Project description:Coronavirus RNA-dependent RNA polymerases produce subgenomic RNAs (sgRNAs) that encode viral structural and accessory proteins. The kinetics and efficiency of sgRNAs production during viral replication in different cell types or sgRNA transcription by individual viral strains or variants are yet to be studied to shed light on fundamental mechanisms necessary for viral replication. User-friendly bioinformatic tools to detect and quantify sgRNA production are urgently needed to study a growing number of next-generation sequencing (NGS) data of SARS-CoV-2. Starting from DI-tector, a bioinformatic tool for the detection of viral defective interfering genomes, here we introduced sgDI-tector to identify and quantify sgRNA in SARS-CoV-2 NGS data. This new tool allowed detection of sgRNA without initial knowledge of the transcription-regulatory sequences. As a proof of principle, we analyzed new data sets and successfully detected the nested set of sgRNAs produced with the ranking M>ORF3a>N>ORF6>ORF7a>ORF8>S>E>ORF7b. Our study also compared, for the first time for SARS-CoV-2, the level of sgRNA production with other types of viral RNA products such as defective interfering viral genomes.
Project description:Using next-generation sequencing (NGS) combined with bioinformatics tools, we characterized two major 5’copy-back defective interfering (5’cb DI) genomes generated during SAD replication. Furthermore, we identified a specific interaction of 5’cb DI genomes and RIG-I that correlated with a high stimulation of the type I IFN signaling
Project description:Coronavirus RNA-dependent RNA polymerases produce subgenomic RNAs (sgRNAs) that encode viral structural and accessory proteins. User-friendly bioinformatic tools to detect and quantify sgRNA production are urgently needed to study the growing number of next-generation sequencing (NGS) data of SARS-CoV-2. We introduced sgDI-tector to identify and quantify sgRNA in SARS-CoV-2 NGS data. sgDI-tector allowed detection of sgRNA without initial knowledge of the transcription-regulatory sequences. We produced NGS data and successfully detected the nested set of sgRNAs with the ranking M > ORF3a > N>ORF6 > ORF7a > ORF8 > S > E>ORF7b. We also compared the level of sgRNA production with other types of viral RNA products such as defective interfering viral genomes.
Project description:Influenza defective interfering (DI) viruses have long been considered promising antiviral candidates because of their ability to interfere with replication-competent viruses and to induce antiviral immunity. However, the mechanisms underlying DI-mediated antiviral immunity have not been extensively explored. Here, we demonstrated interferon (IFN) independent protection conferred by influenza DI virus against homologous virus infection in mice deficient in type I and III IFN signaling. By integrating transcriptional and post-transcriptional regulatory data we identified unique host signatures in response to DI co-infection. DI-treated mice exhibited reduced viral transcription, less intense inflammatory and innate immune responses, and primed multiciliated cell differentiation in their lungs at an early stage of infection, even in the absence of type I or III IFNs. This increased multiciliogenesis could also be detected at the protein level by immunofluorescence staining of lung tissue from DI-treated mice. Overall, our study provides mechanistic insight into the protection mediated by DIs, implying a unifying theme involving inflammation and multiciliogenesis in maintaining respiratory homeostasis, and reveals their IFN-independent antiviral activity.
Project description:To clarify that the interfering effect in iPS induction was not because of extraordinary gene expression which was caused by overexpression of infected genes, transcriptional profile of the cells infected six genes were analysed using microarray analysis. As result, overexpression of each of the 6 interfering TFs in NSEB5-2C did not compromise transcriptional profile compared with the five non-interfering TFs.
Project description:To clarify that the interfering effect in iPS induction was not because of extraordinary gene expression which was caused by overexpression of infected genes, transcriptional profile of the cells infected six genes were analysed using microarray analysis. As result, overexpression of each of the 6 interfering TFs in NSEB5-2C did not compromise transcriptional profile compared with the five non-interfering TFs. The cells were infected by retroviruses (carrying each ORF in pMXs-IRESNeo) at the titre in which around 95% of cells express the transgene. After 24hr of the infection, G418 was added to eliminate non-expressing cells. Each cells were harvested at 72hr after the infection.
Project description:A missense mutation (G158R) in Ikzf3 gene resulted in defective generation of B cells in mice. Pre-B cells were profoundly decreased in homozygous mutant mice. Heterozygous mutant mice showed milder B cell developmental defects, and decreased B cells in the secondary lymphoid organs were observed. Ikzf3 encodes Aiolos, which makes heterodimer with Ikaros. Our findings indicate that the loss-of-function mutation in Aiolos hinders B cell development by interfering Ikaros' function via formation of heterodimers.
Project description:Parasitic elements of the viral population which are unable to replicate on their own yet rise to high frequencies, defective interfering particles are found in a variety of different viruses. Their presence is associated with a loss of population fitness, both through the depletion of key cellular resources and the stimulation of innate immunity. For influenza A virus, these particles contain large internal deletions in the genomic segments which encode components of the heterotrimeric polymerase. Using a library-based approach, we comprehensively profile the growth and replication of defective species, demonstrating they possess an advantage during genome replication, and that exclusion during packaging reshapes population composition in a manner consistent with their final, observed, distribution in natural populations. We find that innate immunity is not linked to the size of a deletion; however, replication of defective segments can enhance their immunostimulatory properties. Overall, our results address several key questions in defective influenza A virus biology, and the methods we have developed to answer those questions may be broadly applied to other defective viruses.
Project description:Panicum mosaic virus (PMV) is a recently molecularly characterized RNA virus with the unique feature of supporting the replication of two subviral RNAs in a few species of the family Gramineae. The subviral agents include a satellite RNA (satRNA) that is devoid of a coding region and the unrelated satellite panicum mosaic virus (SPMV) that encodes its own capsid protein. Here we report the association of this complex with a new entity in the RNA world, a defective-interfering RNA (DI) of a satellite virus. The specificity of interactions governing this four-component viral system is illustrated by the ability of the SPMV DIs to strongly interfere with the accumulation of the parental SPMV. The SPMV DIs do not interfere with PMV satRNA, but they do slightly enhance the rate of spread and titer of PMV. The SPMV-derived DIs provide an additional avenue by which to investigate fundamental biological questions, including the evolution and interactions of infectious RNAs.
Project description:Viruses thrive by exploiting the cells they infect, but in order to replicate and infect other cells they must produce viral proteins. As a result, viruses are also susceptible to exploitation by defective versions of themselves that do not produce such proteins. A defective viral genome with deletions in protein-coding genes could still replicate in cells coinfected with full-length viruses. Such a defective genome could even replicate faster due to its shorter size, interfering with the replication of the virus. We have created a synthetic defective interfering version of SARS-CoV-2, the virus causing the Covid-19 pandemic, assembling parts of the viral genome that do not code for any functional protein but enable the genome to be replicated and packaged. This synthetic defective genome replicates three times faster than SARS-CoV-2 in coinfected cells, and interferes with it, reducing the viral load of infected cells by half in 24 hours. The synthetic genome is transmitted as efficiently as the full-length genome, suggesting the location of the putative packaging signal of SARS-CoV-2. A version of such a synthetic construct could be used as a self-promoting antiviral therapy: by enabling replication of the synthetic genome, the virus would promote its own demise.