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
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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.
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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
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
7.7 Metabolism of lactose
7.9 Negative control of the lac operon
7.10 Positive control of the lac operon by glucose
Transcriptional Regulation
• More complex in eukaryotes • Controlled at initiation or elongation• Proteins bind regulatory sequences and
• mRNA localization used in eggs, embryos, nerve cells and moving fibroblasts, to allow protein production in specific locations at appropriate time
8.15 Polysomes
8.16 Translational regulation of ferritin
8.17 Translational repressor binding to 3’ untranslated sequences
8.18 Localization of mRNA in Xenopus oocytes
8.19 Regulation of translation by miRNAs
8.20 Regulation of translation by phosphorylation of eIF2 and eIF2B (Part 1)
8.20 Regulation of translation by phosphorylation of eIF2 and eIF2B (Part 2)
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)
8.21 Action of chaperones during translation
8.22 Action of chaperones during protein transport
8.23 Sequential actions of chaperones
8.27 Proteolytic processing of insulin
8.28 Linkage of carbohydrate side chains to glycoproteins
8.34 Palmitoylation
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
8.36 Feedback inhibition
8.38 Protein kinases and phosphatases
8.39 Regulation of glycogen breakdown by protein phosphorylation
8.42 The ubiquitin-proteasome pathway
8.43 Cyclin degradation during the cell cycle
8.44 Autophagy
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