Chemical synthesis and thermodynamic characterization of oxanine-containing oligodeoxynucleotides

Oxanine (Oxa, O), one of the major damaged bases from guanine generated by NO- or HNO(2)-induced nitrosative deamination, has been considered as a mutagen-potent lesion. For exploring more detailed properties of Oxa, large-scale preparation of Oxa-containing oligodeoxynucleotide (Oxa-ODN) with the desired base sequence is a prerequisite. In the present study, we have developed a chemical synthesis procedure of Oxa-ODNs and characterized thermodynamic properties of Oxa in DNA strands. First, 2′-deoxynucleoside of Oxa (dOxo) obtained from 2′-deoxyguanosine by HNO(2)-nitrosation was subjected to 5′-O-selective tritylation to give 5′-O-(4,4′-dimethoxytrityl)-dOxo (DMT-dOxo) with a maximum yield of 70%. Subsequently, DMT-dOxo was treated with conventional phosphoramidation, which resulted in DMT-dOxo-amidite monomer with a maximum yield of 72.5%. The amidite obtained was used for synthesizing Oxa-ODNs: the coupling yields for Oxa incorporation were over 93%. The prepared Oxa-ODNs were employed for analyzing the thermodynamic properties of DNA duplexes containing base-matches of O:N [N; C (cytosine), T (thymine), G (guanine) or A (adenine)]. Melting temperatures (T(m)) and thermodynamic stability ([Formula: see text]) were found to be lower by 6.83∼13.41°C and 2.643∼6.047 kcal mol(−1), respectively, compared with those of oligodeoxynucleotides, which had the same base sequence except that O:N was replaced by G:C (wild type). It has also been found that Oxa-pairing with cytosine shows relatively high stability in DNA duplex compared with other base combinations. The orders of [Formula: see text] were O:C > O:T > O:A > O:G. The chemical synthesis procedure and thermodynamic characteristics of Oxa-ODNs established here will be helpful for elucidating the biological significance of Oxa in relation to genotoxic and repair mechanisms

Repair activity of base and nucleotide excision repair enzymes for guanine lesions induced by nitrosative stress

Nitric oxide (NO) induces deamination of guanine, yielding xanthine and oxanine (Oxa). Furthermore, Oxa reacts with polyamines and DNA binding proteins to form cross-link adducts. Thus, it is of interest how these lesions are processed by DNA repair enzymes in view of the genotoxic mechanism of NO. In the present study, we have examined the repair capacity for Oxa and Oxa–spermine cross-link adducts (Oxa–Sp) of enzymes involved in base excision repair (BER) and nucleotide excision repair (NER) to delineate the repair mechanism of nitrosative damage to guanine. Oligonucleotide substrates containing Oxa and Oxa–Sp were incubated with purified BER and NER enzymes or cell-free extracts (CFEs), and the damage-excising or DNA-incising activity was compared with that for control (physiological) substrates. The Oxa-excising activities of Escherichia coli and human DNA glycosylases and HeLa CFEs were 0.2–9% relative to control substrates, implying poor processing of Oxa by BER. In contrast, DNA containing Oxa–Sp was incised efficiently by UvrABC nuclease and SOS-induced E.coli CFEs, suggesting a role of NER in ameliorating genotoxic effects associated with nitrosative stress. Analyses of the activity of CFEs from NER-proficient and NER-deficient human cells on Oxa–Sp DNA confirmed further the involvement of NER in the repair of nitrosative DNA damage

A Case Report of Spindle Cell Carcinoma with Osteoid and Cartilage Formation in the Tongue

Spindle cell carcinoma (SCSCC) with osteoid and/or cartilage formation in the head and neck is rare; only one case was reported in the tongue. Herein, we report an SCSCC with osteoid and cartilage formation of the tongue developed in an 85-year-old man, and then review the report

Annexin A2-STAT3-Oncostatin M receptor axis drives phenotypic and mesenchymal changes in glioblastoma

Glioblastoma (GBM) is characterized by extensive tumor cell invasion, angiogenesis, and proliferation. We previously established subclones of GBM cells with distinct invasive phenotypes and identified annexin A2 (ANXA2) as an activator of angiogenesis and perivascular invasion. Here, we further explored the role of ANXA2 in regulating phenotypic transition in GBM. We identified oncostatin M receptor (OSMR) as a key ANXA2 target gene in GBM utilizing microarray analysis and hierarchical clustering analysis of the Ivy Glioblastoma Atlas Project and The Cancer Genome Atlas datasets. Overexpression of ANXA2 in GBM cells increased the expression of OSMR and phosphorylated signal transducer and activator of transcription 3 (STAT3) and enhanced cell invasion, angiogenesis, proliferation, and mesenchymal transition. Silencing of OSMR reversed the ANXA2-induced phenotype, and STAT3 knockdown reduced OSMR protein expression. Exposure of GBM cells to hypoxic conditions activated the ANXA2-STAT3-OSMR signaling axis. Mice bearing ANXA2-overexpressing GBM exhibited shorter survival times compared with control tumor-bearing mice, whereas OSMR knockdown increased the survival time and diminished ANXA2-mediated tumor invasion, angiogenesis, and growth. Further, we uncovered a significant relationship between ANXA2 and OSMR expression in clinical GBM specimens, and demonstrated their correlation with tumor histopathology and patient prognosis. Our results indicate that the ANXA2-STAT3-OSMR axis regulates malignant phenotypic changes and mesenchymal transition in GBM, suggesting that this axis is a promising therapeutic target to treat GBM aggressiveness

The endonucleolytic RNA cleavage function of nsp1 of middle east respiratory syndrome coronavirus promotes the production of infectious virus particles in specific human cell lines

Middle East respiratory syndrome coronavirus (MERS-CoV) nsp1 suppresses host gene expression in expressed cells by inhibiting translation and inducing endonucleolytic cleavage of host mRNAs, the latter of which leads to mRNA decay. We examined the biological functions of nsp1 in infected cells and its role in virus replication by using wild-type MERS-CoV and two mutant viruses with specific mutations in the nsp1; one mutant lacked both biological functions, while the other lacked the RNA cleavage function but retained the translation inhibition function. In Vero cells, all three viruses replicated efficiently with similar replication kinetics, while wild-type virus induced stronger host translational suppression and host mRNA degradation than the mutants, demonstrating that nsp1 suppressed host gene expression in infected cells. The mutant viruses replicated less efficiently than wild-type virus in Huh-7 cells, HeLa-derived cells, and 293-derived cells, the latter two of which stably expressed a viral receptor protein. In 293-derived cells, the three viruses accumulated similar levels of nsp1 and major viral structural proteins and did not induce IFN-β and IFN-λ mRNAs; however, both mutants were unable to generate intracellular virus particles as efficiently as wild-type virus, leading to inefficient production of infectious viruses. These data strongly suggest that the endonucleolytic RNA cleavage function of the nsp1 promoted MERS-CoV assembly and/or budding in a 293-derived cell line. MERS-CoV nsp1 represents the first CoV gene 1 protein that plays an important role in virus assembly/budding and is the first identified viral protein whose RNA cleavage-inducing function promotes virus assembly/budding. IMPORTANCE MERS-CoV represents a high public health threat. Because CoV nsp1 is a major viral virulence factor, uncovering the biological functions of MERS-CoV nsp1 could contribute to our understanding of MERS-CoV pathogenicity and spur development of medical countermeasures. Expressed MERS-CoV nsp1 suppresses host gene expression, but its biological functions for virus replication and effects on host gene expression in infected cells are largely unexplored. We found that nsp1 suppressed host gene expression in infected cells. Our data further demonstrated that nsp1, which was not detected in virus particles, promoted virus assembly or budding in a 293-derived cell line, leading to efficient virus replication. These data suggest that nsp1 plays an important role in MERS-CoV replication and possibly affects virus-induced diseases by promoting virus particle production in infected hosts. Our data, which uncovered an unexpected novel biological function of nsp1 in virus replication, contribute to further understanding of the MERS-CoV replication strategies

Antifibrotic effects of CXCR4 antagonist in bleomycin-induced pulmonary fibrosis in mice

Circulating fibrocytes had been reported to migrate into the injured lungs, and contribute to fibrogenesis via chemokine-chemokine receptor systems including CXCL12-CXCR4 axis. Here we hypothesized that blockade of CXCR4 might inhibit the migration of fibrocytes to the injured lungs and the subsequent pulmonary fibrosis. To explore the antifibrotic effects of blockade of CXCR4, we used a specific antagonist for CXCR4, AMD3100, in bleomycin-induced pulmonary fibrosis model in mice. Administration of AMD3100 significantly improved the loss of body weight of mice treated with bleomycin, and inhibited the fibrotic lesion in subpleural areas of the lungs. The quantitative analysis demonstrated that treatment with AMD3100 reduced the collagen content and fibrotic score (Aschcroft score) in the lungs. Although AMD3100 did not affect cell classification in bronchoalveolar lavage fluid on day 7, the percentage of lymphocytes was reduced by AMD3100 on day 14. AMD3100 directly inhibited the migration of human fibrocytes in response to CXCL12 in vitro, and reduced the trafficking of fibrocytes into the lungs treated with bleocmycin in vivo. These results suggest that the blockade of CXCR4 might be useful strategy for therapy of patients with pulmonary fibrosis via inhibiting the migration of circulating fibrocytes