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12 recordsLinked to original sources

PubMed2027

Epitope Tagging and Coimmunoprecipitation to Identify Viral Protein Interactors.

Affinity purification-mass spectrometry (AP-MS) is a powerful proteomic approach for dissecting the interaction network between virus and host. Traditional AP-MS employs overexpression of viral proteins as baits to enrich host interactors. However, overexpressed viral proteins may mislocalize to inappropriate cellular compartments and trigger endoplasmic reticulum stress by overwhelming the protein-folding machinery, which leads to false identification of host factors. To overcome these limitations, we introduce an AP-MS strategy based on direct infection with an epitope-tagged chikungunya virus (CHIKV/myc-E2), which we used to successfully uncover two new antiviral factors in CHIKV cellular reservoirs-macrophages. In this protocol, we will describe this technique step by step: (1) design and construction of myc-tagged virus by advanced multi-fragment assembly, (2) in vitro transcription and preparation of infectious myc-tagged virus stocks, and (3) immunoprecipitation of myc-tagged viral protein and its interactome for mass spectrometry analysis. This strategy enables accurate identification of viral interactors in a physiologically relevant context, providing a framework for future proteomic studies using tagged viruses.

Chikungunya virus↗

PubMed2026

Selective Enrichment of Newly Synthesized Proteins Using Phos-Tag Click Tip Enables Nascent Proteome Analysis in Influenza A Virus Infection.

Profiling of newly synthesized proteins (NSPs) provides access to dynamic changes in protein production that accompany acute cellular responses. Bioorthogonal noncanonical amino acid tagging (BONCAT)-based approaches enable selective labeling of NSPs; however, their broader application remains constrained by labor-intensive enrichment workflows and limited sensitivity for direct peptide-level analysis. Here, we developed a workflow termed "Phos-tag Click Tip" by integrating a phosphorylated variant of bicyclononyne (pBCN) with Phos-tag affinity purification to selectively capture azidohomoalanine (AHA)-labeled peptides for newly synthesized proteome analysis (NSProteomics). This approach overcomes key limitations of conventional proteomics and BONCAT-based strategies by enabling efficient enrichment and sensitive detection of NSP-derived peptides. Using this workflow, we performed comprehensive NSP profiling of host cells during influenza A virus infection. We identified dynamic changes in distinct NSP profiles associated with viral replication, host restriction, and immune responses, many of which were not readily detected with conventional whole-cell- or phospho-proteomic analyses. Overall, the Phos-tag Click Tip workflow provides a complementary approach for stimulus-responsive NSP profiling, offering functionally relevant insights into host-virus interactions and cellular response mechanisms.

Proteome↗

PubMed2026

Viral tags as keys to advancing invasion genomics.

Invasion genetics and genomics have greatly advanced the study of biological invasions, yet they often fail to resolve population dynamics at the fine spatiotemporal scales characteristic of most invasions. We propose shifting the focus away from the higher-order target species towards their viral symbionts, harnessing these as high-resolution 'genetic tags' to overcome many of these limitations. Owing to their comparably smaller genomes, shorter generation times, and higher mutation rates, most viruses evolve on timescales comparable to the invasion dynamics of their higher-order hosts, potentially better proxying and revealing recent dispersal patterns. We present a conceptual framework outlining how virus evolution may shed light on the contemporary spread of their non-native hosts, opening new avenues for invasion genetics, genomics, and management.

Genomics↗

PubMed2025

Establishment of reverse genetics systems for Colorado tick fever virus.

The Colorado tick fever virus (CTFV), which has 12-segmented double-stranded RNA genomes, is a pathogenic arbovirus that causes severe diseases in humans. However, little progress has been made in the analysis of replication mechanisms and pathogenicity. This virological constraint is due to the absence of a reverse genetics system for CTFV; therefore, we aimed to establish the system. Initially, the efficacy of CTFV replication was investigated in various cell lines. CTFV was found to grow in many cell types derived from different hosts and organs. Subsequently, BHK-T7 cells stably expressing T7 RNA polymerase were transfected with plasmids encoding each of the 12 CTFV gene segments, expression plasmids encoding all CTFV proteins, and a vaccinia virus RNA-capping enzyme. Following transfection, the cells were co-cultured with Vero or HeLa cells. Using this system, we rescued monoreassortants and recombinant viruses harboring peptide-tagged viral proteins. Furthermore, an improved system using Expi293F cells expressing T7 RNA polymerase was established, which enabled the generation of recombinant reporter CTFVs. In conclusion, these reverse genetics systems for CTFV will greatly contribute to the understanding of viral replication mechanisms, pathogenesis, and transmission, ultimately facilitating the development of rational treatments and candidate vaccines.

Animals↗

PubMed2025

Proximity Proteomics to Profile Ebola Virus Protein Interactome in Its Functional Context.

Proximity labeling-based proteomics (proximity proteomics) has emerged as a popular and versatile approach to illuminate the molecular interactions between viruses and their hosts. In this approach, a proximity labeling enzyme tag is fused to a bait protein and labels neighboring proteins with a chemical handle such as biotin, allowing for downstream affinity purification. Compared to another widely used technique, affinity purification coupled mass spectrometry, proximity proteomics enables the detection of low affinity or transient interactors that might have important functions in the viral life cycle. Further, proximity proteomics can identify interactors of a labile bait protein, of which affinity purification is technically challenging. Here, we describe a proximity proteomic protocol to identify cellular interactors of the Ebola virus polymerase. A similar strategy is readily applicable to elucidate the virus-host interactions for Marburg virus.

Ebolavirus↗

PubMed2025

Development of a replication competent murine norovirus reporter system.

Caliciviruses are significant agricultural and human pathogens that are poorly understood due to the dearth of molecular tools, including reporter systems. We report the development of a robust luciferase-based reporter system for a model calicivirus, murine norovirus (MNoV). Genetic insertion of a HiBiT tag, an 11 amino acid fragment of nanolucifersase, at the junction of the nonstructural proteins NS4 and NS5 yields infectious virus. The resultant MNoV-HiBiT produces a robust signal that is detected early in infection and occurs only in cells susceptible to MNoV infection. The MNoV-HiBiT reporter is effective at monitoring acute infection in STAT1 deficient mice. Furthermore, we used this tool to characterize two unappreciated host directed anti-MNoV compounds. The use of the MNoV-HiBiT virus enables new mechanistic studies by a rapid and quantitative means of measuring MNoV replication. The HiBiT insertion strategy we describe may be useful for the generation of other calicivirus reporters.

Animals↗

PubMed2026

CgMYC2 directly activates jasmonate-induced naringin biosynthesis in Citrus grandis 'Tomentosa'.

CgMYC2 links jasmonate signaling to naringin biosynthesis by binding G-box motifs and activating flavonoid-pathway promoters in Citrus grandis 'Tomentosa' Naringin, the predominant bitter-flavanone glycoside in Citrus grandis 'Tomentosa', has well-characterized biosynthetic enzymes, yet the transcriptional regulators coupling hormonal signals to pathway activation remain poorly understood. We demonstrate that CgMYC2, a jasmonate-responsive bHLH transcription factor, functions as a central activator of naringin biosynthesis. Exogenous methyl jasmonate (MeJA) treatment increased naringin content 3.45-fold in seedlings, coinciding with a rapid 6.6-fold induction of CgMYC2 that preceded the peak transcription of five core biosynthetic genes (CgPAL5, CgCHS, CgFNS, Cg7GlcT, and Cg1,2RhaT). Physical interaction between CgMYC2 and the JAZ protein CgJAZ3 was confirmed by pull-down and Co-IP assays, placing CgMYC2 within the canonical jasmonate signaling cascade. Y1H confirmed CgMYC2 binding to the Cg1,2RhaT promoter, EMSA demonstrated direct G-box-dependent binding to all five pathway promoters, and dual-luciferase assays showed transactivation of all five promoters, with the strongest activation for CgCHS. As complementary chromatin-level support, a single-sample CUT&Tag profile revealed G-box-enriched CgMYC2-associated chromatin regions across jasmonate-responsive and secondary-metabolic loci. Virus-induced gene silencing (VIGS) of CgMYC2 reduced naringin content by ~21% and suppressed biosynthetic gene expression, supporting its positive contribution. Furthermore, heterologous overexpression in tomato activated the flavonoid pathway and elevated 16 flavonoid compounds, consistent with evolutionary conservation of the MYC2-G-box regulatory logic. These findings establish CgMYC2 as a central, JA-responsive activator bridging jasmonate perception and naringin biosynthesis, providing a molecular framework for the targeted improvement of bitter-flavonoid traits in citrus.

Citrus↗

PubMed2026

Monitoring kinetic changes and restriction of influenza A virus RNA species during infection using a Flu-Stranded CRISPR platform.

UNLABELLED: Influenza A virus (IAV) generates three closely related RNA species: viral RNA (vRNA), complementary RNA (cRNA), and messenger RNA (mRNA), whose strand-specific quantification remains limited by sensitivity and quantitative dynamic range, particularly at low RNA abundance. Here, we developed Flu-Stranded CRISPR-Cas12a, a strand-specific detection platform integrating tagged reverse transcription, segment-specific PCR, and Cas12a collateral cleavage to support quantitative analysis of all three RNA species across a broad dynamic range. The assay enables reliable detection down to 102 copies per reaction, extending the lower quantitative boundary relative to both SYBR Green and TaqMan reverse transcription quantitative PCR (RT-qPCR) under matched conditions. Validated in infected cell lines, murine lung tissues, and clinical nasopharyngeal specimens, the platform enabled subtype-discriminating, strand-resolved detection, including samples near or below the quantitative range of SYBR Green RT-qPCR. Using finely resolved infection time-course analyses in NP and NA segments, we identified a reproducible early vRNA decline within the early post-infection phase. This decline was partially attenuated in RIG-I knockout A549 cells, while subsequent vRNA accumulation was enhanced, consistent with a modulatory rather than essential role for RIG-I in early viral RNA dynamics. Subcellular fractionation localized this decline to cytoplasmic incoming genomes. In contrast, importazole-mediated inhibition of nuclear import abolished vRNA recovery without affecting the early decline, indicating that nuclear entry functionally separates early genome reduction from subsequent productive replication. These findings establish Flu-Stranded CRISPR-Cas12a as a strand-resolved framework for monitoring IAV RNA dynamics and reveal an early window of genome vulnerability during cytoplasmic transit that shapes infection outcome. IMPORTANCE: The early fate of incoming influenza virus genomes remains unclear, limiting our understanding of how infection is established or aborted in host cells. We developed Flu-Stranded CRISPR-Cas12a, a strand-specific platform for sensitive and quantitative analysis of influenza viral RNA (vRNA), complementary RNA (cRNA), and messenger RNA (mRNA) across experimental and clinical samples. Using high-resolution time-course analysis, we identified a reproducible early decline in vRNA during the post-entry phase. Our data suggest that this early genome loss arises from multiple processes, with RIG-I acting as a modulatory factor rather than a primary driver. Subcellular fractionation localized this effect to cytoplasmic incoming genomes, whereas importin-β-mediated nuclear entry was required for subsequent vRNA recovery. These findings support a model of an early cytoplasmic phase of genome attrition that is distinct from replication and provide a framework for understanding early influenza RNA kinetics and for guiding strand-resolved diagnostics and antiviral evaluation.

CRISPR-Cas12a↗

PubMed2026

Development of a cell-based nanoluciferase reporter system for high-throughput screening of HBV cccDNA inhibitors.

Hepatitis B virus (HBV) persistence is sustained by the viral covalently closed circular DNA (cccDNA) minichromosome, which remains a major barrier to curative antiviral therapies. The lack of reliable quantitative cccDNA detection methods and surrogate markers has hindered efforts to target cccDNA in antiviral high-throughput screening (HTS). Here, we established a novel inducible cccDNA-dependent nanoluciferase (NLuc) reporter cell line, designated HepBLE12, by inserting an in-frame 11-amino acid split-NLuc HiBiT tag into the precore (pC) coding region of an HBV transgene. The resulting 1.3-kDa HiBiT tag on pC serves as the detection module of the split NLuc system, generating quantitative luminescence upon high-affinity complementation with the cognate 18-kDa LgBiT subunit in cell lysates. Notably, the HiBiT assay enables direct detection of intracellular HiBiT-pC protein rather than secreted HBeAg, providing a reporter signal more closely linked to cccDNA activity. HepBLE12 cells exhibited inducible and robust viral DNA replication, and the cccDNA-dependent HiBiT signal was validated under diverse experimental conditions that modulate cccDNA formation or transcription. We further miniaturized the assay to a 384-well format and optimized key parameters following standard HTS assay development practices. The assay was successfully automated and demonstrated excellent performance in a multi-day variability study and a pilot screen, with signal-to-background (S/B) ≈ 9, coefficient of variance (CV) < 10%, and average Z-factor value of 0.74, exceeding canonical HTS quality benchmarks. Together, the HepBLE12 cell-based HTS platform provides a robust and practical tool for identifying inhibitors targeting HBV cccDNA.

Hepatitis B virus↗

PubMed2026

Triacylglycerol metabolism is a novel target to combat West Nile virus infection.

West Nile virus (WNV) is a zoonotic Orthoflavivirus transmitted by mosquitoes that is responsible for outbreaks of meningitis and encephalitis worldwide. Driven by climate change, WNV has expanded as a global public health concern, particularly in temperate regions. However, there are still no specific approved therapies, reinforcing the need for antiviral development. Previous works have documented that WNV multiplication strictly depends on certain cellular lipids. To identify novel lipid-related therapeutic targets, we analyzed the infection driven alterations in the CNS lipidome, the primary tissue supporting WNV replication. Our results indicated that the major alterations in the brain lipid content of WNV-infected mice corresponded to triacylglycerols (TAGs). Moreover, transcriptomic analysis showed that infected brains underwent changes in the expression of TAG metabolism. Supplementation with exogenous fatty acids increased lipid droplets (LD) content and promoted viral replication in cell culture models. On the contrary, pharmacological intervention in TAG metabolism using diacylglycerol acyltransferase inhibitors (DGATi) suppressed WNV multiplication in cell culture models. As a proof-of-concept of the therapeutic potential of DGATi, treatment of mice with A922500 reduced viral burden in the brain and proinflammatory cytokine production. Overall, our results unveil the importance of LDs and glycerolipid metabolism for WNV and highlight the potential of therapeutic interventions targeting this pathway to control viral replication and neuroinflammation.

West Nile virus; lipid↗

PubMed2026

Direct interaction between RSV polymerase L and active Rab11a mediates viral ribonucleoprotein transport to assembly sites.

Respiratory syncytial virus (RSV) is an enveloped, negative-sense, single-stranded RNA virus whose ribonucleoproteins (vRNPs) must be transported from cytoplasmic viral factories to the plasma membrane for efficient virion assembly. Viral vRNPs comprise genomic RNA encapsidated by nucleoprotein N and associated with the polymerase complex (L, P, and M2-1). It was previously demonstrated that newly synthesized vRNPs are transported along microtubules by hijacking Rab11a, a small GTPase involved in the regulation of recycling endosomes. In our previous study, we showed an interaction between Rab11a and vRNPs in infected cells by immunoprecipitation assays, nevertheless the molecular mechanisms underlying Rab11a viral hijacking remained unknown. Here, we provide the first comprehensive characterization of the interaction between RSV vRNPs and Rab11a using immunoprecipitation, immunofluorescence colocalization, GST pull-down assays, and biolayer interferometry. We demonstrate that the viral polymerase L is the sole vRNPs component responsible for Rab11a recognition: immunoprecipitation of L specifically co-precipitates HA-tagged Rab11a, whereas other vRNPs proteins show no interaction. In vitro binding studies confirm that L interacts directly and specifically with the active, GTP-bound form of Rab11a with sub-micromolar affinity. Domain mapping using truncated constructs reveals that this interaction requires the C-terminal methyltransferase and CTD domains of L (residues 1756-2165) and depends on Rab11a's Switch I region, known to mediate interactions with cellular Rab11a partners. Mutagenesis further highlights leucine 1860 in the L polymerase as critical for Rab11a binding. Competitive inhibition of the interaction between Rab11a and L using the minimal Rab11a-binding domain significantly impairs vRNP dynamics during infection, indicating that Rab11a-L binding is involved in the transport of vRNPs. Together, these findings establish RSV polymerase L as the key mediator of Rab11a engagement, define the molecular interface of their interaction, and reveal a potentially conserved viral strategy for genome transport. Targeting the L-Rab11a interaction could therefore be a promising strategy for the development of RSV-specific or broad-spectrum antiviral therapies.

rab GTP-Binding Proteins↗

PubMed2025

Pooled PPIseq: Screening the SARS-CoV-2 and human interface with a scalable multiplexed protein-protein interaction assay platform.

Protein-Protein Interactions (PPIs) are a key interface between virus and host, and these interactions are important to both viral reprogramming of the host and to host restriction of viral infection. In particular, viral-host PPI networks can be used to further our understanding of the molecular mechanisms of tissue specificity, host range, and virulence. At higher scales, viral-host PPI screening could also be used to screen for small-molecule antivirals that interfere with essential viral-host interactions, or to explore how the PPI networks between interacting viral and host genomes co-evolve. Current high-throughput PPI assays have screened entire viral-host PPI networks. However, these studies are time consuming, often require specialized equipment, and are difficult to further scale. Here, we develop methods that make larger-scale viral-host PPI screening more accessible. This approach combines the mDHFR split-tag reporter with the iSeq2 interaction-barcoding system to permit massively-multiplexed PPI quantification by simple pooled engineering of barcoded constructs, integration of these constructs into budding yeast, and fitness measurements by pooled cell competitions and barcode-sequencing. We applied this method to screen for PPIs between SARS-CoV-2 proteins and human proteins, screening in triplicate >180,000 ORF-ORF combinations represented by >1,000,000 barcoded lineages. Our results complement previous screens by identifying 74 putative PPIs, including interactions between ORF7A with the taste receptors TAS2R41 and TAS2R7, and between NSP4 with the transmembrane KDELR2 and KDELR3. We show that this PPI screening method is highly scalable, enabling larger studies aimed at generating a broad understanding of how viral effector proteins converge on cellular targets to effect replication.

Humans↗