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Biology subjects

Huang, C.

Publications and source records attributed to Huang, C..

At least 37 records · Page 2Linked to original sources

DNMT mRNA stability and YB-1 cooperatively regulate ABCB1 to drive cisplatin chemoresistance in cholangiocarcinoma

Background and AimsIntrahepatic cholangiocarcinoma (iCCA) is a tumor type with a high lethality due to late diagnosis and profound resistance to conventional chemotherapy. To date the molecular mechanisms underlying multidrug resistance remain poorly defined. Here, we integrate single-cell transcriptomics, clinicopathological analysis, and functional genomics to elucidate the molecular basis of cisplatin resistance in iCCA. Approach and ResultsSingle-cell RNA sequencing of iCCA and adjacent liver tissues revealed pronounced expression of Y-box-binding protein 1 (YB-1) in aneuploid malignant cholangiocarcinoma cells, with YB-1 expression progressively increasing during malignant evolution and strongly associated with chemoresistance. Clinically, elevated YB-1 expression-particularly its nuclear localization-robustly predicts poor overall survival and chemotherapy failure in patients with iCCA. Mechanistically, we demonstrate that cisplatin induces phosphorylation-dependent nuclear translocation of YB-1, enabling direct transcriptional activation of the drug efflux transporter ABCB1. Importantly, this process requires ABCB1 promoter demethylation, which is driven by cisplatin-induced, mA-dependent destabilization of DNMT1 and DNMT3B mRNAs. This destabilization occurs through disruption of the YB-1-IGF2BP1/3-DNMT mRNA stabilizing complex and subsequent recruitment of DNMT transcripts to YTHDF2-mediated processing bodies for degradation. ConclusionsOur findings uncover a previously unrecognized YB-1-mA-DNMT regulatory axis that drives chemotherapeutic resistance in iCCA, highlighting YB-1 as both a prognostic biomarker and a promising therapeutic target.

molecular biology↗

Dual histone methylation reader ZCWPW2 links histone methylation to initiation of meiotic recombination

Meiotic homologous recombination initiates with the formation of programmed DNA double-strand breaks (DSBs) by complexes comprising SPO11 and accessory proteins at discrete sites called recombination hotspots. In mammals, PRDM9-dependent H3K4me3 and H3K36me3 define recombination hotspots, but how these epigenetic characteristics determine the physiological DSB formation remains unknown. Here we show that dual histone methylation reader ZCWPW2 can recognize H3K4me3 and H3K36me3 marks in testis. The binding activity of ZCWPW2 to histone methylation is dependent on PRDM9 function. Moreover, we find the epigenetic writer-reader axis PRDM9-ZCWPW2 is essential for DSB formation at meiotic recombination hotspots, which may be partly explained by the finding that ZCWPW2 can physically interact with HORMAD1, IHO1, MEI4, and REC114. Finally, the absence of ZCWPW2 leads to disrupted chromosomal synapsis and recombination, thereby obstructing meiotic progression. Taken together, our findings provide new insights into how histone modifications and their associated regulatory proteins collectively regulate meiotic homologous recombination initiation.

cell biology↗

Hierarchical Immune Suppressive Functions of Regulatory T Cells Built on Mechanical Force

Regulatory T (Treg) cells maintain immune tolerance via contact-dependent inhibition and soluble mediators. While canonical suppressive mechanisms are well characterized, their hierarchical spatiotemporal organization remains unclear. We previously showed Foxp3 represses ER Ca2+ channel RyR2, reducing cytoplasmic Ca2+ to inactivate m-Calpain (Calpain-2) and stabilize high-affinity LFA-1-mediated Treg-dendritic cell (DC) adhesion--an early step blocking DC antigen presentation. Using m-Calpain as a molecular switch, we generated mechanically deficient Tregs (TregFD) with constitutively active m-Calpain that abrogated high-force Treg-DC adhesion. TregFD retained a near-wild-type transcriptome (differential expression limited to adhesion pathways), yet failed to suppress autoimmunity or DC-driven T cell proliferation. Stable adhesion was required for localized TGF-{beta}/IL-10 delivery to DCs. Single-cell RNA sequencing of rescued Scurfy mouse lymphoid tissues revealed organ-specific division of labor: non-mechanical modules support homeostasis/tissue repair, while mechanical modules dominate epithelial barrier/antigen presentation suppression. Combined TregFD and RyR2-deficient Tconv transfer restored wild-type Treg activity, demonstrating module synergism. These findings establish a mechanical force-centered, two-tiered hierarchical model of Treg suppression, providing a framework for targeting Treg mechanics in autoimmunity and inflammation.

immunology↗

B3GNT7 regulates mucin glycosylation and protects against colitis and infection

Mucus covers and protects colonic epithelial cells. Mucus is mainly composed of heavily O-glycosylated proteins called mucins, and disruption of normal mucin glycosylation occurs in ulcerative colitis (UC). Mucin-2 (MUC2) is the major colonic mucin, and MUC2 O-glycans are often extended with sulfated polyLacNAc, also known as keratan sulfate (KS). The GlcNAc residues in KS are added by B3GNT family members. B3GNT7 is highly expressed in the colon, and B3GNT7 expression is dramatically reduced in UC. However, the function of B3GNT7 in colonic physiology is unexplored. Here we show that B3gnt7 is a key player in colonic physiology through its function in controlling the structure of mucus glycans. We found that B3GNT7 prefers to extend a sulfated acceptor substrate and is required for production of polyLacNAc-modified mucus in a human goblet cell model. In vivo, B3GNT7 regulates Muc2, Muc13, and Muc17 O-glycosylation. Intestinal B3GNT7 deficiency increases susceptibility to colitis and enteric infection in mice, showing that B3GNT7-dependent glycosylation confers protective properties to colonic mucus. Taken together, these results demonstrate that B3GNT7 has a function distinct from other B3GNT family members and is critical for maintaining colonic homeostasis. SIGNIFICANCE STATEMENTUlcerative colitis is a chronic inflammatory bowel disease that affects 5 million people globally. The colonic mucus layer forms a protective barrier over colonic epithelial cells and is disrupted in ulcerative colitis. Mucus is composed of mucin proteins decorated by carbohydrates, called glycans. Glycans confer protective properties to the mucus barrier, and mucin glycans change in ulcerative colitis. B3GNT7 is an enzyme that elongates glycans and is downregulated in ulcerative colitis. In this study, we use in vitro and in vivo models to demonstrate that B3GNT7 regulates colonic mucus glycans and protects mice against colitis and infection. Our findings provide molecular insight into the contributions of B3GNT7-dependent glycans to colonic homeostasis.

biochemistry↗

Monocyte Migration Emerges from a Divergent Chemokine Signaling Network

Migration of leukocytes in the context of immune homeostasis or inflammatory diseases is regulated by activation of chemokine receptors by chemokine ligands. To elucidate how these interactions give rise to cell migration, we mapped the chemokine-stimulated signal transduction network in monocytic THP-1 cells. Global phosphoproteomics revealed 630 time-resolved changes in phosphorylated proteins downstream of the chemokine receptor CCR2. We used the "PHONEMeS" network modeling algorithm to generate the most parsimonious signal transduction network consistent with the observed protein phosphorylation data. The CCR2 signaling network is highly divergent, acting via multiple branches to regulate proteins required for cell migration. We validated this model using kinase inhibitors targeting different branches of the network and successfully blocked chemokine-stimulated cell migration. Thus, chemotaxis is an emergent property resulting from an integrated cellular response to divergent signaling pathways. This paradigm suggests that physiological regulation or pharmacological blockade of chemokine-driven inflammation could potentially be achieved by inhibiting any of the divergent pathways within the network.

systems biology↗

Estimating Visual Receptive Fields from EEG

The visual receptive field (RF) characterizes the spatiotemporal properties of the visual pathway and serves as a fundamental unit for information encoding. While RFs have been extensively studied across various neural modalities, such as functional Magnetic Resonance Imaging (fMRI), Electrocorticography (ECoG), and Magnetoencephalography (MEG), their investigation via Electroencephalography (EEG) remains limited. In this study, we introduce a stimulation paradigm that combines white noise image sequences with a letter detection task to elicit central visual field EEG responses. Using the aligned/shuffled reverse correlation, we estimate RFs across different resolutions and demonstrate that the resulting RFs exhibit rich spatiotemporal characteristics. To validate the reliability of the estimated RFs, we constructed a visual EEG reconstruction model, which achieved good performance in a classification task. The same RF estimation method was subsequently applied to high-density EEG recordings to investigate the information gain afforded by high-density configurations in visual space. This work fills a gap in the study of visual RFs regarding the EEG modality and may inform the paradigm design of visual brain-computer interfaces.

neuroscience↗

Circulating MicroRNAs as Potential Diagnostic Biomarkers for Heart Failure: A Systematic Review and Meta-Analysis

BackgroundCurrent heart failure (HF) biomarkers (e.g., BNP/NT-proBNP) have limitations in specificity and performance in HF with preserved ejection fraction (HFpEF). Circulating microRNAs (miRNAs) are promising novel biomarkers. This study aimed to comprehensively evaluate the diagnostic stability of circulating miRNAs for HF, identify novel candidates, and prioritize them for clinical translation. MethodsWe conducted a systematic review and meta-analysis. PubMed, Embase, and Cochrane Central were searched from inception to March 2025. Studies comparing miRNA expression in HF versus control groups using blood or tissue samples were included. Data were extracted, and study quality was assessed using the Newcastle-Ottawa Scale (human) and SYRCLEs tool (animal). A random-effects model pooled log odds ratios (logORs) for each miRNA. Subgroup analyses were based on species, ethnicity, and sample type. Evidence quality was graded using the GRADE framework. ResultsEighty-six studies (61 human, 25 animal) with 3,023 samples were included. Meta-analysis identified 71 consistently dysregulated circulating miRNAs (58 up, 13 down) in HF. Key upregulated miRNAs included miR-21 (logOR=8.15, 95% CI: 7.55-8.74), miR-423-5p, and miR-210. Key downregulated miRNAs included miR-144 and miR-126. Subgroup analyses revealed differences by species, ethnicity (Asian vs. non-Asian), and sample type (serum vs. plasma). GRADE assessment classified five miRNAs (miR-1, miR-21, miR-221, miR-423-5p, miR-148a) as high-quality evidence. ConclusionsThis meta-analysis identifies a panel of circulating miRNAs with stable expression in HF, with miR-21 and miR-423-5p being the most robust. Evidence grading provides a clear priority list (e.g., miR-21, miR-423-5p) for clinical validation. Subgroup heterogeneity highlights the need for standardized protocols and precision diagnostics in future biomarker development.

pharmacology and toxicology↗

High-throughput Single-cell Proteomics Enabled by Integrating nPOP-workflow with Quantitative Hyperplexing

Single-cell proteomics (scProteomics) has emerged as a powerful approach to dissect cellular heterogeneity and dynamic molecular mechanisms at unprecedented resolution. However, achieving high proteome coverage and quantitative accuracy while maintaining high-throughput remains a major challenge. In this study, we established a high-throughput scProteomics workflow that integrates a modified nano-proteomic sample preparation (nPOP) workflow with an IBT16 and TMT16 quantitative hyperplexing strategy. Through systematic optimization of chromatographic and mass spectrometric conditions, we established a label-free workflow for high-sensitivity and high quantification accuracy. On average, more than 3,000 protein groups were identified from individual 293T and HeLa cells on timsTOF SCP. When applied to single cholangiocarcinoma (CCA) cells and matched paracancerous cells dissociated from human fresh-frozen CCA tissue, approximately 2,000 protein groups were quantified per cell, revealing distinct metabolic and translational regulation patterns consistent with previously reported molecular features of CCA subtypes. To achieve high-throughput scProteomics, we then established an nPOP-based IBT16-TMT16 quantitative hyperplexing workflow. Across four human cell lines (293T, HeLa, A549, and LM3), our quantitative hyperplexing strategy achieved over 95% labelling efficiency and consistently identified 1,400 to 2,000 protein groups from single cells with a dynamic range spanning five orders of magnitude. In comparison to conventional multiplexing methods, our hyperplexing strategy not only enhanced proteome depth but also achieved ultrahigh-throughput ([~] 2,000 single cells per day if use Orbitrap Astral Zoom or timsUltra AIP etc.). Overall, our label-free and quantitative hyperplexing workflows provide an efficient and scalable platform for large scale scProteomics studies and clinical applications.

cell biology↗

Connectome lateralization in autism across the first 14 years: heterogeneity related to developmental stage, hemisphere, and pathophysiology

Hemispheric lateralization is fundamental feature to neurodevelopment, yet its dynamic evolution in autism across childhood and underlying molecular mechanisms remain unknown. Thus, using a large-scale resting-state fMRI dataset (n = 1553, ages 1-14), we investigated developmental heterogeneity in connectome lateralization. At the group level, abnormalities in dynamic connectome lateralization strength (DCLS) progressed from focal patterns in early childhood ([≤] 6 years) to widespread distributions by late childhood ([≤] 14 years), independent of symptom severity. The late-stage patterns were validated using the ABIDE dataset (n=153). Late childhood also showed marked increases in inter-individual heterogeneity. These alterations were significantly associated with clinical phenotypes, transcriptomic profiles, and multiple neurotransmitter systems, with distinct patterns across childhood groups. Our findings reveal a developmentally dynamic trajectory of connectome lateralization in autism and highlight late childhood as a critical window for stage- and individual-specific interventions tailored to substantial individual heterogeneity.

neuroscience↗

PantheonOS: An Evolvable Multi-Agent Framework for Automatic Genomics Discovery

The convergence of large language model-powered autonomous agent systems and single-cell biology promises a paradigm shift in biomedical discovery. However, existing biological agent systems, building upon single-agent architectures, are narrowly specialized or overly general, limiting applications to routine analyses. We introduce PantheonOS (https://PantheonOS.stanford.edu), an evolvable, privacy-preserving multi-agent framework designed to reconcile generality with domain specificity. Critically, PantheonOS enables agentic code evolution, allowing evolving state-of-the-art batch correction and our reinforcement-learning augmented gene panel selection algorithms to achieve super-human performance. PantheonOS drives biological discoveries across systems: uncovering asymmetric paracrine Cer1-Nodal inhibition in proximal-distal axis formation of novel early mouse embryo 3D data; integrating human fetal heart multi-omics with whole-heart data to reveal molecular programs underpin heart diseases; and adaptively selecting virtual cell models to predict cardiac regulatory and perturbation effects. Together, PantheonOS points towards a future where scientific discoveries are increasingly driven by self-evolving AI systems across biology and beyond. Websitehttps://pantheonos.stanford.edu Ecosystemhttps://github.com/aristoteleo SummaryLarge language model-powered agent systems are driving a paradigm shift in scientific discovery by automating, scaling, and accelerating data analysis. This transformation is particularly profound in biology, where the rapid expansion of single-cell and spatial genomics has effectively reshaped the field into a data-intensive science. However, existing biological agent systems are typically constrained to single-agent designs, are narrowly specialized, or are overly general without sufficient domain expertise, limiting their applicability to routine or shallow analyses. Here, we introduce PantheonOS (https://pantheonos.stanford.edu), an evolvable, privacy-preserving, and general-purpose multi-agent framework designed to reconcile generality with deep domain specificity. PantheonOS provides an abstract, extensible architecture that enables customized agent composition and supports end-to-end single-cell and multi-omics analysis, spanning reinforcement-learning-augmented gene panel design, raw FASTQ processing, multimodal data integration, and three-dimensional spatial genomics reconstruction. Central to this framework, Pantheon-Evolve enables agentic code evolution, allowing the system to autonomously improve state-of-the-art batch-correction algorithms and new reinforcement-learning based gene panel design algorithms, achieving performance beyond manually designed baselines. We demonstrate the power of PantheonOS across multiple biological domains. In early mouse embryogenesis, PantheonOS automatically reconstructs three-dimensional spatial gene expression landscapes and resolves asymmetric Cer1 expression and paracrine Cer1-Nodal inhibition, revealing a robust proximal-distal axis at embryonic day six (E6.0). In human development, PantheonOS integrates fetal heart single-cell multi-omics with whole-heart 3D MERFISH+ data at post-conception week 12, uncovering spatially resolved molecular programs underlying heart disease ontogeny. Finally, an intelligent model-routing mechanism enables PantheonOS to adaptively select optimal virtual cell models across heterogeneous tasks, revealing minimal regulatory networks of cardiogenesis and predicting spatially resolved perturbation effects in the developing heart. Together, PantheonOS establishes a foundation for fully automated, evolvable, and domain-aware agentic analysis in genomics, and points toward a future in which scientific discovery is increasingly driven by self-improving AI systems across biology and beyond.

bioinformatics↗

Saline-free preparation for chronic in vivo imaging in adult Drosophila

Longitudinal brain imaging is essential for understanding neural mechanisms. Here, we present a saline-free, chronic preparation for repeated neural recording in adult Drosophila over multiple days. We describe steps for mounting flies, performing manual surgery on the head cuticle without external saline, and resealing the opening to create a transparent optical window. We demonstrate the utility of this approach by tracking single-neuron spiking and neuronal calcium dynamics over 7-10 days. This protocol is potentially applicable to other insect species. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/706199v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@abeb34org.highwire.dtl.DTLVardef@deaf93org.highwire.dtl.DTLVardef@1d8fc24org.highwire.dtl.DTLVardef@91a696_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

Subcellular proteomic profiling of human skeletal muscle reveals exercise-induced coordinated and compartment-specific protein remodeling

Exercise training induces extensive protein modifications in skeletal muscle, yet how acute exercise and training-induced molecular responses are spatially coordinated across muscle subcellular compartments remains unclear. Using subcellular fractionation combined with data-independent acquisition mass spectrometry, we profiled skeletal muscle mitochondrial, nuclear, and cytosolic proteomes in response to an acute bout of intense cycling (pre-, mid-, post- and 3 h post-exercise) and after eight weeks of endurance training in 40 healthy adults (20 males and 20 females). Acute exercise triggered coordinated, compartment-specific proteomic remodelling, including reductions in protein translation and import machinery concomitant with increased redox-related proteins. Notably, acute exercise increased markers of ribosomal translation within the mitochondrial fraction, revealing ribosomal scaffold protein RACK1 as a potential regulator of subcellular translational control under contractile stress (confirmed by targeted immunoblotting). The nuclear proteome displayed transient remodelling of RNA-processing and chromatin-associated proteins, while cytosolic changes were modest. Endurance training induced robust proteomic remodelling across all compartments, including increased markers of mitochondrial oxidative metabolism and proteostasis. While there were sex differences at baseline, subcellular proteomic responses were largely conserved between sexes. We provide the first comprehensive, time-course subcellular characterisation of the skeletal muscle proteome, revealing regulation of translational machinery underlying the acute exercise response.

physiology↗

A consensus spinal cord cell type atlas across mouse, macaque, and human

The spinal cord contains evolutionarily conserved cell types critical for motor function, sensory processing, and autonomic regulation, many of which are implicated in diverse neurological diseases and injuries. Yet the field lacks a comprehensive molecular characterization of cellular diversity in human, macaque, and mouse spinal cord. Here, we present a unified, cross-species cell type atlas based on the integration of single-nucleus gene expression, chromatin accessibility, and spatial transcriptomic data from segments within cervical, thoracic, lumbar, and sacral regions, including motor neurons (MNs) sampled across the entire rostro-caudal axis of the macaque spinal cord. Leveraging the spatial distributions of our molecularly defined cell types, we generated a cell type-guided anatomical map of spinal cord laminae and nuclei. We identified both conserved and species-specific cellular features, including gene expression patterns across distinct MN subtypes in the primate spinal cord. Cross-species cis-regulatory analysis and deep learning sequence models dissected the enhancer logic underlying viral targeting, uncovering conserved transcription factor grammar encoding cellular identity. Together, these results establish a unifying molecular and anatomical taxonomy of spinal cord cell types across species.

neuroscience↗

Enhancer-based AAV approach for selective AADC delivery reduces motor symptoms and dyskinesia in Parkinson's mouse models

Degeneration of midbrain dopamine (DA) neurons and the resulting loss of striatal dopamine signaling are hallmarks of Parkinsons disease (PD). Although the dopamine precursor levodopa (L-DOPA) provides symptomatic relief, prolonged treatment often leads to abnormal involuntary movements (dyskinesia). Previous adeno-associated virus (AAV) approaches delivering aromatic L-amino acid decarboxylase (AADC) to the striatum under a ubiquitous promoter enhanced local dopamine synthesis and improved PD motor deficits, but this broad targeting strategy limited insight into the cellular populations underlying the behavioral improvements. Here, we engineered enhancer-driven AAVs to direct AADC expression to defined striatal and midbrain cell populations and paired these regulatory elements with a blood-brain barrier-penetrant capsid to enable both systemic and direct delivery. Targeted expression restored motor performance at reduced L-DOPA doses and decreased dyskinesia-like behaviors, producing improvements comparable to or greater than those achieved with ubiquitous expression. Distinct neuronal and non-neuronal populations each supported motor rescue but improved different behavioral domains to different extents, indicating complementary cell type-specific roles within PD-relevant circuits. Together, these findings establish enhancer-driven, cell type-specific AADC delivery as a better-tolerated strategy that enables rescue of motor deficits at lower L-DOPA doses in PD models.

neuroscience↗

Structures of tRNA-bound CRISPR-Cas13 reveal universal HEPN RNase mechanisms

Ribonucleases (RNases) are ubiquitous drivers of RNA metabolism across life. Higher eukaryotes and prokaryotes nucleotide-binding (HEPN) domain-containing RNases form a nuclease superfamily whose mechanisms of substrate selection and catalysis remain poorly understood. Here, we report substrate preferences for diverse Cas13 HEPN RNases, revealing precise cleavage of tRNA anticodons and acceptor stems. Using cryo-EM, we present a series of activated Leptotrichia buccalis Cas13a (LbuCas13a) structures engaged with substrate tRNA. We show LbuCas13a captures tRNA through shape- and sequence-specific recognition, cleaving U-rich anticodons independently of tRNA modifications. Leveraging these insights, we reprogram Cas13 specificity and engineer variants with accelerated RNase activity. These findings establish the molecular basis for Cas13 tRNase activity and indicate that the HEPN RNase superfamily obeys universally conserved mechanisms of substrate recognition and catalysis.

biochemistry↗

Lifelong maintenance of locomotion by embryonically active dopamine neurons

Locomotor skills arise early in life and are maintained throughout an animals lifespan, yet how this continuity is achieved despite major neural remodeling remains unclear. Using Drosophila, which undergoes complete metamorphosis, we show that the activity of embryonically established dopamine neurons (DANs) is essential for locomotion across all developmental stages and adulthood. Through stage-specific behavioral assays, optogenetics, in vivo brain imaging, and fluorescent neuronal tracking, we identify a subset of ventral nervous system (VNS) DANs that modulate locomotor function throughout life. Transcriptomic analyses reveal that they maintain expression of developmental transcription factors. Knocking down these factors, particularly Antp and Pdm2, in post-mitotic VNS DANs reduces neurite arborization and impairs adult locomotion. These findings uncover a previously overlooked function for embryonic DANs and suggest that stable locomotion during nervous system maturation relies on persistent developmental regulator expression coupled with structural remodeling.

neuroscience↗

Atmospheric hydrogen consumption is regulated by catabolite repression in mycobacteria

Consumption of atmospheric hydrogen (H2) enables diverse aerobic microorganisms to grow and persist in resource-deprived environments. In the aerobic saprophyte Mycobacterium smegmatis, hydrogen oxidation is catalyzed by two differentially expressed, high-affinity, oxygen-insensitive uptake hydrogenases, Huc and Hhy. Huc enables mixotrophic growth and facilitates the transition from growth to dormancy. Although the huc operon is known to be upregulated in response to organic carbon deprivation, the specific signals and regulators modulating its expression remain unresolved. Here, we show that GylR, a glycerol-3-phosphate-sensing regulator of glycerol metabolism, plays a role in repression of huc expression in response to the availability of glycerol but not other carbon sources. Based on proteomic analyses and activity assays, mutation or knockdown of gylR leads to enhanced Huc production and activity. GylR and other key catabolite repressor proteins (Crp1, Crp2) do not directly bind the huc operon, indicating repression is mediated by unidentified transcription factors, with GylR acting as an upstream sensor. Here, we present data that suggests atmospheric H2 oxidation is regulated in response to organic carbon source availability through the process of catabolite repression. By identifying a key signal that prompts atmospheric H2 oxidation, these findings advance understanding of how aerobic bacteria adapt to changing environmental conditions and suggest that organic carbon levels are a key factor regulating the main sink of atmospheric H2 in soils globally. ImportanceSoil microorganisms collectively consume 70 million tonnes of atmospheric H2 a year, regulating atmospheric composition and climate change. In turn, consuming this dependable trace gas enables these microorganisms to survive even when their preferred organic energy sources are exhausted. Despite the importance of H2 consumption for soil biodiversity and atmospheric regulation, the signals and sensors that regulate this process remain to be understood. Here, we demonstrate that a model soil bacterium turns on the machinery required for atmospheric H2 consumption in direct response to being limited by organic carbon availability, through the process of catabolite repression. Specifically, in the absence of a sensor of the organic carbon source glycerol, a H2-consuming hydrogenase is highly expressed and active. These findings suggest that organic carbon levels have a major role in regulating trace gas oxidation, with implications for predicting how trace gas consumption and soil biodiversity respond to environmental change.

microbiology↗

In extracto cryo-EM reveals eEF2 as a major hibernation factor on 60S and 80S particles

Cryogenic electron microscopy (cryo-EM) made impressive progress in resolving cellular macromolecules and their detailed interactions. Single-particle cryo-EM traditionally relies on purified macromolecules and lacks the complexity of cellular environments, whereas in situ cryo-EM or cryo-ET require extensive sample preparation and data acquisition, presenting challenges in achieving high resolution. We describe cryo-EM of cellular lysates--in extracto cryo-EM--allowing the flexibility and high-resolution of cryo-EM in the context of cellular components. High-resolution 2D template matching (2DTM) yields [~]2.2 [A] maps of the mammalian translational apparatus. Elongating ribosome abundances in primate cell lines (MCF-7 and BSC-1) and rabbit reticulocyte lysates range from [~]70% to [~]10%, reflecting translational stress responses. Non-translating (hibernating) ribosomes carrying no mRNA, feature numerous proteins shielding ribosomal functional centers. Elongation factor 2 (eEF2) is the most abundant hibernation factor bound to >95% of ribosomes and, unexpectedly, to 60S subunits. eEF2*GDP is stabilized by interactions with the sarcin-ricin loop and protein uL14. Hibernating ribosomes also feature LARP1 involved in initiation and mTOR signaling; eIF5A implicated in elongation and termination; and other factors, exposing the variety of hibernation scenarios. Our work underscores the efficiency and potential of in extracto cryo-EM to discover native cellular complexes and mechanisms at near-atomic resolution.

molecular biology↗