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2Alecture+22+big+color - Lecture 22 Eukaryo/c gene...

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5/23/11 Lecture 22: Eukaryo/c gene regula/on General/Core transcrip/on factors Transcrip/onal ac/va/on factors (and repressors) consist of 2 to 3 dis/nct domains DNA binding and ac/va/on, and (some/mes) signal-­૒sensing Chap: 16.3, 16.4 A promoter is…. a.A DNA sequence b.An RNA sequence c. A protein d.A micro RNA
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5/23/11 A promoter includes a.A site that binds mRNA b.A site that binds RNA polymerase c. A site that binds regulatory factors d.A site that binds ribosomes Possible modes of Transcrip/onal control Nega/ve control: Turning off transcrip/on by blocking access to the promoter Promoter Regulatory Region (operator) transcript In bacteria, its easy for RNA polymerase to locate promoters
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5/23/11 Nega/ve control: Example from lac operon Promoter Regulatory Region (operator) Genes for lactose import and digestion lacI Regulatory protein (Active Lac Repressor) Nega/ve control: Blocking access to the gene Promoter Regulatory Region (operator) lacI Regulatory protein (Active Repressor) RNA pol NO TRANSCRIPTION of lacZ,Y, A ???
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5/23/11 Nega/ve control: Blocking access to the gene Promoter Regulatory Region (operator) lacI Regulatory protein (Active Repressor) RNA pol Coded for by a gene elsewhere in the DNA!!! How can you turn the gene on? Promoter Regulatory Region (operator) lacI Regulatory protein (Active Repressor) RNA pol ???
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5/23/11 How might you turn the gene on? A. Mutate the operator B. Mutate the repressor C. Degrade (= destroy) the repressor D. Inac/vate the repressor E. Switch off the gene for the repressor Promoter Regulatory Region (operator) repressor How could the gene be turned on? Promoter Regulatory protein (Repressor) Small inducer molecule (lactose) Which induces what, exactly? A.Expression of the lacI gene B.Activity of the lacI protein C.Expression of the lac Z, Y, and A genes
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5/23/11 How could the gene be turned on? Promoter Regulatory protein (Repressor) Small inducer molecule (lactose) How does it induce anything? A.By inhibiting a repressor B.By activating a repressor C.By activating an activator D.By inhibiting an activator How could the gene be turned on? Promoter Regulatory protein (Inactive Repressor) RNA pol Change in shape of Repressor (allosteric inhibition)
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5/23/11 How could the gene be turned on? Promoter RNA pol Change in shape of Repressor (allosteric inhibition) Gene is transcribed In eukaryotes, areas of ac/ve chroma/n have to be maintained-­૒ groomed-­૒ by proteins like HATs (histone acetyl transferases).
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5/23/11 Heterochromatin - methylated DNA, particular methylated lysines Euchromatin - Acetylated and phosphorylated nucleosomes, different methylated lysines Eukaryotic DNA is wound around nucleosomes- this results in greater or lesser degrees of accessibility, depending on the doo-dads that are decorating the nucleosomes.
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