In human reticulocytes, the critical balancing of α- and β-globin synthesis may be controlled in part by differential translation of the three major adult globin messenger RNAs (mRNAs), α1, α2, and β. In this study, we determined, as a parameter of translational efficiency, the relative ribosome loading of these three mRNAs. Using oligonucleotide probes specific for the α1- and α2-globin mRNAs, we find that these two mRNAs have identical translational profiles. Their distribution contrasts with that of β-globin mRNA, which is present on heavier polyribosomes and is less prevalent in pre-80S messenger ribonucleoprotein fractions. The relative distribution of α- vs. β-globin mRNA is consistent with more efficient β-globin translation. In contrast, the parallel distributions of α1- and α2-globin mRNAs suggests they are translated with equal efficiencies. Considering the relative concentrations of the two α-globin mRNAs in normal reticulocytes, this result of predicts a dominant role for the α2-globin locus in human α-globin expression.
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