FIGURE 1.

The Caudal vertebrate homologues mouse Cdx1, Cdx2, and Cdx4 are core promoter-preferential activators. Drosophila S2R+ cells were co-transfected with expression vectors for either full-length Drosophila Caudal or mouse Cdx1, Cdx2, or Cdx4 expression vectors as well as firefly luciferase reporter constructs driven by the ftz enhancer-promoter containing either the WT sequence, mTATA, mDPE, or mTATA + mDPE. A, schematic representation of the natural ftz transcriptional control region. The ftz core promoter contains both DPE and TATA box motifs. The reporter constructs contain ftz enhancer and promoter sequences from −988 to +40 relative to the +1 start site and are identical except for having a WT sequence, mTATA, mDPE, or mTATA + mDPE as depicted. To normalize for variations in transfection efficiency, cells were co-transfected with a Pol III-Renilla luciferase control plasmid and assayed for Dual-Luciferase activity. B, normalized firefly to Renilla luciferase activities. C, the luciferase activities depicted in B are reported relative to the activities of the promoters in the absence of a co-transfected Caudal or Cdx expression plasmid, which were defined to be 1. The graph represents an average of three independent experiments. Error bars represent S.E. **, 0.001 ≤ p ≤ 0.01; ***, p ≤ 0.001.