RNA synthesis in unfertilized sea urchin eggs☆
[摘要] Wehaveexaminedthesynthesisofmessenger-likeRNAinunfertilizedseaurchineggs.MostoftheRNAsynthesizedisrestrictedtothenucleusandsedimentsfrom16to30S.AsmallfractioncanbeisolatedfromthepostmitochondrialsupernatantanddisplaysasedimentationprofiletypicalofembryonicmRNAwithpeaksat9and18S.ThiscytoplasmicRNAislargelypresentasfreeRNPsandweestimatethatlessthan20%oftheRNAisinpolysomes.TheRNAmadeintheeggisunstableandreachesasteadystatewithahalf-timeofabout30min.WehaveexaminedtheaccumulationofRNAintheeggandhavecalculatedarateofsynthesisof1.4×10−14gofRNA/min/eggwhichissimilar,onaper-nucleusbasis,tothatfoundinthejust-fertilizedeggandveryearlyembryo.Itisapproximately10timesgreaterthantherateofRNAsynthesisintheblastulanucleus.WeestimatethattheRNAsynthesizedbytheunfertilizedeggamountstoamaximumof3×10−13gofpotentialmRNAatthetimeoffertilization,or10–15%ofitsimmediateneeds.ThisRNAcannotaccountfortheincreaseinproteinsynthesisthatoccursafterfertilization,whichmustbetheresultofthetranslationofanotherpopulationofmorestableeggoroogenicmRNAthatiskineticallydistinctfromtheRNAwehavemeasured.Thesteady-stateleveloflabeledRNApresentintheeggdoesnotchangeuponfertilizationuntilafterthefirstcleavage,atabout2.5hrafterfertilization.ThustheRNAsynthesisthatoccursinthejust-fertilizedzygoteappearstobemerelyacontinuation(atleastquantitatively)oftheRNAsynthesistakingplaceintheegg.
[发布日期] [发布机构]
[效力级别] [学科分类] 生物科学（综合）
[关键词] [时效性]
