Model for the Interaction Between TBP and Promoters (a)TATA-containing promoter (b)TATA-less promoter with Inr and DPE (c)TATA-less promoter with GC boxes TATA DP 250 250 250 60 80 40 60 80 80 110 110 110 30B 30B 150 TBP 150 150 TATA DPE 250 250 250 110 150 150 150 TATA Inr DPE
11-11 Model for the Interaction Between TBP and Promoters
The modol of transcription enhancement by activators The activator::Nuclear transcription factor-1(核转录因子-1，NTF-1) Cal4:a expression vector (a)TAFll250 does not interact with Sp1 or NTF-1,so no activation take place (b)NTF-1 can interact with either TAFll150 or TAFll 60 and activate transcription;Sp1 can not interact with either of these TAFs or with TAFll250 and does not activate transcription. (c)NTF-1 interact with TAFIl150 and Sp1 interact with TAFll110,so both factor 110 activate transcription. (d)Holo-TFIID contains the complete assortment of TAFlls,so it can respond to a wide variety of activator at top
11-12 The modol of transcription enhancement by activators The activator: Nuclear transcription factor-1 (核转录因子-1, NTF-1) (a) TAFII250 does not interact with Sp1 or NTF-1, so no activation take place Cal4: a expression vector (b) NTF-1 can interact with either TAFII150 or TAFII 60 and activate transcription; Sp1 can not interact with either of these TAFs or with TAFII250 and does not activate transcription. (c) NTF-1 interact with TAFII150 and Sp1 interact with TAFII110, so both factor activate transcription. (d) Holo-TFIID contains the complete assortment of TAFIIs, so it can respond to a wide variety of activator at top
Exceptions to the Universality of TAFs and TBP (TAFs和TBP统一性的例外) TAFs are not universally required for transcription of class‖genes Even TBP is not universally required Some promoters in higher eukaryotes respond to an alternative protein such as TRF1 (TBP-related factor 1) The general transcription factor NC2(Negative factor 2): Stimulates transcription from DPE-containing promoters Represses transcription from TATA-containing promoters 11-13
11-13 Exceptions to the Universality of TAFs and TBP (TAFs 和 TBP统一性的例外) ✓ TAFs are not universally required for transcription of class II genes ✓ Even TBP is not universally required ✓ Some promoters in higher eukaryotes respond to an alternative protein such as TRF1 (TBP-related factor 1) ✓ The general transcription factor NC2 (Negative factor 2): – Stimulates transcription from DPE-containing promoters – Represses transcription from TATA-containing promoters