Time- and Dose-Dependent Induction of HSP70 in Lemna minor Exposed to Different Environmental Stressors

The objective of this study was to examine the influence of different stressors, including cadmium (heavy metal), anthracene (polycyclic aromatic hydrocarbon—PAH) and chloridazon (herbicide), on population growth and biosynthesis of cytoplasmic HSP70 in Lemna minor (duckweed) in short (4 h)- and long (7 days)-term tests. A heat shock response was confirmed in Lemna exposed to high temperature: 35, 37.5, 40, or 42.5°C in short-term (4 h) treatments. The chemicals tested stimulated the biosynthesis of the cytoplasmic HSP70 protein in a concentration-dependent way (0.5–5 μM), higher in fronds exposed to lower doses of stressors. Additionally, production of HSP70 was greater after 4 h of incubation than after 7 days. The results suggest that HSP70 could be applied as a non-specific and sensitive detector of stress induced by different chemicals at concentrations below those that produce the type of response observed in classical cytotoxicity tests, such as growth inhibition

Structural phase transition in TbFe2.5Ga0.5(BO3)4 single crystal

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The Raman spectra of the TbFe2.5Ga0.5(BO3)4 single crystal in the temperature range from 8 to 400 K have been observed. The condensation and restoration of the soft modes have been found. The soft modes are associated with the structural phase transition from the R32 phase to the P3(1)21 phase. The behavior of the hard modes confirms the structural phase transition close to the tricritical point. The temperature of the structural phase transition T(1) = 33 K is established

Mechanistic studies on the application of DNA aptamers as inhibitors of 2-oxoglutarate-dependent oxygenases.

The Escherichia coli (E. coli) AlkB protein and its functional human homologues belong to a subfamily of 2-oxoglutarate (2OG) dependent oxygenases (2OG oxygenases for simplicity) that enable the repair of cytotoxic methylation damage in nucleic acids and that catalyze t-RNA oxidations. DNA alkylation is a major mechanism of action for cytotoxic anticancer drugs. Thus, the inhibition of oxidative demethylation, catalyzed by these enzymes, has the potential to improve the efficacy of chemotherapies. Here we report that oligonucleotide aptamers constitute a new class of potent inhibitors of 2OG oxygenases. DNA aptamers can selectively bind to AlkB, with nanomolar affinity, and efficiently inhibit catalysis. The mechanism of inhibition was studied by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. Inhibition constants of the aptamers were determined and shown to correlate well with K(d) values. The results of kinetic analyses imply that the aptamers bind AlkB away from the active site. Our findings should stimulate the development of oligonucleotide aptamers for human homologues of AlkB and further their study as potential enhancers of chemotherapy efficiency

DNA aptamers for as analytical tools for the quantitative analysis of DNA-dealkylating enzymes.

The AlkB family of oxygenases catalyze the removal of alkyl groups from nucleic acid substrates in an iron and 2-oxoglutarate-dependent manner and have roles including in DNA repair. To understand the biological functions of these DNA-dealkylating enzymes it is desirable to measure their expression levels in vitro and in vivo in complex biological matrixes. Quantitative analyses of the enzymes require affinity probes capable of binding AlkB family members selectively and with high affinity. Here we report that DNA aptamers can serve as efficient affinity probes for quantitative detection of such enzymes in vitro. Nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) was applied as a general tool for: (i) selection of DNA aptamers, (ii) characterization of binding parameters for the aptamers, and (iii) quantitative detection of the target in an aptamer-based affinity analysis. The selected aptamers have a range of K(d) values between 20 and 240nM. The aptamers enabled accurate quantitative analysis of AlkB even in the presence of the Escherichia coli cell lysate. Aptamers can likely be developed for other nucleic acid repair enzymes. They may also be developed for use in in vitro and potentially in vivo studies of known nucleic acid-modifying enzymes including for functional analysis

Direct analysis of enzyme-catalyzed DNA demethylation.

N/O-methylation of DNA can be cytotoxic and mutagenic; therefore, enzymes that reverse DNA methylation are essential for organism survival. Several 2-oxoglutarate-dependent oxygenases and methyltransferases that remove a methyl group from a methylated DNA base have been identified. Studies of their kinetics and search for their inhibitors have been retarded by the lack of an approach to directly quantitate DNA substrates and products that differ by a single methyl group. Here, we introduce such an approach, which is based on capillary electrophoresis with laser-induced fluorescence detection. We achieved baseline separation of a fluorescently labeled 15-nucleotide-long single-base methylated DNA substrate from its demethylated product, followed by its quantitative detection. We then used this approach to study the kinetics of AlkB-catalyzed DNA demethylation and screen a number of potential inhibitors of this reaction. Ten new inhibitors, which can be used as templates in developing therapies targeting AlkB-like enzymes, were identified. Our approach will be applicable for in vitro kinetic studies of known DNA demethylating and methylating enzymes and in the discovery of new ones

miR-620 promotes tumor radioresistance by targeting 15-hydroxyprostaglandin dehydrogenase (HPGD).

MicroRNA contribute to tumor radiation resistance, which is an important clinical problem, and thus we are interested in identifying and characterizing their function. We demonstrate that miR-620 contributes to radiation resistance in cancer cells by increasing proliferation, and decreasing the G2/M block. We identify the hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (HPGD/15-PGDH) tumor suppressor gene as a direct miR-620 target, which results in increased prostaglandin E2 (PGE2) levels. Furthermore, we show that siRNA targeting of HPGD or administration of exogenous PGE2 recapitulates radioresistance. Targeting of the EP2 receptor that responds to PGE2 using pharmacological or genetic approaches, abrogates radioresistance. Tumor xenograft experiments confirm that miR-620 increases proliferation and tumor radioresistance in vivo. Regulation of PGE2 levels via targeting of HPGD by miR-620 is an innovative manner by which a microRNA can induce radiation resistance

miR-620 promotes tumor radioresistance by targeting 15-hydroxyprostaglandin dehydrogenase (HPGD).

MicroRNA contribute to tumor radiation resistance, which is an important clinical problem, and thus we are interested in identifying and characterizing their function. We demonstrate that miR-620 contributes to radiation resistance in cancer cells by increasing proliferation, and decreasing the G2/M block. We identify the hydroxyprostaglandin dehydrogenase 15-(nicotinamide adenine dinucleotide) (HPGD/15-PGDH) tumor suppressor gene as a direct miR-620 target, which results in increased prostaglandin E2 (PGE2) levels. Furthermore, we show that siRNA targeting of HPGD or administration of exogenous PGE2 recapitulates radioresistance. Targeting of the EP2 receptor that responds to PGE2 using pharmacological or genetic approaches, abrogates radioresistance. Tumor xenograft experiments confirm that miR-620 increases proliferation and tumor radioresistance in vivo. Regulation of PGE2 levels via targeting of HPGD by miR-620 is an innovative manner by which a microRNA can induce radiation resistance