Interferon-stimulated gene 15 (ISG15) is a member of the family of ubiquitin-like proteins. Similar to ubiquitin, conjugation of ISG15 to cellular proteins requires cascade reactions catalyzed by at least 2 enzymes, UbE1L and UbcH8. Expression of ISG15 and its conjugates is up-regulated in many cancer cells, yet the underlying mechanism of up-regulation is still unclear. In this study, we showed that TNF-α, similar to the response by IFN-β, could directly induce expression of ISG15 and its conjugation machinery, UbE1L and UbcH8, in human lung carcinoma, A549. The early response of their expression was effectively blocked by specific inhibitors of p38 MAPK (SB202190) and JNK (SP600125), but not by B18R, a soluble type-I IFN receptor. In addition, luciferase reporter assay together with serial deletions and site-directed mutagenesis identified a putative C/EBPβ binding element in the ISG15 promoter, which is necessary to the response by TNF-α. Taken together, expression of ISG15 and ISG15 conjugation machinery in cancer cells is directly up-regulated by TNF-α via p38 MAPK and JNK pathways through the activation of C/EBPβ binding element in the ISG15 promoter. This study provides a new insight toward understanding the molecular mechanism of ISG15 system and inflammatory response in cancer progression.

中文翻译：

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肿瘤坏死因子-α通过p38 MAPK和JNK信号通路在人肺癌中上调干扰素刺激基因15及其结合机制、UbE1L和UbcH8表达。

干扰素刺激基因 15 (ISG15) 是泛素样蛋白家族的成员。与泛素类似，ISG15 与细胞蛋白的结合需要由至少 2 种酶 UbE1L 和 UbcH8 催化的级联反应。ISG15 及其结合物的表达在许多癌细胞中上调，但上调的潜在机制仍不清楚。在这项研究中，我们发现 TNF-α 与 IFN-β 的反应相似，可直接诱导人肺癌 A549 中 ISG15 及其结合机制 UbE1L 和 UbcH8 的表达。它们表达的早期反应被 p38 MAPK (SB202190) 和 JNK (SP600125) 的特异性抑制剂有效阻断，但不被可溶性 I 型 IFN 受体 B18R 阻断。此外，萤光素酶报告基因检测与连续缺失和定点诱变一起在 ISG15 启动子中鉴定了推​​定的 C/EBPβ 结合元件，这是 TNF-α 反应所必需的。总之，通过激活 ISG15 启动子中的 C/EBPβ 结合元件，TNF-α 通过 p38 MAPK 和 JNK 途径直接上调癌细胞中 ISG15 和 ISG15 缀合机制的表达。本研究为了解 ISG15 系统的分子机制和癌症进展中的炎症反应提供了新的见解。通过激活 ISG15 启动子中的 C/EBPβ 结合元件，TNF-α 通过 p38 MAPK 和 JNK 途径直接上调 ISG15 和 ISG15 缀合机制在癌细胞中的表达。本研究为了解 ISG15 系统的分子机制和癌症进展中的炎症反应提供了新的见解。通过激活 ISG15 启动子中的 C/EBPβ 结合元件，TNF-α 通过 p38 MAPK 和 JNK 途径直接上调 ISG15 和 ISG15 缀合机制在癌细胞中的表达。本研究为了解 ISG15 系统的分子机制和癌症进展中的炎症反应提供了新的见解。