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. Author manuscript; available in PMC: 2010 Oct 14.
Published in final edited form as: Adv Immunol. 2010;105:159–191. doi: 10.1016/S0065-2776(10)05006-6

FIGURE 2.

FIGURE 2

Targeting elements for SHM in the Ig loci. For all loci, the relative mutation frequency is shown by shaded peaks over the V region or S region. P, promoter; arrows, start of transcription; iE, intronic enhancer; triangles, location of donor splice sites in the leader exon, V(D)J exon, and iEμ intronic exon. AID may be active in the V regions by transcription bubbles, and in the S regions by R-loops. 3’ enhancers downstream of the C genes are shown on a different scale. For the mouse Igh chain locus, 3’ enhancers include 4 hypersensitive (HS) sites. For the mouse Igκ locus, there are two enhancers, 3’E and Ed. For the chicken DT40 Igλ locus, identified enhancers are 3’E and a regulatory region, 3’RR.