1. Chapter 16 Control of Gene Expression

2. Topics to discuss DNA binding proteins Prokaryotic gene regulation 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 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 The Tryptophan operon

13. Francois Jacob and Jacques Monod 1961 Studied lactose metabolism in prokayotes

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

15. Building the lac operon

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

17. Lactose Metabolism Requires Coordination of all these genes!

18. Negative inducible operon

21. Conditions: No glucose but lactose is present

22. Lactose Metabolism Requires Coordination of all these genes!

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

24. Overview of: Mutational Analysis of the lac operon 3-24p. Lab manua

25. Monod and Jacob Discovery of lac operon control

26. Try out your ability to reason through the questions. I geneP geneZ,A,Y genes I+I+ P+P+ Z +,A +, Y + I-I- P-P- Z - or A -, or Y - IsIs O O+ Oc

27. LactoseNo lactoseLactose I+P+O+Z+Y+I+P+O+Z+Y+ - + I-P+O+Z+Y+I-P+O+Z+Y+ ---- I+P-O+Z+Y+I+P-O+Z+Y+ ---- I+P+OcZ+Y+I+P+OcZ+Y+ ++++ I + P + O + Z - Y - / I - P + O + Z + Y + -+-+ I + P + O c Z + Y - / I + P + O + Z - Y + ++-+ I + P + O c Z - Y + / I - P + O + Z + Y - -+++ I S P + O + Z + Y - / I - P + O + Z - Y + ---- I + P - O c Z + Y + / I + P + O + Z - Y - ---- Β-galactosidasePermease No Lactose 1 2 3 4 5 6 7 8 9 - +

28. Now, back to glucose and the lac operon! Lac

29. Question: what happens when both lactose and glucose are present together in the same cell?

30. Conditions: glucose present and lactose

31. Need to understand this reaction Adenylyl cyclase Cyclic AMP ATP Glucose may inhibit this enzyme catabolite activator protein +

33. The promoter needs to be in an ideal conformation for RNA polymerase.

34. How CAP and cAMP affects the promoter

35. Trypthophan Operon

36. 5 genes involved in the synthesis of the amino acid trypthophan

37. Negative repressible operon

38. 2 shapes to the mRNA

40. attenuation

41. Eukaryotic Gene Regulation

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

44. Changes in Chromatin structure and eukaryotic gene regulation DNase hypersensitivity Histone acetylation DNA methylation

47. For Your Information Next 4 slides

48. Experimental tests on the repressor: I + cells synthesize full levels of the lac enzymes only in the presence of an inducer I - mutations NO DNA BINDING ACTIVITY, TRANSCRIPTION OCCURS EVEN IN ABSENCE OF INDUCER! I s mutation NO LACTOSE BINDING ACTIVITY but has DNA BINDING ACTIVITY. NO TRANSCRIPTION EVEN WITH INDUCER! Oc mutation: constitutive activity

49. Trans (across) acting product

50. Oc= constitutive operator, notice how it affects transcription.

51. Mutations to inducer binding domain of repressor

52. Extra slides

53. Table I.

54. Table 2.

55. Table 3.

57. Allosteric affect of DNA binding protein

58. The Lac promoter and its role in lac transcription

59. Repressor has two binding sites. Lactose binding site DNA Operator binding site

60. ITPG: Binds repressor but is not cleaved.