Nucleolin promotes in vitro translation of feline calicivirus genomic RNA

Feline calicivirus depends on host-cell proteins for its replication. We previously showed that knockdown of nucleolin (NCL), a phosphoprotein involved in ribosome biogenesis, resulted in the reduction of FCV protein synthesis and virus yield. Here, we found that NCL may not be involved in FCV binding and entry into cells, but it binds to both ends of the FCV genomic RNA, and stimulates its translation in vitro. AGRO100, an aptamer that specifically binds and inactivates NCL, caused a strong reduction in FCV protein synthesis. This effect could be reversed by the addition of full-length NCL but not by a ΔrNCL, lacking the N-terminal domain. Consistent with this, FCV infection of CrFK cells stably expressing ΔrNCL led to a reduction in virus protein translation. These results suggest that NCL is part of the FCV RNA translational complex, and that the N-terminal part of the protein is required for efficient FCV replication.