Shivakumar C V, Brown D R, Deb S, Deb S P
Department of Microbiology, University of Texas Health Science Center at San Antonio 78284, USA.
Mol Cell Biol. 1995 Dec;15(12):6785-93. doi: 10.1128/MCB.15.12.6785.
The wild-type p53 protein is a transcriptional activator implicated in the control of cellular growth-related gene expression. Here, using a number of different cell lines and transient-transfection-transcription assays, we demonstrate that at low levels, wild-type p53 transactivates the human proliferating cell nuclear antigen (PCNA) promoter. When expressed at a similar level, the tumor-derived p53 mutants did not transactivate the PCNA promoter. We identified a p53-binding site on the human PCNA promoter with which p53 interacts sequence specifically. When placed on a heterologous synthetic promoter, the binding site functions as a wild-type p53 response element in either orientation. Deletion of the p53-binding site renders the PCNA promoter p53 nonresponsive, showing that wild-type p53 transactivates the PCNA promoter by binding to the site. At a higher concentration, wild-type p53 inhibits the PCNA promoter but p53 mutants activate. Transactivation by p53 mutants does not require the p53-binding site. These observations suggest that moderate elevation of the cellular wild-type p53 level induces PCNA production to help in DNA repair.
野生型p53蛋白是一种转录激活因子，参与细胞生长相关基因表达的调控。在此，我们使用多种不同的细胞系和瞬时转染-转录分析方法，证明在低水平时，野生型p53可激活人增殖细胞核抗原（PCNA）启动子。当以相似水平表达时，肿瘤来源的p53突变体不能激活PCNA启动子。我们在人PCNA启动子上鉴定出一个p53结合位点，p53可与该位点进行特异性序列相互作用。当置于异源合成启动子上时，该结合位点在任一方向均可作为野生型p53反应元件发挥作用。删除p53结合位点会使PCNA启动子对p53无反应，表明野生型p53通过与该位点结合来激活PCNA启动子。在较高浓度时，野生型p53抑制PCNA启动子，但p53突变体则激活该启动子。p53突变体的转录激活不需要p53结合位点。这些观察结果表明，细胞野生型p53水平的适度升高可诱导PCNA产生，以帮助进行DNA修复。
