CHARACTERIZATION OF A FUNCTIONAL PROMOTER FOR THE XENOPUS WNT-1 GENE IN-VIVO

The Xenopus homolog of the proto-oncogene wnt-1 (int-1) is transiently expressed during neurula and tailbud stages of early development. To determine the mechanisms involved in the transcriptional regulation of the Xwnt-1 gene, we isolated Xwnt-1 genomic sequences. The promoter a ctivity of the 5' flanking region of the gene was analysed by microinj ection of chimeric luciferase reporter constructs into embryos. It is shown that the proximal 220 bp of the Xwnt-1 promoter is able to confe r activation of the reporter gene at the early neurula stage. DNaseI f ootprinting analysis of the proximal promoter region with nuclear prot ein extracts from neurula stage embryos revealed five protein binding regions. Deletion and mutation analysis shows that one of these five p rotein binding regions is essential for promoter activity. Gel shift e xperiments indicate that a sequence element resembling the GT-I and GT -II motifs of the SV40 enhancer is important for the Xwnt-1 promoter a ctivity in vivo.