5Gene%20regulation - Modeling regulation of gene...

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1 Modeling regulation of gene expression (http://www.biochemistry.bham.a c.uk/sjwb/sjwb.html) Overview of gene expression regulation • Potential mechanisms of transcriptional regulation in bacteria - regulatory DNA sequences (e.g., Sequence I) - regulatory proteins or siRNA (activators or repressors) that bind to control sites in the sequences (e.g. Lac I, CAP) - effector molecules that change the binding affinity of regulatory proteins (e.g., cAMP, lactose) • Types of regulation - mRNA synthesis and degradation ( at transcription level) - protein synthesis and degradation ( at translation level )
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2 Glucose-mediated regualation of lactose metabolism in bacteria • Three genes are involved in glucose metabolism - Lac Y gene: coding lactose permease (a transporter for lactose in cell membrane) - Lac Z gene: coding β -galactosidase (facilitate breaking lactose into glucose and galactose) - Lac A gene: coding thiogalactoside transacetylase (unknown function) Z A Y Operon which is a cluster of genes transcribed as a single mRNA. It is common in bacteria. I P O Z A Y Spacer DNA Control site regulatory gene Lac operon Components involved in regulation of Lac operon expression - Sequence O: operator (it is the binding site of repressor protein.) - Sequence P: promoter (it controls binding of RNA polymerase) - Sequence I: repressor (a regulatory gene that encodes repressor protein, Lac I, which can bind to operon to stop mRNA synthesis) (1) Negative regulation: down regulate, reduce, decrease, etc. • The regulation starts with Lac I that binds to the operator to block RNA polymerase binding to the promoter.
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5Gene%20regulation - Modeling regulation of gene...

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