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Abstract

The β-hemoglobinopathies sickle cell disease and β-thalassemia are among the most common human genetic disorders worldwide. Hemoglobin A2 (HbA2, α2δ2) and fetal hemoglobin (HbF, α2γ2) both inhibit the polymerization of hemoglobin S that results in erythrocyte sickling. Expression of erythroid Kruppel-like factor (EKLF) and GATA1 is critical for transitioning hemoglobin from HbF to hemoglobin A (HbA, α2β2) and HbA2. The lower levels of δ-globin expression compared with β-globin expression seen in adulthood are likely due to the absence of an EKLF-binding motif in the δ-globin proximal promoter. In an effort to upregulate δ-globin to increase HbA2 expression, we created a series of EKLF-GATAl fusion constructs composed of the transactivation domain of EKLF and the DNA-binding domain of GATAl and then tested their effects on hemoglobin expression. EKLF-GATAl fusion proteins activated δ-, γ-, and β-globin promoters in K562 cells, and significantly upregulated δ- and γ-globin RNA transcript and protein expression in K562 and/or CD34+ cells. The binding of EKLF-GATA1 fusion proteins at the GATA1 consensus site in the δ-globin promoter was confirmed by chromatin immunoprecipitation assay. Our studies demonstrate that EKLF-GATA1 fusion proteins can enhance δ-globin expression through interaction with the δ-globin promoter, and may represent a new genetic therapeutic approach to β-hemoglobinopathies.

  • Submitted July 9, 2010.
  • Accepted December 17, 2010.