CobB-mediated deacetylation of the chaperone CesA regulates Escherichia coli O157:H7 virulence.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a common food-borne pathogen that can cause acute diseases. Lysine acetylation is a post-translational modification (PTM) that occurs in various prokaryotes and is regulated by CobB, the only deacetylase found in bacteria. Here, we demonstrated that CobB plays an important role in the virulence of EHEC O157:H7 and that deletion of cobB significantly decreased the intestinal colonization ability of bacteria. Using acetylation proteomic studies, we systematically identified several proteins that could be regulated by CobB in EHEC O157:H7. Among these CobB substrates, we found that acetylation at the K44 site of CesA, a chaperone for the type-III secretion system (T3SS) translocator protein EspA, weakens its binding to EspA, thereby reducing the stability of this virulence factor; this PTM ultimately attenuating the virulence of EHEC O157:H7. Furthermore, we showed that deacetylation of the K44 site, which is deacetylated by CobB, promotes the interaction between CesA and EspA, thereby increasing bacterial virulence in vitro and in animal experiments. In summary, we showed that acetylation influences the virulence of EHEC O157:H7, and uncovered the mechanism by which CobB contributes to bacterial virulence based on the regulation of CesA deacetylation.

Active Adjustment of the Subreflector Shape for the Large Dual-Reflector Antenna.

A shape adjustment method for subreflectors based on minimizing the residual wavefront error of the large dual-reflector antenna is presented. This method is used to compensate for the antenna structural deformation caused by environment loading. The shape of the subreflector is adjusted using actuators fixed under the panels. The shape adjustment response function for the subreflector shape and the actuators' adjustment amount is established, which is based on the inverse distance weighting function, and then the control function of the subreflector shape is obtained. The actuators' adjustment amount can be calculated using the least squares matrix transformation with the minimum residual wavefront error. Analysis of the experiment's results shows the residual wavefront error and primary aberration are greatly reduced under different elevation angles, and the effectiveness of the proposed method is verified.

Hepatotoxic effects of inhalation exposure to polycyclic aromatic hydrocarbons on lipid metabolism of C57BL/6 mice.

Inhalation from ambient air and cigarette smoke is a common route of human exposure to polycyclic aromatic hydrocarbons (PAHs). Little information is available regarding hepatotoxicities of inhaled PAHs so for. In this study, we evaluated the toxic effects of intratracheally instilled benzo[a]pyrene (B[a]P) on hepatic lipid metabolism of C57BL/6 mice at relevant environmental exposure levels by using two different mass-based lipidomics approaches. The results of mass spectrometry imaging analysis showed that both the abundance and spatial distribution of several lysophosphatidylcholine (LysoPC), phosphatidylcholine (PC) and sphingomyelin (SM) in the liver section were different and changed after inhalation exposure to B[a]P. Liquid chromatography coupled with mass spectrometry-based lipidomics analysis and multivariate statistical analysis found that B[a]P exposure markedly altered glycerophospholipids, glycerolipids, and fatty acid metabolism in the mouse liver, with increasing of triacylglycerol (TG), phosphatidylinositol (PI) and PC, and decreasing of LysoPCs phosphatidylethanolamines (PEs), lysophosphatidylethanolamine (LysoPEs), free fatty acids (FFAs) and eicosanoids. B[a]P-induced lipid metabolic disorders showed a time-dependent effect, which generated three response trajectories with different change trends. Consequently, B[a]P exposure induced alteration of hepatic lipids by promoting the uptake from blood or the biosynthesis and transformation in the liver, might contribute to non-alcoholic fatty liver disease, hepatocyte membrane injury, inflammation, and signal system disturbance.

Dysregulation of lipid metabolism induced by airway exposure to polycyclic aromatic hydrocarbons in C57BL/6 mice.

Polycyclic aromatic hydrocarbons (PAHs), originated from cigarette smoke and fine particle matter (PM2.5), are important inducers of lung cancer. Lipid metabolic disorder is an important biological feature in the progression of lung cancer. However, the dysregulation of lipid metabolism induced by airway exposure to PAHs remains unknown. In this study, an untargeted lipidomics approach was performed to characterize the effects of airway exposure to benzo[a]pyrene (BaP) on lipid metabolism of C57BL/6 mice. Lipidome of serum samples were analyzed with an ultra-performance liquid chromatography coupled with quadrupole-orbitrap mass spectrometer. Lipid profiling and multivariate statistical analysis results demonstrated that airway exposure to BaP mainly disturbed glycerophospholipid metabolism of mice. Moreover, sex-dependent and time-dependent effects of BaP exposure on lipids profile of mice were observed. Several phosphatidylcholines (PCs), Lysophosphatidylcholines (LysoPCs), phosphatidylethanolamines (PEs), Lysophosphatidylethanolamines (LysoPEs) and phosphatidylinositols (PIs) were significantly down-regulated in mice serum after BaP exposure. Meanwhile, these altered lipids showed different susceptibility and change trends in male and female mice. Our results are corresponding with the lipid metabolic alterations induced by cigarette smoke and PM2.5 in animals or human. Compared with the dysregulation of lipid metabolism in patients with lung cancer, these results indicated that the lipid metabolism response to PAHs airway exposure may contribute to the lung cancer progression.

Self-Assembled DNA Hydrogel Based on Enzymatically Polymerized DNA for Protein Encapsulation and Enzyme/DNAzyme Hybrid Cascade Reaction.

DNA hydrogel is a promising biomaterial for biological and medical applications due to its native biocompatibility and biodegradability. Herein, we provide a novel, versatile, and cost-effective approach for self-assembly of DNA hydrogel using the enzymatically polymerized DNA building blocks. The X-shaped DNA motif was elongated by terminal deoxynucleotidyl transferase (TdT) to form the building blocks, and hybridization between dual building blocks via their complementary TdT-polymerized DNA tails led to gel formation. TdT polymerization dramatically reduced the required amount of original DNA motifs, and the hybridization-mediated cross-linking of building blocks endows the gel with high mechanical strength. The DNA hydrogel can be applied for encapsulation and controllable release of protein cargos (for instance, green fluorescent protein) due to its enzymatic responsive properties. Moreover, this versatile strategy was extended to construct a functional DNAzyme hydrogel by integrating the peroxidase-mimicking DNAzyme into DNA motifs. Furthermore, a hybrid cascade enzymatic reaction system was constructed by coencapsulating glucose oxidase and ß-galactosidase into DNAzyme hydrogel. This efficient cascade reaction provides not only a potential method for glucose/lactose detection by naked eye but also a promising modular platform for constructing a multiple enzyme or enzyme/DNAzyme hybrid system.

A universal platform for building molecular logic circuits based on a reconfigurable three-dimensional DNA nanostructure.

Molecular logic gates are capable of performing various logic tasks for biomarker detection, disease diagnostics and therapy, and controlling biological progress. Herein, we integrated multiple components of a logic device into a single DNA 3D nano-assembly with a triangular prism structure. Compared with the separate construction of each component in previously reported DNA logic gate systems, such an integrated design strategy made the 3D DNA nanoprism universal for logic gates, it can be reconfigured to execute diverse logic operations. Binary basic logic gates (OR, AND, INHIBIT and XOR), combinatorial gates (INHIBIT-OR), and multi-valued logic gates (ternary INHIBIT gate) were readily achieved by taking this DNA nanoprism as a universal platform. Moreover, a logic gate system for identification of even numbers and odd numbers from natural numbers was established successfully by employing only this single DNA nanoprism and four short single-stranded DNA. The universality of this nanoprism greatly simplified the design of DNA logic gate system. Additionally, this nanoprism was able to perform logic operation steadily in a biological matrix, indicating that this box-like DNA nanostructure applies to logic gates in a complicated environment. This study provided a unique opportunity to design versatile 3D DNA nanostructure-based intelligent nanodevices, which show great potential in biocomputing, multi-parameter sensing, and intelligent disease diagnostics and therapy.

Intra-molecular G-quadruplex structure generated by DNA-templated click chemistry: "turn-on" fluorescent probe for copper ions.

A novel homogenous fluorescent sensor for signal-on detection of Cu(2+) has been developed based on intra-molecular G-quadruplex formed by DNA-templated click reaction and crystal violet (CV) as label-free signal reporter. The clickable DNA probe consists of two G-rich strands (A and B) bearing azide and alkyne group, respectively, and a template strand (C) locating two proximate reactants by pairing with A and B. The sequences of A and B are derived from asymmetric split of the G-quadruplex sequence (TTAGGG)4. In the presence of Cu(2+), the whole G-quadruplex sequence A-B is generated by chemical ligation of A and B via copper ion-catalyzed alkyne-azide cycloaddition, then released from template by toehold strand displacement, and consequently forming a stable intra-molecular G-quadruplex, which binds with CV to generate a strong fluorescent signal. Oppositely, weak fluorescence was obtained without Cu(2+) because of unstable intermolecular G-quadruplex formed by A and B and lack of lateral loop connection. Therefore, the Cu(2+) can be sensitively and specifically detected by the fluorescence of the CV-stained G-quadruplex with a low detection limit of 65nM and a linear range of 0.1-3µM. This method rationally integrated the DNA-templated synthesis and G-quadruplex structure-switch, presenting a simple and promising approach for biosensor development.