Extracellular catalase induces cyclooxygenase 2, interleukin 8, and stromelysin genes in primary human chondrocytes

We investigated the expression of genes in response to exposure of primary human chondrocytes to extracellular catalase. The addition of catalase to culture medium caused a significant up-regulation of cyclooxygenase 2, interleukin 8, and stromelysin mRNA levels. Similar pattern of gene activation occurred in chondrocytes incubated with horseradish peroxidase. On the contrary, ebselen, a glutathione peroxidase mimetic agent, did not affect expression of catalase-inducible genes. Taken together, these observations imply that catalase action is mediated by its side peroxidase-like activity, rather than elimination of H2O2. Genistein suppressed catalase-mediated effects on gene expression. This finding implies that tyrosine kinases are implicated in underlying signaling pathway.     

Crystal structure of the ENT domain of human EMSY

EMSY is a recently discovered gene encoding a BRCA2-associated protein and is amplified in some sporadic breast and ovarian cancers. The EMSY sequence contains no known domain except for a conserved approximately 100 residue segment at the N terminus. This so-called ENT domain is unique in the human genome, although multiple copies are found in Arabidopsis proteins containing members of the Royal family of chromatin remodelling domains. Here, we report the crystal structure of the ENT domain of EMSY, consisting of a unique arrangement of five alpha-helices that fold into a helical bundle arrangement. The fold shares regions of structural homology with the DNA-binding domain of homeodomain proteins. The ENT domain forms a homodimer via the anti-parallel packing of the extended N-terminal alpha-helix of each molecule. It is stabilized mainly by hydrophobic residues at the dimer interface and has a dissociation constant in the low micromolar range. The dimerisation of EMSY mediated by the ENT domain could provide flexibility for it to bind two or more different substrates simultaneously.     

Structures of p53 cancer mutants and mechanism of rescue by second-site suppressor mutations

We have solved the crystal structures of three oncogenic mutants of the core domain of the human tumor suppressor p53. The mutations were introduced into a stabilized variant. The cancer hot spot mutation R273H simply removes an arginine involved in DNA binding without causing structural distortions in neighboring residues. In contrast, the "structural" oncogenic mutations H168R and R249S induce substantial structural perturbation around the mutation site in the L2 and L3 loops, respectively. H168R is a specific intragenic suppressor mutation for R249S. When both cancer mutations are combined in the same molecule, Arg(168) mimics the role of Arg(249) in wild type, and the wild type conformation is largely restored in both loops. Our structural and biophysical data provide compelling evidence for the mechanism of rescue of mutant p53 by intragenic suppressor mutations and reveal features by which proteins can adapt to deleterious mutations.     

Cytokine-driven cell cycling is mediated through Cdc25A

Lymphocytes are the central mediators of the immune response, requiring cytokines for survival and proliferation. Survival signaling targets the Bcl-2 family of apoptotic mediators, however, the pathway for the cytokine-driven proliferation of lymphocytes is poorly understood. Here we show that cytokine-induced cell cycle progression is not solely dependent on the synthesis of cyclin-dependent kinases (Cdks) or cyclins. Rather, we observe that in lymphocyte cell lines dependent on interleukin-3 or interleukin-7, or primary lymphocytes dependent on interleukin 7, the phosphatase Cdc25A is the critical mediator of proliferation. Withdrawal of IL-7 or IL-3 from dependent lymphocytes activates the stress kinase, p38 MAPK, which phosphorylates Cdc25A, inducing its degradation. As a result, Cdk/cyclin complexes remain phosphorylated and inactive and cells arrest before the induction of apoptosis. Inhibiting p38 MAPK or expressing a mutant Cdc25A, in which the two p38 MAPK target sites, S75 and S123, are altered, renders cells resistant to cytokine withdrawal, restoring the activity of Cdk/cyclin complexes and driving the cell cycle independent of a growth stimulus.     

Phylogenetic position of the genus Gonocerca Manter, 1925 (Trematoda,Hemiuroidea), based on partial sequences of 28S rRNA gene and a reconsideration of taxonomic status of Gonocercinae Skrjabin et Guschanskaja, 1955

Adult trematodes of the genus Gonocerca Manter, 1925, are parasites of marine fishes. Identification of the phylogenetic positions and a revision of the taxonomic status of the subfamily Gonocercinae Skrjabin et Guschanskaja, 1955 (Derogenidae) are the main purposes of this research article. Four Gonocerca species were used in the study, including the type-species G. phycidis Manter, 1925. Molecular phylogenetic analysis, based on partial sequences of 28S rRNA gene, revealed that Gonocerca spp. are phylogenetically distant from other hemiuroid trematodes, including Derogenes varicus (Müller, 1784), representative of the type-genus of the family Derogenidae. The taxonomic rank of Gonocercinae should be raised to the family level. The generic composition of the family Gonocercidae Skrjabin et Guschanskaja, 1955 stat. nov., requires further clarification as the molecular data do not support the inclusion of the genus Hemipera Nicoll, 1913, in this family.     

The Role of the Electrode Surface in Na–Air Batteries: Insights in Electrochemical Product Formation and Chemical Growth of NaO2

The Na–air battery, because of its high energy density and low charging overpotential, is a promising candidate for low‐cost energy storage, hence leading to intensive research. However, to achieve such a battery, the role of the positive electrode material in the discharge process must be understood. This issue is herein addressed by exploring the electrochemical reduction of oxygen, as well as the chemical formation and precipitation of NaO₂ using different electrodes. Whereas a minor influence of the electrode surface is demonstrated on the electrochemical formation of NaO₂, a strong dependence of the subsequent chemical precipitation of NaO₂ is identified. In the origin, this effect stems from the surface energy and O₂/O₂^? affinity of the electrode. The strong interaction of Au with O₂/O₂^? increases the nucleation rate and leads to an altered growth process when compared to C surfaces. Consequently, thin (3 µm) flakes of NaO₂ are found on Au, whereas on C large cubes (10 µm) of NaO₂ are formed. This has significant impact on the cell performance and leads to four times higher capacity when C electrodes with low surface energy and O₂/O₂^? affinity are used. It is hoped that these findings will enable the design of new positive electrode materials with optimized surfaces.