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. Author manuscript; available in PMC: 2015 Nov 20.
Published in final edited form as: Biochem Cell Biol. 1999;77(4):257–264.

Fig. 1.

Fig. 1

Preinitiation complex formation on a class II promoter. The GTFs (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH) and Pol II can assemble sequentially onto the promoter DNA in vitro. Alternatively, the Pol II holoenzyme, which typically contains core Pol II, a number of GTFs, and several additional polypeptides, can bind to the promoter in a single step. TFIID (TBP and TAFIIs) or TBP alone bind to the TATA box of promoters to begin preinitiation complex formation close to the transcriptional initiation site (+1).