Barnase-Barstar Pair: Contemporary Application in Cancer Research and Nanotechnology.

Barnase is an extracellular ribonuclease secreted by Bacillus amyloliquefaciens that was originally studied as a small stable enzyme with robust folding. The identification of barnase intracellular inhibitor barstar led to the discovery of an incredibly strong protein-protein interaction. Together, barnase and barstar provide a fully genetically encoded toxin-antitoxin pair having an extremely low dissociation constant. Moreover, compared to other dimerization systems, the barnase-barstar module provides the exact one-to-one ratio of the complex components and possesses high stability of each component in a complex and high solubility in aqueous solutions without self-aggregation. The unique properties of barnase and barstar allow the application of this pair for the engineering of different variants of targeted anticancer compounds and cytotoxic supramolecular complexes. Using barnase in suicide gene therapy has also found its niche in anticancer therapy. The application of barnase and barstar in contemporary experimental cancer therapy is reflected in the review.

Intrinsic Dynamics of Protein-Peptide Unbinding.

The dynamics of peptide-protein binding and unbinding of a variant of the RNase S system has been investigated. To initiate the process, a photoswitchable azobenzene moiety has been covalently linked to the S-peptide, thereby switching its binding affinity to the S-protein. Transient fluorescence quenching was measured with the help of a time-resolved fluorometer, which has been specifically designed for these experiments and is based on inexpensive light-emitting diodes and laser diodes only. One mutant shows on-off behavior with no specific binding detectable in one of the states of the photoswitch. Unbinding is faster by at least 2 orders of magnitude, compared to that of other variants of the RNase S system. We conclude that unbinding is essentially barrier-less in that case, revealing the intrinsic dynamics of the unbinding event, which occurs on a time scale of a few hundred microseconds in a strongly stretched-exponential manner.

Antimicrobial Role of RNASET2 Protein During Innate Immune Response in the Medicinal Leech Hirudo verbana.

The innate immune response represents a first-line defense against pathogen infection that has been widely conserved throughout evolution. Using the invertebrate Hirudo verbana (Annelida, Hirudinea) as an experimental model, we show here that the RNASET2 ribonuclease is directly involved in the immune response against Gram-positive bacteria. Injection of lipoteichoic acid (LTA), a key component of Gram-positive bacteria cell wall, into the leech body wall induced a massive migration of granulocytes and macrophages expressing TLR2 (the key receptor involved in the response to Gram-positive bacteria) toward the challenged/inoculated area. We hypothesized that the endogenous leech RNASET2 protein (HvRNASET2) might be involved in the antimicrobial response, as already described for other vertebrate ribonucleases, such as RNase3 and RNase7. In support of our hypothesis, HvRNASET2 was mainly localized in the granules of granulocytes, and its release in the extracellular matrix triggered the recruitment of macrophages toward the area stimulated with LTA. The activity of HvRNASET2 was also evaluated on Staphylococcus aureus living cells by means of light, transmission, and scanning electron microscopy analysis. HvRNASET2 injection triggered the formation of S. aureus clumps following a direct interaction with the bacterial cell wall, as demonstrated by immunogold assay. Taken together, our data support the notion that, during the early phase of leech immune response, granulocyte-released HvRNASET2 triggers bacterial clumps formation and, at the same time, actively recruits phagocytic macrophages in order to elicit a rapid and effective eradication of the infecting microorganisms from inoculated area.

RNA binding proteins in the control of autoimmune diseases.

Autoimmune disease is induced by the breakdown of immune tolerance to self-antigens. This is brought about by an imbalance between the activation and the repression of immune responses. Dysregulation of the immune response is driven by the excess of proinflammatory cytokines such as IL-6 and TNF, which play a central role in the pathogenesis of a set of autoimmune diseases. The expression of proinflammatory mediator genes is tightly controlled by post-transcriptional regulation, which is mediated by a set of immune-related RNA binding proteins, such as tristetraprolin, Roquin, and Regnase-1. These proteins coordinately control the stability of proinflammatory mRNAs to regulate aberrant immune reactions. In this review, we discuss the roles of RNA binding proteins which are associated with the immune regulation and autoimmune pathogenesis.

Modulating Protein Stability to Switch Toxic Protein Function On and Off in Living Cells.

Toxic proteins are prime targets for molecular farming (the generation of pharmacologically active or biotechnologically usable compounds in plants) and are also efficient tools for targeted cell ablation in genetics, developmental biology, and biotechnology. However, achieving conditional activity of cytotoxins and maintaining the toxin-expressing plants as stably transformed lines remain challenging. Here, we produce a switchable version of the highly cytotoxic bacterial RNase barnase by fusing the protein to a portable protein degradation cassette, the low-temperature degron cassette. This method allows conditional genetics based on conditional protein degradation via the N-end rule or N-degron pathway and has been used to vice versa accumulate and/or deplete a diverse variety of highly active, unstable or stable target proteins in different living multicellular organisms and cell systems. Moreover, we expressed the barnase fusion under control of the trichome-specific TRIPTYCHON promoter. This enabled efficient temperature-dependent control of protein accumulation in Arabidopsis (Arabidopsis thaliana) leaf hairs (trichomes). By tuning the levels of the protein, we were able to control the fate of trichomes in vivo. The on-demand formation of trichomes through manipulating the balance between stabilization and destabilization of barnase provides proof of concept for a robust and powerful tool for conditional switchable cell arrest. We present this tool as a potential strategy for the manufacture and accumulation of cytotoxic proteins and toxic high-value products in plants or for conditional genetic cell ablation.

Role of Zc3h12a in enhanced IL-6 production by newborn mononuclear cells in response to lipopolysaccharide.

BACKGROUND: The uncontrolled inflammatory response following infection is closely related to the morbidity and mortality of neonates. Interleukin 6 (IL-6) plays an important role in the pathogenesis and prognosis of this process. To better elucidate the secretion of IL-6 following infection in neonates, we investigated the IL-6 level and mechanism of IL-6/TLR4 signaling pathways. METHODS: We compared the IL-6, procalcitonin (PCT), and CRP levels between septic neonates and toddlers. In vitro cord blood samples from healthy term neonates and peripheral venous blood from healthy adult volunteers were collected. Protein expression was analyzed by Western blotting, mRNA expression by real-time PCR and membrane molecule expression by flow cytometry. RESULTS: The IL-6 concentrations were significantly higher in the neonate group than in the toddler group (p < 0.05). In the toddler group, the IL-6 concentrations were correlated positively with both PCT and CRP (PCT: r = 0.451, p = 0.001; CRP: r = 0.243, p = 0.023). In vitro, the secretion of IL-6 increased with the rising concentrations of LPS; at 1000 ng/ml LPS, IL-6 secretion from the monocytes of neonates was significantly higher than that of adults. There was a marked decreased level of MyD88 in neonate monocytes compared with that in adult monocytes. Additionally, the mRNA levels of Zc3h12a in neonate monocytes were significantly lower than those in adult monocytes following LPS stimulation. CONCLUSION: Neonates displayed enhanced IL-6 production after infection. Our study, for the first time, reported a significant decrease in the expression of Zc3h12a in neonates. Thus, Zc3h12a may be a key factor for the aberrant increase in IL-6 after neonate infection.

Mouse eosinophil associated ribonucleases: Mechanism of cytotoxic, antibacterial and antiparasitic activities.

Ribonuclease A family is a group of proteins having similar structures and catalytic mechanism but different functions. Human eosinophil granules contain two ribonucleases belonging to the RNase A family, eosinophil cationic protein (ECP) and eosinophil derived neurotoxin (EDN). In mouse, 15 orthologs of EDN and ECP, called mouse eosinophil associated ribonucleases (mEARs) have been reported which are expressed under different pathophysiological conditions. In this study, we have characterized mEAR2, mEAR5, mEAR7 and mEAR11, and compared them with ECP for their catalytic, cytotoxic, antibacterial and antiparasitic activities. All four mEARs had cytotoxic, antibacterial and antiparasitic activities. Generally, mEAR5 and mEAR2 were more cytotoxic than mEAR7, mEAR11 and ECP. The antimicrobial activities of mEAR7 and mEAR5 were higher than those of mEAR11 and mEAR2. The cytotoxic activity appeared to be associated with the basicity and RNase activity of mEARs, whereas no such correlation was observed for antimicrobial activities. The differential selective expression of mEARs under various pathophysiological conditions may be associated with the different biological activities of various mEARs.

Virus-Mediated Alterations in miRNA Factors and Degradation of Viral miRNAs by MCPIP1.

Kaposi's sarcoma-associated herpesvirus (KSHV), the causative agent of Kaposi's sarcoma, encodes 25 mature viral miRNAs. MCP-1-induced protein-1 (MCPIP1), a critical regulator of immune homeostasis, has been shown to suppress miRNA biosynthesis via cleavage of precursor miRNAs through its RNase domain. We demonstrate that MCPIP1 can directly cleave KSHV and EBV precursor miRNAs and that MCPIP1 expression is repressed following de novo KSHV infection. In addition, repression with siRNAs to MCPIP1 in KSHV-infected cells increased IL-6 and KSHV miRNA expression, supporting a role for MCPIP1 in IL-6 and KSHV miRNA regulation. We also provide evidence that KSHV miRNAs repress MCPIP1 expression by targeting the 3'UTR of MCPIP1. Conversely, expression of essential miRNA biogenesis components Dicer and TRBP is increased following latent KSHV infection. We propose that KSHV infection inhibits a negative regulator of miRNA biogenesis (MCPIP1) and up-regulates critical miRNA processing components to evade host mechanisms that inhibit expression of viral miRNAs. KSHV-mediated alterations in miRNA biogenesis represent a novel mechanism by which KSHV interacts with its host and a new mechanism for the regulation of viral miRNA expression.

Macrophage-derived MCPIP1 mediates silica-induced pulmonary fibrosis via autophagy.

BACKGROUND: Silicosis is characterized by accumulation of fibroblasts and excessive deposition of extracellular matrix. Monocyte chemotactic protein-1-induced protein 1 (MCPIP1) plays a critical role in fibrosis induced by SiO2. However, the details of the downstream events of MCPIP1 activity in pulmonary fibrosis remain unclear. To elucidate the role of MCPIP1-induced autophagy in SiO2-induced fibrosis, both the upstream molecular mechanisms and the functional effects of SiO2 on cell apoptosis, proliferation and migration were investigated. RESULTS: Experiments using primary cultures of alveolar macrophages from healthy donors and silicosis patients as well as differentiated U937 macrophages demonstrated the following results: 1) SiO2 induced macrophage autophagy in association with enhanced expression of MCPIP1; 2) autophagy promoted apoptosis and activation of macrophages exposed to SiO2, and these events induced the development of silicosis; 3) MCPIP1 facilitated macrophage apoptosis and activation via p53 signaling-mediated autophagy; and 4) SiO2-activated macrophages promoted the proliferation and migration of fibroblasts via the MCPIP1/p53-mediated autophagy pathway. CONCLUSIONS: Our results elucidated a link between SiO2-induced fibrosis and MCPIP1/p53 signaling-mediated autophagy. These findings provide novel insight into the potential targeting of MCPIP1 or autophagy in the development of potential therapeutic strategies for silicosis.

RNASET2 is required for ROS propagation during oxidative stress-mediated cell death.

RNASET2 is a ubiquitously expressed acidic ribonuclease that has been implicated in diverse pathophysiological processes including tumorigeneis, vitiligo, asthenozoospermia, and neurodegeneration. Prior studies indicate that RNASET2 is induced in response to oxidative stress and that overexpression of RNASET2 sensitizes cells to reactive oxygen species (ROS)-induced cell death through a mechanism that is independent of catalytic activity. Herein, we report a loss-of-function genetic screen that identified RNASET2 as an essential gene for lipotoxic cell death. Haploinsufficiency of RNASET2 confers increased antioxidant capacity and generalized resistance to oxidative stress-mediated cell death in cultured cells. This function is critically dependent on catalytic activity. Furthermore, knockdown of RNASET2 in the Drosophila fat body confers increased survival in the setting of oxidative stress inducers. Together, these findings demonstrate that RNASET2 regulates antioxidant tone and is required for physiological ROS responses.

MCPIP1 Regulates Fibroblast Migration in 3-D Collagen Matrices Downstream of MAP Kinases and NF-κB.

The fibroblast-populated three-dimensional (3-D) collagen matrix has been used to model matrix contraction, cell motility, and general fibroblast biology. MCPIP1 (monocyte chemotactic protein-induced protein 1) has been shown to regulate inflammation, angiogenesis, and cellular motility. In the present study, we demonstrated induction of MCPIP1 in human fibroblasts embedded in the stress-released 3-D collagen matrix, which occurred through activation of mitogen-activated protein kinases, phosphoinositide 3-kinase, and NF-κB. Furthermore, MCPIP1 induction was associated with inhibition of fibroblast migration out of the nested collagen matrix. MCPIP1 induction or ectopic expression also upregulated p53. RNA interference of p53 prevented the inhibition of migration produced by induction or ectopic expression of MCPIP1. Our findings suggest a new role for MCPIP1 as a molecular switch that regulates fibroblast migration in the nested collagen matrix model.

Amplifying renal immunity: the role of antimicrobial peptides in pyelonephritis.

Urinary tract infections (UTIs), including pyelonephritis, are among the most common and serious infections encountered in nephrology practice. UTI risk is increased in selected patient populations with renal and urinary tract disorders. As the prevalence of antibiotic-resistant uropathogens increases, novel and alternative treatment options will be needed to reduce UTI-associated morbidity. Discoveries over the past decade demonstrate a fundamental role for the innate immune system in protecting the urothelium from bacterial challenge. Antimicrobial peptides, an integral component of this urothelial innate immune system, demonstrate potent bactericidal activity toward uropathogens and might represent a novel class of UTI therapeutics. The urothelium of the bladder and the renal epithelium secrete antimicrobial peptides into the urinary stream. In the kidney, intercalated cells--a cell-type involved in acid-base homeostasis--have been shown to be an important source of antimicrobial peptides. Intercalated cells have therefore become the focus of new investigations to explore their function during pyelonephritis and their role in maintaining urinary tract sterility. This Review provides an overview of UTI pathogenesis in the upper and lower urinary tract. We describe the role of intercalated cells and the innate immune response in preventing UTI, specifically highlighting the role of antimicrobial peptides in maintaining urinary tract sterility.

Role of extracellular RNA in atherosclerotic plaque formation in mice.

BACKGROUND: Atherosclerosis and vascular remodeling after injury are driven by inflammation and mononuclear cell infiltration. Extracellular RNA (eRNA) has recently been implicated to become enriched at sites of tissue damage and to act as a proinflammatory mediator. Here, we addressed the role of eRNA in high-fat diet-induced atherosclerosis and neointima formation after injury in atherosclerosis-prone mice. METHODS AND RESULTS: The presence of eRNA was revealed in atherosclerotic lesions from high-fat diet-fed low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice in a time-progressive fashion. RNase activity in plasma increased within the first 2 weeks (44±9 versus 70±7 mU/mg protein; P=0.0012), followed by a decrease to levels below baseline after 4 weeks of high-fat diet (44±9 versus 12±2 mU/mg protein; P<0.0001). Exposure of bone marrow-derived macrophages to eRNA resulted in a concentration-dependent upregulation of the proinflammatory mediators tumor necrosis factor-α, arginase-2, interleukin-1ß, interleukin-6, and interferon-γ. In a model of accelerated atherosclerosis after arterial injury in apolipoprotein E-deficient (ApoE(-/-)) mice, treatment with RNase1 diminished the increased plasma level of eRNA evidenced after injury. Likewise, RNase1 administration reduced neointima formation in comparison with vehicle-treated ApoE(-/-) controls (25.0±6.2 versus 46.9±6.9×10(3) µm(2), P=0.0339) and was associated with a significant decrease in plaque macrophage content. Functionally, RNase1 treatment impaired monocyte arrest on activated smooth muscle cells under flow conditions in vitro and inhibited leukocyte recruitment to injured carotid arteries in vivo. CONCLUSIONS: Because eRNA is associated with atherosclerotic lesions and contributes to inflammation-dependent plaque progression in atherosclerosis-prone mice, its targeting with RNase1 may serve as a new treatment option against atherosclerosis.

RNase J participates in a pentatricopeptide repeat protein-mediated 5' end maturation of chloroplast mRNAs.

Nucleus-encoded ribonucleases and RNA-binding proteins influence chloroplast gene expression through their roles in RNA maturation and stability. One mechanism for mRNA 5' end maturation posits that sequence-specific pentatricopeptide repeat (PPR) proteins define termini by blocking the 5'→3' exonucleolytic activity of ribonuclease J (RNase J). To test this hypothesis in vivo, virus-induced gene silencing was used to reduce the expression of three PPR proteins and RNase J, both individually and jointly, in Nicotiana benthamiana. In accordance with the stability-conferring function of the PPR proteins PPR10, HCF152 and MRL1, accumulation of the cognate RNA species atpH, petB and rbcL was reduced when the PPR-encoding genes were silenced. In contrast, RNase J reduction alone or combined with PPR deficiency resulted in reduced abundance of polycistronic precursor transcripts and mature counterparts, which were replaced by intermediately sized species with heterogeneous 5' ends. We conclude that RNase J deficiency can partially mask the absence of PPR proteins, and that RNase J is capable of processing chloroplast mRNAs up to PPR protein-binding sites. These findings support the hypothesis that RNase J is the major ribonuclease responsible for maturing chloroplast mRNA 5' termini, with RNA-binding proteins acting as barriers to its activity.

RNASET2--an autoantigen in anaplastic large cell lymphoma identified by protein array analysis.

Characterising tumour-associated antigens (TAAs) not only represents an important approach to the identification of new diagnostic/prognostic markers, but can also provide information on disease processes and additional potential therapeutic targets. Preliminary screening of a protein macroarray, containing more than 12,000 different proteins, with sera from anaplastic lymphoma kinase (ALK)-negative and ALK-positive anaplastic large cell lymphoma (ALCL) patients identified ribonuclease and tumour suppressor protein Ribonuclease T2 (RNASET2), phosphatase lipid phosphate phosphatase-related protein type 3 (LPPR3) and apoptotic adaptor molecule Fas-associating protein (FADD) as ALK-negative ALCL-associated TAAs. Further validation of these observations was confirmed using the ALCL sera in reverse ELISAs. The circulating anti-RNASET2 autoantibodies present in ALCL patients' sera also recognised eukaryotically expressed RNASET2 protein. RNASET2 expression was then investigated in normal tissues and in lymphomas to explore its clinical potential. RNASET2 protein and mRNA levels showed highest expression in the spleen, leucocytes and pancreas. RNASET2 protein expression was not restricted to ALK-negative ALCL (81%), being expressed in ALK-positive ALCL (65%) as well as in a number of other lymphomas. The immunological recognition of RNASET2, its expression in ALCL and other lymphomas together with its known tumourigenic properties suggest that further studies on this autoantigen are warranted.

Molecular signature induced by RNASET2, a tumor antagonizing gene, in ovarian cancer cells.

Using the Hey3Met2 human ovarian cancer cell line, we previously found the RNASET2 gene to possess a remarkable in vivo tumor suppressor activity, although no in vitro features such as inhibition of cell proliferation, clonogenic potential, impaired growth in soft agar and increase in apoptotic rate could be detected. This is reminiscent of the behavior of genes belonging to the class of tumor antagonizing genes (TAG) which act mainly within the context of the microenvironment. Here we present transcriptional profiles analysis which indicates that investigations of the mechanisms of TAG biological functions require a comparison between the in vitro and in vivo expression patterns. Indeed several genes displaying a biological function potentially related to tumor suppression could not be validated by subsequent in vivo expression analysis. On the other hand the fact that we could find congruency for three genes both in vivo and in vitro adds a warning to a too much stringent categorization of this class of genes which relies on the sensitivity of the methodological approaches.

Virulence gene regulation by CvfA, a putative RNase: the CvfA-enolase complex in Streptococcus pyogenes links nutritional stress, growth-phase control, and virulence gene expression.

Streptococcus pyogenes, a multiple-auxotrophic human pathogen, regulates virulence gene expression according to nutritional availability during various stages in the infection process or in different infection sites. We discovered that CvfA influenced the expression of virulence genes according to growth phase and nutritional status. The influence of CvfA in C medium, rich in peptides and poor in carbohydrates, was most pronounced at the stationary phase. Under these conditions, up to 30% of the transcriptome exhibited altered expression; the levels of expression of multiple virulence genes were altered, including the genes encoding streptokinase, CAMP factor, streptolysin O, M protein (more abundant in the CvfA(-) mutant), SpeB, mitogenic factor, and streptolysin S (less abundant). The increase of carbohydrates or peptides in media restored the levels of expression of the virulence genes in the CvfA(-) mutant to wild-type levels (emm, ska, and cfa by carbohydrates; speB by peptides). Even though the regulation of gene expression dependent on nutritional stress is commonly linked to the stringent response, the levels of ppGpp were not altered by deletion of cvfA. Instead, CvfA interacted with enolase, implying that CvfA, a putative RNase, controls the transcript decay rates of virulence factors or their regulators according to nutritional status. The virulence of CvfA(-) mutants was highly attenuated in murine models, indicating that CvfA-mediated gene regulation is necessary for the pathogenesis of S. pyogenes. Taken together, the CvfA-enolase complex in S. pyogenes is involved in the regulation of virulence gene expression by controlling RNA degradation according to nutritional stress.

T2 Family ribonucleases: ancient enzymes with diverse roles.

Ribonucleases of the T2 family are found in the genomes of protozoans, plants, bacteria, animals and viruses. A broad range of biological roles for these ribonucleases have been suggested, including scavenging of nucleic acids, degradation of self-RNA, serving as extra- or intracellular cytotoxins, and modulating host immune responses. Recently, RNaseT2 family members have been implicated in human pathologies such as cancer and parasitic diseases. Interestingly, certain functions of RNaseT2 family members are independent of their nuclease activity, suggesting that these proteins have additional functions. Moreover, humans lacking RNASET2 manifest a defect in neurological development, perhaps due to aberrant control of the immune system. We review the basic structure and function of RNaseT2 family members and their biological roles.

Ribonucleases in tumor growth.

This review summarizes data on ambiguous biological functions of ribonucleases (RNases) at tumor growth. In some cases the raised level of enzyme activity in biological fluids can be regarded as an additional marker of malignant growth (pancreas cancer, chronic myeloid leukemia, etc.). At the same time the activity of RNases is often lowered in tumor tissue. High substrate specificity of particular RNases provides metabolic balance between various kinds of RNAs with various half-time exchange turn. RNases are the important factors of epigenetic regulation of gene activity in cells. The activity of RNases is adjustable by inhibitors and other factors, and defines time of existence of different kinds of RNAs. RNases (the modified variants of RNase A, RNases of semen fluid of the cattle, RNase of amphibia oocytes) can be used as anti-tumor therapeutic agents. On the other hand, some inhibitors of RNases of natural or synthetic origin were demonstrated to be perspective drugs that inhibit tumor growth.