Caspase Alone Can Induce DNA Fragmentation In Isolated Nuclei
Apoptosis is a programmed cell death characterized by the cellular and nuclear changes including chromosomal DNA fragmentation(DF). For the nuclear DF the activation of pro-caspase to processed caspase, an apoptosis-specific cysteine protease, is required. The protease alone, however, was known to be unable to induce the DF in nucleus(reviewed in Nature, 401:127) and cellular factor(s) such as DFF40/CAD was reported to be necessay. In this study, however, it is shown that the DF can occur by caspase-3 and 7(but not by 6 and 8) without the aid of any cytoplasmic factors. For the maximal DF 50~75 mM NaCl or KCl is necessary. The DF can be inhibited by ICAD protein, the CAD specific inhibitor. Fractionation of nuclear extract by size-exclusion column and the following Western blotting experiments indicates the involvement of DFF40/CAD-related DNase in the process.