Context Respiratory syncytial virus (RSV) is the chief viral cause of severe acute respiratory tract illness in infants and n calves worldwide. After fifty years of research, there is still no vaccine available for humans. So far, no efficient specific inhibitors are avalible against these viruses. RSV belongs to the Mononegavirales (MNV) order and is a member of the Paramyxoviridae family. It is an enveloped virus and its negative strand RNA genome is encapsidated by the nucleoprotein N, which forms a helical ribonucleoprotein complex (RNP). This RNP template is recognized by the RNA-dependent RNA polymerase (RdRp) composed of L (the catalytic subunit), P (which is an essential cofactor of L), N and two small proteins, M2-1 (22K) and M2-2, which act as transcription and replication co-factors, respectively. RSV infection induces the formation of spherical inclusion bodies (IBs) of a few µm in diameter that are found in the cytoplasm of infected cells. The co-expression of RSV N and P is necessary and sufficient to induce the formation of these IBs. IBs of various sizes have been immunostained with antibodies to the N, P, M, M2-1, NS2 and L proteins. Viral genomic RNA also has been detected either within IBs or around their perimeter, depending on their size. Some cellular proteins, such as Hsp70, also associate with RSV IBs. However, the architecture, ultrastructure, the exact composition, organization and functioning of RSV IBs remains unknown. The Brazilian team has already identified some cellular partners for several RSV proteins including N, P and M. In order to study RSV IBs by high resolution microscopy, we have made constructions with P, L and M2-1 carrying photo-activable fluorescent proteins, and these fusion proteins still allow RNA synthesis, as analyzed by minireplicon assay, and are still localized in IBs. Proposal This ambitious proposal was initiated by collaboration between the groups of Dr. Eléouët (INRA) and Dr. Ventura (USP), and is based on the collaborative work of several groups with complementary competences and knowledge. The Eléouët laboratory has built all the necessary tools to track the viral proteins within infected cells and on replicon system. He has also developed protocols to produce recombinant proteins for studying their structure and function in vitro. The collaboration with the Rey group has results in the first high-resolution view of the ribonucleoprotein complex of RSV, published in Science in 2009. Similarly, the collaboration with the Sizun group has led to the NMR structure of the RSV transcription antiterminator M2-1 protein. Our common goal here is to characterize virus-cell interactions at the molecular level, to investigate the structure and composition of IBs where genome transcription and replication take place using new technologies, and to define molecular targets for the development of antivirals. We will search for cellular partners for RSV cytoplasmic proteins. Preliminary experiments performed by the Brazilian team have identified at least 5 cellular partners for RSV cytoplasmic proteins N, P, and M. First, using recombinant proteins, deletions and site-directed mutagenesis, we will identify the domains and the residues involved in these interactions. The effect of the residues identified as critical for these interactions on the replication, transcription or assembly of RSV will be analyzed in living cells using an RSV minireplicon and microscopy. The atomic structure of cellular-viral protein complexes will be investigated by NMR and X-ray crystallography. Precious structural and functional information on the relationships between RSV RdRp complex and cellular proteins will be collected. These data will allow a better understanding of the functioning of the viral RNA polymerase and the matrix protein, and will also be useful for drug design and development.

The study of minimal Cantor systems and zero entropy dynamical systems provided recently striking results. Topological full groups of minimal subshifts provide finitely generated groups with original properties: they are simple, amenable, may have intermediate growth for some zero entropy subshifts. Frantzikinakis-Host proved the Sarnak conjecture for the logarithmic average and zero entropy dynamical systems with at most countably many invariant measures. Adamczewski-Bugeaud constructed transcendantal numbers from zero entropy subshifts. Hence a deep understanding of zero entropy systems is of particular importance by itself and for other topics like number, group theory but also for applications to quasicristallography, computer science or statistical physics. Despite substantial efforts to understand zero entropy and although many families are well understood few general results have been obtained. We aim to unify parts of existing results and to go deeper into zero entropy.