Direct activation of telomerase by EGF through Ets-mediated transactivation of TERT via MAP kinase signaling pathway
Direct activation of telomerase by EGF through Ets-mediated transactivation of TERT via MAP kinase signaling pathway
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DOI：
10.1038/sj.onc.1205509
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发表时间：
2002-06-13
期刊：
影响因子：
8
通讯作者：
Inoue, M
中科院分区：
文献类型：
--
作者：
Maida, Y;Kyo, S;Inoue, M
端粒酶是一种受调控的酶，其活性与细胞增殖密切相关。这种关联的机制尚不清楚，但特定的生长因子可能调节端粒酶活性。本研究探讨了表皮生长因子（EGF）对端粒酶活性的影响，并确定了参与这一过程的信号转导途径。EGF可上调EGF受体阳性细胞中端粒酶活性，激活端粒酶逆转录酶（TERT）mRNA的表达。这种激活是快速的，6或12小时后达到峰值，并没有被封锁的同时暴露于放线菌酮，这表明直接影响的EGF对TERT转录。瞬时表达分析表明，EGF激活hTERT启动子，近端核心启动子负责这种调节。EGF对hTERTmRNA表达的激活被MEK抑制剂特异性阻断，体外激酶测定表明ERK响应EGF而被激活。瞬时表达试验表明，突变体报告质粒的ETS基序位于核心启动子的hTERT的EGF诱导的反式激活所需的。野生型Ets在细胞中过表达增强EGF对hTERT转录的影响，而显性负性Ets显著抑制EGF的作用。这些研究结果表明，EGF通过直接激活TERT转录来激活端粒酶，其中Ras/MEK/ERK途径和Ets因子发挥主要作用。我们的数据支持生长因子通过特定的信号转导途径直接调节端粒酶的观点。
Telomerase is a regulated enzyme and its activity is tightly associated with cell proliferation. The mechanisms of this association are unclear, but specific growth factors may regulate telomerase activity. The present study examines the effect of epidermal growth factor (EGF) on telomerase activity and identifies the signal transduction pathway involved in this process. EGF upregulated telomerase activity in EGF receptor-positive cells after the activation of telomerase reverse transcriptase (TERT) mRNA expression. This activation was rapid, peaked after 6 or 12 h and was not blocked by the concurrent exposure to cycloheximide, suggesting a direct effect of EGF on TERT transcription. Transient expression assays revealed that EGF activates the hTERT promoter and that the proximal core promoter is responsible for this regulation. The activation of hTERT mRNA expression by EGF was specifically blocked by MEK inhibitor, and in vitro kinase assays demonstrated that ERK is activated in response to EGF. Transient expression assays using mutant reporter plasmids revealed that an ETS motif located in the core promoter of hTERT is required for the EGF-induced transactivation of hTERT. Overexpression of wild type Ets in cells enhanced the EGF effect on hTERT transcription, while that of dominant negative Ets significantly repressed EGF action. These findings suggest that EGF activates telomerase through the direct activation of TERT transcription, in which the Ras/MEK/ERK pathway and Ets factor play major roles. Our data support the notion that growth factors directly regulate telomerase via specific signal transduction pathways.