Figure 1.

 β-Catenin responsive regions of the siamois promoter. (A) Diagram of the siamois promoter deletion constructs used in this study. The length that each promoter fragment extends upstream of the siamois translation start site is indicated at left; each horizontal line represents the relative length of the promoter fragments. Δ−45/−357 represents a 312-bp deletion of the siamois promoter proximal to the TATA box, which is represented by an open box. Each siamois promoter fragment was fused to a luciferase reporter gene at the same point, as indicated. (B) β-Catenin responsive regions of the siamois promoter. The indicated constructs were injected into the animal pole of both blastomeres of two-cell embryos in the presence (+) or absence (−) of β-catenin RNA. Three pools of five stage 10 Xenopus embryos were assayed, and the mean and standard error of the resulting luciferase activities, in relative luciferase units (RLUs), are shown. The average fold induction by β-catenin (β-cat. Induction) is indicated above each data set. (N.S.) No significant β-catenin induction.