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Rahman RS, Wesemann DR. Whence and wherefore IgE? Immunol Rev 2024; 326:48-65. [PMID: 39041740 PMCID: PMC11436312 DOI: 10.1111/imr.13373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Despite the near ubiquitous presence of Ig-based antibodies in vertebrates, IgE is unique to mammals. How and why it emerged remains mysterious. IgE expression is greatly constrained compared to other IgH isotypes. While other IgH isotypes are relatively abundant, soluble IgE has a truncated half-life, and IgE plasma cells are mostly short-lived. Despite its rarity, IgE is consequential and can trigger life-threatening anaphylaxis. IgE production reflects a dynamic steady state with IgG memory B cells feeding short-lived IgE production. Emerging evidence suggests that IgE may also potentially be produced in longer-lived plasma cells as well, perhaps as an aberrancy stemming from its evolutionary roots from an antibody isotype that likely functioned more like IgG. As a late derivative of an ancient systemic antibody system, the benefits of IgE in mammals likely stems from the antibody system's adaptive recognition and response capability. However, the tendency for massive, systemic, and long-lived production, common to IgH isotypes like IgG, were likely not a good fit for IgE. The evolutionary derivation of IgE from an antibody system that for millions of years was good at antigen de-sensitization to now functioning as a highly specialized antigen-sensitization function required heavy restrictions on antibody production-insufficiency of which may contribute to allergic disease.
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Affiliation(s)
- Rifat S Rahman
- Department of Internal Medicine, Columbia University Irving Medical Center, New York, New York, USA
| | - Duane R Wesemann
- Department of Medicine, Division of Allergy and Clinical Immunology, Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
- Ragon Institute of MGH, MIT, and Harvard, Boston, Massachusetts, USA
- Broad Institute of MIT and Harvard, Boston, Massachusetts, USA
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2
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Polλ promotes microhomology-mediated end-joining. Nat Struct Mol Biol 2023; 30:107-114. [PMID: 36536104 DOI: 10.1038/s41594-022-00895-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 11/04/2022] [Indexed: 12/24/2022]
Abstract
The double-strand break (DSB) repair pathway called microhomology-mediated end-joining (MMEJ) is thought to be dependent on DNA polymerase theta (Polθ) and occur independently of nonhomologous end-joining (NHEJ) factors. An unresolved question is whether MMEJ is facilitated by a single Polθ-mediated end-joining pathway or consists of additional undiscovered pathways. We find that human X-family Polλ, which functions in NHEJ, additionally exhibits robust MMEJ activity like Polθ. Polλ promotes MMEJ in mammalian cells independently of essential NHEJ factors LIG4/XRCC4 and Polθ, which reveals a distinct Polλ-dependent MMEJ mechanism. X-ray crystallography employing in situ photo-induced DSB formation captured Polλ in the act of stabilizing a microhomology-mediated DNA synapse with incoming nucleotide at 2.0 Å resolution and reveals how Polλ performs replication across a DNA synapse joined by minimal base-pairing. Last, we find that Polλ is semisynthetic lethal with BRCA1 and BRCA2. Together, these studies indicate Polλ MMEJ as a distinct DSB repair mechanism.
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3
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Lieber MR. Pol X DNA polymerases contribute to NHEJ flexibility. Nat Struct Mol Biol 2023; 30:5-8. [PMID: 36587186 PMCID: PMC9940989 DOI: 10.1038/s41594-022-00904-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
New work on DNA polymerase λ highlights its remarkable flexibility. This fits with the generally adaptable nature of the DNA-repair process in which this enzyme is involved — nonhomologous end-joining — which allows this mechanism to handle diverse types of broken DNA ends in order to restore the duplex structure, albeit with a loss of information at the join.
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4
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Bai W, Zhao B, Gu M, Dong J. Alternative end-joining in BCR gene rearrangements and translocations. Acta Biochim Biophys Sin (Shanghai) 2022; 54:782-795. [PMID: 35593472 PMCID: PMC9828324 DOI: 10.3724/abbs.2022051] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Programmed DNA double-strand breaks (DSBs) occur during antigen receptor gene recombination, namely V(D)J recombination in developing B lymphocytes and class switch recombination (CSR) in mature B cells. Repair of these DSBs by classical end-joining (c-NHEJ) enables the generation of diverse BCR repertoires for efficient humoral immunity. Deletion of or mutation in c-NHEJ genes in mice and humans confer various degrees of primary immune deficiency and predisposition to lymphoid malignancies that often harbor oncogenic chromosomal translocations. In the absence of c-NHEJ, alternative end-joining (A-EJ) catalyzes robust CSR and to a much lesser extent, V(D)J recombination, but the mechanisms of A-EJ are only poorly defined. In this review, we introduce recent advances in the understanding of A-EJ in the context of V(D)J recombination and CSR with emphases on DSB end processing, DNA polymerases and ligases, and discuss the implications of A-EJ to lymphoid development and chromosomal translocations.
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Affiliation(s)
- Wanyu Bai
- Department of ImmunologyZhongshan School of MedicineSun Yat-sen UniversityGuangzhou510080China,Key Laboratory of Tropical Disease Control (Sun Yat-sen University)Ministry of EducationGuangzhou510080China
| | - Bo Zhao
- Department of ImmunologyZhongshan School of MedicineSun Yat-sen UniversityGuangzhou510080China,Key Laboratory of Tropical Disease Control (Sun Yat-sen University)Ministry of EducationGuangzhou510080China
| | - Mingyu Gu
- Department of ImmunologyZhongshan School of MedicineSun Yat-sen UniversityGuangzhou510080China,Key Laboratory of Tropical Disease Control (Sun Yat-sen University)Ministry of EducationGuangzhou510080China
| | - Junchao Dong
- Department of ImmunologyZhongshan School of MedicineSun Yat-sen UniversityGuangzhou510080China,Key Laboratory of Tropical Disease Control (Sun Yat-sen University)Ministry of EducationGuangzhou510080China,Correspondence address. Tel: +86-20-87330571; E-mail:
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5
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Luo S, Qiao R, Zhang X. DNA Damage Response and Repair in Adaptive Immunity. Front Cell Dev Biol 2022; 10:884873. [PMID: 35663402 PMCID: PMC9157429 DOI: 10.3389/fcell.2022.884873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 03/31/2022] [Indexed: 11/16/2022] Open
Abstract
The diversification of B-cell receptor (BCR), as well as its secreted product, antibody, is a hallmark of adaptive immunity, which has more specific roles in fighting against pathogens. The antibody diversification is from recombination-activating gene (RAG)-initiated V(D)J recombination, activation-induced cytidine deaminase (AID)-initiated class switch recombination (CSR), and V(D)J exon somatic hypermutation (SHM). The proper repair of RAG- and AID-initiated DNA lesions and double-strand breaks (DSBs) is required for promoting antibody diversification, suppressing genomic instability, and oncogenic translocations. DNA damage response (DDR) factors and DSB end-joining factors are recruited to the RAG- and AID-initiated DNA lesions and DSBs to coordinately resolve them for generating productive recombination products during antibody diversification. Recently, cohesin-mediated loop extrusion is proposed to be the underlying mechanism of V(D)J recombination and CSR, which plays essential roles in promoting the orientation-biased deletional end-joining . Here, we will discuss the mechanism of DNA damage repair in antibody diversification.
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Affiliation(s)
- Sha Luo
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
- Academy for Advanced Interdisciplinery Studies, Peking University, Beijing, China
| | - Ruolin Qiao
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
- Academy for Advanced Interdisciplinery Studies, Peking University, Beijing, China
| | - Xuefei Zhang
- Biomedical Pioneering Innovation Center, Innovation Center for Genomics, Peking University, Beijing, China
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6
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Ramsden DA, Carvajal-Garcia J, Gupta GP. Mechanism, cellular functions and cancer roles of polymerase-theta-mediated DNA end joining. Nat Rev Mol Cell Biol 2022; 23:125-140. [PMID: 34522048 DOI: 10.1038/s41580-021-00405-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/21/2021] [Indexed: 02/08/2023]
Abstract
Cellular pathways that repair chromosomal double-strand breaks (DSBs) have pivotal roles in cell growth, development and cancer. These DSB repair pathways have been the target of intensive investigation, but one pathway - alternative end joining (a-EJ) - has long resisted elucidation. In this Review, we highlight recent progress in our understanding of a-EJ, especially the assignment of DNA polymerase theta (Polθ) as the predominant mediator of a-EJ in most eukaryotes, and discuss a potential molecular mechanism by which Polθ-mediated end joining (TMEJ) occurs. We address possible cellular functions of TMEJ in resolving DSBs that are refractory to repair by non-homologous end joining (NHEJ), DSBs generated following replication fork collapse and DSBs present owing to stalling of repair by homologous recombination. We also discuss how these context-dependent cellular roles explain how TMEJ can both protect against and cause genome instability, and the emerging potential of Polθ as a therapeutic target in cancer.
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Affiliation(s)
- Dale A Ramsden
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
| | - Juan Carvajal-Garcia
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Gaorav P Gupta
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
- Department of Radiation Oncology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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7
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Ye Z, Shi Y, Lees-Miller SP, Tainer JA. Function and Molecular Mechanism of the DNA Damage Response in Immunity and Cancer Immunotherapy. Front Immunol 2021; 12:797880. [PMID: 34970273 PMCID: PMC8712645 DOI: 10.3389/fimmu.2021.797880] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 11/15/2021] [Indexed: 12/21/2022] Open
Abstract
The DNA damage response (DDR) is an organized network of multiple interwoven components evolved to repair damaged DNA and maintain genome fidelity. Conceptually the DDR includes damage sensors, transducer kinases, and effectors to maintain genomic stability and accurate transmission of genetic information. We have recently gained a substantially improved molecular and mechanistic understanding of how DDR components are interconnected to inflammatory and immune responses to stress. DDR shapes both innate and adaptive immune pathways: (i) in the context of innate immunity, DDR components mainly enhance cytosolic DNA sensing and its downstream STimulator of INterferon Genes (STING)-dependent signaling; (ii) in the context of adaptive immunity, the DDR is needed for the assembly and diversification of antigen receptor genes that is requisite for T and B lymphocyte development. Imbalances between DNA damage and repair impair tissue homeostasis and lead to replication and transcription stress, mutation accumulation, and even cell death. These impacts from DDR defects can then drive tumorigenesis, secretion of inflammatory cytokines, and aberrant immune responses. Yet, DDR deficiency or inhibition can also directly enhance innate immune responses. Furthermore, DDR defects plus the higher mutation load in tumor cells synergistically produce primarily tumor-specific neoantigens, which are powerfully targeted in cancer immunotherapy by employing immune checkpoint inhibitors to amplify immune responses. Thus, elucidating DDR-immune response interplay may provide critical connections for harnessing immunomodulatory effects plus targeted inhibition to improve efficacy of radiation and chemotherapies, of immune checkpoint blockade, and of combined therapeutic strategies.
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Affiliation(s)
- Zu Ye
- Department of Molecular and Cellular Oncology, and Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Yin Shi
- Department of Immunology, Zhejiang University School of Medicine, Hangzhou, China
- Division of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
| | - Susan P. Lees-Miller
- Department of Biochemistry and Molecular Biology, Robson DNA Science Centre, Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada
| | - John A. Tainer
- Department of Molecular and Cellular Oncology, and Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, United States
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8
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Bai W, Zhu G, Xu J, Chen P, Meng F, Xue H, Chen C, Dong J. The 3'-flap endonuclease XPF-ERCC1 promotes alternative end joining and chromosomal translocation during B cell class switching. Cell Rep 2021; 36:109756. [PMID: 34592150 DOI: 10.1016/j.celrep.2021.109756] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/06/2021] [Accepted: 09/02/2021] [Indexed: 11/17/2022] Open
Abstract
Robust alternative end joining (A-EJ) in classical non-homologous end joining (c-NHEJ)-deficient murine cells features double-strand break (DSB) end resection and microhomology (MH) usage and promotes chromosomal translocation. The activities responsible for removing 3' single-strand overhangs following resection and MH annealing in A-EJ remain unclear. We show that, during class switch recombination (CSR) in mature mouse B cells, the structure-specific endonuclease complex XPF-ERCC1SLX4, although not required for normal CSR, represents a nucleotide-excision-repair-independent 3' flap removal activity for A-EJ-mediated CSR. B cells deficient in DNA ligase 4 and XPF-ERCC1 exhibit further impaired class switching, reducing joining to the resected S region DSBs without altering the MH pattern in S-S junctions. In ERCC1-deficient A-EJ cells, 3' single-stranded DNA (ssDNA) flaps that are generated predominantly in S/G2 phase of the cell cycle are susceptible to nuclease resolution. Moreover, ERCC1 promotes c-myc-IgH translocation in Lig4-/- cells. Our study reveals an important role of the flap endonuclease XPF-ERCC1 in A-EJ and oncogenic translocation in mouse B cells.
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Affiliation(s)
- Wanyu Bai
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
| | - Guangchao Zhu
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
| | - Jiejie Xu
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
| | - Pingyue Chen
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China
| | - Feilong Meng
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Hongman Xue
- Department of Pediatrics, the Seventh Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518107, China
| | - Chun Chen
- Department of Pediatrics, the Seventh Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518107, China.
| | - Junchao Dong
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Guangzhou, China; Department of Pediatrics, the Seventh Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong 518107, China.
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9
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Sun X, Liu M, Bai J, Xu J, Zhu C, Dong J, Chen C. ATR kinase activity promotes antibody class switch recombination in B cells through cell cycle regulation without suppressing DSB resection and microhomology usage. J Leukoc Biol 2021; 110:1101-1112. [PMID: 33884660 DOI: 10.1002/jlb.2ma0321-064r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/30/2021] [Accepted: 03/31/2021] [Indexed: 12/16/2022] Open
Abstract
Class switch recombination (CSR) changes the effector functions of antibodies and is carried out by classical and alternative nonhomologous end joining (c-NHEJ and A-EJ) of repetitive switch (S) region double-strand breaks (DSBs). The master DNA damage response (DDR) kinase ataxia-telangiectasia mutated (ATM) is critical for CSR in part by suppressing S region DSB resection. However, whether another related DDR kinase ATM- and Rad3-related (ATR) plays similar role in CSR remains elusive. In this study, we investigated the requirement for ATR kinase activity on CSR in both c-NHEJ competent and deficient B cell lines with high-throughput sequencing of S-S junctions. We found that ATR kinase inhibition efficiently blocked both c-NHEJ- and A-EJ-mediated CSR without affecting germline transcription and activation-induced cytosine deaminase expression. In contrast to ATM, ATR does not suppress S region DSB resection and microhomology usage. In addition, ATR kinase inhibition did not affect Cas9-generated DSB end joining by either c-NHEJ and A-EJ. ATR kinase-inhibited stimulated B cells proliferate much slower than controls and exhibited altered cell cycle profile with increased G1 and G2/M phase cells. In summary, our data revealed a role for ATR in promoting both c-NHEJ- and A-EJ-mediated CSR through regulating cell proliferation upon damage without negatively influencing DSB end-joining features.
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Affiliation(s)
- Xikui Sun
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China.,Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Shenzhen, Guangdong Province, China
| | - Meiling Liu
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China.,Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Shenzhen, Guangdong Province, China
| | - Jingning Bai
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China.,Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Shenzhen, Guangdong Province, China
| | - Jiejie Xu
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China.,Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Shenzhen, Guangdong Province, China
| | - Chengming Zhu
- Science Center, the Seventh Affiliated Hospital of Sun Yat-Sen University, Shenzhen, Guangdong Province, China
| | - Junchao Dong
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China.,Key Laboratory of Tropical Disease Control (Sun Yat-sen University), Ministry of Education, Shenzhen, Guangdong Province, China
| | - Chun Chen
- Department of Pediatrics, The Seventh Affiliated Hospital of Sun Yat-Sen University, Zhongshan School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong Province, China
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10
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Repair of programmed DNA lesions in antibody class switch recombination: common and unique features. ACTA ACUST UNITED AC 2021; 2:115-125. [PMID: 33817557 PMCID: PMC7996122 DOI: 10.1007/s42764-021-00035-0] [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: 02/04/2021] [Revised: 02/22/2021] [Accepted: 03/04/2021] [Indexed: 01/31/2023]
Abstract
The adaptive immune system can diversify the antigen receptors to eliminate various pathogens through programmed DNA lesions at antigen receptor genes. In immune diversification, general DNA repair machineries are applied to transform the programmed DNA lesions into gene mutation or recombination events with common and unique features. Here we focus on antibody class switch recombination (CSR), and review the initiation of base damages, the conversion of damaged base to DNA double-strand break, and the ligation of broken ends. With an emphasis on the unique features in CSR, we discuss recent advances in the understanding of DNA repair/replication coordination, and ERCC6L2-mediated deletional recombination. We further elaborate the application of CSR in end-joining, resection and translesion synthesis assays. In the time of the COVID-19 pandemic, we hope it help to understand the generation of therapeutic antibodies.
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11
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Tatiossian KJ, Clark RDE, Huang C, Thornton ME, Grubbs BH, Cannon PM. Rational Selection of CRISPR-Cas9 Guide RNAs for Homology-Directed Genome Editing. Mol Ther 2021; 29:1057-1069. [PMID: 33160457 PMCID: PMC7934447 DOI: 10.1016/j.ymthe.2020.10.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 09/27/2020] [Accepted: 10/08/2020] [Indexed: 01/27/2023] Open
Abstract
Homology-directed repair (HDR) of a DNA break allows copying of genetic material from an exogenous DNA template and is frequently exploited in CRISPR-Cas9 genome editing. However, HDR is in competition with other DNA repair pathways, including non-homologous end joining (NHEJ) and microhomology-mediated end joining (MMEJ), and the efficiency of HDR outcomes is not predictable. Consequently, to optimize HDR editing, panels of CRISPR-Cas9 guide RNAs (gRNAs) and matched homology templates must be evaluated. We report here that CRISPR-Cas9 indel signatures can instead be used to identify gRNAs that maximize HDR outcomes. Specifically, we show that the frequency of deletions resulting from MMEJ repair, characterized as deletions greater than or equal to 3 bp, better predicts HDR frequency than consideration of total indel frequency. We further demonstrate that tools that predict gRNA indel signatures can be repurposed to identify gRNAs to promote HDR. Finally, by comparing indels generated by S. aureus and S. pyogenes Cas9 targeted to the same site, we add to the growing body of data that the targeted DNA sequence is a major factor governing genome editing outcomes.
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Affiliation(s)
- Kristina J Tatiossian
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Robert D E Clark
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Chun Huang
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Matthew E Thornton
- Department of Obstetrics and Gynecology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Brendan H Grubbs
- Department of Obstetrics and Gynecology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Paula M Cannon
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA.
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12
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Saha T, Sundaravinayagam D, Di Virgilio M. Charting a DNA Repair Roadmap for Immunoglobulin Class Switch Recombination. Trends Biochem Sci 2020; 46:184-199. [PMID: 33250286 DOI: 10.1016/j.tibs.2020.10.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 10/08/2020] [Accepted: 10/23/2020] [Indexed: 01/18/2023]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) is the process occurring in mature B cells that diversifies the effector component of antibody responses. CSR is initiated by the activity of the B cell-specific enzyme activation-induced cytidine deaminase (AID), which leads to the formation of programmed DNA double-strand breaks (DSBs) at the Ig heavy chain (Igh) locus. Mature B cells use a multilayered and complex regulatory framework to ensure that AID-induced DNA breaks are channeled into productive repair reactions leading to CSR, and to avoid aberrant repair events causing lymphomagenic chromosomal translocations. Here, we review the DNA repair pathways acting on AID-induced DSBs and their functional interplay, with a particular focus on the latest developments in their molecular composition and mechanistic regulation.
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Affiliation(s)
- Tannishtha Saha
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany
| | - Devakumar Sundaravinayagam
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany.
| | - Michela Di Virgilio
- Laboratory of Genome Diversification and Integrity, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin 13125, Germany; Charité-Universitätsmedizin Berlin, Berlin 10117, Germany.
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13
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CtIP-mediated DNA resection is dispensable for IgH class switch recombination by alternative end-joining. Proc Natl Acad Sci U S A 2020; 117:25700-25711. [PMID: 32989150 DOI: 10.1073/pnas.2010972117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
To generate antibodies with different effector functions, B cells undergo Immunoglobulin Heavy Chain (IgH) class switch recombination (CSR). The ligation step of CSR is usually mediated by the classical nonhomologous end-joining (cNHEJ) pathway. In cNHEJ-deficient cells, a remarkable ∼25% of CSR can be achieved by the alternative end-joining (Alt-EJ) pathway that preferentially uses microhomology (MH) at the junctions. While A-EJ-mediated repair of endonuclease-generated breaks requires DNA end resection, we show that CtIP-mediated DNA end resection is dispensable for A-EJ-mediated CSR using cNHEJ-deficient B cells. High-throughput sequencing analyses revealed that loss of ATM/ATR phosphorylation of CtIP at T855 or ATM kinase inhibition suppresses resection without altering the MH pattern of the A-EJ-mediated switch junctions. Moreover, we found that ATM kinase promotes Alt-EJ-mediated CSR by suppressing interchromosomal translocations independent of end resection. Finally, temporal analyses reveal that MHs are enriched in early internal deletions even in cNHEJ-proficient B cells. Thus, we propose that repetitive IgH switch regions represent favored substrates for MH-mediated end-joining contributing to the robustness and resection independence of A-EJ-mediated CSR.
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14
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DNA-PKcs phosphorylation at the T2609 cluster alters the repair pathway choice during immunoglobulin class switch recombination. Proc Natl Acad Sci U S A 2020; 117:22953-22961. [PMID: 32868446 DOI: 10.1073/pnas.2007455117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The DNA-dependent protein kinase (DNA-PK), which is composed of the KU heterodimer and the large catalytic subunit (DNA-PKcs), is a classical nonhomologous end-joining (cNHEJ) factor. Naïve B cells undergo class switch recombination (CSR) to generate antibodies with different isotypes by joining two DNA double-strand breaks at different switching regions via the cNHEJ pathway. DNA-PK and the cNHEJ pathway play important roles in the DNA repair phase of CSR. To initiate cNHEJ, KU binds to DNA ends and recruits and activates DNA-PK. Activated DNA-PK phosphorylates DNA-PKcs at the S2056 and T2609 clusters. Loss of T2609 cluster phosphorylation increases radiation sensitivity but whether T2609 phosphorylation has a role in physiological DNA repair remains elusive. Using the DNA-PKcs 5A mouse model carrying alanine substitutions at the T2609 cluster, here we show that loss of T2609 phosphorylation of DNA-PKcs does not affect the CSR efficiency. Yet, the CSR junctions recovered from DNA-PKcs 5A/5A B cells reveal increased chromosomal translocations, extensive use of distal switch regions (consistent with end resection), and preferential usage of microhomology-all signs of the alternative end-joining pathway. Thus, these results uncover a role of DNA-PKcs T2609 phosphorylation in promoting cNHEJ repair pathway choice during CSR.
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15
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Immunoglobulin Class Switch Recombination Is Initiated by Rare Cytosine Deamination Events at Switch Regions. Mol Cell Biol 2020; 40:MCB.00125-20. [PMID: 32513818 DOI: 10.1128/mcb.00125-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 06/01/2020] [Indexed: 11/20/2022] Open
Abstract
Activation-induced cytidine deaminase (AID) initiates immunoglobulin (Ig) class switch recombination (CSR), somatic hypermutation (SHM), and gene conversion by converting DNA cytosines to uracils at specific genomic regions. In this study, we examined AID footprints across the entire length of an engineered switch region in cells ablated for uracil repair. We found that AID deamination occurs predominantly at WRC hot spots (where W is A or T and R is A or G) and that the deamination frequency remains constant across the entire switch region. Importantly, we analyzed monoallelic AID deamination footprints on both DNA strands occurring within a single cell cycle. We found that AID generates few and mostly isolated uracils in the switch region, although processive AID deaminations are evident in some molecules. The frequency of molecules containing deamination on both DNA strands at the acceptor switch region correlates with the class switch efficiency, raising the possibility that the minimal requirement for DNA double-strand break (DSB) formation is as low as even one AID deamination event on both DNA strands.
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16
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Wang XS, Lee BJ, Zha S. The recent advances in non-homologous end-joining through the lens of lymphocyte development. DNA Repair (Amst) 2020; 94:102874. [PMID: 32623318 DOI: 10.1016/j.dnarep.2020.102874] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 05/16/2020] [Accepted: 05/24/2020] [Indexed: 12/17/2022]
Abstract
Lymphocyte development requires ordered assembly and subsequent modifications of the antigen receptor genes through V(D)J recombination and Immunoglobulin class switch recombination (CSR), respectively. While the programmed DNA cleavage events are initiated by lymphocyte-specific factors, the resulting DNA double-strand break (DSB) intermediates activate the ATM kinase-mediated DNA damage response (DDR) and rely on the ubiquitously expressed classical non-homologous end-joining (cNHEJ) pathway including the DNA-dependent protein kinase (DNA-PK), and, in the case of CSR, also the alternative end-joining (Alt-EJ) pathway, for repair. Correspondingly, patients and animal models with cNHEJ or DDR defects develop distinct types of immunodeficiency reflecting their specific DNA repair deficiency. The unique end-structure, sequence context, and cell cycle regulation of V(D)J recombination and CSR also provide a valuable platform to study the mechanisms of, and the interplay between, cNHEJ and DDR. Here, we compare and contrast the genetic consequences of DNA repair defects in V(D)J recombination and CSR with a focus on the newly discovered cNHEJ factors and the kinase-dependent structural roles of ATM and DNA-PK in animal models. Throughout, we try to highlight the pending questions and emerging differences that will extend our understanding of cNHEJ and DDR in the context of primary immunodeficiency and lymphoid malignancies.
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Affiliation(s)
- Xiaobin S Wang
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Graduate Program of Pathobiology and Molecular Medicine, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States
| | - Brian J Lee
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States
| | - Shan Zha
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Pediatrics, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States; Department of Immunology and Microbiology, Vagelos College of Physicians and Surgeons, Columbia University, New York City, NY 10032, United States.
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17
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Liu X, Liu T, Shang Y, Dai P, Zhang W, Lee BJ, Huang M, Yang D, Wu Q, Liu LD, Zheng X, Zhou BO, Dong J, Yeap LS, Hu J, Xiao T, Zha S, Casellas R, Liu XS, Meng FL. ERCC6L2 promotes DNA orientation-specific recombination in mammalian cells. Cell Res 2020; 30:732-744. [PMID: 32355287 PMCID: PMC7608219 DOI: 10.1038/s41422-020-0328-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 04/16/2020] [Indexed: 01/05/2023] Open
Abstract
Programmed DNA recombination in mammalian cells occurs predominantly in a directional manner. While random DNA breaks are typically repaired both by deletion and by inversion at approximately equal proportions, V(D)J and class switch recombination (CSR) of immunoglobulin heavy chain gene overwhelmingly delete intervening sequences to yield productive rearrangement. What factors channel chromatin breaks to deletional CSR in lymphocytes is unknown. Integrating CRISPR knockout and chemical perturbation screening we here identify the Snf2-family helicase-like ERCC6L2 as one such factor. We show that ERCC6L2 promotes double-strand break end-joining and facilitates optimal CSR in mice. At the cellular levels, ERCC6L2 rapidly engages in DNA repair through its C-terminal domains. Mechanistically, ERCC6L2 interacts with other end-joining factors and plays a functionally redundant role with the XLF end-joining factor in V(D)J recombination. Strikingly, ERCC6L2 controls orientation-specific joining of broken ends during CSR, which relies on its helicase activity. Thus, ERCC6L2 facilitates programmed recombination through directional repair of distant breaks.
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Affiliation(s)
- Xiaojing Liu
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Tingting Liu
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yafang Shang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Pengfei Dai
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wubing Zhang
- Clinical Translational Research Center, Shanghai Pulmonary Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, 200092, China
| | - Brian J Lee
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, 10032, USA
| | - Min Huang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Dingpeng Yang
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qiu Wu
- Clinical Translational Research Center, Shanghai Pulmonary Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, 200092, China
| | - Liu Daisy Liu
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoqi Zheng
- Department of Mathematics, Shanghai Normal University, Shanghai, 200234, China
| | - Bo O Zhou
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Junchao Dong
- Department of Immunology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, 510080, China
| | - Leng-Siew Yeap
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jiazhi Hu
- The MOE Key Laboratory of Cell Proliferation and Differentiation, Genome Editing Research Center, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, 100871, Beijing, China
| | - Tengfei Xiao
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA
| | - Shan Zha
- Institute for Cancer Genetics, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, 10032, USA
| | - Rafael Casellas
- Lymphocyte Nuclear Biology, NIAMS, Center of Cancer Research, NCI, NIH, Bethesda, MD, 20892, USA
| | - X Shirley Liu
- Department of Data Sciences, Dana-Farber Cancer Institute and Harvard T.H.Chan School of Public Health, Boston, MA, 02215, USA
| | - Fei-Long Meng
- State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
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18
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Musilli S, Abramowski V, Roch B, de Villartay JP. An in vivo study of the impact of deficiency in the DNA repair proteins PAXX and XLF on development and maturation of the hemolymphoid system. J Biol Chem 2020; 295:2398-2406. [PMID: 31915249 DOI: 10.1074/jbc.ac119.010924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/03/2020] [Indexed: 12/22/2022] Open
Abstract
Repair of DNA double-strand breaks by the nonhomologous end joining pathway is central for proper development of the adaptive immune system. This repair pathway involves eight factors, including XRCC4-like factor (XLF)/Cernunnos and the paralog of XRCC4 and XLF, PAXX nonhomologous end joining factor (PAXX). Xlf-/- and Paxx-/- mice are viable and exhibit only a mild immunophenotype. However, mice lacking both PAXX and XLF are embryonic lethal because postmitotic neurons undergo massive apoptosis in embryos. To decipher the roles of PAXX and XLF in both variable, diversity, and joining recombination and immunoglobulin class switch recombination, here, using Cre/lox-specific deletion to prevent double-KO embryonic lethality, we developed two mouse models of a conditional Xlf KO in a Paxx-/- background. Cre expressed under control of the iVav or CD21 promoter enabled Xlf deletion in early hematopoietic progenitors and splenic mature B cells, respectively. We demonstrate the XLF and PAXX interplay during variable, diversity, and joining recombination in vivo but not during class switch recombination, for which PAXX appeared to be fully dispensable. Xlf/Paxx double KO in hematopoietic progenitors resulted in a shorter lifespan associated with onset of thymic lymphomas, revealing a genome caretaking function of XLF/PAXX.
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Affiliation(s)
- Stefania Musilli
- Laboratory of Genome Dynamics in the Immune System, Imagine Institute, INSERM UMR 1163, Université de Paris, 75015 Paris, France
| | - Vincent Abramowski
- Laboratory of Genome Dynamics in the Immune System, Imagine Institute, INSERM UMR 1163, Université de Paris, 75015 Paris, France
| | - Benoit Roch
- Laboratory of Genome Dynamics in the Immune System, Imagine Institute, INSERM UMR 1163, Université de Paris, 75015 Paris, France
| | - Jean-Pierre de Villartay
- Laboratory of Genome Dynamics in the Immune System, Imagine Institute, INSERM UMR 1163, Université de Paris, 75015 Paris, France.
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19
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Shukla V, Halabelian L, Balagere S, Samaniego-Castruita D, Feldman DE, Arrowsmith CH, Rao A, Aravind L. HMCES Functions in the Alternative End-Joining Pathway of the DNA DSB Repair during Class Switch Recombination in B Cells. Mol Cell 2019; 77:384-394.e4. [PMID: 31806351 DOI: 10.1016/j.molcel.2019.10.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Revised: 09/06/2019] [Accepted: 10/22/2019] [Indexed: 01/08/2023]
Abstract
HMCES (5hmC binding, embryonic stem cell-specific-protein), originally identified as a protein capable of binding 5-hydroxymethylcytosine (5hmC), an epigenetic modification generated by TET proteins, was previously reported to covalently crosslink to DNA at abasic sites via a conserved cysteine. We show here that Hmces-deficient mice display normal hematopoiesis without global alterations in 5hmC. HMCES specifically enables DNA double-strand break repair through the microhomology-mediated alternative-end-joining (Alt-EJ) pathway during class switch recombination (CSR) in B cells, and HMCES deficiency leads to a significant defect in CSR. HMCES mediates Alt-EJ through its SOS-response-associated-peptidase domain (SRAPd), a function that requires DNA binding but is independent of its autopeptidase and DNA-crosslinking activities. We show that HMCES is recruited to switch regions of the immunoglobulin locus and provide a potential structural basis for the interaction of HMCES with long DNA overhangs generated by Alt-EJ during CSR. Our studies provide further evidence for a specialized role for HMCES in DNA repair.
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Affiliation(s)
- Vipul Shukla
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Levon Halabelian
- Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Sanjana Balagere
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Daniela Samaniego-Castruita
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA
| | - Douglas E Feldman
- Department of Pathology, University of Southern California, Keck School of Medicine, Los Angeles, CA 93033, USA
| | - Cheryl H Arrowsmith
- Structural Genomics Consortium, University of Toronto, Toronto, ON M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada; Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada.
| | - Anjana Rao
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA; Department of Pharmacology and Moores Cancer Center, University of San Diego, California, 9500 Gilman Drive, La Jolla, CA 92093, USA; Sanford Consortium for Regenerative Medicine, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA.
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA.
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20
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Yu K, Lieber MR. Current insights into the mechanism of mammalian immunoglobulin class switch recombination. Crit Rev Biochem Mol Biol 2019; 54:333-351. [PMID: 31509023 PMCID: PMC6856442 DOI: 10.1080/10409238.2019.1659227] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 08/13/2019] [Accepted: 08/20/2019] [Indexed: 12/12/2022]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) is the gene rearrangement process by which B lymphocytes change the Ig heavy chain constant region to permit a switch of Ig isotype from IgM to IgG, IgA, or IgE. At the DNA level, CSR occurs via generation and joining of DNA double strand breaks (DSBs) at intronic switch regions located just upstream of each of the heavy chain constant regions. Activation-induced deaminase (AID), a B cell specific enzyme, catalyzes cytosine deaminations (converting cytosines to uracils) as the initial DNA lesions that eventually lead to DSBs and CSR. Progress on AID structure integrates very well with knowledge about Ig class switch region nucleic acid structures that are supported by functional studies. It is an ideal time to review what is known about the mechanism of Ig CSR and its relation to somatic hypermutation. There have been many comprehensive reviews on various aspects of the CSR reaction and regulation of AID expression and activity. This review is focused on the relation between AID and switch region nucleic acid structures, with a particular emphasis on R-loops.
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Affiliation(s)
- Kefei Yu
- Michigan State University, Department of Microbiology & Molecular Genetics, 5175 Biomedical Physical Sciences, East Lansing, MI 48824
| | - Michael R. Lieber
- USC Norris Comprehensive Cancer Ctr., Departments of Pathology, of Molecular Microbiology & Immunology, of Biochemistry & Molecular Biology, and of the Section of Molecular & Computational Biology within the Department of Biological Sciences, 1441 Eastlake Ave., NTT5428, Los Angeles, CA 90089-9176
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21
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So CC, Ramachandran S, Martin A. E3 Ubiquitin Ligases RNF20 and RNF40 Are Required for Double-Stranded Break (DSB) Repair: Evidence for Monoubiquitination of Histone H2B Lysine 120 as a Novel Axis of DSB Signaling and Repair. Mol Cell Biol 2019; 39:e00488-18. [PMID: 30692271 PMCID: PMC6447412 DOI: 10.1128/mcb.00488-18] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/13/2018] [Accepted: 01/23/2019] [Indexed: 01/13/2023] Open
Abstract
Histone posttranslational modifications play fundamental roles in the regulation of double-stranded DNA break (DSB) repair. RNF20/RNF40-mediated monoubiquitination of histone H2B on lysine 120 (H2Bub) has been suggested as a potential mediator of DSB repair, although the nature and function of this posttranslational modification remain enigmatic. In this report, we demonstrate that RNF20 and RNF40 are required for DSB repair leading to homologous recombination (HR) and class switch recombination, a process driven by nonhomologous end joining (NHEJ), in mouse B cells. These findings suggest a role for RNF20 and RNF40 in DSB repair proximal to NHEJ/HR pathway choice and likely in the signaling of DSBs. We found that DSBs led to a global increase in H2Bub but not the transcription-associated posttranslational modifications H3K4me3 and H3K79me2. We also found that H2AX phosphorylation was dispensable for H2Bub and that ATM and ATR jointly regulate ionizing radiation (IR)-induced H2Bub. Together, our results suggest that RNF20, RNF40, and H2Bub may represent a novel pathway for DSB sensing and repair.
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Affiliation(s)
- Clare C So
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | | | - Alberto Martin
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
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22
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DSB structure impacts DNA recombination leading to class switching and chromosomal translocations in human B cells. PLoS Genet 2019; 15:e1008101. [PMID: 30946744 PMCID: PMC6467426 DOI: 10.1371/journal.pgen.1008101] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 04/16/2019] [Accepted: 03/19/2019] [Indexed: 12/26/2022] Open
Abstract
Class switch recombination (CSR) requires activation-induced cytidine deaminase (AID) to trigger DNA double strand breaks (DSBs) at the immunoglobulin heavy chain (IGH) in B cells. Joining of AID-dependent DSBs within IGH facilitate CSR and effective humoral immunity, but ligation to DSBs in non-IGH chromosomes leads to chromosomal translocations. Thus, the mechanism by which AID-dependent DSBs are repaired requires careful examination. The random activity of AID in IGH leads to a spectrum of DSB structures. In this report, we investigated how DSB structure impacts end-joining leading to CSR and chromosomal translocations in human B cells, for which models of CSR are inefficient and not readily available. Using CRISPR/Cas9 to model AID-dependent DSBs in IGH and non-IGH genes, we found that DSBs with 5’ and 3’ overhangs led to increased processing during end-joining compared to blunt DSBs. We observed that 5’ overhangs were removed and 3’ overhangs were filled in at recombination junctions, suggesting that different subsets of enzymes are required for repair based on DSB polarity. Surprisingly, while Cas9-mediated switching preferentially utilized NHEJ regardless of DSB structure, A-EJ strongly preferred repairing blunt DSBs leading to translocations in the absence of NHEJ. We found that DSB polarity influenced frequency of Cas9-mediated switching and translocations more than overhang length. Lastly, recombination junctions from staggered DSBs exhibited templated insertions, suggesting iterative resection and filling in during repair. Our results demonstrate that DSB structure biases repair towards NHEJ or A-EJ to complete recombination leading to CSR and translocations, thus helping to elucidate the mechanism of genome rearrangements in human B cells. The production of different classes of antibodies/immunoglobulins (IgM, IgG, etc.) is essential for protection against diverse pathogens and effective immunity. This cellular process is triggered by the enzyme activation-induced cytidine deaminase (AID). AID mutates DNA predominantly in antibody genes, generating different types of DNA breaks. Repair of DNA breaks initiated by AID leads to the production of different antibody classes. Erroneous repair of this damage can also lead to chromosomal translocations, a hallmark of lymphomas and other cancers. In this study, we used CRISPR/Cas9 technology to model the different types of DNA breaks physiologically produced by AID. We found that the specific structure of these DNA breaks strongly influenced how they were repaired. That is, different types of DNA breaks inform different modes of rejoining. Our findings show that not all types of DNA breaks are treated equally by genome maintenance machinery in the cell. These observations provide insight into the molecular mechanisms behind antibody-dependent immunity and lymphomagenesis.
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23
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The H2B deubiquitinase Usp22 promotes antibody class switch recombination by facilitating non-homologous end joining. Nat Commun 2018. [PMID: 29520062 PMCID: PMC5843634 DOI: 10.1038/s41467-018-03455-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Class switch recombination (CSR) has a fundamental function during humoral immune response and involves the induction and subsequent repair of DNA breaks in the immunoglobulin (Ig) switch regions. Here we show the role of Usp22, the SAGA complex deubiquitinase that removes ubiquitin from H2B-K120, in the repair of programmed DNA breaks in vivo. Ablation of Usp22 in primary B cells results in defects in γH2AX and impairs the classical non-homologous end joining (c-NHEJ), affecting both V(D)J recombination and CSR. Surprisingly, Usp22 depletion causes defects in CSR to various Ig isotypes, but not IgA. We further demonstrate that IgG CSR primarily relies on c-NHEJ, whereas CSR to IgA is more reliant on the alternative end joining pathway, indicating that CSR to different isotypes involves distinct DNA repair pathways. Hence, Usp22 is the first deubiquitinase reported to regulate both V(D)J recombination and CSR in vivo by facilitating c-NHEJ.
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24
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Double-stranded DNA break polarity skews repair pathway choice during intrachromosomal and interchromosomal recombination. Proc Natl Acad Sci U S A 2018; 115:2800-2805. [PMID: 29472448 DOI: 10.1073/pnas.1720962115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Activation-induced cytidine deaminase (AID) inflicts DNA damage at Ig genes to initiate class switch recombination (CSR) and chromosomal translocations. However, the DNA lesions formed during these processes retain an element of randomness, and thus knowledge of the relationship between specific DNA lesions and AID-mediated processes remains incomplete. To identify necessary and sufficient DNA lesions in CSR, the Cas9 endonuclease and nickase variants were used to program DNA lesions at a greater degree of predictability than is achievable with conventional induction of CSR. Here we show that Cas9-mediated nicks separated by up to 250 nucleotides on opposite strands can mediate CSR. Staggered double-stranded breaks (DSBs) result in more end resection and junctional microhomology than blunt DSBs. Moreover, Myc-Igh chromosomal translocations, which are carried out primarily by alternative end joining (A-EJ), were preferentially induced by 5' DSBs. These data indicate that DSBs with 5' overhangs skew intrachromosomal and interchromosomal end-joining toward A-EJ. In addition to lending potential insight to AID-mediated phenomena, this work has broader carryover implications in DNA repair and lymphomagenesis.
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25
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DNA double-strand break response factors influence end-joining features of IgH class switch and general translocation junctions. Proc Natl Acad Sci U S A 2018; 115:762-767. [PMID: 29311308 DOI: 10.1073/pnas.1719988115] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ig heavy chain (IgH) class switch recombination (CSR) in B lymphocytes switches IgH constant regions to change antibody functions. CSR is initiated by DNA double-strand breaks (DSBs) within a donor IgH switch (S) region and a downstream acceptor S region. CSR is completed by fusing donor and acceptor S region DSB ends by classical nonhomologous end-joining (C-NHEJ) and, in its absence, by alternative end-joining that is more biased to use longer junctional microhomologies (MHs). Deficiency for DSB response (DSBR) factors, including ataxia telangiectasia-mutated (ATM) and 53BP1, variably impair CSR end-joining, with 53BP1 deficiency having the greatest impact. However, studies of potential impact of DSBR factor deficiencies on MH-mediated CSR end-joining have been technically limited. We now use a robust DSB joining assay to elucidate impacts of deficiencies for DSBR factors on CSR and chromosomal translocation junctions in primary mouse B cells and CH12F3 B-lymphoma cells. Compared with wild-type, CSR and c-myc to S region translocation junctions in the absence of 53BP1, and, to a lesser extent, other DSBR factors, have increased MH utilization; indeed, 53BP1-deficient MH profiles resemble those associated with C-NHEJ deficiency. However, translocation junctions between c-myc DSB and general DSBs genome-wide are not MH-biased in ATM-deficient versus wild-type CH12F3 cells and are less biased in 53BP1- and C-NHEJ-deficient cells than CSR junctions or c-myc to S region translocation junctions. We discuss potential roles of DSBR factors in suppressing increased MH-mediated DSB end-joining and features of S regions that may render their DSBs prone to MH-biased end-joining in the absence of DSBR factors.
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26
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Khan FA, Ali SO. Physiological Roles of DNA Double-Strand Breaks. J Nucleic Acids 2017; 2017:6439169. [PMID: 29181194 PMCID: PMC5664317 DOI: 10.1155/2017/6439169] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 09/24/2017] [Indexed: 12/20/2022] Open
Abstract
Genomic integrity is constantly threatened by sources of DNA damage, internal and external alike. Among the most cytotoxic lesions is the DNA double-strand break (DSB) which arises from the cleavage of both strands of the double helix. Cells boast a considerable set of defences to both prevent and repair these breaks and drugs which derail these processes represent an important category of anticancer therapeutics. And yet, bizarrely, cells deploy this very machinery for the intentional and calculated disruption of genomic integrity, harnessing potentially destructive DSBs in delicate genetic transactions. Under tight spatiotemporal regulation, DSBs serve as a tool for genetic modification, widely used across cellular biology to generate diverse functionalities, ranging from the fundamental upkeep of DNA replication, transcription, and the chromatin landscape to the diversification of immunity and the germline. Growing evidence points to a role of aberrant DSB physiology in human disease and an understanding of these processes may both inform the design of new therapeutic strategies and reduce off-target effects of existing drugs. Here, we review the wide-ranging roles of physiological DSBs and the emerging network of their multilateral regulation to consider how the cell is able to harness DNA breaks as a critical biochemical tool.
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Affiliation(s)
- Farhaan A. Khan
- School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Hills Road, Cambridge CB2 0SP, UK
| | - Syed O. Ali
- School of Clinical Medicine, Addenbrooke's Hospital, University of Cambridge, Hills Road, Cambridge CB2 0SP, UK
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27
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Seol JH, Shim EY, Lee SE. Microhomology-mediated end joining: Good, bad and ugly. Mutat Res 2017; 809:81-87. [PMID: 28754468 DOI: 10.1016/j.mrfmmm.2017.07.002] [Citation(s) in RCA: 149] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/21/2017] [Accepted: 07/03/2017] [Indexed: 01/06/2023]
Abstract
DNA double-strand breaks (DSBs) are induced by a variety of genotoxic agents, including ionizing radiation and chemotherapy drugs for treating cancers. The elimination of DSBs proceeds via distinctive error-free and error-prone pathways. Repair by homologous recombination (HR) is largely error-free and mediated by RAD51/BRCA2 gene products. Classical non-homologous end joining (C-NHEJ) requires the Ku heterodimer and can efficiently rejoin breaks, with occasional loss or gain of DNA information. Recently, evidence has unveiled another DNA end-joining mechanism that is independent of recombination factors and Ku proteins, termed alternative non-homologous end joining (A-NHEJ). While A-NHEJ-mediated repair does not require homology, in a subtype of A-NHEJ, DSB breaks are sealed by microhomology (MH)-mediated base-pairing of DNA single strands, followed by nucleolytic trimming of DNA flaps, DNA gap filling, and DNA ligation, yielding products that are always associated with DNA deletion. This highly error-prone DSB repair pathway is termed microhomology-mediated end joining (MMEJ). Dissecting the mechanisms of MMEJ is of great interest because of its potential to destabilize the genome through gene deletions and chromosomal rearrangements in cells deficient in canonical repair pathways, including HR and C-NHEJ. In addition, evidence now suggests that MMEJ plays a physiological role in normal cells.
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Affiliation(s)
- Ja-Hwan Seol
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States
| | - Eun Yong Shim
- Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States
| | - Sang Eun Lee
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States; Department of Radiation Oncology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, United States.
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28
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Non-homologous DNA end joining and alternative pathways to double-strand break repair. Nat Rev Mol Cell Biol 2017; 18:495-506. [PMID: 28512351 DOI: 10.1038/nrm.2017.48] [Citation(s) in RCA: 1032] [Impact Index Per Article: 147.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
DNA double-strand breaks (DSBs) are the most dangerous type of DNA damage because they can result in the loss of large chromosomal regions. In all mammalian cells, DSBs that occur throughout the cell cycle are repaired predominantly by the non-homologous DNA end joining (NHEJ) pathway. Defects in NHEJ result in sensitivity to ionizing radiation and the ablation of lymphocytes. The NHEJ pathway utilizes proteins that recognize, resect, polymerize and ligate the DNA ends in a flexible manner. This flexibility permits NHEJ to function on a wide range of DNA-end configurations, with the resulting repaired DNA junctions often containing mutations. In this Review, we discuss the most recent findings regarding the relative involvement of the different NHEJ proteins in the repair of various DNA-end configurations. We also discuss the shunting of DNA-end repair to the auxiliary pathways of alternative end joining (a-EJ) or single-strand annealing (SSA) and the relevance of these different pathways to human disease.
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29
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Robert I, Gaudot L, Yélamos J, Noll A, Wong HK, Dantzer F, Schreiber V, Reina-San-Martin B. Robust immunoglobulin class switch recombination and end joining in Parp9-deficient mice. Eur J Immunol 2017; 47:665-676. [PMID: 28105679 DOI: 10.1002/eji.201646757] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 12/16/2016] [Accepted: 01/18/2017] [Indexed: 12/15/2022]
Abstract
To mount highly specific and adapted immune responses, B lymphocytes assemble and diversify their antibody repertoire through mechanisms involving the formation of programmed DNA damage. Immunoglobulin class switch recombination (CSR) is triggered by DNA lesions induced by activation-induced cytidine deaminase, which are processed to double-stranded DNA break (DSB) intermediates. These DSBs activate the cellular DNA damage response and enroll numerous DNA repair factors, involving poly(ADP-ribose) polymerases Parp1, Parp2, and Parp3 to promote appropriate DNA repair and efficient long-range recombination. The macroParp Parp9, which is overexpressed in certain lymphomas, has been recently implicated in DSB repair, acting together with Parp1. Here, we examine the contribution of Parp9 to the resolution of physiological DSBs incurred during V(D)J recombination and CSR by generating Parp9-/- mice. We find that Parp9-deficient mice are viable, fertile, and do not show any overt phenotype. Moreover, we find that Parp9 is dispensable for B-cell development. Finally, we show that CSR and DNA end-joining are robust in the absence of Parp9, indicating that Parp9 is not essential in vivo to achieve physiological DSB repair, or that strong compensatory mechanisms exist.
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Affiliation(s)
- Isabelle Robert
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Centre National de Recherche Scientifique, UMR7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - Léa Gaudot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Centre National de Recherche Scientifique, UMR7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
| | - José Yélamos
- Cancer Research Program, Hospital del Mar Medical Research Institute (IMIM), Barcelona, Spain.,Department of Immunology, Hospital del Mar, Barcelona, Spain.,Network Center for Biomedical Research on Hepatic and Digestive Diseases, Madrid, Spain
| | - Aurélia Noll
- Centre National de Recherche Scientifique, UMR7242, Illkirch, France.,Laboratoire d'Excellence Medalis, Université de Strasbourg, Illkirch, France.,Institut de Recherche de l'Ecole de Biotechnologie de Strasbourg, Illkirch, France.,Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch, France
| | - Heng-Kuan Wong
- Centre National de Recherche Scientifique, UMR7242, Illkirch, France.,Laboratoire d'Excellence Medalis, Université de Strasbourg, Illkirch, France.,Institut de Recherche de l'Ecole de Biotechnologie de Strasbourg, Illkirch, France.,Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch, France
| | - Françoise Dantzer
- Centre National de Recherche Scientifique, UMR7242, Illkirch, France.,Laboratoire d'Excellence Medalis, Université de Strasbourg, Illkirch, France.,Institut de Recherche de l'Ecole de Biotechnologie de Strasbourg, Illkirch, France.,Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch, France
| | - Valérie Schreiber
- Centre National de Recherche Scientifique, UMR7242, Illkirch, France.,Laboratoire d'Excellence Medalis, Université de Strasbourg, Illkirch, France.,Institut de Recherche de l'Ecole de Biotechnologie de Strasbourg, Illkirch, France.,Ecole Supérieure de Biotechnologie de Strasbourg, Illkirch, France
| | - Bernardo Reina-San-Martin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.,Centre National de Recherche Scientifique, UMR7104, Illkirch, France.,Université de Strasbourg, Illkirch, France
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30
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Zan H, Tat C, Qiu Z, Taylor JR, Guerrero JA, Shen T, Casali P. Rad52 competes with Ku70/Ku86 for binding to S-region DSB ends to modulate antibody class-switch DNA recombination. Nat Commun 2017; 8:14244. [PMID: 28176781 PMCID: PMC5309807 DOI: 10.1038/ncomms14244] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 12/12/2016] [Indexed: 12/13/2022] Open
Abstract
Antibody class-switch DNA recombination (CSR) is initiated by AID-introduced DSBs in the switch (S) regions targeted for recombination, as effected by Ku70/Ku86-mediated NHEJ. Ku-deficient B cells, however, undergo (reduced) CSR through an alternative(A)-NHEJ pathway, which introduces microhomologies in S-S junctions. As microhomology-mediated end-joining requires annealing of single-strand DNA ends, we addressed the contribution of single-strand annealing factors HR Rad52 and translesion DNA polymerase θ to CSR. Compared with their Rad52+/+ counterparts, which display normal CSR, Rad52-/- B cells show increased CSR, fewer intra-Sμ region recombinations, no/minimal microhomologies in S-S junctions, decreased c-Myc/IgH translocations and increased Ku70/Ku86 recruitment to S-region DSB ends. Rad52 competes with Ku70/Ku86 for binding to S-region DSB ends. It also facilitates a Ku-independent DSB repair, which favours intra-S region recombination and mediates, particularly in Ku absence, inter-S-S recombination, as emphasized by the significantly greater CSR reduction in Rad52-/- versus Rad52+/+ B cells on Ku86 knockdown.
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Affiliation(s)
- Hong Zan
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Connie Tat
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Zhifang Qiu
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Julia R. Taylor
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Justin A. Guerrero
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Tian Shen
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Paolo Casali
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
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31
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Bromberg KD, Mitchell TRH, Upadhyay AK, Jakob CG, Jhala MA, Comess KM, Lasko LM, Li C, Tuzon CT, Dai Y, Li F, Eram MS, Nuber A, Soni NB, Manaves V, Algire MA, Sweis RF, Torrent M, Schotta G, Sun C, Michaelides MR, Shoemaker AR, Arrowsmith CH, Brown PJ, Santhakumar V, Martin A, Rice JC, Chiang GG, Vedadi M, Barsyte-Lovejoy D, Pappano WN. The SUV4-20 inhibitor A-196 verifies a role for epigenetics in genomic integrity. Nat Chem Biol 2017; 13:317-324. [DOI: 10.1038/nchembio.2282] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 11/23/2016] [Indexed: 12/30/2022]
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32
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MBD4 Facilitates Immunoglobulin Class Switch Recombination. Mol Cell Biol 2017; 37:MCB.00316-16. [PMID: 27777312 DOI: 10.1128/mcb.00316-16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 09/30/2016] [Indexed: 01/02/2023] Open
Abstract
Immunoglobulin heavy chain class switch recombination (CSR) requires targeted formation of DNA double-strand breaks (DSBs) in repetitive switch region elements followed by ligation between distal breaks. The introduction of DSBs is initiated by activation-induced cytidine deaminase (AID) and requires base excision repair (BER) and mismatch repair (MMR). The BER enzyme methyl-CpG binding domain protein 4 (MBD4) has been linked to the MMR pathway through its interaction with MutL homologue 1 (MLH1). We find that when Mbd4 exons 6 to 8 are deleted in a switching B cell line, DSB formation is severely reduced and CSR frequency is impaired. Impaired CSR can be rescued by ectopic expression of Mbd4 Mbd4 deficiency yields a deficit in DNA end processing similar to that found in MutS homologue 2 (Msh2)- and Mlh1-deficient B cells. We demonstrate that microhomology-rich S-S junctions are enriched in cells in which Mbd4 is deleted. Our studies suggest that Mbd4 is a component of MMR-directed DNA end processing.
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33
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Le MX, Haddad D, Ling AK, Li C, So CC, Chopra A, Hu R, Angulo JF, Moffat J, Martin A. Kin17 facilitates multiple double-strand break repair pathways that govern B cell class switching. Sci Rep 2016; 6:37215. [PMID: 27853268 PMCID: PMC5112545 DOI: 10.1038/srep37215] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 10/13/2016] [Indexed: 11/09/2022] Open
Abstract
Class switch recombination (CSR) in B cells requires the timely repair of DNA double-stranded breaks (DSBs) that result from lesions produced by activation-induced cytidine deaminase (AID). Through a genome-wide RNAi screen, we identified Kin17 as a gene potentially involved in the maintenance of CSR in murine B cells. In this study, we confirm a critical role for Kin17 in CSR independent of AID activity. Furthermore, we make evident that DSBs generated by AID or ionizing radiation require Kin17 for efficient repair and resolution. Our report shows that reduced Kin17 results in an elevated deletion frequency following AID mutational activity in the switch region. In addition, deficiency in Kin17 affects the functionality of multiple DSB repair pathways, namely homologous recombination, non-homologous end-joining, and alternative end-joining. This report demonstrates the importance of Kin17 as a critical factor that acts prior to the repair phase of DSB repair and is of bona fide importance for CSR.
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Affiliation(s)
- Michael X. Le
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Dania Haddad
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Alexanda K. Ling
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Conglei Li
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Clare C. So
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Amit Chopra
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Rui Hu
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
| | - Jaime F. Angulo
- Laboratoire de Radio Toxicologie, CEA, Université Paris-Saclay, Arpajon, 91297, France
| | - Jason Moffat
- Donnelly Centre and Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario, M5S1A8, Canada
| | - Alberto Martin
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, Ontario, M5S1A8, Canada
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34
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Guan J, Zhao Q, Mao W. Nuclear PTEN interferes with binding of Ku70 at double-strand breaks through post-translational poly(ADP-ribosyl)ation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:3106-3115. [PMID: 27741411 DOI: 10.1016/j.bbamcr.2016.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/27/2016] [Accepted: 10/07/2016] [Indexed: 01/12/2023]
Abstract
PTEN is a tumor suppressor gene characterized as a phosphatase that antagonizes the phosphatidylinositol 3-kinase signaling pathway in the cytoplasm. Nuclear PTEN plays roles in chromosomal stability, in which the double-strand breaks (DSB) repair mediated by homologous recombination (HR) and non-homologous end joining (NHEJ) is critical. Herein, the role of nuclear PTEN in DSB repair and the underlying molecular mechanism was investigated in this study. Using human breast cancer BT549 and MDA-MB-231 cell lines, we reveal a specific feature of PTEN that controls poly(ADP-ribosyl)ation of Ku70 and interferes with binding of Ku70 at DSB. Plasmid-based end joining and reporter assays showed that nuclear PTEN restrained NHEJ efficacy. Electrophoretic mobility shift assays showed that nuclear PTEN impaired Ku70 complex binding to DSB by 3-fold. Co-immunoprecipitation assay showed PTEN regulated poly(ADP-ribosyl)ation of Ku70 instead of directly interacting with Ku70, while PTEN promoted the poly(ADP-ribosyl)ation of PARP1 and induced the degradation of PARP1 in PTEN-WT cells exposed to DSB agents. Of note, the role of PTEN in DSB repair mostly depends on its nuclear localization rather than its phosphatase activity. As a result, the absence of nuclear PTEN rather than phosphatase-negative PTEN confers cell hypersensitivity to anti-tumor DNA damage drugs. This finding contributes to understanding the effect of PTEN in repair of DSB and using defined anti-tumor DSB drugs to treat tumor cells with aberrant PTEN.
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Affiliation(s)
- Jiawei Guan
- Department of Biotechnology, College of Basic Medical Sciences, Dalian Medical University, Dalian 116044, China
| | - Qian Zhao
- Department of Biotechnology, College of Basic Medical Sciences, Dalian Medical University, Dalian 116044, China
| | - Weifeng Mao
- Department of Biotechnology, College of Basic Medical Sciences, Dalian Medical University, Dalian 116044, China.
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35
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PAXX and XLF DNA repair factors are functionally redundant in joining DNA breaks in a G1-arrested progenitor B-cell line. Proc Natl Acad Sci U S A 2016; 113:10619-24. [PMID: 27601633 DOI: 10.1073/pnas.1611882113] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Classical nonhomologous end joining (C-NHEJ) is a major mammalian DNA double-strand break (DSB) repair pathway. Core C-NHEJ factors, such as XRCC4, are required for joining DSB intermediates of the G1 phase-specific V(D)J recombination reaction in progenitor lymphocytes. Core factors also contribute to joining DSBs in cycling mature B-lineage cells, including DSBs generated during antibody class switch recombination (CSR) and DSBs generated by ionizing radiation. The XRCC4-like-factor (XLF) C-NHEJ protein is dispensable for V(D)J recombination in normal cells, but because of functional redundancy, it is absolutely required for this process in cells deficient for the ataxia telangiectasia-mutated (ATM) DSB response factor. The recently identified paralogue of XRCC4 and XLF (PAXX) factor has homology to these two proteins and variably contributes to ionizing radiation-induced DSB repair in human and chicken cells. We now report that PAXX is dispensable for joining V(D)J recombination DSBs in G1-arrested mouse pro-B-cell lines, dispensable for joining CSR-associated DSBs in a cycling mouse B-cell line, and dispensable for normal ionizing radiation resistance in both G1-arrested and cycling pro-B lines. However, we find that combined deficiency for PAXX and XLF in G1-arrested pro-B lines abrogates DSB joining during V(D)J recombination and sensitizes the cells to ionizing radiation exposure. Thus, PAXX provides core C-NHEJ factor-associated functions in the absence of XLF and vice versa in G1-arrested pro-B-cell lines. Finally, we also find that PAXX deficiency has no impact on V(D)J recombination DSB joining in ATM-deficient pro-B lines. We discuss implications of these findings with respect to potential PAXX and XLF functions in C-NHEJ.
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36
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Ramachandran S, Haddad D, Li C, Le MX, Ling AK, So CC, Nepal RM, Gommerman JL, Yu K, Ketela T, Moffat J, Martin A. The SAGA Deubiquitination Module Promotes DNA Repair and Class Switch Recombination through ATM and DNAPK-Mediated γH2AX Formation. Cell Rep 2016; 15:1554-1565. [PMID: 27160905 DOI: 10.1016/j.celrep.2016.04.041] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 02/26/2016] [Accepted: 04/05/2016] [Indexed: 01/06/2023] Open
Abstract
Class switch recombination (CSR) requires activation-induced deaminase (AID) to instigate double-stranded DNA breaks at the immunoglobulin locus. DNA breaks activate the DNA damage response (DDR) by inducing phosphorylation of histone H2AX followed by non-homologous end joining (NHEJ) repair. We carried out a genome-wide screen to identify CSR factors. We found that Usp22, Eny2, and Atxn7, members of the Spt-Ada-Gcn5-acetyltransferase (SAGA) deubiquitination module, are required for deubiquitination of H2BK120ub following DNA damage, are critical for CSR, and function downstream of AID. The SAGA deubiquitinase activity was required for optimal irradiation-induced γH2AX formation, and failure to remove H2BK120ub inhibits ATM- and DNAPK-induced γH2AX formation. Consistent with this effect, these proteins were found to function upstream of various double-stranded DNA repair pathways. This report demonstrates that deubiquitination of histone H2B impacts the early stages of the DDR and is required for the DNA repair phase of CSR.
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Affiliation(s)
- Shaliny Ramachandran
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Dania Haddad
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Conglei Li
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Michael X Le
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Alexanda K Ling
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Clare C So
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Rajeev M Nepal
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Jennifer L Gommerman
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada
| | - Kefei Yu
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Troy Ketela
- Princess Margaret Genomics Centre, University Health Network, Toronto, ON M5G 1L7, Canada
| | - Jason Moffat
- Donnelly Centre and Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Alberto Martin
- Department of Immunology, University of Toronto, Medical Sciences Building, Toronto, ON M5S 1A8, Canada.
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37
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Redundant function of DNA ligase 1 and 3 in alternative end-joining during immunoglobulin class switch recombination. Proc Natl Acad Sci U S A 2016; 113:1261-6. [PMID: 26787901 DOI: 10.1073/pnas.1521630113] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nonhomologous end-joining (NHEJ) is the major DNA double-strand break (DSB) repair pathway in mammals and resolves the DSBs generated during both V(D)J recombination in developing lymphocytes and class switch recombination (CSR) in antigen-stimulated B cells. In contrast to the absolute requirement for NHEJ to resolve DSBs associated with V(D)J recombination, DSBs associated with CSR can be resolved in NHEJ-deficient cells (albeit at a reduced level) by a poorly defined alternative end-joining (A-EJ) pathway. Deletion of DNA ligase IV (Lig4), a core component of the NHEJ pathway, reduces CSR efficiency in a mouse B-cell line capable of robust cytokine-stimulated CSR in cell culture. Here, we report that CSR levels are not further reduced by deletion of either of the two remaining DNA ligases (Lig1 and nuclear Lig3) in Lig4(-/-) cells. We conclude that in the absence of Lig4, Lig1, and Lig3 function in a redundant manner in resolving switch region DSBs during CSR.
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38
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Ligase I and ligase III mediate the DNA double-strand break ligation in alternative end-joining. Proc Natl Acad Sci U S A 2016; 113:1256-60. [PMID: 26787905 DOI: 10.1073/pnas.1521597113] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In eukaryotes, DNA double-strand breaks (DSBs), one of the most harmful types of DNA damage, are repaired by homologous repair (HR) and nonhomologous end-joining (NHEJ). Surprisingly, in cells deficient for core classic NHEJ factors such as DNA ligase IV (Lig4), substantial end-joining activities have been observed in various situations, suggesting the existence of alternative end-joining (A-EJ) activities. Several putative A-EJ factors have been proposed, although results are mostly controversial. By using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system, we generated mouse CH12F3 cell lines in which, in addition to Lig4, either Lig1 or nuclear Lig3, representing the cells containing a single DNA ligase (Lig3 or Lig1, respectively) in their nucleus, was completely ablated. Surprisingly, we found that both Lig1- and Lig3-containing complexes could efficiently catalyze A-EJ for class switching recombination (CSR) in the IgH locus and chromosomal deletions between DSBs generated by CRISPR/Cas9 in cis-chromosomes. However, only deletion of nuclear Lig3, but not Lig1, could significantly reduce the interchromosomal translocations in Lig4(-/-) cells, suggesting the unique role of Lig3 in catalyzing chromosome translocation. Additional sequence analysis of chromosome translocation junction microhomology revealed the specificity of different ligase-containing complexes. The data suggested the existence of multiple DNA ligase-containing complexes in A-EJ.
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Maezawa S, Nakano S, Kuniya T, Koiwai O, Koiwai K. Double-strand break repair based on short-homology regions is suppressed under terminal deoxynucleotidyltransferase expression, as revealed by a novel vector system for analysing DNA repair by nonhomologous end joining. FEBS Open Bio 2016; 6:16-23. [PMID: 27047738 PMCID: PMC4794791 DOI: 10.1002/2211-5463.12001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 10/16/2015] [Accepted: 11/18/2015] [Indexed: 11/24/2022] Open
Abstract
We have constructed a novel, nonhomologous end‐joining (NHEJ) assay vector (NAV), containing mKate2, Venus and ccdB genes. Cotransfection of NAV with a construct expressing the restriction enzyme I‐SceI generated a double‐strand break (DSB) in NAV that excised mKate2 and ccdB. Repair of this DSB produced an intact vector that expressed Venus, a green fluorescent protein. Because cells bearing the repaired NAV lacked the ccdB gene which slows cell proliferation, the cultures were enriched in cells containing repaired DSBs. DNA sequence analysis of the DSB junctions indicated that the repair was carried out mainly by using the closest homology sequence. Use of the NAV yielded rapid results within 3 days after transfection. We then used the NAV to analyse NHEJ in cells overexpressing terminal deoxynucleotidyltransferase (TdT). The results indicated that TdT suppresses DNA repair that is based on short (one‐ or two‐base) homology regions, to efficiently add deoxynucleotides during VDJ recombination in lymphoid cells.
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Affiliation(s)
- So Maezawa
- Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Saori Nakano
- Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Takaaki Kuniya
- Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Osamu Koiwai
- Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Kotaro Koiwai
- Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
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Iliakis G, Murmann T, Soni A. Alternative end-joining repair pathways are the ultimate backup for abrogated classical non-homologous end-joining and homologous recombination repair: Implications for the formation of chromosome translocations. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2015; 793:166-75. [DOI: 10.1016/j.mrgentox.2015.07.001] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 07/01/2015] [Indexed: 01/15/2023]
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Rivera-Munoz P, Abramowski V, Jacquot S, André P, Charrier S, Lipson-Ruffert K, Fischer A, Galy A, Cavazzana M, de Villartay JP. Lymphopoiesis in transgenic mice over-expressing Artemis. Gene Ther 2015; 23:176-86. [PMID: 26361272 DOI: 10.1038/gt.2015.95] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 08/28/2015] [Accepted: 09/08/2015] [Indexed: 12/27/2022]
Abstract
Artemis is a factor of the non-homologous end joining pathway involved in DNA double-strand break repair that has a critical role in V(D)J recombination. Mutations in DCLRE1C/ARTEMIS gene result in radiosensitive severe combined immunodeficiency in humans owing to a lack of mature T and B cells. Given the known drawbacks of allogeneic hematopoietic stem cell transplantation (HSCT), gene therapy appears as a promising alternative for these patients. However, the safety of an unregulated expression of Artemis has to be established. We developed a transgenic mouse model expressing human Artemis under the control of the strong CMV early enhancer/chicken beta actin promoter through knock-in at the ROSA26 locus to analyze this issue. Transgenic mice present a normal development, maturation and function of T and B cells with no signs of lymphopoietic malignancies for up to 15 months. These results suggest that the over-expression of Artemis in mice (up to 40 times) has no deleterious effects in early and mature lymphoid cells and support the safety of gene therapy as a possible curative treatment for Artemis-deficient patients.
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Affiliation(s)
- P Rivera-Munoz
- Laboratory of Genome Dynamics in the Immune System (DGSI), INSERM UMR1163, Paris, France.,Paris-Descartes, Sorbonne Paris Cité University, Imagine Institute, Paris, France
| | - V Abramowski
- Laboratory of Genome Dynamics in the Immune System (DGSI), INSERM UMR1163, Paris, France.,Paris-Descartes, Sorbonne Paris Cité University, Imagine Institute, Paris, France
| | - S Jacquot
- Institut Clinique de la Souris, PHENOMIN, CNRS, INSERM, Université de Strasbourg, Illkirch, France
| | - P André
- Institut Clinique de la Souris, PHENOMIN, CNRS, INSERM, Université de Strasbourg, Illkirch, France
| | | | - K Lipson-Ruffert
- Service des Animaux Transgéaniques, UPS44, CNRS, Villejuif, France
| | - A Fischer
- Paris-Descartes, Sorbonne Paris Cité University, Imagine Institute, Paris, France.,Unité d'Immunologie et Hématologie Pédiatrique, AP/HP, Hôpital Necker-Enfants Malades, Paris, France.,Collège de France, Paris, France
| | | | - M Cavazzana
- Paris-Descartes, Sorbonne Paris Cité University, Imagine Institute, Paris, France.,Unité d'Immunologie et Hématologie Pédiatrique, AP/HP, Hôpital Necker-Enfants Malades, Paris, France
| | - J-P de Villartay
- Laboratory of Genome Dynamics in the Immune System (DGSI), INSERM UMR1163, Paris, France.,Paris-Descartes, Sorbonne Paris Cité University, Imagine Institute, Paris, France
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Parp3 negatively regulates immunoglobulin class switch recombination. PLoS Genet 2015; 11:e1005240. [PMID: 26000965 PMCID: PMC4441492 DOI: 10.1371/journal.pgen.1005240] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 04/26/2015] [Indexed: 12/11/2022] Open
Abstract
To generate highly specific and adapted immune responses, B cells diversify their antibody repertoire through mechanisms involving the generation of programmed DNA damage. Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by the recruitment of activation-induced cytidine deaminase (AID) to immunoglobulin loci and by the subsequent generation of DNA lesions, which are differentially processed to mutations during SHM or to double-stranded DNA break intermediates during CSR. The latter activate the DNA damage response and mobilize multiple DNA repair factors, including Parp1 and Parp2, to promote DNA repair and long-range recombination. We examined the contribution of Parp3 in CSR and SHM. We find that deficiency in Parp3 results in enhanced CSR, while SHM remains unaffected. Mechanistically, this is due to increased occupancy of AID at the donor (Sμ) switch region. We also find evidence of increased levels of DNA damage at switch region junctions and a bias towards alternative end joining in the absence of Parp3. We propose that Parp3 plays a CSR-specific role by controlling AID levels at switch regions during CSR. During infections, B cells diversify the antibodies they produce by two mechanisms: somatic hypermutation (SHM) and class switch recombination (CSR). SHM mutates the regions encoding the antigen-binding site, generating high-affinity antibodies. CSR allows B cells to switch the class of antibody they produce (from IgM to IgA, IgG or IgE), providing novel effector functions. Together, SHM and CSR establish highly specific and pathogen-adapted antibody responses. SHM and CSR are initiated by the recruitment of the activation-induced cytidine deaminase (AID) enzyme to antibody genes. Once recruited, AID induces DNA lesions that are processed into mutations during SHM or chromosomal DNA breaks during CSR. These breaks activate multiple DNA repair proteins and are resolved by replacing the IgM gene segments by those encoding IgA, IgG or IgE. AID carries a significant oncogenic potential that needs to be controlled to preserve genome integrity. Nevertheless, the underlying mechanisms remain poorly understood. Here we show that Poly(ADP)ribose polymerase 3 (Parp3), an enzyme recently implicated in DNA repair, contributes to antibody diversification by negatively regulating CSR without affecting SHM. We show that Parp3 facilitates the repair of AID-induced DNA damage and controls AID levels on chromatin. We propose that Parp3 protects antibody genes from sustained AID-dependent DNA damage.
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Stavnezer J, Schrader CE. IgH chain class switch recombination: mechanism and regulation. THE JOURNAL OF IMMUNOLOGY 2015; 193:5370-8. [PMID: 25411432 DOI: 10.4049/jimmunol.1401849] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
IgH class switching occurs rapidly after activation of mature naive B cells, resulting in a switch from expression of IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of Abs to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional recombination between two switch regions, each of which is associated with a H chain constant region gene. Class switch recombination (CSR) is instigated by activation-induced cytidine deaminase, which converts cytosines in switch regions to uracils. The uracils are subsequently removed by two DNA-repair pathways, resulting in mutations, single-strand DNA breaks, and the double-strand breaks required for CSR. We discuss several aspects of CSR, including how CSR is induced, CSR in B cell progenitors, the roles of transcription and chromosomal looping in CSR, and the roles of certain DNA-repair enzymes in CSR.
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Affiliation(s)
- Janet Stavnezer
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605
| | - Carol E Schrader
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA 01605
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Zhang ZZ, Pannunzio NR, Hsieh CL, Yu K, Lieber MR. Complexities due to single-stranded RNA during antibody detection of genomic rna:dna hybrids. BMC Res Notes 2015; 8:127. [PMID: 25890199 PMCID: PMC4393563 DOI: 10.1186/s13104-015-1092-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 03/24/2015] [Indexed: 12/21/2022] Open
Abstract
Background Long genomic R-loops in eukaryotes were first described at the immunoglobulin heavy chain locus switch regions using bisulfite sequencing and functional studies. A mouse monoclonal antibody called S9.6 has been used for immunoprecipitation (IP) to identify R-loops, based on the assumption that it is specific for RNA:DNA over other nucleic acid duplexes. However, recent work has demonstrated that a variable domain of S9.6 binds AU-rich RNA:RNA duplexes with a KD that is only 5.6-fold weaker than for RNA:DNA duplexes. Most IP protocols do not pre-clear the genomic nucleic acid with RNase A to remove free RNA. Fold back of ssRNA can readily generate RNA:RNA duplexes that may bind the S9.6 antibody, and adventitious binding of RNA may also create short RNA:DNA regions. Here we investigate whether RNase A is needed to obtain reliable IP with S9.6. Findings As our test locus, we chose the most well-documented site for kilobase-long mammalian genomic R-loops, the immunoglobulin heavy chain locus (IgH) class switch regions. The R-loops at this locus can be induced by using cytokines to stimulate transcription from germline transcript promoters. We tested IP using S9.6 with and without various RNase treatments. The RNase treatments included RNase H to destroy the RNA in an RNA:DNA duplex and RNase A to destroy single-stranded (ss) RNA to prevent it from binding S9.6 directly (as duplex RNA) and to prevent the ssRNA from annealing to the genome, resulting in adventitious RNA:DNA hybrids. We find that optimal detection of RNA:DNA duplexes requires removal of ssRNA using RNase A. Without RNase A treatment, known regions of R-loop formation containing RNA:DNA duplexes can not be reliably detected. With RNase A treatment, a signal can be detected over background, but only within a limited 2 or 3-fold range, even with a stable kilobase-long genomic R-loop. Conclusion Any use of the S9.6 antibody must be preceded by RNase A treatment to remove free ssRNA that may compete for the S9.6 binding by forming RNA:RNA regions or short, transient RNA:DNA duplexes. Caution should be used when interpreting S9.6 data, and confirmation by independent structural and functional methods is essential. Electronic supplementary material The online version of this article (doi:10.1186/s13104-015-1092-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zheng Z Zhang
- USC Norris Comprehensive Cancer Ctr. Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA. .,Departments of Pathology, Biochemistry & Molecular Biology; Molecular Microbiology & Immunology; Urology, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA.
| | - Nicholas R Pannunzio
- USC Norris Comprehensive Cancer Ctr. Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA. .,Departments of Pathology, Biochemistry & Molecular Biology; Molecular Microbiology & Immunology; Urology, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA.
| | - Chih-Lin Hsieh
- USC Norris Comprehensive Cancer Ctr. Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA. .,Departments of Pathology, Biochemistry & Molecular Biology; Molecular Microbiology & Immunology; Urology, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA.
| | - Kefei Yu
- Department of Microbiology and Molecular Genetics, Michigan State University, 5175 Biomedical Physical Sciences, East Lansing, MI, 48824, USA.
| | - Michael R Lieber
- USC Norris Comprehensive Cancer Ctr. Molecular and Computational Biology Program, Department of Biological Sciences, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA. .,Departments of Pathology, Biochemistry & Molecular Biology; Molecular Microbiology & Immunology; Urology, University of Southern California Keck School of Medicine, 1441 Eastlake Ave., Rm. 5428, Los Angeles, CA, 90089-9176, USA.
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45
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DNA ligase C1 mediates the LigD-independent nonhomologous end-joining pathway of Mycobacterium smegmatis. J Bacteriol 2014; 196:3366-76. [PMID: 24957619 DOI: 10.1128/jb.01832-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Nonhomologous end joining (NHEJ) is a recently described bacterial DNA double-strand break (DSB) repair pathway that has been best characterized for mycobacteria. NHEJ can religate transformed linear plasmids, repair ionizing radiation (IR)-induced DSBs in nonreplicating cells, and seal I-SceI-induced chromosomal DSBs. The core components of the mycobacterial NHEJ machinery are the DNA end binding protein Ku and the polyfunctional DNA ligase LigD. LigD has three autonomous enzymatic modules: ATP-dependent DNA ligase (LIG), DNA/RNA polymerase (POL), and 3' phosphoesterase (PE). Although genetic ablation of ku or ligD abolishes NHEJ and sensitizes nonreplicating cells to ionizing radiation, selective ablation of the ligase activity of LigD in vivo only mildly impairs NHEJ of linearized plasmids, indicating that an additional DNA ligase can support NHEJ. Additionally, the in vivo role of the POL and PE domains in NHEJ is unclear. Here we define a LigD ligase-independent NHEJ pathway in Mycobacterium smegmatis that requires the ATP-dependent DNA ligase LigC1 and the POL domain of LigD. Mycobacterium tuberculosis LigC can also support this backup NHEJ pathway. We also demonstrate that, although dispensable for efficient plasmid NHEJ, the activities of the POL and PE domains are required for repair of IR-induced DSBs in nonreplicating cells. These findings define the genetic requirements for a LigD-independent NHEJ pathway in mycobacteria and demonstrate that all enzymatic functions of the LigD protein participate in NHEJ in vivo.
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Matthews AJ, Husain S, Chaudhuri J. Binding of AID to DNA does not correlate with mutator activity. THE JOURNAL OF IMMUNOLOGY 2014; 193:252-7. [PMID: 24879790 DOI: 10.4049/jimmunol.1400433] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The DNA deaminase activation-induced cytidine deaminase (AID) initiates somatic hypermutation (SHM) and class switch recombination (CSR) by deaminating cytidines to uridines at V region (V) genes and switch (S) regions. The mechanism by which AID is recruited to V genes and S region DNA is poorly understood. In this study, we used the CH12 B lymphoma line to demonstrate that, although S regions can efficiently recruit AID and undergo mutations and deletions, AID neither binds to nor mutates the V gene, thus clearly demonstrating intraimmunoglobulin locus specificity. Depletion of the RNA-binding protein polypyrimidine tract binding protein-2, previously shown to promote recruitment of AID to S regions, enables stable association of AID with the V gene. Surprisingly, AID binding to the V gene does not induce SHM. These results unmask a striking lack of correlation between AID binding and its mutator activity, providing evidence for the presence of factors required downstream of AID binding to effect SHM. Furthermore, our findings suggest that S regions are preferred targets for AID and, aided by polypyrimidine tract binding protein-2, act as "sinks" to sequester AID activity from other genomic regions.
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Affiliation(s)
- Allysia J Matthews
- Immunology Program, Memorial Sloan-Kettering Cancer Center, Gerstner Sloan-Kettering Graduate School, New York, NY 10065; andImmunology and Microbial Pathogenesis Program, Weill-Cornell Medical School, New York, NY 10065
| | - Solomon Husain
- Immunology Program, Memorial Sloan-Kettering Cancer Center, Gerstner Sloan-Kettering Graduate School, New York, NY 10065; andImmunology and Microbial Pathogenesis Program, Weill-Cornell Medical School, New York, NY 10065
| | - Jayanta Chaudhuri
- Immunology Program, Memorial Sloan-Kettering Cancer Center, Gerstner Sloan-Kettering Graduate School, New York, NY 10065; andImmunology and Microbial Pathogenesis Program, Weill-Cornell Medical School, New York, NY 10065
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47
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DNA ligase I is not essential for mammalian cell viability. Cell Rep 2014; 7:316-320. [PMID: 24726358 PMCID: PMC4593317 DOI: 10.1016/j.celrep.2014.03.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/06/2014] [Accepted: 03/07/2014] [Indexed: 11/22/2022] Open
Abstract
Of the three DNA ligases present in all vertebrates, DNA ligase I (Lig1) has been considered essential for ligating Okazaki fragments during DNA replication and thereby essential for cell viability. Here, we report the striking finding that a Lig1-null murine B cell line is viable. Surprisingly, the Lig1-null cells exhibit normal proliferation and normal immunoglobulin heavy chain class switch recombination and are not hypersensitive to a wide variety of DNA damaging agents. These findings demonstrate that Lig1 is not absolutely required for cellular DNA replication and repair and that either Lig3 or Lig4 can substitute for the role of Lig1 in joining Okazaki fragments. The establishment of a Lig1-null cell line will greatly facilitate the characterization of DNA ligase function in mammalian cells, but the finding alone profoundly reprioritizes the role of ligase I in DNA replication, repair, and recombination.
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48
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Non-homologous end joining often uses microhomology: implications for alternative end joining. DNA Repair (Amst) 2014; 17:74-80. [PMID: 24613510 DOI: 10.1016/j.dnarep.2014.02.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 01/27/2014] [Accepted: 02/10/2014] [Indexed: 11/20/2022]
Abstract
Artemis and PALF (also called APLF) appear to be among the primary nucleases involved in non-homologous end joining (NHEJ) and responsible for most nucleolytic end processing in NHEJ. About 60% of NHEJ events show an alignment of the DNA ends that use 1 or 2bp of microhomology (MH) between the two DNA termini. Thus, MH is a common feature of NHEJ. For most naturally occurring human chromosomal deletions (e.g., after oxidative damage or radiation) and translocations, such as those seen in human neoplasms and as well as inherited chromosomal structural variations, MH usage occurs at a frequency that is typical of NHEJ, and does not suggest major involvement of alternative pathways that require more extensive MH. Though we mainly focus on human NHEJ at double-strand breaks, comparison on these points to other eukaryotes, primarily S. cerevisiae, is informative.
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49
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Frit P, Barboule N, Yuan Y, Gomez D, Calsou P. Alternative end-joining pathway(s): bricolage at DNA breaks. DNA Repair (Amst) 2014; 17:81-97. [PMID: 24613763 DOI: 10.1016/j.dnarep.2014.02.007] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 02/01/2014] [Accepted: 02/10/2014] [Indexed: 10/25/2022]
Abstract
To cope with DNA double strand break (DSB) genotoxicity, cells have evolved two main repair pathways: homologous recombination which uses homologous DNA sequences as repair templates, and non-homologous Ku-dependent end-joining involving direct sealing of DSB ends by DNA ligase IV (Lig4). During the last two decades a third player most commonly named alternative end-joining (A-EJ) has emerged, which is defined as any Ku- or Lig4-independent end-joining process. A-EJ increasingly appears as a highly error-prone bricolage on DSBs and despite expanding exploration, it still escapes full characterization. In the present review, we discuss the mechanism and regulation of A-EJ as well as its biological relevance under physiological and pathological situations, with a particular emphasis on chromosomal instability and cancer. Whether or not it is a genuine DSB repair pathway, A-EJ is emerging as an important cellular process and understanding A-EJ will certainly be a major challenge for the coming years.
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Affiliation(s)
- Philippe Frit
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), BP 64182, 205 route de Narbonne, 31077 Toulouse, Cedex4, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France; Equipe labellisée Ligue Nationale Contre le Cancer, France
| | - Nadia Barboule
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), BP 64182, 205 route de Narbonne, 31077 Toulouse, Cedex4, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France; Equipe labellisée Ligue Nationale Contre le Cancer, France
| | - Ying Yuan
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), BP 64182, 205 route de Narbonne, 31077 Toulouse, Cedex4, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France; Equipe labellisée Ligue Nationale Contre le Cancer, France
| | - Dennis Gomez
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), BP 64182, 205 route de Narbonne, 31077 Toulouse, Cedex4, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France; Equipe labellisée Ligue Nationale Contre le Cancer, France
| | - Patrick Calsou
- CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), BP 64182, 205 route de Narbonne, 31077 Toulouse, Cedex4, France; Université de Toulouse, UPS, IPBS, F-31077 Toulouse, France; Equipe labellisée Ligue Nationale Contre le Cancer, France.
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50
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Wyatt MD. Advances in understanding the coupling of DNA base modifying enzymes to processes involving base excision repair. Adv Cancer Res 2014; 119:63-106. [PMID: 23870509 DOI: 10.1016/b978-0-12-407190-2.00002-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This chapter describes some of the recent, exciting developments that have characterized and connected processes that modify DNA bases with DNA repair pathways. It begins with AID/APOBEC or TET family members that covalently modify bases within DNA. The modified bases, such as uracil or 5-formylcytosine, are then excised by DNA glycosylases including UNG or TDG to initiate base excision repair (BER). BER is known to preserve genome integrity by removing damaged bases. The newer studies underscore the necessity of BER following enzymes that deliberately damage DNA. This includes the role of BER in antibody diversification and more recently, its requirement for demethylation of 5-methylcytosine in mammalian cells. The recent advances have shed light on mechanisms of DNA demethylation, and have raised many more questions. The potential hazards of these processes have also been revealed. Dysregulation of the activity of base modifying enzymes, and resolution by unfaithful or corrupt means can be a driver of genome instability and tumorigenesis. The understanding of both DNA and histone methylation and demethylation is now revealing the true extent to which epigenetics influence normal development and cancer, an abnormal development.
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Affiliation(s)
- Michael D Wyatt
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, USA.
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