Mayka Sanchez, PhD
Director's Research
EMBL
Meyerhofstrasse 1
D-69117 Heidelberg
Germany
Phone: +49-6221-387-8164 Fax: +49-6221-387-8518 email: sanchez@embl.de
Mayka Sanchez, PhD |
|
Searching
for new IRE containing genes
(IRE = iron response element)
Iron is an essential nutrient required by almost every
organism. Its capacity to exchange electrons makes it essential for fundamental cell
functions, like DNA synthesis, transport of oxygen and the respiratory chain. However,
it is also a potential catalyst for chemical reactions involving free-radical formation
and subsequent cell damage. Therefore, cellular iron levels have to be carefully
regulated inside the cells.
Intracellular iron homeostasis is mainly regulated postranscriptionally by the interaction
of iron-regulatory proteins (IRP-1 and IRP-2) with non-coding sequences termed iron-responsive
elements (IREs) present in iron metabolism-related genes, such
as transferrin receptor, L- and H-ferritins, e-ALAS, ferroportin and divalent cationic
transporter 1 (Fig. 1).
Fig.1. IRE structures found in mRNA coding for iron metabolism proteins.
In response to fluctuations in the level of the labile iron pool, IRPs bind to IREs. Depending on the IRE location, they regulate gene expression by different mechanisms. IRP binding to an IRE in the 5' untranslated region (UTR), as is the case in the ferritin mRNA, mediates translational repression (Muckenthaler M, Gray NK, Hentze MW. IRP-1 binding to ferritin mRNA prevents the recruitment of the small ribosomal subunit by the cap-binding complex eIF4F. Mol Cell. 1998 2:383-8). IRP binding to several IREs in the 3'UTR of the transferrin receptor mRNA enhances the mRNA half-life by protecting it from the action of RNases (Schlegl J, Gegout V, Schlager B, Hentze MW, Westhof E, Ehresmann C, Ehresmann B, Romby P. Probing the structure of the regulatory region of human transferrin receptor messenger RNA and its interaction with iron regulatory protein-1. RNA. 1997 3:1159-72). Therefore, the IRPs act as key regulators of cellular iron homoeostasis as a result of the expression control of a number of iron metabolism-related genes (Fig. 2).
Fig. 2. The IRE/IRP regulatory system.
To fully understand the complex interplay between players of iron metabolism additional
proteins may exist and due to the important role of the IRE/IRP regulatory network,
it is likely that some of these undiscovered genes could contain an IRE.
My work is focus on the identification of these new genes containing the IRE motif.
To identify novel IRE containing genes we developed an innovative strategy that combines
immunoprecipitations, microarray technology and biocomputational approaches. We isolated
IRE/IRP mRNA-protein complexes by immunoprecipitation experiments and subsequently
identified these mRNAs by genome-wide microarray analysis (Fig. 3). In a complementary
approach IRE-containing mRNAs were selected by biocomputational methods from Genome
databases, spotted on the IronChip cDNA microarray platform and further investigated
by hybridization with mRNA isolated from the immunoprecipitation reactions (Fig.
3). Using this strategy we have successfully identified novel IRE containing genes
and Iím currently working on the regulatory mechanisms that the IRPs plays on these
candidates via their IRE sequence.
Fig.3. Strategy to identify new IRE containing genes.
If you want to find out more about iron metabolism and its regulation, please visit also the homepages of Dunja or Bruno.
If you want to find out more about IronChip microarray platform, please visit also the homepage of Yevhen.
Publications
Sanchez M., B. Galy, M.W. Hentze, and M.U. Muckenthaler (2007) Identification of
target mRNAs of regulatory RNA-binding proteins using mRNP immunopurification and
microarrays. Nat. Protoc. 2:2033-2042
Sanchez M., B. Galy, M.U. Muckenthaler, and M.W. Hentze (2007) Iron-regulatory proteins
limit hypoxia-inducible factor-2alpha expression in iron deficiency. Nat. Struct.
Mol. Biol. 14:420-426
Roy CN , Custodio AO, de Graaf J, Schneider S, Akpan I, Montross LK,Sanchez
M, Gaudino A, Hentze MW, Andrews NC and Muckenthaler M. (2004) An Hfe-dependent pathway
mediates hyposideremia in response to lipopolysaccharide-induced inflammation in
mice. Nat. Genet. 36:481-5.
assembled by: B.Galy
last update: 12/2007
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