The stability of human β-globin mRNA is dependent on structural determinants positioned within its 3′ untranslated region

Abstract

Controls that act at both transcriptional and posttranscriptional levels assure that globin genes are highly expressed in developing erythroid cells. The extraordinary stabilities of α- and β-globin mRNAs permit globin proteins to accumulate to substantial levels in these cells, even in the face of physiologic transcriptional silencing. Structural features that determine α-globin mRNA stability have recently been identified within its 3′UTR; in contrast, the structural features that determine β-globin mRNA stability remain obscure. The current study begins to define the structural basis for β-globin mRNA stability. Two tandem antitermination mutations are introduced into the wild-type human β-globin gene that permit ribosomes to read into the 3′UTR of the encoded β-globin mRNA. The readthrough β-globin mRNA is destabilized in cultured erythroid cells, indicating that, as in human α-globin mRNA, an unperturbed 3′UTR is crucial to maintaining mRNA stability. Additional experiments show that the β-globin and α-globin mRNA 3′UTRs provide equivalent levels of stability to a linked β-globin mRNA coding region, suggesting a parallel in their function(s). However, destabilization of the antiterminated β-globin mRNA is independent of active translation into the 3′UTR, whereas translation into the α-globin mRNA 3′UTR destabilizes a linked β-globin coding region in a translationally dependent manner. This indicates that the α- and β-globin 3′UTRs may stabilize linked mRNAs through distinct mechanisms. Finally, it is shown that neither of the two mutations that, in combination, destabilize the β-globin mRNA have any effect on β-globin mRNA stability when present singly, suggesting potential redundancy of stabilizing elements. In sum, the current study shows that a functionally intact β-globin mRNA 3′UTR is crucial to maintaining β-globin mRNA stability and provides a level of stability that is functionally equivalent to, although potentially mechanistically distinct from, the previously characterized α-globin mRNA 3′UTR stability element. © 1996 by The American Society of Hematology.