title: The transcriptional activity of RNA polymerase I is a key determinant for the level of all ribosome components.
abstract: Regulation of ribosome biogenesis is a key element of cell biology, not only because ribosomes are directly required for growth, but also because ribosome production monopolizes nearly 80% of the global transcriptional activity in rapidly growing yeast cells. These observations underscore the need for a tight regulation of ribosome synthesis in response to environmental conditions. In eukaryotic cells, ribosome synthesis involves the activities of the three nuclear RNA polymerases (Pol). Although postulated, there is no clear evidence indicating whether the maintenance of an equimolar supply of ribosomal components reflects communication between the nuclear transcriptional machineries. Here, by constructing a yeast strain expressing a Pol I that remains constitutively competent for the initiation of transcription under stress conditions, we demonstrate that derepression of Pol I transcription leads to a derepression of Pol II transcription that is restricted to the genes encoding ribosomal proteins. Furthermore, we show that the level of 5S rRNA, synthesized by Pol III, is deregulated concomitantly with Pol I transcription. Altogether, these results indicate that a partial derepression of Pol I activity drives an abnormal accumulation of all ribosomal components, highlighting the critical role of the regulation of Pol I activity within the control of ribosome biogenesis.
authors.affiliation: Laboratoire de Transcription des Gènes, Service de Biochimie et de Génétique Moléculaire, CEA/Saclay, F-Gif sur Yvette, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Laferté
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Favry
authors.forename: André
authors.initials: A
authors.lastname: Sentenac
authors.forename: Michel
authors.initials: M
authors.lastname: Riva
authors.forename: Christophe
authors.initials: C
authors.lastname: Carles
authors.forename: Stéphane
authors.initials: S
authors.lastname: Chédin
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D005786:Gene Expression Regulation; D035463:Pol1 Transcription Initiation Complex Proteins / Q000378:metabolism*; D012318:RNA Polymerase I / Q000502:physiology*; D012319:RNA Polymerase II / Q000502:physiology*; D012341:RNA, Ribosomal, 5S / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D035463:Pol1 Transcription Initiation Complex Proteins; D012341:RNA, Ribosomal, 5S; D012319:RNA Polymerase II; D012318:RNA Polymerase I