The minimum requirement for an active RNA-dependent RNA polymerase of respiratory syncytial virus (RSV) is a complex made of two viral proteins, the polymerase large protein (L) and the phosphoprotein (P). Here we have investigated the domain on P that is responsible for this critical P-L interaction. By use of recombinant proteins and serial deletions, an L binding site was mapped in the C-terminal region of P, just upstream of the N-RNA binding site. The role of this molecular recognition element of about 30 amino acid residues in the L-P interaction and RNA polymerase activity was evaluated in cellula using an RSV minigenome system and site-directed mutagenesis. The results highlighted the critical role of hydrophobic residues located in this region. IMPORTANCERespiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants. Since no vaccine and no good antivirals against RSV are available, it is essential to better understand how the viral machinery functions in order to develop new antiviral strategies. Like all negative-strand RNA viruses, RSV codes for its own machinery to replicate and transcribe its genome. The core of this machinery is composed of two proteins, the phosphoprotein (P) and the large protein (L). Here, using recombinant proteins, we have mapped and characterized the P domain responsible for this L-P interaction and the formation of an active L-P complex. These findings extend our understanding of the mechanism of action of RSV RNA polymerase and allow us to define a new target for the development of drugs against RSV.H uman respiratory syncytial virus (HRSV) is the leading cause of acute respiratory infections in infants worldwide and is the primary cause of infant hospitalization for respiratory infections (1). Moreover, RSV is increasingly recognized as a significant cause of disease in the elderly population and can often be fatal for patients with compromised immune systems (2). In parallel with its human counterpart, bovine RSV (BRSV) constitutes a major cause of respiratory disease in calves, resulting in substantial economic losses to the cattle industry worldwide (3). Despite the substantial health and economic burden caused by RSV illness, there is currently no human vaccine or antiviral drug available. The only significant preventive treatment available is prophylaxis with palivizumab (Synagis), a humanized monoclonal antibody that has provided about 50% protection to high-risk children. Therefore, there is an urgent need to discover compounds capable of blocking RSV infection. Protein-protein interactions are potential targets for antiviral chemotherapy (4). The viral RNA-dependent RNA polymerase (RdRp) complex represents an attractive target for drug discovery, because the different components have no cellular ortholog and are highly conserved between RSV strains. The mechanism of action of this complex involves highly specific and regulated protein-protein and RNA-protein interactions that we need to understand in order to facilitat...

The somatostatin (SST) family members are a group of neuropeptides that are best known for their role in the regulation of growth, development and metabolism. The occurrence of six paralogous SST genes named SST1, SST2, SST3, SST4, SST5 and SST6 has been reported in vertebrates. It has been proposed that SST1, SST2 and SST5 arose in 2R from a common ancestral gene. SST3 and SST6 would have been subsequently generated by tandem duplications of the SST1 and SST2 genes respectively, at the base of the actinopterygian lineage. SST4 is thought to have appeared more recently from SST1, in teleost-specific 3R. In order to gain more insights into the SST gene family in vertebrates, we sought to identify which paralogs of this family are present in cartilaginous fish. For this purpose, we first searched the recently available genome and transcriptome databases from the catshark Scyliorhinus canicula. In a previous study, three S. canicula SST genes, called at that time SSTa, SSTb and SSTc, were identified and proposed to correspond to SST1, SST5 and SST2 respectively. In the present work, two additional SST genes, called SSTd and SSTe, were found in S. canicula plus two other chondrichtyan species, elephant shark (Callorhinchus milii) and whale shark (Rhincodon typus). Phylogeny and synteny analyses were then carried out in order to reveal the evolutionary relationships of SSTd and SSTe with other vertbrates SSTs. We showed that SSTd and SSTe correspond to SST2 and SST3 respectively, while SSTc corresponds to SST6 and not to SST2 as initially proposed. Our investigations in other vertebrate species also led us to find that the so-called SST2 gene in chicken, lungfish, sturgeons and teleosts actually corresponds to SST6. Conversely, the so-called SST6 gene in actinopterygians corresponds to SST2. Taken together, our results suggest that: i) SST3 and SST6 were already present in the gnathostome ancestor, much earlier than previously thought; ii) SST6 was also present in the tetrapod ancestor and still occurs in living birds; with this respect, it is likely that SST6 was independently lost several times during evolution: in euteleosts, amphibians, squamates and mammals; iii) SST2, SST3 and SST5 were probably lost in euteleosts, sarcopterygians and tetrapods, respectively. whale shark, Rhincodon typus (Read et al. 2017) and the elephant shark, C. milii (Venkatesh et al. 2014). We found two novel S. canicula SST genes that we propose to provisionally call SSTd and SSTe (according to the nomenclature initially proposed in Quan et al. 2013). S. canicula SSTd was shown to be the ortholog of the L. erinacea and C. milii atypical SST-like gene abovementioned, while S. canicula SSTe appeared as a totally new SST gene. In both R. typus and C. milii, four SST genes were found that correspond SSTa, SSTc, SSTd and SSTe. Taking advantage of the genome assembly of various representative species from other vertebrate groups, we then carried out phylogeny and synteny analyses in order to reveal the evolutionary relationships of chondrichthy...

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Shadoo belongs to the prion protein family, an evolutionary conserved and extensively studied family due to the implication of prp in transmissible Spongiform encephalopathies. However, the biological function of these genes remains poorly understood. While Sprn-knockdown experiments suggested an involvement of Shadoo during mouse embryonic development, Sprn-knockout experiments in 129Pas/ C57BL/6J or 129Pas/FVB/NCr mice did not confirm it. In the present study, we analyzed the impact of Sprn gene invalidation in a pure FVB/NJ genetic background, using a zinc finger nuclease approach. The in-depth analysis of the derived knockout transgenic mice revealed a significant increase in embryonic lethality at early post-implantation stages, a growth retardation of young Sprn-knockout pups fed by wild type mice and a lactation defect of Sprn-knockout females. Histological and transcriptional analyses of knockout E7.5 embryos, E14.5 placentas and G7.5 mammary glands revealed specific roles of the Shadoo protein in mouse early embryogenesis, tissue development and differentiation with a potential antagonist action between prp and Shadoo. this study thus highlights the entanglement between the proteins of the prion family.