Trans-regulation of ecdysterone-induced protein synthesis in Drosophila melanogaster salivary glands

摘要

Asetofcoordinatelyexpressedgenesisactivelytranscribedafteradramaticincreaseintheecdysteronetiterinlatethird-instardevelopmentofDrosophilamelanogaster,asshownbytheappearanceofanumberofpuffsinsalivaryglandchromosomesandbythesynthesisofanumberofnewproteins.Previousworkhassuggestedthataproductoftheecsgene,whichislocatedwithinthe2B3-5puff,isnecessaryforprovidingalterationsintranscriptionalactivityatthesitesofecdysterone-dependentpuffs.Theexperimentsreportedhereweredesignedtodeterminewhethertheecsgene'sregulatoryeffectonpuffingisconfirmedbyitsregulatoryeffectonthesynthesisofecdysterone-inducibleproteins(EIPs).Thefirstseriesofexperimentsshowedthatinsalivaryglandsinvivoecdysteroneinduces24EIPsandinvitroinduces26EIPs.Thesetsofpolypeptidesrevealedareingoodconformity.ThesecondsetofexperimentsdemonstratedthatmutationsintheecslocusdisturbEIPsynthesis:ecsl(1)t10andecsl(1)t143mutationsaffectEIPsynthesistoalesserextent,whileecsl(1)t435andecsl(1)t324,aswellasthe2B3-5puffdeficiency,preventEIPsynthesiscompletely.TheexperimentsondosagedependencyrevealedtwoEIPswhoserateofsynthesiscorrelateswiththedosageofthe2B3-5X-chromosomalregion.TheseEIPsareshowntobeinfactsmallheat-shockproteins23and28K,whichareknowntobeencodedwithinthe67Bpuffandareunderdualcontrola€”transientanddevelopmental.Thefinalsetofexperimentsfollowedthe2B3-5dosagedependencyinvitroandshowedthat15EIPsdisplayeitheranaffectedrateofsynthesisor,mainly,aquickerinductiontime.Dataobtainedshowthattheecslocusistrans-regulatoryandthatitsproductisnecessaryforspreadingtheeffectofecdysteronetootherloci.