The asynchrony of γ- and β-chain synthesis during human erythroid cell maturation: III. γ- and β-mRNA in immature and mature erythroid clones☆☆☆

[摘要] GlobinchainsynthesisandtheaccumulationofglobinmRNAswereexaminedinimmatureandmatureerythroidclonesproducedbycirculatingerythroidprogenitors(burstformingunits)oftheneonate.Immaturecloneswerecomposedofearlyerythroblastscontaininglittlehemoglobinwhilethematureclonesappearedatlaterdaysincultureandwerecomposedofwellhemoglobinizederythroblasts.Therewasastrikinglyhigherγγ+βchainsyntheticratiointhenonhemoglobinizedclonescomparedtotheirfullyhemoglobinizedcounterparts.RNAwaspreparedfromimmatureandfrommaturecoloniesandα-,β-,andγ-mRNAcontentwasmeasuredbysolutionhybridizationtoα-,β-,andγ-[32P]DNAprobes.Theprobesweresensestrandcodingglobinsequencespreparedfromchimericplasmidsbyisolationofnick-translated[32P]DNAwhichannealedtocordbloodoradultreticulocyteglobinmRNA.Inthreeexperiments,theγγ+βmRNAratiosinimmatureburstswere0.58,0.55,and0.70whileratiosinthematurecounterpartswere0.21,0.38,and0.45.TherewasexcellentagreementbetweenglobinchainsyntheticratiosandglobinmRNAratiossuggestingthattheglobinmRNAspeciespresentinimmatureandmatureerythroblastsaretranslatedwithsimilarefficiencies.Thesedatasuggestthatthematurationalmodulationofnon-α-globinchainsynthesisisnotundertranslationalcontrol.TheabsolutemRNAvalues(moleculespercell)consistentlyshowedsimilaramountsofγ-mRNApercellinboththeimmatureandthematurecellpopulations.Themoststrikingeffectofmaturationwastheincreaseintheamountofβ-mRNApercell(andtheconcomitantincreaseinα-mRNA).Thesedata,togetherwithpreviouslypublishedresultsonglobinchainbiosynthesissuggestthatthematurationrelateddeclineinγ/γ+βchainratiosisduetoasynchronyinγ-andβ-mRNAaccumulation.Apparentlyγ-mRNAaccumulatesearly(atorneartheonsetofglobinsynthesis)andtheaccumulationofβ-mRNAfollows.ThisasynchronyinmRNAaccumulationresultsinadeclineintherelativesynthesisoffetalhemoglobinduringmaturation.

[学科分类] 生物科学（综合）