Mediator (coactivator)
Encyclopedia
Mediator is a multiprotein complex that functions as a transcriptional coactivator
. It was discovered by Roger D. Kornberg
, winner of the 2006 Nobel Prize in Chemistry
. It is also referred to in scientific literature as the Vitamin D Receptor Interacting Protein (DRIP) coactivator complex and the Thyroid Hormone Receptor-associated Proteins (TRAP).
The Mediator complex is required for the successful transcription
of nearly all class II gene
promoters in yeast. It works in the same manner in mammals. The human Mediator complex has 26 subunits and is 1.2 MDa in size. Its large surface area provides great potential for protein–protein interaction, even though its sequences do not contain many predicted functional domains. Mediator has been shown to associate with general transcription factors, as well as RNA polymerase II, and is essential for activator-dependent transcription. It has also been demonstrated that the Mediator complex is involved in activator-independent transcription, implying that it may provide a fundamental control of the formation of the initiation complex. Mediator functions as a coactivator and binds to the C-terminal domain of RNA polymerase II
holoenzyme, acting as a bridge between this enzyme and transcription factor
s.
Coactivator (genetics)
A coactivator is a protein that increases gene expression by binding to an activator which contains a DNA binding domain. The coactivator is unable to bind DNA by itself....
. It was discovered by Roger D. Kornberg
Roger D. Kornberg
Roger David Kornberg is an American biochemist and professor of structural biology at Stanford University School of Medicine.Kornberg was awarded the Nobel Prize in Chemistry in 2006 for his studies of the process by which genetic information from DNA is copied to RNA, "the molecular basis of...
, winner of the 2006 Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
. It is also referred to in scientific literature as the Vitamin D Receptor Interacting Protein (DRIP) coactivator complex and the Thyroid Hormone Receptor-associated Proteins (TRAP).
The Mediator complex is required for the successful transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
of nearly all class II gene
Class II gene
A class II gene is a type of gene that codes for a protein. Class II genes are transcribed by RNAP II.Class II genes have a promoter that often contains a TATA box.Basal transcription of class II genes requires the formation of a preinitiation complex....
promoters in yeast. It works in the same manner in mammals. The human Mediator complex has 26 subunits and is 1.2 MDa in size. Its large surface area provides great potential for protein–protein interaction, even though its sequences do not contain many predicted functional domains. Mediator has been shown to associate with general transcription factors, as well as RNA polymerase II, and is essential for activator-dependent transcription. It has also been demonstrated that the Mediator complex is involved in activator-independent transcription, implying that it may provide a fundamental control of the formation of the initiation complex. Mediator functions as a coactivator and binds to the C-terminal domain of RNA polymerase II
RNA polymerase II
RNA polymerase II is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase...
holoenzyme, acting as a bridge between this enzyme and transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...
s.
Component proteins
Human genes which encoded component proteins of the mediator complex include:- MED1MED1Mediator of RNA polymerase II transcription subunit 1 is a protein that in humans is encoded by the MED1 gene.- Function :The activation of gene transcription is a multistep process that is triggered by factors that recognize transcriptional enhancer sites in DNA. These factors work with...
, MED4MED4Mediator of RNA polymerase II transcription subunit 4 also known as mediator complex subunit 4 or vitamin D3 receptor-interacting protein complex 36 kDa component is a protein that in humans is encoded by the MED4 gene....
, MED6MED6Mediator of RNA polymerase II transcription subunit 6 is an enzyme that in humans is encoded by the MED6 gene.-Interactions:MED6 has been shown to interact with Thyroid hormone receptor alpha, Estrogen receptor alpha, MED21 and Cyclin-dependent kinase 8.-Further reading:...
, MED7MED7Mediator of RNA polymerase II transcription subunit 7 is an enzyme that in humans is encoded by the MED7 gene.-Further reading:...
, MED8MED8Mediator of RNA polymerase II transcription subunit 8 is an enzyme that in humans is encoded by the MED8 gene.-Further reading:...
, MED9, MED10, MED11 - MED12MED12Mediator of RNA polymerase II transcription, subunit 12 homolog , also known as MED12, is a human gene found on the X chromosome...
, MED13, MED13L, MED14MED14Mediator of RNA polymerase II transcription subunit 14 is an enzyme that in humans is encoded by the MED14 gene.-Interactions:MED14 has been shown to interact with PPARGC1A, Estrogen receptor alpha, STAT2, Cyclin-dependent kinase 8, Glucocorticoid receptor and Hepatocyte nuclear factor 4...
, MED15MED15Mediator of RNA polymerase II transcription subunit 15, also known as Gal11,Spt13 in yeast and PCQAP, ARC105, or TIG-1 in humans is a protein encoded by the MED15 gene.- Function :...
, MED16MED16Mediator of RNA polymerase II transcription subunit 16 is an enzyme that in humans is encoded by the MED16 gene.-Interactions:MED16 has been shown to interact with Thyroid hormone receptor alpha, Estrogen receptor alpha and Cyclin-dependent kinase 8....
, MED17MED17Mediator of RNA polymerase II transcription subunit 17 is an enzyme that in humans is encoded by the MED17 gene.-Interactions:MED17 has been shown to interact with PPARGC1A, Cyclin-dependent kinase 8 and BRCA1.-Further reading:... - MED18, MED19, MED20MED20Mediator complex subunit 20 is a protein that in humans is encoded by the MED20 gene....
, MED21MED21Mediator of RNA polymerase II transcription subunit 21 is an enzyme that in humans is encoded by the MED21 gene.-Interactions:MED21 has been shown to interact with Cyclin-dependent kinase 8, BRCA1, GTF2H4, MED6, POLR2A and GTF2F1.-Further reading:...
, MED22MED22Mediator of RNA polymerase II transcription subunit 22 is an enzyme that in humans is encoded by the MED22 gene.-Further reading:...
, MED23, MED24MED24Mediator of RNA polymerase II transcription subunit 24 is an enzyme that in humans is encoded by the MED24 gene.-Interactions:MED24 has been shown to interact with Estrogen receptor alpha, Cyclin-dependent kinase 8, Calcitriol receptor and BRCA1.... - MED25MED25Mediator of RNA polymerase II transcription subunit 25 is an enzyme that in humans is encoded by the MED25 gene.-External links:*...
, MED26MED26Mediator of RNA polymerase II transcription subunit 26 is an enzyme that in humans is encoded by the MED26 gene.-Interactions:MED26 has been shown to interact with MED8, Cyclin-dependent kinase 8, POLR2A, MED12 and MED28.-Further reading:...
, MED27MED27Mediator of RNA polymerase II transcription subunit 27 is an enzyme that in humans is encoded by the MED27 gene.-Further reading:...
, MED28MED28Mediator of RNA polymerase II transcription subunit 28 is an enzyme that in humans is encoded by the MED28 gene.-Interactions:MED28 has been shown to interact with Merlin, Grb2 and MED26.-Further reading:...
, MED29, MED30MED30Mediator of RNA polymerase II transcription subunit 30 is an enzyme that in humans is encoded by the MED30 gene.-Further reading:...
, MED31MED31Mediator of RNA polymerase II transcription subunit 31 is an enzyme that in humans is encoded by the MED31 gene.-Further reading:... - CCNC, CDK8, CDK19