Identification of novel genes containing an Iron Responsive Element

Mayka Sanchez

At present, only a small number of mRNAs that are regulated by the iron regulatory protein (IRP)/ iron-responsive element (IRE) system is known. To reveal the scope of this regulatory network and to identify novel IRE containing mRNAs we integrated biochemical, biocomputational and microarray-based experimental approaches. IRP/IRE mRNPs were immunoselected and their mRNA composition was analyzed using an IronChip microarray enriched for genes predicted computationally to contain IRE-like motifs (Sanchez et al., Nat Protoc 2(8):2033-2042, 2007). Using this approach we discovered two novel and functional IRE containing mRNAs: (1) CDC14A, a gene involved in cell cycle control (Sanchez et al., J Biol Chem. 281:22865-74, 2006) and (2) HIF2alpha; a hypoxia-regulated transcription factor controlling erythropoietin (EPO) expression.  Because EPO stimulates erythropoiesis, the major iron utilization pathway, these results uncover a regulatory link that permits feedback control between iron availability (that regulates IRP binding) and iron utilization (Sanchez et al., Nature Struct Mol Biol. 14:420-6, 2007). Indeed, although mutations in the IRE of
HIF2alpha have not been found in familial erythrocytosis cases (Percy et al., Blood 2007; 110 (7):2776-2777), coding mutations have been recently identified in those families (Percy et al., N Engl J Med. 2008; 358(2):162-8) supporting the idea that HIF2alpha plays a central role in regulating erythropoietin production.

Project related publications:

• Sánchez M, Galy B, Hentze MW., and Muckenthaler MU. Identification of target mRNAs of regulatory RNA binding proteins using mRNP immunopurification and microarrays. Nature Protocols  2(8):2033-2042; 2007
• Sánchez M, Galy B, Dandekar T, Bengert P, Vainshtein Y, Stolte J, Muckenthaler MU, and Hentze MW. Iron regulation and the cell cycle: Identification of an Iron-Responsive Element in the 3’- unstranslated region of human CDC14A mRNA by a refined microarray-based screening strategy. Journal of Biological Chemistry 281(32):22865-74.; 2006
• Sánchez M, Galy B, Muckenthaler MU, and Hentze MW. Iron-regulatory proteins limit hypoxia-inducible factor 2a expression in iron deficiency. Nature Structural & Molecular Biology 14(5):420-426; 2007
• Percy MJ*, Sánchez M*, Swierczek S*, McMullin MF, Mojica-Henshaw MP, Martina U Muckenthaler MU, Prchal JT, and Hentze MW. Is congenital Secondary Erythrocytosis/Polycythemia  caused by activating mutations within the HIF-2aplha iron responsive element? Blood  110(7):2776-2777; 2007 (* equal  contribution authors)