Release of eIF6 (p27BBP) from the 60S subunit allows 80S ribosome assembly

The assembly of 80S ribosomes requires joining of the 40S and 60S subunits, which is triggered by the formation of an initiation complex on the 40S subunit. This event is rate-limiting for translation, and depends on external stimuli and the status of the cell. Here we show that 60S subunits are activated by release of eIF6 (also termed p27BBP). In the cytoplasm, eIF6 is bound to free 60S but not to 80S. Furthermore, eIF6 interacts in the cytoplasm with RACK1, a receptor for activated protein kinase C (PKC). RACK1 is a major component of translating ribosomes, which harbour significant amounts of PKC. Loading 60S subunits with eIF6 caused a dose-dependent translational block and impairment of 80S formation, which were reversed by expression of RACK1 and stimulation of PKC in vivo and in vitro. PKC stimulation led to eIF6 phosphorylation, and mutation of a serine residue in the carboxy terminus of eIF6 impaired RACK1/PKC-mediated translational rescue. We propose that eIF6 release regulates subunit joining, and that RACK1 provides a physical and functional link between PKC signalling and ribosome activation.     

Fringe is a glycosyltransferase that modifies Notch

Notch receptors function in highly conserved intercellular signalling pathways that direct cell-fate decisions, proliferation and apoptosis in metazoans. Fringe proteins can positively and negatively modulate the ability of Notch ligands to activate the Notch receptor. Here we establish the biochemical mechanism of Fringe action. Drosophila and mammalian Fringe proteins possess a fucose-specific beta1,3 N-acetylglucosaminyltransferase activity that initiates elongation of O-linked fucose residues attached to epidermal growth factor-like sequence repeats of Notch. We obtained biological evidence that Fringe-dependent elongation of O-linked fucose on Notch modulates Notch signalling by using co-culture assays in mammalian cells and by expression of an enzymatically inactive Fringe mutant in Drosophila. The post-translational modification of Notch by Fringe represents a striking example of modulation of a signalling event by differential receptor glycosylation and identifies a mechanism that is likely to be relevant to other signalling pathways.     

Beeinflussung der Antennendifferenzierung durch Colchicin bei derDrosophilamutanteAristopedia

Summary A decrease in growth rate of the antennal bud by means of colchicine deflects the differentiation of theAristopedia antenna towards an arista.

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DieDrosophilamutanteAristopedia unterscheidet sich von der Wildform durch die Umwandlung der Fühlergeißel (=Arista) in einen Fuß.     

An Integrated Causal Path Identification Method

Finding causality merely from observed data is a fundamental problem in science. The most basic form of this causal problem is to determine whether X leads to Y or Y leads to X in the case of joint observation of two variables X, Y. In statistics, path analysis is used to describe the direct dependence between a set of variables. But in fact, we usually do not know the causal order between variables. However, ignoring the direction of the causal path will prevent researchers from analyzing or using causal models. In this study, we propose a method for estimating causality based on observed data. First, observed variables are cleaned and valid variables are retained. Then, a direct linear non-Gaussian acyclic graph models(DirectLiNGAM) estimates the causal order K between variables. The third step is to estimate the adjacency matrix B of the causal relationship based on K. Next, since B is not convenient for model interpretation, we use adaptive lasso to prune the causal path and variables. Further, a causal path graph and a recursive model are established. Finally, we test and debug the recursive model, obtain a causal model with good fit, and estimate the direct, indirect and total effects between causal variables. This paper overcomes the randomness assigning causal order to variables. This study is different from the researcher's understanding of his own model by generating some form of simulation data. The simplest and relatively unsmooth statistical learning method used in this study has obvious advantages in the field of interpretable machine learning.     

Tissue-specific activation of a cloned alpha-fetoprotein gene during differentiation of a transfected embryonal carcinoma cell line

To identify cis-acting DNA elements involved in the activation of the alpha-fetoprotein gene during differentiation, modified copies of the gene were introduced into murine F9 embryonal carcinoma cells. The differentiation of the transformants to either parietal or visceral endoderm was accompanied by induction of the exogenous template in a manner qualitatively, but not quantitatively, identical to that of the endogenous alpha-fetoprotein gene.     

Retarded enzymatic degradation of heterologous eledoisin sequences

Zusammenfassung Analoge des Eledoisin-Oktapeptides 4–11, die Hydrazid-Komponenten enthalten, sind durch Aminopeptidasen nur bis zur Heterobindung abbaubar. Sie werden wesentlich langsamer als die native Sequenz bzw. nicht durch Organhomogenate inaktiviert, wenn die Substitution im N-terminalen Bereich erfolgt. Mögliche sterische Veränderungen des Peptids durch eingebaute Fremdbausteine sind diskutiert.     

An extant cichlid fish radiation emerged in an extinct Pleistocene lake

The haplochromine cichlid fish of the East African Great Lakes represent some of the fastest and most species-rich adaptive radiations known, but rivers in most of Africa accommodate only a few morphologically similar species of haplochromine cichlid fish. This has been explained by the wealth of ecological opportunity in large lakes compared with rivers. It is therefore surprising that the rivers of southern Africa harbour many, ecologically diverse haplochromines. Here we present genetic, morphological and biogeographical evidence suggesting that these riverine cichlids are products of a recent adaptive radiation in a large lake that dried up in the Holocene. Haplochromine species richness peaks steeply in an area for which geological data reveal the historical existence of Lake palaeo-Makgadikgadi. The centre of this extinct lake is now a saltpan north of the Kalahari Desert, but it once hosted a rapidly evolving fish species radiation, comparable in morphological diversity to that in the extant African Great Lakes. Importantly, this lake seeded all major river systems of southern Africa with ecologically diverse cichlids. This discovery reveals how local evolutionary processes operating during a short window of ecological opportunity can have a major and lasting effect on biodiversity on a continental scale.     

Chemical communication: butterfly anti-aphrodisiac lures parasitic wasps

To locate their hosts, parasitic wasps can 'eavesdrop' on the intraspecific chemical communications of their insect hosts. Here we describe an example in which the information exploited by the parasitic wasp Trichogramma brassicae is a butterfly anti-aphrodisiac that is passed from male to female Pieris brassicae butterflies during mating, to render them less attractive to conspecific males. When the tiny wasp detects the odour of a mated female butterfly, it rides on her (Fig. 1) to her egg-laying sites and then parasitizes the freshly laid eggs. If this fascinating strategy is widespread in nature, it could severely constrain the evolution of sexual communication between hosts.     

C19- and C18-steroids in cerebrospinal fluid,plasma and urine after intravenous administration of 7α-3H-DHEA35S-sulphate

Zusammenfassung Nach i.v. Injektion von 7-H-DHEA-³⁶S-sulfat wurden Liquor, Plasma und 24-Stundenharn eines Mannes auf freie und konjugierte, markierte C₁₉- und C₁₈-Steroide untersucht. Es zeigte sich, dass schon 30 Minuten nach Versuchsbeginn im Liquor fast nur doppelt-markierte Steroid-sulfatide mit praktisch unverändertem Isotopenverhältnis³H/³⁵S enthalten waren. Da weiterhin DHEA und seine Metaboliten im Liquor eine weitaus niedrigere spezifische³H-Aktivität besassen als die entsprechenden Verbindungen im Plasma, ist anzunehmen, dass der Übertritt von lipophilen Steroid-sulfatiden zwar verhältnismässig rasch, aber nur in begrenztem Umfang erfolgte.