A novel RNA molecular signature for activation of 2′-5′ oligoadenylate synthetase-1

Abstract

Human 2′-5′ oligoadenylate synthetase-1 (OAS1) is central in innate immune system detection of cytoplasmic double-stranded RNA (dsRNA) and promotion of host antiviral responses. However, the molecular signatures that promote OAS1 activation are currently poorly defined. We show that the 3′-end polyuridine sequence of viral and cellular RNA polymerase III non-coding transcripts is critical for their optimal activation of OAS1. Potentiation of OAS1 activity was also observed with a model dsRNA duplex containing an OAS1 activation consensus sequence. We determined that the effect is attributable to a single appended 3′-end residue, is dependent upon its single-stranded nature with strong preference for pyrimidine residues and is mediated by a highly conserved OAS1 residue adjacent to the dsRNA binding surface. These findings represent discovery of a novel signature for OAS1 activation, the 3′-single-stranded pyrimidine (3′-ssPy) motif, with potential functional implications for OAS1 activity in its antiviral and other anti-proliferative roles.

RNA regulation of the antiviral protein 2′‐5′‐oligoadenylate synthetase

“…nc886 adopts two distinct structures which differ in their migration on native polyacrylamide gels and their ability to inhibit PKR: the slower migrating form ("Conformer 1") is a potent PKR inhibitor while the faster migrating form ("Conformer 2") is a weak PKR activator that acts as a pseudoinhibitor at higher concentrations in the presence of another PKR-activator such as poly(I:C) RNA. As noted earlier, we also showed that nc886 can activate OAS1 in vitro as a mixture of conformers (Vachon et al, 2015). A more recent detailed study of OAS1 activation by nc886 in vitro and in A549 cells revealed that most activity is conferred by a unique tertiary structure motif present only in the apical stem-loop of nc886 Conformer 1 (Calderon & Conn, 2018).…”

Exome-wide association study identifies four novel loci for systemic lupus erythematosus in Han Chinese population

“…Of them, rs1051042 is the lead eQTL SNP (ie, eSNP) on the OAS1 gene, suggesting potential causality of the OAS1 gene. The OAS1 gene synthesises an antiviral enzyme and then results in viral RNA degradation39 and may inhibit virus replication, which is a common environment trigger for SLE, and affect the risk and disease activity of SLE 40 41. The A risk allele of SNP rs1335532 significantly upregulates the expression level of the CD58 gene 24.…”

A human cellular noncoding RNA activates the antiviral protein 2′–5′-oligoadenylate synthetase 1

“…To dissect the activity of each conformer on OAS1, we purified the individual nc886 conformers by native PAGE. An established in vitro OAS1 activation assay (27,28) was then used to measure PP i production, the by-product of 2-5A synthesis, in the presence of each nc886 conformer. nc886 conformer 1 strongly activates OAS1 ( Fig.…”

“…Our previous work has demonstrated that nc886 RNA adopts two structurally distinct conformers, distinguished by their apical stem-loop structures, that possess opposing activi-ties in the regulation of PKR (26). We also previously reported that the mixture of nc886 conformers appeared to strongly activate OAS1 and that this activity was only modestly reduced by deletion of the 3Ј-single-stranded pyrimidine (3Ј-ssPy) motif that more significantly potentiates activity by viral noncoding RNAs (27). Here, we show that the two nc886 conformers exhibit profound differences in their capacity to activate the OAS/RNase L pathway: one nc886 conformer is a potent activator of OAS1 in vitro and in human A549 cells whereas the other conformer activates OAS1 only very weakly.…”