1. Copyright (c) by W. H. Freeman and Company Chapter 10 Regulation of Transcription Initiation

2. Copyright (c) by W. H. Freeman and Company 10.1 Bacterial gene control: the Jacob- Monod model Figure 10-2

3. Copyright (c) by W. H. Freeman and Company 10.1 Experimental evidence for cis-acting DNA sequences Figure 10-3

4. Copyright (c) by W. H. Freeman and Company 10.1 Experimental evidence for trans- acting genes/proteins Figure 10-4

5. Copyright (c) by W. H. Freeman and Company 10.2 Bacterial transcription initiation  RNA polymerase initiates transcription of most genes at a unique DNA position lying upstream of the coding sequence  The base pair where transcription initiates is termed the transcription-initiation site or start site  By convention, the transcription-initiation site in the DNA sequence is designated +1, and base pairs extending in the direction of transcription (downstream) are assigned positive numbers which those extending in the opposite direction (upstream) are assigned negative numbers  Various proteins (RNA polymerase, activators, repressors) interact with DNA at or near the promoter to regulate transcription initiation

6. Copyright (c) by W. H. Freeman and Company 10.2 DNase I footprinting assays identify protein-DNA interactions Figure 10-6

7. Copyright (c) by W. H. Freeman and Company 10.2 Gel-shift assays identify protein-DNA interactions Figure 10-7

8. Copyright (c) by W. H. Freeman and Company 10.2 The footprint of RNA polymerase and lac repressor on the lac control region Figure 10-8

9. Copyright (c) by W. H. Freeman and Company 10.2 The lac control region contains three critical cis-acting sites Figure 10-9

10. Copyright (c) by W. H. Freeman and Company 10.2 RNA polymerase binds to specific promoter sequences to initiate transcription Figure 10-10 Each subunit has a specific function

11. Copyright (c) by W. H. Freeman and Company 10.2 Differences in E. coli promoter sequences affect the frequency of transcription initiation Figure 10-11

12. Copyright (c) by W. H. Freeman and Company 10.2 Most operator sequences are short inverted repeats Figure 10-12 The lac operator

13. Copyright (c) by W. H. Freeman and Company 10.2 Most bacterial repressors are dimers containing  helices that insert into adjacent major grooves of operator DNA Figure 10-13

14. Copyright (c) by W. H. Freeman and Company 10.2 Ligand-induced conformational changes alter affinity of many repressors for DNA Figure 10-14 Tryptophan binding induces a conformational change in the trp aporepressor

15. Copyright (c) by W. H. Freeman and Company 10.2 Positive control of the lac operon is exerted by cAMP-CAP Figure 10-16 CAP = catabolite activator protein

16. Copyright (c) by W. H. Freeman and Company 10.2 Cooperative binding of cAMP-CAP and RNA polymerase to the lac contol region activates transcription Figure 10-17

17. Copyright (c) by W. H. Freeman and Company 10.2 Transcription from some promoters is initiated by alternative sigma (  ) factors

18. Copyright (c) by W. H. Freeman and Company 10.2 Activation of  54 -containing RNA polymerase at glnA promotor by NtrC Figure 10-19

19. Copyright (c) by W. H. Freeman and Company 10.2 Visualization of DNA looping and interaction of bound NtrC and  54 - polymerase Figure 10-20

20. Copyright (c) by W. H. Freeman and Company 10.2 Many bacterial responses are controlled by two-component regulatory systems Figure 10-21 The PhoR/PhoB two-component regulatory system in E. coli