Cain K, Inayat-Hussain S H, Kokileva L, Cohen G M
MRC Toxicology Unit, University of Leicester, UK.
FEBS Lett. 1995 Jan 30;358(3):255-61. doi: 10.1016/0014-5793(94)01436-5.
DNA fragmentation in isolated rat liver nuclei is a Mg(2+)-dependent, multi-step process which is potentiated by Ca2+ and cleaves the DNA into > or = 700, 200-300 and 30-50 kilobase pair (kbp) fragments, prior to internucleosomal cleavage by Ca2+/Mg(2+)-dependent endonuclease(s). We now show that Cd2+, Hg2+, dichloroisocoumarin (DCI, a serine protease inhibitor) and N-ethylmaleimide (NEM) block both Mg2+ and Ca2+/Mg(2+)-dependent processes. Inhibition of DNA cleavage produced an increase in the size of the DNA fragments, from mono-/oligonucleosomes to 30-50, 200-300, > or = 700 kbp and finally to intact DNA. NEM and DCI inhibition was blocked by dithiothreitol, and it is proposed that a critical thiol(s) is involved in the DNA cleavage reactions which are a feature of the apoptotic process.
分离的大鼠肝细胞核中的DNA片段化是一个依赖Mg(2+)的多步骤过程，该过程由Ca2+增强，并在Ca2+/Mg(2+)依赖的核酸内切酶进行核小体间切割之前，将DNA切割成≥700、200 - 300和30 - 50千碱基对(kbp)的片段。我们现在表明，Cd2+、Hg2+、二氯异香豆素(DCI，一种丝氨酸蛋白酶抑制剂)和N - 乙基马来酰亚胺(NEM)会阻断Mg2+和Ca2+/Mg(2+)依赖的过程。DNA切割的抑制导致DNA片段大小增加，从单/寡核小体增加到30 - 50、200 - 300、≥700 kbp，最终增加到完整的DNA。NEM和DCI的抑制作用可被二硫苏糖醇阻断，有人提出一个关键的巯基参与了作为凋亡过程特征的DNA切割反应。
