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Ben-Tov D, Mafessoni F, Cucuy A, Honig A, Melamed-Bessudo C, Levy AA. Uncovering the dynamics of precise repair at CRISPR/Cas9-induced double-strand breaks. Nat Commun 2024; 15:5096. [PMID: 38877047 PMCID: PMC11178868 DOI: 10.1038/s41467-024-49410-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 06/05/2024] [Indexed: 06/16/2024] Open
Abstract
CRISPR/Cas9 is widely used for precise mutagenesis through targeted DNA double-strand breaks (DSBs) induction followed by error-prone repair. A better understanding of this process requires measuring the rates of cutting, error-prone, and precise repair, which have remained elusive so far. Here, we present a molecular and computational toolkit for multiplexed quantification of DSB intermediates and repair products by single-molecule sequencing. Using this approach, we characterize the dynamics of DSB induction, processing and repair at endogenous loci along a 72 h time-course in tomato protoplasts. Combining this data with kinetic modeling reveals that indel accumulation is determined by the combined effect of the rates of DSB induction processing of broken ends, and precise versus error repair. In this study, 64-88% of the molecules were cleaved in the three targets analyzed, while indels ranged between 15-41%. Precise repair accounts for most of the gap between cleavage and error repair, representing up to 70% of all repair events. Altogether, this system exposes flux in the DSB repair process, decoupling induction and repair dynamics, and suggesting an essential role of high-fidelity repair in limiting the efficiency of CRISPR-mediated mutagenesis.
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Affiliation(s)
- Daniela Ben-Tov
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Fabrizio Mafessoni
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Amit Cucuy
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Arik Honig
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Cathy Melamed-Bessudo
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel.
| | - Avraham A Levy
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 76100, Israel.
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2
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Villiger L, Joung J, Koblan L, Weissman J, Abudayyeh OO, Gootenberg JS. CRISPR technologies for genome, epigenome and transcriptome editing. Nat Rev Mol Cell Biol 2024; 25:464-487. [PMID: 38308006 DOI: 10.1038/s41580-023-00697-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2023] [Indexed: 02/04/2024]
Abstract
Our ability to edit genomes lags behind our capacity to sequence them, but the growing understanding of CRISPR biology and its application to genome, epigenome and transcriptome engineering is narrowing this gap. In this Review, we discuss recent developments of various CRISPR-based systems that can transiently or permanently modify the genome and the transcriptome. The discovery of further CRISPR enzymes and systems through functional metagenomics has meaningfully broadened the applicability of CRISPR-based editing. Engineered Cas variants offer diverse capabilities such as base editing, prime editing, gene insertion and gene regulation, thereby providing a panoply of tools for the scientific community. We highlight the strengths and weaknesses of current CRISPR tools, considering their efficiency, precision, specificity, reliance on cellular DNA repair mechanisms and their applications in both fundamental biology and therapeutics. Finally, we discuss ongoing clinical trials that illustrate the potential impact of CRISPR systems on human health.
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Affiliation(s)
- Lukas Villiger
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA
| | - Julia Joung
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Luke Koblan
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jonathan Weissman
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Omar O Abudayyeh
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA.
| | - Jonathan S Gootenberg
- McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, Cambridge, MA, USA.
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3
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Telomeric-Like Repeats Flanked by Sequences Retrotranscribed from the Telomerase RNA Inserted at DNA Double-Strand Break Sites during Vertebrate Genome Evolution. Int J Mol Sci 2021; 22:ijms222011048. [PMID: 34681704 PMCID: PMC8537989 DOI: 10.3390/ijms222011048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 01/28/2023] Open
Abstract
Interstitial telomeric sequences (ITSs) are stretches of telomeric-like repeats located at internal chromosomal sites. We previously demonstrated that ITSs have been inserted during the repair of DNA double-strand breaks in the course of evolution and that some rodent ITSs, called TERC-ITSs, are flanked by fragments retrotranscribed from the telomerase RNA component (TERC). In this work, we carried out an extensive search of TERC-ITSs in 30 vertebrate genomes and identified 41 such loci in 22 species, including in humans and other primates. The fragment retrotranscribed from the TERC RNA varies in different lineages and its sequence seems to be related to the organization of TERC. Through comparative analysis of TERC-ITSs with orthologous empty loci, we demonstrated that, at each locus, the TERC-like sequence and the ITS have been inserted in one step in the course of evolution. Our findings suggest that telomerase participated in a peculiar pathway of DNA double-strand break repair involving retrotranscription of its RNA component and that this mechanism may be active in all vertebrate species. These results add new evidence to the hypothesis that RNA-templated DNA repair mechanisms are active in vertebrate cells.
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4
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Ghosh D, Raghavan SC. 20 years of DNA Polymerase μ, the polymerase that still surprises. FEBS J 2021; 288:7230-7242. [DOI: 10.1111/febs.15852] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 03/02/2021] [Accepted: 03/01/2021] [Indexed: 12/22/2022]
Affiliation(s)
- Dipayan Ghosh
- Department of Biochemistry Indian Institute of Science Bangalore India
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5
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Fang T, Zhang Y, Chang VY, Roos M, Termini CM, Signaevskaia L, Quarmyne M, Lin PK, Pang A, Kan J, Yan X, Javier A, Pohl K, Zhao L, Scott P, Himburg HA, Chute JP. Epidermal growth factor receptor-dependent DNA repair promotes murine and human hematopoietic regeneration. Blood 2020; 136:441-454. [PMID: 32369572 PMCID: PMC7378456 DOI: 10.1182/blood.2020005895] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 04/13/2020] [Indexed: 02/07/2023] Open
Abstract
Chemotherapy and irradiation cause DNA damage to hematopoietic stem cells (HSCs), leading to HSC depletion and dysfunction and the risk of malignant transformation over time. Extrinsic regulation of HSC DNA repair is not well understood, and therapies to augment HSC DNA repair following myelosuppression remain undeveloped. We report that epidermal growth factor receptor (EGFR) regulates DNA repair in HSCs following irradiation via activation of the DNA-dependent protein kinase-catalytic subunit (DNA-PKcs) and nonhomologous end joining (NHEJ). We show that hematopoietic regeneration in vivo following total body irradiation is dependent upon EGFR-mediated repair of DNA damage via activation of DNA-PKcs. Conditional deletion of EGFR in hematopoietic stem and progenitor cells (HSPCs) significantly decreased DNA-PKcs activity following irradiation, causing increased HSC DNA damage and depressed HSC recovery over time. Systemic administration of epidermal growth factor (EGF) promoted HSC DNA repair and rapid hematologic recovery in chemotherapy-treated mice and had no effect on acute myeloid leukemia growth in vivo. Further, EGF treatment drove the recovery of human HSCs capable of multilineage in vivo repopulation following radiation injury. Whole-genome sequencing analysis revealed no increase in coding region mutations in HSPCs from EGF-treated mice, but increased intergenic copy number variant mutations were detected. These studies demonstrate that EGF promotes HSC DNA repair and hematopoietic regeneration in vivo via augmentation of NHEJ. EGF has therapeutic potential to promote human hematopoietic regeneration, and further studies are warranted to assess long-term hematopoietic effects.
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Affiliation(s)
| | | | - Vivian Y Chang
- Pediatric Hematology/Oncology
- Jonsson Comprehensive Cancer Center
| | - Martina Roos
- Jonsson Comprehensive Cancer Center
- Division of Hematology/Oncology, Department of Medicine
- Broad Stem Cell Research Center, and
| | | | | | | | - Paulina K Lin
- Division of Hematology/Oncology, Department of Medicine
| | - Amara Pang
- Division of Hematology/Oncology, Department of Medicine
| | - Jenny Kan
- Division of Hematology/Oncology, Department of Medicine
| | - Xiao Yan
- Department of Molecular and Medical Pharmacology
| | - Anna Javier
- Division of Hematology/Oncology, Department of Medicine
| | | | - Liman Zhao
- Division of Hematology/Oncology, Department of Medicine
| | - Peter Scott
- Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA
| | | | - John P Chute
- Jonsson Comprehensive Cancer Center
- Division of Hematology/Oncology, Department of Medicine
- Broad Stem Cell Research Center, and
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6
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Bader AS, Bushell M. DNA:RNA hybrids form at DNA double-strand breaks in transcriptionally active loci. Cell Death Dis 2020; 11:280. [PMID: 32332801 PMCID: PMC7181826 DOI: 10.1038/s41419-020-2464-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/24/2020] [Accepted: 04/02/2020] [Indexed: 12/17/2022]
Abstract
The recent discovery of DNA:RNA hybrids, or R-loops, actively forming at DNA double-strand breaks (DSBs) has unlocked fresh insight into how RNA participates in DNA repair. However, the manner of DSB-induced R-loop formation is vital in determining its mechanism of action and is currently under debate. Here, we analyse published DNA:RNA-hybrid sequencing to elucidate the features that determine DSB-induced R-loop formation. We found that pre-existing transcriptional activity was critical for R-loop generation at break sites, suggesting that these RNAs are transcribed prior to break induction. In addition, this appeared to be a specific DSB response at the break, distinct from traditional, co-transcriptionally formed R-loops. We hypothesise that R-loop formation is orchestrated by the damage response at transcriptionally active DSB loci to specifically maintain these genomic regions. Further investigation is required to fully understand how canonical repair processes regulate R-loops at breaks and how they participate in the repair process.
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Affiliation(s)
- Aldo S Bader
- Cancer Research UK Beatson Institute, Glasgow, G61 1BD, UK
| | - Martin Bushell
- Cancer Research UK Beatson Institute, Glasgow, G61 1BD, UK.
- Institute of Cancer Sciences, University of Glasgow, Glasgow, G61 1QH, UK.
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7
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He D, Li T, Sheng M, Yang B. Exonuclease 1 (Exo1) Participates in Mammalian Non-Homologous End Joining and Contributes to Drug Resistance in Ovarian Cancer. Med Sci Monit 2020; 26:e918751. [PMID: 32167078 PMCID: PMC7092659 DOI: 10.12659/msm.918751] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Background Exonuclease 1 (Exo1) participates in a variety of DNA damage repair, including mismatch repair, nucleotide excision repair, and homologous recombination. Genetic study in yeast indicates a role of Exo1 in non-homologous end joining (NHEJ), acting as a regulator for accuracy repairing DNA. This study aimed to investigate the effects of human Exo1 in NHEJ and drug resistance in ovarian cells. Material/Methods Ectopic expression of Exo1 was carried out using pcDNA3.1-EXO1 plasmid in SKOV3 cells. GST-tagged human Exo1 was purified using pTXB1-gst-EXO1 and the his-tagged-Ku was collected using pET15b.his.Ku. Exo1 and Ku70 proteins expressed in bacteria were harvested and purified. DNA-protein binding was examined using affinity capture assay. The cells were treated using drugs for 72 hours. Then, the viabilities of cells were evaluated with sulforhodamine B cell viability analysis. The protein expression was evaluated using western blot assay. Results As expected, human cells that deficient of Exo1 were sensitive to ionizing radiation and DNA damaging drugs (cisplatin and doxorubicin). Cisplatin resistant ovarian cancer cell line and Exo1 deficient cell lines were successfully generated. Exo1 interacts with NHEJ required factor Ku70 and affects NHEJ efficiency. We observed that Exo1 expression level was upregulated in drug resistant cell line and knockdown of Exo1 in drug resistant cells sensitized cells to cisplatin and doxorubicin. Conclusions Exo1 participated in mammalian non-homologous end joining and contributed to drug resistance in ovarian cancer.
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Affiliation(s)
- Dongyun He
- Department of Gynaecology and Obstetrics, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China (mainland)
| | - Tao Li
- Department of Anesthesiology, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China (mainland)
| | - Minjia Sheng
- Department of Gynaecology and Obstetrics, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China (mainland)
| | - Ben Yang
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China (mainland)
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8
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Chauhan V, Sherman S, Said Z, Yauk CL, Stainforth R. A case example of a radiation-relevant adverse outcome pathway to lung cancer. Int J Radiat Biol 2020; 97:68-84. [PMID: 31846388 DOI: 10.1080/09553002.2019.1704913] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Adverse outcome pathways (AOPs) describe how a measurable sequence of key events, beginning from a molecular initiator, can lead to an adverse outcome of relevance to risk assessment. An AOP is modular by design, comprised of four main components: (1) a Molecular Initiating Event (MIE), (2) Key Events (KEs), (3) Key Event Relationships (KERs) and (4) an Adverse Outcome (AO). PURPOSE Here, we illustrate the utility of the AOP concept through a case example in the field of ionizing radiation, using the Organisation for Economic Cooperation and Development (OECD) Users' Handbook. This AOP defines a classic targeted response to a radiation insult with an AO of lung cancer that is relevant to radon gas exposure. MATERIALS AND METHODS To build this AOP, over 500 papers were reviewed and categorized based on the modified Bradford-Hill Criteria. Data-rich key events from the MIE, to several measurable KEs and KERs related to DNA damage response/repair were identified. RESULTS The components for this AOP begin with direct deposition of energy as the MIE. Energy deposited into a cell can lead to multiple ionization events to targets such as DNA. This energy can damage DNA leading to double-strand breaks (DSBs) (KE1), this will initiate repair activation (KE2) in higher eukaryotes through mechanisms that are quick and efficient, but error-prone. If DSBs occur in regions of the DNA transcribing critical genes, then mutations (KE3) generated through faulty repair may alter the function of these genes or may cause chromosomal aberrations (KE4). This can impact cellular pathways such as cell growth, cell cycling and then cellular proliferation (KE5). This will form hyperplasia in lung cells, leading eventually to lung cancer (AO) induction and metastasis. The weight of evidence for the KERs was built using biological plausibility, incidence concordance, dose-response, time-response and essentiality studies. The uncertainties and inconsistencies surrounding this AOP are centered on dose-response relationships associated with dose, dose-rates and radiation quality. CONCLUSION Overall, the AOP framework provided an effective means to organize the scientific knowledge surrounding the KERs and identify those with strong dose-response relationships and those with inconsistencies. This case study is an example of how the AOP methodology can be applied to sources of radiation to help support areas of risk assessment.
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Affiliation(s)
- Vinita Chauhan
- Consumer and Clinical Radiation Protection Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Canada
| | - Samantha Sherman
- Consumer and Clinical Radiation Protection Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Canada
| | - Zakaria Said
- Consumer and Clinical Radiation Protection Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Canada
| | - Carole L Yauk
- Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Canada
| | - Robert Stainforth
- Consumer and Clinical Radiation Protection Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Canada
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9
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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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10
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Gassner FJ, Schubert M, Rebhandl S, Spandl K, Zaborsky N, Catakovic K, Blaimer S, Hebenstreit D, Greil R, Geisberger R. Imprecision and DNA Break Repair Biased towards Incompatible End Joining in Leukemia. Mol Cancer Res 2017; 16:428-438. [PMID: 29222170 DOI: 10.1158/1541-7786.mcr-17-0373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 09/28/2017] [Accepted: 11/09/2017] [Indexed: 01/14/2023]
Abstract
Cancer is a genetic disease caused by mutations and chromosomal abnormalities that contribute to uncontrolled cell growth. In addition, cancer cells can rapidly respond to conventional and targeted therapies by accumulating novel and often specific genetic lesions leading to acquired drug resistance and relapsing disease. In chronic lymphocytic leukemia (CLL), however, diverse chromosomal aberrations often occur. In many cases, improper repair of DNA double-strand breaks (DSB) is a major source for genomic abnormalities. Therefore, this study examined the repair of DNA DSBs by nonhomologous end joining (NHEJ) in CLL by performing plasmid-based repair assays in primary CLL cells and normal B cells, isolated from patients, as well as TALEN/Cas9-induced chromosomal deletions in the CLL cell line Mec1. It is demonstrated that DNA repair is aberrant in CLL cells, featuring perturbed DNA break structure preference with efficient joining of noncohesive ends and more deletions at repair junctions. In addition, increased microhomology-mediated end joining (MMEJ) of DNA substrates was observed in CLL together with increased expression of MMEJ-specific repair factors. In summary, these data identify major differences in DNA repair efficiency between CLL cells and normal B cells isolated from patients.Implications: This study suggests inherently aberrant DNA DSB repair in the acquisition of subclonal genomic structural variations important for clonal evolution and treatment resistance in CLL. Mol Cancer Res; 16(3); 428-38. ©2017 AACR.
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Affiliation(s)
- Franz Josef Gassner
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Maria Schubert
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Stefan Rebhandl
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Karina Spandl
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Nadja Zaborsky
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Kemal Catakovic
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Stephanie Blaimer
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Daniel Hebenstreit
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Richard Greil
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria.,Cancer Cluster Salzburg, Salzburg, Austria
| | - Roland Geisberger
- Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectious Disease, Rheumatology, Oncologic Center, Laboratory for Immunological and Molecular Cancer Research, Paracelsus Medical University Salzburg, Austria. .,Cancer Cluster Salzburg, Salzburg, Austria
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11
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Chaikind B, Bessen JL, Thompson DB, Hu JH, Liu DR. A programmable Cas9-serine recombinase fusion protein that operates on DNA sequences in mammalian cells. Nucleic Acids Res 2016; 44:9758-9770. [PMID: 27515511 PMCID: PMC5175349 DOI: 10.1093/nar/gkw707] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Revised: 08/01/2016] [Accepted: 08/02/2016] [Indexed: 02/07/2023] Open
Abstract
We describe the development of ‘recCas9’, an RNA-programmed small serine recombinase that functions in mammalian cells. We fused a catalytically inactive dCas9 to the catalytic domain of Gin recombinase using an optimized fusion architecture. The resulting recCas9 system recombines DNA sites containing a minimal recombinase core site flanked by guide RNA-specified sequences. We show that these recombinases can operate on DNA sites in mammalian cells identical to genomic loci naturally found in the human genome in a manner that is dependent on the guide RNA sequences. DNA sequencing reveals that recCas9 catalyzes guide RNA-dependent recombination in human cells with an efficiency as high as 32% on plasmid substrates. Finally, we demonstrate that recCas9 expressed in human cells can catalyze in situ deletion between two genomic sites. Because recCas9 directly catalyzes recombination, it generates virtually no detectable indels or other stochastic DNA modification products. This work represents a step toward programmable, scarless genome editing in unmodified cells that is independent of endogenous cellular machinery or cell state. Current and future generations of recCas9 may facilitate targeted agricultural breeding, or the study and treatment of human genetic diseases.
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Affiliation(s)
- Brian Chaikind
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical institute, Harvard University, Cambridge, MA 02138 USA
| | - Jeffrey L Bessen
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Howard Hughes Medical institute, Harvard University, Cambridge, MA 02138 USA
| | - David B Thompson
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138, USA
| | - Johnny H Hu
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA 02138, USA
| | - David R Liu
- Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA 02138, USA .,Howard Hughes Medical institute, Harvard University, Cambridge, MA 02138 USA
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12
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Liang Z, Sunder S, Nallasivam S, Wilson TE. Overhang polarity of chromosomal double-strand breaks impacts kinetics and fidelity of yeast non-homologous end joining. Nucleic Acids Res 2016; 44:2769-81. [PMID: 26773053 PMCID: PMC4824102 DOI: 10.1093/nar/gkw013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 01/05/2016] [Indexed: 12/21/2022] Open
Abstract
Non-homologous end joining (NHEJ) is the main repair pathway for DNA double-strand breaks (DSBs) in cells with limited 5′ resection. To better understand how overhang polarity of chromosomal DSBs affects NHEJ, we made site-specific 5′-overhanging DSBs (5′ DSBs) in yeast using an optimized zinc finger nuclease at an efficiency that approached HO-induced 3′ DSB formation. When controlled for the extent of DSB formation, repair monitoring suggested that chromosomal 5′ DSBs were rejoined more efficiently than 3′ DSBs, consistent with a robust recruitment of NHEJ proteins to 5′ DSBs. Ligation-mediated qPCR revealed that Mre11-Rad50-Xrs2 rapidly modified 5′ DSBs and facilitated protection of 3′ DSBs, likely through recognition of overhang polarity by the Mre11 nuclease. Next-generation sequencing revealed that NHEJ at 5′ DSBs had a higher mutation frequency, and validated the differential requirement of Pol4 polymerase at 3′ and 5′ DSBs. The end processing enzyme Tdp1 did not impact joining fidelity at chromosomal 5′ DSBs as in previous plasmid studies, although Tdp1 was recruited to only 5′ DSBs in a Ku-independent manner. These results suggest distinct DSB handling based on overhang polarity that impacts NHEJ kinetics and fidelity through differential recruitment and action of DSB modifying enzymes.
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Affiliation(s)
- Zhuobin Liang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sham Sunder
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | | | - Thomas E Wilson
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
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Wu J, Starr S. Low-fidelity compensatory backup alternative DNA repair pathways may unify current carcinogenesis theories. Future Oncol 2015; 10:1239-53. [PMID: 24947263 DOI: 10.2217/fon.13.272] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The somatic mutation carcinogenesis theory has dominated for decades. The alternative theory, tissue organization field theory, argues that the development of cancer is determined by the surrounding microenvironment. However, neither theory can explain all features of cancer. As cancers share the features of uncontrolled proliferation and genomic instability, they are likely to have the same pathogenesis. It has been found that various DNA repair pathways within a cell crosstalk with one another, forming a DNA repair network. When one DNA repair pathways is defective, the others may work as compensatory backups. The latter pathways are explored for synthetic lethal anticancer therapy. In this article, we extend the concept of compensatory alternative DNA repair to unify the theories. We propose that the microenvironmental stress can activate low-fidelity compensatory alternative DNA repair, causing mutations. If the mutation occurs to a DNA repair gene, this secondarily mutated gene can lead to even more mutated genes, including those related to other DNA repair pathways, eventually destabilizing the genome. Therefore, the low-fidelity compensatory alternative DNA repair may mediate microenvironment-dependent carcinogenesis. The proposal seems consistent with the view of evolution: the environmental stress causes mutations to adapt to the changing environment.
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Affiliation(s)
- Jiaxi Wu
- Central Laboratories, Xuhui Central Hospital, Shanghai Clinical Research Center, Chinese Academy of Sciences, 966 Middle Huaihai Road, Shanghai 200031, China
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14
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DNA Double-Strand Break Repair Inhibitors as Cancer Therapeutics. ACTA ACUST UNITED AC 2015; 22:17-29. [DOI: 10.1016/j.chembiol.2014.11.013] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 10/26/2014] [Accepted: 11/10/2014] [Indexed: 12/29/2022]
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15
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Vahidi Ferdousi L, Rocheteau P, Chayot R, Montagne B, Chaker Z, Flamant P, Tajbakhsh S, Ricchetti M. More efficient repair of DNA double-strand breaks in skeletal muscle stem cells compared to their committed progeny. Stem Cell Res 2014; 13:492-507. [PMID: 25262445 DOI: 10.1016/j.scr.2014.08.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 07/14/2014] [Accepted: 08/15/2014] [Indexed: 01/17/2023] Open
Abstract
The loss of genome integrity in adult stem cells results in accelerated tissue aging and is possibly cancerogenic. Adult stem cells in different tissues appear to react robustly to DNA damage. We report that adult skeletal stem (satellite) cells do not primarily respond to radiation-induced DNA double-strand breaks (DSBs) via differentiation and exhibit less apoptosis compared to other myogenic cells. Satellite cells repair these DNA lesions more efficiently than their committed progeny. Importantly, non-proliferating satellite cells and post-mitotic nuclei in the fiber exhibit dramatically distinct repair efficiencies. Altogether, reduction of the repair capacity appears to be more a function of differentiation than of the proliferation status of the muscle cell. Notably, satellite cells retain a high efficiency of DSB repair also when isolated from the natural niche. Finally, we show that repair of DSB substrates is not only very efficient but, surprisingly, also very accurate in satellite cells and that accurate repair depends on the key non-homologous end-joining factor DNA-PKcs.
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Affiliation(s)
- Leyla Vahidi Ferdousi
- Institut Pasteur, Yeast Molecular Genetics, Dept. of Genomes and Genetics, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS UMR 3525, Team Stability of Nuclear and Mitochondrial DNA, Paris, France; Sorbonne Universités, UPMC, University of Paris 06, IFD-ED 515, Place Jussieu, Paris, 72252, France
| | - Pierre Rocheteau
- Institut Pasteur, Stem Cells & Development, Dept. of Developmental and Stem Cell Biology, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS URA 2578, Paris, France
| | - Romain Chayot
- Institut Pasteur, Yeast Molecular Genetics, Dept. of Genomes and Genetics, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS UMR 3525, Team Stability of Nuclear and Mitochondrial DNA, Paris, France
| | - Benjamin Montagne
- Institut Pasteur, Yeast Molecular Genetics, Dept. of Genomes and Genetics, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS UMR 3525, Team Stability of Nuclear and Mitochondrial DNA, Paris, France
| | - Zayna Chaker
- Institut Pasteur, Yeast Molecular Genetics, Dept. of Genomes and Genetics, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS UMR 3525, Team Stability of Nuclear and Mitochondrial DNA, Paris, France
| | - Patricia Flamant
- Institut Pasteur, Stem Cells & Development, Dept. of Developmental and Stem Cell Biology, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS URA 2578, Paris, France
| | - Shahragim Tajbakhsh
- Institut Pasteur, Stem Cells & Development, Dept. of Developmental and Stem Cell Biology, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS URA 2578, Paris, France
| | - Miria Ricchetti
- Institut Pasteur, Yeast Molecular Genetics, Dept. of Genomes and Genetics, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France; CNRS UMR 3525, Team Stability of Nuclear and Mitochondrial DNA, Paris, France.
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16
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Vu GTH, Cao HX, Watanabe K, Hensel G, Blattner FR, Kumlehn J, Schubert I. Repair of Site-Specific DNA Double-Strand Breaks in Barley Occurs via Diverse Pathways Primarily Involving the Sister Chromatid. THE PLANT CELL 2014; 26:2156-2167. [PMID: 24876253 PMCID: PMC4079375 DOI: 10.1105/tpc.114.126607] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 04/24/2014] [Accepted: 05/07/2014] [Indexed: 05/18/2023]
Abstract
DNA double-strand break (DSB) repair mechanisms differ in their requirements for a homologous repair template and in the accuracy of the result. We aimed to quantify the outcome of repair of a single targeted DSB in somatic cells of young barley (Hordeum vulgare) plants. Amplicon sequencing of three reporter constructs revealed 47 to 58% of reads as repaired via nonhomologous end-joining (NHEJ) with deletions and/or small (1 to 3 bp) insertions. Alternative NHEJ revealed 2 to 5 bp microhomology (15.7% of cases) or new replication-mediated short duplications at sealed breaks. Although deletions outweigh insertions in barley, this bias was less pronounced and deleted sequences were shorter than in Arabidopsis thaliana. Between 17 and 33% of reads likely represent restoration of the original sequence. Depending on the construct, 20 to 33% of reads arose via gene conversion (homologous recombination). Remarkably, <1 to >8% of reads apparently display synthesis-dependent strand annealing linked with NHEJ, inserting 4 to 61 bp, mostly originating from the surrounding of breakpoints. Positional coincidence of >81% of sister chromatid exchanges with target loci is unprecedented for higher eukaryotes and indicates that most repair events for staggered DSBs, at least in barley, involve the sister chromatid and occur during S or G2 phase of the cell cycle.
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Affiliation(s)
- Giang T H Vu
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Hieu X Cao
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Koichi Watanabe
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Goetz Hensel
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Frank R Blattner
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Jochen Kumlehn
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany
| | - Ingo Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research, D-06466 Gatersleben, Germany Faculty of Science and Central European Institute of Technology, Masaryk University, CZ-61137 Brno, Czech Republic
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17
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Rath A, Hromas R, De Benedetti A. Fidelity of end joining in mammalian episomes and the impact of Metnase on joint processing. BMC Mol Biol 2014; 15:6. [PMID: 24655462 PMCID: PMC3998112 DOI: 10.1186/1471-2199-15-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 03/12/2014] [Indexed: 12/13/2022] Open
Abstract
Background Double Stranded Breaks (DSBs) are the most serious form of DNA damage and are repaired via homologous recombination repair (HRR) or non-homologous end joining (NHEJ). NHEJ predominates in mammalian cells at most stages of the cell cycle, and it is viewed as ‘error-prone’, although this notion has not been sufficiently challenged due to shortcomings of many current systems. Multi-copy episomes provide a large pool of genetic material where repair can be studied, as repaired plasmids can be back-cloned into bacteria and characterized for sequence alterations. Here, we used EBV-based episomes carrying 3 resistance marker genes in repair studies where a single DSB is generated with virally-encoded HO endonuclease cleaving rapidly at high efficiency for a brief time post-infection. We employed PCR and Southern blot to follow the kinetics of repair and formation of processing intermediates, and replica plating to screen for plasmids with altered joints resulting in loss of chloramphenicol resistance. Further, we employed this system to study the role of Metnase. Metnase is only found in humans and primates and is a key component of the NHEJ pathway, but its function is not fully characterized in intact cells. Results We found that repair of episomes by end-joining was highly accurate in 293 T cells that lack Metnase. Less than 10% of the rescued plasmids showed deletions. Instead, HEK293 cells (that do express Metnase) or 293 T transfected with Metnase revealed a large number of rescued plasmids with altered repaired joint, typically in the form of large deletions. Moreover, quantitative PCR and Southern blotting revealed less accurately repaired plasmids in Metnase expressing cells. Conclusions Our careful re-examination of fidelity of NHEJ repair in mammalian cells carrying a 3′ cohesive overhang at the ends revealed that the repair is efficient and highly accurate, and predominant over HRR. However, the background of the cells is important in establishing accuracy; with human cells perhaps surprisingly much more prone to generate deletions at the repaired junctions, if/when Metnase is abundantly expressed.
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Affiliation(s)
| | | | - Arrigo De Benedetti
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA.
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18
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Bétermier M, Bertrand P, Lopez BS. Is non-homologous end-joining really an inherently error-prone process? PLoS Genet 2014; 10:e1004086. [PMID: 24453986 PMCID: PMC3894167 DOI: 10.1371/journal.pgen.1004086] [Citation(s) in RCA: 283] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
DNA double-strand breaks (DSBs) are harmful lesions leading to genomic instability or diversity. Non-homologous end-joining (NHEJ) is a prominent DSB repair pathway, which has long been considered to be error-prone. However, recent data have pointed to the intrinsic precision of NHEJ. Three reasons can account for the apparent fallibility of NHEJ: 1) the existence of a highly error-prone alternative end-joining process; 2) the adaptability of canonical C-NHEJ (Ku- and Xrcc4/ligase IV-dependent) to imperfect complementary ends; and 3) the requirement to first process chemically incompatible DNA ends that cannot be ligated directly. Thus, C-NHEJ is conservative but adaptable, and the accuracy of the repair is dictated by the structure of the DNA ends rather than by the C-NHEJ machinery. We present data from different organisms that describe the conservative/versatile properties of C-NHEJ. The advantages of the adaptability/versatility of C-NHEJ are discussed for the development of the immune repertoire and the resistance to ionizing radiation, especially at low doses, and for targeted genome manipulation.
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Affiliation(s)
- Mireille Bétermier
- CNRS, Centre de Génétique Moléculaire, UPR3404, Gif-sur-Yvette, France
- CNRS, Centre de Recherches de Gif-sur-Yvette, FRC3115, Gif-sur-Yvette, France
- Université Paris-Sud, Département de Biologie, Orsay, France
| | - Pascale Bertrand
- CEA, DSV, Institut de Radiobiologie Moléculaire et Cellulaire, Laboratoire Réparation et Vieillissement, Fontenay-aux-Roses, France
- UMR 8200 CNRS, Villejuif, France
| | - Bernard S. Lopez
- Université Paris-Sud, Département de Biologie, Orsay, France
- UMR 8200 CNRS, Villejuif, France
- Institut de Cancérologie, Gustave Roussy, Villejuif, France
- * E-mail:
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19
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Li Y, Qian H, Wang Y, Cucinotta FA. A stochastic model of DNA fragments rejoining. PLoS One 2012; 7:e44293. [PMID: 23028515 PMCID: PMC3441539 DOI: 10.1371/journal.pone.0044293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 08/01/2012] [Indexed: 11/18/2022] Open
Abstract
When cells are exposed to ionizing radiation, DNA damages in the form of single strand breaks (SSBs), double strand breaks (DSBs), base damage or their combinations are frequent events. It is known that the complexity and severity of DNA damage depends on the quality of radiation, and the microscopic dose deposited in small segments of DNA, which is often related to the linear transfer energy (LET) of the radiation. Experimental studies have suggested that under the same dose, high LET radiation induces more small DNA fragments than low-LET radiation, which affects Ku efficiently binding with DNA end and might be a main reason for high-LET radiation induced RBE [1] since DNA DSB is a major cause for radiation-induced cell death. In this work, we proposed a mathematical model of DNA fragments rejoining according to non-homologous end joining (NHEJ) mechanism. By conducting Gillespie's stochastic simulation, we found several factors that impact the efficiency of DNA fragments rejoining. Our results demonstrated that aberrant DNA damage repair can result predominantly from the occurrence of a spatial distribution of DSBs leading to short DNA fragments. Because of the low efficiency that short DNA fragments recruit repair protein and release the protein residue after fragments rejoining, Ku-dependent NHEJ is significantly interfered with short fragments. Overall, our work suggests that inhibiting the Ku-dependent NHEJ may significantly contribute to the increased efficiency for cell death and mutation observed for high LET radiation.
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Affiliation(s)
- Yongfeng Li
- Division of Space Life Sciences, Universities Space Research Association, Houston, Texas, United States of America
| | - Hong Qian
- Department of Applied Mathematics, University of Washington, Seattle, Washington, United States of America
| | - Ya Wang
- Department of Radiation Oncology, Emory University, Atlanta, Georgia, United States of America
| | - Francis A. Cucinotta
- NASA, Lyndon B. Johnson Space Center, Houston, Texas, United States of America
- * E-mail:
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20
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Chayot R, Montagne B, Ricchetti M. DNA polymerase μ is a global player in the repair of non-homologous end-joining substrates. DNA Repair (Amst) 2012; 11:22-34. [DOI: 10.1016/j.dnarep.2011.09.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 09/23/2011] [Accepted: 09/27/2011] [Indexed: 12/25/2022]
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21
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Poplawski T, Pastwa E, Blasiak J. Non-homologous DNA end joining in normal and cancer cells and its dependence on break structures. Genet Mol Biol 2010; 33:368-73. [PMID: 21637496 PMCID: PMC3036873 DOI: 10.1590/s1415-47572010005000018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 10/06/2009] [Indexed: 11/21/2022] Open
Abstract
DNA double-strand breaks (DSBs) are a serious threat to the cell, for if not or miss-repaired, they can lead to chromosomal aberration, mutation and cancer. DSBs in human cells are repaired via non-homologous DNA end joining (NHEJ) and homologous recombination repair pathways. In the former process, the structure of DNA termini plays an important role, as does the genetic constitution of the cells, through being different in normal and pathological cells. In order to investigate the dependence of NHEJ on DSB structure in normal and cancer cells, we used linearized plasmids with various, complementary or non-complementary, single-stranded or blunt DNA termini, as well as whole-cell extract isolated from normal human lymphocytes, chronic myeloid leukemia K562 cells and lung cancer A549 cells. We observed a pronounced variability in the efficacy of NHEJ reaction depending on the type of ends. Plasmids with complementary and blunt termini were more efficiently repaired than the substrate with 3' protruding single-strand ends. The hierarchy of the effectiveness of NHEJ was on average, from the most effective to the least, A549/ normal lymphocytes/ K562. Our results suggest that the genetic constitution of the cells together with the substrate terminal structure may contribute to the efficacy of the NHEJ reaction. This should be taken into account on considering its applicability in cancer chemo- or radiotherapy by pharmacologically modulating NHEJ cellular responses.
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Affiliation(s)
- Tomasz Poplawski
- Department of Molecular Genetics, University of Lodz, Banacha, Lodz Poland
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22
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Nergadze SG, Santagostino MA, Salzano A, Mondello C, Giulotto E. Contribution of telomerase RNA retrotranscription to DNA double-strand break repair during mammalian genome evolution. Genome Biol 2008; 8:R260. [PMID: 18067655 PMCID: PMC2246262 DOI: 10.1186/gb-2007-8-12-r260] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 11/28/2007] [Accepted: 12/07/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In vertebrates, tandem arrays of TTAGGG hexamers are present at both telomeres and intrachromosomal sites (interstitial telomeric sequences (ITSs)). We previously showed that, in primates, ITSs were inserted during the repair of DNA double-strand breaks and proposed that they could arise from either the capture of telomeric fragments or the action of telomerase. RESULTS An extensive comparative analysis of two primate (Homo sapiens and Pan troglodytes) and two rodent (Mus musculus and Rattus norvegicus) genomes allowed us to describe organization and insertion mechanisms of all the informative ITSs present in the four species. Two novel observations support the hypothesis of telomerase involvement in ITS insertion: in a highly significant fraction of informative loci, the ITSs were introduced at break sites where a few nucleotides homologous to the telomeric hexamer were exposed; in the rodent genomes, complex ITS loci are present in which a retrotranscribed fragment of the telomerase RNA, far away from the canonical template, was inserted together with the telomeric repeats. Moreover, mutational analysis of the TTAGGG arrays in the different species suggests that they were inserted as exact telomeric hexamers, further supporting the participation of telomerase in ITS formation. CONCLUSION These results strongly suggest that telomerase was utilized, in some instances, for the repair of DNA double-strand breaks occurring in the genomes of rodents and primates during evolution. The presence, in the rodent genomes, of sequences retrotranscribed from the telomerase RNA strengthens the hypothesis of the origin of telomerase from an ancient retrotransposon.
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Affiliation(s)
- Solomon G Nergadze
- Dipartimento di Genetica e Microbiologia 'Adriano Buzzati-Traverso', Università degli Studi di Pavia, Via Ferrata, 27100 Pavia, Italy
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Boyko A, Zemp F, Filkowski J, Kovalchuk I. Double-strand break repair in plants is developmentally regulated. PLANT PHYSIOLOGY 2006; 141:488-97. [PMID: 16474027 PMCID: PMC1475443 DOI: 10.1104/pp.105.074658] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
In this study, we analyzed double-strand break (DSB) repair in Arabidopsis (Arabidopsis thaliana) at various developmental stages. To analyze DSB repair, we used a homologous recombination (HR) and point mutation reversion assays based on nonfunctional beta-glucuronidase reporter genes. Activation of the reporter gene through HR or point mutation reversion resulted in the appearance of blue sectors after histochemical staining. Scoring of these sectors at 3-d intervals from 2 to 31 d post germination (dpg) revealed that, although there was a 100-fold increase in the number of genomes per plant, the recombination frequency only increased 30-fold. This translates to a recombination rate at 31 dpg (2.77 x 10(-8)) being only 30% of the recombination rate at 2 dpg (9.14 x 10(-8)). Conversely, the mutation frequency increased nearly 180-fold, resulting in a 1.8-fold increase in mutation rate from 2 to 31 dpg. Additional analysis of DSBs over the early developmental stages revealed a substantial increase in the number of strand breaks per unit of DNA. Furthermore, RNA analysis of Ku70 and Rad51, two key enzymes in two different DSB repair pathways, and further protein analysis of Ku70 revealed an increase in Ku70 levels and a decrease of Rad51 levels in the developing plants. These data suggest that DSB repair mechanisms are developmentally regulated in Arabidopsis, whereby the proportion of breaks repaired via HR substantially decreases as the plants mature.
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Affiliation(s)
- Alexander Boyko
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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Boyko A, Filkowski J, Hudson D, Kovalchuk I. Homologous recombination in plants is organ specific. Mutat Res 2006; 595:145-55. [PMID: 16442571 DOI: 10.1016/j.mrfmmm.2005.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Revised: 10/27/2005] [Accepted: 11/03/2005] [Indexed: 05/06/2023]
Abstract
In this paper we analysed the genome stability of various Arabidopsis thaliana plant organs using a transgenic recombination system. The system was based on two copies of non-functional GUS (lines #651 and #11) or LUC (line #15D8) reporter genes serving as a recombination substrate. Both reporter assays showed that recombination in flowers or stems were rare events. Most of the recombination sectors were found in leaves and roots, with leaves having over 2-fold greater number of the recombination events per single cell genome as compared to roots. The recombination events per single genome were 9.7-fold more frequent on the lateral half of the leaves than on the medial halves. This correlated with a 2.5-fold higher metabolic activity in the energy source (lateral) versus energy sink (medial) of leaves. Higher metabolic activity was paralleled by a higher anthocyanin production in lateral halves. The level of double strand break (DSB) occurrence was also different among plant organs; the highest level was observed in roots and the lowest in leaves. High level of DSBs strongly positively correlated with the activity of the key repair enzymes, AtKU70 and AtRAD51. The ratio of AtRAD51 to AtKU70 expression was the highest in leaves, supporting the more active involvement of homologous recombination pathway in the repair of DSBs in this organ. Western blot analysis confirmed the real time PCR expression data for AtKU70 gene.
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Affiliation(s)
- Alexander Boyko
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alta., Canada T1K 3M4
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25
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Kegel A, Martinez P, Carter SD, Åström SU. Genome wide distribution of illegitimate recombination events in Kluyveromyces lactis. Nucleic Acids Res 2006; 34:1633-45. [PMID: 16549875 PMCID: PMC1405753 DOI: 10.1093/nar/gkl064] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 01/21/2006] [Accepted: 02/28/2006] [Indexed: 11/13/2022] Open
Abstract
Illegitimate recombination (IR) is the process by which two DNA molecules not sharing homology to each other are joined. In Kluyveromyces lactis, integration of heterologous DNA occurred very frequently therefore constituting an excellent model organism to study IR. IR was completely dependent on the nonhomologous end-joining (NHEJ) pathway for DNA double strand break (DSB) repair and we detected no other pathways capable of mediating IR. NHEJ was very versatile, capable of repairing both blunt and non-complementary ends efficiently. Mapping the locations of genomic IR-events revealed target site preferences, in which intergenic regions (IGRs) and ribosomal DNA were overrepresented six-fold compared to open reading frames (ORFs). The IGR-events occurred predominantly within transcriptional regulatory regions. In a rad52 mutant strain IR still preferentially occurred at IGRs, indicating that DSBs in ORFs were not primarily repaired by homologous recombination (HR). Introduction of ectopic DSBs resulted in the efficient targeting of IR to these sites, strongly suggesting that IR occurred at spontaneous mitotic DSBs. The targeting efficiency was equal when ectopic breaks were introduced in an ORF or an IGR. We propose that spontaneous DSBs arise more frequently in transcriptional regulatory regions and in rDNA and such DSBs can be mapped by analyzing IR target sites.
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Affiliation(s)
- Andreas Kegel
- Department of Developmental Biology, Wennergren Institute, Stockholm UniversitySE-106 91 Stockholm, Sweden
| | - Paula Martinez
- Department of Developmental Biology, Wennergren Institute, Stockholm UniversitySE-106 91 Stockholm, Sweden
| | - Sidney D. Carter
- Department of Developmental Biology, Wennergren Institute, Stockholm UniversitySE-106 91 Stockholm, Sweden
| | - Stefan U. Åström
- Department of Developmental Biology, Wennergren Institute, Stockholm UniversitySE-106 91 Stockholm, Sweden
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Abstract
The tumor suppressor gene BRCA1 was cloned in 1994 based on its linkage to early-onset breast and ovarian cancer. Although the BRCA1 protein has been implicated in multiple cellular functions, the precise mechanism that determines its tumor suppressor activity is not defined. Currently, the emerging picture is that BRCA1 plays an important role in maintaining genomic integrity by protecting cells from double-strand breaks (DSB) that arise during DNA replication or after DNA damage. The DSB repair pathways available in mammalian cells are homologous recombination and nonhomologous end-joining. BRCA1 function seems to be regulated by specific phosphorylations in response to DNA damage and we will focus this review on the roles played by BRCA1 in DNA repair and cell cycle checkpoints. Finally, we will explore the idea that tumor suppression by BRCA1 depends on its control of DNA DSB repair, resulting in the promotion of error-free and the inhibition of error-prone recombinational repair.
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Affiliation(s)
- Junran Zhang
- Department of Radiation Oncology, Washington University in St. Louis, 4511 Forest Park Boulevard, St. Louis, Missouri 63108, USA
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27
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Sasaki S, Sato M, Katsura Y, Kurimasa A, Chen DJ, Takeda S, Kuwano H, Yokota J, Kohno T. Rapid assessment of two major repair activities against DNA double-strand breaks in vertebrate cells. Biochem Biophys Res Commun 2006; 339:583-90. [PMID: 16310168 DOI: 10.1016/j.bbrc.2005.11.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2005] [Accepted: 11/10/2005] [Indexed: 01/06/2023]
Abstract
A linearized plasmid DNA, in which tandem repeats of 400bp flank the breakpoints, was transfected into vertebrate cells, and breakpoint junctions of plasmid DNA circularized in the cells were analyzed to assess the repair activities against DNA double-strand break (DSB) by non-homologous end joining and homology-directed repair (i.e., homologous recombinational repair and single-strand annealing). The circularization by non-homologous end joining repair of the breakpoints depended on the expression of DNA-PKcs, while that by homology-directed repair through the repeats depended on the length of the repeats, indicating that these two DSB repair activities can be rapidly assessed by this assay. Predominance in circularization by either non-homologous end joining or homology-directed repair differed among cells examined, and circularization was exclusively undertaken by homology-directed repair in DT40 cells known to show a high homologous recombination rate against gene-targeting vectors. Thus, this assay will be helpful in studies on mechanisms and inter-cellular variations of DSB repair.
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Affiliation(s)
- Shigeru Sasaki
- Biology Division, National Cancer Center Research Institute, Tokyo, Japan
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28
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Virsik-Köpp P, Hofman-Hüther H, Rave-Fränk M, Schmidberger H. The Effect of Wortmannin on Radiation-Induced Chromosome Aberration Formation in the Radioresistant Tumor Cell Line WiDr. Radiat Res 2005; 164:148-56. [PMID: 16138421 DOI: 10.1667/rr3396.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We analyzed the formation of radiation-induced chromosome aberrations in the cells of the radioresistant colon carcinoma cell line WiDr after treatment with wortmannin, an inhibitor of PI-3 kinases, including DNA-PK. Cells irradiated in G0/G1 phase with 200 kV X rays were treated with wortmannin before or after irradiation. Chromosome-type and chromatid-type aberrations were scored in metaphase cells by either Giemsa staining or FISH. Moreover, DNA-PK activity was measured in the absence and presence of wortmannin. In irradiated G0/G1-phase WiDr cells, only chromosome-type aberrations, including simple and complex exchanges and excess acentrics, were observed. After addition of 1 to 20 microM wortmannin, the formation of chromosome-type exchange aberrations was completely suppressed. The irradiated cells displayed exclusively chromatid-type aberrations including simple and complex chromatid exchanges and chromatid/isochromatid breaks. Whether the chromatid-type aberrations arise during G0/G1 as a result of homologous recombination processes coping with damaged DNA or whether DNA damage induced during G0/G1 phase persists until S and G2 phase and is then processed by homologous recombination pathways must be investigated further.
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Affiliation(s)
- Patricia Virsik-Köpp
- Abteilung für Umweltmedizin und Hygiene, Medizinische Fakultät, Georg-August-Universität Göttingen, D-37075 Göttingen, Germany.
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29
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Rebuzzini P, Khoriauli L, Azzalin CM, Magnani E, Mondello C, Giulotto E. New mammalian cellular systems to study mutations introduced at the break site by non-homologous end-joining. DNA Repair (Amst) 2005; 4:546-55. [PMID: 15811627 DOI: 10.1016/j.dnarep.2004.12.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Accepted: 12/27/2004] [Indexed: 01/03/2023]
Abstract
The non-homologous end-joining (NHEJ) pathway is a mechanism to repair DNA double strand breaks, which can introduce mutations at repair sites. We constructed new cellular systems to specifically analyze sequence modifications occurring at the repair site. In particular, we looked for the presence of telomeric repeats at the repair junctions, since our previous work indicated that telomeric sequences could be inserted at break sites in germ-line cells during primate evolution. To induce specific DNA breaks, we used the I-SceI system of Saccharomyces cerevisiae or digestion with restriction enzymes. We isolated human and hamster cell lines containing the I-SceI target site integrated in a single chromosomal locus and we exposed the cells to a continuous expression of the I-SceI endonuclease gene. Additionally, we isolated human cell lines that expressed constitutively the I-SceI endonuclease and we introduced the target site on an episomal plasmid stably transfected into the cells. These strategies allowed us to recover repair junctions in which the I-SceI target site was modified at high frequency (100% in hamster cells and about 70% in human cells). Finally, we analyzed junctions produced on an episomal plasmid linearized by restriction enzymes. In all the systems studied, sequence analysis of individual repair junctions showed that deletions were the most frequent modifications, being present in more than 80% of the junctions. On the episomal plasmids, the average deletion length was greater than at intrachromosomal sites. Insertions of nucleotides or deletions associated with insertions were rare events. Junction organization suggested different mechanisms of formation. To check for the insertion of telomeric sequences, we screened plasmid libraries representing about 3.5 x 10(5) junctions with a telomeric repeat probe. No positive clones were detected, suggesting that the addition of telomeric sequences during double strand break repair in somatic cells in culture is either a very rare event or does not occur at all.
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Affiliation(s)
- Paola Rebuzzini
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, via Abbiategrasso 207, 27100 Pavia, Italy
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30
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Boyko A, Filkowski J, Kovalchuk I. Homologous recombination in plants is temperature and day-length dependent. Mutat Res 2005; 572:73-83. [PMID: 15790491 DOI: 10.1016/j.mrfmmm.2004.12.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Revised: 12/10/2004] [Accepted: 12/20/2004] [Indexed: 12/23/2022]
Abstract
Homologous recombination (HR) as a strand break repair mechanism was shown to be influenced by various factors. The balance of different vitamins, macro- and microelements, light spectrum, sodium chloride concentration as well as various environmental mutagens were shown to influence the frequency of HR. In this paper we analysed the influence of temperature (4, 22, and 32 degrees C) and day/night duration on the genome stability of plants. We analyzed the HR frequency in transgenic Arabidopsis thaliana plants carrying beta-glucuronidase based homologous recombination substrate. To find the recombination rate (RR), we related the HR frequency to the number of genomes present in plants grown under different conditions. The RR was also standardized to the transcription activity of the transgene. We found RR to be higher in plants grown at suboptimal temperatures (either 4 or 32 degrees C) as compared to plants grown at 22 degrees C. This negatively correlated with the plant metabolic rate and positively correlated with concentration of peroxide produced by plant. In contrast, the RR in plants grown at different day length (8-24 h) was the lowest in plants grown at the longest day (24 h) and highest in the plants grown at the shortest day (8 h). Over 15-fold difference in the RR between plants grown at the shortest and the longest day was observed. Such a difference in recombination rate was primarily due to the higher transgene activity and higher endoreduplication levels in plants grown at longer days. Our data suggests that even "moderate" changes of environmental conditions may have a significant effect on plant genome stability.
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Affiliation(s)
- Alexander Boyko
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alta., Canada T1K 3M4
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31
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Elliott B, Richardson C, Jasin M. Chromosomal translocation mechanisms at intronic alu elements in mammalian cells. Mol Cell 2005; 17:885-94. [PMID: 15780943 DOI: 10.1016/j.molcel.2005.02.028] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2004] [Revised: 02/04/2005] [Accepted: 02/24/2005] [Indexed: 01/05/2023]
Abstract
Repetitive elements comprise nearly half of the human genome. Chromosomal rearrangements involving these elements occur in somatic and germline cells and are causative for many diseases. To begin to understand the molecular mechanisms leading to these rearrangements in mammalian cells, we developed an intron-based system to specifically induce chromosomal translocations at Alu elements, the most numerous family of repetitive elements in humans. With this system, we found that when double-strand breaks (DSBs) were introduced adjacent to identical Alu elements, translocations occurred at high frequency and predominantly arose from repair by the single-strand annealing (SSA) pathway (85%). With diverged Alu elements, translocation frequency was unaltered, yet pathway usage shifted such that nonhomologous end joining (NHEJ) predominated as the translocation pathway (93%). These results emphasize the fluidity of mammalian DSB repair pathway usage. The intron-based system is highly adaptable to addressing a number of issues regarding molecular mechanisms of genomic rearrangements in mammalian cells.
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Affiliation(s)
- Beth Elliott
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10021, USA
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32
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Dudásová Z, Dudás A, Chovanec M. Non-homologous end-joining factors of Saccharomyces cerevisiae. FEMS Microbiol Rev 2005; 28:581-601. [PMID: 15539075 DOI: 10.1016/j.femsre.2004.06.001] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Revised: 06/02/2004] [Accepted: 06/02/2004] [Indexed: 01/09/2023] Open
Abstract
DNA double-strand breaks (DSB) are considered to be a severe form of DNA damage, because if left unrepaired, they can cause a cell death and, if misrepaired, they can lead to genomic instability and, ultimately, the development of cancer in multicellular organisms. The budding yeast Saccharomyces cerevisiae repairs DSB primarily by homologous recombination (HR), despite the presence of the KU70, KU80, DNA ligase IV and XRCC4 homologues, essential factors of the mammalian non-homologous end-joining (NHEJ) machinery. S. cerevisiae, however, lacks clear DNA-PKcs and ARTEMIS homologues, two important additional components of mammalian NHEJ. On the other hand, S. cerevisiae is endowed with a regulatory NHEJ component, Nej1, which has not yet been found in other organisms. Furthermore, there is evidence in budding yeast for a requirement for the Mre11/Rad50/Xrs2 complex for NHEJ, which does not appear to be the case either in Schizosaccharomyces pombe or in mammals. Here, we comprehensively describe the functions of all the S. cerevisiae NHEJ components identified so far and present current knowledge about the NHEJ process in this organism. In addition, this review depicts S. cerevisiae as a powerful model system for investigating the utilization of either NHEJ or HR in DSB repair.
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Affiliation(s)
- Zuzana Dudásová
- Laboratory of Molecular Genetics, Cancer Research Institute, Slovak Academy of Sciences, Vlárska 7, 833 91 Bratislava 37, Slovak Republic
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33
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Nick McElhinny SA, Ramsden DA. Sibling rivalry: competition between Pol X family members in V(D)J recombination and general double strand break repair. Immunol Rev 2005; 200:156-64. [PMID: 15242403 DOI: 10.1111/j.0105-2896.2004.00160.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nonhomologous end-joining pathway is a major means for repairing double-strand breaks (DSBs) in all mitotic cell types. This repair pathway is also the only efficient means for resolving DSB intermediates in V(D)J recombination, a lymphocyte-specific genome rearrangement required for assembly of antigen receptors. A role for polymerases in end-joining has been well established. They are a major factor in determining the character of repair junctions but, in contrast to 'core' end-joining factors, typically appear to have a subtle impact on the efficiency of end-joining. Recent work implicates several members of the Pol X family in end-joining and suggests surprising complexity in the control of how these different polymerases are employed in this pathway.
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Affiliation(s)
- Stephanie A Nick McElhinny
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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34
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Jacob S, Miquel C, Sarasin A, Praz F. Effects of camptothecin on double-strand break repair by non-homologous end-joining in DNA mismatch repair-deficient human colorectal cancer cell lines. Nucleic Acids Res 2005; 33:106-13. [PMID: 15642697 PMCID: PMC546142 DOI: 10.1093/nar/gki154] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Loss of a functional mismatch repair (MMR) system in colorectal cancer (CRC) cells is associated with microsatellite instability and increased sensitivity to topoisomerase inhibitors. In this study, we have investigated whether a defect in double-strand break (DSB) repair by non-homologous end-joining (NHEJ) could explain why MMR-deficient CRC cells are hypersensitive to camptothecin (CPT), a topoisomerase I inhibitor. To evaluate the efficiency and the fidelity of DSB repair, we have transiently transfected plasmids containing cohesive or non-complementary ends in cells with various MMR defects. We have observed that the repair efficiency of DSB with cohesive and non-complementary ends is comparable in all cell lines. In contrast to the MMR-proficient cell line HT29, the MMR-deficient cell lines were highly accurate in repairing DSB with cohesive ends, but this characteristic could not be directly assigned to the primary MMR deficiency. Furthermore, CPT treatment had no detectable effect on the repair of cohesive ends but significantly decreased the repair efficiency of non-complementary DSB. In conclusion, although our observations show that DSB repair efficiency by NHEJ decreases upon treatment with CPT, which possibly contributes to its cytotoxicity, it is quite unlikely that it accounts for the hypersensitivity of MMR-deficient cells to topoisomerase inhibitors.
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Affiliation(s)
| | | | | | - Françoise Praz
- To whom correspondence should be addressed. Tel: +33 1 42 11 49 58; Fax: +33 1 42 11 50 08;
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35
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Weterings E, van Gent DC. The mechanism of non-homologous end-joining: a synopsis of synapsis. DNA Repair (Amst) 2004; 3:1425-35. [PMID: 15380098 DOI: 10.1016/j.dnarep.2004.06.003] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2004] [Indexed: 11/18/2022]
Abstract
Repair of DNA double-strand breaks (DSBs) by non-homologous end-joining (NHEJ) is required for resistance to genotoxic agents, such as ionizing radiation, but also for proper development of the vertebrate immune system. Much progress has been made in identifying the factors that are involved in this repair pathway. We are now entering the phase in which we begin to understand basic concepts of the reaction mechanism and regulation of non-homologous end-joining. This review concentrates on novel insights into damage recognition and subsequent tethering, processing and joining of DNA ends.
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Affiliation(s)
- Eric Weterings
- Department of Cell Biology and Genetics, Erasmus Medical Center, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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36
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Bentley J, Diggle CP, Harnden P, Knowles MA, Kiltie AE. DNA double strand break repair in human bladder cancer is error prone and involves microhomology-associated end-joining. Nucleic Acids Res 2004; 32:5249-59. [PMID: 15466592 PMCID: PMC521655 DOI: 10.1093/nar/gkh842] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In human cells DNA double strand breaks (DSBs) can be repaired by the non-homologous end-joining (NHEJ) pathway. In a background of NHEJ deficiency, DSBs with mismatched ends can be joined by an error-prone mechanism involving joining between regions of nucleotide microhomology. The majority of joins formed from a DSB with partially incompatible 3' overhangs by cell-free extracts from human glioblastoma (MO59K) and urothelial (NHU) cell lines were accurate and produced by the overlap/fill-in of mismatched termini by NHEJ. However, repair of DSBs by extracts using tissue from four high-grade bladder carcinomas resulted in no accurate join formation. Junctions were formed by the non-random deletion of terminal nucleotides and showed a preference for annealing at a microhomology of 8 nt buried within the DNA substrate; this process was not dependent on functional Ku70, DNA-PK or XRCC4. Junctions were repaired in the same manner in MO59K extracts in which accurate NHEJ was inactivated by inhibition of Ku70 or DNA-PK(cs). These data indicate that bladder tumour extracts are unable to perform accurate NHEJ such that error-prone joining predominates. Therefore, in high-grade tumours mismatched DSBs are repaired by a highly mutagenic, microhomology-mediated, alternative end-joining pathway, a process that may contribute to genomic instability observed in bladder cancer.
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Affiliation(s)
- Johanne Bentley
- Cancer Research UK Clinical Centre, St James's University Hospital, Leeds, LS9 7TF, UK.
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37
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Nergadze SG, Rocchi M, Azzalin CM, Mondello C, Giulotto E. Insertion of telomeric repeats at intrachromosomal break sites during primate evolution. Genome Res 2004; 14:1704-10. [PMID: 15310657 PMCID: PMC515315 DOI: 10.1101/gr.2778904] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Short blocks of telomeric-like DNA (Interstitial Telomeric Sequences, ITSs) are found far from chromosome ends. We addressed the question as to how such sequences arise by comparing the loci of 10 human ITSs with their genomic orthologs in 12 primate species. The ITSs did not derive from expansion of pre-existing TTAGGG units, as described for other microsatellites, but appeared suddenly during evolution. Nine insertion events were dated along the primate evolutionary tree, the dates ranging between 40 and 6 million years ago. Sequence comparisons suggest that in each case the block of (TTAGGG)n DNA arose as a result of double-strand break repair. In fact, ancestral sequences were either interrupted precisely by the tract of telomeric-like repeats or showed the typical modifications observed at double-strand break repair sites such as short deletions, addition of random sequences, or duplications. Similar conclusions were drawn from the analysis of a chimpanzee-specific ITS. We propose that telomeric sequences were inserted by the capture of a telomeric DNA fragment at the break site or by the telomerase enzyme. Our conclusions indicate that human ITSs are relics of ancient breakage rather than fragile sites themselves, as previously suggested.
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Affiliation(s)
- Solomon G Nergadze
- Dipartimento di Genetica e Microbiologia, Università degli Studi di Pavia, 27100 Pavia, Italy
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38
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Guirouilh-Barbat J, Huck S, Bertrand P, Pirzio L, Desmaze C, Sabatier L, Lopez BS. Impact of the KU80 pathway on NHEJ-induced genome rearrangements in mammalian cells. Mol Cell 2004; 14:611-23. [PMID: 15175156 DOI: 10.1016/j.molcel.2004.05.008] [Citation(s) in RCA: 262] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2003] [Revised: 03/11/2004] [Accepted: 04/19/2004] [Indexed: 11/26/2022]
Abstract
Using a substrate measuring deletion or inversion of an I-SceI-excised fragment and both accurate and inaccurate rejoining, we determined the impact of non-homologous end-joining (NHEJ) on mammalian chromosome rearrangements. Deletion is 2- to 8-fold more efficient than inversion, independent of the DNA ends structure. KU80 controls accurate rejoining, whereas in absence of KU mutagenic rejoining, particularly microhomology-mediated repair, occurs efficiently. In cells bearing both the NHEJ and a homologous recombination (HR) substrate containing a third I-SceI site, we show that NHEJ is at least 3.3-fold more efficient than HR, and translocation of the I-SceI fragment from the NHEJ substrate locus into the HR-I-SceI site can occur, but 50- to 100-fold less frequently than deletion. Deletions and translocations show both accurate and inaccurate rejoining, suggesting that they correspond to a mix of KU-dependent and KU-independent processes. Thus these processes should represent prominent pathways for DSB-induced genetic instability in mammalian cells.
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Affiliation(s)
- Josée Guirouilh-Barbat
- UMR CNRS/CEA 217, Laboratoire d'étude des Mécanismes de la Recombinaison, Direction des Sciences du vivant, Département de Radiobiologie et Radiopathologie, 18 route du Panorama, 92265 Fontenay-aux-Roses CEDEX, France
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39
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Kovalchuk I, Abramov V, Pogribny I, Kovalchuk O. Molecular aspects of plant adaptation to life in the Chernobyl zone. PLANT PHYSIOLOGY 2004; 135:357-63. [PMID: 15133154 PMCID: PMC429389 DOI: 10.1104/pp.104.040477] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 03/08/2004] [Accepted: 03/09/2004] [Indexed: 05/19/2023]
Abstract
With each passing year since the Chernobyl accident of 1986, more questions arise about the potential for organisms to adapt to radiation exposure. Often this is thought to be attributed to somatic and germline mutation rates in various organisms. We analyzed the adaptability of native Arabidopsis plants collected from areas with different levels of contamination around the Chernobyl nuclear power plant from 1986 to 1992. Notably, progeny of Chernobyl plants resisted higher concentrations of the mutagens Rose Bengal and methyl methane sulfonate. We analyzed the possible molecular mechanisms of their resistance to mutagens and found a more than 10-fold lower frequency of extrachromosomal homologous recombination, significant differences in the expression of radical scavenging (CAT1 and FSD3) and DNA-repair (RAD1 and RAD51-like) genes upon exposure to mutagens (Rose Bengal and x-rays), and a higher level of global genome methylation. This data suggests that adaptation to ionizing radiation is a complex process involving epigenetic regulation of gene expression and genome stabilization that improves plants' resistance to environmental mutagens.
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Affiliation(s)
- Igor Kovalchuk
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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40
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Abstract
In this work, genome maintenance strategies of organisms belonging to different kingdoms (animals versus plants) but of similar genome size were investigated using a novel, universal double-strand break (DSB) repair assay. Different plasmids linearised with KpnI, Acc65I or EcoRV yielding either 3' or 5' protruding or blunt DNA termini, respectively, were transfected into HeLa cells and Nicotiana plumbaginifolia protoplasts and assayed for the efficiency and fidelity of DSB repair. We show that the mechanism of break sealing is similar but that drastic differences are seen in the fidelity of repair: in HeLa cells, 50-55% DSBs were repaired precisely, compared to as little as 15-30% in tobacco cells. Moreover, the DSB repair in plants resulted in 30-40% longer deletions and significantly shorter insertions. Combined, these led to more than twofold larger net DNA loss in tobacco cells. Our observations point to possible differences in the strategies of DSB repair and genome maintenance in plants and animals.
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Affiliation(s)
- Pawel Pelczar
- Friedrich Miescher Institute, PO Box 2543, CH-4002 Basel, Switzerland
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41
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Sasaki S, Kitagawa Y, Sekido Y, Minna JD, Kuwano H, Yokota J, Kohno T. Molecular processes of chromosome 9p21 deletions in human cancers. Oncogene 2003; 22:3792-8. [PMID: 12802286 DOI: 10.1038/sj.onc.1206589] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Interstitial deletions of the chromosome 9p21 segment encoding the p16/CDKN2A tumor suppressor gene (i.e., 9p21 deletions) are frequently observed in a variety of human cancers. A majority of these deletions in lymphoid leukemia have been indicated to be mediated by illegitimate V(D)J recombination. In the present study, to elucidate the molecular processes of 9p21 deletions in nonlymphocytic malignancies, breakpoints for these deletions were analysed in 21 lung cancer cell lines and 32 nonlymphocytic cancer cell lines of nine other histological types. In all, 32 breakpoints in 21 lung cancer cell lines and 56 breakpoints in 32 nonlung cancer cell lines were mapped in a 450-kb segment encompassing the CDKN2A locus with a 10-kb resolution. The largest number of breakpoints (i.e., seven breakpoints in lung cancer and 12 breakpoints in nonlung cancers) was mapped in a 10-kb region containing the CDKN2A gene. More precise mapping of these seven and 12 breakpoints revealed that none of these breakpoints were located within 50-bp intervals to each other in this 10 kb region. Cloning and sequencing of breakpoints in 18 representative cell lines (six lung and 12 nonlung cancers) further revealed that there were no significant homologies among breakpoints in these 18 cell lines. In 11 (61%) cell lines, 1-5-bp nucleotides were overlapped at breakpoint junctions. These results indicate that DNA double-strand breaks triggering 9p21 deletions do not occur at specific DNA sequences, although they preferentially occur in or near the CDKN2A locus. It was also indicated that two broken DNA ends are rejoined by nonhomologous end-joining repair, preferentially utilizing microhomologies of DNA ends, in the occurrence of 9p21 deletions.
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Affiliation(s)
- Shigeru Sasaki
- Biology Division, National Cancer Center Research Institute, Tokyo 104-0045, Japan
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42
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Smith J, Riballo E, Kysela B, Baldeyron C, Manolis K, Masson C, Lieber MR, Papadopoulo D, Jeggo P. Impact of DNA ligase IV on the fidelity of end joining in human cells. Nucleic Acids Res 2003; 31:2157-67. [PMID: 12682366 PMCID: PMC153745 DOI: 10.1093/nar/gkg317] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A DNA ligase IV (LIG4)-null human pre-B cell line and human cell lines with hypomorphic mutations in LIG4 are significantly impaired in the frequency and fidelity of end joining using an in vivo plasmid assay. Analysis of the null line demonstrates the existence of an error-prone DNA ligase IV-independent rejoining mechanism in mammalian cells. Analysis of lines with hypomorphic mutations demonstrates that residual DNA ligase IV activity, which is sufficient to promote efficient end joining, nevertheless can result in decreased fidelity of rejoining. Thus, DNA ligase IV is an important factor influencing the fidelity of end joining in vivo. The LIG4-defective cell lines also showed impaired end joining in an in vitro assay using cell-free extracts. Elevated degradation of the terminal nucleotide was observed in a LIG4-defective line, and addition of the DNA ligase IV-XRCC4 complex restored end protection. End protection by DNA ligase IV was not dependent upon ligation. Finally, using purified proteins, we demonstrate that DNA ligase IV-XRCC4 is able to protect DNA ends from degradation by T7 exonuclease. Thus, the ability of DNA ligase IV-XRCC4 to protect DNA ends may contribute to the ability of DNA ligase IV to promote accurate rejoining in vivo.
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Affiliation(s)
- Julianne Smith
- UMR 218 CNRS, Institut Curie-Recherche, 26 rue d'Ulm, 75248 Paris, France
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43
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Frank-Vaillant M, Marcand S. Transient stability of DNA ends allows nonhomologous end joining to precede homologous recombination. Mol Cell 2002; 10:1189-99. [PMID: 12453425 DOI: 10.1016/s1097-2765(02)00705-0] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The stability of DNA ends generated by the HO endonuclease in yeast is surprisingly high with a half-life of more than an hour. This transient stability is unaffected by mutations that abolish nonhomologous end joining (NHEJ). The unprocessed ends interact with Yku70p and Yku80p, two proteins required for NHEJ, but not significantly with Rad52p, a protein involved in homologous recombination (HR). Repair of a double-strand break by NHEJ is unaffected by the possibility of HR, although the use of HR is increased in NHEJ-defective cells. Partial in vitro 5' strand processing suppresses NHEJ but not HR. These results show that NHEJ precedes HR temporally, and that the availability of substrate dictates the particular pathway used. We propose that transient stability of DNA ends is a foundation for the permanent stability of telomeres.
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Affiliation(s)
- Marie Frank-Vaillant
- Laboratoire du Cycle Cellulaire, Service de Biochimie et de Génétique Moléculaire, CEA/Saclay, 91191 Gif sur Yvette Cedex, France
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44
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Mahajan KN, Nick McElhinny SA, Mitchell BS, Ramsden DA. Association of DNA polymerase mu (pol mu) with Ku and ligase IV: role for pol mu in end-joining double-strand break repair. Mol Cell Biol 2002; 22:5194-202. [PMID: 12077346 PMCID: PMC139779 DOI: 10.1128/mcb.22.14.5194-5202.2002] [Citation(s) in RCA: 223] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mammalian DNA polymerase mu (pol mu) is related to terminal deoxynucleotidyl transferase, but its biological role is not yet clear. We show here that after exposure of cells to ionizing radiation (IR), levels of pol mu protein increase. pol mu also forms discrete nuclear foci after IR, and these foci are largely coincident with IR-induced foci of gammaH2AX, a previously characterized marker of sites of DNA double-strand breaks. pol mu is thus part of the cellular response to DNA double-strand breaks. pol mu also associates in cell extracts with the nonhomologous end-joining repair factor Ku and requires both Ku and another end-joining factor, XRCC4-ligase IV, to form a stable complex on DNA in vitro. pol mu in turn facilitates both stable recruitment of XRCC4-ligase IV to Ku-bound DNA and ligase IV-dependent end joining. In contrast, the related mammalian DNA polymerase beta does not form a complex with Ku and XRCC4-ligase IV and is less effective than pol mu in facilitating joining mediated by these factors. Our data thus support an important role for pol mu in the end-joining pathway for repair of double-strand breaks.
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Affiliation(s)
- Kiran N Mahajan
- Lineberger Comprehensive Cancer Center, Mason Farm Road, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA
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Preston CR, Engels W, Flores C. Efficient repair of DNA breaks in Drosophila: evidence for single-strand annealing and competition with other repair pathways. Genetics 2002; 161:711-20. [PMID: 12072467 PMCID: PMC1462149 DOI: 10.1093/genetics/161.2.711] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We show evidence that DNA double-strand breaks induced in the Drosophila germ line can be repaired very efficiently by the single-strand annealing (SSA) mechanism. A double-strand break was made between two copies of a 1290-bp direct repeat by mobilizing a P transposon. In >80% of the progeny that acquired this chromosome, repair resulted in loss of the P element and loss of one copy of the repeat, as observed in SSA. The frequency of this repair was much greater than seen for gene conversion using an allelic template, which is only approximately 7%. A similar structure, but with a smaller duplication of only 158 bp, also yielded SSA-like repair events, but at a reduced frequency, and gave rise to some products by repair pathways other than SSA. The 1290-bp repeats carried two sequence polymorphisms that were examined in the products. The allele nearest to a nick in the putative heteroduplex intermediate was lost most often. This bias is predicted by the SSA model, although other models could account for it. We conclude that SSA is the preferred repair pathway in Drosophila for DNA breaks between sequence repeats, and it competes with gene conversion by the synthesis-dependent strand annealing (SDSA) pathway.
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Affiliation(s)
- Christine R Preston
- Laboratory of Genetics, University of Wisconsin, Madison, Wisconsin 53706, USA
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Baldeyron C, Jacquemin E, Smith J, Jacquemont C, De Oliveira I, Gad S, Feunteun J, Stoppa-Lyonnet D, Papadopoulo D. A single mutated BRCA1 allele leads to impaired fidelity of double strand break end-joining. Oncogene 2002; 21:1401-10. [PMID: 11857083 DOI: 10.1038/sj.onc.1205200] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2001] [Revised: 11/21/2001] [Accepted: 11/27/2001] [Indexed: 01/29/2023]
Abstract
Heterozygosity for mutations in the BRCA1 gene in humans confers high risk for developing breast cancer, but a biochemical basis for this phenotype has not yet been determined. Evidence has accumulated implicating BRCA1, in the maintenance of genomic integrity and the protection of cells against DNA double strand breaks (DSB). Here we present evidence that human cells heterozygous for BRCA1 mutations exhibit impaired DNA end-joining, which is the major DSB repair pathway in mammalian somatic cells. Using an in vivo host cell end-joining assay, we observed that the fidelity of DNA end-joining is strongly reduced in three BRCA1(+/-) cell lines in comparison to two control cell lines. Moreover, cell-free BRCA1(+/-) extracts are unable to promote accurate DNA end-joining in an in vitro reaction. The steady-state level of the wild type BRCA1 protein was significantly lower than the 50% expected in BRCA1(+/-) cells and thus may underlie the observed end-joining defect. Together, these data strongly suggest that BRCA1 is necessary for faithful rejoining of broken DNA ends and that a single mutated BRCA1 allele is sufficient to impair this process. This defect will compromise genomic stability in BRCA1 germ-line mutation carriers, triggering the genetic changes necessary for the initiation of neoplastic transformation.
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Affiliation(s)
- Céline Baldeyron
- UMR 218 du CNRS, Institut Curie, Section de Recherche, Paris 75248, cedex05, France
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