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  • Drew Ellegaard posted an update 2 days, 10 hours ago

    Although Escherichia coli has been a popular tool for plasmid construction, this bacterium was believed to be “unsuitable” for constructing a large plasmid whose size exceeds 500 kilobases. We assumed that traditional plasmid vectors may lack some regulatory DNA elements required for the stable replication and segregation of such a large plasmid. In addition, the use of a few site-specific recombination systems may facilitate cloning of large DNA segments. Here we show two strategies for constructing 1-megabase (1-Mb) secondary chromosomes by using new bacterial artificial chromosome (BAC) vectors. First, the 3-Mb genome of a genome-reduced E. coli strain was split into two chromosomes (2-Mb and 1-Mb), of which smaller one has the origin of replication and the partitioning locus of the Vibrio tubiashii secondary chromosome. This chromosome fission method (Flp-POP cloning) works via flippase-mediated excision which coincides with the reassembly of a split chloramphenicol resistance gene, allowing chloramphenicol selection. Next, we developed a new cloning method (oriT-POP cloning) and a fully-equipped BAC vector (pMegaBAC1H) for developing a 1-Mb plasmid. Two 0.5-Mb genomic regions were sequentially transferred from two donor strains to a recipient strain via conjugation and captured by pMegaBAC1H in the recipient strain to produce a 1-Mb plasmid. This 1-Mb plasmid was transmissible to another E. coli strain via conjugation. Furthermore, these 1-Mb secondary chromosomes were amplifiable in vitro by using the reconstituted E. coli chromosome replication cycle reaction (RCR). These strategies and technologies would make popular E. coli cells a productive factory for designer chromosome engineering.Background Cardiac sympathetic denervation (CSD) is being used in the management of refractory ventricular tachycardia and electrical storm. However, data on the role of CSD in the management of ventricular arrhythmia is limited. Methods We performed a meta-analysis of retrospective studies to calculate the pooled rate of freedom from VT and the standard mean difference of ICD shocks before and after CSD. Results 14 non-randomized studies with a total of 311 patients with refractory VT or electrical storm were included. At a mean follow up of 15 ± 10.7 months, the pooled rate of freedom from VT (VT non-recurrence rate) after CSD in all causes of arrhythmia was 60% (range 48.8% to 70%, I2 = 43%). When analysis was restricted to only arrhythmias caused by conditions other than Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) and Long QT Syndrome (LQTS), the pooled VT non-recurrence rate was 50% (range 41% to 58%, I2 = 5%). After CSD, mean total number of ICD shocks per person diminished by 3.01 (95% CI 1.09-4.94, p = 0.002, I2 = 96%) in overall analysis and by 0.97(95% CI 0.41-1.5, p = 0.001, I2 = 45%) when CPVT and LQTS were excluded. Conclusion In patients with refractory VT or electrical storm, CSD is associated with pooled VT non-recurrence rate of 60% at a mean follow-up of 15 ± 10.7 months. read more CSD was also associated with significantly lower mean number ICD shocks per person. Further studies are needed to validate this finding in a prospective setting. This article is protected by copyright. All rights reserved.Prostate cancer is one of the leading causes of cancer-related death in men. The identification of new therapeutics to selectively target prostate cancer cells is therefore vital. Recently, the rotenoids rotenone (1) and deguelin (2) were reported to selectively kill prostate cancer cells, and the inhibition of mitochondrial complex I was established as essential to their mechanism of action. However, these hydrophobic rotenoids readily cross the blood-brain barrier and induce symptoms characteristic of Parkinson’s disease in animals. Since hydroxylated derivatives of 1 and 2 are more hydrophilic and less likely to readily cross the blood-brain barrier, 29 natural and unnatural hydroxylated derivatives of 1 and 2 were synthesized for evaluation. The inhibitory potency (IC50) of each derivative against complex I was measured, and its hydrophobicity (Slog10P) predicted. Amorphigenin (3), dalpanol (4), dihydroamorphigenin (5), and amorphigenol (6) were selected and evaluated in cell-based assays using C4-2 and C4-2B prostate cancer cells alongside control PNT2 prostate cells. These rotenoids inhibit complex I in cells, decrease oxygen consumption, and selectively inhibit the proliferation of prostate cancer cells, leaving control cells unaffected. The greatest selectivity and antiproliferative effects were observed with 3 and 5. The data highlight these molecules as promising therapeutic candidates for further evaluation in prostate cancer models.RNA editing is a posttranscriptional process that changes nucleotide sequences, among which cytosine-to-uracil by a deamination reaction can revert non-neutral codon mutations. Pentatricopeptide repeat (PPR) proteins comprise a family of RNA-binding proteins, with members acting as editing trans-factors that recognize specific RNA cis-elements and perform the deamination reaction. PPR proteins are classified into P and PLS subfamilies. In this work, we have designed RNA biotinylated probes based in soybean plastid RNA editing sites to perform trans-factor specific protein isolation. Soybean cis-elements from these three different RNA probes show differences in respect to other species. Pulldown samples were submitted to mass spectrometry for protein identification. Among detected proteins, five corresponded to PPR proteins. More than one PPR protein, with distinct functional domains, was pulled down with each one of the RNA probes. Comparison of the soybean PPR proteins to Arabidopsis allowed identification of the closest homologous. Differential gene expression analysis demonstrated that the PPR locus Glyma.02G174500 doubled its expression under salt stress, which correlates with the increase of its potential rps14 editing. The present study represents the first identification of RNA editing trans-factors in soybean. Data also indicated that potential multiple trans-factors should interact with RNA cis-elements to perform the RNA editing.

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