PA1 Protein, a New Competitive Decelerator Acting at More than One Step to Impede Glucocorticoid Receptor-mediated Transactivation
PA1 Protein, a New Competitive Decelerator Acting at More than One Step to Impede Glucocorticoid Receptor-mediated Transactivation
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DOI：
10.1074/jbc.m112.427740
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发表时间：
2013-01-04
影响因子：
4.8
通讯作者：
Simons, S. Stoney, Jr.
中科院分区：
文献类型：
--
作者：
Zhang, Zhenhuan;Sun, Yunguang;Simons, S. Stoney, Jr.
许多辅助因子通过影响以下三个主要转录特性中的一个或多个来调节糖皮质激素受体（gr）的基因调控活性：激动剂的最大活性（A(max)）、激动剂的效力（EC50）和抗类固醇的部分激动剂活性（PAA）。在这里，我们报道了最近描述的核蛋白Pax2反活化结构域相互作用蛋白(PTIP)-相关蛋白1 （PA1）是GR反活化的新抑制剂。PA1抑制Amax，增加EC50，并以独立于相关PTIP的方式降低外源报告基因的PAA。PA1与GR的c端完全活跃，并与之强结合。PA1逆转了辅激活因子TIF2对GR介导的基因诱导的作用，但不能增强辅抑制因子SMRT的作用。利用外源报告基因分析PA1和TIF2之间的竞争分析表明，PA1作用的动力学定义是在TIF2起作用的上游两个位点的竞争减速剂。PA1与内源基因IGFBP1和IP6K3一起抑制GR诱导，增加EC50，降低PAA。ChIP和re-ChIP实验表明，PA1通过以下不同的机制实现了对这两个基因的抑制：PA1似乎增加了IGFBP1启动子区域的GR解离并减少了GR的转激活，但阻断了GR与IP6K3启动子的结合。我们得出的结论是，PA1是一种新的竞争性GR转激活减速剂，并且可以在一个以上的分子定义步骤中以取决于特定基因的方式起作用。
Numerous cofactors modulate the gene regulatory activity of glucocorticoid receptors (GRs) by affecting one or more of the following three major transcriptional properties: the maximal activity of agonists (A(max)), the potency of agonists (EC50), and the partial agonist activity of antisteroids (PAA). Here, we report that the recently described nuclear protein, Pax2 transactivation domain interaction protein (PTIP)-associated protein 1 (PA1), is a new inhibitor of GR transactivation. PA1 suppresses Amax, increases the EC50, and reduces the PAA of an exogenous reporter gene in a manner that is independent of associated PTIP. PA1 is fully active with, and strongly binds to, the C-terminal half of GR. PA1 reverses the effects of the coactivator TIF2 on GR-mediated gene induction but is unable to augment the actions of the corepressor SMRT. Analysis of competition assays between PA1 and TIF2 with an exogenous reporter indicates that the kinetic definition of PA1 action is a competitive decelerator at two sites upstream from where TIF2 acts. With the endogenous genes IGFBP1 and IP6K3, PA1 also represses GR induction, increases the EC50, and decreases the PAA. ChIP and re-ChIP experiments indicate that PA1 accomplishes this inhibition of the two genes via different mechanisms as follows: PA1 appears to increase GR dissociation from and reduce GR transactivation at the IGFBP1 promoter regions but blocks GR binding to the IP6K3 promoter. We conclude that PA1 is a new competitive decelerator of GR transactivation and can act at more than one molecularly defined step in a manner that depends upon the specific gene.