Our result showed that NSD206-230 dominantly localized at cytoplasm. Previous study showed that rec-ZHD210-230 (recombinant ZH548 encoding an in-frame truncation in NSs at 210-230) could induce IFN-b mRNA due to a lack of SAP30-binding domain in infected cells [26] . It was also shown that NSs binding to SAP30 is required for NSs filaments to target pericentromeric DNA and induce nuclear anomalies [78] . They described that rec-ZHD210-230 expresses a stable NSs protein located in the nucleus in the discussion [78] . Thus, it might be possible that NSs encoding 20 aa. does not change the nuclear localization. On the other hand, NSD6-30, NSD31-55, NSD56-80 and NSD249-265, all of which encode SAP30-binding domain at aa.210-130, could be accumulated in nucleus, whereas they did not inhibit IFN-b gene, suggesting that NSs has another structural requirement to inhibit IFN-b gene activation in addition to SAP30 binding. The requirement of NSs localization and IFN-b gene suppression should be further studied to understand the detailed mechanism of IFN-b gene regulation by RVFV NSs.