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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