Messenger Moira M, Saulnier Ronald B, Gilchrist Andrew D, Diamond Phaedra, Gorbsky Gary J, Litchfield David W
Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
J Biol Chem. 2002 Jun 21;277(25):23054-64. doi: 10.1074/jbc.M200111200. Epub 2002 Apr 8.
The peptidyl-prolyl isomerase Pin1 interacts in a phosphorylation-dependent manner with several proteins involved in cell cycle events. In this study, we demonstrate that Pin1 interacts with protein kinase CK2, an enzyme that generally exists in tetrameric complexes composed of two catalytic CK2 alpha and/or CK2 alpha' subunits together with two regulatory CK2 beta subunits. Our results indicate that Pin1 can interact with CK2 complexes that contain CK2 alpha. Furthermore, Pin1 can interact directly with the C-terminal domain of CK2 alpha that contains residues that are phosphorylated in vitro by p34(Cdc2) and in mitotic cells. Substitution of the phosphorylation sites of CK2 alpha with alanines resulted in decreased interactions between Pin1 and CK2. The other catalytic isoform of CK2, designated CK2 alpha', is not phosphorylated in mitotic cells and does not interact with Pin1, but a chimeric protein consisting of CK2 alpha' with the C terminus of CK2 alpha was phosphorylated in mitotic cells and interacts with Pin1, further implicating the phosphorylation sites in the interaction. In vitro, Pin1 inhibits the phosphorylation of Thr-1342 on human topoisomerase II alpha by CK2. Topoisomerase II alpha also interacts with Pin1 suggesting that the effect of Pin1 on the phosphorylation of Thr-1342 could result from its interactions with CK2 and/or topoisomerase II alpha. As compared with wild-type Pin1, isomerase-deficient and WW domain-deficient mutants of Pin1 are impaired in their ability to interact with CK2 and to inhibit the CK2-catalyzed phosphorylation of topoisomerase II alpha. Collectively, these results indicate that Pin1 and CK2 alpha interact and suggest a possible role for Pin1 in the regulation of topoisomerase II alpha. Furthermore, these results provide new insights into the functional role of the mitotic phosphorylation of CK2 and provide a new mechanism for selectively regulating the ability of CK2 to phosphorylate one of its mitotic targets.
肽基脯氨酰异构酶Pin1以磷酸化依赖的方式与几种参与细胞周期事件的蛋白质相互作用。在本研究中，我们证明Pin1与蛋白激酶CK2相互作用，CK2是一种通常以四聚体复合物形式存在的酶，该复合物由两个催化性CK2α和/或CK2α'亚基以及两个调节性CK2β亚基组成。我们的结果表明，Pin1可以与含有CK2α的CK2复合物相互作用。此外，Pin1可以直接与CK2α的C末端结构域相互作用，该结构域包含在体外被p34（Cdc2）和有丝分裂细胞中磷酸化的残基。用丙氨酸取代CK2α的磷酸化位点导致Pin1与CK2之间的相互作用减少。CK2的另一种催化同工型，称为CK2α'，在有丝分裂细胞中不被磷酸化，也不与Pin1相互作用，但由CK2α'与CK2α的C末端组成的嵌合蛋白在有丝分裂细胞中被磷酸化并与Pin1相互作用，进一步表明磷酸化位点在这种相互作用中起作用。在体外，Pin1抑制CK2对人拓扑异构酶IIα上Thr-1342的磷酸化。拓扑异构酶IIα也与Pin1相互作用，这表明Pin1对Thr-1342磷酸化的影响可能是由于其与CK2和/或拓扑异构酶IIα的相互作用。与野生型Pin1相比，Pin1的异构酶缺陷型和WW结构域缺陷型突变体在与CK2相互作用以及抑制CK2催化的拓扑异构酶IIα磷酸化的能力方面受损。总的来说，这些结果表明Pin1与CK2α相互作用，并暗示Pin1在拓扑异构酶IIα调节中可能发挥的作用。此外，这些结果为CK2的有丝分裂磷酸化的功能作用提供了新的见解，并为选择性调节CK2磷酸化其有丝分裂靶标之一的能力提供了新机制。
