中文摘要：

为了在 p53 缺乏的肿瘤房间，在 G1 的同步 HeLa 房间， S 和 G2/M 在房间周期前进上探索 DNA 损坏的效果，阶段与甲基 methanesulfnate (公里) 被对待。结果证明 MMS 处理在所有 3 个阶段导致了房间周期拘捕或延期，当 S 阶段房间对公里最敏感时。当房间与公里被对待时，进一步的研究证明 ATM-Chk2 和 p38 MAPK 发信号小径在所有 3 个阶段被激活；而 Chk1 在药处理下面仅仅在 S 阶段被激活，明确地显示那 Chk1 参予了 S 阶段检查点。在 S 阶段检查点分析 Chk1 的角色，我们管理了一个特定的 Chk1 禁止者， UCN-01，到 S 阶段房间。结果证明没有完成 DNA 复制，与 MMS+UCN-01 对待的 S 阶段房间能进入异常有丝分裂，显示 Chk1 主要在 DNA 损坏检查点而非在复制检查点工作。另外，公里处理独自禁止了 cyclin B1 的累积， M 阶段 CDK-cyclin 建筑群的一个关键部件在 S 阶段房间，而 Chk1 激活的抑制在对待公里的 S 阶段房间导致了 cyclin B1 的累积。这观察进一步支持损坏 DNA 的 S 阶段房间进入的看法反常有丝分裂当 Chk1 激活被禁止时。我们的结果证明 Chk1 是在导致公里的 S 阶段 DNA 损坏检查点起一个重要作用的特定的 kinase。当 p53 不涉及这个过程， Chk1 可以是为 p53 缺乏的肿瘤治疗的一个潜在的目标。

英文摘要：

To explore effects of DNA damage on cell-cycle progression in p53-deficient tumor cells, synchronized HeLa cells at G1, S and G2/M phases were treated with methyl methanesulfnate （MMS）. The results showed that the MMS treatment resulted in the cell-cycle arrest or delay in all 3 phases, while the S-phase cells were the most sensitive to MMS. Further studies demonstrated that ATM-Chk2 and p38 MAPK signaling pathways were activated in all 3 phases when the cells were treated with MMS; whereas Chk1 was activated only in S phase under the drug treatment, indicating that Chk1 specifically participated in S-phase checkpoints. To analyze the role of Chk1 in S-phase checkpoints, we administered a specific Chk1 inhibitor, UCN-01, to the S-phase cells. The results showed that the S-phase cells treated with MMS＋UCN-01 could enter aberrant mitosis without finishing DNA replication, indicating that Chk1 mainly functions in the DNA damage checkpoint rather than in the replication checkpoint. In addition, MMS treatment alone inhibited the accumulation of cyclin B1, a key component of M-phase CDK-cyclin complex, in the S-phase cells, whereas the inhibition of Chk1 activation resulted in the accumulation of cyclin B1 in the MMS-treated S-phase cells. This observation further supports the view that DNA-damaged S-phase cells enter abnormal mitosis when Chk1 activation is inhibited. Our results demonstrate that Chk1 is a specific kinase that plays an important role in the MMS-induced S-phase DNA damage checkpoint. As p53 is not involved in this process, Chk1 may be a potential target for p53-deficient tumor therapy.