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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 2024:10.1007/s11427-024-2615-1. [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] [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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Vaisman A, Woodgate R. Mysterious and fascinating: DNA polymerase ɩ remains enigmatic 20 years after its discovery. DNA Repair (Amst) 2020; 93:102914. [PMID: 33087280 DOI: 10.1016/j.dnarep.2020.102914] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
With the publication of the first paper describing the biochemical properties of DNA polymerase iota (polɩ), the question immediately arose as to why cells harbor such a low-fidelity enzyme which often violates the Watson-Crick base pairing rules? Yet 20 years after its discovery, the cellular function of polɩ remains unknown. Here, we provide a graphical review of the unique biochemical properties of polɩ and speculate about the cellular pathways in which enigmatic polɩ may participate.
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Affiliation(s)
- Alexandra Vaisman
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
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Thompson PS, Cortez D. New insights into abasic site repair and tolerance. DNA Repair (Amst) 2020; 90:102866. [PMID: 32417669 PMCID: PMC7299775 DOI: 10.1016/j.dnarep.2020.102866] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 04/21/2020] [Accepted: 04/21/2020] [Indexed: 12/13/2022]
Abstract
Thousands of apurinic/apyrimidinic (AP or abasic) sites form in each cell, each day. This simple DNA lesion can have profound consequences to cellular function, genome stability, and disease. As potent blocks to polymerases, they interfere with the reading and copying of the genome. Since they provide no coding information, they are potent sources of mutation. Due to their reactive chemistry, they are intermediates in the formation of lesions that are more challenging to repair including double-strand breaks, interstrand crosslinks, and DNA protein crosslinks. Given their prevalence and deleterious consequences, cells have multiple mechanisms of repairing and tolerating these lesions. While base excision repair of abasic sites in double-strand DNA has been studied for decades, new interest in abasic site processing has come from more recent insights into how they are processed in single-strand DNA. In this review, we discuss the source of abasic sites, their biological consequences, tolerance mechanisms, and how they are repaired in double and single-stranded DNA.
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Affiliation(s)
- Petria S Thompson
- Vanderbilt University School of Medicine, Department of Biochemistry, Nashville, TN, 37232, USA
| | - David Cortez
- Vanderbilt University School of Medicine, Department of Biochemistry, Nashville, TN, 37232, USA.
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McIntyre J. Polymerase iota - an odd sibling among Y family polymerases. DNA Repair (Amst) 2019; 86:102753. [PMID: 31805501 DOI: 10.1016/j.dnarep.2019.102753] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 12/14/2022]
Abstract
It has been two decades since the discovery of the most mutagenic human DNA polymerase, polymerase iota (Polι). Since then, the biochemical activity of this translesion synthesis (TLS) enzyme has been extensively explored, mostly through in vitro experiments, with some insight into its cellular activity. Polι is one of four members of the Y-family of polymerases, which are the best characterized DNA damage-tolerant polymerases involved in TLS. Polι shares some common Y-family features, including low catalytic efficiency and processivity, high infidelity, the ability to bypass some DNA lesions, and a deficiency in 3'→5' exonucleolytic proofreading. However, Polι exhibits numerous properties unique among the Y-family enzymes. Polι has an unusual catalytic pocket structure and prefers Hoogsteen over Watson-Crick pairing, and its replication fidelity strongly depends on the template; further, it prefers Mn2+ ions rather than Mg2+ as catalytic activators. In addition to its polymerase activity, Polι possesses also 5'-deoxyribose phosphate (dRP) lyase activity, and its ability to participate in base excision repair has been shown. As a highly error-prone polymerase, its regulation is crucial and mostly involves posttranslational modifications and protein-protein interactions. The upregulation and downregulation of Polι are correlated with different types of cancer and suggestions regarding the possible function of this polymerase have emerged from studies of various cancer lines. Nonetheless, after twenty years of research, the biological function of Polι certainly remains unresolved.
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Affiliation(s)
- Justyna McIntyre
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5a, 02-106, Warsaw, Poland.
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Kazachenko KY, Miropolskaya NA, Gening LV, Tarantul VZ, Makarova AV. Alternative splicing at exon 2 results in the loss of the catalytic activity of mouse DNA polymerase iota in vitro. DNA Repair (Amst) 2017; 50:77-82. [DOI: 10.1016/j.dnarep.2017.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/27/2016] [Accepted: 01/03/2017] [Indexed: 12/16/2022]
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Maul RW, MacCarthy T, Frank EG, Donigan KA, McLenigan MP, Yang W, Saribasak H, Huston DE, Lange SS, Woodgate R, Gearhart PJ. DNA polymerase ι functions in the generation of tandem mutations during somatic hypermutation of antibody genes. J Exp Med 2016; 213:1675-83. [PMID: 27455952 PMCID: PMC4995076 DOI: 10.1084/jem.20151227] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 06/01/2016] [Indexed: 11/04/2022] Open
Abstract
DNA polymerase ι (Pol ι) is an attractive candidate for somatic hypermutation in antibody genes because of its low fidelity. To identify a role for Pol ι, we analyzed mutations in two strains of mice with deficiencies in the enzyme: 129 mice with negligible expression of truncated Pol ι, and knock-in mice that express full-length Pol ι that is catalytically inactive. Both strains had normal frequencies and spectra of mutations in the variable region, indicating that loss of Pol ι did not change overall mutagenesis. We next examined if Pol ι affected tandem mutations generated by another error-prone polymerase, Pol ζ. The frequency of contiguous mutations was analyzed using a novel computational model to determine if they occur during a single DNA transaction or during two independent events. Analyses of 2,000 mutations from both strains indicated that Pol ι-compromised mice lost the tandem signature, whereas C57BL/6 mice accumulated significant amounts of double mutations. The results support a model where Pol ι occasionally accesses the replication fork to generate a first mutation, and Pol ζ extends the mismatch with a second mutation.
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Affiliation(s)
- Robert W Maul
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Thomas MacCarthy
- Department of Applied Mathematics and Statistics, State University of New York, Stony Brook, NY 11794
| | - Ekaterina G Frank
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850
| | - Katherine A Donigan
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850
| | - Mary P McLenigan
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850
| | - William Yang
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Huseyin Saribasak
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
| | - Donald E Huston
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850
| | - Sabine S Lange
- Department of Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center Science Park, Smithville, TX 78957
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Rockville, MD 20850
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224
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Zanotti KJ, Gearhart PJ. Antibody diversification caused by disrupted mismatch repair and promiscuous DNA polymerases. DNA Repair (Amst) 2016; 38:110-116. [PMID: 26719140 PMCID: PMC4740194 DOI: 10.1016/j.dnarep.2015.11.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/30/2015] [Indexed: 10/25/2022]
Abstract
The enzyme activation-induced deaminase (AID) targets the immunoglobulin loci in activated B cells and creates DNA mutations in the antigen-binding variable region and DNA breaks in the switch region through processes known, respectively, as somatic hypermutation and class switch recombination. AID deaminates cytosine to uracil in DNA to create a U:G mismatch. During somatic hypermutation, the MutSα complex binds to the mismatch, and the error-prone DNA polymerase η generates mutations at A and T bases. During class switch recombination, both MutSα and MutLα complexes bind to the mismatch, resulting in double-strand break formation and end-joining. This review is centered on the mechanisms of how the MMR pathway is commandeered by B cells to generate antibody diversity.
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Affiliation(s)
- Kimberly J Zanotti
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Patricia J Gearhart
- Laboratory of Molecular Biology and Immunology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
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Abstract
The structural features that enable replicative DNA polymerases to synthesize DNA rapidly and accurately also limit their ability to copy damaged DNA. Direct replication of DNA damage is termed translesion synthesis (TLS), a mechanism conserved from bacteria to mammals and executed by an array of specialized DNA polymerases. This chapter examines how these translesion polymerases replicate damaged DNA and how they are regulated to balance their ability to replicate DNA lesions with the risk of undesirable mutagenesis. It also discusses how TLS is co-opted to increase the diversity of the immunoglobulin gene hypermutation and the contribution it makes to the mutations that sculpt the genome of cancer cells.
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Affiliation(s)
- Julian E Sale
- Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
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Menezes MR, Sweasy JB. Mouse models of DNA polymerases. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:645-665. [PMID: 23001998 DOI: 10.1002/em.21731] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 08/01/2012] [Accepted: 08/07/2012] [Indexed: 06/01/2023]
Abstract
In 1956, Arthur Kornberg discovered the mechanism of the biological synthesis of DNA and was awarded the Nobel Prize in Physiology or Medicine in 1959 for this contribution, which included the isolation and characterization of Escherichia coli DNA polymerase I. Now there are 15 known DNA polymerases in mammalian cells that belong to four different families. These DNA polymerases function in many different cellular processes including DNA replication, DNA repair, and damage tolerance. Several biochemical and cell biological studies have provoked a further investigation of DNA polymerase function using mouse models in which polymerase genes have been altered using gene-targeting techniques. The phenotypes of mice harboring mutant alleles reveal the prominent role of DNA polymerases in embryogenesis, prevention of premature aging, and cancer suppression.
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Affiliation(s)
- Miriam R Menezes
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, USA
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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: 3.3] [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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Makarova AV, Tarantul VZ, Gening LV. Evolution of DNA polymerase ι structure and function in eukaryotes. BIOCHEMISTRY (MOSCOW) 2011; 73:346-52. [DOI: 10.1134/s0006297908030176] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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12
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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: 1.7] [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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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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Guo C, Kosarek-Stancel JN, Tang TS, Friedberg EC. Y-family DNA polymerases in mammalian cells. Cell Mol Life Sci 2009; 66:2363-81. [PMID: 19367366 PMCID: PMC11115694 DOI: 10.1007/s00018-009-0024-4] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 03/05/2009] [Accepted: 03/23/2009] [Indexed: 11/26/2022]
Abstract
Eukaryotic genomes are replicated with high fidelity to assure the faithful transmission of genetic information from one generation to the next. The accuracy of replication relies heavily on the ability of replicative DNA polymerases to efficiently select correct nucleotides for the polymerization reaction and, using their intrinsic exonuclease activities, to excise mistakenly incorporated nucleotides. Cells also possess a variety of specialized DNA polymerases that, by a process called translesion DNA synthesis (TLS), help overcome replication blocks when unrepaired DNA lesions stall the replication machinery. This review considers the properties of the Y-family (a subset of specialized DNA polymerases) and their roles in modulating spontaneous and genotoxic-induced mutations in mammals. We also review recent insights into the molecular mechanisms that regulate PCNA monoubiquitination and DNA polymerase switching during TLS and discuss the potential of using Y-family DNA polymerases as novel targets for cancer prevention and therapy.
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Affiliation(s)
- Caixia Guo
- Laboratory of Molecular Pathology, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9072, USA.
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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: 1.7] [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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Mutation frequency vs. mutation patterns: A comparison of the results in spleen and Peyer's patches. DNA Repair (Amst) 2008; 7:1408-10; author reply 1411-2. [DOI: 10.1016/j.dnarep.2008.06.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Accepted: 06/03/2008] [Indexed: 11/23/2022]
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Martomo SA, Saribasak H, Yokoi M, Hanaoka F, Gearhart PJ. Reevaluation of the role of DNA polymerase theta in somatic hypermutation of immunoglobulin genes. DNA Repair (Amst) 2008; 7:1603-8. [PMID: 18485835 PMCID: PMC2561943 DOI: 10.1016/j.dnarep.2008.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 04/01/2008] [Accepted: 04/02/2008] [Indexed: 01/02/2023]
Abstract
DNA polymerase theta has been implicated in the process of somatic hypermutation in immunoglobulin variable genes based on several reports of alterations in the frequency and spectra of mutations from Polq(-/-) mice. However, these studies have contrasting results on mutation frequencies and the types of nucleotide substitutions, which question the role of polymerase theta in hypermutation. DNA polymerase eta has a dominant effect on mutation and may substitute in the absence of polymerase theta to affect the pattern. Therefore, we have examined mutation in mice deficient for both polymerases theta and eta. The mutation frequencies in rearranged variable genes from Peyer's patches were similar in wild type, Polq(-/-), Polh(-/-), and Polq(-/-)Polh(-/-) mice. The types of substitutions were also similar between wild type and Polq(-/-) clones, and between Polh(-/-) and Polq(-/-)Polh(-/-) clones. Furthermore, there was no difference in heavy chain class switching in splenic B cells from the four groups of mice. These results indicate that polymerase theta does not play a significant role in the generation of somatic mutation in immunoglobulin genes.
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Affiliation(s)
- Stella A. Martomo
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, United States
| | - Huseyin Saribasak
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, United States
| | - Masayuki Yokoi
- Faculty of Science, Gakushuin University, Toshima-ku, Tokyo 171-8588, Japan
| | - Fumio Hanaoka
- Faculty of Science, Gakushuin University, Toshima-ku, Tokyo 171-8588, Japan
| | - Patricia J. Gearhart
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, United States
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Poltoratsky V, Horton JK, Prasad R, Beard WA, Woodgate R, Wilson SH. Negligible impact of pol iota expression on the alkylation sensitivity of pol beta-deficient mouse fibroblast cells. DNA Repair (Amst) 2008; 7:830-3. [PMID: 18434259 DOI: 10.1016/j.dnarep.2008.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Revised: 02/26/2008] [Accepted: 02/28/2008] [Indexed: 12/16/2022]
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Abstract
To cope with an unpredictable variety of potential pathogenic insults, the immune system must generate an enormous diversity of recognition structures, and it does so by making stepwise modifications at key genetic loci in each lymphoid cell. These modifications proceed through the action of lymphoid-specific proteins acting together with the general DNA-repair machinery of the cell. Strikingly, these general mechanisms are usually diverted from their normal functions, being used in rather atypical ways in order to privilege diversity over accuracy. In this Review, we focus on the contribution of a set of DNA polymerases discovered in the past decade to these unique DNA transactions.
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Yang W, Woodgate R. What a difference a decade makes: insights into translesion DNA synthesis. Proc Natl Acad Sci U S A 2007; 104:15591-8. [PMID: 17898175 PMCID: PMC2000391 DOI: 10.1073/pnas.0704219104] [Citation(s) in RCA: 310] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Living organisms are continually under attack from a vast array of DNA-damaging agents that imperils their genomic integrity. As a consequence, cells possess an army of enzymes to repair their damaged chromosomes. However, DNA lesions often persist and pose a considerable threat to survival, because they can block the cell's replicase and its ability to complete genome duplication. It has been clear for many years that cells must possess a mechanism whereby the DNA lesion could be tolerated and physically bypassed. Yet it was only within the past decade that specialized DNA polymerases for "translesion DNA synthesis" or "TLS" were identified and characterized. Many of the TLS enzymes belong to the recently described "Y-family" of DNA polymerases. By possessing a spacious preformed active site, these enzymes can physically accommodate a variety of DNA lesions and facilitate their bypass. Flexible DNA-binding domains and a variable binding pocket for the replicating base pair further allow these TLS polymerases to select specific lesions to bypass and favor distinct non-Watson-Crick base pairs. Consequently, TLS polymerases tend to exhibit much lower fidelity than the cell's replicase when copying normal DNA, which results in a dramatic increase in mutagenesis. Occasionally this can be beneficial, but it often speeds the onset of cancer in humans. Cells use both transcriptional and posttranslational regulation to keep these low-fidelity polymerases under strict control and limit their access to a replication fork. Our perspective focuses on the mechanistic insights into TLS by the Y-family polymerases, how they are regulated, and their effects on genomic (in)stability that have been described in the past decade.
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Affiliation(s)
- Wei Yang
- National Institute of Diabetes and Digestive and Kidney Diseases and Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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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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22
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Masuda K, Ouchida R, Hikida M, Kurosaki T, Yokoi M, Masutani C, Seki M, Wood RD, Hanaoka F, O-Wang J. DNA polymerases eta and theta function in the same genetic pathway to generate mutations at A/T during somatic hypermutation of Ig genes. J Biol Chem 2007; 282:17387-94. [PMID: 17449470 DOI: 10.1074/jbc.m611849200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Somatic hypermutation of the Ig genes requires the activity of multiple DNA polymerases to ultimately introduce mutations at both A/T and C/G base pairs. Mice deficient for DNA polymerase eta (POLH) exhibited an approximately 80% reduction of the mutations at A/T, whereas absence of polymerase (POLQ) resulted in approximately 20% reduction of both A/T and C/G mutations. To investigate whether the residual A/T mutations observed in the absence of POLH are generated by POLQ and how these two polymerases might cooperate or compete with each other to generate A/T mutations, here we have established mice deficient for both POLH and POLQ. Polq(-/-)Polh(-/-) mice, however, did not show a further decrease of A/T mutations as compared with Polh(-/-) mice, suggesting that POLH and POLQ function in the same genetic pathway in the generation of these mutations. Frequent misincorporation of nucleotides, in particular opposite template T, is a known feature of POLH, but the efficiency of extension beyond the misincorporation differs significantly depending on the nature of the mispairing. Remarkably, we found that POLQ catalyzed extension more efficiently than POLH from all types of mispaired termini opposite A or T. Moreover, POLQ was able to extend mispaired termini generated by POLH albeit at a relatively low efficiency. These results reveal genetic and biochemical interactions between POLH and POLQ and suggest that POLQ might cooperate with POLH to generate some of the A/T mutations during the somatic hypermutation of Ig genes.
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Affiliation(s)
- Keiji Masuda
- Laboratory for Immune Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama 230-0045, Japan
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23
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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: 4.2] [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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24
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Delbos F, Aoufouchi S, Faili A, Weill JC, Reynaud CA. DNA polymerase eta is the sole contributor of A/T modifications during immunoglobulin gene hypermutation in the mouse. ACTA ACUST UNITED AC 2006; 204:17-23. [PMID: 17190840 PMCID: PMC2118439 DOI: 10.1084/jem.20062131] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Mutations at A/T bases within immunoglobulin genes have been shown to be generated by a repair pathway involving the DNA-binding moiety of the mismatch repair complex constituted by the MSH2–MSH6 proteins, together with DNA polymerase η (pol η). However, residual A/T mutagenesis is still observed upon inactivation in the mouse of each of these factors, suggesting that the panel of activities involved might be more complex. We reported previously (Delbos, F., A. De Smet, A. Faili, S. Aoufouchi, J.-C. Weill, and C.-A. Reynaud. 2005. J. Exp. Med. 201:1191–1196) that residual A/T mutagenesis in pol η–deficient mice was likely contributed by another enzyme not normally involved in hypermutation, DNA polymerase κ, which is mobilized in the absence of the normal polymerase partner. We report the complete absence of A/T mutations in MSH2–pol η double-deficient mice, thus indicating that the residual A/T mutagenesis in MSH2-deficient mice is contributed by pol η, now recruited by uracil N-glycosylase, the second DNA repair pathway involved in hypermutation. We propose that this particular recruitment of pol η corresponds to a profound modification of the function of uracil glycosylase in the absence of the mismatch repair complex, suggesting that MSH2–MSH6 actively prevent uracil glycosylase from error-free repair during hypermutation. pol η thus appears to be the sole contributor of A/T mutations in the normal physiological context.
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Affiliation(s)
- Frédéric Delbos
- Institut National de la Santé et de la Recherche Médicale U783 (Développement du système immunitaire) and Université Paris René Descartes, Faculté de Médecine René Descartes, Site Necker-Enfants Malades, 75730 Paris Cedex 15, France
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25
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Dumstorf CA, Clark AB, Lin Q, Kissling GE, Yuan T, Kucherlapati R, McGregor WG, Kunkel TA. Participation of mouse DNA polymerase iota in strand-biased mutagenic bypass of UV photoproducts and suppression of skin cancer. Proc Natl Acad Sci U S A 2006; 103:18083-8. [PMID: 17114294 PMCID: PMC1838710 DOI: 10.1073/pnas.0605247103] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA polymerase iota (pol iota) is a conserved Y family enzyme that is implicated in translesion DNA synthesis (TLS) but whose cellular functions remain uncertain. To test the hypothesis that pol iota performs TLS in cells, we compared UV-induced mutagenesis in primary fibroblasts derived from wild-type mice to mice lacking functional pol eta, pol iota, or both. A deficiency in mouse DNA polymerase eta (pol eta) enhanced UV-induced Hprt mutant frequencies. This enhanced UV-induced mutagenesis and UV-induced mutagenesis in wild-type cells were strongly diminished in cells deficient in pol iota, indicating that pol iota participates in the bypass of UV photoproducts in cells. Moreover, a clear strand bias among UV-induced base substitutions was observed in wild-type cells that was diminished in pol eta- and pol iota-deficient mouse cells and abolished in cells deficient in both enzymes. These data suggest that these enzymes bypass UV photoproducts in an asymmetric manner. To determine whether pol iota status affects cancer susceptibility, we compared the UV-induced skin cancer susceptibility of wild-type mice to mice lacking functional pol eta, pol iota, or both. Although pol iota deficiency alone had no effect, UV-induced skin tumors in pol eta-deficient mice developed 4 weeks earlier in mice concomitantly deficient in pol iota. Collectively, these data reveal functions for pol iota in bypassing UV photoproducts and in delaying the onset of UV-induced skin cancer.
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Affiliation(s)
- Chad A. Dumstorf
- *Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202-1786
| | - Alan B. Clark
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, and
| | - Qingcong Lin
- Harvard Medical School–Partners Healthcare Center for Genetics and Genomics and Harvard Medical School, Boston, MA 02115
| | - Grace E. Kissling
- Biostatistics Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709; and
| | - Tao Yuan
- Harvard Medical School–Partners Healthcare Center for Genetics and Genomics and Harvard Medical School, Boston, MA 02115
| | - Raju Kucherlapati
- Harvard Medical School–Partners Healthcare Center for Genetics and Genomics and Harvard Medical School, Boston, MA 02115
| | - W. Glenn McGregor
- *Department of Pharmacology and Toxicology and James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202-1786
| | - Thomas A. Kunkel
- Laboratory of Molecular Genetics and Laboratory of Structural Biology, and
- To whom correspondence should be addressed. E-mail:
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26
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Masuda K, Ouchida R, Hikida M, Nakayama M, Ohara O, Kurosaki T, O-Wang J. Absence of DNA polymerase theta results in decreased somatic hypermutation frequency and altered mutation patterns in Ig genes. DNA Repair (Amst) 2006; 5:1384-91. [PMID: 16890500 DOI: 10.1016/j.dnarep.2006.06.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 06/09/2006] [Accepted: 06/13/2006] [Indexed: 11/27/2022]
Abstract
Multiple DNA polymerases participate in somatic hypermutation of immunoglobulin (Ig) genes. Mutations at A/T are largely dependent on DNA polymerase eta (POLH) whereas mutations at C/G appear to be generated by several DNA polymerases. We have previously shown that mice expressing a catalytically inactive POLQ (Polq-inactive) have a reduction in C/G mutations. Here we have generated mice that completely lack Polq expression (Polq-null). Polq-null mice have no obvious abnormality in B or T cell differentiation, and their splenic B cells responded normally to various activation signals and underwent normal Ig gene class switching. The mutant mice mounted relatively normal immune responses against a T-dependent antigen although there was a slight decrease in antigen specific antibodies. Polq-null mice exhibited a mild reduction in the overall mutation frequency, however, in contrast to Polq-inactive mice where the reduction mostly affected mutations at C/G, Polq-null mice showed a reduction of both C/G and A/T mutations and there was a significant increase of G to C transversions. These results confirm a role for POLQ in somatic hypermutation and suggest that in the complete absence of POLQ other polymerases may functionally substitute, resulting in a mutation pattern different from that found in Polq-inactive mice.
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Affiliation(s)
- Keiji Masuda
- Laboratory for Antigen Receptor Diversity, Research Center for Allergy and Immunology, RIKEN Yokohama Institute, Yokohama 230-0045, Japan
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27
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Ohkumo T, Kondo Y, Yokoi M, Tsukamoto T, Yamada A, Sugimoto T, Kanao R, Higashi Y, Kondoh H, Tatematsu M, Masutani C, Hanaoka F. UV-B radiation induces epithelial tumors in mice lacking DNA polymerase eta and mesenchymal tumors in mice deficient for DNA polymerase iota. Mol Cell Biol 2006; 26:7696-706. [PMID: 17015482 PMCID: PMC1636855 DOI: 10.1128/mcb.01076-06] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
DNA polymerase eta (Pol eta) is the product of the Polh gene, which is responsible for the group variant of xeroderma pigmentosum, a rare inherited recessive disease which is characterized by susceptibility to sunlight-induced skin cancer. We recently reported in a study of Polh mutant mice that Pol eta is involved in the somatic hypermutation of immunoglobulin genes, but the cancer predisposition of Polh-/- mice has not been examined until very recently. Another translesion synthesis polymerase, Pol iota, a Pol eta paralog encoded by the Poli gene, is naturally deficient in the 129 mouse strain, and the function of Pol iota is enigmatic. Here, we generated Polh Poli double-deficient mice and compared the tumor susceptibility of them with Polh- or Poli-deficient animals under the same genetic background. While Pol iota deficiency does not influence the UV sensitivity of mouse fibroblasts irrespective of Polh genotype, Polh Poli double-deficient mice show slightly earlier onset of skin tumor formation. Intriguingly, histological diagnosis after chronic treatment with UV light reveals that Pol iota deficiency leads to the formation of mesenchymal tumors, such as sarcomas, that are not observed in Polh(-/-) mice. These results suggest the involvement of the Pol eta and Pol iota proteins in UV-induced skin carcinogenesis.
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Affiliation(s)
- Tsuyoshi Ohkumo
- Cellular Biology Laboratory, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan
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28
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Casali P, Pal Z, Xu Z, Zan H. DNA repair in antibody somatic hypermutation. Trends Immunol 2006; 27:313-21. [PMID: 16737852 PMCID: PMC4623574 DOI: 10.1016/j.it.2006.05.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 04/04/2006] [Accepted: 05/11/2006] [Indexed: 12/28/2022]
Abstract
Somatic hypermutation (SHM) underlies the generation of a diverse repertoire of high-affinity antibodies. It is effected by a two-step process: (i) DNA lesions initiated by activation-induced cytidine deaminase (AID), and (ii) lesion repair by the combined intervention of DNA replication and repair factors that include mismatch repair (MMR) proteins and translesion DNA synthesis (TLS) polymerases. AID and TLS polymerases that are crucial to SHM, namely polymerase (pol) theta, pol zeta and pol eta, are induced in B cells by the stimuli that are required to trigger this process: B-cell receptor crosslinking and CD40 engagement by CD154. These polymerases, together with MMR proteins and other DNA replication and repair factors, could assemble to form a multimolecular complex ("mutasome") at the site of DNA lesions. Molecular interactions in the mutasome would result in a "polymerase switch", that is, the substitution of the high-fidelity replicative pol delta and pol epsilon with the TLS pol theta, pol eta, Rev1, pol zeta and, perhaps, pol iota, which are error-prone and crucially insert mismatches or mutations while repairing DNA lesions. Here, we place these concepts in the context of the existing in vivo and in vitro findings, and discuss an integrated mechanistic model of SHM.
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Affiliation(s)
- Paolo Casali
- Center for Immunology, School of Medicine and School of Biological Sciences, University of California, Irvine, CA 92697-4120, USA.
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29
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Martomo SA, Gearhart PJ. Somatic hypermutation: subverted DNA repair. Curr Opin Immunol 2006; 18:243-8. [PMID: 16616477 DOI: 10.1016/j.coi.2006.03.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Accepted: 03/27/2006] [Indexed: 01/06/2023]
Abstract
Somatic hypermutation generates high-affinity antibodies of different isotypes that efficiently protect us against a plethora of pathogens. Recent analyses of the types of mutations produced in gene-deficient mice have indicated how DNA repair proteins are drawn into the pathway. Activation-induced cytosine deaminase begins the process by deaminating cytosine to uracil in DNA. The uracils are then recognized by the base excision repair protein uracil DNA glycosylase and by the mismatch repair proteins MutS homologue 2 and MutS homologue 6. Instead of repairing the uracils, these proteins attract low fidelity DNA polymerases, which synthesize nucleotide substitutions at an unprecedented level.
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Affiliation(s)
- Stella A Martomo
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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30
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Pavlov YI, Shcherbakova PV, Rogozin IB. Roles of DNA Polymerases in Replication, Repair, and Recombination in Eukaryotes. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 255:41-132. [PMID: 17178465 DOI: 10.1016/s0074-7696(06)55002-8] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The functioning of the eukaryotic genome depends on efficient and accurate DNA replication and repair. The process of replication is complicated by the ongoing decomposition of DNA and damage of the genome by endogenous and exogenous factors. DNA damage can alter base coding potential resulting in mutations, or block DNA replication, which can lead to double-strand breaks (DSB) and to subsequent chromosome loss. Replication is coordinated with DNA repair systems that operate in cells to remove or tolerate DNA lesions. DNA polymerases can serve as sensors in the cell cycle checkpoint pathways that delay cell division until damaged DNA is repaired and replication is completed. Eukaryotic DNA template-dependent DNA polymerases have different properties adapted to perform an amazingly wide spectrum of DNA transactions. In this review, we discuss the structure, the mechanism, and the evolutionary relationships of DNA polymerases and their possible functions in the replication of intact and damaged chromosomes, DNA damage repair, and recombination.
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Affiliation(s)
- Youri I Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, Departments of Biochemistry and Molecular Biology, and Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA
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