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Lefranc MP, Lefranc G. Immunoglobulins or Antibodies: IMGT ® Bridging Genes, Structures and Functions. Biomedicines 2020; 8:E319. [PMID: 32878258 PMCID: PMC7555362 DOI: 10.3390/biomedicines8090319] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 08/23/2020] [Accepted: 08/25/2020] [Indexed: 12/18/2022] Open
Abstract
IMGT®, the international ImMunoGeneTics® information system founded in 1989 by Marie-Paule Lefranc (Université de Montpellier and CNRS), marked the advent of immunoinformatics, a new science at the interface between immunogenetics and bioinformatics. For the first time, the immunoglobulin (IG) or antibody and T cell receptor (TR) genes were officially recognized as 'genes' as well as were conventional genes. This major breakthrough has allowed the entry, in genomic databases, of the IG and TR variable (V), diversity (D) and joining (J) genes and alleles of Homo sapiens and of other jawed vertebrate species, based on the CLASSIFICATION axiom. The second major breakthrough has been the IMGT unique numbering and the IMGT Collier de Perles for the V and constant (C) domains of the IG and TR and other proteins of the IG superfamily (IgSF), based on the NUMEROTATION axiom. IMGT-ONTOLOGY axioms and concepts bridge genes, sequences, structures and functions, between biological and computational spheres in the IMGT® system (Web resources, databases and tools). They provide the IMGT Scientific chart rules to identify, to describe and to analyse the IG complex molecular data, the huge diversity of repertoires, the genetic (alleles, allotypes, CNV) polymorphisms, the IG dual function (paratope/epitope, effector properties), the antibody humanization and engineering.
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Affiliation(s)
- Marie-Paule Lefranc
- IMGT, The International ImMunoGeneTics Information System, Laboratoire d’ImmunoGénétique Moléculaire LIGM, Institut de Génétique Humaine IGH, Université de Montpellier UM, Centre National de la Recherche Scientifique CNRS, UMR 9002 CNRS-UM, 141 Rue de la Cardonille, CEDEX 5, 34396 Montpellier, France
| | - Gérard Lefranc
- IMGT, The International ImMunoGeneTics Information System, Laboratoire d’ImmunoGénétique Moléculaire LIGM, Institut de Génétique Humaine IGH, Université de Montpellier UM, Centre National de la Recherche Scientifique CNRS, UMR 9002 CNRS-UM, 141 Rue de la Cardonille, CEDEX 5, 34396 Montpellier, France
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2
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Lambert JM, Srour N, Delpy L. The Yin and Yang of RNA surveillance in B lymphocytes and antibody-secreting plasma cells. BMB Rep 2019. [PMID: 31619318 PMCID: PMC6941761 DOI: 10.5483/bmbrep.2019.52.12.232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The random V(D)J recombination process ensures the diversity of the primary immunoglobulin (Ig) repertoire. In two thirds of cases, imprecise recombination between variable (V), diversity (D), and joining (J) segments induces a frameshift in the open reading frame that leads to the appearance of premature termination codons (PTCs). Thus, many B lineage cells harbour biallelic V(D)J-rearrangements of Ig heavy or light chain genes, with a productively-recombined allele encoding the functional Ig chain and a nonproductive allele potentially encoding truncated Ig polypeptides. Since the pattern of Ig gene expression is mostly biallelic, transcription initiated from nonproductive Ig alleles generates considerable amounts of primary transcripts with out-of-frame V(D)J junctions. How RNA surveillance pathways cooperate to control the noise from nonproductive Ig genes will be discussed in this review, focusing on the benefits of nonsense-mediated mRNA decay (NMD) activation during B-cell development and detrimental effects of nonsense-associated altered splicing (NAS) in terminally differentiated plasma cells.
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Affiliation(s)
- Jean-Marie Lambert
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
| | - Nivine Srour
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
| | - Laurent Delpy
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
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3
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Bétermier M, Bertrand P, Lopez BS. Is non-homologous end-joining really an inherently error-prone process? PLoS Genet 2014; 10:e1004086. [PMID: 24453986 PMCID: PMC3894167 DOI: 10.1371/journal.pgen.1004086] [Citation(s) in RCA: 280] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
DNA double-strand breaks (DSBs) are harmful lesions leading to genomic instability or diversity. Non-homologous end-joining (NHEJ) is a prominent DSB repair pathway, which has long been considered to be error-prone. However, recent data have pointed to the intrinsic precision of NHEJ. Three reasons can account for the apparent fallibility of NHEJ: 1) the existence of a highly error-prone alternative end-joining process; 2) the adaptability of canonical C-NHEJ (Ku- and Xrcc4/ligase IV-dependent) to imperfect complementary ends; and 3) the requirement to first process chemically incompatible DNA ends that cannot be ligated directly. Thus, C-NHEJ is conservative but adaptable, and the accuracy of the repair is dictated by the structure of the DNA ends rather than by the C-NHEJ machinery. We present data from different organisms that describe the conservative/versatile properties of C-NHEJ. The advantages of the adaptability/versatility of C-NHEJ are discussed for the development of the immune repertoire and the resistance to ionizing radiation, especially at low doses, and for targeted genome manipulation.
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Affiliation(s)
- Mireille Bétermier
- CNRS, Centre de Génétique Moléculaire, UPR3404, Gif-sur-Yvette, France
- CNRS, Centre de Recherches de Gif-sur-Yvette, FRC3115, Gif-sur-Yvette, France
- Université Paris-Sud, Département de Biologie, Orsay, France
| | - Pascale Bertrand
- CEA, DSV, Institut de Radiobiologie Moléculaire et Cellulaire, Laboratoire Réparation et Vieillissement, Fontenay-aux-Roses, France
- UMR 8200 CNRS, Villejuif, France
| | - Bernard S. Lopez
- Université Paris-Sud, Département de Biologie, Orsay, France
- UMR 8200 CNRS, Villejuif, France
- Institut de Cancérologie, Gustave Roussy, Villejuif, France
- * E-mail:
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4
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Goodarzi AA, Jeggo PA. The repair and signaling responses to DNA double-strand breaks. ADVANCES IN GENETICS 2013; 82:1-45. [PMID: 23721719 DOI: 10.1016/b978-0-12-407676-1.00001-9] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A DNA double-strand break (DSB) has long been recognized as a severe cellular lesion, potentially representing an initiating event for carcinogenesis or cell death. The evolution of DSB repair pathways as well as additional processes, such as cell cycle checkpoint arrest, to minimize the cellular impact of DSB formation was, therefore, not surprising. However, the depth and complexity of the DNA damage responses being revealed by current studies were unexpected. Perhaps the most surprising finding to emerge is the dramatic changes to chromatin architecture that arise in the DSB vicinity. In this review, we overview the cellular response to DSBs focusing on DNA repair pathways and the interface between them. We consider additional events which impact upon these DSB repair pathways, including regulated arrest of cell cycle progression and chromatin architecture alterations. Finally, we discuss the impact of defects in these processes to human disease.
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Affiliation(s)
- Aaron A Goodarzi
- Department of Biochemistry & Molecular Biology, Southern Alberta Cancer Research Institute, University of Calgary, Calgary, Alberta, Canada
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Boubakour-Azzouz I, Bertrand P, Claes A, Lopez BS, Rougeon F. Terminal deoxynucleotidyl transferase requires KU80 and XRCC4 to promote N-addition at non-V(D)J chromosomal breaks in non-lymphoid cells. Nucleic Acids Res 2012; 40:8381-91. [PMID: 22740656 PMCID: PMC3458542 DOI: 10.1093/nar/gks585] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Terminal deoxynucleotidyl transferase (TdT) is a DNA polymerase that increases the repertoire of antigen receptors by adding non-templated nucleotides (N-addition) to V(D)J recombination junctions. Despite extensive in vitro studies on TdT catalytic activity, the partners of TdT that enable N-addition remain to be defined. Using an intrachromosomal substrate, we show here that, in Chinese hamter ovary (CHO) cells, ectopic expression of TdT efficiently promotes N-additions at the junction of chromosomal double-strand breaks (DSBs) generated by the meganuclease I-SceI and that the size of the N-additions is comparable with that at V(D)J junctions. Importantly, no N-addition was observed in KU80- or XRCC4-deficient cells. These data show that, in a chromosomal context of non-lymphoid cells, TdT is actually able to promote N-addition at non-V(D)J DSBs, through a process that strictly requires the components of the canonical non-homologous end-joining pathway, KU80 and XRCC4.
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Parra ZE, Lillie M, Miller RD. A model for the evolution of the mammalian t-cell receptor α/δ and μ loci based on evidence from the duckbill Platypus. Mol Biol Evol 2012; 29:3205-14. [PMID: 22593227 PMCID: PMC3457774 DOI: 10.1093/molbev/mss128] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The specific recognition of antigen by T cells is critical to the generation of adaptive immune responses in vertebrates. T cells recognize antigen using a somatically diversified T-cell receptor (TCR). All jawed vertebrates use four TCR chains called α, β, γ, and δ, which are expressed as either a αβ or γδ heterodimer. Nonplacental mammals (monotremes and marsupials) are unusual in that their genomes encode a fifth TCR chain, called TCRµ, whose function is not known but is also somatically diversified like the conventional chains. The origins of TCRµ are also unclear, although it appears distantly related to TCRδ. Recent analysis of avian and amphibian genomes has provided insight into a model for understanding the evolution of the TCRδ genes in tetrapods that was not evident from humans, mice, or other commonly studied placental (eutherian) mammals. An analysis of the genes encoding the TCRδ chains in the duckbill platypus revealed the presence of a highly divergent variable (V) gene, indistinguishable from immunoglobulin heavy (IgH) chain V genes (VH) and related to V genes used in TCRµ. They are expressed as part of TCRδ repertoire (VHδ) and similar to what has been found in frogs and birds. This, however, is the first time a VHδ has been found in a mammal and provides a critical link in reconstructing the evolutionary history of TCRµ. The current structure of TCRδ and TCRµ genes in tetrapods suggests ancient and possibly recurring translocations of gene segments between the IgH and TCRδ genes, as well as translocations of TCRδ genes out of the TCRα/δ locus early in mammals, creating the TCRµ locus.
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Affiliation(s)
- Zuly E Parra
- Department of Biology, Center for Evolutionary & Theoretical Immunology, University of New Mexico
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Hwang BJ, Kuttamperoor F, Wu J, Steinberg ML. Spectrum of mitochondrial DNA deletions within the common deletion region induced by low levels of UVB irradiation of human keratinocytes in vitro. Gene 2009; 440:23-7. [PMID: 19345726 PMCID: PMC2706008 DOI: 10.1016/j.gene.2009.03.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 03/25/2009] [Accepted: 03/26/2009] [Indexed: 11/30/2022]
Abstract
We show that a single low-dose exposure of human epidermal keratinocytes (NHEK) to an FS20 light source in vitro can induce the formation of mitochondrial DNA deletions in a PCR detection assay. We used primer sets specifically designed to exclude amplification of segments containing the common deletion, but which could detect possibly lower abundance deletions generated within the same region of the mitochondrial genome. We characterized eight novel deletions of which six were generated from cut sites within, or adjacent to, short direct repeats. Two deletions involved cut sites in inverted tetrameric repeats; one of these also involved an insertion.
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Affiliation(s)
- Bor-Jang Hwang
- Department of Chemistry, The City College of the City University of New York, New York, NY 10031
| | - Francis Kuttamperoor
- Department of Chemistry, The City College of the City University of New York, New York, NY 10031
| | - Julia Wu
- Department of Chemistry, The City College of the City University of New York, New York, NY 10031
| | - Mark L. Steinberg
- Department of Chemistry, The City College of the City University of New York, New York, NY 10031
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8
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Bleakley K, Lefranc MP, Biau G. Recovering probabilities for nucleotide trimming processes for T cell receptor TRA and TRG V-J junctions analyzed with IMGT tools. BMC Bioinformatics 2008; 9:408. [PMID: 18831754 PMCID: PMC2576266 DOI: 10.1186/1471-2105-9-408] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 10/02/2008] [Indexed: 11/21/2022] Open
Abstract
Background Nucleotides are trimmed from the ends of variable (V), diversity (D) and joining (J) genes during immunoglobulin (IG) and T cell receptor (TR) rearrangements in B cells and T cells of the immune system. This trimming is followed by addition of nucleotides at random, forming the N regions (N for nucleotides) of the V-J and V-D-J junctions. These processes are crucial for creating diversity in the immune response since the number of trimmed nucleotides and the number of added nucleotides vary in each B or T cell. IMGT® sequence analysis tools, IMGT/V-QUEST and IMGT/JunctionAnalysis, are able to provide detailed and accurate analysis of the final observed junction nucleotide sequences (tool "output"). However, as trimmed nucleotides can potentially be replaced by identical N region nucleotides during the process, the observed "output" represents a biased estimate of the "true trimming process." Results A probabilistic approach based on an analysis of the standardized tool "output" is proposed to infer the probability distribution of the "true trimmming process" and to provide plausible biological hypotheses explaining this process. We collated a benchmark dataset of TR alpha (TRA) and TR gamma (TRG) V-J rearranged sequences and junctions analysed with IMGT/V-QUEST and IMGT/JunctionAnalysis, the nucleotide sequence analysis tools from IMGT®, the international ImMunoGeneTics information system®, . The standardized description of the tool output is based on the IMGT-ONTOLOGY axioms and concepts. We propose a simple first-order model that attempts to transform the observed "output" probability distribution into an estimate closer to the "true trimming process" probability distribution. We use this estimate to test the hypothesis that Poisson processes are involved in trimming. This hypothesis was not rejected at standard confidence levels for three of the four trimming processes: TRAV, TRAJ and TRGV. Conclusion By using trimming of rearranged TR genes as a benchmark, we show that a probabilistic approach, applied to IMGT® standardized tool "outputs" opens the way to plausible hypotheses on the events involved in the "true trimming process" and eventually to an exact quantification of trimming itself. With increasing high-throughput of standardized immunogenetics data, similar probabilistic approaches will improve understanding of processes so far only characterized by the "output" of standardized tools.
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Affiliation(s)
- Kevin Bleakley
- Institut Curie, Centre de Recherche, Paris, F-75248, France.
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9
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Abstract
DNA palindromes are a source of instability in eukaryotic genomes but remain under-investigated because they are difficult to study. Nonetheless, progress in the last year or so has begun to form a coherent picture of how DNA palindromes cause damage in eukaryotes and how this damage is opposed by cellular mechanisms. In yeast, the features of double strand DNA interruptions that appear at palindromic sites in vivo suggest that a resolvase-type activity creates the fractures by attacking a palindrome after it extrudes into a cruciform structure. Induction of DNA breaks in this fashion could be deterred through a Center-Break palindrome revision process as investigated in detail in mice. The MRX/MRN likely plays a pivotal role in prevention of palindrome-induced genome damage in eukaryotes.
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Affiliation(s)
- Susanna M Lewis
- Graduate Department of Molecular and Medical Genetics, University of Toronto, Ont., Canada.
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10
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Abstract
RAG1 and RAG2 cleave DNA to generate blunt signal ends and hairpin coding ends at antigen receptor loci in lymphoid cells. During V(D)J recombination, repair of these RAG-generated double-strand breaks (DSBs) by the nonhomologous end-joining (NHEJ) pathway contributes substantially to the antigen receptor diversity necessary for immune system function, although recent evidence also supports the ability of RAG-generated breaks to undergo homology-directed repair (HDR). We have determined that RAG-generated chromosomal breaks can be repaired by pathways other than NHEJ in mouse embryonic stem (ES) cells, although repair by these pathways occurs at a significantly lower frequency than NHEJ. HDR frequency was estimated to be >or=40-fold lower than NHEJ frequency for both coding end and signal end reporters. Repair by single-strand annealing was estimated to occur at a comparable or lower frequency than HDR. As expected, V(D)J recombination was substantially impaired in cells deficient for the NHEJ components Ku70, XRCC4, and DNA-PKcs. Concomitant with decreased NHEJ, RAG-induced HDR was increased in each of the mutants, including cells lacking DNA-PKcs, which has been implicated in hairpin opening. HDR was increased to the largest extent in Ku70-/- cells, implicating the Ku70/80 DNA end-binding protein in regulating pathway choice. Thus, RAG-generated DSBs are typically repaired by the NHEJ pathway in ES cells, but in the absence of NHEJ components, a substantial fraction of breaks can be efficiently channeled into alternative pathways in these cells.
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Affiliation(s)
- David M Weinstock
- Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA
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11
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Abstract
The genes that encode immunoglobulin and T cell receptor proteins are assembled from component gene segments in a reaction known as V(D)J recombination. The reaction, and its crucial mediators RAG1 and RAG2, are essential for lymphocyte development and hence for adaptive immunity. Here we consider the biochemistry of this reaction, focusing on the DNA transactions and the proteins involved. We discuss how the RAG proteins interact with DNA and how coordinate cleavage of the DNA at two sites might be achieved. Finally, we consider the RAG proteins and V(D)J recombination from an evolutionary point of view.
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Affiliation(s)
- D G Schatz
- Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520-8011, USA.
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12
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Dudley DD, Chaudhuri J, Bassing CH, Alt FW. Mechanism and control of V(D)J recombination versus class switch recombination: similarities and differences. Adv Immunol 2006; 86:43-112. [PMID: 15705419 DOI: 10.1016/s0065-2776(04)86002-4] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
V(D)J recombination is the process by which the variable region exons encoding the antigen recognition sites of receptors expressed on B and T lymphocytes are generated during early development via somatic assembly of component gene segments. In response to antigen, somatic hypermutation (SHM) and class switch recombination (CSR) induce further modifications of immunoglobulin genes in B cells. CSR changes the IgH constant region for an alternate set that confers distinct antibody effector functions. SHM introduces mutations, at a high rate, into variable region exons, ultimately allowing affinity maturation. All of these genomic alteration processes require tight regulatory control mechanisms, both to ensure development of a normal immune system and to prevent potentially oncogenic processes, such as translocations, caused by errors in the recombination/mutation processes. In this regard, transcription of substrate sequences plays a significant role in target specificity, and transcription is mechanistically coupled to CSR and SHM. However, there are many mechanistic differences in these reactions. V(D)J recombination proceeds via precise DNA cleavage initiated by the RAG proteins at short conserved signal sequences, whereas CSR and SHM are initiated over large target regions via activation-induced cytidine deaminase (AID)-mediated DNA deamination of transcribed target DNA. Yet, new evidence suggests that AID cofactors may help provide an additional layer of specificity for both SHM and CSR. Whereas repair of RAG-induced double-strand breaks (DSBs) involves the general nonhomologous end-joining DNA repair pathway, and CSR also depends on at least some of these factors, CSR requires induction of certain general DSB response factors, whereas V(D)J recombination does not. In this review, we compare and contrast V(D)J recombination and CSR, with particular emphasis on the role of the initiating enzymes and DNA repair proteins in these processes.
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Affiliation(s)
- Darryll D Dudley
- Howard Hughes Medical Institute, The Children's Hospital Boston, CBR Institute for Biomedical Research, and Harvard Medical School, Boston, MA 02115, USA
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van der Burg M, van Veelen LR, Verkaik NS, Wiegant WW, Hartwig NG, Barendregt BH, Brugmans L, Raams A, Jaspers NGJ, Zdzienicka MZ, van Dongen JJM, van Gent DC. A new type of radiosensitive T-B-NK+ severe combined immunodeficiency caused by a LIG4 mutation. J Clin Invest 2005; 116:137-45. [PMID: 16357942 PMCID: PMC1312018 DOI: 10.1172/jci26121] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Accepted: 10/18/2005] [Indexed: 12/30/2022] Open
Abstract
V(D)J recombination of Ig and TCR loci is a stepwise process during which site-specific DNA double-strand breaks (DSBs) are made by RAG1/RAG2, followed by DSB repair by nonhomologous end joining. Defects in V(D)J recombination result in SCID characterized by absence of mature B and T cells. A subset of T-B-NK+ SCID patients is sensitive to ionizing radiation, and the majority of these patients have mutations in Artemis. We present a patient with a new type of radiosensitive T-B-NK+ SCID with a defect in DNA ligase IV (LIG4). To date, LIG4 mutations have only been described in a radiosensitive leukemia patient and in 4 patients with a designated LIG4 syndrome, which is associated with chromosomal instability, pancytopenia, and developmental and growth delay. The patient described here shows that a LIG4 mutation can also cause T-B-NK+ SCID without developmental defects. The LIG4-deficient SCID patient had an incomplete but severe block in precursor B cell differentiation, resulting in extremely low levels of blood B cells. The residual D(H)-J(H) junctions showed extensive nucleotide deletions, apparently caused by prolonged exonuclease activity during the delayed D(H)-J(H) ligation process. In conclusion, different LIG4 mutations can result in either a developmental defect with minor immunological abnormalities or a SCID picture with normal development.
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Affiliation(s)
- Mirjam van der Burg
- Department of Immunology and Department of Cell Biology and Genetics, Erasmus Medical Center, Rotterdam, The Netherlands
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14
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Lewis SM, Chen S, Strathern JN, Rattray AJ. New approaches to the analysis of palindromic sequences from the human genome: evolution and polymorphism of an intronic site at the NF1 locus. Nucleic Acids Res 2005; 33:e186. [PMID: 16340004 PMCID: PMC1310899 DOI: 10.1093/nar/gni189] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The nature of any long palindrome that might exist in the human genome is obscured by the instability of such sequences once cloned in Escherichia coli. We describe and validate a practical alternative to the analysis of naturally-occurring palindromes based upon cloning and propagation in Saccharomyces cerevisiae. With this approach we have investigated an intronic sequence in the human Neurofibromatosis 1 (NF1) locus that is represented by multiple conflicting versions in GenBank. We find that the site is highly polymorphic, exhibiting different degrees of palindromy in different individuals. A side-by-side comparison of the same plasmids in E.coli versus. S.cerevisiae demonstrated that the more palindromic alleles were inevitably corrupted upon cloning in E.coli, but could be propagated intact in yeast. The high quality sequence obtained from the yeast-based approach provides insight into the various mechanisms that destabilize a palindrome in E.coli, yeast and humans, into the diversification of a highly polymorphic site within the NF1 locus during primate evolution, and into the association between palindromy and chromosomal translocation.
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Affiliation(s)
- Susanna M Lewis
- Program in Genetics and Genomic Biology, Hospital for Sick Children Research Institute, Toronto, ON, Canada.
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15
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Raghavan SC, Tong J, Lieber MR. Hybrid joint formation in human V(D)J recombination requires nonhomologous DNA end joining. DNA Repair (Amst) 2005; 5:278-85. [PMID: 16275127 DOI: 10.1016/j.dnarep.2005.09.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Revised: 09/07/2005] [Accepted: 09/13/2005] [Indexed: 10/25/2022]
Abstract
In V(D)J recombination, the RAG proteins bind at a pair of signal sequences adjacent to the V, D, or J coding regions and cleave the DNA, resulting in two signal ends and two hairpinned coding ends. The two coding ends are joined to form a coding joint, and the two signal ends are joined to form a signal joint; this joining is done by the nonhomologous DNA end joining (NHEJ) pathway. A recombinational alternative in which a signal end is recombined with a coding end can also occur in a small percentage of the V(D)J recombination events in murine and human cells, and these are called hybrids (or hybrid joints). Two mechanisms have been proposed for the formation of these hybrids. One mechanism is via NHEJ, after initial cutting by RAGs. The second mechanism does not rely on NHEJ, but rather invokes that the RAGs can catalyze joining of the signal to the hairpinned coding end, by using the 3'OH of the signal end as a nucleophile to attack the phosphodiester bonds of the hairpinned coding end. In the present study, we addressed the question of which type of hybrid joining occurs in a physiological environment, where standard V(D)J recombination presumably occurs and normal RAG proteins are endogenously expressed. We find that all hybrids in vivo require DNA ligase IV in human cells, which is the final component of the NHEJ pathway. Hence, hybrid joints rely on NHEJ rather than on the RAG complex for joining.
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Affiliation(s)
- Sathees C Raghavan
- USC Norris Comprehensive Cancer Center Room 5428, Department of Pathology, Biochemistry & Molecular Biology, University of Southern California, Keck School of Medicine, 1441 Eastlake Avenue, MC9176, Los Angeles, CA 90033, USA
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16
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Abstract
Hairpin DNA ends are evolutionarily conserved intermediates in DNA recombination. The hairpin structures present on the ends of the adeno-associated virus (AAV) genome are substrates for recombination that give rise to persistent circular and concatemeric DNA episomes through intramolecular and intermolecular recombination, respectively. We have developed circularization-dependent and orientation-specific self-complementary AAV (scAAV) vectors as a reporter system to examine recombination events involving distinct hairpin structures, i.e., closed versus open hairpins. The results suggest that intramolecular recombination (circularization) is far more efficient than intermolecular recombination (concatemerization). Among all possible combinations of terminal repeats (TRs) involved in intermolecular recombination, the closed-closed TR structures are twice as efficient as the open-open TR substrates for recombination. In addition, both intramolecular recombination and intermolecular recombination exhibit the common dependency on specific DNA polymerases and topoisomerases. The circularization-dependent and orientation-specific scAAV vectors can serve as an efficient and controlled system for the delivery of DNA structures that mimic mammalian recombination intermediates and should be useful in assaying recombination in different experimental settings as well as elucidating the molecular mechanism of recombinant AAV genome persistence.
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MESH Headings
- Aphidicolin/pharmacology
- Base Sequence
- Camptothecin/pharmacology
- DNA Topoisomerases, Type I/metabolism
- DNA Topoisomerases, Type II/metabolism
- DNA, Circular/chemistry
- DNA, Circular/genetics
- DNA, Circular/metabolism
- DNA, Viral/chemistry
- DNA, Viral/genetics
- DNA, Viral/metabolism
- Dependovirus/chemistry
- Dependovirus/genetics
- Etoposide/pharmacology
- Genes, Reporter
- Genetic Vectors
- Genome, Viral
- HeLa Cells
- Humans
- Hydroxyurea/pharmacology
- Nucleic Acid Conformation/drug effects
- Recombination, Genetic
- Terminal Repeat Sequences
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Affiliation(s)
- Vivian W Choi
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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17
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Nick McElhinny SA, Ramsden DA. Sibling rivalry: competition between Pol X family members in V(D)J recombination and general double strand break repair. Immunol Rev 2005; 200:156-64. [PMID: 15242403 DOI: 10.1111/j.0105-2896.2004.00160.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nonhomologous end-joining pathway is a major means for repairing double-strand breaks (DSBs) in all mitotic cell types. This repair pathway is also the only efficient means for resolving DSB intermediates in V(D)J recombination, a lymphocyte-specific genome rearrangement required for assembly of antigen receptors. A role for polymerases in end-joining has been well established. They are a major factor in determining the character of repair junctions but, in contrast to 'core' end-joining factors, typically appear to have a subtle impact on the efficiency of end-joining. Recent work implicates several members of the Pol X family in end-joining and suggests surprising complexity in the control of how these different polymerases are employed in this pathway.
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Affiliation(s)
- Stephanie A Nick McElhinny
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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18
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Jackson KJL, Gaeta B, Sewell W, Collins AM. Exonuclease activity and P nucleotide addition in the generation of the expressed immunoglobulin repertoire. BMC Immunol 2004; 5:19. [PMID: 15345030 PMCID: PMC517710 DOI: 10.1186/1471-2172-5-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Accepted: 09/02/2004] [Indexed: 12/03/2022] Open
Abstract
Background Immunoglobulin rearrangement involves random and imprecise processes that act to both create and constrain diversity. Two such processes are the loss of nucleotides through the action of unknown exonuclease(s) and the addition of P nucleotides. The study of such processes has been compromised by difficulties in reliably aligning immunoglobulin genes and in the partitioning of nucleotides between segment ends, and between N and P nucleotides. Results A dataset of 294 human IgM sequences was created and partitioned with the aid of a probabilistic model. Non-random removal of nucleotides is seen between the three IGH gene types with the IGHV gene averaging removals of 1.2 nucleotides compared to 4.7 for the other gene ends (p < 0.001). Individual IGHV, IGHD and IGHJ gene subgroups also display statistical differences in the level of nucleotide loss. For example, within the IGHJ group, IGHJ3 has average removals of 1.3 nucleotides compared to 6.4 nucleotides for IGHJ6 genes (p < 0.002). Analysis of putative P nucleotides within the IgM and pooled datasets revealed only a single putative P nucleotide motif (GTT at the 3' D-REGION end) to occur at a frequency significantly higher then would be expected from random N nucleotide addition. Conclusions The loss of nucleotides due to the action of exonucleases is not random, but is influenced by the nucleotide composition of the genes. P nucleotides do not make a significant contribution to diversity of immunoglobulin sequences. Although palindromic sequences are present in 10% of immunologlobulin rearrangements, most of the 'palindromic' nucleotides are likely to have been inserted into the junction during the process of N nucleotide addition. P nucleotides can only be stated with confidence to contribute to diversity of less than 1% of sequences. Any attempt to identify P nucleotides in immunoglobulins is therefore likely to introduce errors into the partitioning of such sequences.
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Affiliation(s)
- Katherine JL Jackson
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Bruno Gaeta
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - William Sewell
- Garvan Institute of Medical Research, Sydney, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney, Australia
| | - Andrew M Collins
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
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19
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Cunningham LA, Coté AG, Cam-Ozdemir C, Lewis SM. Rapid, stabilizing palindrome rearrangements in somatic cells by the center-break mechanism. Mol Cell Biol 2003; 23:8740-50. [PMID: 14612414 PMCID: PMC262683 DOI: 10.1128/mcb.23.23.8740-8750.2003] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2003] [Revised: 08/11/2003] [Accepted: 08/28/2003] [Indexed: 02/01/2023] Open
Abstract
DNA palindromes are associated with rearrangement in a variety of organisms. A unique opportunity to examine the impact of a long palindrome in mammals is afforded by the Line 78 strain of mice. Previously it was found that the transgene in Line 78 is likely to be palindromic and that the symmetry of the transgene was responsible for a high level of germ line instability. Here we prove that Line 78 mice harbor a true 15.4-kb palindrome, and through the establishment of cell lines from Line 78 mice we have shown that the palindrome rearranges at the impressive rate of about 0.5% per population doubling. The rearrangements observed to arise from rapid palindrome modification are consistent with a center-break mechanism where double-strand breaks, created through hairpin nicking of an extruded cruciform, are imprecisely rejoined, thus introducing deletions at the palindrome center. Significantly, palindrome rearrangements in somatic tissue culture cells almost completely mirrored the structures generated in vivo in the mouse germ line. The close correspondence between germ line and somatic events indicates the possibility that center-break modification of palindromes is an important mechanism for preventing mutation in both contexts. Permanent cell lines carrying a verified palindrome provide an essential tool for future mechanistic analyses into the consequences of palindromy in the mammalian genome.
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20
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Abstract
Cellular DNA continuously incurs damage and a range of damage response mechanisms function to maintain genomic integrity in the face of this onslaught. During the development of the immune response, the cell utilises three defined processes, V(D)J recombination, class switch recombination and somatic hypermutation, to create genetic diversity in developing T and B cells. Curiously, the damage response mechanisms employed to maintain genomic stability in somatic cells have been exploited and adapted to help generate diversity during immune development. As a consequence of this overlap, there is mounting evidence that disorders attributable to impaired damage response mechanisms display associated immunodeficiency. Since double strand breaks (DSB) are created during at least two of the mechanisms used to create immunoglobulin diversity, namely V(D)J recombination and class switch recombination, it is not surprising that disorders associated with defects in the response to double strand breaks are those most associated with immunodeficiency. Here, we review the steps involved in the generation of genetic diversity during immune development with a focus on the damage response mechanisms employed and then consider human immunodeficiency disorders associated with impaired damage response mechanisms.
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Affiliation(s)
- Mark O'Driscoll
- Genome Damage and Stability Centre, University of Sussex, East Sussex, BN1 9RR, UK
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21
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El Amri C, Mauffret O, Santamariar F, Tevanian G, Rayner S, Fermandjian S. NMR study of a heterochiral DNA hairpin:impact of L-enantiomery in the loop. J Biomol Struct Dyn 2001; 19:459-70. [PMID: 11790144 DOI: 10.1080/07391102.2001.10506754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
We carried out a structural study of the DNA heterochiral strand d (AGCTTATCAT(L)CGATAAGCT), -AT(L)C-, where T(L) (L thymine ) replaces T (natural D-thymine). -AT(L)C- is a structural analog of -ATC- that belongs to a strong topoisomerase II DNA cleavage site and which has been shown to resolve into a hairpin structure with a stem formed by eight Waston-Crick base-pairs and a single residue loop closed by an A.C sheared base-pair. Although - AT(L)C-, like its parent -ATC-, folds into a hairpin structure at low and high DNA concentrations it displays a lower stability (Tm of 56 degrees C versus 58.5 degrees C). Several NMR features in -AT(L)C- account for the disruption of the A.C pairing in the loop and a weakening of the C.G base-pair stability at the stem-loop junction. For instance, the exchange of the loop imino protons with solvent is accelerated compared with the natural oligonucleotide -ATC-. The higher flexibility of the heterochiral loop is confirmed by the results of NMR restrained molecular dynamics. In the calculated final structures of -AT(L)C-, the T10(L) residue moves the A9 and C11 residues away, thus preventing the loop closure through a C.A sheared base-pair and the achievement of a good base-base or sugar-base stacking. Actually, most of the stabilizing interactions present in -ATC- are lost in the heterochiral - AT(L)C- explaining its weaker stability.
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Affiliation(s)
- C El Amri
- Department de Biologie et Pharmacologie Structurales, UMR 8532, CNRS, PR2, Institut Gustave-Roussy, 39, rue Camille-Desmoulins, 94805 Villejuif Cedex, France
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22
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Zhou ZH, Akgūn E, Jasin M. Repeat expansion by homologous recombination in the mouse germ line at palindromic sequences. Proc Natl Acad Sci U S A 2001; 98:8326-33. [PMID: 11459971 PMCID: PMC37439 DOI: 10.1073/pnas.151008498] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Genetic instability can be induced by unusual DNA structures and sequence repeats. We have previously demonstrated that a large palindrome in the mouse germ line derived from transgene integration is extremely unstable and undergoes stabilizing rearrangements at high frequency, often through deletions that produce asymmetry. We have now characterized other palindrome rearrangements that arise from complex homologous recombination events. The structure of the recombinants is consistent with homologous recombination occurring by a noncrossover gene conversion mechanism in which a break induced in the palindrome promotes homologous strand invasion and repair synthesis, similar to mitotic break repair events reported in mammalian cells. Some of the homologous recombination events led to expansion in the size of the palindromic locus, which in the extreme case more than doubled the number of repeats. These results may have implications for instability observed at naturally occurring palindromic or quasipalindromic sequences.
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Affiliation(s)
- Z H Zhou
- Cell Biology Program, Sloan-Kettering Institute and Cornell University Graduate School of Medical Sciences, 1275 York Avenue, New York, NY 10021, USA
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23
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Qiu JX, Kale SB, Yarnell Schultz H, Roth DB. Separation-of-function mutants reveal critical roles for RAG2 in both the cleavage and joining steps of V(D)J recombination. Mol Cell 2001; 7:77-87. [PMID: 11172713 DOI: 10.1016/s1097-2765(01)00156-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The only established physiological function of the V(D)J recombinase, comprising RAG1 and RAG2, is to perform DNA cleavage. The molecular roles of RAG2 in cleavage, the mechanisms used to join the broken DNA ends, and the identity of nuclease(s) that open the hairpin coding ends have been unknown. Site-directed mutagenesis targeting each conserved basic amino acid in RAG2 revealed several separation-of-function mutants that address these questions. Analysis of these mutants reveals that RAG2 helps recognize or cleave distorted DNA intermediates and plays an essential role in the joining step of V(D)J recombination. Moreover, the discovery that some mutants block RAG-mediated hairpin opening in vitro provides a critical link between this biochemical activity and coding joint formation in vivo.
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Affiliation(s)
- J X Qiu
- Department of Immunology, Baylor College of Medicine, Houston, TX 77030, USA
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24
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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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25
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Abstract
Unintended DNA rearrangements in a differentiating lymphocyte can have severe, oncogenic consequences, but the mechanisms for avoiding pathogenic outcomes in V(D)J recombination are not well understood. The first level at which fidelity is instituted is in discrimination by the recombination proteins between authentic and inauthentic recombination signal sequences. Nevertheless, this discrimination is not absolute and cannot fully eliminate targeting errors. To learn more about the basis of specificity during V(D)J recombination, we have investigated whether it is possible for the recombination machinery to detect an inaccurately targeted sequence subsequent to cleavage. These studies indicate that even postcleavage steps in V(D)J recombination are sequence specific and that noncanonical sequences will not efficiently support the resolution of recombination intermediates in vivo. Accordingly, interventions after a mistargeting event conceivably occur at a late stage in the joining process and the likelihood may well be crucial to enforcing fidelity during antigen receptor gene rearrangement.
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Affiliation(s)
- E A Agard
- Program in Genetics and Genomic Biology, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada M5G 1X8
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26
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Abstract
The antigen-receptor genes of vertebrates are rearranged by a specialized somatic recombination mechanism in developing lymphocytes - and, unexpectedly, also in the germline of cartilaginous fishes. The recombination system that carries out these DNA rearrangements may thus be a significant evolutionary force, perhaps not limited to rearrangements at antigen-receptor loci.
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Affiliation(s)
- D B Roth
- Howard Hughes Medical Institute and Department of Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.
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27
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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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28
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Binnie A, Olson S, Wu GE, Lewis SM. Gamma-Irradiation Directly Affects the Formation of Coding Joints in SCID Cell Lines. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.10.5418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
SCID mice have a defect in the catalytic subunit of the DNA-dependent protein kinase, causing increased sensitivity to ionizing radiation in all tissues and severely limiting the development of B and T cell lineages. SCID T and B cell precursors are unable to undergo normal V(D)J recombination: coding joint and signal joint products are less frequently formed and often will exhibit abnormal structural features. Paradoxically, irradiation of newborn SCID mice effects a limited rescue of T cell development. It is not known whether irradiation has a direct impact on the process of V(D)J joining, or whether irradiation of the thymus allows the outgrowth of rare recombinants. To investigate this issue, we sought to demonstrate an irradiation effect ex vivo. Here we have been able to reproducibly detect low-frequency coding joint products with V(D)J recombination reporter plasmids introduced into SCID cell lines. Exposure of B and T lineage cells to 100 cGy of gamma irradiation made no significant difference with respect to the number of coding joint and signal joint recombination products. However, in the absence of irradiation, the coding joints produced in SCID cells had high levels of P nucleotide insertion. With irradiation, markedly fewer P insertions were seen. The effect on coding joint structure is evident in a transient assay, in cultured cells, establishing that irradiation has an immediate impact on the process of V(D)J recombination. A specific proposal for how the DNA-dependent protein kinase catalytic subunit influences the opening of hairpin DNA intermediates during coding joint formation in V(D)J recombination is presented.
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Affiliation(s)
- Alexandra Binnie
- *Department of Immunology, University of Toronto, Toronto, Ontario, Canada
| | - Stacy Olson
- †The Ontario Cancer Institute, Toronto, Ontario, Canada; and
| | - Gillian E. Wu
- *Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- †The Ontario Cancer Institute, Toronto, Ontario, Canada; and
| | - Susanna M. Lewis
- *Department of Immunology, University of Toronto, Toronto, Ontario, Canada
- ‡The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
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29
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Abstract
The lymphoid cell-specific proteins RAG1 and RAG2 initiate V(D)J recombination by cleaving DNA adjacent to recombination signals, generating blunt signal ends and covalently sealed, hairpin coding ends. A critical next step in the reaction is opening of the hairpins, but the factor(s) responsible has not been identified and had been thought to be a ubiquitous component(s) of the DNA repair machinery. Here we demonstrate that RAG1 and RAG2 possess an intrinsic single-stranded nuclease activity capable of nicking hairpin coding ends at or near the hairpin tip. In Mn2+, a synthetic hairpin is nicked 5 nucleotides (nt) 5' of the hairpin tip, with more distant sites of nicking suppressed by HMG2. In Mg2+, hairpins generated by V(D)J cleavage are nicked whereas synthetic hairpins are not. Cleavage-generated hairpins are nicked at the tip and predominantly 1 to 2 nt 5' of the tip. RAG1 and RAG2 may therefore be responsible for initiating the processing of coding ends and for the generation of P nucleotides during V(D)J recombination.
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Affiliation(s)
- P E Shockett
- Howard Hughes Medical Institute and Section of Immunobiology, Yale University School of Medicine, New Haven, Connecticut 06520-8011, USA
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30
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Affiliation(s)
- S M Lewis
- Program in Genetics and Genomic Biology, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
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31
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Abstract
Unusual DNA structures promote genetic instability. One such example is hairpin DNA, which can form from palindromic sequences and triplet repeats, and is also a characteristic intermediate in V(D)J recombination. We previously found that a large 15.3-kb palindrome that was introduced as a transgene into the mouse germline was highly unstable. Although it could be transmitted, the transgene was found to be rearranged in up to 56% of the progeny, and rearrangement events often involved deletion at the center of symmetry. Here, the fine structure of centrally deleted palindromes was sampled by analysis of recombinant junctions isolated from testes DNA, providing further evidence for a model, previously proposed, that accounts for such deletions on the basis of a hairpin-tip nicking activity. In addition to central deletions, gene conversion events were also elevated in the transgenic palindrome. We have now analyzed instability in two mouse sublines in which (as a result of inversion) the transgenic palindrome had been shortened to 4.2 kb. In these sublines, the transgene was still subject to both rearrangement and gene conversion events at a high frequency, similar to the original 15.3-kb palindrome. Recombination was not limited to the sequences constituting the inverted repeat, but was seen to include sequences lying outside the palindrome. As discussed, the salient feature in all of these observations, a high level of genetic change associated with palindromic DNA, underscores the significance of hairpin DNA and hairpin-tip nicking in genome stability.
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Affiliation(s)
- S Lewis
- Program in Genetics and Genomic Biology, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
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32
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Abstract
V(D)J recombination, normally an intramolecular process, assembles immunoglobulin and T cell receptor genes from V, D, and J coding segments. Oncogenic chromosome translocations can result from aberrant rearrangements, such as occur in intermolecular V(D)J recombination. How this is normally prevented remains unclear; DNA cleavage, joining, or both could be impaired when the recombination signal sequences (RSS) are located in trans, on separate DNA molecules. Here, we show that both trans cleavage and joining of signal ends occur efficiently in vivo. Unexpectedly, trans joining of coding ends is severely impaired (100-to 1000-fold), indicating that protection against intermolecular V(D)J recombination is established at the joining step. These findings suggest a novel surveillance mechanism for eliminating cells containing aberrant V(D)J rearrangements.
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Affiliation(s)
- J O Han
- Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030, USA
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33
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Chang Y, Brown ML. Formation of coding joints in V(D)J recombination-inducible severe combined immune deficient pre-B cell lines. Proc Natl Acad Sci U S A 1999; 96:191-6. [PMID: 9874794 PMCID: PMC15115 DOI: 10.1073/pnas.96.1.191] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Characterization of the severe combined immune deficient (scid) defect in the recombination process has provided many insights into the underlying mechanisms of variable (diversity) joining recombination. By using recombination-inducible scid pre-B cell lines transformed with the temperature-sensitive Abelson-murine leukemia virus, we show that large quantities of recombination intermediates can be generated, and their resolution can be followed during further cell culture. In this study, we demonstrate that the ability of these scid pre-B cell lines to resolve coding ends depends on the cell culture temperature. At the nonpermissive temperature of 39 degreesC, scid pre-B cell lines fail to form coding joints and contain mostly unresolved hairpin-coding ends. Once the cell culture is returned to the permissive temperature of 33 degreesC, these same cells make a significant amount of coding joints concomitant with the disappearance of hairpin-coding ends. Thus, the scid cells are capable of resolving coding ends under certain culture conditions. However, the majority of the recovered coding joints contains extensive deletions, indicating that the temperature-dependent resolution of coding ends is still scid-like. Our results suggest that the inability of scid cells to promptly nick hairpin-coding ends may lead to aberrant joining in these cells.
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Affiliation(s)
- Y Chang
- Department of Microbiology, Molecular and Cellular Biology Program, Arizona State University, Tempe, AZ 85287-2701, USA.
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34
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Besmer E, Mansilla-Soto J, Cassard S, Sawchuk DJ, Brown G, Sadofsky M, Lewis SM, Nussenzweig MC, Cortes P. Hairpin coding end opening is mediated by RAG1 and RAG2 proteins. Mol Cell 1998; 2:817-28. [PMID: 9885569 DOI: 10.1016/s1097-2765(00)80296-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Despite the importance of hairpin opening in antigen receptor gene assembly, the molecular machinery that mediates this reaction has not been defined. Here, we show that RAG1 plus RAG2 can open DNA hairpins. Hairpin opening by RAGs is not sequence specific, but in Mg2+, hairpin opening occurs only in the context of a regulated cleavage complex. The chemical mechanism of hairpin opening by RAGs resembles RSS cleavage and 3' end processing by HIV integrase and Mu transposase in that these reactions can proceed through alcoholysis. Mutations in either RAG1 or RAG2 that interfere with RSS cleavage also interfere with hairpin opening, suggesting that RAGs have a single active site that catalyzes several distinct DNA cleavage reactions.
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Affiliation(s)
- E Besmer
- Laboratory of Molecular Immunology, Rockefeller University, New York, New York 10021, USA
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35
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Smider V, Rathmell WK, Brown G, Lewis S, Chu G. Failure of hairpin-ended and nicked DNA To activate DNA-dependent protein kinase: implications for V(D)J recombination. Mol Cell Biol 1998; 18:6853-8. [PMID: 9774698 PMCID: PMC109268 DOI: 10.1128/mcb.18.11.6853] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
V(D)J recombination is initiated by a coordinated cleavage reaction that nicks DNA at two sites and then forms a hairpin coding end and blunt signal end at each site. Following cleavage, the DNA ends are joined by a process that is incompletely understood but nevertheless depends on DNA-dependent protein kinase (DNA-PK), which consists of Ku and a 460-kDa catalytic subunit (DNA-PKCS or p460). Ku directs DNA-PKCS to DNA ends to efficiently activate the kinase. In vivo, the mouse SCID mutation in DNA-PKCS disrupts joining of the hairpin coding ends but spares joining of the open signal ends. To better understand the mechanism of V(D)J recombination, we measured the activation of DNA-PK by the three DNA structures formed during the cleavage reaction: open ends, DNA nicks, and hairpin ends. Although open DNA ends strongly activated DNA-PK, nicked DNA substrates and hairpin-ended DNA did not. Therefore, even though efficient processing of hairpin coding ends requires DNA-PKCS, this may occur by activation of the kinase bound to the cogenerated open signal end rather than to the hairpin end itself.
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Affiliation(s)
- V Smider
- Departments of Medicine and Biochemistry, Stanford University Medical Center, Stanford, California 94305, USA
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36
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Bridges SL. Frequent N addition and clonal relatedness among immunoglobulin lambda light chains expressed in rheumatoid arthritis synovia and PBL, and the influence of V lambda gene segment utilization on CDR3 length. Mol Med 1998; 4:525-53. [PMID: 9742508 PMCID: PMC2230400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND In rheumatoid arthritis (RA), B-lineage cells in the synovial membrane secrete large amounts of immunoglobulin that contribute to tissue destruction. The CDR3 of an immunoglobulin light chain is formed by rearrangements of VL and JL gene segments. Addition of non-germline-encoded (N) nucleotides at V(D)J joins by the enzyme terminal deoxynucleotidyl transferase (TdT) enhances antibody diversity. TdT was previously thought to be active in B cells only during heavy chain rearrangement, but we and others reported unexpectedly high levels of N addition in kappa light chains. We also found clonally related kappa chains bearing unusually long CDR3 intervals in RA synovium, suggesting oligoclonal expansion of a set of atypical B lymphocytes. In this study, we analyzed lambda light chain expression to determine if N addition occurs throughout immunoglobulin gene rearrangement and to compare CDR3 lengths of lambda and kappa light chains in RA patients and normal individuals. MATERIALS AND METHODS Reverse transcription-polymerase chain reaction (RT-PCR) amplification of V lambda III transcripts was performed on RA synovia and peripheral blood lymphocytes (PBL) and normal PBL for which kappa repertoires were previously analyzed. Representative lambda + PCR products were cloned and sequenced. RESULTS Analysis of 161 cDNA clones revealed that N addition occurs in lambda light chains of RA patients and normal controls. The lambda light chain repertoires in RA were enriched for long CDR3 intervals. In both RA and controls, CDR3 lengths were strongly influenced by which V lambda gene segment was present in the rearrangement. Five sets of clonally related sequences were found in RA synovia and PBL; one set was found in normal PBL. CONCLUSIONS In humans, unlike mice, N addition enhances antibody diversity at all stages of immunoglobulin assembly, and the structural diversity of lambda CDR3 intervals is greater than that of kappa light chains. Clonally related V lambda gene segments in RA support an antigen-driven B-cell response.
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Affiliation(s)
- S L Bridges
- Department of Medicine, University of Alabama at Birmingham, USA.
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Frequent N Addition and Clonal Relatedness among Immunoglobulin Lambda Light Chains Expressed in Rheumatoid Arthritis Synovia and PBL, and the Influence of Vλ Gene Segment Utilization on CDR3 Length. Mol Med 1998. [DOI: 10.1007/bf03401757] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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38
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Connelly JC, Kirkham LA, Leach DR. The SbcCD nuclease of Escherichia coli is a structural maintenance of chromosomes (SMC) family protein that cleaves hairpin DNA. Proc Natl Acad Sci U S A 1998; 95:7969-74. [PMID: 9653124 PMCID: PMC20913 DOI: 10.1073/pnas.95.14.7969] [Citation(s) in RCA: 185] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Hairpin structures can inhibit DNA replication and are intermediates in certain recombination reactions. We have shown that the purified SbcCD protein of Escherichia coli cleaves a DNA hairpin. This cleavage does not require the presence of a free (3' or 5') DNA end and generates products with 3'-hydroxyl and 5'-phosphate termini. Electron microscopy of SbcCD has revealed the "head-rod-tail" structure predicted for the SMC (structural maintenance of chromosomes) family of proteins, of which SbcC is a member. This work provides evidence consistent with the proposal that SbcCD cleaves hairpin structures that halt the progress of the replication fork, allowing homologous recombination to restore DNA replication.
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Affiliation(s)
- J C Connelly
- Institute of Cell and Molecular Biology, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JR, United Kingdom
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39
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Akgün E, Zahn J, Baumes S, Brown G, Liang F, Romanienko PJ, Lewis S, Jasin M. Palindrome resolution and recombination in the mammalian germ line. Mol Cell Biol 1997; 17:5559-70. [PMID: 9271431 PMCID: PMC232404 DOI: 10.1128/mcb.17.9.5559] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Genetic instability is promoted by unusual sequence arrangements and DNA structures. Hairpin DNA structures can form from palindromes and from triplet repeats, and they are also intermediates in V(D)J recombination. We have measured the genetic stability of a large palindrome which has the potential to form a one-stranded hairpin or a two-stranded cruciform structure and have analyzed recombinants at the molecular level. A palindrome of 15.3 kb introduced as a transgene was found to be transmitted at a normal Mendelian ratio in mice, in striking contrast to the profound instability of large palindromes in prokaryotic systems. In a significant number of progeny mice, however, the palindromic transgene is rearranged; between 15 and 56% of progeny contain rearrangements. Rearrangements within the palindromic repeat occur both by illegitimate and homologous, reciprocal recombination. Gene conversion within the transgene locus, as quantitated by a novel sperm fluorescence assay, is also elevated. Illegitimate events often take the form of an asymmetric deletion that eliminates the central symmetry of the palindrome. Such asymmetric transgene deletions, including those that maintain one complete half of the palindromic repeat, are stabilized so that they cannot undergo further illegitimate rearrangements, and they also exhibit reduced levels of gene conversion. By contrast, transgene rearrangements that maintain the central symmetry continue to be unstable. Based on the observed events, we propose that one mechanism promoting the instability of the palindrome may involve breaks generated at the hairpin structure by a hairpin-nicking activity, as previously detected in somatic cells. Because mammalian cells are capable of efficiently repairing chromosome breaks through nonhomologous processes, the resealing of such breaks introduces a stabilizing asymmetry at the center of the palindrome. We propose that the ability of mammalian cells to eliminate the perfect symmetry in a palindromic sequence may be an important DNA repair pathway, with implications regarding the metabolism of palindromic repeats, the mutability of quasipalindromic triplet repeats, and the early steps in gene amplification events.
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Affiliation(s)
- E Akgün
- Cell Biology and Genetics Program, Sloan-Kettering Institute and Cornell University Graduate School of Medical Sciences, New York, New York 10021, USA
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40
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Bogue MA, Wang C, Zhu C, Roth DB. V(D)J recombination in Ku86-deficient mice: distinct effects on coding, signal, and hybrid joint formation. Immunity 1997; 7:37-47. [PMID: 9252118 DOI: 10.1016/s1074-7613(00)80508-7] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ku, a heterodimer of 70 and 86 kDa subunits, plays a critical but poorly understood role in V(D)J recombination. Although Ku86-deficient mice are defective in coding and signal joint formation, rare recombination products have been detected by PCR. Here, we report nucleotide sequences of 99 junctions from Ku86-deficient mice. Over 90% of the coding joints, but not signal or hybrid joints, exhibit short sequence homologies, indicating that homology is required to join coding ends in the absence of Ku86. Our results suggest that Ku86 may normally have distinct functions in the formation of these different types of junctions. Furthermore, Ku86(-/-) joints are unexpectedly devoid of N-region diversity, suggesting a novel role for Ku in the addition of N nucleotides by terminal deoxynucleotidyl transferase.
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MESH Headings
- Animals
- Antigens, Nuclear
- Base Sequence
- Bone Marrow Cells
- DNA Helicases
- DNA Nucleotidylexotransferase/metabolism
- DNA Repair
- DNA-Binding Proteins/physiology
- Gene Rearrangement
- Gene Rearrangement, T-Lymphocyte
- Immunoglobulin Heavy Chains/genetics
- Immunoglobulin Heavy Chains/metabolism
- Immunoglobulin Joining Region/genetics
- Immunoglobulin Joining Region/metabolism
- Ku Autoantigen
- Mice
- Mice, SCID
- Molecular Sequence Data
- Nuclear Proteins/physiology
- Polymerase Chain Reaction
- Receptors, Antigen, T-Cell, gamma-delta/genetics
- Receptors, Antigen, T-Cell, gamma-delta/metabolism
- Recombination, Genetic
- Stem Cells/metabolism
- Transcription Factors/deficiency
- Transcription Factors/physiology
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Affiliation(s)
- M A Bogue
- Department of Microbiology and Immunology, Baylor College of Medicine, Houston, Texas 77030, USA
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41
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Nadel B, Feeney AJ. Nucleotide deletion and P addition in V(D)J recombination: a determinant role of the coding-end sequence. Mol Cell Biol 1997; 17:3768-78. [PMID: 9199310 PMCID: PMC232228 DOI: 10.1128/mcb.17.7.3768] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
During V(D)J recombination, the coding ends to be joined are extensively modified. Those modifications, termed coding-end processing, consist of removal and addition of various numbers of nucleotides. We previously showed in vivo that coding-end processing is specific for each coding end, suggesting that specific motifs in a coding-end sequence influence nucleotide deletion and P-region formation. In this study, we created a panel of recombination substrates containing actual immunoglobulin and T-cell receptor coding-end sequences and dissected the role of each motif by comparing its processing pattern with those of variants containing minimal nucleotide changes from the original sequence. Our results demonstrate the determinant role of specific sequence motifs on coding-end processing and also the importance of the context in which they are found. We show that minimal nucleotide changes in key positions of a coding-end sequence can result in dramatic changes in the processing pattern. We propose that each coding-end sequence dictates a unique hairpin structure, the result of a particular energy conformation between nucleotides organizing the loop and the stem, and that the interplay between this structure and specific sequence motifs influences the frequency and location of nicks which open the coding-end hairpin. These findings indicate that the sequences of the coding ends determine their own processing and have a profound impact on the development of the primary B- and T-cell repertoires.
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Affiliation(s)
- B Nadel
- Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA
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42
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Ezekiel UR, Sun T, Bozek G, Storb U. The composition of coding joints formed in V(D)J recombination is strongly affected by the nucleotide sequence of the coding ends and their relationship to the recombination signal sequences. Mol Cell Biol 1997; 17:4191-7. [PMID: 9199354 PMCID: PMC232272 DOI: 10.1128/mcb.17.7.4191] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
V(D)J recombination proceeds in two stages. Precise cleavage at the border of the conserved recombination signal sequences (RSSs) and the coding ends results in flush double-stranded signal ends and coding ends terminating in hairpins. In the second stage, the signal and coding ends are processed into signal and coding joints. Coding ends containing certain nucleotide homopolymers affect the efficiency of V(D)J recombination. In this study, we have tested the effect of small changes in coding-end nucleotide composition on the frequency of coding- and signal joint formation. Furthermore, we have determined the sequences of coding joints resulting from recombination of coding ends with different compositions. We found that the presence of two T nucleotides 5' of both RSSs, but not a single T, reduces the frequency of signal joint formation, i.e., interferes with the cleavage stage of V(D)J recombination. However, coding-joint processing is sensitive even to a single T. Both the sequence of the coding ends and the particular RSS (12-mer or 23-mer) with which the coding end is associated affect the final composition of the coding joints. Thus, the presence of P nucleotides, the conservation of one undeleted coding end, the formation of joints without any deletions, and the template-dependent insertion of nucleotides are strongly influenced by the coding-end nucleotide composition and/or RSS association. The implications of these results with respect to the processing of coding ends are discussed.
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Affiliation(s)
- U R Ezekiel
- Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637, USA
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43
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Affiliation(s)
- M Gellert
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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44
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Zhu C, Bogue MA, Lim DS, Hasty P, Roth DB. Ku86-deficient mice exhibit severe combined immunodeficiency and defective processing of V(D)J recombination intermediates. Cell 1996; 86:379-89. [PMID: 8756720 DOI: 10.1016/s0092-8674(00)80111-7] [Citation(s) in RCA: 349] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Ku is a heterodimeric DNA end binding complex composed of 70 and 86 kDa subunits. Here, we show that Ku86 is essential for normal V(D)J recombination in vivo, as Ku86-deficient mice are severely defective for formation of coding joints. Unlike severe combined immunodeficient (scid) mice, Ku86-deficient mice are also defective for signal joint formation. Both hairpin coding ends and blunt full-length signal ends accumulate. Contrary to expectation, Ku86 is evidently not required for protection of either type of V(D)J recombination intermediate. Instead, V(D)J recombination appears to be arrested after the cleavage step in Ku86-deficient mice. We suggest that Ku86 may be required to remodel or disassemble DNA-protein complexes containing broken ends, making them available for further processing and joining.
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Affiliation(s)
- C Zhu
- Department of Microbiology and Immunology Baylor College of Medicine Houston, Texas 77030, USA
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45
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Tombline G, Bellizzi D, Sgaramella V. Heterogeneity of primer extension products in asymmetric PCR is due both to cleavage by a structure-specific exo/endonuclease activity of DNA polymerases and to premature stops. Proc Natl Acad Sci U S A 1996; 93:2724-8. [PMID: 8610108 PMCID: PMC39698 DOI: 10.1073/pnas.93.7.2724] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In PCR, DNA polymerases from thermophilic bacteria catalyze the extension of primers annealed to templates as well as the structure-specific cleavage of the products of primer extension. Here we show that cleavage by Thermus aquaticus and Thermus thermophilus DNA polymerases can be precise and substantial: it occurs at the base of the stem-loop structure assumed by the single strand products of primer extension using as template a common genetic element, the promoter-operator of the Escherichia coli lactose operon, and may involve up to 30% of the products. The cleavage is independent of primer, template, and triphosphates, is dependent on substrate length and temperature, requires free ends and Mg2+, and is absent in DNA polymerases lacking the 5'-->3' exonuclease, such as the Stoffel fragment and the T7 DNA polymerase. Heterogeneity of the extension products results also from premature detachment of the enzyme approaching the 5' end of the template.
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Affiliation(s)
- G Tombline
- Labortory of Molecular Genetics and Informatics, The Rockfeller University, New York, NY 10021-6399, USA
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46
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Abstract
V(D)J recombination can be separated into two basic operations: DNA cleavage and joining of broken ends. Our understanding of both reactions has increased substantially in the past year. Major advances include the development of a cell-free system capable of cleavage and the identification of several proteins involved in both V(D)J recombination and double-strand break repair.
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Affiliation(s)
- M Bogue
- Department of Microbiology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA
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47
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Affiliation(s)
- K Schwarz
- Section of Molecular Biology, Pediatrics II, University of Ulm, Germany
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48
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Steen SB, Zhu C, Roth DB. Double-strand breaks, DNA hairpins, and the mechanism of V(D)J recombination. Curr Top Microbiol Immunol 1996; 217:61-77. [PMID: 8787618 DOI: 10.1007/978-3-642-50140-1_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- S B Steen
- Cell and Molecular Biology Program, Baylor College of Medicine, Houston, TX 77030, USA
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49
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Abstract
We have analyzed a large collection of coding junctions generated in human cells. From this analysis, we infer the following about nucleotide processing at coding joints in human cells. First, the pattern of nucleotide loss from coding ends is influenced by the base composition of the coding end sequences. AT-rich sequences suffer greater loss than do GC-rich sequences. Second, inverted repeats can occur at ends that have undergone nucleolytic processing. Previously, inverted repeats (P nucleotides) have been noted only at coding ends that have not undergone nucleolytic processing, this observation being the basis for a model in which a hairpin intermediate is formed at the coding ends early in the reaction. Here, inverted repeats at processed coding ends were present at approximately twice the number of junctions as P nucleotide additions. Terminal deoxynucleotidyl transferase (TdT) is required for the appearance of the inverted repeats at processed ends (but not full-length coding ends), yet statistical analysis shows that it is virtually impossible for the inverted repeats to be polymerized by TdT. Third, TdT additions are not random. It has long been noted that TdT has a G utilization preference. In addition to the G preference, we find that TdT adds strings of purines or strings of pyrimidines at a highly significant frequency. This tendency suggests that nucleotide-stacking interactions affect TdT polymerization. All three of these features place constraints on the extent of junctional diversity in human V(D)J recombination.
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Affiliation(s)
- G H Gauss
- Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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50
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Chu G. Role of the Ku autoantigen in V(D)J recombination and double-strand break repair. Curr Top Microbiol Immunol 1996; 217:113-32. [PMID: 8787621 DOI: 10.1007/978-3-642-50140-1_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- G Chu
- Department of Medicine, Stanford University Medical Center, CA 94305, USA
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