A Novel Pzg-NURF Complex Regulates Notch Target Gene Activity

Drosophila putzig was identified as a member of the TRF2–DREF complex that is involved in core promoter selection. Additionally, putzig regulates Notch signaling, however independently of DREF. Here, we show that Putzig associates with the NURF complex. Loss of any NURF component including the NURF-specific subunit Nurf 301 impedes binding of Putzig to Notch target genes, suggesting that NURF recruits Putzig to these sites. Accordingly, Putzig can be copurified with any NURF member. Moreover, Nurf 301 mutants show reduced Notch target gene activity and enhance Notch mutant phenotypes. These data suggest a novel Putzig–NURF chromatin complex required for epigenetic activation of Notch targets.     

Optimization of Protein Extraction from <Emphasis Type="Italic">Hypericum perforatum</Emphasis> Tissues and Immunoblotting Detection of Hyp-1 at Different Stages of Leaf Development

Sample preparation is crucial for obtaining high-quality proteins for the purpose of electrophoretic separation and further analysis from tissues that contain high levels of interfering compounds. Hypericum perforatum is a medicinal plant that contains high amounts of phenolic compounds, of which hypericins, hyperforins, and flavonoids contribute to the antidepressant activities of the plant. This study focuses on obtaining optimized amounts of high-quality proteins from H. perforatum, which are suitable for electrophoretic analyses. From the tested protein extraction solutions, sodium borate buffers at pH 9 and 10 gave the best protein yields from mature H. perforatum leaves. With these buffers, relatively high protein yields could also be obtained from roots, stems, and flower buds. The protein extracts of all organs were well resolved in SDS-PAGE after an efficient removal of non-protein contaminants with PVPP, phenol extraction, and methanolic ammonium acetate precipitation. The method was suitable for high-quality protein extraction also from other tested species of genus Hypericum. The applicability of the protocol for immunoblotting was demonstrated by detecting Hyp-1 in H. perforatum leaves at different stages of development. Hyp-1, which has been suggested to attend to the biosynthesis of hypericin, accumulated in high amounts in H. perforatum leaves at mature stage.     

Single chain TNF derivatives with individually mutated receptor binding sites reveal differential stoichiometry of ligand receptor complex formation for TNFR1 and TNFR2

Most members of the tumor necrosis factor ligand family form noncovalently linked homotrimers, capable to bind up to three molecules of the respective membrane receptors. For several receptors a membrane distal homophilic interaction domain has been identified, called pre-ligand binding assembly domain. Accordingly, affinity values determined by typical equilibrium binding studies are likely to be influenced by avidity effects. Using our recently introduced covalently stabilized TNF (single chain TNF, scTNF), we have here investigated receptor–ligand binding stoichiometry in our well characterized system of TNFR–Fas chimeras. We produced scTNF derivatives with functionally deleted individual receptor binding sites, resulting in TNF mutants capable to only bind to one or two receptor molecules, rather than three. Equilibrium binding affinity studies on ice with these molecules revealed no significant changes after a single receptor binding site had been functionally deleted. In contrast, functional abrogation of two receptor binding sites showed a strong decrease in both, affinity and bioactivity on TNFR2–Fas. In contrast, TNFR1–Fas ligand binding and receptor activation was only affected after functional deletion of all three receptor binding sites. Our data demonstrate pivotal differences in ligand/receptor interactions between TNFR1–Fas and TNFR2–Fas, arguing for avidity effects important for TNF binding and downstream signaling of TNFR2, but to a lesser extent of TNFR1. These results are supported by data revealed from chemical crosslinking experiments suggesting the existence of preformed TNFR–Fas homodimers.     

A functional RNAi screen identifies hexokinase 1 as a modifier of type II apoptosis

Tumor necrosis factor alpha (TNF-α) signals through NF-κB, JNK, and caspase modules to drive physiological responses that range from inflammation to apoptosis. The balance between the individual modules determines the nature of the response, and deregulated TNF signaling has been implicated in numerous pathological conditions. We used a quantitative high-throughput RNA interference assay to probe the entire complement of human kinases and phosphatases for gene products that tilt the balance of TNF signal transduction in favor of cell death or cell viability. Of all gene products tested, loss of hexokinase 1 resulted in the greatest elevations in TNF-dependent death. In secondary assays, we demonstrated that hexokinase 1 does not alter TNF-dependent activation of NF-κB or JNK modules. Instead, hexokinase 1 modifies the induction of caspase-driven cell death. Specifically, we showed that hexokinase 1 inhibits the formation of active, pro-apoptotic caspases in response to extrinsic inducers of apoptosis. These data are the first loss-of-function reports to examine the involvement of hexokinase 1 in the transduction of cell death signals and indicate that hexokinases are critical determinants of the viability of cells in response to extrinsic apoptotic cues.     

Evaluation of ultrasound velocity measurements for estimating protease activities using casein as substrate

Ultrasonic resonator technology (URT) was compared with the well established UV–Vis/ninhydrin assay to estimate protease activities in defined buffer systems. Hydrolysis of casein was measured using subtilisin, trypsin, halophilic protease from Haloferax mediterranei and Bacillus lentus alkaline protease. Sensitivity, reproducibility, working range as well as the limit of detection and the limit of quantification were comparable for both methods. Salt concentrations (0.5 M NaCl) interfered with the URT method. The quantification of protease activity by URT was possible when the product concentration measured by the UV–Vis/ninhydrin assay was correlated to the corresponding ultrasonic velocity signals.     

Structural Changes of Cell Wall and Lignifying Enzymes Modulations in Bean Roots in Response to Copper Stress

Fourteen-day-old bean seedlings were cultured in nutrient solution containing Cu²⁺ ions at various concentrations (50 and 75 μM of CuSO₄) for 3 days. This excess of copper induced a reduction in the water volume absorbed by the plants. Moreover, this reduction was accompanied by an increase of the amount of copper taken up by the roots. Analysis by native gel electrophoresis of cell wall peroxidase activities in the roots revealed a stimulation of two anionic isoforms (A₂ and A₃) under cupric stress conditions. Moreover, the activity of phenylalanine ammonia lyase (EC. 4.3.1.5), which plays an important role in plant defense, was enhanced. Copper-treated bean roots showed modifications in the cell walls of various tissues. Label for lignin, callose, and suberin with berberine-aniline blue revealed abnormal cell wall thickenings in the endodermis, the phloem, and the xylem, especially in plants treated with 75 μM CuSO₄.     

Autosomal-Dominant Striatal Degeneration Is Caused by a Mutation in the Phosphodiesterase 8B Gene

Autosomal-dominant striatal degeneration (ADSD) is an autosomal-dominant movement disorder affecting the striatal part of the basal ganglia. ADSD is characterized by bradykinesia, dysarthria, and muscle rigidity. These symptoms resemble idiopathic Parkinson disease, but tremor is not present. Using genetic linkage analysis, we have mapped the causative genetic defect to a 3.25 megabase candidate region on chromosome 5q13.3-q14.1. A maximum LOD score of 4.1 (Θ = 0) was obtained at marker D5S1962. Here we show that ADSD is caused by a complex frameshift mutation (c.94G>C+c.95delT) in the phosphodiesterase 8B (PDE8B) gene, which results in a loss of enzymatic phosphodiesterase activity. We found that PDE8B is highly expressed in the brain, especially in the putamen, which is affected by ADSD. PDE8B degrades cyclic AMP, a second messenger implied in dopamine signaling. Dopamine is one of the main neurotransmitters involved in movement control and is deficient in Parkinson disease. We believe that the functional analysis of PDE8B will help to further elucidate the pathomechanism of ADSD as well as contribute to a better understanding of movement disorders.     

Quantification of phytochelatins in Chlamydomonas reinhardtii using ferrocene-based derivatization

A method for the identification and quantification of canonic and isoforms of phytochelatins (PCs) from Chlamydomonas reinhardtii was developed. After disulfide reduction with tris(2-carboxyethyl)phosphine (TCEP) PCs were derivatized with ferrocenecarboxylic acid (2-maleimidoyl)ethylamide (FMEA) in order to avoid oxidation of the free thiol functions during analysis. Liquid chromatography (LC) coupled to electrospray mass spectrometry (ESI-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) was used for rapid and quantitative analysis of the precolumn derivatized PCs. PC(2-4), CysGSH, CysPC(2-4), CysPC(2)desGly, CysPC(2)Glu and CysPC(2)Ala were determined in the algal samples depending on the exposure of the cells to cadmium ions.