Title

DNA polymerase beta is able to repair breaks in switch regions and plays an inhibitory role during immunoglobulin class switch recombination

UMMS Affiliation

Department of Molecular Genetics and Microbiology

Date

7-9-2007

Document Type

Article

Subjects

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

Disciplines

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

Abstract

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.

Rights and Permissions

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

Related Resources

Link to article in PubMed

PubMed ID

17591858