Allan Lindsey A, Clarke Paul R
Biomedical Research Centre, Level 5, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland, UK.
Mol Cell. 2007 Apr 27;26(2):301-10. doi: 10.1016/j.molcel.2007.03.019.
Proliferating metazoan cells respond to damage that has the potential to cause genomic instability by restricting the cell division cycle or by initiating apoptosis. The molecular mechanisms determining the balance between these responses are not well understood. Here, we show that the apoptotic initiator protease caspase-9 is regulated during the cell cycle through periodic phosphorylation at an inhibitory site, Thr125. This site is phosphorylated by CDK1/cyclin B1 during mitosis and in response to microtubule poisons that arrest cells at this stage of the cell cycle. Using an RNA interference strategy, we show that induction of apoptosis from mitosis in response to these drugs is caspase-9 dependent and is greatly increased when endogenous caspase-9 is replaced by a nonphosphorylatable mutant. Thus, phosphorylation of caspase-9 at Thr125 sets the threshold for activation of the intrinsic apoptotic pathway during the cell cycle, restrains apoptosis during mitosis, and determines sensitivity to antimitotic drugs.
增殖的后生动物细胞通过限制细胞分裂周期或启动凋亡来应对可能导致基因组不稳定的损伤。决定这些反应之间平衡的分子机制尚未完全清楚。在这里，我们表明凋亡起始蛋白酶caspase-9在细胞周期中通过在抑制位点Thr125的周期性磷酸化而受到调控。该位点在有丝分裂期间被CDK1/细胞周期蛋白B1磷酸化，并响应于使细胞在细胞周期的这个阶段停滞的微管毒物。使用RNA干扰策略，我们表明在有丝分裂期响应这些药物诱导的凋亡是caspase-9依赖性的，并且当内源性caspase-9被不可磷酸化的突变体取代时，凋亡大大增加。因此，caspase-9在Thr125处的磷酸化设定了细胞周期中内源性凋亡途径激活的阈值，在有丝分裂期间抑制凋亡，并决定对抗有丝分裂药物的敏感性。
