Abstract
Interferon (IFN)-induced 2′-5′-oligoadenylate synthetase (OAS) proteins exhibit an extensive and efficient antiviral effect against flavivirus infection in mammals and birds. Only the 2′-5′-oligoadenylate synthetase-like (OASL) gene has been identified thus far in birds, except for ostrich, which has both OAS1 and OASL genes. In this study, we first investigated the antiviral activity of goose OASL (goOASL) protein against a duck-origin Tembusu virus (DTMUV) in duck embryo fibroblast cells (DEFs). To investigate the relationship of conserved amino acids that are related to OAS enzyme activity and ubiquitin-like (UBL) domains with the antiviral activity of goOASL, a series of mutant goOASL plasmids was constructed, including goOASL-S64C/D76E/D78E/D144T, goOASL∆UBLs and goOASL∆UBLs-S64C/D76E/D78E/D144T. Interestingly, all these mutant proteins significantly inhibited the replication of DTMUV in DEFs in a dose-dependent manner. Immunofluorescence analysis showed that the goOASL, goOASL-S64C/D76E/D78E/D144T, goOASL∆UBLs and goOASL∆UBLs-S64C/D76E/D78E/D144T proteins were located not only in the cytoplasm where DTMUV replicates but also in the nucleus of DEFs. However, the goOASL and goOASL mutant proteins were mainly colocalized with DTMUV in the cytoplasm of infected cells. Our data indicated that goOASL could significantly inhibit DTMUV replication in vitro, while the active-site residues S64, D76, D78 and D144, which were associated with OAS enzyme activity, the UBL domains were not required for the antiviral activity of goOASL protein.
Highlights
The 20 -50 -oligoadenylate synthetase (OAS) family proteins are interferon (IFN)-induced antiviral factors and belong to the nucleotidyltransferase (NTase) superfamily [1,2]
duck embryo fibroblast cells (DEFs) seeded in a 12-well plate were transfected with pcDNA3.1 (+) vector, goose OASL (goOASL), goOASL-S64C/D76E/D78E/D144T, goOASL∆UBLs and goOASL∆UBLs-S64C/D76E/D78E/D144T
Western blotting analysis showed that the goOASL protein could be detected at 24 h, 36 h and 48 h in DEFs transfected with goOASL (Figure 2A)
Summary
The 20 -50 -oligoadenylate synthetase (OAS) family proteins are interferon (IFN)-induced antiviral factors and belong to the nucleotidyltransferase (NTase) superfamily [1,2]. There are normally two ubiquitin-like (UBL) domains located in the C-terminus of OASL protein, which is different from the other three OAS members [5]. Five conserved motifs have been identified in the OAS protein family: P-loop, D-box, LIRL, YALELLT and RPVILDPADP [6]. When activated by double-stranded RNA (dsRNA), the enzymatically active OAS protein can polymerize ATP into 20 , 50 -linked oligoadenylate (2-5A), depending on its nucleotidyltransferase (NTase) activity [7]. Some conserved residues associated with NTase activity were identified in some reports, including Gly-Ser in the P-loop motif and Asp in D-box [9,10]; these residues were obviously related to the OAS enzyme activity. There have been some reports that the mutation of two of three of the Asp residues in D-box can lead to loss of OAS protein enzyme activity, as identified in porcine
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
