Upstream sequences required for transcription of the TFIIIA gene in Xenopus oocytes.

The DNA sequences required for efficient initiation of transcription of the Xenopus transcription factor IIIA (TFIIIA) gene were determined by microinjecting a series of deletion and linker substitution mutants into Xenopus oocyte nuclei. An upstream activating sequence, which resides between residues -283 and -238, and perhaps a second sequence between -167 and -122 preceding the transcription start site, together stimulate transcription about 30-fold. The distance between the two sequences and the distance from them to the initiation site can vary by at least 13 base pairs without loss of activity. The TFIIIA upstream sequences can stimulate transcription of other genes, for example, they stimulate transcription from the herpes thymidine kinase promoter about 30-fold.