Eukaryotic RNA polymerases, unlike their bacterial counterparts, are incapable of binding by themselves to their respective promoters. Instead, they rely on proteins called transcription factors to show them the way. Such factors are grouped into two classes: general transcription factors and gene-specifi c transcription factors (activators). In this chapter we will survey the general transcription factors that interact with all three RNA polymerases and their promoters. | Molecular Biology Fourth Edition Chapter 11 General Transcription Factors in Eukaryotes Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class II Factors General transcription factors combine with RNA polymerase to form a preinitiation complex This complex is able to initiate transcription when nucleotides are available Tight binding involves formation of an open promoter complex with DNA at transcription start site melted While the class II complex is quite involved, explore it first, then those of classes I and III 11- The Class II Preinitiation Complex Class II preinitiation complex contains: Polymerase II 6 general transcription factors: TFIIA TFIIB TFIID TFIIE TFIIH The transcription factors (TF) and polymerase bind the preinitiation complex in a specific order 11- Four Distinct Preinitiation Complexes TFIID with help from TFIIA binds to the TATA box forming the DA complex . | Molecular Biology Fourth Edition Chapter 11 General Transcription Factors in Eukaryotes Lecture PowerPoint to accompany Robert F. Weaver Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class II Factors General transcription factors combine with RNA polymerase to form a preinitiation complex This complex is able to initiate transcription when nucleotides are available Tight binding involves formation of an open promoter complex with DNA at transcription start site melted While the class II complex is quite involved, explore it first, then those of classes I and III 11- The Class II Preinitiation Complex Class II preinitiation complex contains: Polymerase II 6 general transcription factors: TFIIA TFIIB TFIID TFIIE TFIIH The transcription factors (TF) and polymerase bind the preinitiation complex in a specific order 11- Four Distinct Preinitiation Complexes TFIID with help from TFIIA binds to the TATA box forming the DA complex TFIIB binds next generating the DAB complex TFIIF helps RNA polymerase bind to a region from -34 to +17, now it is DABPolF complex Last the TFIIE then TFIIH bind to form the complete preinitiation complex = DABPolFEH In vitro the participation of TFIIA seems to be optional 11- Model of Formation of the DABPolF Complex 11- Structure and Function of TFIID TFIID contains several subunits TATA-box binding protein (TBP) Highly evolutionarily conserved Binds to the minor groove of the TATA box Saddle-shaped TBP lines up with DNA Underside of the saddle forces open the minor groove The TATA box is bent into 80° curve 8 to 10 copies of TBP-associated factors (TAFIIs) specific for class II 11- The Versatility of TBP Genetic studies have demonstrated TBP mutant cell extracts are deficient in: Transcription of class II genes Transcription of class I and III genes TBP is a universal transcription factor required by all three classes of genes Required in transcription of at least some .
