1. Regulation of Gene Expression

2. Prokaryotes –Constituitive Gene Expression (promoters) –Regulating Metabolism (promoters and operators) –Regulating Development (sigma switches) Eukaryotes –Regulating genes in multicellular organisms

3. Constituitive Gene Expression (promoters) promoter coding sequence

4. Regulating Metabolism (promoters and operators) promoter coding sequence operator

5. Metabolic signals and repressor activity the regulatory protein is an allosteric protein metabolic signal molecule DNA binding site repressor protein gene off gene ongene off gene on repressor activated repressor deactivated repressor deactivated repressor activated

6. repressor activated genes OFF repressor deactivated genes ON repressor activated genes OFF repressor deactivated genes ON precursor moleculesmacromolecule energy substrate product Synthetic Pathway Degradative Pathway Repressors & metabolic pathways repression induction

7. Many regulatory proteins are dimers and bind to palindromes negative controlpositive control

8. The Tryptophan Operon: Negative control of a synthetic pathway

9. the lac operon

10. Negative Control When activated by binding of the metabolic signal molecule, the lac repressor binds to the operator, blocking RNA polymerase

11. Positive Control cAMP is present when glucose is unavailable cAMP binds to CAP protein, which then binds to the promoter binding of the CAP-cAMP complex to the promoter, activates it

13. The Lactose Operon: Control of a degredative pathway

14. Practice

15. Answers

16. Control of development: Sigma switching

17. RNA polymerase in bacteria core enzyme sigma Sigma factors recognize promoters and disassociate when the RNA polymerase binds to the promoter, leaving the core enzyme to make the transcript RNA polymerase

18. Each sigma can find a certain promoter RNA polymerases 1234567

19. Phage SPOI (in B. subtilis) 3 phases of gene expression –Early phase –Mid phase –Late phase Each phase uses a different sigma, each recognizing a different promoter The genes of each phase all have the same kind of promoter, recognized by one of the sigma factors

20. Early phase. Early genes have promoters recognized by the host’s RNA polymerase. gp28 is an early protein that acts as a sigma factor for the middle phase genes. gp28 has a higher affinity for the CORE’s binding site than it’s own sigma, thus displacing the host’s sigma and turning off the early genes and turning on the mid genes. Middle phase. Middle phase genes have promoters recognized by gp28. Gp33 and gp34 are middle proteins that act as a sigma factor for the late genes. Late phase early transcripts early proteins, including gp28 host sigma late transcripts late proteins gp33-34 sigma middle transcripts middle proteins, including gp33, gp34 gp28 sigma Sigma Switching

21. Eukaryotes

22. Prokaryote versus Eukaryote Comparison Step 1 promoter Step 2 Prokaryotes Step 1 promoter Step 2 Eukaryotes promoter sigma Transcription Factor (eukaryotic sigma)

23. Positive control in eukaryotes - gene enhancers

24. Gene activation in Eukaryotes: A different complicated initiation complex for each different context in which a gene is expressed