IDENTIFICATION OF THE SEQUENCE RESPONSIBLE FOR THE NUCLEAR ACCUMULATION OF THE INFLUENZA-VIRUS NUCLEOPROTEIN IN XENOPUS OOCYTES

Influenza virus nucleoprotein (NP), synthesized in Xenopus oocytes after injection of cloned NP c[complementary]DNA, enters and accumulates in the nucleus. In vitro mutagenesis of this cDNA was used to study the cellular distribution of mutated NP polypeptides. Mutants lacking amino acids 327-345 of wild-type NP enter the nucleus but do not accumulate there to the same extent as the wild-type protein, suggesting that this region has a role in nuclear accumulation. This possibility is further strengthened by similar studies involving the production of fusion proteins in which various amino-terminal sequences of the NP gene are fused to the complete chimpanzee .alpha.1-globin sequence: when globin cDNA was injected into and expressed in oocytes the protein remains exclusively in the cytosol; however, when the globin cDNA is fused to a portion of NP cDNA that includes the region encoding amino acids 327-345, the resulting fusion protein enters and accumulates in the nucleus. Fusion proteins lacking this region of the NP enter but do not accumulate in the nucleus.