[Apoptosis: its molecular mechanisms and biological roles]

Apoptosis is a mechanism for eliminating unwanted cells from the cell community of multicellular organisms. Abnormalities in the regulation of apoptosis may play a part in the aetiology of cancer, autoimmune diseases, AIDS, degenerative nerve diseases and malformation. On of the hallmarks of apoptosis is the enzymatic cleavage of genomic DNA into nucleosomal oligomers. The identification of an endonuclease responsible for apoptosis might help to explain how this cell suicide is regulated and why DNA is cleaved. Here, we found that gamma type of DNase was retained in apoptotic rat thymocyte nuclei. The mode of DNA cleavage, 3'-hydroxyl (OH)/5'-phosphoryl (P) ends, by homogeneously purified DNase gamma (Mr = 33 kDa) and its Zn2+ sensitivity match those observed in apoptosis in thymocytes induced by irradiation or glucocorticoid treatment, indicating that this endonuclease is a central component of the thymic apoptosis machinery.