Abstract
Activation-induced deaminase (AID) initiates diversity of immunoglobulin genes through deamination of cytosine to uracil. Two opposing models have been proposed for the deamination of DNA or RNA by AID. Although most data support DNA deamination, there is no physical evidence of uracil residues in immunoglobulin genes. Here we demonstrate their presence by determining the sensitivity of DNA to digestion with uracil DNA glycosylase (UNG) and abasic endonuclease. Using several methods of detection, we identified uracil residues in the variable and switch regions. Uracil residues were generated within 24 h of B cell stimulation, were present on both DNA strands and were found to replace mainly cytosine bases. Our data provide direct evidence for the model that AID functions by deaminating cytosine residues in DNA.
Publication types
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Research Support, N.I.H., Intramural
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Research Support, Non-U.S. Gov't
MeSH terms
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AICDA (Activation-Induced Cytidine Deaminase)
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Animals
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Antigenic Variation / genetics
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B-Lymphocytes / immunology
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B-Lymphocytes / metabolism*
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B-Lymphocytes / pathology
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Cells, Cultured
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Cytidine Deaminase / genetics
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Cytidine Deaminase / metabolism*
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DNA-(Apurinic or Apyrimidinic Site) Lyase / genetics
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DNA-(Apurinic or Apyrimidinic Site) Lyase / metabolism*
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Immunoglobulin Class Switching
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Immunoglobulin Variable Region
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Interleukin-4 / immunology
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Interleukin-4 / metabolism
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Lipopolysaccharides / immunology
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Lipopolysaccharides / metabolism
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Lymphocyte Activation / genetics
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Models, Chemical
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Spleen / pathology
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Uracil / analysis
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Uracil-DNA Glycosidase / genetics
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Uracil-DNA Glycosidase / metabolism*
Substances
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Immunoglobulin Variable Region
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Lipopolysaccharides
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Interleukin-4
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Uracil
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Uracil-DNA Glycosidase
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AICDA (Activation-Induced Cytidine Deaminase)
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Cytidine Deaminase
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Apex1 protein, mouse
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DNA-(Apurinic or Apyrimidinic Site) Lyase