Multimolecular complex of Par-4 and E2F1 binding to Smac promoter contributes to glutamate-induced apoptosis in human-bone mesenchymal stem cells

Neural cells undergo glutamate-induced apoptosis in ischaemic brain tissue,in which prostate apoptosis response-4 gene (Par-4)is involved.Human-bone mesenehymal stem cells can be utilized as an effective therapy for ischemic brain injury.In this study,we found that glutamate could induce apoptosis in human-bone mesenehymal stem cells,accompanied by increased expression of Par-4 gene and Smac release from mitochondria.Repressing Par-4 expression attenuated the glutamate-induced apoptosis.Both Par-4 protein and E2F1 protein could bind to E2F1-binding BS3 site on Smac promoter and participated in the formation of a pro- teins-DNA complex.Moreover,in the eomplex,E2F1,not Par-4,was found to be directly bound to the Smac promoter,suggesting that Par-4 exerted indireetly its transcriptional control on the Smac gene though interacting with E2F1.Expression of full-length Par-4 in human-bone mesenchymal cells resulted in increased activity of the Smac promoter.In addition,the indirect transcripional regula- tion of Par-4 on Smac depended on its COOH terminus-mediated interaction between Par-4 and E2F1.We conclude that the forma- tion of proteins-DNA complex,containing Par-4 protein,E2F1 protein and the Smac promoter,contributes to the pro-apoptotic effect on glutamate-treated human-bone mesenchymal stem cells.

Neural cells undergo glutamate-induced apoptosis in ischaemic brain tissue, in which prostate apoptosis response-4 gene （Par-4） is involved. Human-bone mesenchymal stem cells can be utilized as an effective therapy for isehemic brain injury. In this study, we found that glutamate could induce apoptosis in human-bone mesenchymal stem cells, accompanied by increased expression of Par-4 gene and Smae release from mitochondria. Repressing Par-4 expression attenuated the glutamate-induced apoptosis. Both Par-4 protein and E2F1 protein could bind to E2F1-binding BS3 site on Smac promoter and participated in the formation of a pro- teins-DNA complex. Moreover, in the complex, E2F1, not Par-4, was found to be directly bound to the Smac promoter, suggesting that Par-4 exerted indirectly its transcriptional control on the Smac gene though interacting with E2F1. Expression of full-length Par-4 in human-bone mesenchymal cells resulted in increased activity of the Smac promoter. In addition, the indirect transcfipional regulation of Par-4 on Smac depended on its COOH terminus-mediated interaction between Par-4 and E2F1. We conclude that the formation of proteins-DNA complex, containing Par-4 protein, E2F1 protein and the Smac promoter, contributes to the pro-apoptotic effect on glutamate-treated human-bone mesenchymal stem cells.