FIG. 3.

E47 DNA-binding activity is not detected in developing Sertoli cells. EMSAs using probes containing a consensus E-box selective for E47 binding (A), the Trf promoter E-box (B), the Id2 promoter E-box (C), or a CREB-binding site (D) were incubated with nuclear extracts from enriched Sertoli cells isolated 5 and 11 days after birth or with CD19⁺ B cells isolated from mouse spleen. The DNA-protein complexes formed by E47, E12, and CREB1 are indicated. The complexes were identified from the results of separate supershift assays using E47- and E12-selective antisera (data not shown). Assays for E47-selective-binding probes were exposed for 7 days, while CREB1 binding complexes were detected after 12 h.