Schematic representation of how cellular iron status controls erythropoietin production through the IRP1-HIF-2α axis. In this scheme, the cell of interest is a specialized interstitial renal fibroblast that responds to tissue hypoxia by producing erythropoietin. The IRP1/IRE-mediated translational control primarily influences HIF-2α synthesis: the final impact on erythropoietin production depends also on oxygen tension (see text). Professional illustration by Alice Y. Chen.