Kang Zhigang, Pirskanen Asta, Jänne Olli A, Palvimo Jorma J
Biomedicum Helsinki, Institute of Biomedicine (Physiology), University of Helsinki and Helsinki University Central Hospital, Finland.
J Biol Chem. 2002 Dec 13;277(50):48366-71. doi: 10.1074/jbc.M209074200. Epub 2002 Oct 9.
We have used the chromatin immunoprecipitation technique to analyze the formation of the androgen receptor (AR) transcription complex onto prostate-specific antigen (PSA) and kallikrein 2 promoters in LNCaP cells. Our results show that loading of holo-AR and recruitment of RNA polymerase II to the promoters occur transiently. The cyclic nature of AR transcription complex assembly is also illustrated by transient association of coactivators GRIP1 and CREB-binding protein and acetylated histone H3 with the PSA promoter. Treatment of cells with the pure antiandrogen bicalutamide also elicits occupancy of the promoter by AR. In contrast to the agonist-liganded AR, bicalutamide-bound receptor is not capable of recruiting polymerase II, GRIP1, or CREB-binding protein, indicating that the conformation of AR bound to anti-androgen is not competent to assemble transcription complexes. Proteasome is involved in the regulation of AR-dependent transcription, as a proteasome inhibitor, MG-132, prevents the release of the receptor from the PSA promoter, and it also blocks the androgen-induced PSA mRNA accumulation. Furthermore, occupancy of the PSA promoter by the 19 S proteasome subcomplex parallels that by AR. Collectively, formation of the AR transcription complex, encompassing AR, polymerase II, and coactivators, on a regulated promoter is a cyclic process involving proteasome function.
我们运用染色质免疫沉淀技术，分析了雄激素受体（AR）转录复合物在LNCaP细胞中前列腺特异性抗原（PSA）和激肽释放酶2启动子上的形成情况。我们的结果表明，全AR的加载以及RNA聚合酶II在启动子上的募集是瞬时发生的。共激活因子GRIP1和CREB结合蛋白以及乙酰化组蛋白H3与PSA启动子的瞬时结合，也说明了AR转录复合物组装的循环性质。用纯抗雄激素比卡鲁胺处理细胞也会引发AR对启动子的占据。与激动剂配体结合的AR不同，比卡鲁胺结合的受体不能募集聚合酶II、GRIP1或CREB结合蛋白，这表明与抗雄激素结合的AR的构象无法组装转录复合物。蛋白酶体参与AR依赖性转录的调控，因为蛋白酶体抑制剂MG - 132可阻止受体从PSA启动子上释放，并且它还能阻断雄激素诱导的PSA mRNA积累。此外，19S蛋白酶体亚复合物对PSA启动子的占据情况与AR相似。总体而言，在一个受调控的启动子上，包含AR、聚合酶II和共激活因子的AR转录复合物的形成是一个涉及蛋白酶体功能的循环过程。
