mol16 - BIMM100 - Finishing Chapter 7, beginning Chapter 8...

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BIMM100 - Finishing Chapter 7, beginning Chapter 8 Practice fnal and Review Guide will be posted on WebCT with schedule o± events Regulating initiation, transcription ±actors STOP Techniques Chromatin immunoprecipitation (ChIP) (Yeast) two-hybrid analysis: identi±ying protein interactions Transcriptional regulation at initiation positive and negative regulation regulatory sequences and ±actors mechanisms: assembly and chromatin modifcation beyond initiation: termination Pol I and Pol III initiation Application: (the two-hybrid system) transcription ±actor modularity promotes interaction discovery big complexes Regulation o± transcription ±actor activity example: nuclear receptors & hormonal control
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Mechanisms of regulation the in vivo template for transcription is chromatin chromatin -- DNA + histones (+ others) histones -- lysine-rich N-terminal ʻ tails ʼ subject to modiFcation: acetylation, phosphorylation, ubiquitination, methylation chromatin modiFcation affects transcription examples -- deacetylation (negative) -- acetylation (positive) Lecture 12, revisited -- methylation (negative) heterochromatin is correlated with silenced transcription stains darkly, is more condensed; physically inaccessible example: cell type control and telomere-proximal genes in yeast C MATa or ! ! a gene T T gene silencer sequences; trans-regulators (4 Sir proteins) modiFed 7-33* evidence for chromatin involvement: any gene (even Pol III tx ʼ d tRNA gene) is silenced E. coli methyltransferase: blocked from silenced regions mutation of histone tails could de-repress, restore methyltransferase accessibility We are not focusing on the ʻ switching ʼ of mating type info
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MCB 7-35 Model of silencing mechanism at yeast telomeres RAP1 (R epressor-A ctivator P rotein) and the SIR (Silent-Information Regulator) Proteins is itself a histone deacetylase!! SIR2 Key: histone tail hypoacetylation conFrmed by mutation and (in mutants, INCREASED acetylation) activator-directed hyperacetylation Used to map modiFcation status of different regions of the genome Requires antisera directed against speciFcally modiFed forms of histones MCB 7-37 (also maps occupancy) (or other protein of interest)
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ChIP reveals modifcation state oF particular genomic regions ChIP reveals modifcation state oF particular genomic regions Example: ! -H4 Ac WT(+) and sir2 cells M Input No Ab 1 2 + + + + Regions to be amplifed
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Model for mechanism of acetylation effects on chromatin transcription and repression activator-directed hyperacetylation MCB 7-38 repressor-directed deacetylation MCB 7-38 Model for mechanism of acetylation effects on chromatin transcription and repression activator-directed hyperacetylation repressor-directed deacetylation Net dynamic regulation: see 7-36 for Polycomb repression (Me)
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Mechanisms of regulation -
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This note was uploaded on 06/03/2010 for the course BIMM Pillus taught by Professor Molecularbiology during the Spring '10 term at UCSD.

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mol16 - BIMM100 - Finishing Chapter 7, beginning Chapter 8...

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