RNA polymerase I termination: Where is the end?

The synthesis of ribosomal RNA (rRNA) precursor molecules by RNA polymerase I (Pol I) terminates with the dissociation of the protein–DNA–RNA ternary complex. Based on in vitro results the mechanism of Pol I termination appeared initially to be rather conserved and simple until this process was more thoroughly re-investigated in vivo. A picture emerged that Pol I termination seems to be connected to co-transcriptional processing, re-initiation of transcription and, possibly, other processes downstream of Pol I transcription units. In this article, our current understanding of the mechanism of Pol I termination and how this process might be implicated in other biological processes in yeast and mammals is summarized and discussed. This article is part of a Special Issue entitled: Transcription by Odd Pols.

► Characterisation of a new termination factor and its impact on the mechanism of termination. ► Factors required to dissociate the ternary transcription complex in mammals and yeast. ► Co-transcriptional pre-rRNA cleavage and termination. ► The possible role of termination for rDNA-loop formation and stimulation of transcription. ► The possible role of termination in rDNA stability and aging.