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Selenocysteine tRNA s as Central Components of Selenoprotein Biosynthesis in Eukaryotes

By Sherry Hunt,2014-09-22 18:28
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Selenocysteine tRNA s as Central Components of Selenoprotein Biosynthesis in Eukaryotesas,of,in,tRNAs,tRNA

    Selenocysteine tRNA s as Central Components of Selenoprotein Biosynthesis

    in Eukaryotes

BIOMEDICALANDENVIRONMENTALSCIENCES10,116124(1997)

    ;SeIenOCySteinetRNAsasCentralComponentsof

    ;SelenOprOtejnBiosynthesisinEukaryotes

    ;SANGICKPARK.JINMoPARK,HAROLDS.CHITTUM,EUNSUNG

    ;YANG.BRADLEYA.’CARLSON,BYEONGJArLEE,AND

    ;DOLPHL.HATFIELD,

    ;LaboratoryofExperimentalCarcinogenesis,NationalCancerInsti- ;tute,NationalInstitutesofHealth,Bethesda,MD20892

    ;USA;+LaboratoryofMolecularGenetics,Institute

    ;{orMolecularBiologyandGenetics.SeoulNational

    ;University,Seoul151742,Korea

    ;Selenocysteine(See)tRNAsservea5carriermoleculesforthebiosynthesisofSecfrom

    ;serineandtodonateSectoproteininresponsetospecificUGAcodons.Inthisstudy.wede

    ;scribethecurrentstatusofSeetRNAsinhigheranimalsandfurtherweex&rf~net(i)theSec

    ;tRNApopulationinDrosophila;(ii)transcriptionoftheSectRNAinvivo(inXenopus

    ;oocytes)andinvitro(inXenopusoocyteextracts);(iii)theeffectofseleniumontheSec

    ;tRNApoPulationinvariousrattissuesfollowingreplenishmentofextremelyseleniumdeficient

    ;ratswiththiselement;andfiv)thebiosynthesisofthemodifiedbasesonSectRNAinXTlO.

    ;pusooeytes.

    ;INTRODUCTION

    ;Theselenocysteine(Sec)tRNAswereoriginallyidentifiedastwominorserine

    ;isoacceptorsinbovineliverthatrecognizedthenonsensecodonUGA(Hatfieldand

    ;Portugal,1970;Hatfield,1972).ThesetRNAswerealsofoundtobethesametR

    ;NAs(Hatfieldeta1.,1982)thathadpreviouslybeenshowntoforrnphosphosery1.

    ;tRNA(MfienpfifiandBernfield,1970;SharpandStewart,1977).Theysuppress

    ;UGAcodonsinproteinsynthesis,arehighlyundermodifiedcomparedtoothertRNAs

    ;andare90nucleotidesinlengthmakingthemthelongesteukaryotictRNAsse. ;quencedtodate(Diamondeta1.,1981;Hatfieldeta1.,1982;Katoeta1.,1983). ;Thesetwoisoacceptorscontainonlyfourmodifiedbasesandtheonlydifferencebe.

    ;tweenthemisflmethylgroupinthe2’-0

    ribosepositionofthewobblenucleoside(Di

    ;amondeta1.,1993).Thenucleosideinthewobblepositionis5methylcar

    ;boxymethyluridine(Diamondeta1.,1993;Arnbergeta1.,1993).Secwasidenti

    ;fledonbothisoacceptorsbylabelingratmammarytumorcellsinculturewithseleni

    ;um-75andisolatingandcharacterizingtheaminoacidattachedtothecorresponding

    ;isoacceptor(Leeeta1.,1989a).Hence,thesetRNAshavefldualfunctionofserving

    ;ascarriermoleculesforthebiosynthesisofSecandfordonatingSeetothegrowing

    ;.ToWhomCorrespondenceshouldbesent:LaboratoryofExperimentalCarcinogenesis,Building37Room

    ;3C23,Nat~nalCancerInstitute,NationalInstitutesofHealth,Bethesda,MD20892USA.

    ;116

;08953988/97

    ;CN11.2816

    ;CopyrIght@1997byCAPM

    ;

    ;SELEN0CYSTEINEtRNAs117

    ;polypeptidechaininresponsetospecificUGAcodons.Sincetheyarefirstaminoacy

    ;latedwithserine,butyetareactuallySectRNAs,theseisoacceptorsaredesignated

    ;tRNALserJ(Hatfieldeta1.,1992a).

    ;ThecloverleafmodelofSectRNALrJSeiSshowninFig.1.Thismodelwas ;originallyproposedbyB6cketa1.(1991)andtheconfigurationshowninthefigure

    ;hasbeensupportedbyenzymaticandchemicalprobingofboththebiochemically

    ;synthesizedandnaturallyoccurringspecies(Sturchlereta1.,1993;Gabryszuk

    ;eta1.,1995).Thismodelisuniqueinthatitcontains9basepairsintheaccepto/”

    ;stem.6basepairsintheDstemand4basepairsintheTOCstem.Themodifie

    d

    ;bases,inadditionto5

    methylcarboxymethyluridine(mcmU)and5.methylcar.

;boxylmethyluridine~2.0.methylribose(mcm’Um)inthewobbleposition,ar

    e1

    ;methyladenosine(mA)atposition58,pseudouridine(‘fI)atposition55andN.

    

    ;isopentenlyadenosine(i6A)atposition37.

    ;3.

    ;A

    ;C

    ;C

    ;5.G

    ;‘G—C

    ;C?G

    ;CG

    ;C?G

    ;G?C

    ;GU

    ;AU

    ;?U?U ;G?C?UU ;U10 ;g

    ;A--

;

    ;U

    ;GC5cG??’Ul

    ;Fm.1.ClovedeafmodelofSectRNA]isoacceptorS

    ;fromratliver.ThesetRNAsweresequencedbyDiamond ;a1.(1993).Evidencefortheconfiguratipnshownisgiven ;inSturchlereta1.(1993)andGabryszuketa1.(1995) ;UniversalityofUGAasaCodonforSec

    ;FollowingtheidentificationofaSectRNAthatdecodesUGAinE. ;c0li(Lein-

    ;feldereta1.,1989)andinmammaliancells(Leeeta1.,1989a),thistRNA,orthe

    ;correspondinggene,wasfoundtobeubiquitousinthesubkingdomofEubacteria

    ;(Heideretal,1989),andintheanimalkingdom’(LeePt

    Z.,1990).Further

    ;

    ;118PARKETAL

    ;more,wefoundaSec.tRNAthatdecodesUGAintwodiverseprotis, ;ts,trahy.

    ;mnborealisandThalassiosiorapseudonana(Hatfieldeta1.,1991a),, ;inahi

    ;.

;g

    ;.

    ;he

    ;Dlant,B已?口

    guris,andinafilamentousfungi,Gliocladiumvirens(Hatfieldet ;

    z..1992b).Thus,aSectRNAthatdecodesUGAwasobservedinrepresentat1ve ;organismsfromallfiveofthelifekingdoms,Monera(withitstwosubk. ;ingdom,u

    ;bacteriaandArcheabacteria),Protists,Plants,AnimalsandFungi(Margulisand

    ;Schwartz.1988).SelenoproteinsoccurinArcheabacteriareviewedinINScKetat’,

    ;1991;IwandBerry,1996),eventhoughaSectRNAthatdecodesUGAhasnot ;beenobservedinthissubkingdom.We,therefore,haveassignedSeetoUGAinthe

    ;universalgeneticcode(seeFig.2andHatfieldandDiamond,1993). ;\M?dl.Mle/BaseUCAG/s.e.J3.Base

    ;PhenylalanineSedneTyrosineCysteineU

    ;UPhenylalanineSerJneTyrosineCysteineCLeucineSedneTerminator.}A ;LeuciReSenneTerminatorTryptophanG

    ;LeuciReProlineHis~dineArginineU

    ;CLeuciReProlineHisSdineArginineCLeucineProlineGlutamineArginineAGLeurineProlineGlutamineArginine

    ;IsoleucineThreonineAsDaragineSedneU

    ;AIsoIeuckleThreon~neAsparagineSeneCIsoleucineThreonineLysineArginineA

    ;G.}ThreonineLys~neArginine

    ;ValineAIanineAsperSeAddGlycineU

    ;GValineAIanineAsperSeAddG~ycineCVaIir.eAIanineGIutamicAddGlycineAGValineAIanineGIutamicAddGlyc~ne

    ;FIG.2.TheuniversalgeneticcodeshowingUGAasacodewordforSecandfortermination.One

    ;othereodeword,AUG,alsohasadualfunctionintheuniversalgeneticcodeandAUGcodesfor

    ;theinitiationofproteinsynthesisandforMetatinternalpositionsofprotein(Nirenbergeta1.,

    ;1966)

    ;AnalysisoftheSectRNAPopulationinDrosophila

    ;AsingleSectRNAgenewasidentified,isolatedandsequencedfromDrosophila

    ;(Leeeta1.,1990).WehavealsorecentlyexaminedtheSectRNApopulationin ;Drosophila.TWOmajorisoacceptorswereidentifiedandquantitatedinvariousdevel

    ;opmentalstagesincludingembryonic,thefirst,secondandthirdlarvalstages,pupae

    ;andadult(S.I.Park,B.J.LeeandD.L.Hatfield,manuscriptinpreparation). ;Thesetwoisoacceptorsarisefromthesinglecopygeneandmust,therefore,differ

    ;

    ;SELENoCYSTEINEtRNAs119

    ;fromeachotherbyposttranscriptionalmodificationasisknowntooccurinthetwo

    ;Secisoacceptorsobservedinhighervertebrates(Leeeta1.,1989b;Choieta1., ;1994).NosignificantchangesinamountsofSectRNAswereobservedduringdevel

    ;opment.TheSectRNAshavebeeniSolatedinsufficientquantitiesforsequencingand

    ;formodifiedbasecomposition.Wearepresentlypursuingseleniumdeficientandtoxic

    ;dietsforfurtherstudyofseleniummetabolisminDrosophila. ;Locati07zoftheSectRNA[]GeneintheGenomeofHumans,Miceand ;Drosophila

    ;TheSectRNArJSegenehasbeenfoundtooccurinsinglecopyinthegenomes ;ofanumberofanimalsincludinghumans(O’Neilleta1.,1985),rabbits(Prattet

    ;.,1985).cattle(Diamondeta1.,1990),mice(CIhamaetal,,1994a;B6slet ;.,1995),chickens(Hatfieldeta1.,1983),Xenopus,DrosophilaandC.ele

    ;gans(Leeeta1.,1990).Theevolutionarychangesthathaveoccurredinthisgene

    ;havebeendiscussedelsewhere(Hatfieldeta1.,1994).ThetRNArJgenehasal

    ;sobeenmappedandlocalizedonitschromosomeinhumans,miceandDrosophila.It

    ;mappedtochromosome19inhumans(McBrideeta1.,1987),waslocalizedon ;bandsq13.2

    q13.3andorderedwithrespecttoothergenesinthisregion(Mitchell ;eta1..1992).ThetRNALJSegenewasfoundtooccupyasimilarchromosomalpo

    ;sitioninmiceandtobealignedwithsimilargenesasthosefoundinhumans(Ohama

    ;eta1..1994a;B6sleta1.,1995).InDrosophila,thisgenemappedtochromosome

    ;2Randwaslocalizedonbands47E

    47F(S.I.Park,B.J.LeeandD.L.Hatfield,

    ;manuscriptinpreparation).

    ;IdentityElementsinSectRNAr]SecandSertRNAforSeryltRNASyntheta

    se

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