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: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: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:UnlabelledThe replication of plus-strand RNA virus genomes is mediated by virally encoded RNA-dependent RNA polymerases (RdRps). We have investigated the role of the C-proximal region in the RdRp of tomato bushy stunt virus (TBSV) in mediating viral RNA synthesis. TBSV is the prototype species in the genus Tombusvirus, family Tombusviridae, and its RdRp is responsible for replicating the viral genome, transcribing two subgenomic mRNAs, and supporting replication of defective interfering RNAs. Comparative sequence analysis of the RdRps of tombusvirids identified three highly conserved motifs in their C-proximal regions, and these sequences were subsequently targeted for mutational analysis in TBSV. The results revealed that these motifs are important for (i) synthesizing viral genomic RNA and subgenomic mRNAs, (ii) facilitating plus- and/or minus-strand synthesis, and (iii) modulating trans-replication of a defective interfering RNA. These motifs were also found to be conserved in other plant viruses as well as in a fungal and insect virus. The collective findings are discussed in relation to viral RNA synthesis and taxonomy.ImportanceLittle is currently known about the structure and function of the viral polymerases that replicate the genomes of RNA plant viruses. Tombusviruses, the prototype of the tombusvirids, have been used as model plus-strand RNA plant viruses for understanding many of the steps in the infectious process; however, their polymerases remain poorly characterized. To help address this issue, the function of the C-terminal region of the polymerase of a tombusvirus was investigated. Three conserved motifs were identified and targeted for mutational analysis. The results revealed that these polymerase motifs are important for determining what type of viral RNA is produced, facilitating different steps in viral RNA production, and amplifying subgenomic RNA replicons. Accordingly, the C-terminal region of the tombusvirus polymerase is needed for a variety of fundamental activities. Furthermore, as these motifs are also present in distantly related viruses, the significance of these results extends beyond tombusvirids.
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:SARS-CoV-2 lineage B.1.1.7 viruses are more transmissible, may lead to greater clinical severity, and result in modest reductions in antibody neutralization. Subgenomic RNA(sgRNA) is produced by discontinuous transcription of the SARS-CoV-2 genome. Applying our tool(periscope) to ARTIC Network Nanopore genomic sequencing data from 4400 SARS-CoV-2 positive clinical samples, we show that normalised sgRNA is significantly increased in B.1.1.7(alpha) infections(n=879). This increase is seen over the previous dominant circulating UK lineage, B.1.177(n=943), which is independent of genomic reads, E-gene cycle-threshold and days since symptom onset at sampling. A noncanonical sgRNA which could represent ORF9b is found in 98.4% of B.1.1.7 SARS-CoV-2 infections compared with only 13.8% of other lineages, with a 16-fold increase in median sgRNA abundance. We demonstrate that ORF9b protein levels are increased 6-fold in B.1.1.7 compared to a B lineage virus during in vitro culture. We hypothesise that this enhanced presence of ORF9b in B.1.1.7 viruses is a direct consequence of a triple nucleotide mutation in nucleocapsid(28280:GAT>CAT,D3L) creating a transcription regulatory-like sequence complementary to a region 3’ of the genomic leader. These findings provide a unique insight into the biology of B.1.1.7 and support monitoring of sgRNA profiles in sequence data to evaluate emerging potential variants of concern.
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.