Spring 09 lecture 29

Spring 09 lecture 29 - Control of gene expression overall...

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1 Transcription initiation Direct influence of A and R on initiation Activators (A), repressors (R) and remodeling proteins and chromatin structure Methylation Hormones and other “external” signals RNA processing Capping and polyadenylation Alternative splicing and trans-splicing Transport through the nuclear pore Posttranscriptional / pretranslational control (events on/with mRNA before ribosomes) Localization of mRNA RNA editing Post-transcriptional silencing by siRNA or miRNA Translational control switch RNA stability (degradation and stabilization) Translational control (mRNA/ribosomes) Phosphorylation of translation initiation factors Upstream AUG codons IRES Protein activity control Posttranslational modification and transport Control of gene expression: overall
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2 2. Pre-translational control : RNA editing - Alteration in the sequence of the mRNA
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3 RNA editing in mitochondria of protozoa, mitochondria and chloroplasts in plants: addition or deletion of U residues - Guide RNAs Extreme form of RNA editing - many nucleotides removed or added Directed by small guide RNAs (gRNA) 5’ of gRNA binds to 3’ of intermediate transcript (rarely to primary) and directs changes Repetitive process- few gRNAs are required to edit whole RNA Enzyme cascade involved in U-deletion or-U addition U-Deletion
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4 U-Insertion TUTase – terminal uracyl transferase
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5 RNA editing in mammals (S. Maas) Deamination of A to I (inosine) this is happening on un- spliced RNA template due to partial complementarity between intron and exon sequence in translation I is recognized as G change in the aa sequence of the protein RNA sequence is altered in a single-nucleotide , site-specific, manner.
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6 AI editing - catalyzed by the dsRNA binding ADARs From: Levanon et al. (2004) NBT 33, 1001 Only one enzyme needed: ADAR – a denosine d eaminase a ctive on R NA (has to be dsRNA)
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7 Deamination of C to U
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This note was uploaded on 08/03/2009 for the course BIOL BIOL308 taught by Professor Miskovic during the Spring '09 term at Waterloo.

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Spring 09 lecture 29 - Control of gene expression overall...

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