TRANSCRIPTION TERMINATION OF RNA-POLYMERASE-I DUE TO A T-RICH ELEMENTINTERACTING WITH REB1P

All transcription terminators for RNA polymerase I (pol I) that have b een studied so far, ranging from yeast to humans, require a specific D NA binding protein to cause termination. In yeast, this terminator pro tein has been identified as Reb1p. We now show that, in addition to th e binding site for Reblp, the yeast pol I terminator also requires the presence of a T-rich region coding for the last 12 nucleotides of the transcript. Reblp cooperates with this T-rich element, both to pause the polymerase and to effect release of the transcript. These findings have implications for the termination mechanism used by all three nuc lear RNA polymerases, since all three are known to pause at this termi nator.