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Hao Q, Li J, Yeap LS. Molecular mechanisms of DNA lesion and repair during antibody somatic hypermutation. SCIENCE CHINA. LIFE SCIENCES 2024; 67:2344-2353. [PMID: 39048716 DOI: 10.1007/s11427-024-2615-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 05/08/2024] [Indexed: 07/27/2024]
Abstract
Antibody diversification is essential for an effective immune response, with somatic hypermutation (SHM) serving as a key molecular process in this adaptation. Activation-induced cytidine deaminase (AID) initiates SHM by inducing DNA lesions, which are ultimately resolved into point mutations, as well as small insertions and deletions (indels). These mutational outcomes contribute to antibody affinity maturation. The mechanisms responsible for generating point mutations and indels involve the base excision repair (BER) and mismatch repair (MMR) pathways, which are well coordinated to maintain genomic integrity while allowing for beneficial mutations to occur. In this regard, translesion synthesis (TLS) polymerases contribute to the diversity of mutational outcomes in antibody genes by enabling the bypass of DNA lesions. This review summarizes our current understanding of the distinct molecular mechanisms that generate point mutations and indels during SHM. Understanding these mechanisms is critical for elucidating the development of broadly neutralizing antibodies (bnAbs) and autoantibodies, and has implications for vaccine design and therapeutics.
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Affiliation(s)
- Qian Hao
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Jinfeng Li
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Leng-Siew Yeap
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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Daliri K, Hescheler J, Pfannkuche KP. Prime Editing and DNA Repair System: Balancing Efficiency with Safety. Cells 2024; 13:858. [PMID: 38786078 PMCID: PMC11120019 DOI: 10.3390/cells13100858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Revised: 04/24/2024] [Accepted: 05/12/2024] [Indexed: 05/25/2024] Open
Abstract
Prime editing (PE), a recent progression in CRISPR-based technologies, holds promise for precise genome editing without the risks associated with double-strand breaks. It can introduce a wide range of changes, including single-nucleotide variants, insertions, and small deletions. Despite these advancements, there is a need for further optimization to overcome certain limitations to increase efficiency. One such approach to enhance PE efficiency involves the inhibition of the DNA mismatch repair (MMR) system, specifically MLH1. The rationale behind this approach lies in the MMR system's role in correcting mismatched nucleotides during DNA replication. Inhibiting this repair pathway creates a window of opportunity for the PE machinery to incorporate the desired edits before permanent DNA repair actions. However, as the MMR system plays a crucial role in various cellular processes, it is important to consider the potential risks associated with manipulating this system. The new versions of PE with enhanced efficiency while blocking MLH1 are called PE4 and PE5. Here, we explore the potential risks associated with manipulating the MMR system. We pay special attention to the possible implications for human health, particularly the development of cancer.
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Affiliation(s)
- Karim Daliri
- Institute for Neurophysiology, Centre for Physiology and Pathophysiology, Medical Faculty and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany (K.P.P.)
- Marga and Walter Boll-Laboratory for Cardiac Tissue Engineering, University of Cologne, 50931 Cologne, Germany
| | - Jürgen Hescheler
- Institute for Neurophysiology, Centre for Physiology and Pathophysiology, Medical Faculty and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany (K.P.P.)
| | - Kurt Paul Pfannkuche
- Institute for Neurophysiology, Centre for Physiology and Pathophysiology, Medical Faculty and University Hospital of Cologne, University of Cologne, 50931 Cologne, Germany (K.P.P.)
- Marga and Walter Boll-Laboratory for Cardiac Tissue Engineering, University of Cologne, 50931 Cologne, Germany
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931 Cologne, Germany
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Bello A, Hirth G, Voigt S, Tepper S, Jungnickel B. Mechanism and regulation of secondary immunoglobulin diversification. Cell Cycle 2023; 22:2070-2087. [PMID: 37909747 PMCID: PMC10761156 DOI: 10.1080/15384101.2023.2275397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/18/2023] [Accepted: 10/20/2023] [Indexed: 11/03/2023] Open
Abstract
Secondary immunoglobulin diversification by somatic hypermutation and class switch recombination in B cells is instrumental for an adequate adaptive humoral immune response. These genetic events may, however, also introduce aberrations into other cellular genes and thereby cause B cell malignancies. While the basic mechanism of somatic hypermutation and class switch recombination is now well understood, their regulation and in particular the mechanism of their specific targeting to immunoglobulin genes is still rather mysterious. In this review, we summarize the current knowledge on the mechanism and regulation of secondary immunoglobulin diversification and discuss known mechanisms of physiological targeting to immunoglobulin genes and mistargeting to other cellular genes. We summarize open questions in the field and provide an outlook on future research.
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Affiliation(s)
- Amanda Bello
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Gianna Hirth
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Stefanie Voigt
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Sandra Tepper
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
| | - Berit Jungnickel
- Institute of Biochemistry and Biophysics, Faculty of Biological Sciences, Friedrich Schiller University, Jena, Germany
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4
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Hao Q, Zhan C, Lian C, Luo S, Cao W, Wang B, Xie X, Ye X, Gui T, Voena C, Pighi C, Wang Y, Tian Y, Wang X, Dai P, Cai Y, Liu X, Ouyang S, Sun S, Hu Q, Liu J, Ye Y, Zhao J, Lu A, Wang JY, Huang C, Su B, Meng FL, Chiarle R, Pan-Hammarström Q, Yeap LS. DNA repair mechanisms that promote insertion-deletion events during immunoglobulin gene diversification. Sci Immunol 2023; 8:eade1167. [PMID: 36961908 PMCID: PMC10351598 DOI: 10.1126/sciimmunol.ade1167] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 03/01/2023] [Indexed: 03/26/2023]
Abstract
Insertions and deletions (indels) are low-frequency deleterious genomic DNA alterations. Despite their rarity, indels are common, and insertions leading to long complementarity-determining region 3 (CDR3) are vital for antigen-binding functions in broadly neutralizing and polyreactive antibodies targeting viruses. Because of challenges in detecting indels, the mechanism that generates indels during immunoglobulin diversification processes remains poorly understood. We carried out ultra-deep profiling of indels and systematically dissected the underlying mechanisms using passenger-immunoglobulin mouse models. We found that activation-induced cytidine deaminase-dependent ±1-base pair (bp) indels are the most prevalent indel events, biasing deleterious outcomes, whereas longer in-frame indels, especially insertions that can extend the CDR3 length, are rare outcomes. The ±1-bp indels are channeled by base excision repair, but longer indels require additional DNA-processing factors. Ectopic expression of a DNA exonuclease or perturbation of the balance of DNA polymerases can increase the frequency of longer indels, thus paving the way for models that can generate antibodies with long CDR3. Our study reveals the mechanisms that generate beneficial and deleterious indels during the process of antibody somatic hypermutation and has implications in understanding the detrimental genomic alterations in various conditions, including tumorigenesis.
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Affiliation(s)
- Qian Hao
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Chuanzong Zhan
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Chaoyang Lian
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Simin Luo
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Wenyi Cao
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Binbin Wang
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Xia Xie
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Xiaofei Ye
- Department of Biosciences and Nutrition, Karolinska Institutet; SE141-83, Huddinge, Stockholm, Sweden
- Present address: Kindstar Global Precision Medicine Institute, Wuhan, China and Kindstar Biotech, Wuhan, China
| | - Tuantuan Gui
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Claudia Voena
- Department of Molecular Biotechnology and Health Sciences, University of Torino; 10126 Torino, Italy
| | - Chiara Pighi
- Department of Molecular Biotechnology and Health Sciences, University of Torino; 10126 Torino, Italy
- Department of Pathology, Boston Children’s Hospital, and Harvard Medical School; Boston, MA 02115, USA
| | - Yanyan Wang
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Ying Tian
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Xin Wang
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Pengfei Dai
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Yanni Cai
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Xiaojing Liu
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Shengqun Ouyang
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Shiqi Sun
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Qianwen Hu
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Jun Liu
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Youqiong Ye
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Jingkun Zhao
- Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Aiguo Lu
- Department of General Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Ji-Yang Wang
- Department of Immunology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
- Department of Microbiology and Immunology, College of Basic Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Chuanxin Huang
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
| | - Bing Su
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Departments of Endocrinology and Gastroenterology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Shanghai Jiao Tong University School of Medicine-Yale Institute for Immune Metabolism, Shanghai Jiao Tong University School of Medicine, Shanghai 200025
| | - Fei-Long Meng
- State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences; 320 Yueyang Road, Shanghai 200031, China
| | - Roberto Chiarle
- Department of Molecular Biotechnology and Health Sciences, University of Torino; 10126 Torino, Italy
- Department of Pathology, Boston Children’s Hospital, and Harvard Medical School; Boston, MA 02115, USA
| | - Qiang Pan-Hammarström
- Department of Biosciences and Nutrition, Karolinska Institutet; SE141-83, Huddinge, Stockholm, Sweden
| | - Leng-Siew Yeap
- Center for Immune-Related Diseases at Shanghai Institute of Immunology, Department of Endocrinology and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Shanghai Institute of Immunology, Department of Immunology and Microbiology, State Key Laboratory of Oncogenes and Related Genes, Shanghai Jiao Tong University School of Medicine; 280 South Chongqing Road, Shanghai, 200025, China
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Lozinski M, Bowden NA, Graves MC, Fay M, Tooney PA. DNA damage repair in glioblastoma: current perspectives on its role in tumour progression, treatment resistance and PIKKing potential therapeutic targets. Cell Oncol (Dordr) 2021; 44:961-981. [PMID: 34057732 DOI: 10.1007/s13402-021-00613-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 05/17/2021] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The aggressive, invasive and treatment resistant nature of glioblastoma makes it one of the most lethal cancers in humans. Total surgical resection is difficult, and a combination of radiation and chemotherapy is used to treat the remaining invasive cells beyond the tumour border by inducing DNA damage and activating cell death pathways in glioblastoma cells. Unfortunately, recurrence is common and a major hurdle in treatment, often met with a more aggressive and treatment resistant tumour. A mechanism of resistance is the response of DNA repair pathways upon treatment-induced DNA damage, which enact cell-cycle arrest and repair of DNA damage that would otherwise cause cell death in tumour cells. CONCLUSIONS In this review, we discuss the significance of DNA repair mechanisms in tumour formation, aggression and treatment resistance. We identify an underlying trend in the literature, wherein alterations in DNA repair pathways facilitate glioma progression, while established high-grade gliomas benefit from constitutively active DNA repair pathways in the repair of treatment-induced DNA damage. We also consider the clinical feasibility of inhibiting DNA repair in glioblastoma and current strategies of using DNA repair inhibitors as agents in combination with chemotherapy, radiation or immunotherapy. Finally, the importance of blood-brain barrier penetrance when designing novel small-molecule inhibitors is discussed.
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Affiliation(s)
- Mathew Lozinski
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia
- Centre for Drug Repurposing and Medicines Research, University of Newcastle, Newcastle, NSW, Australia
- Hunter Medical Research Institute, Newcastle, NSW, Australia
| | - Nikola A Bowden
- Centre for Drug Repurposing and Medicines Research, University of Newcastle, Newcastle, NSW, Australia
- Hunter Medical Research Institute, Newcastle, NSW, Australia
- School of Medicine and Public Health, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia
| | - Moira C Graves
- Centre for Drug Repurposing and Medicines Research, University of Newcastle, Newcastle, NSW, Australia
- Hunter Medical Research Institute, Newcastle, NSW, Australia
- School of Medicine and Public Health, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia
| | - Michael Fay
- Centre for Drug Repurposing and Medicines Research, University of Newcastle, Newcastle, NSW, Australia
- Hunter Medical Research Institute, Newcastle, NSW, Australia
- Genesis Cancer Care, Gateshead, New South Wales, Australia
| | - Paul A Tooney
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Newcastle, NSW, Australia.
- Centre for Drug Repurposing and Medicines Research, University of Newcastle, Newcastle, NSW, Australia.
- Hunter Medical Research Institute, Newcastle, NSW, Australia.
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6
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Cowman S, Pizer B, Sée V. Downregulation of both mismatch repair and non-homologous end-joining pathways in hypoxic brain tumour cell lines. PeerJ 2021; 9:e11275. [PMID: 33986995 PMCID: PMC8092103 DOI: 10.7717/peerj.11275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 03/24/2021] [Indexed: 01/11/2023] Open
Abstract
Glioblastoma, a grade IV astrocytoma, has a poor survival rate in part due to ineffective treatment options available. These tumours are heterogeneous with areas of low oxygen levels, termed hypoxic regions. Many intra-cellular signalling pathways, including DNA repair, can be altered by hypoxia. Since DNA damage induction and subsequent activation of DNA repair mechanisms is the cornerstone of glioblastoma treatment, alterations to DNA repair mechanisms could have a direct influence on treatment success. Our aim was to elucidate the impact of chronic hypoxia on DNA repair gene expression in a range of glioblastoma cell lines. We adopted a NanoString transcriptomic approach to examine the expression of 180 DNA repair-related genes in four classical glioblastoma cell lines (U87-MG, U251-MG, D566-MG, T98G) exposed to 5 days of normoxia (21% O2), moderate (1% O2) or severe (0.1% O2) hypoxia. We observed altered gene expression in several DNA repair pathways including homologous recombination repair, non-homologous end-joining and mismatch repair, with hypoxia primarily resulting in downregulation of gene expression. The extent of gene expression changes was dependent on hypoxic severity. Some, but not all, of these downregulations were directly under the control of HIF activity. For example, the downregulation of LIG4, a key component of non-homologous end-joining, was reversed upon inhibition of the hypoxia-inducible factor (HIF). In contrast, the downregulation of the mismatch repair gene, PMS2, was not affected by HIF inhibition. This suggests that numerous molecular mechanisms lead to hypoxia-induced reprogramming of the transcriptional landscape of DNA repair. Whilst the global impact of hypoxia on DNA repair gene expression is likely to lead to genomic instability, tumorigenesis and reduced sensitivity to anti-cancer treatment, treatment re-sensitising might require additional approaches to a simple HIF inhibition.
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Affiliation(s)
- Sophie Cowman
- Institute of Systems, Molecular and Integrative Biology, Department of Molecular Physiology and Cell Signalling, University of Liverpool, Liverpool, Merseyside, United Kingdom.,Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt-Lake-City, Utah, United States
| | - Barry Pizer
- Paediatric Oncology, Alder Hey Children's NHS Foundation Trust, Liverpool, Merseyside, United Kingdom
| | - Violaine Sée
- Institute of Systems, Molecular and Integrative Biology, Department of Molecular Physiology and Cell Signalling, University of Liverpool, Liverpool, Merseyside, United Kingdom
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Feng Y, Seija N, Di Noia JM, Martin A. AID in Antibody Diversification: There and Back Again. Trends Immunol 2020; 41:586-600. [PMID: 32434680 PMCID: PMC7183997 DOI: 10.1016/j.it.2020.04.009] [Citation(s) in RCA: 89] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 04/16/2020] [Accepted: 04/20/2020] [Indexed: 01/01/2023]
Abstract
Activation-Induced cytidine Deaminase (AID) initiates affinity maturation and isotype switching by deaminating deoxycytidines within immunoglobulin genes, leading to somatic hypermutation (SHM) and class switch recombination (CSR). AID thus potentiates the humoral response to clear pathogens. Marking the 20th anniversary of the discovery of AID, we review the current understanding of AID function. We discuss AID biochemistry and how error-free forms of DNA repair are co-opted to prioritize mutagenesis over accuracy during antibody diversification. We discuss the regulation of DNA double-strand break (DSB) repair pathways during CSR. We describe genomic targeting of AID as a multilayered process involving chromatin architecture, cis- and trans-acting factors, and determining mutagenesis – distinct from AID occupancy at loci that are spared from mutation. Subverted base excision repair (BER) and mismatch repair (MMR) pathways act concertedly to generate antibody sequence diversity during SHM. In CSR, DNA DSBs are repaired by the nonhomologous end-joining pathway involving the 53BP1–Rif1–Shieldin axis, and by an alternative end-joining pathway involving HMCES (5-Hydroxymethylcytosine binding, ES-cell-specific) that binds and protects resected DSB ends. Genomic targeting of AID appears to be multilayered, with inbuilt redundancy, but robust enough to ensure that most of the genome is spared from AID activity. Cis elements and genome topology act together with trans-acting factors involved in transcription and RNA processing to determine AID activity at specific Ig regions. Other loci sharing genomic and transcriptional features with the Ig are collaterally targeted during SHM and CSR.
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Affiliation(s)
- Yuqing Feng
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Noé Seija
- Institute de Recherches Cliniques de Montréal, Montréal, QC, Canada; Molecular Biology Programs, Department of Medicine, University of Montreal, Montréal, QC, Canada
| | - Javier M Di Noia
- Institute de Recherches Cliniques de Montréal, Montréal, QC, Canada; Molecular Biology Programs, Department of Medicine, University of Montreal, Montréal, QC, Canada.
| | - Alberto Martin
- Department of Immunology, University of Toronto, Toronto, ON, Canada.
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8
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Pilzecker B, Jacobs H. Mutating for Good: DNA Damage Responses During Somatic Hypermutation. Front Immunol 2019; 10:438. [PMID: 30915081 PMCID: PMC6423074 DOI: 10.3389/fimmu.2019.00438] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 02/19/2019] [Indexed: 11/13/2022] Open
Abstract
Somatic hypermutation (SHM) of immunoglobulin (Ig) genes plays a key role in antibody mediated immunity. SHM in B cells provides the molecular basis for affinity maturation of antibodies. In this way SHM is key in optimizing antibody dependent immune responses. SHM is initiated by targeting the Activation-Induced Cytidine Deaminase (AID) to rearranged V(D)J and switch regions of Ig genes. The mutation rate of this programmed mutagenesis is ~10-3 base pairs per generation, a million-fold higher than the non-AID targeted genome of B cells. AID is a processive enzyme that binds single-stranded DNA and deaminates cytosines in DNA. Cytosine deamination generates highly mutagenic deoxy-uracil (U) in the DNA of both strands of the Ig loci. Mutagenic processing of the U by the DNA damage response generates the entire spectrum of base substitutions characterizing SHM at and around the initial U lesion. Starting from the U as a primary lesion, currently five mutagenic DNA damage response pathways have been identified in generating a well-defined SHM spectrum of C/G transitions, C/G transversions, and A/T mutations around this initial lesion. These pathways include (1) replication opposite template U generates transitions at C/G, (2) UNG2-dependent translesion synthesis (TLS) generates transversions at C/G, (3) a hybrid pathway comprising non-canonical mismatch repair (ncMMR) and UNG2-dependent TLS generates transversions at C/G, (4) ncMMR generates mutations at A/T, and (5) UNG2- and PCNA Ubiquitination (PCNA-Ub)-dependent mutations at A/T. Furthermore, specific strand-biases of SHM spectra arise as a consequence of a biased AID targeting, ncMMR, and anti-mutagenic repriming. Here, we review mammalian SHM with special focus on the mutagenic DNA damage response pathways involved in processing AID induced Us, the origin of characteristic strand biases, and relevance of the cell cycle.
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Affiliation(s)
| | - Heinz Jacobs
- Division of Tumor Biology & Immunology, The Netherlands Cancer Institute, Amsterdam, Netherlands
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9
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The biochemistry of activation-induced deaminase and its physiological functions. Semin Immunol 2012; 24:255-63. [DOI: 10.1016/j.smim.2012.05.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 05/18/2012] [Indexed: 01/26/2023]
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10
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Saribasak H, Gearhart PJ. Does DNA repair occur during somatic hypermutation? Semin Immunol 2012; 24:287-92. [PMID: 22728014 DOI: 10.1016/j.smim.2012.05.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 05/18/2012] [Indexed: 11/25/2022]
Abstract
Activation-induced deaminase (AID) initiates a flood of DNA damage in the immunoglobulin loci, leading to abasic sites, single-strand breaks and mismatches. It is compelling that some proteins in the canonical base excision and mismatch repair pathways have been hijacked to increase mutagenesis during somatic hypermutation. Thus, the AID-induced mutagenic pathways involve a mix of DNA repair proteins and low fidelity DNA polymerases to create antibody diversity. In this review, we analyze the roles of base excision repair, mismatch repair, and mutagenesis during somatic hypermutation of rearranged variable genes. The emerging view is that faithful base excision repair occurs simultaneously with mutagenesis, whereas faithful mismatch repair is mostly absent.
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Affiliation(s)
- Huseyin Saribasak
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States
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11
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Chahwan R, van Oers JMM, Avdievich E, Zhao C, Edelmann W, Scharff MD, Roa S. The ATPase activity of MLH1 is required to orchestrate DNA double-strand breaks and end processing during class switch recombination. ACTA ACUST UNITED AC 2012; 209:671-8. [PMID: 22451719 PMCID: PMC3328365 DOI: 10.1084/jem.20111531] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
MLH1 ATPase activity is essential for class switch recombination but not for somatic hypermutation. Antibody diversification through somatic hypermutation (SHM) and class switch recombination (CSR) are similarly initiated in B cells with the generation of U:G mismatches by activation-induced cytidine deaminase but differ in their subsequent mutagenic consequences. Although SHM relies on the generation of nondeleterious point mutations, CSR depends on the production of DNA double-strand breaks (DSBs) and their adequate recombination through nonhomologous end joining (NHEJ). MLH1, an ATPase member of the mismatch repair (MMR) machinery, is emerging as a likely regulator of whether a U:G mismatch progresses toward mutation or DSB formation. We conducted experiments on cancer modeled ATPase-deficient MLH1G67R knockin mice to determine the function that the ATPase domain of MLH1 mediates in SHM and CSR. Mlh1GR/GR mice displayed a significant decrease in CSR, mainly attributed to a reduction in the generation of DSBs and diminished accumulation of 53BP1 at the immunoglobulin switch regions. However, SHM was normal in these mice, which distinguishes MLH1 from upstream members of the MMR pathway and suggests a very specific role of its ATPase-dependent functions during CSR. In addition, we show that the residual switching events still taking place in Mlh1GR/GR mice display unique features, suggesting a role for the ATPase activity of MLH1 beyond the activation of the endonuclease functions of its MMR partner PMS2. A preference for switch junctions with longer microhomologies in Mlh1GR/GR mice suggests that through its ATPase activity, MLH1 also has an impact in DNA end processing, favoring canonical NHEJ downstream of the DSB. Collectively, our study shows that the ATPase domain of MLH1 is important to transmit the CSR signaling cascade both upstream and downstream of the generation of DSBs.
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Affiliation(s)
- Richard Chahwan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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12
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The mismatch repair pathway functions normally at a non-AID target in germinal center B cells. Blood 2011; 118:3013-8. [DOI: 10.1182/blood-2011-03-345991] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Abstract
Deficiency in Msh2, a component of the mismatch repair (MMR) system, leads to an approximately 10-fold increase in the mutation frequency in most tissues. By contrast, Msh2 deficiency in germinal center (GC) B cells decreases the mutation frequency at the IgH V region as a dU:dG mismatch produced by AID initiates modifications by MMR, resulting in mutations at nearby A:T base pairs. This raises the possibility that GC B cells express a factor that converts MMR into a globally mutagenic pathway. To test this notion, we investigated whether MMR corrects mutations in GC B cells at a gene that is not mutated by AID. Strikingly, we found that GC B cells accumulate 5 times more mutations at a reporter gene than during the development of the mouse. Notably, the mutation frequency at this reporter gene was approximately 10 times greater in Msh2−/− compared with wild-type GC B cells cells. In contrast to the V region, the increased level of mutations at A:T base pairs in GC B cells was not caused by MMR. These results show that in GC B cells, (1) MMR functions normally at an AID-insensitive gene and (2) the frequency of background mutagenesis is greater in GC B cells than in their precursor follicular B cells.
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13
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Maul RW, Gearhart PJ. Controlling somatic hypermutation in immunoglobulin variable and switch regions. Immunol Res 2010; 47:113-22. [PMID: 20082153 DOI: 10.1007/s12026-009-8142-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Activation-induced deaminase (AID) is a B-cell-specific enzyme required for initiating the mechanisms of affinity maturation and isotype switching of antibodies. AID functions by deaminating cytosine to uracil in DNA, which initiates a cascade of events resulting in mutations and strand breaks in the immunoglobulin loci. There is an intricate interplay between faithful DNA repair and mutagenic DNA repair during somatic hypermutation, in that some proteins from accurate repair pathways are also involved in mutagenesis. One factor that shifts the balance from faithful to mutagenic repair is the genomic sequence of the switch regions. Indeed, the sequence of the switch mu region is designed to maximize AID access to increase the abundance of clustered dU bases. The frequency and proximity of these dU nucleotides then in turn inhibit faithful repair and promote strand breaks.
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Affiliation(s)
- Robert W Maul
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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14
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Duvvuri B, Duvvuri VRSK, Grigull J, Martin A, Pan-Hammarström Q, Wu GE, Larijani M. Altered spectrum of somatic hypermutation in common variable immunodeficiency disease characteristic of defective repair of mutations. Immunogenetics 2010; 63:1-11. [PMID: 20938659 DOI: 10.1007/s00251-010-0483-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 09/25/2010] [Indexed: 01/08/2023]
Abstract
Pathogenic common variable immunodeficiency diseases (CVID) are genetic, usually inherited diseases for which a limited number of genetic defects have been implicated. As CVID presents with a wide range of clinical characteristics, there are likely diverse and for the most part unidentified genetic causes. In some individuals, defects in somatic hypermutation (SHM) have been suggested as the underlying cause of CVID. To address the mechanisms of SHM defects in CVID, we conducted a comprehensive mutational analysis of immunoglobulin heavy chain sequences from CVID patients. We identified several remarkably specific alterations in the spectra of SHM in comparison to healthy individuals. We provide evidence that some CVID cases are associated with defective repair of AID-induced mutations by the DNA mismatch repair (MMR) machinery. Our findings together with reports of increased chromosomal radiosensitivity and associated lymphoproliferative disorders amongst CVID patients, suggest that altered DNA damage repair may be a cause of CVID.
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Affiliation(s)
- Bhargavi Duvvuri
- The School of Kinesiology and Health Science, Faculty of Health, York University, Toronto, Ontario, Canada, M3J 1P3.
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15
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Abstract
In response to an assault by foreign organisms, peripheral B cells can change their antibody affinity and isotype by somatically mutating their genomic DNA. The ability of a cell to modify its DNA is exceptional in light of the potential consequences of genetic alterations to cause human disease and cancer. Thus, as expected, this mechanism of antibody diversity is tightly regulated and coordinated through one protein, activation-induced deaminase (AID). AID produces diversity by converting cytosine to uracil within the immunoglobulin loci. The deoxyuracil residue is mutagenic when paired with deoxyguanosine, since it mimics thymidine during DNA replication. Additionally, B cells can manipulate the DNA repair pathways so that deoxyuracils are not faithfully repaired. Therefore, an intricate balance exists which is regulated at multiple stages to promote mutation of immunoglobulin genes, while retaining integrity of the rest of the genome. Here we discuss and summarize the current understanding of how AID functions to cause somatic hypermutation.
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Affiliation(s)
- Robert W Maul
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA
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16
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Kracker S, Gardes P, Mazerolles F, Durandy A. Immunoglobulin class switch recombination deficiencies. Clin Immunol 2010; 135:193-203. [DOI: 10.1016/j.clim.2010.01.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2009] [Revised: 01/25/2010] [Accepted: 01/25/2010] [Indexed: 01/01/2023]
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17
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The concerted action of Msh2 and UNG stimulates somatic hypermutation at A . T base pairs. Mol Cell Biol 2009; 29:5148-57. [PMID: 19596785 DOI: 10.1128/mcb.00647-09] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mismatch repair plays an essential role in reducing the cellular mutation load. Paradoxically, proteins in this pathway produce A . T mutations during the somatic hypermutation of immunoglobulin genes. Although recent evidence implicates the translesional DNA polymerase eta in producing these mutations, it is unknown how this or other translesional polymerases are recruited to immunoglobulin genes, since these enzymes are not normally utilized in conventional mismatch repair. In this report, we demonstrate that A . T mutations were closely associated with transversion mutations at a deoxycytidine. Furthermore, deficiency in uracil-N-glycolase (UNG) or mismatch repair reduced this association. These data reveal a previously unknown interaction between the base excision and mismatch repair pathways and indicate that an abasic site generated by UNG within the mismatch repair tract recruits an error-prone polymerase, which then introduces A . T mutations. Our analysis further indicates that repair tracts typically are approximately 200 nucleotides long and that polymerase eta makes approximately 1 error per 300 T nucleotides. The concerted action of Msh2 and UNG in stimulating A . T mutations also may have implications for mutagenesis at sites of spontaneous cytidine deamination.
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18
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Saribasak H, Rajagopal D, Maul RW, Gearhart PJ. Hijacked DNA repair proteins and unchained DNA polymerases. Philos Trans R Soc Lond B Biol Sci 2009; 364:605-11. [PMID: 19008198 DOI: 10.1098/rstb.2008.0188] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Somatic hypermutation of immunoglobulin (Ig) genes occurs at a frequency that is a million times greater than the mutation in other genes. Mutations occur in variable genes to increase antibody affinity, and in switch regions before constant genes to cause switching from IgM to IgG. Hypermutation is initiated in activated B cells when the activation-induced deaminase protein deaminates cytosine in DNA to uracil. Uracils can be processed by either a mutagenic pathway to produce mutations or a non-mutagenic pathway to remove mutations. In the mutagenic pathway, we first studied the role of mismatch repair proteins, MSH2, MSH3, MSH6, PMS2 and MLH1, since they would recognize mismatches. The MSH2-MSH6 heterodimer is involved in hypermutation by binding to U:G and other mismatches generated during repair synthesis, but the other proteins are not necessary. Second, we analysed the role of low-fidelity DNA polymerases eta, iota and theta in synthesizing mutations, and conclude that polymerase eta is the dominant participant by generating mutations at A:T base pairs. In the non-mutagenic pathway, we examined the role of the Cockayne syndrome B protein that interacts with other repair proteins. Mice deficient in this protein had normal hypermutation and class switch recombination, showing that it is not involved.
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Affiliation(s)
- Huseyin Saribasak
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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19
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Sale JE, Batters C, Edmunds CE, Phillips LG, Simpson LJ, Szüts D. Timing matters: error-prone gap filling and translesion synthesis in immunoglobulin gene hypermutation. Philos Trans R Soc Lond B Biol Sci 2009; 364:595-603. [PMID: 19008194 DOI: 10.1098/rstb.2008.0197] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
By temporarily deferring the repair of DNA lesions encountered during replication, the bypass of DNA damage is critical to the ability of cells to withstand genomic insults. Damage bypass can be achieved either by recombinational mechanisms that are generally accurate or by a process called translesion synthesis. Translesion synthesis involves replacing the stalled replicative polymerase with one of a number of specialized DNA polymerases whose active sites are able to tolerate a distorted or damaged DNA template. While this property allows the translesion polymerases to synthesize across damaged bases, it does so with the trade-off of an increased mutation rate. The deployment of these enzymes must therefore be carefully regulated. In addition to their important role in general DNA damage tolerance and mutagenesis, the translesion polymerases play a crucial role in converting the products of activation induced deaminase-catalysed cytidine deamination to mutations during immunoglobulin gene somatic hypermutation. In this paper, we specifically consider the control of translesion synthesis in the context of the timing of lesion bypass relative to replication fork progression and arrest at sites of DNA damage. We then examine how recent observations concerning the control of translesion synthesis might help refine our view of the mechanisms of immunoglobulin gene somatic hypermutation.
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Affiliation(s)
- Julian E Sale
- Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
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20
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Péron S, Metin A, Gardès P, Alyanakian MA, Sheridan E, Kratz CP, Fischer A, Durandy A. Human PMS2 deficiency is associated with impaired immunoglobulin class switch recombination. ACTA ACUST UNITED AC 2008; 205:2465-72. [PMID: 18824584 PMCID: PMC2571921 DOI: 10.1084/jem.20080789] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) deficiencies are rare primary immunodeficiencies characterized by the lack of switched isotype (IgG/IgA/IgE) production. In some cases, CSR deficiencies can be associated with abnormal somatic hypermutation. Analysis of CSR deficiencies has helped reveal the key functions of CSR-triggering molecules, i.e., CD40L, CD40, and effector molecules such as activation-induced cytidine deaminase and uracil N-glycosylase. We report a new form of B cell–intrinsic CSR deficiency found in three patients with deleterious, homozygous mutations in the gene encoding the PMS2 component of the mismatch repair machinery. CSR was found partially defective in vivo and markedly impaired in vitro. It is characterized by the defective occurrence of double-strand DNA breaks (DSBs) in switch regions and abnormal formation of switch junctions. This observation strongly suggests a role for PMS2 in CSR-induced DSB generation.
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Affiliation(s)
- Sophie Péron
- Institut National de Santé et de Recherche Médicale, U768, 75015 Paris, France
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21
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B-cell clonal diversification and gut-lymph node trafficking in ulcerative colitis revealed using lineage tree analysis. Eur J Immunol 2008; 38:2600-9. [DOI: 10.1002/eji.200838333] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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22
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Wright BE, Schmidt KH, Minnick MF, Davis N. I. VH gene transcription creates stabilized secondary structures for coordinated mutagenesis during somatic hypermutation. Mol Immunol 2008; 45:3589-99. [PMID: 18585784 DOI: 10.1016/j.molimm.2008.02.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2008] [Accepted: 02/29/2008] [Indexed: 02/01/2023]
Abstract
During the adaptive immune response, antigen challenge triggers a million-fold increase in mutation rates in the variable-region antibody genes. The frequency of mutation is causally and directly linked to transcription, which provides ssDNA and drives supercoiling that stabilizes secondary structures containing unpaired, intrinsically mutable bases. Simulation analysis of transcription in VH5 reveals a dominant 65nt secondary structure in the non-transcribed strand containing six sites of mutable ssDNA that have also been identified independently in human B cell lines and in primary mouse B cells. This dominant structure inter-converts briefly with less stable structures and is formed repeatedly during transcription, due to periodic pauses and backtracking. In effect, this creates a stable yet dynamic "mutability platform" consisting of ever-changing patterns of unpaired bases that are simultaneously exposed and therefore able to coordinate mutagenesis. Such a complex of secondary structures may be the source of ssDNA for enzyme-based diversification, which ultimately results in high affinity antibodies.
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Affiliation(s)
- Barbara E Wright
- Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA.
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23
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Tang ES, Martin A. Immunoglobulin gene conversion: Synthesizing antibody diversification and DNA repair. DNA Repair (Amst) 2007; 6:1557-71. [PMID: 17600774 DOI: 10.1016/j.dnarep.2007.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 05/15/2007] [Accepted: 05/15/2007] [Indexed: 10/23/2022]
Abstract
Recent developments in the field of antibody (Ab) diversification have rapidly advanced our understanding of the molecular mechanism underlying these events. Key to these developments was the identification of activation-induced cytidine deaminase (AID) as the central regulator of secondary Ab diversification, and the elucidation of its primary function as a DNA deaminase. Incredibly, current literature suggests the existence of a shared pathway, common to all secondary diversification processes, from which the separate outcomes branch outwards at various points. Immunoglobulin gene conversion (IGC) is one of these mechanisms and is used by a number of vertebrate species in both the development of the pre-immune repertoire and in affinity maturation. In a manner similar to other Ab diversification mechanisms, IGC has managed to co-opt a normal DNA repair pathway for the generation of receptor diversity. In the case of IGC specifically, that pathway is homologous recombination (HR). A burgeoning wealth of genetic, biochemical and structural data has clarified the roles of many key HR factors, allowing new insight into its molecular mechanism. These insights, combined with those from the common mechanism of AID action, synergize to develop an emerging picture of the mechanism underlying IGC.
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Affiliation(s)
- Ephraim S Tang
- Department of Immunology, University of Toronto, Medical Sciences Bldg. 5265, Toronto, Canada M5S 1A8
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24
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Abstract
Functional antibody genes are assembled by V-D-J joining and then diversified by somatic hypermutation. This hypermutation results from stepwise incorporation of single nucleotide substitutions into the V gene, underpinning much of antibody diversity and affinity maturation. Hypermutation is triggered by activation-induced deaminase (AID), an enzyme which catalyzes targeted deamination of deoxycytidine residues in DNA. The pathways used for processing the AID-generated U:G lesions determine the variety of base substitutions observed during somatic hypermutation. Thus, DNA replication across the uracil yields transition mutations at C:G pairs, whereas uracil excision by UNG uracil-DNA glycosylase creates abasic sites that can also yield transversions. Recognition of the U:G mismatch by MSH2/MSH6 triggers a mutagenic patch repair in which polymerase eta plays a major role and leads to mutations at A:T pairs. AID-triggered DNA deamination also underpins immunoglobulin variable (IgV) gene conversion, isotype class switching, and some oncogenic translocations in B cell tumors.
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Affiliation(s)
- Javier M Di Noia
- Institut de Recherches Cliniques de Montréal, H2W 1R7 Montréal, Québec, Canada.
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25
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Abstract
Somatic hypermutation (SHM) is a major means by which diversity is achieved in antibody genes, and it is initiated by the deamination of cytosines to uracils in DNA by activation-induced deaminase (AID). However, the process that leads from these initiating deamination events to mutations at other residues remains poorly understood. We demonstrate that a single cytosine on the top (nontemplate) strand is sufficient to recruit AID and lead to mutations of upstream and downstream A/T residues. In contrast, the targeting of cytosines on the bottom strand by AID does not lead to substantial mutation of neighboring residues. This strand asymmetry is eliminated in mice deficient in mismatch repair, indicating that the error-prone mismatch repair machinery preferentially targets top-strand uracils in a way that promotes SHM during the antibody response.
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Affiliation(s)
- Shyam Unniraman
- Howard Hughes Medical Institute and Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06511, USA
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26
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Begum NA, Izumi N, Nishikori M, Nagaoka H, Shinkura R, Honjo T. Requirement of Non-canonical Activity of Uracil DNA Glycosylase for Class Switch Recombination. J Biol Chem 2007; 282:731-42. [PMID: 17090531 DOI: 10.1074/jbc.m607439200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation-induced cytidine deaminase (AID) and uracil DNA glycosylase (UNG) are required for class switch recombination (CSR). AID is involved in the DNA cleavage step of CSR, but the precise role of UNG is not yet understood. Mutations and deletions are footprints of abortive DNA cleavage in the immunoglobulin switch region in splenic B cells stimulated to undergo CSR. However, a UNG deficiency did not reduce the number of such footprints, indicating UNG is dispensable for the DNA cleavage step. Mutagenesis experiments revealed that the role of UNG in CSR depends on its WXXF motif. This motif is also essential for the interaction of UNG with the HIV viral peptide Vpr, which recruits UNG to the HIV particle. Furthermore, exogenous Vpr had a dominant-negative effect on CSR. These results suggest that UNG is recruited to the CSR machinery through its WXXF motif by a Vpr-like host factor and plays a novel non-canonical role in a CSR step that follows DNA cleavage.
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Affiliation(s)
- Nasim A Begum
- Department of Immunology and Genomic Medicine, Graduate School of Medicine, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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27
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Pan-Hammarström Q, Zhao Y, Hammarström L. Class switch recombination: a comparison between mouse and human. Adv Immunol 2007; 93:1-61. [PMID: 17383538 DOI: 10.1016/s0065-2776(06)93001-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Humans and mice separated more than 60 million years ago. Since then, evolution has led to a multitude of changes in their genomic sequences. The divergence of genes has resulted in differences both in the innate and adaptive immune systems. In this chapter, we focus on species difference with regard to immunoglobulin class switch recombination (CSR). We have compared the immunoglobulin constant region gene loci from human and mouse, with an emphasis on the switch regions, germ line transcription promoters, and 3' enhancers. We have also compared pathways/factors that are involved in CSR. Although there are remarkable similarities in the cellular machinery involved in CSR, there are also a number of unique features in each species.
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Affiliation(s)
- Qiang Pan-Hammarström
- Department of Laboratory Medicine, Division of Clinical Immunology, Karolinska University Hospital Huddinge, SE-14186 Stockholm, Sweden
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28
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Takizawa M, Sugane K, Agematsu K. Role of Tonsillar IgD+CD27+ Memory B Cells in Humoral Immunity Against Pneumococcal Infection. Hum Immunol 2006; 67:966-75. [PMID: 17174745 DOI: 10.1016/j.humimm.2006.10.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 09/25/2006] [Accepted: 10/02/2006] [Indexed: 11/21/2022]
Abstract
IgD+CD27+ memory B cells are a major compartment of circulating memory B cells. However, the characteristics of these cells in the tonsils have been unclear. In this study, IgD+CD27+ memory B cells residing in the tonsillar marginal zone were found to exhibit similar characteristics as IgD+CD27+ memory B cells in the periphery, namely large morphology, expression of surface molecules, and hypermutated Ig variable region genes. Furthermore, these IgD+CD27+ memory B cells predominantly produced IgM, including IgM specific against pneumococcal polysaccharides. Taken together, these results provide convincing evidence that tonsillar IgD+CD27+ memory B cells impart protective humoral immunity against pneumococcal infection by producing high-affinity IgM.
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Affiliation(s)
- Masahiro Takizawa
- Department of Infectious Immunology and Pediatrics, Graduate School of Medicine, Shinshu University, Matsumoto, Japan
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29
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Shen HM, Tanaka A, Bozek G, Nicolae D, Storb U. Somatic Hypermutation and Class Switch Recombination in Msh6−/−Ung−/−Double-Knockout Mice. THE JOURNAL OF IMMUNOLOGY 2006; 177:5386-92. [PMID: 17015724 DOI: 10.4049/jimmunol.177.8.5386] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by activation-induced cytosine deaminase (AID). The uracil, and potentially neighboring bases, are processed by error-prone base excision repair and mismatch repair. Deficiencies in Ung, Msh2, or Msh6 affect SHM and CSR. To determine whether Msh2/Msh6 complexes which recognize single-base mismatches and loops were the only mismatch-recognition complexes required for SHM and CSR, we analyzed these processes in Msh6(-/-)Ung(-/-) mice. SHM and CSR were affected in the same degree and fashion as in Msh2(-/-)Ung(-/-) mice; mutations were mostly C,G transitions and CSR was greatly reduced, making Msh2/Msh3 contributions unlikely. Inactivating Ung alone reduced mutations from A and T, suggesting that, depending on the DNA sequence, varying proportions of A,T mutations arise by error-prone long-patch base excision repair. Further, in Msh6(-/-)Ung(-/-) mice the 5' end and the 3' region of Ig genes was spared from mutations as in wild-type mice, confirming that AID does not act in these regions. Finally, because in the absence of both Ung and Msh6, transition mutations from C and G likely are "footprints" of AID, the data show that the activity of AID is restricted drastically in vivo compared with AID in cell-free assays.
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Affiliation(s)
- Hong Ming Shen
- Department of Molecular Genetic and Cell Biology, University of Chicago, Chicago, IL 60637, USA
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30
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Inlay MA, Gao HH, Odegard VH, Lin T, Schatz DG, Xu Y. Roles of the Ig κ Light Chain Intronic and 3′ Enhancers in Igk Somatic Hypermutation. THE JOURNAL OF IMMUNOLOGY 2006; 177:1146-51. [DOI: 10.4049/jimmunol.177.2.1146] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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31
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Wu X, Tsai CY, Patam MB, Zan H, Chen JP, Lipkin SM, Casali P. A role for the MutL mismatch repair Mlh3 protein in immunoglobulin class switch DNA recombination and somatic hypermutation. THE JOURNAL OF IMMUNOLOGY 2006; 176:5426-37. [PMID: 16622010 PMCID: PMC4621967 DOI: 10.4049/jimmunol.176.9.5426] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Class switch DNA recombination (CSR) and somatic hypermutation (SHM) are central to the maturation of the Ab response. Both processes involve DNA mismatch repair (MMR). MMR proteins are recruited to dU:dG mispairs generated by activation-induced cytidine deaminase-mediated deamination of dC residues, thereby promoting S-S region synapses and introduction of mismatches (mutations). The MutL homolog Mlh3 is the last complement of the mammalian set of MMR proteins. It is highly conserved in evolution and is essential to meiosis and microsatellite stability. We used the recently generated knockout mlh3(-/-) mice to address the role of Mlh3 in CSR and SHM. We found that Mlh3 deficiency alters both CSR and SHM. mlh3(-/-) B cells switched in vitro to IgG and IgA but displayed preferential targeting of the RGYW/WRCY (R = A or G, Y = C or T, W = A or T) motif by Sgamma1 and Sgamma3 breakpoints and introduced more insertions and fewer donor/acceptor microhomologies in Smu-Sgamma1 and Smu-Sgamma3 DNA junctions, as compared with mlh3(+/+) B cells. mlh3(-/-) mice showed only a slight decrease in the frequency of mutations in the intronic DNA downstream of the rearranged J(H)4 gene. However, the residual mutations were altered in spectrum. They comprised a decreased proportion of mutations at dA/dT and showed preferential RGYW/WRCY targeting by mutations at dC/dG. Thus, the MMR Mlh3 protein plays a role in both CSR and SHM.
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Affiliation(s)
- Xiaoping Wu
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Connie Y. Tsai
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Marienida B. Patam
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Hong Zan
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Jessica P. Chen
- Department of Medicine, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Steve M. Lipkin
- Department of Medicine, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
| | - Paolo Casali
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
- Department of Medicine, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697
- Address correspondence and reprint requests to Professor Paolo Casali, Center for Immunology, 3028 Hewitt Hall, University of California, Irvine, CA 92657-4120.
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32
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Affiliation(s)
- Ravi R Iyer
- Department of Biochemistry and Howard Hughes Medical Institute, Duke University Medical Center, Durham, North Carolina 27710, USA
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33
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Li Z, Peled JU, Zhao C, Svetlanov A, Ronai D, Cohen PE, Scharff MD. A role for Mlh3 in somatic hypermutation. DNA Repair (Amst) 2006; 5:675-82. [PMID: 16564751 DOI: 10.1016/j.dnarep.2006.02.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Revised: 02/03/2006] [Accepted: 02/06/2006] [Indexed: 12/15/2022]
Abstract
Somatic hypermutation (SHM) and class switch recombination (CSR) allow B cells to make high affinity antibodies of various isotypes. Both processes are initiated by activation-induced cytidine deaminase (AID) to generate dG:dU mismatches in the immunoglobulin genes that are resolved differently in SHM and CSR to introduce point mutations and recombination, respectively. The MutL homolog MLH3 has been implicated in meiosis and DNA mismatch repair (MMR). Since it interacts with MLH1, which plays a role in SHM and CSR, we examined these processes in Mlh3-deficient mice. Although deficiencies in other MMR proteins result in defects in SHM, Mlh3(-/-) mice exhibited an increased frequency of mutations in their immunoglobulin variable regions, compared to wild type littermates. Alterations of mutation spectra were observed in the Jh4 flanking region in Mlh3(-/-) mice. Nevertheless, Mlh3(-/-) mice were able to switch to IgG3 or IgG1 with similar frequencies to control mice. This is the first instance where a loss of a DNA repair protein has a positive impact on the rate of SHM, suggesting that Mlh3 normally inhibits the accumulation of mutations in SHM.
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Affiliation(s)
- Ziqiang Li
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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34
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Samaranayake M, Bujnicki JM, Carpenter M, Bhagwat AS. Evaluation of molecular models for the affinity maturation of antibodies: roles of cytosine deamination by AID and DNA repair. Chem Rev 2006; 106:700-19. [PMID: 16464021 PMCID: PMC4593474 DOI: 10.1021/cr040496t] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mala Samaranayake
- Department of Chemistry, Wayne State University, Detroit, MI 48202, U.S.A
| | - Janusz M. Bujnicki
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, Trojdena 4, PL-02-109 Warsaw, Poland, and Bioinformatics Laboratory, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, PL-61-614 Poznan, Poland
| | - Michael Carpenter
- Department of Chemistry, Wayne State University, Detroit, MI 48202, U.S.A
| | - Ashok S. Bhagwat
- Department of Chemistry, Wayne State University, Detroit, MI 48202, U.S.A
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35
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Abstract
Three processes alter genomic sequence and structure at the immunoglobulin genes of B lymphocytes: gene conversion, somatic hypermutation, and class switch recombination. Though the molecular signatures of these processes differ, they occur by a shared pathway which is induced by targeted DNA deamination by a B cell-specific factor, activation induced cytidine deaminase (AID). Ubiquitous factors critical for DNA repair carry out all downstream steps, creating mutations and deletions in genomic DNA. This review focuses on the genetic and biochemical mechanisms of diversification of immunoglobulin genes.
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Affiliation(s)
- Nancy Maizels
- Department of Immunology, University of Washington Medical School, Seattle, Washington 98195-7650, USA.
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36
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Bowen S, Roberts C, Wheals AE. Patterns of polymorphism and divergence in stress-related yeast proteins. Yeast 2005; 22:659-68. [PMID: 16032761 DOI: 10.1002/yea.1240] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Yeast genomes contain variable number tandem repeats (VNTRs) within coding regions of DNA. A significant number of these genes are involved in cell rescue, defence and virulence and are regulated by genetic elements associated with stress. Alleles that encode variable length, single amino acid tracts, are mainly associated with transcription and proteins localized within the nucleus. Alleles that encode proteins containing oligopeptide repeats or minisatellites are over-represented in cell wall and extracellular space locations. Functional analysis of the latter group reveals that these proteins are involved in biogenesis of cellular components and in interaction with the cellular environment, especially in relation to stress resistance, heat shock response, temperature perception and adhesion. A significantly high number of these proteins have regions rich in threonine and/or serine that contain repeated sequences, variable in length within yeast species. DNA sequences encoding serine- and/or threonine-rich regions give rise to polymorphic alleles and therefore may confer a selective advantage to cells. We propose that these regions are the focus of mutational and recombination events that, when coupled with directed selection, may contribute to genetic variation within stress-related genes.
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Affiliation(s)
- Suzanne Bowen
- Department of Genetics, University of Leicester, Leicester LE2 7RH, UK
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37
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Rogozin IB, Pavlov YI. The cytidine deaminase AID exhibits similar functional properties in yeast and mammals. Mol Immunol 2005; 43:1481-4. [PMID: 16219354 DOI: 10.1016/j.molimm.2005.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Indexed: 11/27/2022]
Abstract
A recent work published in Molecular Immunology examined the editing activity of activation-induced deaminase (AID) in yeast (Krause, K., Marcu, K.B., Greeve, J., 2006. The cytidine deaminases AID and APOBEC-1 exhibit distinct functional properties in a novel yeast selectable system. Mol. Immunol.). It was proposed that expression of AID in yeast is not sufficient for the generation of point mutations in a highly transcribed gene due to the lack of cofactors for AID-induced somatic hypermutation, which are unique to B cells. It was suggested that, on its own, AID does not have an intrinsic specificity for its target sequences. However, it has been shown previously that expression of the human AID gene in yeast was moderately mutagenic in a wild-type strain and highly mutagenic in an ung1 uracil-DNA glycosylase-deficient strain (Mayorov, V.I., Rogozin, I.B., Adkison, L.R., Frahm, C.R., Kunkel T.A., Pavlov Y. I., 2005. Expression of human AID in yeast induces mutations in context similar to the context of somatic hypermutation at G-C pairs in immunoglobulin genes. BMC Immunol. 6, 10; Poltoratsky, V.P., Wilson, S.H., Kunkel, T.A., Pavlov, Y.I., 2004. Recombinogenic phenotype of human activation-induced cytosine deaminase. J. Immunol. 172, 4308-4313). The vast majority of mutations were at G-C pairs. Mutations showed a clear DNA sequence context specificity which resembled the specificity of somatic hypermutation at G-C pairs in immunoglobulin genes and AID mutation specificity in vitro. The inability to detect mutator effects of AID by Krause et al. is likely to be caused by the use of the wild-type yeast strain and a small sample of clones examined for the presence of mutations. In addition, we show that non-uniformity of the mutation hotspot distribution is a factor potentially decreasing the chances of detecting mutations.
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Affiliation(s)
- Igor B Rogozin
- National Center for Biotechnology Information NLM, National Institutes of Health, 8600 Rockville Pike, Bldg. 38A/room 5N505A, Bethesda, MD 20894, USA.
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38
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Abstract
It is generally believed that in cells undergoing Ig somatic hypermutation, more cell divisions result in more mutations. This is because DNA synthesis and replication is thought to play roles in the known mechanisms-cytidine deamination and subsequent conversion to thymidine, uracil-DNA glycosylase-mediated repair, mismatch repair, and DNA synthesis by error-prone polymerases. In this study, we manipulated the number of cell generations by varying the rate at which cultures of a mouse cell line were replenished with fresh medium. We found that the frequency of mutants does not necessarily increase with the number of cell generations. On the contrary, a greater number of divisions can lead to a lower frequency of mutants, indicating that cell division is not a rate-limiting step in the hypermutation process. Thus, when comparing mutation rates, we suggest that rates are more appropriately expressed as mutations per day than per cell generation.
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Affiliation(s)
- Clifford L Wang
- Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA.
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39
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Wilson TM, Vaisman A, Martomo SA, Sullivan P, Lan L, Hanaoka F, Yasui A, Woodgate R, Gearhart PJ. MSH2-MSH6 stimulates DNA polymerase eta, suggesting a role for A:T mutations in antibody genes. ACTA ACUST UNITED AC 2005; 201:637-45. [PMID: 15710654 PMCID: PMC2213055 DOI: 10.1084/jem.20042066] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Activation-induced cytidine deaminase deaminates cytosine to uracil (dU) in DNA, which leads to mutations at C:G basepairs in immunoglobulin genes during somatic hypermutation. The mechanism that generates mutations at A:T basepairs, however, remains unclear. It appears to require the MSH2–MSH6 mismatch repair heterodimer and DNA polymerase (pol) η, as mutations of A:T are decreased in mice and humans lacking these proteins. Here, we demonstrate that these proteins interact physically and functionally. First, we show that MSH2–MSH6 binds to a U:G mismatch but not to other DNA intermediates produced during base excision repair of dUs, including an abasic site and a deoxyribose phosphate group. Second, MSH2 binds to pol η in solution, and endogenous MSH2 associates with the pol in cell extracts. Third, MSH2–MSH6 stimulates the catalytic activity of pol η in vitro. These observations suggest that the interaction between MSH2–MSH6 and DNA pol η stimulates synthesis of mutations at bases located downstream of the initial dU lesion, including A:T pairs.
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Affiliation(s)
- Teresa M Wilson
- Radiation Oncology Research Laboratory, Department of Radiation Oncology, University of Maryland, Baltimore, MD 21201, USA
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40
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Zhao Y, Pan-Hammarström Q, Zhao Z, Hammarström L. Identification of the activation-induced cytidine deaminase gene from zebrafish: an evolutionary analysis. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2005; 29:61-71. [PMID: 15325524 DOI: 10.1016/j.dci.2004.05.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2004] [Revised: 05/02/2004] [Accepted: 05/15/2004] [Indexed: 05/24/2023]
Abstract
In the present study, we report the identification of the activation-induced cytidine deaminase (AID) encoding gene in frog, dog and chimpanzee, where both somatic hypermutation and class switch recombination (CSR) occurs and in zebrafish and fugu, species lacking CSR. The cDNA sequence of the zebrafish AID reported here suggests both N and C ends of the previously predicted protein sequence are incorrect. A comparison of AID sequences among mammals, birds, amphibians and fish revealed conserved aa residues which may be essential for AID activity, although the cytidine deaminase active motif in the latter is nine amino acids longer. Furthermore, an aa deletion, and extensive substitutions in the C terminal end of AID from bony fish indicate that the molecule may not yet have developed a capacity to recruit the specific cofactor(s) needed to initiate CSR.
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Affiliation(s)
- Yaofeng Zhao
- Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska Institute at Huddinge Hospital, SE-141 86 Stockholm, Sweden.
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41
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Min IM, Selsing E. Antibody class switch recombination: roles for switch sequences and mismatch repair proteins. Adv Immunol 2005; 87:297-328. [PMID: 16102577 DOI: 10.1016/s0065-2776(05)87008-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mechanisms and targeting of antibody class switch DNA recombination are reviewed. Particular emphasis is on the roles for the DNA sequences comprising switch (S) regions, including the S-region tandem repeats, and on the roles of proteins that are involved in both DNA mismatch repair and in class switch recombination.
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Affiliation(s)
- Irene M Min
- Genetics Program, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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42
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Ramiro AR, Jankovic M, Eisenreich T, Difilippantonio S, Chen-Kiang S, Muramatsu M, Honjo T, Nussenzweig A, Nussenzweig MC. AID is required for c-myc/IgH chromosome translocations in vivo. Cell 2004; 118:431-8. [PMID: 15315756 DOI: 10.1016/j.cell.2004.08.006] [Citation(s) in RCA: 357] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 06/24/2004] [Accepted: 07/30/2004] [Indexed: 11/27/2022]
Abstract
Chromosome translocations between c-myc and immunoglobulin (Ig) are associated with Burkitt's lymphoma in humans and with pristane- and IL6-induced plasmacytomas in mice. These translocations frequently involve Ig switch regions, suggesting that they might be the result of aberrant Ig class switch recombination (CSR). However, a direct link between CSR and chromosome translocations has not been established. We have examined c-myc/IgH translocations in IL6 transgenic mice that are mutant for activation induced cytidine deaminase (AID), the enzyme that initiates CSR. Here we report that AID is essential for the c-myc/IgH chromosome translocations induced by IL6.
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Affiliation(s)
- Almudena R Ramiro
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10021, USA
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43
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Dunn-Walters DK, Edelman H, Mehr R. Immune system learning and memory quantified by graphical analysis of B-lymphocyte phylogenetic trees. Biosystems 2004; 76:141-55. [PMID: 15351138 DOI: 10.1016/j.biosystems.2004.05.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2003] [Revised: 07/11/2003] [Accepted: 08/01/2003] [Indexed: 11/22/2022]
Abstract
The immune system learns from its encounters with pathogens and memorizes its experiences. One of the mechanisms it uses for this purpose is the intra-individual evolution of antigen receptors on B lymphocytes, achieved via hypermutation and selection of antigen receptor variable region genes during an immune response. We have developed a novel method for analyzing the graphical properties of phylogenetic trees of receptor genes which have been mutated and selected during an immune response. In the study presented here, we address the artifacts introduced by experimental methods of cell collection for DNA analysis, the meaning of each parameter measured on the tree graphs, and the differences between the dynamics of the humoral immune response in different lymphoid tissues.
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44
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Mehr R, Edelman H, Sehgal D, Mage R. Analysis of mutational lineage trees from sites of primary and secondary Ig gene diversification in rabbits and chickens. THE JOURNAL OF IMMUNOLOGY 2004; 172:4790-6. [PMID: 15067055 DOI: 10.4049/jimmunol.172.8.4790] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Lineage trees of mutated rearranged Ig V region sequences in B lymphocyte clones often serve to qualitatively illustrate claims concerning the dynamics of affinity maturation. In this study, we use a novel method for analyzing lineage tree shapes, using terms from graph theory to quantify the differences between primary and secondary diversification in rabbits and chickens. In these species, Ig gene diversification starts with rearrangement of a single (in chicken) or a few (in rabbit) V(H) genes. Somatic hypermutation and gene conversion contribute to primary diversification in appendix of young rabbits or in bursa of Fabricius of embryonic and young chickens and to secondary diversification during immune responses in germinal centers (GCs). We find that, at least in rabbits, primary diversification appears to occur at a constant rate in the appendix, and the type of Ag-specific selection seen in splenic GCs is absent. This supports the view that a primary repertoire is being generated within the expanding clonally related B cells in appendix of young rabbits and emphasizes the important role that gut-associated lymphoid tissues may play in early development of mammalian immune repertoires. Additionally, the data indicate a higher rate of hypermutation in rabbit and chicken GCs, such that the balance between hypermutation and selection tends more toward mutation and less toward selection in rabbit and chicken compared with murine GCs.
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Affiliation(s)
- Ramit Mehr
- Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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45
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Spillmann FJX, Wabl M. Endogenous Expression of Activation-Induced Cytidine Deaminase in Cell Line WEHI-231. THE JOURNAL OF IMMUNOLOGY 2004; 173:1858-67. [PMID: 15265918 DOI: 10.4049/jimmunol.173.3.1858] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Because of its susceptibility to apoptosis on Ag receptor cross-linking, cells of the mouse cell line WEHI-231 have been classified as immature B cells. Surprisingly, however, the cell line expresses activation-induced cytidine deaminase, the enzyme that mediates hypermutation and Ig class switch recombination in activated B cells. Although both cDNA sequence and protein expression of activation-induced cytidine deaminase appear normal, the cell line does not hypermutate an indicator plasmid. For the readout, the indicator plasmid depends on the removal of deoxyuridine after transition from C to U and, therefore, on functional expression of uracil N-glycosylase 2, which is normal in WEHI-231. At the endogenous Ig locus, however, WEHI-231 does undergo the canonical hypermutation of G. C to A. T base pairs to some extent. The cell line also expresses the germline transcripts of the Ig gamma 2b, epsilon, and alpha loci, but it does not switch its IgM surface Ig.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, Nuclear/biosynthesis
- Antigens, Nuclear/genetics
- Base Pairing
- Base Sequence
- Cell Line, Tumor/enzymology
- Cytidine Deaminase/biosynthesis
- Cytidine Deaminase/genetics
- Cytidine Deaminase/physiology
- DNA Glycosylases/genetics
- DNA Glycosylases/metabolism
- DNA, Complementary/genetics
- DNA-Binding Proteins/biosynthesis
- DNA-Binding Proteins/genetics
- Enzyme Induction
- Genes, Immunoglobulin
- Genes, Reporter
- Green Fluorescent Proteins
- Immunoglobulin Class Switching
- Immunoglobulin Heavy Chains/genetics
- Immunoglobulin M/genetics
- Ku Autoantigen
- Luminescent Proteins/genetics
- Lymphoma, B-Cell/enzymology
- Lymphoma, B-Cell/pathology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred NZB
- Molecular Sequence Data
- Plasmids/genetics
- Receptors, Antigen, B-Cell/genetics
- Sequence Alignment
- Sequence Homology
- Somatic Hypermutation, Immunoglobulin
- Transfection
- Uracil-DNA Glycosidase
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Affiliation(s)
- Freia J X Spillmann
- Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA
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46
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McBride KM, Barreto V, Ramiro AR, Stavropoulos P, Nussenzweig MC. Somatic hypermutation is limited by CRM1-dependent nuclear export of activation-induced deaminase. J Exp Med 2004; 199:1235-44. [PMID: 15117971 PMCID: PMC2211910 DOI: 10.1084/jem.20040373] [Citation(s) in RCA: 181] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Accepted: 03/26/2004] [Indexed: 12/17/2022] Open
Abstract
Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated in activated B lymphocytes by activation-induced deaminase (AID). AID is thought to make lesions in DNA by deaminating cytidine residues in single-stranded DNA exposed by RNA polymerase during transcription. Although this must occur in the nucleus, AID is found primarily in the cytoplasm. Here we show that AID is actively excluded from the nucleus by an exportin CRM1-dependent pathway. The AID nuclear export signal (NES) is found at the carboxyl terminus of AID in a region that overlaps a sequence required for CSR but not SHM. We find that AID lacking a functional NES causes more hypermutation of a nonphysiologic target gene in transfected fibroblasts. However, the NES does not impact on the rate of mutation of immunoglobulin genes in B lymphocytes, suggesting that the AID NES does not limit AID activity in these cells.
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Affiliation(s)
- Kevin M McBride
- Laboratory of Molecular Immunology, The Rockefeller University, New York, NY 10021, USA
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47
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Zeng X, Negrete GA, Kasmer C, Yang WW, Gearhart PJ. Absence of DNA polymerase eta reveals targeting of C mutations on the nontranscribed strand in immunoglobulin switch regions. ACTA ACUST UNITED AC 2004; 199:917-24. [PMID: 15051760 PMCID: PMC2211872 DOI: 10.1084/jem.20032022] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Activation-induced cytosine deaminase preferentially deaminates C in DNA on the nontranscribed strand in vitro, which theoretically should produce a large increase in mutations of C during hypermutation of immunoglobulin genes. However, a bias for C mutations has not been observed among the mutations in variable genes. Therefore, we examined mutations in the mu and gamma switch regions, which can form stable secondary structures, to look for C mutations. To further simplify the pattern, mutations were studied in the absence of DNA polymerase (pol) eta, which may produce substitutions of nucleotides downstream of C. DNA from lymphocytes of patients with xeroderma pigmentosum variant (XP-V) disease, whose polymerase eta is defective, had the same frequency of switching to all four gamma isotypes and hypermutation in mu-gamma switch sites (0.5% mutations per basepair) as control subjects. There were fewer mutations of A and T bases in the XP-V clones, similar to variable gene mutations from these patients, which confirms that polymerase eta produces substitutions opposite A and T. Most importantly, the absence of polymerase eta revealed an increase in C mutations on the nontranscribed strand. This data shows for the first time that C is preferentially mutated in vivo and pol eta generates hypermutation in the mu and gamma switch regions.
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Affiliation(s)
- Xianmin Zeng
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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48
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Bardwell PD, Woo CJ, Wei K, Li Z, Martin A, Sack SZ, Parris T, Edelmann W, Scharff MD. Altered somatic hypermutation and reduced class-switch recombination in exonuclease 1-mutant mice. Nat Immunol 2004; 5:224-9. [PMID: 14716311 DOI: 10.1038/ni1031] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2003] [Accepted: 11/11/2003] [Indexed: 11/09/2022]
Abstract
The generation of protective antibodies requires somatic hypermutation (SHM) and class-switch recombination (CSR) of immunoglobulin genes. Here we show that mice mutant for exonuclease 1 (Exo1), which participates in DNA mismatch repair (MMR), have decreased CSR and changes in the characteristics of SHM similar to those previously observed in mice mutant for the MMR protein Msh2. Exo1 is thus the first exonuclease shown to be involved in SHM and CSR. The phenotype of Exo1(-/-) mice and the finding that Exo1 and Mlh1 are physically associated with mutating variable regions support the idea that Exo1 and MMR participate directly in SHM and CSR.
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Affiliation(s)
- Philip D Bardwell
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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49
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Martin A, Li Z, Lin DP, Bardwell PD, Iglesias-Ussel MD, Edelmann W, Scharff MD. Msh2 ATPase activity is essential for somatic hypermutation at a-T basepairs and for efficient class switch recombination. ACTA ACUST UNITED AC 2003; 198:1171-8. [PMID: 14568978 PMCID: PMC2194233 DOI: 10.1084/jem.20030880] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by activation-induced cytidine deaminase–mediated cytidine deamination of immunoglobulin genes. MutS homologue (Msh) 2−/− mice have reduced A-T mutations and CSR. This suggests that Msh2 may play a role in repairing activation-induced cytidine deaminase–generated G-U mismatches. However, because Msh2 not only initiates mismatch repair but also has other functions, such as signaling for apoptosis, it is not known which activity of Msh2 is responsible for the effects observed, and consequently, many models have been proposed. To further dissect the role of Msh2 in SHM and CSR, mice with a “knockin” mutation in the Msh2 gene that inactivates the adenosine triphosphatase domain were examined. This mutation (i.e., Msh2G674A), which does not affect apoptosis signaling, allows mismatches to be recognized but prevents Msh2 from initiating mismatch repair. Here, we show that, similar to Msh2−/− mice, SHM in Msh2G674A mice is biased toward G-C mutations. However, CSR is partially reduced, and switch junctions are more similar to those of postmeiotic segregation 2−/− mice than to Msh2−/− mice. These results indicate that Msh2 adenosine triphosphatase activity is required for A-T mutations, and suggest that Msh2 has more than one role in CSR.
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Affiliation(s)
- Alberto Martin
- Department of Immunology, University of Toronto, Medical Sciences Bldg., Toronto, Canada, M5S 1A8.
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50
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Min IM, Schrader CE, Vardo J, Luby TM, D'Avirro N, Stavnezer J, Selsing E. The Smu tandem repeat region is critical for Ig isotype switching in the absence of Msh2. Immunity 2003; 19:515-24. [PMID: 14563316 DOI: 10.1016/s1074-7613(03)00262-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Deficiencies of the Msh2 protein or the Smu tandem repeat (SmuTR) sequences each reduce isotype switching in mice by about 2- to 3-fold. We find that switching in mice deficient for both Msh2 and SmuTR is nearly ablated. We propose that the SmuTR provides closely spaced cleavage sites that can undergo switch recombination independent of Msh2, whereas cleavages in sequences flanking the SmuTR require Msh2 processing to allow recombinational joining. We also find that changes in Smu sequences alter the focus of switch junctions within Sgamma sequences, indicating that sequences of switch regions act together in the choice of switch recombination junctions. These findings help to explain the conservation of tandemly repeated switch regions associated with heavy chain constant genes in species capable of switching.
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Affiliation(s)
- Irene M Min
- Genetics Program, Tufts University School of Medicine, Boston, MA 02111, USA
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