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Influenza A virus ribonucleoprotein complex (RNP) is responsible for viral genome replication, thus playing essential roles in the virus life cycle. RNP formation occurs in the nuclei of infected cells; however, little is known about the nuclear domains involved in this process.

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The influenza A virus genome is composed of eight single-stranded negative-sense RNA segments (vRNAs). The eight vRNAs are selectively packaged into each progeny virion. This process likely involves specific interactions between the vRNAs via segment-specific packaging signals located in both the 3' and 5' terminal regions of the respective vRNAs. To assess the importance of vRNA–vRNA interactions via packaging signals for selective genome packaging, we generated mutant viruses possessing silent mutations in the packaging signal region of the hemagglutinin (HA) vRNA. A mutant virus possessing silent mutations in nucleotides 1664 to 1676 resulted in defects in HA vRNA incorporation and showed a reduction in viral growth. After serial passage, the mutant virus acquired additional mutations in the 5' terminal packaging signal regions of both the HA and polymerase basic 2 (PB2) vRNAs. These mutations contributed to the recovery of viral growth and HA vRNA packaging efficiency. In addition, an RNA–RNA interaction between the 5' ends of HA and PB2 vRNAs was confirmed in vitro , and this interaction was disrupted following the introduction of silent mutations in the HA vRNA. Thus, our results demonstrated that RNA–RNA interactions between the packaging signal regions of HA vRNA and PB2 vRNA are important for selective genome packaging. Importance While numerous viral genomes comprise a single genome segment, the influenza A virus possesses eight segmented genomes. Influenza A virus can benefit from having a segmented genome because the segments can reassort with other strains of the influenza virus to create new genetically distinct strains. The influenza A virus efficiently incorporates one copy of each of its eight genomic segments per viral particle. However, the mechanism by which each segment is specifically selected is poorly understood. The genome segments contain RNA signals that facilitate the incorporation of segments into virus particles. These regions may facilitate specific interactions between the genome segments, creating an eight-segment complex, which can then be packaged into individual particles. In this study, we provide evidence that RNA signals contribute to specific interactions between two of the influenza virus genome segments.

Some bicyclic ethers containing a cyclopropane ring, i.e., 3-oxabicyclo [3.1.0] hexane derivatives, have been synthesized. Two methods have been used in the syntheses of these compounds. One of them has been the dehydration of cis-1,2-dimethylolcyclopropane derivatives, and the other, the addition of some carbenes to 2,5-dihydrofuran. The Simmons-Smith method has also been adopted. The NMR spectra of these bicyclic ethers have been examined. The types of their spectra are fairly simple. The chemical shifts and the coupling constant of some protons have also been measured. Attempts to polymerize these bicyclic ethers, unfortunately, have been unsuccessful.