The GW/WG repeats of Drosophila GW182 function as effector motifs for miRNA-mediated repression

The control of messenger RNA (mRNA) function by micro RNAs (miRNAs) in animal cells requires the GW182 protein. GW182 is recruited to the miRNA repression complex via interaction with Argonaute protein, and functions downstream to repress protein synthesis. Interaction with Argonaute is mediated by GW/WG repeats, which are conserved in many Argonaute-binding proteins involved in RNA interference and miRNA silencing, from fission yeast to mammals. GW182 contains at least three effector domains that function to repress target mRNA. Here, we analyze the functions of the N-terminal GW182 domain in repression and Argonaute1 binding, using tethering and immunoprecipitation assays in Drosophila cultured cells. We demonstrate that its function in repression requires intact GW/WG repeats, but does not involve interaction with the Argonaute1 protein, and is independent of the mRNA polyadenylation status. These results demonstrate a novel role for the GW/WG repeats as effector motifs in miRNA-mediated repression.     

Statistical optimization of <Emphasis Type="Italic">Bacillus alcalophilus</Emphasis> α-amylase immobilization on iron-oxide magnetic nanoparticles

We report the statistical optimization of the immobilization of alkaline α-amylase [E.C. 3.2.1.1] from Bacillus alcalophilus onto nano-sized supermagnetic ironoxide nanoparticles (MNPs) for augmenting the cost effective industrial application of MNP-bound α-amylase. Both Plackett-Burman factorial design and response surface methodology (RSM) were employed to screen the influence of different parameters and the central effect of response on the α-amylase-iron oxide MNP binding process. The high coefficient of determination (R2) and analysis of variance (ANOVA) of the quadratic model indicated the competence of the proposed model. The size of the MNPs was confirmed by X-ray diffraction and scanning electron microscope analyses in which Fourier transform infrared spectroscopy suggested immobilization of the enzyme on iron-oxide MNPs. A significant improvement (∼ 26-fold) in specific activity, thermal and storage stability, and reusability of α-amylase after binding with iron-oxide MNP reinforced the improved biotechnological potential of the α-amylase iron-oxide MNP bioconjugate compared to free α-amylase. These results open new avenues for applying this MNP immobilized enzyme in different industrial sectors, notably in the paper and brewing industries.     

Phytochemical analysis of <Emphasis Type="Italic">Andrographis paniculata</Emphasis> extract and its antimicrobial activity

The present study describes the phytochemical profile and antimicrobial activity of Andrographis paniculata. For the present investigation, two samples of A. paniculata extracts, obtained by extraction in chloroform and chloroform + HCl, respectively, were compared for their antimicrobial activity and further subjected to GC-MS analysis to find out the nature of the compounds responsible for the antimicrobial activity. The antibacterial activities were assessed by measuring the diameter of the inhibition zones, MIC and MBC values. Compared to the chloroform + HCl extract, the chloroform extract showed better antimicrobial activity against all the nine pathogenic bacterial strains tested. The chloroform extract was observed to be active against the opportunistic and pathogenic gram-negative bacteria, indicating its potential application related to noscomial infections. GC-MS results revealed phenols, aromatic carboxylic acids and esters in the chloroform extract to be the molecules responsible for the antimicrobial activity of A. paniculata. This is the first report on analysis of antimicrobial components from A. paniculata, and our results confer the utility of this plant extract in developing a novel broad spectrum antimicrobial agent.     

Effect of Chronic Fenvalerate Intoxication on Tissue Concentration of Copper in Goats and Further Exploration of Its Mechanism

This experiment was designed to assess the effect of chronic fenvalerate toxicity on tissue Cu concentration in goats and to explore the pathways responsible for it. A significant decrease in tissue Cu concentration of kidney, heart, and brain while an increase in the liver were recorded in fenvalerate intoxicated goats at 15 mg/kg b.w. orally daily for 270 days. Concentration of total Cu, protein-free Cu, and protein-bound Cu in the wet intestine of fenvalerate-treated goats revealed a significant decrease in Cu concentration of the intestine due to the decrease in trichloroacetic acid (TCA)-insoluble Cu, while TCA-soluble Cu remained almost unaffected. Rabbit duodenal loop technique was used to assess the relative absorption of nonisotopic copper in a living animal. This technique enabled to compare Cu absorption from the lumen of three closely associated loops, each receiving 100 µg of copper along with different doses (0, 15, and 30 µg) of fenvalerate. A significant dose-dependent decrease in Cu absorption from the lumen due to fenvalerate treatment was recorded. A decrease in total copper (TCA-insoluble fraction) suggested an interference in active transport of copper due to the inhibition of absorption of protein-bound copper. It was concluded that fenvalerate interfered in copper absorption mostly by inhibiting its active or mediated transport.     

Purification and immunochemical characterization of the cytoplasmic androgen-binding protein of rat liver

The cytoplasmic androgen-binding (CAB) protein of the male rat liver has been implicated to play a role in the androgen-dependent regulation of alpha 2u-globulin synthesis. The liver of the adult male rat contains about 50 fmol of specific high-affinity androgen-binding activity per milligram of total cytosolic protein. Photoaffinity labeling with [3H]R-1881 followed by SDS-polyacrylamide gel electrophoresis and autoradiography shows that the CAB is a 31-kilodalton protein. By means of DEAE-cellulose chromatography and preparative SDS-polyacrylamide gel electrophoresis, we have purified the CAB protein to electrophoretic homogeneity and have raised polyclonal rabbit antiserum that is monospecific to this protein. In the sucrose density gradient, the antiserum reacted with the androgen-binding component of the male liver cytosol prelabeled with tritiated dihydrotestosterone. Western blot analysis of the liver cytosol showed that the antiserum recognizes only the 31-kDa androgen-binding component. Such immunoblotting also showed that unlike the young adult, the androgen-insensitive states during prepuberty and senescence are associated with a marked reduction in the hepatic concentration of the immunoreactive CAB protein. No immuno-chemical cross-reactivity between CAB and another androgen-binding component of Mr 29K (which is associated with androgen insensitivity during prepuberty and senescence) was observed. The latter finding favors the possibility that 31- and 29-kDa androgen-binding components may have distinct sequence structure.