Cap-snatching inhibitors of influenza virus are inhibitory to the in vitro transcription of rice stripe virus

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Rice stripe virus (RSV) is one of the most important viral pathogens of rice in East Asia. The transcription of RSV is initiated by cap-snatching, a mechanism shared by influenza virus (IFV). This lends the possibility that antiviral compounds targeting the cap-snatching of IFV, many of which have been commercially available, may inhibit RSV transcription. A convenient and inexpensive system allowing researchers to test this idea, however, has been unavailable to date. Here, we show that purified RSV performs transcription in vitro and the transcription was readily detectable by nested reverse transcription-polymerase chain reaction (RT-PCR). With this system, we tested the effects of 2,4-dioxo-4-phenylbutanoic acid (DPBA) and pimodivir, two well-known IFV cap-snatching inhibitors, as well as ribavirin, a broad-spectrum antiviral compound whose targets remain elusive. In reaction mixtures containing 2.5 ng/µL of purified RSV, DPBA and pimodivir abolished RSV transcription at a concentration of 10 and 100 µM, respectively. In contrast, no inhibitory effect was detected from ribavirin, even at a concentration as high as 400 µM. These results suggest that at least some cap-snatching inhibitors of IFV are inhibitory to RSV transcription. These compounds, which can be identified with the experimental system described here, may serve as starting points in developing antivirals against RSV or related plant viruses.