Recombinant erythroid Kruppel-like factor fused to GATA1 up-regulates delta- and gamma-globin expression in erythroid cells.

摘要

The beta-hemoglobinopathies sickle cell disease and beta-thalassemia are among the most common human genetic disorders worldwide. Hemoglobin A2 (HbA2, alphadelta) and fetal hemoglobin (HbF, alphagamma) both inhibit the polymerization of hemoglobin S, which results in erythrocyte sickling. Expression of erythroid Kruppel-like factor (EKLF) and GATA1 is critical for transitioning hemoglobin from HbF to hemoglobin A (HbA, alphabeta) and HbA2. The lower levels of delta-globin expression compared with beta-globin expression seen in adulthood are likely due to the absence of an EKLF-binding motif in the delta-globin proximal promoter. In an effort to up-regulate delta-globin to increase HbA2 expression, we created a series of EKLF-GATA1 fusion constructs composed of the transactivation domain of EKLF and the DNA-binding domain of GATA1, and then tested their effects on hemoglobin expression. EKLF-GATA1 fusion proteins activated delta-, gamma-, and beta-globin promoters in K562 cells, and significantly up-regulated delta- and gamma-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 delta-globin promoter was confirmed by chromatin immunoprecipitation assay. Our studies demonstrate that EKLF-GATA1 fusion proteins can enhance delta-globin expression through interaction with the delta-globin promoter, and may represent a new genetic therapeutic approach to beta-hemoglobinopathies.