Cell - 8 September 2016

Figure S4. Med-PIC Modeling, Related toFigure 2
(A) Docking of RNA pol II crystal structure shown in the canonical front view.
(B) Path ofHIS4promoter DNA through the Med-PIC complex with bend 37 nucleotides upstream of start-site (
37) indicated. The central portion of the DNA path
is obstructed from view by TFIIF density.
(C) Architectural model of the Mediator Middle module. Middle density (left, gold) is shown in the context of the Med-PIC structure (gray). Middle module crystal
structure and homology models were positioned in the Middle module density by automatic docking (right, Med-PIC Map Interpretation and Model Building in
STAR Methods). The position of Middle subunits lacking atomic models are derived from a Mediator 3D architectural model (Figure 7A) and Med-PIC cross-links
and colored according to the Mediator model.
(D) Head density (left, aquamarine) and docking of the modifiedS. cerevisiaeHead module crystal structure (right, PDB ID 4gwp).
(E) Structural changes in the Head module upon association with pol II in the Med-PIC complex. Upon PIC binding the mobile and fixed jaws of the Head module
swing away from the Neck domain to give a more open conformation.