Spontaneous release of nucleosome cores from embryoblast chromatin☆
[摘要] Duringinvitroincubationoftherabbitblastocyst,chromatinfragmentsofthenucleosomeseriesarereleasedspontaneouslybycellsofthepluripotentembryoblastbutnotbythedevelopmentallyrestrictedtrophoblast.TheDNAofthesefragmentsisdoublestrandedandlinear,andrepresentstotalgenomicDNA.Thefragmentsarestableforatleast24hrandareinitiallyfoundinthecytoplasmofintactcells.ThekineticsofradiolabelingoftheDNAcomponentofthesefragmentssuggestthattheyoriginatefromactivelyreplicatingcells,possiblyonlyatthetimeofmitosis.DNaseII-likeactivity,oneoftheendonucleasesknownpreferentiallytoattackspacerDNAbetweennucleosomecores,isreadilydetectableintheblastocyst,althoughtheevidenceforitsinvolvementintheobservedchromatinfragmentationremainscircumstantial.Thesenonrandomchromatinbreaks,presumablyrepresentinganearlyeventincelldeath,occurmorefrequentlyundersuboptimalconditionsofincubationbutarestilldetectableinembryosdevelopingnormally.Thereisnoevidenceforlysosomalactivationinthesedyingcells.Thesefindings,togetherwithpreviousreportsofidenticalchromatinfragmentationinothercellsystems,suggestthatthisformofcelldeathintheembryoblastmaybeonlyonepossibleresultofanactiveprocess,andthatthemechanismsresponsibleforgeneratingdouble-strandbreaksininternucleosomalDNAmaybeofmorebiologicalsignificancethanDNAdegradationalone.
[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]
