Changes upon fertilization in the distribution of RNA-containing particles in sea urchin eggs☆

[摘要] ThedistributionoflabeledRNA'ssynthesizedandconservedduringoogenesishasbeenexaminedinhomogenatesofunfertilizedandoffertilizedeggsoftheseaurchinLytechinuspictus.Theresultsshowedthatappreciablenumbersofribosomalaggregateswerepresentinhomogenatesofunfertilizedeggs.Abouttwo-thirdsoftheaggregateswereassociatedwithlow-speedsedimentablematerial.Approximatelytwotothreetimesmoreribosomalaggregateswerepresentinhomogenatesofeggs2hoursafterfertilization.Halfofthesewereinthelow-speedpelletsofthehomogenate.Thus,theriseinthenumberofribosomalaggregatesafterfertilizationwasconfinedtothesupernatantfractionofhomogenates.Ribosomalpreparationsofunfertilizedeggswerecomparedwiththoseoffertilizedeggsfortheirabilitytoincorporateendogenouslyvaline-14Cintoproteininacell-freesystem.Equivalentpreparationsshowedthatthosefromfertilizedeggsincorporatedaboutfifteentimesmoreaminoacidsintoproteininhalfanhourthanthosefromunfertilizedeggs.RNA'swereextractedwithphenolfromtheribosomalandthepostribosomalregionofsucrosedensitygradientsofhomogenatesoflabeledunfertilizedeggs.Theformershowedpredominantly28Sand18Sradioactivity;thelatteryieldedprimarily(about75%)polydisperseradioactivity,andtheremainder28Sand18S.Most(about75%)oftheheterogeneouslysedimentingpostribosomallabeloccurredinthelow-speedsupernatantfractionofthehomogenateandrelativelylittleinthecorrespondingpellet.TheamountofpostribosomalradioactivityinhomogenatesofeggspreloadedwithlabeledRNAdidnotdecreaseby2hoursafterfertilization.TheresultsarediscussedinrelationtothepresenceofmaskedmRNAinunfertilizedeggs.

[学科分类] 生物科学（综合）