Quantitative principles of cis-translational control by general mRNA sequence features in eukaryotes.

BackgroundGeneral translational cis-elements are present in the mRNAs of all genes and affect the recruitment, assembly, and progress of preinitiation complexes and the ribosome under many physiological states. These elements include mRNA folding, upstream open reading frames, specific nucleotides flanking the initiating AUG codon, protein coding sequence length, and codon usage. The quantitative contributions of these sequence features and how and why they coordinate to control translation rates are not well understood.ResultsHere, we show that these sequence features specify 42-81% of the variance in translation rates in Saccharomyces cerevisiae, Schizosaccharomyces pombe, Arabidopsis thaliana, Mus musculus, and Homo sapiens. We establish that control by RNA secondary structure is chiefly mediated by highly folded 25-60 nucleotide segments within mRNA 5' regions, that changes in tri-nucleotide frequencies between highly and poorly translated 5' regions are correlated between all species, and that control by distinct biochemical processes is extensively correlated as is regulation by a single process acting in different parts of the same mRNA.ConclusionsOur work shows that general features control a much larger fraction of the variance in translation rates than previously realized. We provide a more detailed and accurate understanding of the aspects of RNA structure that directs translation in diverse eukaryotes. In addition, we note that the strongly correlated regulation between and within cis-control features will cause more even densities of translational complexes along each mRNA and therefore more efficient use of the translation machinery by the cell

Chemical composition and antioxidant activity of Marrubium vulgare L. essential oil from Tunisia

In this study, the essential oil of the aerial parts of Marrubium vulgare L. obtained by hydrodistillation was analyzed by gas chromatography coupled to mass spectrometry (GC-MS) in order to determine their chemical composition. Thirty-four (34) components in the oil of M. vulgare were identified. The results demonstrated that the major components of the essential oil were y-eudesmol (11.93%),β - citronellol (9.90%), citronellyl formate (9.50%) and germacrene D (9.37%). Antioxidant effectiveness was examined by three different methods: The DPPH (1,1-diphenyl-2-picrylhydrazyl) assay, the β-carotene bleaching test and the reducing power assay. The results showed that this oil can be considered an effective source of antioxidants of natural origin. This is the first report on chemical composition of M. vulgare essential oil cultivated in Tunisia and the original study on the antioxidant activity of M. vulgare essential oil.Key words: Marrubium vulgare, essential oil, chemical composition, antioxidant activity

Chemical composition and in vitro antioxidant activities of Thymelaea hirsuta L. essential oil from Tunisia

This study was designed to examine for the first time, the chemical composition and in vitro antioxidant activities of the essential oil obtained from the aerial parts of Thymelaea hirsuta L. The essential oil was subjected to hydrodistillation and was analyzed by GC-FID and GC-MS. The chemical composition was dominated by the presence of hydrocarbon sesquiterpenes (26.91%) with germacrene D (12.98%) as the major component, while oxygenated sesquiterpenes and monoterpenes amounted to 13.82 and 13.29%, respectively. The antioxidant properties of the studied essential oil were determined by three methods: diphenylpicrylhydrazyl (DPPH) assay, -carotene bleaching assay and reducing power test and the results were compared to the reference BHT (butyl hydroxy toluene). In the three earlier mentioned assays, the essential oil demonstrated a potential antioxidant which may be considered as potent agent in food preservation and drug discovery.Key words: Thymelaea hirsuta, essential oil, antioxidant activities

A novel hepatopancreatic phospholipase A2 from Hexaplex trunculus with digestive and toxic activities.

A marine snail digestive phospholipase A2 (mSDPL) was purified from delipidated hepatopancreas. Unlike known digestive phospholipases A2, which are 14 kDa proteins, the purified mSDPL has a molecular mass of about 30 kDa. It has a specific activity of about 180 U/mg measured at 50 degrees C and pH 8.5 using phosphatidylcholine liposomes as a substrate in the presence of 4 mM NaTDC and 6mM CaCl2. The N-terminal amino-acid of the purified mSDPL does not share any homology with known phospholipases. Moreover, the mSDPL exhibits hemolytic activity in intact erythrocytes and can penetrate phospholipid monolayers at high surface pressure, comparable to snake venom PLA2. These observations suggest that mSDPL could be toxic to mammal cells. However, mSDPL can be classified as a member of a new family of enzymes. It should be situated between the class of toxic phospholipase A2 from venoms and another class of non toxic pancreatic phospholipase A2 from mammals.Persona