Transcription factor

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In gene expression, the transcription of DNA to RNA is controlled by proteins called transcription factors. In eukaryotes there are 6 general transcription factors (GTFs): TFIIA, TFIIB, TFIID, TFIIE, TFIIF and TFIIH, each of which has a different role in regulating gene transcription. All GTFs are multi-subunit, except for TFIIB.

The GTFs are involved in the preinitiation complex (PIC) assembly which positions RNA polymerase II and separates the template strand at the transcription start site through a number of steps as outlined:

  1. TFIIA facilitates and stabilises TFIID binding to the TATA box.
  2. TFIID recruits the single subunit factor TFIIB.
  3. With this interaction, TFIIB recruits RNA polymerase II-TFIIF complex (TFIIF is joined toRNA polymerase II before this recruitment.)
  4. The recruitment of the RNA polymerase II-TFIIF allows TFIIE and then finally TFIIH to bind, completing the PIC assembly.

This is known as the classical pathway; not all promoters are turned on in this way.

Function of GTFs

TFIID: Binds to the TATA box, recruits TFIIB

TFIIA: Stabilizes TFIID binding, anti repression function

TFIIB: Recruits RNA pol II-TFIIF, important for start site selection

TFIIF: Stimulates elongation, destabilizes non specific RNA pol II-DNA interactions

TFIIE: Recruits TFIIH and modulates TFIIH activity

TFIIH: Promoter melting and clearance, CTD kinase activity, DNA repair coupling[1]

Reference

  1. Harvey L, Arnold B, Chris A, Monty K, Anthony B, Hidde P, Angelika A, Kelsey C, 2016, Molecular Cell Biology, 8th edition, New York: W. H. Freeman
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