Giannini Ana Lucia, Gao Yifang, Bijlmakers Marie-José
Department of Immunobiology, King's College London, 2nd Floor New Guy's House, Guy's Hospital, St Thomas Street, London SE1 9RT, UK.
Biochem J. 2008 Feb 15;410(1):101-11. doi: 10.1042/BJ20070995.
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.
最近发现的RNF125[RING（真的很有趣的新基因）指蛋白125]，即TRAC-1（激活时的T细胞RING蛋白1），在泛素连接酶中是独一无二的，它是T细胞激活的正调节因子。此外，TRAC-1已被证明可下调HIV复制并抑制病原体诱导的细胞因子产生。然而，除了存在一个N端C3HC4（半胱氨酸（3）-组氨酸-半胱氨酸（4））RING结构域外，TRAC-1蛋白仍未得到充分表征。在本文中，我们报告了TRAC-1的新相互作用和修饰，并阐明了其结构域组织。具体而言，我们确定TRAC-1与膜结合，并通过肉豆蔻酰化被排除在细胞核外。我们的数据进一步证明了C端在TRAC-1功能中的关键作用。在该区域，通过鉴定三种密切相关的蛋白RNF114、RNF138和RNF166识别出了新结构域。发现TRAC-1及其相关蛋白除了RING结构域外，还含有一个C2HC（半胱氨酸（2）-组氨酸-半胱氨酸）和两个C2H2（半胱氨酸（2）-组氨酸（2））型锌指，以及一个UIM（泛素相互作用基序）。TRAC-1的UIM结合赖氨酸（48）连接的多聚泛素链，并且与RING结构域一起是自身泛素化所必需的。作为自身泛素化的结果，TRAC-1的半衰期短于30分钟。这些新修饰、相互作用、结构域和相关蛋白的鉴定显著拓宽了研究TRAC-1活性和调节的背景。
