10 주차 수업자료

1. 10주차 수업자료

2. Chapter 16. Regulation of Transcription in Prokaryotes

3. Regulation of gene expression • Transcription • Access to coding DNA • Recognition of promoter by RNA polymerase (alternative sigma factor for different genes) • Initiation of RNA synthesis • Elongation rate • Premature termination or anti-terminator protein • Processing of primary transcript • mRNA stability • Translation • Processing of polypeptide chain • Control of enzyme activity • Protein degradation

4. Regulation of heat shock sigma factors • HSP: chaperonin for repair & protease for degradation • Heat shock sigma factor: RpoH level is regulated by chaperonin DnaK and HflB protease • Promoter of rpoH gene is recognized by RpoE (>50 °C) as well as RpoD (<50 °C)

5. Cascade of alternative sigma factors Pre-sigma E • Regulation of spore formation in gram-positive bacteria Bacillus. • Sigma E, K, F, G Pre-sigma K

6. Anti-sigma factors • Sigma F is inactive first by anti-sigma factor, SpoII AB • Sigma F becomes active when anti-sigma factor is released by anti-anti-sigma factor, SpoII AA

7. Positive and negative regulation • Positive regulation by inducer (activator) • Negative regulation by repressor

8. Operon model (lacO) allolactose IPTG cannot bind DNA • Polycistronic mRNA in prokaryotes • Specific regulation of lac operon • lacI LacI repressor (tetramer)  bind to operator site (lacO) • lacZ  β-galactosidase [lactose  allolactose (inducer)  galactose + glucose] • lacY  lactose permease (transport lactose) • lacA  lactose acetylase • Natural inducer (short-term induction) vs. gratuitous inducer (IPTG: not metabolized  long-term induction!!!)

9. Repressor or Activator? repressor activator metabolize arabinose • Depending on binding sites • AraC regulatory protein (depending on binding of arabinose)

10. Regulation of repressor activity No glucose Ready for glucose uptake • Co-repressor (e.g., ArgR repressor becomes active when co-repressor Arg is bound) • Binding of repressor to other protein (e.g., Mlc repressor & PtsG protein) Regulation of glucose uptake by Mlc repressor : Also, binding of Mlc to DNA repress genes involved in glucose uptake and metabolism

11. Covalent modification of regulatory protein • By oxidation and reduction • OxyR: active when oxidized by oxidizing agent  activate genes involved in protecting oxidative damage • Fnr: active when iron sulfur cluster is reduced under anaerobic condition  activate genes involved in anaerobic respiration

12. Two-component regulatory system • Regulation by phosphorylation • Membrane component: sensor kinase • Cytoplasmic component: DNA-binding regulator • Four domain phosphorelay • ArcAB: ArcB (sensor for anaerobic condition) & ArcA (regulator to repress genes for aerobic condition and activate genes for anaerobic condition)

13. Specific regulation vs. global regulation ON/OFF of lac operon by lacI/Crp • Specific regulation: lacI repressor • Global regulation: cAMP receptor protein (Crp) • Regulon: genes regulated by the same regulatory protein despite of different localization on chromosome

14. Looping of DNA for transcriptional activation • For nitrogen metabolism, RpoN sigma factor is required • Regulation by NtrBC two-component regulatory system • under low nitrogen, NtrB phosphorylates NtrC • NtrC-P binds to the upstream element (NtrC site) • DNA bending by IHF (integrated host factor)

15. Regulation by anti-termination • Anti-termination factor • Sigma factor for transcriptional initiation • NusA protein for transcriptional termination • NusB + NusE protein for anti-termination