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Download Bio200 Au13 Lec19 10-29 Slides
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Eukaryotic Gene Regulation: Data Set 4 Random Call for an explanation of this… Protein-coding mRNA region for Gene Z Amino-acid primary Sequence for Gene Z = Lysine ‘Life span’ of the mutant protein (Life span of non-mutant protein Z) Location of amino-acid-changing mutation How to read this graph: If you made a mutation in the 4th amino acid (blue), then the lifespan of the mutant protein would be just a little bit shorter on average than the non-mutant protein Z. Eukaryotic Gene Regulation: Post-translational Ubiquitination Eukaryotic Gene Regulation: Other post-translational modifications Ubiquitination by UbiE3s Phosphates Addition: kinase Removal: phosphorylase Acetylation Cleavage by proteases Addition of carbohydrates Homework: Gene Regulation Chart Type of regulation Histone acetylation Enhancer site Silencer-binding protein Splicing Ubiquitin addition to the product 5’ Cap and 3’ Poly-A tail ? Found in prokaryotes or eukaryotes? Mechanism? Level (dna, txn, tsl, post-tsl?) Increase or decrease expression? Key Concepts • Eukaryotic gene regulation is typically more complex than regulation of prokaryotes. • Eukaryotic DNA is packed onto histone proteins. • The looseness or tightness of this packing can effect expression. • DNA can be loosened by enzymatic addition of acetyl groups • Eukaryotic mRNA is heavily processed before being used • A 5’ protein cap and a 3’ poly-A tail are added to give stability • Non-coding introns are spliced out of the mRNA by the spliceosome • Eukaryotic genes can have promoter-influencing elements that are far upstream or downstream of the protein-coding region. • These silencers and enhancers work through DNA binding proteins that either help to recruit to repel RNA polymerase. DNA flexibility is essential. • Post-translational modifications can be used by the cell to regulate enzyme activity • These can be additions, subtractions, or destructions of part or all of the proteins. • These modifications are usually performed by other enzymes which may have their own regulation schemes. Oct 29th, 2013 Lecture 19 Outline Questions Understanding Protein Trafficking and the Endomembrane System • What is the endomembrane system? • Why is the endomembrane system necessary? – How does the Rough ER help protein construction? – What is the common feature between the Rough ER and the Smooth ER? – Why does Golgi vesicle movement result in sorting of proteins? • How are proteins directed to particular regions of the cell? – Where is the trafficking information stored? – What molecular factors assist in protein transport and direction? Translation into the Rough ER: Signal Sequence Cytosol Ribosome SRP RNA Signal sequence Emerging Protein Lumen of rough ER SRP receptor Protein EMS Organelles: The Rough ER A Protein Synthesis and Processing Complex • • • • The rough ER is contiguous with the nuclear membrane New proteins are directly inserted into the ER Microenvironment: noncytoplasmic molecular conditions for protein folding Lumen of After processing, proteins are transported to other destinations rough ER by controlled vesicle budding Ribosomes on outside Free ribosomes in cytoplasm EMS Organelles: Smooth ER A Lipid-Handling Center and Storage Site • The smooth ER is the major processing zone for lipids • Smooth ER lacks ribosomes, naturally • ER hosts non-cytoplasmic molecular conditions and specialized enzymes • After processing, lipids are transported to other destinations by controlled vesicle budding Smooth endoplasmic reticulum Lumen of smooth ER Golgi apparatus: The cellular “post office” 11 EMS Organelles: The Golgi Apparatus A Site of Protein Processing The cis face is oriented towards the rough ER • • • • A site for carbohydrate modification of proteins Packaging and transport to cellular locations with vesicles Formed by a series of stacked flat membranous sacs called cisternae. Receives products from the rough ER and sends finished products to the cell surface in vesicles. The trans face is oriented away from the rough ER Golgi apparatus cis face Vesicle Lumen Cisternae Vesicles trans face How do proteins get where they need to go in the cell? Different protein ZIP codes ….. different destinations 13 Key Concepts • Protein trafficking is the process of: – translating, – folding, and – transporting proteins • Proteins that are sent through the endomembrane system are eventually active in: – organelles, – the plasma membrane, or – outside of the cell. • Trafficking signals are embedded information in the structure of the molecules. – In proteins, this is often in the form of small trafficking ‘tags’ that are short stretches of amino-acids. – These tags are recognized by mediating molecules. • The endoplasmic reticulums process molecules for use in non-cytoplasmic environments. – The Rough ER processes proteins. – The Smooth ER processes lipids. – Molecules are sent by vesicle through the Golgi apparatus for movement to different parts of the cell.