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How mouse RAG recombinase avoids DNA transposition. Nat Struct Mol Biol 2020; 27:127-133. [PMID: 32015553 PMCID: PMC8291384 DOI: 10.1038/s41594-019-0366-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 12/17/2019] [Indexed: 11/12/2022]
Abstract
The RAG1-RAG2 recombinase (RAG) cleaves DNA to initiate V(D)J recombination. But RAG also belongs to the RNH-type transposase family. To learn how RAG-catalyzed transposition is inhibited in developing lymphocytes, we determined the structure of a DNA strand-transfer complex of mouse RAG at 3.1 Å resolution. The target DNA is a T form (T for transpositional target), which contains two >80° kinks towards the minor groove, only 3 bp apart. RAG2, a late evolutionary addition in V(D)J recombination, appears to enforce the sharp kinks and additional inter-segment twisting in target DNA and thus attenuate unwanted transposition. In contrast to strand-transfer complexes of genuine transposases, where severe kinks occur at the integration sites of target DNA and thus prevent the reverse reaction, the sharp kink with RAG is 1 bp away from the integration site. As a result, RAG efficiently catalyzes the disintegration reaction that restores the RSS (donor) and target DNA.
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2
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Canela A, Sridharan S, Sciascia N, Tubbs A, Meltzer P, Sleckman BP, Nussenzweig A. DNA Breaks and End Resection Measured Genome-wide by End Sequencing. Mol Cell 2016; 63:898-911. [PMID: 27477910 PMCID: PMC6299834 DOI: 10.1016/j.molcel.2016.06.034] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 06/14/2016] [Accepted: 06/21/2016] [Indexed: 12/18/2022]
Abstract
DNA double-strand breaks (DSBs) arise during physiological transcription, DNA replication, and antigen receptor diversification. Mistargeting or misprocessing of DSBs can result in pathological structural variation and mutation. Here we describe a sensitive method (END-seq) to monitor DNA end resection and DSBs genome-wide at base-pair resolution in vivo. We utilized END-seq to determine the frequency and spectrum of restriction-enzyme-, zinc-finger-nuclease-, and RAG-induced DSBs. Beyond sequence preference, chromatin features dictate the repertoire of these genome-modifying enzymes. END-seq can detect at least one DSB per cell among 10,000 cells not harboring DSBs, and we estimate that up to one out of 60 cells contains off-target RAG cleavage. In addition to site-specific cleavage, we detect DSBs distributed over extended regions during immunoglobulin class-switch recombination. Thus, END-seq provides a snapshot of DNA ends genome-wide, which can be utilized for understanding genome-editing specificities and the influence of chromatin on DSB pathway choice.
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MESH Headings
- Animals
- Ataxia Telangiectasia Mutated Proteins/genetics
- Ataxia Telangiectasia Mutated Proteins/immunology
- B-Lymphocytes/cytology
- B-Lymphocytes/immunology
- Chromatin/chemistry
- Chromatin/immunology
- DNA/genetics
- DNA/immunology
- DNA Breaks, Double-Stranded
- DNA Replication
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/immunology
- Gene Expression Regulation
- Genome
- High-Throughput Nucleotide Sequencing/methods
- Histones/genetics
- Histones/immunology
- Immunoglobulin Class Switching/genetics
- Mice
- Precursor Cells, B-Lymphoid/cytology
- Precursor Cells, B-Lymphoid/immunology
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Recombination, Genetic
- Thymocytes/cytology
- Thymocytes/immunology
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Affiliation(s)
- Andres Canela
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Sriram Sridharan
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Nicholas Sciascia
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Anthony Tubbs
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Paul Meltzer
- Genetics Branch, National Cancer Institute, NIH, Bethesda, MD 20892, USA
| | - Barry P Sleckman
- Department of Pathology and Laboratory Medicine, Weil Cornell Medical College, New York, NY 10065, USA
| | - André Nussenzweig
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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3
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Jasin M, Haber JE. The democratization of gene editing: Insights from site-specific cleavage and double-strand break repair. DNA Repair (Amst) 2016; 44:6-16. [PMID: 27261202 DOI: 10.1016/j.dnarep.2016.05.001] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
DNA double-strand breaks (DSBs) are dangerous lesions that if not properly repaired can lead to genomic change or cell death. Organisms have developed several pathways and have many factors devoted to repairing DSBs, which broadly occurs by homologous recombination, which relies on an identical or homologous sequence to template repair, or nonhomologous end-joining. Much of our understanding of these repair mechanisms has come from the study of induced DNA cleavage by site-specific endonucleases. In addition to their biological role, these cellular pathways can be co-opted for gene editing to study gene function or for gene therapy or other applications. While the first gene editing experiments were done more than 20 years ago, the recent discovery of RNA-guided endonucleases has simplified approaches developed over the years to make gene editing an approach that is available to the entire biomedical research community. Here, we review DSB repair mechanisms and site-specific cleavage systems that have provided insight into these mechanisms and led to the current gene editing revolution.
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Affiliation(s)
- Maria Jasin
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
| | - James E Haber
- Department of Biology and Rosenstiel Basic Medical Sciences Research Center, Brandeis University, 02454-9110, USA.
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4
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Gentil Dit Maurin A, Lemercier C, Collin-Faure V, Marche PN, Jouvin-Marche E, Candéias SM. Developmental regulation of p53-dependent radiation-induced thymocyte apoptosis in mice. Clin Exp Immunol 2015; 179:30-8. [PMID: 24635132 DOI: 10.1111/cei.12329] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2014] [Indexed: 12/13/2022] Open
Abstract
The production of T cell receptor αβ(+) (TCRαβ(+) ) T lymphocytes in the thymus is a tightly regulated process that can be monitored by the regulated expression of several surface molecules, including CD4, CD8, cKit, CD25 and the TCR itself, after TCR genes have been assembled from discrete V, D (for TCR-β) and J gene segments by a site-directed genetic recombination. Thymocyte differentiation is the result of a delicate balance between cell death and survival: developing thymocytes die unless they receive a positive signal to proceed to the next stage. This equilibrium is altered in response to various physiological or physical stresses such as ionizing radiation, which induces a massive p53-dependent apoptosis of CD4(+) CD8(+) double-positive (DP) thymocytes. Interestingly, these cells are actively rearranging their TCR-α chain genes. To unravel an eventual link between V(D)J recombination activity and thymocyte radio-sensitivity, we analysed the dynamics of thymocyte apoptosis and regeneration following exposure of wild-type and p53-deficient mice to different doses of γ-radiation. p53-dependent radio-sensitivity was already found to be high in immature CD4(-) CD8(-) (double-negative, DN) cKit(+) CD25(+) thymocytes, where TCR-β gene rearrangement is initiated. However, TCR-αβ(-) CD8(+) immature single-positive thymocytes, an actively cycling intermediate population between the DN and DP stages, are the most radio-sensitive cells in the thymus, even though their apoptosis is only partially p53-dependent. Within the DP population, TCR-αβ(+) thymocytes that completed TCR-α gene recombination are more radio-resistant than their TCR-αβ(-) progenitors. Finally, we found no correlation between p53 activation and thymocyte sensitivity to radiation-induced apoptosis.
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Affiliation(s)
- A Gentil Dit Maurin
- CEA, DSV, iRTSV-BGE, Grenoble, France; INSERM U1038, Grenoble, France; Grenoble Alpes Université, Grenoble, France
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5
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Satterlee JS, Beckel-Mitchener A, Little R, Procaccini D, Rutter JL, Lossie AC. Neuroepigenomics: Resources, Obstacles, and Opportunities. NEUROEPIGENETICS 2015; 1:2-13. [PMID: 25722961 PMCID: PMC4337407 DOI: 10.1016/j.nepig.2014.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Long-lived post-mitotic cells, such as the majority of human neurons, must respond effectively to ongoing changes in neuronal stimulation or microenvironmental cues through transcriptional and epigenomic regulation of gene expression. The role of epigenomic regulation in neuronal function is of fundamental interest to the neuroscience community, as these types of studies have transformed our understanding of gene regulation in post-mitotic cells. This perspective article highlights many of the resources available to researchers interested in neuroepigenomic investigations and discusses some of the current obstacles and opportunities in neuroepigenomics.
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Affiliation(s)
- John S. Satterlee
- National Institute on Drug Abuse (NIDA), Division of Basic Neurobiology and Behavioral Research, 6001 Executive Boulevard, Bethesda, MD 20850, USA
| | - Andrea Beckel-Mitchener
- National Institute on Mental Health (NIMH), Division of Neuroscience and Basic Behavioral Science, 6001 Executive Boulevard Bethesda, MD 20892-9641, USA
| | - Roger Little
- National Institute on Drug Abuse (NIDA), Division of Basic Neurobiology and Behavioral Research, 6001 Executive Boulevard, Bethesda, MD 20850, USA
| | - Dena Procaccini
- National Institute on Drug Abuse (NIDA), Division of Basic Neurobiology and Behavioral Research, 6001 Executive Boulevard, Bethesda, MD 20850, USA
| | - Joni L. Rutter
- National Institute on Drug Abuse (NIDA), Division of Basic Neurobiology and Behavioral Research, 6001 Executive Boulevard, Bethesda, MD 20850, USA
| | - Amy C. Lossie
- Office of Behavioral and Social Sciences Research (OBSSR), Division of Program Coordination, Planning, and Strategic Initiatives, Office of the Director/National Institutes of Health (NIH), 31 Center Drive, Bethesda, MD 20892, USA
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6
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Abstract
In this review, we discuss the repair of DNA double-strand breaks (DSBs) using a homologous DNA sequence (i.e., homologous recombination [HR]), focusing mainly on yeast and mammals. We provide a historical context for the current view of HR and describe how DSBs are processed during HR as well as interactions with other DSB repair pathways. We discuss the enzymology of the process, followed by studies on DSB repair in living cells. Whenever possible, we cite both original articles and reviews to aid the reader for further studies.
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Affiliation(s)
- Maria Jasin
- Developmental Biology Program, Memorial Sloan-Kettering Cancer Center New York, New York 10065
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Currall BB, Chiang C, Talkowski ME, Morton CC. Mechanisms for Structural Variation in the Human Genome. CURRENT GENETIC MEDICINE REPORTS 2013; 1:81-90. [PMID: 23730541 DOI: 10.1007/s40142-013-0012-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
It has been known for several decades that genetic variation involving changes to chromosomal structure (i.e., structural variants) can contribute to disease; however this relationship has been brought into acute focus in recent years largely based on innovative new genomics approaches and technology. Structural variants (SVs) arise from improperly repaired DNA double-strand breaks (DSB). DSBs are a frequent occurrence in all cells and two major pathways are involved in their repair: homologous recombination and non-homologous end joining. Errors during these repair mechanisms can result in SVs that involve losses, gains and rearrangements ranging from a few nucleotides to entire chromosomal arms. Factors such as rearrangements, hotspots and induced DSBs are implicated in the formation of SVs. While de novo SVs are often associated with disease, some SVs are conserved within human subpopulations and may have had a meaningful influence on primate evolution. As the ability to sequence the whole human genome rapidly evolves, the diversity of SVs is illuminated, including very complex rearrangements involving multiple DSBs in a process recently designated as "chromothripsis". Elucidating mechanisms involved in the etiology of SVs informs disease pathogenesis as well as the dynamic function associated with the biology and evolution of human genomes.
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Affiliation(s)
- Benjamin B Currall
- Departments of Obstetrics, Gynecology and Reproductive Biology, Brigham and Women's Hospital and Harvard Medical School, New Research Building, Room 160D, 77 Avenue Louis Pasteur, Boston, MA 02115, USA. Harvard Medical School, Boston, MA, USA
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8
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Ko TM, Chen YT. T-cell receptor and carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: understanding a hypersensitivity reaction. Expert Rev Clin Immunol 2012; 8:467-77. [PMID: 22882221 DOI: 10.1586/eci.12.31] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ample evidence exists to support the view that drug hypersensitivity is mediated by adaptive immunity, which involves MHC-restricted drug presentation, activation and clonal expansion of T cells. The specific MHC molecules implicated in hypersensitivity have been identified; for example, HLA-B*5701 in abacavir-induced drug hypersensitivity and HLA-B*1502 in carbamazepine-induced Stevens-Johnson syndrome. However, little is known about the role of drug-specific T cells and their T-cell receptors (TCRs) in the pathogenesis of drug hypersensitivity. Using the combination of a strong HLA-B*1502 predisposition in carbamazepine-induced Stevens-Johnson syndrome and applying global analysis of the TCR repertoire, restricted and common TCR usage in the development of severe drug hypersensitivity have recently been documented. This article reviews recent advances in the understanding of the pathogenic role of drug-specific T cells and their TCRs in the development of drug hypersensitivity and provides an analysis of their potential clinical implications.
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Affiliation(s)
- Tai-Ming Ko
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
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9
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Andres SN, Vergnes A, Ristic D, Wyman C, Modesti M, Junop M. A human XRCC4-XLF complex bridges DNA. Nucleic Acids Res 2012; 40:1868-78. [PMID: 22287571 PMCID: PMC3287209 DOI: 10.1093/nar/gks022] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
DNA double-strand breaks pose a significant threat to cell survival and must be repaired. In higher eukaryotes, such damage is repaired efficiently by non-homologous end joining (NHEJ). Within this pathway, XRCC4 and XLF fulfill key roles required for end joining. Using DNA-binding and -bridging assays, combined with direct visualization, we present evidence for how XRCC4-XLF complexes robustly bridge DNA molecules. This unanticipated, DNA Ligase IV-independent bridging activity by XRCC4-XLF suggests an early role for this complex during end joining, in addition to its more well-established later functions. Mutational analysis of the XRCC4-XLF C-terminal tail regions further identifies specialized functions in complex formation and interaction with DNA and DNA Ligase IV. Based on these data and the crystal structure of an extended protein filament of XRCC4-XLF at 3.94 Å, a model for XRCC4-XLF complex function in NHEJ is presented.
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Affiliation(s)
- Sara N Andres
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada
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10
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Abstract
Developing lymphocytes must assemble antigen receptor genes encoding the B cell and T cell receptors. This process is executed by the V(D)J recombination reaction, which can be divided into DNA cleavage and DNA joining steps. The former is carried out by a lymphocyte-specific RAG endonuclease, which mediates DNA cleavage at two recombining gene segments and their flanking RAG recognition sequences. RAG cleavage generates four broken DNA ends that are repaired by nonhomologous end joining forming coding and signal joints. On rare occasions, these DNA ends may join aberrantly forming chromosomal lesions such as translocations, deletions and inversions that have the potential to cause cellular transformation and lymphoid tumors. We discuss the activation of DNA damage responses by RAG-induced DSBs focusing on the component pathways that promote their normal repair and guard against their aberrant resolution. Moreover, we discuss how this DNA damage response impacts processes important for lymphocyte development.
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Affiliation(s)
- Beth A Helmink
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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11
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Arnal SM, Holub AJ, Salus SS, Roth DB. Non-consensus heptamer sequences destabilize the RAG post-cleavage complex, making ends available to alternative DNA repair pathways. Nucleic Acids Res 2010; 38:2944-54. [PMID: 20139091 PMCID: PMC2875030 DOI: 10.1093/nar/gkp1252] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
V(D)J recombination entails double-stranded DNA cleavage at the antigen receptor loci by the RAG1/2 proteins, which recognize conserved recombination signal sequences (RSSs) adjoining variable (V), diversity (D) and joining (J) gene segments. After cleavage, RAG1/2 remain associated with the coding and signal ends (SE) in a post-cleavage complex (PCC), which is critical for their proper joining by classical non-homologous end joining (NHEJ). Certain mutations in RAG1/2 destabilize the PCC, allowing DNA ends to access inappropriate repair pathways such as alternative NHEJ, an error-prone pathway implicated in chromosomal translocations. The PCC is thus thought to discourage aberrant rearrangements by controlling repair pathway choice. Since interactions between RAG1/2 and the RSS heptamer element are especially important in forming the RAG-SE complex, we hypothesized that non-consensus heptamer sequences might affect PCC stability. We find that certain non-consensus heptamers, including a cryptic heptamer implicated in oncogenic chromosomal rearrangements, destabilize the PCC, allowing coding and SEs to be repaired by non-standard pathways, including alternative NHEJ. These data suggest that some non-consensus RSS, frequently present at chromosomal translocations in lymphoid neoplasms, may promote genomic instability by a novel mechanism, disabling the PCC’s ability to restrict repair pathway choice.
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Affiliation(s)
- Suzzette M Arnal
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA
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12
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Brandt VL, Roth DB. Recent insights into the formation of RAG-induced chromosomal translocations. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 650:32-45. [PMID: 19731799 DOI: 10.1007/978-1-4419-0296-2_3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Chromosomal translocations are found in many types of tumors, where they may be either a cause or a result of malignant transformation. In lymphoid neoplasms, however, it is dear that pathogenesis is initiated by any of a number of recurrent DNA rearrangements. These particular translocations typically place an oncogene under the regulatory control of an Ig or TCR gene promoter, dysregulating cell growth, differentiation, or apoptosis. Given that physiological DNA rearrangements (V(D)J and class switch recombination) are integral to lymphocyte development, it is critical to understand how genomic stability is maintained during these processes. Recent advances in our understanding of DNA damage signaling and repair have provided clues to the kinds of mechanisms that lead to V(D)J-mediated translocations. In turn, investigations into the regulation of V(D)J joining have illuminated a formerly obscure pathway of DNA repair known as alternative NHEJ, which is error-prone and frequently involved in translocations. In this chapter we consider recent advances in our understanding of the functions of the RAG proteins, RAG interactions with DNA repair pathways, damage signaling and chromosome biology, all of which shed light on how mistakes at different stages of V(D)J recombination might lead to leukemias and lymphomas.
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Affiliation(s)
- Vicky L Brandt
- Department of Pathology and Program in Molecular Pathogenesis, The Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
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13
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DNA damage and repair during lymphoid development: antigen receptor diversity, genomic integrity and lymphomagenesis. Immunol Res 2008; 41:103-22. [PMID: 18214391 DOI: 10.1007/s12026-008-8015-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Lymphocyte maturation requires generation of a large diversity of antigen receptors, which involves somatic rearrangements at the antigen receptor genes in a process termed V(D)J recombination. Upon encountering specific antigens, B-lymphocytes undergo rearrangements in the constant region of the immunoglobulin genes to optimize immune responses in a process called class switch recombination. Activated B-cells also undergo somatic hypermutation in the variable regions of the immunoglobulin genes to enhance their antigenic affinity. These somatic events are initiated by the infliction of DNA lesions within the antigen receptor genes that are strictly confined to a specific developmental window and cell-cycle stage. DNA lesions are then repaired by one of the general DNA repair mechanisms, such as non-homologous end-joining. Mutations in key factors of these pathways lead to the interruption of these processes and immunodeficiency, making it possible to study the mechanisms of cellular response to DNA lesions and their repair. This review briefly summarizes some of the recently developed animal models with focus on current advances in the understanding of the mechanism of DNA end-joining activities, and its role in the maintenance of genomic stability and the prevention of tumorigenesis.
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Kiefer K, Nakajima PB, Oshinsky J, Seeholzer SH, Radic M, Bosma GC, Bosma MJ. Antigen receptor editing in anti-DNA transitional B cells deficient for surface IgM. THE JOURNAL OF IMMUNOLOGY 2008; 180:6094-106. [PMID: 18424731 DOI: 10.4049/jimmunol.180.9.6094] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In response to encounter with self-Ag, autoreactive B cells may undergo secondary L chain gene rearrangement (receptor editing) and change the specificity of their Ag receptor. Knowing at what differentiative stage(s) developing B cells undergo receptor editing is important for understanding how self-reactive B cells are regulated. In this study, in mice with Ig transgenes coding for anti-self (DNA) Ab, we report dsDNA breaks indicative of ongoing secondary L chain rearrangement not only in bone marrow cells with a pre-B/B cell phenotype but also in immature/transitional splenic B cells with little or no surface IgM (sIgM(-/low)). L chain-edited transgenic B cells were detectable in spleen but not bone marrow and were still found to produce Ab specific for DNA (and apoptotic cells), albeit with lower affinity for DNA than the unedited transgenic Ab. We conclude that L chain editing in anti-DNA-transgenic B cells is not only ongoing in bone marrow but also in spleen. Indeed, transfer of sIgM(-/low) anti-DNA splenic B cells into SCID mice resulted in the appearance of a L chain editor (Vlambdax) in the serum of engrafted recipients. Finally, we also report evidence for ongoing L chain editing in sIgM(low) transitional splenic B cells of wild-type mice.
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Affiliation(s)
- Kerstin Kiefer
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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15
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Raval P, Kriatchko AN, Kumar S, Swanson PC. Evidence for Ku70/Ku80 association with full-length RAG1. Nucleic Acids Res 2008; 36:2060-72. [PMID: 18281312 PMCID: PMC2330247 DOI: 10.1093/nar/gkn049] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Antigen receptor genes are assembled by a site-specific DNA rearrangement process called V(D)J recombination. This process proceeds through two distinct phases: a cleavage phase in which the RAG1 and RAG2 proteins introduce DNA double-strand breaks at antigen receptor gene segments, and a joining phase in which the resulting DNA breaks are processed and repaired via the non-homologous end-joining (NHEJ) repair pathway. Genetic and biochemical evidence suggest that the RAG proteins play an active role in guiding the repair of DNA breaks introduced during V(D)J recombination to the NHEJ pathway. However, evidence for specific association between the RAG proteins and any of the factors involved in NHEJ remains elusive. Here we present evidence that two components of the NHEJ pathway, Ku70 and Ku80, interact with full-length RAG1, providing a biochemical link between the two phases of V(D)J recombination.
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Affiliation(s)
- Prafulla Raval
- Department of Medical Microbiology and Immunology, Creighton University Medical Center, Omaha, NE 68178, USA
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16
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Arnal SM, Roth DB. Excised V(D)J recombination byproducts threaten genomic integrity. Trends Immunol 2007; 28:289-92. [PMID: 17544847 DOI: 10.1016/j.it.2007.05.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Revised: 04/19/2007] [Accepted: 05/17/2007] [Indexed: 11/19/2022]
Abstract
Signal joints were long considered to be inert byproducts of V(D)J recombination that protect the genome from illegitimate rearrangements. However, increasing evidence suggests that signal joints are not inert and could pose a threat to genomic stability. A recent study from Nadel and colleagues shows that episomal signal joints readily undergo trans recombination, resulting in their insertion into chromosomal DNA.
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Affiliation(s)
- Suzzette M Arnal
- The Kimmel Center for Biology and Medicine of the Skirball Institute and Department of Pathology, New York University School of Medicine, USA
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17
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Kawai K, Osakada Y, Sugimoto A, Fujitsuka M, Majima T. Hole Transfer Rates in A-Form DNA/2′-OMeRNA Hybrid. Chemistry 2007; 13:2386-91. [PMID: 17163564 DOI: 10.1002/chem.200601210] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The hole transfer rates in the DNA/DNA B-form duplex and DNA/2'-OMeRNA A-form duplex were measured which occurred in the time range of approximately 100 micros. The hole transfer rates in the A-form duplexes were slower and more strongly dependent on the temperature compared to those in the B-form duplexes, suggesting that the A-form is more rigid than the B-form duplex in this time scale.
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Affiliation(s)
- Kiyohiko Kawai
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
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18
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Kawai K, Kimura T, Yoshida H, Sugimoto A, Tojo S, Fujitsuka M, Majima T. Formation of Pyrene Dimer Radical Cation at the Minor Groove of DNA. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2006. [DOI: 10.1246/bcsj.79.312] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Curry JD, Geier JK, Schlissel MS. Single-strand recombination signal sequence nicks in vivo: evidence for a capture model of synapsis. Nat Immunol 2005; 6:1272-9. [PMID: 16286921 DOI: 10.1038/ni1270] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 09/16/2005] [Indexed: 11/08/2022]
Abstract
Variable (diversity) joining (V(D)J) recombination is initiated by the introduction of single-strand DNA breaks (nicks) at recombination signal sequences (RSSs). The importance and fate of these RSS nicks for the regulation of the V(D)J rearrangement and their potential contribution to genomic instability are poorly understood. Using two new methodologies, we were able to detect and quantify specific RSS nicks introduced into genomic DNA by incubation with recombination-activating gene proteins in vitro. In vivo, however, we found that nicks mediated by recombination-activating gene (RAG) proteins were detectable only in gene segments associated with RSSs containing 12-base pair spacers but not in those containing 23-base pair spacers. These data support a model of capture rather than synapsis for pairwise RSS cleavage during V(D)J recombination.
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Affiliation(s)
- John D Curry
- Department of Molecular and Cell Biology, Division of Immunology, University of California, Berkeley, California 94720-3200, USA
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20
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Abstract
Proper repair of DNA double-strand breaks (DSBs) is necessary for the maintenance of genomic integrity. Here, a new simple assay was used to study extrachromosomal DSB repair in Schizosaccharomyces pombe. Strikingly, DSB repair was associated with the capture of fission yeast mitochondrial DNA (mtDNA) at high frequency. Capture of mtDNA fragments required the Lig4p/Pku70p nonhomologous end-joining (NHEJ) machinery and its frequency was highly increased in fission yeast cells grown to stationary phase. The fission yeast Mre11 complex Rad32p/Rad50p/Nbs1p was also required for efficient capture of mtDNA at DSBs, supporting a role for the complex in promoting intermolecular ligation. Competition assays further revealed that microsatellite DNA from higher eukaryotes was preferentially captured at yeast DSBs. Finally, cotransformation experiments indicated that, in NHEJ-deficient cells, capture of extranuclear DNA at DSBs was observed if homologies--as short as 8 bp--were present between DNA substrate and DSB ends. Hence, whether driven by NHEJ, microhomology-mediated end-joining, or homologous recombination, DNA capture associated with DSB repair is a mutagenic process threatening genomic stability.
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Affiliation(s)
- Anabelle Decottignies
- Cellular Genetics, Christian de Duve Institute of Cellular Pathology, Catholic University of Louvain, Avenue Hippocrate 74+3, 1200 Brussels, Belgium.
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21
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Kawai K, Yoshida H, Sugimoto A, Fujitsuka M, Majima T. Kinetics of Transient End-to-End Contact of Single-Stranded DNAs. J Am Chem Soc 2005; 127:13232-7. [PMID: 16173752 DOI: 10.1021/ja0524999] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The formation of the pyrene (Py) dimer radical cation (Py(2)(*+)) was used to measure the kinetics of the intrastrand end-to-end contact rates of single-stranded DNAs (ssDNAs) in the 10 nanoseconds to the tens of microseconds time range. ssDNAs labeled with Py at both ends with the lengths of 3, 6, and 9 mer were synthesized, and the two-photon ionization method was employed to generate a Py(*+), which enables the measurements of the end-to-end contact rates from 10 ns. The formation rate of Py(2)(*+) depended on the length and the sequence of the ssDNAs, and about 1 order of magnitude faster rates were observed for the T-rich ssDNAs compared to those for the corresponding length of A-rich ssDNAs, showing that ssDNA made from adenines is much more rigid than that composed of thymidines. As for the T-rich ssDNAs, the formation of Py(2)(*+) attributed to the misfolded structures was also observed, which is consistent with the configurational diffusion model suggested by Ansari and co-workers.
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Affiliation(s)
- Kiyohiko Kawai
- The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Ibaraki, Osaka 567-0047, Japan.
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22
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Takahashi A, Ohnishi T. Does gammaH2AX foci formation depend on the presence of DNA double strand breaks? Cancer Lett 2005; 229:171-9. [PMID: 16129552 DOI: 10.1016/j.canlet.2005.07.016] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 07/10/2005] [Indexed: 10/25/2022]
Abstract
H2AX is a histone variant that is systematically found and ubiquitously distributed throughout the genome. Since it has been reported that DNA double-strand breaks (DSBs) induce phosphorylation of H2AX at serine 139 (gammaH2AX), an immunocytochemical assay with antibodies recognizing gammaH2AX has become the gold standard for the detection of DSBs. This assay is quite sensitive and is a specific indicator for the existence of a DSB. Until now, it has been reported that various kinds of physical, chemical, and biological factors induce the formation of the gammaH2AX foci detected using this assay. Even when gammaH2AX foci were detected, it was not always possible to conclude that the detected DSBs were produced by environmental stresses in the absence of any known radiation. In this review, emphasis is on discussing whether gammaH2AX foci formation depends on the formation of DSBs.
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Affiliation(s)
- Akihisa Takahashi
- Department of Biology, Nara Medical University School of Medicine, Shijo-cho 840, Kashihara, Nara 634-8521, Japan
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23
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Olaru A, Petrie HT, Livák F. Beyond the 12/23 rule of VDJ recombination independent of the Rag proteins. THE JOURNAL OF IMMUNOLOGY 2005; 174:6220-6. [PMID: 15879119 DOI: 10.4049/jimmunol.174.10.6220] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The combinatorial repertoire of AgRs is established through somatic recombination of V, D, and J gene segments during lymphocyte development. Incorporation of D segments into IgH, TCRbeta, and TCRdelta chains also contributes to junctional diversification by substantially extending the length of the third CDR. The V, D, and J gene segments are flanked by recombination signals (RS) of 12- or 23-mer spacer length that direct recombination according to the 12/23 rule. D genes in the TCRbeta and TCRdelta loci are flanked by a 12RS and 23RS, and their incorporation is controlled by mechanisms "beyond the 12/23 rule." In the TCRbeta locus, selective interactions between Rag proteins and the RS flanking the V-D and D-J genes, respectively, are sufficient to enforce D gene usage. In this article, we report that in the TCRdelta locus, the Rag proteins are not the major determinant of D gene incorporation. In developing mouse and human thymocytes, the two Ddelta genes rearrange predominantly to form D-D coding joints. In contrast, when tested in ex vivo transfection assays in a nonlymphoid cell line, the flanking RS mediate deletion, rather than incorporation, of the two D genes on both exogenous recombination substrates and the endogenous locus. These results suggest that selective Rag-RS interactions are not the sole regulators of D gene segment incorporation, and additional, perhaps lymphocyte-specific, mechanisms exist that allow proper shaping of the primary AgR repertoire.
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Affiliation(s)
- Alexandru Olaru
- Department of Microbiology and Immunology, Graduate Program in Molecular and Cellular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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24
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Abstract
Antigen receptor genes exist in the germline in a "split" configuration and are assembled in developing B and T lymphocytes by V(D)J recombination. This site-specific recombination reaction is initiated by a complex containing the RAG1 and RAG2 proteins and completed by general DNA repair factors. RAG1 and RAG2, like the adaptive immune system itself, are found exclusively in jawed vertebrates, and are thought to have entered the vertebrate genome by horizontal transmission as components of a transposable element. This review discusses the structure of antigen receptor genes and the mechanisms by which they are assembled and diversified, and then goes on to consider the evolutionary implications of the arrival of the hypothetical "RAG transposon".
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Affiliation(s)
- David G Schatz
- Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06510, USA.
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25
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Chatterji M, Tsai CL, Schatz DG. New concepts in the regulation of an ancient reaction: transposition by RAG1/RAG2. Immunol Rev 2005; 200:261-71. [PMID: 15242411 DOI: 10.1111/j.0105-2896.2004.00167.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The lymphoid-specific factors, recombination-activating gene 1 (RAG1) and RAG2, initiate V(D)J recombination by introducing DNA double-stand breaks at specific sites in the genome. In addition to this critical endonuclease activity, the RAG proteins catalyze other chemical reactions that can affect the outcome of V(D)J recombination, one of which is transposition. While the transposition activity of the RAG proteins is thought to have been critical for the evolution of modern antigen-receptor loci, it has also been proposed to contribute to chromosomal translocations and lymphoid malignancy. A major challenge has been to determine how the transposition activity of the RAG proteins is regulated in vivo. Although a variety of mechanisms have been suggested by recent studies, a clear resolution of this issue remains elusive.
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Affiliation(s)
- Monalisa Chatterji
- Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA
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26
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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: 17.9] [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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27
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Abstract
First observed in mouse pre-B-cell lines and then in knock-in mice carrying self-reactive IgH transgenes, VH replacement has now been shown to contribute to the primary B-cell repertoire in humans. Through recombination-activating gene (RAG)-mediated recombination between a cryptic recombination signal sequence (RSS) present in almost all VH genes and the flanking 23 base pair RSS of an upstream VH gene, VH replacement renews the entire VH-coding region, while leaving behind a short stretch of nucleotides as a VH replacement footprint. In addition to extending the CDR3 region, the VH replacement footprints preferentially contribute charged amino acids. VH replacement rearrangement in immature B cells may either eliminate a self-reactive B-cell receptor or contribute to the generation of self-reactive antibodies. VH replacement may also rescue non-productive or dysfunctional VHDJH rearrangement in pro-B and pre-B cells. Conversely, VH replacement of a productive immunoglobulin H gene may generate non-productive VH replacement to disrupt or temporarily reverse the B-cell differentiation process. VH replacement can thus play a complex role in the generation of the primary B-cell repertoire.
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Affiliation(s)
- Zhixin Zhang
- Division of Developmental and Clinical Immunology, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA
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28
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Le Deist F, Poinsignon C, Moshous D, Fischer A, de Villartay JP. Artemis sheds new light on V(D)J recombination. Immunol Rev 2004; 200:142-55. [PMID: 15242402 DOI: 10.1111/j.0105-2896.2004.00169.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
V(D)J recombination represents one of the three mechanisms that contribute to the diversity of the immune repertoire of B lymphocytes and T lymphocytes. It also constitutes a major checkpoint during the development of the immune system. Indeed, any V(D)J recombination deficiency leads to a block of B-cell and T-cell maturation in humans and animal models, leading to severe combined immunodeficiency (T-B-SCID). Nine factors have been identified so far to participate in V(D)J recombination. The discovery of Artemis, mutated in a subset of T-B-SCID, provided some new information regarding one of the missing V(D)J recombinase activities: hairpin opening at coding ends prior to DNA repair of the recombination activating genes 1/2-generated DNA double-strand break. New conditions of immune deficiency in humans are now under investigations and should lead to the identification of additional V(D)J recombination/DNA repair factors.
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Affiliation(s)
- Françoise Le Deist
- Développement Normal et Pathologique du Système Immunitaire, INSERM U429, Paris, France
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29
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Abstract
A chromosome fragmentation assay was used to measure the efficiency and genetic control of break-induced replication (BIR) in Saccharomyces cerevisiae. Formation of a chromosome fragment by de novo telomere generation at one end of the linear vector and recombination-dependent replication of 100 kb of chromosomal sequences at the other end of the vector occurred at high frequency in wild-type strains. RAD51 was required for more than 95% of BIR events involving a single-end invasion and was essential when two BIR events were required for generation of a chromosome fragment. The similar genetic requirements for BIR and gene conversion suggest a common strand invasion intermediate in these two recombinational repair processes. Mutation of RAD50 or RAD59 conferred no significant defect in BIR in either RAD51 or rad51 strains. RAD52 was shown to be essential for BIR at unique chromosomal sequences, although rare recombination events were detected between the subtelomeric Y' repeats.
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Affiliation(s)
- Allison P Davis
- Department of Microbiology and Institute of Cancer Research, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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30
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Jiang H, Ross AE, Desiderio S. Cell cycle-dependent accumulation in vivo of transposition-competent complexes between recombination signal ends and full-length RAG proteins. J Biol Chem 2003; 279:8478-86. [PMID: 14660558 DOI: 10.1074/jbc.m311219200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
V(D)J recombination is initiated by a specialized transposase consisting of RAG-1 and RAG-2. Because full-length RAG proteins are insoluble under physiologic conditions, most previous analyses of RAG activity in vitro have used truncated core RAG-1 and RAG-2 fragments. These studies identified an intermediate in V(D)J recombination, the signal end complex (SEC), in which core RAG proteins remain associated with recombination signal sequences at the cleaved signal ends. From transfected cells expressing affinity-tagged RAG proteins, we have isolated in vivo assembled SECs containing full-length RAG proteins and cleaved recombination substrates. SEC formation in vivo did not require the repair proteins DNA-dependent protein kinase, Ku80, or XRCC4. In the presence of full-length RAG-2, SEC formation in vivo was cell cycle-regulated and restricted to the G(0)/G(1) phases. In contrast, complexes accumulated throughout cell cycle in cells expressing a RAG-2 CDK2 phosphorylation site mutant. Both core and full-length SECs supported transposition in vitro with similar efficiencies. Intracellular SECs, which are likely to persist in the absence of coding ends, represent potential donors whose transposition is not suppressed by the non-core regions of the RAG proteins.
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Affiliation(s)
- Hao Jiang
- Department of Molecular Biology and Genetics, Program in Immunology, Institute for Cell Engineering, and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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31
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Lee AI, Fugmann SD, Cowell LG, Ptaszek LM, Kelsoe G, Schatz DG. A functional analysis of the spacer of V(D)J recombination signal sequences. PLoS Biol 2003; 1:E1. [PMID: 14551903 PMCID: PMC212687 DOI: 10.1371/journal.pbio.0000001] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2003] [Accepted: 07/10/2003] [Indexed: 11/18/2022] Open
Abstract
During lymphocyte development, V(D)J recombination assembles antigen receptor genes from component V, D, and J gene segments. These gene segments are flanked by a recombination signal sequence (RSS), which serves as the binding site for the recombination machinery. The murine Jbeta2.6 gene segment is a recombinationally inactive pseudogene, but examination of its RSS reveals no obvious reason for its failure to recombine. Mutagenesis of the Jbeta2.6 RSS demonstrates that the sequences of the heptamer, nonamer, and spacer are all important. Strikingly, changes solely in the spacer sequence can result in dramatic differences in the level of recombination. The subsequent analysis of a library of more than 4,000 spacer variants revealed that spacer residues of particular functional importance are correlated with their degree of conservation. Biochemical assays indicate distinct cooperation between the spacer and heptamer/nonamer along each step of the reaction pathway. The results suggest that the spacer serves not only to ensure the appropriate distance between the heptamer and nonamer but also regulates RSS activity by providing additional RAG:RSS interaction surfaces. We conclude that while RSSs are defined by a "digital" requirement for absolutely conserved nucleotides, the quality of RSS function is determined in an "analog" manner by numerous complex interactions between the RAG proteins and the less-well conserved nucleotides in the heptamer, the nonamer, and, importantly, the spacer. Those modulatory effects are accurately predicted by a new computational algorithm for "RSS information content." The interplay between such binary and multiplicative modes of interactions provides a general model for analyzing protein-DNA interactions in various biological systems.
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Affiliation(s)
- Alfred Ian Lee
- 1Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of MedicineNew Haven, ConnecticutUnited States of America
| | - Sebastian D Fugmann
- 1Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of MedicineNew Haven, ConnecticutUnited States of America
| | - Lindsay G Cowell
- 2Department of Immunology, Duke University Medical CenterDurham, North CarolinaUnited States of America
| | - Leon M Ptaszek
- 3Ruttenberg Cancer Center, Mount Sinai School of Medicine of New York UniversityNew York, New YorkUnited States of America
| | - Garnett Kelsoe
- 2Department of Immunology, Duke University Medical CenterDurham, North CarolinaUnited States of America
| | - David G Schatz
- 1Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of MedicineNew Haven, ConnecticutUnited States of America
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32
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Abstract
Chromosome breakage--a dangerous event that has triggered the evolution of several double-strand break repair pathways--has been co-opted by the immune system as an integral part of B- and T-cell development. This is a daring strategy, as improper repair can be deadly for the cell, if not for the whole organism. Even more daring, however, is the choice of a promiscuous transposase as the nuclease responsible for chromosome breakage, as the possibility of transposition brings an entirely new set of risks. What mechanisms constrain the dangerous potential of the recombinase and preserve genomic integrity during immune-system development?
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Affiliation(s)
- David B Roth
- Department of Pathology, Program in Molecular Pathogenesis, Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York 10016, USA.
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33
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Tsai CL, Schatz DG. Regulation of RAG1/RAG2-mediated transposition by GTP and the C-terminal region of RAG2. EMBO J 2003; 22:1922-30. [PMID: 12682024 PMCID: PMC154477 DOI: 10.1093/emboj/cdg185] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The RAG1 and RAG2 proteins perform critical DNA recognition and cleavage functions in V(D)J recombination, and also catalyze efficient DNA transposition in vitro. No transposition in vivo by the RAG proteins has been reported, suggesting regulation of the reaction by as yet unknown mechanisms. Here we report that RAG-mediated transposition is suppressed by physiological concentrations of the guanine nucleotide GTP, and by the full-length RAG2 protein. Both GTP and full-length RAG2 inhibit transposition by blocking the non-covalent 'capture' of target DNA, and both are capable of inhibiting RAG-mediated hybrid joint formation in vitro. We also observe that another intracellular signaling molecule, Ca(2+), stimulates RAG-mediated transposition and is capable of activating transposition even in reactions containing full-length RAG2 and GTP. RAG-mediated transposition has been proposed to contribute to the chromosomal translocations that underlie the development of lymphoid malignancies, and our findings highlight regulatory mechanisms that might prevent such occurrences, and circumstances in which these regulatory mechanisms could be overcome.
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Affiliation(s)
- Chia-Lun Tsai
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
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34
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Abstract
V(D)J recombination is the specialized DNA rearrangement used by cells of the immune system to assemble immunoglobulin and T-cell receptor genes from the preexisting gene segments. Because there is a large choice of segments to join, this process accounts for much of the diversity of the immune response. Recombination is initiated by the lymphoid-specific RAG1 and RAG2 proteins, which cooperate to make double-strand breaks at specific recognition sequences (recombination signal sequences, RSSs). The neighboring coding DNA is converted to a hairpin during breakage. Broken ends are then processed and joined with the help of several factors also involved in repair of radiation-damaged DNA, including the DNA-dependent protein kinase (DNA-PK) and the Ku, Artemis, DNA ligase IV, and Xrcc4 proteins, and possibly histone H2AX and the Mre11/Rad50/Nbs1 complex. There may be other factors not yet known. V(D)J recombination is strongly regulated by limiting access to RSS sites within chromatin, so that particular sites are available only in certain cell types and developmental stages. The roles of enhancers, histone acetylation, and chromatin remodeling factors in controlling accessibility are discussed. The RAG proteins are also capable of transposing RSS-ended fragments into new DNA sites. This transposition helps to explain the mechanism of RAG action and supports earlier proposals that V(D)J recombination evolved from an ancient mobile DNA element.
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Affiliation(s)
- Martin Gellert
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892-0540, USA.
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35
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Nakajima PB, Bosma MJ. Variable diversity joining recombination: nonhairpin coding ends in thymocytes of SCID and wild-type mice. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:3094-104. [PMID: 12218126 DOI: 10.4049/jimmunol.169.6.3094] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Initiation of V(D)J recombination results in broken DNA molecules with blunt recombination signal ends and covalently sealed (hairpin) coding ends. In SCID mice, coding joint formation is severely impaired and hairpin coding ends accumulate as a result of a deficiency in the catalytic subunit of DNA-dependent protein kinase, an enzyme involved in the repair of DNA double-strand breaks. In this study, we report that not all SCID coding ends are hairpinned. We have detected open Jdelta1 and Ddelta2 coding ends at the TCRdelta locus in SCID thymocytes. Approximately 25% of 5'Ddelta2 coding ends were found to be open. Large deletions and abnormally long P nucleotide additions typical of SCID Ddelta2-Jdelta1 coding joints were not observed. Most Jdelta1 and Ddelta2 coding ends exhibited 3' overhangs, but at least 20% had unique 5' overhangs not previously detected in vivo. We suggest that the SCID DNA-dependent protein kinase deficiency not only reduces the efficiency of hairpin opening, but also may affect the specificity of hairpin nicking, as well as the efficiency of joining open coding ends.
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Affiliation(s)
- Pamela B Nakajima
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
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36
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Jones JM, Gellert M. Ordered assembly of the V(D)J synaptic complex ensures accurate recombination. EMBO J 2002; 21:4162-71. [PMID: 12145216 PMCID: PMC126141 DOI: 10.1093/emboj/cdf394] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recombination of gene segments at the immunoglobulin and T-cell receptor loci requires that the RAG1 and RAG2 proteins bring together DNA signal sequences (RSSs) with 12- and 23-bp spacers into a synaptic complex and cleave the DNA. A RAG1/2 multimer that can cleave both signals is shown to assemble on an isolated RSS, and the complementary RSS enters this complex as naked DNA. When RAG1/2 is allowed to bind 12 and 23 RSSs separately prior to their mixing, synaptic complex assembly and cleavage activity are greatly reduced, indicating that only a complex initially assembled on a single RSS leads to productive cleavage. RAG1/2 complexes assembled on 12 RSSs will only incorporate 23 partners, while complexes assembled on 23 RSSs show a 5- to 6-fold preference for 12 partners. Thus, initial assembly on a 12 RSS most accurately reflects the strict 12/23 coupled cleavage observed in the cell. Additional cellular factors such as chromatin may ensure that RAG1/2 first assembles on a 12 RSS, and then a free 23 RSS enters to activate cleavage.
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Affiliation(s)
- Jessica M Jones
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 5/Room 241, Bethesda, MD 20892, USA
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37
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Neiditch MB, Lee GS, Huye LE, Brandt VL, Roth DB. The V(D)J recombinase efficiently cleaves and transposes signal joints. Mol Cell 2002; 9:871-8. [PMID: 11983177 DOI: 10.1016/s1097-2765(02)00494-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
V(D)J recombination generates two types of products: coding joints, which constitute the rearranged variable regions of antigen receptor genes, and signal joints, which often form on immunologically irrelevant, excised circular molecules that are lost during cell division. It has been widely believed that signal joints simply convert reactive broken DNA ends into safe, inert products. Yet two curious in vivo observations made us question this assumption: signal ends are far more abundant than coding ends, and signal joints form only after RAG expression is downregulated. In fact, we find that signal joints are not at all inert; they are cleaved quite efficiently in vivo and in vitro by a nick-nick mechanism and form an excellent substrate for RAG-mediated transposition in vitro, possibly explaining how genomic stability in lymphocytes may be compromised.
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Affiliation(s)
- Matthew B Neiditch
- Department of Immunology, Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA
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38
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Neiditch MB, Lee GS, Landree MA, Roth DB. RAG transposase can capture and commit to target DNA before or after donor cleavage. Mol Cell Biol 2001; 21:4302-10. [PMID: 11390658 PMCID: PMC87090 DOI: 10.1128/mcb.21.13.4302-4310.2001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The discovery that the V(D)J recombinase functions as a transposase in vitro suggests that transposition by this system might be a potent source of genomic instability. To gain insight into the mechanisms that regulate transposition, we investigated a phenomenon termed target commitment that reflects a functional association between the RAG transposase and the target DNA. We found that the V(D)J recombinase is quite promiscuous, forming productive complexes with target DNA both before and after donor cleavage, and our data indicate that the rate-limiting step for transposition occurs after target capture. Formation of stable target capture complexes depends upon the presence of active-site metal binding residues (the DDE motif), suggesting that active-site amino acids in RAG-1 are critical for target capture. The ability of the RAG transposase to commit to target prior to cleavage may result in a preference for transposition into nearby targets, such as immunoglobulin and T-cell receptor loci. This could bias transposition toward relatively "safe" regions of the genome. A preference for localized transposition may also have influenced the evolution of the antigen receptor loci.
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Affiliation(s)
- M B Neiditch
- Department of Immunology, Baylor College of Medicine, Houston, Texas 77030, USA
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39
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Huye LE, Roth DB. Differential requirements for cis and trans V(D)J cleavage: effects of substrate length. Nucleic Acids Res 2000; 28:4903-11. [PMID: 11121481 PMCID: PMC115234 DOI: 10.1093/nar/28.24.4903] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The assembly of productive synaptic complexes is a critical, but poorly understood, regulatory step in V(D)J recombination. Several lines of evidence suggest that there may be important differences between recombination involving sites situated in cis (on the same DNA molecule) and in trans (on separate molecules). Because biochemical experiments using both purified RAG proteins and crude extracts have failed to detect trans cleavage of plasmid substrates it has been thought that there is a substantial bias against trans synapsis. In conflict with these results are more recent studies showing that purified RAG proteins can catalyze trans cleavage of short oligonucleotide substrates. Furthermore, recent experiments have detected efficient trans cleavage of plasmid substrates in vivo. We sought to investigate why these different systems yield such divergent results. We found that, unexpectedly, the ability of both purified RAG proteins and crude extracts to cleave DNA substrates in trans is a function of substrate length. Our data raise two critical issues: first, oligonucleotides, which are the most commonly used substrates to study V(D)J recombination in vitro, do not mimic the behavior of plasmid substrates; second, in the trans cleavage reaction current purified RAG systems do not accurately reflect the in vivo situation. We propose a unifying model to explain the effects of substrate length and coniguration (cis or trans) on the efficiency of synapsis.
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Affiliation(s)
- L E Huye
- Department of Immunology and Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030, USA
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40
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Kang LE, Symington LS. Aberrant double-strand break repair in rad51 mutants of Saccharomyces cerevisiae. Mol Cell Biol 2000; 20:9162-72. [PMID: 11094068 PMCID: PMC102174 DOI: 10.1128/mcb.20.24.9162-9172.2000] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A number of studies of Saccharomyces cerevisiae have revealed RAD51-independent recombination events. These include spontaneous and double-strand break-induced recombination between repeated sequences, and capture of a chromosome arm by break-induced replication. Although recombination between inverted repeats is considered to be a conservative intramolecular event, the lack of requirement for RAD51 suggests that repair can also occur by a nonconservative mechanism. We propose a model for RAD51-independent recombination by one-ended strand invasion coupled to DNA synthesis, followed by single-strand annealing. The Rad1/Rad10 endonuclease is required to trim intermediates formed during single-strand annealing and thus was expected to be required for RAD51-independent events by this model. Double-strand break repair between plasmid-borne inverted repeats was less efficient in rad1 rad51 double mutants than in rad1 and rad51 strains. In addition, repair events were delayed and frequently associated with plasmid loss. Furthermore, the repair products recovered from the rad1 rad51 strain were primarily in the crossover configuration, inconsistent with conservative models for mitotic double-strand break repair.
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Affiliation(s)
- L E Kang
- Department of Microbiology and Institute of Cancer Research, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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41
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Brown ML, Lew S, Chang Y. The scid recombination-inducible cell line: a model to study DNA-PK-independent V(D)J recombination. Immunol Lett 2000; 75:21-6. [PMID: 11163862 DOI: 10.1016/s0165-2478(00)00283-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
To investigate the molecular mechanisms of the variable (diversity) joining (V(D)J) recombination process at an endogenous gene locus, recombination-inducible cell lines were made from both bcl-2-bearing severe combined immune deficiency (scid) homozygous and scid heterozyous (s/ + ) mice by transforming pre-B cells with the temperature-sensitive Abelson murine leukemia virus (ts-Ab-MLV). These transformants can be induced to undergo immunoglobulin light-chain gene rearrangements by incubating them at the non-permissive temperature. In the case of transformed scid cells, a significant amount of hairpin coding ends are accumulated during recombination induction, but few coding joints are generated. After being shifted to the permissive temperature. however, these cells are capable of opening hairpin ends and forming coding joints. Thus, ts-Ab-MLV transformed scid cells can be readily manipulated for both recombination cleavage and end resolution. However, unlike the rapid coding joint formation in s/ + cells that have the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), the process for resolving coding ends in scid cells is slow and error prone, and also appears to be correlated with a reduction in the RAG1/2 expression. Apparently, this process is mediated by a DNA-PK-independent pathway. The fact that the activity of this pathway can be manipulated in vitro makes it possible to delineate the mechanisms in end opening, processing and joining. Therefore, these ts-Ab-MLV transformed scid cell lines offer a model to study the molecular nature as well as the regulation of the DNA-PK-independent pathway in coding end resolution.
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Affiliation(s)
- M L Brown
- Department of Microbiology, Arizona State University, Tempe 85287-2701, USA
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42
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Livak F, Burtrum DB, Rowen L, Schatz DG, Petrie HT. Genetic modulation of T cell receptor gene segment usage during somatic recombination. J Exp Med 2000; 192:1191-6. [PMID: 11034609 PMCID: PMC2195867 DOI: 10.1084/jem.192.8.1191] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2000] [Accepted: 09/01/2000] [Indexed: 11/04/2022] Open
Abstract
Lymphocyte antigen receptors are not encoded by germline genes, but rather are produced by combinatorial joining between clusters of gene segments in somatic cells. Within a given cluster, gene segment usage during recombination is thought to be largely random, with biased representation in mature T lymphocytes resulting from protein-mediated selection of a subset of the total repertoire. Here we show that T cell receptor D beta and J beta gene segment usage is not random, but is patterned at the time of recombination. The hierarchy of gene segment usage is independent of gene segment proximity, but rather is influenced by the ability of the flanking recombination signal sequences (RSS) to bind the recombinase and/or to form a paired synaptic complex. Importantly, the relative frequency of gene segment usage established during recombination is very similar to that found after protein-mediated selection, suggesting that in addition to targeting recombinase activity, the RSS may have evolved to bias the naive repertoire in favor of useful gene products.
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Affiliation(s)
- F Livak
- Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 08360, USA
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43
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Fugmann SD, Lee AI, Shockett PE, Villey IJ, Schatz DG. The RAG proteins and V(D)J recombination: complexes, ends, and transposition. Annu Rev Immunol 2000; 18:495-527. [PMID: 10837067 DOI: 10.1146/annurev.immunol.18.1.495] [Citation(s) in RCA: 450] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
V(D)J recombination proceeds through a series of protein:DNA complexes mediated in part by the RAG1 and RAG2 proteins. These proteins are responsible for sequence-specific DNA recognition and DNA cleavage, and they appear to perform multiple postcleavage roles in the reaction as well. Here we review the interaction of the RAG proteins with DNA, the chemistry of the cleavage reaction, and the higher order complexes in which these events take place. We also discuss postcleavage functions of the RAG proteins, including recent evidence indicating that they initiate the process of coding end processing by nicking hairpin DNA termini. Finally, we discuss the evolutionary and functional implications of the finding that RAG1 and RAG2 constitute a transposase, and we consider RAG protein biochemistry in the context of several bacterial transposition systems. This suggests a model of the RAG protein active site in which two divalent metal ions serve alternating and opposite roles as activators of attacking hydroxyl groups and stabilizers of oxyanion leaving groups.
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Affiliation(s)
- S D Fugmann
- Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA
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44
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Hansen JD, McBlane JF. Recombination-activating genes, transposition, and the lymphoid-specific combinatorial immune system: a common evolutionary connection. Curr Top Microbiol Immunol 2000; 248:111-35. [PMID: 10793476 DOI: 10.1007/978-3-642-59674-2_6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Affiliation(s)
- J D Hansen
- Basel Institute for Immunology, Switzerland.
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45
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Yoshida T, Tsuboi A, Ishiguro KI, Nagawa F, Sakano H. The DNA-bending protein, HMG1, is required for correct cleavage of 23 bp recombination signal sequences by recombination activating gene proteins in vitro. Int Immunol 2000; 12:721-9. [PMID: 10784618 DOI: 10.1093/intimm/12.5.721] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
DNA-bending proteins are known to facilitate the in vitro V(D)J joining of antigen receptor genes. Here we report that the high-mobility group protein, HMG1, is necessary for the correct nicking of the 23 bp recombination signal sequence (23-RSS) by the recombination [corrected] activating gene (RAG) proteins, RAG1 and RAG2. Without HMG1, the mouse Jkappa1 23-RSS was recognized as if it were the 12-RSS and nicked at a site 12 + 7 nucleotides away from the 9mer signal, even though no 7mer-like sequence was evident at the cryptic nicking site. When increased amounts of HMG1 were added, the 23-RSS substrate was nicked correctly at a site 23 + 7 nucleotides from the 9mer, and nicking at the cryptic site disappeared. Unlike the 23-RSS, the 12-RSS did not require HMG1 for correct nicking, although HMG1 was found to increase the interaction between RSS and RAG proteins. Modification-interference assays demonstrated that HMG1 caused changes in the interaction between the 23-RSS and RAG proteins specifically at the 7mer and the cryptic nicking site.
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Affiliation(s)
- T Yoshida
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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46
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Abstract
V(D)J recombination assembles functional immunoglobulin and T cell receptor genes from individual gene segments [1]. A common recombination mechanism, initiated by the proteins RAG1 and RAG2 at conserved recombination signal sequences (RSSs), operates at all rearranging loci [2] [3]. It has been proposed that the key regulator of the reaction is 'accessibility' of the RSS within chromatin [4]. Recently, the packaging of RSSs into nucleosomes was shown to inhibit initiation of V(D)J recombination [5] [6]. Nevertheless, the tight tissue specificity of regulation cannot be explained by nucleosome-mediated repression alone because a significant fraction of RSSs would be predicted to lie in linker regions between nucleosomes. Therefore, some aspect of the regulation of the recombination reaction must rely on the disruption of higher-order chromatin structure. Here, we report that histone acetylation directly stimulates the recombination reaction in vivo in the correct cell- and stage-specific manner. Neither expression of RAG genes nor activity of RAG proteins was increased by acetylation. Furthermore, histone acetylation failed to overcome nucleosome-mediated repression of RSS recognition and cleavage in vitro. Our data suggest a role for histone acetylation in stimulating recombination in vivo through disruption of higher-order chromatin structures.
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Affiliation(s)
- F McBlane
- Basel Institute for Immunology, Basel, CH-4005, Switzerland.
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47
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Shanmugam A, Shi MJ, Yauch L, Stavnezer J, Kenter AL. Evidence for class-specific factors in immunoglobulin isotype switching. J Exp Med 2000; 191:1365-80. [PMID: 10770803 PMCID: PMC2193137 DOI: 10.1084/jem.191.8.1365] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/1999] [Accepted: 01/21/2000] [Indexed: 11/04/2022] Open
Abstract
Immunoglobulin class switch recombination (SR) occurs by a B cell-specific, intrachromosomal deletional process between switch regions. We have developed a plasmid-based transient transfection assay for SR to test for the presence of transacting switch activities. The plasmids are novel in that they lack a eukaryotic origin of DNA replication. The recombination activity of these switch substrates is restricted to a subset of B cell lines that support isotype switching on their endogenous loci and to mitogen-activated normal splenic B cells. The factors required for extrachromosomal plasmid recombination are constitutively expressed in proliferating splenic B cells and in B cell lines capable of inducibly undergoing immunoglobulin SR on their chromosomal genes. These studies suggest that mitogens that induce switching on the chromosome induce accessibility rather than switch recombinase activity. Finally, we provide evidence for two distinct switching activities which independently mediate mu-->alpha and mu-->gamma3 SR.
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Affiliation(s)
- Ananth Shanmugam
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612
| | - Meng-Jiao Shi
- Department of Molecular Genetics and Microbiology and the Program in Immunology and Virology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
| | - Lauren Yauch
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612
| | - Janet Stavnezer
- Department of Molecular Genetics and Microbiology and the Program in Immunology and Virology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
| | - Amy L. Kenter
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612
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48
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Abstract
V(D)J recombination plays a prominent role in the generation of the antigen receptor repertoires of B and T lymphocytes. It is also likely to be involved in the formation of chromosomal translocations, some of which may result from interchromosomal recombination. We have investigated the potential of the V(D)J recombination machinery to perform intermolecular recombination between two plasmids, either unlinked or linked by catenation. In either case, recombination occurs in trans to yield signal and coding joints, and the results do not support the existence of a mechanistic block to the formation of coding joints in trans. Instead, we observe that linearization of the substrate, which does not alter the cis or trans status of the recombination signals, causes a specific and dramatic reduction in coding joint formation. This unexpected result leads us to propose a "release and recapture" model for V(D)J recombination in which coding ends are frequently released from the postcleavage complex and the efficiency of coding joint formation is influenced by the efficiency with which such ends are recaptured by the complex. This implies the existence of mechanisms, operative during recombination of chromosomal substrates, that act to prevent coding end release or to facilitate coding end recapture.
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Affiliation(s)
- A Tevelev
- Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA
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49
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Wang C, Bogue MA, Nguyen AP, Roth DB. Irradiation-Induced Rescue of Thymocyte Differentiation and V(D)J Recombination in Mice Lacking the Catalytic Subunit of DNA-Dependent Protein Kinase. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.11.6065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Scid mice express a truncated form of the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) and are unable to properly rearrange their Ig and TCR genes, resulting in a severe combined immunodeficiency that is characterized by arrested differentiation of B and T lymphocytes. Treatment of scid mice with low doses of gamma irradiation rescues rearrangements at several TCR loci and promotes limited thymocyte differentiation. The machinery responsible for sensing DNA damage and the mechanism by which irradiation compensates for the scid defect in TCR recombination remain unknown. Because DNA-PKcs is present in scid thymocytes, it may mediate some or all of the irradiation effects. To test this hypothesis, we examined the effects of irradiation on DNA-PKcs-deficient (slip) mice. Our data provide the first evidence that DNA-PKcs is not required for limited rescue of thymocyte differentiation or TCR rearrangements.
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Affiliation(s)
- Chiyu Wang
- *Department of Microbiology and Immunology and
| | | | | | - David B. Roth
- *Department of Microbiology and Immunology and
- †Howard Hughes Medical Institute, Baylor College of Medicine, Houston, TX 77030
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50
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Schatz DG. Transposition mediated by RAG1 and RAG2 and the evolution of the adaptive immune system. Immunol Res 1999; 19:169-82. [PMID: 10493171 DOI: 10.1007/bf02786485] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The RAG1 and RAG2 proteins together initiate V(D)J recombination by performing cleavage of chromosomal DNA adjacent to antigen receptor gene segments. Like the adaptive immune system itself, RAG1 and RAG2 are found only in jawed vertebrates. The hypothesis that RAG1 and RAG2 arose in evolution as components of a transposable element has received dramatic support from our recent finding that the RAG proteins are a fully functional transposase in vitro. This result strongly suggests that antigen receptor genes acquired their unusual structure as a consequence of the insertion of a transposable element into an ancestral receptor gene by RAG1 and RAG2 approx 450 million years ago.
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Affiliation(s)
- D G Schatz
- Yale University School of Medicine, New Haven, CT 06520-8011, USA.
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