1. MRE11/RAD50 cleaves DNA in the AID/UNG-dependent pathway of immunoglobulin gene diversification.
- Author
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Larson ED, Cummings WJ, Bednarski DW, and Maizels N
- Subjects
- Acid Anhydride Hydrolases, Cells, Cultured, DNA Glycosylases genetics, DNA Repair physiology, DNA Repair Enzymes genetics, DNA, Single-Stranded genetics, DNA-(Apurinic or Apyrimidinic Site) Lyase genetics, DNA-(Apurinic or Apyrimidinic Site) Lyase metabolism, DNA-Binding Proteins genetics, Humans, Immunoglobulin G genetics, Immunoglobulin G metabolism, MRE11 Homologue Protein, B-Lymphocytes metabolism, DNA Glycosylases metabolism, DNA Repair Enzymes metabolism, DNA, Single-Stranded metabolism, DNA-Binding Proteins metabolism, Somatic Hypermutation, Immunoglobulin physiology
- Abstract
MRE11/RAD50/NBS1 (MRN) is a ubiquitous complex that participates in the response to DNA damage and in immunoglobulin (Ig) gene diversification. Ig gene diversification is initiated by deamination of cytosine to uracil, followed by removal of uracil to create an abasic (AP) site. We find that MRE11 associates specifically with rearranged Ig genes in hypermutating B cells, whereas APE1, the major AP-endonuclease in faithful base excision repair, does not. We show that purified, recombinant MRE11/RAD50 can cleave DNA at AP sites and that this AP-lyase activity is conserved from humans to Archaea. MRE11/RAD50 cleaves at AP sites within single-stranded regions of DNA, suggesting that at transcribed Ig genes, cleavage may be coordinated with deamination by AID and deglycosylation by UNG2 to produce single-strand breaks (SSBs) that undergo subsequent mutagenic repair and recombination. These results identify MRN with DNA cleavage in the AID-initiated pathway of Ig gene diversification.
- Published
- 2005
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