CtBP2 Promotes Human Cancer Cell Migration by Transcriptional Activation of Tiam1.
CtBP2 Promotes Human Cancer Cell Migration by Transcriptional Activation of Tiam1.
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DOI：
10.1177/1947601912463695
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发表时间：
2012-07-01
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影响因子：
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通讯作者：
Grossman, Steven R
中科院分区：
文献类型：
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作者：
Paliwal, Seema;Ho, Ngoc;Grossman, Steven R
哺乳动物羧基末端结合蛋白（CtBPs）CtBP 1和CtBP 2是代谢调节的转录辅阻遏物，其在急性暴露于替代阅读框架（ARF）肿瘤抑制物时降解。我们以前报道过CtBP在某些情况下通过抑制PTEN转录和激活磷脂酰肌醇3-激酶（PI 3 K）途径刺激细胞迁移。我们现在已经确定了CtBP通过调节T细胞淋巴瘤侵袭和转移1（Tiam 1）蛋白刺激细胞迁移的额外和直接机制。Tiam 1是Rac GT3的鸟嘌呤核苷酸交换因子（GEF），其在调节细胞粘附、侵袭和迁移中起关键作用，并直接参与促进癌症进展和转移。我们注意到CtBP 2和Tiam 1表达水平之间存在严格的正相关性，并且CtBP促进细胞迁移需要CtBP依赖的Tiam 1转录激活。RNA干扰（RNAi）介导的CtBP 2在人结肠癌或肺癌细胞中的敲低导致Tiam 1蛋白和mRNA表达降低，而CtBP 2的过表达增加Tiam 1表达水平。RNAi和过表达研究也表明Tiam 1是CtBP 2介导的细胞迁移的关键下游介质。对Tiam 1启动子的分析揭示了与CtBP相互作用的Kruppel样因子8（KLF 8）的结合位点，并且在KLF 8和CtBP 2存在的情况下诱导了Tiam 1启动子荧光素酶报告基因，这与Tiam 1的KLF 8依赖性CtBP反式激活一致。染色质免疫沉淀分析表明，CtBP 2占用的Tiam 1启动子，这是依赖于KLF 8的存在。我们的研究结果表明，Tiam 1是CtBP 2的转录激活靶点，这种相互作用促进了CtBP 2的促癌功能，导致癌细胞迁移。因此，转录激活与先前表征的CtBP共阻遏物功能一起沿着在CtBP促癌功能中起作用。
The mammalian COOH-terminal binding proteins (CtBPs) CtBP1 and CtBP2 are metabolically regulated transcriptional co-repressors that are degraded upon acute exposure to the alternative reading frame (ARF) tumor suppressor. We reported previously that CtBP stimulates cell migration in certain contexts via repression of PTEN transcription and activation of the phosphatidylinositol 3-kinase (PI3K) pathway. We have now identified an additional and direct mechanism for CtBP stimulation of cell migration via regulation of T-cell lymphoma invasion and metastasis 1 (Tiam1) protein. Tiam1 is a guanine nucleotide exchange factor (GEF) for Rac GTPase that plays a critical role in regulating cell adhesion, invasion, and migration and has been directly implicated in the promotion of cancer progression and metastasis. We noted a strict positive correlation between CtBP2 and Tiam1 expression levels and that CtBP promotion of cell migration required CtBP-dependent transcriptional activation of Tiam1. RNA interference (RNAi)-mediated knockdown of CtBP2 in human colon or lung carcinoma cells led to decreased Tiam1 protein and mRNA expression, while overexpression of CtBP2 increased Tiam1 expression levels. RNAi and overexpression studies also demonstrated that Tiam1 is a key downstream mediator of CtBP2-mediated cell migration. An analysis of the Tiam1 promoter revealed binding sites for the CtBP-interacting Kruppel-like factor 8 (KLF8), and a Tiam1 promoter luciferase reporter was induced in the presence of both KLF8 and CtBP2, consistent with KLF8-dependent CtBP transactivation of Tiam1. Chromatin immunoprecipitation analyses demonstrated CtBP2 occupancy of the Tiam1 promoter that was dependent on the presence of KLF8. Our results indicate that Tiam1 is a transcriptional activation target of CtBP2 and that this interaction promotes the pro-oncogenic function of CtBP2 leading to cancer cell migration. Transcriptional activation thus plays a role in CtBP pro-oncogenic functions along with the previously characterized CtBP co-repressor function.