Regulation of respiratory syncytial virus nucleoprotein oligomerization by phosphorylation

The negative-sense RNA genome of respiratory syncytial virus (RSV) is encapsidated by the viral nucleoprotein N, forming a left-handed helical nucleocapsid which serves as template for the viral polymerase. Specific oligomerization of N along the viral genome necessitates a switch of conformation of N, from the neosynthesized monomeric and RNA-free N protein, named N⁰, to N-RNA oligomers. Although the binding of the N-terminal part of RSV phosphoprotein P plays the role of chaperone to impair RNA binding to N, N⁰-P interaction alone is not sufficient to prevent N oligomerization. Here, we explored the potential role of post translational modifications that could participate in the stability of N⁰. Among the post translational modifications specifically identified on recombinant monomeric N, we validated the presence of a phosphorylation site on residue Y88 of N which modulates N oligomerization. Our results suggest that RSV N oligomerization depends on the regulation by post translational modifications.