scholarly journals Frequency of immunoglobulin E class switching is autonomously determined and independent of prior switching to other classes.

1994 ◽  
Vol 179 (6) ◽  
pp. 2023-2026 ◽  
Author(s):  
S Jung ◽  
G Siebenkotten ◽  
A Radbruch
Keyword(s):  
Immunoglobulin E ◽  
Low Frequency ◽  
Switch Region ◽  
Major Fraction ◽  
Class Switching ◽  
Class Switch ◽  
Inherent Feature ◽  
Functional Implications ◽  
Switch Regions ◽  
Sequential Switching

Both, in humans and in mice, a major fraction of immunoglobulin E (IgE)-expressing B lymphocytes develops by sequential Ig class switching from IgM via IgG to IgE. This sequential class switch might have functional implications for the frequency and repertoire of IgE+ cells. Here we show that in mutant mice, in which sequential switching to IgE via IgG1 is blocked, the frequency of cells switching to IgE is not affected. Thus, sequential class switching to IgE merely reflects the simultaneous accessibility of two acceptor switch regions for switch recombination, induced by one cytokine, but with markedly distinct efficiency. Analysis of switch recombination on both IgH alleles of switched cells shows that the low frequency of switching to IgE is an inherent feature of the S epsilon switch region and its control elements.

scholarly journals Quantitative Regulation of Class Switch Recombination by Switch Region Transcription

2001 ◽  
Vol 194 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Chung-Gi Lee ◽  
Kazuo Kinoshita ◽  
Arulvathani Arudchandran ◽  
Susana M. Cerritelli ◽  
Robert J. Crouch ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
Switch Region ◽  
Class Switching ◽  
Quantitative Correlation ◽  
Class Switch ◽  
Transcript Processing ◽  
Lymphoma Line ◽  
Artificial Dna ◽  
Switching Efficiency

The isotype specificity of immunoglobulin (Ig) class switching is regulated by a cytokine which induces transcription of a specific switch (S) region, giving rise to so-called germline transcripts. Although previous studies have demonstrated that germline transcription of an S region is required for class switch recombination (CSR) of that particular S region, it has not been shown whether the level of S region transcription affects the efficiency of CSR. We addressed this question by using an artificial DNA construct containing a constitutively transcribed μ switch (Sμ) region and an α switch (Sα) region driven by a tetracycline-responsive promoter. The construct was introduced into a switch-inducible B lymphoma line and the quantitative correlation between Sα region transcription and class switching efficiency was evaluated. The level of Sα transcription was linearly correlated with CSR efficiency, reaching a plateau at saturation. On the other hand, we failed to obtain the evidence to support involvement of either RNA–DNA heteroduplex or trans germline transcripts in CSR. Taken together, it is likely that S region transcription and/or transcript processing in situ may be required for CSR. We propose that because of the unusual properties of S region DNA, transcription induces the DNA to transiently be single stranded, permitting secondary structure(s) to form. Such structures may be recognition targets of a putative class switch recombinase.

scholarly journals AID from bony fish catalyzes class switch recombination

2005 ◽  
Vol 202 (6) ◽  
pp. 733-738 ◽  
Author(s):  
Vasco M. Barreto ◽  
Qiang Pan-Hammarstrom ◽  
Yaofeng Zhao ◽  
Lennart Hammarstrom ◽  
Ziva Misulovin ◽  
...  
Keyword(s):  
B Cells ◽  
Catalytic Domain ◽  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Class Switch Recombination ◽  
Adaptive Immune System ◽  
Bony Fish ◽  
Class Switching ◽  
Class Switch ◽  
Switch Regions

Class switch recombination was the last of the lymphocyte-specific DNA modification reactions to appear in the evolution of the adaptive immune system. It is absent in cartilaginous and bony fish, and it is common to all tetrapods. Class switching is initiated by activation-induced cytidine deaminase (AID), an enzyme expressed in cartilaginous and bony fish that is also required for somatic hypermutation. Fish AID differs from orthologs found in tetrapods in several respects, including its catalytic domain and carboxy-terminal region, both of which are essential for the switching reaction. To determine whether evolution of class switch recombination required alterations in AID, we assayed AID from Japanese puffer and zebra fish for class-switching activity in mouse B cells. We find that fish AID catalyzes class switch recombination in mammalian B cells. Thus, AID had the potential to catalyze this reaction before the teleost and tetrapod lineages diverged, suggesting that the later appearance of a class-switching reaction was dependent on the evolution of switch regions and multiple constant regions in the IgH locus.

scholarly journals H2AX Is Required for Recombination Between Immunoglobulin Switch Regions but Not for Intra-Switch Region Recombination or Somatic Hypermutation

2003 ◽  
Vol 197 (12) ◽  
pp. 1767-1778 ◽  
Author(s):  
Bernardo Reina-San-Martin ◽  
Simone Difilippantonio ◽  
Leif Hanitsch ◽  
Revati F. Masilamani ◽  
André Nussenzweig ◽  
...  
Keyword(s):  
B Cells ◽  
Posttranslational Modifications ◽  
Somatic Hypermutation ◽  
Dna Lesions ◽  
Switch Region ◽  
Histone H2ax ◽  
Class Switch ◽  
Switch Regions ◽  
Precise Role

Changes in chromatin structure induced by posttranslational modifications of histones are important regulators of genomic function. Phosphorylation of histone H2AX promotes DNA repair and helps maintain genomic stability. Although B cells lacking H2AX show impaired class switch recombination (CSR), the precise role of H2AX in CSR and somatic hypermutation (SHM) has not been defined. We show that H2AX is not required for SHM, suggesting that the processing of DNA lesions leading to SHM is fundamentally different from CSR. Impaired CSR in H2AX−/− B cells is not due to alterations in switch region transcription, accessibility, or aberrant joining. In the absence of H2AX, short-range intra-switch region recombination proceeds normally while long-range inter-switch region recombination is impaired. Our results suggest a role for H2AX in regulating the higher order chromatin remodeling that facilitates switch region synapsis.

Regulation of ϵ germline transcription and switch region mutations by IgH locus 3′ enhancers in transgenic mice

Blood ◽  
2006 ◽  
Vol 109 (1) ◽  
pp. 159-167 ◽  
Author(s):  
Jurga Laurencikiene ◽  
Vytas Tamosiunas ◽  
Eva Severinson
Keyword(s):  
B Cells ◽  
Cytidine Deaminase ◽  
Switch Region ◽  
Endogenous Gene ◽  
Class Switch ◽  
Germline Transcription ◽  
Igh Locus ◽  
Activation Induced Cytidine Deaminase ◽  
Switch Regions ◽  
Transgenic Lines

Abstract Germline (GL) transcription is regulated by specific promoters and immunoglobulin heavy chain (IgH) 3′ locus enhancers and is necessary for Ig class-switch recombination (CSR). We have generated different transgenic lines containing the GL ϵ promoter, switch (S) ϵ region, and constant (C) ϵ region with or without the DNase I–sensitive regions (HS) 3A-HS1,2 or HS3B-HS4 3′ IgH enhancer pairs. The enhancerless construct was expressed in B cells activated by interleukin (IL)–4 and CD40, thus resembling regulation of the endogenous gene. Both enhancer-containing transgenes efficiently increased expression in B cells and were strongly up-regulated by stimuli. In addition, Sϵ regions of the transgene containing HS3B-HS4 were mutated in activated, sorted B cells. Such mutations are known to precede CSR and are dependent on activation-induced cytidine deaminase (AID). Our findings show that all elements necessary for recruitment of the recombination machinery are present in the transgene containing HS3 and HS4. These enhancers probably provide something more specific than mere increased accessibility of switch regions. We propose that transcription factors binding the enhancers help to target the recombination machinery to the switch regions.

scholarly journals Immunoglobulin Class Switch Recombination Is Initiated by Rare Cytosine Deamination Events at Switch Regions

2020 ◽  
Vol 40 (16) ◽  
Author(s):  
Ahrom Kim ◽  
Li Han ◽  
Kefei Yu
Keyword(s):  
Somatic Hypermutation ◽  
Cytidine Deaminase ◽  
Class Switch Recombination ◽  
Strand Break ◽  
Switch Region ◽  
Cytosine Deamination ◽  
Class Switch ◽  
Switch Regions ◽  
Dna Strands ◽  
Uracil Repair

ABSTRACT Activation-induced cytidine deaminase (AID) initiates immunoglobulin (Ig) class switch recombination (CSR), somatic hypermutation (SHM), and gene conversion by converting DNA cytosines to uracils at specific genomic regions. In this study, we examined AID footprints across the entire length of an engineered switch region in cells ablated for uracil repair. We found that AID deamination occurs predominantly at WRC hot spots (where W is A or T and R is A or G) and that the deamination frequency remains constant across the entire switch region. Importantly, we analyzed monoallelic AID deamination footprints on both DNA strands occurring within a single cell cycle. We found that AID generates few and mostly isolated uracils in the switch region, although processive AID deaminations are evident in some molecules. The frequency of molecules containing deamination on both DNA strands at the acceptor switch region correlates with the class switch efficiency, raising the possibility that the minimal requirement for DNA double-strand break (DSB) formation is as low as even one AID deamination event on both DNA strands.

scholarly journals Fine-Structure Analysis of Activation-Induced Deaminase Accessibility to Class Switch Region R-Loops

2005 ◽  
Vol 25 (5) ◽  
pp. 1730-1736 ◽  
Author(s):  
Kefei Yu ◽  
Deepankar Roy ◽  
Melina Bayramyan ◽  
Ian S. Haworth ◽  
Michael R. Lieber
Keyword(s):  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Site Preference ◽  
Switch Region ◽  
Class Switch ◽  
High Resolution Analysis ◽  
Switch Regions ◽  
Resolution Analysis ◽  
Activation Induced Deaminase ◽  
Dna Strand

ABSTRACT Activation-induced deaminase (AID) is essential for class switch recombination and somatic hypermutation, and it has the ability to deaminate single-stranded DNA at cytidines. Mammalian class switch regions form R-loops upon transcription in the physiological orientation. The displaced DNA strand of an R-loop is forced to wrap around the RNA-DNA hybrid; hence, it may not have complete exposure to proteins. A fundamental question concerns the extent to which AID is accessible to the displaced strand of a transcription-generated R-loop. We used a minimal R-loop to carry out high-resolution analysis of the precise locations of AID action. We found that AID deaminates on the displaced DNA strand across the entire length of the R-loop. Displaced strand locations with a WRC (where W is A or T and R is A or G) sequence are preferred targets, but there are clear exceptions. These WRC deviations may be due to steric constraints on the accessibility of AID to these sites as the displaced strand twists around the RNA-DNA duplex. This phenomenon may explain the lack of WRC site preference at the mutations surrounding class switch recombination junctions.

scholarly journals Examination of Msh6- and Msh3-deficient Mice in Class Switching Reveals Overlapping and Distinct Roles of MutS Homologues in Antibody Diversification

2004 ◽  
Vol 200 (1) ◽  
pp. 47-59 ◽  
Author(s):  
Ziqiang Li ◽  
Stefan J. Scherer ◽  
Diana Ronai ◽  
Maria D. Iglesias-Ussel ◽  
Jonathan U. Peled ◽  
...  
Keyword(s):  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Class Switching ◽  
Class Switch ◽  
Base Substitutions ◽  
Antibody Diversification ◽  
Switch Regions ◽  
Somatic Diversification ◽  
Deficient Mice

Somatic hypermutation and class switch recombination (CSR) contribute to the somatic diversification of antibodies. It has been shown that MutS homologue (Msh)6 (in conjunction with Msh2) but not Msh3 is involved in generating A/T base substitutions in somatic hypermutation. However, their roles in CSR have not yet been reported. Here we show that Msh6−/− mice have a decrease in CSR, whereas Msh3−/− mice do not. When switch regions were analyzed for mutations, deficiency in Msh6 was associated with an increase in transition mutations at G/C basepairs, mutations at RGYW/WRCY hotspots, and a small increase in the targeting of G/C bases. In addition, Msh6−/− mice exhibited an increase in the targeting of recombination sites to GAGCT/GGGGT consensus repeats and hotspots in Sγ3 but not in Sμ. In contrast to Msh2−/− mice, deficiency in Msh6 surprisingly did not change the characteristics of Sμ-Sγ3 switch junctions. However, Msh6−/− mice exhibited a change in the positioning of Sμ and Sγ3 junctions. Although none of these changes were seen in Msh3−/− mice, they had a higher percentage of large inserts in their switch junctions. Together, our data suggest that MutS homologues Msh2, Msh3, and Msh6 play overlapping and distinct roles during antibody diversification processes.

scholarly journals Processing of Switch Transcripts Is Required for Targeting of Antibody Class Switch Recombination

1998 ◽  
Vol 188 (12) ◽  
pp. 2369-2374 ◽  
Author(s):  
Katharina Hein ◽  
Matthias G.O. Lorenz ◽  
Gregor Siebenkotten ◽  
Katja Petry ◽  
Rainer Christine ◽  
...  
Keyword(s):  
Donor Site ◽  
Class Switch Recombination ◽  
Mutant Mice ◽  
Splice Donor Site ◽  
Chain Gene ◽  
Switch Region ◽  
Splice Donor ◽  
Class Switch ◽  
Switch Regions ◽  
Antibody Class

Antibody class switching is mediated by somatic recombination between switch regions of the immunoglobulin heavy chain gene locus. Targeting of recombination to particular switch regions is strictly regulated by cytokines through the induction of switch transcripts starting 5′ of the repetitive switch regions. However, switch transcription as such is not sufficient to target switch recombination. This has been shown in mutant mice, in which the I-exon and its promoter upstream of the switch region were replaced with heterologous promoters. Here we show that, in the murine germline targeted replacement of the endogenous γ1 promoter, I-exon, and I-exon splice donor site by heterologous promoter and splice donor sites directs switch recombination in activated B lymphocytes constitutively to the γ1 switch region. In contrast, switch recombination to IgG1 is inhibited in mutant mice, in which the replacement does not include the heterologous splice donor site. Our data unequivocally demonstrate that targeting of switch recombination to IgG1 in vivo requires processing of the Iγ1 switch transcripts. Either the processing machinery or the processed transcripts are involved in class switch recombination.

scholarly journals ATM Is Required for Efficient Recombination between Immunoglobulin Switch Regions

2004 ◽  
Vol 200 (9) ◽  
pp. 1103-1110 ◽  
Author(s):  
Bernardo Reina-San-Martin ◽  
Hua Tang Chen ◽  
André Nussenzweig ◽  
Michel C. Nussenzweig
Keyword(s):  
Somatic Hypermutation ◽  
Serum Antibody ◽  
Strand Break ◽  
Cell Cycle Checkpoints ◽  
Immunoglobulin Gene ◽  
Switch Region ◽  
Atm Kinase ◽  
Class Switch ◽  
Gene Diversification ◽  
Switch Regions

Ataxia telangiectasia mutated (ATM) kinase is critical for initiating the signaling pathways that lead to cell cycle checkpoints and DNA double strand break repair. In the absence of ATM, humans and mice show a primary immunodeficiency that includes low serum antibody titers, but the role of ATM in antigen-driven immunoglobulin gene diversification has not been defined. Here, we show that although ATM is dispensable for somatic hypermutation, it is required for efficient class switch recombination (CSR). The defect in CSR is not due to alterations in switch region transcription, accessibility, DNA damage checkpoint protein recruitment, or short-range intra-switch region recombination. Only long-range inter-switch recombination is defective, indicating an unexpected role for ATM in switch region synapsis during CSR.

scholarly journals Structure and expression of germline epsilon transcripts in human B cells induced by interleukin 4 to switch to IgE production.

1990 ◽  
Vol 172 (2) ◽  
pp. 463-473 ◽  
Author(s):  
J F Gauchat ◽  
D A Lebman ◽  
R L Coffman ◽  
H Gascan ◽  
J E de Vries
Keyword(s):  
T Cells ◽  
Heavy Chain ◽  
Regulatory Mechanisms ◽  
Interleukin 4 ◽  
Switch Region ◽  
Class Switching ◽  
Rna Analysis ◽  
Human B Cells ◽  
Switch Regions ◽  
Ige Synthesis

Interleukin 4 (IL-4)-induced IgE production coincides with the appearance of the 2.2-kb productive epsilon-mRNA, but is preceded by synthesis of a 1.7-kb epsilon-RNA. Analysis of cDNA copies of the 5' end of this RNA indicated that the 1.7-kb epsilon-RNA is a germline epsilon immunoglobulin heavy chain transcript with an exon mapping 5' to the switch region. Transcription through switch regions has been implicated in the control of class switching. However, IL-4 or cloned CD4+ T cells were able to induce germline epsilon transcripts without inducing IgE synthesis, for which both signals were required. These results indicate that induction of human germline epsilon-RNA does not necessarily result in IgE synthesis, and that additional regulatory mechanisms are involved in class switching.

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