NAB2, a corepressor of EGR-1, inhibits vascular endothelial growth factor-mediated gene induction and angiogenic responses of endothelial cells

In this study we have investigated the role of a specific corepressor of EGR-1, NAB2, to down-regulate vascular endothelial growth factor (VEGF)-induced gene expression in endothelial cells and to inhibit angiogenesis. Firstly, we show a reciprocal regulation of EGR-1 and NAB2 following VEGF treatment. During the initial phase EGR-1 is rapidly induced and NAB2 levels are down-regulated. This is followed by a reduction of EGR-1 and a concomitant increase of NAB2. Secondly, using the tissue factor gene as a readout for VEGF-induced and EGR-1-regulated gene expression we demonstrate that NAB2 can completely block VEGF-induced tissue factor reporter gene activity. Thirdly, by adenovirus-mediated expression we show that NAB2 inhibits up-regulation of tissue factor, VEGF receptor-1, and urokinase plasminogen activator mRNAs even when a combination of VEGF and bFGF is used for induction. In addition, NAB2 overexpression significantly reduced tubule and sprout formation in two different in vitro angiogenesis assays and largely prevented the invasion of cells and formation of vessel-like structures in the murine Matrigel model. These data suggest that NAB2 regulation represents a mechanism to guarantee transient EGR-1 activity following exposure of endothelial cells to VEGF and that NAB2 overexpression could be used to inhibit signals involved in the early phase of angiogenesis.     

Helicobacter pylori CagA protein targets the c-Met receptor and enhances the motogenic response

Infection with the human microbial pathogen Helicobacter pylori is assumed to lead to invasive gastric cancer. We find that H. pylori activates the hepatocyte growth factor/scatter factor receptor c-Met, which is involved in invasive growth of tumor cells. The H. pylori effector protein CagA intracellularly targets the c-Met receptor and promotes cellular processes leading to a forceful motogenic response. CagA could represent a bacterial adaptor protein that associates with phospholipase Cgamma but not Grb2-associated binder 1 or growth factor receptor-bound protein 2. The H. pylori-induced motogenic response is suppressed and blocked by the inhibition of PLCgamma and of MAPK, respectively. Thus, upon translocation, CagA modulates cellular functions by deregulating c-Met receptor signaling. The activation of the motogenic response in H. pylori-infected epithelial cells suggests that CagA could be involved in tumor progression.     

Germline mutation induction at mouse repeat DNA loci by chemical mutagens

Mutation rates at two expanded simple tandem repeat (ESTR) loci were studied in the germline of male mice exposed to two monofunctional alkylating agents, ethylnitrosourea (ENU) and isopropyl methanesulfonate (iPMS), and a topoisomerase II inhibitor, etoposide. Pre-meiotic exposure to the alkylating agents resulted in a highly significant increase in ESTR mutation rate, but did not alter post-meiotically exposed cells. Pre-meiotic mutation induction by ENU and iPMS was linear within the interval of doses from 12.5 to 25mg/kg and reached a plateau at higher concentrations. Paternal exposure to etoposide resulted in ESTR mutation induction at meiotic stages but did not affect post- or pre-meiotic cells. The pattern of ESTR mutation induction after pre-meiotic and meiotic exposure to chemical mutagens was similar to that previously obtained by various traditional approaches for monitoring germline mutation in mice. The results of this study show that ESTR loci provide a new efficient experimental system for monitoring the genetic effects of chemical mutagens, capable of detecting increases in mutation rates at low doses of exposure.     

Glucose and mannitol diffusion in human dura mater

An in vitro experimental study of the control of the human dura mater optical properties at administration of aqueous solutions of glucose and mannitol has been presented. The significant increase of the dura mater optical transmittance under action of immersion liquids has been demonstrated. Diffusion coefficients of glucose and mannitol in the human dura mater tissue at 20 degrees C have been estimated as (1.63 +/- 0.29) x 10(-6)cm(2)/s and as (1.31 +/- 0.41) x 10(-6) cm(2)/s, respectively. Experiments show that administration of immersion liquids allows for the effective control of tissue optical characteristics that make dura mater more transparent, thereby increasing the ability of light penetration through the tissue.     

Interaction of ochratoxin A with human serum albumin. Binding sites localized by competitive interactions with the native protein and its recombinant fragments

Competitive interactions of ochratoxin A (OTA) and several other acidic compounds were utilized to gain insight into the localization of binding sites and the nature of binding interactions between anionic species and human serum albumin (HSA). Depolarization of OTA fluorescence in the presence of a competing anion was used to quantify ligand-protein interactions. The results obtained were rationalized in terms of OTA displacement from its major binding site. Based on their ability to displace OTA, two distinct groups of the anionic ligands were revealed. The first group contained structurally diverse compounds that shared a common binding site in subdomain IIA (Sudlow Site I). The second group consisted of three non-steroidal anti-inflammatory drugs, which showed much lower affinity to Site I than the OTA dianion. The major site for these drugs was located in domain III. Fluorescence spectroscopy measurements of OTA, warfarin (WAR) and naproxen (NAP) complexes with recombinant proteins corresponding to the domains of HSA (D1-D3) revealed binding to all domains but with different affinities. The binding constants for OTA and WAR decreased in the series D2z.Gt;D3>D1. In contrast, NAP showed the most favorable interaction with D3 and comparable affinities to the two remaining domains. The OTA binding constant for D2, 7.9 x 10(5) M(-1), was smaller than the largest constant for HSA by a factor of approximately 7. The binding constant for OTA with D3, 1.1 x 10(5) M(-1), was very close to that of the secondary binding site for HSA.     

Isolation and metabolic characteristics of previously uncultured members of the order aquificales in a subsurface gold mine

Culture-dependent and -independent techniques were combined to characterize the physiological properties and the ecological impacts of culture-resistant phylotypes of thermophiles within the order Aquificales from a subsurface hot aquifer of a Japanese gold mine. Thermophilic bacteria phylogenetically associated with previously uncultured phylotypes of Aquificales were successfully isolated. 16S ribosomal DNA clone analysis of the entire microbial DNA assemblage and fluorescence in situ whole-cell hybridization analysis indicated that the isolates dominated the microbial population in the subsurface aquifer. The isolates were facultatively anaerobic, hydrogen- or sulfur/thiosulfate-oxidizing, thermophilic chemolithoautotrophs utilizing molecular oxygen, nitrate, ferric iron, arsenate, selenate, and selenite as electron acceptors. Their versatile energy-generating systems may reflect the geochemical conditions of their habitat in the geothermally active subsurface gold mine.     

Potassium-controlled synthesis of heterotopic macrocycles based on isothiosemicarbazide

The macrocyclisation reaction of 3,3′-(3,6-dioxaoctane-1,8-diyldioxy)-bis(2-hydroxybenzaldehyde) (1) with S-methylisothiosemicarbazide hydroiodide (H₂NNC(SCH₃)NH₂·HI) in the presence of potassium triflate, followed by addition of M(CH₃COO)₂·nH₂O, where M=Ni, Cu, Zn, afforded [NiLKI₃] (2), [NiLK(CF₃SO₃)] (3), [CuLK(CF₃SO₃)(CH₃OH)] (4) and [(ZnILK)₂CH₃OH] (5), respectively. Compounds 2-5 have been characterised by X-ray crystallography. IR, electronic, mass, ¹H, ¹³C{¹H} and ¹⁹F{¹H} NMR spectra are reported. Magnetic susceptibility measurements and ESR spectra of 4 indicate weak intermolecular spin-spin interactions, which are mostly dipolar in origin.     

Regulation of proton-to-electron stoichiometry in photosynthetic electron transport: physiological function in photoprotection

The primary stable products of photosynthetic electron flow are NADPH and ATP. Stoichiometry of their production depends on the ratio of protons pumped across the thylakoid membrane to electrons passed through the electron transport pathway (H(+)/e(-) ratio). Flexible requirements of the ATP/NADPH ratio by various assimilatory reactions in chloroplasts must be fulfilled by the H(+)/e(-) ratio during the electron flow. In addition to the well-known role of Delta pH during ATP synthesis, Delta pH also functions as a trigger of the down-regulation of photosystem II (PSII) photochemistry. Excessive light energy is safely dissipated as heat by this regulatory process to suppress the generation of toxic reactive oxygen species. Thus, regulation of the H(+)/e(-) ratio may function in the photoprotection, as well as in the regulation of the ATP/NADPH production ratio. It has long been the consensus that the H(+)/e(-) ratio can be controlled by regulating the proton-transporting Q-cycle in the cytochrome b(6)f complex and by the cyclic electron flow around photosystem I (PSI). Despite the possible physiological importance and the long history of interest, the molecular identity of Q-cycle regulation and the cyclic electron flow around PSI have been remained unclear. The recent improvements in research tools, including the genetic approach using chlorophyll fluorescence imaging and establishment of the chloroplast transformation technique, are providing new insights into classical topics. In this review, we focus on regulation of the H(+)/e(-) ratio especially from the view of photosynthetic regulation.     

Selection in the evolution of gene duplications

Background  

Gene duplications have a major role in the evolution of new biological functions. Theoretical studies often assume that a duplication per se is selectively neutral and that, following a duplication, one of the gene copies is freed from purifying (stabilizing) selection, which creates the potential for evolution of a new function.