Control mechanisms regulating gene expression during normal differentiation of myeloid leukemic cells: Differentiation defective mutants blocked in mRNA production and mRNA translation☆

[摘要] Regulationofgeneexpressionduringmyeloidcelldifferentiationhasbeenanalyzedusingclonesofmyeloidleukemiccellsthatdifferintheircompetencetobeinducedtodifferentiatebythenormalmacrophage-andgranulocyte-inducingproteinMGI.Changesintherelativerateofsynthesisforspecificproteinswerecomparedtochangesintherelativeamountsofcorrespondingtranslatablepoly(A)+mRNAs,assayedinthereticulocytecell-freetranslationsystem,usingtwo-dimensionalgelelectrophoresis.Ofthe217proteinswhichchangedduringMGI-induceddifferentiationofnormallydifferentiatingMGI+D+leukemiccells,136couldbeidentifiedasproductsofcell-freetranslation.Eighty-fourpercentofthe70decreasesinsynthesis,mostofwhichoccurredearlyduringdifferentiation,werenotaccompaniedbyaparalleldecreaseintheamountoftranslatablemRNA,butwereaccompaniedbyaparallelshiftofthecorrespondingmRNAsfromthepolysomaltothemonosomalandfreemRNAfractions.Theseresultsindicatethatmostoftheearlydecreasesinthesynthesisofproteinsweretranslationallyregulated.Incontrast,81%oftheproteinswhichincreasedinsynthesisand71%oftheproteinsthatwereinduceddenovowereregulatedatthelevelofmRNAproduction.ExperimentswithdifferentiationdefectivemutantshaveshownthattheywereblockedbothatthelevelofmRNAproductionandmRNAtranslation.Thedatawiththesemutantshavesuggestedthatthereweredifferentsubsetsoftranslationallyregulatedproteinswhichwereseparatelyregulated.ThetranslationalblocksforseveralproteinsinthesemutantcloneshavealsomadeitpossibletoidentifyadditionaltranslationalsitesofregulationforproteinchangesthatwerecontrolledatthelevelofmRNAproductionduringnormaldifferentiation.TheresultsindicatethattranslationalregulationmaypredominantlyhaveadifferentfunctionincelldifferentiationthanregulationbymRNAproduction,andthatdifferentiation-defectivemutantscanbeblockedateitherlevel.

[学科分类] 生物科学（综合）