Ablation of XRCC2/3 transforms immunoglobulin V gene conversion into somatic hypermutation.
After gene rearrangement, immunoglobulin V genes are further diversified by either somatic hypermutation or gene conversion. Hypermutation (in man and mouse) occurs by the fixation of individual, non-templated nucleotide substitutions. Gene conversion (in chicken) is templated by a set of upstream V pseudogenes. Here we show that if the RAD51 paralogues XRCC2, XRCC3 or RAD51B are ablated the pattern of diversification of the immunoglobulin V gene in the chicken DT40 B-cell lymphoma line exhibits a marked shift from one of gene conversion to one of somatic hypermutation. Non-templated, single-nucleotide substitutions are incorporated at high frequency specifically into the V domain, largely at G/C and with a marked hotspot preference. These mutant DT40 cell lines provide a tractable model for the genetic dissection of immunoglobulin hypermutation and the results support the idea that gene conversion and somatic hypermutation constitute distinct pathways for processing a common lesion in the immunoglobulin V gene. The marked induction of somatic hypermutation that is achieved by ablating the RAD51 paralogues is probably a consequence of modifying the recombination-mediated repair of such initiating lesions.
Sale
J E
JE
Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK. jes@mrc-lmb.cam.ac.uk
Calandrini
D M
DM
Takata
M
M
Takeda
S
S
Neuberger
M S
MS
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D002460:Cell Line; D002645:Chickens; D002999:Clone Cells; D004247:DNA; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005785:Gene Conversion; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D007135:Immunoglobulin Variable Region; C110901:X-ray repair cross complementing protein 3; C491866:Xrcc2 protein, mouse; D004247:DNA