Proteasome Inhibitor MG132 Induces BAG3 Expression Through Activation of Heat Shock Factor 1
Proteasome Inhibitor MG132 Induces BAG3 Expression Through Activation of Heat Shock Factor 1
复制标题
蛋白酶体抑制剂 MG132 通过激活热休克因子 1 诱导 BAG3 表达
DOI：
10.1002/jcp.21634
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发表时间：
2009-03-01
影响因子：
5.6
通讯作者：
Wang, Hua-Qin
中科院分区：
文献类型：
--
作者：
Du, Zhen-Xian;Zhang, Hai-Yan;Wang, Hua-Qin
BAG3蛋白是BAG共伴侣蛋白家族的一员，通过与热休克蛋白（HSP） 70、Bcl-2、raf - 1等多种伴侣蛋白的相互作用，维持多种正常和肿瘤细胞类型的细胞存活。热休克、重金属暴露等应激刺激可诱导BAG3的表达。我们已经报道蛋白酶体抑制剂也可以在转录水平诱导BAG3表达，并且诱导BAG3损害蛋白酶体抑制剂介导的细胞凋亡。然而，BAG3上调的分子机制尚未阐明。在本研究中，我们提供证据表明热休克转录因子I （HSFI）参与了蛋白酶体抑制剂MG132诱导BAG3的过程。我们将BAG 3基因的一系列不同长度的5'侧区插入荧光素酶报告载体中，发现MG132通过-326/—233和825/—689区域刺激启动子活性，这两个区域分别包含一个用于hsfi结合的热休克响应元件（HSE）。在MG132处理下，位点定向删除使报告基因活性增强。染色质免疫沉淀实验表明，HSFI直接结合到BAG3启动子上的mg132反应位点。MG132在BAG3上调的同时激活HSFI。此外，通过小干扰RNA敲除HSFI可减弱MG132引起的BAG3上调。这些结果表明。蛋白酶体抑制剂MG132通过激活HSFI诱导BAG3表达。
BAG3 protein, a member of the BAG co-chaperones family, sustains cell survival in a variety of normal and neoplastic cell types, via its interaction with a variety of partners, such as the heat shock protein (HSP) 70, Bcl-2, Raf-I and others. Expression of BAG3 is induced by some stressful stimuli, such as heat shock, heavy metal exposure. We have reported that proteasome inhibitors can also induce BAG3 expression at the transcriptional level and the induction of BAG3 compromises proteasome inhibitors-mediated apoptosis. However, the molecular mechanism of BAG3 upregulation has not been elucidated. In the current study, we provide evidence that heat shock transcription factor I (HSFI) is involved in BAG3 induction by proteasome inhibitor MG132. Using a series of varying lengths of 5'-flanking region of the BAG 3 gene into luciferase reporter vectors, we found that MG132 stimulated the promoter activity via the -326/--233 and 825/--689 regions, which contains one putative heat shock-responsive element (HSE) for HSFI-binding, respectively. Site-directed deletion of the sites abrogated the enhanced reporter activity in response to MG132 treatment. Chromatin immunoprecipitation assay demonstrated that HSFI directly bound to the MG132-responsive site on the BAG3 promoter. Activation of HSFI occurred with MG132 along with BAG3 upregulation. Furthermore, knockdown HSFI by small interfering RNA attenuated the BAG3 upregulation due to MG132. These results indicate that the. proteasome inhibitor MG132 induces BAG3 expression through HSFI activation.