Fabrizio d'Adda di Fagagna
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy.
- Institute of Molecular Genetics IGM-CNR "Luigi Luca Cavalli-Sforza", Pavia, Italy.
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13
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Lee J, Lee J, Sohn EJ, Taglialatela A, O’Sullivan RJ, Ciccia A, Min J. Extrachromosomal Telomeres Derived from Excessive Strand Displacements. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.31.551186. [PMID: 37577643 PMCID: PMC10418088 DOI: 10.1101/2023.07.31.551186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Alternative Lengthening of Telomeres (ALT) is a telomere maintenance mechanism mediated by break-induced replication (BIR), evident in approximately 15% of human cancers. A characteristic feature of ALT cancers is the presence of C-circles, circular single-stranded telomeric DNAs composed of C-rich sequences. Despite the fact that extrachromosomal C-rich single-stranded DNAs (ssDNAs), unique to ALT cells, are considered potential precursors of C-circles, their generation process remains undefined. Here, we introduce a highly sensitive method to detect single stranded telomeric DNA, called 4SET (Strand-Specific Southern-blot for Single-stranded Extrachromosomal Telomeres) assay. Utilizing 4SET, we are able to capture C-rich single stranded DNAs that are near 200 to 1500 nucleotides in size. Both linear C-rich ssDNAs and C-circles are abundant in the fractions of cytoplasm and nucleoplasm, which supports the idea that linear C-rich ssDNA accumulation may indeed precede C-circle formation. We also found that C-rich ssDNAs originate during Okazaki fragment processing during lagging strand DNA synthesis. The generation of C-rich ssDNA requires CST-PP (CTC1/STN1/TEN1-PRIMASE-Polymerase alpha) complex-mediated priming of the C-strand DNA synthesis and subsequent excessive strand displacement of the C-rich strand mediated by the DNA Polymerase delta and the BLM helicase. Our work proposes a new model for the generation of C-rich ssDNAs and C-circles during ALT-mediated telomere elongation.
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Affiliation(s)
- Junyeop Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Jina Lee
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Eric J. Sohn
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Roderick J. O’Sullivan
- Department of Pharmacology and Chemical Biology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, USA
| | - Alberto Ciccia
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Genetics and Development, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
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14
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Sung S, Kim E, Niida H, Kim C, Lee J. Distinct characteristics of two types of alternative lengthening of telomeres in mouse embryonic stem cells. Nucleic Acids Res 2023; 51:9122-9143. [PMID: 37496110 PMCID: PMC10516625 DOI: 10.1093/nar/gkad617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 06/27/2023] [Accepted: 07/13/2023] [Indexed: 07/28/2023] Open
Abstract
Telomere length must be maintained in actively dividing cells to avoid cellular arrest or death. In the absence of telomerase activity, activation of alternative lengthening of telomeres (ALT) allows the maintenance of telomeric length and prolongs the cellular lifespan. Our previous studies have established two types of ALT survivors from mouse embryonic stem cells. The key differences between these ALT survivors are telomere-constituting sequences: non-telomeric sequences and canonical telomeric repeats, with each type of ALT survivors being referred to as type I and type II, respectively. We explored how the characteristics of the two types of ALT lines reflect their fates using multi-omics approaches. The most notable gene expression signatures of type I and type II ALT cell lines were chromatin remodelling and DNA repair, respectively. Compared with type II cells, type I ALT cells accumulated more mutations and demonstrated persistent telomere instability. These findings indicate that cells of the same origin have separate routes for survival, thus providing insights into the plasticity of crisis-suffering cells and cancers.
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Affiliation(s)
- Sanghyun Sung
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
| | - Eunkyeong Kim
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
| | - Hiroyuki Niida
- Department of Molecular Biology, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka 431-3192, Japan
| | - Chuna Kim
- Aging Convergence Research Center, Korea Research Institute of Bioscience and Biotechnology, Gwahak-ro 125, Daejeon 34141, Korea
- Department of Bioinformatics, KRIBB School of Bioscience, Korea University of Science and Technology (UST), Daejeon 34113, Korea
| | - Junho Lee
- Department of Biological Sciences, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
- Institute of Molecular Biology and Genetics, Seoul National University, Gwanak-ro 1, Seoul 08826, Korea
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15
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Liu H, Xu C, Diplas BH, Brown A, Strickland LM, Yao H, Ling J, McLendon RE, Keir ST, Ashley DM, He Y, Waitkus MS. Cancer-associated SMARCAL1 loss-of-function mutations promote alternative lengthening of telomeres and tumorigenesis in telomerase-negative glioblastoma cells. Neuro Oncol 2023; 25:1563-1575. [PMID: 36689342 PMCID: PMC10484176 DOI: 10.1093/neuonc/noad022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Telomere maintenance mechanisms are required to enable the replicative immortality of malignant cells. While most cancers activate the enzyme telomerase, a subset of cancers uses telomerase-independent mechanisms termed alternative lengthening of telomeres (ALT). ALT occurs via homology-directed-repair mechanisms and is frequently associated with ATRX mutations. We previously showed that a subset of adult glioblastoma (GBM) patients with ATRX-expressing ALT-positive tumors harbored loss-of-function mutations in the SMARCAL1 gene, which encodes an annealing helicase involved in replication fork remodeling and the resolution of replication stress. However, the causative relationship between SMARCAL1 deficiency, tumorigenesis, and de novo telomere synthesis is not understood. METHODS We used a patient-derived ALT-positive GBM cell line with native SMARCAL1 deficiency to investigate the role of SMARCAL1 in ALT-mediated de novo telomere synthesis, replication stress, and gliomagenesis in vivo. RESULTS Inducible rescue of SMARCAL1 expression suppresses ALT indicators and inhibits de novo telomere synthesis in GBM and osteosarcoma cells, suggesting that SMARCAL1 deficiency plays a functional role in ALT induction in cancers that natively lack SMARCAL1 function. SMARCAL1-deficient ALT-positive cells can be serially propagated in vivo in the absence of detectable telomerase activity, demonstrating that the SMARCAL1-deficient ALT phenotype maintains telomeres in a manner that promotes tumorigenesis. CONCLUSIONS SMARCAL1 deficiency is permissive to ALT and promotes gliomagenesis. Inducible rescue of SMARCAL1 in ALT-positive cell lines permits the dynamic modulation of ALT activity, which will be valuable for future studies aimed at understanding the mechanisms of ALT and identifying novel anticancer therapeutics that target the ALT phenotype.
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Affiliation(s)
- Heng Liu
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Cheng Xu
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Bill H Diplas
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Alexandrea Brown
- 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
| | - Laura M Strickland
- 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
| | - Haipei Yao
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Jinjie Ling
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Roger E McLendon
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Stephen T Keir
- 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
| | - 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
| | - Yiping He
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - 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
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16
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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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17
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Aguilera P, Dubarry M, Géli V, Simon MN. NPCs and APBs: two HUBs of non-canonical homology-based recombination at telomeres? Cell Cycle 2023; 22:1163-1168. [PMID: 37128641 PMCID: PMC10193864 DOI: 10.1080/15384101.2023.2206350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 10/05/2022] [Accepted: 10/10/2022] [Indexed: 05/03/2023] Open
Abstract
Apart from a few rare exceptions, the maintenance of functional telomeres by recombination-based mechanisms is restricted to accidental and/or pathological situations. Originally described in the yeast S. cerevisiae, this mode of telomere repair has gained interest with the discovery of telomerase negative cancers that use alternative lengthening of telomeres (ALT cancer) dependent on homologous recombination. In both yeast and humans, it has been shown that recombination at telomeres is spatially regulated and occurs preferentially at the nuclear pore complexes (NPCs) in yeast and at ALT-associated promyelocytic leukemia nuclear bodies (APBs) in human cells. Here, we discuss the potential relationships between these two membrane-less structures and their role in enabling unconventional recombination pathways.
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Affiliation(s)
- Paula Aguilera
- Centro Andaluz de Biologia Molecular y Medicina Regenerativa (CABIMER), Consejo Superior de Investigaciones Cientificas (CSIC), Universidad de Sevilla, Universidad Pablo de Olavide, Seville, Spain
| | - Marion Dubarry
- MAP Laboratory, INSA Lyon, Claude Bernard University UMR5240, Villeurbanne, France
| | - Vincent Géli
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisee Ligue, Aix Marseille University, Marseille, France
| | - Marie-Noëlle Simon
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe labellisee Ligue, Aix Marseille University, Marseille, France
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18
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Singh M, MacKenzie D, Desai S, Batista N, Zhang D. Diagnostic Biomarkers and Therapeutic Targets of Alternative Lengthening of Telomeres-Positive Cancers. Genet Test Mol Biomarkers 2023; 27:123-125. [PMID: 37115645 DOI: 10.1089/gtmb.2023.29069.mas] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
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19
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Sohn EJ, Goralsky JA, Shay JW, Min J. The Molecular Mechanisms and Therapeutic Prospects of Alternative Lengthening of Telomeres (ALT). Cancers (Basel) 2023; 15:cancers15071945. [PMID: 37046606 PMCID: PMC10093677 DOI: 10.3390/cancers15071945] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 04/14/2023] Open
Abstract
As detailed by the end replication problem, the linear ends of a cell's chromosomes, known as telomeres, shorten with each successive round of replication until a cell enters into a state of growth arrest referred to as senescence. To maintain their immortal proliferation capacity, cancer cells must employ a telomere maintenance mechanism, such as telomerase activation or the Alternative Lengthening of Telomeres pathway (ALT). With only 10-15% of cancers utilizing the ALT mechanism, progress towards understanding its molecular components and associated hallmarks has only recently been made. This review analyzes the advances towards understanding the ALT pathway by: (1) detailing the mechanisms associated with engaging the ALT pathway as well as (2) identifying potential therapeutic targets of ALT that may lead to novel cancer therapeutic treatments. Collectively, these studies indicate that the ALT molecular mechanisms involve at least two distinct pathways induced by replication stress and damage at telomeres. We suggest exploiting tumor dependency on ALT is a promising field of study because it suggests new approaches to ALT-specific therapies for cancers with poorer prognosis. While substantial progress has been made in the ALT research field, additional progress will be required to realize these advances into clinical practices to treat ALT cancers and improve patient prognoses.
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Affiliation(s)
- Eric J Sohn
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Julia A Goralsky
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
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20
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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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21
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The alternative lengthening of telomeres mechanism jeopardizes telomere integrity if not properly restricted. Proc Natl Acad Sci U S A 2022; 119:e2208669119. [PMID: 36122232 PMCID: PMC9522348 DOI: 10.1073/pnas.2208669119] [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] [Indexed: 11/24/2022] Open
Abstract
A substantial number of human cancers are telomerase-negative and elongate physiologically damaged telomeres through a break-induced replication (BIR)-based mechanism known as alternative lengthening of telomeres (ALT). We recently demonstrated that inhibiting the transcription of the telomeric long noncoding RNA TERRA suppresses telomere damage and ALT features, indicating that telomere transcription is a main trigger of ALT activity. Here we show that experimentally increased TERRA transcription not only increases ALT features, as expected, but also causes rapid loss of telomeric DNA through a pathway that requires the endonuclease Mus81. Our data indicate that the ALT mechanism can endanger telomere integrity if not properly controlled and point to TERRA transcription as a uniquely versatile target for therapy.
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