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.

Recurrent disruption of the Iμ splice donor site in t(14;18) positive lymphomas : A potential molecular basis for aberrant downstream class switch recombination

2007 ◽  
Vol 46 (8) ◽  
pp. 735-744 ◽  
Author(s):  
Philippe Ruminy ◽  
Fabrice Jardin ◽  
Dominique Penther ◽  
Jean-Michel Picquenot ◽  
Françoise Parmentier ◽  
...  
Keyword(s):  
Molecular Basis ◽  
Donor Site ◽  
Class Switch Recombination ◽  
Splice Donor Site ◽  
Splice Donor ◽  
Class Switch

scholarly journals Mlh1 Can Function in Antibody Class Switch Recombination Independently of Msh2

2003 ◽  
Vol 197 (10) ◽  
pp. 1377-1383 ◽  
Author(s):  
Carol E. Schrader ◽  
Joycelyn Vardo ◽  
Janet Stavnezer
Keyword(s):  
B Cells ◽  
Somatic Hypermutation ◽  
Class Switch Recombination ◽  
Variable Region ◽  
Class Switch ◽  
Switch Regions ◽  
Substitution Mutations ◽  
Antibody Class ◽  
Variable Region Genes ◽  
Mmr Proteins

Mismatch repair proteins participate in antibody class switch recombination, although their roles are unknown. Previous nucleotide sequence analyses of switch recombination junctions indicated that the roles of Msh2 and the MutL homologues, Mlh1 and Pms2, differ. We now asked if Msh2 and Mlh1 function in the same pathway during switch recombination. Splenic B cells from mice deficient in both these proteins were induced to undergo switching in culture. The frequency of switching is reduced, similarly to that of B cells singly deficient in Msh2 or Mlh1. However, the nucleotide sequences of the Sμ-Sγ3 junctions resemble junctions from Mlh1- but not from Msh2-deficient cells, suggesting Mlh1 functions either independently of or before Msh2. The substitution mutations within S regions that are known to accompany switch recombination are increased in Msh2- and Mlh1 single-deficient cells and further increased in the double-deficient cells, again suggesting these proteins function independently in class switch recombination. The finding that MMR functions to reduce mutations in switch regions is unexpected since MMR proteins have been shown to contribute to somatic hypermutation of antibody variable region genes.

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 The μ Switch Region Tandem Repeats Are Important, but Not Required, for Antibody Class Switch Recombination

2001 ◽  
Vol 193 (2) ◽  
pp. 159-168 ◽  
Author(s):  
Thomas M. Luby ◽  
Carol E. Schrader ◽  
Janet Stavnezer ◽  
Erik Selsing
Keyword(s):  
Tandem Repeats ◽  
Repeated Sequence ◽  
Chain Gene ◽  
Switch Region ◽  
Sequence Element ◽  
Class Switch ◽  
Sequence Elements ◽  
Switch Mechanism ◽  
Selection For ◽  
Antibody Class

Class switch DNA recombinations change the constant (C) region of the antibody heavy (H) chain expressed by a B cell and thereby change the antibody effector function. Unusual tandemly repeated sequence elements located upstream of H chain gene exons have long been thought to be important in the targeting and/or mechanism of the switch recombination process. We have deleted the entire switch tandem repeat element (Sμ) from the murine μ H chain gene. We find that the Sμ tandem repeats are not required for class switching in the mouse immunoglobulin H-chain locus, although the efficiency of switching is clearly reduced. Our data demonstrate that sequences outside of the Sμ tandem repeats must be capable of directing the class switch mechanism. The maintenance of the highly repeated Sμ element during evolution appears to reflect selection for a highly efficient switching process rather than selection for a required sequence element.

scholarly journals Biallelic variants in COPB1 cause a novel, severe intellectual disability syndrome with cataracts and variable microcephaly

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
William L. Macken ◽  
Annie Godwin ◽  
Gabrielle Wheway ◽  
Karen Stals ◽  
Liliya Nazlamova ◽  
...  
Keyword(s):  
Genome Sequencing ◽  
Donor Site ◽  
Xenopus Tropicalis ◽  
Splice Donor Site ◽  
Homologous Region ◽  
Disease Genes ◽  
Coat Proteins ◽  
Splice Donor ◽  
Severe Intellectual Disability

Abstract Background Coat protein complex 1 (COPI) is integral in the sorting and retrograde trafficking of proteins and lipids from the Golgi apparatus to the endoplasmic reticulum (ER). In recent years, coat proteins have been implicated in human diseases known collectively as “coatopathies”. Methods Whole exome or genome sequencing of two families with a neuro-developmental syndrome, variable microcephaly and cataracts revealed biallelic variants in COPB1, which encodes the beta-subunit of COPI (β-COP). To investigate Family 1’s splice donor site variant, we undertook patient blood RNA studies and CRISPR/Cas9 modelling of this variant in a homologous region of the Xenopus tropicalis genome. To investigate Family 2’s missense variant, we studied cellular phenotypes of human retinal epithelium and embryonic kidney cell lines transfected with a COPB1 expression vector into which we had introduced Family 2’s mutation. Results We present a new recessive coatopathy typified by severe developmental delay and cataracts and variable microcephaly. A homozygous splice donor site variant in Family 1 results in two aberrant transcripts, one of which causes skipping of exon 8 in COPB1 pre-mRNA, and a 36 amino acid in-frame deletion, resulting in the loss of a motif at a small interaction interface between β-COP and β’-COP. Xenopus tropicalis animals with a homologous mutation, introduced by CRISPR/Cas9 genome editing, recapitulate features of the human syndrome including microcephaly and cataracts. In vitro modelling of the COPB1 c.1651T>G p.Phe551Val variant in Family 2 identifies defective Golgi to ER recycling of this mutant β-COP, with the mutant protein being retarded in the Golgi. Conclusions This adds to the growing body of evidence that COPI subunits are essential in brain development and human health and underlines the utility of exome and genome sequencing coupled with Xenopus tropicalis CRISPR/Cas modelling for the identification and characterisation of novel rare disease genes.

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