BB lecture 11-26 gene regulation- eukaryotes

BB lecture 11-26 gene regulation- eukaryotes - Chapter 19...

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Unformatted text preview: Chapter 19 (pp.362-370) Gene regulation in eukaryotes Learning objectives Know the stages in gene expression that can be regulated in eukaryotic cells Explain how DNA methylation affects the regulation of transcription. Explain how histone acetylation affects chromatin structure and the regulation of transcription. Define control elements and explain how they influence transcription. Be able to explain how enhancers and proteins called transcription factors interact with a gene Explain what is meant by coordinate gene expression DNA RNA mRNA Protein I. Chromatin Structure & Chemical Modification II. Transcription III. RNA Processing IV. Nuclear Export VI. Protein Modification & Trafficking Overview: Gene Expression Control Points (Eukaryotes) V. Translation cytoplasm nucleus Three major regulatory chemical reactions . (a) Acetylation- addition of an acetyl group to lysine's R group by acetyltransferase . (b) Methylation- addition of a methyl group to DNA's base (e.g. cytosine) by methylase. (c) Phosphorylation- addition of a phosphate group to the R group of tyrosine , serine or threonine (only tyrosine is shown here) by protein kinase . Figure 19.3 Stages in gene expression that can be regulated in eukaryotic cells Signal NUCLEUS Chromatin Chromatin modification: DNA unpacking involving histone acetylation and DNA demethlation Gene DNA Gene available for transcription RNA Exon Transcription Primary transcript RNA processing Transport to cytoplasm Intron Cap mRNA in nucleus Tail CYTOPLASM mRNA in cytoplasm Degradation of mRNA Translation Polypetide Cleavage Chemical modification Transport to cellular destination Active protein Degradation of protein Degraded protein 1. Chromatin modification 1. Transcription (most common reg. point) 3. RNA processing 4. RNA degradation 5. Translation 6. Protein modification 7. Protein degradation Regulation of Chromatin Structure Genes within highly packed heterochromatin are usually not expressed Chemical modifications to histones and DNA of chromatin influence both chromatin structure and gene expression Histone Modification In histone acetylation , acetyl groups are attached to positively charged lysines in histone tails This process seems to loosen chromatin structure, thereby promoting the initiation of transcription Figure 19-4 Histone tails Amino acids available for chemical modification DNA double helix Histone tails protrude outward from a nucleosome Acetylation of histone tails promotes loose chromatin structure that permits transcription Unacetylated histones Acetylated histones DNA Methylation DNA methylation, the addition of methyl groups to certain bases (e.g., cytosine) in DNA , is associated with reduced transcription in some species In some species, DNA methylation causes long-term inactivation of genes in cellular differentiation Figure 19.3 Stages in gene expression that can be regulated in eukaryotic Figure 19....
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BB lecture 11-26 gene regulation- eukaryotes - Chapter 19...

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