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Cleavage of CAD inhibitor in CAD activation and DNA degradation during apoptosis (see comments)

机译:在细胞凋亡期间CAD激活中的CAD抑制剂裂解和DNA降解(参见评论)

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Various molecules such as cytokines and anticancer drugs, as well as factor deprivation, rapidly induce apoptosis (programmed cell death), which is morphologically characterized by cell shrinkage and the blebbing of plasma membranes and by nuclear condensation. Caspases, particularly caspase 3, are proteases that are activated during apoptosis and which cleave substrates such as poly(ADP-ribose) polymerase, actin, fodrin, and lamin. Apoptosis is also accompanied by the internucleosomal degradation of chromosomal DNA. In the accompanying Article, we have identified and molecularly cloned a caspase-activated deoxyribonuclease (CAD) and its inhibitor (ICAD). Here we show that caspase 3 cleaves ICAD and inactivates its CAD-inhibitory effect. We identified two caspase-3 cleavage sites in ICAD by site-directed mutagenesis. When human Jurkat cells were transformed with ICAD-expressing plasmid, occupation of the receptor Fas, which normally triggers apoptosis, did not result in DNA degradation. The ICAD transformants were also resistant to staurosporine-induced DNA degradation, although staurosporine still killed the cells by activating caspase. Our results indicate that activation of CAD downstream of the caspase cascade is responsible for internucleosomal DNA degradation during apoptosis, and that ICAD works as an inhibitor of this process.
机译:诸如细胞因子和抗癌药之类的各种分子以及因子剥夺迅速诱导凋亡(程序性细胞死亡),其形态学特征是细胞萎缩,质膜起泡和核浓缩。胱天蛋白酶,特别是胱天蛋白酶3,是在凋亡过程中被激活并切割底物的蛋白酶,例如聚(ADP-核糖)聚合酶,肌动蛋白,铁蛋白和层粘连蛋白。凋亡还伴随着染色体DNA的核小体间降解。在随附的文章中,我们确定并分子克隆了caspase激活的脱氧核糖核酸酶(CAD)及其抑制剂(ICAD)。在这里,我们显示半胱天冬酶3裂解ICAD并失活其CAD抑制作用。我们通过定点诱变在ICAD中鉴定了两个caspase-3切割位点。当用表达ICAD的质粒转化人Jurkat细胞时,通常触发细胞凋亡的Fas受体的占领并不会导致DNA降解。尽管星形孢菌素仍通过激活胱天蛋白酶而杀死细胞,但ICAD转化体也抵抗星形孢菌素诱导的DNA降解。我们的结果表明,caspase级联下游的CAD激活是导致细胞凋亡期间核小体间DNA降解的原因,而ICAD可以作为该过程的抑制剂。

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