Intracellular localization of rice stripe virus RNA-dependent RNA polymerase and its interaction with nucleocapsid protein.

The RNA-dependent RNA polymerase (RdRp) of rice stripe virus (RSV) is critical for both the transcription and replication of the viral genome. Despite its importance, little is known about how it functions in cells. In the present study, RSV RdRp was split into three pieces, since expression of the full protein could not be achieved. Then, the intracellular localization of these three RdRp fragments and their interactions with nucleocapsid protein (NP) were investigated, which is another viral protein required for viral RNA synthesis. The data showed that all three RdRp fragments displayed punctuate staining patterns in the cytoplasm, and the C-terminal fragment co-localized with NP in the perinuclear region. Both bimolecular fluorescence complementation and co-immunoprecipitation experiments demonstrated that of the three RdRp fragments, only the C-terminal fragment could interact with NP. Further analysis using a series of truncated NPs identified the N-terminal 50-amino-acid region within NP as the determinant for its interaction with the C-terminus of RdRp.