Active chromatin of oocytes injected with somatic cell nuclei or cloned DNA

[摘要] IthasbeenpreviouslyfoundthatsomaticcellnucleiinjectedintoXenopusoocytesundergomajorchangesinstructureandgreatlyincreasetheirrateofRNAsynthesis.Weshowherethatthesechangesarenotaccompaniedbyageneraldisplacementofhistonesorofthenon-histonechromosomalproteinsknownasHMGs,whencompletenucleiorinvitroassembledDNA-proteincomplexesareinjectedandanalyzed.FurthermoreinjectednucleidonotundergoanygeneralchangefromthetranscriptionallyinactiveconformationtoanHMG-binding“active”conformation.Chromatinassembledbysaltdialysiswitha145-basepairspacingofnucleosomesisnotchangedtothetypical200-basepairspacing.Weconcludethatthechangesingeneactivityundergonebysomaticnucleiinoocytesaffectaspecificminorityofgenesandarenotachievedbygrosschromosomalchanges.Wehavealsoanalyzedthenucleo-proteinstructuresformedfrompurifiedDNAinjectedintooocytes.Althoughthemajorityoftheseareknownfrompreviousworktobetransciptionallyinactive,wefindthattheyareinan“active”HMG-bindingconformation.ThisisattributabletotheundermethylatedstateoftheinjectedclonedDNA,sincethesameDNAaftermethylationinvitroisassembledinoocytesintoastructurewhichdoesnotbindHMGs.TheHMG-bindingstructuresformedfrominjectedDNAcontainalowlevelofHMGproteins,whichwefindtobepresentinunusuallysmallamountsinXenopusoocytesandeggs.

[学科分类] 生物科学（综合）