Eukaryotic gene expression is tightly regulated post-transcriptionally by RNA-binding proteins (RBPs) and microRNAs. The RBP AU-rich-binding factor 1 (AUF1) isoform p37 was found to have high affinity for the micro-RNA let-7b in vitro (K d = ∼6 nM) in cells. Ribonucleoprotein immunoprecipitation, in vitro association, and single-molecule-binding analyses revealed that AUF1 promoted let-7b loading onto Argonaute 2 (AGO2), the catalytic component of the RNA-induced silencing complex (RISC). In turn, AGO2-let-7 triggered target mRNA decay. Our findings uncover a novel mechanism by which AUF1 binding and transfer of microRNA let-7 to AGO2 facilitates let-7-elicited gene silencing.

Protease sensors for point-of-care testing (POCT) require simple operation, a detection period of less than 20 minutes, and a detection limit of less than 1 ng mL(-1). However, it is difficult to meet these requirements with protease sensors that are based on proteolytic cleavage. This paper reports a highly reproducible protease sensor that allows the sensitive and simple electrochemical detection of the botulinum neurotoxin type E light chain (BoNT/E-LC), which is obtained using (i) low nonspecific adsorption, (ii) high signal-to-background ratio, and (iii) one-step solution treatment. The BoNT/E-LC detection is based on two-step proteolytic cleavage using BoNT/E-LC (endopeptidase) and l-leucine-aminopeptidase (LAP, exopeptidase). Indium-tin oxide (ITO) electrodes are modified partially with reduced graphene oxide (rGO) to increase their electrocatalytic activities. Avidin is then adsorbed on the electrodes to minimize the nonspecific adsorption of proteases. Low nonspecific adsorption allows a highly reproducible sensor response. Electrochemical-chemical (EC) redox cycling involving p-aminophenol (AP) and dithiothreitol (DTT) is performed to obtain a high signal-to-background ratio. After adding a C-terminally AP-labeled oligopeptide, DTT, and LAP simultaneously to a sample solution, no further treatment of the solution is necessary during detection. The detection limits of BoNT/E-LC in phosphate-buffered saline are 0.1 ng mL(-1) for an incubation period of 15 min and 5 fg mL(-1) for an incubation period of 4 h. The detection limit in commercial bottled water is 1 ng mL(-1) for an incubation period of 15 min. The developed sensor is selective to BoNT/E-LC among the four types of BoNTs tested. These results indicate that the protease sensor meets the requirements for POCT.

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2,4,6,8-(3)-Tetranitrophenyl-3,7-diazabicyclo[3.3.1]nonan-9-one (B16), a bispidinone analog, was synthesized to investigate its effects on cell viability, the cell cycle, and apoptotic pathways in HeLa human cervical cancer cells. B16 decreased the percentage of viable cells in WST-8 assays, and morphological changes associated with apoptotic cell death were observed, including cell shrinkage and disruption. Annexin V-FITC/PI dual staining assays showed that B16 significantly increased the early apoptosis of HeLa cells after 24 h of treatment. Moreover, DNA content analysis and [3H]-thymidine incorporation assays showed that B16 induced S-phase cell cycle arrest and inhibited DNA replication after 24 h of treatment. Following treatment with 25 µM of B16, an increase in reactive oxygen species and a decrease in mitochondrial membrane potential were observed by flow cytometry. In addition, the expression levels of caspase cascade and Bcl-2 family proteins determined by western blotting suggested that the induction of apoptosis by B16 was associated with a caspase- and mitochondrial-dependent pathway in HeLa cells. In conclusion, B16 induced early apoptosis and S-phase cell cycle arrest in HeLa cells via a caspase- and mitochondrial‑dependent pathway.

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