AID is required to initiate Nbs1/gamma-H2AX focus formation and mutations at sites of class switching.
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.
Petersen
Simone
S
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Casellas
Rafael
R
Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
Reina-San-Martin
Bernardo
B
Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
Chen
Hua Tang
HT
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Difilippantonio
Michael J
MJ
Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Wilson
Patrick C
PC
Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
Hanitsch
Leif
L
Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
Celeste
Arkady
A
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Muramatsuk
Masamichi
M
Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Pilch
Duane R
DR
Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Redon
Christophe
C
Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Ried
Thomas
T
Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Bonner
William M
WM
Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Honjo
Tasuku
T
Department of Medical Chemistry, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
Nussenzweig
Michel C
MC
Laboratory of Molecular Immunology, The Rockefeller University, and Howard Hughes Medical Institute, New York, New York 10021, USA.
Nussenzweig
André
A
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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)
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