Cloning and characterization of a novel coactivator, ANT-1, for androgen receptor AF-1 domain

我们以前已经发现了雄激素受体(AR)激活功能-1(AF-1)结构域的一个新的共激活子。这种共激活因子被命名为雄激素受体N端域反式激活蛋白-1(ANT-1)，因为ANT-1是U5小核核糖核蛋白(SnRNP)的组成部分，从而增加了AR-AF-1可能通过ANT-1参与转录-剪接偶联的可能性。我们确定了ANT-1作为唯一的AR共激活因子所需的四个功能域，它们是反式激活域、AR-AF-1结合域、核转位信号域和核内斑点形成域。在由941个氨基酸残基组成的ANT-1中，从291aa到C末端约三分之二的分子含有19个四肽重复序列(TPR)，它们被认为在蛋白质-蛋白质相互作用中发挥作用。有趣的是，ANT-1的AR-AF-1结合域和斑点形成域都被分配在这个包含多个TPR基序的长区内，而反式激活域和核转位信号只位于1到172个氨基酸残基。此外，ANT-1的反式激活结构域不是AR所特有的，即它甚至增强了非特异性的病毒提示。反式激活ANT-1的受体特异性仅由TPR的含有区决定。这些结果表明，ANT-1实际上包含四个不同的分子内功能结构域，从而表明ANT-1在体内发挥着重要的作用。

We have previously identified a novel coactivator for the activation function-1 (AF-1) domain of the androgen receptor (AR). This coactivator, named androgen receptor N-terminal domain transactivating protein-1 (ANT-1), is unique, since the ANT-1 is a component of U5 small nuclear ribonucleoparticle (snRNP), thus raising the possibility that the AR-AF-1 may be involved in the transcription-splicing coupling via ANT-1. We identified four distinguished functional domains required for ANT-1 to play a role as a unique coactivator for AR ; which were transactivating domain, AR-AF-1 binding domain, nuclear translocation signal domain, and intranuclear speckle formation domain. In the ANT-1, consisted of 941 amino acid (aa) residues, about two thirds of the molecule from 291 aa to the C-terminal end contains 19 tetratricopeptide repeat (TPR) motifs which has been speculated to play a role in protein-protein interactions. Interestingly both AR-AF-1 binding domain and the speckle formation domain of ANT-1 were assigned within this long region containing multiple TPR motifs, while transactivating domain and the nuclear translocation signal resided only in the 1 to 172 aa residues. Furthermore, the transactivating domain of ANT-1 was not specific for the AR, that is it enhanced even non-specific viral prompters. The receptor specificity of ANT-1 transactivation was simply determined by the TPR containing region. These results indicated that the ANT-1 actually contained four distinguished intramolecular functional domains, thus suggesting that the ANT-1 play a significant role in vivo.