Potential coupling between SARS-CoV-2 replicative fitness and interactions of its nucleoprotein with human 14-3-3 proteins

Abstract

AbstractThe SARS-CoV-2 nucleocapsid protein (N) is responsible for the viral genome packaging and virion assembly. Being highly abundant in the host cell, N interacts with numerous human proteins and undergoes multisite phosphorylation in vivo. When phosphorylated within its Ser/Arg-rich region, a tract highly prone to mutations as exemplified in the Omicron and Delta variants, N recruits human 14-3-3 proteins, potentially hijacking their functions. Here, we show that in addition to phosphorylated Ser197, an alternative, less conserved phosphosite at Thr205, absent in SARS-CoV N, binds 14-3-3 with micromolar affinity and is in fact the preferred binding site. Fluorescence anisotropy reveals a distinctive pT205/pS197 binding selectivity towards the seven human 14-3-3 isoforms. While explaining the structural basis for the discovered selectivity towards SARS-CoV-2 N phosphopeptides, our crystal structures enable prediction of N interactions with 14-3-3, suggesting a link between the strength of this interaction and replicative fitness of emerging coronavirus variants.