Iron induced eukaryotic initiation factor/ mRNA binding affinity change

Abstract

Cellular iron metabolism is regulated by expression of iron responsive element (IRE) containing‐mRNA to control iron related protein levels (e.g. ferritin). The cytoplasmic iron regulatory proteins, IRPs, bind to iron response element (IRE) mRNAs, which represses IRE‐mRNA translation. IRE‐RNA binds to Fe2+ (in the absence of oxygen to prevent insoluble oxides) and the iron metabolite change the IRE‐RNA conformation resulting in decreased IRP (repressor) binding and increased eIF4F (enhancer) binding. eIF4F binds IRE‐RNA with high affinity (Kd=39.8±5.6nM) and further eIF4F: IRP competitively binds to IRE‐mRNA. eIF4G, a component of eIF4F, is also found to bind to the IRE‐RNA. The eIF4G middle domain binding affinity to the ferrtin IRE is lower than eIF4F and IRE binding doses not respond to metal concentration changes. While the eIF4G middle domain contains the RNA binding domain, additional protein domains and/or initiation factors (e.g. eIF4A, eIF4E) are necessary for functioning of the iron metabolite IRE‐ribo regulator.This work is supported in whole or in part, by National Institutes of Health Grants DK20251 (D.J.G. and E.C.T.) and National Science Foundation Grant MCB 0814051 (D.J.G.)