Mediator

Mediator

The mediator, found in the yeast S. cerevisiae, connects repressors and activators bound to regulatory DNA with RNA polymerase II (Pol II). As a result, the mediator is an important regulator of eukaryotic transcription.^[1] Also, mediator is currently being studied because of its ability and role to regulate gene expression.^[2] Mediator is in the form of three main modules, which are the tail, arm, and head. The of the mediator is split into three domains that go through significant conformational changes, and it interacts with the Rpb7 and Rpb4 subunits of Pol II and TATA binding protein subunit of transcription factor TFIID.^[3]

Structure

The of mediator from S.cerevisiae is made of seven subunits which are Med22(Srb6), Med20(Srb2), Med18(Srb5), Med17(Srb4), Med11, Med6, and Med8.^[3] Of these subunits, Med11, Med17(Srb4), and Med22(Srb6) make the mini-head of the head module. The subunits of the core-head plus the subunits of the mini-head are what make up full head structure. The structure shows the three domains: the neck, which is shown by pink helices, the fixed jaw, which is shown by mostly pink helices and a few yellow beta sheets, and the movable jaw, which is shown by mostly yellow beta sheets and a few pink helices. The tail module of yeast mediator is made up of Med2, Med3, Med14, Med15 and Med16. The middle module of yeast mediator is made up of Med1, Med4, Med5, Med7, Med10, Med12, Med13, Med19, Med21, Med26, Med31, CycC and Cdk8.