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Updated: Jul 18, 2026

Induction and Assessment of Class Switch Recombination in Purified Murine B Cells
Published on: August 13, 2010
Enhanced intra-switch region recombination during immunoglobulin class switch recombination in 53BP1-/- B cells
Bernardo Reina-San-Martin1, Junjie Chen, André Nussenzweig
1Laboratory of Molecular Immunology, Howard Hughes Medical Institute, The Rockefeller University, New York, USA. reinab@igbmc.u-strasbg.fr
Abstract:
Immunoglobulin class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID), an enzyme that deaminates cytidine residues in single-stranded DNA. U:G mismatches created by AID are processed to produce lesions that recruit and activate DNA damage response proteins including Ataxia-telangiectasia mutated (ATM), histone H2AX, Nijmegen breakage syndrome 1 (Nbs1), and p53 binding protein 1 (53BP1). Among these proteins, absence of 53BP1 produces the most severe impairment of class switching. Here, we demonstrate that AID is targeted normally to switch region DNA and that intra-switch region recombination is enhanced in 53BP1-/- B cells. In addition, Smicro-Sgamma1 switch region junctions cloned from 53BP1-/- B cells show unusual insertions suggestive of failed class switching. Our data are consistent with a role for 53BP1 in stabilizing the synapsis of switch regions during CSR.
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