1. Chapter 16 Control of Gene Expression

2. Topics to discuss DNA binding proteins Prokaryotic gene regulation –negative inducible: lac operon –negative repressible: trp operon Eukaryotic gene regulation

3. 6 groups of DNA-binding regulatory proteins have been identified

5. Prokaryotic Gene Regulation

6. Operons Operons provide coordinate expression

7. A model operon

8. Now let’s look at 2 (of four) groups of operons Negative inducible operons Negative repressible operons

9. INDUCIBLE Negative inducible operon

10. Turned on

11. repressor

12. Now let’s look at 2 specific operons The Lactose operon: negative inducible The Tryptophan operon: negative repressible

13. Francois Jacob and Jacques Monod 1961 Studied lactose metabolism/operon in prokayotes J. Monod Won the Nobel Prize in 1965

14. Sources of prokaryotic energy 1. Disaccharide 2. Monosaccharide Lactose Glucose

15. Sources of prokaryotic energy Monosaccharide Disaccharide Glucose Lactose

16. Building the lac operon

17. ZYAOP I Lac Operon and Proposed Arrangement with control I gene Not technically part of the “operon”

18. Lactose Metabolism Requires Coordination of all these genes!

19. Negative inducible operon

21. (assume only lactose is present)

22. Next: let’s review just the pattern of expression when: When only lactose is present. When only glucose is present. Glucose and lactose are present in the cell

23. “Why does the presence of glucose influence lactose metabolism? Lac

24. To answer this question you need to understand this reaction Adenylyl cyclase Cyclic AMP ATP Glucose may inhibit this enzyme catabolite activator protein +

25. Now put the pieces all together.

26. How CAP and cAMP affects the promoter

27. So….Conditions: Only lactose is present

28. But…Conditions: Only glucose

29. And Finally….Glucose and Lactose

30. Summary

31. Trypthophan Operon 5 genes involved in the synthesis of the amino acid trypthophan

32. Negative repressible operon

33. 2 shapes to the mRNA When trp is high When trp is low

34. Ribosome does not stall

35. Ribosome stalls

36. Changes in Chromatin structure and eukaryotic gene regulation Histone acetylation DNA methylation RNA silencing

38. Do eukaryotes show coordinate gene regulation? Yes, the same response element may be found in related genes.

39. Also remember gene expression through RNA interference!