Rodriguez Rene, Meuth Mark
Institute for Cancer Studies, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield S10 2RX, United Kingdom.
Mol Biol Cell. 2006 Jan;17(1):402-12. doi: 10.1091/mbc.e05-07-0594. Epub 2005 Nov 9.
Cells respond to DNA replication stress by triggering cell cycle checkpoints, repair, or death. To understand the role of the DNA damage response pathways in determining whether cells survive replication stress or become committed to death, we examined the effect of loss of these pathways on cellular response to agents that slow or arrest DNA synthesis. We show that replication inhibitors such as excess thymidine, hydroxyurea, and camptothecin are normally poor inducers of apoptosis. However, these agents become potent inducers of death in S-phase cells upon small interfering RNA-mediated depletion of the checkpoint kinase Chk1. This death response is independent of p53 and Chk2. p21-deficient cells, on the other hand, produce a more robust apoptotic response upon Chk1 depletion. p21 is normally induced only late after thymidine treatment. In Chk1-depleted cells p21 induction occurs earlier and does not require p53. Thus, Chk1 plays a primary role in the protection of cells from death induced by replication fork stress, whereas p21 mediates through its role in regulating entry into S phase. These findings are of potential importance to cancer therapy because we demonstrate that the efficacy of clinically relevant agents can be enhanced by manipulation of these signaling pathways.
细胞通过触发细胞周期检查点、修复或死亡来应对DNA复制应激。为了了解DNA损伤反应途径在决定细胞是在复制应激中存活还是走向死亡方面的作用，我们研究了这些途径缺失对细胞对减缓或阻止DNA合成的试剂的反应的影响。我们发现，诸如过量胸苷、羟基脲和喜树碱等复制抑制剂通常是较弱的凋亡诱导剂。然而，在小干扰RNA介导的检查点激酶Chk1缺失后，这些试剂在S期细胞中成为强效的死亡诱导剂。这种死亡反应独立于p53和Chk2。另一方面，p21缺陷细胞在Chk1缺失后产生更强有力的凋亡反应。p21通常仅在胸苷处理后较晚时被诱导。在Chk1缺失的细胞中，p21的诱导发生得更早且不需要p53。因此，Chk1在保护细胞免受复制叉应激诱导的死亡中起主要作用，而p21通过其在调节进入S期的作用来介导。这些发现对癌症治疗具有潜在重要性，因为我们证明了通过操纵这些信号通路可以提高临床相关试剂的疗效。
