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

Michael Pilsl (1) , Corinne Crucifix (2) , Gabor Papai (2) , Ferdinand Krupp (2) , Robert Steinbauer (1) , Joachim Griesenbeck (1) , Philipp Milkereit (1) , Herbert Tschochner (1) , Patrick Schultz (2)

1 Universität Regensburg, Biochemie-Zentrum Regensburg (BZR), Lehrstuhl Biochemie III, Regensburg, Germany
2 IGBMC - Institut de Génétique et de Biologie Moléculaire et Cellulaire

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 reorganizes 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.

Domaines: Biologie structurale [q-bio.BM]

Michael Pilsl, Corinne Crucifix, Gabor Papai, Ferdinand Krupp, Robert Steinbauer, et al.. Structure of the initiation-competent RNA polymerase I and its implication for transcription. Nature Communications, 2016, 7 (1), pp.12126. ⟨10.1038/ncomms12126⟩. ⟨hal-03535654⟩