MED25 is distinct from TRAP220/MED1 in cooperating with CBP for retinoid receptor activation
MED25 is distinct from TRAP220/MED1 in cooperating with CBP for retinoid receptor activation
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DOI：
10.1038/sj.emboj.7601797
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发表时间：
2007-08-08
期刊：
影响因子：
11.4
通讯作者：
Um, Soo-Jong
中科院分区：
文献类型：
--
作者：
Lee, Hye-Kyung;Park, Ui-Hyun;Um, Soo-Jong
我们通过C末端核激素受体(NR)box/LxxLL基序分离到与视黄酸(RA)结合的视黄酸受体(RAR)结合的MED25，并增强RAR/RXR介导的转录。当与启动子结合时，MED25在其PTOV结构域中显示出内在的转录活性，这可能是通过与CBP直接结合来实现的。利用MED25的显性负性进行的报告分析表明，在CBP和RAR/RXR结合中，N端介体结合和C端结构域是重要的，它们影响MED25的活性。MED25的下调特异性地降低了RAR，但不会降低甲状腺激素受体(TR)的活性。MED25对RAR的刺激作用与体内增强的RA细胞毒性相关。染色质免疫沉淀(ChIP)分析显示，MED25对RARβ2启动子具有RA依赖的募集作用。MED25 NR盒缺失突变体的过表达以及MED25 siRNA的处理使CBP和TRAP220的募集减少。时间-过程芯片分析表明，CBP与RAR和MED25一起被招募得较早，而TRAP220被招募到启动子的时间较晚。我们的数据表明，MED25通过其不同的结构域与CBP和介体合作，对RAR/RXR的激活施加了选择性优势。
We isolated MED25, which associates with retinoic acid ( RA)-bound retinoic acid receptor (RAR) through the C-terminal nuclear hormone receptor (NR) box/LxxLL motif, and increases RAR/RXR-mediated transcription. When tethered to a promoter, MED25 showed intrinsic transcriptional activity in its PTOV domain, which is likely accomplished by direct association with CBP. Reporter assays using dominant negatives of MED25 demonstrated the importance of the N-terminal Mediator-binding and C-terminal domains in CBP and RAR/RXR binding, which affect MED25 activity. Downregulation of MED25 specifically reduced RAR but not thyroid hormone receptor (TR) activity. Stimulation of RAR by MED25 was correlated with enhanced RA cytotoxicity in vivo. Chromatin immunoprecipitation (ChIP) assays revealed the RA-dependent recruitment of MED25 to the RAR beta 2 promoter. Recruitment of CBP and TRAP220 was diminished by the overexpression of a MED25 NR box deletion mutant, and by treatment with MED25 siRNA. Time-course ChIP assays indicated that CBP, together with RAR and MED25, is recruited early, whereas TRAP220 is recruited later to the promoter. Our data suggest that MED25, in cooperation with CBP and Mediators through its distinct domains, imposes a selective advantage on RAR/RXR activation.