13BIS101S2013GeneRegulLect13-1

The modulation of transcription from the lac lac

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Unformatted text preview: r producing the cyclic bond in ATP). The reverse happens when glucose is high. reverse BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 30 CAP Binding Site in Lac Promoter -75 -65 -55 -45 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez -35 31 Relationship between glucose and cyclicAMP The net result of catabolite repression is the linkage of a The positive regulatory mechanism (CAP stimulating transcription) with a negative regulatory mechanism (repressor inhibition of transcription). The modulation of transcription from the lac lac promoter in response to varying concentrations of glucose is shown below (assume lactose is present in the cell). shown [glucose] [catabolite?] [cAMP/CAP/RNAP] [cAMP] [cAMP/CAP] [ß-gal mRNA] BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 32 Relationship between glucose and cyclicAMP The net result of catabolite repression is the linkage of a The positive regulatory mechanism (CAP stimulating transcription) with a negative regulatory mechanism (repressor inhibition of transcription). The modulation of transcription from the lac lac promoter in response to varying concentrations of glucose is shown below (assume lactose is present in the cell). shown [glucose] [catabolite?] [cAMP/CAP/RNAP] [cAMP] [cAMP/CAP] [ß-gal mRNA] BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 33 Transcription review Eukaryotic Gene Regulation: Eukaryotic Galactose (Gal) Metabolism in Yeast Galactose BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 34 Example of Gal mRNA Induction by Galactose BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 35 Introduction The GAL gene system in yeast is an excellent example of eukaryotic The GAL gene regulation. In addition to common cis-acting elements like the cis-acting transcription initiation or cap site, the TATA box and CAAT box, the GAL GAL genes also employ transcriptional enhancers called "upstream activator genes sequences" or UASs. sequences or UASs. Regulation of the GAL genes involves induction by galactose and Regulation GAL repression by glucose with the help of both positive and negative-acting protein transcription factors. Six genes (GAL1, 2, 5, 7, 10 and MEL1) are required for yeast to convert MEL1 are the disaccharide melibiose to Glu-6-P which is then used in glycolysis. melibiose The product of the MEL1 gene (α -galactosidase) iis secreted outside the s MEL1 cell where it converts melibiose to galactos...
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