New model for the yeast RNA polymerase I transcription cycle.
Using an immobilized template assay, we observed two steps in assembly of the yeast RNA polymerase I (Pol I) preinitiation complex: stable binding of upstream activating factor (UAF) followed by recruitment of Pol I-Rrn3p and core factor (CF). Pol I is required for stable association of CF with the promoter and can be recruited in the absence of Rrn3p. Upon transcription initiation, Pol I-Rrn3p and CF dissociate from the promoter while UAF remains behind. These findings support a novel model in which the Pol I basal machinery cycles on and off the promoter with each round of transcription. This model accounts for previous observations that rRNA synthesis may be controlled by regulating both promoter accessibility and polymerase activity.
Aprikian
P
P
Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
Moorefield
B
B
Reeder
R H
RH
D015153:Blotting, Western; D050657:Core Binding Factor alpha Subunits; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D004789:Enzyme Activation; D008954:Models, Biological; D035463:Pol1 Transcription Initiation Complex Proteins; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012318:RNA Polymerase I / Q000235:genetics* / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic
D050657:Core Binding Factor alpha Subunits; D004268:DNA-Binding Proteins; D035463:Pol1 Transcription Initiation Complex Proteins; D012335:RNA, Ribosomal; C101161:RRN3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C406688:core binding factor alpha; C402483:upstream activation factor, S cerevisiae; D012318:RNA Polymerase I