The composition of the RNA polymerase I transcription machinery switches from initiation to elongation mode
- 23 March 2004
- journal article
- Published by Wiley in FEBS Letters
- Vol. 564 (1-2) , 41-46
- https://doi.org/10.1016/s0014-5793(04)00311-4
Abstract
The amounts of RNA polymerase I (Pol I) and basal rDNA transcription factors were determined in yeast whole cell extracts. A 17‐fold excess of Pol I was found compared to the Pol I‐specific initiation factors upstream activating factor (UAF) and core factor (CF) which underlines that both initiation factors interact with a minor fraction of Pol I when rDNA transcription is active. Surprisingly, Rrn3p, another Pol I‐specific initiation factor, is more abundant in cell lysates than UAF and CF. Our analyses revealed that a large fraction of cellular Rrn3p is not associated with Pol I. However, the amount of initiation‐active Rrn3p which forms a stable complex with Pol I corresponds to the levels of UAF and CF which have been shown to bind the promoter. Initiation‐active Rrn3p dissociates from the template during or immediately after Pol I has switched from initiation to elongation. Our data support a model in which the elongating Pol I leaves the initiation factors UAF, CF and Rrn3p close by the promoter.Keywords
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