1. Regulation of Gene Expression All genes not expressed at all times All genes not expressed in all cells Regulation of gene expression is necessary to ensure production of necessary products in correct cells at most appropriate times Gene expression is regulated at various stages in prokaryotes and eukaryotes, with various methods being used

2. Transcriptional Regulation Mostly occurs at level of initiation in bacteria Negative regulation: some protein products only transcribed and translated in presence of inducers Conserves unnecessary use of cellular energy to produce RNAs and proteins Multiple genes expressed as operon – Operator near transcription initiation site controls transcription – Repressor binds to operator to block transcription – Inducer must be present to block repressor for transcription to occur – Operator is cis-acting, repressor is trans-acting

3. 7.7 Metabolism of lactose

4. 7.9 Negative control of the lac operon

5. 7.10 Positive control of the lac operon by glucose

6. Transcriptional Regulation More complex in eukaryotes Controlled at initiation or elongation Proteins bind regulatory sequences and modulate RNA polymerase activity: repressors, enhancers, promoters Modifications of chromatin structure plays a role Cis-acting sequences regulate eukaryote expression

7. 7.20 The SV40 enhancer

8. 7.21 Action of enhancers (Part 1)

9. 7.21 Action of enhancers (Part 2)

10. 7.22 DNA looping

11. 7.23 The immunoglobulin enhancer

12. 7.32 Action of eukaryotic repressors

13. 7.37 Regulation of transcription by miRNAs

14. 7.39 DNA methylation

15. 7.41 Maintenance of methylation patterns

16. Translational Regulation mRNA translation regulated in prokaryotes and eukaryotes in response to cell stress, nutrient availability, growth factor stimulation Accomplished by repressor proteins, noncoding microRNAs, controlled polyadenylation, initiation factor modulation mRNA localization used in eggs, embryos, nerve cells and moving fibroblasts, to allow protein production in specific locations at appropriate time

17. 8.15 Polysomes

18. 8.16 Translational regulation of ferritin

19. 8.17 Translational repressor binding to 3’ untranslated sequences

20. 8.18 Localization of mRNA in Xenopus oocytes

21. 8.19 Regulation of translation by miRNAs

22. 8.20 Regulation of translation by phosphorylation of eIF2 and eIF2B (Part 1)

23. 8.20 Regulation of translation by phosphorylation of eIF2 and eIF2B (Part 2)

24. Protein Folding and Processing Polypeptide products must be folded into 3-D conformation to function Some protein products consist of multiple polypeptide complexes Some proteins additionally modified by cleavage or attachment of other functional groups (carbohydrates and lipids)

25. 8.21 Action of chaperones during translation

26. 8.22 Action of chaperones during protein transport

27. 8.23 Sequential actions of chaperones

28. 8.27 Proteolytic processing of insulin

29. 8.28 Linkage of carbohydrate side chains to glycoproteins

30. 8.34 Palmitoylation

31. Protein Regulation Regulation of enzyme activity necessary for proper catalysis of biological reactions Accomplished through gene expression by regulating protein production, or regulation of protein function and activity in the cell Allosteric binding, phosphorylation, protein degradation used to regulate enzymatic function

32. 8.36 Feedback inhibition

33. 8.38 Protein kinases and phosphatases

34. 8.39 Regulation of glycogen breakdown by protein phosphorylation

35. 8.42 The ubiquitin-proteasome pathway

36. 8.43 Cyclin degradation during the cell cycle

37. 8.44 Autophagy

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