Department of Dermatology, Oregon Health and Science University, Portland, Oregon, United States of America.
PLoS One. 2012;7(5):e37636. doi: 10.1371/journal.pone.0037636. Epub 2012 May 23.
Negative regulation of the NF-κB transcription factor is essential for tissue homeostasis in response to stress and inflammation. NF-κB activity is regulated by a variety of biochemical mechanisms including phosphorylation, acetylation, and ubiquitination. In this study, we provide the first experimental evidence that NF-κB is regulated by SUMOylation, where the RelA subunit of NF-κB is SUMOylated by PIAS3, a member of the PIAS (protein inhibitor of activated STAT) protein family with E3 SUMO ligase activity. PIAS3-mediated NF-κB repression was compromised by either RelA mutant resistant to SUMOylation or PIAS3 mutant defective in SUMOylation. PIAS3-mediated SUMOylation of endogenous RelA was induced by NF-κB activation thus forming a negative regulatory loop. The SUMOylation of endogenous RelA was enhanced in IκBα null as compared with wild type fibroblasts. The RelA SUMOylation was induced by TNFα but not leptomycin B mediated RelA nuclear translocation. Furthermore, RelA mutants defective in DNA binding were not SUMOylated by PIAS3, suggesting that RelA DNA binding is a signal for PIAS3-mediated SUMOylation. These results support a novel negative feedback mechanism for NF-κB regulation by PIAS3-mediated RelA SUMOylation.
NF-κB 转录因子的负调控对于组织应对应激和炎症的内稳态至关重要。NF-κB 的活性受到多种生化机制的调节，包括磷酸化、乙酰化和泛素化。在这项研究中，我们提供了第一个实验证据，证明 NF-κB 受到 SUMO 化的调节，其中 NF-κB 的 RelA 亚基被 PIAS3 SUMO 化，PIAS3 是具有 E3 SUMO 连接酶活性的 PIAS（激活 STAT 蛋白抑制剂）蛋白家族的成员。PIAS3 介导的 NF-κB 抑制作用被 RelA 突变体（对 SUMO 化有抗性）或 PIAS3 突变体（SUMO 化缺陷）削弱。PIAS3 介导的内源性 RelA 的 SUMO 化是由 NF-κB 激活诱导的，从而形成一个负反馈调节环。与野生型成纤维细胞相比，IκBα 缺失型细胞中的内源性 RelA SUMO 化增强。TNFα 诱导 RelA SUMO 化，但不是 Leptomycin B 介导的 RelA 核易位。此外，PIAS3 不能对 DNA 结合缺陷的 RelA 突变体进行 SUMO 化，这表明 RelA DNA 结合是 PIAS3 介导的 SUMO 化的信号。这些结果支持了一种新的负反馈机制，即 PIAS3 介导的 RelA SUMO 化调节 NF-κB。
