Department of Molecular Biosciences, Northwestern University, Evanston, United States
Chunli Yan
Department of Chemistry, Georgia State University, Atlanta, United States; Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, United States
Thi Hoang Duong Nguyen
Howard Hughes Medical Institute, University of California, Berkeley, United States
Ashleigh J Jackobel
Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, United States
Ivaylo Ivanov
Department of Chemistry, Georgia State University, Atlanta, United States; Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, United States
Transcription initiation by RNA Polymerase I (Pol I) depends on the Core Factor (CF) complex to recognize the upstream promoter and assemble into a Pre-Initiation Complex (PIC). Here, we solve a structure of Saccharomyces cerevisiae Pol I-CF-DNA to 3.8 Å resolution using single-particle cryo-electron microscopy. The structure reveals a bipartite architecture of Core Factor and its recognition of the promoter from −27 to −16. Core Factor’s intrinsic mobility correlates well with different conformational states of the Pol I cleft, in addition to the stabilization of either Rrn7 N-terminal domain near Pol I wall or the tandem winged helix domain of A49 at a partially overlapping location. Comparison of the three states in this study with the Pol II system suggests that a ratchet motion of the Core Factor-DNA sub-complex at upstream facilitates promoter melting in an ATP-independent manner, distinct from a DNA translocase actively threading the downstream DNA in the Pol II PIC.
