Projet ANR-13-JSV8-0004 – IKKp73 : Etude de la stabilisation de l’oncogène deltaNp73-alpha par la kinase IKK-beta en utilisant une approche de Biologie Structurale Intégrative
Programme : JCJC - SVSE 8 - Biochimie, biologie moléculaire et structurale (JCJC SVSE 8) 2013
Année de financement : 2013
Coordinateur du projet : Madame Katia ZANIER (Centre National de la Recherche Scientifique-Biotechnologie et Signalisation Cellulaire)
Partenaires : Institut de Recherche de L’École de Biotechnologie de Strasbourg
Montant : 249999.0 euros
Date de début : 2014
Durée : 42 mois
Résumé : The inhibitor of kB kinase (IKK) is a regulator of inflammatory, immune and apoptotic responses, best known for its role in the activation of nuclear factor kB (NF-kB). This Ser/Thr kinase is an enzymatic complex consisting of two catalytic and one regulatory subunits. The catalytic IKKß subunit accounts for nearly all kinase activity implicated in the activation of NF-kB. 
It has been proposed that IKK acts as a bridge between inflammation and cancer by operating in a number of pathways that promote tumorigenesis. A recent investigation has shown that IKKß regulates the stability of oncogenic deltaNp73-alpha. This latter protein is an isoform of p73 (a member of the tumor suppressor p53 protein family) that lacks the N-terminal transactivation domain. It exerts anti-apoptotic functions and promotes cellular transformation by competing with full-length p53 proteins for binding at p53 regulatory elements within DNA promoter regions. Massimo Tommasino and Rosita Accardi, who participate to this project, have discovered that IKKß phosphorylation at Ser422 of deltaNp73-alpha leads to the stabilization and a strong nuclear accumulation of deltaNp73-alpha and that this results in the inhibition of the expression of p53-regulated genes. 
Intriguingly, the interaction between IKKß and deltaNp73-alpha appears to be enhanced by Ser422 phosphorylation. The proposed project aims at characterizing the IKKß/deltaNp73-alpha interaction using an integrated Structural Biology approach, which encompasses x-ray crystallography, NMR spectroscopy and Surface Plasmon Resonance coupled with a number of in vitro and in vivo activity assays and functional studies. Structural studies will provide three-dimensional high-resolution structures or models of IKKß/deltaNp73-alpha complexes, which will be complemented with binding kinetics and kinase activity data. Together structural and activity data will enable to elucidate the mechanisms governing this interaction. Subsequently, specific mutants of IKKß and deltaNp73-alpha will be designed based on knowledge of the interaction mechanisms. These mutants will be tested in a number functional assays in order to better define the role of the IKKß/deltaNp73-alpha interaction in nuclear accumulation of deltaNp73-alpha and subsequent inhibition of the expression of p53-regulated genes.
Both IKKß and deltaNp73-alpha have been found to be upregulated in many human malignancies, including breast, prostate, liver, lung and thyroid cancers. For this reason IKKß and deltaNp73-alpha represent potentially important therapeutic targets. We believe that the present project has the potential to unveil important mechanisms regulating cancer and therefore to be of high impact for public heath.