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21 - Transcription (Eukaryotes); Overview of RNAPs

21 - Transcription (Eukaryotes); Overview of RNAPs - Review...

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Review: control of initiation of transcription in E. coli Repressor ( trans-acting factor ) will block transcription initiation when bound to the operator ( cis-acting element ) negative control One way: sites for RNAP (promoter) and repressor (operator) could overlap - repressor binding blocks RNAP from interacting with DNA at the start site Presence of auxiliary operators additional repressor binding sites Affinity of repressor for operator depends on presence/absence of effector (repressor / inducer and corepressor / aporepressor) its binding changes repressor’s conformation change in activity There are proteins - activators that could increase binding of RNAP to start site - positive control Binding sites for activators are called enhancers (elements) Affinity of activator for enhancer also sometimes depends on presence/absence of effector
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