FIGURE 6.

Isl-1 binding sites in Re1 and Re2. A and B, as a screen of putative Isl-1 binding elements, the radiolabeled MafA-R3 Isl-1 site probe (17) was used in reactions with in vitro translated Isl-1-Myc and MafA-R3, Re1, or Re2 competitor oligonucleotides. Isl-1 and Myc-epitope antibodies were used to localize the Isl-1-Myc:MafA complex. Ab, antibody; IVT, in vitro translation; Neg, without Isl-1-Myc; Pos, with Isl-1-Myc. C, Re2–2, Re2–3, and Re2–6 probes were incubated with αTC1–6 nuclear extract. The specificity of Isl-1:Arx-Re2 binding was determined by Isl-1 antibody addition and competition with excess of unlabeled wild-type (WT) and Isl-1 binding site mutant (MT).