V gene rearrangement is required to fully activate the hypermutation mechanism in B cells.
Nonproductively rearranged H and L chain loci of B cell hybridoma lines expressing heavily mutated antibodies were cloned and partially sequenced. The results confirm earlier data showing that somatic point mutations are as frequent in nonproductively rearranged loci containing a rearranged V gene as in productively rearranged loci. They establish in addition that in nonproductive H chain loci which bear a DJH rearrangement the frequency of somatic mutations is more than 10 times lower (0.2%) than in VDJH loci expressed by the same cells (2.5%). Thus, the hypermutation mechanism operating in B cell differentiation is targeted at V genes rearranged to the J locus and may require nucleotide sequences associated with both V and J elements in order to be fully activated. An inversion of the JH2 segment was detected in one DJH locus. This inversion appears to be the result of a secondary joining event occurring occasionally in the course of B cell development.
Roes
J
J
Institute for Genetics, University of Cologne, FRG.
Hüppi
K
K
Rajewsky
K
K
Sablitzky
F
F
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D001483:Base Sequence; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D005803:Genes, Immunoglobulin; D006825:Hybridomas / Q000032:analysis; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007133:Immunoglobulin Joining Region / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009154:Mutation
D007143:Immunoglobulin Heavy Chains; D007133:Immunoglobulin Joining Region; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains