title: Altering the pathway of immunoglobulin hypermutation by inhibiting uracil-DNA glycosylase.
abstract: A functional immune system depends on the production of a wide range of immunoglobulin molecules. Immunoglobulin variable region (IgV) genes are diversified after gene rearrangement by hypermutation. In the DNA deamination model, we have proposed that deamination of dC residues to dU by activation-induced deaminase (AID) triggers this diversification. In hypermutating chicken DT40 B cells, most IgV mutations are dC --> dG/dA or dG --> dC/dT transversions, which are proposed to result from replication over sites of base loss produced by the excision activity of uracil-DNA glycosylase. Blocking the activity of uracil-DNA glycosylase should instead lead to replication over the dU lesion, resulting in dC --> dT (and dG --> dA) transitions. Here we show that expression in DT40 cells of a bacteriophage-encoded protein that inhibits uracil-DNA glycosylase shifts the pattern of IgV gene mutations from transversion dominance to transition dominance. This is good evidence that antibody diversification involves dC --> dU deamination within the immunoglobulin locus itself.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Javier
authors.initials: J
authors.lastname: Di Noia
authors.forename: Michael S
authors.initials: MS
authors.lastname: Neuberger
mesh_terms: D000818:Animals; D000916:Antibody Diversity / Q000235:genetics*; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D003564:Cytidine Deaminase / Q000378:metabolism; D045647:DNA Glycosylases; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D005347:Fibroblasts; D017353:Gene Deletion; D005803:Genes, Immunoglobulin / Q000235:genetics*; D051379:Mice; D016296:Mutagenesis / Q000235:genetics*; D009699:N-Glycosyl Hydrolases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D027041:Somatic Hypermutation, Immunoglobulin; D014162:Transfection; D051981:Uracil-DNA Glycosidase; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
chemical_list: D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D014764:Viral Proteins; C491866:Xrcc2 protein, mouse; C027619:uracil-DNA glycosylase inhibitor protein, B. subtilis bacteriophage; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D003564:Cytidine Deaminase