A lambda 1 transgene under the control of a heavy chain promoter and enhancer does not undergo somatic hypermutation.
To identify cis-acting elements responsible for targeting somatic hypermutation to immunoglobulin variable regions, we generated transgenic mice which carry a rearranged lambda 1 gene regulated by the heavy chain intron enhancer, E mu, and the heavy chain promoter PH186.2 from the VH186.2 variable region. C57BL/6 x SJL founders were bred with C57BL/6 mice to establish a line carrying a single copy of the transgene. Somatic hypermutation was studied by generating hybridoma cell lines from mice immunized with the hapten (4-hydroxy-3-nitrophenyl)acetyl (NP) coupled to chicken gamma globulin. The immune response in this transgenic line was dominated by the endogenous VH186.2 heavy chain variable region and the transgenic lambda 1 light chain, and the transgene was actively expressed in all hybridomas analyzed. In this work we show that the transgenic V lambda 1 regions do not undergo hypermutation, despite high levels of expression, while the expressed heavy chain V regions accumulate mutations at a rate typical of the NP response in C57BL/6 mice. Thus, within the same B cell, the PH186.2 promoter in connection with E mu drives efficient expression of both a VH and a V lambda region, but only the VH is a target for somatic hypermutation. Our observations show that cis-acting sequences that activate immunoglobulin gene transcription are not sufficient to target somatic hypermutation.
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06510.
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Hengstschläger
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Williams
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Maizels
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D004252:DNA Mutational Analysis; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D006825:Hybridomas; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007146:Immunoglobulin lambda-Chains / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*
D007143:Immunoglobulin Heavy Chains; D007146:Immunoglobulin lambda-Chains