Transcription factor
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:
- TFIIA facilitates and stabilises TFIID binding to the TATA box.
- TFIID recruits the single subunit factor TFIIB.
- With this interaction, TFIIB recruits RNA polymerase II-TFIIF complex (TFIIF is joined toRNA polymerase II before this recruitment.)
- 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
- ↑ 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