Binding and Sliding Dynamics of the Hepatitis C Virus Polymerase: Hunting the 3' Terminus.

The hepatitis C virus (HCV) nonstructural protein 5B (NS5B) polymerase catalyzes the replication of the (+) single-stranded RNA genome of HCV. In vitro studies have shown that replication can be performed in the absence of a primer. However, the dynamics and mechanism by which NS5B locates the 3'-terminus of the RNA template to initiate de novo synthesis remain elusive. Here, we performed single-molecule fluorescence studies based on protein-induced fluorescence enhancement reporting on NS5B dynamics on a short model RNA substrate. Our results suggest that NS5B exists in a fully open conformation in solution wherefrom it accesses its binding site along RNA and then closes. Our results revealed two NS5B binding modes: an unstable one resulting in rapid dissociation, and a stable one characterized by a larger residence time on the substrate. We associate these bindings to an unproductive and productive orientation, respectively. Addition of extra mono (Na+)- and divalent (Mg2+) ions increases the mobility of NS5B along its RNA substrate. However, only Mg2+ ions induce a decrease in NS5B residence time. Dwell times of residence increase with the length of the single-stranded template, suggesting that NS5B unbinds its substrate by unthreading the template rather than by spontaneous opening.

Socio-Emotional Competencies and School Performance in Adolescence: What Role for School Adjustment?

There is growing evidence in the literature of positive relationships between socio-emotional competencies and school performance. Several hypotheses have been used to explain how these variables may be related to school performance. In this paper, we explored the role of various school adjustment variables in the relationship between interpersonal socio-emotional competencies and school grades, using a weighted network approach. This network approach allowed us to analyze the structure of interrelations between each variable, pointing to both central and mediatory school and socio-emotional variables within the network. Self-reported data from around 3,400 French vocational high school students were examined. This data included a set of interpersonal socio-emotional competencies (cognitive and affective empathy, socio-emotional behaviors and collective orientation), school adjustment measures (adaptation to the institution, school anxiety, self-regulation at school, and self-perceived competence at school) as well as grades in mathematics and French language. The results showed that self-regulation at school weighted the most strongly on the whole network, and was the most important mediatory pathway. More specifically, self-regulation mediated the relationships between interpersonal socio-emotional competencies and school grades.

Non-Genetically Improving the Natural Cytotoxicity of Natural Killer (NK) Cells.

The innate lymphocyte lineage natural killer (NK) is now the target of multiple clinical applications, although none has received an agreement from any regulatory agency yet. Transplant of naïve NK cells has not proven efficient enough in the vast majority of clinical trials. Hence, new protocols wish to improve their medical use by producing them from stem cells and/or modifying them by genetic engineering. These techniques have given interesting results but these improvements often hide that natural killers are mainly that: natural. We discuss here different ways to take advantage of NK physiology to improve their clinical activity without the need of additional modifications except for in vitro activation and expansion and allograft in patients. Some of these tactics include combination with monoclonal antibodies (mAb), drugs that change metabolism and engraftment of specific NK subsets with particular activity. Finally, we propose to use specific NK cell subsets found in certain patients that show increase activity against a specific disease, including the use of NK cells derived from patients.