Mediator 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

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 encoded by the MED15 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

MED15 is a general transcriptional cofactor of the mediator complex involved in RNA polymerase II dependent transcription, originally called Gal11 and Spt13 and found in yeast as an essential factor for Gal4-dependent transactivation by T.Fukasawa and F.Winston labs. Transcription factors Gcn4, Pho4, Msn2, Ino2, members of the Gal4 family - Gal4/ Oaf1/ Pdr1, and viral VP16 have been reported to interact with yeast MED15.

Most of these transcription factors share the same transactivation domain, 9aaTAD, which directly interacts with KIX domain of the MED15.

Furthermore, human MED15 cooperates in mediator complex (previously known as PC2, ARC, or DRIP) with transcription factors like VP16 and SREBP

Sterol regulatory element binding protein

Sterol Regulatory Element-Binding Proteins are transcription factors that bind to the sterol regulatory element DNA sequence TCACNCCAC. Mammalian SREBPs are encoded by the genes SREBF1 and SREBF2. SREBPs belong to the basic-helix-loop-helix leucine zipper class of transcription factors...

. Human SREBP regulates sterol responsive gene expression, and this regulatory action is conserved in the genetic model organism C. elegans

Caenorhabditis elegans

Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...

, a roundworm (homologues MDT-15 and SBP-1). Also in C. elegans, MDT-15 is essential for the response to several stresses (fasting, heavy metal, toxin, and oxidative stress); at least in part the fasting response is conferred by interactions of MDT-15 with nuclear receptor

Nuclear receptor

In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules...

s, including NHR-49.

Gene

The MED15 gene contains stretches of trinucleotide repeats and is located in the chromosome 22 region which is deleted in DiGeorge's syndrome. Two transcript variants encoding different isoforms have been found for this gene.

Further reading