SPECIFIC INTERACTION OF THE MURINE TRANSCRIPTION TERMINATION FACTOR TTF-I WITH CLASS-I RNA-POLYMERASES

THE 18-base-pair sequence element AGGTCGACCAGTACTCCG (the Sal box) signals termination of mouse ribosomal gene transcription1. This sequence is recognized by a sequence-specific DNA-binding protein, TTF I, which mediates the termination of transcription by RNA polymerase I (poi I) 2,3. Subsequently, the ends of the primary transcripts are trimmed by 10 nucleotides in a sequence-dependent 3′-terminal processing reaction4. We have now investigated whether TTF I bound to its target sequence will block elongation by any RNA polymerase by steric hindrance, or whether it is specific for elongation by pol I. The results demon-strate that TTF I directs transcription termination with RNA poly-merase I from species as divergent as mouse and yeast, but fails to affect elongation by heterologous polymerases (eukaryotic RNA polymerases II and III, Escherichia coli or bacteriophage T3 RNA polymerase). By contrast, purified lac represser bound to its operator sequence stops elongation by both RNA polymerase I and II. © 1990 Nature Publishing Group.