Why ribonucleases cause death of cancer cells

Molecular properties and possible mechanisms of action of cytotoxic ribonucleases (RNases), potential antitumor therapeutics, are characterized. The analysis of recent publications and own experimental results have allowed the authors, on the one hand, to distinguish cellular components that are responsible for selective activity of exogenous RNases towards malignant cells, and on the other - to identify the contribution of definite molecular determinants to the enzyme cytotoxicity. The predominant effect of the RNase molecule charge on the cell death induction is shown. The RNase cytotoxic effects are caused by catalytic cleavage of available RNA, by products of its hydrolysis, as well as by non-catalytic electrostatic interaction of exogenous enzyme with cell components. Potential targets for RNase action in a cancer cell have been revealed. The role of modulation of the membrane calcium-dependent potassium channels and ras-oncogene functions in the RNase-induced cell damage is defined. The effect of cytotoxic RNases on gene expression via influencing the RNA interference is discussed

Shuttling of Spin Polarized Electrons in Molecular Transistors

Shuttling of electrons in single-molecule transistors with magnetic leads in the presence of an external magnetic field is considered theoretically. For a current of partially spin-polarized electrons a shuttle instability is predicted to occur for a finite interval of external magnetic field strengths. The lower critical magnetic field is determined by the degree of spin polarization and it vanishes as the spin polarization approaches 100%. The feasibility of detecting magnetic shuttling in a $C_{60}$-based molecular transistor with magnetic (Ni) electrodes is discussed [A.~N.~Pasupathy et al., Science 306, 86 (2004)].Comment: Submitted to a special issue of "Synthetic Metals" to appear in March 201

Mechanically Induced Thermal Breakdown in Magnetic Shuttle Structures

A theory of a thermally induced single-electron "shuttling" instability in a magnetic nanomechanical device subject to an external magnetic field is presented in the Coulomb blockade regime of electron transport. The model magnetic shuttle device considered comprises a movable metallic grain suspended between two magnetic leads, which are kept at different temperatures and assumed to be fully spin polarized with antiparallel magnetizations. For a given temperature difference shuttling is found to occur for a region of external magnetic fields between a lower and an upper critical field strength, which separate the shuttling regime from normal small-amplitude "vibronic" regimes. We find that (i) the upper critical magnetic field saturates to a constant value in the high temperature limit and that the shuttle instability domain expands with a decrease of the temperature, (ii) the lower critical magnetic field depends not only on the temperature independent phenomenological friction coefficient used in the model but also on intrinsic friction (which vanishes in the high temperature limit) caused by magnetic exchange forces and electron tunneling between the quantum dot and the leads. The feasibility of using thermally driven magnetic shuttle systems to harvest thermal breakdown phenomena is discussed.Comment: 9 pages, 2 figure

Binase and other microbial RNases as potential anticancer agents

Some RNases possess preferential cytotoxicity against malignant cells. The best known of these RNases, onconase, was isolated from frog oocytes; and is in clinical trials as anticancer therapy. Here we propose an alternative platform for anticancer therapy based on T1 RNases of microbial origin, in particular binase from Bacillus Intermedius and RNase Sa from Streptomyces aureofaciens. We discuss their advantages and the most promising directions of research for their potential clinical applications. © 2008 Wiley Periodicals, Inc

Mg²⁺ Enhances the Formation of 2′,3′-cGMP, an Intermediate of RNA Cleavage by Binase

© 2016, Springer Science+Business Media New York.Binase, the ribonuclease secreted by Bacillus pumilus, is an endonuclease that cleaves the phosphodiester bond between the 3′-guanyl residue and 5′-OH residue of an adjacent nucleotide, with the formation of a corresponding intermediate, 2′,3′-cGMP on the first stage of a catalytic reaction. Binase possesses selective antitumor effect and induces apoptosis of lung carcinoma A549 cells. It was shown that the 2′,3′-cGMP messenger could exist in the reaction mixture over an hour. Furthermore, the addition of divalent non-transition metal Mg2+ increases the level of 2′,3′-cGMP formed by binase and that could be associated with the stabilization of RNA tertiary structure by this metal. It has been shown that exogenous 2′,3′-cGMP does not induce apoptosis of A549 cells, which are sensitive to binase. However, taking into account the cell-penetrating ability of binase, it can be concluded that 2′,3′-cGMP contributes to apoptogenic binase action only when it is formed intracellularly

Cell targets of antitumor ribonucleases

Several ribonucleases (RNases) are known to exert a toxic effect on tumor cells, but the mechanism of their antitumor activity is still poorly understood. The review considers the RNase-cell component interaction that leads to induction of apoptosis in the tumor cell. The cell surface structures that potentially act as acceptors of exogenous RNases include acidic lipids, glycoproteins, heparan sulfate-containing proteoglycans, actin, and RNA-associated proteins. Normal and malignant cells differ in the membrane composition of these components, and the difference is to a great extent responsible for the selectivity of the RNase effect. Various RNAs may act as intracellular RNase targets, and there is evidence that exogenous RNases may intervene in RNA interference. Potassium channels, the NF-κB signaling pathway, and various caspases play a role in exogenous RNase-induced apoptosis. The cell sensitivity to exogenous RNases proved to be related to expression of certain oncogenes, such as RAS, KIT, and AML1-ETO. Understanding the mechanisms that sustain RNase cytotoxicity in susceptible malignant cells is thought to provide a basis for designing new drugs for targeted anticancer therapy. © 2014 Pleiades Publishing, Inc

Salt Stress Induced Biosynthesis of Binase II, the Second Bacillus pumilus 7P Ribonuclease with Therapeutic Potential

© 2016, Springer Science+Business Media New York.Besides the dominant well-studied low-molecular weight ribonuclease (RNase) binase I, Bacillus pumilus secretes a high-molecular weight binase II which differs from binase I by the absence of substrate specificity and the mode of RNA cleavage. Similar to many other RNases, binase II was proposed to have therapeutic potential. Deciphering molecular mechanisms of binase II biosynthesis regulation is required to boost expression of this RNase. Here, we have shown that increase of salinity in growth medium leads to elevated biosynthesis level of binase II. We detected in the binase II promoter the gene sequences homologous to the recognition sites of response regulator DegU. DegS-DegU signal transduction system is stimulated by high salt concentrations. Using the Bacillus subtilis strains with various mutations in DegU gene, we have shown that the DegS-DegU system is responsible for the increase of binase II gene expression under salt stress, indeed

Bacterial communities inhabiting toxic industrial wastewater generated during nitrocellulose production

© 2016 Institute of Molecular Biology, Slovak Academy of Sciences.Investigating the microbial community structure and composition of toxic industrial wastes contaminated with nitrocellulose and various by-products is crucial for understanding the fate of these pollutants in the environment and for the development and application of efiective bioremediation processes. In this study, we investigated the chemical properties and toxic potential of wastewater generated during nitrocellulose production. The analyzed wastewater from settling pond contained nitrocellulose powder particles as well as increased ammonium (570-760 mg/L), sulfate (1625-2045 mg/L) and sulfite (864-1014 mg/L) concentrations. The toxicity test results demonstrated that the wastewater samples present acute toxicity for Paramecium caudatum and Daphnia magna. Furthermore, bacterial community structure in the samples was characterized by pyrosequencing of 16S rRNA genes. Phylogenetic analysis of bacterial sequences indicated that Proteobacteria, Bacteroidetes and Firmicutes were the main phyla in the sample near inlet, whereas various phylotypes of the phyla Proteobacteria, Chlorobi, Bacteroidetes and Gemmatimonadetes dominated in the sample near outlet. Some bacterial members observed in the current work can be considered as agents capable of performing biodegradation of various hazardous contaminants, indicating that the described bacterial communities have a high potential for the development of efiective bioremediation strategies

Induction of apoptosis in tumor cells by binase

The possibility of inducing apoptosis in K562 myelogenic erythroleukemia cells, A549 lung carcinoma cells, and normal human lymphocytes was studied for Bacillus intermedius RNase (binase) and its mutants Lys26 Ala and His101 Glu with impaired catalytic activity. Selective induction of apoptosis in leukemic blood cells by binase was demonstrated for the first time. Binase did not exert an antiproliferative or proapoptotic effect on peripheral blood lymphocytes of healthy donors. Low-molecular-weight (less than 50 kb in size) oligonucleosomal DNA fragments, which are early markers of apoptosis, were observed in human solid-tumor cells treated with binase. Studies with the binase mutants showed that a decrease in catalytic activity to 2.5% of the level characteristic of the wild-type enzyme deprives binase of its proapoptotic effect. The selective proapoptotic effect of binase on malignant cells provides evidence that bacterial RNases are promising for designing alternative antitumor drugs. © 2005 Pleiades Publishing, Inc

Induction of apoptosis of tumor cells by binase

An induction of apoptosis by RNase from Bacillus intermedius (binase) and its mutants characterized with low catalytic activity (Lys 26Ala and His 101Glu) in human myelogenic erythroleukemia K562 cells, human lung carcinoma A549 cells and human peripheral blood mononuclear cells was studied. For the first time selective apoptogenic effects of binase toward leukemic blood cells was determined. Neither antiproliferative nor apoptotic effects of binase were detected in normal human peripheral blood mononuclear cells. Formation of low molecular weight oligonucleosomal DNA fragments (less than 50 Kb) which are an early marks of apoptosis was registered in solid tumor cells treated by binase. Using mutant RNases it was shown that decrease of catalytic activity to 2.5% of wild type enzyme activity leads to the loss of apoptogenic properties of enzyme. Selective apoptogenicity of binase found towards malignant cells confirmed that antitumor agents based on bacterial RNases could be considered as an alternative to standard chemotherapeutic drugs