Nibrin functions in Ig class-switch recombination.
Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by predisposition to hematopoietic malignancy, cell-cycle checkpoint defects, and ionizing radiation sensitivity. NBS is caused by a hypomorphic mutation of the NBS1 gene, encoding nibrin, which forms a protein complex with Mre11 and Rad50, both involved in DNA repair. Nibrin localizes to chromosomal sites of class switching, and B cells from NBS patients show an enhanced presence of microhomologies at the sites of switch recombination. Because nibrin is crucial for embryonic survival, direct demonstration by targeted deletion that nibrin functions in class switch recombination has been lacking. Here, we show by cell-type-specific conditional inactivation of Nbn, the murine homologue of NBS1, that nibrin plays a role in the repair of gamma-irradiation damage, maintenance of chromosomal stability, and the recombination of Ig constant region genes in B lymphocytes.
Kracker
Sven
S
German Rheumatism Research Center, Schumannstrasse 21-22, 10117 Berlin, Germany.
Bergmann
Yvonne
Y
Demuth
Ilja
I
Frappart
Pierre-Olivier
PO
Hildebrand
Gabriele
G
Christine
Rainer
R
Wang
Zhao-Qi
ZQ
Sperling
Karl
K
Digweed
Martin
M
Radbruch
Andreas
A
D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000276:immunology / Q000502:physiology*; D004268:DNA-Binding Proteins; D005720:Gamma Rays; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007134:Immunoglobulin Switch Region / Q000276:immunology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D009687:Nuclear Proteins / Q000276:immunology / Q000502:physiology*; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D007127:Immunoglobulin Constant Regions; D008070:Lipopolysaccharides; C112156:NBN protein, human; C466108:Nijmegen breakage syndrome 1 protein, mouse; D009687:Nuclear Proteins