Binding of a Cytosolic Protein to the Iron-Responsive Element of Human Ferritin Messenger RNA

The human ferritin H chain messenger RNA contains a specific iron-responsive element (IRE) in its 5$^{\prime}$ untranslated region, which mediates regulation by iron of ferritin translation. An RNA gel retardation assay was used to demonstrate the affinity of a specific cytosolic binding protein for the IRE. A single-base deletion in the IRE eliminated both the interaction of the cytoplasmic protein with the IRE and translational regulation. Thus, the regulatory potential of the IRE correlates with its capacity to specifically interact with proteins. Titration curves of binding activity after treatment of cells with an iron chelator suggest that the factor acts as a repressor of ferritin translation.