Figure 7.

IRE sequences from known proteins involved in iron metabolism. IRE sequences can be localized at 5′ or 3′. In the absence of iron, IRP1 binds the sequences located at 5′ of blocking the translation of the RNA. Ferritin, ALAS and Ferroportin are proteins involved in iron storage, heme synthesis and iron export, respectively. In the same situation, IRP binding to 3′ sequences, stabilizes the RNA promoting the translation of, for example, Transferrin receptor, involved in iron import. In the opposite situation, with high iron levels, IRP binds to iron, which unbinds the IREs, thus promoting translation of Ferritin, ALAS and Ferroportin and leading to Transferrin receptor RNA decay, which is no more protected by IRP1. Green nucleotides form the six-nucleotide apical loop of IRE.