Biochemical and structural insights into a 5' to 3' RNA ligase reveal a potential role in tRNA ligation.

ATP-grasp superfamily enzymes contain a hand-like ATP-binding fold and catalyze a variety of reactions using a similar catalytic mechanism. More than 30 protein families are categorized in this superfamily, and they are involved in a plethora of cellular processes and human diseases. Here we identify C12orf29 as an atypical ATP-grasp enzyme that ligates RNA. Human C12orf29 and its homologs auto-adenylate on an active site Lys residue as part of a reaction intermediate that specifically ligates RNA halves containing a 5'-phosphate and a 3'-hydroxyl. C12orf29 binds tRNA in cells and can ligate tRNA within the anticodon loop in vitro. Genetic depletion of c12orf29 in female mice alters global tRNA levels in brain. Furthermore, crystal structures of a C12orf29 homolog from Yasminevirus bound to nucleotides reveal a minimal and atypical RNA ligase fold with a unique active site architecture that participates in catalysis. Collectively, our results identify C12orf29 as an RNA ligase and suggest its involvement in tRNA biology.

Lewis Acid-Driven Inverse Hydride Shuttle Catalysis.

Inverse hydride shuttle catalysis provides a multicomponent platform for the highly efficient synthesis of alkaloid frameworks with exquisite diastereoselectivity. However, a number of limitations hinder this method, primarily the strict requirement for highly electron-deficient acceptors. Herein, we present a general Lewis acid-driven approach to address this constraint, and have developed two broad strategies enabling the modular synthesis of complex azabicycles that were entirely unattainable using the previous method. The enhanced synthetic flexibility facilitates a streamlined asymmetric cyclization, leading to a concise total synthesis of the alkaloid (-)-tashiromine.

Target-directed microRNA degradation regulates developmental microRNA expression and embryonic growth in mammals.

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutive or conditional deletion of Zswim8, which encodes an essential TDMD factor. Loss of Zswim8 resulted in developmental defects in the heart and lungs, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD and greatly expanded the known catalog of miRNAs regulated by this pathway. These experiments also uncovered novel features of TDMD-regulated miRNAs, including their enrichment in cotranscribed clusters and examples in which TDMD underlies "arm switching," a phenomenon wherein the dominant strand of a miRNA precursor changes in different tissues or conditions. Importantly, deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8-null embryos, directly implicating the TDMD pathway as a regulator of mammalian body size. These data illuminate the broad landscape and developmental role of TDMD in mammals.

Target-directed microRNA degradation regulates developmental microRNA expression and embryonic growth in mammals.

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutive or conditional deletion of Zswim8 , which encodes an essential TDMD factor. Loss of Zswim8 resulted in developmental defects in heart and lung, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD and greatly expanded the known catalog of miRNAs regulated by this pathway. These experiments also uncovered novel features of TDMD-regulated miRNAs, including their enrichment in co-transcribed clusters and examples in which TDMD underlies 'arm switching', a phenomenon wherein the dominant strand of a miRNA precursor changes in different tissues or conditions. Importantly, deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8 null embryos, directly implicating the TDMD pathway as a regulator of mammalian body size. These data illuminate the broad landscape and developmental role of TDMD in mammals.

A dedicated robotic bedside physician assistant significantly enhances trainee console operating time in general thoracic surgery.

Objective: As trainees rotate through thoracic subspecialties within their curricula, a crucial portion of their robotic training consists of actual console operating time. The more time spent on the surgeon console, the greater the development will be through the course of their training. Implementing a physician assistant at the bedside may increase the operative console time for the trainee and develop robotic skills in a more expeditious rate. The objective was to evaluate the impact a designated robotic physician assistant can have on trainee console learning opportunity. Methods: Operating room data collected consisted of all robotic general thoracic surgical cases that trainees participated in with and without a physician assistant present. Metrics regarding case efficiency included anesthesia ready-to-incision, incision-to-console, and raw resident console times. By using PRISM software, a nonparametric t test was used to analyze each averaged data group compared between when a physician assistant was present and not present. Results: The mean resident console time without and with a physician assistant assist was 45.8 minutes and 80.9 minutes, respectively (P < .0001). The average portion of a case performed by a trainee similarly without and with a physician assistant present was 28.0% and 77.1%, respectively (P < .0001). Case efficiency metrics between physician assistant presence cohorts showed no difference. Conclusions: Thoracic surgical trainees have increased opportunity for robotic skill development within a fellowship or resident program curriculum when a designated robotic physician assistant is present in the operating room. These findings are significant for the improvement of residency and fellowship robotic training models moving forward by incorporating robotic-specialized physician assistants in academic institutions.

Cyclopropane-Fused N-Heterocycles via Aza-Heck-Triggered C(sp3)-H Functionalization Cascades.

Unique examples of aza-Heck-based C(sp3)-H functionalization cascades are described. Under Pd(0)-catalyzed conditions, the aza-Heck-type cyclization of N-(pentafluorobenzoyloxy)carbamates generates alkyl-Pd(II) intermediates that effect C(sp3)-H palladation en route to cyclopropanes. Key factors that control the site selectivity of the cyclopropanation process have been elucidated such that selective access to a wide range of ring- or spiro-fused systems can be achieved.

Complex Polyheterocycles and the Stereochemical Reassignment of Pileamartine A via Aza-Heck Triggered Aryl C-H Functionalization Cascades.

Structurally complex benzo- and spiro-fused N-polyheterocycles can be accessed via intramolecular Pd(0)-catalyzed alkene 1,2-aminoarylation reactions. The method uses N-(pentafluorobenzoyloxy)carbamates as the initiating motif, and this allows aza-Heck-type alkene amino-palladation in advance of C-H palladation of the aromatic component. The chemistry is showcased in the first total synthesis of the complex alkaloid (+)-pileamartine A, which has resulted in the reassignment of its absolute stereochemistry.

A ubiquitin ligase mediates target-directed microRNA decay independently of tailing and trimming.

MicroRNAs (miRNAs) act in concert with Argonaute (AGO) proteins to repress target messenger RNAs. After AGO loading, miRNAs generally exhibit slow turnover. An important exception occurs when miRNAs encounter highly complementary targets, which can trigger a process called target-directed miRNA degradation (TDMD). During TDMD, miRNAs undergo tailing and trimming, suggesting that this is an important step in the decay mechanism. We identified a cullin-RING ubiquitin ligase (CRL), containing the substrate adaptor ZSWIM8, that mediates TDMD. The ZSWIM8 CRL interacts with AGO proteins, promotes TDMD in a tailing and trimming-independent manner, and regulates miRNA expression in multiple cell types. These findings suggest a model in which the ZSWIM8 ubiquitin ligase mediates TDMD by directing proteasomal decay of miRNA-containing complexes engaged with highly complementary targets.

Complete Genome Sequence of Proteus mirabilis Phage Mydo.

Proteus mirabilis is a pathogen that has been linked to nosocomial infections. Studies on phages infecting P. mirabilis may provide therapeutics for infections caused by antibiotic-resistant strains of this pathogen. Here, we announce the complete genome sequence of a P. mirabilis myophage, Mydo, which is distantly related to Escherichia coli phage rv5.

miR-26 suppresses adipocyte progenitor differentiation and fat production by targeting Fbxl19.

Fat storage in adult mammals is a highly regulated process that involves the mobilization of adipocyte progenitor cells (APCs) that differentiate to produce new adipocytes. Here we report a role for the broadly conserved miR-26 family of microRNAs (miR-26a-1, miR-26a-2, and miR-26b) as major regulators of APC differentiation and adipose tissue mass. Deletion of all miR-26-encoding loci in mice resulted in a dramatic expansion of adipose tissue in adult animals fed normal chow. Conversely, transgenic overexpression of miR-26a protected mice from high-fat diet-induced obesity. These effects were attributable to a cell-autonomous function of miR-26 as a potent inhibitor of APC differentiation. miR-26 blocks adipogenesis, at least in part, by repressing expression of Fbxl19, a conserved miR-26 target without a previously known role in adipocyte biology that encodes a component of SCF-type E3 ubiquitin ligase complexes. These findings have therefore revealed a novel pathway that plays a critical role in regulating adipose tissue formation in vivo and suggest new potential therapeutic targets for obesity and related disorders.

Loss of Dis3l2 partially phenocopies Perlman syndrome in mice and results in up-regulation of Igf2 in nephron progenitor cells.

Loss of function of the DIS3L2 exoribonuclease is associated with Wilms tumor and the Perlman congenital overgrowth syndrome. LIN28, a Wilms tumor oncoprotein, triggers the DIS3L2-mediated degradation of the precursor of let-7, a microRNA that inhibits Wilms tumor development. These observations have led to speculation that DIS3L2-mediated tumor suppression is attributable to let-7 regulation. Here we examine new DIS3L2-deficient cell lines and mouse models, demonstrating that DIS3L2 loss has no effect on mature let-7 levels. Rather, analysis of Dis3l2-null nephron progenitor cells, a potential cell of origin of Wilms tumors, reveals up-regulation of Igf2, a growth-promoting gene strongly associated with Wilms tumorigenesis. These findings nominate a new potential mechanism underlying the pathology associated with DIS3L2 deficiency.

Measured Saturation Vapor Pressures of Phenolic and Nitro-aromatic Compounds.

Phenolic and nitro-aromatic compounds are extremely toxic components of atmospheric aerosol that are currently not well understood. In this Article, solid and subcooled-liquid-state saturation vapor pressures of phenolic and nitro-aromatic compounds are measured using Knudsen Effusion Mass Spectrometry (KEMS) over a range of temperatures (298-318 K). Vapor pressure estimation methods, assessed in this study, do not replicate the observed dependency on the relative positions of functional groups. With a few exceptions, the estimates are biased toward predicting saturation vapor pressures that are too high, by 5-6 orders of magnitude in some cases. Basic partitioning theory comparisons indicate that overestimation of vapor pressures in such cases would cause us to expect these compounds to be present in the gas state, whereas measurements in this study suggest these phenolic and nitro-aromatic will partition into the condensed state for a wide range of ambient conditions if absorptive partitioning plays a dominant role. While these techniques might have both structural and parametric uncertainties, the new data presented here should support studies trying to ascertain the role of nitrogen containing organics on aerosol growth and human health impacts.