MCB 252 Topic 14 mRNA Processing mRNA Turnover and Translation part2 Prof David Rivier MCB 252 Spring 2015 Reading Lodish sections 8 1 and 8 3 Lecture Outline Mechanism and Regulation of mRNA turnover RNA localization Global Regulation of Translation mRNA controlled degradation 60S 40S A E e iF 4 A A A A A A A AA A A A AA AA AA A 40S Polyribosome 60S 40S 60S 40S 60S mRNA controlled degradation Deadenylation dependent pathways 1 5 UTR 3 UTR AAA 200 Poly A Shortening 5 UTR 3 UTR AAA Exosome mRNA controlled degradation Deadenylation dependent pathways 2 5 UTR 3 UTR AAA 200 Poly A Shortening Decapping 5 UTR enzyme 3 UTR AAA mRNA controlled degradation Deadenylation independent pathways 1 Decapping 5 UTR enzyme 3 UTR AAA 200 mRNA controlled degradation Deadenylation independent pathways 2 5 UTR 3 UTR Endonuclease Exosome AAA 200 mRNA controlled degradation In summary mRNA controlled degradation 5 and 3 Untranslated Regions UTRs contian information regulate translation regulate mRNA turnover stability mRNA localization mRNA controlled degradation Some mRNAs have an AU rich signal sequence in their 3 UTR that recruits specific protein factors which in turn recruit deadenylating nucleases 5 UTR ry o t la u AUUUA g Re actor f deadenylase AAA 200 Exosome mRNA controlled degradation The transferrin mRNA is a good example of an mRNA containing AU destabilizing sequences mRNA controlled degradation The transferrin mRNA is a good example of an mRNA containing AU destabilizing sequences High Iron AUUUA ory t a l u Reg r facto deadenylase AAA 200 Deadenylation and rapid degradation mRNA controlled degradation The transferrin mRNA is a good example of an mRNA containing AU destabilizing sequences ry o t a l Regu r facto Low Iron AUUUA IRE Binding Protein AAA 200 Stabilization and translation mRNA controlled degradation The transferrin mRNA is a good example of an mRNA containing AU destabilizing sequences A AA AA A A A A A AAAAA AA AA A mRNP particle Were all the EJCs removed Inhibition of translation Yes Global or specific No Rapid degradation non sense mediated decay Inhibition of translation and Specific sub cellular distribution Translation Degradation Signal Translation Lecture Outline Mechanism and Regulation of mRNA turnover RNA localization Global Regulation of Translation mRNA controlled degradation 5 and 3 Untranslated Regions UTRs contian information regulate translation regulate mRNA turnover stability mRNA localization mRNA subcellular distribution Oskar protein Oskar mRNA mRNA subcellular distribution The sub cellular distribution of mRNAs usually relies on the 3 UTR and specific associated protein factors 5 UTR 3 UTR AAA 200 Inhibition of the Pre initiation complex Transport to specific cytoplasmic locations mRNA subcellular distribution The sub cellular distribution of mRNAs usually relies on the 3 UTR and specific associated protein factors 5 UTR Oskar mRNA ORF Inhibition of the Pre initiation complex 3 UTR AAA 200 Staufen Transport to specific cytoplasmic locations mRNA subcellular distribution The accumulation of Oskar mRNA at the posterior pole of the oocyte depends on the protein Staufen Oskar mRNA Oskar protein Staufen protein mRNA subcellular distribution 1 mRNPs are produced and exported 2 mRNPs diffuse randomly throughout the cytosol 3 mRNPs are bound by specific localized complexes mRNA subcellular distribution 1 mRNPs are massively produced and exported 2 mRNPs diffuse randomly throughout the cytosol 3 mRNPs are bound by specific localized complexes 4 Unbound mRNPs are rapidly degraded mRNA subcellular distribution 1 mRNPs are produced and exported 2 mRNPs are actively transported onto microtubules by molecular motors ATP hydrolysis is needed to power these motors 3 mRNPs are bound by specific localized complexes mRNA subcellular distribution Directed transport Random diffusion and trapping Generalized degradation local protection Lecture Outline Mechanism and Regulation of mRNA turnover RNA localization Global Regulation of Translation A AA AA A A A A A AAAAA AA AA A mRNP particle Were all the EJCs removed Inhibition of translation Yes Global or specific No Rapid degradation non sense mediated decay Inhibition of translation and Specific sub cellular distribution Translation Degradation Signal Translation 60S 40S A E e iF 4 A A A A A A A AA A A A AA AA AA A 40S Polyribosome 60S 40S 60S 40S 60S eiF2B GTP eIF2 Met GTP GDP 40S Translation initiation Sequestration of eIF2 eiF2B GTP eIF2 Met P eIF2 kinase GDP 40S Signal viral infection or lack of amino acids in the culture medium Translation initiation