title: AID is required to initiate Nbs1/gamma-H2AX focus formation and mutations at sites of class switching.
abstract: Class switch recombination (CSR) is a region-specific DNA recombination reaction that replaces one immunoglobulin heavy-chain constant region (Ch) gene with another. This enables a single variable (V) region gene to be used in conjunction with different downstream Ch genes, each having a unique biological activity. The molecular mechanisms that mediate CSR have not been defined, but activation-induced cytidine deaminase (AID), a putative RNA-editing enzyme, is required for this reaction. Here we report that the Nijmegen breakage syndrome protein (Nbs1) and phosphorylated H2A histone family member X (gamma-H2AX, also known as gamma-H2afx), which facilitate DNA double-strand break (DSB) repair, form nuclear foci at the Ch region in the G1 phase of the cell cycle in cells undergoing CSR, and that switching is impaired in H2AX-/- mice. Localization of Nbs1 and gamma-H2AX to the Igh locus during CSR is dependent on AID. In addition, AID is required for induction of switch region (S mu)-specific DNA lesions that precede CSR. These results place AID function upstream of the DNA modifications that initiate CSR.
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Simone
authors.initials: S
authors.lastname: Petersen
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
authors.forename: Rafael
authors.initials: R
authors.lastname: Casellas
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Reina-San-Martin
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Hua Tang
authors.initials: HT
authors.lastname: Chen
authors.affiliation: Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Difilippantonio
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Wilson
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
authors.forename: Leif
authors.initials: L
authors.lastname: Hanitsch
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Arkady
authors.initials: A
authors.lastname: Celeste
authors.affiliation: Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Muramatsuk
authors.affiliation: Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Duane R
authors.initials: DR
authors.lastname: Pilch
authors.affiliation: Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Christophe
authors.initials: C
authors.lastname: Redon
authors.affiliation: Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ried
authors.affiliation: Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Bonner
authors.affiliation: Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Honjo
authors.affiliation: Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
authors.forename: Michel C
authors.initials: MC
authors.lastname: Nussenzweig
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000502:physiology; D019313:BRCA1 Protein / Q000502:physiology; D001483:Base Sequence; D002453:Cell Cycle; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003564:Cytidine Deaminase / Q000235:genetics / Q000502:physiology*; D004247:DNA; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000502:physiology; D006657:Histones / Q000502:physiology*; D017578:Immunoglobulin Class Switching / Q000502:physiology*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000502:physiology*; D051135:Rad51 Recombinase; D011995:Recombination, Genetic; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D019313:BRCA1 Protein; D004268:DNA-Binding Proteins; D006657:Histones; D007143:Immunoglobulin Heavy Chains; D009687:Nuclear Proteins; D004247:DNA; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase