Lecture.19.Fall.2013

Expression eukaryotic gene expression all the general

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Unformatted text preview: and RNA can be used to regulate gene expression Eukaryotic Gene Expression • All the general mechanisms of prokaryotic regulation are used in eukaryotes • The eukaryotic system is more complex – More potential levels of regulation • Much larger genome, with many associated proteins (histones, etc.) bacteria=no chromatin Eukaryotic Gene Expression • Transcription and translation are separated transcripts must be stable, bacteria transcripts are always being degraded • Transcripts are extensively processed (capping, poly-A tail, splicing) used to regulate stability and increase life span of usage • mRNA is much more stable – Allows extensive translational control Levels of Control of Eukaryotic Gene Expression • Chromatin Structure • Histone modifications • Epigenetic effects • Transcriptional – Promoters and enhancers Levels of Control of Eukaryotic Gene Expression regulate…. • mRNA processing – Splicing • Translational control – 5’ and 3’ UTRs • Post-translational regulation – phosphorylation Changes in chromatin structure affect gene expression Chromatin structure becomes more open for gene expression At least four mechanisms: Histone methylation Histone acetylation Chromatin-remodeling complexes DNA methylation Histone Methylation Addition of methyl groups to histone tails Can lead to activation or repression, depending on which amino acid is methylated Example: H3K4me3 (3 methyl groups added to lysine 4 of histone 3) H3K4me3 recruits NURF leads to activation NURF = nucleosome remodeling factor unwinds Recognizes and binds to H3K4me3 and and alters chromatin packing (making it “looser”) H3K4me3 recruits NURF wildtype flc mutant Example: Arabidopsis flowering Flowering time is controlled by the repressor protein FLC (more FLC = later flowering) FLC controls transcription of “flowering genes” H3K4me3 recruits NURF wildtype flc mutant Example: Arabidopsis flowering FLD encodes a histone de-methylase, which removes methyl groups from histones in the FLC gene more methyl...
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