EUKARYOTIC TRANSCRIPTION COMPLEXES

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DESCRIPTION: Efficient transcription initiation at eukaryotic protein- encoding genes requires RNA polymerase II and six general transcription factors (GTFs): i.e., TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. Human RNA polymerase II contains 10 to 12 polypeptide chains; collectively, TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH contain at least 25 distinct polypeptide chains. Understanding human transcription initiation and transcription regulation will require elucidation of the organization of these at least 35 distinct polypeptide chains relative to promoter DNA and relative to each other. TFIID, a multisubunit factor consisting of the TATA-element binding protein (TBP) and at least eight TBP-associated factors (TAFs), is the factor responsible for recognition of promoter DNA. TFIID, or isolated TBP, binds to promoter DNA and nucleates the subsequent, step-wise binding of TFIIA, TFIIB, TFIIF-RNA polymerase II, TFIIE, and TFIIH. It is believed that TBP contains determinants for protein-protein interactions with RNA polymerase II, GTFs, TAFs, and a number of transcription activators and repressors. The recent availability of the crystallographic structure of the TBP-DNA complex makes possible a detailed structure-function determination of TBP-RNA polymerase II, TBP-GTF, TBP-TAF, TBP-activator, and TBP- repressor interactions.