Catchpoole D R, Stewart B W
Childrens Leukaemia and Cancer Research Centre, University of New South Wales, Prince of Wales Children's Hospital, Randwick, Sydney, Australia.
Exp Cell Res. 1995 Jan;216(1):169-77. doi: 10.1006/excr.1995.1021.
The onset of apoptosis is often coincident with internucleosomal DNA fragmentation or ladders which are considered a hallmark of the process. However, several studies have indicated that MOLT-4 human lymphoblastoid cells exposed to various agents, including VP16, display some apoptotic characteristics in the absence of either internucleosomal ladders or production of apoptotic bodies. The present study records that, in the presence of aurintricarboxylic acid (ATA), internucleosomal ladders were detected in DNA isolated from VP16-treated MOLT-4 cells; a paradoxical result in view of inhibition by ATA of nuclease activity in cell free preparations. The activity of ATA in mediating genomic fragmentation was dose- and time-dependent. Moreover, addition of ATA to VP16-treated MOLT-4 cells also resulted in production of apoptotic bodies, this effect being quantified by morphological examination and flow cytometry. Detection of ladders and apoptotic bodies after addition of ATA was not attributable to increased toxicity in cells exposed to the combined treatment relative to VP16 alone. A similar response, that is the appearance of both internucleosomal fragmentation and apoptotic bodies, occurred after exposure of MOLT-4 cells to the mitotic inhibitor podophyllotoxin. The consistent association between internucleosomal fragmentation of DNA and formation of apoptotic bodies exhibited during death of MOLT-4 cells, insofar as both characteristics are either present or absent following different agents, suggests interdependence.
细胞凋亡的发生通常与核小体间DNA片段化或梯状条带同时出现，这些被视为该过程的标志。然而，多项研究表明，暴露于包括VP16在内的各种试剂的MOLT-4人淋巴母细胞样细胞，在没有核小体间梯状条带或凋亡小体产生的情况下也表现出一些凋亡特征。本研究记录了，在金精三羧酸（ATA）存在的情况下，从经VP16处理的MOLT-4细胞中分离的DNA中检测到了核小体间梯状条带；鉴于ATA在无细胞制剂中对核酸酶活性的抑制作用，这是一个自相矛盾的结果。ATA介导基因组片段化的活性呈剂量和时间依赖性。此外，向经VP16处理的MOLT-4细胞中添加ATA还导致了凋亡小体的产生，这种效应通过形态学检查和流式细胞术进行定量。添加ATA后梯状条带和凋亡小体的检测并非归因于与单独使用VP16相比，联合处理的细胞中毒性增加。MOLT-4细胞暴露于有丝分裂抑制剂鬼臼毒素后也出现了类似的反应，即核小体间片段化和凋亡小体的出现。在MOLT-4细胞死亡过程中，DNA的核小体间片段化与凋亡小体形成之间始终存在关联，因为在不同试剂作用后这两种特征要么都存在，要么都不存在，这表明它们相互依存。
