title: T-cell regulator RNF125/TRAC-1 belongs to a novel family of ubiquitin ligases with zinc fingers and a ubiquitin-binding domain.
abstract: The recently identified RNF125 [RING (really interesting new gene) finger protein 125], or TRAC-1 (T-cell RING protein in activation 1), is unique among ubiquitin ligases in being a positive regulator of T-cell activation. In addition, TRAC-1 has been shown to down-modulate HIV replication and to inhibit pathogen-induced cytokine production. However, apart from the presence of an N-terminal C3HC4 (Cys(3)-His-Cys(4)) RING domain, the TRAC-1 protein remains uncharacterized. In the present paper, we report novel interactions and modifications for TRAC-1, and elucidate its domain organization. Specifically, we determine that TRAC-1 associates with membranes and is excluded from the nucleus through myristoylation. Our data are further consistent with a crucial role for the C-terminus in TRAC-1 function. In this region, novel domains were recognized through the identification of three closely related proteins: RNF114, RNF138 and RNF166. TRAC-1 and its relatives were found to contain, apart from the RING domain, a C2HC (Cys(2)-His-Cys)- and two C2H2 (Cys(2)-His(2))-type zinc fingers, as well as a UIM (ubiquitin-interacting motif). The UIM of TRAC-1 binds Lys(48)-linked polyubiquitin chains and is, together with the RING domain, required for auto-ubiquitination. As a consequence of auto-ubiquitination, the half-life of TRAC-1 is shorter than 30 min. The identification of these novel modifications, interactions, domains and relatives significantly widens the contexts for investigating TRAC-1 activity and regulation.
authors.affiliation: Department of Immunobiology, King's College London, 2nd Floor New Guy's House, Guy's Hospital, St Thomas Street, London SE1 9RT, UK.
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Giannini
authors.forename: Yifang
authors.initials: Y
authors.lastname: Gao
authors.forename: Marie-José
authors.initials: MJ
authors.lastname: Bijlmakers
mesh_terms: D001665:Binding Sites; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D056971:Nuclear Receptor Co-Repressor 1; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: C539127:NCOR1 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D012097:Repressor Proteins; D025801:Ubiquitin