Zhang Bao-Le, Ni Hai-Bo, Liu Jie, Lei Yu, Li Heng, Xiong Ye, Yao Ruiqin, Yu Zheng-Quan, Gao Dian-Shuai
Department of Neurobiology and Anatomy, Xuzhou Medical College, Xuzhou 221004, Jiangsu, China.
Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu, China.
Biochim Biophys Acta. 2014 Nov;1839(11):1161-9. doi: 10.1016/j.bbagrm.2014.08.014. Epub 2014 Sep 6.
Abnormally high transcription of the glial cell-line derived neurotrophic factor (gdnf) gene in glioma cells is related to the hyperacetylation of histone H3 lysine 9 (H3K9) in its promoter region II, but the mechanism remains unclear. There are three consecutive putative binding sites for the transcription factor early growth response protein 1(Egr-1) in promoter region II of the gdnf gene, and Egr-1 participates in gdnf gene transcription activation. Here we show that the acetylation level of H3K9 at Egr-1 binding sites in gdnf gene promoter region II in rat C6 astroglioma cells was significantly higher than that in normal astrocytes, and the binding capacity was also significantly higher. In C6 astroglioma cells, gdnf gene transcription significantly decreased after Egr-1 knock-down. In addition, the deletion or mutation of the Egr-1 binding site also significantly down-regulated the activity of promoter region II of this gene in vitro. When curcumin decreased the acetylation level of H3K9 at the Egr-1 binding site, the binding of Egr-1 to promoter region II and GDNF mRNA levels significantly decreased. In contrast, trichostatin A treatment significantly increased H3K9 acetylation at the Egr-1 binding site, which significantly increased both the binding of Egr-1 with promoter region II and GDNF mRNA levels. In this context, knocking down Egr-1 significantly reduced the elevation in gdnf gene transcription. Collectively, our results demonstrate that the hyperacetylation of H3K9 at Egr-1 binding sites in promoter region II of the gdnf gene can up-regulate the binding of Egr-1 to increase gdnf gene transcription in glioma cells.
神经胶质瘤细胞中胶质细胞源性神经营养因子（gdnf）基因的异常高转录与其启动子区域II中组蛋白H3赖氨酸9（H3K9）的高乙酰化有关，但其机制尚不清楚。gdnf基因启动子区域II中有三个连续的转录因子早期生长反应蛋白1（Egr-1）推定结合位点，且Egr-1参与gdnf基因转录激活。在此我们表明，大鼠C6星形胶质瘤细胞中gdnf基因启动子区域II中Egr-1结合位点处H3K9的乙酰化水平显著高于正常星形胶质细胞，且结合能力也显著更高。在C6星形胶质瘤细胞中，Egr-1敲低后gdnf基因转录显著降低。此外，Egr-1结合位点的缺失或突变在体外也显著下调了该基因启动子区域II的活性。当姜黄素降低Egr-1结合位点处H3K9的乙酰化水平时，Egr-1与启动子区域II的结合及GDNF mRNA水平显著降低。相反，曲古抑菌素A处理显著增加了Egr-1结合位点处H3K9的乙酰化，这显著增加了Egr-1与启动子区域II的结合及GDNF mRNA水平。在此情况下，敲低Egr-1显著降低了gdnf基因转录的升高。总体而言，我们的结果表明，gdnf基因启动子区域II中Egr-1结合位点处H3K9的高乙酰化可上调Egr-1的结合以增加神经胶质瘤细胞中gdnf基因的转录。
