Mediator head module structure and functional interactions.

Department of Cell Biology, The Scripps Research Institute, La Jolla, California, USA.
We used single-particle electron microscopy to characterize the structure and subunit organization of the Mediator Head module that controls Mediator-RNA polymerase II (RNAPII) and Mediator-promoter interactions. The Head module adopts several conformations differing in the position of a movable jaw formed by the Med18-Med20 subcomplex. We also characterized, by structural, biochemical and genetic means, the interactions of the Head module with TATA-binding protein (TBP) and RNAPII subunits Rpb4 and Rpb7. TBP binds near the Med18-Med20 attachment point and stabilizes an open conformation of the Head module. Rpb4 and Rpb7 bind between the Head jaws, establishing contacts essential for yeast-cell viability. These results, and consideration of the structure of the Mediator-RNAPII holoenzyme, shed light on the stabilization of the pre-initiation complex by Mediator and suggest how Mediator might influence initiation by modulating polymerase conformation and interaction with promoter DNA.
Mesh Terms:
Mediator Complex, Microscopy, Electron, Models, Molecular, Protein Binding, Protein Structure, Tertiary, RNA Polymerase II, Saccharomyces cerevisiae Proteins, Structure-Activity Relationship, Transcription, Genetic
Nat. Struct. Mol. Biol. Mar. 01, 2010; 17(3);273-9 [PUBMED:20154708]
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