1. more regulating gene expression

2. We looked at the mechanisms of gene expression, now we will look at its regulation.
Combinations of 3 nucleotides code for each 1 amino acid in a protein.

3. Gene Expression is controlled at all of these steps: DNA packaging
Transcription
RNA processing and transport
RNA degradation
Translation
Post-translational
Fig 15.1
Fig 16.1

4. Gene Expression is controlled at all of these steps:
DNA packaging
Transcription
RNA processing and transport
RNA degradation
Translation
Post-translational
Fig 15.1
Fig 16.1

5. Eukaryotic transcription must be activated by binding of transcription factors
Fig 12.14

6. Mutations in the promoter show critical nucleotides

7. Fig 15.12
Enhancers are regulatory regions located some distance away from the promoter

8. Proteins that help bend DNA can play an important role in transcription
Fig 15.12

9. DNA bends to bring different areas in to close contact.
Fig 15.12
DNA bends to bring different areas in to close contact.

10. How do eukaryotic cells jointly express several proteins (without operons)?

11. Promoter sequences where transcription factors can bind activating multiple gene in response to the environment

12. Promoters typically have several regulatory sequences
Fig 12.13
Promoters typically have several regulatory sequences

13. Steroid response element

14. Steroids bind to receptors/transcription factors inside cell
Fig 15.6
Steroids bind to receptors/transcription factors inside cell
get translocated to the nucleus
bind to promoters and activate transcription.
cytoplasm

15. Gene Expression is controlled at all of these steps:
DNA packaging
Transcription
RNA processing and transport
RNA degradation
Translation
Post-translational
Fig 15.1
Fig 16.1

16. Alternate Splicing in Drosophila Sex Determination
Fig 23.25
Alternate Splicing in Drosophila Sex Determination

17. Alternate splicing leads to sex determination in fruit flies
Fig 23.25
Alternate splicing leads to sex determination in fruit flies

18. Mammalian mRNA Splice-Isoform Selection Is Tightly Controlled
Jennifer L. Chisa and David T. Burke
Genetics, Vol. 175: , March 2007
Regulation of gene expression is often in response to a changing environment.
But how stable can alternative splicing be, and does it play a role in maintaining homeostasis?

19. Alternative splicing modifies at least half of all primary mRNA transcripts in mammals.
More than one alternative splice isoform can be maintained concurrently in the steady state mRNA pool of a single tissue or cell type, and changes in the ratios of isoforms have been associated with physiological variation and susceptibility to disease.
Splice isoforms with opposing functions can be generated; for example, different isoforms of Bcl-x have pro-apoptotic and anti-apoptotic function.
Chisa, J. L. et al. Genetics 2007;175: Fig. 1

20. Alternatively spliced versions of different genes were identified
Chisa, J. L. et al. Genetics 2007;175: Fig. 1

21. variation in splice-isoform ratios is conserved in two genetically diverse mouse populations
Black= genetically heterogeneous population UMHET3
Red= a population of hybrid females
Chisa, J. L. et al. Genetics 2007;175: Fig. 4

22. In different individuals splice isoforms in different tissues are conserved
Chisa, J. L. et al. Genetics 2007;175: Fig. 5

23. Conclusions:
Alternate splicing for some genes is tightly regulated between different individuals.
Slight differences in alternative splicing may be indicative of abnormalities (disease).

24. mRNA transport is an important regulatory step
Molecular Biology of the Cell 4th ed. Alberts et al. Fig 6.40

25. mRNA can be localized to a specific parts of a cell (from Drosophila embryo)
Molecular Biology of the Cell 4th ed. Alberts et al. Fig 7.52

26. At least 3 mechanisms are involved:
Molecular Biology of the Cell 4th ed. Alberts et al. Fig 7.98
Directed transport via cytoskeleton
Random diffusion and trapping
Degradation and local protection

27. A processed mRNA ready for translation
5’ untranslated region
3’ untranslated region
Protects from degradation/ recognition for ribosome
Protects from degradation/ transport to cytoplasm

28. mRNA with 3’ UTR properly localized
mRNA without 3’ UTR improperly localized
Molecular Biology of the Cell 4th ed. Alberts et al. Fig 7.99

29. Gene Expression is controlled at all of these steps:
DNA packaging
Transcription
RNA processing and transport
RNA degradation
Translation
Post-translational
Fig 15.1
Fig 16.1