Stark Lesley A, Dunlop Malcolm G
Colon Cancer Genetics Group, University of Edinburgh Division of Oncology, MRC Human Genetics Unit, Western General Hospital, Crewe Rd., Edinburgh, Scotland.
Mol Cell Biol. 2005 Jul;25(14):5985-6004. doi: 10.1128/MCB.25.14.5985-6004.2005.
The molecular mechanisms that regulate nuclear NF-kappaB to determine whether the stimulation of this pathway has a pro- or anti-apoptotic effect on cells have yet to be fully defined. Nuclear compartmentalization is increasingly recognized as an important mechanism for regulating the activity of transcription-related proteins and modulating cell growth and death. We have investigated whether such compartmentalization serves as a mechanism for regulating NF-kappaB transcriptional activity. We demonstrate that the RelA component of NF-kappaB is sequestered in the nucleolus in response to the proapoptotic NF-kappaB stimuli aspirin, serum withdrawal, and UV-C radiation. In contrast, RelA is excluded from the nucleolus in response to the cytokines tumor necrosis factor and TRAIL. We identify an N-terminal motif of RelA that is essential for the nucleolar localization of the protein and show that deleting this motif inhibits the translocation of RelA from the nucleoplasm to the nucleolus. We demonstrate that the nucleolar accumulation of RelA is paralleled by a decrease in basal levels of NF-kappaB transcriptional activity and by apoptosis. Furthermore, we show that the retention of RelA in the nucleoplasm inhibits this decrease in NF-kappaB-driven transcription and blocks apoptosis induced by aspirin and UV-C radiation. This work identifies a novel cellular mechanism for regulating NF-kappaB-driven transcription and apoptosis, involving the nucleolar sequestration of a key NF-kappaB subunit. These data contribute to the understanding of the complexities of NF-kappaB function and have considerable relevance to cancer prevention and therapy.
调节细胞核内NF-κB以确定该信号通路的激活对细胞具有促凋亡还是抗凋亡作用的分子机制尚未完全明确。细胞核区室化越来越被认为是调节转录相关蛋白活性以及调控细胞生长和死亡的重要机制。我们研究了这种区室化是否作为一种调节NF-κB转录活性的机制。我们证明，响应促凋亡的NF-κB刺激物阿司匹林、血清剥夺和UV-C辐射，NF-κB的RelA亚基会被隔离在核仁中。相反，响应细胞因子肿瘤坏死因子和TRAIL时，RelA会被排除在核仁之外。我们鉴定出RelA的一个N端基序，该基序对于该蛋白的核仁定位至关重要，并表明删除该基序会抑制RelA从核质向核仁的转运。我们证明，RelA在核仁中的积累与NF-κB转录活性基础水平的降低以及细胞凋亡平行。此外，我们表明RelA保留在核质中会抑制NF-κB驱动的转录的这种降低，并阻断阿司匹林和UV-C辐射诱导的细胞凋亡。这项工作确定了一种调节NF-κB驱动的转录和细胞凋亡的新细胞机制，涉及关键NF-κB亚基的核仁隔离。这些数据有助于理解NF-κB功能的复杂性，并且与癌症预防和治疗具有相当大的相关性。
