Iron regulates mRNA translation initiation through RNA iron responsive element (IRE)

Iron regulates mRNA translation initiation through RNA iron responsive element (IRE) By Jia Ma Advisor: Professor Dixie J. Goss The non-coding IRE-RNA structure, a 30 nt stem loop structure, regulates synthesis of proteins in iron trafficking, cell cycling, and nervous system function. IRE-RNA binding with iron regulatory protein (IRP) proteins inhibits ribosome accessing mRNA. Increasing iron concentration decreases IRP binding with IRE-RNA. Previous models of IRE-mRNA translation regulation concentrate on Fe-S binding to IRP and IRP degradation after release from IRE-RNA. These models lack information on the details of decreasing IRE-RNA/IRP protein binding with iron concentration elevation. This research shows 1. Eukaryotic initiation factor 4F (eIF4F) binds to IRE-RNA with high affinity and works as a positive control element in mRNA translation. 2. eIF4F, IRP competitively bind to IRE-RNA. 3. Fe 2+ increases eIF4F/IRE-RNA binding affinity, which outcompetes IRP binding. 4. Fe 2+ induces an IRE-RNA conformation change leading to changes in binding affinity with eIF4F and IRP. 5. M 7 GTP cap doesn’t affect eIF4F or IPR1 binding with 73 nt of the 5’ noncoding region mRNA which includes the IRE 6. eIF4F/IRE-RNA has a much longer life time than IRP1/IRE-RNA which suggests both kinetics and stability of the complexes are important. 7. eIF4G, a subunit of eIF4F, binds to IRE-RNA without other subunits. A novel regulatory mechanism is proposed where metabolic iron (Fe 2+ ) induces IRE-RNA conformation change to decrease inhibitor protein (IRP) binding and increase activator protein (eIF4F) binding, indicating IRE-RNA act as a riboregulator.