Fig. 3.

Identification of cis elements involved in the regulation of Isl1 expression. a The ³²P-ATP labeled oligonucleotides are indicated as Oligo-1, -2, -3, -4, and -5. Octamer motif is highlighted by dark gray box. b EMSA was performed using the labeled probes and nuclear extracts (NE) prepared from induced day 4 P19CL6 cells. The DNA–protein complexes formed are indicated as C1, C2, and C3. c DNase I footprinting identified the protected region by NE on the Isl1 minimal promoter. d The bases responsible for DNA binding activities on the Isl1 minimal promoter were determined by EMSA. The mutant probes are labeled as mt1 to mt17