The roles of RNA helicases and other ribosome biogenesis factors during small subunit maturation

RNA helicases are a highly conserved family of proteins that act as RNA-dependent NTPases. These proteins contain a conserved helicase core consisting of two RecA-like domains that are responsible for unwinding or annealing RNA duplexes and remodelling RNP complexes in an NTP-dependent manner. As most RNA helicases perform their unwinding activity in a sequence independent manner, protein-protein interactions with cofactors can modulate their activity or provide substrate specificity. In line with their molecular functions, these proteins are central players in important cellular processes involving RNA, including pre-mRNA splicing, translation and ribosome biogenesis. The production of mature eukaryotic ribosomes is a highly dynamic and energy-consuming process that involves four rRNAs, ~80 ribosomal proteins and more than 200 trans-acting factors. In the yeast S. cerevisiae, 21 RNA helicases are involved in the assembly steps of the small and large subunits (SSU and LSU respectively), where general roles have been attributed to RNA helicases in remodelling rRNAs and modulating the dynamics of small nucleolar (sno)RNPs on pre-ribosomes. In recent years, the identification of binding sites of different RNA helicases on the rRNA as well as structural analyses of preribosomal particles has facilitated a deeper understanding of how these proteins act in ribosome biogenesis. However, for other RNA helicases, the lack of information regarding their rRNA binding sites and their molecular targets has prevented further characterisation of their functions in ribosome biogenesis. This study focused on the uncharacterised DEAD-box helicase Fal1 and the MIF4G domain-containing protein Sgd1, which are both required for SSU maturation. Analyses of pre-rRNA processing upon protein depletion demonstrated that Fal1 and Sgd1 are both required for early pre-rRNA cleavages at sites A0, A1 and A2, and complementation experiments showed that the ATPase activity of the helicase is required for this function. Fal1 and Sgd1 were shown to associate in vivo, and in vitro analyses determined that the MIF4G domain of Sgd1 mediates the interaction with Fal1. Excitingly, the data suggest that the MIF4G domain of Sgd1 can stimulate the ATPase activity of Fal1 in vitro, suggesting a role of Sgd1 as an MIF4G domain-containing cofactor of Fal1. The UV crosslinking and analysis of cDNA (CRAC) approach allowed the identification of a Sgd1 binding site within the 18S rRNA sequence, which is in line with a suggested role in the early stages of pre-SSU assembly. Interestingly, expression of different Sgd1 truncations for in vivo crosslinking experiments highlighted the C-terminal region of Sgd1 as responsible for the association with RNA. Anisotropy experiments demonstrated that the C-terminal region of Sgd1 can bind RNA in vitro in a non-sequence specific manner, suggesting that Sgd1 can simultaneously bind Fal1 through the MIF4G domain and the rRNA through the C-terminal region. Altogether, these findings expand our understanding of the role of Fal1 and Sgd1 in ribosome biogenesis, and suggest a common function of these proteins in the early stages of ribosome assembly, likely as an RNA helicasecofactor complex

Les pratiques des intervenants oeuvrant dans l'évaluation et le suivi de la libération des justiciables racisés

L’objectif de cette étude est de comprendre les pratiques des intervenants oeuvrant dans l’évaluation et le suivi de la libération des justiciables racisés. À travers des entrevues semi-dirigées, nous nous sommes intéressées aux propos de 16 intervenants oeuvrant dans l’évaluation (milieu carcéral) et dans le suivi (milieu communautaire) de la libération des justiciables. À l’aide de la théorie des représentations sociales, nous avons analysé le regard que les participants portent sur les justiciables racisés ainsi qu’au regard qu’ils portent sur leurs pratiques et sur leurs relations avec ces derniers. Il ressort des analyses que les représentations sociales des intervenants concernant ces justiciables sont assez justes, puisqu’ils semblent conscients de leurs difficultés au sein du système pénal. Toutefois, ces représentations ne sont pas vraiment ancrées dans leurs représentations sociales. La grande incompréhension et confusion auxquelles ils font face entrainent des pratiques frileuses concernant l’adaptation culturelle de leurs interventions.The objective of this study is to understand the professional practices of professionals working in the release assessment and follow-up of inmates who are members of racialized groups. By conducting semi-directed interviews, we focused on the takes of 16 professionals working in the release assessment (prison) and follow-up (community setting) of inmates. We used the social representations theory to analyze the participants’ views on inmates who are members of racialized groups and also on their practices and relationship with them. It appears that their social representations about those inmates are quite corrects because they seem aware of their difficulties in the criminal justice system. However, these practices aren’t really anchored in their social representations. The important misunderstanding and confusion that they face, cause overcautious practices when it concerns the cultural adaptation of their interventions

Concentrated Growth Factors vs. Leukocyte-and-Platelet-Rich Fibrin for Enhancing Postextraction Socket Healing. A Longitudinal Comparative Study

Platelet concentrates (PCs) have been used for over 20 years in dentistry, as an adjunct to oral surgery procedures, to improve hard and soft tissue healing and control postoperative symptoms. Among various PCs, Leukocyte and Platelet-Rich Fibrin (L-PRF) has become very popular due to its excellent cost-effectiveness ratio, and to the simple preparation protocol, but comparative clinical studies with other PCs are lacking. The aim of this split-mouth cohort study was to evaluate the effect of Concentrated Growth Factors (CGF), a recently introduced PC, as compared to L-PRF for enhancing post-extraction socket healing. Methods: Patients in need of bilateral tooth extractions were included. Each side was treated with either CGF or L-PRF. Pain, socket closure and healing index were the main outcomes. Results: Forty-five patients (24 women), aged 60.52 ± 11.75 years (range 37–87 years) were treated. No significant difference in outcomes was found, except for Pain at day 1 (p < 0.001) and socket closure in the vestibulo-palatal/lingual dimension at day 7 post-extraction (p = 0.04), both in favor of CGF. Conclusions: based on the present results, CGF proved to be as effective and safe as L-PRF, representing a valid alternative option for improving alveolar socket healing and reducing postoperative discomfort