Mediator (coactivator)
Subunit No Human gene C. elegans gene D. melanogaster gene S. cerevisiae gene Sch . pombe gene
MED1 MED1 Sop3/mdt-1.1 , 1.2 MED1 MED1 med1
MED4 MED4 MED4 MED4 med4
MED6 MED6 MDT-6 MED6 MED6 med6
MED7 MED7 MDT-7/let-49 MED7 MED7 med7
MED8 MED8 MDT-8 MED8 MED8 med8
MED9 MED9 MED9 CSE2
MED10 MED10 MDT-10 NUT2 med10
MED11 MED11 MDT-11 MED11 MED11 med11
MED12 MED12 MDT-12/dpy-22 MED12 SRB8 srb8
MED13 MED13 MDT-13/let-19 MED13 SSN2 srb9
MED14 MED14 MDT-14/rgr-1 MED14 RGR1 med14
MED15 MED15 mdt-15 MED15 GAL11 YN91_SCHPO
MED16 MED16 MED16 SIN4
MED17 MED17 MDT-17 MED17 SRB4 med17
MED18 MED18 MDT-18 MED18 SRB5 med18
MED19 MED19 MDT-19 MED19 med19
In other species
Below is a cross-species comparison of mediator complex subunits . [ 36 ] [ 37 ]
Mediator is a multiprotein complex that functions as a transcriptional coactivator in all eukaryotes. It was discovered in 1990 in the lab of Roger D. Kornberg, winner of the 2006 Nobel Prize in Chemistry. Mediator complexes interact with transcription factors and RNA polymerase II. The main function of mediator complexes is to transmit signals from the transcription factors to the polymerase. Mediator complexes are variable at the evolutionary, compositional and conformational levels. The first image shows only one snapshot of what a particular mediator complex might be composed of, but it certainly does not accurately depict the conformation of the complex in vivo. During evolution, mediator has become more complex. The yeast Saccharomyces cerevisiae (a simple eukaryote) is thought to have up to 21 subunits in the core mediator (exclusive of the CDK module), while mammals have up to 26. Individual subunits can be absent or replaced by other subunits under different conditions. Also, there are many intrinsically disordered regions in mediator proteins, which may contribute to the conformational flexibility seen both with and without other bound proteins or protein complexes. A more realistic model of a mediator complex without the CDK module is shown in the second figure. The mediator complex is required for the successful transcription by RNA polymerase II.