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.

• PMID: 15094040
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Reference Type

Journal Article | Research Support, Non-U.S. Gov't

Authors

Bier M, Fath S, Tschochner H

Primary Lit For

RRN6 | RRN9 | RNA polymerase I upstream activating factor complex | RNA polymerase I core factor complex | DNA-directed RNA Polymerase I complex

Additional Lit For

RPA12 | RPA34 | RPC10 | RPA49 | RPB5 | RPA14 | RRN3 | RPC40 | RPC19 | RPO26 | RPB10 | ... Show allRPB8 | RPA43 | RPA190 | RPA135 Show fewer

Review For