期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 105, 期 43, 页码 16508-16512出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0805327105
关键词
antibody; B cell; cotranscriptional hybrid; G4 DNA; switch recombination
资金
- National Institutes of Health [R01 GM39799, R01 GM65988]
Eukaryotic exonuclease 1 functions in replication, recombination, mismatch repair, telomere maintenance, immunoglobulin (Ig) gene class switch recombination, and somatic hypermutation. The enzyme has 5'-3' exonuclease, flap endonuclease, and weak RNaseH activity in vitro, but it has been difficult to reconcile these activities with its diverse biological functions. We report robust cleavage by human exonuclease 1 of transcribed G-rich DNA sequences with potential to form G loops and G4 DNA. Predicted Ig switch recombination intermediates are substrates for both exonucleolytic and 5' flap endonucleolytic cleavage. Excision is nick-dependent and structure-dependent. These results lead to a model for exonuclease 1 function in class switch recombination in which cleavage at activation-induced deaminase (AID)-initiated nicks produces gaps that become substrates for further attack by AID and subsequent repair.
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