Interaction of severe acute respiratory syndrome (SARS) nucleocapsid protein with macrophage migration inhibitory factor protein (MIF)

The nucleocapsid (N) protein of SARS coronavirus (SARS-CoV) is a major structural component of virions, which appears to be a multifunctional protein involved in viral RNA replication and translation. However, how N protein interacts with host protein remains largely elusive. To identify cellular proteins that interact with the N protein and to elucidate the possible involvement of N protein in SARS-Cov replication and translation, a human lung cDNA library was screened using a yeast two-hybrid system assay. In this study, we have identified Macrophage migration inhibitory factor protein (MIF) as a novel interaction partner of N protein by yeast two-hybrid system. The direct interaction and co-localization of N protein with MIF were confirmed by immunoprecipitation and confocal microscopy analysis, respectively. The mapping studies localized the critical N sequences for this interaction to amino acid 140-210 including SR motif by yeast two-hybrid system. To the best of our knowledge, this is the first report that SARS-N protein interacts with the MIF within host cells, which enhance our understanding of the molecular mechanisms of SARS replication.