Cloning of Xenopus TFIIS and its expression in oocytes and early embryos

The transcriptional factor TFIIS has been cloned from Xenopus laevis. The length of the cDNA is 1668bp and contains the complete open reading frame of 303 amino acids. Xenopus TFIIS has high homologies to its human and mouse counterparts. In Northern blot analyses, TFIIS mRNAs that consisted of four different sizes were expressed relatively highly from the early stages of Xenopus oogenesis. During oocyte maturation, the pattern of Xenopus TFIIS messages showed a transient peak of expression. TFIIS mRNA occurred maternally and its level increased in later stage embryos. These data suggest that TFIIS mRNA is expressed in a developmentally regulated way in Xenopus laevis.