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2022 ◽  
Vol 119 (3) ◽  
pp. e2107111119
Author(s):  
Samantha L. Schwartz ◽  
Debayan Dey ◽  
Julia Tanquary ◽  
Camden R. Bair ◽  
Anice C. Lowen ◽  
...  

The 2’-5’-oligoadenylate synthetases (OAS) are innate immune sensors of cytosolic double-stranded RNA (dsRNA) that play a critical role in limiting viral infection. How these proteins are able to avoid aberrant activation by cellular RNAs is not fully understood, but adenosine-to-inosine (A-to-I) editing has been proposed to limit accumulation of endogenous RNAs that might otherwise cause stimulation of the OAS/RNase L pathway. Here, we aim to uncover whether and how such sequence modifications can restrict the ability of short, defined dsRNAs to activate the single-domain form of OAS, OAS1. Unexpectedly, we find that all tested inosine-containing dsRNAs have an increased capacity to activate OAS1, whether in a destabilizing (I•U) or standard Watson–Crick-like base pairing (I–C) context. Additional variants with strongly destabilizing A•C mismatches or stabilizing G–C pairs also exhibit increased capacity to activate OAS1, eliminating helical stability as a factor in the relative ability of the dsRNAs to activate OAS1. Using thermal difference spectra and molecular dynamics simulations, we identify both increased helical dynamics and specific local changes in helical structure as important factors in the capacity of short dsRNAs to activate OAS1. These helical features may facilitate more ready adoption of the distorted OAS1-bound conformation or stabilize important structures to predispose the dsRNA for optimal binding and activation of OAS1. These studies thus reveal the molecular basis for the greater capacity of some short dsRNAs to activate OAS1 in a sequence-independent manner.


2021 ◽  
Author(s):  
Courtney Comar ◽  
Clayton Otter ◽  
Jessica Pfannenstiel ◽  
Ethan Doerger ◽  
David Renner ◽  
...  

Middle East respiratory syndrome coronavirus (MERS CoV) emerged into humans in 2012, causing highly lethal respiratory disease. The severity of disease may be in part because MERS CoV is adept at antagonizing early innate immune pathways; these include interferon (IFN) production and signaling, protein kinase R (PKR), and oligoadenylate synthetase ribonuclease L (OAS/RNase L), all activated in response to viral double stranded (ds)RNA generated during genome replication. This is in contrast to SARS CoV 2, which we recently reported activates PKR and RNase L and to some extent, IFN signaling. We previously found that MERS-CoV accessory proteins NS4a (dsRNA binding protein) and NS4b (phosphodiesterase) could weakly suppress these pathways, but ablation of each had minimal effect on virus replication. Here we investigated the antagonist effects of the conserved coronavirus endoribonuclease (EndoU), in combination with NS4a or NS4b. Inactivation of EndoU catalytic activity alone in a recombinant MERS-CoV caused little if any effect on activation of the innate immune pathways during infection. However, infection with recombinant viruses containing combined mutations with inactivation of EndoU and deletion of NS4a or inactivation of the NS4b phosphodiesterase promoted robust activation of the dsRNA-induced innate immune pathways. This resulted in ten-fold attenuation of replication in human lung derived A549 and primary nasal cells. Furthermore, replication of these recombinant viruses could be rescued to the level of WT MERS CoV by knockout of host immune mediators MAVS, PKR, or RNase L. Thus, EndoU and accessory proteins NS4a and NS4b together suppress dsRNA induced innate immunity during MERS CoV infection in order to optimize viral replication.


2021 ◽  
Vol 118 (46) ◽  
pp. e2102134118
Author(s):  
Alisha Chitrakar ◽  
Kristina Solorio-Kirpichyan ◽  
Eliza Prangley ◽  
Sneha Rath ◽  
Jin Du ◽  
...  

Double-stranded RNA (dsRNA), a hallmark viral material that activates antiviral interferon (IFN) responses, can appear in human cells also in the absence of viruses. We identify phosphorothioate DNAs (PS DNAs) as triggers of such endogenous dsRNA (endo-dsRNA). PS DNAs inhibit decay of nuclear RNAs and induce endo-dsRNA via accumulation of high levels of intronic and intergenic inverted retroelements (IIIR). IIIRs activate endo-dsRNA responses distinct from antiviral defense programs. IIIRs do not turn on transcriptional RIG-I/MDA5/IFN signaling, but they trigger the dsRNA-sensing pathways of OAS3/RNase L and PKR. Thus, nuclear RNA decay and nuclear-cytosolic RNA sorting actively protect from these innate immune responses to self. Our data suggest that the OAS3/RNase L and PKR arms of innate immunity diverge from antiviral IFN responses and monitor nuclear RNA decay by sensing cytosolic escape of IIIRs. OAS3 provides a receptor for IIIRs, whereas RNase L cleaves IIIR-carrying introns and intergenic RNAs.


2021 ◽  
Vol 5 (3) ◽  
pp. 160-165
Author(s):  
Fabian Hauck

Typ-I-Interferonopathien sind autoinflammatorische Störungen der angeborenen Nukleinsäure-Immunität, die zusätzlich zu Epitop-spezifischer Autoimmunität prädispositionieren. In der Immunbiologie ist die Nukleinsäure-Immunität vermittelt durch die cGAS-STING- und OAS-RNase-L-Signalwege weitgehend verstanden. In der translationellen und klinischen Immunologie zeigen angeborene Störungen dieser Signalwege deren physiologische Relevanz an der Schnittstelle zwischen Selbst- und Fremd-Nukleinsäure-Erkennung und führen zu einem neuen Verständnis von seit Langem bekannten Krankheitsbildern. Dieser Übersichtsartikel fasst aktuelle pathophysiologische Konzepte und deren klinische Implikationen zur unkontrollierten cGAS- und OAS1-Aktivierung durch biallelische LSM11 und RNU7-1-loss-of-function-, monoallelische ATAD3A dominant-negative und monoallelische OAS1-gain-of-function-Varianten zusammen. Eine murine monoallelische dominante Oas2-Variante wird als Modell für eine mögliche Organ-spezifische humane Typ-I-Interferonopathie diskutiert.


2021 ◽  
Vol 60 (40) ◽  
Author(s):  
Xiaoxuan Su ◽  
Wenxiao Ma ◽  
Di Feng ◽  
Boyang Cheng ◽  
Qian Wang ◽  
...  

2021 ◽  
Vol 133 (40) ◽  
Author(s):  
Xiaoxuan Su ◽  
Wenxiao Ma ◽  
Di Feng ◽  
Boyang Cheng ◽  
Qian Wang ◽  
...  

Coronaviruses ◽  
2021 ◽  
Vol 02 ◽  
Author(s):  
Chellapandi P ◽  
Saranya S

: Coronavirus disease (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a new coronavirus isolated from Wuhan, China. It is a global health emergency, and there is no effective antiviral therapeutics available to date. Continuous structural genomic insights of SARS-CoV-2 proteins provide a warranty for the development of rational-based antivirals. Nevertheless, a structure-based drug candidate with multiple therapeutic actions would be a practical choice of medication in the treatment of severe COVID-19 patients. Cordycepin from medicinal fungi (Cordyceps spp.) and its nucleoside analogs targeting viral RNA-dependent RNA polymerase and human RNase L have potent antiviral activity against various human viruses with additional immunomodulatory and anti-inflammatory effects. Anti-inflammation treatment is of pivotal importance and should be timely tailored to the individual patient along with antivirals. Our perspective on the combined antiviral and anti-inflammatory effects of cordycepin and its analogs suggests them as new therapeutics in the treatment of systemic COVID-19 infection.


2021 ◽  
Vol 27 (1) ◽  
Author(s):  
Mei Tao ◽  
Ming Zheng ◽  
Yanhua Xu ◽  
Shuo Ma ◽  
Weiwei Zhang ◽  
...  

AbstractCircular RNAs (circRNAs), a novel type of non-coding RNAs (ncRNAs), have a covalently closed circular structure resulting from pre-mRNA back splicing via spliceosome and ribozymes. They can be classified differently in accordance with different criteria. As circRNAs are abundant, conserved, and stable, they can be used as diagnostic markers in various diseases and targets to develop new therapies. There are various functions of circRNAs, including sponge for miR/proteins, role of scaffolds, templates for translation, and regulators of mRNA translation and stability. Without m7G cap and poly-A tail, circRNAs can still be degraded in several ways, including RNase L, Ago-dependent, and Ago-independent degradation. Increasing evidence indicates that circRNAs can be modified by N-6 methylation (m6A) in many aspects such as biogenesis, nuclear export, translation, and degradation. In addition, they have been proved to play a regulatory role in the progression of various cancers. Recently, methods of detecting circRNAs with high sensitivity and specificity have also been reported. This review presents a detailed overview of circRNAs regarding biogenesis, biomarker, functions, degradation, and dynamic modification as well as their regulatory roles in various cancers. It’s particularly summarized in detail in the biogenesis of circRNAs, regulation of circRNAs by m6A modification and mechanisms by which circRNAs affect tumor progression respectively. Moreover, existing circRNA detection methods and their characteristics are also mentioned.


Blood ◽  
2021 ◽  
Author(s):  
Qiang Wang ◽  
Zhijuan Lin ◽  
Zhuo Wang ◽  
Lingqun Ye ◽  
Miao Xian ◽  
...  

Proteasome inhibitors (PIs) such as bortezomib (Btz) and carfilzomib (Cfz) are highly efficacious for patients with multiple myeloma (MM). However, relapses are frequent and acquired resistance to PI treatment emerges in most patients. Here we performed a high-throughput screen of 1855 FDA-approved drugs and identified all-trans retinoic acid (ATRA), which alone has no antimyeloma effect, as a potent drug that enhanced MM sensitivity to Cfz-induced cytotoxicity and re-sensitized Cfz-resistant MM cells to Cfz in vitro. ATRA activated RARγ and IFN-β response pathway, leading to upregulated expression of IRF1. IRF1 in turn initiated the transcription of OAS1, which synthesized 2-5A upon binding to dsRNA induced by Cfz and resulted in cellular RNA degradation by RNase L and cell death. Similar to ATRA, BMS961, a selective RARγ agonist, could also (re)sensitize MM cells to Cfz in vitro, and both ATRA and BMS961 significantly enhanced the therapeutic effects of Cfz in established MM in vivo. In support of these findings, analyses of large patient's gene-profiling datasets showed a strong and positive correlation between RARγ and OAS1 expression and patient's response to PI treatment. Thus, this study highlights the potential for RARγ agonists to sensitize and overcome MM resistance to Cfz treatment in patients.


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