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Abstract MicroRNAs (miRNAs) regulate cancer cell proliferation by binding directly to the untranslated regions of messenger RNA (mRNA). MicroRNA-148a (miR-148a) is expressed at low levels in breast cancer (BC). However, little attention has been paid to the sequestration of miR-148a. Here, we performed a knockdown of miR-148a using anti-miRNA oligonucleotides (AMOs) and investigated the effect on BC cell proliferation. BC cell proliferation was significantly suppressed by AMO flanked by interstrand cross-linked duplexes (CL-AMO), whereas single-stranded and commercially available AMOs had no effect. The suppression was caused by sequestering specifically miR-148a. Indeed, miR-148b, another member of the miR-148 family, was not affected. Importantly, the downregulation of miR-148a induced a greater and longer-lasting inhibition of BC cell proliferation than the targeting of oncogenic microRNA-21 (miR-21) did. We identified thioredoxin-interacting protein (TXNIP), a tumor suppressor gene, as a target of miR-148a and showed that CL-AMO provoked an increase in TXNIP mRNA expression. This study provide evidence that lowly expressed miRNAs such as miR-148a have an oncogenic function and might be a promising target for cancer treatment.

Abstract Background Abasic sites are formed spontaneously and by nucleobase chemical modifications and base excision repair. A chemically stable abasic site analog was site-specifically introduced into replicable plasmid DNAs, which were transfected into human U2OS cells. The amplified DNAs were recovered from the cells and used for the transformation of a bacterial indicator strain. Results Large deletion mutations were induced by the analog, in addition to point mutations at the modified site. No apparent sequence homology at the deletion junctions was found. Conclusion These results suggested that the large deletions induced by the abasic site analog are formed by homology-independent events.

MicroRNA (miRNA)-guided argonaute (Ago) controls gene expression upon binding to the 3′ UTR of mRNA. The miRNA function can be competitively inhibited by single-stranded anti-miRNA oligonucleotides (AMOs). In this study, we constructed a novel type of AMO flanked by interstrand cross-linked 2′-O-methylated RNA duplexes (CLs) that confer a stable helical conformation. Compared with other structured AMOs, AMO flanked by CLs at the 5′ and 3′ termini exhibited much higher inhibitory activity in cells. Anti-miRNA activity, nuclease resistance, and miRNA modification pattern distinctly differed according to the CL-connected positions in AMOs. Moreover, we found that the 3′-side CL improves nuclease resistance, whereas the 5′-side CL contributes to stable binding with miRNA in Ago upon interaction with the 3′ part of miRNA. These structure-function relationship analyses of AMOs provide important insights into the function control of Ago-miRNA complexes, which will be useful for basic miRNA research as well as for determining therapeutic applications of AMO.

We studied a dissolved oxygen sensor in aqueous media based on a mesoporous Pt microelectrode with the aim of obtaining a large sensor output. Mesoporous Pt structures were fabricated via Pt thin film deposition on a skeleton of nanoporous gold. The dissolved oxygen was measured via adoptive stripping voltammetry, i.e., the dissolved oxygen was adsorped on the surface of the mesostructured platinum microelectrode over a certain period. Accumulated oxygen on the surface of themesostructures was reduced through voltammetrywith a large current. This led to a linear increase in the reduction current as a function of the active surface area of the Pt mesostructures, indicating that the entire surface area of the mesostructures is utilized to adsorb and reduce oxygen in the given experimental condition. The proposed method could obtain a lager sensor output compared with sensors under diffusion-controlled reactions and better fits for oxygen sensors in micro total analysis systems. [ABSTRACT FROM AUTHOR]

A nanoporous gold (NPG) structure consisting of pores and ligaments is prepared by anodizing a polycrystalline gold disk electrode for 15min in 35mM HCl solution. Smaller/narrower ligaments sizes are obtained compared with that of the reported NPG structures obtained by anodization in higher (>1M) concentrations of chloride ion. The present NPG structure is highly effective for direct electron transfer between human cytochrome P450 and the electrode. [ABSTRACT FROM AUTHOR]

We prepared Nile Blue (NB)-modified 17-mer DNA duplexes with thiol/disulfide end tethers for immobilization onto gold electrodes to understand the effect of the tether structure of DNA on its electron-transfer (ET) reactions. The longer thiol tether allowed electron transfer between the NB and the electrode through the DNA duplex, whereas the direct ET pathway became predominant in the shorter disulfide tether. Importantly, the insertion of a spacer chain into the disulfide tether changed the direct ET pathway to a through-DNA pathway. [ABSTRACT FROM AUTHOR]

Abasic sites are formed in cells by various factors including environmental mutagens and considered to be involved in cancer initiation, promotion, and progression. A chemically stable abasic site analog (tetrahydrofuran-type analog, THF) induces untargeted base substitutions as well as targeted substitution and large deletion mutations in human cells. The untargeted substitutions may be initiated by the cleavage of the DNA strand bearing THF by the human apurinic/apyrimidinic endonuclease 1 (APE1) protein, the major repair enzyme for THF and abasic sites. To examine the effects of lower APE1 levels, the protein was knocked down by siRNA in human U2OS cells. A plasmid containing a single THF modification outside the supF gene was introduced into the knockdown cells, and the untargeted substitution mutations in the reporter gene were analyzed. Unexpectedly, the knockdown had no evident impact on their frequency and spectrum. The G bases of 5′-GpA-3′ dinucleotides on the modified strand were quite frequently substituted, with and without the APE1 knockdown. These results suggested that the DNA strand cleavage by APE1 is not essential for the THF-induced untargeted base substitutions. [ABSTRACT FROM AUTHOR]