Iron chelation and regulation of the cell cycle:: 2 mechanisms of posttranscriptional regulation of the universal cyclin-dependent kinase inhibitor p21CIP1/WAF1 by iron depletion
Iron chelation and regulation of the cell cycle:: 2 mechanisms of posttranscriptional regulation of the universal cyclin-dependent kinase inhibitor p21CIP1/WAF1 by iron depletion
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DOI：
10.1182/blood-2007-03-076737
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发表时间：
2007-07-15
期刊：
影响因子：
20.3
通讯作者：
Richardson, Des R.
中科院分区：
文献类型：
--
作者：
Fu, Dong;Richardson, Des R.
铁 (Fe) 在增殖中起着至关重要的作用，Fe 缺乏会导致 G(1)/S 停滞和细胞凋亡。然而，Fe 在细胞周期控制中的确切作用仍不清楚。我们观察到，Fe 消耗增加了通用细胞周期蛋白依赖性激酶抑制剂 p21(C1P1/WAF1) 的 mRNA，但其蛋白水平并未升高。这一观察结果对于 Fe 剥夺后观察到的 G1/S 停滞是独特的，因为当其他刺激诱导停滞时，通常会发现 p21(CIP1/WAF1) mRNA 和蛋白质增加。在这项研究中，我们检查了Fe耗尽后p21（CIP1/WAF1）的转录后调控，并证明其下调是由于两种机制：（1）抑制p21（CIP1/WAF1）mRNA从细胞核到胞质翻译机制的易位； (2)诱导不依赖于泛素的蛋白酶体降解。铁螯合显着 (P < .01) 将 p21(CIP1/WAF1) 蛋白半衰期从 61（+/- 4 分钟；n = 3）降低至 28（+/- 9 分钟，n = 3）。蛋白酶体抑制剂可以挽救螯合剂介导的 p21(CIP1/WAF1) 蛋白减少，而促溶酶体药物则无效。在 Fe 充足的细胞中，p21(CIP1/WAF1) 以泛素依赖性方式降解，而 Fe 耗尽后，发生泛素依赖性蛋白酶体降解。这些结果对于考虑铁耗竭介导的细胞周期停滞和细胞凋亡的机制以及螯合剂作为抗肿瘤药物的功效非常重要。
Iron (Fe) plays a critical role in proliferation, and Fe deficiency results in G(1)/S arrest and apoptosis. However, the precise role of Fe in cell-cycle control remains unclear. We observed that Fe depletion increased the mRNA of the universal cyclin-dependent kinase inhibitor, p21(C1P1/WAF1), while its protein level was not elevated. This observation is unique to the G1/S arrest seen after Fe deprivation, as increased p21(CIP1/WAF1) mRNA and protein are usually found when arrest is induced by other stimuli. In this study, we examined the posttranscriptional regulation of p21(CIP1/WAF1) after Fe depletion and demonstrated that its down-regulation was due to 2 mechanisms: (1) inhibited translocation of p21(CIP1/WAF1) mRNA from the nucleus to cytosolic translational machinery; and (2) induction of ubiquitin-independent proteasomal degradation. Iron chelation significantly (P < .01) decreased p21(CIP1/WAF1) protein half-life from 61 (+/- 4 minutes; n = 3) to 28 (+/- 9 minutes, n = 3). Proteasomal inhibitors rescued the chelator-mediated decrease in p21(CIP1/WAF1) protein, while lysosomotropic agents were not effective. In Fe-replete cells, p21(CIP1/WAF1) was degraded in an ubiquitin-dependent manner, while after Fe depletion, ubiquitinin-dependent proteasomal degradation occurred. These results are important for considering the mechanism of Fe depletion-mediated cell-cycle arrest and apoptosis and the efficacy of chelators as antitumor agents.