Regulation-notes

Regulation-notes - Regulation and signaling O verview Cells...

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© M. S. Shell 2009 1/8 last modified 11/30/2009 Regulation and signaling Overview Cells need to regulate the amounts of different proteins they express, depending on cell development (skin vs liver cell) cell stage environmental conditions (food, temperature, mechanical stimuli) Regulation affects gene expression Regulation is in response to various intracellular and extracellular signals , which are usually chemical entities (specific molecules) The principles of recognition enable a specific response b however, many recognition events are often put together to build more robust signaling cascades or networks Control of gene expression Cells can target many parts of the protein production pathway for control transcription RNA processing RNA transport translation mRNA degradation protein activity Transcriptional regulation Common regulatory mechanism targets transcription itself Transcription requires initiation with a promoter sequence b proteins that bind to these sequences, transcription regulators , can modify transcription rates repressor – prevents binding of RNA polymerase
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© M. S. Shell 2009 2/8 last modified 11/30/2009 activator – facilitates binding of RNA polymerase In eukaryotes, chromatin structure also affects expression b can be controlled by regulating concentrations of chromatin-remodeling protein Logic gates Multiple activators and a repressors can control the same gene. Consider two: repressor activator gene expression OFF OFF OFF ON OFF OFF ON ON OFF OFF ON ON Feedback control can be initiated using allosteric principles. Example:control of tryptophan concentration in E. coli Complex regulatory signals in eukaryotes Because transcription requires the assembly of many factors at the initiation site in eukaryotes, gene expression can result from the combination of many different signals Different genes require different initiation complexes gene promoter sequence DNA transcription, translation into tryptophan-producing enzymes tryptophan production binding to Trp repressor, conformational change Trp repressor expressed from another gene active Trp repressor binds to, inhibits promoter inactive Trp repressor
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© M. S. Shell 2009 3/8 last modified 11/30/2009 Lack of key proteins or other ligands in the assembled complex at the initiation site will result in low gene expression levels The same molecule may be key to controlling many different genes because it participates in multiple initiation complexes, for different genes b we call this the same signal . Gene expression controls the
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This note was uploaded on 12/29/2011 for the course CHE 170 taught by Professor Ceweb during the Fall '10 term at UCSB.

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Regulation-notes - Regulation and signaling O verview Cells...

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