Death by endonuclease

The apoptotic suicide programme involves fragmentation of nucleosomal DNA. In the July 5 Nature, two groups report identification of a mitochondrial nuclease that induces DNA degradation associated with apoptosis in both worms and mammals. Parrish et al. performed a genetic screen in Caenorhabditis elegans to search for suppressors of an activated cell-death protease (CED-3) mutant (Nature 2001, 412:90-94). After screening 3,000 mutagenized haploid genomes, they identified an apoptosis-related gene that they named cps-6 (CED-3 protease suppressor). Analysis of the cps-6 mutation and RNAi gene inactivation experiments revealed delayed appearance of cell corpses during nematode development. The cps-6 gene is homologous to the mammalian mitochondrial endonuclease G. In an accompanying paper, Li et al. show that the role of endonuclease G in apoptosis is conserved in human cells (Nature 2001, 412:95-99). They used a reconstituted in vitro system to demonstrate the release of a DNase from mitochondria...