TIFA activates IκB kinase (IKK) by promoting oligomerization and ubiquitination of TRAF6
TIFA activates IκB kinase (IKK) by promoting oligomerization and ubiquitination of TRAF6
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DOI：
10.1073/pnas.0404132101
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发表时间：
2004-10-26
影响因子：
11.1
通讯作者：
Chen, ZJJ
中科院分区：
文献类型：
--
作者：
Ea, CK;Sun, L;Chen, ZJJ
TRAF 6（肿瘤坏死因子受体相关因子6）是一种RING（真正有趣的新基因）结构域泛素（Ub）连接酶，其通过催化通过Ub的Lys-63连接的独特的多聚泛素链的形成来介导蛋白激酶的活化，例如转化生长因子β激活激酶（TAK 1）和IkappaB激酶（IKK）。在这里，我们提出的证据表明，TIFA（TRAF相互作用蛋白与叉头相关的结构域，也被称为T2 BP）激活IKK通过促进寡聚化和Ub连接酶活性的TRAF 6。我们表明，重组TIFA蛋白，但不是TRAF 6结合缺陷的突变体，可以激活IKK粗胞质提取物。此外，TIFA在由纯化蛋白质组成的体外重建系统中激活IKK，所述纯化蛋白质包括TRAF 6、TAK 1激酶复合物和Ub-缀合酶复合物Ubc 13-Uev 1A。有趣的是，重组TIFA蛋白的一部分以高分子量寡聚体的形式存在，并且只有这些寡聚体形式的TIFA可以激活IKK。重要的是，TIFA诱导TRAM的寡聚化和多泛素化，这导致TAK 1和IKK通过蛋白酶体非依赖性机制激活。
TRAF6 (tumor necrosis factor receptor-associated factor 6) is a RING (really interesting new gene) domain ubiquitin (Ub) ligase that mediates the activation of protein kinases, such as transforming growth factor beta-activated kinase (TAK1) and IkappaB kinase (IKK), by catalyzing the formation of a unique polyubiquitin chain linked through Lys-63 of Ub. Here, we present evidence that TIFA (TRAF-interacting protein with a forkhead-associated domain, also known as T2BP) activates IKK by promoting the oligomerization and Ub ligase activity of TRAF6. We show that recombinant TIFA protein, but not TRAF6-binding-defective mutant, can activate IKK in crude cytosolic extracts. Furthermore, TIFA activates IKK in an in vitro reconstitution system consisting of purified proteins, including TRAF6, the TAK1 kinase complex, and Ub-conjugating enzyme complex Ubc13-Uev1A. Interestingly, a fraction of recombinant TIFA protein exists as high-molecular-weight oligomers, and only these oligomeric forms of TIFA can activate IKK. Importantly, TIFA induces the oligomerization and polyubiquitination of TRAM which leads to the activation of TAK1 and IKK through a proteasome-independent mechanism.