Figure 3.

Caudal, a conserved master regulator of the Hox gene network, is a core-promoter-specific activator. (A) Caudal activates transcription with the Antp P2 DPE motif but not with the AdML TATA element. The two reporter constructs are identical except for the TATA and DPE sequences. Drosophila S2 cells were transfected with firefly luciferase reporter constructs as well as a Caudal expression plasmid, where indicated. To normalize for transfection efficiency, cells were cotransfected with a Pol III-Renilla luciferase control plasmid and assayed for dual luciferase activity. Error bars represent the SEM. (B) The Adh distal enhancer activates transcription with both the AdML TATA box and the Antp P2 DPE motif. The four reporter constructs are identical except for the presence or absence of the TATA, DPE, and Adh distal enhancer, as indicated. The Adh distal enhancer contains two binding sites for the Adf-1 transcription factor, which is present in S2 cells. Transfection assays were performed with the indicated constructs as in A. Error bars represent the SEM. (C) Caudal activates transcription with the E74B DPE motif and, to a lesser extent, the Adh proximal TATA element. Transfection assays were performed with the indicated constructs as in A. Error bars represent the SEM.