Relationship between the structure and the DNA binding properties of diazoniapolycyclic duplex- and triplex-DNA binders: efficiency, selectivity, and binding mode

The association of dicationic polycyclic ligands, namely, four diazoniapentaphene derivatives, three diazoniaanthra[1,2-a]anthracenes, diazoniahexaphene, and a partly saturated hydroxy-substituted diazoniapentaphene with double-stranded and triple-helical DNA, was investigated by spectrophotometric and viscosimetric titrations, CD and LD spectroscopy, DNA melting experiments, and molecular modeling studies. All experimental and theoretical data reveal an intercalative DNA-binding mode of the diazoniapentaphenes and diazoniaanthra[1,2-a]anthracenes; the latter have approximately 10-fold higher affinity for the DNA duplex. CD spectroscopic investigations and molecular modeling studies show that only one azonianaphthalene part of the ligand is intercalated between the DNA base pairs, whereas the remaining part of the ligand points outside the intercalation pocket. In contrast, the diazoniahexaphene is a DNA groove binder, which binds selectively to [poly(dAdT)]2. At low ligand-to-DNA ratios (r < 0.15), the diazoniahexaphene also behaves as an intercalator; however, all spectroscopic and viscosimetric data are consistent with significant groove binding of this ligand at r > 0.2. Studies of the interaction of diazoniapolycyclic ions with triplex DNA reveal a preferential binding of both diazoniapentaphenes and diazoniaanthra[1,2-a]anthracenes to the triplex and stabilization thereof. These properties are more pronounced in the case of the hexacyclic diazoniaanthra[1,2-a]anthracenes; however, the diazoniahexaphene shows no preferential binding to the triplex. The DNA binding properties of the diazoniapentaphene derivatives remain essentially the same upon variation of the positions of nitrogen atoms or substitution with methyl groups. In contrast, the interactions of the diazoniaanthra[1,2-a]anthracence isomers with triplex DNA are slightly different. Notably, the 14a,16a-diazoniaanthra[1,2-a]anthracene is among the most efficient triplex stabilizers, with a 9-fold larger binding affinity for the triplex than for the DNA duplex. Moreover, the diazoniapentaphene and diazoniaanthra[1,2-a]anthracene derivatives represent the first examples of triplex-DNA binders that do not require additional aminoalkyl side chains for efficient triplex stabilization.     

Genomic-assisted characterisation of Pseudomonas sp. strain Pf4, a potential biocontrol agent in hydroponics

In an attempt to select potential biocontrol agents against Pythium spp. and Rhizoctonia spp. root pathogens for use in soilless systems, 12 promising bacteria were selected for further investigations. Sequence analysis of the 16S rRNA gene revealed that three strains belonged to the genus Enterobacter, whereas nine strains belonged to the genus Pseudomonas. In in vitro assays, one strain of Pseudomonas sp., Pf4, closely related to Pseudomonas protegens (formerly Pseudomonas fluorescens), showed noteworthy antagonistic activity against two strains of Pythium aphanidermatum and two strains of Rhizoctonia solani AG 1-IB, with average inhibition of mycelial growth >80%. Strain Pf4 was used for in vivo treatments on lamb’s lettuce against R. solani root rot in small-scale hydroponics. Pf4-treated and untreated plants were daily monitored for symptom development and after two weeks of infection, a significant protective effect of Pf4 against root rot was recorded. The survival and population density of Pf4 on roots were also checked, demonstrating a density above the threshold value of 10⁵?CFU?g^?1 of root required for disease suppression. Known loci for the synthesis of antifungal metabolites, detected using PCR, and draft-genome sequencing of Pf4 demonstrated that Pseudomonas sp. Pf4 has the potential to produce an arsenal of secondary metabolites (plt, phl, ofa and fit-rzx gene clusters) very similar to that of the well-known biocontrol P. protegens strain Pf-5.     

Long-Term GABA Administration Induces Alpha Cell-Mediated Beta-like Cell Neogenesis

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An aberrant phase transition of stress granules triggered by misfolded protein and prevented by chaperone function

Stress granules (SG) are membrane‐less compartments involved in regulating mRNAs during stress. Aberrant forms of SGs have been implicated in age‐related diseases, such as amyotrophic lateral sclerosis (ALS), but the molecular events triggering their formation are still unknown. Here, we find that misfolded proteins, such as ALS‐linked variants of SOD1, specifically accumulate and aggregate within SGs in human cells. This decreases the dynamics of SGs, changes SG composition, and triggers an aberrant liquid‐to‐solid transition of in vitro reconstituted compartments. We show that chaperone recruitment prevents the formation of aberrant SGs and promotes SG disassembly when the stress subsides. Moreover, we identify a backup system for SG clearance, which involves transport of aberrant SGs to the aggresome and their degradation by autophagy. Thus, cells employ a system of SG quality control to prevent accumulation of misfolded proteins and maintain the dynamic state of SGs, which may have relevance for ALS and related diseases.     

ER–mitochondria contacts control surface glycan expression and sensitivity to killer lymphocytes in glioma stem‐like cells

Glioblastoma is a highly heterogeneous aggressive primary brain tumor, with the glioma stem‐like cells (GSC) being more sensitive to cytotoxic lymphocyte‐mediated killing than glioma differentiated cells (GDC). However, the mechanism behind this higher sensitivity is unclear. Here, we found that the mitochondrial morphology of GSCs modulates the ER–mitochondria contacts that regulate the surface expression of sialylated glycans and their recognition by cytotoxic T lymphocytes and natural killer cells. GSCs displayed diminished ER–mitochondria contacts compared to GDCs. Forced ER–mitochondria contacts in GSCs increased their cell surface expression of sialylated glycans and reduced their susceptibility to cytotoxic lymphocytes. Therefore, mitochondrial morphology and dynamism dictate the ER–mitochondria contacts in order to regulate the surface expression of certain glycans and thus play a role in GSC recognition and elimination by immune effector cells. Targeting the mitochondrial morphology, dynamism, and contacts with the ER could be an innovative strategy to deplete the cancer stem cell compartment to successfully treat glioblastoma.     

Newly Discovered Ebola Virus Associated with Hemorrhagic Fever Outbreak in Uganda

Over the past 30 years, Zaire and Sudan ebolaviruses have been responsible for large hemorrhagic fever (HF) outbreaks with case fatalities ranging from 53% to 90%, while a third species, Côte d''Ivoire ebolavirus, caused a single non-fatal HF case. In November 2007, HF cases were reported in Bundibugyo District, Western Uganda. Laboratory investigation of the initial 29 suspect-case blood specimens by classic methods (antigen capture, IgM and IgG ELISA) and a recently developed random-primed pyrosequencing approach quickly identified this to be an Ebola HF outbreak associated with a newly discovered ebolavirus species (Bundibugyo ebolavirus) distantly related to the Côte d''Ivoire ebolavirus found in western Africa. Due to the sequence divergence of this new virus relative to all previously recognized ebolaviruses, these findings have important implications for design of future diagnostic assays to monitor Ebola HF disease in humans and animals, and ongoing efforts to develop effective antivirals and vaccines.     

Design, synthesis and preliminary pharmacological evaluation of new analogues of DM232 (unifiram) and DM235 (sunifiram) as cognition modulators

A series of amides, structurally related to DM232 (unifiram) and DM235 (sunifiram), characterized by a 1,2,3,4-tetrahydropyrazino[2,1-a]isoindol-6(2H)-one, 1,4-diamino-cyclohexane or 1,4-diaminobenzene ring, have been synthesized and tested for cognition-enhancing activity in the mouse passive-avoidance test. Some of the compounds display good antiamnesic and procognitive activity, with higher potency than piracetam, while some cyclohexane derivatives are endowed with amnesia inducing properties.     

Protective effect of new S-acylglutathione derivatives against amyloid-induced oxidative stress

Recent data support the role of oxidative stress in the pathogenesis of Alzheimer disease (AD). In particular, glutathione (GSH) metabolism is altered and its levels are decreased in affected brain regions and peripheral cells from AD patients and in experimental models of AD. In the past decade, interest in the protective effects of various antioxidants aimed at increasing intracellular GSH content has been growing. Because much experimental evidence suggests a possible protective role of unsaturated fatty acids in age-related diseases, we designed the synthesis of new S-acylglutathione (acyl-SG) thioesters. S-Lauroylglutathione (lauroyl-SG) and S-palmitoleoylglutathione (palmitoleoyl-SG) were easily internalized into the cells and they significantly reduced Abeta42-induced oxidative stress in human neurotypic SH-SY5Y cells. In particular, acyl-SG thioesters can prevent the impairment of intracellular ROS scavengers, intracellular ROS accumulation, lipid peroxidation, and apoptotic pathway activation. Palmitoleoyl-SG seemed more effective in cellular protection against Abeta-induced oxidative damage than lauroyl-SG, suggesting a valuable role for the monounsaturated fatty acid. In this study, we demonstrate that acyl-SG derivatives completely avoid the sharp lipoperoxidation in primary fibroblasts from familial AD patients occurring after exposure to Abeta42 aggregates. Hence, we put forward these derivatives as new antioxidant compounds which could be excellent candidates for therapeutic treatment of AD and other oxidative stress-related diseases.