Histone H2A ubiquitination does not preclude histone H1 binding, but it facilitates its association with the nucleosome

Histone H2A ubiquitination is a bulky posttranslational modification that occurs at the vicinity of the binding site for linker histones in the nucleosome. Therefore, we took several experimental approaches to investigate the role of ubiquitinated H2A (uH2A) in the binding of linker histones. Our results showed that uH2A was present in situ in histone H1-containing nucleosomes. Notably in vitro experiments using nucleosomes reconstituted onto 167-bp random sequence and 208-bp (5 S rRNA gene) DNA fragments showed that ubiquitination of H2A did not prevent binding of histone H1 but it rather enhanced the binding of this histone to the nucleosome. We also showed that ubiquitination of H2A did not affect the positioning of the histone octamer in the nucleosome in either the absence or the presence of linker histones.     

Widespread Occurrence of Chemical Residues in Beehive Matrices from Apiaries Located in Different Landscapes of Western France

Background

The honey bee, Apis mellifera, is frequently used as a sentinel to monitor environmental pollution. In parallel, general weakening and unprecedented colony losses have been reported in Europe and the USA, and many factors are suspected to play a central role in these problems, including infection by pathogens, nutritional stress and pesticide poisoning. Honey bee, honey and pollen samples collected from eighteen apiaries of western France from four different landscape contexts during four different periods in 2008 and in 2009 were analyzed to evaluate the presence of pesticides and veterinary drug residues.

Methodology/Findings

A multi-residue analysis of 80 compounds was performed using a modified QuEChERS method, followed by GC-ToF and LC−MS/MS. The analysis revealed that 95.7%, 72.3% and 58.6% of the honey, honey bee and pollen samples, respectively, were contaminated by at least one compound. The frequency of detection was higher in the honey samples (n = 28) than in the pollen (n = 23) or honey bee (n = 20) samples, but the highest concentrations were found in pollen. Although most compounds were rarely found, some of the contaminants reached high concentrations that might lead to adverse effects on bee health. The three most frequent residues were the widely used fungicide carbendazim and two acaricides, amitraz and coumaphos, that are used by beekeepers to control Varroa destructor. Apiaries in rural-cultivated landscapes were more contaminated than those in other landscape contexts, but the differences were not significant. The contamination of the different matrices was shown to be higher in early spring than in all other periods.

Conclusions/Significance

Honey bees, honeys and pollens are appropriate sentinels for monitoring pesticide and veterinary drug environmental pollution. This study revealed the widespread occurrence of multiple residues in beehive matrices and suggests a potential issue with the effects of these residues alone or in combination on honey bee health.     

The Essential Oil of Bupleurum fruticosum L. from Corsica: A Comprehensive Study

A detailed analysis of Bupleurum fruticosum oil was carried out by combination of GC (RI), GC/MS, and ¹³C‐NMR analyses. After fractionation by column chromatography, 34 components accounting for 97.8% of the oils were identified. The main component was β‐phellandrene (67.7%), followed by sabinene (9.3%), and limonene (5.6%). The evolution of the chemical composition according to the stages of development of the plant was investigated as well as the composition of leaf, twig, and flower oils. A solvent‐free microwave extraction (SFME) of aerial parts was carried out and the composition of the extract compared with that of the essential oil. Finally, 57 oil samples isolated from aerial parts of individual plants, collected all around Corsica, were analyzed, and the data were submitted to statistical analysis. Although the contents of the main components varied, only one group emerged, accompanied with some atypical compositions.     

Intestinal gluconeogenesis is a key factor for early metabolic changes after gastric bypass but not after gastric lap-band in mice

Unlike the adjustable gastric banding procedure (AGB), Roux-en-Y gastric bypass surgery (RYGBP) in humans has an intriguing effect: a rapid and substantial control of type 2 diabetes mellitus (T2DM). We performed gastric lap-band (GLB) and entero-gastro anastomosis (EGA) procedures in C57Bl6 mice that were fed a high-fat diet. The EGA procedure specifically reduced food intake and increased insulin sensitivity as measured by endogenous glucose production. Intestinal gluconeogenesis increased after the EGA procedure, but not after gastric banding. All EGA effects were abolished in GLUT-2 knockout mice and in mice with portal vein denervation. We thus provide mechanistic evidence that the beneficial effects of the EGA procedure on food intake and glucose homeostasis involve intestinal gluconeogenesis and its detection via a GLUT-2 and hepatoportal sensor pathway.     

Grazing dynamics in intertidal rockpools: Connectivity of microhabitats

Differences between rockpool and emergent rock communities are often attributed to their contrasting physical conditions. However, differences in grazing pressure between rockpools and open rock could also exert an important structuring role. Greater densities and/or the lack of tidal constraints on foraging may allow grazing intensity to be greater in rockpools. Here, wax discs were deployed to compare grazing intensity between rockpool and emergent rock habitats at each of three tidal heights on a moderately exposed shore in SW England. Grazing intensity was then examined in relation to herbivore density. Grazing intensity in pools was twice that on emergent rock, despite a lower density of herbivores in the rockpools. Of these herbivores, patellid limpets are the dominant grazers on rocky shores throughout the NE Atlantic and are recognised to have a major role in structuring intertidal communities. Thus, subsequent experiments focussed on the influence of limpets in determining the differences in consumer pressure between rockpools and emergent rock. Three alternative explanations were considered: (1) the effect of continuous immersion on grazing intensity in rockpools; (2) differences in limpet species abundance between the two habitats; (3) movement of limpets from emergent rock into pools to feed. The level of grazing pressure exerted by Patella ulyssiponensis (Gmelin), the predominant species living constantly immersed in rockpools, was similar to that of P. vulgata (Linnaeus) which is predominantly found on emergent rock. P. vulgata were observed moving from emergent rock into rockpools during high tide. Manipulative experiments confirmed that these foraging excursions resulted in a 2-fold increase in grazing intensity in the pools. Grazing activity of P. vulgata in rockpools was not consistent between sites and may be influenced by differences in wave exposure and/or the abundance of microbial resources. Elevated consumer pressure in rockpools may be an important factor influencing algal assemblages and probably explains the predominance of grazer resistant-species in these pools.     

Expression of a Yersinia pseudotuberculosis Type VI Secretion System Is Responsive to Envelope Stresses through the OmpR Transcriptional Activator

The Type VI secretion system (T6SS) is a macromolecular complex widespread in Gram-negative bacteria. Although several T6SS are required for virulence towards host models, most are necessary to eliminate competitor bacteria. Other functions, such as resistance to amoeba predation, biofilm formation or adaptation to environmental conditions have also been reported. This multitude of functions is reflected by the large repertoire of regulatory mechanisms shown to control T6SS expression, production or activation. Here, we demonstrate that one T6SS gene cluster encoded within the Yersinia pseudotuberculosis genome, T6SS-4, is regulated by OmpR, the response regulator of the two-component system EnvZ-OmpR. We first identified OmpR in a transposon mutagenesis screen. OmpR does not control the expression of the four other Y. pseudotuberculosis T6SS gene clusters and of an isolated vgrG gene, and responds to osmotic stresses to bind to and activate the T6SS-4 promoter. Finally, we show that T6SS-4 promotes Y. pseudotuberculosis survival in high osmolarity conditions and resistance to deoxycholate.     

B cell receptors and complement receptors target the antigen to distinct intracellular compartments

The processing of exogenous Ags is an essential step for the generation of immunogenic peptides that will be presented to T cells. This processing relies on the efficient intracellular targeting of Ags, because it depends on the content of the compartments in which Ags are delivered in APCs. Opsonization of Ags by the complement component C3 strongly enhances their presentation by B cells and increases their immunogenicity in vivo. To investigate the role of C3 in the targeting of Ags, we compared the intracellular traffic of proteins internalized by complement receptor (CR) and B cell receptor (BCR) in B lymphocytes. Whereas both receptors are able to induce efficient Ag presentation, their intracellular pathways are different. CR ligand is delivered to compartments containing MHC class II molecules (MHC-II) but devoid of transferrin receptor and Lamp-2, whereas BCR rapidly targets its ligand toward Lamp-2-positive, late endosomal MHC-II-enriched compartments through intracellular vesicles containing transferrin receptor. CR and BCR are delivered to distinct endocytic pathways, and the kinetic evolution of the protein content of these pathways is very different. Both types of compartments contain MHC-II, but CR-targeted compartments receive less neosynthesized MHC-II than do BCR-targeted compartments. The targeting induced by CR toward compartments that are distinct from BCR-targeted compartments probably participates in C3 modulation of Ag presentation.     

Bisphenol A induces otolith malformations during vertebrate embryogenesis

Background  

The plastic monomer and plasticizer bisphenol A (BPA), used for manufacturing polycarbonate plastic and epoxy resins, is produced at over 2.5 million metric tons per year. Concerns have been raised that BPA acts as an endocrine disruptor on both developmental and reproductive processes and a large body of evidence suggests that BPA interferes with estrogen and thyroid hormone signaling. Here, we investigated BPA effects during embryonic development using the zebrafish and Xenopus models.     

The helical content of the YscP molecular ruler determines the length of the Yersinia injectisome

The length of the Yersinia injectisome needle is determined by the protein YscP, which could act as a molecular ruler. The analysis of the correlation between the size of YscP and the needle length in seven wild-type strains of Yersinia enterocolitica reinforced this hypothesis but hinted that the secondary structure of YscP might influence needle length. Hence, 11 variants of YscP₅₁₅ were generated by multiple Pro or Gly substitutions. The needle length changed in inverse function of the helical content, indicating that not only the number of residues but also their structure controls length. Taking the secondary motifs into account, Pro/Gly-variants were subjected to in silico modelling to simulate the extension of YscP upon needle growth. The calculated lengths when the helical content is preserved correlated strikingly with the measured needle length, with a constant difference of ∼29 nm, which corresponds approximately to the size of the basal body. These data support the ruler model and show that the functional ruler has a helical structure.     

Application paléoécologique de la méthode d'analyse factorielle en composantes principales: interprétation des microfaunes de foraminifères planctoniques quaternaires en méditerranée. II. Étude des espèces de méditerranée orientale

The principal component analysis method is applied to the study of associations of different Pleistocene and Holocene planktonic Foraminifera in five cores from the eastern Mediterranean. Comparison of the fossil foraminiferal distribution with the distribution of living species leads to grouping of the fossil microfauna on the basis of paleoecological controls. Factor 1 is interpreted as representing thermal control. We recognize as warm-water species Globigerinoides trilobus, Globigerinoides trilobus sacculifer, Orbulina universa, Globigerinella siphonifera, Globigerinoides ruber. Cold-water species are Globigerina pachyderma, Globorotalia scitula, Globigerina quinqueloba, Globigerinita glutinata. Species considered to be of intermediate character are Globigerina bulloides, Globorotalia inflata and Globorotalia truncatulinoides. Factor 2 also leads to the grouping of these last species and may reflect the contributing influence of productivity phenomena. A quadratic liaison interpreted as the “Guttman effect” relates factors 1 and 2. Factor 3 introduces complications resulting from apparently sporadic, irregular events affecting the distribution of certain species, notably Globoratalia inflata, Globorotalia truncatulinoides and Globigerina dutertrei.