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The composition of the RNA polymerase I transcription machinery switches from initiation to elongation mode
Author(s) -
Bier Mirko,
Fath Stephan,
Tschochner Herbert
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(04)00311-4
Subject(s) - rna polymerase ii , biology , rna polymerase iii , transcription (linguistics) , transcription factor ii d , elongation factor , rna polymerase i , general transcription factor , initiation factor , microbiology and biotechnology , transcription factor ii f , rna polymerase , rna , genetics , promoter , gene expression , gene , ribosome , linguistics , philosophy
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.