Dissertations, Theses, and Capstone Projects

Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biochemistry

Advisor

Dixie J. Goss

Subject Categories

Biochemistry

Keywords

eIF4F, IRE, Iron, IRP1, mRNA translation

Abstract

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. Fe2+ increases eIF4F/IRE-RNA binding affinity, which outcompetes IRP binding. 4. Fe2+ induces an IRE-RNA conformation change leading to changes in binding affinity with eIF4F and IRP. 5. M7GTP 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 (Fe2+) induces IRE-RNA conformation change to decrease inhibitor protein (IRP) binding and increase activator protein (eIF4F) binding, indicating IRE-RNA act as a riboregulator.

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