title: ORF9p phosphorylation by ORF47p is crucial for the formation and egress of varicella-zoster virus viral particles.
abstract: The role of the tegument during the herpesvirus lytic cycle is still not clearly established, particularly at the late phase of infection, when the newly produced viral particles need to be fully assembled before being released from the infected cell. The varicella-zoster virus (VZV) protein coded by open reading frame (ORF) 9 (ORF9p) is an essential tegument protein, and, even though its mRNA is the most expressed during the productive infection, little is known about its functions. Using a GalK positive/negative selection technique, we modified a bacterial artificial chromosome (BAC) containing the complete VZV genome to create viruses expressing mutant versions of ORF9p. We showed that ORF9p is hyperphosphorylated during the infection, especially through its interaction with the viral Ser/Thr kinase ORF47p; we identified a consensus site within ORF9p recognized by ORF47p and demonstrated its importance for ORF9p phosphorylation. Strikingly, an ultrastructural analysis revealed that the mutation of this consensus site (glutamate 85 to arginine) strongly affects viral assembly and release, reproducing the ORF47 kinase-dead VZV phenotype. It also slightly diminishes the infectivity toward immature dendritic cells. Taken together, our results identify ORF9p as a new viral substrate of ORF47p and suggest a determinant role of this phosphorylation for viral infectivity, especially during the process of viral particle formation and egress.
authors.affiliation: University of Liege (ULg), GIGA-Infection Immunity and Inflammation, Laboratory of Virology and Immunology, Liege, Belgium.
authors.forename: Laura
authors.initials: L
authors.lastname: Riva
authors.forename: Marc
authors.initials: M
authors.lastname: Thiry
authors.forename: Sebastien
authors.initials: S
authors.lastname: Bontems
authors.forename: Aline
authors.initials: A
authors.lastname: Joris
authors.forename: Jacques
authors.initials: J
authors.lastname: Piette
authors.forename: Marielle
authors.initials: M
authors.lastname: Lebrun
authors.forename: Catherine
authors.initials: C
authors.lastname: Sadzot-Delvaux
mesh_terms: D045744:Cell Line, Tumor; D022202:Chromosomes, Artificial, Bacterial; D003713:Dendritic Cells / Q000276:immunology; D057809:HEK293 Cells; D014645:Herpesvirus 3, Human / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D006801:Humans; D009154:Mutation; D016366:Open Reading Frames; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism; D014771:Virion / Q000502:physiology / Q000648:ultrastructure; D019065:Virus Assembly; D057074:Virus Release; D014779:Virus Replication
chemical_list: C503396:ORF47 protein, varicella-zoster virus; D014764:Viral Proteins; D015678:Viral Structural Proteins; D011494:Protein Kinases