A meiotic XPF-ERCC1-like complex recognizes joint molecule recombination intermediates to promote crossover formation

Meiotic crossover formation requires the stabilization of early recombination intermediates by a set of proteins and occurs within the environment of the chromosome axis, a structure important for the regulation of meiotic recombination events. The molecular mechanisms underlying and connecting crossover recombination and axis localization are elusive. Here, we identified the ZZS (Zip2–Zip4–Spo16) complex, required for crossover formation, which carries two distinct activities: one provided by Zip4, which acts as hub through physical interactions with components of the chromosome axis and the crossover machinery, and the other carried by Zip2 and Spo16, which preferentially bind branched DNA molecules in vitro. We found that Zip2 and Spo16 share structural similarities to the structure-specific XPF–ERCC1 nuclease, although it lacks endonuclease activity. The XPF domain of Zip2 is required for crossover formation, suggesting that, together with Spo16, it has a noncatalytic DNA recognition function. Our results suggest that the ZZS complex shepherds recombination intermediates toward crossovers as a dynamic structural module that connects recombination events to the chromosome axis. The identification of the ZZS complex improves our understanding of the various activities required for crossover implementation and is likely applicable to other organisms, including mammals

Etude des fonctions du nucléole (approche protéomique)

Afin de poser les bases moléculaires des rôles biologiques des nucléoles, nous avons entrepris de caractériser son contenu protéique par une approche protéomique. 210 protéines différentes ont été identifiées. Ces protéines ont été groupées dans 10 classes représentant chacune un processus biologique particulier. Cette analyse renforce la notion de plurifonctionalité des nucléoles, et a permis de proposer qu'ils jouent un rôle dans le contrôle de l'expression génique. La construction de cartes protéomiques a permis de suivre les variations du contenu protéique nucléolaire lors de l'infection par le virus herpes simplex de type 1. Ainsi, le taux de synthèse des protéines nucléolaires, à la différence de celui des protéines d'autres compartiments cellulaires, est maintenu à un niveau élevé au cours de l'infection. Enfin, la participation probable à la biogenèse des ribosomes d'une protéine pour laquelle aucun rôle biologique n'avait été décrit auparavant, a été mise en évidence.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Quantitative proteomics reveals the link between minichromosome maintenance complex and glucose-induced proliferation of rat pancreatic INS-1E β-cells

Proper functioning of pancreatic β-cells is a crucial for glucose homeostasis control, and therefore a main problem regarding type 2 diabetes onset and evolution. The ability of β-cells to proliferate upon certain stimuli, such as elevated glucose concentration, is an essential property to overpass a major problem of the pathology: the decrease of β-cell mass leading to a lack of insulin production. However, high glucose concentrations are also an inducer of β-cell dysfunction, when proliferation become unable to overcome insulin demand. The control of β-cell proliferation could represent an interesting target for the development of therapeutic molecules for type 2 diabetes treatment. To get new insights on β-cell replication, we investigated the modulation of nuclear proteins of INS-1E cells submitted to medium and high glucose concentrations for 24h. Indeed, the nucleus should contain proteins responsible of proliferation-related events. The SILAC approach allowed us identifying 24 nuclear proteins whose expressions were modified by chronic high glucose. A wide Downstream Effects Analysis assigned the majority of the differentially expressed proteins to functions such as proliferation and cell cycle. Interestingly, our study linked for the first time the increase of expression of the 6 MCM components to glucose-induced stimulation in β-cells

Uses and misuses of the fudge factor in quantitative discovery proteomics

International audienc

Modulation of neuronal pentraxin 1 expression in rat pancreatic β-cells submitted to chronic glucotoxic stress

Insulin secretory granules are β-cell vesicles dedicated to insulin processing, storage, and release. The secretion of insulin secretory granule content in response to an acute increase of glucose concentration is a highly regulated process allowing normal glycemic homeostasis. Type 2 diabetes is a metabolic disease characterized by chronic hyperglycemia. The consequent prolonged glucose exposure is known to exert deleterious effects on the function of various organs, notably impairment of insulin secretion by pancreatic β-cells and induction of apoptosis. It has also been described as modifying gene and protein expression in β-cells. Therefore, we hypothesized that a modulation of insulin secretory granule protein expression induced by chronic hyperglycemia may partially explain β-cell dysfunction. To identify the potential early molecular mechanisms underlying β-cell dysfunction during chronic hyperglycemia, we performed SILAC and mass spectrometry experiments to monitor changes in the insulin secretory granule proteome from INS-1E rat insulinoma β-cells cultivated either with 11 or 30 mm of glucose for 24 h. Fourteen proteins were found to be differentially expressed between these two conditions, and several of these proteins were not described before to be present in β-cells. Among them, neuronal pentraxin 1 was only described in neurons so far. Here we investigated its expression and intracellular localization in INS-1E cells. Furthermore, its overexpression in glucotoxic conditions was confirmed at the mRNA and protein levels. According to its role in hypoxia-ischemia-induced apoptosis described in neurons, this suggests that neuronal pentraxin 1 might be a new β-cell mediator in the AKT/GSK3 apoptotic pathway. In conclusion, the modification of specific β-cell pathways such as apoptosis and oxidative stress may partially explain the impairment of insulin secretion and β-cell failure, observed after prolonged exposure to high glucose concentrations

Synthesis of Artemisinin-Derived Dimers, Trimers and Dendrimers: Investigation of Their Antimalarial and Antiviral Activities Including Putative Mechanisms of Action

International audienc

Glucotoxicity and pancreatic proteomics

Chronic hyperglycaemia is one of the main characteristics of a diabetic state. This is also the first cause of diabetic complications. However, it is now generally accepted that glucotoxicity also participates in the worsening of type 2 diabetes, by affecting the secretion of beta-cells. So far, different mechanisms have been proposed to explain the adverse effects of chronic hyperglycaemia. One of them suggests that the modulation of expression of several key proteins during a hyperglycaemia state, may explain the toxic effect of glucotoxicity. Therefore, proteomic analysis of biological samples represents an interesting method to study the effect of chronic hyperglycaemia on protein expression. The discovery of new proteins for which the expression could be modulated by chronic hyperglycaemia may probably help to better understand the mechanisms underlying glucotoxicity. In this review, we will first present an introduction of the different mechanisms known to be involved in the control of glucose homeostasis and in the development of glucotoxicity. In a second part, some proteomic data linked with the effect of glucotoxicity in pancreas, pancreatic islets and beta-cells will be presented and discussed

Hybrid cluster proteins in a photosynthetic microalga

International audienceHybrid cluster proteins (HCP) are metalloproteins characterized by the presence of an iron-sulfur-oxygen cluster. These proteins occur in all three domains of life. In eukaryotes, HCPs have so far been found only in a few anaerobic parasites and photosynthetic microalgae. With respect to all species harboring an HCP, the green microalga Chlamydomonas reinhardtii stands out by the presence of four HCP genes. The study of the gene and protein structures as well as the phylogenetic analyses strongly support a model in which the HCP family in the alga has emerged from a single gene of alpha proteobacterial origin and then expanded by several rounds of duplications. The spectra and redox properties of HCP1 and HCP3, produced heterologously in Escherichia coli, were analyzed by electron paramagnetic resonance spectroscopy on redox-titrated samples. Both proteins contain a [4Fe-4S]-cluster as well as a [4Fe-2O-2S]-hybrid cluster with paramagnetic properties related to those of HCPs from Desulfovibrio species. Immunoblotting experiments combined with mass spectrometry-based proteomics showed that both nitrate and darkness contribute to the strong up-regulation of the HCP levels in C. reinhardtii growing under oxic conditions. The link to the nitrate metabolism is discussed in the light of recent data on the potential role of HCP in S-nitrosylation in bacteria

The Long Hunt for pssR —Looking for a Phospholipid Synthesis Transcriptional Regulator, Finding the Ribosome

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