UMMS Affiliation

Department of Molecular Genetics and Microbiology

Publication Date


Document Type



Animals; B-Lymphocytes/enzymology/*immunology; Cytidine Deaminase/*metabolism; Cytosine/metabolism; DNA Polymerase beta/deficiency/genetics/*physiology; DNA Primers; Immunoglobulin A/immunology; Immunoglobulin G/immunology; Immunoglobulin Switch Region/*genetics/immunology; Lipopolysaccharides/pharmacology; Mice; Mice, Inbred C57BL; Mutation; *Recombination, Genetic; Reverse Transcriptase Polymerase Chain Reaction; Uracil/metabolism; Uracil-DNA Glycosidase/*metabolism


Life Sciences | Medicine and Health Sciences | Women's Studies


Immunoglobulin (Ig) class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID), which converts cytosines to uracils in switch (S) regions. Subsequent excision of dU by uracil DNA glycosylase (UNG) of the base excision repair (BER) pathway is required to obtain double-strand break (DSB) intermediates for CSR. Since UNG normally initiates faithful repair, it is unclear how the AID-instigated S region lesions are converted into DSBs rather than correctly repaired by BER. Normally, DNA polymerase beta (Polbeta) would replace the dC deaminated by AID, leading to correct repair of the single-strand break, thereby preventing CSR. We address the question of whether Polbeta might be specifically down-regulated during CSR or inhibited from accessing the AID-instigated lesions, or whether the numerous AID-initiated S region lesions might simply overwhelm the BER capacity. 2875We find that nuclear Polbeta levels are induced upon activation of splenic B cells to undergo CSR. When Polbeta(-/-) B cells are activated to switch in culture, they switch slightly better to IgG2a, IgG2b, and IgG3 and have more S region DSBs and mutations than wild-type controls. We conclude that Polbeta attempts to faithfully repair S region lesions but fails to repair them all.

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DOI of Published Version



J Exp Med. 2007 Jul 9;204(7):1677-89. Epub 2007 Jun 25. Link to article on publisher's site

Journal/Book/Conference Title

The Journal of experimental medicine

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PubMed ID


Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.