Biology subjects

Tafforeau, L.

Publications and source records attributed to Tafforeau, L..

4 recordsLinked to original sources

bioRxiv2025

The cellular Activating Protein 1 cFos regulates Influenza A virus replication

Previous research has demonstrated that Influenza A virus (IAV) infection activates AP-1 transcription factors as part of the antiviral response. In this study, we identified cFos as the most upregulated AP-1 transcription factor during IAV infection in A549 human lung cells. Surprisingly, the knockdown of cFos resulted in impaired IAV replication. Fluorescence microscopy and functional analyses indicated that cFos is implicated in IAV infection through its nuclear function, rather than its cytoplasmic role as an activator of lipid synthesis. The investigation into the role of cFos in IAV infection revealed increased apoptosis and elevated interferon-{beta} mRNA levels in cFos-knockdown A549 cells during IAV infection. This suggests that cFos may enhance cell survival and reduce interferon-{beta} expression during infection, thereby facilitating IAV proliferation. Furthermore, the levels of viral NA mRNA and the expression of late viral proteins NA and M2 decreased upon cFos knockdown. Overall, this study identifies cFos as a proviral factor for IAV, through the modulation of innate immunity and apoptosis during infection, and potentially by supporting the viral transcription. Author SummaryInfluenza A viruses pose a significant threat to global public health. Understanding the interaction between the virus and host is essential for the development of antiviral therapies. We identified cFos, a cellular Activating Protein-1, as a pro-viral factor for influenza A viruses. cFos was found to enhance cell survival and regulate the expression of certain cytokines during viral infection. Our findings also suggested a potential role for cFos in the viral transcription, especially of the viral proteins expressed late in the viral cycle.

microbiology↗

bioRxiv2023

Identification and characterization of interactions between Influenza A Virus NS1 protein and the human ubiquitin proteasome system

As a key player involved in various cellular pathways, including innate immune response activation, the human ubiquitin-proteasome system (UPS) is particularly targeted by viral proteins upon infection. Indeed, most viruses have evolved to counteract and hijack this system, as it is the case for the influenza A virus (IAV). The non-structural protein 1 (NS1) is described as the main IAV virulence factor, which is known to interact with several cellular proteins, including some UPS factors that are important for the viral escape of the immune cell response. In this study, we profiled the overall interplay between the NS1 proteins of multiple IAV strains and the human UPS. We identified 98 UPS factors directly interacting with NS1 of all or a subset of the studied strains, and we functionally studied 18 of them. We highlighted the involvement of these UPS factors in the IAV life cycle by performing viral titrations, minigenome replicon assays and an ISRE-luc (IFN pathway) assays. Furthermore, we analyzed the expression and subcellular localizations of FZR1, MKRN3, RC3H2 and SHKBP1 upon IAV infection. This interactomics approach allows for an improved understanding of the interplay between NS1 and UPS pathway in the context of an IAV-mediated inhibition of cellular anti-viral responses. ImportanceInfluenza A viruses (IAV) are pathogens responsible for annual flu epidemics causing up to 650,000 deaths each year, resulting in a significant impact in public health and global economy. IAV are also responsible of occasionally pandemic outbreaks in human population, such as in 1918 that caused the death of 50-100 million people. Non-structural protein 1 (NS1) is the main IAV virulence factor; it acts by direct interactions with several cellular proteins, leading to the host shut-off and to the inhibition of the host cell innate immune response. Since the ubiquitin-proteasome system (UPS) plays a crucial role in the innate immune response activation, it is a designated target for NS1 upon infection. Our research thus focused on the identification of interactions between NS1 of 6 different IAV strains and the UPS, to better understand the interplay between this viral protein and the UPS upon viral infection.

molecular biology↗

bioRxiv2021

Systematic mapping of rRNA 2'-O methylation during frog development and involvement of the methyltransferase Fibrillarin in eye and craniofacial development in Xenopus laevis

Ribosomes are essential nanomachines responsible for protein production. Although ribosomes are present in every living cell, ribosome biogenesis dysfunction diseases, called ribosomopathies, impact particular tissues specifically. Here, we evaluate the importance of the box C/D snoRNA-associated ribosomal RNA methyltransferase fibrillarin (Fbl) in the early embryonic development of Xenopus laevis. We report that in developing embryos, the neural plate, neural crest cells (NCCs), and NCC derivatives are rich in fbl transcripts. Fbl knockdown leads to striking morphological defects affecting the eyes and craniofacial skeleton, due to lack of NCC survival caused by massive p53-dependent apoptosis. Fbl is required for efficient pre-rRNA processing and 18S rRNA production, which explains the early developmental defects. Using RiboMethSeq, we systematically reinvestigated ribosomal RNA 2-O methylation in X. laevis, confirming all 89 previously mapped sites and identifying 15 novel putative positions in 18S and 28S rRNA. Twenty-three positions, including 10 of the new ones, were validated orthogonally by low dNTP primer extension. Bioinformatic screening of the X. laevis transcriptome revealed candidate box C/D snoRNAs for all methylated positions. Mapping of 2-O methylation at six developmental stages in individual embryos indicated a trend towards reduced methylation at specific positions during development. We conclude that fibrillarin knockdown in early Xenopus embryos causes reduced production of functional ribosomal subunits, thus impairing NCC formation and migration. AUTHOR SUMMARYRibosomes are essential nanomachines responsible for protein production in all cells. Ribosomopathies are diseases caused by improper ribosome formation due to mutations in ribosomal proteins or ribosome assembly factors. Such diseases primarily affect the brain and blood, and it is unclear how malfunctioning of a process as general as ribosome formation can lead to tissue-specific diseases. Here we have examined how fibrillarin, an enzyme which modifies ribosomal RNA by adding methyl groups at specific sites, affects early embryonic development in the frog Xenopus laevis. We have revealed its importance in the maturation of cells forming an embryonic structure called the neural crest. Fibrillarin depletion leads to reduced eye size and abnormal head shape, reminiscent of other conditions such as Treacher Collins syndrome. Molecularly, the observed phenotypes are explainable by increased p53-dependent programmed cell death triggered by inhibition of certain pre-rRNA processing steps. Our systematic investigation of the ribosomal RNA 2-O methylation repertoire across development has further revealed hypomodification at a late stage of development, which might play a role in late developmental transitions involving differential translation by compositionally different ribosomes.

developmental biology↗

bioRxiv2020

HIV-1 and HIV-2 differentially regulate NF-κB activity during the late stages of the replication cycle through BST-2/tetherin antagonism

HIV-2 is the second causative agent of AIDS and is commonly considered as an attenuated form of retroviral infection. Most of HIV-2-infected individuals display a slow-progressing disease, lower viral loads and a stronger immunological control of viral infection as compared with HIV-1-infected patients. The main hypothesis that could explain the difference of disease progression between HIV-1 and HIV-2 implies a more efficient T cell-mediated immunity in the control of HIV-2 infection. Herein, we investigate the effects of the HIV-2 envelope glycoprotein (Env) and its antitetherin function in the NF-{kappa}B signaling pathway during single-round infection of CD4+ T cells. First, we report an essential role of the Env cytoplasmic tail (CT) in the activation of this signaling pathway and we also demonstrate that the HIV-2 Env CT activates NF-{kappa}B in a TRAF6-dependent but TAK1-independent manner. Further, we show that HIV-2 reference strains and clinical isolates are unable to completely inhibit NF-{kappa}B mainly via the Env-mediated BST-2/tetherin antagonism in the late stages of the viral replication cycle in CD4+ T cells, in striking contrast to the HIV-1 Vpu-mediated counteraction of tetherin. We observe that this inability of HIV-2 to suppress NF-{kappa}B signaling pathway promotes stimulation of numerous genes involved in the antiviral immune response, such as il-6, il-21 and ifn-{beta} genes. Therefore, HIV-1 and HIV-2 differentially regulate the NF-{kappa}B-induced antiviral immune response mainly through the BST-2/tetherin antagonism. These new insights highlight molecular mechanisms determining, at least partly, the distinct immune control and disease outcomes of HIV-1 and HIV-2 infections. IMPORTANCEThis study explores how HIV-1 and HIV-2 diverge in their regulation of the NF-{kappa}B signaling pathway. We revealed that HIV-2 fails to completely inhibit NF-{kappa}B activity, thereby inducing a stronger antiviral response than HIV-1. We demonstrated that the ability to antagonize the cellular restriction factor BST-2/tetherin largely governs the regulation of the NF-{kappa}B pathway: at the late stages of the viral replication cycle, HIV-1 Vpu blocks this pathway whereas HIV-2 Env does not. We also demonstrated that several NF-{kappa}B-targeted genes are upregulated in CD4+ T cells infected with HIV-2, but not with HIV-1. This stronger NF-{kappa}B-induced antiviral response may explain the better immune control of HIV-2 infection and the differences between HIV-1 and HIV-2 pathogenesis. Moreover, we observed in this study that non-pathogenic isolates of HIV-2 have an impaired NF-{kappa}B inhibitory capacity compared to pathogenic ones.

microbiology↗