title: HTLV-1 Tax Induces Formation of the Active Macromolecular IKK Complex by Generating Lys63- and Met1-Linked Hybrid Polyubiquitin Chains.
abstract: The Tax protein of human T-cell leukemia virus type 1 (HTLV-1) is crucial for the development of adult T-cell leukemia (ATL), a highly malignant CD4+ T cell neoplasm. Among the multiple aberrant Tax-induced effects on cellular processes, persistent activation of transcription factor NF-κB, which is activated only transiently upon physiological stimulation, is essential for leukemogenesis. We and others have shown that Tax induces activation of the IκB kinase (IKK) complex, which is a critical step in NF-κB activation, by generating Lys63-linked polyubiquitin chains. However, the molecular mechanism underlying Tax-induced IKK activation is controversial and not fully understood. Here, we demonstrate that Tax recruits linear (Met1-linked) ubiquitin chain assembly complex (LUBAC) to the IKK complex and that Tax fails to induce IKK activation in cells that lack LUBAC activity. Mass spectrometric analyses revealed that both Lys63-linked and Met1-linked polyubiquitin chains are associated with the IKK complex. Furthermore, treatment of the IKK-associated polyubiquitin chains with Met1-linked-chain-specific deubiquitinase (OTULIN) resulted in the reduction of high molecular weight polyubiquitin chains and the generation of short Lys63-linked ubiquitin chains, indicating that Tax can induce the generation of Lys63- and Met1-linked hybrid polyubiquitin chains. We also demonstrate that Tax induces formation of the active macromolecular IKK complex and that the blocking of Tax-induced polyubiquitin chain synthesis inhibited formation of the macromolecular complex. Taken together, these results lead us to propose a novel model in which the hybrid-chain-dependent oligomerization of the IKK complex triggered by Tax leads to trans-autophosphorylation-mediated IKK activation.
authors.affiliation: Division of Cellular and Molecular Biology, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Yuri
authors.identifier: 0000-0003-4625-5722
authors.initials: Y
authors.lastname: Shibata
authors.affiliation: Department of Pathobiochemistry, Graduate School of Medicine, Osaka City University, Osaka, Japan.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Tokunaga
authors.affiliation: Department of Pathobiochemistry, Graduate School of Medicine, Osaka City University, Osaka, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Goto
authors.affiliation: Division of Cellular and Molecular Biology, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Ginga
authors.initials: G
authors.lastname: Komatsu
authors.affiliation: Research Center for Asian Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Jin
authors.identifier: 0000-0002-9929-9879
authors.initials: J
authors.lastname: Gohda
authors.affiliation: Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Saeki
authors.affiliation: Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Proteo-Science Center, Ehime University, Ehime, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Proteo-Science Center, Ehime University, Ehime, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sawasaki
authors.affiliation: Department of Anti-Aging Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Inoue
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oshiumi
authors.affiliation: Department of Microbiology and Immunology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
authors.affiliation: Department of Biochemistry, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Nakano
authors.affiliation: Division of Immunology, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan.
authors.forename: Yuetsu
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Department of Molecular and Cellular Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Iwai
authors.affiliation: Division of Cellular and Molecular Biology, Department of Cancer Biology, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Jun-Ichiro
authors.identifier: 0000-0001-6389-7036
authors.initials: JI
authors.lastname: Inoue
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000502:physiology*; D016356:Gene Products, tax / Q000378:metabolism*; D057809:HEK293 Cells; D015490:HTLV-I Infections / Q000378:metabolism*; D015368:Human T-lymphotropic virus 1 / Q000472:pathogenicity; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D019169:Jurkat Cells; D016328:NF-kappa B / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection
chemical_list: D016356:Gene Products, tax; D016328:NF-kappa B; D051550:I-kappa B Kinase