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Wentink MWJ, Kalina T, Perez-Andres M, Del Pino Molina L, IJspeert H, Kavelaars FG, Lankester AC, Lecrevisse Q, van Dongen JJM, Orfao A, van der Burg M. Delineating Human B Cell Precursor Development With Genetically Identified PID Cases as a Model. Front Immunol 2019; 10:2680. [PMID: 31849931 PMCID: PMC6901940 DOI: 10.3389/fimmu.2019.02680] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 10/30/2019] [Indexed: 01/22/2023] Open
Abstract
B-cell precursors (BCP) arise from hematopoietic stem cells in bone marrow (BM). Identification and characterization of the different BCP subsets has contributed to the understanding of normal B-cell development. BCP first rearrange their immunoglobulin (Ig) heavy chain (IGH) genes to form the pre-B-cell receptor (pre-BCR) complex together with surrogate light chains. Appropriate signaling via this pre-BCR complex is followed by rearrangement of the Ig light chain genes, resulting in the formation, and selection of functional BCR molecules. Consecutive production, expression, and functional selection of the pre-BCR and BCR complexes guide the BCP differentiation process that coincides with corresponding immunophenotypic changes. We studied BCP differentiation in human BM samples from healthy controls and patients with a known genetic defect in V(D)J recombination or pre-BCR signaling to unravel normal immunophenotypic changes and to determine the effect of differentiation blocks caused by the specific genetic defects. Accordingly, we designed a 10-color antibody panel to study human BCP development in BM by flow cytometry, which allows identification of classical preB-I, preB-II, and mature B-cells as defined via BCR-related markers with further characterization by additional markers. We observed heterogeneous phenotypes associated with more than one B-cell maturation pathway, particularly for the preB-I and preB-II stages in which V(D)J recombination takes place, with asynchronous marker expression patterns. Next Generation Sequencing of complete IGH gene rearrangements in sorted BCP subsets unraveled their rearrangement status, indicating that BCP differentiation does not follow a single linear pathway. In conclusion, B-cell development in human BM is not a linear process, but a rather complex network of parallel pathways dictated by V(D)J-recombination-driven checkpoints and pre-BCR/BCR mediated-signaling occurring during B-cell production and selection. It can also be described as asynchronous, because precursor B-cells do not differentiate as full population between the different stages, but rather transit as a continuum, which seems influenced (in part) by V-D-J recombination-driven checkpoints.
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Affiliation(s)
- Marjolein W J Wentink
- Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Tomas Kalina
- Department of Paediatric Haematology and Oncology, Second Faculty of Medicine, Charles University and University Hospital Motol, Prague, Czechia
| | - Martin Perez-Andres
- Department of Medicine-Service Cytometry, Cancer Research Center (IBMCC-CSIC/USAL) and University of Salamanca, Salamanca, Spain
| | - Lucia Del Pino Molina
- Department of Clinical Immunology, La Paz University Hospital, Lymphocyte Pathophysiology in Immunodeficiencies Group La Paz Institute for Health Research (IdiPAZ), Madrid, Spain
| | - Hanna IJspeert
- Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - François G Kavelaars
- Department of Hematology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Arjan C Lankester
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, Netherlands
| | - Quentin Lecrevisse
- Department of Medicine-Service Cytometry, Cancer Research Center (IBMCC-CSIC/USAL) and University of Salamanca, Salamanca, Spain
| | - Jacques J M van Dongen
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, Netherlands
| | - Alberto Orfao
- Department of Medicine-Service Cytometry, Cancer Research Center (IBMCC-CSIC/USAL) and University of Salamanca, Salamanca, Spain
| | - Mirjam van der Burg
- Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands.,Department of Pediatrics, Leiden University Medical Center, Leiden, Netherlands
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Funck T, Barnkob MB, Holm N, Ohm-Laursen L, Mehlum CS, Möller S, Barington T. Nucleotide Composition of Human Ig Nontemplated Regions Depends on Trimming of the Flanking Gene Segments, and Terminal Deoxynucleotidyl Transferase Favors Adding Cytosine, Not Guanosine, in Most VDJ Rearrangements. THE JOURNAL OF IMMUNOLOGY 2018; 201:1765-1774. [PMID: 30097530 DOI: 10.4049/jimmunol.1800100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Accepted: 07/05/2018] [Indexed: 01/12/2023]
Abstract
The formation of nontemplated (N) regions during Ig gene rearrangement is a major contributor to Ab diversity. To gain insights into the mechanisms behind this, we studied the nucleotide composition of N regions within 29,962 unique human VHDJH rearrangements and 8728 unique human DJH rearrangements containing exactly one identifiable D gene segment and thus two N regions, N1 and N2. We found a distinct decreasing content of cytosine (C) and increasing content of guanine (G) across each N region, suggesting that N regions are typically generated by concatenation of two 3' overhangs synthesized by addition of nucleoside triphosphates with a preference for dCTP. This challenges the general assumption that the terminal deoxynucleotidyl transferase favors dGTP in vivo. Furthermore, we found that the G and C gradients depended strongly on whether the germline gene segments were trimmed or not. Our data show that C-enriched N addition preferentially happens at trimmed 3' ends of VH, D, and JH gene segments, indicating a dependency of the transferase mechanism upon the nuclease mechanism.
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Affiliation(s)
- Tina Funck
- Department of Clinical Biochemistry, Zealand University Hospital, Roskilde 4000, Denmark.,Department of Clinical Immunology, Odense University Hospital, Odense 5000, Denmark
| | - Mike Bogetofte Barnkob
- Department of Clinical Immunology, Odense University Hospital, Odense 5000, Denmark.,Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, University of Oxford, Oxfordshire OX3 9DS, United Kingdom
| | - Nanna Holm
- Department of Clinical Immunology, Odense University Hospital, Odense 5000, Denmark
| | - Line Ohm-Laursen
- Randall Centre for Cell and Molecular Biophysics, School of Basic and Medical Biosciences, King's College London, London SE1 1UL, United Kingdom
| | - Camilla Slot Mehlum
- Department of Otorhinolaryngology-Head and Neck Surgery, Odense University Hospital, Odense 5000, Denmark
| | - Sören Möller
- OPEN, Odense Patient Data Explorative Network, Odense University Hospital, Odense 5000, Denmark; and.,Clinical Department, University of Southern Denmark, Odense 5000, Denmark
| | - Torben Barington
- Department of Clinical Immunology, Odense University Hospital, Odense 5000, Denmark; .,Clinical Department, University of Southern Denmark, Odense 5000, Denmark
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3
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Abstract
V(D)J recombination, the mechanism responsible for generating antigen receptor diversity, has the potential to generate aberrant DNA rearrangements in developing lymphocytes. Indeed, the recombinase has been implicated in several different kinds of errors leading to oncogenic transformation. Here we review the basic aspects of V(D)J recombination, mechanisms underlying aberrant DNA rearrangements, and the types of aberrant events uncovered in recent genomewide analyses of lymphoid neoplasms.
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4
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Multhaup MM, Podetz-Pedersen KM, Karlen AD, Olson ER, Gunther R, Somia NV, Blazar BR, Cowan MJ, McIvor RS. Role of transgene regulation in ex vivo lentiviral correction of artemis deficiency. Hum Gene Ther 2015; 26:232-43. [PMID: 25738323 DOI: 10.1089/hum.2014.062] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Artemis is a single-stranded endonuclease, deficiency of which results in a radiation-sensitive form of severe combined immunodeficiency (SCID-A) most effectively treated by allogeneic hematopoietic stem cell (HSC) transplantation and potentially treatable by administration of genetically corrected autologous HSCs. We previously reported cytotoxicity associated with Artemis overexpression and subsequently characterized the human Artemis promoter with the intention to provide Artemis expression that is nontoxic yet sufficient to support immunodevelopment. Here we compare the human Artemis promoter (APro) with the moderate-strength human phosphoglycerate kinase (PGK) promoter and the strong human elongation factor-1α (EF1α) promoter to regulate expression of Artemis after ex vivo lentiviral transduction of HSCs in a murine model of SCID-A. Recipient animals treated with the PGK-Artemis vector exhibited moderate repopulation of their immune compartment, yet demonstrated a defective proliferative T lymphocyte response to in vitro antigen stimulation. Animals treated with the EF1α-Artemis vector displayed high levels of T lymphocytes but an absence of B lymphocytes and deficient lymphocyte function. In contrast, ex vivo transduction with the APro-Artemis vector supported effective immune reconstitution to wild-type levels, resulting in fully functional T and B lymphocyte responses. These results demonstrate the importance of regulated Artemis expression in immune reconstitution of Artemis-deficient SCID.
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Affiliation(s)
- Megan M Multhaup
- 1 Department of Genetics, Cell Biology, and Development, University of Minnesota , Minneapolis, MN 55455
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5
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Wang G, Dhar K, Swanson PC, Levitus M, Chang Y. Real-time monitoring of RAG-catalyzed DNA cleavage unveils dynamic changes in coding end association with the coding end complex. Nucleic Acids Res 2012; 40:6082-96. [PMID: 22434887 PMCID: PMC3401440 DOI: 10.1093/nar/gks255] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
During V(D)J recombination, the RAG1/2 recombinase is thought to play an active role in transferring newly excised recombination ends from the RAG post-cleavage complex (PCC) to the non-homologous end joining (NHEJ) machinery to promote appropriate antigen receptor gene assembly. However, this transfer mechanism is poorly understood, partly because of the technical difficulty in revealing weak association of coding ends (CEs) with one of the PCCs, coding end complex (CEC). Using fluorescence resonance energy transfer (FRET) and anisotropy measurement, we present here real-time monitoring of the RAG1/2-catalyzed cleavage reaction, and provide unequivocal evidence that CEs are retained within the CEC in the presence of Mg(2+). By examining the dynamic fluorescence changes during the cleavage reaction, we compared the stability of CEC assembled with core RAG1 paired with full-length RAG2, core RAG2 or a frameshift RAG2 mutant that was speculated to destabilize the PCC, leading to increased aberrant joining. While the latter two CECs exhibit similar stability, the full-length RAG2 renders a less stable CEC unless H3K4me3 peptides are added. Interestingly, the RAG2 mutant appears to modulate the structure of the RAG-12RSS pre-cleavage complex. Thus, the fluorescence-based detection offers a sensitive, quantitative and continuous assessment of pre-cleavage complex assembly and CEC stability.
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Affiliation(s)
- Guannan Wang
- Center of Infectious Disease and Vaccinology, The Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
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6
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Jackson KJL, Wang Y, Gaeta BA, Pomat W, Siba P, Rimmer J, Sewell WA, Collins AM. Divergent human populations show extensive shared IGK rearrangements in peripheral blood B cells. Immunogenetics 2011; 64:3-14. [PMID: 21789596 DOI: 10.1007/s00251-011-0559-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 07/12/2011] [Indexed: 11/28/2022]
Abstract
We have analysed the transcribed immunoglobulin kappa (IGK) repertoire of peripheral blood B cells from four individuals from two genetically distinct populations, Papua New Guinean and Australian, using high-throughput DNA sequencing. The depth of sequencing data for each individual averaged 5,548 high-quality IGK reads, and permitted genotyping of the inferred IGKV and IGKJ germline gene segments for each individual. All individuals were homozygous at each IGKJ locus and had highly similar inferred IGKV genotypes. Preferential gene usage was seen at both the IGKV and IGKJ loci, but only IGKV segment usage varied significantly between individuals. Despite the differences in IGKV gene utilisation, the rearranged IGK repertoires showed extensive identity at the amino acid level. Public rearrangements (those shared by two or more individuals) made up 60.2% of the total sequenced IGK rearrangements. The total diversity of IGK rearrangements of each individual was estimated to range from just 340 to 549 unique amino acid sequences. Thus, the repertoire of unique expressed IGK rearrangements is dramatically less than previous theoretical estimates of IGK diversity, and the majority of expressed IGK rearrangements are likely to be extensively shared in individual human beings.
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7
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Multhaup MM, Gurram S, Podetz-Pedersen KM, Karlen AD, Swanson DL, Somia NV, Hackett PB, Cowan MJ, McIvor RS. Characterization of the human artemis promoter by heterologous gene expression in vitro and in vivo. DNA Cell Biol 2011; 30:751-61. [PMID: 21663454 DOI: 10.1089/dna.2011.1244] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Artemis is an endonucleolytic enzyme involved in nonhomologous double-strand break repair and V(D)J recombination. Deficiency of Artemis results in a B- T- radiosensitive severe combined immunodeficiency, which may potentially be treatable by Artemis gene transfer into hematopoietic stem cells. However, we recently found that overexpression of Artemis after lentiviral transduction resulted in global DNA damage and increased apoptosis. These results imply the necessity of effecting natural levels of Artemis expression, so we isolated a 1 kilobase DNA sequence upstream of the human Artemis gene to recover and characterize the Artemis promoter (APro). The sequence includes numerous potential transcription factor-binding sites, and several transcriptional start sites were mapped by 5' rapid amplification of cDNA ends. APro and deletion constructs conferred significant reporter gene expression in vitro that was markedly reduced in comparison to expression regulated by the human elongation factor 1-α promoter. Ex vivo lentiviral transduction of an APro-regulated green fluorescent protein (GFP) construct in mouse marrow supported GFP expression throughout hematopoeitic lineages in primary transplant recipients and was sustained in secondary recipients. The human Artemis promoter thus provides sustained and moderate levels of gene expression that will be of significant utility for therapeutic gene transfer into hematopoeitic stem cells.
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Affiliation(s)
- Megan M Multhaup
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455, USA
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8
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van der Burg M, Gennery AR. Educational paper. The expanding clinical and immunological spectrum of severe combined immunodeficiency. Eur J Pediatr 2011; 170:561-71. [PMID: 21479529 PMCID: PMC3078321 DOI: 10.1007/s00431-011-1452-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 03/10/2011] [Indexed: 12/20/2022]
Abstract
Severe combined immunodeficiency (SCID) is one of the most severe forms of primary immunodeficiency characterized by absence of functional T lymphocytes. It is a paediatric emergency, which is life-threatening when recognized too late. The clinical presentation varies from the classical form of SCID through atypical SCID to Omenn syndrome. In addition, there is a considerable immunological variation, which can hamper the diagnosis. In this educational review, we describe the immunopathological background, clinical presentations and diagnostic process of SCID, as well as the therapeutic possibilities.
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Affiliation(s)
- Mirjam van der Burg
- Department of Immunology, Erasmus MC, University Medical Center Rotterdam, Dr. Molewaterplein 50, Rotterdam 3015 GE, The Netherlands.
| | - Andy R. Gennery
- Department of Pediatric Immunology, Great North Children’s Hospital, Royal Victoria Infirmary, Newcastle upon Tyne, UK ,Institute of Cellular Medicine, Child Health, University of Newcastle upon Tyne, Newcastle upon Tyne, UK
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9
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Multhaup M, Karlen AD, Swanson DL, Wilber A, Somia NV, Cowan MJ, McIvor RS. Cytotoxicity associated with artemis overexpression after lentiviral vector-mediated gene transfer. Hum Gene Ther 2010; 21:865-75. [PMID: 20163250 DOI: 10.1089/hum.2009.162] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Artemis is a hairpin-opening endonuclease involved in nonhomologous end-joining and V(D)J recombination. Deficiency of Artemis results in radiation-sensitive severe combined immunodeficiency (SCID) characterized by complete absence of T and B cells due to an arrest at the receptor recombination stage. We have generated several lentiviral vectors for transduction of the Artemis sequence, intending to complement the deficient phenotype. We found that transduction by a lentiviral vector in which Artemis is regulated by a strong EF-1alpha promoter resulted in a dose-dependent loss of cell viability due to perturbed cell cycle distribution, increased DNA damage, and increased apoptotic cell frequency. This toxic response was not observed in cultures exposed to identical amounts of control vector. Loss of cell viability was also observed in cells transfected with an Artemis expression construct, indicating that toxicity is independent of lentiviral transduction. Reduced toxicity was observed when cells were transduced with a moderate-strength phosphoglycerate kinase promoter to regulate Artemis expression. These results present a novel challenge in the establishment of conditions that support Artemis expression at levels that are nontoxic yet sufficient to correct the T(-)B(-) phenotype, crucial for preclinical studies and clinical application of Artemis gene transfer in the treatment of human SCID-A.
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Affiliation(s)
- Megan Multhaup
- Gene Therapy Program, Institute of Human Genetics, Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
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10
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Bhattacharyya A, Jones JM. Requirement for ubiquitin conjugation and 26S proteasome activity at an early stage in V(D)J recombination. Mol Immunol 2010; 47:1173-80. [PMID: 20116856 DOI: 10.1016/j.molimm.2010.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 01/08/2010] [Indexed: 10/19/2022]
Abstract
V(D)J recombination, the process that rearranges gene segments to assemble mature antigen receptor genes, relies on a recombinase comprising the RAG1 and RAG2 proteins. RAG1 is a multi-functional enzyme including DNA binding and cleavage as well as ubiquitin ligase activities, all of which appear to contribute to its role in recombination. Here we demonstrate that components of the ubiquitin conjugation machinery and the 26S proteasome are required for an early step in V(D)J recombination. Inhibitors of the 26S proteasome and ubiquitin activating enzyme (E1) blocked both chromosomal and extra-chromosomal recombination when added 1h following transfection/induction, but they had no effect when added 16 h later. There was no effect on expression of RAG1, and recombination did not require transit through the cell cycle, confirming that inhibition was not due to an indirect effect on cell cycle arrest or protein expression. Experiments in which RAG1 translation was blocked with cyclohexamide after 16 h of expression indicated that many active recombination complexes were formed within this window, although recombination products continued to accumulate for 48 h. These data suggest that ubiquitin-dependent degradation is an early step in complex assembly or activation, and are consistent with our previous hypothesis that degradation of a negative regulator is required to trigger recombination.
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Affiliation(s)
- Anamika Bhattacharyya
- Department of Biochemistry and Molecular and Cellular Sciences, Georgetown University, Washington, DC 20057, USA
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11
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Karyopherin alpha 1 is a putative substrate of the RAG1 ubiquitin ligase. Mol Immunol 2008; 46:1319-25. [PMID: 19118899 DOI: 10.1016/j.molimm.2008.11.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 11/23/2008] [Indexed: 11/22/2022]
Abstract
The RAG1 recombinase, which participates in DNA manipulation during rearrangement of antigen receptor genes in developing immune cells, possesses ubiquitin ligase activity. The nuclear transport protein karyopherin alpha 1 (KPNA1) binds to RAG1 upstream of its ubiquitin ligase domain, but this interaction is not required for nuclear localization of RAG1. We found that the isolated ubiquitin ligase domain of RAG1 (amino acids 218-389) promoted ubiquitylation of purified KPNA1. While RAG1 auto-ubiquitylation is dependent on the ubiquitin conjugating enzyme CDC34, ubiquitylation of KPNA1 was best supported by UbcH2/Rad6 and UbcH5a. Ubiquitylation of KPNA1 required the lysine/arginine-rich region spanning RAG1 amino acids 218-263 upstream of the RAG1 ubiquitin ligase domain, but RAG1 was still able to undergo auto-ubiquitylation in this region even in the presence of KPNA1. This is the first putative substrate identified for the RAG1 ubiquitin ligase, and to our knowledge it is the first reported case of ubiquitylation of KPNA1.
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12
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Dudley DD, Sekiguchi J, Zhu C, Sadofsky MJ, Whitlow S, DeVido J, Monroe RJ, Bassing CH, Alt FW. Impaired V(D)J recombination and lymphocyte development in core RAG1-expressing mice. ACTA ACUST UNITED AC 2003; 198:1439-50. [PMID: 14581608 PMCID: PMC2194253 DOI: 10.1084/jem.20030627] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
RAG1 and RAG2 are the lymphocyte-specific components of the V(D)J recombinase. In vitro analyses of RAG function have relied on soluble, highly truncated “core” RAG proteins. To identify potential functions for noncore regions and assess functionality of core RAG1 in vivo, we generated core RAG1 knockin (RAG1c/c) mice. Significant B and T cell numbers are generated in RAG1c/c mice, showing that core RAG1, despite missing ∼40% of the RAG1 sequence, retains significant in vivo function. However, lymphocyte development and the overall level of V(D)J recombination are impaired at the progenitor stage in RAG1c/c mice. Correspondingly, there are reduced numbers of peripheral RAG1c/c B and T lymphocytes. Whereas normal B lymphocytes undergo rearrangement of both JH loci, substantial levels of germline JH loci persist in mature B cells of RAG1c/c mice, demonstrating that DJH rearrangement on both IgH alleles is not required for developmental progression to the stage of VH to DJH recombination. Whereas VH to DJH rearrangements occur, albeit at reduced levels, on the nonselected alleles of RAG1c/c B cells that have undergone D to JH rearrangements, we do not detect VH to DH rearrangements in RAG1c/c B cells that retain germline JH alleles. We discuss the potential implications of these findings for noncore RAG1 functions and for the ordered assembly of VH, DH, and JH segments.
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Affiliation(s)
- Darryll D Dudley
- Howard Hughes Medical Institute, The Children's Hospital, The Center for Blood Research, Harvard Medical School, Boston, MA 02115, USA
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13
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Gu Y, Jin S, Gao Y, Weaver DT, Alt FW. Ku70-deficient embryonic stem cells have increased ionizing radiosensitivity, defective DNA end-binding activity, and inability to support V(D)J recombination. Proc Natl Acad Sci U S A 1997; 94:8076-81. [PMID: 9223317 PMCID: PMC21559 DOI: 10.1073/pnas.94.15.8076] [Citation(s) in RCA: 322] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/1997] [Indexed: 02/04/2023] Open
Abstract
V(D)J recombination requires both lymphoid-specific and generally expressed enzymatic activities. All three known generally expressed activities involved in V(D)J recombination are also involved in DNA double-strand break repair (DSBR). Two of these are components of the DNA-dependent protein kinase (DNA-PK) and include Ku80 and DNA-PK catalytic subunit (DNA-PKcs); the third, XRCC4, is a protein of unknown function. The Ku70 protein is an additional component of DNA-PK; Ku70 forms a heterodimer with Ku80 to generate the DNA end-binding component of the enzyme. To test putative functions for Ku70, we have used gene-targeted mutation to generate a murine embryonic stem cell line which lacks Ku70 expression. We find that the Ku70(-/-) cells produce no detectable Ku70 and very little Ku80, suggesting a direct interrelationship between their levels. Correspondingly, these cells lack the nonspecific DNA end-binding activity associated with Ku. Significantly, the Ku70(-/-) embryonic stem cells have markedly increased sensitivity to gamma-irradiation relative to Ku70(+/-) or wild-type embryonic stem cells. Furthermore, the Ku70(-/-) cells lack the ability to effectively rejoin signal and coding ends liberated in transiently introduced V(D)J recombination substrates by enforced RAG-1 and RAG-2 expression. We conclude that the Ku70 gene product is involved in DSBR and V(D)J recombination and confirm that the Ku70 gene can be classified as a member of the x-ray cross-complementation group 6 (XRCC6). Potential differences between the Ku70(-/-) and Ku80(-/-) V(D)J recombination defects are discussed.
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Affiliation(s)
- Y Gu
- Children's Hospital, Boston, MA 02115, USA
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14
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Jessberger R, Schär P, Robins P, Ferrari E, Riwar B, Hübscher U. Regulation of DNA metabolic enzymes upon induction of preB cell development and V(D)J recombination: up-regulation of DNA polymerase delta. Nucleic Acids Res 1997; 25:289-96. [PMID: 9016556 PMCID: PMC146443 DOI: 10.1093/nar/25.2.289] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Withdrawal of interleukin-7 from cultured murine preB lymphocytes induces cell differentiation including V(D)J immunoglobulin gene rearrangements and cell cycle arrest. Advanced steps of the V(D)J recombination reaction involve processing of coding ends by several largely unidentified DNA metabolic enzymes. We have analyzed expression and activity of DNA polymerases alpha, beta, delta and epsilon, proliferating cell nuclear antigen (PCNA), topoisomerases I and II, terminal deoxynucleotidyl transferase (TdT) and DNA ligases I, III and IV upon induction of preB cell differentiation. Despite the immediate arrest of cell proliferation, DNA polymerase delta protein levels remained unchanged for approximately 2 days and its activity was up-regulated several-fold, while PCNA was continuously present. Activity of DNA polymerases alpha,beta and epsilon decreased. Expression and activity of DNA ligase I were drastically reduced, while those of DNA ligases III and IV remained virtually constant. No changes in DNA topoisomerases I or II expression and activity occurred and TdT expression was moderately increased early after induction. Our results render DNA polymerase delta a likely candidate acting in DNA synthesis related to V(D)J recombination in lymphocytes.
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Affiliation(s)
- R Jessberger
- Basel Institute for Immunology, Grenzacherstrasse 487, CH-4005 Basel, Switzerland.
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