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c-fos mRNA instability determinants present within both the coding and the 3' non coding region link the degradation
J L Veyrune1, S Carillo, A Vié
1Institut de Génétique Moléculaire de Montpellier, UMR 9942, CNRS BP 5051, France.
Abstract:
The instability of oncogenic mRNA such as c-fos mRNA is controlled in cis by sequences present in both the coding and the 3' untranslated regions (3'UTR). The latter contains AU-rich elements (ARE) which, depending on the cellular context, mediate either their rapid degradation or inhibit their translation. These observations, along with the known increase of the life spans of many unstable mRNA promoted by inhibitors of protein synthesis, raise the possibility that both processes are linked. To investigate further the putative involvement of translation in both coding region and ARE-mediated rapid decay of c-fos mRNA, we designed an expression vector based on the use of the ferritin mRNA iron regulatory element (IRE). The latter structure links translation to intracellular iron concentration when inserted at the proper location within the 5'UTR. Rapid degradation of a beta-globin/c-fos 3'UTR construct was prevented by Desferrioxamine, an iron chelator, and facilitated by ferric ammonium citrate or hemin, while stability of other mRNAs not containing the IRE or the ARE were unchanged. The same conclusion was reached when the stability of a c-fos mRNA devoid of ARE was assessed in function of iron availability.
Insights
This study reveals that iron levels regulate oncogenic mRNA stability. Iron availability controls the decay rate of c-fos mRNA, linking translation and degradation pathways.
Area of Science:
- Molecular Biology
- Gene Regulation
- mRNA Stability
Background:
- Oncogenic mRNAs like c-fos are unstable, controlled by cis-acting elements in coding and 3' untranslated regions (3'UTR).
- AU-rich elements (ARE) in the 3'UTR mediate mRNA degradation or translational repression.
- The link between translation and mRNA decay, particularly ARE-mediated decay, requires further investigation.
Purpose of the Study:
- To investigate the role of translation in coding region and ARE-mediated rapid decay of c-fos mRNA.
- To explore the potential involvement of iron regulation in mRNA stability.
Main Methods:
- Designed an expression vector utilizing the ferritin mRNA iron regulatory element (IRE) to link translation to iron concentration.
- Assessed the stability of a beta-globin/c-fos 3'UTR construct under varying iron conditions (Desferrioxamine, ferric ammonium citrate, hemin).
- Evaluated the stability of c-fos mRNA lacking ARE in response to iron availability.
Main Results:
- Iron availability modulated the degradation rate of the beta-globin/c-fos 3'UTR construct; iron chelation prevented degradation, while iron addition facilitated it.
- mRNA constructs lacking the IRE or ARE showed unchanged stability, indicating specificity of the observed effect.
- c-fos mRNA stability was directly influenced by intracellular iron concentration, even in the absence of ARE.
Conclusions:
- Translation is involved in both coding and ARE-mediated rapid decay of c-fos mRNA.
- Intracellular iron concentration is a key regulator of oncogenic mRNA stability.
- The ferritin IRE system provides a novel tool to study the interplay between translation and mRNA decay.