Gene Regulation

1. Gene Regulation 2/23/09

2. Fig. 18-2 Precursor Feedback inhibition trpE gene Enzyme 1 trpD gene Regulation of gene expression trpC gene Enzyme 2 trpB gene Enzyme 3 trpA gene Tryptophan (a) Regulation of enzyme activity (b) Regulation of enzyme production

3. Fig. 18-3a Negative gene regulation: repressible operons The trpoperon trp operon Promoter Promoter Genes of operon DNA trpD trpR trpE trpC trpB trpA Operator Regulatory gene Stop codon Start codon 3 mRNA 5 RNA polymerase mRNA 5 B A D C E Protein Inactive repressor Polypeptide subunits that make up enzymes for tryptophan synthesis (a) Tryptophan absent, repressor inactive, operon on

4. Fig. 18-3b-1 Negative gene regulation: repressible operons The trpoperon DNA No RNA made mRNA Protein Active repressor Tryptophan (corepressor) (b) Tryptophan present, repressor active, operon off

5. Fig. 18-3b-2 Negative gene regulation: repressible operons The trpoperon DNA No RNA made mRNA Protein Active repressor Tryptophan (corepressor) (b) Tryptophan present, repressor active, operon off

6. Fig. 18-4a Negative gene regulation: inducible operons The lacoperon Regulatory gene Promoter Operator lacI lacZ DNA No RNA made 3 mRNA RNA polymerase 5 Active repressor Protein (a) Lactose absent, repressor active, operon off

7. Fig. 18-4b Negative gene regulation: inducible operons The lacoperon lac operon lacY DNA lacI lacZ lacA RNA polymerase 3 mRNA mRNA 5 5 Permease Transacetylase -Galactosidase Protein Inactive repressor Allolactose (inducer) (b) Lactose present, repressor inactive, operon on

8. Fig. 18-5 Promoter positive gene regulation: The lacoperon Operator DNA lacI lacZ RNA polymerase binds and transcribes CAP-binding site Active CAP cAMP Inactive lac repressor Inactive CAP Allolactose (a) Lactose present, glucose scarce (cAMP level high): abundant lac mRNA synthesized Promoter Operator DNA lacI lacZ CAP-binding site RNA polymerase less likely to bind Inactive CAP Inactive lac repressor (b) Lactose present, glucose present (cAMP level low): little lac mRNA synthesized

9. Fig. 18-6 Signal NUCLEUS Chromatin Eukaryotic gene regulation can occur at all stages Chromatin modification DNA Gene available for transcription Gene Transcription RNA Exon Primary transcript Intron RNA processing Tail mRNA in nucleus Cap Transport to cytoplasm CYTOPLASM mRNA in cytoplasm Translation Degradation of mRNA Polypeptide Protein processing Active protein Degradation of protein Transport to cellular destination Cellular function

10. Fig. 18-9-1 Promoter Activators Gene DNA Distal control element Enhancer TATA box

11. Fig. 18-9-2 Promoter Activators Gene DNA Distal control element Enhancer TATA box General transcription factors DNA-bending protein Group of mediator proteins

12. Fig. 18-9-3 Promoter Activators Gene DNA Distal control element Enhancer TATA box General transcription factors DNA-bending protein Group of mediator proteins RNA polymerase II RNA polymerase II Transcription initiation complex RNA synthesis

13. Fig. 18-10 Enhancer Promoter Combinatorial control Albumin gene Control elements Crystallin gene LIVER CELL NUCLEUS LENS CELL NUCLEUS Available activators Available activators Albumin gene not expressed Albumin gene expressed Crystallin gene not expressed Crystallin gene expressed (a) Liver cell (b) Lens cell

14. Chromatin Structure 147bp

15. Fig. 18-6 Signal NUCLEUS Chromatin Eukaryotic gene regulation can occur at all stages Chromatin modification DNA Gene available for transcription Gene Transcription RNA Exon Primary transcript Intron RNA processing Tail mRNA in nucleus Cap Transport to cytoplasm CYTOPLASM mRNA in cytoplasm Translation Degradation of mRNA Polypeptide Protein processing Active protein Degradation of protein Transport to cellular destination Cellular function

16. Cytoplasmic determinants in single-celled worm embryos From the Kemphues lab website Cornell University

17. Induction

18. Fig. 18-16-1 Nucleus Master regulatory gene myoD Other muscle-specific genes DNA Embryonic precursor cell OFF OFF

19. Fig. 18-16-2 Nucleus Master regulatory gene myoD Other muscle-specific genes DNA Embryonic precursor cell OFF OFF OFF mRNA MyoD protein (transcription factor) Myoblast (determined)

20. Fig. 18-16-3 Nucleus Master regulatory gene myoD Other muscle-specific genes DNA Embryonic precursor cell OFF OFF OFF mRNA MyoD protein (transcription factor) Myoblast (determined) mRNA mRNA mRNA mRNA Myosin, other muscle proteins, and cell cycle– blocking proteins MyoD Another transcription factor Part of a muscle fiber (fully differentiated cell)

21. Fig. 18-17 Thorax Head Abdomen 0.5 mm Dorsal Right BODY AXES Anterior Posterior Left Ventral (a) Adult Follicle cell Egg cell developing within ovarian follicle 1 Nucleus Egg cell Nurse cell Egg shell Unfertilized egg 2 Depleted nurse cells Fertilization Laying of egg Fertilized egg 3 Embryonic development Segmented embryo 4 0.1 mm Body segments Hatching Larval stage 5 (b) Development from egg to larva

22. Fig. 18-18 Eye Leg Antenna Wild type Mutant

23. Fig. 18-19a EXPERIMENT Tail Head A8 T1 T2 A7 T3 A6 A1 A5 A2 A3 A4 Wild-type larva Tail Tail A8 A8 A7 A7 A6 Mutant larva (bicoid)

24. Fig. 18-19b RESULTS Fertilization, translation of bicoid mRNA Anterior end 100 µm Bicoid mRNA in mature unfertilized egg Bicoid protein in early embryo

25. Fig. 18-19c CONCLUSION Nurse cells Egg bicoid mRNA Bicoid mRNA in mature unfertilized egg Developing egg Bicoid protein in early embryo