title: Differential roles of phosphorylation in the formation of transcriptional active RNA polymerase I.
abstract: Regulation of rDNA transcription depends on the formation and dissociation of a functional complex between RNA polymerase I (pol I) and transcription initiation factor Rrn3p. We analyzed whether phosphorylation is involved in this molecular switch. Rrn3p is a phosphoprotein that is predominantly phosphorylated in vivo when it is not bound to pol I. In vitro, Rrn3p is able both to associate with pol I and to enter the transcription cycle in its nonphosphorylated form. By contrast, phosphorylation of pol I is required to form a stable pol I-Rrn3p complex for efficient transcription initiation. Furthermore, association of pol I with Rrn3p correlates with a change in the phosphorylation state of pol I in vivo. We suggest that phosphorylation at specific sites of pol I is a prerequisite for proper transcription initiation and that phosphorylation/dephosphorylation of pol I is one possibility to modulate cellular rDNA transcription activity.
authors.affiliation: Biochemie-Zentrum Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Fath
authors.forename: P
authors.initials: P
authors.lastname: Milkereit
authors.forename: G
authors.initials: G
authors.lastname: Peyroche
authors.forename: M
authors.initials: M
authors.lastname: Riva
authors.forename: C
authors.initials: C
authors.lastname: Carles
authors.forename: H
authors.initials: H
authors.lastname: Tschochner
mesh_terms: D004926:Escherichia coli / Q000235:genetics; D046911:Macromolecular Substances; D010766:Phosphorylation; D035463:Pol1 Transcription Initiation Complex Proteins; D012318:RNA Polymerase I / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D046911:Macromolecular Substances; D035463:Pol1 Transcription Initiation Complex Proteins; C101161:RRN3 protein, S cerevisiae; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012318:RNA Polymerase I