Structural and Functional Insights on an Uncharacterized Aγ-Globin-Gene Polymorphism Present in Four β(0)-Thalassemia Families with High Fetal Hemoglobin Levels

Several DNA polymorphisms have been associated with high production of fetal hemoglobin (HbF), although the molecular basis is not completely understood. In order to identify and characterize novel HbF-associated elements, we focused on five probands and their four families (from Egypt, Iraq and Iran) with thalassemia major (either b0-IVSII-1 or b0-IVSI-1) and unusual HbF elevation ([98 %), congenital or acquired after rejection of bone marrow transplantation, suggesting an anticipated favorable genetic background to high HbF expression. Patient recruitment, genomic DNA sequencing, western blotting, electrophoretic mobility shift assays, surface plasmon resonance (SPR) biospecific interaction analysis, bioinformatics analyses based on docking experiments. A polymorphism of the Ac-globin gene is here studiedin four families withb0-thalassemia (b0-IVSII-1 andb0-IVSI-1) and expressing unusual high HbF levels, congenital or acquired after rejection of bone marrow transplantation. This (G to A) polymorphism is present at position +25 of the Acglobin genes, corresponding to a 50 -UTR region of the Acglobin mRNA and, when present, is physically linked in chromosomes 11 of all the familiar members studied to the XmnI polymorphism and to the b0-thalassemia mutations. The region corresponding to the +25(G to A) polymorphism of the Ac-globin gene belongs to a sequence recognized by DNAbinding protein complexes, including LYAR (Ly-1 antibody reactive clone), a zinc-finger transcription factor previously proposedto beinvolvedin down-regulation ofthe expression of c-globin genes in erythroid cells. We found a novel polymorphism of the Acglobin gene in four families with b0-thalassemia and high levels of HbF expression. Additionally, we report evidence suggesting that the Ac-globin gene +25(G toA) polymorphism decreases the efficiency of the interaction between this sequence and specific DNA binding protein complexes.