Genomic cloning of Xenopus TFIIS (TCEA1) and identification of its transcription start site.

We previously cloned the cDNA of the transcription factor TFIIS (SII) from Xenopus laevis and showed that its expression was not constant during Xenopus development. To investigate its regulation, we cloned the genomic DNA of Xenopus TFIIS, focusing on the 5'-promoter region. Here, we present the Xenopus TFIIS genomic sequence (-1730 to +214) and transcription start site (cap site). We define the position of the primary cap site as the adenine located 142 bp upstream from the adenine of the ATG (Met) codon. Another putative start-site region, where 13 transcriptional start sites are clustered within 12 bp, was mapped about 100 bp downstream of the primary cap site. Although a computer search found putative trans-element binding sites proximal to two Xenopus TFIIS transcription start sites, we could not identify typical "TATA" or "CAATT" boxes upstream of the primary cap site, probably owing to TFIIS's character as a "house keeping gene".