CopyrightThe McGraw-Hill Companies,Inc.Permission required for reproduction or display. Chapter 11 General Transcription Factors in Eukaryotes Oscar L.Miller/SPL/Photo Researchers,Inc
Chapter 11 General Transcription Factors in Eukaryotes
Polymerases need help to find the promoters The factors that attract polymerases to their respective promoters are called general transcription factors(转录因子，TF) √General transcription factors(通用转录因子) combine with an RNA polymerase to form an open promoter complex(开放启动子复合物)ora preinnitiation complex(起始前复合物)to activate transcription Class II factors work with Pol II. 11-2
11-2 Polymerases need help to find the promoters ✓The factors that attract polymerases to their respective promoters are called general transcription factors (转录因子, TF) ✓General transcription factors (通用转录因子) combine with an RNA polymerase to form an open promoter complex (开放启动子复合物) or a preinnitiation complex (起始前复合物) to activate transcription ✓Class II factors work with Pol II
11.1 Class lI 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 ll complex is quite involved, explore it first,then those of classes I and 川 11-3
11-3 11.1 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
The Class ll Preinitiation Complex Class ll preinitiation complex contains: -Polymerase ll -6 general transcription factors: 。TFIIA ·TFIIB ·TFIID ·TFIIE ·TFIH The transcription factors (TF)and polymerase bind the preinitiation complex in a specific order 11-4
11-4 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
Class II preinitiation complex Preinitiation complex is assembled in a precise order,and forming four Distinct Preinitiation Complexes in the process. D→DA→DAB→DAB-PolF→DAB-PolF-EH Copyright The McGraw-Hill Companies,Inc.Permission required for reproduction or display. Pol II Pol Il DABPolF: DAB: Pol II TATA -5 TATA
11-5 Class II preinitiation complex Preinitiation complex is assembled in a precise order, and forming four Distinct Preinitiation Complexes in the process. D DA DAB DAB-PolF DAB-PolF-EH ➢Last the TFIIE then TFIIH bind to form the complete preinitiation complex = DABPolFEH ➢In vitro the participation of TFIIA seems to be optional ➢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
Structure and Function of TFIID TFIID binds to TATA box,composed of TATA-box- binding protein(TATA盒结合蛋白，TBP)and8-10TBP- associated factors(TBP结合因子，TAFs) TBP Highly evolutionarily conserved C-terminal 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 TAFus are specific for class ll 11-6
11-6 Structure and Function of TFIID TFIID binds to TATA box, composed of TATA-boxbinding protein (TATA盒结合蛋白, TBP) and 8-10 TBPassociated factors (TBP结合因子, TAFs) – TBP • Highly evolutionarily conserved • C-terminal binds to the minor groove of the TATA box – Saddle(鞍)-shaped TBP lines up with DNA – Underside of the saddle forces open the minor groove – The TATA box is bent into 80° curve – TAFIIs are specific for class II
The Versatility of TBP Genetic studies have demonstrated TBP mutant cell extracts are deficient in: -Transcription of class ll genes -Transcription of class I and lll genes TBP is a universal transcription factor required by all three classes of genes Required in transcription of at least some genes of the Archaea(古菌)，single-celled organisms lacking nuclei TBP not only functions with Pol ll promoters with TATA box,but also with TATA-less pol ll promoters. 11-7
11-7 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 genes of the Archaea(古菌), single-celled organisms lacking nuclei ✓ TBP not only functions with Pol II promoters with TATA box, but also with TATA-less pol II promoters
The TBP-Associated Factors (TAFIls) -25 What are the Upstream TATA Inr Downstream element element roles of TAFs? E1B E4 AdML Hsp70 89 89 TAFIIs help TBP with transcirption from promoters with initiators an downstream elemens 2 34 56 8 E1B,E4- TATA AdML,Hsp70- TATA Inr DPE 11-8
11-8 What are the roles of TAFs? TAFIIs help TBP with transcirption from promoters with initiators an downstream elemens The TBP-Associated Factors (TAFIIs)
The TBP-Associated Factors (TAFs) 8 different proteins are rTFID kD 200 TAF 250 designated by MW -TAF,150 116 -TAF,110 Most are evolutionarily 98 TAF,80 66 -TAF 60 conserved in eukaryotes Several functions discovered: 43 二腮40 Interaction with the core promoter TAF 30B TAF 30c elements Interaction with gene-specific 250 transcription factors 80 When attached to TBP extend the 30 binding of TFIID beyond the TATA box 11-9
11-9 The TBP-Associated Factors (TAFIIs) ✓ 8 different proteins are designated by MW ✓ Most are evolutionarily conserved in eukaryotes ✓ Several functions discovered: – Interaction with the core promoter elements – Interaction with gene-specific transcription factors – When attached to TBP extend the binding of TFIID beyond the TATA box
Roles of TAF250 and TAF150 The TAF250 and TAF150 help the TFIID bind to the initiator and DPE of promoters Also aid in TFlID interaction with specificity protein1(特异蛋白1，Sp1)that is bound to GC boxes upstream of the transcription start site They enable TBP to bind to: TATA-less promoters that contain elements such as a GC box TAF250 has 2 enzymatic activities: -Histone acetyltransferase(乙酰转移酶) - Protein kinase(蛋白激酶) Acetylation and phosphorylation:Transcription activating event 11-10
11-10 Roles of TAFII250 and TAFII150 ✓ The TAFII250 and TAFII150 help the TFIID bind to the initiator and DPE of promoters ✓ Also aid in TFIID interaction with specificity protein 1(特异蛋白1, Sp1) that is bound to GC boxes upstream of the transcription start site ✓ They enable TBP to bind to: – TATA-less promoters that contain elements such as a GC box ✓ TAFII250 has 2 enzymatic activities: – Histone acetyltransferase (乙酰转移酶) – Protein kinase (蛋白激酶） Acetylation and phosphorylation: Transcription activating event