A novel RNA binding surface of the TAM domain of TIP5/BAZ2A mediates epigenetic regulation of rRNA genes

The chromatin remodeling complex NoRC, comprising the subunits SNF2h and TIP5/BAZ2A, mediates heterochromatin formation at major clusters of repetitive elements, including rRNA genes, centromeres and telomeres. Association with chromatin requires the interaction of the TAM (TIP5/ARBP/MBD) domain of TIP5 with noncoding RNA, which targets NoRC to specific genomic loci. Here, we show that the NMR structure of the TAM domain of TIP5 resembles the fold of the MBD domain, found in methyl-CpG binding proteins. However, the TAM domain exhibits an extended MBD fold with unique C-terminal extensions that constitute a novel surface for RNA binding. Mutation of critical amino acids within this surface abolishes RNA binding in vitro and in vivo. Our results explain the distinct binding specificities of TAM and MBD domains to RNA and methylated DNA, respectively, and reveal structural features for the interaction of NoRC with non-coding RNA.     

Possible role of the neuronal environment in the vascularization of an intracerebral graft

Fetal thalamic cells implanted into the excitotoxically lesioned thalamus of adult rats construct a neo-nucleus. This study shows that the vascular network of this neo-nucleus exhibits normal characteristics considering both the morphology (at the light and ultrastructural levels) and the presence of a blood-brain barrier for macromolecules. A role of the neuronal environment in this reconstruction is suggested.     

Le Campanien-Maastrichtien du bassin des Aurès,Algérie : biostratigraphie,paléoenvironnements et leurs implications

An integrated study of the lithological, micropaleontoligical, sedimentological and statistical data has been done on samples taken from four geological sections (El Gaaga, Tighanimine and El Kantara) spread in different sea areas. This allowed to redefine the stratigraphy of the studied area to provide information about the benefits of some kinds of foraminifera, planktonic and ostracods in knowing the palaeoenvironment and identifying the types referring to the latter during the late cretaceous. The late creataceous appeared in Aures in a form of two hills separated by a light lowness. This morphology corresponds generally to the tripartite composition of the Campanian-Manstrichtian with lower member of limestone-marl (Haraoua Member), a median marl member (Akhdar Member) and an upper member of massive limestones (Ncham member). The regularity of this trilogy changed in the anticline of Dj. El Azereg through a reduction, visibly affecting the tree members. The study of the foraminifera in the late cretaceous (Campanian-Manstrichtian) in the Aures proved the existence of 141 species (48 planktonic and 93 benthic foraminifera). Applying the concepts of biostratigraphy mainly on the foraminifera allowed to distinguish different bizones, ranging from lower Campanian of El Gaaga and El Kantara cuts (Globotruncanita elevata biozone) and Maastrichtian (Contusotruncana contusa biozone). The biostratigraphical framework is thus relatively precise and helps precising for instance the position of some inconsistent boundaries.     

Pseudomonas contamination of a fungus-based biopesticide: Implications for honey bee (Hymenoptera: Apidae) health and Varroa mite (Acari: Varroidae) control

The ectoparasitic mite Varroa destructor is a major honey bee pest, and its control using pathogen-based biopesticides would resolve many of the problems, such as contamination and pesticide resistance, experienced with chemical control. A biopesticide, formulated with commercially-prepared conidia of a strain of Beauveria bassiana isolated from V. destructor was tested against the mites in bee colonies in southern France. The impact of treatment on hive survivorship, weight and mite infestation levels were very different from those of previous experiments using laboratory-prepared conidia: bee hives treated with the biopesticide died at a higher rate, lost more weight, and had higher mite densities at the end of the study than control hives. The biopesticide was subsequently found to be contaminated with bacteria. Two strains of bacteria were identified, by biotyping and sequencing data of the 16S rRNA and rpoB regions, and while the strains were distinct both were Pseudomonas sp. belonging to the P. fluorescens group. In dual cultures B. bassiana growth was slowed or suppressed when bacterial cfu density was about equal or greater than that of B. bassiana. Experiments using caged adult bees showed that bees ingesting diet and sugar solution treated with B. bassiana and kept at 30 °C had significantly lower survival times than those treated with one of the bacterial strains, but the opposite was true at 33 °C. Because one arthropod (honey bees) was treated for infestation by another (V. destructor), the impact of bacterial contamination was likely more noticeable than in most uses of biopesticides, such as treating plants against phytophagous insects. To reduce such risk in biopesticide development, a systematic screening for bacterial contamination prior to field application is recommended.