Roles for Transcription in Antibody Diversity

National Institute On Aging

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Abstract

Activation-induced deaminase (AID) is a cytosine DNA deaminase. AID introduces mutations to support increased antibody affinity (somatic hypermutation) and changed antibody effector function (class switch recombination). For somatic hypermutation, AID targeting to the variable region is poorly understood. AID is associated with transcription and starts at the promoter preceding each rearranged V gene. To firmly delineate the map of mutation, we sequenced mutations from the VH exon to the Emu enhancer. We did this for each V gene segment rearranged to either JH1, JH2, JH3, and JH4 gene segments, using DNA from Peyers patch B cells in mice. Sequences were also obtained for Vk genes rearranged to either Jk1, Jk2, Jk4, and Jk5 gene segments. Preliminary results indicate that mutations were most abundant within a 1 kilobase distance downstream of the promoter, regardless of which JH or Jk gene segment was used. We will next determine why mutations stop after 1 kilobase. For this, we generated a knockin mouse strain with a defined V-D-J1 gene placed into the IgH locus. Homozygous mice are being bred to determine which transcription proteins are recruited to this region by ChIP analysis.