Hypoxia-inducible factor-1α mRNA: a new target for destabilization by tristetraprolin in endothelial cells.
Hypoxia-inducible factor-1α mRNA: a new target for destabilization by tristetraprolin in endothelial cells.
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DOI：
10.1091/mbc.e10-07-0617
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发表时间：
2011-09
影响因子：
3.3
通讯作者：
Cherradi N
中科院分区：
文献类型：
--
作者：
Chamboredon S;Ciais D;Desroches-Castan A;Savi P;Bono F;Feige JJ;Cherradi N
该研究为以下结论提供了新的证据：mRNA去稳定蛋白Tristetraprolin是HIF-1α mRNA周转的调节剂，可能在内皮细胞对缺氧的适应性反应中参与HIF-1α及其靶基因表达的调控。内皮细胞（EC）是血氧浓度变化的主要传感器。它们利用低氧诱导因子-1 α（HIF-1α）转录因子的低氧敏感稳定性来参与响应氧变化的特定转录程序。HIF-1α表达的调控在蛋白水平上有很好的记录，但对其mRNA稳定性的控制知之甚少。利用小干扰RNA敲低实验、报告基因分析、核糖核蛋白免疫沉淀和mRNA半衰期测定，我们报道了内皮细胞中HIF-1α表达的一种新的调节机制。结果表明：1）持续低氧可使HIF-1α mRNA表达水平逐渐下降，而HIF-1α蛋白表达水平在3 h后迅速达到峰值，然后缓慢下降; 2）沉默内皮细胞中的mRNA失稳蛋白tristetraprolin（TTP）可逆转低氧诱导的HIF-1α mRNA的下调; 3）在长时间缺氧后观察到的荧光素酶-HIF-1α-3 MobiUTR报告基因转录本半衰期的减少是由TTP介导的; 4）TTP与HIF-1α 3′UTR特异性结合; 5）HIF-1α 3′UTR中存在的最远端富含AU的元件（由两个六聚体组成）足以进行TTP介导的阻遏。最后，我们提出证据表明，沉默TTP表达增强缺氧诱导的HIF-1α蛋白水平的增加，伴随着碳酸酐酶CA IX水平的增加，从而表明TTP在生理上控制一组HIF-1α靶基因的表达。总之，这些数据揭示了一个新的作用，TTP在控制基因表达过程中的内皮细胞对缺氧的反应。
The study provides new evidence that the mRNA-destabilizing protein Tristetraprolin is a modulator of HIF-1α mRNA turnover and may contribute to the control of HIF-1α and HIF-1α target gene expression during the adaptive response of endothelial cells to hypoxia. Endothelial cells (ECs) are the primary sensors of variations in blood oxygen concentrations. They use the hypoxia-sensitive stabilization of the hypoxia-inducible factor-1α (HIF-1α) transcription factor to engage specific transcriptional programs in response to oxygen changes. The regulation of HIF-1α expression is well documented at the protein level, but much less is known about the control of its mRNA stability. Using small interfering RNA knockdown experiments, reporter gene analyses, ribonucleoprotein immunoprecipitations, and mRNA half-life determinations, we report a new regulatory mechanism of HIF-1α expression in ECs. We demonstrate that 1) sustained hypoxia progressively decreases HIF-1α mRNA while HIF-1α protein levels rapidly peak after 3 h and then slowly decay; 2) silencing the mRNA-destabilizing protein tristetraprolin (TTP) in ECs reverses hypoxia-induced down-regulation of HIF-1α mRNA; 3) the decrease in the half-life of Luciferase-HIF-1α-3′UTR reporter transcript that is observed after prolonged hypoxia is mediated by TTP; 4) TTP binds specifically to HIF-1α 3′UTR; and 5) the most distal AU-rich elements present in HIF-1α 3′UTR (composed of two hexamers) are sufficient for TTP-mediated repression. Finally, we bring evidence that silencing TTP expression enhances hypoxia-induced increase in HIF-1α protein levels with a concomitant increase in the levels of the carbonic anhydrase enzyme CA IX, thus suggesting that TTP physiologically controls the expression of a panel of HIF-1α target genes. Altogether, these data reveal a new role for TTP in the control of gene expression during the response of endothelial cell to hypoxia.