EIF3 Regulate Translation Control Of Metabolic Energy

elF3 is the largest and most complex initiation factor,comprising of 13 subunits.we have found that eIF3e and d lacking in s pombe specifically decreases the production of mitochondrial proteins,particularly electron transport chain(ETC)proteins.Not all eIF3 subunits are essential for protein synthesis and cell survival,suggesting that some have mRNA selective function in translation.Using a series of proteomic approaches to quantitatively profile protein synthesis,we have found that subunits elF3e and d constitute a module that specifically promotes the production of mitochondrial proteins,in particular electron transport chain(ETC)proteins.With the re-emerging focus on the essential role of the mitochondrial ETC in cell proliferation,cancer stem cell maintenance,and drug resistance,it is conceivable that the ETC promoting function of eIF3 discovered in our studies underlies,at least in part,its tumor promoting activity.In this model,elF3 would be limiting for mitochondrially produced energy and building blocks which fuel cancer cell anabolism and thus represents an intriguing novel cancer drug target.Nevertheless,mechanistic insight into the mRNA selective functions of elF3 remains scarce and no drugs exist to target the tumor promoting activity of elF3.ln summary,we would like to answer two questions:one is Which mRNAs are selectively regulated by elF3 subunits?In order to address this question,we have been performing a series of global approaches to identify subunit-specific subsets of eIF3-regulated mRNAs.The techniques we have used include ribosome profiling,polysome profiling followed by RNA sequencing,RNA immunoprecipitation and sequencing(RIP-Seq)as well as pulsed SILAC-based proteomics.So far,these studies have confirmed that elF3 regulates metabolic mRNAs.Another question is How do eIF3 subunits mediate mRNA selectivity?To address this question,we have set up an in vitro translation system to measure the activity of luciferase reporter genes fused to the 5’-UTRs of eIF3 sensitive mRNAs(especially mRNAs encoding mitochondrial proteins).This assay system will allow us to use mutagenesis and binding assays to identify mRNA sequence motifs mediating eIF3-dependent control.