Mitochondrial transcription factor A induction by redox activation of nuclear respiratory factor 1
Mitochondrial transcription factor A induction by redox activation of nuclear respiratory factor 1
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DOI：
10.1074/jbc.m508805200
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发表时间：
2006-01-06
影响因子：
4.8
通讯作者：
Suliman, HB
中科院分区：
文献类型：
--
作者：
Piantadosi, CA;Suliman, HB
线粒体转录因子A（Tfam）的核表达是线粒体DNA（mtDNA）转录和复制所必需的，必须与细胞的能量需求相关联。由于呼吸产生活性氧作为副产物，我们测试了活性氧通过核呼吸因子（NRF-1）的磷酸化和与Tfam启动子的结合来调节Tfam表达的想法。在富含NRF-1的大鼠肝癌细胞中，发现Tfam表达和mtDNA含量的基础和氧化剂诱导的增加。电泳迁移率变动分析和染色质免疫沉淀证实了NRF-1与Tfam启动子的特异性结合。NRF-1-Tfam结合在促氧化剂条件下增强。NRF-1基因沉默导致Tfam表达1：1下调，线粒体DNA含量降低。为了评估NRF-1在Tfam表达中的氧化还原（redox）调节，使用上游磷脂酰肌醇3-激酶的阻断来证明NRF-1磷酸化和Tfam表达的氧化剂刺激的损失。Akt/蛋白激酶B的特异性抑制也消除了氧化反应。NRF-1氨基酸序列的检查揭示了Akt磷酸化共识，在该共识处，定点诱变消除了Akt对NRF-1的磷酸化。最后，Akt磷酸化和NRF-1易位可预测地在不具有PTEN肿瘤抑制因子的癌细胞系（HCC 1937细胞）中缺乏氧化剂调节。本研究公开了通过磷脂酰肌醇3，4，5-三磷酸激酶/Akt信号传导在通过抗氧化剂促存活网络控制Tfam诱导中对NRF-1磷酸化和核转位的新的氧化还原调节。
The nuclear expression of mitochondrial transcription factor A (Tfam), which is required for mitochondrial DNA ( mtDNA) transcription and replication, must be linked to cellular energy needs. Because respiration generates reactive oxygen species as a side-product, we tested the idea that reactive oxygen species regulate Tfam expression through phosphorylation of nuclear respiratory factor (NRF-1) and binding to the Tfam promoter. In mitochondria-rich rat hepatoma cells that overexpress NRF-1, basal and oxidant-induced increases were found in Tfam expression and mtDNA content. Specific binding of NRF-1 to Tfam promoter was demonstrated by electrophoretic mobility shift assay and chromatin immunoprecipitation. NRF-1-Tfam binding was augmented under pro-oxidant conditions. NRF-1 gene silencing produced 1:1 knockdown of Tfam expression and decreased mtDNA content. To evaluate oxidation-reduction (redox) regulation of NRF-1 in Tfam expression, blockade of upstream phosphatidylinositol 3-kinase was used to demonstrate loss of oxidant stimulation of NRF-1 phosphorylation and Tfam expression. The oxidant response was also abrogated by specific inhibition of Akt/protein kinase B. Examination of the NRF-1 amino acid sequence revealed an Akt phosphorylation consensus at which site-directed mutagenesis abolished NRF-1 phosphorylation by Akt. Finally, Akt phosphorylation and NRF-1 translocation predictably lacked oxidant regulation in a cancer line having no PTEN tumor suppressor (HCC1937 cells). This study discloses novel redox regulation of NRF-1 phosphorylation and nuclear translocation by phosphatidylinositol 3,4,5-triphosphate kinase/Akt signaling in controlling Tfam induction by an anti-oxidant pro-survival network.