UC San Diego

When influenza A releases its genomic segments into the cell, these segments travel to the nucleus where they are subsequently transcribed. As newly translated viral polymerase and nucleoprotein reach high levels, the virus switches from transcription to replication. Disruption of this regulation could endanger viral output hampering infection of the host. In our attempt to generate a genome mimetic based fluorescent flu reporter, we discovered a viral self loading mechanism in which the virus may be preventing compromised infection. We observed that naked RNA is incorporated well in a minigenome assay, but actively excluded during viral infection. This exclusion could be serving as a viral policing mechanism in which the virus actively excludes host naked RNA such as tRNA, rRNA, and snRNA. As a result, the virus would be utilizing most of its proteins allowing for maximum viral output. Through a series of experiments pre-expressing a variety of viral proteins before viral infection, polymerase components cotransfection, or nucleoprotein transfection, we discovered that NEP is an active factor that prevents viral inclusion of naked RNA. However, further analysis is required to determine the exact mechanism by which NEP mitigates this naked RNA exclusion, and whether other viral active factors are causing naked RNA exclusion.