Abstract
Class switch recombination (CSR) diversifies antibodies by joining highly repetitive DNA elements, which are separated by 60-200 kbp. CSR is initiated by activation-induced cytidine deaminase, an enzyme that produces multiple DNA double-strand breaks (DSBs) in switch regions. Switch regions are joined by a mechanism that requires an intact DNA damage response and classical or alternative nonhomologous end joining (A-NHEJ). Among the DNA damage response factors, 53BP1 has the most profound effect on CSR. We explore the role of 53BP1 in intrachromosomal DNA repair using I-SceI to introduce paired DSBs in the IgH locus. We find that the absence of 53BP1 results in an ataxia telangiectasia mutated-dependent increase in DNA end resection and that resected DNA is preferentially repaired by microhomology-mediated A-NHEJ. We propose that 53BP1 favors long-range CSR in part by protecting DNA ends against resection, which prevents A-NHEJ-dependent short-range rejoining of intra-switch region DSBs.
Publication types
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Research Support, N.I.H., Extramural
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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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Animals
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Ataxia Telangiectasia Mutated Proteins
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B-Lymphocytes / drug effects
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B-Lymphocytes / metabolism
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Cell Cycle Proteins / antagonists & inhibitors
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Cell Cycle Proteins / metabolism
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Chromosomal Proteins, Non-Histone
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Chromosome Pairing / genetics
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Cytidine Deaminase / genetics
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DNA Breaks, Double-Stranded
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DNA Repair / physiology*
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DNA-Binding Proteins / antagonists & inhibitors
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DNA-Binding Proteins / metabolism
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Deoxyribonucleases, Type II Site-Specific / genetics
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Immunoglobulin Class Switching / physiology*
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Immunoglobulin Heavy Chains / genetics
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Integrases / genetics
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Interleukin-4 / pharmacology
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Intracellular Signaling Peptides and Proteins / physiology*
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Lipopolysaccharides / pharmacology
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Transgenic
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / metabolism
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Recombination, Genetic / physiology*
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Tumor Suppressor Proteins / antagonists & inhibitors
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Tumor Suppressor Proteins / metabolism
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Tumor Suppressor p53-Binding Protein 1
Substances
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Cell Cycle Proteins
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Chromosomal Proteins, Non-Histone
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DNA-Binding Proteins
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Immunoglobulin Heavy Chains
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Intracellular Signaling Peptides and Proteins
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Lipopolysaccharides
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Trp53bp1 protein, mouse
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Tumor Suppressor Proteins
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Tumor Suppressor p53-Binding Protein 1
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Interleukin-4
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Ataxia Telangiectasia Mutated Proteins
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Atm protein, mouse
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Protein Serine-Threonine Kinases
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Cre recombinase
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Integrases
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Deoxyribonucleases, Type II Site-Specific
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AICDA (activation-induced cytidine deaminase)
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Cytidine Deaminase