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Regulatory promoter

Y Core promoter

Transcription start site

13.16 The promoters of genes transcribed by RNA polymerase II consist of a core promoter and a regulatory promoter that contain consensus sequences. Not all the consensus sequences shown are found in all promoters.

approximately +30 bp downstream of the start site in many promoters that also have Inr; the consensus sequence of DPE is R G A/T C G T G. All of these consensus sequences in the core promoter are recognized by transcription factors that bind to them and serve as a platform for the assembly of the basal transcription apparatus.

Assembly of the basal transcription apparatus The basic transcriptional machinery that binds to DNA at the start site is called the basal transcription apparatus and is required to initiate minimal levels of transcription. It consists of RNA polymerase, a series of general transcription factors, and a complex of proteins known as the mediator

(iFigure 13.17). The general transcription factors include TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH, in which TFII stands for transcription factor for RNA polymerase II and the letter designates the individual factor.

TFIID binds to the TATA box and positions the active site of RNA polymerase II so that it begins transcription at the correct place. TFIID consists of at least nine polypep-tides. One of them is the TATA-binding protein (TBP), which recognizes and binds to the TATA box on the DNA template. The TATA-binding protein binds to the minor groove and straddles the DNA as a molecular saddle (iFigure 13.18), bending the DNA and partly unwinding it. Other proteins, called TBP-associated factors (TAFs),

Regulatory promoter

TATA box

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