Figure 3.

Identification of three DNA elements for promoter opening by using EMSA. (A) Effect of top single-stranded sequences. The terminal bp of the fork junction was placed at either −12, −11, or −13 (■). Top strands of differing lengths (•) were annealed to labeled bottom strands. The EMSA heparin challenge results on each series are shown. (B) Effect of mutations at top strand −7 and −11 on probes with the optimal fork junction structure (−12 bp terminus). The top strand base present is indicated above each lane. (C) Effect of bottom single-stranded sequences.