Chapter 13

Chapter 13 - Chapter 13 Regulation of Gene Transcription...

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Chapter 13 Regulation of Gene Transcription DNA ® RNA •Response to environmental signals may alter transcription rates of genes (signal transduction). •In prokaryotes, coordinately regulated genes are clustered and transcribed as multigenic mRNAs. •The lac system is a model of negative regulation. •Positive regulation requires protein factors to activate transcription. •Regulatory proteins share common features. •In eukaryotes, regulatory sites may be at considerable distance from regulated gene. •Some regulation is epigenetic, modulated by parentage or cell division history. Regulatory proteins •Themselves product of transcription and translation •Several regulatory domains –sequence-specific DNA-binding surface to recognize DNA docking (target) site –surface to recognize basal transcription apparatus –surface to interact with proteins binding to nearby docking sites (may or may not be present) –surface to act as sensor of environmental conditions (may or may not be present) •Many variations and interactions Prokaryotic transcriptional regulation •Promoter –determines where transcription begins, including identification of template strand –binds RNA polymerase •Operator –adjacent to or overlapping promoter –binds activator or repressor proteins •In positive regulation , binding of activator to docking site is required for transcription •In negative regulation , operator must be free of bound protein for transcription to occur Activator and repressor proteins •Usually have at least two sites –DNA-binding domain –allosteric site •binds effector molecule •toggles DNA-binding domain between functional and nonfunctional
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Chapter 13 - Chapter 13 Regulation of Gene Transcription...

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