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 prior to 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