title: E6AP ubiquitin ligase mediates ubiquitylation and degradation of hepatitis C virus core protein.
abstract: Hepatitis C virus (HCV) core protein is a major component of viral nucleocapsid and a multifunctional protein involved in viral pathogenesis and hepatocarcinogenesis. We previously showed that the HCV core protein is degraded through the ubiquitin-proteasome pathway. However, the molecular machinery for core ubiquitylation is unknown. Using tandem affinity purification, we identified the ubiquitin ligase E6AP as an HCV core-binding protein. E6AP was found to bind to the core protein in vitro and in vivo and promote its degradation in hepatic and nonhepatic cells. Knockdown of endogenous E6AP by RNA interference increased the HCV core protein level. In vitro and in vivo ubiquitylation assays showed that E6AP promotes ubiquitylation of the core protein. Exogenous expression of E6AP decreased intracellular core protein levels and supernatant HCV infectivity titers in the HCV JFH1-infected Huh-7 cells. Furthermore, knockdown of endogenous E6AP by RNA interference increased intracellular core protein levels and supernatant HCV infectivity titers in the HCV JFH1-infected cells. Taken together, our results provide evidence that E6AP mediates ubiquitylation and degradation of HCV core protein. We propose that the E6AP-mediated ubiquitin-proteasome pathway may affect the production of HCV particles through controlling the amounts of viral nucleocapsid protein.
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shirakura
authors.forename: Kyoko
authors.initials: K
authors.lastname: Murakami
authors.forename: Tohru
authors.initials: T
authors.lastname: Ichimura
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Suzuki
authors.forename: Tetsu
authors.initials: T
authors.lastname: Shimoji
authors.forename: Kouichirou
authors.initials: K
authors.lastname: Fukuda
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Abe
authors.forename: Shigeko
authors.initials: S
authors.lastname: Sato
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Fukasawa
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nishijima
authors.forename: Kohji
authors.initials: K
authors.lastname: Moriishi
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Takaji
authors.initials: T
authors.lastname: Wakita
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Peter M
authors.initials: PM
authors.lastname: Howley
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Miyamura
authors.forename: Ikuo
authors.initials: I
authors.lastname: Shoji
mesh_terms: D002460:Cell Line; D016174:Hepacivirus / Q000737:chemistry*; D006801:Humans; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism*; D014758:Viral Core Proteins / Q000378:metabolism*
chemical_list: D014452:Ubiquitins; D014758:Viral Core Proteins; D044767:Ubiquitin-Protein Ligases