THE PROMOTER OF THE XWNT-5C GENE CONTAINS OCTAMER AND AP-2 MOTIFS FUNCTIONAL IN XENOPUS-EMBRYOS

The Xwnt-5C gene is expressed in Xenopus embryos from the early gastru la stage onwards. The transcription of Xwnt-5C is regulated differenti ally with respect to transcript size, timing and localization. To gain insight into the generation of the Xwnt-5C expression pattern, we sta rted to analyze the transcriptional regulation of this gene. We isolat ed Xwnt-5C genomic DNA sequences. By microinjection of chimaeric repor ter constructs into Xenopus embryos we demonstrate that the upstream r egion contains a promoter functional in vivo. Of the several putative binding sites for trans-acting factors, present in a minimal promoter fragment, some have been studied in more detail. Mutations in an octam er motif and in an AP-2 consensus sequence interfere with the activity of the Xwnt-5C minimal promoter. In vitro binding assays with extract s from gastrula stage Xenopus embryos show that the octamer motif of t he Xwnt-5C promoter can bind several Octamer binding factors, one of w hich is Oct1.