Figure 1.

Mediator dynamics during activated transcription in yeast. (a) Mediator is recruited to UASs by DNA sequence-specific activator proteins via tail module subunits. Mediator then engages PIC components and transits to the proximal promoter region, with accompanying loss of the kinase module. Although the precise mechanism of Mediator transit from UAS to proximal promoter and engagement with the PIC remains unknown, TBP is required for this step. Mediator remains at the proximal promoter only transiently, with eviction accompanying promoter escape by Pol II, but can be captured at this stage by preventing Pol II promoter escape. (b) Browser scans showing occupancy of Mediator tail (Med15) or head (Med18) subunits at the LEU1 and PMA1 promoters (left) and RPS9B and RPL21A promoters (right) with or without depletion of Kin28 or Kin28 and TBP. The box indicates the PMA1 UAS; the peak to the left at the proximal promoter is seen only when Kin28 is depleted and TBP is not. Relative scales normalized to the total number of mapped reads are indicated. All browser scans were produced using the integrative genome viewer [85]. Data is from [31,71].