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Chapter 15: Problem 27

Describe how the binding of iron regulatory protein to an IRE affects the mRNAs for ferritin and the transferrin receptor. How does iron \(\left(\mathrm{Fe}^{3+}\right)\) influence this process?

Short Answer

Expert verified
In iron homeostasis, IRP binds to IREs on mRNAs of ferritin and transferrin receptor. In low iron levels, this binding inhibits translation of ferritin mRNA and promotes translation of transferrin receptor mRNA, reducing iron storage and enhancing iron uptake, respectively. In high iron levels, iron binds to IRP preventing it from binding to IRE; resulting in increased iron storage (Ferritin synthesis) and decreased uptake (degradation of transferrin receptor mRNA).

Step by step solution

01

The Role of Iron Regulatory Protein (IRP)

Iron Regulatory Protein (IRP) binds to Iron Responsive Elements (IRE) located on mRNAs of ferritin and the transferrin receptor. The binding of IRP to IREs has different effects on each mRNA, based on the location of the IRE within the mRNA.
02

Impact on Ferritin mRNA

The IRE is located at the 5' untranslated region (UTR) of the ferritin mRNA. When there's low iron (Fe3+) concentration, IRP binds to the IRE of ferritin mRNA, preventing translation and thus inhibiting ferritin synthesis. Ferritin is responsible for storing iron, so this mechanism helps to prevent excess iron storage when iron levels are already low.
03

Impact on Transferrin Receptor mRNA

The IREs are located at the 3' UTR of the transferrin receptor mRNA. When iron (Fe3+) concentration is low, IRP binding to these IREs stabilizes the mRNA, promoting synthesis of transferrin receptors. These receptors increase iron uptake from the bloodstream, helping to increase cellular iron levels.
04

The Influence of Iron (Fe3+)

When there are high concentrations of iron (Fe3+) in the cell, the iron binds to IRP causing a conformational change that prevents its binding to IRE. This results in the translation of ferritin mRNA (increasing iron storage) and degradation of transferrin receptor mRNA (reducing iron uptake). Thus, iron levels directly influence the IRP-IRE interaction and subsequently, cellular iron homeostasis.

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Most popular questions from this chapter

Is each of the following statements true or false? A. An enhancer is a type of regulatory element. B. A core promoter is a type of regulatory element. C. Regulatory transcription factors bind to regulatory elements. D. An enhancer may cause the down regulation of transcription.

What is an insulator? Describe two different ways that insulators may exert their effects.

Histones are thought to be displaced as RNA polymerase is transcribing a gene. What would be the potentially harmful consequences if histones were not put back onto a gene after RNA polymerase had passed?

Discuss the structure and function of regulatory elements. Where are they located relative to the core promoter?

Transcription factors usually contain one or more motifs that play key roles in their function. What is the function of the following motifs? A. Helix-turn-helix B. Zinc finger C. Leucine zipper
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