TFIIA/TFIIB/TFIID/TFIIE/TFIIF/TFIIH

TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH are the general transcription factors. TFIID is also the TATA-box binding protein and is associated with TAFs (TBP associated factors). 

TFIIF is found in a pre-formed complex with RNA polymerase II and suppresses the nonspecific binding of RNA polymerase to DNA. TFIIF supports the association of RNA polymerase with the promotor-bound complex of TFIIA, TFIIB and TFIID. TFIIE binds TFIIH to assist the latter with the melting of the promotor. 

Fig. 3. Initiation of transcription by RNA polymerase II. TFIID binds to the TATA box followed in order by the binding of TFIIA, TFIIB and a pre-formed complex of TFIIF. RNA polymerase II. Subsequently TFIIE, TFIIH and TFIIJ bind in order and transcription then starts about 25 bp downstream from the TATA box. Note that the placement of the various factors in this diagram is arbitrary their exact positions in the complex are not yet known.

TFIID (which contains the TATA-box binding protein, TBP) binds to the TATA box. TFIIA and TFIIB then bind, followed by recruitment of RNA polymerase II and TFIIF. TFIIH and TFIIE then bind to form the preinitiation complex (PIC). Kinases phosphorylate the C-terminal domain of Pol II, leading to the open complex in which the DNA strands are separated. RNA is produced during elongation as Pol II and TFIIF leave the promoter and the other general transcription factors behind. Pol II dissociates during the termination phase, and the CTD is dephosphorylated. Pol II/TFIIF is then recycled to bind to another promoter. 

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