The zinc finger protein ras-responsive element binding protein-1 is a coregulator of the androgen receptor: implications for the role of the ras pathway in enhancing androgenic signaling in prostate cancer
The zinc finger protein ras-responsive element binding protein-1 is a coregulator of the androgen receptor: implications for the role of the ras pathway in enhancing androgenic signaling in prostate cancer
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DOI：
10.1210/me.2006-0503
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发表时间：
2007-09-01
影响因子：
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通讯作者：
Freeman, Michael R.
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文献类型：
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作者：
Mukhopadhyay, Nishit K.;Cinar, Bekir;Freeman, Michael R.
雄激素受体（AR）在正常前列腺功能以及前列腺癌的病因学中都起着重要作用。AR的激活由激素结合以及与辅调节因子的相互作用所决定。其中一些辅调节因子是Ras相关信号的已知靶点。近期证据表明，Ras激活可能在前列腺癌向更恶性且对激素不敏感的表型进展中起因果作用。在本研究中，我们使用一种转录因子 - 转录因子相互作用阵列方法，将锌指蛋白Ras反应元件结合蛋白（RREB - 1）鉴定为AR的伙伴和辅调节因子。在LNCaP前列腺癌细胞中，通过免疫共沉淀、谷胱甘肽S - 转移酶下拉实验和免疫荧光分析确定，RREB - 1与内源性AR形成复合物。通过染色质免疫沉淀评估，RREB - 1结合到前列腺特异性抗原（PSA）启动子上。RREB - 1的瞬时表达下调AR介导的启动子活性并抑制PSA蛋白的表达。通过共转染活化的Ras，RREB - 1的抑制活性显著减弱。此外，显性负性N - 17 - Ras的表达，或者使用MAPK激酶抑制剂PD98059[2 - (2 - 氨基 - 3 - 甲氧基苯基) - 4H - 1 - 苯并吡喃 - 4 - 酮]消除了Ras在减弱RREB - 1介导的抑制作用中的效果。再者，通过RNA干扰抑制RREB - 1的表达增强了Ras对PSA启动子活性和PSA表达的影响。此外，Ras通路的激活使RREB - 1/AR复合物中的AR减少。总之，我们的数据首次将RREB - 1鉴定为AR的一种抑制因子，并进一步表明Ras/MAPK激酶通路可能是RREB - 1对雄激素信号抑制作用的拮抗剂。
Androgen receptor ( AR) plays an important role in normal prostate function as well as in the etiology of prostate cancer. Activation of AR is dictated by hormone binding and by interactions with coregulators. Several of these coregulators are known targets of Ras-related signals. Recent evidence suggests that Ras activation may play a causal role in the progression of prostate cancer toward a more malignant and hormone-insensitive phenotype. In the present study, we used a transcription factor-transcription factor interaction array method to identify the zinc finger protein Ras-responsive element binding protein ( RREB-1) as a partner and coregulator of AR. In LNCaP prostate cancer cells, RREB-1 was found to be present in a complex with endogenous AR as determined by coimmunoprecipitation, glutathione S-transferase pull down, and immunofluorescence analyses. RREB-1 bound to the prostate-specific antigen ( PSA) promoter as assessed by chromatin immunoprecipitation. Transient expression of RREB-1 down-regulated AR-mediated promoter activity and suppressed expression of PSA protein. The repressor activity of RREB-1 was significantly attenuated by cotransfection of activated Ras. Moreover, expression of the dominant-negative N-17-Ras or, alternatively, use of the MAPK kinase inhibitor PD98059 [ 2-( 2-amino-3-methyoxyphenyl)4H-1-benzopyran-4-one] abolished the effect of Ras in attenuating RREB-1-mediated repression. Furthermore, inhibition of RREB-1 expression by RNA interference enhanced the effect of Ras on PSA promoter activity and PSA expression. In addition, activation of the Ras pathway depleted AR from the RREB-1/AR complex. Collectively, our data for the first time identify RREB-1 as a repressor of AR and further implicate the Ras/ MAPK kinase pathway as a likely antagonist of the inhibitory effects of RREB-1 on androgenic signaling.