Promoters are modular upstream caat box 70 to 80 binds

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Unformatted text preview: 7-8 bp, A-T rich promoters have directionality, regulate directionaiity Transcriptional Control: Promoters • Eukaryotic promoters are modular: upstream – CAAT box (-70 to -80): binds proteins required for transcription (transcription factors) – G box (-90): GGGCGG; binds transcription factors – CAAT and G boxes are similar to enhancers, but much more universal (found in nearly all regulatory regions) Transcriptional Control: Enhancers • Control level and location of expression (efficiency of promoter activation) how often • Can be anywhere relative to the gene (as long as it’s in cis) and in any orientation • Enhancers are also modular, but: – Modules vary widely between enhancers (tissue, timing, conditionspecific) not true of promoters – Can include binding sites for both activators and repressors – If moved to a location near a different gene, the “new” gene will be expressed in the same pattern as the “original” Transcriptional Control: Transcription Factors • Transcription factors (TFs) = proteins required for transcription – “general” vs. “specific” – General TFs are the “basal transcription complex”, required for all gene expression – Abbreviated “TFII” for “Transcription Factor for RNA Polymerase II” Transcriptional Control: Transcription Factors – Specific TFs = proteins required for control of expression of particular genes - Bind enhancer elements - Positive factors (activators) increase transcription - Negative factors (repressors) decrease transcription Transcriptional Control: Activators • Often have two protein domains: – DNA-binding (not always) – Transactivation: binds RNA polymerase and/or other transcription factors and increases efficiency of initiation – The image above is of p53, a transcription factor involved in cancer Example: Yeast Gal Genes • Control utilization of galactose • Induced by presence of galactose when [glucose] is low (catabolite repression) Example: Yeast Ga...
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This document was uploaded on 02/25/2014.

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