1
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Sang PB, Jaiswal RK, Lyu X, Chai W. Human CST complex restricts excessive PrimPol repriming upon UV induced replication stress by suppressing p21. Nucleic Acids Res 2024; 52:3778-3793. [PMID: 38348929 DOI: 10.1093/nar/gkae078] [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: 09/05/2023] [Revised: 01/18/2024] [Accepted: 01/26/2024] [Indexed: 04/25/2024] Open
Abstract
DNA replication stress, caused by various endogenous and exogenous agents, halt or stall DNA replication progression. Cells have developed diverse mechanisms to tolerate and overcome replication stress, enabling them to continue replication. One effective strategy to overcome stalled replication involves skipping the DNA lesion using a specialized polymerase known as PrimPol, which reinitiates DNA synthesis downstream of the damage. However, the mechanism regulating PrimPol repriming is largely unclear. In this study, we observe that knockdown of STN1 or CTC1, components of the CTC1/STN1/TEN1 complex, leads to enhanced replication progression following UV exposure. We find that such increased replication is dependent on PrimPol, and PrimPol recruitment to stalled forks increases upon CST depletion. Moreover, we find that p21 is upregulated in STN1-depleted cells in a p53-independent manner, and p21 depletion restores normal replication rates caused by STN1 deficiency. We identify that p21 interacts with PrimPol, and STN1 depletion stimulates p21-PrimPol interaction and facilitates PrimPol recruitment to stalled forks. Our findings reveal a previously undescribed interplay between CST, PrimPol and p21 in promoting repriming in response to stalled replication, and shed light on the regulation of PrimPol repriming at stalled forks.
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Affiliation(s)
- Pau Biak Sang
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Department of Microbiology, University of Delhi South Campus, New Delhi, India
| | - Rishi K Jaiswal
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Xinxing Lyu
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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2
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Knowles S, Chai W. Conditional Depletion of STN1 in Mouse Embryonic Fibroblasts. Bio Protoc 2024; 14:e4977. [PMID: 38686350 PMCID: PMC11056013 DOI: 10.21769/bioprotoc.4977] [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: 12/18/2023] [Revised: 03/20/2024] [Accepted: 03/21/2024] [Indexed: 05/02/2024] Open
Abstract
The CTC1-STN1-TEN1 (CST) complex is a single-strand DNA-binding protein complex that plays an important role in genome maintenance in various model eukaryotes. Dysfunction of CST is the underlying cause of the rare genetic disorder known as Coats plus disease. In addition, down regulation of STN1 promotes colorectal cancer development in mice. While prior studies have utilized RNAi to knock down CST components in mammalian cells, this approach is associated with off-target effects. Attempts to employ CRISPR/Cas9-based knockout of CST components in somatic cell lines have been unsuccessful due to CST's indispensable role in DNA replication and cell proliferation. To address these challenges, we outline a novel approach utilizing a Cre-loxP-based conditional knockout in mouse embryonic fibroblasts (MEFs). This method offers an alternative means to investigate the function and characteristics of the CST complex in mammalian systems, potentially shedding new light on its roles in genome maintenance. Key features • Conditional depletion of mammalian STN1 using mouse embryonic fibroblast (MEFs). • Analysis of oxidative damage sensitivity using STN1-depleted MEFs. • This protocol requires Stn1flox/flox mice.
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Affiliation(s)
- Sara Knowles
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
- Center for Genetic Diseases, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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3
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Hou L, Hong H, Cao W, Wei L, Weng L, Yuan S, Xiao C, Zhang Q, Wang Q, Lai D. Identification and characterization of multipotential stem cells in immortalized normal ovarian surface epithelial cells. Acta Biochim Biophys Sin (Shanghai) 2024; 56:239-254. [PMID: 38243680 PMCID: PMC10984850 DOI: 10.3724/abbs.2023253] [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: 07/22/2023] [Accepted: 09/21/2023] [Indexed: 01/21/2024] Open
Abstract
The ovarian surface epithelium (OSE) is a single layer of squamous-to-cuboidal epithelial cells that experience repetitive ovulatory rupture and subsequent repair. However, the characteristics of human immortalized ovarian surface epithelial cells (IOSE80) remain elusive. This study aims to determine whether IOSE80 cells have the characteristics of stem cell proliferation and multilineage differentiation and their application in regenerative medicine. IOSE80 cells are sequenced by high-throughput transcriptome analysis, and 5 sets of public data are used to compare the differences between IOSE80 cells and bone marrow mesenchymal stem cells, pluripotent stem cells, and oocytes in transcriptome profiling. The IOSE80 cells present a cobblestone-like monolayer and express the epithelial cell marker KRT18; the stem cell markers IFITM3, ALDH1A1, and VIM; lowly express stem cell marker LGR5 and germ cell markers DDX4 and DAZL. In addition, the GO terms "regulation of stem cell proliferation", "epithelial cell proliferation", etc., are significantly enriched ( P<0.05). IOSE80 cells have the potential to act as mesenchymal stem cells to differentiate into adipocytes with lipid droplets, osteoblasts, and chondroblasts in vitro. IOSE80 cells express pluripotent stem cell markers, including OCT4, SSEA4, TRA-1-60, and TRA-1-81, and they can be induced into three germ layers in vitro. IOSE80 cells also form oocyte-like cells in vitro and in vivo. In addition, IOSE80 cells exhibit robust proliferation, migration, and ovarian repair functions after in vivo transplantation. This study demonstrates that IOSE80 cells have the characteristics of pluripotent/multipotent stem cells, indicating their important role in tissue engineering and regenerative medicine.
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Affiliation(s)
- Lin Hou
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Hanqing Hong
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Wenjiao Cao
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Liutong Wei
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Lichun Weng
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Shuang Yuan
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Chengqi Xiao
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Qiuwan Zhang
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Qian Wang
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
| | - Dongmei Lai
- The International Peace Maternity and Child Health HospitalSchool of MedicineShanghai Jiao Tong UniversityShanghai200030China
- Shanghai Key Laboratory of Embryo Original DiseasesShanghai200030China
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4
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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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5
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Lu X, Liu L. Genome stability from the perspective of telomere length. Trends Genet 2024; 40:175-186. [PMID: 37957036 DOI: 10.1016/j.tig.2023.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 11/15/2023]
Abstract
Telomeres and their associated proteins protect the ends of chromosomes to maintain genome stability. Telomeres undergo progressive shortening with each cell division in mammalian somatic cells without telomerase, resulting in genome instability. When telomeres reach a critically short length or are recognized as a damage signal, cells enter a state of senescence, followed by cell cycle arrest, programmed cell death, or immortalization. This review provides an overview of recent advances in the intricate relationship between telomeres and genome instability. Alongside well-established mechanisms such as chromosomal fusion and telomere fusion, we will delve into the perspective on genome stability by examining the role of retrotransposons. Retrotransposons represent an emerging pathway to regulate genome stability through their interactions with telomeres.
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Affiliation(s)
- Xinyi Lu
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, Tianjin 300350, China.
| | - Lin Liu
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, Tianjin 300350, China; Frontiers Science Center for Cell Responses, College of Life Science, Nankai University, Tianjin, Tianjin 300071, China; Haihe Laboratory of Cell Ecosystem, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300020, China; Institute of Translational Medicine, Tianjin Union Medical Center, Nankai University, Tianjin 300000, China.
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6
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King A, Reichl P, Metson JS, Parker R, Munro D, Oliveira C, Becker JR, Biggs D, Preece C, Davies B, Chapman JR. Shieldin and CST co-orchestrate DNA polymerase-dependent tailed-end joining reactions independently of 53BP1-governed repair pathway choice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572534. [PMID: 38187711 PMCID: PMC10769304 DOI: 10.1101/2023.12.20.572534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
53BP1 regulates DNA end-joining in lymphocytes, diversifying immune antigen receptors. This involves nucleosome-bound 53BP1 at DNA double-stranded breaks (DSBs) recruiting RIF1 and shieldin, a poorly understood DNA-binding complex. The 53BP1-RIF1-shieldin axis is pathological in BRCA1-mutated cancers, blocking homologous recombination (HR) and driving illegitimate non-homologous end-joining (NHEJ). However, how this axis regulates DNA end-joining and HR suppression remains unresolved. We investigated shieldin and its interplay with CST, a complex recently implicated in 53BP1-dependent activities. Immunophenotypically, mice lacking shieldin or CST are equivalent, with class-switch recombination co-reliant on both complexes. ATM-dependent DNA damage signalling underpins this cooperation, inducing physical interactions between these complexes that reveal shieldin as a DSB-responsive CST adaptor. Furthermore, DNA polymerase ζ functions downstream of shieldin, establishing DNA fill-in synthesis as the physiological function of shieldin-CST. Lastly, 53BP1 suppresses HR and promotes NHEJ in BRCA1-deficient mice and cells independently of shieldin. These findings showcase the resilience of the 53BP1 pathway, achieved through the collaboration of chromatin-bound 53BP1 complexes and DNA end-processing effector proteins.
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Affiliation(s)
- Ashleigh King
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Pia Reichl
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Jean S. Metson
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Robert Parker
- Centre for ImmunoOncology, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Daniella Munro
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Catarina Oliveira
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Jordan R. Becker
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
| | - Daniel Biggs
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Chris Preece
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Benjamin Davies
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
- Francis Crick Institute, 1 Midland Rd, London, UK
| | - J. Ross Chapman
- Genome Integrity laboratory, Medical Research Council Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, The University of Oxford, Oxford, UK
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7
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Carvalho Borges PC, Bouabboune C, Escandell JM, Matmati S, Coulon S, Ferreira MG. Pot1 promotes telomere DNA replication via the Stn1-Ten1 complex in fission yeast. Nucleic Acids Res 2023; 51:12325-12336. [PMID: 37953281 PMCID: PMC10711446 DOI: 10.1093/nar/gkad1036] [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: 01/20/2023] [Revised: 10/19/2023] [Accepted: 10/31/2023] [Indexed: 11/14/2023] Open
Abstract
Telomeres are nucleoprotein complexes that protect the chromosome-ends from eliciting DNA repair while ensuring their complete duplication. Pot1 is a subunit of telomere capping complex that binds to the G-rich overhang and inhibits the activation of DNA damage checkpoints. In this study, we explore new functions of fission yeast Pot1 by using a pot1-1 temperature sensitive mutant. We show that pot1 inactivation impairs telomere DNA replication resulting in the accumulation of ssDNA leading to the complete loss of telomeric DNA. Recruitment of Stn1 to telomeres, an auxiliary factor of DNA lagging strand synthesis, is reduced in pot1-1 mutants and overexpression of Stn1 rescues loss of telomeres and cell viability at restrictive temperature. We propose that Pot1 plays a crucial function in telomere DNA replication by recruiting Stn1-Ten1 and Polα-primase complex to telomeres via Tpz1, thus promoting lagging-strand DNA synthesis at stalled replication forks.
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Affiliation(s)
| | - Chaïnez Bouabboune
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Equipe labellisée par la Ligue Nationale contre le Cancer, Marseille, F-13009, France
| | | | - Samah Matmati
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Equipe labellisée par la Ligue Nationale contre le Cancer, Marseille, F-13009, France
| | - Stéphane Coulon
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Equipe labellisée par la Ligue Nationale contre le Cancer, Marseille, F-13009, France
| | - Miguel Godinho Ferreira
- Instituto Gulbenkian de Ciência, Oeiras, 2781-901, Portugal
- Institute for Research on Cancer and Aging of Nice (IRCAN), INSERM U1081 UMR7284 CNRS, 06107 Nice, France
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8
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Liu L, Luo H, Sheng Y, Kang X, Peng H, Luo H, Fan LL. A novel mutation of CTC1 leads to telomere shortening in a chinese family with interstitial lung disease. Hereditas 2023; 160:37. [PMID: 37978541 PMCID: PMC10656953 DOI: 10.1186/s41065-023-00299-4] [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: 06/28/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023] Open
Abstract
Interstitial lung diseases (ILDs), or diffuse pulmonary lung disease, are a subset of lung diseases that primarily affect lung alveoli and the space around interstitial tissue and bronchioles. It clinically manifests as progressive dyspnea, and patients often exhibit a varied decrease in pulmonary diffusion function. Recently, variants in telomere biology-related genes have been identified as genetic lesions of ILDs. Here, we enrolled 82 patients with interstitial pneumonia from 2017 to 2021 in our hospital to explore the candidate gene mutations of these patients via whole-exome sequencing. After data filtering, a novel heterozygous mutation (NM_025099: p.Gly131Arg) of CTC1 was identified in two affected family members. As a component of CST (CTC1-STN1-TEN1) complex, CTC1 is responsible for maintaining telomeric structure integrity and has also been identified as a candidate gene for IPF, a special kind of chronic ILD with insidious onset. Simultaneously, real-time PCR revealed that two affected family members presented with short telomere lengths, which further confirmed the effect of the mutation in the CTC1 gene. Our study not only expanded the mutation spectrum of CTC1 and provided epidemiological data on ILDs caused by CTC1 mutations but also further confirmed the relationship between heterozygous mutations in CTC1 and ILDs, which may further contribute to understanding the mechanisms underlying ILDs.
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Affiliation(s)
- Lv Liu
- Department of Pulmonary and Critical Care Medicine, Research Unit of Respiratory Disease, Hunan Diagnosis and Treatment Center of Respiratory Disease, the Second Xiangya Hospital, Central South University, Changsha, China
- Department of Cell biology, School of Life Science, Central South University, Changsha, China
| | - Hua Luo
- Department of Cardio-Thoracic Surgery, Changsha Medical School, the Affiliated Changsha Central Hospital, University of South China, Changsha, China
| | - Yue Sheng
- Department of Cell biology, School of Life Science, Central South University, Changsha, China
| | - Xi Kang
- Department of Pulmonary and Critical Care Medicine, Research Unit of Respiratory Disease, Hunan Diagnosis and Treatment Center of Respiratory Disease, the Second Xiangya Hospital, Central South University, Changsha, China
| | - Hong Peng
- Department of Pulmonary and Critical Care Medicine, Research Unit of Respiratory Disease, Hunan Diagnosis and Treatment Center of Respiratory Disease, the Second Xiangya Hospital, Central South University, Changsha, China
| | - Hong Luo
- Department of Pulmonary and Critical Care Medicine, Research Unit of Respiratory Disease, Hunan Diagnosis and Treatment Center of Respiratory Disease, the Second Xiangya Hospital, Central South University, Changsha, China.
| | - Liang-Liang Fan
- Department of Cell biology, School of Life Science, Central South University, Changsha, China.
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9
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Takasugi T, Gu P, Liang F, Staco I, Chang S. Pot1b -/- tumors activate G-quadruplex-induced DNA damage to promote telomere hyper-elongation. Nucleic Acids Res 2023; 51:9227-9247. [PMID: 37560909 PMCID: PMC10516629 DOI: 10.1093/nar/gkad648] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 07/14/2023] [Accepted: 07/22/2023] [Indexed: 08/11/2023] Open
Abstract
Malignant cancers must activate telomere maintenance mechanisms to achieve replicative immortality. Mutations in the human Protection of Telomeres 1 (POT1) gene are frequently detected in cancers with abnormally long telomeres, suggesting that the loss of POT1 function disrupts the regulation of telomere length homeostasis to promote telomere elongation. However, our understanding of the mechanisms leading to elongated telomeres remains incomplete. The mouse genome encodes two POT1 proteins, POT1a and POT1b possessing separation of hPOT1 functions. We performed serial transplantation of Pot1b-/- sarcomas to better understand the role of POT1b in regulating telomere length maintenance. While early-generation Pot1b-/- sarcomas initially possessed shortened telomeres, late-generation Pot1b-/- cells display markedly hyper-elongated telomeres that were recognized as damaged DNA by the Replication Protein A (RPA) complex. The RPA-ATR-dependent DNA damage response at telomeres promotes telomerase recruitment to facilitate telomere hyper-elongation. POT1b, but not POT1a, was able to unfold G-quadruplex present in hyper-elongated telomeres to repress the DNA damage response. Our findings demonstrate that the repression of the RPA-ATR DDR is conserved between POT1b and human POT1, suggesting that similar mechanisms may underly the phenotypes observed in human cancers harboring human POT1 mutations.
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Affiliation(s)
- Taylor Takasugi
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Peili Gu
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Fengshan Liang
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Isabelle Staco
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Sandy Chang
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Pathology, Yale University School of Medicine, New Haven, CT 06520, USA
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10
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Kamaletdinova T, Zong W, Urbánek P, Wang S, Sannai M, Grigaravičius P, Sun W, Fanaei-Kahrani Z, Mangerich A, Hottiger MO, Li T, Wang ZQ. Poly(ADP-Ribose) Polymerase-1 Lacking Enzymatic Activity Is Not Compatible with Mouse Development. Cells 2023; 12:2078. [PMID: 37626888 PMCID: PMC10453916 DOI: 10.3390/cells12162078] [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: 06/24/2023] [Revised: 08/11/2023] [Accepted: 08/11/2023] [Indexed: 08/27/2023] Open
Abstract
Poly(ADP-ribose) polymerase-1 (PARP1) binds DNA lesions to catalyse poly(ADP-ribosyl)ation (PARylation) using NAD+ as a substrate. PARP1 plays multiple roles in cellular activities, including DNA repair, transcription, cell death, and chromatin remodelling. However, whether these functions are governed by the enzymatic activity or scaffolding function of PARP1 remains elusive. In this study, we inactivated in mice the enzymatic activity of PARP1 by truncating its C-terminus that is essential for ART catalysis (PARP1ΔC/ΔC, designated as PARP1-ΔC). The mutation caused embryonic lethality between embryonic day E8.5 and E13.5, in stark contrast to PARP1 complete knockout (PARP1-/-) mice, which are viable. Embryonic stem (ES) cell lines can be derived from PARP1ΔC/ΔC blastocysts, and these mutant ES cells can differentiate into all three germ layers, yet, with a high degree of cystic structures, indicating defects in epithelial cells. Intriguingly, PARP1-ΔC protein is expressed at very low levels compared to its full-length counterpart, suggesting a selective advantage for cell survival. Noticeably, PARP2 is particularly elevated and permanently present at the chromatin in PARP1-ΔC cells, indicating an engagement of PARP2 by non-enzymatic PARP1 protein at the chromatin. Surprisingly, the introduction of PARP1-ΔC mutation in adult mice did not impair their viability; yet, these mutant mice are hypersensitive to alkylating agents, similar to PARP1-/- mutant mice. Our study demonstrates that the catalytically inactive mutant of PARP1 causes the developmental block, plausibly involving PARP2 trapping.
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Affiliation(s)
- Tatiana Kamaletdinova
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
| | - Wen Zong
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (W.Z.); (S.W.); (W.S.); (T.L.)
| | - Pavel Urbánek
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
| | - Sijia Wang
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (W.Z.); (S.W.); (W.S.); (T.L.)
| | - Mara Sannai
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
| | - Paulius Grigaravičius
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
| | - Wenli Sun
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (W.Z.); (S.W.); (W.S.); (T.L.)
| | - Zahra Fanaei-Kahrani
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
| | - Aswin Mangerich
- Molecular Toxicology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany;
- Nutritional Toxicology, Institute of Nutritional Science, University of Potsdam, 14469 Potsdam, Germany
| | - Michael O. Hottiger
- Department of Molecular Mechanisms of Disease, University of Zürich, 8057 Zürich, Switzerland;
| | - Tangliang Li
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (W.Z.); (S.W.); (W.S.); (T.L.)
| | - Zhao-Qi Wang
- Leibniz Institute on Aging—Fritz Lipmann Institute (FLI), 07745 Jena, Germany; (T.K.); (P.U.); (M.S.); (P.G.); (Z.F.-K.)
- State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao 266237, China; (W.Z.); (S.W.); (W.S.); (T.L.)
- Faculty of Biological Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany
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11
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Vaurs M, Naiman K, Bouabboune C, Rai S, Ptasińska K, Rives M, Matmati S, Carr AM, Géli V, Coulon S. Stn1-Ten1 and Taz1 independently promote replication of subtelomeric fragile sequences in fission yeast. Cell Rep 2023; 42:112537. [PMID: 37243596 DOI: 10.1016/j.celrep.2023.112537] [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: 09/15/2022] [Revised: 03/01/2023] [Accepted: 05/03/2023] [Indexed: 05/29/2023] Open
Abstract
Efficient replication of terminal DNA is crucial to maintain telomere stability. In fission yeast, Taz1 and the Stn1-Ten1 (ST) complex play prominent roles in DNA-ends replication. However, their function remains elusive. Here, we have analyzed genome-wide replication and show that ST does not affect genome-wide replication but is crucial for the efficient replication of a subtelomeric region called STE3-2. We further show that, when ST function is compromised, a homologous recombination (HR)-based fork restart mechanism becomes necessary for STE3-2 stability. While both Taz1 and Stn1 bind to STE3-2, we find that the STE3-2 replication function of ST is independent of Taz1 but relies on its association with the shelterin proteins Pot1-Tpz1-Poz1. Finally, we demonstrate that the firing of an origin normally inhibited by Rif1 can circumvent the replication defect of subtelomeres when ST function is compromised. Our results help illuminate why fission yeast telomeres are terminal fragile sites.
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Affiliation(s)
- Mélina Vaurs
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France
| | - Karel Naiman
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France; Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Chaïnez Bouabboune
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France
| | - Sudhir Rai
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France
| | - Katarzyna Ptasińska
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Marion Rives
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France
| | - Samah Matmati
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France
| | - Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer BN1 9RQ, UK
| | - Vincent Géli
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France.
| | - Stéphane Coulon
- CNRS, INSERM, Aix Marseille Univ, Institut Paoli-Calmettes, CRCM, Ligue Nationale Contre le Cancer (équipe labellisée), Marseille, France.
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12
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Jiang F, Hedaya OM, Khor E, Wu J, Auguste M, Yao P. RNA binding protein PRRC2B mediates translation of specific mRNAs and regulates cell cycle progression. Nucleic Acids Res 2023; 51:5831-5846. [PMID: 37125639 PMCID: PMC10287950 DOI: 10.1093/nar/gkad322] [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: 12/08/2022] [Revised: 03/28/2023] [Accepted: 04/24/2023] [Indexed: 05/02/2023] Open
Abstract
Accumulating evidence suggests that posttranscriptional control of gene expression, including RNA splicing, transport, modification, translation and degradation, primarily relies on RNA binding proteins (RBPs). However, the functions of many RBPs remain understudied. Here, we characterized the function of a novel RBP, Proline-Rich Coiled-coil 2B (PRRC2B). Through photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation and sequencing (PAR-CLIP-seq), we identified transcriptome-wide CU- or GA-rich PRRC2B binding sites near the translation initiation codon on a specific cohort of mRNAs in HEK293T cells. These mRNAs, including oncogenes and cell cycle regulators such as CCND2 (cyclin D2), exhibited decreased translation upon PRRC2B knockdown as revealed by polysome-associated RNA-seq, resulting in reduced G1/S phase transition and cell proliferation. Antisense oligonucleotides blocking PRRC2B interactions with CCND2 mRNA decreased its translation, thus inhibiting G1/S transition and cell proliferation. Mechanistically, PRRC2B interactome analysis revealed RNA-independent interactions with eukaryotic translation initiation factors 3 (eIF3) and 4G2 (eIF4G2). The interaction with translation initiation factors is essential for PRRC2B function since the eIF3/eIF4G2-interacting defective mutant, unlike wild-type PRRC2B, failed to rescue the translation deficiency or cell proliferation inhibition caused by PRRC2B knockdown. Altogether, our findings reveal that PRRC2B is essential for efficiently translating specific proteins required for cell cycle progression and cell proliferation.
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Affiliation(s)
- Feng Jiang
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Omar M Hedaya
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - EngSoon Khor
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Jiangbin Wu
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Matthew Auguste
- Undergraduate Program in Biology and Medicine, Department of Biological Sciences: Molecular Genetics, University of Rochester, Rochester, NY 14642, USA
| | - Peng Yao
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- The Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- The Center for Biomedical Informatics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
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13
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Nguyen DD, Kim E, Le NT, Ding X, Jaiswal RK, Kostlan RJ, Nguyen TNT, Shiva O, Le MT, Chai W. Deficiency in mammalian STN1 promotes colon cancer development via inhibiting DNA repair. SCIENCE ADVANCES 2023; 9:eadd8023. [PMID: 37163605 PMCID: PMC10171824 DOI: 10.1126/sciadv.add8023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 04/05/2023] [Indexed: 05/12/2023]
Abstract
Despite the high lethality of colorectal cancers (CRCs), only a limited number of genetic risk factors are identified. The mammalian ssDNA-binding protein complex CTC1-STN1-TEN1 protects genome stability, yet its role in tumorigenesis is unknown. Here, we show that attenuated CTC1/STN1 expression is common in CRCs. We generated an inducible STN1 knockout mouse model and found that STN1 deficiency in young adult mice increased CRC incidence, tumor size, and tumor load. CRC tumors exhibited enhanced proliferation, reduced apoptosis, and elevated DNA damage and replication stress. We found that STN1 deficiency down-regulated multiple DNA glycosylases, resulting in defective base excision repair (BER) and accumulation of oxidative damage. Collectively, this study identifies STN1 deficiency as a risk factor for CRC and implicates the previously unknown STN1-BER axis in protecting colon tissues from oxidative damage, therefore providing insights into the CRC tumor-suppressing mechanism.
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Affiliation(s)
- Dinh Duc Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Eugene Kim
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Nhat Thong Le
- School of Biotechnology, International University, Ho Chi Minh City, Vietnam
| | - Xianzhong Ding
- Department of Pathology, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Rishi Kumar Jaiswal
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Raymond Joseph Kostlan
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Thi Ngoc Thanh Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Olga Shiva
- Office of Research, Washington State University-Spokane, Spokane, WA, USA
| | - Minh Thong Le
- School of Biotechnology, International University, Ho Chi Minh City, Vietnam
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
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14
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Nelson N, Feurstein S, Niaz A, Truong J, Holien JK, Lucas S, Fairfax K, Dickinson J, Bryan TM. Functional genomics for curation of variants in telomere biology disorder associated genes: A systematic review. Genet Med 2023; 25:100354. [PMID: 36496180 DOI: 10.1016/j.gim.2022.11.021] [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: 06/28/2022] [Revised: 11/28/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Patients with an underlying telomere biology disorder (TBD) have variable clinical presentations, and they can be challenging to diagnose clinically. A genomic diagnosis for patients presenting with TBD is vital for optimal treatment. Unfortunately, many variants identified during diagnostic testing are variants of uncertain significance. This complicates management decisions, delays treatment, and risks nonuptake of potentially curative therapies. Improved application of functional genomic evidence may reduce variants of uncertain significance classifications. METHODS We systematically searched the literature for published functional assays interrogating TBD gene variants. When possible, established likely benign/benign and likely pathogenic/pathogenic variants were used to estimate the assay sensitivity, specificity, positive predictive value, negative predictive value, and odds of pathogenicity. RESULTS In total, 3131 articles were screened and 151 met inclusion criteria. Sufficient data to enable a PS3/BS3 recommendation were available for TERT variants only. We recommend that PS3 and BS3 can be applied at a moderate and supportive level, respectively. PS3/BS3 application was limited by a lack of assay standardization and limited inclusion of benign variants. CONCLUSION Further assay standardization and assessment of benign variants are required for optimal use of the PS3/BS3 criterion for TBD gene variant classification.
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Affiliation(s)
- Niles Nelson
- The Menzies Institute for Medical Research, College of Health and Medicine, The University of Tasmania, Hobart, Tasmania, Australia; Department of Molecular Medicine, The Royal Hobart Hospital, Hobart, Tasmania, Australia; Department of Molecular Haematology, The Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
| | - Simone Feurstein
- Section of Hematology, Oncology, and Rheumatology, Department of Internal Medicine, Heidelberg University Hospital, Heidelberg, Germany
| | - Aram Niaz
- Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, New South Wales, Australia
| | - Jia Truong
- School of Science, STEM College, RMIT University, Bundoora, Victoria, Australia
| | - Jessica K Holien
- School of Science, STEM College, RMIT University, Bundoora, Victoria, Australia
| | - Sionne Lucas
- The Menzies Institute for Medical Research, College of Health and Medicine, The University of Tasmania, Hobart, Tasmania, Australia
| | - Kirsten Fairfax
- The Menzies Institute for Medical Research, College of Health and Medicine, The University of Tasmania, Hobart, Tasmania, Australia
| | - Joanne Dickinson
- The Menzies Institute for Medical Research, College of Health and Medicine, The University of Tasmania, Hobart, Tasmania, Australia
| | - Tracy M Bryan
- Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, New South Wales, Australia
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15
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Mirman Z, Cai S, de Lange T. CST/Polα/primase-mediated fill-in synthesis at DSBs. Cell Cycle 2023; 22:379-389. [PMID: 36205622 PMCID: PMC9879193 DOI: 10.1080/15384101.2022.2123886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 08/27/2022] [Accepted: 09/06/2022] [Indexed: 01/29/2023] Open
Abstract
DNA double-strand breaks (DSBs) pose a major threat to the genome, so the efficient repair of such breaks is essential. DSB processing and repair is affected by 53BP1, which has been proposed to determine repair pathway choice and/or promote repair fidelity. 53BP1 and its downstream effectors, RIF1 and shieldin, control 3' overhang length, and the mechanism has been a topic of intensive research. Here, we highlight recent evidence that 3' overhang control by 53BP1 occurs through fill-in synthesis of resected DSBs by CST/Polα/primase. We focus on the crucial role of fill-in synthesis in BRCA1-deficient cells treated with PARPi and discuss the notion of fill-in synthesis in other specialized settings and in the repair of random DSBs. We argue that - in addition to other determinants - repair pathway choice may be influenced by the DNA sequence at the break which can impact CST binding and therefore the deployment of Polα/primase fill-in.
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Affiliation(s)
- Zachary Mirman
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY, USA
- Department of Genetics, Harvard Medical School, Division of Genetics, Brigham and Women’s Hospital, HHMI, Boston, MA, USA
| | - Sarah Cai
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY, USA
- Laboratory for Molecular Electron Microscopy, The Rockefeller University, New York, NY
| | - Titia de Lange
- Laboratory for Cell Biology and Genetics, The Rockefeller University, New York, NY, USA
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16
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Casari E, Gnugnoli M, Rinaldi C, Pizzul P, Colombo CV, Bonetti D, Longhese MP. To Fix or Not to Fix: Maintenance of Chromosome Ends Versus Repair of DNA Double-Strand Breaks. Cells 2022; 11:cells11203224. [PMID: 36291091 PMCID: PMC9601279 DOI: 10.3390/cells11203224] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/07/2022] [Accepted: 10/12/2022] [Indexed: 02/08/2023] Open
Abstract
Early work by Muller and McClintock discovered that the physical ends of linear chromosomes, named telomeres, possess an inherent ability to escape unwarranted fusions. Since then, extensive research has shown that this special feature relies on specialized proteins and structural properties that confer identity to the chromosome ends, thus allowing cells to distinguish them from intrachromosomal DNA double-strand breaks. Due to the inability of conventional DNA replication to fully replicate the chromosome ends and the downregulation of telomerase in most somatic human tissues, telomeres shorten as cells divide and lose this protective capacity. Telomere attrition causes the activation of the DNA damage checkpoint that leads to a cell-cycle arrest and the entering of cells into a nondividing state, called replicative senescence, that acts as a barrier against tumorigenesis. However, downregulation of the checkpoint overcomes this barrier and leads to further genomic instability that, if coupled with re-stabilization of telomeres, can drive tumorigenesis. This review focuses on the key experiments that have been performed in the model organism Saccharomyces cerevisiae to uncover the mechanisms that protect the chromosome ends from eliciting a DNA damage response, the conservation of these pathways in mammals, as well as the consequences of their loss in human cancer.
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17
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Zaug AJ, Goodrich KJ, Song JJ, Sullivan AE, Cech TR. Reconstitution of a telomeric replicon organized by CST. Nature 2022; 608:819-825. [PMID: 35831508 PMCID: PMC9402439 DOI: 10.1038/s41586-022-04930-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 06/06/2022] [Indexed: 11/20/2022]
Abstract
Telomeres, the natural ends of linear chromosomes, comprise repeat-sequence DNA and associated proteins1. Replication of telomeres allows continued proliferation of human stem cells and immortality of cancer cells2. This replication requires telomerase3 extension of the single-stranded DNA (ssDNA) of the telomeric G-strand ((TTAGGG)n); the synthesis of the complementary C-strand ((CCCTAA)n) is much less well characterized. The CST (CTC1–STN1–TEN1) protein complex, a DNA polymerase α-primase accessory factor4,5, is known to be required for telomere replication in vivo6–9, and the molecular analysis presented here reveals key features of its mechanism. We find that human CST uses its ssDNA-binding activity to specify the origins for telomeric C-strand synthesis by bound Polα-primase. CST-organized DNA polymerization can copy a telomeric DNA template that folds into G-quadruplex structures, but the challenges presented by this template probably contribute to telomere replication problems observed in vivo. Combining telomerase, a short telomeric ssDNA primer and CST–Polα–primase gives complete telomeric DNA replication, resulting in the same sort of ssDNA 3′ overhang found naturally on human telomeres. We conclude that the CST complex not only terminates telomerase extension10,11 and recruits Polα–primase to telomeric ssDNA4,12,13 but also orchestrates C-strand synthesis. Because replication of the telomere has features distinct from replication of the rest of the genome, targeting telomere-replication components including CST holds promise for cancer therapeutics. The Polα–primase-associated CST complex organizes telomeric C-strand DNA synthesis, and, in combination with telomerase, it carries out complete replication of the single-stranded DNA overhang found at human telomeres.
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Affiliation(s)
- Arthur J Zaug
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.,BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA.,Howard Hughes Medical Institute, University of Colorado Boulder, Boulder, CO, USA
| | - Karen J Goodrich
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.,BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA.,Howard Hughes Medical Institute, University of Colorado Boulder, Boulder, CO, USA
| | - Jessica J Song
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Ashley E Sullivan
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA
| | - Thomas R Cech
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA. .,BioFrontiers Institute, University of Colorado Boulder, Boulder, CO, USA. .,Howard Hughes Medical Institute, University of Colorado Boulder, Boulder, CO, USA.
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18
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Riquelme J, Takada S, van Dijk T, Peña F, Boogaard MW, van Duyvenvoorde HA, Pico-Knijnenburg I, Wit JM, van der Burg M, Mericq V, Losekoot M. Primary Ovarian Failure in Addition to Classical Clinical Features of Coats Plus Syndrome in a Female Carrying 2 Truncating Variants of CTC1. Horm Res Paediatr 2022; 94:448-455. [PMID: 34706368 DOI: 10.1159/000520410] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 10/22/2021] [Indexed: 11/19/2022] Open
Abstract
Coats plus syndrome is an autosomal recessive multisystemic and pleiotropic disorder affecting the eyes, brain, bone, and gastrointestinal tract, usually caused by compound heterozygous variants of the conserved telomere maintenance component 1 gene (CTC1), involved in telomere homeostasis and replication. So far, most reported patients are compound heterozygous for a truncating mutation and a missense variant. The phenotype is believed to result from telomere dysfunction, with accumulation of DNA damage, cellular senescence, and stem cell depletion. Here, we report a 23-year-old female with prenatal and postnatal growth retardation, microcephaly, osteopenia, recurrent fractures, intracranial calcification, leukodystrophy, parenchymal brain cysts, bicuspid aortic valve, and primary ovarian failure. She carries a previously reported maternally inherited pathogenic variant in exon 5 (c.724_727del, p.(Lys242Leufs*41)) and a novel, paternally inherited splice site variant (c.1617+5G>T; p.(Lys480Asnfs*17)) in intron 9. CTC1 transcript analysis showed that the latter resulted in skipping of exon 9. A trace of transcripts was normally spliced resulting in the presence of a low level of wild-type CTC1 transcripts. We speculate that ovarian failure is caused by telomere shortening or chromosome cohesion failure in oocytes and granulosa cells, with early decrease in follicular reserve. This is the first patient carrying 2 truncating CTC1 variants and the first presenting primary ovarian failure.
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Affiliation(s)
- Joel Riquelme
- Department of Pediatrics, University of Chile, Hospital San Juan de Dios, Santiago, Chile.,Department of Pediatrics, Clínica Las Condes, Santiago, Chile
| | - Sanami Takada
- Department of Pediatrics, Laboratory for Pediatric Immunology, Leiden University Medical Center, Leiden, The Netherlands
| | - Tessa van Dijk
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Fernanda Peña
- Department of Pediatrics, Hospital San Juan de Dios, Santiago, Chile
| | - Merel W Boogaard
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Ingrid Pico-Knijnenburg
- Department of Pediatrics, Laboratory for Pediatric Immunology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jan M Wit
- Department of Pediatrics, Leiden University Medical Center, Leiden, The Netherlands
| | - Mirjam van der Burg
- Department of Pediatrics, Laboratory for Pediatric Immunology, Leiden University Medical Center, Leiden, The Netherlands
| | - Veronica Mericq
- Department of Pediatrics, Clínica Las Condes, Santiago, Chile.,Institute of Maternal and Child Research, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Monique Losekoot
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
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19
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Lim YS, Nguyen MT, Pham TX, Huynh TT, Park EM, Choi DH, Kang SM, Tark D, Hwang SB. Hepatitis C Virus Nonstructural 5A Protein Interacts with Telomere Length Regulation Protein: Implications for Telomere Shortening in Patients Infected with HCV. Mol Cells 2022; 45:148-157. [PMID: 34949741 PMCID: PMC8926864 DOI: 10.14348/molcells.2021.0167] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 10/17/2021] [Accepted: 10/27/2021] [Indexed: 11/27/2022] Open
Abstract
Hepatitis C virus (HCV) is a major cause of chronic liver disease and is highly dependent on cellular proteins for viral propagation. Using protein microarray analysis, we identified 90 cellular proteins as HCV nonstructural 5A (NS5A) interacting partners, and selected telomere length regulation protein (TEN1) for further study. TEN1 forms a heterotrimeric complex with CTC and STN1, which is essential for telomere protection and maintenance. Telomere length decreases in patients with active HCV, chronic liver disease, and hepatocellular carcinoma. However, the molecular mechanism of telomere length shortening in HCV-associated disease is largely unknown. In the present study, protein interactions between NS5A and TEN1 were confirmed by immunoprecipitation assays. Silencing of TEN1 reduced both viral RNA and protein expression levels of HCV, while ectopic expression of the siRNA-resistant TEN1 recovered the viral protein level, suggesting that TEN1 was specifically required for HCV propagation. Importantly, we found that TEN1 is re-localized from the nucleus to the cytoplasm in HCV-infected cells. These data suggest that HCV exploits TEN1 to promote viral propagation and that telomere protection is compromised in HCV-infected cells. Overall, our findings provide mechanistic insight into the telomere shortening in HCV-infected cells.
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Affiliation(s)
- Yun-Sook Lim
- Laboratory of RNA Viral Diseases, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
| | - Men T.N. Nguyen
- Ilsong Institute of Life Science, Hallym University, Seoul 07247, Korea
| | - Thuy X. Pham
- Laboratory of RNA Viral Diseases, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
| | - Trang T.X. Huynh
- Laboratory of RNA Viral Diseases, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
| | - Eun-Mee Park
- Center for Immunology and Pathology, National Institute of Health, Korea Center for Disease Control & Prevention, Cheongju 28159, Korea
| | - Dong Hwa Choi
- Biocenter, Gyeonggido Business & Science Accelerator, Suwon 16229, Korea
| | - Sang Min Kang
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
| | - Dongseob Tark
- Laboratory for Infectious Disease Prevention, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
| | - Soon B. Hwang
- Laboratory of RNA Viral Diseases, Korea Zoonosis Research Institute, Jeonbuk National University, Iksan 54531, Korea
- Ilsong Institute of Life Science, Hallym University, Seoul 07247, Korea
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20
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Telomeres and Cancer. Life (Basel) 2021; 11:life11121405. [PMID: 34947936 PMCID: PMC8704776 DOI: 10.3390/life11121405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 12/01/2021] [Accepted: 12/06/2021] [Indexed: 12/18/2022] Open
Abstract
Telomeres cap the ends of eukaryotic chromosomes and are indispensable chromatin structures for genome protection and replication. Telomere length maintenance has been attributed to several functional modulators, including telomerase, the shelterin complex, and the CST complex, synergizing with DNA replication, repair, and the RNA metabolism pathway components. As dysfunctional telomere maintenance and telomerase activation are associated with several human diseases, including cancer, the molecular mechanisms behind telomere length regulation and protection need particular emphasis. Cancer cells exhibit telomerase activation, enabling replicative immortality. Telomerase reverse transcriptase (TERT) activation is involved in cancer development through diverse activities other than mediating telomere elongation. This review describes the telomere functions, the role of functional modulators, the implications in cancer development, and the future therapeutic opportunities.
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21
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Lei KH, Yang HL, Chang HY, Yeh HY, Nguyen DD, Lee TY, Lyu X, Chastain M, Chai W, Li HW, Chi P. Crosstalk between CST and RPA regulates RAD51 activity during replication stress. Nat Commun 2021; 12:6412. [PMID: 34741010 PMCID: PMC8571288 DOI: 10.1038/s41467-021-26624-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 10/06/2021] [Indexed: 11/09/2022] Open
Abstract
Replication stress causes replication fork stalling, resulting in an accumulation of single-stranded DNA (ssDNA). Replication protein A (RPA) and CTC1-STN1-TEN1 (CST) complex bind ssDNA and are found at stalled forks, where they regulate RAD51 recruitment and foci formation in vivo. Here, we investigate crosstalk between RPA, CST, and RAD51. We show that CST and RPA localize in close proximity in cells. Although CST stably binds to ssDNA with a high affinity at low ionic strength, the interaction becomes more dynamic and enables facilitated dissociation at high ionic strength. CST can coexist with RPA on the same ssDNA and target RAD51 to RPA-coated ssDNA. Notably, whereas RPA-coated ssDNA inhibits RAD51 activity, RAD51 can assemble a functional filament and exhibit strand-exchange activity on CST-coated ssDNA at high ionic strength. Our findings provide mechanistic insights into how CST targets and tethers RAD51 to RPA-coated ssDNA in response to replication stress.
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Affiliation(s)
- Kai-Hang Lei
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Han-Lin Yang
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Hao-Yen Chang
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Hsin-Yi Yeh
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Dinh Duc Nguyen
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Tzu-Yu Lee
- Department of Chemistry, National Taiwan University, Taipei, Taiwan
| | - Xinxing Lyu
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Megan Chastain
- Office of Research, Washington State University, Spokane, WA, USA
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Hung-Wen Li
- Department of Chemistry, National Taiwan University, Taipei, Taiwan.
| | - Peter Chi
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan. .,Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.
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22
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The Intrinsically Disordered Region in the Human STN1 OB-Fold Domain Is Important for Protecting Genome Stability. BIOLOGY 2021; 10:biology10100977. [PMID: 34681076 PMCID: PMC8533325 DOI: 10.3390/biology10100977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/17/2021] [Accepted: 09/24/2021] [Indexed: 11/17/2022]
Abstract
Simple Summary The human CTC1–STN1–TEN1 (CST) complex is an ssDNA-binding protein complex that is thought to be related to the RPA70/RPA32/RPA14 complex. While recent studies have shown that CST plays key roles in multiple genome maintenance pathways, including protecting fork stability under perturbed replication, promoting efficient replication of difficult-to-replicate DNA, repairing DNA double-stranded breaks, and maintaining telomere integrity, it is poorly understood how CST function is regulated in genome maintenance. In this study, we identify an intrinsically disordered region (IDR) in the OB domain of STN1 and analyze the functions of cancer-associated IDR variants and a number of alanine substitutions of individual polar or hydrophilic residues in this IDR. We observe that these variants confer replication-associated genome instability, reduced cellular viability, and increased HU sensitivity. Analysis of protein–protein interactions using IDR variants and IDR deletion shows that the IDR is critical for STN1–POLα interaction, but not CST–RAD51 interaction or CST complex formation. Together, our results identify the IDR in STN1-OB as an important element modulating CST function in protecting genome stability under replication stress. Abstract The mammalian CTC1–STN1–TEN1 (CST) complex is an ssDNA-binding protein complex that has emerged as an important player in protecting genome stability and preserving telomere integrity. Studies have shown that CST localizes at stalled replication forks and is critical for protecting the stability of nascent strand DNA. Recent cryo-EM analysis reveals that CST subunits possess multiple OB-fold domains that can form a decameric supercomplex. While considered to be RPA-like, CST acts distinctly from RPA to protect genome stability. Here, we report that while the OB domain of STN1 shares structural similarity with the OB domain of RPA32, the STN1-OB domain contains an intrinsically disordered region (IDR) that is important for maintaining genome stability under replication stress. Single mutations in multiple positions in this IDR, including cancer-associated mutations, cause genome instabilities that are elevated by replication stress and display reduced cellular viability and increased HU sensitivity. While IDR mutations do not impact CST complex formation or CST interaction with its binding partner RAD51, they diminish RAD51 foci formation when replication is perturbed. Interestingly, the IDR is critical for STN1–POLα interaction. Collectively, our results identify the STN1 IDR as an important element in regulating CST function in genome stability maintenance.
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Distinct functions of POT1 proteins contribute to the regulation of telomerase recruitment to telomeres. Nat Commun 2021; 12:5514. [PMID: 34535663 PMCID: PMC8448735 DOI: 10.1038/s41467-021-25799-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 08/27/2021] [Indexed: 01/07/2023] Open
Abstract
Human shelterin components POT1 and TPP1 form a stable heterodimer that protects telomere ends from ATR-dependent DNA damage responses and regulates telomerase-dependent telomere extension. Mice possess two functionally distinct POT1 proteins. POT1a represses ATR/CHK1 DNA damage responses and the alternative non-homologous end-joining DNA repair pathway while POT1b regulates C-strand resection and recruits the CTC1-STN1-TEN1 (CST) complex to telomeres to mediate C-strand fill-in synthesis. Whether POT1a and POT1b are involved in regulating the length of the telomeric G-strand is unclear. Here we demonstrate that POT1b, independent of its CST function, enhances recruitment of telomerase to telomeres through three amino acids in its TPP1 interacting C-terminus. POT1b thus coordinates the synthesis of both telomeric G- and C-strands. In contrast, POT1a negatively regulates telomere length by inhibiting telomerase recruitment to telomeres. The identification of unique amino acids between POT1a and POT1b helps us understand mechanistically how human POT1 switches between end protective functions and promoting telomerase recruitment.
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24
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Par S, Vaides S, VanderVere-Carozza PS, Pawelczak KS, Stewart J, Turchi JJ. OB-Folds and Genome Maintenance: Targeting Protein-DNA Interactions for Cancer Therapy. Cancers (Basel) 2021; 13:3346. [PMID: 34283091 PMCID: PMC8269290 DOI: 10.3390/cancers13133346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/09/2021] [Accepted: 07/01/2021] [Indexed: 12/14/2022] Open
Abstract
Genome stability and maintenance pathways along with their requisite proteins are critical for the accurate duplication of genetic material, mutation avoidance, and suppression of human diseases including cancer. Many of these proteins participate in these pathways by binding directly to DNA, and a subset employ oligonucleotide/oligosaccharide binding folds (OB-fold) to facilitate the protein-DNA interactions. OB-fold motifs allow for sequence independent binding to single-stranded DNA (ssDNA) and can serve to position specific proteins at specific DNA structures and then, via protein-protein interaction motifs, assemble the machinery to catalyze the replication, repair, or recombination of DNA. This review provides an overview of the OB-fold structural organization of some of the most relevant OB-fold containing proteins for oncology and drug discovery. We discuss their individual roles in DNA metabolism, progress toward drugging these motifs and their utility as potential cancer therapeutics. While protein-DNA interactions were initially thought to be undruggable, recent reports of success with molecules targeting OB-fold containing proteins suggest otherwise. The potential for the development of agents targeting OB-folds is in its infancy, but if successful, would expand the opportunities to impinge on genome stability and maintenance pathways for more effective cancer treatment.
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Affiliation(s)
- Sui Par
- Indiana University Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (S.P.); (S.V.)
| | - Sofia Vaides
- Indiana University Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (S.P.); (S.V.)
| | | | | | - Jason Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA;
| | - John J. Turchi
- Indiana University Comprehensive Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA; (S.P.); (S.V.)
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- NERx Biosciences, Indianapolis, IN 46202, USA;
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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25
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Lyu X, Sang PB, Chai W. CST in maintaining genome stability: Beyond telomeres. DNA Repair (Amst) 2021; 102:103104. [PMID: 33780718 PMCID: PMC8081025 DOI: 10.1016/j.dnarep.2021.103104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 12/12/2022]
Abstract
The human CST (CTC1-STN1-TEN1) complex is an RPA-like single-stranded DNA binding protein complex. While its telomeric functions have been well investigated, numerous studies have revealed that hCST also plays important roles in maintaining genome stability beyond telomeres. Here, we review and discuss recent discoveries on CST in various global genome maintenance pathways, including findings on the CST supercomplex structure, its functions in unperturbed DNA replication, stalled replication, double-strand break repair, and the ATR-CHK1 activation pathway. By summarizing these recent discoveries, we hope to offer new insights into genome maintenance mechanisms and the pathogenesis of CST mutation-associated diseases.
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Affiliation(s)
- Xinxing Lyu
- Institute of Basic Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, 250062, China; Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, 60153, United States
| | - Pau Biak Sang
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, 60153, United States
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, 60153, United States.
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26
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Choudhury A, Mohammad T, Samarth N, Hussain A, Rehman MT, Islam A, Alajmi MF, Singh S, Hassan MI. Structural genomics approach to investigate deleterious impact of nsSNPs in conserved telomere maintenance component 1. Sci Rep 2021; 11:10202. [PMID: 33986331 PMCID: PMC8119478 DOI: 10.1038/s41598-021-89450-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 04/14/2021] [Indexed: 02/07/2023] Open
Abstract
Conserved telomere maintenance component 1 (CTC1) is an important component of the CST (CTC1-STN1-TEN1) complex, involved in maintaining the stability of telomeric DNA. Several non-synonymous single-nucleotide polymorphisms (nsSNPs) in CTC1 have been reported to cause Coats plus syndrome and Dyskeratosis congenital diseases. Here, we have performed sequence and structure analyses of nsSNPs of CTC1 using state-of-the-art computational methods. The structure-based study focuses on the C-terminal OB-fold region of CTC1. There are 11 pathogenic mutations identified, and detailed structural analyses were performed. These mutations cause a significant disruption of noncovalent interactions, which may be a possible reason for CTC1 instability and consequent diseases. To see the impact of such mutations on the protein conformation, all-atom molecular dynamics (MD) simulations of CTC1-wild-type (WT) and two of the selected mutations, R806C and R806L for 200 ns, were carried out. A significant conformational change in the structure of the R806C mutant was observed. This study provides a valuable direction to understand the molecular basis of CTC1 dysfunction in disease progression, including Coats plus syndrome.
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Affiliation(s)
- Arunabh Choudhury
- Department of Computer Science, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Taj Mohammad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Nikhil Samarth
- National Centre for Cell Science, NCCS Complex, Ganeshkhind, SP Pune University, Campus, Pune, 411007, India
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
| | - Mohamed F Alajmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Shailza Singh
- National Centre for Cell Science, NCCS Complex, Ganeshkhind, SP Pune University, Campus, Pune, 411007, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India.
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27
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Bonnell E, Pasquier E, Wellinger RJ. Telomere Replication: Solving Multiple End Replication Problems. Front Cell Dev Biol 2021; 9:668171. [PMID: 33869233 PMCID: PMC8047117 DOI: 10.3389/fcell.2021.668171] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 03/10/2021] [Indexed: 12/19/2022] Open
Abstract
Eukaryotic genomes are highly complex and divided into linear chromosomes that require end protection from unwarranted fusions, recombination, and degradation in order to maintain genomic stability. This is accomplished through the conserved specialized nucleoprotein structure of telomeres. Due to the repetitive nature of telomeric DNA, and the unusual terminal structure, namely a protruding single stranded 3′ DNA end, completing telomeric DNA replication in a timely and efficient manner is a challenge. For example, the end replication problem causes a progressive shortening of telomeric DNA at each round of DNA replication, thus telomeres eventually lose their protective capacity. This phenomenon is counteracted by the recruitment and the activation at telomeres of the specialized reverse transcriptase telomerase. Despite the importance of telomerase in providing a mechanism for complete replication of telomeric ends, the majority of telomere replication is in fact carried out by the conventional DNA replication machinery. There is significant evidence demonstrating that progression of replication forks is hampered at chromosomal ends due to telomeric sequences prone to form secondary structures, tightly DNA-bound proteins, and the heterochromatic nature of telomeres. The telomeric loop (t-loop) formed by invasion of the 3′-end into telomeric duplex sequences may also impede the passage of replication fork. Replication fork stalling can lead to fork collapse and DNA breaks, a major cause of genomic instability triggered notably by unwanted repair events. Moreover, at chromosomal ends, unreplicated DNA distal to a stalled fork cannot be rescued by a fork coming from the opposite direction. This highlights the importance of the multiple mechanisms involved in overcoming fork progression obstacles at telomeres. Consequently, numerous factors participate in efficient telomeric DNA duplication by preventing replication fork stalling or promoting the restart of a stalled replication fork at telomeres. In this review, we will discuss difficulties associated with the passage of the replication fork through telomeres in both fission and budding yeasts as well as mammals, highlighting conserved mechanisms implicated in maintaining telomere integrity during replication, thus preserving a stable genome.
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Affiliation(s)
- Erin Bonnell
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Emeline Pasquier
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Raymund J Wellinger
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Cancer Research Pavilion, Université de Sherbrooke, Sherbrooke, QC, Canada
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28
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Pol α-primase dependent nuclear localization of the mammalian CST complex. Commun Biol 2021; 4:349. [PMID: 33731801 PMCID: PMC7969954 DOI: 10.1038/s42003-021-01845-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 02/11/2021] [Indexed: 01/31/2023] Open
Abstract
The human CST complex composed of CTC1, STN1, and TEN1 is critically involved in telomere maintenance and homeostasis. Specifically, CST terminates telomere extension by inhibiting telomerase access to the telomeric overhang and facilitates lagging strand fill in by recruiting DNA Polymerase alpha primase (Pol α-primase) to the telomeric C-strand. Here we reveal that CST has a dynamic intracellular localization that is cell cycle dependent. We report an increase in nuclear CST several hours after the initiation of DNA replication, followed by exit from the nucleus prior to mitosis. We identify amino acids of CTC1 involved in Pol α-primase binding and nuclear localization. We conclude, the CST complex does not contain a nuclear localization signal (NLS) and suggest that its nuclear localization is reliant on Pol α-primase. Hypomorphic mutations affecting CST nuclear import are associated with telomere syndromes and cancer, emphasizing the important role of this process in health.
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29
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Ackerson SM, Gable CI, Stewart JA. Human CTC1 promotes TopBP1 stability and CHK1 phosphorylation in response to telomere dysfunction and global replication stress. Cell Cycle 2020; 19:3491-3507. [PMID: 33269665 PMCID: PMC7781613 DOI: 10.1080/15384101.2020.1849979] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 10/30/2020] [Accepted: 11/07/2020] [Indexed: 01/21/2023] Open
Abstract
CST (CTC1-STN1-TEN1) is a heterotrimeric, RPA-like complex that binds to single-stranded DNA (ssDNA) and functions in the replication of telomeric and non-telomeric DNA. Previous studies demonstrated that deletion of CTC1 results in decreased cell proliferation and telomere DNA damage signaling. However, a detailed analysis of the consequences of conditional CTC1 knockout (KO) has not been fully elucidated. Here, we investigated the effects of CTC1 KO on cell cycle progression, genome-wide replication and activation of the DNA damage response. Consistent with previous findings, we demonstrate that CTC1 KO results in decreased cell proliferation, G2 arrest and RPA-bound telomeric ssDNA. However, despite the increased levels of telomeric RPA-ssDNA, global ATR-dependent CHK1 and p53 phosphorylation was not detected in CTC1 KO cells. Nevertheless, we show that RPA-ssDNA does activate ATR, leading to the phosphorylation of RPA and autophosphorylation of ATR. Further analysis determined that inactivation of ATR, but not CHK1 or ATM, suppressed the accumulation of G2 arrested cells and phosphorylated RPA following CTC1 removal. These results suggest that ATR is localized and active at telomeres but is unable to elicit a global checkpoint response through CHK1. Furthermore, CTC1 KO inhibited CHK1 phosphorylation following hydroxyurea-induced replication stress. Additional studies revealed that this suppression of CHK1 phosphorylation, following replication stress, is caused by decreased levels of the ATR activator TopBP1. Overall, our results identify CST as a novel regulator of the ATR-CHK1 pathway.
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Affiliation(s)
| | - Caroline I. Gable
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Jason A. Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
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30
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Lyu X, Lei KH, Biak Sang P, Shiva O, Chastain M, Chi P, Chai W. Human CST complex protects stalled replication forks by directly blocking MRE11 degradation of nascent-strand DNA. EMBO J 2020; 40:e103654. [PMID: 33210317 DOI: 10.15252/embj.2019103654] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 10/07/2020] [Accepted: 10/20/2020] [Indexed: 01/31/2023] Open
Abstract
Degradation and collapse of stalled replication forks are main sources of genomic instability, yet the molecular mechanisms for protecting forks from degradation/collapse are not well understood. Here, we report that human CST (CTC1-STN1-TEN1) proteins, which form a single-stranded DNA-binding complex, localize at stalled forks and protect stalled forks from degradation by the MRE11 nuclease. CST deficiency increases MRE11 binding to stalled forks, leading to nascent-strand degradation at reversed forks and ssDNA accumulation. In addition, purified CST complex binds to 5' DNA overhangs and directly blocks MRE11 degradation in vitro, and the DNA-binding ability of CST is required for blocking MRE11-mediated nascent-strand degradation. Our results suggest that CST inhibits MRE11 binding to reversed forks, thus antagonizing excessive nascent-strand degradation. Finally, we uncover that CST complex inactivation exacerbates genome instability in BRCA2 deficient cells. Collectively, our findings identify the CST complex as an important fork protector that preserves genome integrity under replication perturbation.
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Affiliation(s)
- Xinxing Lyu
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA.,Department of Biomedical Sciences, ESF College of Medicine, Washington State University, Spokane, WA, USA
| | - Kai-Hang Lei
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Pau Biak Sang
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
| | - Olga Shiva
- Department of Biomedical Sciences, ESF College of Medicine, Washington State University, Spokane, WA, USA
| | - Megan Chastain
- Department of Biomedical Sciences, ESF College of Medicine, Washington State University, Spokane, WA, USA
| | - Peter Chi
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.,Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, USA
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31
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Mazzucco G, Huda A, Galli M, Piccini D, Giannattasio M, Pessina F, Doksani Y. Telomere damage induces internal loops that generate telomeric circles. Nat Commun 2020; 11:5297. [PMID: 33082350 PMCID: PMC7576219 DOI: 10.1038/s41467-020-19139-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 09/28/2020] [Indexed: 12/21/2022] Open
Abstract
Extrachromosomal telomeric circles are commonly invoked as important players in telomere maintenance, but their origin has remained elusive. Using electron microscopy analysis on purified telomeres we show that, apart from known structures, telomeric repeats accumulate internal loops (i-loops) that occur in the proximity of nicks and single-stranded DNA gaps. I-loops are induced by single-stranded damage at normal telomeres and represent the majority of telomeric structures detected in ALT (Alternative Lengthening of Telomeres) tumor cells. Our data indicate that i-loops form as a consequence of the exposure of single-stranded DNA at telomeric repeats. Finally, we show that these damage-induced i-loops can be excised to generate extrachromosomal telomeric circles resulting in loss of telomeric repeats. Our results identify damage-induced i-loops as a new intermediate in telomere metabolism and reveal a simple mechanism that links telomere damage to the accumulation of extrachromosomal telomeric circles and to telomere erosion.
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Affiliation(s)
- Giulia Mazzucco
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Armela Huda
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Martina Galli
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Daniele Piccini
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Michele Giannattasio
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy.,Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Via Festa del Perdono 7, Milan, 20122, Italy
| | - Fabio Pessina
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy
| | - Ylli Doksani
- IFOM, the FIRC Institute of Molecular Oncology, via Adamello 16, 20139, Milan, Italy.
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32
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Liang T, Zhang X, Xu Y, Zhao P. Ophthalmic findings and a novel CTC1 gene mutation in coats plus syndrome: a case report. Ophthalmic Genet 2020; 42:79-83. [PMID: 33034244 DOI: 10.1080/13816810.2020.1827443] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Coats plus syndrome is a rare multisystem disorder, and is also a telomere-related disorder caused by CTC1 gene mutation. We reported ophthalmic findings in a Chinese child with genetically confirmed Coats plus syndrome. MATERIALS AND METHODS The comprehensive ophthalmic findings were presented, as well as treatment history and systemic manifestations. In addition, genetic testing was performed to confirm the diagnosis. RESULTS Examination under anesthesia showed notable retinal vasculopathy, including vascular tortuosity and dilation, abnormal vascular anastomosis, retinal telangiectasias and mild exudation, extensive peripheral avascularity, as well as the presence of retinal neovascularization. The patient developed vitreous hemorrhage and tractional retinal detachment, and then underwent vitrectomy. Meanwhile, the patient was noted to have growth retardation and leukoencephalopathy. Gene testing identified a compound heterozygous mutation in CTC1 gene: a novel splicing site mutation (c.33 + 1 G > T) and a deletion mutation (c.2954_2956del, p.C985del), which were inherited from his mother and father, respectively. CONCLUSIONS The present report expanded the genotype and phenotype spectrum of CTC1 gene associated with Coats plus syndrome.
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Affiliation(s)
- Tingyi Liang
- Department of Ophthalmology, Xinhua Hospital, Affiliated to Shanghai Jiao Tong University School of Medicine , Shanghai, China
| | - Xiang Zhang
- Department of Ophthalmology, Xinhua Hospital, Affiliated to Shanghai Jiao Tong University School of Medicine , Shanghai, China
| | - Yu Xu
- Department of Ophthalmology, Xinhua Hospital, Affiliated to Shanghai Jiao Tong University School of Medicine , Shanghai, China
| | - Peiquan Zhao
- Department of Ophthalmology, Xinhua Hospital, Affiliated to Shanghai Jiao Tong University School of Medicine , Shanghai, China
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33
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Nguyen DD, Kim EY, Sang PB, Chai W. Roles of OB-Fold Proteins in Replication Stress. Front Cell Dev Biol 2020; 8:574466. [PMID: 33043007 PMCID: PMC7517361 DOI: 10.3389/fcell.2020.574466] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 08/25/2020] [Indexed: 12/20/2022] Open
Abstract
Accurate DNA replication is essential for maintaining genome stability. However, this stability becomes vulnerable when replication fork progression is stalled or slowed - a condition known as replication stress. Prolonged fork stalling can cause DNA damage, leading to genome instabilities. Thus, cells have developed several pathways and a complex set of proteins to overcome the challenge at stalled replication forks. Oligonucleotide/oligosaccharide binding (OB)-fold containing proteins are a group of proteins that play a crucial role in fork protection and fork restart. These proteins bind to single-stranded DNA with high affinity and prevent premature annealing and unwanted nuclease digestion. Among these OB-fold containing proteins, the best studied in eukaryotic cells are replication protein A (RPA) and breast cancer susceptibility protein 2 (BRCA2). Recently, another RPA-like protein complex CTC1-STN1-TEN1 (CST) complex has been found to counter replication perturbation. In this review, we discuss the latest findings on how these OB-fold containing proteins (RPA, BRCA2, CST) cooperate to safeguard DNA replication and maintain genome stability.
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Affiliation(s)
| | | | | | - Weihang Chai
- Department of Cancer Biology, Cardinal Bernardin Cancer Center, Loyola University Chicago Stritch School of Medicine, Maywood, IL, United States
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34
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Protective Mechanisms Against DNA Replication Stress in the Nervous System. Genes (Basel) 2020; 11:genes11070730. [PMID: 32630049 PMCID: PMC7397197 DOI: 10.3390/genes11070730] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/25/2020] [Accepted: 06/25/2020] [Indexed: 02/06/2023] Open
Abstract
The precise replication of DNA and the successful segregation of chromosomes are essential for the faithful transmission of genetic information during the cell cycle. Alterations in the dynamics of genome replication, also referred to as DNA replication stress, may lead to DNA damage and, consequently, mutations and chromosomal rearrangements. Extensive research has revealed that DNA replication stress drives genome instability during tumorigenesis. Over decades, genetic studies of inherited syndromes have established a connection between the mutations in genes required for proper DNA repair/DNA damage responses and neurological diseases. It is becoming clear that both the prevention and the responses to replication stress are particularly important for nervous system development and function. The accurate regulation of cell proliferation is key for the expansion of progenitor pools during central nervous system (CNS) development, adult neurogenesis, and regeneration. Moreover, DNA replication stress in glial cells regulates CNS tumorigenesis and plays a role in neurodegenerative diseases such as ataxia telangiectasia (A-T). Here, we review how replication stress generation and replication stress response (RSR) contribute to the CNS development, homeostasis, and disease. Both cell-autonomous mechanisms, as well as the evidence of RSR-mediated alterations of the cellular microenvironment in the nervous system, were discussed.
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35
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Grabuschnig S, Soh J, Heidinger P, Bachler T, Hirschböck E, Rosales Rodriguez I, Schwendenwein D, Sensen CW. Circulating cell-free DNA is predominantly composed of retrotransposable elements and non-telomeric satellite DNA. J Biotechnol 2020; 313:48-56. [DOI: 10.1016/j.jbiotec.2020.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/26/2020] [Accepted: 03/04/2020] [Indexed: 12/19/2022]
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36
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Gong Y, Stock AJ, Liu Y. The enigma of excessively long telomeres in cancer: lessons learned from rare human POT1 variants. Curr Opin Genet Dev 2020; 60:48-55. [PMID: 32155570 DOI: 10.1016/j.gde.2020.02.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/17/2020] [Accepted: 02/02/2020] [Indexed: 01/10/2023]
Abstract
The discovery that rare POT1 variants are associated with extremely long telomeres and increased cancer predisposition has provided a framework to revisit the relationship between telomere length and cancer development. Telomere shortening is linked with increased risk for cancer. However, over the past decade, there is increasing evidence to show that extremely long telomeres caused by mutations in shelterin components (POT1, TPP1, and RAP1) also display an increased risk of cancer. Here, we will review current knowledge on germline mutations of POT1 identified from cancer-prone families. In particular, we will discuss some common features presented by the mutations through structure-function studies. We will further provide an overview of how POT1 mutations affect telomere length regulation and tumorigenesis.
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Affiliation(s)
- Yi Gong
- Biomedical Research Center, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD, USA.
| | - Amanda J Stock
- Biomedical Research Center, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD, USA
| | - Yie Liu
- Biomedical Research Center, National Institute on Aging/National Institutes of Health, 251 Bayview Blvd, Baltimore, MD, USA.
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37
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Srinivas N, Rachakonda S, Kumar R. Telomeres and Telomere Length: A General Overview. Cancers (Basel) 2020; 12:E558. [PMID: 32121056 PMCID: PMC7139734 DOI: 10.3390/cancers12030558] [Citation(s) in RCA: 129] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/24/2020] [Accepted: 02/26/2020] [Indexed: 02/06/2023] Open
Abstract
Telomeres are highly conserved tandem nucleotide repeats that include proximal double-stranded and distal single-stranded regions that in complex with shelterin proteins afford protection at chromosomal ends to maintain genomic integrity. Due to the inherent limitations of DNA replication and telomerase suppression in most somatic cells, telomeres undergo age-dependent incremental attrition. Short or dysfunctional telomeres are recognized as DNA double-stranded breaks, triggering cells to undergo replicative senescence. Telomere shortening, therefore, acts as a counting mechanism that drives replicative senescence by limiting the mitotic potential of cells. Telomere length, a complex hereditary trait, is associated with aging and age-related diseases. Epidemiological data, in general, support an association with varying magnitudes between constitutive telomere length and several disorders, including cancers. Telomere attrition is also influenced by oxidative damage and replicative stress caused by genetic, epigenetic, and environmental factors. Several single nucleotide polymorphisms at different loci, identified through genome-wide association studies, influence inter-individual variation in telomere length. In addition to genetic factors, environmental factors also influence telomere length during growth and development. Telomeres hold potential as biomarkers that reflect the genetic predisposition together with the impact of environmental conditions and as targets for anti-cancer therapies.
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Affiliation(s)
| | | | - Rajiv Kumar
- Division of Functional Genome Analysis, German Cancer Research Center, Im Neunheimer Feld 580, 69120 Heidelberg, Germany; (N.S.); (S.R.)
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38
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Structural Features of Nucleoprotein CST/Shelterin Complex Involved in the Telomere Maintenance and Its Association with Disease Mutations. Cells 2020; 9:cells9020359. [PMID: 32033110 PMCID: PMC7072152 DOI: 10.3390/cells9020359] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/23/2020] [Accepted: 01/24/2020] [Indexed: 12/29/2022] Open
Abstract
Telomere comprises the ends of eukaryotic linear chromosomes and is composed of G-rich (TTAGGG) tandem repeats which play an important role in maintaining genome stability, premature aging and onsets of many diseases. Majority of the telomere are replicated by conventional DNA replication, and only the last bit of the lagging strand is synthesized by telomerase (a reverse transcriptase). In addition to replication, telomere maintenance is principally carried out by two key complexes known as shelterin (TRF1, TRF2, TIN2, RAP1, POT1, and TPP1) and CST (CDC13/CTC1, STN1, and TEN1). Shelterin protects the telomere from DNA damage response (DDR) and regulates telomere length by telomerase; while, CST govern the extension of telomere by telomerase and C strand fill-in synthesis. We have investigated both structural and biochemical features of shelterin and CST complexes to get a clear understanding of their importance in the telomere maintenance. Further, we have analyzed ~115 clinically important mutations in both of the complexes. Association of such mutations with specific cellular fault unveils the importance of shelterin and CST complexes in the maintenance of genome stability. A possibility of targeting shelterin and CST by small molecule inhibitors is further investigated towards the therapeutic management of associated diseases. Overall, this review provides a possible direction to understand the mechanisms of telomere borne diseases, and their therapeutic intervention.
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39
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Porreca RM, Herrera-Moyano E, Skourti E, Law PP, Gonzalez Franco R, Montoya A, Faull P, Kramer H, Vannier JB. TRF1 averts chromatin remodelling, recombination and replication dependent-break induced replication at mouse telomeres. eLife 2020; 9:49817. [PMID: 31934863 PMCID: PMC6986873 DOI: 10.7554/elife.49817] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 01/11/2020] [Indexed: 12/29/2022] Open
Abstract
Telomeres are a significant challenge to DNA replication and are prone to replication stress and telomere fragility. The shelterin component TRF1 facilitates telomere replication but the molecular mechanism remains uncertain. By interrogating the proteomic composition of telomeres, we show that mouse telomeres lacking TRF1 undergo protein composition reorganisation associated with the recruitment of DNA damage response and chromatin remodellers. Surprisingly, mTRF1 suppresses the accumulation of promyelocytic leukemia (PML) protein, BRCA1 and the SMC5/6 complex at telomeres, which is associated with increased Homologous Recombination (HR) and TERRA transcription. We uncovered a previously unappreciated role for mTRF1 in the suppression of telomere recombination, dependent on SMC5 and also POLD3 dependent Break Induced Replication at telomeres. We propose that TRF1 facilitates S-phase telomeric DNA synthesis to prevent illegitimate mitotic DNA recombination and chromatin rearrangement.
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Affiliation(s)
- Rosa Maria Porreca
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Emilia Herrera-Moyano
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Eleni Skourti
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Pui Pik Law
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Roser Gonzalez Franco
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Alex Montoya
- Biological Mass Spectrometry and Proteomics, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom
| | - Peter Faull
- Biological Mass Spectrometry and Proteomics, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,The Francis Crick Institute, Proteomics Mass Spectrometry Science and Technology Platform, London, United Kingdom
| | - Holger Kramer
- Biological Mass Spectrometry and Proteomics, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom
| | - Jean-Baptiste Vannier
- Telomere Replication and Stability group, Medical Research Council - London Institute of Medical Sciences, London, United Kingdom.,Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
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40
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Zhang M, Wang B, Li T, Liu R, Xiao Y, Geng X, Li G, Liu Q, Price CM, Liu Y, Wang F. Mammalian CST averts replication failure by preventing G-quadruplex accumulation. Nucleic Acids Res 2019; 47:5243-5259. [PMID: 30976812 PMCID: PMC6547417 DOI: 10.1093/nar/gkz264] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/28/2019] [Accepted: 04/03/2019] [Indexed: 11/12/2022] Open
Abstract
Human CST (CTC1-STN1-TEN1) is an RPA-like complex that associates with G-rich single-strand DNA and helps resolve replication problems both at telomeres and genome-wide. We previously showed that CST binds and disrupts G-quadruplex (G4) DNA in vitro, suggesting that CST may prevent in vivo blocks to replication by resolving G4 structures. Here, we demonstrate that CST binds and unfolds G4 with similar efficiency to RPA. In cells, CST is recruited to telomeric and non-telomeric chromatin upon G4 stabilization, even when ATR/ATM pathways were inhibited. STN1 depletion increases G4 accumulation and slows bulk genomic DNA replication. At telomeres, combined STN1 depletion and G4 stabilization causes multi-telomere FISH signals and telomere loss, hallmarks of deficient telomere duplex replication. Strand-specific telomere FISH indicates preferential loss of C-strand DNA while analysis of BrdU uptake during leading and lagging-strand telomere replication shows preferential under-replication of lagging telomeres. Together these results indicate a block to Okazaki fragment synthesis. Overall, our findings indicate a novel role for CST in maintaining genome integrity through resolution of G4 structures both ahead of the replication fork and on the lagging strand template.
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Affiliation(s)
- Miaomiao Zhang
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Bing Wang
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Tingfang Li
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Rui Liu
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Yingnan Xiao
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Xin Geng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Guang Li
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
| | - Qiang Liu
- Department of Radiobiology, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College,Tianjin 300192, PR China
| | - Carolyn M Price
- Departments of Cancer and Cell Biology, University of Cincinnati, Cincinnati, OH, USA
| | - Yang Liu
- Department of Radiobiology, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College,Tianjin 300192, PR China
| | - Feng Wang
- Department of Genetics, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, PR China
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41
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Wang Y, Chai W. Pathogenic CTC1 mutations cause global genome instabilities under replication stress. Nucleic Acids Res 2019; 46:3981-3992. [PMID: 29481669 PMCID: PMC5934659 DOI: 10.1093/nar/gky114] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 02/09/2018] [Indexed: 12/13/2022] Open
Abstract
Coats plus syndrome is a complex genetic disorder that can be caused by mutations in genes encoding the CTC1–STN1–TEN1 (CST) complex, a conserved single-stranded DNA binding protein complex. Studies have demonstrated that mutations identified in Coats plus patients are defective in telomere maintenance, and concluded that Coats plus may be caused by telomere dysfunction. Recent studies have established that CST also plays an important role in countering replication stress and protecting the stability of genomic fragile sites. However, it is unclear whether instabilities at genomic regions may promote Coats plus development. Here, we characterize eleven reported disease-causing CTC1 missense and small deletion mutations in maintaining genome stability. Our results show that these mutations induce spontaneous chromosome breakage and severe chromosome fragmentation that are further elevated by replication stress, leading to global genome instabilities. These mutations abolish or reduce CST interaction with RAD51, disrupt RAD51 foci formation, and/or diminish binding to GC-rich genomic fragile sites under replication stress. Furthermore, CTC1 mutations limit cell proliferation under unstressed condition and significantly reduce clonal viability under replication stress. Results also suggest that the aa 600–989 region of CTC1 contains a RAD51-interacting domain. Our findings thus provide molecular evidence linking replication-associated genomic defects with CP disease pathology.
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Affiliation(s)
- Yuan Wang
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210, USA
| | - Weihang Chai
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, PO Box 1495, Spokane, WA 99210, USA
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42
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Beh CW, Zhang Y, Zheng YL, Sun B, Wang TH. Fluorescence spectroscopic detection and measurement of single telomere molecules. Nucleic Acids Res 2019; 46:e117. [PMID: 30010842 PMCID: PMC6212783 DOI: 10.1093/nar/gky627] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 06/28/2018] [Indexed: 01/26/2023] Open
Abstract
Telomeres are the end-caps of chromosomes that serve to protect the integrity of the genome. Below certain critical lengths, the telomeres can no longer fulfill their protective function, and chromosomal instability ensues. Telomeres shorten during normal cell division due to the end replication problem and are implicated in the development of various aging-associated diseases, including cancer. Telomere length has the potential to serve as a useful biomarker in the field of aging and cancer. However, existing methods of telomere measurement are either too laborious, unable to provide absolute measurement of individual telomere lengths, or limited to certain chromosomes or cell types. Here, we describe an easy single-molecule, fluorescence spectroscopic method for measuring the length of telomeres that permits the profiling of absolute telomere lengths in any DNA sample. We have demonstrated the accurate detection of telomeres as short as 100 bp using cloned telomere standards, and have profiled telomere lengths in human cancer cell lines and primary cells. Since this method allows direct comparison between samples, it could greatly improve the clinical utility of telomere biomarkers.
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Affiliation(s)
- Cyrus W Beh
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Ye Zhang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Yun-Ling Zheng
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Bing Sun
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Tza-Huei Wang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.,Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.,Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD 21218, USA
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43
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Shastrula PK, Rice CT, Wang Z, Lieberman PM, Skordalakes E. Structural and functional analysis of an OB-fold in human Ctc1 implicated in telomere maintenance and bone marrow syndromes. Nucleic Acids Res 2019; 46:972-984. [PMID: 29228254 PMCID: PMC5778599 DOI: 10.1093/nar/gkx1213] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 11/23/2017] [Indexed: 12/18/2022] Open
Abstract
The human CST (Ctc1, Stn1 and Ten1) complex binds the telomeric overhang and regulates telomere length by promoting C-strand replication and inhibiting telomerase-dependent G-strand synthesis. Structural and biochemical studies on the human Stn1 and Ten1 complex revealed its mechanism of assembly and nucleic acid binding. However, little is known about the structural organization of the multi-domain Ctc1 protein and how each of these domains contribute to telomere length regulation. Here, we report the structure of a central domain of human Ctc1. The structure reveals a canonical OB-fold with the two identified disease mutations (R840W and V871M) contributing to the fold of the protein. In vitro assays suggest that although this domain is not contributing directly to Ctc1’s substrate binding properties, it affects full-length Ctc1 localization to telomeres and Stn1-Ten1 binding. Moreover, functional assays show that deletion of the entire OB-fold domain leads to significant increase in telomere length, frequency of internal single G-strands and fragile telomeres. Our findings demonstrate that a previously unknown OB-fold domain contributes to efficient Ctc1 telomere localization and chromosome end maintenance.
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Affiliation(s)
- Prashanth K Shastrula
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Cory T Rice
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Zhuo Wang
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Paul M Lieberman
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
| | - Emmanuel Skordalakes
- The Wistar Institute, Gene expression and regulation program, 3601 Spruce Street, Philadelphia, PA 19104, USA
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44
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Amir M, Mohammad T, Kumar V, Alajmi MF, Rehman MT, Hussain A, Alam P, Dohare R, Islam A, Ahmad F, Hassan MI. Structural Analysis and Conformational Dynamics of STN1 Gene Mutations Involved in Coat Plus Syndrome. Front Mol Biosci 2019; 6:41. [PMID: 31245382 PMCID: PMC6581698 DOI: 10.3389/fmolb.2019.00041] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 05/17/2019] [Indexed: 11/13/2022] Open
Abstract
The human CST complex (CTC1-STN1-TEN1) is associated with telomere functions including genome stability. We have systemically analyzed the sequence of STN and performed structure analysis to establish its association with the Coat Plus (CP) syndrome. Many deleterious non-synonymous SNPs have been identified and subjected for structure analysis to find their pathogenic association and aggregation propensity. A 100-ns all-atom molecular dynamics simulation of WT, R135T, and D157Y structures revealed significant conformational changes in the case of mutants. Changes in hydrogen bonds, secondary structure, and principal component analysis further support the structural basis of STN1 dysfunction in such mutations. Free energy landscape analysis revealed the presence of multiple energy minima, suggesting that R135T and D157Y mutations destabilize and alter the conformational dynamics of STN1 and thus may be associated with the CP syndrome. Our study provides a valuable direction to understand the molecular basis of CP syndrome and offer a newer therapeutics approach to address CP syndrome.
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Affiliation(s)
- Mohd Amir
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Taj Mohammad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Vijay Kumar
- Amity Institute of Neuropsychology and Neurosciences, Amity University Noida, Noida, India
| | - Mohammed F Alajmi
- Department of Pharmacognosy College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Md Tabish Rehman
- Department of Pharmacognosy College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Afzal Hussain
- Department of Pharmacognosy College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Perwez Alam
- Department of Pharmacognosy College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Ravins Dohare
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Asimul Islam
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Faizan Ahmad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
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45
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Luo Z, Wang W, Li F, Songyang Z, Feng X, Xin C, Dai Z, Xiong Y. Pan-cancer analysis identifies telomerase-associated signatures and cancer subtypes. Mol Cancer 2019; 18:106. [PMID: 31179925 PMCID: PMC6556968 DOI: 10.1186/s12943-019-1035-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 05/29/2019] [Indexed: 01/09/2023] Open
Abstract
Background Cancer cells become immortalized through telomere maintenance mechanisms, such as telomerase reverse transcriptase (TERT) activation. In addition to maintaining telomere length, TERT activates manifold cell survival signaling pathways. However, telomerase-associated gene signatures in cancer remain elusive. Methods We performed a systematic analysis of TERT high (TERThigh) and low (TERTlow) cancers using multidimensional data from The Cancer Genome Atlas (TCGA). Multidimensional data were analyzed by propensity score matching weight algorithm. Coexpression networks were constructed by weight gene coexpression network analysis (WGCNA). Random forest classifiers were generated to identify cancer subtypes. Results The TERThigh-specific mRNA expression signature is associated with cell cycle-related coexpression modules across cancer types. Experimental screening of hub genes in the cell cycle module suggested TPX2 and EXO1 as potential regulators of telomerase activity and cell survival. MiRNA analysis revealed that the TERThigh-specific miR-17-92 cluster can target biological processes enriched in TERTlow cancer and that its expression is negatively correlated with the tumor/normal telomere length ratio. Intriguingly, TERThigh cancers tend to have mutations in extracellular matrix organization genes and amplify MAPK signaling. By mining the clinical actionable gene database, we uncovered a number of TERThigh-specific somatic mutations, amplifications and high expression genes containing therapeutic targets. Finally, a random forest classifier integrating telomerase-associated multi-omics signatures identifies two cancer subtypes showed profound differences in telomerase activity and patient survival. Conclusions In summary, our results depict a telomerase-associated molecular landscape in cancers and provide therapeutic opportunities for cancer treatment. Electronic supplementary material The online version of this article (10.1186/s12943-019-1035-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhenhua Luo
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510006, China.,Division of Gastroenterology, Hepatology and Nutrition, Cincinnati Children's Hospital Medical Center and the Department of Pediatrics Cincinnati, Ohio, 45229, USA
| | - Weixu Wang
- College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Feng Li
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510006, China
| | - Zhou Songyang
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510006, China.,Verna and Marrs Mclean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Xuyang Feng
- Department of Cancer Biology, University of Cincinnati, Cincinnati, OH, 45230, USA.,The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510275, China
| | - Changchang Xin
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510006, China
| | - Zhiming Dai
- School of Data and Computer Science, Sun Yat-Sen University, Guangzhou, 510006, China.
| | - Yuanyan Xiong
- Key Laboratory of Gene Engineering of the Ministry of Education and State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510006, China.
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46
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Doksani Y. The Response to DNA Damage at Telomeric Repeats and Its Consequences for Telomere Function. Genes (Basel) 2019; 10:genes10040318. [PMID: 31022960 PMCID: PMC6523756 DOI: 10.3390/genes10040318] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/13/2019] [Accepted: 04/18/2019] [Indexed: 01/17/2023] Open
Abstract
Telomeric repeats, coated by the shelterin complex, prevent inappropriate activation of the DNA damage response at the ends of linear chromosomes. Shelterin has evolved distinct solutions to protect telomeres from different aspects of the DNA damage response. These solutions include formation of t-loops, which can sequester the chromosome terminus from DNA-end sensors and inhibition of key steps in the DNA damage response. While blocking the DNA damage response at chromosome ends, telomeres make wide use of many of its players to deal with exogenous damage and replication stress. This review focuses on the interplay between the end-protection functions and the response to DNA damage occurring inside the telomeric repeats, as well as on the consequences that telomere damage has on telomere structure and function.
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Affiliation(s)
- Ylli Doksani
- IFOM, The FIRC Institute of Molecular Oncology, via Adamello 16, 20139 Milan, Italy.
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47
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Wang Y, Brady KS, Caiello BP, Ackerson SM, Stewart JA. Human CST suppresses origin licensing and promotes AND-1/Ctf4 chromatin association. Life Sci Alliance 2019; 2:2/2/e201800270. [PMID: 30979824 PMCID: PMC6464128 DOI: 10.26508/lsa.201800270] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 12/17/2022] Open
Abstract
Human CTC1-STN1-TEN1 (CST) is an RPA-like single-stranded DNA-binding protein that interacts with DNA polymerase α-primase (pol α) and functions in telomere replication. Previous studies suggest that CST also promotes replication restart after fork stalling. However, the precise role of CST in genome-wide replication remains unclear. In this study, we sought to understand whether CST alters origin licensing and activation. Replication origins are licensed by loading of the minichromosome maintenance 2-7 (MCM) complex in G1 followed by replisome assembly and origin firing in S-phase. We find that CST directly interacts with the MCM complex and disrupts binding of CDT1 to MCM, leading to decreased origin licensing. We also show that CST enhances replisome assembly by promoting AND-1/pol α chromatin association. Moreover, these interactions are not dependent on exogenous replication stress, suggesting that CST acts as a specialized replication factor during normal replication. Overall, our findings implicate CST as a novel regulator of origin licensing and replisome assembly/fork progression through interactions with MCM, AND-1, and pol α.
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Affiliation(s)
- Yilin Wang
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Kathryn S Brady
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Benjamin P Caiello
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Stephanie M Ackerson
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Jason A Stewart
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA .,Center for Colon Cancer Research, University of South Carolina, Columbia, SC, USA
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48
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Escandell JM, Carvalho ES, Gallo-Fernandez M, Reis CC, Matmati S, Luís IM, Abreu IA, Coulon S, Ferreira MG. Ssu72 phosphatase is a conserved telomere replication terminator. EMBO J 2019; 38:embj.2018100476. [PMID: 30796050 PMCID: PMC6443209 DOI: 10.15252/embj.2018100476] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 01/21/2019] [Accepted: 01/28/2019] [Indexed: 01/31/2023] Open
Abstract
Telomeres, the protective ends of eukaryotic chromosomes, are replicated through concerted actions of conventional DNA polymerases and elongated by telomerase, but the regulation of this process is not fully understood. Telomere replication requires (Ctc1/Cdc13)‐Stn1‐Ten1, a telomeric ssDNA‐binding complex homologous to RPA. Here, we show that the evolutionarily conserved phosphatase Ssu72 is responsible for terminating the cycle of telomere replication in fission yeast. Ssu72 controls the recruitment of Stn1 to telomeres by regulating Stn1 phosphorylation at Ser74, a residue located within its conserved OB‐fold domain. Consequently, ssu72∆ mutants are defective in telomere replication and exhibit long 3′‐ssDNA overhangs, indicative of defective lagging‐strand DNA synthesis. We also show that hSSU72 regulates telomerase activation in human cells by controlling recruitment of hSTN1 to telomeres. These results reveal a previously unknown yet conserved role for the phosphatase SSU72, whereby this enzyme controls telomere homeostasis by activating lagging‐strand DNA synthesis, thus terminating the cycle of telomere replication.
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Affiliation(s)
| | | | | | - Clara C Reis
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
| | - Samah Matmati
- Equipe Labellisée Ligue, CRCM, CNRS, Inserm, Institut Paoli-Calmettes, Aix-Marseille University, Marseille, France
| | - Inês Matias Luís
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Isabel A Abreu
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Stéphane Coulon
- Equipe Labellisée Ligue, CRCM, CNRS, Inserm, Institut Paoli-Calmettes, Aix-Marseille University, Marseille, France
| | - Miguel Godinho Ferreira
- Instituto Gulbenkian de Ciência, Oeiras, Portugal .,Institute for Research on Cancer and Aging of Nice (IRCAN), INSERM U1081 UMR7284, CNRS, Nice, France
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49
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Macrophage achieves self-protection against oxidative stress-induced ageing through the Mst-Nrf2 axis. Nat Commun 2019; 10:755. [PMID: 30765703 PMCID: PMC6376064 DOI: 10.1038/s41467-019-08680-6] [Citation(s) in RCA: 142] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 01/22/2019] [Indexed: 12/24/2022] Open
Abstract
Reactive oxygen species (ROS) production in phagocytes is a major defense mechanism against pathogens. However, the cellular self-protective mechanism against such potential damage from oxidative stress remains unclear. Here we show that the kinases Mst1 and Mst2 (Mst1/2) sense ROS and maintain cellular redox balance by modulating the stability of antioxidant transcription factor Nrf2. Site-specific ROS release recruits Mst1/2 from the cytosol to the phagosomal or mitochondrial membrane, with ROS subsequently activating Mst1/2 to phosphorylate kelch like ECH associated protein 1 (Keap1) and prevent Keap1 polymerization, thereby blocking Nrf2 ubiquitination and degradation to protect cells against oxidative damage. Treatment with the antioxidant N-acetylcysteine disrupts ROS-induced interaction of Mst1/2 with phagosomes or mitochondria, and thereby diminishes the Mst-Nrf2 signal. Consistently, loss of Mst1/2 results in increased oxidative injury, phagocyte ageing and death. Thus, our results identify the Mst-Nrf2 axis as an important ROS-sensing and antioxidant mechanism during an antimicrobial response. Immune cells produce reactive oxygen species (ROS) to eliminate pathogens, but cell-spontaneous death and ageing may also be induced. Here the authors show that, upon sensing ROS, Mst1/2 kinases modulate the activity of Nrf2 transcription factor and downstream genetic programs to protect mouse macrophages from death and ageing.
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50
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Coluzzi E, Leone S, Sgura A. Oxidative Stress Induces Telomere Dysfunction and Senescence by Replication Fork Arrest. Cells 2019; 8:cells8010019. [PMID: 30609792 PMCID: PMC6356380 DOI: 10.3390/cells8010019] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 12/29/2018] [Indexed: 12/12/2022] Open
Abstract
Oxidative DNA damage, particularly 8-oxoguanine, represents the most frequent DNA damage in human cells, especially at the telomeric level. The presence of oxidative lesions in the DNA can hinder the replication fork and is able to activate the DNA damage response. In this study, we wanted to understand the mechanisms by which oxidative damage causes telomere dysfunction and senescence in human primary fibroblasts. After acute oxidative stress at telomeres, our data demonstrated a reduction in TRF1 and TRF2, which are involved in proper telomere replication and T-loop formation, respectively. Furthermore, we observed a higher level of γH2AX with respect to 53BP1 at telomeres, suggesting a telomeric replication fork stall rather than double-strand breaks. To confirm this finding, we studied the replication of telomeres by Chromosome Orientation-FISH (CO-FISH). The data obtained show an increase in unreplicated telomeres after hydrogen peroxide treatment, corroborating the idea that the presence of 8-oxoG can induce replication fork arrest at telomeres. Lastly, we analyzed the H3K9me3 histone mark after oxidative stress at telomeres, and our results showed an increase of this marker, most likely inducing the heterochromatinization of telomeres. These results suggest that 8-oxoG is fundamental in oxidative stress-induced telomeric damage, principally causing replication fork arrest.
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Affiliation(s)
- Elisa Coluzzi
- Department of Science, University of Rome "Roma TRE", Viale Guglielmo Marconi, 446, 00146 Rome, Italy.
| | - Stefano Leone
- Department of Science, University of Rome "Roma TRE", Viale Guglielmo Marconi, 446, 00146 Rome, Italy.
| | - Antonella Sgura
- Department of Science, University of Rome "Roma TRE", Viale Guglielmo Marconi, 446, 00146 Rome, Italy.
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