Module 7: Transcription Regulation

• where is the most common point of regulation?

  at promoter/initiation
• transcription regulation changes activity of RNA polymerase
• what are the 2 domains of regulatory protein?

  DNA-binding and allosteric
• negative regulator: binding of active repressor causes decrease in transcription
• why does transcription decrease with negative regulators?

  RNA polymerase can't recognize promoter
• what inactivates a repressor in negative regulation?

  inducer
• what are the 2 types of negative regulation?

  induction and repression
• induction: repressor protein is synthesized in active state
• repression: repressor is synthesized in inactive state and activated by co-repressor
• positive regulation: binding of activator protein increases transcription
• how does positive regulation increase transcription?

  recruits RNA polymerase
• antisense RNA: complementary sequence that binds to mRNA and stops translation
• cis antisense RNA: transcript from complementary strand of DNA
• trans antisense RNA: transcript from seperate gene
• riboswitches: small molecule binds RNA and disrupts translation/transcription
• how do riboswitches disrupt translation and transcription?

  changes secondary structure and blocks shine-dalgarno sequence
• how is lac operon regulated?

  induction (negative regulation)
• lacl repressor protein blocks transcription (lac operon)
• allolactose inactivates lacl repressor (inducer/allosteric effector molecule)
• lac operon is a catabolic pathway, breaks lactose into galactose and glucose
• how is trp operon regulated?

  repression (negative regulation)
• trp operon is anabolic pathway, synthesizes tryptophan
• TrpR repressor: synthesized in inactive state
• co-repressor of trp operon: tryptophan
• how does tryptophan regulate trp operon?

  high tryptophan stops transcription
• attenuation in trp operon:

  • leader peptide contains tryptophan codon
  • removes RNA polymerase if high tryptophan concentration
• feedback inhibition in trp operon: post-translational regulation

  • tryptophan: negative effector
  • stops anthranilate synthase, further tryptophan synthesis