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Influenza B viruses (IBVs), though often overshadowed by influenza A viruses (IAVs), remain a significant global public health concern, particularly during seasons when they predominate. However, the molecular mechanisms underlying IBV pathogenicity remain largely unknown. In this study, we identified two amino acid substitutions, PB2-N460S and NP-I163T, from IBV clinical isolates with distinct replication and pathogenicity profiles. Using reverse genetics, we generated recombinant IBV viruses to evaluate the impact of these substitutions. In vitro and in vivo infections revealed that viral replication and pathogenicity were not significantly affected by either substitution alone but were substantially enhanced when both substitutions occurred together. Lung transcriptomics in mice infected with virus containing PB2-N460S/NP-I163T substitutions showed heightened immune activation. This was characterized by upregulated transcription of antiviral and immune-related genes, contributing to excessive inflammation and severe disease outcomes. Mechanistic investigations demonstrated that each substitution independently increased protein expression and strengthened PB2-NP interactions. However, only the combined presence of PB2-N460S and NP-I163T significantly enhanced polymerase activity. Structural modeling indicated that PB2–460 residue is positioned at the PB2-NP interface, while NP-163 site resides distally, suggesting an indirect functional interplay. These findings provide new insights into the molecular determinants of IBV pathogenesis, highlighting the synergistic effect of PB2-N460S and NP-I163T in enhancing viral fitness and worsening disease outcomes.

GABAB receptor is a Class C G protein‐coupled receptor (GPCR) for γ‐aminobutyric acid (GABA), the principal inhibitory neurotransmitter. It forms an obligatory heterodimer consisting of two subunits, GB1 and GB2. Whether the activation mechanism of the GABAB receptor is conserved during evolution remains unknown. Here, the cryogenic electron microscopy (cryo‐EM) structures of the drosophila GABAB receptor in both antagonist‐bound inactive state and GABA‐bound active state in complex with Gi protein are reported. The drosophila GABAB receptor exhibits an asymmetric activation, mirroring its human homolog. However, a larger inactive interface prevents drosophila GABAB receptor constitutive activity. Four key residues, which are not conserved in drosophila GABAB receptor, are responsible for the activity of the positive allosteric modulator in its human homolog. Whereas the intracellular loop 2 of drosophila GB2 (dGB2) is less involved, the ordered C terminus of dGB2 and its corresponding region in its human homolog are required for G protein coupling. These evolutionary variations provide a complete understanding of the activation mechanism of the GABAB receptor and new insights for future development of allosteric modulators for medication and insecticides. This study explores the structural and functional mechanisms of the drosophila GABAB receptor, a key role in neurotransmission. Using cryo‐EM, the research reveals how the receptor's activation differs from its human counterpart, highlighting unique evolutionary features. These findings offer valuable insights for developing GABAB‐targeted allosteric modulators with therapeutic potential for medication and insecticides.

G protein coupled receptors (GPCRs) oligomerization may allow signal integration from different GPCR units. The GABAB receptor, activated by the main inhibitory transmitter, GABA, is an obligatory heterodimer. It is the target of two therapeutic drugs, baclofen and GHB, and can form stable oligomers. The existence, roles, and possible allosteric interaction of GABAB oligomers remain elusive. Here, we show that GABAB oligomers exist in neurons. Their function can be specifically affected by human disease-associated mutations, demonstrating their essential role for normal brain function. The cryo-EM structure of a hetero-tetramer in the apo state reveals the heterodimers interacting in an asymmetrical way to prevent one unit from being activated. This represents a nice example of a negative allosteric interaction between GPCRs related to human diseases.G protein coupled receptors (GPCRs) oligomerization may allow signal integration from different GPCR units. The GABAB receptor, activated by the main inhibitory transmitter, GABA, is an obligatory heterodimer. It is the target of two therapeutic drugs, baclofen and GHB, and can form stable oligomers. The existence, roles, and possible allosteric interaction of GABAB oligomers remain elusive. Here, we show that GABAB oligomers exist in neurons. Their function can be specifically affected by human disease-associated mutations, demonstrating their essential role for normal brain function. The cryo-EM structure of a hetero-tetramer in the apo state reveals the heterodimers interacting in an asymmetrical way to prevent one unit from being activated. This represents a nice example of a negative allosteric interaction between GPCRs related to human diseases.

Nipah virus (NiV) and related viruses form a distinct henipavirus genus within the Paramyxoviridae family. NiV continues to spillover into the humans causing deadly outbreaks with increasing human-bat interaction. NiV encodes the large protein (L) and phosphoprotein (P) to form the viral RNA polymerase machinery. Their sequences show limited homologies to those of non- henipavirus paramyxoviruses. We report two cryo-electron microscopy (cryo-EM) structures of the Nipah virus (NiV) polymerase L-P complex, expressed and purified in either its full-length or truncated form. The structures resolve the RNA-dependent RNA polymerase (RdRp) and polyribonucleotidyl transferase (PRNTase) domains of the L protein, as well as a tetrameric P protein bundle bound to the L-RdRp domain. L-protein C-terminal regions are unresolved, indicating flexibility. Two PRNTase domain zinc-binding sites, conserved in most Mononegavirales, are confirmed essential for NiV polymerase activity. The structures further reveal anchoring of the P protein bundle and P protein X domain (XD) linkers on L, via an interaction pattern distinct among Paramyxoviridae. These interactions facilitate binding of a P protein XD linker in the nucleotide entry channel and distinct positioning of other XD linkers. We show that the disruption of the L-P interactions reduces NiV polymerase activity. The reported structures should facilitate rational antiviral-drug discovery and provide a guide for the functional study of NiV polymerase.

In Saccharomyces cerevisiae , cryptic transcription at the coding region is prevented by the activity of Sin3 histone deacetylase (HDAC) complex Rpd3S, which is carried by the transcribing RNA polymerase II (RNAPII) to deacetylate and stabilize chromatin. Despite its fundamental importance, the mechanisms by which Rpd3S deacetylates nucleosomes and regulates chromatin dynamics remain elusive. Here, we determined several cryo-EM structures of Rpd3S in complex with nucleosome core particles (NCPs), including the H3/H4 deacetylation states, the alternative deacetylation state, the linker tightening state, and a state in which Rpd3S co-exists with the Hho1 linker histone on NCP. These structures suggest that Rpd3S utilizes a conserved Sin3 basic surface to navigate through the nucleosomal DNA, guided by its interactions with H3K36 methylation and the extra-nucleosomal DNA linkers, to target acetylated H3K9 and sample other histone tails. Furthermore, our structures illustrate that Rpd3S reconfigures the DNA linkers and acts in concert with Hho1 to engage the NCP, potentially unraveling how Rpd3S and Hho1 work in tandem for gene silencing.

GABA B receptor is a Class C G protein‐coupled receptor (GPCR) for γ‐aminobutyric acid (GABA), the principal inhibitory neurotransmitter. It forms an obligatory heterodimer consisting of two subunits, GB1 and GB2. Whether the activation mechanism of the GABA B receptor is conserved during evolution remains unknown. Here, the cryogenic electron microscopy (cryo‐EM) structures of the drosophila GABA B receptor in both antagonist‐bound inactive state and GABA‐bound active state in complex with G i protein are reported. The drosophila GABA B receptor exhibits an asymmetric activation, mirroring its human homolog. However, a larger inactive interface prevents drosophila GABA B receptor constitutive activity. Four key residues, which are not conserved in drosophila GABA B receptor, are responsible for the activity of the positive allosteric modulator in its human homolog. Whereas the intracellular loop 2 of drosophila GB2 (dGB2) is less involved, the ordered C terminus of dGB2 and its corresponding region in its human homolog are required for G protein coupling. These evolutionary variations provide a complete understanding of the activation mechanism of the GABA B receptor and new insights for future development of allosteric modulators for medication and insecticides.

G protein coupled receptors (GPCRs) oligomerization may allow signal integration from different GPCR units. The GABA receptor, activated by the main inhibitory transmitter, GABA, is an obligatory heterodimer. It is the target of two therapeutic drugs, baclofen and GHB, and can form stable oligomers. The existence, roles, and possible allosteric interaction of GABA oligomers remain elusive. Here, we show that GABA oligomers exist in neurons. Their function can be specifically affected by human disease-associated mutations, demonstrating their essential role for normal brain function. The cryo-EM structure of a hetero-tetramer in the apo state reveals the heterodimers interacting in an asymmetrical way to prevent one unit from being activated. This represents a nice example of a negative allosteric interaction between GPCRs related to human diseases.

The mammalian SWI/SNF family of chromatin remodelers comprises BRG1/BRM-associated factor (cBAF), Polybromo-associated BAF (PBAF), and non-canonical BAF (ncBAF) complexes, which slide and disassemble nucleosomes to regulate gene expression and chromatin structure dependent on ATP hydrolysis energy. While the chromatin engagement mechanisms of cBAF and PBAF have been structurally resolved, the molecular architecture governing ncBAF interaction with chromatin remains elusive. In this study, by integrating cryo-electron microscopy, biochemical assays and cross-linking mass spectrometry, we resolved the conformational transition of ncBAF-nucleosome complexes from nucleotide-free to nucleotide-bound states. Our analyses establish BCL7 proteins as dynamic molecular tethers connecting the ARP module to the nucleosomal acidic patch and demonstrate that BCL7B promotes ncBAF-mediated nucleosome remodeling, with BRG1-catalyzed ATP hydrolysis triggering conformational changes that modulate BCL7-mediated histone association. Structurally and biochemically, we further demonstrate that β-actin within the BCL7-containing ARP module retains ATP hydrolysis activity, rendering its exposed pointed end structurally compatible with incorporation into the barbed end of nuclear actin filaments, which provides a potential molecular basis for coordinating nuclear actin networks with chromatin remodeling. Collectively, our findings unravel a dynamic role of BCL7 in regulating ncBAF-mediated chromatin remodeling and establish a distinct chromatin engagement mode of ncBAF from that of cBAF/PBAF.

Accurate instance-level segmentation of organelles in electron microscopy (EM) is critical for quantitative analysis of subcellular morphology and inter-organelle interactions. However, current benchmarks, based on small, curated datasets, fail to capture the inherent heterogeneity and large spatial context of in-the-wild EM data, imposing fundamental limitations on current patch-based methods. To address these limitations, we developed a large-scale, multi-source benchmark for multi-organelle instance segmentation, comprising over 100,000 2D EM images across variety cell types and five organelle classes that capture real-world variability. Dataset annotations were generated by our designed connectivity-aware Label Propagation Algorithm (3D LPA) with expert refinement. We further benchmarked several state-of-the-art models, including U-Net, SAM variants, and Mask2Former. Our results show several limitations: current models struggle to generalize across heterogeneous EM data and perform poorly on organelles with global, distributed morphologies (e.g., Endoplasmic Reticulum). These findings underscore the fundamental mismatch between local-context models and the challenge of modeling long-range structural continuity in the presence of real-world variability. The benchmark dataset and labeling tool will be publicly released soon.

Research on the CBP gene family in plants is scarce, with only sporadic reports on its association with immune responses. No systematic study has explored how CBP family genes regulate pepper resistance against Phytophthora capsici. Here, we focused on pepper CaCBP2, an RNA-binding protein, whose expression was significantly induced by P. capsici. Functional validation via VIGS and heterologous overexpression confirmed CaCBP2 as a negative regulator of pepper resistance to P. capsici. Based on physiological assays, transcriptome sequencing and WGCNA, we speculate it may mediate immune responses by regulating antioxidant systems, defense hormone metabolism, and disease resistance-related genes. Our findings fill the relevant research gap, enrich the role of RNA-binding proteins in plant anti-phytophthora defense, and provide a novel target for crop disease-resistant breeding.