Identification of RBM3 as a novel regulator of human fetal hemoglobin expression

Sickle cell disease (SCD) and β-thalassemia are autosomal recessive genetic disorders caused by abnormal synthesis of β-globin chains. Reversing the transition of fetal-to-adult hemoglobin after birth shows great potential in the treatment of these disorders. Here, we identified an RNA-binding protein, RBM3, as a novel HbF (HbF, α₂γ₂) suppressor. Specifically, downregulation of RBM3 in the erythroid progenitor cell line HUDEP-2 robustly induced γ-globin expression at both the mRNA and protein levels, with a slight impact on β-globin levels. Conversely, overexpression of RBM3 in HUDEP-2 cells led to a marked reduction in γ-globin expression. According to the previous study, we introduced specific inhibitors targeting FAK and Src to block RBM3 protein synthesis. Surprisingly, treatment with the FAK inhibitor resulted in a significant increase in γ-globin expression, whereas the Src inhibitor had little effect. Mechanistically, RBM3 depletion accelerated the degradation of BCL11A protein at the post-transcriptional level, without affecting its mRNA stability. Moreover, RBM3 silencing restricted the overall translation efficiency while selectively lifting the ratio of γ-globin mRNA in polysomes. Importantly, downregulation of RBM3 did not impair erythropoiesis progression, suggesting a safe and effective therapeutic strategy for SCD and β-thalassemia. Our findings identify RBM3 as a negative regulator of HbF expression and reveal it as a novel molecular target for modulating the fetal-to-adult hemoglobin switch, holding great promise for the treatment of SCD and β-thalassemia.