Explore the vast range of titles available.

Biogenesis of viral replication organelles (VROs) is critical for replication of positive-strand RNA viruses. In this work, we demonstrate that tomato bushy stunt virus (TBSV) and the closely related carnation Italian ringspot virus (CIRV) hijack the retromer to facilitate building VROs in the surrogate host yeast and in plants. Depletion of retromer proteins, which are needed for biogenesis of endosomal tubular transport carriers, strongly inhibits the peroxisome-associated TBSV and the mitochondria-associated CIRV replication in yeast and in planta. In vitro reconstitution revealed the need for the retromer for the full activity of the viral replicase. The viral p33 replication protein interacts with the retromer complex, including Vps26, Vps29, and Vps35. We demonstrate that TBSV p33-driven retargeting of the retromer into VROs results in delivery of critical retromer cargoes, such as 1) Psd2 phosphatidylserine decarboxylase, 2) Vps34 phosphatidylinositol 3-kinase (PI3K), and 3) phosphatidylinositol 4-kinase (PI4Kα-like). The recruitment of these cellular enzymes by the co-opted retromer is critical for de novo production and enrichment of phosphatidylethanolamine phospholipid, phosphatidylinositol-3-phosphate [PI(3)P], and phosphatidylinositol-4-phosphate [PI(4)P] phosphoinositides within the VROs. Co-opting cellular enzymes required for lipid biosynthesis and lipid modifications suggest that tombusviruses could create an optimized lipid/membrane microenvironment for efficient VRO assembly and protection of the viral RNAs during virus replication. We propose that compartmentalization of these lipid enzymes within VROs helps tombusviruses replicate in an efficient milieu. In summary, tombusviruses target a major crossroad in the secretory and recycling pathways via coopting the retromer complex and the tubular endosomal network to build VROs in infected cells.

Viroplasms are cytoplasmic, membraneless structures assembled in rotavirus (RV)-infected cells, which are intricately involved in viral replication. Two virus-encoded, non-structural proteins, NSP2 and NSP5, are the main drivers of viroplasm formation. The structures (as far as is known) and functions of these proteins are described. Recent studies using plasmid-only-based reverse genetics have significantly contributed to elucidation of the crucial roles of these proteins in RV replication. Thus, it has been recognized that viroplasms resemble liquid-like protein–RNA condensates that may be formed via liquid–liquid phase separation (LLPS) of NSP2 and NSP5 at the early stages of infection. Interactions between the RNA chaperone NSP2 and the multivalent, intrinsically disordered protein NSP5 result in their condensation (protein droplet formation), which plays a central role in viroplasm assembly. These droplets may provide a unique molecular environment for the establishment of inter-molecular contacts between the RV (+)ssRNA transcripts, followed by their assortment and equimolar packaging. Future efforts to improve our understanding of RV replication and genome assortment in viroplasms should focus on their complex molecular composition, which changes dynamically throughout the RV replication cycle, to support distinct stages of virion assembly.

Many studies on SARS-CoV-2 have been performed over short-time scale, but few have focused on the ultrastructural characteristics of infected cells. We used TEM to perform kinetic analysis of the ultrastructure of SARS-CoV-2-infected cells. Early infection events were characterized by the presence of clusters of single-membrane vesicles and stacks of membrane containing nuclear pores called annulate lamellae (AL). A large network of host cell-derived organelles transformed into virus factories was subsequently observed in the cells. As previously described for other RNA viruses, these replication factories consisted of double-membrane vesicles (DMVs) located close to the nucleus. Viruses released at the cell surface by exocytosis harbored the typical crown of spike proteins, but viral particles without spikes were also observed in intracellular compartments, possibly reflecting incorrect assembly or a cell degradation process.

Human adenoviruses serve as models for studying respiratory viruses and have provided critical insights into viral genome replication and gene expression, as well as the control of virus-host interactions. These processes are coordinated within virus-induced subnuclear microenvironments known as RCs. We conducted quantitative proteome analyses of RC-enriched subnuclear fractions at different times post-infection with human adenovirus species C type 5, revealing a multifaceted network of proteins that participate in the regulation of gene expression, DNA damage response, RNA metabolism, innate immunity, and other cellular antiviral defense mechanisms. Furthermore, we validated the localization of several host proteins to viral RCs using immunofluorescence microscopy and immunoblotting and identified cellular HMGB1 as a proviral factor late during infection. These findings represent the first analysis of the proteomes of isolated RCs and not only enhance our understanding of nuclear organization during infection but also shed light on the complex interplay between viral and host factors within RCs.

The dengue virus (DENV) causes the most prevalent arthropod-borne viral disease worldwide. While its incidence is increasing in many countries, there is no approved antiviral therapy currently available. In infected cells, the DENV induces extensive morphological alterations of the endoplasmic reticulum (ER) to generate viral replication organelles (vRO), which include convoluted membranes (CM) and vesicle packets (VP) hosting viral RNA replication. The viral non-structural protein NS4B localizes to vROs and is absolutely required for viral replication through poorly defined mechanisms, which might involve cellular protein partners. Previous interactomic studies identified the ATPase valosin-containing protein (VCP) as a DENV NS4B-interacting host factor in infected cells. Using both pharmacological and dominant-negative inhibition approaches, we show, in this study, that VCP ATPase activity is required for efficient DENV replication. VCP associates with NS4B when expressed in the absence of other viral proteins while in infected cells, both proteins colocalize within large DENV-induced cytoplasmic structures previously demonstrated to be CMs. Consistently, VCP inhibition dramatically reduces the abundance of DENV CMs in infected cells. Most importantly, using a recently reported replication-independent plasmid-based vRO induction system, we show that de novo VP biogenesis is dependent on VCP ATPase activity. Overall, our data demonstrate that VCP ATPase activity is required for vRO morphogenesis and/or stability. Considering that VCP was shown to be required for the replication of other flaviviruses, our results argue that VCP is a pan-flaviviral host dependency factor. Given that new generation VCP-targeting drugs are currently evaluated in clinical trials for cancer treatment, VCP may constitute an attractive broad-spectrum antiviral target in drug repurposing approaches.

C-C motif ligand 2 (CCL2) plays a regulatory role in the budding and release of HIV-1 in macrophages and HeLa cells. CCL2 signaling mobilizes ALG-2-interacting protein X (ALIX) from the F-actin cytoskeleton to the soluble cytosol, where it is accessible for recruitment by the HIV-1 Gag polyprotein in the assembling virions at the plasma membrane. In previous studies, CCL2 immunodepletion, which blocks CCL2 signaling, resulted in ALIX sequestration to the F-actin cytoskeleton and inhibited virus production. Here, we developed a HeLa CCL2 gene knockout cell line and found that abrogation of CCL2 signaling can be restored by CCL2 addition, as evidenced by the restoration of ALIX to the cytosolic fraction and rescue of HIV-1 release. Employing such a system, we tested Simian Immunodeficiency Virus, Equine Infectious Anemia Virus, Herpes Simplex Virus type 1, Dengue, and Hazara virus for their dependence on ALIX for virus replication. The results indicate that CCL2 signaling and ALIX release from F-actin may play a role in the replication of several viruses.

Mitochondria are good targets for viruses to manipulate their hosts. However, it remains obscure whether respiratory syncytial virus (RSV) target mitochondria to suppress the type I interferon (IFN) responses. Here, we show that nonstructural protein 1 (NS1) protein of RSV interacts with Tu translation elongation factor mitochondrial (TUFM), which can lead to its localization in mitochondria and finally induce TUFM-dependent mitophagy and inhibition of IFNβ. Mechanically, NS1-mediated TUFM-dependent mitophagy does not depend on the PINK1-PARKIN pathway and classic mitophagy receptors. Importantly, NS1 may act as a new receptor protein to bridge mitochondria and autophagosomes by interacting with TUFM and LC3B. The LIR motif of NS1 protein is essential for its interaction with LC3B and is of great importance for its mitophagy induction and IFNβ suppression. Finally, NS1-induced TUFM-dependent mitophagy was essential for its attenuated IFNβ response using autophagy-deficient cells and mice. Our study provides a novel mitophagy receptor molecular and a new antiviral option by suppressing antiviral innate immune via targeting TUFM-dependent mitophagy. It is a worthy concern for us to understand virus-host interactions which affect progression and prognosis of disease. We demonstrated that the non-structural protein 1 of respiratory syncytial virus (RSV NS1) may act as a novel mitophagy receptor to induce mitophagy by binding LC3B and mitochondrial protein TUFM, and finally dampen interferon (IFN) responses induced by RIG1 and RSV infection. TUFM is beneficial for RSV replication in vivo and vitro . It is new and interesting that RSV NS1 may function as a mitophagy receptor to interact with LC3B. The LIR motif of NS1 protein is essential for its interaction with LC3B. We further confirm that RSV NS1 inhibited IFNβ response and promoted RSV replication in autophagy-dependent mechanisms in vivo and vitro . Our study contributes to understanding virus-host interaction, enriching our insights into RSV pathogenic mechanism and exploiting new antiviral treatments targeting TUFM.

Zika virus (ZIKV) infection causes significant human disease that, with no approved treatment or vaccine, constitutes a major public health concern. Its life cycle entirely relies on the cytoplasmic fate of the viral RNA genome (vRNA) through a fine-tuned equilibrium between vRNA translation, replication, and packaging into new virions, all within virus-induced replication organelles (vROs). In this study, with an RNA interference (RNAi) mini-screening and subsequent functional characterization, we have identified insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) as a new host dependency factor that regulates vRNA synthesis. In infected cells, IGF2BP2 associates with viral NS5 polymerase and redistributes to the perinuclear viral replication compartment. Combined fluorescence in situ hybridization-based confocal imaging, in vitro binding assays, and immunoprecipitation coupled to RT-qPCR showed that IGF2BP2 directly interacts with ZIKV vRNA 3’ nontranslated region. Using ZIKV sub-genomic replicons and a replication-independent vRO induction system, we demonstrated that IGF2BP2 knockdown impairs de novo vRO biogenesis and, consistently, vRNA synthesis. Finally, the analysis of immunopurified IGF2BP2 complex using quantitative mass spectrometry and RT-qPCR revealed that ZIKV infection alters the protein and RNA interactomes of IGF2BP2. Altogether, our data support that ZIKV hijacks and remodels the IGF2BP2 ribonucleoprotein complex to regulate vRO biogenesis and vRNA neosynthesis.

Tobamoviruses establish viral replication organelles (VROs) on the host endoplasmic reticulum (ER) for their replication, a process demanding substantial different types of lipids. However, how viruses efficiently transfer these lipids from other compartments like chloroplasts remains incompletely understood. Fibrillin (FBN) proteins are primarily localised to chloroplasts and are intimately linked with lipid metabolism and stress responses in chloroplasts. Here, we report that NbLIP1, a light‐induced FBN1 family protein in Nicotiana benthamiana, directly interacts with the coat protein (CP) of rehmannia mosaic virus (ReMV) and other related tobamoviruses (TMV, YoMV). Upon viral infection, this interaction leads to the relocalisation of NbLIP1 from chloroplasts to ER‐proximal viral replication sites. Functional assays demonstrated that overexpression of NbLIP1 significantly enhanced viral replication, viral protein accumulation, and VRO formation, while silencing NbLIP1 had the opposite effects. These findings unveil a novel viral infection mechanism whereby the viral CP hijacks the host lipid transfer protein NbLIP1 and recruits it to viral replication factories to promote viral replication, potentially by modulating lipid supply or the microenvironment remodelling at the replication sites. This study not only elucidates the role of NbLIP1 as a novel pro‐viral host factor but also provides new insights into how viruses exploit host resources across cellular compartments, suggesting NbLIP1 as a potential antiviral target.

The replication of rotavirus takes place in cytosolic inclusions termed viroplasms. In these inclusions, the distinct 11 double-stranded RNA genome segments are co-packaged to complete a genome in newly generated virus particles. In this study, we show for the first time that the tailless complex polypeptide I ring complex (TRiC), a cellular chaperonin responsible for the folding of at least 10% of the cytosolic proteins, is a component of viroplasms and is required for the synthesis of the viral negative-sense single-stranded RNA. Specifically, TRiC associates with NSP5 and VP2, the cofactor involved in RNA replication. Our study adds a new component to the current model of rotavirus replication, where TRiC is recruited to viroplasms to assist replication.