2. Day 2!

3. Chapter 15 Eukaryotic Gene Regulation

4. Almost all the cells in an organism are genetically identical. Differences between cell types result from differential gene expression, the expression of different genes by cells with the same genome.

5. Stages in gene expression that can be regulated in eukaryotic cells Signal NUCLEUS Chromatin Chromatin modification: DNA unpacking involving histone acetylation and DNA demethylation DNA Gene RNAExon Gene available for transcription Transcription Primary transcript Intron RNA processing Tail mRNA in nucleus Transport to cytoplasm CYTOPLASM mRNA in cytoplasm Translation Degradation of mRNA Polypeptide Cap Protein processing, such as cleavage and chemical modification Active protein Transport to cellular destination Degradation of protein Cellular function (such as enzymatic activity, structural support)

6. Euchromatin Heterochromatin Methylation Acetylation

7. You Must Know The control of gene expression in eukaryotes

8. An activator is a protein that binds to an enhancer and stimulates transcription of a gene. Activators have two domains, one that binds DNA and a second that activates transcription. DNA Upstream Enhancer (distal control elements) Proximal control elements ExonIntron Exon Transcription start site Promoter IntronExon Poly-A signal sequence Transcription termination region Down- stream Activators

9. Figure 14.9 TATA box Promoter Nontemplate strand Start point DNA 3 53 5 TATAAAA ATATTT Transcription factors 3 5 3 5 T Transcription initiation complex RNA transcript 3 5 5 3 3 5 Transcription factors RNA polymerase II Template strand In eukaryotes, high levels of transcription of particular genes depend on interaction between control elements and specific transcription factors.

10. Figure 15.10-3 DNA Enhancer Distal control element Activators Promoter Gene DNA- bending protein Group of mediator proteins General transcription factors TATA box RNA polymerase II RNA synthesis Transcription initiation complex

11. A particular combination of control elements can activate transcription only when the appropriate activator proteins are present. Combinatorial Control of Gene Activation

12. Available activators (a) LIVER CELL NUCLEUS Crystallin gene not expressed Albumin gene expressed Available activators (a) LIVER CELL NUCLEUS

13. Figure 15.11b (b) LENS CELL NUCLEUS Available activators (b) LENS CELL NUCLEUS Available activators Albumin gene not expressed Crystallin gene expressed

14. Iac I Allolactose (inducer) IacZ IacY IacA Iac I DNA lac operon Permease Transacetylase  -Galactosidase mRNA Protein RNA polymerase mRNA 5 3 5 Prokaryotes coordinate gene expression with operons.

15. Eukaryotes coordinated gene expression with activators. The activators recognize specific control elements and promote simultaneous transcription of the genes, even when the genes are on different chromosomes. Activators

16. Chromatin modification Transcription RNA processing Translation mRNA degradation Protein processing and degradation

17. Alternative RNA splicing DNA Primary RNA transcript mRNA or Exons Troponin T gene RNA splicing 1 2 3 4 5 1 2 3 5 1 2 4 5 1 2 3 4 5

18. Chromatin modification Transcription RNA processing mRNA degradation mRNA Coding segment 3 5 5 3 Cap UTR Start codon Stop codon UTR Poly-A tail GP P P AAA  AAA

19. Chromatin modification Transcription RNA processing Translation mRNA degradation Protein processing and degradation The initiation of translation of selected mRNAs can be blocked by regulatory proteins that bind to sequences or structures of the mRNA.

20. Chromatin modification Transcription RNA processing Translation mRNA degradation Protein processing and degradation Translation of all mRNAs in a cell may be regulated simultaneously. For example, translation initiation factors are simultaneously activated in an egg following fertilization.

21. Chromatin modification Transcription RNA processing Translation mRNA degradation Protein processing and degradation