Increased fetal hemoglobin (Hb F; α2γ2) production in adults can ameliorate the clinical severity of sickle cell disease and β-thalassemia major. Thus, understanding the regulation of γ-globin gene expression and its silencing in adults has potential therapeutic implications. We studied a father and son in an Iranian-American family who had elevated Hb F levels and found a novel T-to-G transversion at nucleotide (nt) -567 of the HBG2 promoter. This mutation alters a GATA-1 binding motif to a GAGA sequence located within a previously identified silencing element. DNA-protein binding assays showed that the GATA motif of interest is capable of binding GATA-1 transcription factor in vitro and in vivo. Truncation analyses of the HBG2 promoter linked to a luciferase reporter gene revealed a negative regulatory activity present between nt -675 and -526. In addition, the T-to-G mutation at the GATA motif increased the promoter activity by two- to threefold in transiently transfected erythroid cell lines. The binding motif is uniquely conserved in simian primates with a fetal pattern of γ-globin gene expression. These results suggest that the GATA motif under study has a functional role in silencing γ-globin gene expression in adults. The T-to-G mutation in this motif disrupts GATA-1 binding and the associated repressor complex, abolishing its silencing effect and resulting in the up-regulation of γ-globin gene expression in adults. Copyright

doi.org/10.1128/MCB.00071-08, hdl.handle.net/1765/29467
Molecular and Cellular Biology
Erasmus MC: University Medical Center Rotterdam

Chen, Z., Luo, H. Y., Basran, R., Hsu, T. H., Mang, D., Nuntakarn, L., … Chui, D. H. K. (2008). A T-to-G transversion at nucleotide -567 upstream of HBG2 in a GATA-1 binding motif is associated with elevated hemoglobin F. Molecular and Cellular Biology, 28(13), 4386–4393. doi:10.1128/MCB.00071-08