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Project description:Gene functional study and the emerging mRNA therapy technology heavily rely on in vitro transcribed (IVT) mRNA, but the double-stranded RNA (dsRNA) by-product generated during IVT is often recognized by cells as a marker of virus replication, leading to the integrated stress response (ISR).The biological effects of dsRNA in undifferentiated cells differ significantly from those of differentiated counterparts.Here, we found that dsRNA triggered an unprecedented ISR in zebrafish early embryos, leading to developmental delay, severe cell necrosis, and lethal malformations.Mechanistically, dsRNA stimulation caused a PKR-eIF2α independent global translation inhibition and a burst of p53 signaling. In turn, p53 activated Interferon Stimulated Genes (ISGs) and other defense-related genes in the absence of the IFN system. Unexpectedly, p53 does not promote cell death; instead, it plays a protective role in weakening the damage of translation repression by compromising protein turnover via enhanced ISGylation.This study thus unveils a distinct ISR upon dsRNA stimulation, which may help perform faithful gene overexpression in early embryos and shed light on the strategies of undifferentiated cells against RNA virus infection.
2024-01-01 | GSE234229 | GEO
Project description:Gene functional study and the emerging mRNA therapy technology heavily rely on in vitro transcribed (IVT) mRNA, but the double-stranded RNA (dsRNA) by-product generated during IVT is often recognized by cells as a marker of virus replication, leading to the integrated stress response (ISR).The biological effects of dsRNA in undifferentiated cells differ significantly from those of differentiated counterparts.Here, we found that dsRNA triggered an unprecedented ISR in zebrafish early embryos, leading to developmental delay, severe cell necrosis, and lethal malformations.Mechanistically, dsRNA stimulation caused a PKR-eIF2α independent global translation inhibition and a burst of p53 signaling. In turn, p53 activated Interferon Stimulated Genes (ISGs) and other defense-related genes in the absence of the IFN system. Unexpectedly, p53 does not promote cell death; instead, it plays a protective role in weakening the damage of translation repression by compromising protein turnover via enhanced ISGylation.This study thus unveils a distinct ISR upon dsRNA stimulation, which may help perform faithful gene overexpression in early embryos and shed light on the strategies of undifferentiated cells against RNA virus infection.
2024-01-01 | GSE234227 | GEO
Project description:Double-stranded RNA (dsRNA) is associated with virus infections and is present as by-products during the transcription of synthetic mRNA, which has been widely used in gene gain-of-function studies and serves as a core component in emerging mRNA-based therapies1-4. The presence of dsRNA in host cells induces an integrated stress response that functions to prevent virus replication and infection5,6. Unlike differentiated cells, undifferentiated cells adopt a distinct defense strategy against RNA virus infection7, but the mechanism is unclear. We show a previously unidentified response triggered by dsRNA in the early embryo. Although dsRNA causes a global protein translation inhibition in a PKR-eIF2α independent manner and leads to developmental delay and cell necrosis, it also strongly induces p53 activation, which then upregulates Interferon Stimulated Genes independently of interferon ligands. Importantly, we demonstrate that the burst of p53 signaling dose not result in cell death but functions as a protective mechanism against deleterious translation blockage by slowing down global protein degradation via ISGylation. Our work has identified a distinct dsRNA-induced stress response in the embryo, reflecting an ancient innate immune memory before the establishment of the IFN system. It also raises the provocative question as to the original protective role of p53 during evolution.
2024-04-26 | GSE265771 | GEO
Project description:Mitochondria are descendants of endosymbiotic bacteria and retain essential prokaryotic features such as a compact circular genome. Consequently, in mammals, mitochondrial DNA is subjected to bidirectional transcription that generates overlapping transcripts, which are capable of forming long double-stranded RNA structures1,2. However, to our knowledge, mitochondrial double-stranded RNA has not been previously characterized in vivo. Here we describe the presence of a highly unstable native mitochondrial double-stranded RNA species at single-cell level and identify key roles for the degradosome components mitochondrial RNA helicase SUV3 and polynucleotide phosphorylase PNPase in restricting the levels of mitochondrial double-stranded RNA. Loss of either enzyme results in massive accumulation of mitochondrial double-stranded RNA that escapes into the cytoplasm in a PNPase-dependent manner. This process engages an MDA5-driven antiviral signalling pathway that triggers a type I interferon response. Consistent with these data, patients carrying hypomorphic mutations in the gene PNPT1, which encodes PNPase, display mitochondrial double-stranded RNA accumulation coupled with upregulation of interferon-stimulated genes and other markers of immune activation. The localization of PNPase to the mitochondrial inter-membrane space and matrix suggests that it has a dual role in preventing the formation and release of mitochondrial double-stranded RNA into the cytoplasm. This in turn prevents the activation of potent innate immune defence mechanisms that have evolved to protect vertebrates against microbial and viral attack.
| S-EPMC6570621 | biostudies-literature
Project description:In eukaryotes, tRNAs are transcribed in the nucleus and exported to the cytosol, where they deliver amino acids to ribosomes for protein translation. This nuclear-cytoplasmic movement was believed to be unidirectional. However, active shuttling of tRNAs, named tRNA retrograde transport, between the cytosol and nucleus has been discovered. This pathway is conserved in eukaryotes, suggesting a fundamental function; however, little is known about its role in human cells. Here we report that, in human cells, oxidative stress triggers tRNA retrograde transport, which is rapid, reversible, and selective for certain tRNA species, mostly with shorter 3' ends. Retrograde transport of tRNASeC, which promotes translation of selenoproteins required to maintain homeostatic redox levels in cells, is highly efficient. tRNA retrograde transport is regulated by the integrated stress response pathway via the PERK-REDD1-mTOR axis. Thus, we propose that tRNA retrograde transport is part of the cellular response to oxidative stress.
| S-EPMC6426654 | biostudies-literature
Project description:The airway epithelial barrier is critical for preventing pathogen invasion and translocation of inhaled particles into the lung. Epithelial cells also serve an important sentinel role after infection and release various pro-inflammatory mediators that recruit and activate immune cells. Airway epithelial barrier disruption has been implicated in a growing number of respiratory diseases including viral infections. It is thought that when a pathogen breaks the barrier and gains access to the host tissue, pro-inflammatory mediators increase, which further disrupts the barrier and initiates a vicious cycle of leak. However, it is difficult to study airway barrier integrity in vivo, and little is known about relationship between epithelial barrier function and airway inflammation. Current assays of pulmonary barrier integrity quantify the leak of macromolecules from the vasculature into the airspaces (or "inside/out" leak). However, it is also important to measure the ease with which inhaled particles, allergens, or pathogens can enter the subepithelial tissues (or "outside/in" leak). We challenged mice with inhaled double stranded RNA (dsRNA) and explored the relationship between inside/out and outside/in barrier function and airway inflammation. Using wild-type and gene-targeted mice, we studied the roles of the dsRNA sensors Toll Like Receptor 3 (TLR3) and Melanoma Differentiation-Associated protein 5 (MDA5). Here we report that after acute challenge with inhaled dsRNA, airway barrier dysfunction occurs in a TLR3-dependent manner, whereas leukocyte accumulation is largely MDA5-dependent. We conclude that airway barrier dysfunction and inflammation are regulated by different mechanisms at early time points after exposure to inhaled dsRNA.
| S-EPMC6505938 | biostudies-literature
Project description:Mitochondrial-nuclear communication, known as retrograde signaling, is important for regulating nuclear gene expression in response to mitochondrial dysfunction. Previously, we have found that p32/C1qbp-deficient mice, which have a mitochondrial translation defect, show endoplasmic reticulum (ER) stress response and integrated stress response (ISR) gene expression in the heart and brain. However, the mechanism by which mitochondrial translation inhibition elicits these responses is not clear. Among the transcription factors that respond to mitochondrial stress, activating transcription factor 4 (ATF4) is a key transcription factor in the ISR. Herein, chloramphenicol (CAP), which inhibits mitochondrial DNA (mtDNA)-encoded protein expression, induced eukaryotic initiation factor 2 α subunit (eIF2α) phosphorylation and ATF4 induction, leading to ISR gene expression. However, the expression of the mitochondrial unfolded protein response (mtUPR) genes, which has been shown in Caenorhabditis elegans, was not induced. Short hairpin RNA-based knockdown of ATF4 markedly inhibited the CAP-induced ISR gene expression. We also observed by ChIP analysis that induced ATF4 bound to the promoter region of several ISR genes, suggesting that mitochondrial translation inhibition induces ISR gene expression through ATF4 activation. In the present study, we showed that mitochondrial translation inhibition induced the ISR through ATF4 activation rather than the mtUPR.
| S-EPMC7685009 | biostudies-literature
Project description:Precise genome editing involves homologous recombination between donor DNA and chromosomal sequences subjected to double-stranded DNA breaks made by programmable nucleases. Ideally, genome editing should be efficient, specific, and accurate. However, besides constituting potential translocation-initiating lesions, double-stranded DNA breaks (targeted or otherwise) are mostly repaired through unpredictable and mutagenic non-homologous recombination processes. Here, we report that the coordinated formation of paired single-stranded DNA breaks, or nicks, at donor plasmids and chromosomal target sites by RNA-guided nucleases based on CRISPR-Cas9 components, triggers seamless homology-directed gene targeting of large genetic payloads in human cells, including pluripotent stem cells. Importantly, in addition to significantly reducing the mutagenicity of the genome modification procedure, this in trans paired nicking strategy achieves multiplexed, single-step, gene targeting, and yields higher frequencies of accurately edited cells when compared to the standard double-stranded DNA break-dependent approach.CRISPR-Cas9-based gene editing involves double-strand breaks at target sequences, which are often repaired by mutagenic non-homologous end-joining. Here the authors use Cas9 nickases to generate coordinated single-strand breaks in donor and target DNA for precise homology-directed gene editing.
| S-EPMC5610252 | biostudies-literature
Project description:Virus infections are a major cause of chronic obstructive pulmonary disease (COPD) exacerbations. Recently, Toll-like receptor 3 (TLR3) has been demonstrated to react to double-stranded RNA (dsRNA) and to be involved in the immune responses after viral infections. In the present study, we examined whether oxidative stress, which is involved in the pathogenesis of COPD, enhances the responses of TLR3 in airway epithelial cells. The effect of hydrogen peroxide (H(2)O(2)) on the release of IL-8 from BEAS-2B cells and primary human bronchial epithelial cells after stimulation with polyinosine-polycytidylic acid [poly(I:C)], a synthetic analog of viral dsRNA and a ligand for TLR3, and the signal transduction were examined. One hundred to 150 muM H(2)O(2) significantly potentiated the release of IL-8 from the epithelial cells after stimulation with 10 microg/ml poly(I:C). The H(2)O(2)-augmented IL-8 release was inhibited by treatment with N-acetylcysteine. One hundred micromoles of H(2)O(2) enhanced the translocation of nuclear factor (NF)-kappaB p65, but not that of interferon regulatory factor-3 (IRF-3), into the nucleus and the NF-kappaB DNA binding activity after poly(I:C) stimulation, which effect was inhibited not by the silencing of IRF-3 but by MG132, a proteasome inhibitor, or dexamethasone. One hundred micromoles of H(2)O(2) potentiated the TLR3 expression on the airway epithelial cells treated with poly(I:C). These data suggest that oxidative stress augments the response of TLR3 in airway epithelial cells via NF-kappaB and that this effect might be partly mediated by the enhancement of TLR3 expression. Modulation of this pathway may be a therapeutic target for viral-induced exacerbations of COPD.
| S-EPMC2891495 | biostudies-literature
Project description:In recent years, CRISPR-associated (Cas) nucleases have revolutionized the genome editing field. Being guided by an RNA to cleave double-stranded (ds) DNA targets near a short sequence termed a protospacer adjacent motif (PAM), Cas9 and Cas12 offer unprecedented flexibility, however, more compact versions would simplify delivery and extend application. Here, we present a collection of 10 exceptionally compact (422-603 amino acids) CRISPR-Cas12f nucleases that recognize and cleave dsDNA in a PAM dependent manner. Categorized as class 2 type V-F, they originate from the previously identified Cas14 family and distantly related type V-U3 Cas proteins found in bacteria. Using biochemical methods, we demonstrate that a 5' T- or C-rich PAM sequence triggers dsDNA target cleavage. Based on this discovery, we evaluated whether they can protect against invading dsDNA in Escherichia coli and find that some but not all can. Altogether, our findings show that miniature Cas12f nucleases can protect against invading dsDNA like much larger class 2 CRISPR effectors and have the potential to be harnessed as programmable nucleases for genome editing.
| S-EPMC7229846 | biostudies-literature