protein synthesis in eukaryotes internal initiation

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1、ProteinSynthesisinSecondaryarticleEukaryotes:InternalArticleContents.IntroductionInitiation.ScanningModelforRibosomeBinding.InternalRibosomeBindingNahumSonenberg,McGillUniversity,Montreal,Quebec,Canada.MechanismofInternalInitiation.Trans-actingFactorsinI

2、nternalInitiationInternalinitiationisanalternativemechanismtothegeneralpathwayoftranslation.Perspectiveinitiationineukaryotesandinvolvestheinternalbindingofribosomestoaspecificsequenceinthemessengerribonucleicacid(mRNA)calledtheinternalribosomeentrysite(

3、IRES).ThemRNA5’capstructureandacap-bindingprotein,eukaryoticinitiationfactor(eIF)4E,playakeyroleinthecanonicalmechanismoftranslationinitiation.However,internalinitiationisindependentofthecapstructureandeIF4E.IRES-mediatedtranslationinitiationhasbeendocum

4、entedforviralandcellularmRNAs,andfunctionsduringmitosisandstressconditions,suchasapoptosisandhypoxia.IntroductionpresentonallnucleartranscribedeukaryoticmRNAs.AftertheribosomeinteractswiththemRNAinthevicinityTheprocessoftranslationisdividedintothreemajor

5、steps:ofthecapstructure,itisthoughttocommencescanningof(1)initiation,(2)elongation,and(3)termination.Merrickthe5’untranslatedregion(5’UTR)ina5’to3’directionsummarizesthesestepsinthearticle‘Proteinsynthesisuntilitencountersaninitiationcodon,usuallyanAUG,i

6、ninitiationineukaryotes:initiationfactors’.Initiationoftheappropriatesequencecontext.(seeProteinsynthesistranslationisthestepthatinvolvestherecruitmentofinitiationinprokaryotes.)(seeBacterialribosomes.)(seeMessengerribosomestothemessengerribonucleicacid(

7、mRNA)andRNAinprokaryotes.)(seeMessengerRNAineukaryotes.)theirpositioningatthecorrectinitiationcodon.ThisTheinitiationfactorsthatmediateribosomebindingtoprocessisgenerallytherate-limitingstepintranslation,themRNAandtheirmechanismofactionaredescribedinandi

8、safrequenttargetforregulationinbothprokaryotesthearticlebyMerrick.Tosummarizebriefly,thecapandeukaryotes.Translationinitiationrequirestheparti-structureisrecognizedbyathree-subunitproteincomplexcipationofmanynonribosomalpro