1
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Feng Y, Li C, Stewart JA, Barbulescu P, Seija Desivo N, Álvarez-Quilón A, Pezo RC, Perera MLW, Chan K, Tong AHY, Mohamad-Ramshan R, Berru M, Nakib D, Li G, Kardar GA, Carlyle JR, Moffat J, Durocher D, Di Noia JM, Bhagwat AS, Martin A. FAM72A antagonizes UNG2 to promote mutagenic repair during antibody maturation. Nature 2021; 600:324-328. [PMID: 34819670 PMCID: PMC9425297 DOI: 10.1038/s41586-021-04144-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 10/14/2021] [Indexed: 11/09/2022]
Abstract
Activation-induced cytidine deaminase (AID) catalyses the deamination of deoxycytidines to deoxyuracils within immunoglobulin genes to induce somatic hypermutation and class-switch recombination1,2. AID-generated deoxyuracils are recognized and processed by subverted base-excision and mismatch repair pathways that ensure a mutagenic outcome in B cells3-6. However, why these DNA repair pathways do not accurately repair AID-induced lesions remains unknown. Here, using a genome-wide CRISPR screen, we show that FAM72A is a major determinant for the error-prone processing of deoxyuracils. Fam72a-deficient CH12F3-2 B cells and primary B cells from Fam72a-/- mice exhibit reduced class-switch recombination and somatic hypermutation frequencies at immunoglobulin and Bcl6 genes, and reduced genome-wide deoxyuracils. The somatic hypermutation spectrum in B cells from Fam72a-/- mice is opposite to that observed in mice deficient in uracil DNA glycosylase 2 (UNG2)7, which suggests that UNG2 is hyperactive in FAM72A-deficient cells. Indeed, FAM72A binds to UNG2, resulting in reduced levels of UNG2 protein in the G1 phase of the cell cycle, coinciding with peak AID activity. FAM72A therefore causes U·G mispairs to persist into S phase, leading to error-prone processing by mismatch repair. By disabling the DNA repair pathways that normally efficiently remove deoxyuracils from DNA, FAM72A enables AID to exert its full effects on antibody maturation. This work has implications in cancer, as the overexpression of FAM72A that is observed in many cancers8 could promote mutagenesis.
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Affiliation(s)
- Yuqing Feng
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Conglei Li
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- School of Medicine, The Chinese University of Hong Kong, Shenzhen, China
| | | | - Philip Barbulescu
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Noé Seija Desivo
- Institut de recherches cliniques de Montréal, Montreal, Quebec, Canada
- Molecular Biology Programs, Department of Medicine, University of Montreal, Montreal, Quebec, Canada
| | - Alejandro Álvarez-Quilón
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario, Canada
| | - Rossanna C Pezo
- Sunnybrook Health Sciences Center, Toronto, Ontario, Canada
- Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | | | - Katherine Chan
- Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | - Amy Hin Yan Tong
- Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | | | - Maribel Berru
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Diana Nakib
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Gavin Li
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Gholam Ali Kardar
- Immunology, Asthma and Allergy Research Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - James R Carlyle
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Jason Moffat
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Institute for Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
| | - Daniel Durocher
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Ontario, Canada
| | - Javier M Di Noia
- Institut de recherches cliniques de Montréal, Montreal, Quebec, Canada
- Molecular Biology Programs, Department of Medicine, University of Montreal, Montreal, Quebec, Canada
| | - Ashok S Bhagwat
- Department of Chemistry, Wayne State University, Detroit, MI, USA
- Department of Biochemistry, Microbiology and Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Alberto Martin
- Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
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2
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Safavi S, Larouche A, Zahn A, Patenaude AM, Domanska D, Dionne K, Rognes T, Dingler F, Kang SK, Liu Y, Johnson N, Hébert J, Verdun RE, Rada CA, Vega F, Nilsen H, Di Noia JM. The uracil-DNA glycosylase UNG protects the fitness of normal and cancer B cells expressing AID. NAR Cancer 2021; 2:zcaa019. [PMID: 33554121 PMCID: PMC7848951 DOI: 10.1093/narcan/zcaa019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/09/2020] [Accepted: 08/13/2020] [Indexed: 12/14/2022] Open
Abstract
In B lymphocytes, the uracil N-glycosylase (UNG) excises genomic uracils made by activation-induced deaminase (AID), thus underpinning antibody gene diversification and oncogenic chromosomal translocations, but also initiating faithful DNA repair. Ung−/− mice develop B-cell lymphoma (BCL). However, since UNG has anti- and pro-oncogenic activities, its tumor suppressor relevance is unclear. Moreover, how the constant DNA damage and repair caused by the AID and UNG interplay affects B-cell fitness and thereby the dynamics of cell populations in vivo is unknown. Here, we show that UNG specifically protects the fitness of germinal center B cells, which express AID, and not of any other B-cell subset, coincident with AID-induced telomere damage activating p53-dependent checkpoints. Consistent with AID expression being detrimental in UNG-deficient B cells, Ung−/− mice develop BCL originating from activated B cells but lose AID expression in the established tumor. Accordingly, we find that UNG is rarely lost in human BCL. The fitness preservation activity of UNG contingent to AID expression was confirmed in a B-cell leukemia model. Hence, UNG, typically considered a tumor suppressor, acquires tumor-enabling activity in cancer cell populations that express AID by protecting cell fitness.
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Affiliation(s)
- Shiva Safavi
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Ariane Larouche
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Astrid Zahn
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Anne-Marie Patenaude
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Diana Domanska
- Department of Informatics, University of Oslo, PO Box 1080, Blindern, 0316 Oslo, Norway
| | - Kiersten Dionne
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Torbjørn Rognes
- Department of Informatics, University of Oslo, PO Box 1080, Blindern, 0316 Oslo, Norway
| | - Felix Dingler
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
| | - Seong-Kwi Kang
- ITR Laboratories Canada, Inc., 19601 Clark Graham Ave, Baie-D'Urfe, QC H9X 3T1, Canada
| | - Yan Liu
- Section for Clinical Molecular Biology, Akershus University Hospital, PO 1000, 1478 Lørenskog, Norway
| | - Nathalie Johnson
- Division of Experimental Medicine, Department of Medicine, McGill University, Montréal, QC H4A 3J1, Canada
| | - Josée Hébert
- Department of Medicine, Université de Montréal, C.P. 6128, Montreal, QC H3C 3J7, Canada
| | - Ramiro E Verdun
- Division of Hematology, Department of Medicine, Sylvester Comprehensive Cancer Center, University of Miami, Miami, FL 33136, USA
| | | | - Francisco Vega
- Division of Hematology, Department of Medicine, Sylvester Comprehensive Cancer Center, University of Miami, Miami, FL 33136, USA
| | - Hilde Nilsen
- Section for Clinical Molecular Biology, Akershus University Hospital, PO 1000, 1478 Lørenskog, Norway
| | - Javier M Di Noia
- Institut de Recherches Cliniques de Montréal, 110 Av des Pins Ouest, Montréal, QC H2W 1R7, Canada
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3
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Abe T, Branzei D, Hirota K. DNA Damage Tolerance Mechanisms Revealed from the Analysis of Immunoglobulin V Gene Diversification in Avian DT40 Cells. Genes (Basel) 2018; 9:genes9120614. [PMID: 30544644 PMCID: PMC6316486 DOI: 10.3390/genes9120614] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 11/26/2018] [Accepted: 11/30/2018] [Indexed: 01/19/2023] Open
Abstract
DNA replication is an essential biochemical reaction in dividing cells that frequently stalls at damaged sites. Homologous/homeologous recombination (HR)-mediated template switch and translesion DNA synthesis (TLS)-mediated bypass processes release arrested DNA replication forks. These mechanisms are pivotal for replication fork maintenance and play critical roles in DNA damage tolerance (DDT) and gap-filling. The avian DT40 B lymphocyte cell line provides an opportunity to examine HR-mediated template switch and TLS triggered by abasic sites by sequencing the constitutively diversifying immunoglobulin light-chain variable gene (IgV). During IgV diversification, activation-induced deaminase (AID) converts dC to dU, which in turn is excised by uracil DNA glycosylase and yields abasic sites within a defined window of around 500 base pairs. These abasic sites can induce gene conversion with a set of homeologous upstream pseudogenes via the HR-mediated template switch, resulting in templated mutagenesis, or can be bypassed directly by TLS, resulting in non-templated somatic hypermutation at dC/dG base pairs. In this review, we discuss recent works unveiling IgV diversification mechanisms in avian DT40 cells, which shed light on DDT mode usage in vertebrate cells and tolerance of abasic sites.
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Affiliation(s)
- Takuya Abe
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan.
- IFOM, the FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy.
| | - Dana Branzei
- IFOM, the FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy.
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche (IGM-CNR), Via Abbiategrasso 207, 27100 Pavia, Italy.
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji-shi, Tokyo 192-0397, Japan.
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Caldwell RB, Braselmann H, Heuer S, Schötz U, Zitzelsberger H. Gain-of-function analysis of cis-acting diversification elements in DT40 cells. Immunol Cell Biol 2018; 96:948-957. [PMID: 29665088 DOI: 10.1111/imcb.12158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 04/09/2018] [Accepted: 04/09/2018] [Indexed: 02/02/2023]
Abstract
Activation-induced cytidine deaminase (AID) is required for the immunoglobulin diversification processes of somatic hypermutation, gene conversion and class-switch recombination. The targeting of AID's deamination activity is thought to be a combination of cis- and trans-acting elements, but has not been fully elucidated. Deletion analysis of putative proximal cis-regulatory motifs, while helpful, fails to identify additive versus cumulative effects, redundancy, and may create new motifs where none previously existed. In contrast, gain-of-function analysis can be more insightful with fewer of the same drawbacks and the output is a positive result. Here, we show five defined DNA regions of the avian Igλ locus that are sufficient to confer events of hypermutation to a target gene. In our analysis, the essential cis-targeting elements fully reconstituted diversification of a transgene under heterologous promotion in the avian B-cell line DT40. Furthermore, to the best of our knowledge two of the five regions we report on here have not previously been described as individually having an influence on somatic hypermutation.
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Affiliation(s)
- Randolph B Caldwell
- Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Helmholtz Center Munich - German Research Center for Environmental Health (GmbH), Neuherberg, 85764, Germany
| | - Herbert Braselmann
- Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Helmholtz Center Munich - German Research Center for Environmental Health (GmbH), Neuherberg, 85764, Germany
| | - Steffen Heuer
- Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Helmholtz Center Munich - German Research Center for Environmental Health (GmbH), Neuherberg, 85764, Germany
| | - Ulrike Schötz
- Department of Radiotherapy and Radiooncology, Philipps-University Marburg, University Hospital Gießen and Marburg, Marburg, 35043, Germany
| | - Horst Zitzelsberger
- Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Helmholtz Center Munich - German Research Center for Environmental Health (GmbH), Neuherberg, 85764, Germany.,Helmholtz Center Munich, Clinical Cooperation Group 'Personalized Radiotherapy of Head and Neck Cancer', Neuherberg, 85764, Germany.,Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-Universitaet, University Hospital Munich, Munich, 81377, Germany
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5
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Methot S, Di Noia J. Molecular Mechanisms of Somatic Hypermutation and Class Switch Recombination. Adv Immunol 2017; 133:37-87. [DOI: 10.1016/bs.ai.2016.11.002] [Citation(s) in RCA: 165] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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6
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Moazzeni H, Akbari MT, Yazdani S, Elahi E. Expression of CXCL6 and BBS5 that may be glaucoma relevant genes is regulated by PITX2. Gene 2016; 593:76-83. [PMID: 27520585 DOI: 10.1016/j.gene.2016.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/31/2016] [Accepted: 08/08/2016] [Indexed: 12/26/2022]
Abstract
The transcription factor PITX2 is implicated in glaucoma pathology. In an earlier study we had used microarray analysis to identify genes in the trabecular meshwork (TM) that are affected by knock down of PITX2. Here, those studies were pursued to identify genes that are direct targets of PITX2 and that may be relevant to glaucoma. Initially, bioinformatics tools were used to select among the genes that had been affected by PITX2 knock down those that have PITX2 binding sites and that may be involved in glaucoma related functions. Subsequently, the effect of PITX2 was tested using the dual luciferase assay in four cell cultures including two primary TM cultures co-transfected with vectors containing promoter fragments of six candidate genes upstream of a luciferase gene and a vector that expressed PITX2. Finally, the effect of PITX2 on endogenous expression of two genes was assessed by over expression and knock down of PITX2 in TM cells. Thirty four genes were found to contain PITX2 binding sites in their putative promoter regions, and 16 were found to be associated with TM-specific and/or glaucoma associated functions. Results of dual luciferase assays confirmed that two of six genes tested were directly targeted by PITX2. The two genes were CXCL6 (chemokine (C-X-C motif) ligand 6) and BBS5 (Bardet-Biedl syndrome 5). Over expression and knock down of PITX2 showed that this transcription factor affects endogenous expression of these two genes in TM cells. CXCL6 encodes a pro-inflammatory cytokine, and many studies have suggested that cytokines and other immune system functions are involved in glaucoma pathogenesis. BBS5 is a member of the BBS family of genes that affect ciliary functions, and ciliary bodies in the anterior chamber of the eye produce the aqueous fluid that affects intraocular pressure. Immune related functions and intraocular pressure are both important components of glaucoma pathology. The role of PITX2 in glaucoma may be mediated partly by regulating the expression of CXCL6 and BBS5 and thus affecting immune functions and intraocular pressure.
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Affiliation(s)
- Hamidreza Moazzeni
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box. 14115-331, Tehran, Iran
| | - Mohammad Taghi Akbari
- Department of Medical Genetics, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box. 14115-331, Tehran, Iran.
| | - Shahin Yazdani
- Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Elahe Elahi
- School of Biology, College of Science, University of Tehran, Tehran, Iran; Department of Biotechnology, College of Science, University of Tehran, Tehran, Iran.
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7
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Caldwell RB, Braselmann H, Schoetz U, Heuer S, Scherthan H, Zitzelsberger H. Positive Cofactor 4 (PC4) is critical for DNA repair pathway re-routing in DT40 cells. Sci Rep 2016; 6:28890. [PMID: 27374870 PMCID: PMC4931448 DOI: 10.1038/srep28890] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/09/2016] [Indexed: 01/06/2023] Open
Abstract
PC4 is an abundant single-strand DNA binding protein that has been implicated in transcription and DNA repair. Here, we show that PC4 is involved in the cellular DNA damage response. To elucidate the role, we used the DT40 chicken B cell model, which produces clustered DNA lesions at Ig loci via the action of activation-induced deaminase. Our results help resolve key aspects of immunoglobulin diversification and suggest an essential role of PC4 in repair pathway choice. We show that PC4 ablation in gene conversion (GC)-active cells significantly disrupts GC but has little to no effect on targeted homologous recombination. In agreement, the global double-strand break repair response, as measured by γH2AX foci analysis, is unperturbed 16 hours post irradiation. In cells with the pseudo-genes removed (GC inactive), PC4 ablation reduced the overall mutation rate while simultaneously increasing the transversion mutation ratio. By tagging the N-terminus of PC4, gene conversion and somatic hypermutation are all but abolished even when native non-tagged PC4 is present, indicating a dominant negative effect. Our data point to a very early and deterministic role for PC4 in DNA repair pathway re-routing.
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Affiliation(s)
- Randolph B Caldwell
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH). Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Herbert Braselmann
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH). Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Ulrike Schoetz
- Clinical Cooperation Group 'Personalized Radiotherapy of Head and Neck Cancer', Helmholtz Zentrum München, Ingolstaedter Landstr 1, 85764, Neuherberg, Germany.,Department of Radiotherapy and Radiation Oncology, Ludwig-Maximilians-University Munich, Marchioninistr 15, 81377, Munich, Germany
| | - Steffen Heuer
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH). Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Harry Scherthan
- Bundeswehr Institute of Radiobiology affiliated to the University of Ulm. Neuherbergstr. 11, 80937 Muenchen, Germany
| | - Horst Zitzelsberger
- Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH). Department of Radiation Sciences - Research Unit Radiation Cytogenetics, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.,Clinical Cooperation Group 'Personalized Radiotherapy of Head and Neck Cancer', Helmholtz Zentrum München, Ingolstaedter Landstr 1, 85764, Neuherberg, Germany
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8
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Schmid M, Smith J, Burt DW, Aken BL, Antin PB, Archibald AL, Ashwell C, Blackshear PJ, Boschiero C, Brown CT, Burgess SC, Cheng HH, Chow W, Coble DJ, Cooksey A, Crooijmans RPMA, Damas J, Davis RVN, de Koning DJ, Delany ME, Derrien T, Desta TT, Dunn IC, Dunn M, Ellegren H, Eöry L, Erb I, Farré M, Fasold M, Fleming D, Flicek P, Fowler KE, Frésard L, Froman DP, Garceau V, Gardner PP, Gheyas AA, Griffin DK, Groenen MAM, Haaf T, Hanotte O, Hart A, Häsler J, Hedges SB, Hertel J, Howe K, Hubbard A, Hume DA, Kaiser P, Kedra D, Kemp SJ, Klopp C, Kniel KE, Kuo R, Lagarrigue S, Lamont SJ, Larkin DM, Lawal RA, Markland SM, McCarthy F, McCormack HA, McPherson MC, Motegi A, Muljo SA, Münsterberg A, Nag R, Nanda I, Neuberger M, Nitsche A, Notredame C, Noyes H, O'Connor R, O'Hare EA, Oler AJ, Ommeh SC, Pais H, Persia M, Pitel F, Preeyanon L, Prieto Barja P, Pritchett EM, Rhoads DD, Robinson CM, Romanov MN, Rothschild M, Roux PF, Schmidt CJ, Schneider AS, Schwartz MG, Searle SM, Skinner MA, Smith CA, Stadler PF, Steeves TE, Steinlein C, Sun L, Takata M, Ulitsky I, Wang Q, Wang Y, Warren WC, Wood JMD, Wragg D, Zhou H. Third Report on Chicken Genes and Chromosomes 2015. Cytogenet Genome Res 2015; 145:78-179. [PMID: 26282327 PMCID: PMC5120589 DOI: 10.1159/000430927] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Michael Schmid
- Department of Human Genetics, University of Würzburg, Würzburg, Germany
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9
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Eid MMA, Maeda K, Almofty SA, Singh SK, Shimoda M, Sakaguchi N. GANP regulates the choice of DNA repair pathway by DNA-PKcs interaction in AID-dependent IgV region diversification. THE JOURNAL OF IMMUNOLOGY 2014; 192:5529-39. [PMID: 24808370 DOI: 10.4049/jimmunol.1400021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
RNA export factor germinal center-associated nuclear protein (GANP) interacts with activation-induced cytidine deaminase (AID) and shepherds it from the cytoplasm to the nucleus and toward the IgV region loci in B cells. In this study, we demonstrate a role for GANP in the repair of AID-initiated DNA damage in chicken DT40 B cells to generate IgV region diversity by gene conversion and somatic hypermutation. GANP plays a positive role in IgV region diversification of DT40 B cells in a nonhomologous end joining-proficient state. DNA-PKcs physically interacts with GANP, and this interaction is dissociated by dsDNA breaks induced by a topoisomerase II inhibitor, etoposide, or AID overexpression. GANP affects the choice of DNA repair mechanism in B cells toward homologous recombination rather than nonhomologous end joining repair. Thus, GANP presumably plays a critical role in protection of the rearranged IgV loci by favoring homologous recombination of the DNA breaks under accelerated AID recruitment.
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Affiliation(s)
- Mohammed Mansour Abbas Eid
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Kazuhiko Maeda
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Sarah Ameen Almofty
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Shailendra Kumar Singh
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Mayuko Shimoda
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
| | - Nobuo Sakaguchi
- Department of Immunology, Graduate School of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
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