Jirmanova Ludmila, Bulavin Dmitry V, Fornace Albert J
Laboratory of Immune Cell Biology, National Cancer Institute, Bethesda, Maryland, USA.
Cell Cycle. 2005 Oct;4(10):1428-34. doi: 10.4161/cc.4.10.2055. Epub 2005 Oct 26.
Ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, family members of the PI-3 kinase related proteins, play a key role in checkpoint activation and maintenance of genomic stability following DNA damage. We have used wild type (WT) and p38alpha-deficient mouse embryonic stem (ES) cells to investigate the role of ATR and ATM kinases during embryonic cell cycle. We have found that inhibition of ATR and ATM kinases with caffeine or Chk1 with UCN-01, results in activation of a p38-dependent intra-S-phase checkpoint and activation of apoptosis in ES cells. However, wortmannin at a concentration, that inhibits ATM kinase but not ATR kinase, did not affect cell cycle progression. Furthermore, the presence of caffeine results in activation of p38 kinase, accumulation of p21/Waf1 in a complex with Cdk2 and decrease of Cdk2 kinase activity. In contrast, caffeine-treated p38alpha-/- ES cells show less apoptosis, and fail to trigger an effective S-phase checkpoint and accumulation of p21/Waf1. We conclude that ATR kinase activity is essential for normal cell cycle progression of exponentially proliferating mouse ES cells even in the absence of exogenous DNA damage, and ATR deregulation triggers p38alpha-dependent cell-cycle checkpoint and apoptotic responses.
共济失调毛细血管扩张症突变基因（ATM）和ATM及Rad3相关蛋白（ATR）激酶是PI-3激酶相关蛋白家族的成员，在DNA损伤后检查点激活和基因组稳定性维持中起关键作用。我们利用野生型（WT）和p38α缺陷型小鼠胚胎干细胞（ES细胞）来研究ATR和ATM激酶在胚胎细胞周期中的作用。我们发现，用咖啡因抑制ATR和ATM激酶或用UCN-01抑制Chk1，会导致ES细胞中p38依赖的S期内检查点激活和凋亡激活。然而，浓度能抑制ATM激酶但不抑制ATR激酶的渥曼青霉素并不影响细胞周期进程。此外，咖啡因的存在会导致p38激酶激活、p21/Waf1与Cdk2形成复合物积累以及Cdk2激酶活性降低。相比之下，经咖啡因处理的p38α-/- ES细胞凋亡较少，且无法触发有效的S期检查点和p21/Waf1积累。我们得出结论，即使在没有外源性DNA损伤的情况下，ATR激酶活性对于指数增殖的小鼠ES细胞的正常细胞周期进程也是必不可少的，并且ATR失调会触发p38α依赖的细胞周期检查点和凋亡反应。
