biostudies-literatureTorreira EFundación Ramón ArecesMinisterio de Economía y Competitividade20832https://www.ebi.ac.uk/biostudies/studies/S-EPMC5362265biostudies-literatureUnknown6Cell growth requires synthesis of ribosomal RNA by RNA polymerase I (Pol I). Binding of initiation factor Rrn3 activates Pol I, fostering recruitment to ribosomal DNA promoters. This fundamental process must be precisely regulated to satisfy cell needs at any time. We present in vivo evidence that, when growth is arrested by nutrient deprivation, cells induce rapid clearance of Pol I-Rrn3 complexes, followed by the assembly of inactive Pol I homodimers. This dual repressive mechanism reverts upon nutrient addition, thus restoring cell growth. Moreover, Pol I dimers also form after inhibition of either ribosome biogenesis or protein synthesis. Our mutational analysis, based on the electron cryomicroscopy structures of monomeric Pol I alone and in complex with Rrn3, underscores the central reLifeThe dynamic assembly of distinct RNA polymerase I complexes modulates rDNA transcription.PMC5362265RYC-2011-07967BFU2013-48374-PGonzalez-Polo NDuran AGTorreira ELouro JAPazos ICalvo OGil-Carton DGallego OFernandez-Tornero CTosi SfalseThe dynamic assembly of distinct RNA polymerase I complexes modulates rDNA transcription.Cell growth requires synthesis of ribosomal RNA by RNA polymerase I (Pol I). Binding of initiation factor Rrn3 activates Pol I, fostering recruitment to ribosomal DNA promoters. This fundamental process must be precisely regulated to satisfy cell needs at any time. We present in vivo evidence that, when growth is arrested by nutrient deprivation, cells induce rapid clearance of Pol I-Rrn3 complexes, followed by the assembly of inactive Pol I homodimers. This dual repressive mechanism reverts upon nutrient addition, thus restoring cell growth. Moreover, Pol I dimers also form after inhibition of either ribosome biogenesis or protein synthesis. Our mutational analysis, based on the electron cryomicroscopy structures of monomeric Pol I alone and in complex with Rrn3, underscores the central r2017-01-01T00:00:00Z2017 Mar2026-05-05T18:26:17.361Z2019-03-27T02:39:16ZS-EPMC53622652826209710.7554/eLife.20832