NPI-1, the human homolog of SRP-1, interacts with influenza virus nucleoprotein.
We used the yeast interactive trap system to identify a cellular protein which interacts with the nucleoprotein of influenza A viruses. This protein, nucleoprotein interactor 1 (NPI-1) is the human homolog of the yeast protein SRP1. SRP1 was previously identified as a suppressor of temperature-sensitive RNA polymerase I mutations (R. Yano, M. Oakes, M. Yamaghishi, J. Dodd, and M. Nomura, Mol. Cell. Biol. 12, 5640-5651, 1992). A full-length cDNA clone of NPI-1 was generated from HeLa cell poly A + RNA. The viral nucleoprotein, which had been partially purified from influenza A/PR/8/34 virus-infected embryonated eggs, could be coprecipitated from solution by glutathione agarose beads complexed with a bacterially expressed glutathione-S-transferase-NPI-1 fusion protein, confirming the results of the yeast genetic system. Antisera raised against NPI-1 identified a 60-kDa polypeptide from total cellular extracts of both HeLa and MDBK cells. The viral nucleoprotein was coimmunoprecipitated from influenza A/WSN/33 virus-infected MDBK cells by anti-NPI-1 sera, demonstrating an interaction of these two proteins in infected cells. Similarly, NPI-1 was coimmunoprecipitated from MDBK cells by anti-NP sera. These experiments suggest that NPI-1 plays a role during influenza virus replication.
Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029.
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D009980:Influenza A virus / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins / Q000378:metabolism*; D011485:Protein Binding; D016601:RNA-Binding Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014758:Viral Core Proteins / Q000378:metabolism*; D028901:alpha Karyopherins
D018076:DNA, Complementary; C048842:NP protein, Influenza A virus; D009687:Nuclear Proteins; D019590:Nucleocapsid Proteins; D009698:Nucleoproteins; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins; D028901:alpha Karyopherins