Redwood C, Davies S L, Wells N J, Fry A M, Hickson I D
Imperial Cancer Research Fund Laboratories, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, United Kingdom.
J Biol Chem. 1998 Feb 6;273(6):3635-42. doi: 10.1074/jbc.273.6.3635.
Previous reports have indicated that topoisomerase II (topo II) co-purifies with and is a substrate for casein kinase II. We have carried out a detailed study of the effect that purified casein kinase II has on the activity of purified recombinant human topo IIalpha. Co-incubation of topo IIalpha and casein kinase II led to an apparent activation of the topo IIalpha; however, in experiments in which topo IIalpha was preincubated at 37 degrees C with or without native casein kinase II prior to assaying for decatenation activity, it emerged that the kinase was exerting its "activating" function via a decrease in the rate of topo IIalpha enzyme inactivation during the incubation period. This stabilization of topo IIalpha by casein kinase II was ATP-independent and was observed in both mutated and truncated derivatives of topo IIalpha lacking the major casein kinase II phospho-acceptor sites, indicating the lack of a requirement for phosphorylation. Consistent with a nonenzymatic role for casein kinase II, stoichiometric quantities of kinase were required for topo IIalpha stabilization. These data indicate that casein kinase II plays a significant role in regulating human topo IIalpha protein action via stabilization against thermal inactivation.
先前的报告表明，拓扑异构酶II（topo II）与酪蛋白激酶II共同纯化，并且是酪蛋白激酶II的底物。我们已经对纯化的酪蛋白激酶II对纯化的重组人topo IIα活性的影响进行了详细研究。topo IIα与酪蛋白激酶II共同孵育导致topo IIα明显激活；然而，在测定解连环活性之前，将topo IIα在37℃下与天然酪蛋白激酶II一起或不一起预孵育的实验中，发现该激酶通过在孵育期间降低topo IIα酶失活速率来发挥其“激活”功能。酪蛋白激酶II对topo IIα的这种稳定作用不依赖于ATP，并且在缺乏主要酪蛋白激酶II磷酸化受体位点的topo IIα的突变和截短衍生物中均观察到，表明不需要磷酸化。与酪蛋白激酶II的非酶作用一致，topo IIα稳定需要化学计量的激酶。这些数据表明，酪蛋白激酶II通过稳定抗热失活在调节人topo IIα蛋白作用中起重要作用。
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