Department of Pathology and Laboratory Medicine, Center for Cancer Research, Memphis, TN, USA.
EMBO J. 2011 Aug 2;30(18):3741-53. doi: 10.1038/emboj.2011.264.
The transcription factor nuclear factor κB (NF-κB) regulates various cellular processes such as inflammation and apoptosis. The NF-κB essential modulator (NEMO/IKKγ) is indispensable for NF-κB activation by diverse stimuli including genotoxic stress. Here, we show that NEMO linear ubiquitination on K285/309 is critical for genotoxic NF-κB activation. The E3 ligase linear ubiquitin chain assembly complex (LUBAC) facilitates NEMO linear ubiquitination upon genotoxic stress. Inhibiting LUBAC function interrupts the genotoxic NF-κB signalling cascade by attenuating the activation of IKK and TAK1 in response to DNA damage. We further show that the linear ubiquitination of NEMO is a cytoplasmic event, potentially downstream of NEMO nuclear exportation. Moreover, ELKS ubiquitination appears to facilitate linear ubiquitination of NEMO through stabilizing NEMO:LUBAC association upon DNA damage. Deubiquitinating enzyme CYLD inhibits NEMO linear ubiquitination, possibly by disassembling both K63-linked and linear polyubiquitin. We also found that abrogating linear ubiquitination of NEMO significantly increased genotoxin-induced apoptosis, resulting in enhanced sensitivity to chemodrug in cancer cells. Therefore, LUBAC-dependent NEMO linear ubiquitination is critical for genotoxic NF-κB activation and protects cells from DNA damage-induced apoptosis.
转录因子核因子 κB（NF-κB）调节多种细胞过程，如炎症和细胞凋亡。NF-κB 必需调节剂（NEMO/IKKγ）对于 NF-κB 的激活是必不可少的，其激活途径包括各种刺激，包括遗传毒性应激。在这里，我们表明，NEMO 的 K285/309 线性泛素化对于遗传毒性 NF-κB 的激活至关重要。E3 连接酶线性泛素链组装复合物（LUBAC）在遗传毒性应激下促进 NEMO 的线性泛素化。抑制 LUBAC 的功能通过减弱 IKK 和 TAK1 在 DNA 损伤后的激活，中断遗传毒性 NF-κB 信号级联。我们进一步表明，NEMO 的线性泛素化是一种细胞质事件，可能是在 NEMO 核输出之后发生的。此外，ELKS 泛素化似乎通过在 DNA 损伤时稳定 NEMO：LUBAC 复合物来促进 NEMO 的线性泛素化。去泛素化酶 CYLD 抑制 NEMO 的线性泛素化，可能通过拆开 K63 连接的和线性多泛素。我们还发现，NEMO 线性泛素化的缺失显著增加了遗传毒性诱导的细胞凋亡，从而导致癌细胞对化疗药物的敏感性增加。因此，LUBAC 依赖性 NEMO 线性泛素化对于遗传毒性 NF-κB 的激活至关重要，并保护细胞免受 DNA 损伤诱导的凋亡。
