Explore the vast range of titles available.

Nucleic acids derived from pathogens induce potent innate immune responses 1 – 6 . Cyclic GMP–AMP synthase (cGAS) is a double-stranded DNA sensor that catalyses the synthesis of the cyclic dinucleotide cyclic GMP–AMP, which mediates the induction of type I interferons through the STING–TBK1–IRF3 signalling axis 7 – 11 . cGAS was previously thought to not react with self DNA owing to its cytosolic localization 2 , 12 , 13 ; however, recent studies have shown that cGAS is localized mostly in the nucleus and has low activity as a result of tight nuclear tethering 14 – 18 . Here we show that cGAS binds to nucleosomes with nanomolar affinity and that nucleosome binding potently inhibits its catalytic activity. To elucidate the molecular basis of cGAS inactivation by nuclear tethering, we determined the structure of mouse cGAS bound to human nucleosome by cryo-electron microscopy. The structure shows that cGAS binds to a negatively charged acidic patch formed by histones H2A and H2B via its second DNA-binding site 19 . High-affinity nucleosome binding blocks double-stranded DNA binding and maintains cGAS in an inactive conformation. Mutations of cGAS that disrupt nucleosome binding alter cGAS-mediated signalling in cells. Structural studies show that cyclic GMP–AMP synthase binds to nucleosomes through its DNA-binding site, which maintains it in an inactive conformation and prevents self-DNA binding.

Nucleic acids from bacteria or viruses induce potent immune responses in infected cells 1 – 4 . The detection of pathogen-derived nucleic acids is a central strategy by which the host senses infection and initiates protective immune responses 5 , 6 . Cyclic GMP-AMP synthase (cGAS) is a double-stranded DNA sensor 7 , 8 . It catalyses the synthesis of cyclic GMP-AMP (cGAMP) 9 – 12 , which stimulates the induction of type I interferons through the STING–TBK1–IRF-3 signalling axis 13 – 15 . STING oligomerizes after binding of cGAMP, leading to the recruitment and activation of the TBK1 kinase 8 , 16 . The IRF-3 transcription factor is then recruited to the signalling complex and activated by TBK1 8 , 17 – 20 . Phosphorylated IRF-3 translocates to the nucleus and initiates the expression of type I interferons 21 . However, the precise mechanisms that govern activation of STING by cGAMP and subsequent activation of TBK1 by STING remain unclear. Here we show that a conserved PLPLRT/SD motif within the C-terminal tail of STING mediates the recruitment and activation of TBK1. Crystal structures of TBK1 bound to STING reveal that the PLPLRT/SD motif binds to the dimer interface of TBK1. Cell-based studies confirm that the direct interaction between TBK1 and STING is essential for induction of IFNβ after cGAMP stimulation. Moreover, we show that full-length STING oligomerizes after it binds cGAMP, and highlight this as an essential step in the activation of STING-mediated signalling. These findings provide a structural basis for the development of STING agonists and antagonists for the treatment of cancer and autoimmune disorders. A molecular model of STING-mediated signalling is proposed, as structural analysis identifies a crucial motif for the binding of TBK1 to STING, and a separate model involved in IRF-3 binding.

CD8 + T cells and natural killer (NK) cells are central cellular components of immune responses against pathogens and cancer, which rely on interleukin (IL)-15 for homeostasis. Here we show that IL-15 also mediates homeostatic priming of CD8 + T cells for antigen-stimulated activation, which is controlled by a deubiquitinase, Otub1. IL-15 mediates membrane recruitment of Otub1, which inhibits ubiquitin-dependent activation of AKT, a kinase that is pivotal for T cell activation and metabolism. Otub1 deficiency in mice causes aberrant responses of CD8 + T cells to IL-15, rendering naive CD8 + T cells hypersensitive to antigen stimulation characterized by enhanced metabolic reprograming and effector functions. Otub1 also controls the maturation and activation of NK cells. Deletion of Otub1 profoundly enhances anticancer immunity by unleashing the activity of CD8 + T cells and NK cells. These findings suggest that Otub1 controls the activation of CD8 + T cells and NK cells by functioning as a checkpoint of IL-15-mediated priming. IL-15 has important functions in the activation and homeostasis of cytotoxic T lymphocytes (CTLs) and NK cells. Sun and colleagues demonstrate that the deubiquitinase Otub1 controls CTLs and NK cells in a cell-intrinsic manner by negatively regulating IL-15 signaling.

The recent outbreak of Zika virus (ZIKV) has infected over 1 million people in over 30 countries. ZIKV replicates its RNA genome using virally encoded replication proteins. Nonstructural protein 5 (NS5) contains a methyltransferase for RNA capping and a polymerase for viral RNA synthesis. Here we report the crystal structures of full-length NS5 and its polymerase domain at 3.0 Å resolution. The NS5 structure has striking similarities to the NS5 protein of the related Japanese encephalitis virus. The methyltransferase contains in-line pockets for substrate binding and the active site. Key residues in the polymerase are located in similar positions to those of the initiation complex for the hepatitis C virus polymerase. The polymerase conformation is affected by the methyltransferase, which enables a more efficiently elongation of RNA synthesis in vitro . Overall, our results will contribute to future studies on ZIKV infection and the development of inhibitors of ZIKV replication. Zika virus infection can cause human birth defects and Guillain-Barré syndrome. Here the authors present the structures of the full-length nonstructural protein 5 and its RNA-dependent RNA polymerase domain of Zika virus, which are targets for inhibitors of virus replication.

Type I IFNs are key cytokines mediating innate antiviral immunity. cGMP-AMP synthase, ritinoic acid-inducible protein 1 (RIG-I)–like receptors, and Toll-like receptors recognize microbial double-stranded (ds)DNA, dsRNA, and LPS to induce the expression of type I IFNs. These signaling pathways converge at the recruitment and activation of the transcription factor IRF-3 (IFN regulatory factor 3). The adaptor proteins STING (stimulator of IFN genes), MAVS (mitochondrial antiviral signaling), and TRIF (TIR domain-containing adaptor inducing IFN-β) mediate the recruitment of IRF-3 through a conserved pLxIS motif. Here we show that the pLxIS motif of phosphorylated STING, MAVS, and TRIF binds to IRF-3 in a similar manner, whereas residues upstream of the motif confer specificity. The structure of the IRF-3 phosphomimetic mutant S386/396E bound to the cAMP response element binding protein (CREB)-binding protein reveals that the pLxIS motif also mediates IRF-3 dimerization and activation. Moreover, rotavirus NSP1 (nonstructural protein 1) employs a pLxIS motif to target IRF-3 for degradation, but phosphorylation of NSP1 is not required for its activity. These results suggest a concerted mechanism for the recruitment and activation of IRF-3 that can be subverted by viral proteins to evade innate immune responses.

Digital agriculture serves as a pivotal means of ushering in innovative agricultural practices and achieving sustainable agricultural development. Although agricultural digitalization has received increasing attention, the unbalanced development and regional disparities of digital agriculture are still key obstacles to sustainable agricultural development. Based on the data of 31 provinces in China from 2013 to 2021, this study evaluates the development level of digital agriculture in China, and further analyzes the distribution pattern, spatial characteristics, and transition probabilities of digital agriculture from a regional perspective. The index system of the digital agriculture development level is constructed from five aspects: infrastructure, talent resources, agricultural informatization, the digitization of agricultural production processes, and agricultural production efficiency. Among these, infrastructure and talent resources reflect the resources needed for the development of digital agriculture; agricultural informatization and the digitization of the agricultural production process indicate the role of digitization in the process of agricultural development; and the agricultural production efficiency is the goal of the digital agriculture development, which is a critical criteria of its evaluation. The weighted analysis method of objective sequential analysis, which combines the dynamic level of indicators and sequential relationships, is used to assign weights to the indicators. In addition, to address the regional disparities in the development level of digital agriculture, kernel density estimation, Moran’s index, and (spatial) Markov chain analysis are applied to analyze the spatial dynamic evolution of digital agriculture in China. The findings reveal substantial regional disparities in digital agriculture development within China, particularly in the Western region, where development lags behind. Moreover, this study offers actionable policy recommendations for policymakers to strengthen regional infrastructure and talent cultivation, as well as other aspects of digital agriculture development, to mitigate regional differences and provide reference for other emerging countries.

Dynamic multi-criteria evaluation plays a central role in assessing complex systems based on panel data. However, existing objective weighting methods often suffer from sensitivity to extreme observations and may produce unstable or even negative weights, limiting their reliability in practice. To address these issues, this study proposes an improved dynamic weighting approach by integrating sampling-based resampling with a density-weighted aggregation (DWA) scheme. The proposed method extends the traditional Vertical–Horizontal Scatter Degree (VHSD) framework by stabilizing weight estimation across repeated samples and aggregating weights in a distribution-aware manner. This design effectively reduces the influence of extreme observations and ensures non-negative and consistent weighting results. An empirical analysis based on panel data is conducted to evaluate the performance of the proposed method. The results show that, compared with the classical VHSD, the proposed approach consistently eliminates negative weights, achieves higher stability across different sampling schemes, and demonstrates improved robustness under data perturbations. In addition, the method exhibits greater sensitivity to structural variations in the data while maintaining overall consistency in evaluation outcomes. Overall, the proposed framework provides a transparent and reproducible approach for composite indicator construction and dynamic multi-criteria evaluation, and is particularly suitable for applications involving complex and heterogeneous datasets.

Elucidating how individual mutations affect the protein energy landscape is crucial for understanding how proteins evolve. However, predicting mutational effects remains challenging because of epistasis—the nonadditive interactions between mutations. Here, we investigate the biophysical mechanism of strain-specific epistasis in the nonstructural protein 1 (NS1) of influenza A viruses (IAVs). We integrate structural, kinetic, thermodynamic, and conformational dynamics analyses of four NS1s of influenza strains that emerged between 1918 and 2004. Although functionally near-neutral, strain-specific NS1 mutations exhibit long-range epistatic interactions with residues at the p85β-binding interface. We reveal that strain-specific mutations reshaped the NS1 energy landscape during evolution. Using NMR spin dynamics, we find that the strain-specific mutations altered the conformational dynamics of the hidden network of tightly packed residues, underlying the evolution of long-range epistasis. This work shows how near-neutral mutations silently alter the biophysical energy landscapes, resulting in diverse background effects during molecular evolution. Influenza A virus (IAV) nonstructural protein 1 (NS1) is a multifunctional virulence factor that interacts with several host factors such as phosphatidylinositol-3-kinase (PI3K). NS1 binds specifically to the p85β regulatory subunit of PI3K and subsequently activates PI3K signaling. Here, Kim et al. show that functionally near-neutral, strain-specific NS1 mutations lead to variations in binding kinetics to p85β exhibit long-range epistatic interactions. Applying NMR they provide evidence that the structural dynamics of the NS1 hydrophobic core have evolved over time and contributed to epistasis.

Background Artemisia is important medicinal plants in China and are widely used in medicine, agriculture, and food. Pharmacologically active components of the plants remain to be investigated. Methods This study sought to identify and compare the chemical constituents of three species of Artemisia in Tibet using a widely-targeted metabolomics approach and their antibacterial and antioxidant capacities were determined. Result A total of 1109 metabolites within 10 categories were detected from the three species of Artemisia , including lipids, amino acids, nucleotides, flavonoids, terpenes, coumarins, organic acids, and phenolic acids. 732 different metabolites have been identified between Artemisia sieversiana and Artemisia annua , 751 different metabolites were identified between Artemisia wellbyi and A. sieversiana , and 768 differential metabolites were differentially detected from A. wellbyi and A. annua. Differentially identified compounds included flavonoids, phenolic acids, artemisinins and coumarin. A. annua contained the highest relative content of artemisinin among three Artemisia . The antimicrobial experiments showed that the three Artemisia species had strong antibiotic activities against Bacillus subtilis , Escherichia coli , Staphylococcus aureus , Proteus mirabilis and Pseudomonas aeruginosa . The biochemical analysis showed that the three species of Artemisia have strong antioxidant capacity. Conclusions This is the first reported attempt to comparatively determine the types of the metabolites of the three widely distributed Artemisia species in Tibet. The information should help medicinal research and facilitate comprehensive development and utilization of Artemisia species in Tibet.

Endotoxins are toxic substances that widely exist in the environment and can enter the intestine with food and other substances. Intestinal epithelial cells are protected by a mucus layer that contains MUC2 as its main structural component. However, a detailed understanding of the mechanisms involved in the function of the mucus barrier in endotoxin penetration is lacking. Here, we established the most suitable proportion of Caco-2/HT-29 co-culture cells as a powerful tool to evaluate the intestinal mucus layer. Our findings significantly advance current knowledge as focal adhesion and ECM-receptor interaction were identified as the two most significantly implicated pathways in MUC2 small interfering RNA (siRNA)-transfected Caco-2/HT-29 co-culture cells after 24 h of LPS stimulation. When the mucus layer was not intact, LPS was found to damage the tight junctions of Caco-2/HT29 co-cultured cells. Furthermore, LPS was demonstrated to inhibit the integrin-mediated focal adhesion structure and damage the matrix network structure of the extracellular and actin microfilament skeletons. Ultimately, LPS inhibited the interactive communication between the extracellular matrix and the cytoskeleton for 24 h in the siMUC2 group compared with the LPS(+) and LPS(-) groups. Overall, we recognized the potential of MUC2 as a tool for barrier function in several intestinal bacterial diseases.