Mechanism of the cAco/IRP1 balance and the binding of IRP1 with IRE mRNA. When the level of iron in the cell is high, IRP1 principally exists in the reduced state with a complete ISC, which allows the protein to carry out its enzymatic function. When the level of iron in the cell is low, the interaction of IRP1 with the IRE located in the 5′ UTR of ferritin mRNA guides to inhibition of the translation of these mRNA, and down-expression of ferritin and ultimately to the increase in the free-iron level. At the same time, the binding of IRP1 on the IRE located in the 3′ UTR of the mRNA encoding the transferrin receptor guides the stabilization of this mRNA and, consequently, an increase in its translation, which allows for the intensification of the process of iron uptake.