Chiu Yu-Hsin, Sun Qinmiao, Chen Zhijian J
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA.
Mol Cell. 2007 Sep 21;27(6):1014-23. doi: 10.1016/j.molcel.2007.08.020.
Ubiquitination is catalyzed by a cascade of enzymes consisting of E1, E2, and E3. We report here the identification of an E1-like protein, termed E1-L2, that activates both ubiquitin and another ubiquitin-like protein, FAT10. Interestingly, E1-L2 can transfer ubiquitin to Ubc5 and Ubc13, but not Ubc3 and E2-25K, suggesting that E1-L2 may be specialized in a subset of ubiquitination reactions. E1-L2 forms a thioester with FAT10 in vitro, and this reaction requires the active-site cysteine of E1-L2 and the C-terminal diglycine motif of FAT10. Furthermore, endogenous FAT10 forms a thioester with E1-L2 in cells stimulated with tumor necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma), which induce FAT10 expression. Silencing of E1-L2 expression by RNAi blocks the formation of FAT10 conjugates in cells. Deletion of E1-L2 in mice caused embryonic lethality, suggesting that E1-L2 plays an important role in embryogenesis.
泛素化由一系列由E1、E2和E3组成的酶催化。我们在此报告鉴定出一种类似E1的蛋白，称为E1-L2，它能激活泛素和另一种类泛素蛋白FAT10。有趣的是，E1-L2能将泛素转移至Ubc5和Ubc13，但不能转移至Ubc3和E2-25K，这表明E1-L2可能专门参与泛素化反应的一个子集。E1-L2在体外与FAT10形成硫酯，且该反应需要E1-L2的活性位点半胱氨酸和FAT10的C端双甘氨酸基序。此外，在内源性FAT10表达被肿瘤坏死因子-α（TNFα）和干扰素-γ（IFNγ）诱导的细胞中，内源性FAT10与E1-L2形成硫酯。通过RNA干扰使E1-L2表达沉默会阻断细胞中FAT10缀合物的形成。在小鼠中敲除E1-L2会导致胚胎致死，这表明E1-L2在胚胎发育中起重要作用。
