Chang Yong-Gang, Yan Xian-Zhong, Xie Yuan-Yuan, Gao Xue-Chao, Song Ai-Xin, Zhang Dong-Er, Hu Hong-Yu
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
J Biol Chem. 2008 May 9;283(19):13370-7. doi: 10.1074/jbc.M800162200. Epub 2008 Mar 20.
ISG15 (interferon-stimulated gene 15) is a novel ubiquitin-like (UbL) modifier with two UbL domains in its architecture. We investigated different roles for the two UbL domains in protein modification by ISG15 (ISGylation) and the impact of Influenza B virus NS1 protein (NS1B) on regulation of the pathway. The results show that, although the C-terminal domain is sufficient to link ISG15 to UBE1L and UbcH8, the N-terminal domain is dispensable in the activation and transthiolation steps but required for efficient E3-mediated transfer of ISG15 from UbcH8 to its substrates. NS1B specifically binds to the N-terminal domain of ISG15 but does not affect ISG15 linkage via a thioester bond to its activating and conjugating enzymes. However, it does inhibit the formation of cellular ISG15 conjugates upon interferon treatment. We propose that the N-terminal UbL domain of ISG15 mainly functions in the ligation step and NS1B inhibits ISGylation by competing with E3 ligases for binding to the N-terminal domain.
ISG15（干扰素刺激基因15）是一种新型的类泛素（UbL）修饰因子，其结构中有两个UbL结构域。我们研究了这两个UbL结构域在ISG15介导的蛋白质修饰（ISGylation）中的不同作用，以及乙型流感病毒NS1蛋白（NS1B）对该途径调控的影响。结果表明，虽然C末端结构域足以将ISG15连接到UBE1L和UbcH8，但N末端结构域在激活和硫酯转移步骤中是可有可无的，但在E3介导的ISG15从UbcH8向其底物的有效转移过程中是必需的。NS1B特异性结合ISG15的N末端结构域，但不影响ISG15通过硫酯键与其激活酶和缀合酶的连接。然而，它确实会抑制干扰素处理后细胞内ISG15缀合物的形成。我们提出，ISG15的N末端UbL结构域主要在连接步骤中起作用，而NS1B通过与E3连接酶竞争结合N末端结构域来抑制ISGylation。
