Genome Packaging Mechanism of Influenza A Virus
Abstract: Influenza A virus genome consists of eight-segmented, single-stranded, negative-sense RNAs. Each genomic viral RNA segment (vRNA) forms a ribonucleoprotein (RNP) complex together with viral nucleoproteins and an RNA polymerase complex. Later in infection, progeny virions, which are released from plasm membrane of infected-cell, must incorporate eight separate vRNAs to be infectious. However, the mechanism how the segmented vRNAs are incorporated into each progeny virion remains unclear. To elucidate the genome packaging mechanism of influenza A virus, we examined the architecture of RNPs within progeny virions by using electron microscopic analyses. We demonstrated that each progeny virion incorporates eight RNPs arranged in a specific pattern, in which seven RNPs surround the central one. In addition, there seem to be physical interactions among eight RNPs via nucleic acid-like structures, suggesting that there are specific interactions among eight vRNAs in the form of RNPs. These results indicate that influenza A virion selectively packages a complete set of eight separate vRNAs.
Key words: Influenza A virus, genome packaging, transmission electron microscopy