Soldatenkov V A, Prasad S, Notario V, Dritschilo A
Department of Radiation Medicine, Georgetown University Medical Center, Washington, DC 20007, USA.
Cancer Res. 1995 Oct 1;55(19):4240-2.
Ewing's sarcoma (ES) cells express high levels of poly(ADP-ribose) polymerase (PADPRP) and are responsive to killing by ionizing radiation. We have determined that ionizing radiation induced a pronounced but reversible G2-M phase cell cycle arrest that was maximum by 24 h after exposure. Following the release from this block, floating cells began to appear. These floating cells were shown to be apoptotic by flow cytometric and DNA fragmentation analyses. We found that apoptosis is a significant component of radiation-induced death in ES cells and that this is accomplished in conjunction with proteolytic cleavage of PADPRP. Two fragments of M(r) 25,000 and M(r) 29,000 containing the PADPRP DNA-binding domain were identified in floating (apoptotic) cells, whereas only the full-length M(r) 116,000 native protein was detected in adherent cells that retained DNA intact. These data are consistent with PADPRP cleavage being an early step in the apoptotic cascade of biochemical events in ES cells after ionizing radiation exposure.
尤因肉瘤（ES）细胞表达高水平的聚（ADP-核糖）聚合酶（PADPRP），并且对电离辐射杀伤敏感。我们已经确定，电离辐射诱导明显但可逆的G2-M期细胞周期阻滞，在照射后24小时达到最大值。从该阻滞中解除后，开始出现漂浮细胞。通过流式细胞术和DNA片段化分析表明这些漂浮细胞发生了凋亡。我们发现凋亡是ES细胞中辐射诱导死亡的一个重要组成部分，并且这与PADPRP的蛋白水解切割同时发生。在漂浮（凋亡）细胞中鉴定出包含PADPRP DNA结合结构域的分子量为25,000和29,000的两个片段，而在保留完整DNA的贴壁细胞中仅检测到全长分子量为116,000的天然蛋白。这些数据与PADPRP切割是电离辐射暴露后ES细胞凋亡级联生化事件的早期步骤一致。
