1
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Shi Y, Tan Q, Yang C, Li S, Li Y, He B, Xie H, Duan X, Chen L. Establishment of a Cleavage-Based Single-Plasmid Dual-Luciferase Surrogate Reporter for the Cleavage Efficiency Evaluation of CRISPR-Cas12a Systems and Its Primary Application. CRISPR J 2024; 7:156-167. [PMID: 38922054 DOI: 10.1089/crispr.2024.0038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024] Open
Abstract
CRISPR-Cas technology is a widely utilized gene-editing tool that involves gRNA-guided sequence recognition and Cas nuclease-mediated cleavage. The design and evaluation of gRNA are essential for enhancing CRISPR/Cas editing efficiency. Various assays such as single-strand annealing, in vitro cleavage, and T7 endonuclease I (T7EI) are commonly used to assess gRNA-mediated Cas protein cleavage activity. In this study, a firefly luciferase and Renilla luciferase co-expressed and a cleavage-based single-plasmid dual-luciferase surrogate reporter was built to evaluate the gRNA-mediated Cas12a cleavage efficiency. The cleavage activities of CRISPR-Cas12a can be quantitatively determined by the recovery degree of firefly luciferase activity. The cleavage efficiency of CRISPR-Cas12a can be quantitatively measured by the recovery of firefly luciferase activity. By using this system, the cleavage efficiency of CRISPR-Cas12a on hepatitis B virus (HBV)/D expression plasmid was evaluated, revealing a negative correlation between gRNA cleavage efficiency and HBV gene expression measured using an enzyme-linked immunosorbent assay. This simple, efficient, and quantifiable system only requires the dual-luciferase vector and CRISPR-Cas12a vector, making it a valuable tool for selecting effective gRNAs for gene editing.
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Affiliation(s)
- Yaoqiang Shi
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Qi Tan
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Chunhui Yang
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Shilin Li
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Yujia Li
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Baoren He
- The Joint Laboratory on Transfusion-Transmitted Diseases (TTDs) Between Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Nanning Blood Center, Nanning Blood Center, Nanning, China
| | - He Xie
- The Hospital of Xidian Group, Xi'an, China
| | - Xiaoqiong Duan
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Limin Chen
- Provincial Key Laboratory for Transfusion-Transmitted Infectious Diseases, Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
- The Joint Laboratory on Transfusion-Transmitted Diseases (TTDs) Between Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Nanning Blood Center, Nanning Blood Center, Nanning, China
- The Hospital of Xidian Group, Xi'an, China
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2
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Tan J, Sun X, Zhao H, Guan H, Gao S, Zhou P. Double-strand DNA break repair: molecular mechanisms and therapeutic targets. MedComm (Beijing) 2023; 4:e388. [PMID: 37808268 PMCID: PMC10556206 DOI: 10.1002/mco2.388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 08/29/2023] [Accepted: 09/08/2023] [Indexed: 10/10/2023] Open
Abstract
Double-strand break (DSB), a significant DNA damage brought on by ionizing radiation, acts as an initiating signal in tumor radiotherapy, causing cancer cells death. The two primary pathways for DNA DSB repair in mammalian cells are nonhomologous end joining (NHEJ) and homologous recombination (HR), which cooperate and compete with one another to achieve effective repair. The DSB repair mechanism depends on numerous regulatory variables. DSB recognition and the recruitment of DNA repair components, for instance, depend on the MRE11-RAD50-NBS1 (MRN) complex and the Ku70/80 heterodimer/DNA-PKcs (DNA-PK) complex, whose control is crucial in determining the DSB repair pathway choice and efficiency of HR and NHEJ. In-depth elucidation on the DSB repair pathway's molecular mechanisms has greatly facilitated for creation of repair proteins or pathways-specific inhibitors to advance precise cancer therapy and boost the effectiveness of cancer radiotherapy. The architectures, roles, molecular processes, and inhibitors of significant target proteins in the DSB repair pathways are reviewed in this article. The strategy and application in cancer therapy are also discussed based on the advancement of inhibitors targeted DSB damage response and repair proteins.
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Affiliation(s)
- Jinpeng Tan
- Hengyang Medical CollegeUniversity of South ChinaHengyangHunan ProvinceChina
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
| | - Xingyao Sun
- Hengyang Medical CollegeUniversity of South ChinaHengyangHunan ProvinceChina
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
| | - Hongling Zhao
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
| | - Hua Guan
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
| | - Shanshan Gao
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
| | - Ping‐Kun Zhou
- Hengyang Medical CollegeUniversity of South ChinaHengyangHunan ProvinceChina
- Department of Radiation BiologyBeijing Key Laboratory for RadiobiologyBeijing Institute of Radiation MedicineBeijingChina
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3
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Hacker L, Dorn A, Enderle J, Puchta H. The repair of topoisomerase 2 cleavage complexes in Arabidopsis. THE PLANT CELL 2022; 34:287-301. [PMID: 34524446 PMCID: PMC8773952 DOI: 10.1093/plcell/koab228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/08/2021] [Indexed: 05/04/2023]
Abstract
DNA-protein crosslinks (DPCs) and DNA double-stranded breaks (DSBs), including those produced by stalled topoisomerase 2 cleavage complexes (TOP2ccs), must be repaired to ensure genome stability. The basic mechanisms of TOP2cc repair have been characterized in other eukaryotes, but we lack information for plants. Using CRISPR/Cas-induced mutants, we show that Arabidopsis thaliana has two main TOP2cc repair pathways: one is defined by TYROSYL-DNA-PHOSPHODIESTERASE 2 (TDP2), which hydrolyzes TOP2-DNA linkages, the other by the DNA-dependent protease WSS1A (a homolog of human SPARTAN/yeast weak suppressor of smt3 [Wss1]), which also functions in DPC repair. TDP1 and TDP2 function nonredundantly in TOP1cc repair, indicating that they act specifically on their respective stalled cleavage complexes. The nuclease METHYL METHANESULFONATE AND UV-SENSITIVE PROTEIN 81 (MUS81) plays a major role in global DPC repair and a minor role in TOP2cc repair. DSBs arise as intermediates of TOP2cc repair and are repaired by classical and alternative nonhomologous end joining (NHEJ) pathways. Double-mutant analysis indicates that "clean" DNA ends caused by TDP2 hydrolysis are mainly religated by classical NHEJ, which helps avoid mutation. In contrast, the mutagenic alternative NHEJ pathway mainly processes nonligateable DNA ends. Thus, TDP2 promotes maintenance of plant genome integrity by error-free repair of TOP2cc.
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Affiliation(s)
- Leonie Hacker
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
| | - Annika Dorn
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
| | - Janina Enderle
- Botanical Institute, Molecular Biology and Biochemistry, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany
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4
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Swan RL, Cowell IG, Austin CA. Mechanisms to repair stalled Topoisomerase II-DNA covalent complexes. Mol Pharmacol 2021; 101:24-32. [PMID: 34689119 DOI: 10.1124/molpharm.121.000374] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 10/11/2021] [Indexed: 11/22/2022] Open
Abstract
DNA topoisomerases regulate the topological state of DNA, relaxing DNA supercoils and resolving catenanes and knots that result from biological processes such as transcription and replication. DNA topoisomerase II (TOP2) enzymes achieve this by binding DNA and introducing an enzyme-bridged DNA double-strand break (DSB) where each protomer of the dimeric enzyme is covalently attached to the 5' end of the cleaved DNA via an active site tyrosine phosphodiester linkage. The enzyme then passes a second DNA duplex though the DNA break, before religation and release of the enzyme. However, this activity is potentially hazardous to the cell, as failure to complete religation leads to persistent TOP2 protein-DNA covalent complexes which are cytotoxic. Indeed, this property of topoisomerase has been exploited in cancer therapy in the form of topoisomerase poisons which block the religation stage of the reaction cycle, leading to an accumulation of topoisomerase-DNA adducts. A number of parallel cellular processes have been identified that lead to removal of these covalent TOP2-DNA complexes facilitating repair of the resulting protein-free DSB by standard DNA repair pathways. These pathways presumably arose to repair spontaneous stalled or poisoned TOP2-DNA complexes, but understanding their mechanisms also has implications for cancer therapy, particularly resistance to anti-cancer TOP2 poisons and the genotoxic side effects of these drugs. Here we review recent progress in the understanding of the processing to TOP2 DNA covalent complexes., The basic components and mechanisms plus the additional layer of complexity posed by the post-translational modifications that modulate these pathways. Significance Statement Multiple pathways have been reported for removal and repair of TOP2-DNA covalent complexes to ensure the timely and efficient repair of TOP2-DNA covalent adducts to protect the genome. Post-translational modifications such as ubiquitination and SUMOylation are involved in the regulation of TOP2-DNA complex repair. Small molecule inhibitors of these post translational modifications may help to improve outcomes of TOP2 poison chemotherapy, for example by increasing TOP2 poison cytotoxicity and reducing genotoxicity, but this remains to be determined.
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Affiliation(s)
- Rebecca L Swan
- Biosciences Institute, Newcastle University, United Kingdom
| | - Ian G Cowell
- Institute for Cell and Molecular Biosciences, Newcastle University, United Kingdom
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5
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van de Kamp G, Heemskerk T, Kanaar R, Essers J. DNA Double Strand Break Repair Pathways in Response to Different Types of Ionizing Radiation. Front Genet 2021; 12:738230. [PMID: 34659358 PMCID: PMC8514742 DOI: 10.3389/fgene.2021.738230] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/30/2021] [Indexed: 01/12/2023] Open
Abstract
The superior dose distribution of particle radiation compared to photon radiation makes it a promising therapy for the treatment of tumors. However, the cellular responses to particle therapy and especially the DNA damage response (DDR) is not well characterized. Compared to photons, particles are thought to induce more closely spaced DNA lesions instead of isolated lesions. How this different spatial configuration of the DNA damage directs DNA repair pathway usage, is subject of current investigations. In this review, we describe recent insights into induction of DNA damage by particle radiation and how this shapes DNA end processing and subsequent DNA repair mechanisms. Additionally, we give an overview of promising DDR targets to improve particle therapy.
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Affiliation(s)
- Gerarda van de Kamp
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.,Oncode Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Tim Heemskerk
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.,Oncode Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Roland Kanaar
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.,Oncode Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Jeroen Essers
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.,Department of Vascular Surgery, Erasmus University Medical Center, Rotterdam, Netherlands.,Department of Radiation Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
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6
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Atkins A, Chung CH, Allen AG, Dampier W, Gurrola TE, Sariyer IK, Nonnemacher MR, Wigdahl B. Off-Target Analysis in Gene Editing and Applications for Clinical Translation of CRISPR/Cas9 in HIV-1 Therapy. Front Genome Ed 2021; 3:673022. [PMID: 34713260 PMCID: PMC8525399 DOI: 10.3389/fgeed.2021.673022] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 06/21/2021] [Indexed: 12/26/2022] Open
Abstract
As genome-editing nucleases move toward broader clinical applications, the need to define the limits of their specificity and efficiency increases. A variety of approaches for nuclease cleavage detection have been developed, allowing a full-genome survey of the targeting landscape and the detection of a variety of repair outcomes for nuclease-induced double-strand breaks. Each approach has advantages and disadvantages relating to the means of target-site capture, target enrichment mechanism, cellular environment, false discovery, and validation of bona fide off-target cleavage sites in cells. This review examines the strengths, limitations, and origins of the different classes of off-target cleavage detection systems including anchored primer enrichment (GUIDE-seq), in situ detection (BLISS), in vitro selection libraries (CIRCLE-seq), chromatin immunoprecipitation (ChIP) (DISCOVER-Seq), translocation sequencing (LAM PCR HTGTS), and in vitro genomic DNA digestion (Digenome-seq and SITE-Seq). Emphasis is placed on the specific modifications that give rise to the enhanced performance of contemporary techniques over their predecessors and the comparative performance of techniques for different applications. The clinical relevance of these techniques is discussed in the context of assessing the safety of novel CRISPR/Cas9 HIV-1 curative strategies. With the recent success of HIV-1 and SIV-1 viral suppression in humanized mice and non-human primates, respectively, using CRISPR/Cas9, rigorous exploration of potential off-target effects is of critical importance. Such analyses would benefit from the application of the techniques discussed in this review.
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Affiliation(s)
- Andrew Atkins
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Cheng-Han Chung
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Alexander G. Allen
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Will Dampier
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Theodore E. Gurrola
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Ilker K. Sariyer
- Department of Neuroscience and Center for Neurovirology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Michael R. Nonnemacher
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Brian Wigdahl
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States,Center for Molecular Virology and Translational Neuroscience, Institute for Molecular Medicine and Infectious Disease, Drexel University College of Medicine, Philadelphia, PA, United States,Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA, United States,*Correspondence: Brian Wigdahl
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7
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Huang R, Zhou PK. DNA damage repair: historical perspectives, mechanistic pathways and clinical translation for targeted cancer therapy. Signal Transduct Target Ther 2021; 6:254. [PMID: 34238917 PMCID: PMC8266832 DOI: 10.1038/s41392-021-00648-7] [Citation(s) in RCA: 239] [Impact Index Per Article: 79.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 04/28/2021] [Accepted: 05/13/2021] [Indexed: 02/06/2023] Open
Abstract
Genomic instability is the hallmark of various cancers with the increasing accumulation of DNA damage. The application of radiotherapy and chemotherapy in cancer treatment is typically based on this property of cancers. However, the adverse effects including normal tissues injury are also accompanied by the radiotherapy and chemotherapy. Targeted cancer therapy has the potential to suppress cancer cells' DNA damage response through tailoring therapy to cancer patients lacking specific DNA damage response functions. Obviously, understanding the broader role of DNA damage repair in cancers has became a basic and attractive strategy for targeted cancer therapy, in particular, raising novel hypothesis or theory in this field on the basis of previous scientists' findings would be important for future promising druggable emerging targets. In this review, we first illustrate the timeline steps for the understanding the roles of DNA damage repair in the promotion of cancer and cancer therapy developed, then we summarize the mechanisms regarding DNA damage repair associated with targeted cancer therapy, highlighting the specific proteins behind targeting DNA damage repair that initiate functioning abnormally duo to extrinsic harm by environmental DNA damage factors, also, the DNA damage baseline drift leads to the harmful intrinsic targeted cancer therapy. In addition, clinical therapeutic drugs for DNA damage and repair including therapeutic effects, as well as the strategy and scheme of relative clinical trials were intensive discussed. Based on this background, we suggest two hypotheses, namely "environmental gear selection" to describe DNA damage repair pathway evolution, and "DNA damage baseline drift", which may play a magnified role in mediating repair during cancer treatment. This two new hypothesis would shed new light on targeted cancer therapy, provide a much better or more comprehensive holistic view and also promote the development of new research direction and new overcoming strategies for patients.
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Affiliation(s)
- Ruixue Huang
- Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, Changsha, Hunan, China
| | - Ping-Kun Zhou
- Department of Radiation Biology, Beijing Key Laboratory for Radiobiology, Beijing Institute of Radiation Medicine, AMMS, Beijing, China.
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8
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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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9
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Chandramouly G, Liao S, Rusanov T, Borisonnik N, Calbert ML, Kent T, Sullivan-Reed K, Vekariya U, Kashkina E, Skorski T, Yan H, Pomerantz RT. Polθ promotes the repair of 5'-DNA-protein crosslinks by microhomology-mediated end-joining. Cell Rep 2021; 34:108820. [PMID: 33691100 PMCID: PMC8565190 DOI: 10.1016/j.celrep.2021.108820] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 11/23/2020] [Accepted: 02/12/2021] [Indexed: 12/25/2022] Open
Abstract
DNA polymerase θ (Polθ) confers resistance to chemotherapy agents that cause DNA-protein crosslinks (DPCs) at double-strand breaks (DSBs), such as topoisomerase inhibitors. This suggests Polθ might facilitate DPC repair by microhomology-mediated end-joining (MMEJ). Here, we investigate Polθ repair of DSBs carrying DPCs by monitoring MMEJ in Xenopus egg extracts. MMEJ in extracts is dependent on Polθ, exhibits the MMEJ repair signature, and efficiently repairs 5' terminal DPCs independently of non-homologous end-joining and the replisome. We demonstrate that Polθ promotes the repair of 5' terminal DPCs in mammalian cells by using an MMEJ reporter and find that Polθ confers resistance to formaldehyde in addition to topoisomerase inhibitors. Dual deficiency in Polθ and tyrosyl-DNA phosphodiesterase 2 (TDP2) causes severe cellular sensitivity to etoposide, which demonstrates MMEJ as an independent DPC repair pathway. These studies recapitulate MMEJ in vitro and elucidate how Polθ confers resistance to etoposide.
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Affiliation(s)
- Gurushankar Chandramouly
- Thomas Jefferson University, Sidney Kimmel Cancer Center, Department of Biochemistry and Molecular Biology, Philadelphia, PA 19107, USA
| | - Shuren Liao
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Timur Rusanov
- Washington University School of Medicine, Department of Pathology & Immunology, St. Louis, MO 63110, USA
| | - Nikita Borisonnik
- Thomas Jefferson University, Sidney Kimmel Cancer Center, Department of Biochemistry and Molecular Biology, Philadelphia, PA 19107, USA
| | - Marissa L Calbert
- Thomas Jefferson University, Sidney Kimmel Cancer Center, Department of Biochemistry and Molecular Biology, Philadelphia, PA 19107, USA; Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA
| | - Tatiana Kent
- Thomas Jefferson University, Sidney Kimmel Cancer Center, Department of Biochemistry and Molecular Biology, Philadelphia, PA 19107, USA
| | - Katherine Sullivan-Reed
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA
| | - Umeshkumar Vekariya
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA
| | - Ekaterina Kashkina
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA
| | - Tomasz Skorski
- Fels Cancer Institute for Personalized Medicine, Temple University Lewis Katz School of Medicine, Philadelphia, PA 19140, USA
| | - Hong Yan
- Fox Chase Cancer Center, Philadelphia, PA 19111, USA
| | - Richard T Pomerantz
- Thomas Jefferson University, Sidney Kimmel Cancer Center, Department of Biochemistry and Molecular Biology, Philadelphia, PA 19107, USA.
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10
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Sharma S, Anand R, Zhang X, Francia S, Michelini F, Galbiati A, Williams H, Ronato DA, Masson JY, Rothenberg E, Cejka P, d'Adda di Fagagna F. MRE11-RAD50-NBS1 Complex Is Sufficient to Promote Transcription by RNA Polymerase II at Double-Strand Breaks by Melting DNA Ends. Cell Rep 2021; 34:108565. [PMID: 33406426 PMCID: PMC7788559 DOI: 10.1016/j.celrep.2020.108565] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/19/2020] [Accepted: 12/07/2020] [Indexed: 12/24/2022] Open
Abstract
The MRE11-RAD50-NBS1 (MRN) complex supports the synthesis of damage-induced long non-coding RNA (dilncRNA) by RNA polymerase II (RNAPII) from DNA double-strand breaks (DSBs) by an unknown mechanism. Here, we show that recombinant human MRN and native RNAPII are sufficient to reconstitute a minimal functional transcriptional apparatus at DSBs. MRN recruits and stabilizes RNAPII at DSBs. Unexpectedly, transcription is promoted independently from MRN nuclease activities. Rather, transcription depends on the ability of MRN to melt DNA ends, as shown by the use of MRN mutants and specific allosteric inhibitors. Single-molecule FRET assays with wild-type and mutant MRN show a tight correlation between the ability to melt DNA ends and to promote transcription. The addition of RPA enhances MRN-mediated transcription, and unpaired DNA ends allow MRN-independent transcription by RNAPII. These results support a model in which MRN generates single-strand DNA ends that favor the initiation of transcription by RNAPII.
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Affiliation(s)
- Sheetal Sharma
- IFOM-The FIRC Institute of Molecular Oncology, Milan 20139, Italy; Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India
| | - Roopesh Anand
- Institute for Research in Biomedicine, Università della Svizzera Italiana (USI), Faculty of Biomedical Sciences, Bellinzona 6500, Switzerland
| | - Xuzhu Zhang
- NYU Langone Medical Center, 450 East 29th Street, New York, NY, USA
| | - Sofia Francia
- IFOM-The FIRC Institute of Molecular Oncology, Milan 20139, Italy; Istituto di Genetica Molecolare, CNR-Consiglio Nazionale delle Ricerche, Pavia 2700, Italy
| | - Flavia Michelini
- IFOM-The FIRC Institute of Molecular Oncology, Milan 20139, Italy
| | | | | | - Daryl A Ronato
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Axis, 9 McMahon, Québec City, QC G1R 2J6, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 2J6, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, HDQ Pavilion, Oncology Axis, 9 McMahon, Québec City, QC G1R 2J6, Canada; Department of Molecular Biology, Medical Biochemistry, and Pathology, Laval University Cancer Research Center, Québec City, QC G1R 2J6, Canada
| | - Eli Rothenberg
- NYU Langone Medical Center, 450 East 29th Street, New York, NY, USA
| | - Petr Cejka
- Institute for Research in Biomedicine, Università della Svizzera Italiana (USI), Faculty of Biomedical Sciences, Bellinzona 6500, Switzerland; Department of Biology, Institute of Biochemistry, Eidgenössische Technische Hochschule (ETH), Zürich 8093, Switzerland.
| | - Fabrizio d'Adda di Fagagna
- IFOM-The FIRC Institute of Molecular Oncology, Milan 20139, Italy; Istituto di Genetica Molecolare, CNR-Consiglio Nazionale delle Ricerche, Pavia 2700, Italy.
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11
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Busatto FF, Viero VP, Schaefer BT, Saffi J. Cell growth analysis and nucleotide excision repair modulation in breast cancer cells submitted to a protocol using doxorubicin and paclitaxel. Life Sci 2021; 268:118990. [PMID: 33412214 DOI: 10.1016/j.lfs.2020.118990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 12/13/2020] [Accepted: 12/24/2020] [Indexed: 11/30/2022]
Abstract
INTRODUCTION One of the most used regimens to treat breast cancer is the dose-dense ACT protocol, a combination of anthracycline doxorubicin (DOX) with cyclophosphamide and paclitaxel (PCTX). However, many tumors show resistance to the protocols applied. It is known that the nucleotide excision repair (NER) pathway acts by removing the DOX-generated lesions, and this, together with other DNA repair pathways, can modulate the response to treatment. AIMS To evaluate the in vitro growth profile of breast cancer cells (MCF7), and the modulation of DNA repair genes, submitted to a protocol using DOX and PCTX in a similar regimen to what is used in clinical practice. MAIN METHODS MCF7 cells were treated with repeated cycles of DOX and PCTX and followed-up during and after each of the treatments. The population doubling of the remaining cells was calculated during the complete protocol and DNA repair gene expression was evaluated at different time-points. KEY FINDINGS An increase in all NER genes analyzed after the DOX treatment was observed, but not after the PCTX treatment. MRE11was overexpressed at all evaluated time-points. There was a resumption of NER genes overexpression profile when cells were maintained for follow-up and retook their growth pattern, indicating that DNA repair pathways can modulate their expression during the chemotherapy exposure.
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Affiliation(s)
- Franciele Faccio Busatto
- Laboratory of Genetic Toxicology, Federal University of Health Sciences of Porto Alegre - UFCSPA, Porto Alegre, RS, Brazil; Post-Graduation Program in Molecular and Cell Biology (PPGBCM), Federal University of Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil
| | - Victoria Pereira Viero
- Laboratory of Genetic Toxicology, Federal University of Health Sciences of Porto Alegre - UFCSPA, Porto Alegre, RS, Brazil
| | - Bruna Thaís Schaefer
- Laboratory of Genetic Toxicology, Federal University of Health Sciences of Porto Alegre - UFCSPA, Porto Alegre, RS, Brazil
| | - Jenifer Saffi
- Laboratory of Genetic Toxicology, Federal University of Health Sciences of Porto Alegre - UFCSPA, Porto Alegre, RS, Brazil; Post-Graduation Program in Molecular and Cell Biology (PPGBCM), Federal University of Rio Grande do Sul - UFRGS, Porto Alegre, RS, Brazil.
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12
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Puts G, Jarrett S, Leonard M, Matsangos N, Snyder D, Wang Y, Vincent R, Portney B, Abbotts R, McLaughlin L, Zalzman M, Rassool F, Kaetzel D. Metastasis Suppressor NME1 Modulates Choice of Double-Strand Break Repair Pathways in Melanoma Cells by Enhancing Alternative NHEJ while Inhibiting NHEJ and HR. Int J Mol Sci 2020; 21:ijms21165896. [PMID: 32824412 PMCID: PMC7460576 DOI: 10.3390/ijms21165896] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 01/15/2023] Open
Abstract
Reduced NME1 expression in melanoma cell lines, mouse models of melanoma, and melanoma specimens in human patients is associated with increased metastatic activity. Herein, we investigate the role of NME1 in repair of double-stranded breaks (DSBs) and choice of double-strand break repair (DSBR) pathways in melanoma cells. Using chromatin immunoprecipitation, NME1 was shown to be recruited rapidly and directly to DSBs generated by the homing endonuclease I-PpoI. NME1 was recruited to DSBs within 30 min, in concert with recruitment of ataxia-telangiectasia mutated (ATM) protein, an early step in DSBR complex formation, as well as loss of histone 2B. NME1 was detected up to 5 kb from the break site after DSB induction, suggesting a role in extending chromatin reorganization away from the repair site. shRNA-mediated silencing of NME1 expression led to increases in the homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways of double-strand break repair (DSBR), and reduction in the low fidelity, alternative-NHEJ (A-NHEJ) pathway. These findings suggest low expression of NME1 drives DSBR towards higher fidelity pathways, conferring enhanced genomic stability necessary for rapid and error-free proliferation in invasive and metastatic cells. The novel mechanism highlighted in the current study appears likely to impact metastatic potential and therapy-resistance in advanced melanoma and other cancers.
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Affiliation(s)
- Gemma Puts
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Stuart Jarrett
- Department of Toxicology and Cancer Biology, College of Medicine, University of Kentucky, Lexington, KY 40536, USA;
| | - Mary Leonard
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Nicolette Matsangos
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Devin Snyder
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Ying Wang
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Richard Vincent
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Benjamin Portney
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
| | - Rachel Abbotts
- Department of Radiation Oncology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (R.A.); (L.M.); (F.R.)
- University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
| | - Lena McLaughlin
- Department of Radiation Oncology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (R.A.); (L.M.); (F.R.)
- University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
| | - Michal Zalzman
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
- University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
- Department of Otorhinolaryngology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Feyruz Rassool
- Department of Radiation Oncology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (R.A.); (L.M.); (F.R.)
- University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
| | - David Kaetzel
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (G.P.); (M.L.); (N.M.); (D.S.); (Y.W.); (R.V.); (B.P.); (M.Z.)
- University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center, Baltimore, MD 21201, USA
- Correspondence: ; Tel.: +1-410-706-5080; Fax: +1-410-706-8297
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Liu C, Qiao Y, Xu L, Wu J, Mei Q, Zhang X, Wang K, Li Q, Jia X, Sun H, Wu J, Sun W, Fu S. Association between polymorphisms in MRE11 and HIV-1 susceptibility and AIDS progression in a northern Chinese MSM population. J Antimicrob Chemother 2020; 74:2009-2018. [PMID: 30989233 DOI: 10.1093/jac/dkz132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 02/28/2019] [Accepted: 03/06/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Previous studies reported that DNA damage repair (DDR) genes may play an important role in HIV-1 infection. The MRE11 gene, a member of the MRN complex, plays an essential part in the homologous recombination pathway, which is one of the classical DDR pathways. Previous reports have demonstrated that MRE11 has an effect on HIV-1 replication. However, the role of SNPs in the MRE11 gene and their impact on HIV-1 infection and AIDS progression remain unknown. METHODS In this study, 434 MSM HIV-1-infected patients in northern China and 431 age-matched healthy controls were enrolled. Five SNPs (rs2155209, rs10831234, rs13447720, rs601341 and rs11020803) at the MRE11 gene were genotyped. Another series of cases (409 MSM HIV-1-infected patients) and controls (403 age-matched healthy males) were recruited as the validation set. RESULTS In our study, rs10831234 showed differences in allele frequencies between cases and controls (P = 0.005). Additionally, there was an association between rs10831234 and HIV-1 infection susceptibility in dominant and additive models (P = 0.005 and P = 0.006, respectively). All significant associations were replicated in the validation set, and the associations were still significant after Bonferroni correction for multiple testing when the two data sets were combined. Furthermore, in haplotype association analyses between the case and control groups, the frequencies of the haplotypes Crs11020803Crs10831234 and Trs11020803Trs10831234 showed significant differences (P = 0.0181 and P = 0.0068, respectively). CONCLUSIONS We demonstrated that the MRE11 rs10831234-T allele may confer increased risk of HIV-1 infection.
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Affiliation(s)
- Chang Liu
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Yuandong Qiao
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Lidan Xu
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Jiawei Wu
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Qingbu Mei
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Xuelong Zhang
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Kaili Wang
- Infectious Disease Hospital of Heilongjiang Province, Harbin, China
| | - Qiuyan Li
- Editorial Department of International Journal of Genetics, Harbin Medical University, Harbin, China
| | - Xueyuan Jia
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Haiming Sun
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Jie Wu
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Wenjing Sun
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China
| | - Songbin Fu
- Laboratory of Medical Genetics, Harbin Medical University, 157 Baojian Road, Nangang District, Harbin, China.,Key Laboratory of Medical Genetics, (Harbin Medical University), Heilongjiang Higher Education Institutions, 157 Baojian Road, Nangang District, Harbin, China
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Ceppi I, Howard SM, Kasaciunaite K, Pinto C, Anand R, Seidel R, Cejka P. CtIP promotes the motor activity of DNA2 to accelerate long-range DNA end resection. Proc Natl Acad Sci U S A 2020; 117:8859-8869. [PMID: 32241893 PMCID: PMC7183222 DOI: 10.1073/pnas.2001165117] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
To repair a DNA double-strand break by homologous recombination, 5'-terminated DNA strands must first be resected to reveal 3'-overhangs. This process is initiated by a short-range resection catalyzed by MRE11-RAD50-NBS1 (MRN) stimulated by CtIP, which is followed by a long-range step involving EXO1 or DNA2 nuclease. DNA2 is a bifunctional enzyme that contains both single-stranded DNA (ssDNA)-specific nuclease and motor activities. Upon DNA unwinding by Bloom (BLM) or Werner (WRN) helicase, RPA directs the DNA2 nuclease to degrade the 5'-strand. RPA bound to ssDNA also represents a barrier, explaining the need for the motor activity of DNA2 to displace RPA prior to resection. Using ensemble and single-molecule biochemistry, we show that CtIP also dramatically stimulates the adenosine 5'-triphosphate (ATP) hydrolysis-driven motor activity of DNA2 involved in the long-range resection step. This activation in turn strongly promotes the degradation of RPA-coated ssDNA by DNA2. Accordingly, the stimulatory effect of CtIP is only observed with wild-type DNA2, but not the helicase-deficient variant. Similarly to the function of CtIP to promote MRN, also the DNA2 stimulatory effect is facilitated by CtIP phosphorylation. The domain of CtIP required to promote DNA2 is located in the central region lacking in lower eukaryotes and is fully separable from domains involved in the stimulation of MRN. These results establish how CtIP couples both MRE11-dependent short-range and DNA2-dependent long-range resection and define the involvement of the motor activity of DNA2 in this process. Our data might help explain the less severe resection defects of MRE11 nuclease-deficient cells compared to those lacking CtIP.
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Affiliation(s)
- Ilaria Ceppi
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, 6500, Switzerland
- Institute of Biochemistry, Department of Biology, ETH, Zürich, 8093, Switzerland
| | - Sean M Howard
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, 6500, Switzerland
| | - Kristina Kasaciunaite
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Cosimo Pinto
- Institute of Molecular Cancer Research, University of Zürich, Zürich, 8057, Switzerland
| | - Roopesh Anand
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, 6500, Switzerland
| | - Ralf Seidel
- Peter Debye Institute for Soft Matter Physics, Universität Leipzig, Leipzig, 04103, Germany
| | - Petr Cejka
- Institute for Research in Biomedicine, Faculty of Biomedical Sciences, Università della Svizzera Italiana, Bellinzona, 6500, Switzerland;
- Institute of Biochemistry, Department of Biology, ETH, Zürich, 8093, Switzerland
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15
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Boswell ZK, Canny MD, Buschmann TA, Sang J, Latham MP. Adjacent mutations in the archaeal Rad50 ABC ATPase D-loop disrupt allosteric regulation of ATP hydrolysis through different mechanisms. Nucleic Acids Res 2020; 48:2457-2472. [PMID: 31889185 PMCID: PMC7049730 DOI: 10.1093/nar/gkz1228] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 11/25/2019] [Accepted: 12/20/2019] [Indexed: 11/29/2022] Open
Abstract
DNA damage is the driving force for mutation and genomic instability, which can both lead to cell death or carcinogenesis. DNA double strand breaks are detected and processed in part by the Mre11-Rad50-Nbs1 protein complex. Although the Mre11-Rad50-Nbs1 complex is essential, several spontaneous mutations have been noted in various cancers. One of these mutations, within a conserved motif of Rad50, resulted in an outlier curative response in a clinical trial. We show through biochemical and biophysical characterization that this cancer-associated mutation and a second mutation to the adjacent residue, previously described in a breast cancer patient, both have gain-of-function Rad50 ATP hydrolysis activity that results not from faster association of the ATP-bound form but faster dissociation leading to less stable Rad50 dimer. This disruption impairs the regulatory functions of the protein complex leading to a loss of exonuclease activity from Mre11. Interestingly, these two mutations affect Rad50 structure and dynamics quite differently. These studies describe the relationship between function, structure, and molecular motions in improperly regulated Rad50, which reveal the underlying biophysical mechanism for how these two cancer-associated mutations affect the cell.
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Affiliation(s)
- Zachary K Boswell
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
| | - Marella D Canny
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
| | - Tanner A Buschmann
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
| | - Julie Sang
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
| | - Michael P Latham
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA
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16
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Szlachta K, Raimer HM, Comeau LD, Wang YH. CNCC: an analysis tool to determine genome-wide DNA break end structure at single-nucleotide resolution. BMC Genomics 2020; 21:25. [PMID: 31914926 PMCID: PMC6950916 DOI: 10.1186/s12864-019-6436-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 12/26/2019] [Indexed: 12/11/2022] Open
Abstract
Background DNA double-stranded breaks (DSBs) are potentially deleterious events in a cell. The end structures (blunt, 3′- and 5′-overhangs) at DSB sites contribute to the fate of their repair and provide critical information concerning the consequences of the damage. Therefore, there has been a recent eruption of DNA break mapping and sequencing methods that aim to map at single-nucleotide resolution where breaks are generated genome-wide. These methods provide high resolution data for the location of DSBs, which can encode the type of end-structure present at these breaks. However, genome-wide analysis of the resulting end structures has not been investigated following these sequencing methods. Results To address this analysis gap, we develop the use of a coverage-normalized cross correlation analysis (CNCC) to process the high-precision genome-wide break mapping data, and determine genome-wide break end structure distributions at single-nucleotide resolution. We take advantage of the single-nucleotide position and the knowledge of strandness from every mapped break to analyze the relative shifts between positive and negative strand encoded break nucleotides. By applying CNCC we can identify the most abundant end structures captured by a break mapping technique, and further can make comparisons between different samples and treatments. We validate our analysis with restriction enzyme digestions of genomic DNA and establish the sensitivity of the analysis using end structures that only exist as a minor fraction of total breaks. Finally, we demonstrate the versatility of our analysis by applying CNCC to the breaks resulting after treatment with etoposide and study the variety of resulting end structures. Conclusion For the first time, on a genome-wide scale, our analysis revealed the increase in the 5′ to 3′ end resection following etoposide treatment, and the global progression of the resection. Furthermore, our method distinguished the change in the pattern of DSB end structure with increasing doses of the drug. The ability of this method to determine DNA break end structures without a priori knowledge of break sequences or genomic position should have broad applications in understanding genome instability.
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Affiliation(s)
- Karol Szlachta
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 22903-0733, USA
| | - Heather M Raimer
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 22903-0733, USA
| | - Laurey D Comeau
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 22903-0733, USA
| | - Yuh-Hwa Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, 22903-0733, USA.
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17
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Bian L, Meng Y, Zhang M, Li D. MRE11-RAD50-NBS1 complex alterations and DNA damage response: implications for cancer treatment. Mol Cancer 2019; 18:169. [PMID: 31767017 PMCID: PMC6878665 DOI: 10.1186/s12943-019-1100-5] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 11/08/2019] [Indexed: 01/26/2023] Open
Abstract
Genome instability is a hallmark of cancer cells and can be accelerated by defects in cellular responses to DNA damage. This feature of malignant cells opens new avenues for tumor targeted therapy. MRE11-RAD50-NBS1 complex plays a crucial role in sensing and repair of DNA damage. Through interacting with other important players of DNA damage response, MRE11-RAD50-NBS1 complex is engaged in various DNA damage repair pathways. Mutations in any member of this complex may lead to hypersensitivity to genotoxic agents and predisposition to malignancy. It is assumed that the defects in the complex may contribute to tumorigenesis and that treatments targeting the defect may be beneficial to cancer patients. Here, we summarized the recent research findings of the role of MRE11-RAD50-NBS1 complex in tumorigenesis, cancer treatment and discussed the potential approaches of targeting this complex to treat cancer.
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Affiliation(s)
- Lei Bian
- Department of Radiation Oncology, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Yiling Meng
- Department of Radiation Oncology, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Meichao Zhang
- Department of Radiation Oncology, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Dong Li
- Department of Radiation Oncology, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
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18
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Ali S, Zhang Y, Zhou M, Li H, Jin W, Zheng L, Yu X, Stark JM, Weitzel JN, Shen B. Functional deficiency of DNA repair gene EXO5 results in androgen-induced genomic instability and prostate tumorigenesis. Oncogene 2019; 39:1246-1259. [PMID: 31616062 DOI: 10.1038/s41388-019-1061-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 05/16/2019] [Accepted: 06/12/2019] [Indexed: 12/18/2022]
Abstract
Germline mutations of DNA double-strand break (DSB) response and repair genes that drive tumorigenesis could be a major cause of prostate cancer (PCa) heritability. In this study, we demonstrated the role of novel exonuclease 5 (EXO5) gene in androgen-induced double strand breaks repair via homology-directed repair pathway and prostate tumorigenesis. Using whole-exome sequencing of samples from 20 PCa families, with three or more siblings diagnosed with metastatic PCa, we identified mutations in 31 genes involved in DSB response and repair. Among them, the L151P mutation in the exonuclease 5 (EXO5) gene was present in all affected siblings in three PCa families. We found two other EXO5 SNPs significantly associated with risk of PCa in cases-controls study from databases of genotype and phenotype (dbGaP), which are in linkage disequilibrium (D' = 1) with Exo5 L151P found in PCa family. The L151 residue is conserved across diverse species and its mutation is deleterious for protein functions, as demonstrated by our bioinformatics analyses. The L151P mutation impairs the DNA repair function of EXO5 due to loss of nuclease activity, as well as failure of nuclear localization. CRISPR elimination of EXO5 in a PCa cell line impaired homology-directed recombination repair (HDR) and caused androgen-induced genomic instability, as indicated by frequent occurrence of the oncogenic fusion transcript TMPRSS2-ERG. Genetic and functional validation of the EXO5 mutations indicated that EXO5 is a risk gene for prostate tumorigenesis, likely due to its functions in HDR.
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Affiliation(s)
- Shafat Ali
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Yilan Zhang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Mian Zhou
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Hongzhi Li
- Department of Molecular Medicine, Beckman Research Institute of City of Hope, Duarte, USA
| | - Weiwei Jin
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Li Zheng
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Xiaochun Yu
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Jeremy M Stark
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA
| | - Jeffrey N Weitzel
- Department of Population Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Binghui Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, USA.
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Myler LR, Soniat MM, Zhang X, Deshpande RA, Paull TT, Finkelstein IJ. Purification and Biophysical Characterization of the Mre11-Rad50-Nbs1 Complex. Methods Mol Biol 2019; 2004:269-287. [PMID: 31147924 PMCID: PMC6667175 DOI: 10.1007/978-1-4939-9520-2_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The Mre11-Rad50-Nbs1 (MRN) complex coordinates the repair of DNA double-strand breaks, replication fork restart, meiosis, class-switch recombination, and telomere maintenance. As such, MRN is an essential molecular machine that has homologs in all organisms of life, from bacteriophage to humans. In human cells, MRN is a >500 kDa multifunctional complex that encodes DNA binding, ATPase, and both endonuclease and exonuclease activities. MRN also forms larger assemblies and interacts with multiple DNA repair and replication factors. The enzymatic properties of MRN have been the subject of intense research for over 20 years, and more recently, single-molecule biophysics studies are beginning to probe its many biochemical activities. Here, we describe the methods used to overexpress, fluorescently label, and visualize MRN and its activities on single molecules of DNA.
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Affiliation(s)
- Logan R Myler
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
| | - Michael M Soniat
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, USA
| | - Xiaoming Zhang
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Rajashree A Deshpande
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Tanya T Paull
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA
- The Howard Hughes Medical Institute, The University of Texas at Austin, Austin, TX, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX, USA.
- Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, TX, USA.
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Syed A, Tainer JA. The MRE11-RAD50-NBS1 Complex Conducts the Orchestration of Damage Signaling and Outcomes to Stress in DNA Replication and Repair. Annu Rev Biochem 2018; 87:263-294. [PMID: 29709199 PMCID: PMC6076887 DOI: 10.1146/annurev-biochem-062917-012415] [Citation(s) in RCA: 255] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Genomic instability in disease and its fidelity in health depend on the DNA damage response (DDR), regulated in part from the complex of meiotic recombination 11 homolog 1 (MRE11), ATP-binding cassette-ATPase (RAD50), and phosphopeptide-binding Nijmegen breakage syndrome protein 1 (NBS1). The MRE11-RAD50-NBS1 (MRN) complex forms a multifunctional DDR machine. Within its network assemblies, MRN is the core conductor for the initial and sustained responses to DNA double-strand breaks, stalled replication forks, dysfunctional telomeres, and viral DNA infection. MRN can interfere with cancer therapy and is an attractive target for precision medicine. Its conformations change the paradigm whereby kinases initiate damage sensing. Delineated results reveal kinase activation, posttranslational targeting, functional scaffolding, conformations storing binding energy and enabling access, interactions with hub proteins such as replication protein A (RPA), and distinct networks at DNA breaks and forks. MRN biochemistry provides prototypic insights into how it initiates, implements, and regulates multifunctional responses to genomic stress.
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Affiliation(s)
- Aleem Syed
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA; ,
| | - John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA; ,
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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21
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TALEN-Induced Double-Strand Break Repair of CTG Trinucleotide Repeats. Cell Rep 2018; 22:2146-2159. [DOI: 10.1016/j.celrep.2018.01.083] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 12/19/2017] [Accepted: 01/25/2018] [Indexed: 11/19/2022] Open
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22
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Paudyal SC, Li S, Yan H, Hunter T, You Z. Dna2 initiates resection at clean DNA double-strand breaks. Nucleic Acids Res 2017; 45:11766-11781. [PMID: 28981724 PMCID: PMC5714177 DOI: 10.1093/nar/gkx830] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 08/30/2017] [Accepted: 09/06/2017] [Indexed: 02/07/2023] Open
Abstract
Nucleolytic resection of DNA double-strand breaks (DSBs) is essential for both checkpoint activation and homology-mediated repair; however, the precise mechanism of resection, especially the initiation step, remains incompletely understood. Resection of blocked ends with protein or chemical adducts is believed to be initiated by the MRN complex in conjunction with CtIP through internal cleavage of the 5' strand DNA. However, it is not clear whether resection of clean DSBs with free ends is also initiated by the same mechanism. Using the Xenopus nuclear extract system, here we show that the Dna2 nuclease directly initiates the resection of clean DSBs by cleaving the 5' strand DNA ∼10-20 nucleotides away from the ends. In the absence of Dna2, MRN together with CtIP mediate an alternative resection initiation pathway where the nuclease activity of MRN apparently directly cleaves the 5' strand DNA at more distal sites. MRN also facilitates resection initiation by promoting the recruitment of Dna2 and CtIP to the DNA substrate. The ssDNA-binding protein RPA promotes both Dna2- and CtIP-MRN-dependent resection initiation, but a RPA mutant can distinguish between these pathways. Our results strongly suggest that resection of blocked and clean DSBs is initiated via distinct mechanisms.
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Affiliation(s)
- Sharad C. Paudyal
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Shan Li
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
| | - Hong Yan
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Tony Hunter
- Salk Institute, 10010 N Torrey Pines Road, La Jolla, CA 92037, USA
| | - Zhongsheng You
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S. Euclid Avenue, St. Louis, MO 63110, USA
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23
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Abstract
Vertebrate CtIP, and its fission yeast (Ctp1), budding yeast (Sae2) and plant (Com1) orthologs have emerged as key regulatory molecules in cellular responses to DNA double strand breaks (DSBs). By modulating the nucleolytic 5'-3' resection activity of the Mre11/Rad50/Nbs1 (MRN) DSB repair processing and signaling complex, CtIP/Ctp1/Sae2/Com1 is integral to the channeling of DNA double strand breaks through DSB repair by homologous recombination (HR). Nearly two decades since its discovery, emerging new data are defining the molecular underpinnings for CtIP DSB repair regulatory activities. CtIP homologs are largely intrinsically unstructured proteins comprised of expanded regions of low complexity sequence, rather than defined folded domains typical of DNA damage metabolizing enzymes and nucleases. A compact structurally conserved N-terminus forms a functionally critical tetrameric helical dimer of dimers (THDD) region that bridges CtIP oligomers, and is flexibly appended to a conserved C-terminal Sae2-homology DNA binding and DSB repair pathway choice regulatory hub which influences nucleolytic activities of the MRN core nuclease complex. The emerging evidence from structural, biophysical, and biological studies converges on CtIP having functional roles in DSB repair that include: 1) dynamic DNA strand coordination through direct DNA binding and DNA bridging activities, 2) MRN nuclease complex cofactor functions that direct MRN endonucleolytic cleavage of protein-blocked DSB ends and 3) acting as a protein binding hub targeted by the cell cycle regulatory apparatus, which influences CtIP expression and activity via layers of post-translational modifications, protein-protein interactions and DNA binding.
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Affiliation(s)
- Sara N Andres
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, United States
| | - R Scott Williams
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, US National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, United States.
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Hoogenboom WS, Klein Douwel D, Knipscheer P. Xenopus egg extract: A powerful tool to study genome maintenance mechanisms. Dev Biol 2017; 428:300-309. [PMID: 28427716 DOI: 10.1016/j.ydbio.2017.03.033] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/29/2017] [Accepted: 03/29/2017] [Indexed: 01/09/2023]
Abstract
DNA repair pathways are crucial to maintain the integrity of our genome and prevent genetic diseases such as cancer. There are many different types of DNA damage and specific DNA repair mechanisms have evolved to deal with these lesions. In addition to these repair pathways there is an extensive signaling network that regulates processes important for repair, such as cell cycle control and transcription. Despite extensive research, DNA damage repair and signaling are not fully understood. In vitro systems such as the Xenopus egg extract system, have played, and still play, an important role in deciphering the molecular details of these processes. Xenopus laevis egg extracts contain all factors required to efficiently perform DNA repair outside a cell, using mechanisms conserved in humans. These extracts have been used to study several genome maintenance pathways, including mismatch repair, non-homologous end joining, ICL repair, DNA damage checkpoint activation, and replication fork stability. Here we describe how the Xenopus egg extract system, in combination with specifically designed DNA templates, contributed to our detailed understanding of these pathways.
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Affiliation(s)
- Wouter S Hoogenboom
- Hubrecht Institute - KNAW, University Medical Center Utrecht & Cancer GenomiCs Netherlands, The Netherlands
| | - Daisy Klein Douwel
- Hubrecht Institute - KNAW, University Medical Center Utrecht & Cancer GenomiCs Netherlands, The Netherlands
| | - Puck Knipscheer
- Hubrecht Institute - KNAW, University Medical Center Utrecht & Cancer GenomiCs Netherlands, The Netherlands.
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25
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Allam WR, Ashour ME, Waly AA, El-Khamisy S. Role of Protein Linked DNA Breaks in Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1007:41-58. [PMID: 28840551 DOI: 10.1007/978-3-319-60733-7_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Topoisomerases are a group of specialized enzymes that function to maintain DNA topology by introducing transient DNA breaks during transcription and replication. As a result of abortive topoisomerases activity, topoisomerases catalytic intermediates may be trapped on the DNA forming topoisomerase cleavage complexes (Topcc). Topoisomerases trapping on the DNA is the mode of action of several anticancer drugs, it lead to formation of protein linked DAN breaks (PDBs). PDBs are now considered as one of the most dangerous forms of endogenous DNA damage and a major threat to genomic stability. The repair of PDBs involves both the sensing and repair pathways. Unsuccessful repair of PDBs leads to different signs of genomic instabilities such as chromosomal rearrangements and cancer predisposition. In this chapter we will summarize the role of topoisomerases induced PDBs, identification and signaling, repair, role in transcription. We will also discuss the role of PDBs in cancer with a special focus on prostate cancer.
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Affiliation(s)
- Walaa R Allam
- Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
| | - Mohamed E Ashour
- Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Amr A Waly
- Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Sherif El-Khamisy
- Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt. .,Krebs Institute and Sheffield Institute for Nucleic Acids, Department of Molecular Biology and Biotechnology, Firth Court, University of Sheffield, Sheffield, S10 2TN, UK.
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Yan H, Tammaro M, Liao S. Collision of Trapped Topoisomerase 2 with Transcription and Replication: Generation and Repair of DNA Double-Strand Breaks with 5' Adducts. Genes (Basel) 2016; 7:genes7070032. [PMID: 27376333 PMCID: PMC4962002 DOI: 10.3390/genes7070032] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/17/2016] [Accepted: 06/24/2016] [Indexed: 11/23/2022] Open
Abstract
Topoisomerase 2 (Top2) is an essential enzyme responsible for manipulating DNA topology during replication, transcription, chromosome organization and chromosome segregation. It acts by nicking both strands of DNA and then passes another DNA molecule through the break. The 5′ end of each nick is covalently linked to the tyrosine in the active center of each of the two subunits of Top2 (Top2cc). In this configuration, the two sides of the nicked DNA are held together by the strong protein-protein interactions between the two subunits of Top2, allowing the nicks to be faithfully resealed in situ. Top2ccs are normally transient, but can be trapped by cancer drugs, such as etoposide, and subsequently processed into DSBs in cells. If not properly repaired, these DSBs would lead to genome instability and cell death. Here, I review the current understanding of the mechanisms by which DSBs are induced by etoposide, the unique features of such DSBs and how they are repaired. Implications for the improvement of cancer therapy will be discussed.
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Affiliation(s)
- Hong Yan
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
| | - Margaret Tammaro
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
| | - Shuren Liao
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
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