Figure 1.

Mutation of any protein binding site in the Igκ 3′-enhancer core region reduces enhancer activity. Shown is the 3′-enhancer core region spanning nucleotides 391–523 (23). The relative positions of the κE3′–CRE, PU.1, PIP, and E2A binding sites are indicated. The consequences of mutation of each protein binding site on enhancer activity in pre-B and plasmacytoma cells is shown on the right. These data are summarized from Pongubala and Atchison (22) and represent mutants LSB, LSD, LSF, LSH, and LSJ, respectively.