Local changes in viral RNA sequence drive global changes in influenza nucleoprotein binding.

The genome of influenza A viruses (IAV) consists of eight negative-sense RNA segments that are coated by viral nucleoprotein (NP). Until recently, it was assumed that NP binds viral genomic RNA (vRNA) uniformly along the entire segment. However, genome-wide studies have revised the original model in that NP instead binds preferentially to certain regions of vRNA, while others are depleted for NP binding. Even strains with high sequence similarity exhibit distinct NP-binding profiles. Thus, it remains unknown how NP-binding specificity to vRNA is established. Here we introduced nucleotide changes to vRNA to examine whether primary sequence can affect NP binding. Our findings demonstrate that NP binding is indeed susceptible to sequence alterations, as NP peaks can be lost or appear de novo at mutated sites. Unexpectedly, nucleotide changes not only affect NP binding locally at the site of mutation, but also impact NP binding at distal regions that have not been modified. Taken together, our results suggest that NP binding is not regulated by primary sequence alone, but that a network formed by multiple segments governs the deposition of NP on vRNA.