Molecular cloning, characterization, and expression of duck 2'-5'-oligoadenylate synthetase-like gene.

2'-5'-Oligoadenylate synthetase-like protein (OASL) is an interferon-inducible antiviral protein that exerts antiviral effects through the RNase L- or retinoic acid-inducible gene I (RIG-I)-dependent signalling pathway. In this study, we identified and cloned the OASL gene (named duOASL) from healthy adult Cherry Valley ducks. Full-length duOASL cDNA (1630bp) encoded a 504-amino acid polypeptide containing three conserved domains, namely, nucleotidyltransferase domain, 2'-5'-oligoadenylate synthetase domain, and two ubiquitin-like repeats. DuOASL mRNA expression was quantified by performing quantitative reverse transcription-PCR (qRT-PCR). Results of qRT-PCR showed that duOASL was broadly expressed in all examined tissues, with the highest mRNA expression in the large intestine. Antiviral activity of duOASL was measured by determining its effect on Duck Tembusu virus (DTMUV) replication in vitro. We found that duOASL overexpression slightly inhibited DTMUV replication, whereas duOASL knockdown by using a specific small interfering RNA increased DTMUV replication in DF-1 cells. Thus, we successfully cloned and characterized the antiviral protein duOASL from Cherry Valley ducks and found that it exerted antiviral effects against DTMUV. These results provide a solid foundation for performing further studies to determine the mechanism underlying the antiviral effect of duOASL at the cellular level.