The mTOR regulated RNA-binding protein LARP1 requires PABPC1 for guided mRNA interaction.

The mammalian target of rapamycin (mTOR) is a critical regulator of cell growth, integrating multiple signalling cues and pathways. Key among the downstream activities of mTOR is the control of the protein synthesis machinery. This is achieved, in part, via the co-ordinated regulation of mRNAs that contain a terminal oligopyrimidine tract (TOP) at their 5'ends, although the mechanisms by which this occurs downstream of mTOR signalling are still unclear. We used RNA-binding protein (RBP) capture to identify changes in the protein-RNA interaction landscape following mTOR inhibition. Upon mTOR inhibition, the binding of LARP1 to a number of mRNAs, including TOP-containing mRNAs, increased. Importantly, non-TOP-containing mRNAs bound by LARP1 are in a translationally-repressed state, even under control conditions. The mRNA interactome of the LARP1-associated protein PABPC1 was found to have a high degree of overlap with that of LARP1 and our data show that PABPC1 is required for the association of LARP1 with its specific mRNA targets. Finally, we demonstrate that mRNAs, including those encoding proteins critical for cell growth and survival, are translationally repressed when bound by both LARP1 and PABPC1

Real-time system for monitoring the electro-thermal behaviour of power electronic devices used in boost converters

© 2016 Elsevier Ltd.Reliability of power electronic devices (PEDs) is a key issue to secure power supplies in modern word, especially, those generated from renewable energy sources. Thermal stress due to switching frequency and environmental conditions are commonest cause of currently unsatisfactory PEDs reliability scores. In this paper, the electro thermal performance of PEDs and related parameters are critically investigated using three types of differently manufactured insulated gate bipolar transistors (IGBTs). Namely, punch through (PT), non-punch through (NPT) and field stop (FS) silicon trench gate technologies. First, currents and voltages of the examined IGBTs were measured under different operating temperatures, switching frequencies and electrical loading conditions. Second, power losses of the examined devices were calculated, in real time, based on their measured currents and voltages using realistic mathematical model embedded in a dSPACE system. Subsequently, the power losses for each device were used as an input to a finite element model to graphically predict heat distributions for each of the monitored devices. Compared to expensive measurements taken by high-resolution thermal imaging cameras, the accuracy of the developed system achieved 97%. The obtained results demonstrate the developed model would serve as an inexpensive and powerful tool for monitoring PEDs thermal conditions

Etude du complexe CBC et ses différents rôles dans la biogenèse des ARN

Le CBC intervient dans de nombreuses étapes du métabolisme des ARN, telle que l’épissage, la maturation de l’extrémité 3’, la dégradation, l’export et la traduction. Ainsi, le CBC constitue un complexe majeur qui peut orchestrer les différentes étapes de maturation des ARN. Récemment, nous avons identifié le complexe CBCAP, composé de CBC, ARS2 et PHAX. Nous avons montré que la protéine ARS2 stimule la formation des extrémités 3’ de plusieurs familles d’ARN dont les snARN. De plus, ARS2 stimule le recrutement de PHAX sur le CBC. Ainsi, nous proposons un modèle où CBC-ARS2 stimule la formation de l’extrémité 3’ des pré-snARN et recrute PHAX pour favoriser leur export. Une autre étude a identifié un autre complexe le CBCN, constitué de CBC, Ars2, et de ZC3H18-NEXT au lieu de PHAX. CBCN recrute l’exosome et stimule la dégradation de certains ARN, comme les PROMPTS et les transcrits «read-through » des snARN et des ARNm d’histone. Ainsi, PHAX et ZC3H18 destinent leur ARN cibles vers l’export ou la dégradation. Il a été montré que PHAX reconnait et lie spécialement les ARN de petite taille. D’une manière remarquable, nos données de CLIP-Seq et de RIP suivie par des analyses avec des puces « All genes » montrent que PHAX lie aussi d’autres familles d’ARN. En effet, PHAX lie les ARNm ainsi que des ARN non-codant avec une légère préférence pour les snARN (en comparaison avec ZC3H18). Afin de mieux comprendre le rôle de PHAX et ZC3H18, j’ai tout d’abord démontré si les deux protéines se lient simultanément au CBC. Pour ce faire, J’ai réalisé des tests de compétitions entre PHAX et ZC3H18, in vivo, et j’ai montré que la surexpression de ZC3H18 déplace PHAX du CBC et vice versa. Puis en utilisant la technique de « Tethering Assays » j’ai pu montrer que PHAX et ZC3H18 ont des effets opposés sur la biogénèse des ARNm. De plus PHAX semble avoir un effet positif sur la maturation des ARNm et ce, en empêchant ZC3H18 et l’exosome d’être recruter. Nous avons aussi montré que la déplétion de PHAX et ZC3H18 a des conséquences fonctionnelles sur le taux des formes matures des snARN. Dans le but de caractériser la protéine ZC3H18, j’ai réalisé un crible double-hybride et j’ai montré que ZC3H18 interagit avec plusieurs facteurs d’épissage. J’ai aussi identifié les domaines de ZC3H18 impliqués dans ses différentes interactions. D’une manière intéressante, l’interaction de ZC3H18 avec certains facteurs d’épissage peut être exclusive à son interaction avec NEXT. De plus, des expériences de protéomique réalisés sur un des facteurs d’épissage trouvé dans le crible, montrent qu’il co-purifie au sein d’un complexe qui pourrait faire le lien entre la coiffe et la machinerie d’épissage. En accord avec ces résultats, nos données de RNA-seq montrent que la déplétion de ZC3H18 engendre un défaut d’épissage pour des introns qui sont proches de la coiffe et ceci pour un nombre restreint de gènes. Ainsi, notre travail décode davantage le rôle de la coiffe dans les différentes étapes de maturation des ARN et suggère un modèle où la séquence des transcrits naissant stimule la formation d’un complexe spécifique à cet ARN parmi plusieurs autres.The cap binding complex (CBC) plays a key role in a number of gene expression pathways and has been proposed to participate in the discrimination of RNA families. It also enhances many RNA processing steps, including transcription, splicing, 3’end formation, degradation, export and translation.Recently, we identified the CBCAP complex, composed of CBC, Ars2 and PHAX. We showed that Ars2 stimulates snRNA 3'-end processing as well as PHAX binding to the CBC, hence coupling snRNA maturation with their export. Other studies showed that the CBC and ARS2 can form another complex that contains ZC3H18-NEXT instead of PHAX. This complex, named CBCN, is a cofactor of the RNA exosome and is involved in the degradation of cryptic RNAs such as PROMPTs and read-through transcripts at histone and snRNA genes. Thus, PHAX and ZC3H18 target specific families of capped RNA toward either export or degradation. Previous studies proposed that PHAX binds specifically to small RNAs and discriminates them over other RNA species. Surprisingly, our CLIP-Seq and RIP-microarrays data showed that in contrast to expectations, PHAX was not specific for snRNAs. It also binds mRNAs as well as other non-coding RNAs and has a weak preference for snRNAs comparing to ZC3H18. To better understand the role of PHAX and ZC3H18, Ifirst determined whether PHAX and ZC3H18 can bind simultaneously to the CBC. Competitive LUMIER IPs indicated that binding of these proteins is mutually exclusive. I then used tethering assays and could show that PHAX and ZC3H18 have opposite effect on mRNA biogenesis. These data go against a model where binding of PHAX or ZC3H18 discriminate RNA families, and instead suggest promiscuous binding for these proteins. In addition, PHAX may exert a positive effect on mRNA processing by preventing binding of ZC3H18 and recruitment of the RNA exosome. Last but not least, our RT-QPCR data show that PHAX and ZC3H18 depletions have functional consequences on the level of mature snRNA, and this is due to a competition between both proteins which occur on those snRNA read-through transcripts.To further explore the role of ZC3H18, I performed a two-hybrid screen and identified several splicing factors. I could validate these interactions, identify the domains involved and show that binding of some of these factors is exclusive with that of NEXT. Importantly, proteomic experiments with one of these factors identified a complex that makes the link between the cap and the splicing machinery. In agreement, RNA-Seq analysis of ZC3H18 knock-down cells showed alterations in splicing of cap-proximal introns, for a small set of genes.Altogether, this work reveals how the multiple roles of the RNA cap are achieved at the biochemical level, and suggests that the nascent RNA sequence triggers formation of one among several mutually exclusive complexes

Modelling of Internal Stresses in Sheet Glass during the Cooling

International audienc

A NUMERICAL POWER IGBT MODEL AND ANALYSIS OF IMPROVING SUPPRESSION OF ITS LATCHING Presentation: Oral or Poster. Topics: Power Electronics or Electronics

Abstract During the last few years, great progress in the development of a new power semiconductor devices has been make the new generation of the power semiconductor is capable of conducting more current and blocking higher voltage that is the insulated gate bipolar transistor (IGBT). The aim of this paper, is to present a new approach which consists in defining our computer program (numerical model) of the IGBT based on the finite element technique (FEM), to offer an easy to use IGBT and other devices for our program, showing short computing time and reasonable accuracy, to predict and understand the behavior of various topologies of devices, to perform automated layout of the device to overcome some of the difficulties associated with analytical methods and to identify the failure mechanisms e.g. latch up, current redistribution limiting SOA, are know as the undesirable characteristics of IGBTs devices, then we propose some remedies. The validity of our computer program (this approach) is confirmed by comparison between simulation and theory results as well as the manufacture's data, and a good agreement is recorded for IGBT devices

Effect of Water Corrosion on Cracks and Vickers Imprints in Glass

International audienceErosion and corrosion result in potential material loss. The erosion is a physical phenomenon but corrosion is chemical one. The study of these two phenomena, as functions of time and temperature, would lead to a better understanding of glass surface damage. Results allow one to determine the effects of immersion time, temperature of the water bath and residual stresses generated by Vickers indentation on the radial crack and topography of the imprint on the surface of a soda-lime silica glass. Water corrosion effects are different at the imprint corner and the radial crack tip as compared to edges and faces

Mechanical strength of glass ground by various fractions

International audienceDuring the grinding of glass, a damaged layer is formed at the surface. The damaged layer has a layer of relief, the depth of which corresponds to the maximal roughness criteria, R(max) and a layer of cracks the depth of which is approximately three times larger than the depth of the relief This damaged layer has a deleterious effect on glass properties in particular mechanical strength. The influence of the surface state damaged by grinding with fractions of three different grain size on the biaxial bending strength of soda-lime-silica flat glass is studied