Goto Yuya, Hayashi Reiko, Kang Dongchon, Yoshida Kenichi
Department of Life Sciences, Meiji University Graduate School of Agriculture, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan.
J Cell Physiol. 2006 Dec;209(3):923-34. doi: 10.1002/jcp.20802.
Here, we sought to clarify the comprehensive cellular response to transcription factor E2F1 expression using short interfering RNA (siRNA)-mediated gene silencing to examine the roles of E2F1. For this purpose, we analyzed global gene expression changes in E2F1 knockdown HeLa cells, where no changes in cell growth or apoptosis were observed. Among the identified genes, the mRNA levels of mitochondria-encoded genes were highly elevated in E2F1 siRNA-treated cells, but not in E2F6 siRNA-treated cells, relative to control siRNA-treated cells. These changes were accompanied by a significant increase in the transcription and replication of mitochondria DNA as well as the induction of nuclear-encoded mitochondrial topoisomerase I (TOP1MT) mRNA in E2F1 knockdown cells, but not in E2F6 knockdown cells, whereas the levels of nuclear-encoded mitochondrial transcription factor A (TFAM) mRNA and protein were unchanged, relative to the levels in control siRNA-treated cells. Time-course experiments demonstrated that the induction of TOP1MT coincided with the timing of E2F1 loss. In addition, E2F1 knockdown cells, but not E2F6 knockdown cells, displayed increased ATP levels along with an accumulation of cytochrome b protein. Finally, RNA interference (RNAi)-mediated reduction in E2F1 knockdown HeLa cells, but not in E2F6 knockdown HeLa cells, resulted in increased anticancer drug sensitivity. Taken together, these data demonstrate a novel physiological aspect of E2F1 in human cancer cells, where activated mitochondrial biogenesis occurs as a consequence of the acute loss of E2F1.
在此，我们试图通过使用小干扰RNA（siRNA）介导的基因沉默来阐明对转录因子E2F1表达的全面细胞反应，以研究E2F1的作用。为此，我们分析了E2F1敲低的HeLa细胞中的全局基因表达变化，在这些细胞中未观察到细胞生长或凋亡的变化。在鉴定出的基因中，相对于对照siRNA处理的细胞，线粒体编码基因的mRNA水平在E2F1 siRNA处理的细胞中高度升高，但在E2F6 siRNA处理的细胞中未升高。这些变化伴随着线粒体DNA转录和复制的显著增加以及E2F1敲低细胞中核编码的线粒体拓扑异构酶I（TOP1MT）mRNA的诱导，但在E2F6敲低细胞中未观察到，而相对于对照siRNA处理细胞中的水平，核编码的线粒体转录因子A（TFAM）mRNA和蛋白质的水平没有变化。时间进程实验表明，TOP1MT的诱导与E2F1缺失的时间一致。此外，E2F1敲低细胞而非E2F6敲低细胞显示出ATP水平升高以及细胞色素b蛋白的积累。最后，RNA干扰（RNAi）介导的E2F1敲低HeLa细胞而非E2F6敲低HeLa细胞的减少导致抗癌药物敏感性增加。综上所述，这些数据证明了E2F1在人类癌细胞中的一个新的生理方面，即由于E2F1的急性缺失导致线粒体生物合成激活。
