Center for Health Disparities Research and Molecular Medicine, Division of Biochemistry and Microbiology, Loma Linda University, Loma Linda, CA 92350, United States; Department of Basic Sciences, Division of Biochemistry and Microbiology, Loma Linda University, Loma Linda, CA 92350, United States.
Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263, United States.
Biochem Biophys Res Commun. 2014 Feb 28;445(1):208-13. doi: 10.1016/j.bbrc.2014.01.169. Epub 2014 Feb 4.
The mechanisms for regulation of the Inhibitor of Apoptosis (IAP) Survivin in cells undergoing stress associated with tumor development and the tumor microenvironment are not well understood. The stress response transcription factors HIF-1α and Yin Yang 1 (YY1) were hypothesized to contribute to the upregulation of Survivin in tumor cells. As expected, U2OS cells overexpressing HIF-1α showed a 2- to 3-fold transactivation when transfected. Surprisingly, when YY1 was overexpressed in this survivin promoter reporter system, luciferase expression was repressed 30- to 40-fold. YY1 involvement in survivin promoter repression was confirmed using siRNA directed against YY1. These studies showed that knockdown of YY1 releases the survivin promoter from the observed repression and leads to a 3- to 5-fold increase in promoter activity above basal levels. A U2OS cell line containing a stable YY1 Tet-off system was used to determine whether a temporal increase in YY1 expression affects Survivin protein levels. A low to moderate decrease in Survivin protein was observed 24h and 48h after Tet removal. Studies also confirmed that YY1 is capable of directly binding to the survivin promoter. Collectively, these findings identify novel basal transcriptional requirements of survivin gene expression which are likely to play important roles in the development of cancer and resistance to its treatment.
细胞在肿瘤发生和肿瘤微环境相关的应激条件下，凋亡抑制蛋白（IAP）Survivin 的调节机制尚不清楚。应激反应转录因子 HIF-1α 和 YY1 被假设有助于肿瘤细胞中 Survivin 的上调。正如预期的那样，过表达 HIF-1α 的 U2OS 细胞在转染时显示出 2-3 倍的转录激活。令人惊讶的是，当 YY1 在这个 Survivin 启动子报告系统中过表达时，荧光素酶表达被抑制了 30-40 倍。使用针对 YY1 的 siRNA 确认了 YY1 参与 Survivin 启动子抑制。这些研究表明，YY1 的敲低会使 Survivin 启动子从观察到的抑制中释放出来，并导致启动子活性比基础水平增加 3-5 倍。使用含有稳定 YY1 Tet-off 系统的 U2OS 细胞系来确定 YY1 表达的时间增加是否会影响 Survivin 蛋白水平。在 Tet 去除后 24h 和 48h 观察到 Survivin 蛋白的低到中度减少。研究还证实 YY1 能够直接结合 Survivin 启动子。总之，这些发现确定了 Survivin 基因表达的新的基础转录要求，这些要求可能在癌症的发展和对其治疗的抵抗中发挥重要作用。
