Role of survivin in mitosis

Human survivin is a member of the IAP (Inhibitor of Apoptosis) family. It was reported that survivin expression is associated with drug resistance, cancer progression and low patient survival rate in many cancers. Survivin is implicated in both: inhibition of apoptosis and regulation of cell division. As a member of Chromosomal Passenger Complex (CPC) it is involved in sister chromatids segregation during mitosis. On the other hand, survivin plays an important role in the surveillance mechanism called mitotic spindle assembly checkpoint (MSAC) which regulates metaphase to anaphase transition during mitosis. Additionally, survivin is necessary for cytokinesis progression. The present review is a summary of survivin's functions, focused on its role in cell division in normal and cancer cells, as well as introduction to discussion about anticancer therapies based on survivin depletion.     

Phosphorylation of Type IA restriction-modification complex enzyme EcoKI on the HsdR subunit

Phosphorylation of Type I restriction-modification (R-M) enzymes EcoKI, EcoAI, and EcoR124I - representatives of IA, IB, and IC families, respectively - was analysed in vivo by immunoblotting of endogenous phosphoproteins isolated from Escherichia coli strains harbouring the corresponding hsd genes, and in vitro by a phosphorylation assay using protein kinase present in subcellular fractions of E. coli. From all three R-M enzymes, the HsdR subunit of EcoKI system was the only subunit that was phosphorylated. Further, evidence is presented that HsdR is phosphorylated in vivo only when coproduced with HsdM and HsdS subunits - as part of assembled EcoKI restriction endonuclease, while the individually produced HsdR subunit is not phosphorylated. In vitro phosphorylation of the HsdR subunit of purified EcoKI endonuclease occurs on Thr, and is strictly dependent on the addition of a catalytic amount of cytoplasmic fraction isolated from E. coli. So far this is the first case of phosphorylation of a Type I R-M enzyme reported.     

Membrane binding of pH-sensitive influenza fusion peptides. positioning, configuration, and induced leakage in a lipid vesicle model

pH-sensitive HA2 fusion peptides from influenza virus hemagglutinin have potential as endosomal escape-inducing components in peptide-based drug delivery. Polarized light spectroscopy and tryptophan fluorescence were used to assess the conformation, orientation, effect on lipid order, and binding kinetics of wild-type peptide HA2(1-23) and a glutamic acid-enriched analogue (INF7) in large unilamellar POPC or POPC/POPG (4:1) lipid vesicles (LUVs). pH-sensitive membrane leakage was established for INF7 but not HA2(1-23) using an entrapped-dye assay. A correlation is indicated between leakage and a low degree of lipid chain order (assessed by linear dichroism, LD, of the membrane orientation probe retinoic acid). Both peptides display poor alignment in zwitterionic POPC LUVs compared to POPC/POPG (4:1) LUVs, and it was found that peptide-lipid interactions display slow kinetics (hours), resulting in reduced lipid order and increased tryptophan shielding. At pH 7.4, INF7 displays tryptophan emission and LD features indicative of a surface-orientated peptide, suggesting that its N-terminal glutamic acid residues prevent deep penetration into the hydrocarbon core. At pH 5.0, INF7 displays weaker LD signals, indicating poor orientation, possibly due to aggregation. By contrast, the orientation of the HA2(1-23) peptide backbone supports previously reported oblique insertion ( approximately 60-65 degrees relative to the membrane normal), and aromatic side-chain orientations are consistent with an interfacial (pH-independent) location of the C-terminus. We propose that a conformational change upon reduction of pH is limited to minor rearrangements of the peptide "hinge region" around Trp14 and repositioning of this residue.     

Conformations of flanking bases in HIV-1 RNA DIS kissing complexes studied by molecular dynamics

Explicit solvent molecular dynamics simulations (in total almost 800 ns including locally enhanced sampling runs) were applied with different ion conditions and with two force fields (AMBER and CHARMM) to characterize typical geometries adopted by the flanking bases in the RNA kissing-loop complexes. We focus on flanking base positions in multiple x-ray and NMR structures of HIV-1 DIS kissing complexes and kissing complex from the large ribosomal subunit of Haloarcula marismortui. An initial x-ray open conformation of bulged-out bases in HIV-1 DIS complexes, affected by crystal packing, tends to convert to a closed conformation formed by consecutive stretch of four stacked purine bases. This is in agreement with those recent crystals where the packing is essentially avoided. We also observed variants of the closed conformation with three stacked bases, while nonnegligible populations of stacked geometries with bulged-in bases were detected, too. The simulation results reconcile differences in positions of the flanking bases observed in x-ray and NMR studies. Our results suggest that bulged-out geometries are somewhat more preferred, which is in accord with recent experiments showing that they may mediate tertiary contacts in biomolecular assemblies or allow binding of aminoglycoside antibiotics.     

Cellular Senescence Induced by Prolonged Subculture Adversely Affects Glutamate Uptake in C6 Lineage

Several researchers have recently used C6 cells to evaluate functional properties of high-affinity glutamate transporters. However, it has been demonstrated that this lineage suffers several morphological and biochemical alterations according to the number of passages in culture. Currently, there are no reports showing whether functional properties of high-affinity glutamate transporters comply with these sub culturing-dependent modifications. The present study aimed to compare the functional properties of high-affinity glutamate transporters expressed in early (EPC6) and late (LPC6) passage C6 cells through a detailed pharmacological and biochemical characterization. Between 60–180 min of l-[³H]glu incubation, LPC6 presented an intracellular [³H] 55 % lower than EPC6. Both cultures showed a time-dependent increase of intracellular [³H] reaching maximal levels at 120 min. Cultures incubated with d-[³H]asp showed a time-dependent increase of [³H] until 180 min. Moreover, LPC6 have a d-[³H]asp-derived intracellular [³H] 30–45 % lower than EPC6 until 120 min. Only EAAT3 was immunodetected in cultures and its total content was equal between them. PMA-stimulated EAAT3 trafficking to membrane increased 50 % of l-[³H]glu-derived intracellular [³H] in EPC6 and had no effect in LPC6. LPC6 displayed characteristics that resemble senescence, such as high β-Gal staining, cell enlargement and increase of large and regular nuclei. Our results demonstrated that LPC6 exhibited glutamate uptake impairment, which may have occurred due to its inability to mobilize EAAT3 to cell membrane. This profile might be related to senescent process observed in this culture. Our results suggest that LPC6 cells are an inappropriate glial cellular model to investigate the functional properties of high-affinity glutamate transporters.     

Privacy preserving sub-feature selection based on fuzzy probabilities

The feature selection addresses the issue of developing accurate models for classification in data mining. The aggregated data collection from distributed environment for feature selection makes the problem of accessing the relevant inputs of individual data records. Preserving the privacy of individual data is often critical issue in distributed data mining. In this paper, it proposes the privacy preservation of individual data for both feature and sub-feature selection based on data mining techniques and fuzzy probabilities. For privacy purpose, each party maintains their privacy as the instruction of data miner with the help of fuzzy probabilities as alias values. The techniques have developed for own database of data miner in distributed network with fuzzy system and also evaluation of sub-feature value included for the processing of data mining task. The feature selection has been explained by existing data mining techniques i.e., gain ratio using fuzzy optimization. The estimation of gain ratio based on the relevant inputs for the feature selection has been evaluated within the expected upper and lower bound of fuzzy data set. It mainly focuses on sub-feature selection with privacy algorithm using fuzzy random variables among different parties in distributed environment. The sub-feature selection is uniquely identified for better class prediction. The algorithm provides the idea of selecting sub-feature using fuzzy probabilities with fuzzy frequency data from data miner’s database. The experimental result shows performance of our findings based on real world data set.     

Dynamics of the base of ribosomal A-site finger revealed by molecular dynamics simulations and Cryo-EM

Helix 38 (H38) of the large ribosomal subunit, with a length of 110 Å, reaches the small subunit through intersubunit bridge B1a. Previous cryo-EM studies revealed that the tip of H38 moves by more than 10 Å from the non-ratcheted to the ratcheted state of the ribosome while mutational studies implicated a key role of flexible H38 in attenuation of translocation and in dynamical signaling between ribosomal functional centers. We investigate a region including the elbow-shaped kink-turn (Kt-38) in the Haloarcula marismortui archaeal ribosome, and equivalently positioned elbows in three eubacterial species, located at the H38 base. We performed explicit solvent molecular dynamics simulations on the H38 elbows in all four species. They are formed by at first sight unrelated sequences resulting in diverse base interactions but built with the same overall topology, as shown by X-ray crystallography. The elbows display similar fluctuations and intrinsic flexibilities in simulations indicating that the eubacterial H38 elbows are structural and dynamical analogs of archaeal Kt-38. We suggest that this structural element plays a pivotal role in the large motions of H38 and may act as fulcrum for the abovementioned tip motion. The directional flexibility inferred from simulations correlates well with the cryo-EM results.     

Composition, and anti-inflammatory and antioxidant activities of the volatile oil from the fruit peel of Garcinia brasiliensis

The composition of the volatile oil obtained by hydrodistillation from the fruit peel of Garcinia brasiliensis (Mart.) Planch. et Triana was determined by GC/MS. A total of 38 components were identified, including gamma-muurolene (10.3%), spathulenol (8.7%), delta-cadinene (8.3%), torreyol (8.0%), alpha-cadinol (7.0%), cadalene (6.3%), and gamma-cadinene (5.3%). Oxygenated sesquiterpenes (43%) were the main group of compounds. The anti-inflammatory activity of the volatile oil was evaluated through the rat-paw edema model induced by carrageenan. Inhibition of the inflammatory process was noticed 3 h after carrageenan administration. In addition, the volatile oil showed poor antioxidant activity.