Structure of the human Mediator-bound pre-initiation complex. A) Composite density map for Med-PIC built from the focused refinement maps for cPIC, cTFIIH, MedHead, MedMiddle-CAK, Med14C, MedTail, and Med1. The colors of the subunits will be repeated throughout the manuscript. B) Model of the human Mediator-bound pre-initiation complex. Gray, Pol II; Dark Gray, general transcription factors; Pink, TFIIH core; Salmon, CDK7; Violet, cyclin H; Medium Violet Red, Mat1; Cyan, DNA, Reds, MedHead; Blues, MedMiddle; Yellow, Med14; Greens, MedTail.