49 research outputs found
Decreasing cytosolic translation is beneficial to yeast and human Tafazzin-deficient cells
Cardiolipin (CL) optimizes diverse mitochondrial processes, including oxidative phosphorylation (OXPHOS). To function properly, CL needs to be unsaturated, which requires the acyltransferase Tafazzin (TAZ). Loss-of-function mutations in the TAZ gene are responsible for the Barth syndrome (BTHS), a rare X-linked cardiomyopathy, presumably because of a diminished OXPHOS capacity. Herein we show that a partial inhibition of cytosolic protein synthesis, either chemically with the use of cycloheximide or by specific genetic mutations, fully restores biogenesis and the activity of the oxidative phosphorylation system in a yeast BTHS model (taz1Î). Interestingly, the defaults in CL were not suppressed, indicating that they are not primarily responsible for the OXPHOS deficiency in taz1Î yeast. Low concentrations of cycloheximide in the picomolar range were beneficial to TAZ-deficient HeLa cells, as evidenced by the recovery of a good proliferative capacity. These findings reveal that a diminished capacity of CL remodeling deficient cells to preserve protein homeostasis is likely an important factor contributing to the pathogenesis of BTHS. This in turn, identifies cytosolic translation as a potential therapeutic target for the treatment of this disease
Intracellular Phospholipase A1 and Acyltransferase, Which Are Involved in Caenorhabditis elegans Stem Cell Divisions, Determine the sn-1 Fatty Acyl Chain of Phosphatidylinositol
Phosphatidylinositol (PI) is unique in the abundance of stearic acid at the sn-1 position. This fatty acid is thought to be incorporated through fatty acid remodeling. Here, we identified a phospholipase and acyltransferases involved in the fatty acid remodeling at the sn-1 position of PI and provide a link between the sn-1 fatty acid of PI and asymmetric cell division
Metabolism and Regulation of Glycerolipids in the Yeast Saccharomyces cerevisiae
Due to its genetic tractability and increasing wealth of accessible data, the yeast Saccharomyces cerevisiae is a model system of choice for the study of the genetics, biochemistry, and cell biology of eukaryotic lipid metabolism. Glycerolipids (e.g., phospholipids and triacylglycerol) and their precursors are synthesized and metabolized by enzymes associated with the cytosol and membranous organelles, including endoplasmic reticulum, mitochondria, and lipid droplets. Genetic and biochemical analyses have revealed that glycerolipids play important roles in cell signaling, membrane trafficking, and anchoring of membrane proteins in addition to membrane structure. The expression of glycerolipid enzymes is controlled by a variety of conditions including growth stage and nutrient availability. Much of this regulation occurs at the transcriptional level and involves the Ino2âIno4 activation complex and the Opi1 repressor, which interacts with Ino2 to attenuate transcriptional activation of UASINO-containing glycerolipid biosynthetic genes. Cellular levels of phosphatidic acid, precursor to all membrane phospholipids and the storage lipid triacylglycerol, regulates transcription of UASINO-containing genes by tethering Opi1 to the nuclear/endoplasmic reticulum membrane and controlling its translocation into the nucleus, a mechanism largely controlled by inositol availability. The transcriptional activator Zap1 controls the expression of some phospholipid synthesis genes in response to zinc availability. Regulatory mechanisms also include control of catalytic activity of glycerolipid enzymes by water-soluble precursors, products and lipids, and covalent modification of phosphorylation, while in vivo function of some enzymes is governed by their subcellular location. Genome-wide genetic analysis indicates coordinate regulation between glycerolipid metabolism and a broad spectrum of metabolic pathways
Identification et caractérisation de quatre lysolipide acyltransférases de S. cerevisiae (études in silico, in vitro et in vivo)
BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF
Mutations des éléments cis-régulateurs de l'épissage (rÎle en pathologie humaine)
L'Ă©pissage des ARN pre-messagers joue un rĂŽle fondamental dans l'expression des gĂšnes chez les eucaryotes supĂ©rieurs. La rĂ©gulation de ce processus extrĂȘmement complexe, qui permet l'excision des introns, repose sur la reconnaissance de multiples Ă©lĂ©ments, incluant les sĂ©quences consensus (sites accepteurs et donneurs) et cis-rĂ©gulatrices auxiliaires, dont la combinaison dĂ©finit un "code de l'Ă©pissage" propre Ă chaque exon. Les exemples de mutation associĂ©es Ă des anomalies d'Ă©pissage dans les maladies gĂ©nĂ©tiques humaines sont de plus en plus nombreux, nĂ©anmoins leur contribution reste trĂšs probablement sous estimĂ©e. En effet, un nombre important de variants non classĂ©s (Unknown Variants, UVs) introniques ou exoniques est identifiĂ© par sĂ©quençage des gĂšnes, dont une partie est susceptible d'altĂ©rer l'Ă©pissage. Quand les transcrits spĂ©cifiques des patients ne sont pas accessibles, l'utilisation combinĂ©e d'outils bio-informatiques et de tests fonctionnels basĂ©s sur l'utilisation de minigĂšnes rapporteurs d'Ă©pissage permet d'Ă©valuer l'impact de ces UVs sur l'Ă©pissage. Cette stratĂ©gie, appliquĂ©e aux variants identifiĂ©s dans les gĂšnes responsables du syndrome de Usher, a montrĂ© que 76% des UVs localisĂ©s Ă des positions peu conservĂ©es des sites consensus avaient des consĂ©quences majeures sur l'Ă©pissage. Au cours de ces travaux, nous avons confirmĂ© l'importance de l'interdĂ©pendance des positions nuclĂ©otidiques dans la dĂ©finition des sites d'Ă©pissage, et avons pu Ă©tablir que les positions -1 et +4 du site donneur d'Ă©pissage permettaient de compenser un mĂ©sappariement en position +3 avec la protĂ©ine U1 snRNP. Les Ă©vĂšnements d'Ă©pissage alternatifs jouent Ă©galement un rĂŽle important dans la modulation de sĂ©vĂ©ritĂ© du phĂ©notype en pathologie humaine. On observe ainsi pour le gĂšne DMD (Duchenne muscular Dystrophy) que des mutations non-sens (introduisant un codon stop prĂ©maturĂ©) sont retrouvĂ©es dans des formes modĂ©rĂ©es de la maladie (Myopathie de Becker) lorsqu'elles sont Ă l'origine d'un Ă©pissage alternatif en phase de l'exon mutĂ©. L'identification des Ă©lĂ©ments cis-rĂ©gulateurs de l'Ă©pissage impliquĂ©s (ou SREs, splicing regulatory elements), notamment les sĂ©quences activatrices de type ESE (Exonic Splicing Enhancer), reprĂ©sente un enjeu majeur pour la mise en place des stratĂ©gies thĂ©rapeutiques par saut d'exon dans la myopathie de DuchenneSplicing of pre-messenger RNAs to mature transcripts is a crucial step in eukaryotic gene expression. This highly regulated mechanism involves multiple signals, including the core splice site motifs (donor and acceptor splice sites) and auxiliary ci-regulatory elements, which are part of integrated "splicing code". More and more examples of splicing mutations resulting in genetic diseases are described in the literature, however their true contribution is probably underestimated. Indeed, sequence-based approach to study disease-causing genes in diagnostic procedures leads to the identification of an increasing number of variants of unknown significance (UVs). The biological consequences of the so-called UVs and notably their purative impact of splicing ar unknown. When specific analysis is not achievable in patients, in silico predictions associated with minigene studies are performed to determine the impact of these UVs on splicing. This strategy was applied to a set of UVs located in poorly conserved positions of acceptor and donor splice sites of Usher genes, and 76% of them were found to cause aberrant splicing. From our results, we further confirmed the importance of the overall nucleotidic environment in splice sites selection. In particular, we could establish that positions -1 and +4 in donor splice sites can compensate a mismatch at position +3 with the U1 snRNP and contribute to the correct recognition of such donor splice sites. Alernative splicing events play also a major role in modulation of disease severity. In the DMD gene, nonsense mutations introducing a premature stop codon are found in patients with a milder phenotype (Becker-like) than expected (Duchenne-like), and usually result from the elimination of the truncating mutation from dystrophin mRNA by skipping of an in-frame exon. This kind of disease-causing mutations can contribute to shed light on new cis-regulatory elements, in particular Exonic Splicing Enhancer (ESE) motifs, essential for splicing in the DMD gene, which may be important for the exon skipping therapeuric strategyMONTPELLIER-BU MĂ©decine UPM (341722108) / SudocMONTPELLIER-BU MĂ©decine (341722104) / SudocSudocFranceF
Les bioindicateurs pour la gestion des sites contaminés - Evaluation des risques de transfert dans les chaßnes trophiques terrestres : résultats sur sites ateliers.
International audienceCette prĂ©sentation synthĂ©tise les rĂ©sultats obtenus avec des bio-indicateurs d'accumulation (plantes, escargots) et d'effet (teneurs des feuilles en acides gras) par plusieurs Ă©quipes dans le cadre du programme Bioindicateur conduit sur 13 sites en France. Il est Ă©galement montrĂ© que la biodisponibilitĂ© (Ă©valuĂ©e avec des mĂ©thodes biologiques) ne peut ĂȘtre estimĂ©e par l'Ă©valuation de la disponibilitĂ© (Ă©valuĂ©e avec des mĂ©thodes chimiques)
Sequence Contexts That Determine the Pathogenicity of Base Substitutions at Position+3 of Donor Splice-Sites
Variations at position +3 of 5' splice-sites (5'ss) are reported to induce aberrant splicing in some cases but not in others suggesting that the overall nucleotidic environment can dictate the extent to which 5'ss are correctly selected. Functional studies of three variations identified in donor splice-sites of USH2A and PCDH15 genes sustain this assumption. To gain insights into this question, we compared the nucleotidic context of U2-dependent 5'ss naturally deviated (+3G, +3C, or +3T) from the +3A consensus with 5'ss for which a +3 variation (A>G, A>C, or A>T) was shown to induce aberrant splicing. Statistical differences were found between the two datasets, highlighting the role of one peculiar position in each context (+3G/+4A; +3C/-1G; and +3T/-1G). We provided experimental support to the biostatistical results through the analysis of a series of artificial mutants in reporter minigenes. Moreover, different 5' end-mutated U1 snRNA expression plasmids were used to investigate the importance of the position +3 and of the two identified compensatory positions -1 and +4 in the recognition of 5'ss by the U1 snRNP Overall, our findings establish general properties useful to Molecular geneticists to identify nucleotide substitutions at position +3 that are more likely to alter splicin
Microbial communities in As contaminated agricultural soils â How PK fertiliser can influence As speciation
International audienc
Communautés microbiennes dans les sols agricoles pollués par l'arsenic - comment les engrais KP peuvent influencer la spéciation de l'arsenic
International audienc
The reductase activity of the Arabidopsis Caleosin RESPONSIVE TO DESSICATION20 mediates gibberellin-dependent flowering time, abscisic acid sensitivity, and tolerance to oxidative Stress
International audienceContrasting with the wealth of information available on the multiple roles of jasmonates in plant development and defense, knowledge about the functions and the biosynthesis of hydroxylated oxylipins remains scarce. By expressing the caleosin RESPONSIVE TO DESSICATION20 (RD20) in Saccharomyces cerevisiae, we show that the recombinant protein possesses an unusual peroxygenase activity with restricted specificity toward hydroperoxides of unsaturated fatty acid. Accordingly, Arabidopsis (Arabidopsis thaliana) plants overexpressing RD20 accumulate the product 13-hydroxy-9,11,15-octadecatrienoic acid, a linolenate-derived hydroxide. These plants exhibit elevated levels of reactive oxygen species (ROS) associated with early gibberellin-dependent flowering and abscisic acid hypersensitivity at seed germination. These phenotypes are dependent on the presence of active RD20, since they are abolished in the rd20 null mutant and in lines overexpressing RD20, in which peroxygenase was inactivated by a point mutation of a catalytic histidine residue. RD20 also confers tolerance against stress induced by Paraquat, Rose Bengal, heavy metal, and the synthetic auxins 1-naphthaleneacetic acid and 2,4-dichlorophenoxyacetic acid. Under oxidative stress, 13-hydroxy-9,11,15-octadecatrienoic acid still accumulates in RD20-overexpressing lines, but this lipid oxidation is associated with reduced ROS levels, minor cell death, and delayed floral transition. A model is discussed where the interplay between fatty acid hydroxides generated by RD20 and ROS is counteracted by ethylene during development in unstressed environments