PTEN通过抑制PI3K-AKT信号通路上调Rad51基因的表达

PTEN Upregulates Rad51 Gene Expression Through the Inhibition of PI3K-AKT Signal Pathway

前期研究发现pten缺陷细胞的自发DNA双链断裂损伤水平显著增加.本研究探讨了抑癌基因pten对参与DNA同源重组修复的rad51基因表达的影响和机制.用实时定量PCR技术检测了PTEN野生型和缺陷型细胞rad51的表达水平.结果发现,PTEN缺失会导致rad51的表达降低.PI3K激酶为PTEN的下游负调节靶分子,使用PI3K激酶抑制剂LY294002处理缺陷型细胞后,其rad51表达升高.在PTEN野生型细胞中分别转染Flag-Akt WT(野生型)和Flag-Akt AC(组成型激活),或在PTEN缺陷型细胞中分别转染野生型PTEN和Akt-DN(失去激酶活性的Akt).利用RT-PCR技术检测上述细胞rad51的表达水平,同时利用Western印迹检测上述细胞RAD51蛋白的表达水平.结果发现,转染Flag-Akt WT和Flag-Akt AC后,均能促使PTEN野生型细胞中rad51在mRNA和蛋白水平降低;在PTEN缺陷型细胞中转染野生型PTEN或Akt-DN后,rad51在mRNA和蛋白水平均升高.在PTEN缺陷型细胞中使用siRNA沉默akt后,同样导致RAD51表达升高.结果提示,PTEN可以正向调节RAD51基因表达,PI3K/Akt是其信号通路机制之一.

An increased level of spontaneous DNA double-strand breaks in Pten deficient cells was previously reported. Here we investigated whether and how the anti-oncogene pten may regulate the expression of rad51,a key component for homologous recombination in DNA double-strand break repairs.The rad51 mRNA level in the Pten -/- MEFs cells was down-regulated as shown by real-time PCR. After LY294002 （an antagonist of PTEN to inhibit PI3K） treatment,the RAD51 mRNA was increased. The transfection of Flag-Akt WT （Akt wild-type as the PI3K down-stream target） or Flag-AC （constitutively activated Akt） decreased the RAD51 at both mRNA and protein levels in Pten ＋/＋ MEFs cells. In contrast,the Pten WT or Akt-DN （inactivated Akt） transfection augmented levels of rad51 expression as compared to the cells transfected with the control Flag-Vec vector. The siRNA-mediated suppression of akt resulted in an increased expression of RAD51 protein in pten -/- MEFs cells. The results suggested that PTEN positively regulated rad51 expression,and the PI3K /Akt signaling pathway might be involved.