title: Molecular architecture of the yeast Mediator complex.
abstract: The 21-subunit Mediator complex transduces regulatory information from enhancers to promoters, and performs an essential role in the initiation of transcription in all eukaryotes. Structural information on two-thirds of the complex has been limited to coarse subunit mapping onto 2-D images from electron micrographs. We have performed chemical cross-linking and mass spectrometry, and combined the results with information from X-ray crystallography, homology modeling, and cryo-electron microscopy by an integrative modeling approach to determine a 3-D model of the entire Mediator complex. The approach is validated by the use of X-ray crystal structures as internal controls and by consistency with previous results from electron microscopy and yeast two-hybrid screens. The model shows the locations and orientations of all Mediator subunits, as well as subunit interfaces and some secondary structural elements. Segments of 20-40 amino acid residues are placed with an average precision of 20 Å. The model reveals roles of individual subunits in the organization of the complex.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, United States.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Robinson
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Trnka
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States.|Structural Bioinformatics Unit, Paris, France.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pellarin
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Greenberg
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Bushnell
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, United States.
authors.forename: Ralph
authors.initials: R
authors.lastname: Davis
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.
authors.forename: Alma L
authors.initials: AL
authors.lastname: Burlingame
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, Department of Pharmaceutical Chemistry, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States.
authors.forename: Andrej
authors.initials: A
authors.lastname: Sali
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, United States.
authors.forename: Roger D
authors.initials: RD
authors.lastname: Kornberg
mesh_terms: D003432:Cross-Linking Reagents / Q000378:metabolism; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D013058:Mass Spectrometry; D056892:Mediator Complex / Q000737:chemistry*; D008954:Models, Biological; D008958:Models, Molecular; D012441:Saccharomyces cerevisiae / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D056892:Mediator Complex
keywords: RNA polymerase II; S. cerevisiae; biophysics; cross-linking; mass spectrometry; modeling; structural biology; transcriptional regulation