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Mediator of RNA polymerase II transcription subunit 26 is an enzyme that in humans is encoded by the ''MED26'' gene.〔(【引用サイトリンク】 url = http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=9441 )〕 It forms part of the Mediator complex. ==Activity== MED26 or Transcription factor IIS (TFIIS) is a transcription elongation factor that increases the overall transcription rate of RNA polymerase II by reactivating transcription elongation complexes that have arrested transcription. It does this through recruiting ELL/EAF- and P-TEFb- containing complexes to promoters via a direct interaction with the N-terminal domain (NTD). The MED26 NTD also binds TFIID, and TFIID and elongation complexes interact with MED26 through overlapping binding sites. MED26 NTD may function as a molecular switch contributing to the transition of Pol II into productive elongation. The three structural domains of TFIIS are conserved from yeast to human. The 80 or so N-terminal residues form a protein interaction domain containing a conserved motif, which has been called the LW motif because of the invariant leucine and tryptophan residues it contains. Although the N-terminal domain is not needed for transcriptional activity, a similar sequence has been identified in other transcription factors and proteins that are predominantly nuclear localized,: *MED26 (also known as CRSP70 and ARC70), a subunit of the Mediator complex, which is required for the activity of the enhancer-binding protein Sp1. *Elongin A, a subunit of a transcription elongation factor previously known as SIII. It increases the rate of transcription by suppressing transient pausing of the elongation complex. *PPP1R10, a nuclear regulatory subunit of protein phosphatase 1 that was previously known as p99, FB19 or PNUTS. *PIBP, a small hypothetical protein that could be a phosphoinositide binding protein. *IWS1, which is thought to function in both transcription initiation and elongation. The TFIIS N-terminal domain is a compact four-helix bundle. The hydrophobic core residues of helices 2, 3, and 4 are well conserved among TFIIS domains, although helix 1 is less conserved.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「MED26」の詳細全文を読む スポンサード リンク
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