Size and specific activity of the UTP pool and overall rates of RNA synthesis in early mouse embryos☆

[摘要] Mouseembryosfromtheone-celltotheblastocyststagewereculturedfor2hrinthepresenceof5μM[3H]uridineor10μM[3H]adenosine,andthesizeandspecificactivityoftheUTPandATPpoolsweredeterminedbyanEscherichiacoliRNApolymeraseassayusingsyntheticpoly(dA-dT)astemplate.ThetotalUTPpoolincreasedinsizeandspecificactivitywithdevelopmentfrom0.05pmole(0.06%labeled)intheone-cellstageto0.54pmole(27%labeled)intheblastocyststage.ThetotalATPpoolremainedrelativelyconstantinsizeatabout1pmole/embryo,butincreasedinspecificactivityfrom2.6to52%fromone-celltoblastocyst.Theturnoverofthe[3H]UTPpoolwasalsoexaminedunderpulse-chaseconditionsineight-cellandmorula-stageembryos.TheUTPpooldecayedwithapproximatelyfirst-orderkineticsupto20hrofchase,buttherateofdecaywasslowerineight-cellembryos(t0.5=5.5hr)thaninmorulae(t0.5=2.8hr).TheobservedspecificactivitiesoftheUTPpoolswereusedtocalculatetheoverallratesofuridineincorporationintoacid-precipitablematerialduringearlydevelopment.Therateofuridineincorporationperembryoincreasedfrom3.6×10−3pmole/2hrinthetwo-cellembryoto1.8×10−1pmole/2hrintheblastocyst.TherateofRNAsynthesispercellovera2-hrperiodwasestimatedat2.5pginthetwo-tofour-cellembryo,5pgintheeight-cell,and10pginthemorula-earlyblastocyst.

[学科分类] 生物科学（综合）