LS10Eukaryotictrasncription

LS10Eukaryotictrasncription - Lecture 10: Eukaryotic Gene...

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1 Lecture 10: Eukaryotic Gene Regulation 1. Examples of eukaryotic gene regulation 2. Combinatorial and coordinated control 3. Gene regulation and development Reproductive cloning and therapeutic cloning using genetic information from adult tissues
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2 Question : Almost all cells of an organism are originated from a single cell (zygote -fusion of a sperm and a egg cell), and every cell has the same genome. Why then individual cells will eventually take developmental fate and become different cells, such as blood cells, skin cells, muscle cells, etc? Short answer : Different cells express different sets of genes, so they have different set of proteins. New question : Why different genes express in different ways? What determine when should a gene express? Why regulate gene expression? Red Blood Cell Retinal Rod Cell Hemoglobin Carries Oxygen Rhodopsin Absorbs Light Specialized Cells Specialized Cells Make Specialized Proteins Make Specialized Proteins
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3 Cis and trans-acting factors involved in the regulation eukaryotic gene transcription Modifications of histone tails determine chromatin structure and transcription activity Histones in euchromatin are highly acetylated (hyperacetylation), whereas histones of heterochromatin are rarely acetylated (hypoacetylation)
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4 1. How transcription factors regulate transcription? (1) Transcription repressors (e.g. Ume6 ) binds to URS (upstream repression sequence) to recruit histone deacetylase (e.g. Rpd3 ) to remove acetyl group from histone tail, resulting in hibition of transcription (2) Transcription activator (e.g. Gcn4 ) binds to UAS (upstream activation sequence) to recruit histone acetyltransferase (e.g. Gcn5 ). Histone acetyltransferases add acetyl group to histone tail, resulting in activation of transcription
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5 (3) Transcription factors can recruit co-activator or mediators, which are protein complexes that do not bind DNA but can bind and activate RNA polymerase 1-2. The transcription factor SWI5 bind to enhancers . It recruits DNA helicase (e.g . SWI/SNF) to unwind DNA, de-condense nucleosomes, and expose histone tails for modification 3. After nucleosome decondense, histone acetyltransferase ( Gcn5 ) moves in to acetylate histone tails An example of how transcription factors work together to regulate transcription
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6 4. Histone aceylations further
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LS10Eukaryotictrasncription - Lecture 10: Eukaryotic Gene...

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