Staufen1 (Stau1), a host cellular protein, along with non-structural protein 1 (NS1), an influenza viral protein, associate with each other during influenza viral infection and down-regulation of Stau1 by RNA interference reduces the yield of influenza A virus, suggesting a role for Stau1 in viral replication. In order to develop a new tool to control influenza A virus, we determined the specific regions of Staufen1 protein involved in the interaction with NS1. The linker between RBD3 and 4 was isolated as the binding regions. Expression of RBD3L, the linker including RBD3, inhibited the interaction between Stau1 and NS1, reducing the colocalization of the two proteins in the cytosol and nucleus regions. In addition, yield of influenza A virus in RBD3L-expressing cells was significantly reduced 36 h after infection. These results suggest that disruption of the Stau1-NS1 interaction can be used to control replication of influenza A virus, thereby providing a target for the development of antiviral drugs. (C) 2011 Elsevier Inc. All rights reserved.