Fig. 4.

The requirement of octamer motif for activation of Isl1 minimal promoter. a A series of 2 bp mutants of octamer motif (lowercase letters) and octamer deletion (crossed-out lines) from Oligo-3 were used for EMSA in c. b Luciferase assay was performed to evaluate the transcriptional activity of Isl1 minimal promoter with mutants of octamer motif. × represents two mutant bases and black boxes represent the wild-type bases. Data are shown as percent activation over that of PGL(−246/+133) with mean ± SD (n = 3) [*P < 0.05, vs. PGL(246/+133)]. c EMSA was performed to evaluate the DNA binding affinity of mutant bases within the octamer motif. The binding complexes are indicated as C1 and C2