Chemical Amination/Imination of Carbonothiolated Nucleosides During RNA Hydrolysis.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become the gold-standard technique to study RNA and its various modifications. While most research on RNA nucleosides has been focused on their biological roles, discovery of new modifications remains of interest. With state-of-the-art technology, the presence of artifacts can confound the identification of new modifications. Here, we report the characterization of a non-natural mcm5 isoC ribonucleoside in S. cerevisiae total tRNA hydrolysate by higher-energy collisional dissociation (HCD)-based fingerprints and isotope labeling of RNA. Its discovery revealed a class of amino/imino ribonucleoside artifacts that are generated during RNA hydrolysis under ammonium-buffered mild basic conditions. We then identified digestion conditions that can reduce or eliminate their formation. These finding and method enhancements will improve the accurate detection of new RNA modifications.

Improved application of RNAModMapper - An RNA modification mapping software tool - For analysis of liquid chromatography tandem mass spectrometry (LC-MS/MS) data.

Research into post-transcriptional processing and modification of RNA continues to speed forward, as their ever-emerging role in the regulation of gene expression in biological systems continues to unravel. Liquid chromatography tandem mass spectrometry (LC-MS/MS) has proven for over two decades to be a powerful ally in the elucidation of RNA modification identity and location, but the technique has not proceeded without its own unique technical challenges. The throughput of LC-MS/MS modification mapping experiments continues to be impeded by tedious and time-consuming spectral interpretation, particularly during for the analysis of complex RNA samples. RNAModMapper was recently developed as a tool to improve the interpretation and annotation of LC-MS/MS data sets from samples containing post-transcriptionally modified RNAs. Here, we delve deeper into the methodology and practice of RNAModMapper to provide greater insight into its utility, and remaining hurdles, in current RNA modification mapping experiments.

Pytheas: a software package for the automated analysis of RNA sequences and modifications via tandem mass spectrometry.

Mass spectrometry is an important method for analysis of modified nucleosides ubiquitously present in cellular RNAs, in particular for ribosomal and transfer RNAs that play crucial roles in mRNA translation and decoding. Furthermore, modifications have effect on the lifetimes of nucleic acids in plasma and cells and are consequently incorporated into RNA therapeutics. To provide an analytical tool for sequence characterization of modified RNAs, we developed Pytheas, an open-source software package for automated analysis of tandem MS data for RNA. The main features of Pytheas are flexible handling of isotope labeling and RNA modifications, with false discovery rate statistical validation based on sequence decoys. We demonstrate bottom-up mass spectrometry characterization of diverse RNA sequences, with broad applications in the biology of stable RNAs, and quality control of RNA therapeutics and mRNA vaccines.

Photosynthetic photon flux density and phytochrome B interact to regulate branching in Arabidopsis.

Branching is regulated by environmental signals including phytochrome B (phyB)-mediated responses to the ratio of red to far red light. While the mechanisms associated with phytochrome regulation of branching are beginning to be elucidated, there is little information regarding other light signals, including photosynthetic photon flux density (PPFD) and how it influences phytochrome-mediated responses. This study shows that Arabidopsis (Arabidopsis thaliana) branching is modified by both varying PPFD and phyB status and that significant interactions occur between these variables. While phyB deficiency decreased branching when the PPFD was low, the effect was suppressed by high PPFD and some branching aspects were actually promoted. Photosynthesis measurements showed that PPFD may influence branching in phyB-deficient plants at least partially through a specific signalling pathway rather than directly through energy effects on the shoot. The expression of various genes in unelongated buds of phyB-deficient and phyB-sufficient plants grown under high and low PPFD demonstrated potential roles for several hormones, including auxin, cytokinins and ABA, and also showed imperfect correlation between expression of the branching regulators BRC1 and BRC2 and bud fate. These results may implicate additional undiscovered bud autonomous mechanisms and/or components contributing to bud outgrowth regulation by environmental signals.

Locating chemical modifications in RNA sequences through ribonucleases and LC-MS based analysis.

Knowledge of the structural information is essential for understanding the functional details of modified RNA. Cellular non-coding RNA such as rRNA, tRNA and even viral RNAs contain a number of post-transcriptional modifications with varied degree of diversity and density. In this chapter, we discuss the use of a combination of biochemical and analytical tools such as ribonucleases and liquid chromatography coupled with mass spectrometry approaches for characterization of modified RNA. We present the protocols and alternate strategies for obtaining confident modified sequence information to facilitate the understanding of function.

Ca2+ Selective Host Rotaxane Is Highly Toxic Against Prostate Cancer Cells.

New therapies are needed to eradicate androgen resistant, prostate cancer. Prostate cancer usually metastasizes to bone where the concentration of calcium is high, making Ca2+ a promising toxin. Ionophores can deliver metal cations into cells, but are currently too toxic for human use. We synthesized a new rotaxane (CEHR2) that contains a benzyl 15-crown-5 ether as a blocking group to efficiently bind Ca2+. CEHR2 transfers Ca2+ from an aqueous solution into CHCl3 to greater extent than alkali metal cations and Mg2+. It also transfers Ca2+ to a greater extent than CEHR1, which is a rotaxane with an 18-crown-6 ether as a blocking group. CEHR2 was more toxic against the prostate cancer cell lines PC-3, 22Rv1, and C4-2 than CEHR1. This project demonstrates that crown ether rotaxanes can be designed to bind a targeted metal cation, and this selective cation association can result in enhanced toxicity.

Corrigendum to "Obesity in a model of gpx4 haploinsufficiency uncovers a causal role for lipid-derived aldehydes in human metabolic disease and cardiomyopathy" [Mol Metab 4 (6) (2015) 493-506].

[This corrects the article DOI: 10.1016/j.molmet.2015.04.001.].

Obesity in a model of gpx4 haploinsufficiency uncovers a causal role for lipid-derived aldehydes in human metabolic disease and cardiomyopathy.

OBJECTIVE: Lipid peroxides and their reactive aldehyde derivatives (LPPs) have been linked to obesity-related pathologies, but whether they have a causal role has remained unclear. Glutathione peroxidase 4 (GPx4) is a selenoenzyme that selectively neutralizes lipid hydroperoxides, and human gpx4 gene variants have been associated with obesity and cardiovascular disease in epidemiological studies. This study tested the hypothesis that LPPs underlie cardio-metabolic derangements in obesity using a high fat, high sucrose (HFHS) diet in gpx4 haploinsufficient mice (GPx4(+/-)) and in samples of human myocardium. METHODS: Wild-type (WT) and GPx4(+/-) mice were fed either a standard chow (CNTL) or HFHS diet for 24 weeks, with metabolic and cardiovascular parameters measured throughout. Biochemical and immuno-histological analysis was performed in heart and liver at termination of study, and mitochondrial function was analyzed in heart. Biochemical analysis was also performed on samples of human atrial myocardium from a cohort of 103 patients undergoing elective heart surgery. RESULTS: Following HFHS diet, WT mice displayed moderate increases in 4-hydroxynonenal (HNE)-adducts and carbonyl stress, and a 1.5-fold increase in GPx4 enzyme in both liver and heart, while gpx4 haploinsufficient (GPx4(+/-)) mice had marked carbonyl stress in these organs accompanied by exacerbated glucose intolerance, dyslipidemia, and liver steatosis. Although normotensive, cardiac hypertrophy was evident with obesity, and cardiac fibrosis more pronounced in obese GPx4(+/-) mice. Mitochondrial dysfunction manifesting as decreased fat oxidation capacity and increased reactive oxygen species was also present in obese GPx4(+/-) but not WT hearts, along with up-regulation of pro-inflammatory and pro-fibrotic genes. Patients with diabetes and hyperglycemia exhibited significantly less GPx4 enzyme and greater HNE-adducts in their hearts, compared with age-matched non-diabetic patients. CONCLUSION: These findings suggest LPPs are key factors underlying cardio-metabolic derangements that occur with obesity and that GPx4 serves a critical role as an adaptive countermeasure.