Lecture.19.Fall.2013

Example yeast gal genes uas gal1 uas gal10 gal80

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Unformatted text preview: l Genes UAS GAL1 UAS GAL10 UAS: Upstream Activating Sequence (enhancer element) Example: Yeast Gal Genes UAS GAL1 UAS GAL10 GAL4 protein (activator) is bound to these sites at all times - how is induction regulated? Example: Yeast Gal Genes UAS GAL1 UAS GAL10 GAL80 protein binds GAL4 and blocks the activation domain Example: Yeast Gal Genes UAS GAL1 UAS GAL10 Galactose present, binds GAL80 - conformational change GAL4 transactivation domain exposed - induction mRNA processing Alternative splicing: pre-mRNAs can be spliced in different ways, to include or exclude particular exons. Different proteins can thus be made at different times in different tissues, by regulating which splice events occur Alternative splicing magnifies the total number of genes in the genome Example: Drosophila DSCAM DSCAM = the fly homolog of the Down Syndrome Cell Adhesion Molecule DSCAM is a transmembrane protein required for proper guidance of axons (the “signal-sending” part of neurons) to their targets There are 4 variable regions in this protein: Dscam variable regions Dscam Is an Axon Guidance Receptor 679 12*48*33*2 = 38016 different proteins can be produced There are only 13,702 total GENES in the fly genome Reference: Schmucker et al., 2000 (in Larry Zipursky’s lab) RNA interference (RNAi) Small double-stranded RNA molecules can target larger molecules with which they share homology for degradation As much as 30% of the human genome may be post-transcriptionally regulated by RNAi. Probably evolved as an antiviral mechanism RNAi 1. dsRNA is bound by the Dicer RNAse 2. Dicer cleaves the dsRNA into small fragments (21-23 bp siRNAs) 3. The Argonaute protein forms a RISC with the siRNA (RNAinduced silencing complex) RNAi 4. RISC discards the sense strand, and uses the antisense strand as a guide to find complementary sequences 5. RISC then cleaves the target mRNA into small RNA molecules 6. These molecules serve as additional guides (amplifying the effect) Regulation of translation Both the 5’ and 3’ untranslated regions (UTRs) of a transcript can regulate that transcript’s stability and whether it will be translated 5’ UTR: Regulatory proteins can bind and prevent ribosome binding 3’ UTR: Sequences re...
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This document was uploaded on 02/25/2014.

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