Genetic analyses led to the discovery of a super-active mutant of the RNA polymerase I

by Tommy Darri ère, Michael Pilsl, Marie-Kerguelen Sarthou, Adrien Chauvier, Titouan Genty, Sylvain Audibert, Christophe Dez, Isabelle Léger-Silvestre, Christophe Normand, Anthony K. Henras, Marta Kwapisz, Olga Calvo, Carlos Fernández-Tornero, Herbert Tschochner, Olivier Gadal

Most transcriptional activity of exponentially growing cells is carried out by the RNA Polymerase I (Pol I), which produces a ribosomal RNA (rRNA) precursor. In budding yeast, Pol I is a multimeric enzyme with 14 subunits. Among them, Rpa49 forms with Rpa34 a Pol I-specific heterodimer (homologous to PAF53/CAST heterodimer in human Pol I), which might be responsible for the specific functions of the Pol I. Previous studies provided insight in the involvement of Rpa49 in initiation, elongation, docking and releasing of Rrn3, an essential Pol I transcription factor. Here, we took advantage of the spontaneous occurrence of extragenic suppressors of the growth defect of therpa49 null mutant to better understand the activity of Pol I. Combining genetic approaches, biochemical analysis of rRNA synthesis and investigation of the transcription rate at the individual gene scale, we characterized mutated residues of the Pol I as novel extragenic suppressors of the growth defect caused by the absence of Rpa49. When mapped on the Pol I structure, most of these mutations cluster within the jaw-lobe module, at an interface formed by the lobe in Rpa135 and the jaw made up of regions of Rpa190 and Rpa12.In vivo, th...

Source: PLoS Genetics - May 27, 2019 Category: Genetics & Stem Cells Authors: Tommy Darri ère Source Type: research