Family MED7

The Mediator of transcriptional regulation was first characterized in yeast and is the central coactivator that enables a response of RNA polymerase II (Pol II) to activators and repressors. MED7, a component of the middle module of Mediator, has been shown to serve as a binding platform, with its C-terminus associated with MED21, and its N-terminus associated with MED31. The middle module subunits MED1 and MED10, which bridge to the Mediator tail module, also bind MED7 (PMID:20123732). Crystal structure analysis of the MED7/MED21 heterodimer showed a four helix bundle domain, and a coiled-coil protrusion connected by a flexible hinge. Four putative protein binding sites allow for assembly of the middle module and binding of MED6, which bridges to the Mediator head module. This flexible bridge could account for changes in Mediator conformation upon binding to RNA pol II or activators/repressors. (PMID:15710619). The N-terminal MED7/MED31 submodule shows a conserved novel fold, two proline-rich stretches in the N-terminus of MED7 wrapping around the right-handed four-helix bundle of Med31 (PMID:19057509).