Understanding the antagonism of retinoblastoma protein dephosphorylation by PNUTS provides insights into the PP1 regulatory code
Understanding the antagonism of retinoblastoma protein dephosphorylation by PNUTS provides insights into the PP1 regulatory code
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DOI：
10.1073/pnas.1317395111
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发表时间：
2014-03-18
影响因子：
11.1
通讯作者：
Page, Rebecca
中科院分区：
文献类型：
--
作者：
Choy, Meng S.;Hieke, Martina;Page, Rebecca
丝氨酸/苏氨酸蛋白磷酸酶1(PP1)通过与近200种调节蛋白结合形成高度特异的全酶，使数百个关键的生物靶标去磷酸化。然而，这些蛋白质如何指导PP1的特异性以及预测这些PP1相互作用的蛋白质如何仅从序列中结合PP1的能力仍然缺乏。PP1核靶向亚基(PNUTS)是一种PP1靶向蛋白，与PP1一起在细胞核中发挥核心作用，调节染色质解缩、RNA加工和基本细胞周期蛋白的磷酸化状态，包括视网膜母细胞瘤蛋白(Rb)、p53和MDM2。PNUTS在这些过程中的分子功能完全未知。在这里，我们展示了自由形式的PNUTS本质上是无序的，它以一种高度扩展的方式与PP1强烈相互作用。出乎意料的是，PNUTS阻断了Pp1‘S底物结合槽中的一条，同时保留了活性部位。这个相互作用位点，我们已经命名为精氨酸位点，使我们能够定义独特的PP1结合基序，这提高了我们预测超过四分之一的已知PP1调节器如何与PP1结合的能力。此外，该结构还显示了PNUTS如何通过阻断PP1上的结合位点来抑制PP1介导的关键底物，特别是Rb的去磷酸化，这一见解为选择性增强Rb活性提供了策略。
The serine/threonine protein phosphatase 1 (PP1) dephosphorylates hundreds of key biological targets by associating with nearly 200 regulatory proteins to form highly specific holoenzymes. However, how these proteins direct PP1 specificity and the ability to predict how these PP1 interacting proteins bind PP1 from sequence alone is still missing. PP1 nuclear targeting subunit (PNUTS) is a PP1 targeting protein that, with PP1, plays a central role in the nucleus, where it regulates chromatin decondensation, RNA processing, and the phosphorylation state of fundamental cell cycle proteins, including the retinoblastoma protein (Rb), p53, and MDM2. The molecular function of PNUTS in these processes is completely unknown. Here, we show that PNUTS, which is intrinsically disordered in its free form, interacts strongly with PP1 in a highly extended manner. Unexpectedly, PNUTS blocks one of PP1's substrate binding grooves while leaving the active site accessible. This interaction site, which we have named the arginine site, allowed us to define unique PP1 binding motifs, which advances our ability to predict how more than a quarter of the known PP1 regulators bind PP1. Additionally, the structure shows how PNUTS inhibits the PP1-mediated dephosphorylation of critical substrates, especially Rb, by blocking their binding sites on PP1, insights that are providing strategies for selectively enhancing Rb activity.