Department of Biochemistry and Molecular Biology, Beijing Institute of Radiation Medicine, Beijing, China.
J Cell Physiol. 2011 Dec;226(12):3433-41. doi: 10.1002/jcp.22700.
Lung resistance-related protein (LRP) has roles in multi-drug resistance of tumor cells. Understanding the mechanisms that regulate LRP expression in tumor cells is an important research area. A putative p53 response element in the LRP promoter has been found. Thus, p53-related regulation of LRP expression was explored in this study. We first demonstrated that p53 overexpression inhibited LRP expression both at the protein and mRNA levels. Then, using a dual-luciferase reporter assay, we located the p53 response element to the Y-box (-263~-407) of the LRP promoter, the YB-1 binding site, but not the putative p53 response element. Furthermore, coimmunoprecipitation and chromatin immunoprecipitation showed p53 could bind to the Y-box of the LRP promoter through interaction of p53 with YB-1. YB-1 coexpression with p53 facilitated p53-induced suppression of endogenous LRP expression in MCF-7 cells. HDAC2, a corepressor of p53, was found to also interact with YB-1, and this interaction was mediated by p53. These results showed that the p53-HDAC2 transcriptional repressor complex can bind to the Y-box of the LRP promoter and repress LRP expression through interaction with YB-1. p53-related suppression of LRP expression was completely reversed by doxorubicin treatment and Adr, whereas CP and VP-16 treatment induced LRP expression increased significantly. Inhibition of LRP expression by siRNA facilitated Adr induced apoptosis of MCF-7 cells. All these findings indicated that loss of p53-related suppression of LRP may be the reason for LRP expression increase, and, therefore, chemotherapy resistance in tumor cells.
肺耐药相关蛋白（LRP）在肿瘤细胞的多药耐药中起作用。了解调节肿瘤细胞中 LRP 表达的机制是一个重要的研究领域。已经在 LRP 启动子中发现了一个假定的 p53 反应元件。因此，本研究探讨了 p53 相关的 LRP 表达调控。我们首先证明 p53 过表达在蛋白和 mRNA 水平均抑制 LRP 表达。然后，通过双荧光素酶报告基因检测，我们将 p53 反应元件定位到 LRP 启动子的 Y 盒（-263~-407），即 YB-1 结合位点，但不是假定的 p53 反应元件。此外，共免疫沉淀和染色质免疫沉淀表明，p53 可以通过 p53 与 YB-1 的相互作用结合到 LRP 启动子的 Y 盒上。YB-1 与 p53 共表达促进了 MCF-7 细胞中 p53 诱导的内源性 LRP 表达抑制。发现 p53 的核心抑制因子 HDAC2 也与 YB-1 相互作用，并且这种相互作用是由 p53 介导的。这些结果表明，p53-HDAC2 转录抑制复合物可以结合到 LRP 启动子的 Y 盒上，并通过与 YB-1 的相互作用抑制 LRP 的表达。阿霉素处理和 Adr 完全逆转了 p53 相关的 LRP 表达抑制，而 CP 和 VP-16 处理则显著诱导 LRP 表达增加。siRNA 抑制 LRP 表达促进了 MCF-7 细胞中 Adr 诱导的凋亡。所有这些发现表明，p53 相关抑制 LRP 的丧失可能是肿瘤细胞中 LRP 表达增加和化疗耐药的原因。
