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Translational recoding of selenoprotein mRNAs

Research unit

UPR 9002 - Architecture et réactivité de l'ARN (IBMC)
15, rue Rene Descartes 67084 - Strasbourg Cedex

Group

Name: Évolution des Systèmes d'Initiation de la Traduction chez les Eucaryotes

Group leader: ERIANI Gilbert - g.eriani@ibmc-cnrs.unistra.fr

Group leader's phone: 03 88 41 70 42

Website: Visit website

Group organization:
- Chercheurs: 4
- ITA: 1
- Doctorants: 1
- Post-Docs: 1
- Autres: 1

Publications of the team linked to the topic (3 last years):
1) Wurth L, Gribling-Burrer A.S, Verheggen C, Leichter M, Takeuchi A, Baudrey S, Martin F, Krol A, Bertrand E and Allmang C. (2014). Hypermethylated capped selenoprotein mRNAs in mammals. Nucleic Acids Res. 42, 8663–8677.
2) Boulon S, Marmier-Gourrier N, Pradet-Balade B, Wurth L, Verheggen C, Jády BE, Rothé B, Pescia C, Robert MC, Kiss T, Bardoni B, Krol A, Branlant C, Allmang C*, Bertrand E* and Charpentier B* (2008). The HSP90 chaperone controls the biogenesis of L7Ae RNPs through conserved machinery. J. Cell Biol. 180, 579-595. (*) Corresponding authors
3) Martin, F., Barends, S., Jaeger, S., Schaeffer, L., Prongidi-Fix, L. et Eriani, G. (2011)
Cap-assisted internal initiation of translation of histone H4. Molecular Cell 41, 197-209.

About PhD

PhD Director: ALLMANG-CURA Christine - c.allmang@ibmc-cnrs.unistra.fr

Phone: 03 88 41 70 80

Junior advisor: non

Co-tutely: non

Co-Director: non

About PhD topic :

Title: Translational recoding of selenoprotein mRNAs

Project: Selenoproteins, key players of oxidative stress protection, are synthesized by a co-translational recoding mechanism of an UGASec codon. In mammals, this process involves the assembly of RNA-protein (RNP) complexes to specific stem-loops located in the 3'UTR of selenoprotein mRNAs, called Selenocysteine Insertion Sequences (SECIS). Essential to this process is the SECIS binding protein 2 (SBP2) that binds the SECIS RNA and recruits translation and assembly factors to the mRNP. We have demonstrated that the selenoprotein mRNP assembly (Boulon et al. J Cell Biol, 2008) but also the 5'cap maturation pathways are peculiar. Indeed, eukaryotic mRNAs are characterized by the presence of a 7-methylguanosine (m7G) cap structure added co-transcriptionally to the 5'end. Through its association with various effectors, the m7G cap participates in multiple aspects of RNA metabolism including translation initiation, localization and decay. We have recently discovered that some selenoprotein mRNAs escape this rule and harbor at their 5' end hypermethylated m3G cap structures that should in principle preclude translation by the conventional translation initiation machinery. This surprising discovery raises the possibility of alternative translation initiation mechanisms for selenoprotein mRNAs, that we propose to study in this PhD project.
We will investigate the following points: (1) the translation initiation mechanism of selenoprotein mRNAs, (2) the identification of the factors involved and (3) structural analysis of selenoprotein mRNA/ribosome complexes. Recognition of the 5' cap structure of mRNA by the translation initiation factor eIF4E is a critical step for ribosome recruitment on the mRNA. The key question will be to determine whether selenoprotein translation is dependent on canonical eIF4E, requires a specialized initiation factor or occurs in a cap independent manner. We will address these three possibilities. To this end, molecular and cellular biology approaches will be combined: immunoprecipitation of endogenous RNA-protein complexes in mammalian cells, cell transfection, siRNA, in vitro translation of proteins, ribosome binding assays (sucrose gradients, toeprints) and identification of putative initiation factors (mass spectrometry). Purification of ribosome bound selenoprotein mRNA will be performed and high-throughput analysis (RNA-seq) will be combined to proteomic analysis in order to decipher selenoprotein mRNA translation mechanisms. Cryo-electron microscopy structural studies of selenoprotein mRNA/ribosome complexes will be performed (in collaboration with Y. Hashem) in order to gain structural insight into this mechanism.
We have developed the tools necessary for the realization of this project in the frame of a thesis. The results of this project should increase our knowledge of the pathways of selenoprotein mRNA translation.

Wished skills: The candidate should have a Master 2 in the field of biology and at least one practical experience in a research laboratory. Expertise in molecular and cellular biology is requested (cloning, expression, mutagenesis), protein and nucleic acids biochemistry as well as bioinformatics will be appreciated.

Expertises which will be acquired during the training: Methods to study protein-protein and RNA-protein complexes in vitro and in vivo, eukaryotic cell culture techniques, basic molecular and cellular biology techniques.