Mechanisms of apoptotic cell death caused by radiation-induced perturbation in checkpoint regulations.

为了阐明辐射诱导的有丝分裂检查点调控中染色体不稳定和凋亡的机制，我们分离了调节有丝分裂细胞分裂的丝氨酸/苏氨酸蛋白激酶，并分析了它们与细胞凋亡相关的特性。过去3年的研究结果可概括如下：1.在有丝分裂过程中，组蛋白H3在Ser-10处的磷酸化是维持适当的染色体动力学所必需的。我们发现，外源Aurora-B激酶AIM-1在培养的哺乳动物细胞中的过表达导致有丝分裂过程中Ser-10的磷酸化增加，并伴随着有丝分裂过程中落后染色体的出现，体内过表达的AIM-1细胞的染色体数目不稳定，肿瘤侵袭性增加。这些数据表明，由于AIM-1过表达而导致的H3组蛋白磷酸化增加是染色体不稳定的主要沉淀因素，因此可能在癌症发生中发挥作用。2…更多。为了分析不同哺乳动物细胞在电离辐射下的共同特征--迟发性凋亡的机制，我们检测了γ和UV辐射对细胞凋亡的诱导作用，并比较了线粒体信号通路的激活情况。结果表明，细胞凋亡的延迟或快速形式强烈依赖于辐射类型，可能是由于线粒体中存在调节细胞色素c释放的胞质因子，细胞色素c在凋亡信号通路的上游发挥作用。由于Aurora-A的过度表达和野生型P53功能的丧失导致了类似的染色体不稳定性，这种情况在癌变过程中经常出现，我们分析了Aurora-A的磷酸化与P53活性的关系。我们的数据表明，Aurora-A的过度表达导致P53降解增加，导致检查点反应通路下调和对凋亡细胞死亡的耐受性。较少

To elucidate the mechanisms of chromosome instability and apoptosis caused by radiation-induced perturbations in mitotic checkpoint regulations, we have isolated serin/threonine protein kinases that regulate mitotic cell division and analyzed their properties associated with apoptotic cell death. The results obtained for the past 3 years can be summarized as follows:1. Phosphorylation of histone H3 at Ser-10 is required for maintenance of proper chromosome dynamics during mitosis. We found that exogenous overexpression of Aurora-B kinase AIM-1 in cultured mammalian cells caused increased mitotic Ser-10 phosphorylation with concomitant of lagging chromosomes during mitosis, and that chromosome number instability and increased tumor invasiveness were noted AIM-1 overexpression cell in vivo. These data suggest that increased H3 histone phosphorylation as a result of AIM-1 overexpression is a major precipitating factor of chromosome instability and, thus may play a role in carcinogenesis.2 … More . To analyze the mechanism of delayed form of apoptosis that is a common feature of various mammalian cells when irradiated with ionizing radiation, we examined the induction of apoptosis by γ or UV radiation and compared the activation of mitochondrial signaling pathways. The results indicate that delayed or rapid form of apoptosis strongly depend on types of radiation and might be due to the existence of cytosolic factors regulating release of cytochrome c from mitochondria, which functions at the upstream of apoptosis signaling pathways.3. Since overexpression of Aurora kinase-A and loss of wild-type of p53 function induce similar chromosome instability, which commonly appears in the process of malignant transformation, we have analyzed the relationship between the phosphorylation of Aurora-A and p53 activity. Our data suggest that overexpression of Aurora-A lead to increased degradation of p53, causing downregulation of checkpoint-response pathways and tolerance to apoptotic cells death. Less