Inhibition of corticotrophin-releasing hormone transcription by inducible cAMP-early repressor in the hypothalamic cell line, 4B
Inhibition of corticotrophin-releasing hormone transcription by inducible cAMP-early repressor in the hypothalamic cell line, 4B
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DOI：
10.1111/j.1365-2826.2005.01383.x
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发表时间：
2006-01-01
影响因子：
3.2
通讯作者：
Aguilera, G
中科院分区：
文献类型：
--
作者：
Liu, Y;Kalintchenko, N;Aguilera, G
我们最近发现，应激激活后促肾上腺皮质激素释放激素(CRH)转录的快速下降与cAMP反应元件调节剂(CREM)、诱导型cAMP早期抑制物(ICER)的抑制物亚型CRH启动子的诱导和结合有关。在表达CRH的下丘脑细胞系413中检测了ICER抑制CRH转录的能力。在4B细胞中共转染CREM、ICER I、II和CREMβ抑制亚型，以及CRH启动子-Lucif擦除酶结构，可钝化CRH启动子的基础活性和Forsklin刺激的CRH启动子活性，这种作用可被CRH启动子的Cre突变所消除。Western印迹分析和电泳率凝胶漂移和超漂移显示，Forsklin孵育3h后，内源性ICER增加。与CREM对CRH转录的抑制作用一致，染色质免疫沉淀分析显示，CRH启动子对CREM的募集与Pol II的结合减少。研究表明，用Forskolin长时间刺激或在表达CRH的下丘脑细胞系中导入ICER表达载体后，ICER的产生与CREM与CRH启动子的结合和转录抑制有关。这些数据支持这样一种假设，即CREM阻遏因子亚型的诱导是细胞内反馈机制的一部分，有助于在刺激过程中终止CRH转录。
We have shown recently that the rapid decline in corticotrophin-releasing hormone (CRH) transcription following activation by stress is associated with induction and binding to the CRH promoter of the repressor isoforms of cAMP responsive element modulator (CREM), inducible cAMP early repressor (ICER). The ability of ICER to inhibit CRH transcription was examined in the hypothalamic cell line, 413, which expresses CRH. Co-transfection of the inhibitory isoforms of CREM, ICER I and II and CREM beta, and CRH promoter-lucif erase constructs in 4B cells blunted basal and forskolin-stimulated CRH promoter activity, an effect which was abolished by mutation of the CRE of the CRH promoter. Western blot analyses and electromobility gel-shift and super-shift showed increases in endogenous ICER after 3 h of incubation with forskolin. Consistent with an inhibitory effect of CREM on CRH transcription, chromatin immunoprecipitation assays in cells transfected with ICER I revealed recruitment of CREM by the CRH promoter in conjunction with decreases in Pol II association. The study shows that generation of ICER following prolonged stimulation with forskolin, or transfection of an ICER expression vector in hypothalamic cell lines expressing CRH, is associated with CREM binding to the CRH promoter and transcriptional repression. The data support the hypothesis that induction of repressor isoforms of CREM is part of an intracellular feedback mechanism contributing to the termination of CRH transcription during stimulation.