Figure 6.

ICE1 protein binds to the MYC-recognition elements in the CBF3 promoter. (A) Sequences and positions of oligonucleotides within the CBF3 promoter used in the EMSA. Letters in bold indicate sequences of MYC-recognition motifs in MYC-1 through MYC-5. Bold letters in the P1 oligonucleotide are a putative MYB-recognition motif. (B) Interaction between ICE1 protein and ³²P-labeled MYC-1 through MYC-4 DNA fragments. (C) ICE1 binds to the MYC-2 DNA fragment more strongly than to the other DNA fragments. (D) Consensus nucleotide residues in the MYC-recognition motif are important for the interaction between ICE1 and the MYC-2 DNA fragment. (E) ice1 mutant protein also binds to the MYC-2 DNA fragment. The labeled oligonucleotides used in each experiment are indicated at the top of each panel. Triangles indicate increasing amounts of unlabeled oligonucleotides for competition in B, C and D, which correspond to 50-, 100-, and 250-fold excess of each probe.