Chapter 11 eukaryotic gene expression

Chapter 11 eukaryotic gene expression - Chapter 11...

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5/29/11 Chapter 11 Eukaryotic Gene Expression Suggested problems: #2, 3, 4, 5, 9, 10, 11, 12, 13, 16, 21
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5/29/11 2 key differences between prokaryotic and eukaryotic gene expression: 1. DNA is wrapped up tightly in nucleosomes 5 regulatory regions of DNA are not readily accessible
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5/29/11 The structure of chromatin
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5/29/11 Nucleosomes have to nudged aside for RNA polymerase to access DNA Done by the SWI/SNF complex Nucleosomes are not in fixed positions on the DNA.
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5/29/11 Nucleosome remodeling can expose promoters for RNA polymerase to bind
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5/29/11 Accessibility of DNA is also strongly influenced by histone modifications (=the histone code) Acetylation of histone tails leads to gene activation Histone acetyl transferase s HDACs Histone deacetylas es
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5/29/11 Inactive genes Active genes HATs HDACs
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5/29/11 2 key differences between prokaryotic and eukaryotic gene expression: 1. DNA is wrapped up tightly in nucleosomes 5 regulatory regions of DNA are not readily accessible Activators cause RNA pol to bind activators remodel the chromatin acetylate histone tails:HAT recruit RNA pol Repressors physically block RNA pol repressors make the nucleosomes wrap the DNA more tightly (histone
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5/29/11 Histone depletion causes gene expression to activate Experiment: Deplete histone proteins in yeast cells. When histone levels decreased, the nucleosomes were less dense on the DNA, and the expression of many genes turned on (even in the absence of their normal inducers). 5nucleosome density is important for repression of gene expression
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5/29/11 2 key differences between prokaryotic and eukaryotic gene expression: 1. DNA is wrapped up tightly in nucleosomes 2. Eukaryotes use complex combinations of transcription factors to regulate individual genes. Transcription factors can act at a distance.
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5/29/11 Promoter-proximal elements precede the promoter of a eukaryotic gene
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5/29/11 Example #1: The Gal pathway in yeast
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5/29/11 Transcriptional activator Gal4 binds to UAS elements in yeast UAS (upstream activating sequence) is an enhancer (not right next to promoter) What would happen if: UAS was mutated? Cis acting Gal4 was mutated? Trans acting
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5/29/11 Basic features of transcriptional regulators 1. DNA binding domain 1. Activation domain- activates transcription 1. Dimerization domain- has 2 proteins that are together
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5/29/11 Domains are Modular
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5/29/11 Activity can be regulated by interaction with other proteins Gal80 binds to Gal4 and represses it Gal3 is the allosteric effector (binds galactose) When Gal3 binds galactose, it increases affinity for Gal80, inhibiting it from inhibiting Gal4
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5/29/11 What does an activation domain do? 1. Binds to TFIID 2. Binds to the mediator complex (assists RNA pol binding) 3. Recruits SWI/SNF to remodel nucleosomes.
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5/29/11 How are genes repressed? When glucose is present, the cell would rather use
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This note was uploaded on 05/28/2011 for the course BIO 220 taught by Professor Dr.leatherman during the Spring '10 term at N. Colorado.

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Chapter 11 eukaryotic gene expression - Chapter 11...

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