 Iron regulatory proteins 1 and 2, IRP1 and IRP2, bind to iron responsive elements, IREs, in the untranslated regions of target mRNAs, which controls the expression of genes involved in iron, oxygen and energy metabolism. IRP1 acts as either an RNA binding protein or a cytosolic echinotase, whereas IRP2 only works as an RNA binding protein. Early experiments in cultured cells showed that IRPs play a critical role in regulating cellular iron metabolism. Recent studies in mouse models have revealed additional roles for IRPs in the context of systemic iron homeostasis. For example, IRP1 has been shown to be essential for the proper development of erythrocyte precursors, while IRP2 plays a major role in the regulation of iron uptake and heme biosynthesis in these cells. Furthermore, targeted disruption of either IRP1 or IRP2 in mice results in distinct phenotypes, such as polycythemia and pulmonary hypertension in IRP1 knockout mice and microsit. This article was authored by Nicole E. Wilkinson and Kostas E. Pantopoulos. We are article.tv, links in the description below.