Activation of the Interferon-Inducible (2′-5′) Oligoadenylate Synthetase by the Epstein–Barr Virus RNA, EBER-1

• Published in: Virology (New York, N.Y.) N.Y.), 1999-05, Vol.257 (2), p.303-313
• Main Authors: Sharp, Tyson V., Raine, Daniel A., Gewert, Dirk R., Joshi, Bhavesh, Jagus, Rosemary, Clemens, Michael J.
• Format: Article
• Language: English
• Subjects: 2',5'-Oligoadenylate Synthetase - genetics; 2',5'-Oligoadenylate Synthetase - metabolism; AIDS/HIV; Animals; Cell Line; Enzyme Activation; Epstein-Barr virus; Herpesvirus 4, Human - genetics; Humans; Interferon Inducers - metabolism; Interferons; Poly I-C - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA, Viral - metabolism; Spodoptera - cytology
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1006/viro.1999.9689

The 2′-5′ oligoadenylate synthetases and the protein kinase PKR are both interferon-induced, double-stranded RNA-dependent proteins that play important roles in the antiviral effects of the interferons and in cellular growth control. Both enzymes are activated by natural or synthetic dsRNAs and by single-stranded RNAs that possess extensive secondary structure. This report describes the effects of the small Epstein–Barr virus-encoded RNA EBER-1 on the regulation of 2–5(A) synthetase activity. We demonstrate that EBER-1 RNA binds to and activates the human 40-kDa 2–5(A) synthetase in a dose-dependent manner. The efficiency of EBER-1 as an activator of 2–5(A) synthetase is approximately 25% of that of the synthetic double-stranded RNA poly(I)/poly(C), and poly(I)/poly(C) further stimulates enzyme activity even in the presence of a high concentration of EBER-1. Conversely, EBER-1 neither stimulates nor inhibits 2–5(A) synthetase that has been activated by a high concentration of poly(I)/poly(C). Competitive binding assays suggest that the relative affinity of the enzyme for poly(I)/poly(C) is considerably higher than that for EBER-1. Our data indicate that EBER-1, like VAI RNA of adenovirus, TAR RNA of HIV-1, and Rex-RE RNA of HTLV-1, is able to activate the 2–5(A) synthetases. The significance of why several viruses may activate the 2–5(A) synthetase/RNase L-mediated RNA degradation pathway is discussed.