Chou Y-T, Wang H, Chen Y, Danielpour D, Yang Y-C
Department of Pharmacology and Cancer Center, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4965, USA.
Oncogene. 2006 Sep 7;25(40):5547-60. doi: 10.1038/sj.onc.1209552. Epub 2006 Apr 17.
Cited (CBP/p300-interacting transactivators with glutamic acid (E)/aspartic acid (D)-rich C-terminal domain) 2, which is a CBP/p300-binding transcription co-activator without typical DNA-binding domains, has been implicated in control of cell growth and malignant transformation in Rat1 cells. In this report, we provide evidence that Cited2 is an important regulator of transforming growth factor (TGF)-beta signaling. Overexpression of Cited2 enhanced TGF-beta-mediated transcription of a Smad-Binding Element-containing luciferase reporter construct, SBE4-Luc. This may occur through a direct physical association of Cited2 with Smads 2 and 3, as supported by co-immunoprecipitation, mammalian two-hybrid and glutathione S-transferase-pull down assays. The transcription factor p300, which binds to Smad3, was shown to further enhance the interaction between Cited2 and Smad3, and the transcriptional responses of Smad3 by Cited2 in reporter assays. Cited2 enhances TGF-beta-mediated upregulation of matrix metalloproteinase 9 (MMP9) in Cited2 inducible mouse embryo fibroblasts. Overexpression of Cited2 enhanced TGF-beta-mediated MMP9 promoter reporter activity. Moreover, knockdown of Cited2 in MDA-MB-231 cells attenuated TGF-beta-mediated upregulation of MMP9 and TGF-beta-mediated cell invasion. Chromatin immunoprecipitation showed that Cited2 and Smad3 were recruited to MMP9 promoter upon TGF-beta stimulation. This is the first demonstration that Cited2 functions as a Smad3/p300-interacting transcriptional co-activator in modulating the expression of MMP9, which could affect tumor cell invasion mediated by TGF-beta.
富含谷氨酸（E）/天冬氨酸（D）的C末端结构域的CBP/p300相互作用反式激活因子2（Cited2）是一种不具有典型DNA结合结构域的CBP/p300结合转录共激活因子，已被证明参与大鼠1细胞的细胞生长控制和恶性转化。在本报告中，我们提供证据表明Cited2是转化生长因子（TGF）-β信号的重要调节因子。Cited2的过表达增强了TGF-β介导的含Smad结合元件的荧光素酶报告基因构建体SBE4-Luc的转录。这可能是通过Cited2与Smad 2和3的直接物理结合而发生的，免疫共沉淀、哺乳动物双杂交和谷胱甘肽S-转移酶下拉实验均支持这一点。与Smad3结合的转录因子p300被证明可进一步增强Cited2与Smad3之间的相互作用，以及在报告基因实验中Cited2对Smad3的转录反应。Cited2增强了Cited2诱导的小鼠胚胎成纤维细胞中TGF-β介导的基质金属蛋白酶9（MMP9）的上调。Cited2的过表达增强了TGF-β介导的MMP9启动子报告基因活性。此外，MDA-MB-231细胞中Cited2的敲低减弱了TGF-β介导的MMP9上调和TGF-β介导的细胞侵袭。染色质免疫沉淀显示，TGF-β刺激后，Cited2和Smad3被募集到MMP9启动子上。这首次证明Cited2作为Smad3/p300相互作用的转录共激活因子，在调节MMP9的表达中发挥作用，而MMP9的表达可能影响TGF-β介导的肿瘤细胞侵袭。
