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
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
encoded by the ''MED15''
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
.
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
The Gal4 transcription factor is a positive regulator of gene expression of galactose-induced genes. This protein represents a large fungal family of transcription factors, Gal4 family, which includes over 50 members in the yeast ''Saccharomyces ...
dependent transactivation by T.Fukasawa and F.Winston labs. Transcription factors Gcn4, Pho4, Msn2, Ino2, members of the
Gal4
The Gal4 transcription factor is a positive regulator of gene expression of galactose-induced genes. This protein represents a large fungal family of transcription factors, Gal4 family, which includes over 50 members in the yeast ''Saccharomyces ...
family -
Gal4
The Gal4 transcription factor is a positive regulator of gene expression of galactose-induced genes. This protein represents a large fungal family of transcription factors, Gal4 family, which includes over 50 members in the yeast ''Saccharomyces ...
, Oaf1, Pdr1, and viral VP16 have been reported to interact with yeast MED15.
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Most of these transcription factors share the same transactivation domain, 9aaTAD, which directly interacts with KIX domain of the MED15.
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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 proteins (SREBPs) 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- ...
. Human SREBP regulates sterol responsive gene expression, and this regulatory action is conserved in the genetic model organism
''C. elegans'', 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
In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These receptors work with other proteins to regulate the expression of speci ...
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.
References
Further reading
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{{PDB Gallery, geneid=51586