Transitions in histone variants of the male pronucleus following fertilization and evidence for a maternal store of cleavage-stage histones in the sea urchin egg☆

[摘要] Asystemhasbeendevelopedforthebiochemicalstudyofmalepronuclearhistonesfollowingfertilization.Pronucleiareisolatedinhighyieldandpurityfrompolyspermicallyfertilizedseaurchineggs.Acidextractsofthepronucleiorchromatinareanalyzedbytwo-dimensionalgelelectrophoresis.Duringmalepronucleardecondensation,sperm-specific(Sp)H1iscompletelyreplacedbythecleavage-stage(CS)H1variantandtwospermH2Bspeciesaremoregraduallyreplacedbytwocloselymigratingspecies(O,P)perhapsmodificationsoftheSp2Bs.HistonesCS2AandCS2BbegintoaccumulateonthemalechromatinpredominantlyduringDNAsynthesis,asdoesasubspeciesofH3(3″).Bythetimeofchromosomecondensation,thehistonecomplementischieflyCS1;CS2AandSp2A;CS2BandO,P;threeH3sandtwoH4s.Controlsindicatethatthesepatternsarenotartifactsofcytoplasmicormaternalpronuclearcontaminationormodificationofspermhistonesduringisolation.Thehistonetransitionsoccurevenifproteinsynthesisisinhibited,suggestingamaternalpoolofCShistones.Suchastorecanbedemonstrateddirectlyinacidextractsofwholeeggs.Atleast30haploidequivalentsofCShistonesarestoredperegg.Noα,β,γ,orδvariantsappearonthechromatininthefirstcycle.Thissystemshouldallow,forthefirsttime,detailedbiochemicalstudyofmalepronuclearchromatin.

[学科分类] 生物科学（综合）