B-Thalassemia Mutation at -90C -, T Impairs the Interaction of the Proximal CACCC Box With Both Erythroid and Nonerythroid Factors

The β-globin gene is essential for hemoglobin synthesis, and its promoter's proximal CACCC box plays a critical role in regulating this process. This study investigates the effects of a -90C → T mutation within this box, identified in β-thalassemia carriers of Portuguese and Jewish descent. Our findings indicate that this mutation significantly diminishes the binding affinity of the erythroid Krüppel-like factor (EKLF) to the CACCC box, disrupting normal transcriptional regulation. Using in vitro assays and transient expression studies in HeLa cells, we demonstrate that this mutation leads to a marked reduction in reporter gene transcription, underscoring the mutation's detrimental impact on β-globin expression. This work highlights the crucial interaction between transcription factors and promoter elements in maintaining normal β-globin levels, providing insights into the molecular mechanisms of β-thalassemia and potential targets for therapeutic intervention.