辐射诱发细胞凋亡中DNA大片段的生成

High molecular weight DNA fragmentation in the course of radiation induced apoptosis

目的与方法：ＤＮＡ在核小体间断裂，琼脂糖凝胶电泳时出现梯形谱（ＤＮＡｌａｄｄｅｒ），通常被认为是细胞凋亡的特征性生化标志。利用脉冲场凝胶电泳，对人外周血淋巴细胞受照后ＤＮＡ梯形谱形成前，ＤＮＡ断裂情况进行了观察。结果：人外周血淋巴细胞受照诱发凋亡过程中，ＤＮＡ的断裂分成两步，首先是产生３００ｋｂ到５０ｋｂ的ＤＮＡ大片段，随后才是通常所描述的ＤＮＡ梯形谱。结论：细胞凋亡中核酸内切酶对ＤＮＡ的降解不是一步完成的。

Objective and Methods: Cleavage of DNA into oligonucleosomal fragments, recognized as a DNA ladder on agarose gel electrophoresis, is usually considered as the biochemical hallmark of apoptosis. To determine the high molecular weight DNA fragments prior to internucleosomal fragmentation of radiation induced apoptosis in human peripheral lymphocytes, the pulsed field gel electrophoresis was used. Results: In the course of radiation induced apoptosis of human lymphocytes, DNA fragmentation occurred in two stages. The first was cleavage of DNA into 300 to 50 kb fragments, and the second stage of fragmentation was the formation of DNA ladder previously described. Conclusion: DNA degradation during apoptosis appears to be a multistep process, and the DNA ladder may not be the sole biochemical hallmark of apoptotic cells.