Mediator head module structure and functional interactions.
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.
Cai
Gang
G
Department of Cell Biology, The Scripps Research Institute, La Jolla, California, USA.
Imasaki
Tsuyoshi
T
Yamada
Kentaro
K
Cardelli
Francesco
F
Takagi
Yuichiro
Y
Asturias
Francisco J
FJ
D056892:Mediator Complex / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic
D056892:Mediator Complex; D029701:Saccharomyces cerevisiae Proteins; D012319:RNA Polymerase II; C423309:RPB4 protein, S cerevisiae; C470553:RPB7 protein, S cerevisiae