1. Mechanism of Transcription
Chapter 12
Mechanism of Transcription
4 and 6 October, 2006

2. Overview
Transcription is superficially similar to replication, with important differences.
E. coli RNA polymerase core has an a2bb’w subunit structure.
In Eukaryotes, RNA Pol II transcribes most genes.
Transcription consists of initiation, elongation, and termination.
Initiation occurs at promoters, which are recognized by the s subunit and the a-CTD in bacteria.
Promoter strength depends on a close match to the consensus sequence.
Promoter binding is followed by a transition to the open complex.
RNA polymerase transition to elongation phase involves abortive initiation.
Termination is mediated by signals in the RNA.
In Eukaryotes, promoters contain binding sites for TFIID, TF2B, and TBP.
Initiation involves a multiprotein assembly at the promoter.
Elongation is stimulated by elongation factors, and involves the recruitment of capping, splicing, and polyadenylation proteins.
PolI and PolIII promoters are distinct, but require TBP.

3. Transcription and RNA Polymerases

4. RNA Polymerase Structure

5. Events in Transcription

6. s70 Recognizes Bacterial Promoters

7. Core polymerase binding is enhanced by sigma and increased temperature.

8. Promoter Consensus

9. Polymerase Binding

10. a-CTD contacts the UP element.

11. a-CTD contacts the UP element.

12. RNA Pol Active Site and Channels

13. RNA Polymerase melts -9 to +3

14. The b subunit contains the active site.

15. Termination

16. Termination

17. Rho

18. Three Eukaryotic RNA Polymerases

19. Eukaryotic Promoter

20. SV40 Early transcription starts at the same position relative to the TATA box.

21. Subunit Structure of Pol II

22. PolII Initiation

23. General Factor Order of Addition

24. TBP Minor Groove Interactions

25. TBP Binding

26. TBP Recruits TFIIB

27. TFIID is complex

28. Roles of TFIID Components

29. Activation by SP1 requires TAFII-110

30. TFIID interacts with activators.

31. Binding of TFIIE

32. Phosphorylation of the Preinitiation Complex

33. TFIIH Phosphorylates RNA Pol II

34. TFIIH Helicase Activity

35. Promoter Clearance

36. Transcriptional Initiation with Mediator Complex

37. Mediator

38. Elongation

39. Cap Structure

40. Polyadenylation and Termination

41. Pol I Promoter

42. Pol III Promoter

44. Title

45. Title