Behavior of the Components of Maturation-Promoting Factor, cdc2 Kinase and Cyclin B, during Oocyte Maturation of Goldfish

摘要

Weexaminedthechangesthatoccurredinthetwocomponentsofmaturation-promotingfactor(MPF),cdc2kinaseandcyclinB,duringoocytematurationingoldfish,usingmonoclonalantibodiesagainsttheC-terminalsequenceofgoldfishcdc2kinaseandemEscherichiacoli/em-producedfull-lengthgoldfishcyclinB.Immatureoocytescontaineda35-kDainactivecdc2kinase.Inadditiontothe35-kDaform,a34-kDaactivecdc2kinasewasdetectedinoocytesundergoinggerminalvesiclebreakdown(GVBD).CyclinBwasabsentinimmatureoocytesandappearedjustbeforeGVBD,coincidingexactlywiththeappearanceofthe34-kDaactivecdc2kinase.Precipitationwithp13supsucl/supbeadsandanti-cyclinBantibodyrevealedthatcyclinBformedacomplexwithcdc2kinaseassoonasitappeared.MPFactivationwasinducedby1ngcyclinBafterintroductionintoimmatureoocytesoroocyteextracts.ThiscorrespondstotheamountofcyclinBfoundinmatureoocytes(theconcentrationintheoocyteis2μg/ml).TheseresultssuggestthatMPFactivationinfishoocytesisinducedbycomplexformationwithpreexistingcdc2kinaseandnewlysynthesizedcyclinBduringoocytematuration,asituationdifferingfromthatinemXenopus/emandstarfish,inwhichthecdc2kinase-cyclinBcomplexisalreadypresentinimmatureoocytes.UnlikethatinemXenopus/em,aninhibitionofproteinsynthesisinunfertilizedmaturegoldfishoocytescausedadecreaseinthecdc2kinaseactivity/cyclinBproteinlevelandledtoaprogressionfrommeioticmetaphasetomeioticanaphase.ThisresultindicatesthatthemechanismsofmaintainingMPFactivityinmaturegoldfishoocytesdifferfromthoseinemXenopus./em/p/div