RNA polymerase I transcription on nucleosomal templates: the transcription termination factor TTF-I induces chromatin remodeling and relieves transcriptional repression

Abstract
Eukaryotic ribosomal gene promoters are preceded by a terminator element which is recognized by the transcription termination factor TTF‐I. We have studied the function of this promoter‐proximal terminator and show that binding of TTF‐I is the key event which leads to ATP‐dependent nucleosome remodeling and transcriptional activation of mouse rDNA pre‐assembled into chromatin. We have analyzed TTF‐I mutants for their ability to bind to free or nucleosomal DNA, and show that the DNA binding domain of TTF‐I on its own is not sufficient for interaction with chromatin, indicating that specific protein features exist that endow a transcription factor with chromatin binding and remodeling properties. This first analysis of RNA polymerase I transcription in chromatin provides a clue for the function of the upstream terminator and establishes a dual role for TTF‐I both as a termination factor and a chromatin‐specific transcription activator.