Fig. 6. Six2 binds the Six5 binding site identified in the mouse Igfbp5 promoter. (A) Incubation of the wild-type oligonucleotide probe in the presence of unprogrammed reticulocytes does not result in the formation of a specific retarded complex. Incubation of the probe with Six2-programmed reticulocytes gives rise to a retarded complex (arrow), which is competed by the addition of cold double-stranded wild-type oligonucleotide (wt), but not by oligonucleotide with a nucleotide substitution in the Six5 binding site (m). Cold oligonucleotides were added at 100- and 500-fold molar excess. (B) Incubation of the labeled mutant oligonucleotide does not result in the formation of a specific complex in the presence of Six2-programmed reticulocytes. (C) Sequence of wild-type and mutant oligonucleotides. The nucleotide changed in the mutant oligonucleotide is highlighted in red.