Antiviral Activity of Human OASL Protein Is Mediated by Enhancing Signaling of the RIG-I RNA Sensor

Abstract

SUMMARY Virus infection is sensed in the cytoplasm by retinoic acid-inducible gene I (RIG-I, also known as DDX58), which requires RNA and polyubiquitin binding to induce type I interferon (IFN), and activate cellular innate immunity. We show that the human IFN-inducible oligoadenylate synthetases-like (OASL) protein had antiviral activity and mediated RIG-I activation by mimicking polyubiquitin. Loss of OASL expression reduced RIG-I signaling and enhanced virus replication in human cells. Conversely, OASL expression suppressed replication of a number of viruses in a RIG-I-dependent manner and enhanced RIG-I-mediated IFN induction. OASL interacted and colocalized with RIG-I, and through its C-terminal ubiquitin-like domain specifically enhanced RIG-I signaling. Bone marrow derived macrophages from mice deficient for Oasl2 showed that among the two mouse orthologs of human OASL; Oasl2 is functionally similar to human OASL. Our findings show a mechanism by which human OASL contributes to host antiviral responses by enhancing RIG-I activation.

2′-5′-Oligoadenylate Synthetase-Like Protein Inhibits Respiratory Syncytial Virus Replication and Is Targeted by the Viral Nonstructural Protein 1

“…Recombinant OASL, stably expressed in HEK293 cells, strongly reduced RSV growth, measured by the reduction of progeny viral titer, which paralleled the reduction of intracellular viral RNA and proteins (Fig. 1), confirming our earlier findings (18) and establishing inhibition at the viral genome level. Similar antiviral activity of OASL was also observed using a different cell line, HCT116 ( Fig.…”

“…2A). In complementary studies, enhanced RSV replication was seen when OASL expression was silenced by stable expression of the short hairpin RNA (shRNA) described previously (18) (Fig. 2B).…”

“…Unlike in humans, two OASL isoforms have been identified in the mouse, Oasl1 and Oasl2. We have recently described the (pcDNA), as described before (18), were grown in monolayers on coverslips and infected with RSV Long at a multiplicity of infection of 3. At 18 h postinfection, cells were fixed and immunostained with mouse anti-RSV nucleoprotein (N) antibody (Abnova clone B023), followed by Alex Fluor 610-conjugated donkey anti-mouse IgG (Life Technologies).…”

“…antiviral activities of human OASL and mouse Oasl2, which are mediated through the enhancement of RIG-I signaling (18). In the present study, we examined the antiviral activities of various human and mouse OASL proteins against respiratory syncytial virus (RSV), the founding member of the clinically significant Pneumovirus genus of the Paramyxoviridae family.…”

OutKnocker: a web tool for rapid and simple genotyping of designer nuclease edited cell lines

“…3C,D). In addition to the target regions shown here (TLR2 and UNC93B1), we have generated knockout cell lines for more than 100 independent genes to date using this approach (Ablasser et al 2013(Ablasser et al , 2014Zhu et al 2014; data not shown). Of note, in the case of previously characterized target genes, the phenotype of these knockout cell lines always reflected the expected outcome.…”