Figure 2.

Differential iron- and oxygen-dependent regulation of IRP activity.

Notes: In iron-depleted cells, IRP1 (A) and IRP2 (B) bind to IRE, hence inhibiting mRNA translation or degradation, whereas high iron availability converts IRP1 into the inactive apoform and promotes IRP2 degradation, thus resulting in loss of IRP-binding activity and an opposite effect on gene expression. Hypoxia has a different effect on the two IRPs: inhibition of IRP1-binding activity and stabilization of IRP2.

Abbreviations: IRP, iron regulatory protein; IRE, iron responsive element.