Spatial, Quantitative and Functional Deconstruction of Virus and Host Protein Interactions Inside Intact Cytomegalovirus Particles

Viral infections involve packaging of the viral genome and proteins into virions. Knowing virion composition and structure is critical to understand viral pathogenesis. However, an integrated picture of virion proteome organization of large viruses, such as Herpesviruses, is lacking. Here we use cross-linking mass spectrometry to derive a spatially resolved structural interactome of intact human cytomegalovirus virions. We capture interactions of 82 host and 33 viral proteins, allowing us to de novo allocate them into distinct virion-layers and identify several host proteins as constitutive virion components recruited via specific protein interactions. The abundant viral protein pp150 forms domain-specific interactions with all virion layers and scaffolds numerous viral and host proteins such as PP1 phosphatase and 14-3-3 proteins, which are incorporated via nearby short linear motifs in pp150’s C-terminus. PP1 recruitment antagonizes 14-3-3 proteins and is pivotal during early and late viral replication steps. Collectively, this study gives a spatial and quantitative inventory of the system-wide organization and functional relevance of protein interactions inside native herpesvirus particles.