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12-8-LectureCh31andVirusesPowerpoint2009 11.45.23 PM

12-8-LectureCh31andVirusesPowerpoint2009 11.45.23 PM -...

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CHAPTER 31 Control of Gene Expression Dec.8,2009
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CHAPTER 31: CONTROL OF GENE EXPRESSION SELECTED LECTURE TOPICS: The Big Picture Differential gene expression : prokaryotes and eukaryotes Regulation of gene expression : Transcription regulated by DNA-binding proteins E. coli lactose (lac) operon Helix-turn-helix motif: prokaryotic DNA-binding proteins Eukaryotic gene regulation : Transcriptional activation/repression is mediated by protein–DNA and/or protein-protein interactions
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Evidence of Eukaryotic Differential Gene Expression: Relative amounts of mRNAs (% total RNA) 1,000 or more 0.001 (or less)
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CONTROL OF GENE EXPRESSION Theme: Control involves sequence-specific DNA binding proteins and/or protein-protein interactions Wide Groove DNA binding protein (dimer) Phage repressor protein bound to target sequence : “operator”
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Helix-turn-helix motif of DNA binding regulatory proteins Exception: β -strand interaction is basis of Met operon repressor DNA binding. DNA 34 Angstroms = 1 full turn of DNA helix
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(-) inducer [~ 7% of cell’s total protein] (+) inducer Control of Prokaryotic (Differential) Gene Expression: Example: Transcriptional regulation of the lactose operon β -galactosidase is an inducible enzyme
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lac repressor a (-) regulator Inducer: (+) regulator Lactose operon regulation: an inducible operon
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