scholarly journals Elucidation of the enigmatic IgD class-switch recombination via germline deletion of the IgH 3′ regulatory region

2014 ◽  
Vol 211 (5) ◽  
pp. 975-985 ◽  
Author(s):  
Pauline Rouaud ◽  
Alexis Saintamand ◽  
Faten Saad ◽  
Claire Carrion ◽  
Sandrine Lecardeur ◽  
...  
Keyword(s):  
Somatic Hypermutation ◽  
Regulatory Region ◽  
Class Switch Recombination ◽  
End Joining ◽  
Class Switch ◽  
Classical Class ◽  
Mesenteric Lymph ◽  
Alternative End Joining ◽  
Activation Induced Deaminase ◽  
Deficient Mice

Classical class-switch recombination (cCSR) substitutes the Cμ gene with Cγ, Cε, or Cα, thereby generating IgG, IgE, or IgA classes, respectively. This activation-induced deaminase (AID)–driven process is controlled by the IgH 3′ regulatory region (3′RR). Regulation of rare IgD CSR events has been enigmatic. We show that μδCSR occurs in mouse mesenteric lymph node (MLN) B cells and is AID-dependent. AID attacks differ from those in cCSR because they are not accompanied by extensive somatic hypermutation (SHM) of targeted regions and because repaired junctions exhibit features of the alternative end-joining (A-EJ) pathway. In contrast to cCSR and SHM, μδCSR is 3′RR-independent, as its absence affects neither breakpoint locations in Sμ- and Sδ-like (σδ) nor mutation patterns at Sμ-σδ junctions. Although mutations occur in the immediate proximity of the μδ junctions, SHM is absent distal to the junctions within both Sμ and rearranged VDJ regions. In conclusion, μδCSR is active in MLNs, occurs independently of 3′RR-driven assembly, and is even dramatically increased in 3′RR-deficient mice, further showing that its regulation differs from cCSR.

scholarly journals IgH 3’ regulatory region increases ectopic class switch recombination

PLoS Genetics ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. e1009288
Author(s):  
Sandrine Le Noir ◽  
Amélie Bonaud ◽  
Bastien Hervé ◽  
Audrey Baylet ◽  
François Boyer ◽  
...  
Keyword(s):  
Somatic Hypermutation ◽  
Regulatory Region ◽  
Class Switch Recombination ◽  
Dna Lesions ◽  
Reporter System ◽  
Long Distance ◽  
Class Switch ◽  
Super Enhancer ◽  
Switch Regions ◽  
Activation Induced Deaminase

DNA lesions inflicted by activation-induced deaminase (AID) instrumentally initiate the processes reshaping immunoglobulin genes in mature B-cells, from local somatic hypermutation (SHM) to junctions of distant breaks during class switch recombination (CSR). It remains incompletely understood how these divergent outcomes of AID attacks are differentially and temporally focused, with CSR strictly occurring in the Ig heavy chain (IgH) locus while SHM concentrates on rearranged V(D)J regions in the IgH and Ig light chain loci. In the IgH locus, disruption of either the 3’Regulatory Region (3’RR) super-enhancer or of switch (S) regions preceding constant genes, profoundly affects CSR. Reciprocally, we now examined if these elements are sufficient to induce CSR in a synthetic locus based on the Igκ locus backbone. Addition of a surrogate “core 3’RR” (c3’RR) and of a pair of transcribed and spliced Switch regions, together with a reporter system for “κ-CSR” yielded a switchable Igκ locus. While the c3’RR stimulated SHM at S regions, it also lowered the local SHM threshold necessary for switch recombination to occur. The 3’RR thus both helps recruit AID to initiate DNA lesions, but then also promotes their resolution through long-distance synapses and recombination following double-strand breaks.

scholarly journals The IgH 3′ regulatory region controls somatic hypermutation in germinal center B cells

2013 ◽  
Vol 210 (8) ◽  
pp. 1501-1507 ◽  
Author(s):  
Pauline Rouaud ◽  
Christelle Vincent-Fabert ◽  
Alexis Saintamand ◽  
Rémi Fiancette ◽  
Marie Marquet ◽  
...  
Keyword(s):  
B Cells ◽  
Heavy Chain ◽  
Somatic Hypermutation ◽  
Regulatory Region ◽  
Central Element ◽  
Transcriptional Enhancers ◽  
Class Switch ◽  
Activation Induced Deaminase ◽  
Ig Heavy Chain ◽  
Deficient Mice

Interactions with cognate antigens recruit activated B cells into germinal centers where they undergo somatic hypermutation (SHM) in V(D)J exons for the generation of high-affinity antibodies. The contribution of IgH transcriptional enhancers in SHM is unclear. The Eμ enhancer upstream of Cμ has a marginal role, whereas the influence of the IgH 3′ regulatory region (3′RR) enhancers (hs3a, hs1,2, hs3b, and hs4) is controversial. To clarify the latter issue, we analyzed mice lacking the whole 30-kb extent of the IgH 3′RR. We show that SHM in VH rearranged regions is almost totally abrogated in 3′RR-deficient mice, whereas the simultaneous Ig heavy chain transcription rate is only partially reduced. In contrast, SHM in κ light chain genes remains unaltered, acquitting for any global SHM defect in our model. Beyond class switch recombination, the IgH 3′RR is a central element that controls heavy chain accessibility to activation-induced deaminase modifications including SHM.

scholarly journals Robust immunoglobulin class switch recombination and end joining inParp9-deficient mice

2017 ◽  
Vol 47 (4) ◽  
pp. 665-676 ◽  
Author(s):  
Isabelle Robert ◽  
Léa Gaudot ◽  
José Yélamos ◽  
Aurélia Noll ◽  
Heng-Kuan Wong ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
End Joining ◽  
Immunoglobulin Class ◽  
Class Switch ◽  
Deficient Mice

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 Alternative end-joining catalyzes class switch recombination in the absence of both Ku70 and DNA ligase 4

2010 ◽  
Vol 207 (2) ◽  
pp. 417-427 ◽  
Author(s):  
Cristian Boboila ◽  
Catherine Yan ◽  
Duane R. Wesemann ◽  
Mila Jankovic ◽  
Jing H. Wang ◽  
...  
Keyword(s):  
B Cells ◽  
Class Switch Recombination ◽  
Strand Break ◽  
Nonhomologous End Joining ◽  
Dna Ligase ◽  
End Joining ◽  
Dsb Repair ◽  
Class Switch ◽  
Dna Double Strand Break ◽  
Alternative End Joining

The classical nonhomologous end-joining (C-NHEJ) DNA double-strand break (DSB) repair pathway employs the Ku70/80 complex (Ku) for DSB recognition and the XRCC4/DNA ligase 4 (Lig4) complex for ligation. During IgH class switch recombination (CSR) in B lymphocytes, switch (S) region DSBs are joined by C-NHEJ to form junctions either with short microhomologies (MHs; “MH-mediated” joins) or no homologies (“direct” joins). In the absence of XRCC4 or Lig4, substantial CSR occurs via “alternative” end-joining (A-EJ) that generates largely MH-mediated joins. Because upstream C-NHEJ components remain in XRCC4- or Lig4-deficient B cells, residual CSR might be catalyzed by C-NHEJ using a different ligase. To address this, we have assayed for CSR in B cells deficient for Ku70, Ku80, or both Ku70 and Lig4. Ku70- or Ku80-deficient B cells have reduced, but still substantial, CSR. Strikingly, B cells deficient for both Ku plus Lig4 undergo CSR similarly to Ku-deficient B cells, firmly demonstrating that an A-EJ pathway distinct from C-NHEJ can catalyze CSR end-joining. Ku-deficient or Ku- plus Lig4-deficient B cells are also biased toward MH-mediated CSR joins; but, in contrast to XRCC4- or Lig4-deficient B cells, generate substantial numbers of direct CSR joins. Our findings suggest that more than one form of A-EJ can function in CSR.

scholarly journals AID Mediates Hypermutation by Deaminating Single Stranded DNA

2003 ◽  
Vol 197 (10) ◽  
pp. 1291-1296 ◽  
Author(s):  
Sarah K. Dickerson ◽  
Eleonora Market ◽  
Eva Besmer ◽  
F. Nina Papavasiliou
Keyword(s):  
Gene Conversion ◽  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Functional Link ◽  
Single Stranded Dna ◽  
Class Switch ◽  
Mutational Hotspots ◽  
Activation Induced Deaminase ◽  
Precise Role

Activation-induced deaminase (AID) is a protein indispensable for the diversification of immunoglobulin (Ig) genes by somatic hypermutation (SHM), class switch recombination (CSR), and gene conversion. To date, the precise role of AID in these processes has not been determined. Here we demonstrate that purified, tetrameric AID can deaminate cytidine residues in DNA, but not in RNA. Furthermore, we show that AID will bind and deaminate only single-stranded DNA, which implies a direct, functional link between hypermutation and transcription. Finally, AID does not target mutational hotspots, thus mutational targeting to specific residues must be attributed to different factors.

scholarly journals Alternative end-joining catalyzes class switch recombination in the absence of both Ku70 and DNA ligase 4

2013 ◽  
Vol 210 (3) ◽  
pp. 641-641 ◽  
Author(s):  
Cristian Boboila ◽  
Catherine Yan ◽  
Duane R. Wesemann ◽  
Mila Jankovic ◽  
Jing H. Wang ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
Dna Ligase ◽  
End Joining ◽  
Class Switch ◽  
Alternative End Joining
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