Structure of the initiation-competent RNA polymerase I and its implication for transcription

Nat Commun. 2016 Jul 15;7:12126. doi: 10.1038/ncomms12126.

Abstract

Eukaryotic RNA polymerase I (Pol I) is specialized in rRNA gene transcription synthesizing up to 60% of cellular RNA. High level rRNA production relies on efficient binding of initiation factors to the rRNA gene promoter and recruitment of Pol I complexes containing initiation factor Rrn3. Here, we determine the cryo-EM structure of the Pol I-Rrn3 complex at 7.5 Å resolution, and compare it with Rrn3-free monomeric and dimeric Pol I. We observe that Rrn3 contacts the Pol I A43/A14 stalk and subunits A190 and AC40, that association re-organizes the Rrn3 interaction interface, thereby preventing Pol I dimerization; and Rrn3-bound and monomeric Pol I differ from the dimeric enzyme in cleft opening, and localization of the A12.2 C-terminus in the active centre. Our findings thus support a dual role for Rrn3 in transcription initiation to stabilize a monomeric initiation competent Pol I and to drive pre-initiation complex formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cryoelectron Microscopy / methods
  • Pol1 Transcription Initiation Complex Proteins / genetics
  • Pol1 Transcription Initiation Complex Proteins / metabolism*
  • Promoter Regions, Genetic
  • Protein Domains
  • Protein Multimerization
  • RNA Polymerase I / chemistry*
  • RNA Polymerase I / genetics
  • RNA Polymerase I / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription, Genetic

Substances

  • Pol1 Transcription Initiation Complex Proteins
  • RRN3 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • RNA Polymerase I