1. Chapter 11 Molecular Mechanisms of Gene regulation Jones and Bartlett Publishers © 2005

2. Categories of Protein-Coding Genes in Arabidopsis

3. Regulation of Gene Expression Transcriptional RNA processing Translational mRNA stability Posttranslational control DNA rearrangements

4. Prokaryotic transcriptional regulation How ‘off’ is off? Coordinate regulation

5. Negative / Inducible / Repressible

6. Positive regulation of gene expression

7. Negative Control Inducible System

8. Negative Control Repressible System

9. Positive Control Inducible System

10. Positive Control Repressible System

11. Structure of an Operon

12. Inducible Operon

13. Repressible Operon

14. The lac operon In E. coli, glucose is the preferred carbon source when both glucose and lactose are present. Jacob and Monod, 1950s, studied lactose metabolism and mutants, and won a Nobel Prize in 1965.

15. Kinetics of induction of lactose operon mRNA and proteins

16. Characteristics of partial diploids containing several combinations of lacI, lacO and lacP alleles

17. MutationEffect lacI - Repressor protein cannot bind, constitutive expression results. lacI s Repressor binds tightly to operator, not inducible. lacO c Repressor cannot bind to the operator site; constitutive expression. (cis-dominant) Mutations of lac operon

18. MutationEffect lacP - RNA polymerase cannot bind, no transcription results. lacZ - No  -galactosidase synthesis. lacY - No permease synthesis. Mutations of lac operon, cont.

19. MutationEffect Polar Nonsense- termination of mutations transcription crp - Catabolite activator protein cannot bind to crp site, no RNA binding, no transcription

20. The 3 structural genes in the lac operon and the mechanism of their regulation by the lac repressor

21. lac operon model 2 kinds of genes: structural, regulatory elements. Polycistronic structural genes, with promoter and operator constitute the lac operon. Promoter mutants make no lac mRNA. lacI gene makes a repressor, which binds to the operator. When operator is ‘repressed’ no transcription occurs. Inducers bind to repressor, lac mRNA is made.

22. Positive regulation of lactose operon In presence of glucose, lac operon is ‘off’. How?

23. Structure of cyclic adenosine monophosphate (cAMP)

24. Lac operon is negatively regulated by the lac repressor and positively regulated by the cAMP-CRP complex

25. The 4 critical sequences in the lac operon bound by CRP, RNA polymerase, repressor and the ribosome

26. Structure of the tryptophan (trp) operon showing regulatory elements and the structural genes

27. Binding of tryptophan (the co-repressor) activates an inactive repressor into an active form capable of binding to the trp operator site

28. Structure of the 3’-end of a mRNA terminated at a rho-independent termination site

29. Structure of the leader polypeptide in the trp operon The two tandem tryptophans in the leader peptide act as “stalling sequences” in the absence of tryptophan in the cell

30. Alternative conformations that the trp leader RNA can assume which are important in attenuation

31. Other operons with repeated amino acid sequences that act as “stalling sequence” during attenuation