Inhibitor of ribosomal RNA synthesis in Xenopus laevis embryos: IV. The release of inhibitor from cultured cells☆

[摘要] Previousreportsfromourlaboratoryhaveshownthataculturemedium,conditionedbythegrowthofisolatedcellsofXenopuslaevisblastulae,containsalow-molecular-weightsubstancewhichselectivelyinhibits18and28SribosomalRNA(rRNA)synthesis.Althoughtheoccurrenceofaninhibitorinanacid-solublefractionofblastulaehasrecentlybeendemonstrated,ourobservationofaninhibitorinaconditionedmediumhasnotbeenconfirmedbyotherlaboratories.Toresolvethisdiscrepancy,wehavereexaminedtheeffectsofconditionedmediaandacid-solubleextractsonrRNAsynthesisbyneurulacells.(1)TheinhibitoryactivityforrRNAsynthesiscanconsistentlybeobservedinblastula-conditionedmedia,providedsomeofthecellshavebeenbrokendownduringconditioning.Ifcellruptureisavoided,aninactiveconditionedmediumisobtained.(2)AhomogenateofblastulaeinhibitstotalRNAsynthesisandshowsnoselectiveinhibitionofrRNAsynthesis.(3)CharcoaltreatmentoftheconditionedmediumandhomogenateenhancestheirspecificityforrRNAsynthesis.Itisthenlikelythatcellbreakdownmaybeinvolvedinthereleaseoftheinhibitorintothemediumandthatsomedifferencesinthemethodsofpreparationofconditionedmediummayaccountfortheabovediscrepancy.

[学科分类] 生物科学（综合）