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2 biology tfiif tfiif the 2 tfiif subunits are next

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Unformatted text preview: e preinitiation complex and the unidirectional transcription TFIIB-TBP-promoter TFIIB-TBP-DNA TERNARY COMPLEX TFIIB-TBP-DNA • TFIIB binds TFIIB adjacent to TBP adjacent • TFIIB extends TFIIB contacts along one DNA face that provides surface for RNAP II recognition after TFIIF binding & RNAP recruitment RNAP Weaver 2002 Weaver Molecular Biology Ed. 2 Biology TFIIF TFIIF • The 2 TFIIF subunits are next to join complex The after TFIIB: after -larger TFIIF subunit, RAP74: ATP-dependent -larger DNA helicase that could be involved in melting duplex DNA at initiation melting -smaller subunit, RAP38: homology to -smaller bacterial σ factor regions that contact core polymerase - RAP38 binds tightly to RNAP II polymerase • TFIIF brings RNAP into assembling complex, TFIIF where CTD tail of polymerase interacts with TFIID. As with prokaryotes we get local DNA melting and abortive transcripts and DABPolF COMPLEX DABPolF Weaver 2002 Molecular Biology Ed. 2 • DNase footprinting of promoter DNA DNase with TFIID, A, B, and F, and RNAP II bound increases DNA protection by transcription complex to extend further downstream (to +17) further • Corresponds to RNAP II large size • TFIIF recruits RNAP II Weaver 2002 Molecular Biology Ed. 2 GENERAL TRANSCRIPTION FACTORS (GTFs): GENERAL PROMOTER CLEARANCE & ELONGATION Weaver 2002 Molecular Biology Ed. 2 • Promoter clearance: TFIIE & H required; TFIIE binding extends Promoter protected region to +30 ---> recruits TFIIH protected • TFIIH activities: ATPase, kinase, & also helicase that unwinds TFIIH even more Inr DNA allowing RNAP movement and promoter clearance clearance TFIIH promoter melting TFIIH • • • How does TFIIH mediate promoter How melting? It is now believed that a subunit of TFIIH It acts as an ATP-driven translocator of the double-stranded DNA. This subunit binds to the DNA downstream from polymerase, and feeds double-stranded DNA, with a right-handed threading, into the cleft of the polymerase the This action drives the melting of the This DNA because the upstream promoter DNA is held in fixed positi...
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