Baxter Shannon A, Cheung David Y, Bocangel Patricia, Kim Hae K, Herbert Krista, Douville Josette M, Jangamreddy Jaganmohan R, Zhang Shunzhen, Eisenstat David D, Wigle Jeffrey T
Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, Manitoba, Canada.
Biochim Biophys Acta. 2011 Jan;1813(1):201-12. doi: 10.1016/j.bbamcr.2010.10.015. Epub 2010 Oct 30.
The homeobox transcription factor PROX1 is essential for the development and maintenance of lymphatic vasculature. How PROX1 regulates lymphatic endothelial cell fate remains undefined. PROX1 has been shown to upregulate the expression of Cyclin E, which mediates the G(1) to S transition of the cell cycle. Here we demonstrate that PROX1 activates the mouse Cyclin E1 (Ccne1) promoter via two proximal E2F-binding sites. We have determined that the N-terminal region of PROX1 is sufficient to activate a 1-kb Ccne1 promoter, whereas the homeodomain is dispensable for activation. We have identified that the Prospero domain 1 (PD1) is required for the nuclear localization of PROX1. Our comparison of two DNA-binding-deficient constructs of PROX1 showed a cell-type-specific difference between these two proteins in both their localization and function. We demonstrated that siRNA-mediated knockdown of PROX1 in lymphatic endothelial cells decreases progression from G(1) to S phase of the cell cycle. We conclude that PROX1 activates the Ccne1 promoter independent of DNA binding, and our results illustrate a novel role for PROX1 in the regulation of lymphatic endothelial cell proliferation.
同源框转录因子PROX1对于淋巴管系统的发育和维持至关重要。PROX1如何调节淋巴管内皮细胞命运仍不明确。已表明PROX1可上调细胞周期蛋白E的表达，其介导细胞周期从G(1)期到S期的转变。在此我们证明PROX1通过两个近端E2F结合位点激活小鼠细胞周期蛋白E1（Ccne1）启动子。我们已确定PROX1的N端区域足以激活1 kb的Ccne1启动子，而同源结构域对于激活是可有可无的。我们已确定PROX1的Prospero结构域1（PD1）是PROX1核定位所必需的。我们对PROX1的两种DNA结合缺陷构建体的比较显示，这两种蛋白在定位和功能上存在细胞类型特异性差异。我们证明，在淋巴管内皮细胞中，siRNA介导的PROX1敲低可减少细胞周期从G(1)期到S期的进程。我们得出结论，PROX1独立于DNA结合激活Ccne1启动子，我们的结果阐明了PROX1在调节淋巴管内皮细胞增殖中的新作用。
