title: The MRE11-RAD50-NBS1 complex accelerates somatic hypermutation and gene conversion of immunoglobulin variable regions.
abstract: Targeted diversification of immunoglobulin variable regions is induced by activation-induced deaminase and may occur by either somatic hypermutation or gene conversion. MRE11-RAD50-NBS1 (MRN) is a ubiquitous and conserved nuclease complex critical for DNA break repair and is essential in class-switch recombination. Here we show that ectopic expression of NBS1, the regulatory subunit of MRN, accelerated hypermutation in the human B cell line Ramos and accelerated gene conversion in the chicken B cell line DT40. In both cases, accelerated diversification depended on MRN complex formation. These data suggest that MRN promotes DNA cleavage and/or mutagenic repair of lesions initiated by activation-induced deaminase, acting in the shared pathway of immunoglobulin gene diversification.
authors.affiliation: Department of Immunology, University of Washington School of Medicine, Seattle, Washington 98195-7650, USA.
authors.forename: Munehisa
authors.initials: M
authors.lastname: Yabuki
authors.forename: Monica M
authors.initials: MM
authors.lastname: Fujii
authors.forename: Nancy
authors.initials: N
authors.lastname: Maizels
mesh_terms: D017766:Acid Anhydride Hydrolases; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000276:immunology*; D045744:Cell Line, Tumor; D002645:Chickens; D045643:DNA Repair Enzymes / Q000235:genetics / Q000276:immunology*; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000276:immunology*; D005785:Gene Conversion / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics* / Q000276:immunology; D000076228:MRE11 Homologue Protein; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000235:genetics / Q000276:immunology*; D009687:Nuclear Proteins / Q000235:genetics / Q000276:immunology*; D009700:Nucleoside Deaminases / Q000276:immunology; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics / Q000276:immunology*
chemical_list: D018797:Cell Cycle Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D007135:Immunoglobulin Variable Region; C121766:MRE11 protein, human; D046912:Multiprotein Complexes; C112156:NBN protein, human; D009687:Nuclear Proteins; D000076228:MRE11 Homologue Protein; D009700:Nucleoside Deaminases; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes