The day/night switch of the circadian clock of synechococcus elongatus and hydrogen bonds of dna and rna

The circadian oscillator of the cyanobacterium Synechococcus elongatus is composed of only three proteins, KaiA, KaiB, and KaiC, which together with ATP can generate a self-sustained ~24 hour oscillation of KaiC phosphorylation for several days. KaiA induces KaiC to autophosphorylate whereas KaiB blocks the stimulation of KaiC by KaiA, which allows KaiC to autodephosphorylate. We propose and support a model in which the C-terminal loops of KaiC, the “A-loops”, are the master switch that determines overall KaiC activity. When the A-loops are in their buried state, KaiC is an autophosphatase. When the A-loops are exposed, however, KaiC is an autokinase. The data suggest that KaiA stabilizes the exposed state of the A-loops through direct binding. We also show evidence that if KaiA cannot stabilize the exposed state KaiC remains hypophosphorylated. We propose that KaiB inactivates KaiA by preventing it from stabilizing the exposed state of the A-loops. Thus, KaiA and KaiB likely act by shifting the dynamic equilibrium of the A-loops between exposed and buried states, which shifts the balance of autokinase and autophosphatase activities of KaiC. A-loop exposure likely moves the ATP closer to the sites of phosphorylation and we show evidence in support of how this movement may be accomplished. Density functional theory calculations of isolated Watson–Crick A:U and A:T base pairs predict that adenine 13C2 trans-hydrogen bond deuterium isotope shifts due to isotopic substitution at the pyrimidine H3, 2hΔ13C2, are sensitive to the hydrogen-bond distance between the N1 of adenine and the N3 of uracil or thymine, which supports the notion that 2hΔ13C2 is sensitive to hydrogen-bond strength. Calculated 2hΔ13C2 values at a given N1–N3 distance are the same for isolated A:U and A:T base pairs. Replacing uridine residues in RNA with 5-methyl uridine and substituting deoxythymidines in DNA with deoxyuridines do not statistically shift empirical 2hΔ13C2 values. Thus, we show experimentally and computationally that the C7 methyl group of thymine has no measurable affect on 2hΔ13C2 values. Furthermore, 2hΔ13C2 values of modified and unmodified RNA are more negative than those of modified and unmodified DNA, which supports our hypothesis that RNA hydrogen bonds are stronger than those of DNA. It is also shown here that 2hΔ13C2 is context dependent and that this dependence is similar for RNA and DNA

Selenoprotein W promotes cell cycle recovery from G2 arrest through the activation of CDC25B

AbstractSelenoprotein W (SelW) contains a highly reactive selenocysteine (Sec; U) in the CXXU motif corresponding to the CXXC motif in thioredoxin (Trx) and thus it appears to be involved in regulating the cellular redox state. Recent reports on the interaction between SelW and 14-3-3 suggest that SelW may be redox dependently involved in the cell cycle. However, the precise function of SelW has not yet been elucidated. Here, we show that SelW is involved in the G2–M transition, especially in the recovery from G2 arrest after deoxyribonucleic acid (DNA) damage. Knockdown of SelW significantly accumulated phosphorylated cyclin‐dependent kinase (Cdk1), which eventually led to a delay in recovery from G2 arrest. We also found that inactive Cdk1 is caused by the sustained inactivation of CDC25B, which removes the inhibitory phosphate from Cdk1. Our observation from this study reveals that SelW activated CDC25B by promoting the dissociation of 14-3-3 from CDC25B through the reduction of the intramolecular disulfide bond during recovery. We suggest that SelW plays an important role in the recovery from G2 arrest by determining the dissociation of 14-3-3 from CDC25B in a redox-dependent manner

Oxidized quinones signal onset of darkness directly to the cyanobacterial circadian oscillator

Synchronization of the circadian clock in cyanobacteria with the day/night cycle proceeds without an obvious photoreceptor, leaving open the question of its specific mechanism. The circadian oscillator can be reconstituted in vitro,where the activities of two of its proteins, KaiA and KaiC, are affected by metabolites that reflect photosynthetic activity: KaiC phosphorylation is directly influenced by the ATP/ADP ratio, and KaiA stimulation of KaiC phosphorylation is blocked by oxidized, but not reduced, quinones. Manipulation of the ATP/ADP ratio can reset the timing of KaiC phosphorylation peaks in the reconstituted in vitro oscillator. Here, we show that pulses of oxidized quinones reset the cyanobacterial circadian clock both in vitro and in vivo. Onset of darkness causes an abrupt oxidation of the plastoquinone pool in vivo, which is in contrast to a gradual decrease in the ATP/ADP ratio that falls over the course of hours until the onset of light. Thus, these twometabolicmeasures of photosynthetic activity act in concert to signal both the onset and duration of darkness to the cyanobacterial clock

Selenoprotein W enhances skeletal muscle differentiation by inhibiting TAZ binding to 14-3-3 protein

AbstractSelenoprotein W (SelW) is expressed in various tissues, particularly in skeletal muscle. We have previously reported that SelW is up-regulated during C2C12 skeletal muscle differentiation and inhibits binding of 14-3-3 to its target proteins. 14-3-3 reduces myogenic differentiation by inhibiting nuclear translocation of transcriptional co-activator with PDZ-binding motif (TAZ). Phosphorylation of TAZ at Ser89 is required for binding to 14-3-3, leading to cytoplasmic retention of TAZ and a delay in myogenic differentiation. Here, we show that myogenic differentiation was delayed in SelW-knockdown C2C12 cells. Down-regulation of SelW also increased TAZ binding to 14-3-3, which eventually resulted in decreasing translocation of TAZ to the nucleus. However, phosphorylation of TAZ at Ser89 was not affected. Although phosphorylation of TAZ at Ser89 was sustained by the phosphatase inhibitor okadaic acid, nuclear translocation of TAZ was increased by ectopic expression of SelW. This result was due to decreased binding of TAZ to 14-3-3. We also found that the interaction between TAZ and MyoD was increased by ectopic expression of SelW. Taken together, these findings strongly demonstrate that SelW enhances C2C12 cell differentiation by inhibiting TAZ binding to 14-3-3

Effect of 660 nm Light-Emitting Diode on the Wound Healing in Fibroblast-Like Cell Lines

Light in the red to near-infrared (NIR) range (630–1000 nm), which is generated using low energy laser or light-emitting diode (LED) arrays, was reported to have a range of beneficial biological effects in many injury models. NIR via a LED is a well-accepted therapeutic tool for the treatment of infected, ischemic, and hypoxic wounds as well as other soft tissue injuries in humans and animals. This study examined the effects of exposure to 660 nm red LED light at intensities of 2.5, 5.5, and 8.5 mW/cm2 for 5, 10, and 20 min on wound healing and proliferation in fibroblast-like cells, such as L929 mouse fibroblasts and human gingival fibroblasts (HGF-1). A photo illumination-cell culture system was designed to evaluate the cell proliferation and wound healing of fibroblast-like cells exposed to 600 nm LED light. The cell proliferation was evaluated by MTT assay, and a scratched wound assay was performed to assess the rate of migrating cells and the healing effect. Exposure to the 660 nm red LED resulted in an increase in cell proliferation and migration compared to the control, indicating its potential use as a phototherapeutic agent

Deletion of PLC??1 in GABAergic neurons increases seizure susceptibility in aged mice

Synaptic inhibition plays a fundamental role in the information processing of neural circuits. It sculpts excitatory signals and prevents hyperexcitability of neurons. Owing to these essential functions, dysregulated synaptic inhibition causes a plethora of neurological disorders, including epilepsy, autism, and schizophrenia. Among these disorders, epilepsy is associated with abnormal hyperexcitability of neurons caused by the deficits of GABAergic neuron or decreased GABAergic inhibition at synapses. Although many antiepileptic drugs are intended to improve GABA-mediated inhibition, the molecular mechanisms of synaptic inhibition regulated by GABAergic neurons are not fully understood. Increasing evidence indicates that phospholipase C??1 (PLC??1) is involved in the generation of seizure, while the causal relationship between PLC??1 and seizure has not been firmly established yet. Here, we show that genetic deletion of PLC??1 in GABAergic neurons leads to handling-induced seizure in aged mice. In addition, aged Plcg1F/F; Dlx5/6-Cre mice exhibit other behavioral alterations, including hypoactivity, reduced anxiety, and fear memory deficit. Notably, inhibitory synaptic transmission as well as the number of inhibitory synapses are decreased in the subregions of hippocampus. These findings suggest that PLC??1 may be a key determinant of maintaining both inhibitory synapses and synaptic transmission, potentially contributing to the regulation of E/I balance in the hippocampus

Capacitance of MnO2 Micro-Flowers Decorated CNFs in Alkaline Electrolyte and Its Bi-Functional Electrocatalytic Activity toward Hydrazine Oxidation

Well-dispersed MnO2 micro-flowers were grown directly on carbon nanofibers via a simple hydrothermal technique without any template. Structure and morphology were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) equipped with rapid energy dispersive analysis X-ray (EDX). The appealed characterization techniques specified that the obtained material is carbon nanofibers decorated by MnO2 micro-flowers. Super capacitive performance of the MnO2 micro-flowers decorated CNFs as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium and yield a reasonable specific capacitance of 120 Fg−1 at 5 mV s−1. As an electrocatalyst for hydrazine oxidation, the MnO2 micro-flowers decorated CNFs showed high current density. The impressive bi-functional electrochemical activity of MnO2 micro-flowers decorated CNFs is mainly attributed to its unique architectural structure.This Research was financially supported by National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. 2014R1A4A1008140

Impaired learning and memory in CD38 null mutant mice

CD38 is an enzyme that catalyzes the formation of cyclic ADP ribose and nicotinic acid adenine dinucleotide phosphate, both of which are involved in the mobilization of Ca2+ from intracellular stores. Recently, CD38 has been shown to regulate oxytocin release from hypothalamic neurons. Importantly, CD38 mutations are associated with autism spectrum disorders (ASD) and CD38 knockout (CD38(-/-)) mice display ASD-like behavioral phenotypes including deficient parental behavior and poor social recognition memory. Although ASD and learning deficits commonly co-occur, the role of CD38 in learning and memory has not been investigated. We report that CD38(-/-)mice show deficits in various learning and memory tasks such as the Morris water maze, contextual fear conditioning, and the object recognition test. However, either long-term potentiation or long-term depression is not impaired in the hippocampus of CD38(-/-)mice. Our results provide convincing evidence that CD38(-/-)mice show deficits in various learning and memory tasks including spatial and non-spatial memory tasks. Our data demonstrate that CD38 is critical for regulating hippocampus-dependent learning and memory without modulating synaptic plasticity.open1

Cell Labeling and Tracking Method without Distorted Signals by Phagocytosis of Macrophages

Cell labeling and tracking are important processes in understanding biologic mechanisms and the therapeutic effect of inoculated cells in vivo. Numerous attempts have been made to label and track inoculated cells in vivo; however, these methods have limitations as a result of their biological effects, including secondary phagocytosis of macrophages and genetic modification. Here, we investigated a new cell labeling and tracking strategy based on metabolic glycoengineering and bioorthogonal click chemistry. We first treated cells with tetra-acetylated N-azidoacetyl-D-mannosamine to generate unnatural sialic acids with azide groups on the surface of the target cells. The azide-labeled cells were then transplanted to mouse liver, and dibenzyl cyclooctyne-conjugated Cy5 (DBCO-Cy5) was intravenously injected into mice to chemically bind with the azide groups on the surface of the target cells in vivo for target cell visualization. Unnatural sialic acids with azide groups could be artificially induced on the surface of target cells by glycoengineering. We then tracked the azide groups on the surface of the cells by DBCO-Cy5 in vivo using bioorthogonal click chemistry. Importantly, labeling efficacy was enhanced and false signals by phagocytosis of macrophages were reduced. This strategy will be highly useful for cell labeling and tracking

Clinical relevance of ground glass opacity in 105 patients with miliary tuberculosis

SummaryBackgroundAfter the application of chest computed tomography (CT), ground glass opacity (GGO) was introduced as one of major accompanying findings of miliary tuberculosis (MT) in addition to miliary nodules. However, little is known about whether GGO is associated with the clinical manifestations and outcomes of MT. Therefore, the present study examined the clinical relevance of GGO in patients with MT.MethodsChest radiographs and CT scans of MT patients were retrospectively reviewed. Clinical manifestations and outcomes were compared in terms of the extent of GGO revealed by chest CT.ResultsConfirmed 105 MT patients were included. GGO was observed in 70 (67%) patients. MT patients with an extent of GGO >50% (n = 21) had symptoms of shorter duration, more frequent dyspnea, and more pronounced changes in the levels of acute phase reactants. Miliary nodules were less discernible on CT in those with an extent of GGO >50%. MT patients with an extent of GGO >50% were significantly associated with a longer hospital stay (p = 0.02) and with acute respiratory failure (p < 0.001) than those with an extent of GGO ≤50%. However, mortality among MT patients was not associated with the extent of GGO.ConclusionMT patients with an extent of GGO >50% had more rapidly progressive manifestations and a greater potential for delayed diagnosis and poorer prognosis. Nevertheless, mortality was not higher in confirmed MT patients with an extent of GGO >50% than in those with an extent of GGO ≤50%