title: Varicella-zoster virus ORF49 functions in the efficient production of progeny virus through its interaction with essential tegument protein ORF44.
abstract: The ORF49 tegument protein of varicella-zoster virus (VZV) is one of the core gene products that is conserved among herpesvirus family members. Although ORF49 is known to be a cell-tropic factor, its detailed functions remain elusive. ORF44 is another core gene product reported to be essential, although its characterization and detailed functional analysis have not been reported. These two core gene products form a complex in other herpesviruses beyond the host species and herpesvirus subfamilies. Here, we show that complex formation between ORF44 and ORF49 is conserved in VZV. We serendipitously found that binding is eliminated by an amino acid substitution at position 129 (phenylalanine 129), and four amino acids in the carboxyl-terminal half of the acidic cluster in ORF49 (i.e., aspartate-phenylalanine-aspartate-glutamate from positions 41 to 44 [41DFDE44]) were identified as its binding motif. Alanine substitutions in each domain rendered the ORF44F129A mutation lethal for VZV, similar to deletion of the entire ORF44. The phenotype of the ORF49-41AAAA44 mutation was comparable to that of the ORF49-defective virus, including small-plaque formation, impaired growth, and low infectious virus production. These results suggest that the interaction between ORF44 and ORF49 is essential for their role in VZV infection and that ORF49 is required for the efficient production of infectious progeny virus mediated by the conserved interaction between the two proteins.
authors.affiliation: Division of Clinical Virology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kusunoki-cho, Chuo-ku, Kobe, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Sadaoka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Serada
authors.forename: Junko
authors.initials: J
authors.lastname: Kato
authors.forename: Mayuko
authors.initials: M
authors.lastname: Hayashi
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Gomi
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Naka
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamanishi
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Mori
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D014645:Herpesvirus 3, Human / Q000254:growth & development / Q000502:physiology*; D013058:Mass Spectrometry; D016366:Open Reading Frames; D010948:Viral Plaque Assay; D014764:Viral Proteins / Q000502:physiology*
chemical_list: D017931:DNA Primers; D014764:Viral Proteins