Wardell Suzanne E, Boonyaratanakornkit Viroj, Adelman James S, Aronheim Ami, Edwards Dean P
Program in Molecular Biology, Department of Pathology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Mol Cell Biol. 2002 Aug;22(15):5451-66. doi: 10.1128/MCB.22.15.5451-5466.2002.
The progesterone receptor (PR) contains two transcription activation function (AF) domains, constitutive AF-1 in the N terminus and AF-2 in the C terminus. AF-2 activity is mediated by a hormone-dependent interaction with a family of steroid receptor coactivators (SRCs). SRC-1 can also stimulate AF-1 activity through a secondary domain that interacts simultaneously with the primary AF-2 interaction site. Other protein interactions and mechanisms that mediate AF-1 activity are not well defined. By interaction cloning, we identified an AP-1 family member, Jun dimerization protein 2 (JDP-2), as a novel PR-interacting protein. JDP-2 was first defined as a c-Jun interacting protein that functions as an AP-1 repressor. PR and JDP-2 interact directly in vitro through the DNA binding domain (DBD) of PR and the basic leucine zipper (bZIP) region of JDP-2. The two proteins also physically associate in mammalian cells, as detected by coimmunoprecipitation, and are recruited in vivo to a progesterone-inducible target gene promoter, as detected by a chromatin immunoprecipitation (ChIP) assay. In cell transfection assays, JDP-2 substantially increased hormone-dependent PR-mediated transactivation and worked primarily by stimulating AF-1 activity. JDP-2 is a substantially stronger coactivator of AF-1 than SRC-1 and stimulates AF-1 independent of SRC-1 pathways. The PR DBD is necessary but not sufficient for JDP-2 stimulation of PR activity; the DBD and AF-1 are required together. JDP-2 lacks an intrinsic activation domain and makes direct protein interactions with other coactivators, including CBP and p300 CBP-associated factor (pCAF), but not with SRCs. These results indicate that JDP-2 stimulates AF-1 activity by the novel mechanism of docking to the DBD and recruiting or stabilizing N-terminal PR interactions with other general coactivators. JDP-2 has preferential activity on PR among the nuclear receptors tested and is expressed in progesterone target cells and tissues, suggesting that it has a physiological role in PR function.
孕激素受体（PR）包含两个转录激活功能（AF）结构域，即位于N端的组成型AF-1和位于C端的AF-2。AF-2的活性是通过与一类类固醇受体共激活因子（SRCs）的激素依赖性相互作用介导的。SRC-1还可以通过一个与主要的AF-2相互作用位点同时相互作用的二级结构域来刺激AF-1的活性。介导AF-1活性的其他蛋白质相互作用和机制尚未明确。通过相互作用克隆，我们鉴定出一种AP-1家族成员，即Jun二聚化蛋白2（JDP-2），作为一种新型的与PR相互作用的蛋白。JDP-2最初被定义为一种与c-Jun相互作用的蛋白，其功能是作为一种AP-1阻遏物。PR和JDP-2在体外通过PR的DNA结合结构域（DBD）和JDP-2的碱性亮氨酸拉链（bZIP）区域直接相互作用。通过免疫共沉淀检测发现，这两种蛋白在哺乳动物细胞中也存在物理结合，并且通过染色质免疫沉淀（ChIP）分析检测到它们在体内被募集到一个孕激素诱导的靶基因启动子上。在细胞转染实验中，JDP-2显著增强了激素依赖性PR介导的反式激活作用，并且主要通过刺激AF-1的活性发挥作用。JDP-2是一种比SRC-1更强的AF-1共激活因子，并且独立于SRC-1途径刺激AF-1。PR的DBD对于JDP-2刺激PR活性是必要的，但不是充分的；DBD和AF-1一起才是必需的。JDP-2缺乏内在的激活结构域，并且与其他共激活因子，包括CBP和p300 CBP相关因子（pCAF）直接进行蛋白质相互作用，但不与SRCs相互作用。这些结果表明，JDP-2通过对接DBD并募集或稳定N端PR与其他一般共激活因子的相互作用这一新型机制来刺激AF-1的活性。在测试的核受体中，JDP-2对PR具有优先活性，并且在孕激素靶细胞和组织中表达，这表明它在PR功能中具有生理作用。
