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Roles of G4-DNA and G4-RNA in Class Switch Recombination and Additional Regulations in B-Lymphocytes. Molecules 2023; 28:molecules28031159. [PMID: 36770824 PMCID: PMC9921937 DOI: 10.3390/molecules28031159] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/18/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
Mature B cells notably diversify immunoglobulin (Ig) production through class switch recombination (CSR), allowing the junction of distant "switch" (S) regions. CSR is initiated by activation-induced deaminase (AID), which targets cytosines adequately exposed within single-stranded DNA of transcribed targeted S regions, with a specific affinity for WRCY motifs. In mammals, G-rich sequences are additionally present in S regions, forming canonical G-quadruplexes (G4s) DNA structures, which favor CSR. Small molecules interacting with G4-DNA (G4 ligands), proved able to regulate CSR in B lymphocytes, either positively (such as for nucleoside diphosphate kinase isoforms) or negatively (such as for RHPS4). G4-DNA is also implicated in the control of transcription, and due to their impact on both CSR and transcriptional regulation, G4-rich sequences likely play a role in the natural history of B cell malignancies. Since G4-DNA stands at multiple locations in the genome, notably within oncogene promoters, it remains to be clarified how it can more specifically promote legitimate CSR in physiology, rather than pathogenic translocation. The specific regulatory role of G4 structures in transcribed DNA and/or in corresponding transcripts and recombination hereby appears as a major issue for understanding immune responses and lymphomagenesis.
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2
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Shen HM, Wuerffel R, Cantillo JF, Priyadarshi S, Lei X, Liang J, Wu YL, Kenter AL. Loop extrusion promotes an alternate pathway for isotype switching. Cell Rep 2021; 37:110059. [PMID: 34818547 PMCID: PMC8979556 DOI: 10.1016/j.celrep.2021.110059] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/22/2021] [Accepted: 11/03/2021] [Indexed: 01/02/2023] Open
Abstract
Class-switch recombination (CSR) involves replacement of the Cμ
constant region with another downstream CH region. CSR is initiated
by activation-induced cytidine deaminase (AID)-mediated DNA breaks that are
targeted to transcriptionally active switch (S) regions. S region promoters
(Prs) direct synapsis by associating with the Eμ and 3′Eα
enhancers that jointly anchor a chromatin loop. We report that asymmetric loop
extrusion allows 3′Eα to track along the locus and form Pr-Pr-E
interactions that mediate CSR between downstream S regions, followed by
switching to donor Sμ. This alternative pathway bypasses sequential
switching and creates immunoglobulin (Ig)E+ B cells in the absence of
IgG1 expression. Based on the analysis of diagnostic CSR products in B cell
subsets, we identify a BCR-negative cell intermediate that is pivotal to
efficient CSR. Shen et al. report that 3′Eα tracks along the Igh locus via
unidirectional loop extrusion to form germline transcript promoter (Pr)-Pr-E
interactions that mediate an alternative CSR pathway. B cell intermediates of
CSR are identified, which are AID-dependent, surface BCR-negative, and in the
G1 phase of the cell cycle.
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Affiliation(s)
- Hong Ming Shen
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612-7344, USA
| | - Robert Wuerffel
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612-7344, USA
| | - Jose F Cantillo
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612-7344, USA
| | - Saurabh Priyadarshi
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612-7344, USA
| | - Xue Lei
- Department of Bioengineering, University of Illinois Colleges of Engineering and Medicine, Chicago, IL 60612-7344, USA
| | - Jie Liang
- Department of Bioengineering, University of Illinois Colleges of Engineering and Medicine, Chicago, IL 60612-7344, USA
| | - Yee Ling Wu
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL 60153, USA
| | - Amy L Kenter
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612-7344, USA.
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3
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Dauba A, Khamlichi AA. Long-Range Control of Class Switch Recombination by Transcriptional Regulatory Elements. Front Immunol 2021; 12:738216. [PMID: 34594340 PMCID: PMC8477019 DOI: 10.3389/fimmu.2021.738216] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/17/2021] [Indexed: 01/18/2023] Open
Abstract
Immunoglobulin class switch recombination (CSR) plays a crucial role in adaptive immune responses through a change of the effector functions of antibodies and is triggered by T-cell-dependent as well as T-cell-independent antigens. Signals generated following encounter with each type of antigen direct CSR to different isotypes. At the genomic level, CSR occurs between highly repetitive switch sequences located upstream of the constant gene exons of the immunoglobulin heavy chain locus. Transcription of switch sequences is mandatory for CSR and is induced in a stimulation-dependent manner. Switch transcription takes place within dynamic chromatin domains and is regulated by long-range regulatory elements which promote alignment of partner switch regions in CSR centers. Here, we review recent work and models that account for the function of long-range transcriptional regulatory elements and the chromatin-based mechanisms involved in the control of CSR.
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Affiliation(s)
- Audrey Dauba
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, Université Paul Sabatier, Toulouse, France
| | - Ahmed Amine Khamlichi
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, Université Paul Sabatier, Toulouse, France
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4
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Bruzeau C, Moreau J, Le Noir S, Pinaud E. Panorama of stepwise involvement of the IgH 3' regulatory region in murine B cells. Adv Immunol 2021; 149:95-114. [PMID: 33993921 DOI: 10.1016/bs.ai.2021.03.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Among the multiple events leading to immunoglobulin (Ig) expression in B cells, stepwise activation of the Ig heavy chain locus (IgH) is of critical importance. Transcription regulation of the complex IgH locus has always been an interesting viewpoint to unravel the multiple and complex events required for IgH expression. First, regulatory germline transcripts (GLT) assist DNA remodeling events such as VDJ recombination, class switch recombination (CSR) and somatic hypermutation (SHM). Second, productive spliced transcripts restrict heavy chain protein expression associated either with the surface receptor of developing B cells or secreted in large amounts in plasma cells. One main transcriptional regulator for IgH lies at its 3' extremity and includes both a set of enhancers grouped in a large 3' regulatory region (3'RR) and a cluster of 3'CTCF-binding elements (3'CBEs). In this focused review, we will preferentially refer to evidence reported for the murine endogenous IgH locus, whether it is wt or carries deletions or insertions within the IgH 3' boundary and associated regulatory region.
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Affiliation(s)
- Charlotte Bruzeau
- CNRS, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, Limoges, France; INSERM, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 1262, Limoges, France; Université de Limoges, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, UMR 1262, Limoges, France
| | - Jeanne Moreau
- CNRS, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, Limoges, France; INSERM, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 1262, Limoges, France; Université de Limoges, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, UMR 1262, Limoges, France
| | - Sandrine Le Noir
- CNRS, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, Limoges, France; INSERM, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 1262, Limoges, France; Université de Limoges, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, UMR 1262, Limoges, France
| | - Eric Pinaud
- CNRS, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, Limoges, France; INSERM, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 1262, Limoges, France; Université de Limoges, Contrôle de la Réponse Immune B et des Lymphoproliférations, UMR 7276, UMR 1262, Limoges, France.
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5
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Ros F, Offner S, Klostermann S, Thorey I, Niersbach H, Breuer S, Zarnt G, Lorenz S, Puels J, Siewe B, Schueler N, Dragicevic T, Ostler D, Hansen-Wester I, Lifke V, Kaluza B, Kaluza K, van Schooten W, Buelow R, Tissot AC, Platzer J. Rabbits transgenic for human IgG genes recapitulating rabbit B-cell biology to generate human antibodies of high specificity and affinity. MAbs 2020; 12:1846900. [PMID: 33228444 PMCID: PMC7780963 DOI: 10.1080/19420862.2020.1846900] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Transgenic animals incorporating human antibody genes are extremely attractive for drug development because they obviate subsequent antibody humanization procedures required for therapeutic translation. Transgenic platforms have previously been established using mice, but also more recently rats, chickens, and cows and are now in abundant use for drug development. However, rabbit-based antibody generation, with a strong track record for specificity and affinity, is able to include gene conversion mediated sequence diversification, thereby enhancing binder maturation and improving the variance/selection of output antibodies in a different way than in rodents. Since it additionally frequently permits good binder generation against antigens that are only weakly immunogenic in other organisms, it is a highly interesting species for therapeutic antibody generation. We report here on the generation, utilization, and analysis of the first transgenic rabbit strain for human antibody production. Through the knockout of endogenous IgM genes and the introduction of human immunoglobulin sequences, this rabbit strain has been engineered to generate a highly diverse human IgG antibody repertoire. We further incorporated human CD79a/b and Bcl2 (B-cell lymphoma 2) genes, which enhance B-cell receptor expression and B-cell survival. Following immunization against the angiogenic factor BMP9 (Bone Morphogenetic Proteins 9), we were able to isolate a set of exquisitely affine and specific neutralizing antibodies from these rabbits. Sequence analysis of these binders revealed that both somatic hypermutation and gene conversion are fully operational in this strain, without compromising the very high degree of humanness. This powerful new transgenic strategy will allow further expansion of the use of endogenous immune mechanisms in drug development.
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Affiliation(s)
- Francesca Ros
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Sonja Offner
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Stefan Klostermann
- Roche Pharmaceutical Research and Early Development, Informatics, Roche Innovation Center Munich , Penzberg, Germany
| | - Irmgard Thorey
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Helmut Niersbach
- Roche Pharmaceutical Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Munich , Penzberg, Germany
| | - Sebastian Breuer
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Grit Zarnt
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Stefan Lorenz
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | | | - Basile Siewe
- THE JACKSON LABORATORY JMCRS, Sacramento, CA, USA
| | - Nicole Schueler
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Tajana Dragicevic
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Dominique Ostler
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Imke Hansen-Wester
- Supplier Quality Management, Global External Quality Roche Diagnostics GmbH , Penzberg, Germany
| | - Valeria Lifke
- Personalized Healthcare Solution, Immunoassay Development and System Integration, Roche Diagnostics GmbH , Penzberg, Germany
| | - Brigitte Kaluza
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Klaus Kaluza
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | | | | | - Alain C Tissot
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
| | - Josef Platzer
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Munich , Penzberg, Germany
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6
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Le Noir S, Laffleur B, Carrion C, Garot A, Lecardeur S, Pinaud E, Denizot Y, Skok J, Cogné M. The IgH locus 3' cis-regulatory super-enhancer co-opts AID for allelic transvection. Oncotarget 2017; 8:12929-12940. [PMID: 28088785 PMCID: PMC5355067 DOI: 10.18632/oncotarget.14585] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 01/01/2017] [Indexed: 11/25/2022] Open
Abstract
Immunoglobulin heavy chain (IgH) alleles have ambivalent relationships: they feature both allelic exclusion, ensuring monoallelic expression of a single immunoglobulin (Ig) allele, and frequent inter-allelic class-switch recombination (CSR) reassembling genes from both alleles. The IgH locus 3' regulatory region (3'RR) includes several transcriptional cis-enhancers promoting activation-induced cytidine deaminase (AID)-dependent somatic hypermutation (SHM) and CSR, and altogether behaves as a strong super-enhancer. It can also promote deregulated expression of translocated oncogenes during lymphomagenesis. Besides these rare, illegitimate and pathogenic interactions, we now show that under physiological conditions, the 3'RR super-enhancer supports not only legitimate cis- , but also trans-recruitment of AID, contributing to IgH inter-allelic proximity and enabling the super-enhancer on one allele to stimulate biallelic SHM and CSR. Such inter-allelic activating interactions define transvection, a phenomenon well-known in drosophila but rarely observed in mammalian cells, now appearing as a unique feature of the IgH 3'RR super-enhancer.
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Affiliation(s)
- Sandrine Le Noir
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Brice Laffleur
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Claire Carrion
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Armand Garot
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Sandrine Lecardeur
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Eric Pinaud
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Yves Denizot
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
| | - Jane Skok
- Department of Pathology, New York University School of Medicine, New York, NY, USA
| | - Michel Cogné
- UMR 7276 CNRS and Université de Limoges: Contrôle de la Réponse Immune B et Lymphoprolifération, Limoges, France
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7
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Immunoglobulin genes undergo legitimate repair in human B cells not only after cis- but also frequent trans-class switch recombination. Genes Immun 2014; 15:341-6. [PMID: 24848929 DOI: 10.1038/gene.2014.25] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 03/26/2014] [Accepted: 04/14/2014] [Indexed: 12/23/2022]
Abstract
Immunoglobulin (Ig) genes specifically recruit activation-induced deaminase (AID) for 'on-target' DNA deamination, initiating either variable (V) region somatic hypermutation, or double-strand break intermediates of class switch recombination (CSR). Such breaks overwhelmingly undergo legitimate intra-Ig repair rather than rare illegitimate and potentially oncogenic junctions outside of Ig loci. We show that in human B cells, legitimate synapsis and repair efficiently join Ig genes whether physically linked on one chromosome or located apart on both alleles. This indicates mechanisms faithfully recognizing and/or pairing loci with homology in structure and accessibility, thus licensing interchromosomal trans-CSR junctions while usually preventing illegitimate interchromosomal recombination with AID off-target genes. Physical linkage of IgH genes in cis on the same allele just increases the likelihood of legitimate repair by another fourfold. The strongest force driving CSR might thus be recognition of legitimate target genes. Formation of IgH intra-allelic loops along this process would then constitute a consequence rather than a pre-requisite of this gene-pairing process.
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8
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Ma B, Osborn MJ, Avis S, Ouisse LH, Ménoret S, Anegon I, Buelow R, Brüggemann M. Human antibody expression in transgenic rats: comparison of chimeric IgH loci with human VH, D and JH but bearing different rat C-gene regions. J Immunol Methods 2013; 400-401:78-86. [PMID: 24184135 DOI: 10.1016/j.jim.2013.10.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 10/18/2013] [Accepted: 10/18/2013] [Indexed: 11/28/2022]
Abstract
Expression of human antibody repertoires in transgenic animals has been accomplished by introducing large human Ig loci into mice and, more recently, a chimeric IgH locus into rats. With human VH, D and JH genes linked to the rat C-region antibody expression was significantly increased, similar to wild-type levels not found with fully human constructs. Here we compare four rat-lines containing the same human VH-region (comprising 22 VHs, all Ds and all JHs in natural configuration) but linked to different rat CH-genes and regulatory sequences. The endogenous IgH locus was silenced by zinc-finger nucleases. After breeding, all lines produced exclusively chimeric human H-chain with near normal IgM levels. However, in two lines poor IgG expression and inefficient immune responses were observed, implying that high expression, class-switching and hypermutation are linked to optimal enhancer function provided by the large regulatory region at the 3' end of the IgH locus. Furthermore, exclusion of Cδ and its downstream interval region may assist recombination. Highly diverse IgG and immune responses similar to normal rats were identified in two strains carrying diverse and differently spaced C-genes.
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Affiliation(s)
- Biao Ma
- Recombinant Antibody Technology Ltd., Cambridge, UK
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9
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Shansab M, Eccleston JM, Selsing E. Translocation of an antibody transgene requires AID and occurs by interchromosomal switching to all switch regions except the mu switch region. Eur J Immunol 2011; 41:1456-64. [PMID: 21469111 DOI: 10.1002/eji.201041077] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2010] [Revised: 01/20/2011] [Accepted: 02/09/2011] [Indexed: 11/06/2022]
Abstract
Immunoglobulin (Ig) class switch recombination (CSR) occurs most often by intrachromosomal recombinations between switch (S) regions located on a single chromosome, but it can also occur by interchomosomal recombinations between Ig heavy chain (Igh) S regions located on chomosomal homologs. Interchromosomal recombinations have also been found between chromosomes that are not homologs; examples are Igh/c-myc and Igh/transgene translocations. Most, but not all, studies have indicated that activation-induced cytidine deaminase (AID) is important in Igh/c-myc translocations. The role of AID has not been determined for Igh/transgene translocations. We now show that the majority of Igh/transgene translocations between non-homologs from an Ig transgenic mouse are dependent on AID, but we also find a small number of these translocations that can occur in the absence of AID. Surprisingly, our results also indicate that, although Sγ switch sequences in the endogenous Igh locus participate in chromosomal translocations with the non-homolog transgene-bearing chromosome, Sμ switch sequences do not. This contrasts with the fact that both endogenous Sμ and Sγ sequences participate in intrachromosomal CSR. Our findings suggest the operation of a regulatory mechanism that can differentially control the accessibility of Sμ and Sγ regions for non-homolog translocations even when both are accessible for intrachromosomal recombination.
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Affiliation(s)
- Maryam Shansab
- Program in Immunology and Department of Pathology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
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10
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Pinaud E, Marquet M, Fiancette R, Péron S, Vincent-Fabert C, Denizot Y, Cogné M. The IgH locus 3' regulatory region: pulling the strings from behind. Adv Immunol 2011; 110:27-70. [PMID: 21762815 DOI: 10.1016/b978-0-12-387663-8.00002-8] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Antigen receptor gene loci are among the most complex in mammals. The IgH locus, encoding the immunoglobulin heavy chain (IgH) in B-lineage cells, undergoes major transcription-dependent DNA remodeling events, namely V(D)J recombination, Ig class-switch recombination (CSR), and somatic hypermutation (SHM). Various cis-regulatory elements (encompassing promoters, enhancers, and chromatin insulators) recruit multiple nuclear factors in order to ensure IgH locus regulation by tightly orchestrated physical and/or functional interactions. Among major IgH cis-acting regions, the large 3' regulatory region (3'RR) located at the 3' boundary of the locus includes several enhancers and harbors an intriguing quasi-palindromic structure. In this review, we report progress insights made over the past decade in order to describe in more details the structure and functions of IgH 3'RRs in mouse and human. Generation of multiple cellular, transgenic and knock-out models helped out to decipher the function of the IgH 3' regulatory elements in the context of normal and pathologic B cells. Beside its interest in physiology, the challenge of elucidating the locus-wide cross talk between distant cis-regulatory elements might provide useful insights into the mechanisms that mediate oncogene deregulation after chromosomal translocations onto the IgH locus.
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Affiliation(s)
- Eric Pinaud
- UMR CNRS 6101, Centre National de la Recherche Scientifique, Université de Limoges, Limoges, France
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11
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Sellars M, Reina-San-Martin B, Kastner P, Chan S. Ikaros controls isotype selection during immunoglobulin class switch recombination. ACTA ACUST UNITED AC 2009; 206:1073-87. [PMID: 19414557 PMCID: PMC2715033 DOI: 10.1084/jem.20082311] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Class switch recombination (CSR) allows the humoral immune response to exploit different effector pathways through specific secondary antibody isotypes. However, the molecular mechanisms and factors that control immunoglobulin (Ig) isotype choice for CSR are unclear. We report that deficiency for the Ikaros transcription factor results in increased and ectopic CSR to IgG2b and IgG2a, and reduced CSR to all other isotypes, regardless of stimulation. Ikaros suppresses active chromatin marks, transcription, and activation-induced cytidine deaminase (AID) accessibility at the γ2b and γ2a genes to inhibit class switching to these isotypes. Further, Ikaros directly regulates isotype gene transcription as it directly binds the Igh 3′ enhancer and interacts with isotype gene promoters. Finally, Ikaros-mediated repression of γ2b and γ2a transcription promotes switching to other isotype genes by allowing them to compete for AID-mediated recombination at the single-cell level. Thus, our results reveal transcriptional competition between constant region genes in individual cells to be a critical and general mechanism for isotype specification during CSR. We show that Ikaros is a master regulator of this competition.
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Affiliation(s)
- MacLean Sellars
- Laboratory of Hematopoiesis and Leukemogenesis, and Department of Cancer Biology, Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67400 Illkirch, France
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12
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Guikema JEJ, Schrader CE, Leus NGJ, Ucher A, Linehan EK, Werling U, Edelmann W, Stavnezer J. Reassessment of the role of Mut S homolog 5 in Ig class switch recombination shows lack of involvement in cis- and trans-switching. THE JOURNAL OF IMMUNOLOGY 2009; 181:8450-9. [PMID: 19050263 DOI: 10.4049/jimmunol.181.12.8450] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
When B cells are activated after immunization or infection, they exchange the gene encoding the Ig H chain C region by class switch recombination (CSR). CSR generally occurs by an intrachromosomal deletional recombination within switch (S) region sequences. However, approximately 10% of CSR events occur between chromosome homologs (trans- or interallele CSR), suggesting that the homologous chromosomes are aligned during CSR. Because the Mut S homolog 4 (Msh4) and Msh5 bind to Holliday junctions and are required for homologous recombination during meiosis in germ cells, we hypothesized these proteins might be involved in trans-chromosomal CSR (trans-CSR). Indeed, Msh4-Msh5 has recently been suggested to have a role in CSR. However, we find a large variety of alternative splice variants of Msh5 mRNA in splenic B cells rather than the full-length form found in testis. Most of these mRNAs are unlikely to be stable, suggesting that Msh5 might not be functional. Furthermore, we find that msh5 nullizygous B cells undergo CSR normally, have unaltered levels of trans-CSR, normal levels of DNA breaks in the Smu region, and normal S-S junctions. We also show that the S-S junctions from cis- and trans-CSR events have similar lengths of junctional microhomology, suggesting trans-CSR occurs by nonhomologous end joining as does intrachromosome (cis)-CSR. From these data, we conclude that Msh5 does not participate in CSR.
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Affiliation(s)
- Jeroen E J Guikema
- Department of Molecular Genetics and Microbiology, Program in Immunology and Virology, University of Massachusetts Medical School, Worcester, MA 01655, USA
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13
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Ilić V, Milosević-Jovcić N, Marković D, Petrović S, Stefanović G. A biased Gm haplotype and Gm paraprotein allotype in multiple myeloma suggests a role for the Gm system in myeloma development. Int J Immunogenet 2007; 34:119-25. [PMID: 17373937 DOI: 10.1111/j.1744-313x.2007.00673.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The association between a particular Gm haplotype and susceptibility to multiple myeloma (MM) is not clear. The reason is probably because no investigations have so far been carried out on the relationship between the Gm haplotype, which represents the inherited combination of IgG Gm allotypes, and the Gm allotype expressed at the IgG paraprotein (M-component), which reflects the enhanced gene expression within the haplotype in MM. We studied the incidence of Gm allotypic markers present in IgG subclasses in the serum from 52 patients with MM and in parallel with the isolated IgG paraproteins. The results showed that 84.6% of the patients were heterozygous for haplotypes Gm(a; z; n-; g;)/Gm(f; n+/n-; b1; b0; b5) and 15.3% were homozygous for Gm(f; n/n-; b1; b0; b5), while no homozygous Gm(a; z; n-; g) individuals were found among the studied patients. The incidence of these combinations in the healthy population in Serbia is 34%, 66% and < 1%, respectively. Subjects with Gm(a; z; n-; g)/Gm(f; n+/n-; b1; b0; b5) combination are over 10 times [odds ratio (OR) = 10.69; 95% confidence interval 1.67-68] as likely to be affected by the disease as the subjects with homozygous Gm(f; n+/n-; b1; b0; b5) combination (OR = 0.35, 95% confidence interval 0.06-2.23). However, despite the Gm heterozygosity, most of the Gm(a; z; n-; g;)/Gm(f; n+/n-; b1; b0; b5) positive patients with MM (86.3%) had IgG paraprotein with the allotypic marker from the Gm(f; n+/n-; b1; b0; b5) haplotype. Together with patients homozygous for this haplotype, the relative number of patients with serum IgG paraprotein carrying allotypic marker from the Gm(f; n/n-; b1; b0; b5) haplotype was 88.5%. These results suggest that the development of an M-component could be related to a disturbance on chromosome 14q32 carrying the Gm (f; n+/n-; b1; b0; b5) set of genes.
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Affiliation(s)
- V Ilić
- Institute for Medical Research, University of Belgrade, Belgrade, Serbia.
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