Chen Xinpu, Qin Jun, Cheng Chiang-Min, Tsai Ming-Jer, Tsai Sophia Y
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Mol Endocrinol. 2012 Aug;26(8):1268-77. doi: 10.1210/me.2011-1305. Epub 2012 Jun 25.
Chicken ovalbumin upstream promoter transcription factor (COUP-TF)II has been shown to play a major role in endothelial cell growth and regulation of the Notch signaling pathway to confer vein identity. However, the underlying mechanisms for COUP-TFII regulation in these pathways remain to be defined. Here we employed a genomic approach by using microarray analysis to identify downstream targets in human umbilical vein endothelial cells (HUVEC) cells and found the expression of many genes in the cell cycle pathway and Notch signaling pathway are significantly altered in the COUP-TFII-depleted cells. The expression of E2F transcription factor 1 (E2F1), a key transcription factor that regulates the expression of cell cycle regulators, is reduced in the absence of COUP-TFII. Using chromatin immunoprecipitation experiments, we showed that COUP-TFII directly regulates the expression of E2F1 through tethering to the Sp1 binding sites in the promoter of E2F1 to modulate cell proliferation. In addition, we also demonstrate that Foxc1 and Np-1, two upstream genes of Notch signaling and Hey2, a downstream effector of Notch signaling, are direct targets of COUP-TFII. Furthermore, COUP-TFII suppresses the expression of EphrinB2, an arterial marker, while enhancing the expression of ephrin receptor B4, a venous marker, supporting our in vivo findings that COUP-TFII regulates vein identity by suppressing the Notch signal pathway.
鸡卵清蛋白上游启动子转录因子（COUP-TF）II已被证明在内皮细胞生长以及Notch信号通路调节中发挥主要作用，从而赋予静脉特性。然而，COUP-TFII在这些通路中的调控潜在机制仍有待确定。在此，我们采用基因组学方法，通过微阵列分析来鉴定人脐静脉内皮细胞（HUVEC）中的下游靶点，发现细胞周期通路和Notch信号通路中的许多基因表达在COUP-TFII缺失的细胞中发生了显著改变。E2F转录因子1（E2F1）是一种调节细胞周期调节因子表达的关键转录因子，在缺乏COUP-TFII时其表达降低。通过染色质免疫沉淀实验，我们表明COUP-TFII通过与E2F1启动子中的Sp1结合位点结合，直接调节E2F1的表达，从而调节细胞增殖。此外，我们还证明了Notch信号的两个上游基因Foxc1和Np-1以及Notch信号的一个下游效应分子Hey2是COUP-TFII的直接靶点。此外，COUP-TFII抑制动脉标志物EphrinB2的表达，同时增强静脉标志物ephrin受体B4的表达，这支持了我们的体内研究结果，即COUP-TFII通过抑制Notch信号通路来调节静脉特性。
