A comparison of RNA and protein synthesis in fertilized and unfertilized eggs of Urechis caupo☆

[摘要] AfterfertilizationinUrechiseggs,theapparentrateofproteinsynthesisincreasesapproximatelyonlytwofold,whenexperimentsaredesignedtoavoidthecomplicationofincreasedpermeabilitytoaminoacidsinfertilizedeggs.RNAsynthesisafterfertilizationdropstovirtuallyundetectablelevelsuntilthecompletionofmeiosis.TheRNAsynthesizedduringearlycleavagesedimentsheterogeneouslyinsucrosegradients,butincludesnodistinctpeakof“45S”RNA,andshowshigherlevelsofrelativeincorporationintoRNAsedimentingat18SandlessthantheRNAsynthesizedbyunfertilizedeggs.RibosomalRNAsynthesisappearstoceaseuntilgastrulation.Duringthefirst7hoursofdevelopment(tociliatedblastula)mostoftheRNAlabelisnuclearinautoradiogramsofeggsexposedcontinuouslytouridine-3Hafterfertilization.AtleastsomeoftheRNAsynthesizedinunfertilizedeggspersistsafterfertilization.ThedistributioninsucrosegradientsofthisRNAremainsessentiallyunchangedthroughcompletionofmeiosis,and30SribosomalRNAlabeledpriortofertilizationwithmethionine-methyl-14Cintotheblastulastage.AutoradiogramsshowadispersaloflabeledunfertilizedeggRNAintothecytoplasmfollowinggerminalvesiclebreakdown,andnoreentryintotheinterphasenucleiatthe2-cellstage.

[学科分类] 生物科学（综合）