Figure 4.

Comparison of “apparent” rates of dissociation of AP-2α, Sp3, and Sp1 from an oligonucleotide containing CUP/AP2- and Sp-binding sites. (A) ³²P-end-labeled EF oligonucleotide containing the CUP/AP2- and Sp-(GT-box) binding sites of the C/EBPα gene promoter (nucleotides −258 to −234) was incubated for 15 min at 4°C with 10 μg of 3T3-L1 preadipocyte nuclear extract and then for the indicated times, MIN (in minutes) with a 50-fold excess of unlabeled EF oligonucleotide immediately before EMSA. Gels were analyzed by phosphorimaging. Dash (–) indicates ³²P-end-labeled EF without unlabeled competitor oligonucleotide; EF indicates addition of a 50-fold of unlabeled EF oligonucleotide before ³²P-end-labeled EF oligonucleotide. (B) Graphic presentation of quantitative phosphorimaging results from A above.