Chimeric NP non coding regions between type A and C influenza viruses reveal their role in translation regulation.

Exchange of the non coding regions of the NP segment between type A and C influenza viruses was used to demonstrate the importance not only of the proximal panhandle, but also of the initial distal panhandle strength in type specificity. Both elements were found to be compulsory to rescue infectious virus by reverse genetics systems. Interestingly, in type A influenza virus infectious context, the length of the NP segment 5′ NC region once transcribed into mRNA was found to impact its translation, and the level of produced NP protein consequently affected the level of viral genome replication.