Hydroxyurea-inducible SAR1 gene acts through the Giα/JNK/Jun pathway to regulate γ-globin expression

Area of Science:

• Molecular Biology
• Hematology
• Pharmacology

Background:

• Hydroxyurea (HU) is a standard treatment for β-hemoglobinopathies, increasing fetal hemoglobin (HbF).
• The precise molecular pathways of HU's action remain incompletely understood.
• Previous work implicated the SAR1 gene in HU's effects on erythroid cells.

Purpose of the Study:

• To elucidate the molecular mechanisms of HU-induced fetal hemoglobin (HbF) production.
• To investigate the role of the SAR1 gene in regulating γ-globin expression and cellular responses to HU.
• To identify potential therapeutic targets for β-hemoglobin disorders.

Main Methods:

• Utilized K562 and CD34+ cell lines.
• Investigated nuclear factor-κB (NF-κB) binding to the SAR1 promoter.
• Employed gene silencing (siRNA) for SAR1 and Giα.
• Assessed γ-globin induction and HbF levels.
• Analyzed cell-cycle progression (S-phase arrest) and apoptosis.
• Examined c-Jun N-terminal kinase (JNK)/Jun phosphorylation.
• Performed coimmunoprecipitation assays to detect protein interactions.

Main Results:

• HU stimulates NF-κB interaction with the SAR1 promoter, upregulating SAR1 transcription.
• SAR1 silencing diminishes both basal and HU-induced HbF production.
• SAR1 is crucial for HU-mediated S-phase arrest and apoptosis in K562 cells.
• Giα/JNK/Jun pathway activation is essential for SAR1-mediated γ-globin and HbF induction.
• SAR1 physically associates with Giα2 and Giα3 proteins.

Conclusions:

• HU induces SAR1 expression, which activates γ-globin and HbF production via the Giα/JNK/Jun pathway.
• SAR1 plays a critical role in mediating HU's effects on erythroid differentiation and cell cycle.
• SAR1 represents a promising novel therapeutic target for treating β-hemoglobin disorders like sickle cell disease and thalassemia.