A role for Mlh3 in somatic hypermutation

Ziqiang Li, Jonathan U. Peled, Chunfang Zhao, Anton Svetlanov, Diana Ronai, Paula E. Cohen, Matthew D. Scharff

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Somatic hypermutation (SHM) and class switch recombination (CSR) allow B cells to make high affinity antibodies of various isotypes. Both processes are initiated by activation-induced cytidine deaminase (AID) to generate dG:dU mismatches in the immunoglobulin genes that are resolved differently in SHM and CSR to introduce point mutations and recombination, respectively. The MutL homolog MLH3 has been implicated in meiosis and DNA mismatch repair (MMR). Since it interacts with MLH1, which plays a role in SHM and CSR, we examined these processes in Mlh3-deficient mice. Although deficiencies in other MMR proteins result in defects in SHM, Mlh3-/- mice exhibited an increased frequency of mutations in their immunoglobulin variable regions, compared to wild type littermates. Alterations of mutation spectra were observed in the Jh4 flanking region in Mlh3-/- mice. Nevertheless, Mlh3-/- mice were able to switch to IgG3 or IgG1 with similar frequencies to control mice. This is the first instance where a loss of a DNA repair protein has a positive impact on the rate of SHM, suggesting that Mlh3 normally inhibits the accumulation of mutations in SHM.

Original languageEnglish (US)
Pages (from-to)675-682
Number of pages8
JournalDNA Repair
Issue number6
StatePublished - Jun 10 2006


  • Isotype switching
  • Mismatch repair
  • MutL homolog MLH3
  • Somatic mutation
  • V region
  • Variable region

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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