Niida Hiroyuki, Tsuge Shinji, Katsuno Yuko, Konishi Akimitsu, Takeda Naoki, Nakanishi Makoto
Department of Biochemistry and Cell Biology, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan.
J Biol Chem. 2005 Nov 25;280(47):39246-52. doi: 10.1074/jbc.M505009200. Epub 2005 Sep 13.
Mitotic catastrophe occurs as a result of the uncoupling of the onset of mitosis from the completion of DNA replication, but precisely how the ensuing lethality is regulated or what signals are involved is largely unknown. We demonstrate here the essential role of the ATM/ATR-p53 pathway in mitotic catastrophe from premature mitosis. Chk1 deficiency resulted in a premature onset of mitosis because of abnormal activation of cyclin B-Cdc2 and led to the activation of caspases 3 and 9 triggered by cytoplasmic release of cytochrome c. This deficiency was associated with foci formation by the phosphorylated histone, H2AX (gammaH2AX), specifically at S phase. Ectopic expression of Cdc2AF, a mutant that cannot be phosphorylated at inhibitory sites, also induced premature mitosis and foci formation by gammaH2AX at S phase in both embryonic stem cells and HCT116 cells. Depletion of ATM and ATR protected against cell death from premature mitosis. p53-deficient cells were highly resistant to lethality from premature mitosis as well. Our results therefore suggest that ATM/ATR-p53 is required for mitotic catastrophe that eliminates cells escaping Chk1-dependent mitotic regulation. Loss of this function might be important in mammalian tumorigenesis.
有丝分裂灾难是由于有丝分裂的开始与DNA复制的完成解偶联所致，但究竟如何调节随之而来的细胞死亡或涉及哪些信号，目前仍知之甚少。我们在此证明了ATM/ATR-p53通路在由过早有丝分裂引发的有丝分裂灾难中的重要作用。Chk1缺陷由于细胞周期蛋白B-Cdc2的异常激活导致有丝分裂过早开始，并导致细胞色素c从细胞质释放引发半胱天冬酶3和9的激活。这种缺陷与磷酸化组蛋白H2AX（γH2AX）形成的病灶有关，特别是在S期。异位表达不能在抑制位点被磷酸化的突变体Cdc2AF，在胚胎干细胞和HCT116细胞中均诱导S期过早有丝分裂和γH2AX形成病灶。ATM和ATR的缺失可防止过早有丝分裂导致的细胞死亡。p53缺陷细胞对过早有丝分裂导致的致死性也具有高度抗性。因此，我们的结果表明，ATM/ATR-p53是消除逃避Chk1依赖性有丝分裂调节的细胞的有丝分裂灾难所必需的。该功能的丧失可能在哺乳动物肿瘤发生中起重要作用。
