Nucleotide sequence of the Xenopus siamois promoter −0.8-kb fragment. The first 23 nucleotides of the siamois coding sequence with its deduced amino acids and 817 nucleotides of 5′ siamois promoter sequence are shown. The transcription start site is indicated with an arrow and the TATA box is underlined. The possible Lef/Tcf-binding sites are boxed and identified above the sequence, as S0, S1, S2, S3 and S4. S0, S1, and S3 conform to the Lef/Tcf-binding site consensus, whereas S2 and S4 diverge at the 3′-most base. Nucleotides mutated in the Lef/Tcf-binding sites are underlined. The GenBank accession no. for the Xenopus siamois promoter is AF016226.