Research

The interaction between the measles virus nucleoprotein and the Interferon Regulator Factor 3 relies on a specific cellular environment

Matteo Colombo^1,2 , Jean-Marie Bourhis^1,3 , Celia Chamontin⁴ , Carine Soriano⁴ , Stéphanie Villet⁴ , Stéphanie Costanzo¹ , Marie Couturier¹ , Valérie Belle⁵ , André Fournel⁵ , Hervé Darbon¹ , Denis Gerlier⁴ and Sonia Longhi¹

¹  Architecture et Fonction des Macromolécules Biologiques, UMR 6098 CNRS et Universités Aix-Marseille I et II, 163 Avenue de Luminy, Case 932, 13288 Marseille Cedex 09, France

²  Dept of Biomolecular Sciences and Biotechnology, Universita' degli Studi di Milano, Via Celoria, 26. I-20133 Milan, Italy

³  Institut de Biologie et Chimie des Protéines, UMR 5086 CNRS Université de Lyon, 7, passage du Vercors, 69 367 Lyon cedex 7, France

⁴  VirPatH, FRE 3011, CNRS and Université Lyon 1, Faculté de Médecine RTH Laennec, 69372, Lyon, France

⁵  Bioénergétique et Ingénierie des Protéines, UPR 9036 CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex, France, and Université Aix-Marseille I, 3 place Victor Hugo 13331, Marseille, Cedex 3, France

author email corresponding author email

Virology Journal 2009, 6:59doi:10.1186/1743-422X-6-59

Published:	15 May 2009

Abstract

Background

The genome of measles virus consists of a non-segmented single-stranded RNA molecule of negative polarity, which is encapsidated by the viral nucleoprotein (N) within a helical nucleocapsid. The N protein possesses an intrinsically disordered C-terminal domain (aa 401–525, N_TAIL) that is exposed at the surface of the viral nucleopcapsid. Thanks to its flexible nature, N_TAIL interacts with several viral and cellular partners. Among these latter, the Interferon Regulator Factor 3 (IRF-3) has been reported to interact with N, with the interaction having been mapped to the regulatory domain of IRF-3 and to N_TAIL. This interaction was described to lead to the phosphorylation-dependent activation of IRF-3, and to the ensuing activation of the pro-immune cytokine RANTES gene.

Results

After confirming the reciprocal ability of IRF-3 and N to be co-immunoprecipitated in 293T cells, we thoroughly investigated the N_TAIL-IRF-3 interaction using a recombinant, monomeric form of the regulatory domain of IRF-3. Using a large panel of spectroscopic approaches, including circular dichroism, fluorescence spectroscopy, nuclear magnetic resonance and electron paramagnetic resonance spectroscopy, we failed to detect any direct interaction between IRF-3 and either full-length N or N_TAIL under conditions where these latter interact with the C-terminal X domain of the viral phosphoprotein. Furthermore, such interaction was neither detected in E. coli nor in a yeast two hybrid assay.

Conclusion

Altogether, these data support the requirement for a specific cellular environment, such as that provided by 293T human cells, for the N_TAIL-IRF-3 interaction to occur. This dependence from a specific cellular context likely reflects the requirement for a human or mammalian cellular co-factor.