The +1,506 (A>C) mutation in the 3' untranslated region affects β-globin expression.

The 3' untranslated region (3'UTR) is known to be important to mRNA stability but the stabilization mechanism on the β-globin gene is not fully elucidated. We speculated in our previous report that +1,506 (A>C) mutation (HGVS nomenclature: *32A>C) on the β-globin 3'UTR causes β-thalassemia (β-thal) in order to destabilize the mRNA. To investigate further, we studied the expression efficiency for the mutation with a luciferase assay. We made recombinant pGL4.74 vectors in which the luciferase 3'UTR was replaced with the wild-type and mutant 3'UTR of the β-globin gene. For a comparison experiment, recombinant vectors were made not only for this mutation but also six other mutations in the β-globin 3'UTR which bring about β-thal or affect mRNA stability. The +1,506 mutation led to a 30.0% lower protein expression than normal in this assay. We concluded that this mutation destabilizes mRNA and consequently decreases the β-globin amount to finally cause β-thal. Our study highlights the crucial area of β-globin 3'UTR for protein expression.