Regulation of Transcription In Prokaryotes

Prokaryotic Transcription Regulation

• Involves regulatory transcription factors
• Bind to DNA in the vicinity of a promoter and affect transcription of one or more nearby genes
• Repressors: inhibit transcription   * Negative control
• Activators: increase the rate of transcription   * Positive control
• Transcriptional regulation also involves small effector molecules   * Small effector molecules: binds to regulatory transcription factor and causes conformational change   * Determines whether or not regulatory transcription factor can bind to DNA
• Two domains in regulatory transcription factor that respond to small effector molecules   * Site where protein binds to DNA   * Site specifically for small effector molecule

The Bacterial Operon

• Operon in bacteria: a cluster of genes under transcriptional control of one promoter   * Operator: regulatory region of the operon

• Transcribed into mRNA as polycistronic mRNA   * Polycistronic mRNA: encodes more than one protein

• Allows coordinated regulation of a group of genes with a common function

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