Eukaryotic initiation factor 2 alpha phosphorylation mediates fetal hemoglobin induction through a post-transcriptional mechanism

Strategies to increase fetal hemoglobin (HbF) levels can ameliorate symptoms and improve the lives of beta-hemoglobinopathy patients. Although most studies have focused on induction of gamma-globin gene expression as an approach to induce HbF, we hypothesized that post-transcriptional regulation of HbF plays an underappreciated yet important role in controlling HbF levels. In the present study, we investigated whether increasing eukaryotic initiation factor 2 alpha (eIF2 alpha) phosphorylation, a key regulator of protein translation, could enhance HbF post-transcriptionally in human primary erythroid cells. Initial analysis using a known inhibitor of eIF2 alpha dephosphorylation, salubrinal, revealed that elevated eIF2 alpha phosphorylation enhanced HbF production without changing globin gene expression, proliferation, or cell differentiation. These results were further supported by the post-transcriptional induction of HbF by other pharmacologic activators of the eIF2 alpha pathway and by genetic inactivation of the negative regulators, GADD34 and CReP. Additionally, we found that this novel mechanism of increasing HbF could be combined with clinically relevant transcriptional activators of gamma-globin gene expression to additively enhance HbF. Taken together, these findings identify eIF2 alpha phosphorylation as a post-transcriptional regulator of HbF induction that may be pharmacologically targeted, either alone or in combination, in beta-hemoglobinopathy patients.