Phosphorylation is involved in the activation of metal-regulatory transcription factor 1 in response to metal ions
Phosphorylation is involved in the activation of metal-regulatory transcription factor 1 in response to metal ions
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DOI：
10.1074/jbc.m108313200
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发表时间：
2001-11-09
影响因子：
4.8
通讯作者：
Séguin, C
中科院分区：
文献类型：
--
作者：
LaRochelle, O;Gagné, V;Séguin, C
我们研究了磷酸化在金属调节转录因子-1 (MTF-1) 和金属硫蛋白 (MT) 基因表达激活中的作用。我们发现 MTF-1 在体内被磷酸化，并且锌刺激 MTF-1 磷酸化 2-4 倍。使用几种激酶抑制剂来检查激酶级联在 MTF-1 激活中的可能参与。通过 Northern 分析和使用金属调节元件-荧光素酶报告质粒的共转染实验测定，金属诱导的 MT 基因表达被蛋白激酶 C (PKC)、c-Jun N 末端激酶 (JN-K)、磷酸肌醇 3-激酶和酪氨酸特异性蛋白激酶抑制剂消除。细胞外信号激活蛋白激酶和 p38 激酶级联似乎对于金属激活 Aff 基因转录不是必需的。通过使用 PKC、JNK、丝裂原激活激酶激酶 4 (MKK4) 和 MKK7 的显性失活突变体，我们提供了进一步的证据支持 PKC 和 JNK 在金属反应激活 MTF-1 中的作用。值得注意的是，尽管 MTF-1 介导的基因表达受到强烈抑制，但在用不同激酶抑制剂预孵育的细胞中，响应锌和 MTF-1 核定位而增加的 MTF-1 DNA 结合并未受到抑制。这表明磷酸化对于 MTF-1 反式激活功能至关重要。我们假设金属诱导的 MTF-1 磷酸化是导致 MTF-1 活性增加的主要事件之一。因此，镉等金属离子可以通过刺激MTF-1信号转导途径中的一种或几种激酶来激活MTF-1并诱导MT基因表达。
We have studied the role of phosphorylation in the activation of metal-regulatory transcription factor-1 (MTF-1) and metallothionein (MT) gene expression. We showed that MTF-1 is phosphorylated in vivo and that zinc stimulates MTF-1 phosphorylation 2-4-fold. Several kinase inhibitors were used to examine the possible involvement of kinase cascades in the activation of MTF-1. Metal-induced MT gene expression was abrogated by protein kinase C (PKC), c-Jun N-terminal kinase (JN-K), phosphoinositide 3-kinase, and tyrosine-specific protein kinases inhibitors, as assayed by Northern analysis and by cotransfection experiments using a metal regulatory element-luciferase reporter plasmid. The extracellular signal-activated protein kinase and the p38 kinase cascades did not appear to be essential for the activation Aff gene transcription by metals. By using dominant-negative mutants of PKC, JNK., mitogen-activated kinase kinase 4 (MKK4), and MKK7, we provide further evidence supporting a role for PKC and JNK in the activation of MTF-1 in response to metals. Notably, increased MTF-1 DNA binding in response to zinc and MTF-1 nuclear localization was not inhibited in cells preincubated with the different kinase inhibitors despite strong inhibition of MTF-1-mediated gene expression. This suggests that phosphorylation is essential for MTF-1 transactivation function. We hypothesize that metal-induced phosphorylation of MTF-1 is one of the primary events leading to increased MTF-1 activity. Thus, metal ions such as cadmium could activate MTF-1 and induce MT gene expression by stimulating one or several kinases in the MTF-1 signal transduction pathway.