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Regulating Gene Expression from RNA to Protein 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 A processed mRNA ready for translation 5’ untranslated region Protects from degradation 3’ untranslated region Protects from degradation/ transport 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 Seeds germinated underground begin growing in darkness then emerge into light and begin photosynthesis energy from seed energy from sun The level of this mRNA increases after plants are exposed to light. •How might the cell accomplish this? The level of this mRNA increases after plants are exposed to light. •How might the cell accomplish this? Increased transcription and/or decreased mRNA degradation Northern blot analysis: The level of this mRNA increases after plants are exposed to light. •How might the cell accomplish this? •Does this necessarily lead to increased protein production? 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 Fig 15.25 Regulation of iron assimilation in mammals: Regulating of Translation Ferritin is regulated at translation Fig 15.26 C. elegans is commonly used to study development C. elegans development C. elegans mutants with cells that do not develop properly. C. elegans mutants with cells that do not develop properly. The product of these genes was found to be RNA? MicroRNAs (miRNA) are ~22nt RNAs that play important regulatory roles Cell vol. 116, 281-297 2004 miRNA expressed How do microRNAs control gene expression? Fig 15.23 and miRNA processed to ~22nt RNA Mature miRNA A processed mRNA ready for translation: microRNAs inhibit translation by binding to the 3’ end of mRNA microRNA bind to 3’-UTR 5’-UTR 3’-UTR miRNA expressed the 3’ end with attached microRNA interacts with the 5’ end, blocking translation Fig 15.23 and miRNA processed to ~22nt RNA Mature miRNA miRNAs can lead to methylation of DNA that leads to inhibition of transcription microRNAs primarily target gene products that function during development Tbl 1 tissue specific expression of mouse microRNA PNAS vol. 101 #1 pg 360-365, 2004 Silencing RNAs (siRNA) are artificially induced dsRNA Fig 15.21 siRNA with exact matches to the target mRNA causes degradation of the mRNA microRNA Translation inhibited siRNA mRNA degraded Gene Expression is controlled at all of these steps: •DNA packaging •Transcription •RNA processing and transport •RNA degradation •Translation •Post-translational Fig 16.1 Phosphorylation and dephosphorylation of proteins can change activity Ubiquitinization targets proteins for degradation All protein interactions in an organism compose the interactome Some proteins function in the cytoplasm; others need to be transported to various organelles. How can proteins be delivered to their appropriate destinations? Fig 13.23 Proteins are directed to their destinations via signals in the amino acid sequence Protein Destinations: secretion or membrane • Signal sequences target proteins for secretion Translation of secreted proteins Translation of membrane bound proteins Translation of secreted or membrane bound proteins This step determines secretion or membrane bound. Protein Destinations: nucleus Signal anywhere in protein, Translation in cytoplasm, Signal not removed Protein Destinations: mitochondria or chloroplast Signal translated first, Translation in cytoplasm, Signal removed Protein Destinations: signals in protein determine destination Tbl 13.8 Development: differentiating cells to become an organism