Nucleotide sequences in Xenopus 5S DNA required for transcription termination

We have analyzed the DNA sequences required for termination of Xenopus 5S RNA synthesis in vitro. Termination occurs within clusters of four or more consecutive T residues in the noncoding DNA strand sequence. The 3' flanking sequence following the gene is not required for termination. The distance between the T cluster and the site of transcription initiation as well as the exact nucleotide sequences preceding the T cluster can be varied...