The biochemical changes that characterize apoptosis include nuclear DNA fragmentation and digestion, but the biological importance of undigested apoptotic DNA degradation has been unclear. In October 15 Genes & Development, Naomi Mukae and colleagues at Osaka University Medical School, Osaka, Japan, show that chromosomal DNA that escapes apoptotic degradation can induce activation of the innate immunity in Drosophila (Genes & Development, 20: 2662-2671, October 15, 2002).

Mukae et al. used Drosophila lines deficient in either the gene that controls caspase-activated DNase (ICAD) inhibition or lysosomal acid DNase (dDNase II). They observed that CAD and DNase II work independently to degrade chromosomal DNA during apoptosis. The dDNase II-deficient flies showed enhanced apoptotic DNA fragmentation, yet accumulated a large amount of DNA, particularly in ovaries, and constitutively expressed the genes for antibacterial peptides. In addition, the activation of the antibacterial peptide genes was enhanced in Drosophila mutants that...