XRCC1 suppresses somatic hypermutation and promotes alternative nonhomologous end joining in Igh genes

Huseyin Saribasak, Robert W. Maul, Zheng Cao, Rhonda L. McClure, William Yang, Daniel R. McNeill, David M. Wilson, Patricia J. Gearhart

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Activation-induced deaminase (AID) deaminates cytosine to uracil in immunoglobulin genes. Uracils in DNA can be recognized by uracil DNA glycosylase and abasic endonuclease to produce single-strand breaks. The breaks are repaired either faithfully by DNA base excision repair (BER) or mutagenically to produce somatic hypermutation (SHM) and class switch recombination (CSR). To unravel the interplay between repair and mutagenesis, we decreased the level of x-ray cross-complementing 1 (XRCC1), a scaffold protein involved in BER. Mice heterozygous for XRCC1 showed a significant increase in the frequencies of SHM in Igh variable regions in Peyer's patch cells, and of double-strand breaks in the switch regions during CSR. Although the frequency of CSR was normal in Xrcc1 +/- splenic B cells, the length of microhomology at the switch junctions decreased, suggesting that XRCC1 also participates in alternative nonhomologous end joining. Furthermore, Xrcc1 +/- B cells had reduced Igh/c-myc translocations during CSR, supporting a role for XRCC1 in microhomology-mediated joining. Our results imply that AID-induced single-strand breaks in Igh variable and switch regions become substrates simultaneously for BER and mutagenesis pathways.

Original languageEnglish (US)
Pages (from-to)2209-2216
Number of pages8
JournalJournal of Experimental Medicine
Issue number11
StatePublished - Oct 24 2011
Externally publishedYes

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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