T-cell regulator RNF125/TRAC-1 belongs to a novel family of ubiquitin ligases with zinc fingers and a ubiquitin-binding domain

Department of Immunobiology, King's College London, 2nd Floor New Guy's House, Guy's Hospital, St Thomas Street, London SE1 9RT, UK.
Biochemical Journal (Impact Factor: 4.4). 03/2008; 410(1):101-11. DOI: 10.1042/BJ20070995
Source: PubMed


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.

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Available from: Ana Giannini, Nov 14, 2014
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    • "Among those, we found UPF1, PABPC1, and PABPC4 to be interacting with MOV10 in an RNA-independent manner. In addition, we identified RNF166 belonging to a subfamily of RING ubiquitin ligases (Giannini et al., 2008) and the DEAD box RNA helicase eIF4A3, and the inhibitor of Moloney murine and HIV-1 viruses ZC3HAV1/ZAP (Zhu et al., 2011) as RNA-independent interactors. To confirm the interaction between MOV10 and UPF1, we performed reverse IP experiments using FLAG/HA-tagged UPF1 as bait and identified MOV10 as enriched in both crossover label-swap experiments (Figure 4C and Table S5). "
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    • "However, the precise mechanisms underlying this positional effect remain yet to be elucidated. Also, as the function of RNF166 in vivo is poorly understood, we can only speculate that the protein could constitute a link between TH and the regulation of ubiquitin ligation [35]. Nevertheless, the example of RNF166 demonstrates that mice expressing a tagged nuclear receptor isoform can be used for identifying novel DNA-binding sites in vivo, while circumventing the need for specific antibodies or artificial expression systems. "
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    • "Deletion of the UIM domain also does not affect MEKK1-dependent JNK activation, apoptosis or modification in our B cell reconstitution system. UIM regions contained in other proteins have been shown to directly interact with ubiquitin and can enhance the ubiquitination of these UIM-containing proteins [16], [25]. For example, auto-ubiquitination of TRAC-1 requires both its RING and UIM domains, as point mutations in either domain reduce the amount of ubiquitinated TRAC-1 [25]. "
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