Abstract
Class switch DNA recombination (CSR) crucially diversifies Ab biologic effector functions. 14-3-3γ specifically binds to the 5'-AGCT-3' repeats in the IgH locus switch (S) regions. By interacting directly with the C-terminal region of activation-induced cytidine deaminase (AID), 14-3-3γ targets this enzyme to S regions to mediate CSR. In this study, we showed that 14-3-3γ was expressed in germinal center B cells in vivo and induced in B cells by T-dependent and T-independent primary CSR-inducing stimuli in vitro in humans and mice. Induction of 14-3-3γ was rapid, peaking within 3 h of stimulation by LPSs, and sustained over the course of AID and CSR induction. It was dependent on recruitment of NF-κB to the 14-3-3γ gene promoter. The NF-κB recruitment enhanced the occupancy of the CpG island within the 14-3-3γ promoter by CFP1, a component of the COMPASS histone methyltransferase complex, and promoter-specific enrichment of histone 3 lysine 4 trimethylation (H3K4me3), which is indicative of open chromatin state and marks transcription-competent promoters. NF-κB also potentiated the binding of B cell lineage-specific factor E2A to an E-box motif located immediately downstream of the two closely-spaced transcription start sites for sustained 14-3-3γ expression and CSR induction. Thus, 14-3-3γ induction in CSR is enabled by the CFP1-mediated H3K4me3 enrichment in the promoter, dependent on NF-κB and sustained by E2A.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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14-3-3 Proteins / biosynthesis*
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14-3-3 Proteins / genetics
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3' Untranslated Regions / genetics
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Animals
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B-Lymphocytes / cytology
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B-Lymphocytes / immunology
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B-Lymphocytes / metabolism*
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Base Sequence
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Basic Helix-Loop-Helix Transcription Factors / physiology*
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Cells, Cultured
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Conserved Sequence
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CpG Islands / genetics*
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Cytidine Deaminase / metabolism
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DNA-Binding Proteins / physiology*
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E-Box Elements / genetics
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Germinal Center / metabolism
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HEK293 Cells
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Histone Methyltransferases
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Histone-Lysine N-Methyltransferase / metabolism
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Histones / metabolism
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Humans
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Immunoglobulin Class Switching / physiology*
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Lipopolysaccharides / immunology
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Lipopolysaccharides / pharmacology
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Lymphocyte Cooperation
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Methylation
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Molecular Sequence Data
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NF-kappa B / physiology*
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Promoter Regions, Genetic / genetics*
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Protein Processing, Post-Translational
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Sequence Alignment
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Sequence Homology, Nucleic Acid
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Specific Pathogen-Free Organisms
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Trans-Activators / physiology*
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Transcription Initiation Site
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Up-Regulation / genetics
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Up-Regulation / immunology
Substances
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14-3-3 Proteins
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3' Untranslated Regions
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Basic Helix-Loop-Helix Transcription Factors
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CXXC1 protein, human
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Cxxc1 protein, mouse
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DNA-Binding Proteins
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Histones
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Lipopolysaccharides
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NF-kappa B
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TCF3 protein, human
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Tcf3 protein, mouse
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Trans-Activators
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lipopolysaccharide, E coli O55-B5
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Histone Methyltransferases
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Histone-Lysine N-Methyltransferase
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AICDA (activation-induced cytidine deaminase)
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Cytidine Deaminase