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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.