Molecular architecture of the yeast Mediator complex

Elife. 2015 Sep 24;4:e08719. doi: 10.7554/eLife.08719.

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.

Keywords: RNA polymerase II; S. cerevisiae; biophysics; cross-linking; mass spectrometry; modeling; structural biology; transcriptional regulation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cross-Linking Reagents / metabolism
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Mass Spectrometry
  • Mediator Complex / chemistry*
  • Models, Biological
  • Models, Molecular
  • Saccharomyces cerevisiae / chemistry*

Substances

  • Cross-Linking Reagents
  • Mediator Complex