Ren Jinyu, Shi Mingan, Liu Renshui, Yang Qi-Heng, Johnson Teri, Skarnes William C, Du Chunying
Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):565-70. doi: 10.1073/pnas.0408744102. Epub 2005 Jan 7.
Baculoviral inhibitor of apoptosis repeat-containing (Birc)6 gene/BIRC6 (Bruce/APOLLON) encodes an inhibitor of apoptosis and a chimeric E2/E3 ubiquitin ligase in mammals. The physiological role of Bruce in antiapoptosis is unknown. Here, we show that deletion of the C-terminal half of Bruce, including the UBC domain, causes activation of caspases and apoptosis in the placenta and yolk sac, leading to embryonic lethality. This apoptosis is associated with up-regulation and nuclear localization of the tumor suppressor p53 and activation of mitochondrial apoptosis, which includes up-regulation of Bax, Bak, and Pidd, translocation of Bax and caspase-2 onto mitochondria, release of cytochrome c and apoptosis-inducing factor, and activation of caspase-9 and caspase-3. Mutant mouse embryonic fibroblasts are sensitive to multiple mitochondrial death stimuli but resistant to TNF. In addition, eliminating p53 by RNA interference rescues cell viability induced by Bruce ablation in human cell line H460. This viability preservation results from reduced expression of proapoptotic factors Bax, Bak, and Pidd and from prevention of activation of caspase-2, -9, and -3. The amount of second mitochondrial-derived activator of caspase and Omi does not change. We conclude that p53 is a downstream effector of Bruce, and, in response to loss of Bruce function, p53 activates Pidd/caspase-2 and Bax/Bak, leading to mitochondrial apoptosis.
杆状病毒凋亡抑制重复序列包含（Birc）6基因/BIRC6（Bruce/APOLLON）在哺乳动物中编码一种凋亡抑制因子以及一种嵌合的E2/E3泛素连接酶。Bruce在抗凋亡中的生理作用尚不清楚。在此，我们表明缺失Bruce的C端一半，包括UBC结构域，会导致胎盘和卵黄囊中半胱天冬酶激活和细胞凋亡，从而导致胚胎致死。这种细胞凋亡与肿瘤抑制因子p53的上调和核定位以及线粒体凋亡的激活有关，线粒体凋亡包括Bax、Bak和Pidd的上调，Bax和半胱天冬酶-2转位到线粒体上，细胞色素c和凋亡诱导因子的释放，以及半胱天冬酶-9和半胱天冬酶-3的激活。突变的小鼠胚胎成纤维细胞对多种线粒体死亡刺激敏感，但对肿瘤坏死因子（TNF）有抗性。此外，通过RNA干扰消除p53可挽救人细胞系H460中Bruce缺失诱导的细胞活力。这种活力的保留是由于促凋亡因子Bax、Bak和Pidd的表达降低以及半胱天冬酶-2、-9和-3的激活被阻止。半胱天冬酶的第二种线粒体衍生激活剂和Omi的量没有变化。我们得出结论，p53是Bruce的下游效应物，并且响应于Bruce功能的丧失，p53激活Pidd/半胱天冬酶-2和Bax/Bak，导致线粒体凋亡。
