Structure and expression of a cloned β°thalassaemic globin gene

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Abstract
We have cloned the single β-globin gene from an Italian patient who is a double heterozygote for (β°/δβ° thalassaemia. RNA isolated from nucleated red cells from this patient can be translated in vitro to give detectable levels of Aγ- Gγ and α-globin, but no β-globin. S 1 -mapping transcription studies show that β-globin mRNA is present at about 1–3 % of the level of α- and γ-globin mRNA. In addition, the expression of this gene has been studied by reversed genetics. SV40-plasmid-β°-globin gene recombinants have been transfected into Hela cells and analysed for β-globin mRNA. In contrast to the results obtained with mRNA isolated directly from the blood of this patient, in the transfected Hela cells the same level of β-globin mRNA is seen for the β° thalassaemic globin gene and for a normal β-globin gene. To elucidate the nature of the lesion, the entire DNA sequence of the β-globin gene of this patient has been determined. The sequence shows that this gene contains a termination codon at position 39 (CAG → UAG). Otherwise, there is a remarkable conservation of the entire DNA sequence.