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Chapter 21 (part 1)

Chapter 21 (part 1). Transcription. Central Dogma. RNA Content of E. coli Cells. E. Coli RNA Polymerase. RNA polymerase core enzyme is a multimeric protein a 2 ,b, b ’ , w The b ’ subunit is involved in DNA binding The b subunit contains the polymerase active site

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Chapter 21 (part 1)

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  1. Chapter 21 (part 1) Transcription

  2. Central Dogma

  3. RNA Content of E. coli Cells

  4. E. Coli RNA Polymerase • RNA polymerase core enzyme is a multimeric protein a2,b, b’, w • The b’ subunit is involved in DNA binding • The b subunit contains the polymerase active site • The a subunit acts as scaffold on which the other subunits assemble. • Also requires s-factor for initiation –forms holo enzyme complex Site of DNA binding and RNA polymerization

  5. Promoter Transcribed region terminator 5’ 3’ General Gene Structure

  6. Gene Promoters

  7. Other s-Factors • Standard genes – s70 • Nitrogen regulated genes – s54 • Heat shock regulated genes – s32

  8. Transcriptional Initiation Closed complex Open complex Primer formation Disassociation of s-factor

  9. Pausing induces termination 3’end tends to be AU rich easily to disrupt during pausing. Leads to disassembly of RNA polymerase complex

  10. Rho Dependent Termination • rho is an ATP-dependent helicase • it moves along RNA transcript, finds the "bubble", unwinds it and releases RNA chain

  11. Eukaryotic RNA Polymerases

  12. Eukaryotic RNA Polymerases • RNA polymerase I, II, and III • All 3 are big, multimeric proteins (500-700 kD) • All have 2 large subunits with sequences similar to  and ' in E.coli RNA polymerase, so catalytic site may be conserved

  13. Eukaryotic Gene Promoters • Contain AT rich concensus sequence located –19 to –27 bp from transcription start (TATA box) • Site where RNA polymerase II binds

  14. Transcription Factors • TFAIIA, TFAIIB – components of RNA polymerase II holo-enzyme complex • TFIID – Initiation factor, contains TATA binding protein (TBP) subunit. TATA box recognition. • TFIIF – (RAP30/74) decrease affinity to non-promoter DNA

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