Myb and Ets-2 proteins bind specifically to their predicted sites in the kit promoter. γ-³² P-end labeled double-stranded oligonucleotide probes corresponding either to the canonical Myb (M1 and M2) or Ets-2 (E1, E2 and E3) binding sites within the XhoI-SmaI promoter region fragment (nts-461 to -24) (see Fig 6C) were employed in EMSA. Binding of bacterially expressed Myb (A) or Ets proteins (B) was competed with either wild-type (wt) or mutated (mut) double-stranded oligonucleotides as indicated above each lane. Similar experiments were also performed with nuclear extract derived from K562 cells. Fifteen μg of K562 nuclear extract was incubated in binding buffer with γ-³² P-end labeled double-stranded oligonucleotide probes (lane 1; [C and D]) corresponding either to the canonical Myb (M1 and M2; [C]) or Ets-2– (E1, E2; [D]) binding sites as described above. Specificity of binding was assessed using wild type (lane 2; [C and D]) or mutated (lane 3; [C and D]) double-stranded oligonucleotides as indicated above each lane. Sequences of the double-stranded oligodeoxynucleotides for both mutated and wild-type Myb and Ets-2 binding sites are given in the Materials and Methods section.