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

我们之前已经确定了雄激素受体（AR）的激活功能-1 （AF-1）域的一种新的辅激活剂。这种共激活因子被命名为雄激素受体n端结构域反激活蛋白-1 (ANT-1)，它是独特的，因为ANT-1是U5小核核糖核文章（snRNP）的一个组成部分，因此提高了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AR的独特共激活因子所需的四个不同的功能域；分别为反活化结构域、AR-AF-1结合结构域、核易位信号结构域和核内散斑形成结构域。在由941个氨基酸（aa）残基组成的ANT-1中，从291个氨基酸到c端约三分之二的分子含有19个四肽重复（TPR）基序，这些基序被推测在蛋白质-蛋白质相互作用中起作用。有趣的是，AR-AF-1结合域和ANT-1的斑点形成域都被分配在这个包含多个TPR基序的长区域内，而反激活域和核易位信号仅位于1至172个aa残基中。此外，ANT-1的反激活结构域对AR不是特异性的，也就是说，它甚至可以增强非特异性的病毒提示子。ANT-1转激活的受体特异性仅由TPR含区决定。这些结果表明，ANT-1实际上包含四个不同的分子内功能域，从而表明ANT-1在体内发挥重要作用。

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.