Detection of chromatin-associated single-stranded DNA in regions targeted for somatic hypermutation

Diana Ronai, Maria D. Iglesias-Ussel, Manxia Fan, Ziqiang Li, Alberto Martin, Matthew D. Scharff

Research output: Contribution to journalArticle

61 Scopus citations

Abstract

After encounter with antigen, the antibody repertoire is shaped by somatic hypermutation (SHM), which leads to an increase in the affinity of antibodies for the antigen, and class-switch recombination (CSR), which results in a change in the effector function of antibodies. Both SHM and CSR are initiated by activation-induced cytidine deaminase (AID), which deaminates deoxycytidine to deoxyuridine in single-stranded DNA (ssDNA). The precise mechanism responsible for the formation of ssDNA in V regions undergoing SHM has yet to be experimentally established. In this study, we searched for ssDNA in mutating V regions in which DNA-protein complexes were preserved in the context of chromatin in human B cell lines and in primary mouse B cells. We found that V regions that undergo SHM were enriched in short patches of ssDNA, rather than R loops, on both the coding and noncoding strands. Detection of these patches depended on the presence of DNA-associated proteins and required active transcription. Consistent with this, we found that both DNA strands in the V region were transcribed. We conclude that regions of DNA that are targets of SHM assemble protein-DNA complexes in which ssDNA is exposed, making it accessible to AID. JEM

Original languageEnglish (US)
Pages (from-to)181-190
Number of pages10
JournalJournal of Experimental Medicine
Volume204
Issue number1
DOIs
StatePublished - Jan 22 2007

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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