Rabies virus phosphoprotein interacts with ribosomal protein L9 and affects rabies virus replication

•RABV phosphoprotein (P) binds to L9 both in vitro and in vivo.•The central domain of P and the C terminus of L9 is essential for its interaction.•P stimulates the translocation of L9 from the nucleus to the cytoplasm.•Overexpression or knockdown of L9 affect RABV replication.

Rabies virus is a highly neurotropic virus that can cause fatal infection of the central nervous system in warm-blooded animals. The RABV phosphoprotein (P), an essential cofactor of the virus RNA-dependent RNA polymerase, is required for virus replication. In this study, the ribosomal protein L9, which has functions in protein translation, is identified as P-interacting cellular factor using phage display analysis. Direct binding between the L9 and P was confirmed by protein pull-down and co-immunoprecipitation analyses. It was further demonstrated that L9 translocates from the nucleus to the cytoplasm, where it colocalizes with P in cells infected with RABV or transfected with P gene. RABV replication was reduced with L9 overexpression and enhanced with L9 knockdown. Thus, we propose that during RABV infection, P binds to L9 that translocates from the nucleus to the cytoplasm, inhibiting the initial stage of RABV transcription.